1	// SPDX-License-Identifier: GPL-2.0-only
2	/*
3	* linux/fs/namespace.c
4	*
5	* (C) Copyright Al Viro 2000, 2001
6	*
7	* Based on code from fs/super.c, copyright Linus Torvalds and others.
8	* Heavily rewritten.
9	*/
10
11	#include <linux/syscalls.h>
12	#include <linux/export.h>
13	#include <linux/capability.h>
14	#include <linux/mnt_namespace.h>
15	#include <linux/user_namespace.h>
16	#include <linux/namei.h>
17	#include <linux/security.h>
18	#include <linux/cred.h>
19	#include <linux/idr.h>
20	#include <linux/init.h> /* init_rootfs */
21	#include <linux/fs_struct.h> /* get_fs_root et.al. */
22	#include <linux/fsnotify.h> /* fsnotify_vfsmount_delete */
23	#include <linux/file.h>
24	#include <linux/uaccess.h>
25	#include <linux/proc_ns.h>
26	#include <linux/magic.h>
27	#include <linux/memblock.h>
28	#include <linux/proc_fs.h>
29	#include <linux/task_work.h>
30	#include <linux/sched/task.h>
31	#include <uapi/linux/mount.h>
32	#include <linux/fs_context.h>
33	#include <linux/shmem_fs.h>
34	#include <linux/mnt_idmapping.h>
35	#include <linux/nospec.h>
36
37	#include "pnode.h"
38	#include "internal.h"
39
40	/* Maximum number of mounts in a mount namespace */
41	static unsigned int sysctl_mount_max __read_mostly = 100000;
42
43	static unsigned int m_hash_mask __ro_after_init;
44	static unsigned int m_hash_shift __ro_after_init;
45	static unsigned int mp_hash_mask __ro_after_init;
46	static unsigned int mp_hash_shift __ro_after_init;
47
48	static __initdata unsigned long mhash_entries;
49	static int __init set_mhash_entries(char *str)
50	{
51	if (!str)
52	return 0;
53	mhash_entries = simple_strtoul(str, &str, 0);
54	return 1;
55	}
56	__setup("mhash_entries=", set_mhash_entries);
57
58	static __initdata unsigned long mphash_entries;
59	static int __init set_mphash_entries(char *str)
60	{
61	if (!str)
62	return 0;
63	mphash_entries = simple_strtoul(str, &str, 0);
64	return 1;
65	}
66	__setup("mphash_entries=", set_mphash_entries);
67
68	static u64 event;
69	static DEFINE_IDA(mnt_id_ida);
70	static DEFINE_IDA(mnt_group_ida);
71
72	/* Don't allow confusion with old 32bit mount ID */
73	static atomic64_t mnt_id_ctr = ATOMIC64_INIT(1ULL << 32);
74
75	static struct hlist_head *mount_hashtable __ro_after_init;
76	static struct hlist_head *mountpoint_hashtable __ro_after_init;
77	static struct kmem_cache *mnt_cache __ro_after_init;
78	static DECLARE_RWSEM(namespace_sem);
79	static HLIST_HEAD(unmounted); /* protected by namespace_sem */
80	static LIST_HEAD(ex_mountpoints); /* protected by namespace_sem */
81
82	struct mount_kattr {
83	unsigned int attr_set;
84	unsigned int attr_clr;
85	unsigned int propagation;
86	unsigned int lookup_flags;
87	bool recurse;
88	struct user_namespace *mnt_userns;
89	struct mnt_idmap *mnt_idmap;
90	};
91
92	/* /sys/fs */
93	struct kobject *fs_kobj __ro_after_init;
94	EXPORT_SYMBOL_GPL(fs_kobj);
95
96	/*
97	* vfsmount lock may be taken for read to prevent changes to the
98	* vfsmount hash, ie. during mountpoint lookups or walking back
99	* up the tree.
100	*
101	* It should be taken for write in all cases where the vfsmount
102	* tree or hash is modified or when a vfsmount structure is modified.
103	*/
104	__cacheline_aligned_in_smp DEFINE_SEQLOCK(mount_lock);
105
106	static inline void lock_mount_hash(void)
107	{
108	write_seqlock(sl: &mount_lock);
109	}
110
111	static inline void unlock_mount_hash(void)
112	{
113	write_sequnlock(sl: &mount_lock);
114	}
115
116	static inline struct hlist_head *m_hash(struct vfsmount *mnt, struct dentry *dentry)
117	{
118	unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES);
119	tmp += ((unsigned long)dentry / L1_CACHE_BYTES);
120	tmp = tmp + (tmp >> m_hash_shift);
121	return &mount_hashtable[tmp & m_hash_mask];
122	}
123
124	static inline struct hlist_head *mp_hash(struct dentry *dentry)
125	{
126	unsigned long tmp = ((unsigned long)dentry / L1_CACHE_BYTES);
127	tmp = tmp + (tmp >> mp_hash_shift);
128	return &mountpoint_hashtable[tmp & mp_hash_mask];
129	}
130
131	static int mnt_alloc_id(struct mount *mnt)
132	{
133	int res = ida_alloc(ida: &mnt_id_ida, GFP_KERNEL);
134
135	if (res < 0)
136	return res;
137	mnt->mnt_id = res;
138	mnt->mnt_id_unique = atomic64_inc_return(v: &mnt_id_ctr);
139	return 0;
140	}
141
142	static void mnt_free_id(struct mount *mnt)
143	{
144	ida_free(&mnt_id_ida, id: mnt->mnt_id);
145	}
146
147	/*
148	* Allocate a new peer group ID
149	*/
150	static int mnt_alloc_group_id(struct mount *mnt)
151	{
152	int res = ida_alloc_min(ida: &mnt_group_ida, min: 1, GFP_KERNEL);
153
154	if (res < 0)
155	return res;
156	mnt->mnt_group_id = res;
157	return 0;
158	}
159
160	/*
161	* Release a peer group ID
162	*/
163	void mnt_release_group_id(struct mount *mnt)
164	{
165	ida_free(&mnt_group_ida, id: mnt->mnt_group_id);
166	mnt->mnt_group_id = 0;
167	}
168
169	/*
170	* vfsmount lock must be held for read
171	*/
172	static inline void mnt_add_count(struct mount *mnt, int n)
173	{
174	#ifdef CONFIG_SMP
175	this_cpu_add(mnt->mnt_pcp->mnt_count, n);
176	#else
177	preempt_disable();
178	mnt->mnt_count += n;
179	preempt_enable();
180	#endif
181	}
182
183	/*
184	* vfsmount lock must be held for write
185	*/
186	int mnt_get_count(struct mount *mnt)
187	{
188	#ifdef CONFIG_SMP
189	int count = 0;
190	int cpu;
191
192	for_each_possible_cpu(cpu) {
193	count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_count;
194	}
195
196	return count;
197	#else
198	return mnt->mnt_count;
199	#endif
200	}
201
202	static struct mount *alloc_vfsmnt(const char *name)
203	{
204	struct mount *mnt = kmem_cache_zalloc(k: mnt_cache, GFP_KERNEL);
205	if (mnt) {
206	int err;
207
208	err = mnt_alloc_id(mnt);
209	if (err)
210	goto out_free_cache;
211
212	if (name) {
213	mnt->mnt_devname = kstrdup_const(s: name,
214	GFP_KERNEL_ACCOUNT);
215	if (!mnt->mnt_devname)
216	goto out_free_id;
217	}
218
219	#ifdef CONFIG_SMP
220	mnt->mnt_pcp = alloc_percpu(struct mnt_pcp);
221	if (!mnt->mnt_pcp)
222	goto out_free_devname;
223
224	this_cpu_add(mnt->mnt_pcp->mnt_count, 1);
225	#else
226	mnt->mnt_count = 1;
227	mnt->mnt_writers = 0;
228	#endif
229
230	INIT_HLIST_NODE(h: &mnt->mnt_hash);
231	INIT_LIST_HEAD(list: &mnt->mnt_child);
232	INIT_LIST_HEAD(list: &mnt->mnt_mounts);
233	INIT_LIST_HEAD(list: &mnt->mnt_list);
234	INIT_LIST_HEAD(list: &mnt->mnt_expire);
235	INIT_LIST_HEAD(list: &mnt->mnt_share);
236	INIT_LIST_HEAD(list: &mnt->mnt_slave_list);
237	INIT_LIST_HEAD(list: &mnt->mnt_slave);
238	INIT_HLIST_NODE(h: &mnt->mnt_mp_list);
239	INIT_LIST_HEAD(list: &mnt->mnt_umounting);
240	INIT_HLIST_HEAD(&mnt->mnt_stuck_children);
241	mnt->mnt.mnt_idmap = &nop_mnt_idmap;
242	}
243	return mnt;
244
245	#ifdef CONFIG_SMP
246	out_free_devname:
247	kfree_const(x: mnt->mnt_devname);
248	#endif
249	out_free_id:
250	mnt_free_id(mnt);
251	out_free_cache:
252	kmem_cache_free(s: mnt_cache, objp: mnt);
253	return NULL;
254	}
255
256	/*
257	* Most r/o checks on a fs are for operations that take
258	* discrete amounts of time, like a write() or unlink().
259	* We must keep track of when those operations start
260	* (for permission checks) and when they end, so that
261	* we can determine when writes are able to occur to
262	* a filesystem.
263	*/
264	/*
265	* __mnt_is_readonly: check whether a mount is read-only
266	* @mnt: the mount to check for its write status
267	*
268	* This shouldn't be used directly ouside of the VFS.
269	* It does not guarantee that the filesystem will stay
270	* r/w, just that it is right *now*. This can not and
271	* should not be used in place of IS_RDONLY(inode).
272	* mnt_want/drop_write() will _keep_ the filesystem
273	* r/w.
274	*/
275	bool __mnt_is_readonly(struct vfsmount *mnt)
276	{
277	return (mnt->mnt_flags & MNT_READONLY) || sb_rdonly(sb: mnt->mnt_sb);
278	}
279	EXPORT_SYMBOL_GPL(__mnt_is_readonly);
280
281	static inline void mnt_inc_writers(struct mount *mnt)
282	{
283	#ifdef CONFIG_SMP
284	this_cpu_inc(mnt->mnt_pcp->mnt_writers);
285	#else
286	mnt->mnt_writers++;
287	#endif
288	}
289
290	static inline void mnt_dec_writers(struct mount *mnt)
291	{
292	#ifdef CONFIG_SMP
293	this_cpu_dec(mnt->mnt_pcp->mnt_writers);
294	#else
295	mnt->mnt_writers--;
296	#endif
297	}
298
299	static unsigned int mnt_get_writers(struct mount *mnt)
300	{
301	#ifdef CONFIG_SMP
302	unsigned int count = 0;
303	int cpu;
304
305	for_each_possible_cpu(cpu) {
306	count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_writers;
307	}
308
309	return count;
310	#else
311	return mnt->mnt_writers;
312	#endif
313	}
314
315	static int mnt_is_readonly(struct vfsmount *mnt)
316	{
317	if (READ_ONCE(mnt->mnt_sb->s_readonly_remount))
318	return 1;
319	/*
320	* The barrier pairs with the barrier in sb_start_ro_state_change()
321	* making sure if we don't see s_readonly_remount set yet, we also will
322	* not see any superblock / mount flag changes done by remount.
323	* It also pairs with the barrier in sb_end_ro_state_change()
324	* assuring that if we see s_readonly_remount already cleared, we will
325	* see the values of superblock / mount flags updated by remount.
326	*/
327	smp_rmb();
328	return __mnt_is_readonly(mnt);
329	}
330
331	/*
332	* Most r/o & frozen checks on a fs are for operations that take discrete
333	* amounts of time, like a write() or unlink(). We must keep track of when
334	* those operations start (for permission checks) and when they end, so that we
335	* can determine when writes are able to occur to a filesystem.
336	*/
337	/**
338	* mnt_get_write_access - get write access to a mount without freeze protection
339	* @m: the mount on which to take a write
340	*
341	* This tells the low-level filesystem that a write is about to be performed to
342	* it, and makes sure that writes are allowed (mnt it read-write) before
343	* returning success. This operation does not protect against filesystem being
344	* frozen. When the write operation is finished, mnt_put_write_access() must be
345	* called. This is effectively a refcount.
346	*/
347	int mnt_get_write_access(struct vfsmount *m)
348	{
349	struct mount *mnt = real_mount(mnt: m);
350	int ret = 0;
351
352	preempt_disable();
353	mnt_inc_writers(mnt);
354	/*
355	* The store to mnt_inc_writers must be visible before we pass
356	* MNT_WRITE_HOLD loop below, so that the slowpath can see our
357	* incremented count after it has set MNT_WRITE_HOLD.
358	*/
359	smp_mb();
360	might_lock(&mount_lock.lock);
361	while (READ_ONCE(mnt->mnt.mnt_flags) & MNT_WRITE_HOLD) {
362	if (!IS_ENABLED(CONFIG_PREEMPT_RT)) {
363	cpu_relax();
364	} else {
365	/*
366	* This prevents priority inversion, if the task
367	* setting MNT_WRITE_HOLD got preempted on a remote
368	* CPU, and it prevents life lock if the task setting
369	* MNT_WRITE_HOLD has a lower priority and is bound to
370	* the same CPU as the task that is spinning here.
371	*/
372	preempt_enable();
373	lock_mount_hash();
374	unlock_mount_hash();
375	preempt_disable();
376	}
377	}
378	/*
379	* The barrier pairs with the barrier sb_start_ro_state_change() making
380	* sure that if we see MNT_WRITE_HOLD cleared, we will also see
381	* s_readonly_remount set (or even SB_RDONLY / MNT_READONLY flags) in
382	* mnt_is_readonly() and bail in case we are racing with remount
383	* read-only.
384	*/
385	smp_rmb();
386	if (mnt_is_readonly(mnt: m)) {
387	mnt_dec_writers(mnt);
388	ret = -EROFS;
389	}
390	preempt_enable();
391
392	return ret;
393	}
394	EXPORT_SYMBOL_GPL(mnt_get_write_access);
395
396	/**
397	* mnt_want_write - get write access to a mount
398	* @m: the mount on which to take a write
399	*
400	* This tells the low-level filesystem that a write is about to be performed to
401	* it, and makes sure that writes are allowed (mount is read-write, filesystem
402	* is not frozen) before returning success. When the write operation is
403	* finished, mnt_drop_write() must be called. This is effectively a refcount.
404	*/
405	int mnt_want_write(struct vfsmount *m)
406	{
407	int ret;
408
409	sb_start_write(sb: m->mnt_sb);
410	ret = mnt_get_write_access(m);
411	if (ret)
412	sb_end_write(sb: m->mnt_sb);
413	return ret;
414	}
415	EXPORT_SYMBOL_GPL(mnt_want_write);
416
417	/**
418	* mnt_get_write_access_file - get write access to a file's mount
419	* @file: the file who's mount on which to take a write
420	*
421	* This is like mnt_get_write_access, but if @file is already open for write it
422	* skips incrementing mnt_writers (since the open file already has a reference)
423	* and instead only does the check for emergency r/o remounts. This must be
424	* paired with mnt_put_write_access_file.
425	*/
426	int mnt_get_write_access_file(struct file *file)
427	{
428	if (file->f_mode & FMODE_WRITER) {
429	/*
430	* Superblock may have become readonly while there are still
431	* writable fd's, e.g. due to a fs error with errors=remount-ro
432	*/
433	if (__mnt_is_readonly(file->f_path.mnt))
434	return -EROFS;
435	return 0;
436	}
437	return mnt_get_write_access(file->f_path.mnt);
438	}
439
440	/**
441	* mnt_want_write_file - get write access to a file's mount
442	* @file: the file who's mount on which to take a write
443	*
444	* This is like mnt_want_write, but if the file is already open for writing it
445	* skips incrementing mnt_writers (since the open file already has a reference)
446	* and instead only does the freeze protection and the check for emergency r/o
447	* remounts. This must be paired with mnt_drop_write_file.
448	*/
449	int mnt_want_write_file(struct file *file)
450	{
451	int ret;
452
453	sb_start_write(sb: file_inode(f: file)->i_sb);
454	ret = mnt_get_write_access_file(file);
455	if (ret)
456	sb_end_write(sb: file_inode(f: file)->i_sb);
457	return ret;
458	}
459	EXPORT_SYMBOL_GPL(mnt_want_write_file);
460
461	/**
462	* mnt_put_write_access - give up write access to a mount
463	* @mnt: the mount on which to give up write access
464	*
465	* Tells the low-level filesystem that we are done
466	* performing writes to it. Must be matched with
467	* mnt_get_write_access() call above.
468	*/
469	void mnt_put_write_access(struct vfsmount *mnt)
470	{
471	preempt_disable();
472	mnt_dec_writers(mnt: real_mount(mnt));
473	preempt_enable();
474	}
475	EXPORT_SYMBOL_GPL(mnt_put_write_access);
476
477	/**
478	* mnt_drop_write - give up write access to a mount
479	* @mnt: the mount on which to give up write access
480	*
481	* Tells the low-level filesystem that we are done performing writes to it and
482	* also allows filesystem to be frozen again. Must be matched with
483	* mnt_want_write() call above.
484	*/
485	void mnt_drop_write(struct vfsmount *mnt)
486	{
487	mnt_put_write_access(mnt);
488	sb_end_write(sb: mnt->mnt_sb);
489	}
490	EXPORT_SYMBOL_GPL(mnt_drop_write);
491
492	void mnt_put_write_access_file(struct file *file)
493	{
494	if (!(file->f_mode & FMODE_WRITER))
495	mnt_put_write_access(file->f_path.mnt);
496	}
497
498	void mnt_drop_write_file(struct file *file)
499	{
500	mnt_put_write_access_file(file);
501	sb_end_write(sb: file_inode(f: file)->i_sb);
502	}
503	EXPORT_SYMBOL(mnt_drop_write_file);
504
505	/**
506	* mnt_hold_writers - prevent write access to the given mount
507	* @mnt: mnt to prevent write access to
508	*
509	* Prevents write access to @mnt if there are no active writers for @mnt.
510	* This function needs to be called and return successfully before changing
511	* properties of @mnt that need to remain stable for callers with write access
512	* to @mnt.
513	*
514	* After this functions has been called successfully callers must pair it with
515	* a call to mnt_unhold_writers() in order to stop preventing write access to
516	* @mnt.
517	*
518	* Context: This function expects lock_mount_hash() to be held serializing
519	* setting MNT_WRITE_HOLD.
520	* Return: On success 0 is returned.
521	* On error, -EBUSY is returned.
522	*/
523	static inline int mnt_hold_writers(struct mount *mnt)
524	{
525	mnt->mnt.mnt_flags |= MNT_WRITE_HOLD;
526	/*
527	* After storing MNT_WRITE_HOLD, we'll read the counters. This store
528	* should be visible before we do.
529	*/
530	smp_mb();
531
532	/*
533	* With writers on hold, if this value is zero, then there are
534	* definitely no active writers (although held writers may subsequently
535	* increment the count, they'll have to wait, and decrement it after
536	* seeing MNT_READONLY).
537	*
538	* It is OK to have counter incremented on one CPU and decremented on
539	* another: the sum will add up correctly. The danger would be when we
540	* sum up each counter, if we read a counter before it is incremented,
541	* but then read another CPU's count which it has been subsequently
542	* decremented from -- we would see more decrements than we should.
543	* MNT_WRITE_HOLD protects against this scenario, because
544	* mnt_want_write first increments count, then smp_mb, then spins on
545	* MNT_WRITE_HOLD, so it can't be decremented by another CPU while
546	* we're counting up here.
547	*/
548	if (mnt_get_writers(mnt) > 0)
549	return -EBUSY;
550
551	return 0;
552	}
553
554	/**
555	* mnt_unhold_writers - stop preventing write access to the given mount
556	* @mnt: mnt to stop preventing write access to
557	*
558	* Stop preventing write access to @mnt allowing callers to gain write access
559	* to @mnt again.
560	*
561	* This function can only be called after a successful call to
562	* mnt_hold_writers().
563	*
564	* Context: This function expects lock_mount_hash() to be held.
565	*/
566	static inline void mnt_unhold_writers(struct mount *mnt)
567	{
568	/*
569	* MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers
570	* that become unheld will see MNT_READONLY.
571	*/
572	smp_wmb();
573	mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD;
574	}
575
576	static int mnt_make_readonly(struct mount *mnt)
577	{
578	int ret;
579
580	ret = mnt_hold_writers(mnt);
581	if (!ret)
582	mnt->mnt.mnt_flags |= MNT_READONLY;
583	mnt_unhold_writers(mnt);
584	return ret;
585	}
586
587	int sb_prepare_remount_readonly(struct super_block *sb)
588	{
589	struct mount *mnt;
590	int err = 0;
591
592	/* Racy optimization. Recheck the counter under MNT_WRITE_HOLD */
593	if (atomic_long_read(v: &sb->s_remove_count))
594	return -EBUSY;
595
596	lock_mount_hash();
597	list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) {
598	if (!(mnt->mnt.mnt_flags & MNT_READONLY)) {
599	err = mnt_hold_writers(mnt);
600	if (err)
601	break;
602	}
603	}
604	if (!err && atomic_long_read(v: &sb->s_remove_count))
605	err = -EBUSY;
606
607	if (!err)
608	sb_start_ro_state_change(sb);
609	list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) {
610	if (mnt->mnt.mnt_flags & MNT_WRITE_HOLD)
611	mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD;
612	}
613	unlock_mount_hash();
614
615	return err;
616	}
617
618	static void free_vfsmnt(struct mount *mnt)
619	{
620	mnt_idmap_put(idmap: mnt_idmap(mnt: &mnt->mnt));
621	kfree_const(x: mnt->mnt_devname);
622	#ifdef CONFIG_SMP
623	free_percpu(pdata: mnt->mnt_pcp);
624	#endif
625	kmem_cache_free(s: mnt_cache, objp: mnt);
626	}
627
628	static void delayed_free_vfsmnt(struct rcu_head *head)
629	{
630	free_vfsmnt(container_of(head, struct mount, mnt_rcu));
631	}
632
633	/* call under rcu_read_lock */
634	int __legitimize_mnt(struct vfsmount *bastard, unsigned seq)
635	{
636	struct mount *mnt;
637	if (read_seqretry(sl: &mount_lock, start: seq))
638	return 1;
639	if (bastard == NULL)
640	return 0;
641	mnt = real_mount(mnt: bastard);
642	mnt_add_count(mnt, n: 1);
643	smp_mb(); // see mntput_no_expire()
644	if (likely(!read_seqretry(&mount_lock, seq)))
645	return 0;
646	if (bastard->mnt_flags & MNT_SYNC_UMOUNT) {
647	mnt_add_count(mnt, n: -1);
648	return 1;
649	}
650	lock_mount_hash();
651	if (unlikely(bastard->mnt_flags & MNT_DOOMED)) {
652	mnt_add_count(mnt, n: -1);
653	unlock_mount_hash();
654	return 1;
655	}
656	unlock_mount_hash();
657	/* caller will mntput() */
658	return -1;
659	}
660
661	/* call under rcu_read_lock */
662	static bool legitimize_mnt(struct vfsmount *bastard, unsigned seq)
663	{
664	int res = __legitimize_mnt(bastard, seq);
665	if (likely(!res))
666	return true;
667	if (unlikely(res < 0)) {
668	rcu_read_unlock();
669	mntput(mnt: bastard);
670	rcu_read_lock();
671	}
672	return false;
673	}
674
675	/**
676	* __lookup_mnt - find first child mount
677	* @mnt: parent mount
678	* @dentry: mountpoint
679	*
680	* If @mnt has a child mount @c mounted @dentry find and return it.
681	*
682	* Note that the child mount @c need not be unique. There are cases
683	* where shadow mounts are created. For example, during mount
684	* propagation when a source mount @mnt whose root got overmounted by a
685	* mount @o after path lookup but before @namespace_sem could be
686	* acquired gets copied and propagated. So @mnt gets copied including
687	* @o. When @mnt is propagated to a destination mount @d that already
688	* has another mount @n mounted at the same mountpoint then the source
689	* mount @mnt will be tucked beneath @n, i.e., @n will be mounted on
690	* @mnt and @mnt mounted on @d. Now both @n and @o are mounted at @mnt
691	* on @dentry.
692	*
693	* Return: The first child of @mnt mounted @dentry or NULL.
694	*/
695	struct mount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry)
696	{
697	struct hlist_head *head = m_hash(mnt, dentry);
698	struct mount *p;
699
700	hlist_for_each_entry_rcu(p, head, mnt_hash)
701	if (&p->mnt_parent->mnt == mnt && p->mnt_mountpoint == dentry)
702	return p;
703	return NULL;
704	}
705
706	/*
707	* lookup_mnt - Return the first child mount mounted at path
708	*
709	* "First" means first mounted chronologically. If you create the
710	* following mounts:
711	*
712	* mount /dev/sda1 /mnt
713	* mount /dev/sda2 /mnt
714	* mount /dev/sda3 /mnt
715	*
716	* Then lookup_mnt() on the base /mnt dentry in the root mount will
717	* return successively the root dentry and vfsmount of /dev/sda1, then
718	* /dev/sda2, then /dev/sda3, then NULL.
719	*
720	* lookup_mnt takes a reference to the found vfsmount.
721	*/
722	struct vfsmount *lookup_mnt(const struct path *path)
723	{
724	struct mount *child_mnt;
725	struct vfsmount *m;
726	unsigned seq;
727
728	rcu_read_lock();
729	do {
730	seq = read_seqbegin(sl: &mount_lock);
731	child_mnt = __lookup_mnt(mnt: path->mnt, dentry: path->dentry);
732	m = child_mnt ? &child_mnt->mnt : NULL;
733	} while (!legitimize_mnt(bastard: m, seq));
734	rcu_read_unlock();
735	return m;
736	}
737
738	/*
739	* __is_local_mountpoint - Test to see if dentry is a mountpoint in the
740	* current mount namespace.
741	*
742	* The common case is dentries are not mountpoints at all and that
743	* test is handled inline. For the slow case when we are actually
744	* dealing with a mountpoint of some kind, walk through all of the
745	* mounts in the current mount namespace and test to see if the dentry
746	* is a mountpoint.
747	*
748	* The mount_hashtable is not usable in the context because we
749	* need to identify all mounts that may be in the current mount
750	* namespace not just a mount that happens to have some specified
751	* parent mount.
752	*/
753	bool __is_local_mountpoint(struct dentry *dentry)
754	{
755	struct mnt_namespace *ns = current->nsproxy->mnt_ns;
756	struct mount *mnt, *n;
757	bool is_covered = false;
758
759	down_read(sem: &namespace_sem);
760	rbtree_postorder_for_each_entry_safe(mnt, n, &ns->mounts, mnt_node) {
761	is_covered = (mnt->mnt_mountpoint == dentry);
762	if (is_covered)
763	break;
764	}
765	up_read(sem: &namespace_sem);
766
767	return is_covered;
768	}
769
770	static struct mountpoint *lookup_mountpoint(struct dentry *dentry)
771	{
772	struct hlist_head *chain = mp_hash(dentry);
773	struct mountpoint *mp;
774
775	hlist_for_each_entry(mp, chain, m_hash) {
776	if (mp->m_dentry == dentry) {
777	mp->m_count++;
778	return mp;
779	}
780	}
781	return NULL;
782	}
783
784	static struct mountpoint *get_mountpoint(struct dentry *dentry)
785	{
786	struct mountpoint *mp, *new = NULL;
787	int ret;
788
789	if (d_mountpoint(dentry)) {
790	/* might be worth a WARN_ON() */
791	if (d_unlinked(dentry))
792	return ERR_PTR(error: -ENOENT);
793	mountpoint:
794	read_seqlock_excl(sl: &mount_lock);
795	mp = lookup_mountpoint(dentry);
796	read_sequnlock_excl(sl: &mount_lock);
797	if (mp)
798	goto done;
799	}
800
801	if (!new)
802	new = kmalloc(size: sizeof(struct mountpoint), GFP_KERNEL);
803	if (!new)
804	return ERR_PTR(error: -ENOMEM);
805
806
807	/* Exactly one processes may set d_mounted */
808	ret = d_set_mounted(dentry);
809
810	/* Someone else set d_mounted? */
811	if (ret == -EBUSY)
812	goto mountpoint;
813
814	/* The dentry is not available as a mountpoint? */
815	mp = ERR_PTR(error: ret);
816	if (ret)
817	goto done;
818
819	/* Add the new mountpoint to the hash table */
820	read_seqlock_excl(sl: &mount_lock);
821	new->m_dentry = dget(dentry);
822	new->m_count = 1;
823	hlist_add_head(n: &new->m_hash, h: mp_hash(dentry));
824	INIT_HLIST_HEAD(&new->m_list);
825	read_sequnlock_excl(sl: &mount_lock);
826
827	mp = new;
828	new = NULL;
829	done:
830	kfree(objp: new);
831	return mp;
832	}
833
834	/*
835	* vfsmount lock must be held. Additionally, the caller is responsible
836	* for serializing calls for given disposal list.
837	*/
838	static void __put_mountpoint(struct mountpoint *mp, struct list_head *list)
839	{
840	if (!--mp->m_count) {
841	struct dentry *dentry = mp->m_dentry;
842	BUG_ON(!hlist_empty(&mp->m_list));
843	spin_lock(lock: &dentry->d_lock);
844	dentry->d_flags &= ~DCACHE_MOUNTED;
845	spin_unlock(lock: &dentry->d_lock);
846	dput_to_list(dentry, list);
847	hlist_del(n: &mp->m_hash);
848	kfree(objp: mp);
849	}
850	}
851
852	/* called with namespace_lock and vfsmount lock */
853	static void put_mountpoint(struct mountpoint *mp)
854	{
855	__put_mountpoint(mp, list: &ex_mountpoints);
856	}
857
858	static inline int check_mnt(struct mount *mnt)
859	{
860	return mnt->mnt_ns == current->nsproxy->mnt_ns;
861	}
862
863	/*
864	* vfsmount lock must be held for write
865	*/
866	static void touch_mnt_namespace(struct mnt_namespace *ns)
867	{
868	if (ns) {
869	ns->event = ++event;
870	wake_up_interruptible(&ns->poll);
871	}
872	}
873
874	/*
875	* vfsmount lock must be held for write
876	*/
877	static void __touch_mnt_namespace(struct mnt_namespace *ns)
878	{
879	if (ns && ns->event != event) {
880	ns->event = event;
881	wake_up_interruptible(&ns->poll);
882	}
883	}
884
885	/*
886	* vfsmount lock must be held for write
887	*/
888	static struct mountpoint *unhash_mnt(struct mount *mnt)
889	{
890	struct mountpoint *mp;
891	mnt->mnt_parent = mnt;
892	mnt->mnt_mountpoint = mnt->mnt.mnt_root;
893	list_del_init(entry: &mnt->mnt_child);
894	hlist_del_init_rcu(n: &mnt->mnt_hash);
895	hlist_del_init(n: &mnt->mnt_mp_list);
896	mp = mnt->mnt_mp;
897	mnt->mnt_mp = NULL;
898	return mp;
899	}
900
901	/*
902	* vfsmount lock must be held for write
903	*/
904	static void umount_mnt(struct mount *mnt)
905	{
906	put_mountpoint(mp: unhash_mnt(mnt));
907	}
908
909	/*
910	* vfsmount lock must be held for write
911	*/
912	void mnt_set_mountpoint(struct mount *mnt,
913	struct mountpoint *mp,
914	struct mount *child_mnt)
915	{
916	mp->m_count++;
917	mnt_add_count(mnt, n: 1); /* essentially, that's mntget */
918	child_mnt->mnt_mountpoint = mp->m_dentry;
919	child_mnt->mnt_parent = mnt;
920	child_mnt->mnt_mp = mp;
921	hlist_add_head(n: &child_mnt->mnt_mp_list, h: &mp->m_list);
922	}
923
924	/**
925	* mnt_set_mountpoint_beneath - mount a mount beneath another one
926	*
927	* @new_parent: the source mount
928	* @top_mnt: the mount beneath which @new_parent is mounted
929	* @new_mp: the new mountpoint of @top_mnt on @new_parent
930	*
931	* Remove @top_mnt from its current mountpoint @top_mnt->mnt_mp and
932	* parent @top_mnt->mnt_parent and mount it on top of @new_parent at
933	* @new_mp. And mount @new_parent on the old parent and old
934	* mountpoint of @top_mnt.
935	*
936	* Context: This function expects namespace_lock() and lock_mount_hash()
937	* to have been acquired in that order.
938	*/
939	static void mnt_set_mountpoint_beneath(struct mount *new_parent,
940	struct mount *top_mnt,
941	struct mountpoint *new_mp)
942	{
943	struct mount *old_top_parent = top_mnt->mnt_parent;
944	struct mountpoint *old_top_mp = top_mnt->mnt_mp;
945
946	mnt_set_mountpoint(mnt: old_top_parent, mp: old_top_mp, child_mnt: new_parent);
947	mnt_change_mountpoint(parent: new_parent, mp: new_mp, mnt: top_mnt);
948	}
949
950
951	static void __attach_mnt(struct mount *mnt, struct mount *parent)
952	{
953	hlist_add_head_rcu(n: &mnt->mnt_hash,
954	h: m_hash(mnt: &parent->mnt, dentry: mnt->mnt_mountpoint));
955	list_add_tail(new: &mnt->mnt_child, head: &parent->mnt_mounts);
956	}
957
958	/**
959	* attach_mnt - mount a mount, attach to @mount_hashtable and parent's
960	* list of child mounts
961	* @parent: the parent
962	* @mnt: the new mount
963	* @mp: the new mountpoint
964	* @beneath: whether to mount @mnt beneath or on top of @parent
965	*
966	* If @beneath is false, mount @mnt at @mp on @parent. Then attach @mnt
967	* to @parent's child mount list and to @mount_hashtable.
968	*
969	* If @beneath is true, remove @mnt from its current parent and
970	* mountpoint and mount it on @mp on @parent, and mount @parent on the
971	* old parent and old mountpoint of @mnt. Finally, attach @parent to
972	* @mnt_hashtable and @parent->mnt_parent->mnt_mounts.
973	*
974	* Note, when __attach_mnt() is called @mnt->mnt_parent already points
975	* to the correct parent.
976	*
977	* Context: This function expects namespace_lock() and lock_mount_hash()
978	* to have been acquired in that order.
979	*/
980	static void attach_mnt(struct mount *mnt, struct mount *parent,
981	struct mountpoint *mp, bool beneath)
982	{
983	if (beneath)
984	mnt_set_mountpoint_beneath(new_parent: mnt, top_mnt: parent, new_mp: mp);
985	else
986	mnt_set_mountpoint(mnt: parent, mp, child_mnt: mnt);
987	/*
988	* Note, @mnt->mnt_parent has to be used. If @mnt was mounted
989	* beneath @parent then @mnt will need to be attached to
990	* @parent's old parent, not @parent. IOW, @mnt->mnt_parent
991	* isn't the same mount as @parent.
992	*/
993	__attach_mnt(mnt, parent: mnt->mnt_parent);
994	}
995
996	void mnt_change_mountpoint(struct mount *parent, struct mountpoint *mp, struct mount *mnt)
997	{
998	struct mountpoint *old_mp = mnt->mnt_mp;
999	struct mount *old_parent = mnt->mnt_parent;
1000
1001	list_del_init(entry: &mnt->mnt_child);
1002	hlist_del_init(n: &mnt->mnt_mp_list);
1003	hlist_del_init_rcu(n: &mnt->mnt_hash);
1004
1005	attach_mnt(mnt, parent, mp, beneath: false);
1006
1007	put_mountpoint(mp: old_mp);
1008	mnt_add_count(mnt: old_parent, n: -1);
1009	}
1010
1011	static inline struct mount *node_to_mount(struct rb_node *node)
1012	{
1013	return node ? rb_entry(node, struct mount, mnt_node) : NULL;
1014	}
1015
1016	static void mnt_add_to_ns(struct mnt_namespace *ns, struct mount *mnt)
1017	{
1018	struct rb_node **link = &ns->mounts.rb_node;
1019	struct rb_node *parent = NULL;
1020
1021	WARN_ON(mnt->mnt.mnt_flags & MNT_ONRB);
1022	mnt->mnt_ns = ns;
1023	while (*link) {
1024	parent = *link;
1025	if (mnt->mnt_id_unique < node_to_mount(node: parent)->mnt_id_unique)
1026	link = &parent->rb_left;
1027	else
1028	link = &parent->rb_right;
1029	}
1030	rb_link_node(node: &mnt->mnt_node, parent, rb_link: link);
1031	rb_insert_color(&mnt->mnt_node, &ns->mounts);
1032	mnt->mnt.mnt_flags |= MNT_ONRB;
1033	}
1034
1035	/*
1036	* vfsmount lock must be held for write
1037	*/
1038	static void commit_tree(struct mount *mnt)
1039	{
1040	struct mount *parent = mnt->mnt_parent;
1041	struct mount *m;
1042	LIST_HEAD(head);
1043	struct mnt_namespace *n = parent->mnt_ns;
1044
1045	BUG_ON(parent == mnt);
1046
1047	list_add_tail(new: &head, head: &mnt->mnt_list);
1048	while (!list_empty(head: &head)) {
1049	m = list_first_entry(&head, typeof(*m), mnt_list);
1050	list_del(entry: &m->mnt_list);
1051
1052	mnt_add_to_ns(ns: n, mnt: m);
1053	}
1054	n->nr_mounts += n->pending_mounts;
1055	n->pending_mounts = 0;
1056
1057	__attach_mnt(mnt, parent);
1058	touch_mnt_namespace(ns: n);
1059	}
1060
1061	static struct mount *next_mnt(struct mount *p, struct mount *root)
1062	{
1063	struct list_head *next = p->mnt_mounts.next;
1064	if (next == &p->mnt_mounts) {
1065	while (1) {
1066	if (p == root)
1067	return NULL;
1068	next = p->mnt_child.next;
1069	if (next != &p->mnt_parent->mnt_mounts)
1070	break;
1071	p = p->mnt_parent;
1072	}
1073	}
1074	return list_entry(next, struct mount, mnt_child);
1075	}
1076
1077	static struct mount *skip_mnt_tree(struct mount *p)
1078	{
1079	struct list_head *prev = p->mnt_mounts.prev;
1080	while (prev != &p->mnt_mounts) {
1081	p = list_entry(prev, struct mount, mnt_child);
1082	prev = p->mnt_mounts.prev;
1083	}
1084	return p;
1085	}
1086
1087	/**
1088	* vfs_create_mount - Create a mount for a configured superblock
1089	* @fc: The configuration context with the superblock attached
1090	*
1091	* Create a mount to an already configured superblock. If necessary, the
1092	* caller should invoke vfs_get_tree() before calling this.
1093	*
1094	* Note that this does not attach the mount to anything.
1095	*/
1096	struct vfsmount *vfs_create_mount(struct fs_context *fc)
1097	{
1098	struct mount *mnt;
1099
1100	if (!fc->root)
1101	return ERR_PTR(error: -EINVAL);
1102
1103	mnt = alloc_vfsmnt(name: fc->source ?: "none");
1104	if (!mnt)
1105	return ERR_PTR(error: -ENOMEM);
1106
1107	if (fc->sb_flags & SB_KERNMOUNT)
1108	mnt->mnt.mnt_flags = MNT_INTERNAL;
1109
1110	atomic_inc(v: &fc->root->d_sb->s_active);
1111	mnt->mnt.mnt_sb = fc->root->d_sb;
1112	mnt->mnt.mnt_root = dget(dentry: fc->root);
1113	mnt->mnt_mountpoint = mnt->mnt.mnt_root;
1114	mnt->mnt_parent = mnt;
1115
1116	lock_mount_hash();
1117	list_add_tail(new: &mnt->mnt_instance, head: &mnt->mnt.mnt_sb->s_mounts);
1118	unlock_mount_hash();
1119	return &mnt->mnt;
1120	}
1121	EXPORT_SYMBOL(vfs_create_mount);
1122
1123	struct vfsmount *fc_mount(struct fs_context *fc)
1124	{
1125	int err = vfs_get_tree(fc);
1126	if (!err) {
1127	up_write(sem: &fc->root->d_sb->s_umount);
1128	return vfs_create_mount(fc);
1129	}
1130	return ERR_PTR(error: err);
1131	}
1132	EXPORT_SYMBOL(fc_mount);
1133
1134	struct vfsmount *vfs_kern_mount(struct file_system_type *type,
1135	int flags, const char *name,
1136	void *data)
1137	{
1138	struct fs_context *fc;
1139	struct vfsmount *mnt;
1140	int ret = 0;
1141
1142	if (!type)
1143	return ERR_PTR(error: -EINVAL);
1144
1145	fc = fs_context_for_mount(fs_type: type, sb_flags: flags);
1146	if (IS_ERR(ptr: fc))
1147	return ERR_CAST(ptr: fc);
1148
1149	if (name)
1150	ret = vfs_parse_fs_string(fc, key: "source",
1151	value: name, strlen(name));
1152	if (!ret)
1153	ret = parse_monolithic_mount_data(fc, data);
1154	if (!ret)
1155	mnt = fc_mount(fc);
1156	else
1157	mnt = ERR_PTR(error: ret);
1158
1159	put_fs_context(fc);
1160	return mnt;
1161	}
1162	EXPORT_SYMBOL_GPL(vfs_kern_mount);
1163
1164	struct vfsmount *
1165	vfs_submount(const struct dentry *mountpoint, struct file_system_type *type,
1166	const char *name, void *data)
1167	{
1168	/* Until it is worked out how to pass the user namespace
1169	* through from the parent mount to the submount don't support
1170	* unprivileged mounts with submounts.
1171	*/
1172	if (mountpoint->d_sb->s_user_ns != &init_user_ns)
1173	return ERR_PTR(error: -EPERM);
1174
1175	return vfs_kern_mount(type, SB_SUBMOUNT, name, data);
1176	}
1177	EXPORT_SYMBOL_GPL(vfs_submount);
1178
1179	static struct mount *clone_mnt(struct mount *old, struct dentry *root,
1180	int flag)
1181	{
1182	struct super_block *sb = old->mnt.mnt_sb;
1183	struct mount *mnt;
1184	int err;
1185
1186	mnt = alloc_vfsmnt(name: old->mnt_devname);
1187	if (!mnt)
1188	return ERR_PTR(error: -ENOMEM);
1189
1190	if (flag & (CL_SLAVE | CL_PRIVATE | CL_SHARED_TO_SLAVE))
1191	mnt->mnt_group_id = 0; /* not a peer of original */
1192	else
1193	mnt->mnt_group_id = old->mnt_group_id;
1194
1195	if ((flag & CL_MAKE_SHARED) && !mnt->mnt_group_id) {
1196	err = mnt_alloc_group_id(mnt);
1197	if (err)
1198	goto out_free;
1199	}
1200
1201	mnt->mnt.mnt_flags = old->mnt.mnt_flags;
1202	mnt->mnt.mnt_flags &= ~(MNT_WRITE_HOLD|MNT_MARKED|MNT_INTERNAL|MNT_ONRB);
1203
1204	atomic_inc(v: &sb->s_active);
1205	mnt->mnt.mnt_idmap = mnt_idmap_get(idmap: mnt_idmap(mnt: &old->mnt));
1206
1207	mnt->mnt.mnt_sb = sb;
1208	mnt->mnt.mnt_root = dget(dentry: root);
1209	mnt->mnt_mountpoint = mnt->mnt.mnt_root;
1210	mnt->mnt_parent = mnt;
1211	lock_mount_hash();
1212	list_add_tail(new: &mnt->mnt_instance, head: &sb->s_mounts);
1213	unlock_mount_hash();
1214
1215	if ((flag & CL_SLAVE) ||
1216	((flag & CL_SHARED_TO_SLAVE) && IS_MNT_SHARED(old))) {
1217	list_add(new: &mnt->mnt_slave, head: &old->mnt_slave_list);
1218	mnt->mnt_master = old;
1219	CLEAR_MNT_SHARED(mnt);
1220	} else if (!(flag & CL_PRIVATE)) {
1221	if ((flag & CL_MAKE_SHARED) || IS_MNT_SHARED(old))
1222	list_add(new: &mnt->mnt_share, head: &old->mnt_share);
1223	if (IS_MNT_SLAVE(old))
1224	list_add(new: &mnt->mnt_slave, head: &old->mnt_slave);
1225	mnt->mnt_master = old->mnt_master;
1226	} else {
1227	CLEAR_MNT_SHARED(mnt);
1228	}
1229	if (flag & CL_MAKE_SHARED)
1230	set_mnt_shared(mnt);
1231
1232	/* stick the duplicate mount on the same expiry list
1233	* as the original if that was on one */
1234	if (flag & CL_EXPIRE) {
1235	if (!list_empty(head: &old->mnt_expire))
1236	list_add(new: &mnt->mnt_expire, head: &old->mnt_expire);
1237	}
1238
1239	return mnt;
1240
1241	out_free:
1242	mnt_free_id(mnt);
1243	free_vfsmnt(mnt);
1244	return ERR_PTR(error: err);
1245	}
1246
1247	static void cleanup_mnt(struct mount *mnt)
1248	{
1249	struct hlist_node *p;
1250	struct mount *m;
1251	/*
1252	* The warning here probably indicates that somebody messed
1253	* up a mnt_want/drop_write() pair. If this happens, the
1254	* filesystem was probably unable to make r/w->r/o transitions.
1255	* The locking used to deal with mnt_count decrement provides barriers,
1256	* so mnt_get_writers() below is safe.
1257	*/
1258	WARN_ON(mnt_get_writers(mnt));
1259	if (unlikely(mnt->mnt_pins.first))
1260	mnt_pin_kill(m: mnt);
1261	hlist_for_each_entry_safe(m, p, &mnt->mnt_stuck_children, mnt_umount) {
1262	hlist_del(n: &m->mnt_umount);
1263	mntput(mnt: &m->mnt);
1264	}
1265	fsnotify_vfsmount_delete(mnt: &mnt->mnt);
1266	dput(mnt->mnt.mnt_root);
1267	deactivate_super(sb: mnt->mnt.mnt_sb);
1268	mnt_free_id(mnt);
1269	call_rcu(head: &mnt->mnt_rcu, func: delayed_free_vfsmnt);
1270	}
1271
1272	static void __cleanup_mnt(struct rcu_head *head)
1273	{
1274	cleanup_mnt(container_of(head, struct mount, mnt_rcu));
1275	}
1276
1277	static LLIST_HEAD(delayed_mntput_list);
1278	static void delayed_mntput(struct work_struct *unused)
1279	{
1280	struct llist_node *node = llist_del_all(head: &delayed_mntput_list);
1281	struct mount *m, *t;
1282
1283	llist_for_each_entry_safe(m, t, node, mnt_llist)
1284	cleanup_mnt(mnt: m);
1285	}
1286	static DECLARE_DELAYED_WORK(delayed_mntput_work, delayed_mntput);
1287
1288	static void mntput_no_expire(struct mount *mnt)
1289	{
1290	LIST_HEAD(list);
1291	int count;
1292
1293	rcu_read_lock();
1294	if (likely(READ_ONCE(mnt->mnt_ns))) {
1295	/*
1296	* Since we don't do lock_mount_hash() here,
1297	* ->mnt_ns can change under us. However, if it's
1298	* non-NULL, then there's a reference that won't
1299	* be dropped until after an RCU delay done after
1300	* turning ->mnt_ns NULL. So if we observe it
1301	* non-NULL under rcu_read_lock(), the reference
1302	* we are dropping is not the final one.
1303	*/
1304	mnt_add_count(mnt, n: -1);
1305	rcu_read_unlock();
1306	return;
1307	}
1308	lock_mount_hash();
1309	/*
1310	* make sure that if __legitimize_mnt() has not seen us grab
1311	* mount_lock, we'll see their refcount increment here.
1312	*/
1313	smp_mb();
1314	mnt_add_count(mnt, n: -1);
1315	count = mnt_get_count(mnt);
1316	if (count != 0) {
1317	WARN_ON(count < 0);
1318	rcu_read_unlock();
1319	unlock_mount_hash();
1320	return;
1321	}
1322	if (unlikely(mnt->mnt.mnt_flags & MNT_DOOMED)) {
1323	rcu_read_unlock();
1324	unlock_mount_hash();
1325	return;
1326	}
1327	mnt->mnt.mnt_flags |= MNT_DOOMED;
1328	rcu_read_unlock();
1329
1330	list_del(entry: &mnt->mnt_instance);
1331
1332	if (unlikely(!list_empty(&mnt->mnt_mounts))) {
1333	struct mount *p, *tmp;
1334	list_for_each_entry_safe(p, tmp, &mnt->mnt_mounts, mnt_child) {
1335	__put_mountpoint(mp: unhash_mnt(mnt: p), list: &list);
1336	hlist_add_head(n: &p->mnt_umount, h: &mnt->mnt_stuck_children);
1337	}
1338	}
1339	unlock_mount_hash();
1340	shrink_dentry_list(&list);
1341
1342	if (likely(!(mnt->mnt.mnt_flags & MNT_INTERNAL))) {
1343	struct task_struct *task = current;
1344	if (likely(!(task->flags & PF_KTHREAD))) {
1345	init_task_work(twork: &mnt->mnt_rcu, func: __cleanup_mnt);
1346	if (!task_work_add(task, twork: &mnt->mnt_rcu, mode: TWA_RESUME))
1347	return;
1348	}
1349	if (llist_add(new: &mnt->mnt_llist, head: &delayed_mntput_list))
1350	schedule_delayed_work(dwork: &delayed_mntput_work, delay: 1);
1351	return;
1352	}
1353	cleanup_mnt(mnt);
1354	}
1355
1356	void mntput(struct vfsmount *mnt)
1357	{
1358	if (mnt) {
1359	struct mount *m = real_mount(mnt);
1360	/* avoid cacheline pingpong */
1361	if (unlikely(m->mnt_expiry_mark))
1362	WRITE_ONCE(m->mnt_expiry_mark, 0);
1363	mntput_no_expire(mnt: m);
1364	}
1365	}
1366	EXPORT_SYMBOL(mntput);
1367
1368	struct vfsmount *mntget(struct vfsmount *mnt)
1369	{
1370	if (mnt)
1371	mnt_add_count(mnt: real_mount(mnt), n: 1);
1372	return mnt;
1373	}
1374	EXPORT_SYMBOL(mntget);
1375
1376	/*
1377	* Make a mount point inaccessible to new lookups.
1378	* Because there may still be current users, the caller MUST WAIT
1379	* for an RCU grace period before destroying the mount point.
1380	*/
1381	void mnt_make_shortterm(struct vfsmount *mnt)
1382	{
1383	if (mnt)
1384	real_mount(mnt)->mnt_ns = NULL;
1385	}
1386
1387	/**
1388	* path_is_mountpoint() - Check if path is a mount in the current namespace.
1389	* @path: path to check
1390	*
1391	* d_mountpoint() can only be used reliably to establish if a dentry is
1392	* not mounted in any namespace and that common case is handled inline.
1393	* d_mountpoint() isn't aware of the possibility there may be multiple
1394	* mounts using a given dentry in a different namespace. This function
1395	* checks if the passed in path is a mountpoint rather than the dentry
1396	* alone.
1397	*/
1398	bool path_is_mountpoint(const struct path *path)
1399	{
1400	unsigned seq;
1401	bool res;
1402
1403	if (!d_mountpoint(dentry: path->dentry))
1404	return false;
1405
1406	rcu_read_lock();
1407	do {
1408	seq = read_seqbegin(sl: &mount_lock);
1409	res = __path_is_mountpoint(path);
1410	} while (read_seqretry(sl: &mount_lock, start: seq));
1411	rcu_read_unlock();
1412
1413	return res;
1414	}
1415	EXPORT_SYMBOL(path_is_mountpoint);
1416
1417	struct vfsmount *mnt_clone_internal(const struct path *path)
1418	{
1419	struct mount *p;
1420	p = clone_mnt(old: real_mount(mnt: path->mnt), root: path->dentry, CL_PRIVATE);
1421	if (IS_ERR(ptr: p))
1422	return ERR_CAST(ptr: p);
1423	p->mnt.mnt_flags |= MNT_INTERNAL;
1424	return &p->mnt;
1425	}
1426
1427	/*
1428	* Returns the mount which either has the specified mnt_id, or has the next
1429	* smallest id afer the specified one.
1430	*/
1431	static struct mount *mnt_find_id_at(struct mnt_namespace *ns, u64 mnt_id)
1432	{
1433	struct rb_node *node = ns->mounts.rb_node;
1434	struct mount *ret = NULL;
1435
1436	while (node) {
1437	struct mount *m = node_to_mount(node);
1438
1439	if (mnt_id <= m->mnt_id_unique) {
1440	ret = node_to_mount(node);
1441	if (mnt_id == m->mnt_id_unique)
1442	break;
1443	node = node->rb_left;
1444	} else {
1445	node = node->rb_right;
1446	}
1447	}
1448	return ret;
1449	}
1450
1451	#ifdef CONFIG_PROC_FS
1452
1453	/* iterator; we want it to have access to namespace_sem, thus here... */
1454	static void *m_start(struct seq_file *m, loff_t *pos)
1455	{
1456	struct proc_mounts *p = m->private;
1457
1458	down_read(sem: &namespace_sem);
1459
1460	return mnt_find_id_at(ns: p->ns, mnt_id: *pos);
1461	}
1462
1463	static void *m_next(struct seq_file *m, void *v, loff_t *pos)
1464	{
1465	struct mount *next = NULL, *mnt = v;
1466	struct rb_node *node = rb_next(&mnt->mnt_node);
1467
1468	++*pos;
1469	if (node) {
1470	next = node_to_mount(node);
1471	*pos = next->mnt_id_unique;
1472	}
1473	return next;
1474	}
1475
1476	static void m_stop(struct seq_file *m, void *v)
1477	{
1478	up_read(sem: &namespace_sem);
1479	}
1480
1481	static int m_show(struct seq_file *m, void *v)
1482	{
1483	struct proc_mounts *p = m->private;
1484	struct mount *r = v;
1485	return p->show(m, &r->mnt);
1486	}
1487
1488	const struct seq_operations mounts_op = {
1489	.start = m_start,
1490	.next = m_next,
1491	.stop = m_stop,
1492	.show = m_show,
1493	};
1494
1495	#endif /* CONFIG_PROC_FS */
1496
1497	/**
1498	* may_umount_tree - check if a mount tree is busy
1499	* @m: root of mount tree
1500	*
1501	* This is called to check if a tree of mounts has any
1502	* open files, pwds, chroots or sub mounts that are
1503	* busy.
1504	*/
1505	int may_umount_tree(struct vfsmount *m)
1506	{
1507	struct mount *mnt = real_mount(mnt: m);
1508	int actual_refs = 0;
1509	int minimum_refs = 0;
1510	struct mount *p;
1511	BUG_ON(!m);
1512
1513	/* write lock needed for mnt_get_count */
1514	lock_mount_hash();
1515	for (p = mnt; p; p = next_mnt(p, root: mnt)) {
1516	actual_refs += mnt_get_count(mnt: p);
1517	minimum_refs += 2;
1518	}
1519	unlock_mount_hash();
1520
1521	if (actual_refs > minimum_refs)
1522	return 0;
1523
1524	return 1;
1525	}
1526
1527	EXPORT_SYMBOL(may_umount_tree);
1528
1529	/**
1530	* may_umount - check if a mount point is busy
1531	* @mnt: root of mount
1532	*
1533	* This is called to check if a mount point has any
1534	* open files, pwds, chroots or sub mounts. If the
1535	* mount has sub mounts this will return busy
1536	* regardless of whether the sub mounts are busy.
1537	*
1538	* Doesn't take quota and stuff into account. IOW, in some cases it will
1539	* give false negatives. The main reason why it's here is that we need
1540	* a non-destructive way to look for easily umountable filesystems.
1541	*/
1542	int may_umount(struct vfsmount *mnt)
1543	{
1544	int ret = 1;
1545	down_read(sem: &namespace_sem);
1546	lock_mount_hash();
1547	if (propagate_mount_busy(real_mount(mnt), 2))
1548	ret = 0;
1549	unlock_mount_hash();
1550	up_read(sem: &namespace_sem);
1551	return ret;
1552	}
1553
1554	EXPORT_SYMBOL(may_umount);
1555
1556	static void namespace_unlock(void)
1557	{
1558	struct hlist_head head;
1559	struct hlist_node *p;
1560	struct mount *m;
1561	LIST_HEAD(list);
1562
1563	hlist_move_list(old: &unmounted, new: &head);
1564	list_splice_init(list: &ex_mountpoints, head: &list);
1565
1566	up_write(sem: &namespace_sem);
1567
1568	shrink_dentry_list(&list);
1569
1570	if (likely(hlist_empty(&head)))
1571	return;
1572
1573	synchronize_rcu_expedited();
1574
1575	hlist_for_each_entry_safe(m, p, &head, mnt_umount) {
1576	hlist_del(n: &m->mnt_umount);
1577	mntput(&m->mnt);
1578	}
1579	}
1580
1581	static inline void namespace_lock(void)
1582	{
1583	down_write(sem: &namespace_sem);
1584	}
1585
1586	enum umount_tree_flags {
1587	UMOUNT_SYNC = 1,
1588	UMOUNT_PROPAGATE = 2,
1589	UMOUNT_CONNECTED = 4,
1590	};
1591
1592	static bool disconnect_mount(struct mount *mnt, enum umount_tree_flags how)
1593	{
1594	/* Leaving mounts connected is only valid for lazy umounts */
1595	if (how & UMOUNT_SYNC)
1596	return true;
1597
1598	/* A mount without a parent has nothing to be connected to */
1599	if (!mnt_has_parent(mnt))
1600	return true;
1601
1602	/* Because the reference counting rules change when mounts are
1603	* unmounted and connected, umounted mounts may not be
1604	* connected to mounted mounts.
1605	*/
1606	if (!(mnt->mnt_parent->mnt.mnt_flags & MNT_UMOUNT))
1607	return true;
1608
1609	/* Has it been requested that the mount remain connected? */
1610	if (how & UMOUNT_CONNECTED)
1611	return false;
1612
1613	/* Is the mount locked such that it needs to remain connected? */
1614	if (IS_MNT_LOCKED(mnt))
1615	return false;
1616
1617	/* By default disconnect the mount */
1618	return true;
1619	}
1620
1621	/*
1622	* mount_lock must be held
1623	* namespace_sem must be held for write
1624	*/
1625	static void umount_tree(struct mount *mnt, enum umount_tree_flags how)
1626	{
1627	LIST_HEAD(tmp_list);
1628	struct mount *p;
1629
1630	if (how & UMOUNT_PROPAGATE)
1631	propagate_mount_unlock(mnt);
1632
1633	/* Gather the mounts to umount */
1634	for (p = mnt; p; p = next_mnt(p, root: mnt)) {
1635	p->mnt.mnt_flags |= MNT_UMOUNT;
1636	if (p->mnt.mnt_flags & MNT_ONRB)
1637	move_from_ns(mnt: p, dt_list: &tmp_list);
1638	else
1639	list_move(list: &p->mnt_list, head: &tmp_list);
1640	}
1641
1642	/* Hide the mounts from mnt_mounts */
1643	list_for_each_entry(p, &tmp_list, mnt_list) {
1644	list_del_init(entry: &p->mnt_child);
1645	}
1646
1647	/* Add propogated mounts to the tmp_list */
1648	if (how & UMOUNT_PROPAGATE)
1649	propagate_umount(&tmp_list);
1650
1651	while (!list_empty(head: &tmp_list)) {
1652	struct mnt_namespace *ns;
1653	bool disconnect;
1654	p = list_first_entry(&tmp_list, struct mount, mnt_list);
1655	list_del_init(entry: &p->mnt_expire);
1656	list_del_init(entry: &p->mnt_list);
1657	ns = p->mnt_ns;
1658	if (ns) {
1659	ns->nr_mounts--;
1660	__touch_mnt_namespace(ns);
1661	}
1662	p->mnt_ns = NULL;
1663	if (how & UMOUNT_SYNC)
1664	p->mnt.mnt_flags |= MNT_SYNC_UMOUNT;
1665
1666	disconnect = disconnect_mount(mnt: p, how);
1667	if (mnt_has_parent(mnt: p)) {
1668	mnt_add_count(mnt: p->mnt_parent, n: -1);
1669	if (!disconnect) {
1670	/* Don't forget about p */
1671	list_add_tail(new: &p->mnt_child, head: &p->mnt_parent->mnt_mounts);
1672	} else {
1673	umount_mnt(mnt: p);
1674	}
1675	}
1676	change_mnt_propagation(p, MS_PRIVATE);
1677	if (disconnect)
1678	hlist_add_head(n: &p->mnt_umount, h: &unmounted);
1679	}
1680	}
1681
1682	static void shrink_submounts(struct mount *mnt);
1683
1684	static int do_umount_root(struct super_block *sb)
1685	{
1686	int ret = 0;
1687
1688	down_write(sem: &sb->s_umount);
1689	if (!sb_rdonly(sb)) {
1690	struct fs_context *fc;
1691
1692	fc = fs_context_for_reconfigure(dentry: sb->s_root, SB_RDONLY,
1693	SB_RDONLY);
1694	if (IS_ERR(ptr: fc)) {
1695	ret = PTR_ERR(ptr: fc);
1696	} else {
1697	ret = parse_monolithic_mount_data(fc, NULL);
1698	if (!ret)
1699	ret = reconfigure_super(fc);
1700	put_fs_context(fc);
1701	}
1702	}
1703	up_write(sem: &sb->s_umount);
1704	return ret;
1705	}
1706
1707	static int do_umount(struct mount *mnt, int flags)
1708	{
1709	struct super_block *sb = mnt->mnt.mnt_sb;
1710	int retval;
1711
1712	retval = security_sb_umount(mnt: &mnt->mnt, flags);
1713	if (retval)
1714	return retval;
1715
1716	/*
1717	* Allow userspace to request a mountpoint be expired rather than
1718	* unmounting unconditionally. Unmount only happens if:
1719	* (1) the mark is already set (the mark is cleared by mntput())
1720	* (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount]
1721	*/
1722	if (flags & MNT_EXPIRE) {
1723	if (&mnt->mnt == current->fs->root.mnt ||
1724	flags & (MNT_FORCE | MNT_DETACH))
1725	return -EINVAL;
1726
1727	/*
1728	* probably don't strictly need the lock here if we examined
1729	* all race cases, but it's a slowpath.
1730	*/
1731	lock_mount_hash();
1732	if (mnt_get_count(mnt) != 2) {
1733	unlock_mount_hash();
1734	return -EBUSY;
1735	}
1736	unlock_mount_hash();
1737
1738	if (!xchg(&mnt->mnt_expiry_mark, 1))
1739	return -EAGAIN;
1740	}
1741
1742	/*
1743	* If we may have to abort operations to get out of this
1744	* mount, and they will themselves hold resources we must
1745	* allow the fs to do things. In the Unix tradition of
1746	* 'Gee thats tricky lets do it in userspace' the umount_begin
1747	* might fail to complete on the first run through as other tasks
1748	* must return, and the like. Thats for the mount program to worry
1749	* about for the moment.
1750	*/
1751
1752	if (flags & MNT_FORCE && sb->s_op->umount_begin) {
1753	sb->s_op->umount_begin(sb);
1754	}
1755
1756	/*
1757	* No sense to grab the lock for this test, but test itself looks
1758	* somewhat bogus. Suggestions for better replacement?
1759	* Ho-hum... In principle, we might treat that as umount + switch
1760	* to rootfs. GC would eventually take care of the old vfsmount.
1761	* Actually it makes sense, especially if rootfs would contain a
1762	* /reboot - static binary that would close all descriptors and
1763	* call reboot(9). Then init(8) could umount root and exec /reboot.
1764	*/
1765	if (&mnt->mnt == current->fs->root.mnt && !(flags & MNT_DETACH)) {
1766	/*
1767	* Special case for "unmounting" root ...
1768	* we just try to remount it readonly.
1769	*/
1770	if (!ns_capable(ns: sb->s_user_ns, CAP_SYS_ADMIN))
1771	return -EPERM;
1772	return do_umount_root(sb);
1773	}
1774
1775	namespace_lock();
1776	lock_mount_hash();
1777
1778	/* Recheck MNT_LOCKED with the locks held */
1779	retval = -EINVAL;
1780	if (mnt->mnt.mnt_flags & MNT_LOCKED)
1781	goto out;
1782
1783	event++;
1784	if (flags & MNT_DETACH) {
1785	if (mnt->mnt.mnt_flags & MNT_ONRB ||
1786	!list_empty(head: &mnt->mnt_list))
1787	umount_tree(mnt, how: UMOUNT_PROPAGATE);
1788	retval = 0;
1789	} else {
1790	shrink_submounts(mnt);
1791	retval = -EBUSY;
1792	if (!propagate_mount_busy(mnt, 2)) {
1793	if (mnt->mnt.mnt_flags & MNT_ONRB ||
1794	!list_empty(head: &mnt->mnt_list))
1795	umount_tree(mnt, how: UMOUNT_PROPAGATE|UMOUNT_SYNC);
1796	retval = 0;
1797	}
1798	}
1799	out:
1800	unlock_mount_hash();
1801	namespace_unlock();
1802	return retval;
1803	}
1804
1805	/*
1806	* __detach_mounts - lazily unmount all mounts on the specified dentry
1807	*
1808	* During unlink, rmdir, and d_drop it is possible to loose the path
1809	* to an existing mountpoint, and wind up leaking the mount.
1810	* detach_mounts allows lazily unmounting those mounts instead of
1811	* leaking them.
1812	*
1813	* The caller may hold dentry->d_inode->i_mutex.
1814	*/
1815	void __detach_mounts(struct dentry *dentry)
1816	{
1817	struct mountpoint *mp;
1818	struct mount *mnt;
1819
1820	namespace_lock();
1821	lock_mount_hash();
1822	mp = lookup_mountpoint(dentry);
1823	if (!mp)
1824	goto out_unlock;
1825
1826	event++;
1827	while (!hlist_empty(h: &mp->m_list)) {
1828	mnt = hlist_entry(mp->m_list.first, struct mount, mnt_mp_list);
1829	if (mnt->mnt.mnt_flags & MNT_UMOUNT) {
1830	umount_mnt(mnt);
1831	hlist_add_head(n: &mnt->mnt_umount, h: &unmounted);
1832	}
1833	else umount_tree(mnt, how: UMOUNT_CONNECTED);
1834	}
1835	put_mountpoint(mp);
1836	out_unlock:
1837	unlock_mount_hash();
1838	namespace_unlock();
1839	}
1840
1841	/*
1842	* Is the caller allowed to modify his namespace?
1843	*/
1844	bool may_mount(void)
1845	{
1846	return ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN);
1847	}
1848
1849	/**
1850	* path_mounted - check whether path is mounted
1851	* @path: path to check
1852	*
1853	* Determine whether @path refers to the root of a mount.
1854	*
1855	* Return: true if @path is the root of a mount, false if not.
1856	*/
1857	static inline bool path_mounted(const struct path *path)
1858	{
1859	return path->mnt->mnt_root == path->dentry;
1860	}
1861
1862	static void warn_mandlock(void)
1863	{
1864	pr_warn_once("=======================================================\n"
1865	"WARNING: The mand mount option has been deprecated and\n"
1866	" and is ignored by this kernel. Remove the mand\n"
1867	" option from the mount to silence this warning.\n"
1868	"=======================================================\n");
1869	}
1870
1871	static int can_umount(const struct path *path, int flags)
1872	{
1873	struct mount *mnt = real_mount(mnt: path->mnt);
1874
1875	if (!may_mount())
1876	return -EPERM;
1877	if (!path_mounted(path))
1878	return -EINVAL;
1879	if (!check_mnt(mnt))
1880	return -EINVAL;
1881	if (mnt->mnt.mnt_flags & MNT_LOCKED) /* Check optimistically */
1882	return -EINVAL;
1883	if (flags & MNT_FORCE && !capable(CAP_SYS_ADMIN))
1884	return -EPERM;
1885	return 0;
1886	}
1887
1888	// caller is responsible for flags being sane
1889	int path_umount(struct path *path, int flags)
1890	{
1891	struct mount *mnt = real_mount(mnt: path->mnt);
1892	int ret;
1893
1894	ret = can_umount(path, flags);
1895	if (!ret)
1896	ret = do_umount(mnt, flags);
1897
1898	/* we mustn't call path_put() as that would clear mnt_expiry_mark */
1899	dput(path->dentry);
1900	mntput_no_expire(mnt);
1901	return ret;
1902	}
1903
1904	static int ksys_umount(char __user *name, int flags)
1905	{
1906	int lookup_flags = LOOKUP_MOUNTPOINT;
1907	struct path path;
1908	int ret;
1909
1910	// basic validity checks done first
1911	if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW))
1912	return -EINVAL;
1913
1914	if (!(flags & UMOUNT_NOFOLLOW))
1915	lookup_flags |= LOOKUP_FOLLOW;
1916	ret = user_path_at(AT_FDCWD, name, flags: lookup_flags, path: &path);
1917	if (ret)
1918	return ret;
1919	return path_umount(path: &path, flags);
1920	}
1921
1922	SYSCALL_DEFINE2(umount, char __user *, name, int, flags)
1923	{
1924	return ksys_umount(name, flags);
1925	}
1926
1927	#ifdef __ARCH_WANT_SYS_OLDUMOUNT
1928
1929	/*
1930	* The 2.0 compatible umount. No flags.
1931	*/
1932	SYSCALL_DEFINE1(oldumount, char __user *, name)
1933	{
1934	return ksys_umount(name, flags: 0);
1935	}
1936
1937	#endif
1938
1939	static bool is_mnt_ns_file(struct dentry *dentry)
1940	{
1941	/* Is this a proxy for a mount namespace? */
1942	return dentry->d_op == &ns_dentry_operations &&
1943	dentry->d_fsdata == &mntns_operations;
1944	}
1945
1946	static struct mnt_namespace *to_mnt_ns(struct ns_common *ns)
1947	{
1948	return container_of(ns, struct mnt_namespace, ns);
1949	}
1950
1951	struct ns_common *from_mnt_ns(struct mnt_namespace *mnt)
1952	{
1953	return &mnt->ns;
1954	}
1955
1956	static bool mnt_ns_loop(struct dentry *dentry)
1957	{
1958	/* Could bind mounting the mount namespace inode cause a
1959	* mount namespace loop?
1960	*/
1961	struct mnt_namespace *mnt_ns;
1962	if (!is_mnt_ns_file(dentry))
1963	return false;
1964
1965	mnt_ns = to_mnt_ns(get_proc_ns(dentry->d_inode));
1966	return current->nsproxy->mnt_ns->seq >= mnt_ns->seq;
1967	}
1968
1969	struct mount *copy_tree(struct mount *mnt, struct dentry *dentry,
1970	int flag)
1971	{
1972	struct mount *res, *p, *q, *r, *parent;
1973
1974	if (!(flag & CL_COPY_UNBINDABLE) && IS_MNT_UNBINDABLE(mnt))
1975	return ERR_PTR(error: -EINVAL);
1976
1977	if (!(flag & CL_COPY_MNT_NS_FILE) && is_mnt_ns_file(dentry))
1978	return ERR_PTR(error: -EINVAL);
1979
1980	res = q = clone_mnt(old: mnt, root: dentry, flag);
1981	if (IS_ERR(ptr: q))
1982	return q;
1983
1984	q->mnt_mountpoint = mnt->mnt_mountpoint;
1985
1986	p = mnt;
1987	list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) {
1988	struct mount *s;
1989	if (!is_subdir(r->mnt_mountpoint, dentry))
1990	continue;
1991
1992	for (s = r; s; s = next_mnt(p: s, root: r)) {
1993	if (!(flag & CL_COPY_UNBINDABLE) &&
1994	IS_MNT_UNBINDABLE(s)) {
1995	if (s->mnt.mnt_flags & MNT_LOCKED) {
1996	/* Both unbindable and locked. */
1997	q = ERR_PTR(error: -EPERM);
1998	goto out;
1999	} else {
2000	s = skip_mnt_tree(p: s);
2001	continue;
2002	}
2003	}
2004	if (!(flag & CL_COPY_MNT_NS_FILE) &&
2005	is_mnt_ns_file(dentry: s->mnt.mnt_root)) {
2006	s = skip_mnt_tree(p: s);
2007	continue;
2008	}
2009	while (p != s->mnt_parent) {
2010	p = p->mnt_parent;
2011	q = q->mnt_parent;
2012	}
2013	p = s;
2014	parent = q;
2015	q = clone_mnt(old: p, root: p->mnt.mnt_root, flag);
2016	if (IS_ERR(ptr: q))
2017	goto out;
2018	lock_mount_hash();
2019	list_add_tail(new: &q->mnt_list, head: &res->mnt_list);
2020	attach_mnt(mnt: q, parent, mp: p->mnt_mp, beneath: false);
2021	unlock_mount_hash();
2022	}
2023	}
2024	return res;
2025	out:
2026	if (res) {
2027	lock_mount_hash();
2028	umount_tree(mnt: res, how: UMOUNT_SYNC);
2029	unlock_mount_hash();
2030	}
2031	return q;
2032	}
2033
2034	/* Caller should check returned pointer for errors */
2035
2036	struct vfsmount *collect_mounts(const struct path *path)
2037	{
2038	struct mount *tree;
2039	namespace_lock();
2040	if (!check_mnt(mnt: real_mount(mnt: path->mnt)))
2041	tree = ERR_PTR(error: -EINVAL);
2042	else
2043	tree = copy_tree(mnt: real_mount(mnt: path->mnt), dentry: path->dentry,
2044	CL_COPY_ALL | CL_PRIVATE);
2045	namespace_unlock();
2046	if (IS_ERR(ptr: tree))
2047	return ERR_CAST(ptr: tree);
2048	return &tree->mnt;
2049	}
2050
2051	static void free_mnt_ns(struct mnt_namespace *);
2052	static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *, bool);
2053
2054	void dissolve_on_fput(struct vfsmount *mnt)
2055	{
2056	struct mnt_namespace *ns;
2057	namespace_lock();
2058	lock_mount_hash();
2059	ns = real_mount(mnt)->mnt_ns;
2060	if (ns) {
2061	if (is_anon_ns(ns))
2062	umount_tree(mnt: real_mount(mnt), how: UMOUNT_CONNECTED);
2063	else
2064	ns = NULL;
2065	}
2066	unlock_mount_hash();
2067	namespace_unlock();
2068	if (ns)
2069	free_mnt_ns(ns);
2070	}
2071
2072	void drop_collected_mounts(struct vfsmount *mnt)
2073	{
2074	namespace_lock();
2075	lock_mount_hash();
2076	umount_tree(mnt: real_mount(mnt), how: 0);
2077	unlock_mount_hash();
2078	namespace_unlock();
2079	}
2080
2081	static bool has_locked_children(struct mount *mnt, struct dentry *dentry)
2082	{
2083	struct mount *child;
2084
2085	list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) {
2086	if (!is_subdir(child->mnt_mountpoint, dentry))
2087	continue;
2088
2089	if (child->mnt.mnt_flags & MNT_LOCKED)
2090	return true;
2091	}
2092	return false;
2093	}
2094
2095	/**
2096	* clone_private_mount - create a private clone of a path
2097	* @path: path to clone
2098	*
2099	* This creates a new vfsmount, which will be the clone of @path. The new mount
2100	* will not be attached anywhere in the namespace and will be private (i.e.
2101	* changes to the originating mount won't be propagated into this).
2102	*
2103	* Release with mntput().
2104	*/
2105	struct vfsmount *clone_private_mount(const struct path *path)
2106	{
2107	struct mount *old_mnt = real_mount(mnt: path->mnt);
2108	struct mount *new_mnt;
2109
2110	down_read(sem: &namespace_sem);
2111	if (IS_MNT_UNBINDABLE(old_mnt))
2112	goto invalid;
2113
2114	if (!check_mnt(mnt: old_mnt))
2115	goto invalid;
2116
2117	if (has_locked_children(mnt: old_mnt, dentry: path->dentry))
2118	goto invalid;
2119
2120	new_mnt = clone_mnt(old: old_mnt, root: path->dentry, CL_PRIVATE);
2121	up_read(sem: &namespace_sem);
2122
2123	if (IS_ERR(ptr: new_mnt))
2124	return ERR_CAST(ptr: new_mnt);
2125
2126	/* Longterm mount to be removed by kern_unmount*() */
2127	new_mnt->mnt_ns = MNT_NS_INTERNAL;
2128
2129	return &new_mnt->mnt;
2130
2131	invalid:
2132	up_read(sem: &namespace_sem);
2133	return ERR_PTR(error: -EINVAL);
2134	}
2135	EXPORT_SYMBOL_GPL(clone_private_mount);
2136
2137	int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg,
2138	struct vfsmount *root)
2139	{
2140	struct mount *mnt;
2141	int res = f(root, arg);
2142	if (res)
2143	return res;
2144	list_for_each_entry(mnt, &real_mount(root)->mnt_list, mnt_list) {
2145	res = f(&mnt->mnt, arg);
2146	if (res)
2147	return res;
2148	}
2149	return 0;
2150	}
2151
2152	static void lock_mnt_tree(struct mount *mnt)
2153	{
2154	struct mount *p;
2155
2156	for (p = mnt; p; p = next_mnt(p, root: mnt)) {
2157	int flags = p->mnt.mnt_flags;
2158	/* Don't allow unprivileged users to change mount flags */
2159	flags |= MNT_LOCK_ATIME;
2160
2161	if (flags & MNT_READONLY)
2162	flags |= MNT_LOCK_READONLY;
2163
2164	if (flags & MNT_NODEV)
2165	flags |= MNT_LOCK_NODEV;
2166
2167	if (flags & MNT_NOSUID)
2168	flags |= MNT_LOCK_NOSUID;
2169
2170	if (flags & MNT_NOEXEC)
2171	flags |= MNT_LOCK_NOEXEC;
2172	/* Don't allow unprivileged users to reveal what is under a mount */
2173	if (list_empty(head: &p->mnt_expire))
2174	flags |= MNT_LOCKED;
2175	p->mnt.mnt_flags = flags;
2176	}
2177	}
2178
2179	static void cleanup_group_ids(struct mount *mnt, struct mount *end)
2180	{
2181	struct mount *p;
2182
2183	for (p = mnt; p != end; p = next_mnt(p, root: mnt)) {
2184	if (p->mnt_group_id && !IS_MNT_SHARED(p))
2185	mnt_release_group_id(mnt: p);
2186	}
2187	}
2188
2189	static int invent_group_ids(struct mount *mnt, bool recurse)
2190	{
2191	struct mount *p;
2192
2193	for (p = mnt; p; p = recurse ? next_mnt(p, root: mnt) : NULL) {
2194	if (!p->mnt_group_id && !IS_MNT_SHARED(p)) {
2195	int err = mnt_alloc_group_id(mnt: p);
2196	if (err) {
2197	cleanup_group_ids(mnt, end: p);
2198	return err;
2199	}
2200	}
2201	}
2202
2203	return 0;
2204	}
2205
2206	int count_mounts(struct mnt_namespace *ns, struct mount *mnt)
2207	{
2208	unsigned int max = READ_ONCE(sysctl_mount_max);
2209	unsigned int mounts = 0;
2210	struct mount *p;
2211
2212	if (ns->nr_mounts >= max)
2213	return -ENOSPC;
2214	max -= ns->nr_mounts;
2215	if (ns->pending_mounts >= max)
2216	return -ENOSPC;
2217	max -= ns->pending_mounts;
2218
2219	for (p = mnt; p; p = next_mnt(p, root: mnt))
2220	mounts++;
2221
2222	if (mounts > max)
2223	return -ENOSPC;
2224
2225	ns->pending_mounts += mounts;
2226	return 0;
2227	}
2228
2229	enum mnt_tree_flags_t {
2230	MNT_TREE_MOVE = BIT(0),
2231	MNT_TREE_BENEATH = BIT(1),
2232	};
2233
2234	/**
2235	* attach_recursive_mnt - attach a source mount tree
2236	* @source_mnt: mount tree to be attached
2237	* @top_mnt: mount that @source_mnt will be mounted on or mounted beneath
2238	* @dest_mp: the mountpoint @source_mnt will be mounted at
2239	* @flags: modify how @source_mnt is supposed to be attached
2240	*
2241	* NOTE: in the table below explains the semantics when a source mount
2242	* of a given type is attached to a destination mount of a given type.
2243	* ---------------------------------------------------------------------------
2244	* | BIND MOUNT OPERATION |
2245	* |**************************************************************************
2246	* | source-->| shared | private | slave | unbindable |
2247	* | dest | | | | |
2248	* | | | | | | |
2249	* | v | | | | |
2250	* |**************************************************************************
2251	* | shared | shared (++) | shared (+) | shared(+++)| invalid |
2252	* | | | | | |
2253	* |non-shared| shared (+) | private | slave (*) | invalid |
2254	* ***************************************************************************
2255	* A bind operation clones the source mount and mounts the clone on the
2256	* destination mount.
2257	*
2258	* (++) the cloned mount is propagated to all the mounts in the propagation
2259	* tree of the destination mount and the cloned mount is added to
2260	* the peer group of the source mount.
2261	* (+) the cloned mount is created under the destination mount and is marked
2262	* as shared. The cloned mount is added to the peer group of the source
2263	* mount.
2264	* (+++) the mount is propagated to all the mounts in the propagation tree
2265	* of the destination mount and the cloned mount is made slave
2266	* of the same master as that of the source mount. The cloned mount
2267	* is marked as 'shared and slave'.
2268	* (*) the cloned mount is made a slave of the same master as that of the
2269	* source mount.
2270	*
2271	* ---------------------------------------------------------------------------
2272	* | MOVE MOUNT OPERATION |
2273	* |**************************************************************************
2274	* | source-->| shared | private | slave | unbindable |
2275	* | dest | | | | |
2276	* | | | | | | |
2277	* | v | | | | |
2278	* |**************************************************************************
2279	* | shared | shared (+) | shared (+) | shared(+++) | invalid |
2280	* | | | | | |
2281	* |non-shared| shared (+*) | private | slave (*) | unbindable |
2282	* ***************************************************************************
2283	*
2284	* (+) the mount is moved to the destination. And is then propagated to
2285	* all the mounts in the propagation tree of the destination mount.
2286	* (+*) the mount is moved to the destination.
2287	* (+++) the mount is moved to the destination and is then propagated to
2288	* all the mounts belonging to the destination mount's propagation tree.
2289	* the mount is marked as 'shared and slave'.
2290	* (*) the mount continues to be a slave at the new location.
2291	*
2292	* if the source mount is a tree, the operations explained above is
2293	* applied to each mount in the tree.
2294	* Must be called without spinlocks held, since this function can sleep
2295	* in allocations.
2296	*
2297	* Context: The function expects namespace_lock() to be held.
2298	* Return: If @source_mnt was successfully attached 0 is returned.
2299	* Otherwise a negative error code is returned.
2300	*/
2301	static int attach_recursive_mnt(struct mount *source_mnt,
2302	struct mount *top_mnt,
2303	struct mountpoint *dest_mp,
2304	enum mnt_tree_flags_t flags)
2305	{
2306	struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns;
2307	HLIST_HEAD(tree_list);
2308	struct mnt_namespace *ns = top_mnt->mnt_ns;
2309	struct mountpoint *smp;
2310	struct mount *child, *dest_mnt, *p;
2311	struct hlist_node *n;
2312	int err = 0;
2313	bool moving = flags & MNT_TREE_MOVE, beneath = flags & MNT_TREE_BENEATH;
2314
2315	/*
2316	* Preallocate a mountpoint in case the new mounts need to be
2317	* mounted beneath mounts on the same mountpoint.
2318	*/
2319	smp = get_mountpoint(dentry: source_mnt->mnt.mnt_root);
2320	if (IS_ERR(ptr: smp))
2321	return PTR_ERR(ptr: smp);
2322
2323	/* Is there space to add these mounts to the mount namespace? */
2324	if (!moving) {
2325	err = count_mounts(ns, mnt: source_mnt);
2326	if (err)
2327	goto out;
2328	}
2329
2330	if (beneath)
2331	dest_mnt = top_mnt->mnt_parent;
2332	else
2333	dest_mnt = top_mnt;
2334
2335	if (IS_MNT_SHARED(dest_mnt)) {
2336	err = invent_group_ids(mnt: source_mnt, recurse: true);
2337	if (err)
2338	goto out;
2339	err = propagate_mnt(dest_mnt, dest_mp, source_mnt, &tree_list);
2340	}
2341	lock_mount_hash();
2342	if (err)
2343	goto out_cleanup_ids;
2344
2345	if (IS_MNT_SHARED(dest_mnt)) {
2346	for (p = source_mnt; p; p = next_mnt(p, root: source_mnt))
2347	set_mnt_shared(p);
2348	}
2349
2350	if (moving) {
2351	if (beneath)
2352	dest_mp = smp;
2353	unhash_mnt(mnt: source_mnt);
2354	attach_mnt(mnt: source_mnt, parent: top_mnt, mp: dest_mp, beneath);
2355	touch_mnt_namespace(ns: source_mnt->mnt_ns);
2356	} else {
2357	if (source_mnt->mnt_ns) {
2358	LIST_HEAD(head);
2359
2360	/* move from anon - the caller will destroy */
2361	for (p = source_mnt; p; p = next_mnt(p, root: source_mnt))
2362	move_from_ns(mnt: p, dt_list: &head);
2363	list_del_init(entry: &head);
2364	}
2365	if (beneath)
2366	mnt_set_mountpoint_beneath(new_parent: source_mnt, top_mnt, new_mp: smp);
2367	else
2368	mnt_set_mountpoint(mnt: dest_mnt, mp: dest_mp, child_mnt: source_mnt);
2369	commit_tree(mnt: source_mnt);
2370	}
2371
2372	hlist_for_each_entry_safe(child, n, &tree_list, mnt_hash) {
2373	struct mount *q;
2374	hlist_del_init(n: &child->mnt_hash);
2375	q = __lookup_mnt(mnt: &child->mnt_parent->mnt,
2376	dentry: child->mnt_mountpoint);
2377	if (q)
2378	mnt_change_mountpoint(parent: child, mp: smp, mnt: q);
2379	/* Notice when we are propagating across user namespaces */
2380	if (child->mnt_parent->mnt_ns->user_ns != user_ns)
2381	lock_mnt_tree(mnt: child);
2382	child->mnt.mnt_flags &= ~MNT_LOCKED;
2383	commit_tree(mnt: child);
2384	}
2385	put_mountpoint(mp: smp);
2386	unlock_mount_hash();
2387
2388	return 0;
2389
2390	out_cleanup_ids:
2391	while (!hlist_empty(h: &tree_list)) {
2392	child = hlist_entry(tree_list.first, struct mount, mnt_hash);
2393	child->mnt_parent->mnt_ns->pending_mounts = 0;
2394	umount_tree(mnt: child, how: UMOUNT_SYNC);
2395	}
2396	unlock_mount_hash();
2397	cleanup_group_ids(mnt: source_mnt, NULL);
2398	out:
2399	ns->pending_mounts = 0;
2400
2401	read_seqlock_excl(sl: &mount_lock);
2402	put_mountpoint(mp: smp);
2403	read_sequnlock_excl(sl: &mount_lock);
2404
2405	return err;
2406	}
2407
2408	/**
2409	* do_lock_mount - lock mount and mountpoint
2410	* @path: target path
2411	* @beneath: whether the intention is to mount beneath @path
2412	*
2413	* Follow the mount stack on @path until the top mount @mnt is found. If
2414	* the initial @path->{mnt,dentry} is a mountpoint lookup the first
2415	* mount stacked on top of it. Then simply follow @{mnt,mnt->mnt_root}
2416	* until nothing is stacked on top of it anymore.
2417	*
2418	* Acquire the inode_lock() on the top mount's ->mnt_root to protect
2419	* against concurrent removal of the new mountpoint from another mount
2420	* namespace.
2421	*
2422	* If @beneath is requested, acquire inode_lock() on @mnt's mountpoint
2423	* @mp on @mnt->mnt_parent must be acquired. This protects against a
2424	* concurrent unlink of @mp->mnt_dentry from another mount namespace
2425	* where @mnt doesn't have a child mount mounted @mp. A concurrent
2426	* removal of @mnt->mnt_root doesn't matter as nothing will be mounted
2427	* on top of it for @beneath.
2428	*
2429	* In addition, @beneath needs to make sure that @mnt hasn't been
2430	* unmounted or moved from its current mountpoint in between dropping
2431	* @mount_lock and acquiring @namespace_sem. For the !@beneath case @mnt
2432	* being unmounted would be detected later by e.g., calling
2433	* check_mnt(mnt) in the function it's called from. For the @beneath
2434	* case however, it's useful to detect it directly in do_lock_mount().
2435	* If @mnt hasn't been unmounted then @mnt->mnt_mountpoint still points
2436	* to @mnt->mnt_mp->m_dentry. But if @mnt has been unmounted it will
2437	* point to @mnt->mnt_root and @mnt->mnt_mp will be NULL.
2438	*
2439	* Return: Either the target mountpoint on the top mount or the top
2440	* mount's mountpoint.
2441	*/
2442	static struct mountpoint *do_lock_mount(struct path *path, bool beneath)
2443	{
2444	struct vfsmount *mnt = path->mnt;
2445	struct dentry *dentry;
2446	struct mountpoint *mp = ERR_PTR(error: -ENOENT);
2447
2448	for (;;) {
2449	struct mount *m;
2450
2451	if (beneath) {
2452	m = real_mount(mnt);
2453	read_seqlock_excl(sl: &mount_lock);
2454	dentry = dget(dentry: m->mnt_mountpoint);
2455	read_sequnlock_excl(sl: &mount_lock);
2456	} else {
2457	dentry = path->dentry;
2458	}
2459
2460	inode_lock(inode: dentry->d_inode);
2461	if (unlikely(cant_mount(dentry))) {
2462	inode_unlock(inode: dentry->d_inode);
2463	goto out;
2464	}
2465
2466	namespace_lock();
2467
2468	if (beneath && (!is_mounted(mnt) || m->mnt_mountpoint != dentry)) {
2469	namespace_unlock();
2470	inode_unlock(inode: dentry->d_inode);
2471	goto out;
2472	}
2473
2474	mnt = lookup_mnt(path);
2475	if (likely(!mnt))
2476	break;
2477
2478	namespace_unlock();
2479	inode_unlock(inode: dentry->d_inode);
2480	if (beneath)
2481	dput(dentry);
2482	path_put(path);
2483	path->mnt = mnt;
2484	path->dentry = dget(dentry: mnt->mnt_root);
2485	}
2486
2487	mp = get_mountpoint(dentry);
2488	if (IS_ERR(ptr: mp)) {
2489	namespace_unlock();
2490	inode_unlock(inode: dentry->d_inode);
2491	}
2492
2493	out:
2494	if (beneath)
2495	dput(dentry);
2496
2497	return mp;
2498	}
2499
2500	static inline struct mountpoint *lock_mount(struct path *path)
2501	{
2502	return do_lock_mount(path, beneath: false);
2503	}
2504
2505	static void unlock_mount(struct mountpoint *where)
2506	{
2507	struct dentry *dentry = where->m_dentry;
2508
2509	read_seqlock_excl(sl: &mount_lock);
2510	put_mountpoint(mp: where);
2511	read_sequnlock_excl(sl: &mount_lock);
2512
2513	namespace_unlock();
2514	inode_unlock(inode: dentry->d_inode);
2515	}
2516
2517	static int graft_tree(struct mount *mnt, struct mount *p, struct mountpoint *mp)
2518	{
2519	if (mnt->mnt.mnt_sb->s_flags & SB_NOUSER)
2520	return -EINVAL;
2521
2522	if (d_is_dir(dentry: mp->m_dentry) !=
2523	d_is_dir(dentry: mnt->mnt.mnt_root))
2524	return -ENOTDIR;
2525
2526	return attach_recursive_mnt(source_mnt: mnt, top_mnt: p, dest_mp: mp, flags: 0);
2527	}
2528
2529	/*
2530	* Sanity check the flags to change_mnt_propagation.
2531	*/
2532
2533	static int flags_to_propagation_type(int ms_flags)
2534	{
2535	int type = ms_flags & ~(MS_REC | MS_SILENT);
2536
2537	/* Fail if any non-propagation flags are set */
2538	if (type & ~(MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
2539	return 0;
2540	/* Only one propagation flag should be set */
2541	if (!is_power_of_2(n: type))
2542	return 0;
2543	return type;
2544	}
2545
2546	/*
2547	* recursively change the type of the mountpoint.
2548	*/
2549	static int do_change_type(struct path *path, int ms_flags)
2550	{
2551	struct mount *m;
2552	struct mount *mnt = real_mount(mnt: path->mnt);
2553	int recurse = ms_flags & MS_REC;
2554	int type;
2555	int err = 0;
2556
2557	if (!path_mounted(path))
2558	return -EINVAL;
2559
2560	type = flags_to_propagation_type(ms_flags);
2561	if (!type)
2562	return -EINVAL;
2563
2564	namespace_lock();
2565	if (type == MS_SHARED) {
2566	err = invent_group_ids(mnt, recurse);
2567	if (err)
2568	goto out_unlock;
2569	}
2570
2571	lock_mount_hash();
2572	for (m = mnt; m; m = (recurse ? next_mnt(p: m, root: mnt) : NULL))
2573	change_mnt_propagation(m, type);
2574	unlock_mount_hash();
2575
2576	out_unlock:
2577	namespace_unlock();
2578	return err;
2579	}
2580
2581	static struct mount *__do_loopback(struct path *old_path, int recurse)
2582	{
2583	struct mount *mnt = ERR_PTR(error: -EINVAL), *old = real_mount(mnt: old_path->mnt);
2584
2585	if (IS_MNT_UNBINDABLE(old))
2586	return mnt;
2587
2588	if (!check_mnt(mnt: old) && old_path->dentry->d_op != &ns_dentry_operations)
2589	return mnt;
2590
2591	if (!recurse && has_locked_children(mnt: old, dentry: old_path->dentry))
2592	return mnt;
2593
2594	if (recurse)
2595	mnt = copy_tree(mnt: old, dentry: old_path->dentry, CL_COPY_MNT_NS_FILE);
2596	else
2597	mnt = clone_mnt(old, root: old_path->dentry, flag: 0);
2598
2599	if (!IS_ERR(ptr: mnt))
2600	mnt->mnt.mnt_flags &= ~MNT_LOCKED;
2601
2602	return mnt;
2603	}
2604
2605	/*
2606	* do loopback mount.
2607	*/
2608	static int do_loopback(struct path *path, const char *old_name,
2609	int recurse)
2610	{
2611	struct path old_path;
2612	struct mount *mnt = NULL, *parent;
2613	struct mountpoint *mp;
2614	int err;
2615	if (!old_name || !*old_name)
2616	return -EINVAL;
2617	err = kern_path(old_name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &old_path);
2618	if (err)
2619	return err;
2620
2621	err = -EINVAL;
2622	if (mnt_ns_loop(dentry: old_path.dentry))
2623	goto out;
2624
2625	mp = lock_mount(path);
2626	if (IS_ERR(ptr: mp)) {
2627	err = PTR_ERR(ptr: mp);
2628	goto out;
2629	}
2630
2631	parent = real_mount(mnt: path->mnt);
2632	if (!check_mnt(mnt: parent))
2633	goto out2;
2634
2635	mnt = __do_loopback(old_path: &old_path, recurse);
2636	if (IS_ERR(ptr: mnt)) {
2637	err = PTR_ERR(ptr: mnt);
2638	goto out2;
2639	}
2640
2641	err = graft_tree(mnt, p: parent, mp);
2642	if (err) {
2643	lock_mount_hash();
2644	umount_tree(mnt, how: UMOUNT_SYNC);
2645	unlock_mount_hash();
2646	}
2647	out2:
2648	unlock_mount(where: mp);
2649	out:
2650	path_put(&old_path);
2651	return err;
2652	}
2653
2654	static struct file *open_detached_copy(struct path *path, bool recursive)
2655	{
2656	struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns;
2657	struct mnt_namespace *ns = alloc_mnt_ns(user_ns, true);
2658	struct mount *mnt, *p;
2659	struct file *file;
2660
2661	if (IS_ERR(ptr: ns))
2662	return ERR_CAST(ptr: ns);
2663
2664	namespace_lock();
2665	mnt = __do_loopback(old_path: path, recurse: recursive);
2666	if (IS_ERR(ptr: mnt)) {
2667	namespace_unlock();
2668	free_mnt_ns(ns);
2669	return ERR_CAST(ptr: mnt);
2670	}
2671
2672	lock_mount_hash();
2673	for (p = mnt; p; p = next_mnt(p, root: mnt)) {
2674	mnt_add_to_ns(ns, mnt: p);
2675	ns->nr_mounts++;
2676	}
2677	ns->root = mnt;
2678	mntget(&mnt->mnt);
2679	unlock_mount_hash();
2680	namespace_unlock();
2681
2682	mntput(path->mnt);
2683	path->mnt = &mnt->mnt;
2684	file = dentry_open(path, O_PATH, current_cred());
2685	if (IS_ERR(ptr: file))
2686	dissolve_on_fput(mnt: path->mnt);
2687	else
2688	file->f_mode |= FMODE_NEED_UNMOUNT;
2689	return file;
2690	}
2691
2692	SYSCALL_DEFINE3(open_tree, int, dfd, const char __user *, filename, unsigned, flags)
2693	{
2694	struct file *file;
2695	struct path path;
2696	int lookup_flags = LOOKUP_AUTOMOUNT | LOOKUP_FOLLOW;
2697	bool detached = flags & OPEN_TREE_CLONE;
2698	int error;
2699	int fd;
2700
2701	BUILD_BUG_ON(OPEN_TREE_CLOEXEC != O_CLOEXEC);
2702
2703	if (flags & ~(AT_EMPTY_PATH | AT_NO_AUTOMOUNT | AT_RECURSIVE |
2704	AT_SYMLINK_NOFOLLOW | OPEN_TREE_CLONE |
2705	OPEN_TREE_CLOEXEC))
2706	return -EINVAL;
2707
2708	if ((flags & (AT_RECURSIVE | OPEN_TREE_CLONE)) == AT_RECURSIVE)
2709	return -EINVAL;
2710
2711	if (flags & AT_NO_AUTOMOUNT)
2712	lookup_flags &= ~LOOKUP_AUTOMOUNT;
2713	if (flags & AT_SYMLINK_NOFOLLOW)
2714	lookup_flags &= ~LOOKUP_FOLLOW;
2715	if (flags & AT_EMPTY_PATH)
2716	lookup_flags |= LOOKUP_EMPTY;
2717
2718	if (detached && !may_mount())
2719	return -EPERM;
2720
2721	fd = get_unused_fd_flags(flags: flags & O_CLOEXEC);
2722	if (fd < 0)
2723	return fd;
2724
2725	error = user_path_at(dfd, name: filename, flags: lookup_flags, path: &path);
2726	if (unlikely(error)) {
2727	file = ERR_PTR(error);
2728	} else {
2729	if (detached)
2730	file = open_detached_copy(path: &path, recursive: flags & AT_RECURSIVE);
2731	else
2732	file = dentry_open(path: &path, O_PATH, current_cred());
2733	path_put(&path);
2734	}
2735	if (IS_ERR(ptr: file)) {
2736	put_unused_fd(fd);
2737	return PTR_ERR(ptr: file);
2738	}
2739	fd_install(fd, file);
2740	return fd;
2741	}
2742
2743	/*
2744	* Don't allow locked mount flags to be cleared.
2745	*
2746	* No locks need to be held here while testing the various MNT_LOCK
2747	* flags because those flags can never be cleared once they are set.
2748	*/
2749	static bool can_change_locked_flags(struct mount *mnt, unsigned int mnt_flags)
2750	{
2751	unsigned int fl = mnt->mnt.mnt_flags;
2752
2753	if ((fl & MNT_LOCK_READONLY) &&
2754	!(mnt_flags & MNT_READONLY))
2755	return false;
2756
2757	if ((fl & MNT_LOCK_NODEV) &&
2758	!(mnt_flags & MNT_NODEV))
2759	return false;
2760
2761	if ((fl & MNT_LOCK_NOSUID) &&
2762	!(mnt_flags & MNT_NOSUID))
2763	return false;
2764
2765	if ((fl & MNT_LOCK_NOEXEC) &&
2766	!(mnt_flags & MNT_NOEXEC))
2767	return false;
2768
2769	if ((fl & MNT_LOCK_ATIME) &&
2770	((fl & MNT_ATIME_MASK) != (mnt_flags & MNT_ATIME_MASK)))
2771	return false;
2772
2773	return true;
2774	}
2775
2776	static int change_mount_ro_state(struct mount *mnt, unsigned int mnt_flags)
2777	{
2778	bool readonly_request = (mnt_flags & MNT_READONLY);
2779
2780	if (readonly_request == __mnt_is_readonly(&mnt->mnt))
2781	return 0;
2782
2783	if (readonly_request)
2784	return mnt_make_readonly(mnt);
2785
2786	mnt->mnt.mnt_flags &= ~MNT_READONLY;
2787	return 0;
2788	}
2789
2790	static void set_mount_attributes(struct mount *mnt, unsigned int mnt_flags)
2791	{
2792	mnt_flags |= mnt->mnt.mnt_flags & ~MNT_USER_SETTABLE_MASK;
2793	mnt->mnt.mnt_flags = mnt_flags;
2794	touch_mnt_namespace(ns: mnt->mnt_ns);
2795	}
2796
2797	static void mnt_warn_timestamp_expiry(struct path *mountpoint, struct vfsmount *mnt)
2798	{
2799	struct super_block *sb = mnt->mnt_sb;
2800
2801	if (!__mnt_is_readonly(mnt) &&
2802	(!(sb->s_iflags & SB_I_TS_EXPIRY_WARNED)) &&
2803	(ktime_get_real_seconds() + TIME_UPTIME_SEC_MAX > sb->s_time_max)) {
2804	char *buf = (char *)__get_free_page(GFP_KERNEL);
2805	char *mntpath = buf ? d_path(mountpoint, buf, PAGE_SIZE) : ERR_PTR(error: -ENOMEM);
2806
2807	pr_warn("%s filesystem being %s at %s supports timestamps until %ptTd (0x%llx)\n",
2808	sb->s_type->name,
2809	is_mounted(mnt) ? "remounted" : "mounted",
2810	mntpath, &sb->s_time_max,
2811	(unsigned long long)sb->s_time_max);
2812
2813	free_page((unsigned long)buf);
2814	sb->s_iflags |= SB_I_TS_EXPIRY_WARNED;
2815	}
2816	}
2817
2818	/*
2819	* Handle reconfiguration of the mountpoint only without alteration of the
2820	* superblock it refers to. This is triggered by specifying MS_REMOUNT|MS_BIND
2821	* to mount(2).
2822	*/
2823	static int do_reconfigure_mnt(struct path *path, unsigned int mnt_flags)
2824	{
2825	struct super_block *sb = path->mnt->mnt_sb;
2826	struct mount *mnt = real_mount(mnt: path->mnt);
2827	int ret;
2828
2829	if (!check_mnt(mnt))
2830	return -EINVAL;
2831
2832	if (!path_mounted(path))
2833	return -EINVAL;
2834
2835	if (!can_change_locked_flags(mnt, mnt_flags))
2836	return -EPERM;
2837
2838	/*
2839	* We're only checking whether the superblock is read-only not
2840	* changing it, so only take down_read(&sb->s_umount).
2841	*/
2842	down_read(sem: &sb->s_umount);
2843	lock_mount_hash();
2844	ret = change_mount_ro_state(mnt, mnt_flags);
2845	if (ret == 0)
2846	set_mount_attributes(mnt, mnt_flags);
2847	unlock_mount_hash();
2848	up_read(sem: &sb->s_umount);
2849
2850	mnt_warn_timestamp_expiry(mountpoint: path, mnt: &mnt->mnt);
2851
2852	return ret;
2853	}
2854
2855	/*
2856	* change filesystem flags. dir should be a physical root of filesystem.
2857	* If you've mounted a non-root directory somewhere and want to do remount
2858	* on it - tough luck.
2859	*/
2860	static int do_remount(struct path *path, int ms_flags, int sb_flags,
2861	int mnt_flags, void *data)
2862	{
2863	int err;
2864	struct super_block *sb = path->mnt->mnt_sb;
2865	struct mount *mnt = real_mount(mnt: path->mnt);
2866	struct fs_context *fc;
2867
2868	if (!check_mnt(mnt))
2869	return -EINVAL;
2870
2871	if (!path_mounted(path))
2872	return -EINVAL;
2873
2874	if (!can_change_locked_flags(mnt, mnt_flags))
2875	return -EPERM;
2876
2877	fc = fs_context_for_reconfigure(dentry: path->dentry, sb_flags, MS_RMT_MASK);
2878	if (IS_ERR(ptr: fc))
2879	return PTR_ERR(ptr: fc);
2880
2881	/*
2882	* Indicate to the filesystem that the remount request is coming
2883	* from the legacy mount system call.
2884	*/
2885	fc->oldapi = true;
2886
2887	err = parse_monolithic_mount_data(fc, data);
2888	if (!err) {
2889	down_write(sem: &sb->s_umount);
2890	err = -EPERM;
2891	if (ns_capable(ns: sb->s_user_ns, CAP_SYS_ADMIN)) {
2892	err = reconfigure_super(fc);
2893	if (!err) {
2894	lock_mount_hash();
2895	set_mount_attributes(mnt, mnt_flags);
2896	unlock_mount_hash();
2897	}
2898	}
2899	up_write(sem: &sb->s_umount);
2900	}
2901
2902	mnt_warn_timestamp_expiry(mountpoint: path, mnt: &mnt->mnt);
2903
2904	put_fs_context(fc);
2905	return err;
2906	}
2907
2908	static inline int tree_contains_unbindable(struct mount *mnt)
2909	{
2910	struct mount *p;
2911	for (p = mnt; p; p = next_mnt(p, root: mnt)) {
2912	if (IS_MNT_UNBINDABLE(p))
2913	return 1;
2914	}
2915	return 0;
2916	}
2917
2918	/*
2919	* Check that there aren't references to earlier/same mount namespaces in the
2920	* specified subtree. Such references can act as pins for mount namespaces
2921	* that aren't checked by the mount-cycle checking code, thereby allowing
2922	* cycles to be made.
2923	*/
2924	static bool check_for_nsfs_mounts(struct mount *subtree)
2925	{
2926	struct mount *p;
2927	bool ret = false;
2928
2929	lock_mount_hash();
2930	for (p = subtree; p; p = next_mnt(p, root: subtree))
2931	if (mnt_ns_loop(dentry: p->mnt.mnt_root))
2932	goto out;
2933
2934	ret = true;
2935	out:
2936	unlock_mount_hash();
2937	return ret;
2938	}
2939
2940	static int do_set_group(struct path *from_path, struct path *to_path)
2941	{
2942	struct mount *from, *to;
2943	int err;
2944
2945	from = real_mount(mnt: from_path->mnt);
2946	to = real_mount(mnt: to_path->mnt);
2947
2948	namespace_lock();
2949
2950	err = -EINVAL;
2951	/* To and From must be mounted */
2952	if (!is_mounted(mnt: &from->mnt))
2953	goto out;
2954	if (!is_mounted(mnt: &to->mnt))
2955	goto out;
2956
2957	err = -EPERM;
2958	/* We should be allowed to modify mount namespaces of both mounts */
2959	if (!ns_capable(ns: from->mnt_ns->user_ns, CAP_SYS_ADMIN))
2960	goto out;
2961	if (!ns_capable(ns: to->mnt_ns->user_ns, CAP_SYS_ADMIN))
2962	goto out;
2963
2964	err = -EINVAL;
2965	/* To and From paths should be mount roots */
2966	if (!path_mounted(path: from_path))
2967	goto out;
2968	if (!path_mounted(path: to_path))
2969	goto out;
2970
2971	/* Setting sharing groups is only allowed across same superblock */
2972	if (from->mnt.mnt_sb != to->mnt.mnt_sb)
2973	goto out;
2974
2975	/* From mount root should be wider than To mount root */
2976	if (!is_subdir(to->mnt.mnt_root, from->mnt.mnt_root))
2977	goto out;
2978
2979	/* From mount should not have locked children in place of To's root */
2980	if (has_locked_children(mnt: from, dentry: to->mnt.mnt_root))
2981	goto out;
2982
2983	/* Setting sharing groups is only allowed on private mounts */
2984	if (IS_MNT_SHARED(to) || IS_MNT_SLAVE(to))
2985	goto out;
2986
2987	/* From should not be private */
2988	if (!IS_MNT_SHARED(from) && !IS_MNT_SLAVE(from))
2989	goto out;
2990
2991	if (IS_MNT_SLAVE(from)) {
2992	struct mount *m = from->mnt_master;
2993
2994	list_add(new: &to->mnt_slave, head: &m->mnt_slave_list);
2995	to->mnt_master = m;
2996	}
2997
2998	if (IS_MNT_SHARED(from)) {
2999	to->mnt_group_id = from->mnt_group_id;
3000	list_add(new: &to->mnt_share, head: &from->mnt_share);
3001	lock_mount_hash();
3002	set_mnt_shared(to);
3003	unlock_mount_hash();
3004	}
3005
3006	err = 0;
3007	out:
3008	namespace_unlock();
3009	return err;
3010	}
3011
3012	/**
3013	* path_overmounted - check if path is overmounted
3014	* @path: path to check
3015	*
3016	* Check if path is overmounted, i.e., if there's a mount on top of
3017	* @path->mnt with @path->dentry as mountpoint.
3018	*
3019	* Context: This function expects namespace_lock() to be held.
3020	* Return: If path is overmounted true is returned, false if not.
3021	*/
3022	static inline bool path_overmounted(const struct path *path)
3023	{
3024	rcu_read_lock();
3025	if (unlikely(__lookup_mnt(path->mnt, path->dentry))) {
3026	rcu_read_unlock();
3027	return true;
3028	}
3029	rcu_read_unlock();
3030	return false;
3031	}
3032
3033	/**
3034	* can_move_mount_beneath - check that we can mount beneath the top mount
3035	* @from: mount to mount beneath
3036	* @to: mount under which to mount
3037	* @mp: mountpoint of @to
3038	*
3039	* - Make sure that @to->dentry is actually the root of a mount under
3040	* which we can mount another mount.
3041	* - Make sure that nothing can be mounted beneath the caller's current
3042	* root or the rootfs of the namespace.
3043	* - Make sure that the caller can unmount the topmost mount ensuring
3044	* that the caller could reveal the underlying mountpoint.
3045	* - Ensure that nothing has been mounted on top of @from before we
3046	* grabbed @namespace_sem to avoid creating pointless shadow mounts.
3047	* - Prevent mounting beneath a mount if the propagation relationship
3048	* between the source mount, parent mount, and top mount would lead to
3049	* nonsensical mount trees.
3050	*
3051	* Context: This function expects namespace_lock() to be held.
3052	* Return: On success 0, and on error a negative error code is returned.
3053	*/
3054	static int can_move_mount_beneath(const struct path *from,
3055	const struct path *to,
3056	const struct mountpoint *mp)
3057	{
3058	struct mount *mnt_from = real_mount(mnt: from->mnt),
3059	*mnt_to = real_mount(mnt: to->mnt),
3060	*parent_mnt_to = mnt_to->mnt_parent;
3061
3062	if (!mnt_has_parent(mnt: mnt_to))
3063	return -EINVAL;
3064
3065	if (!path_mounted(path: to))
3066	return -EINVAL;
3067
3068	if (IS_MNT_LOCKED(mnt_to))
3069	return -EINVAL;
3070
3071	/* Avoid creating shadow mounts during mount propagation. */
3072	if (path_overmounted(path: from))
3073	return -EINVAL;
3074
3075	/*
3076	* Mounting beneath the rootfs only makes sense when the
3077	* semantics of pivot_root(".", ".") are used.
3078	*/
3079	if (&mnt_to->mnt == current->fs->root.mnt)
3080	return -EINVAL;
3081	if (parent_mnt_to == current->nsproxy->mnt_ns->root)
3082	return -EINVAL;
3083
3084	for (struct mount *p = mnt_from; mnt_has_parent(mnt: p); p = p->mnt_parent)
3085	if (p == mnt_to)
3086	return -EINVAL;
3087
3088	/*
3089	* If the parent mount propagates to the child mount this would
3090	* mean mounting @mnt_from on @mnt_to->mnt_parent and then
3091	* propagating a copy @c of @mnt_from on top of @mnt_to. This
3092	* defeats the whole purpose of mounting beneath another mount.
3093	*/
3094	if (propagation_would_overmount(from: parent_mnt_to, to: mnt_to, mp))
3095	return -EINVAL;
3096
3097	/*
3098	* If @mnt_to->mnt_parent propagates to @mnt_from this would
3099	* mean propagating a copy @c of @mnt_from on top of @mnt_from.
3100	* Afterwards @mnt_from would be mounted on top of
3101	* @mnt_to->mnt_parent and @mnt_to would be unmounted from
3102	* @mnt->mnt_parent and remounted on @mnt_from. But since @c is
3103	* already mounted on @mnt_from, @mnt_to would ultimately be
3104	* remounted on top of @c. Afterwards, @mnt_from would be
3105	* covered by a copy @c of @mnt_from and @c would be covered by
3106	* @mnt_from itself. This defeats the whole purpose of mounting
3107	* @mnt_from beneath @mnt_to.
3108	*/
3109	if (propagation_would_overmount(from: parent_mnt_to, to: mnt_from, mp))
3110	return -EINVAL;
3111
3112	return 0;
3113	}
3114
3115	static int do_move_mount(struct path *old_path, struct path *new_path,
3116	bool beneath)
3117	{
3118	struct mnt_namespace *ns;
3119	struct mount *p;
3120	struct mount *old;
3121	struct mount *parent;
3122	struct mountpoint *mp, *old_mp;
3123	int err;
3124	bool attached;
3125	enum mnt_tree_flags_t flags = 0;
3126
3127	mp = do_lock_mount(path: new_path, beneath);
3128	if (IS_ERR(ptr: mp))
3129	return PTR_ERR(ptr: mp);
3130
3131	old = real_mount(mnt: old_path->mnt);
3132	p = real_mount(mnt: new_path->mnt);
3133	parent = old->mnt_parent;
3134	attached = mnt_has_parent(mnt: old);
3135	if (attached)
3136	flags |= MNT_TREE_MOVE;
3137	old_mp = old->mnt_mp;
3138	ns = old->mnt_ns;
3139
3140	err = -EINVAL;
3141	/* The mountpoint must be in our namespace. */
3142	if (!check_mnt(mnt: p))
3143	goto out;
3144
3145	/* The thing moved must be mounted... */
3146	if (!is_mounted(mnt: &old->mnt))
3147	goto out;
3148
3149	/* ... and either ours or the root of anon namespace */
3150	if (!(attached ? check_mnt(mnt: old) : is_anon_ns(ns)))
3151	goto out;
3152
3153	if (old->mnt.mnt_flags & MNT_LOCKED)
3154	goto out;
3155
3156	if (!path_mounted(path: old_path))
3157	goto out;
3158
3159	if (d_is_dir(dentry: new_path->dentry) !=
3160	d_is_dir(dentry: old_path->dentry))
3161	goto out;
3162	/*
3163	* Don't move a mount residing in a shared parent.
3164	*/
3165	if (attached && IS_MNT_SHARED(parent))
3166	goto out;
3167
3168	if (beneath) {
3169	err = can_move_mount_beneath(from: old_path, to: new_path, mp);
3170	if (err)
3171	goto out;
3172
3173	err = -EINVAL;
3174	p = p->mnt_parent;
3175	flags |= MNT_TREE_BENEATH;
3176	}
3177
3178	/*
3179	* Don't move a mount tree containing unbindable mounts to a destination
3180	* mount which is shared.
3181	*/
3182	if (IS_MNT_SHARED(p) && tree_contains_unbindable(mnt: old))
3183	goto out;
3184	err = -ELOOP;
3185	if (!check_for_nsfs_mounts(subtree: old))
3186	goto out;
3187	for (; mnt_has_parent(mnt: p); p = p->mnt_parent)
3188	if (p == old)
3189	goto out;
3190
3191	err = attach_recursive_mnt(source_mnt: old, top_mnt: real_mount(mnt: new_path->mnt), dest_mp: mp, flags);
3192	if (err)
3193	goto out;
3194
3195	/* if the mount is moved, it should no longer be expire
3196	* automatically */
3197	list_del_init(entry: &old->mnt_expire);
3198	if (attached)
3199	put_mountpoint(mp: old_mp);
3200	out:
3201	unlock_mount(where: mp);
3202	if (!err) {
3203	if (attached)
3204	mntput_no_expire(mnt: parent);
3205	else
3206	free_mnt_ns(ns);
3207	}
3208	return err;
3209	}
3210
3211	static int do_move_mount_old(struct path *path, const char *old_name)
3212	{
3213	struct path old_path;
3214	int err;
3215
3216	if (!old_name || !*old_name)
3217	return -EINVAL;
3218
3219	err = kern_path(old_name, LOOKUP_FOLLOW, &old_path);
3220	if (err)
3221	return err;
3222
3223	err = do_move_mount(old_path: &old_path, new_path: path, beneath: false);
3224	path_put(&old_path);
3225	return err;
3226	}
3227
3228	/*
3229	* add a mount into a namespace's mount tree
3230	*/
3231	static int do_add_mount(struct mount *newmnt, struct mountpoint *mp,
3232	const struct path *path, int mnt_flags)
3233	{
3234	struct mount *parent = real_mount(mnt: path->mnt);
3235
3236	mnt_flags &= ~MNT_INTERNAL_FLAGS;
3237
3238	if (unlikely(!check_mnt(parent))) {
3239	/* that's acceptable only for automounts done in private ns */
3240	if (!(mnt_flags & MNT_SHRINKABLE))
3241	return -EINVAL;
3242	/* ... and for those we'd better have mountpoint still alive */
3243	if (!parent->mnt_ns)
3244	return -EINVAL;
3245	}
3246
3247	/* Refuse the same filesystem on the same mount point */
3248	if (path->mnt->mnt_sb == newmnt->mnt.mnt_sb && path_mounted(path))
3249	return -EBUSY;
3250
3251	if (d_is_symlink(dentry: newmnt->mnt.mnt_root))
3252	return -EINVAL;
3253
3254	newmnt->mnt.mnt_flags = mnt_flags;
3255	return graft_tree(mnt: newmnt, p: parent, mp);
3256	}
3257
3258	static bool mount_too_revealing(const struct super_block *sb, int *new_mnt_flags);
3259
3260	/*
3261	* Create a new mount using a superblock configuration and request it
3262	* be added to the namespace tree.
3263	*/
3264	static int do_new_mount_fc(struct fs_context *fc, struct path *mountpoint,
3265	unsigned int mnt_flags)
3266	{
3267	struct vfsmount *mnt;
3268	struct mountpoint *mp;
3269	struct super_block *sb = fc->root->d_sb;
3270	int error;
3271
3272	error = security_sb_kern_mount(sb);
3273	if (!error && mount_too_revealing(sb, new_mnt_flags: &mnt_flags))
3274	error = -EPERM;
3275
3276	if (unlikely(error)) {
3277	fc_drop_locked(fc);
3278	return error;
3279	}
3280
3281	up_write(sem: &sb->s_umount);
3282
3283	mnt = vfs_create_mount(fc);
3284	if (IS_ERR(ptr: mnt))
3285	return PTR_ERR(ptr: mnt);
3286
3287	mnt_warn_timestamp_expiry(mountpoint, mnt);
3288
3289	mp = lock_mount(path: mountpoint);
3290	if (IS_ERR(ptr: mp)) {
3291	mntput(mnt);
3292	return PTR_ERR(ptr: mp);
3293	}
3294	error = do_add_mount(newmnt: real_mount(mnt), mp, path: mountpoint, mnt_flags);
3295	unlock_mount(where: mp);
3296	if (error < 0)
3297	mntput(mnt);
3298	return error;
3299	}
3300
3301	/*
3302	* create a new mount for userspace and request it to be added into the
3303	* namespace's tree
3304	*/
3305	static int do_new_mount(struct path *path, const char *fstype, int sb_flags,
3306	int mnt_flags, const char *name, void *data)
3307	{
3308	struct file_system_type *type;
3309	struct fs_context *fc;
3310	const char *subtype = NULL;
3311	int err = 0;
3312
3313	if (!fstype)
3314	return -EINVAL;
3315
3316	type = get_fs_type(name: fstype);
3317	if (!type)
3318	return -ENODEV;
3319
3320	if (type->fs_flags & FS_HAS_SUBTYPE) {
3321	subtype = strchr(fstype, '.');
3322	if (subtype) {
3323	subtype++;
3324	if (!*subtype) {
3325	put_filesystem(fs: type);
3326	return -EINVAL;
3327	}
3328	}
3329	}
3330
3331	fc = fs_context_for_mount(fs_type: type, sb_flags);
3332	put_filesystem(fs: type);
3333	if (IS_ERR(ptr: fc))
3334	return PTR_ERR(ptr: fc);
3335
3336	/*
3337	* Indicate to the filesystem that the mount request is coming
3338	* from the legacy mount system call.
3339	*/
3340	fc->oldapi = true;
3341
3342	if (subtype)
3343	err = vfs_parse_fs_string(fc, key: "subtype",
3344	value: subtype, strlen(subtype));
3345	if (!err && name)
3346	err = vfs_parse_fs_string(fc, key: "source", value: name, strlen(name));
3347	if (!err)
3348	err = parse_monolithic_mount_data(fc, data);
3349	if (!err && !mount_capable(fc))
3350	err = -EPERM;
3351	if (!err)
3352	err = vfs_get_tree(fc);
3353	if (!err)
3354	err = do_new_mount_fc(fc, mountpoint: path, mnt_flags);
3355
3356	put_fs_context(fc);
3357	return err;
3358	}
3359
3360	int finish_automount(struct vfsmount *m, const struct path *path)
3361	{
3362	struct dentry *dentry = path->dentry;
3363	struct mountpoint *mp;
3364	struct mount *mnt;
3365	int err;
3366
3367	if (!m)
3368	return 0;
3369	if (IS_ERR(ptr: m))
3370	return PTR_ERR(ptr: m);
3371
3372	mnt = real_mount(mnt: m);
3373	/* The new mount record should have at least 2 refs to prevent it being
3374	* expired before we get a chance to add it
3375	*/
3376	BUG_ON(mnt_get_count(mnt) < 2);
3377
3378	if (m->mnt_sb == path->mnt->mnt_sb &&
3379	m->mnt_root == dentry) {
3380	err = -ELOOP;
3381	goto discard;
3382	}
3383
3384	/*
3385	* we don't want to use lock_mount() - in this case finding something
3386	* that overmounts our mountpoint to be means "quitely drop what we've
3387	* got", not "try to mount it on top".
3388	*/
3389	inode_lock(inode: dentry->d_inode);
3390	namespace_lock();
3391	if (unlikely(cant_mount(dentry))) {
3392	err = -ENOENT;
3393	goto discard_locked;
3394	}
3395	if (path_overmounted(path)) {
3396	err = 0;
3397	goto discard_locked;
3398	}
3399	mp = get_mountpoint(dentry);
3400	if (IS_ERR(ptr: mp)) {
3401	err = PTR_ERR(ptr: mp);
3402	goto discard_locked;
3403	}
3404
3405	err = do_add_mount(newmnt: mnt, mp, path, mnt_flags: path->mnt->mnt_flags | MNT_SHRINKABLE);
3406	unlock_mount(where: mp);
3407	if (unlikely(err))
3408	goto discard;
3409	mntput(m);
3410	return 0;
3411
3412	discard_locked:
3413	namespace_unlock();
3414	inode_unlock(inode: dentry->d_inode);
3415	discard:
3416	/* remove m from any expiration list it may be on */
3417	if (!list_empty(head: &mnt->mnt_expire)) {
3418	namespace_lock();
3419	list_del_init(entry: &mnt->mnt_expire);
3420	namespace_unlock();
3421	}
3422	mntput(m);
3423	mntput(m);
3424	return err;
3425	}
3426
3427	/**
3428	* mnt_set_expiry - Put a mount on an expiration list
3429	* @mnt: The mount to list.
3430	* @expiry_list: The list to add the mount to.
3431	*/
3432	void mnt_set_expiry(struct vfsmount *mnt, struct list_head *expiry_list)
3433	{
3434	namespace_lock();
3435
3436	list_add_tail(new: &real_mount(mnt)->mnt_expire, head: expiry_list);
3437
3438	namespace_unlock();
3439	}
3440	EXPORT_SYMBOL(mnt_set_expiry);
3441
3442	/*
3443	* process a list of expirable mountpoints with the intent of discarding any
3444	* mountpoints that aren't in use and haven't been touched since last we came
3445	* here
3446	*/
3447	void mark_mounts_for_expiry(struct list_head *mounts)
3448	{
3449	struct mount *mnt, *next;
3450	LIST_HEAD(graveyard);
3451
3452	if (list_empty(head: mounts))
3453	return;
3454
3455	namespace_lock();
3456	lock_mount_hash();
3457
3458	/* extract from the expiration list every vfsmount that matches the
3459	* following criteria:
3460	* - only referenced by its parent vfsmount
3461	* - still marked for expiry (marked on the last call here; marks are
3462	* cleared by mntput())
3463	*/
3464	list_for_each_entry_safe(mnt, next, mounts, mnt_expire) {
3465	if (!xchg(&mnt->mnt_expiry_mark, 1) ||
3466	propagate_mount_busy(mnt, 1))
3467	continue;
3468	list_move(list: &mnt->mnt_expire, head: &graveyard);
3469	}
3470	while (!list_empty(head: &graveyard)) {
3471	mnt = list_first_entry(&graveyard, struct mount, mnt_expire);
3472	touch_mnt_namespace(ns: mnt->mnt_ns);
3473	umount_tree(mnt, how: UMOUNT_PROPAGATE|UMOUNT_SYNC);
3474	}
3475	unlock_mount_hash();
3476	namespace_unlock();
3477	}
3478
3479	EXPORT_SYMBOL_GPL(mark_mounts_for_expiry);
3480
3481	/*
3482	* Ripoff of 'select_parent()'
3483	*
3484	* search the list of submounts for a given mountpoint, and move any
3485	* shrinkable submounts to the 'graveyard' list.
3486	*/
3487	static int select_submounts(struct mount *parent, struct list_head *graveyard)
3488	{
3489	struct mount *this_parent = parent;
3490	struct list_head *next;
3491	int found = 0;
3492
3493	repeat:
3494	next = this_parent->mnt_mounts.next;
3495	resume:
3496	while (next != &this_parent->mnt_mounts) {
3497	struct list_head *tmp = next;
3498	struct mount *mnt = list_entry(tmp, struct mount, mnt_child);
3499
3500	next = tmp->next;
3501	if (!(mnt->mnt.mnt_flags & MNT_SHRINKABLE))
3502	continue;
3503	/*
3504	* Descend a level if the d_mounts list is non-empty.
3505	*/
3506	if (!list_empty(head: &mnt->mnt_mounts)) {
3507	this_parent = mnt;
3508	goto repeat;
3509	}
3510
3511	if (!propagate_mount_busy(mnt, 1)) {
3512	list_move_tail(list: &mnt->mnt_expire, head: graveyard);
3513	found++;
3514	}
3515	}
3516	/*
3517	* All done at this level ... ascend and resume the search
3518	*/
3519	if (this_parent != parent) {
3520	next = this_parent->mnt_child.next;
3521	this_parent = this_parent->mnt_parent;
3522	goto resume;
3523	}
3524	return found;
3525	}
3526
3527	/*
3528	* process a list of expirable mountpoints with the intent of discarding any
3529	* submounts of a specific parent mountpoint
3530	*
3531	* mount_lock must be held for write
3532	*/
3533	static void shrink_submounts(struct mount *mnt)
3534	{
3535	LIST_HEAD(graveyard);
3536	struct mount *m;
3537
3538	/* extract submounts of 'mountpoint' from the expiration list */
3539	while (select_submounts(parent: mnt, graveyard: &graveyard)) {
3540	while (!list_empty(head: &graveyard)) {
3541	m = list_first_entry(&graveyard, struct mount,
3542	mnt_expire);
3543	touch_mnt_namespace(ns: m->mnt_ns);
3544	umount_tree(mnt: m, how: UMOUNT_PROPAGATE|UMOUNT_SYNC);
3545	}
3546	}
3547	}
3548
3549	static void *copy_mount_options(const void __user * data)
3550	{
3551	char *copy;
3552	unsigned left, offset;
3553
3554	if (!data)
3555	return NULL;
3556
3557	copy = kmalloc(PAGE_SIZE, GFP_KERNEL);
3558	if (!copy)
3559	return ERR_PTR(error: -ENOMEM);
3560
3561	left = copy_from_user(to: copy, from: data, PAGE_SIZE);
3562
3563	/*
3564	* Not all architectures have an exact copy_from_user(). Resort to
3565	* byte at a time.
3566	*/
3567	offset = PAGE_SIZE - left;
3568	while (left) {
3569	char c;
3570	if (get_user(c, (const char __user *)data + offset))
3571	break;
3572	copy[offset] = c;
3573	left--;
3574	offset++;
3575	}
3576
3577	if (left == PAGE_SIZE) {
3578	kfree(objp: copy);
3579	return ERR_PTR(error: -EFAULT);
3580	}
3581
3582	return copy;
3583	}
3584
3585	static char *copy_mount_string(const void __user *data)
3586	{
3587	return data ? strndup_user(data, PATH_MAX) : NULL;
3588	}
3589
3590	/*
3591	* Flags is a 32-bit value that allows up to 31 non-fs dependent flags to
3592	* be given to the mount() call (ie: read-only, no-dev, no-suid etc).
3593	*
3594	* data is a (void *) that can point to any structure up to
3595	* PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent
3596	* information (or be NULL).
3597	*
3598	* Pre-0.97 versions of mount() didn't have a flags word.
3599	* When the flags word was introduced its top half was required
3600	* to have the magic value 0xC0ED, and this remained so until 2.4.0-test9.
3601	* Therefore, if this magic number is present, it carries no information
3602	* and must be discarded.
3603	*/
3604	int path_mount(const char *dev_name, struct path *path,
3605	const char *type_page, unsigned long flags, void *data_page)
3606	{
3607	unsigned int mnt_flags = 0, sb_flags;
3608	int ret;
3609
3610	/* Discard magic */
3611	if ((flags & MS_MGC_MSK) == MS_MGC_VAL)
3612	flags &= ~MS_MGC_MSK;
3613
3614	/* Basic sanity checks */
3615	if (data_page)
3616	((char *)data_page)[PAGE_SIZE - 1] = 0;
3617
3618	if (flags & MS_NOUSER)
3619	return -EINVAL;
3620
3621	ret = security_sb_mount(dev_name, path, type: type_page, flags, data: data_page);
3622	if (ret)
3623	return ret;
3624	if (!may_mount())
3625	return -EPERM;
3626	if (flags & SB_MANDLOCK)
3627	warn_mandlock();
3628
3629	/* Default to relatime unless overriden */
3630	if (!(flags & MS_NOATIME))
3631	mnt_flags |= MNT_RELATIME;
3632
3633	/* Separate the per-mountpoint flags */
3634	if (flags & MS_NOSUID)
3635	mnt_flags |= MNT_NOSUID;
3636	if (flags & MS_NODEV)
3637	mnt_flags |= MNT_NODEV;
3638	if (flags & MS_NOEXEC)
3639	mnt_flags |= MNT_NOEXEC;
3640	if (flags & MS_NOATIME)
3641	mnt_flags |= MNT_NOATIME;
3642	if (flags & MS_NODIRATIME)
3643	mnt_flags |= MNT_NODIRATIME;
3644	if (flags & MS_STRICTATIME)
3645	mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME);
3646	if (flags & MS_RDONLY)
3647	mnt_flags |= MNT_READONLY;
3648	if (flags & MS_NOSYMFOLLOW)
3649	mnt_flags |= MNT_NOSYMFOLLOW;
3650
3651	/* The default atime for remount is preservation */
3652	if ((flags & MS_REMOUNT) &&
3653	((flags & (MS_NOATIME | MS_NODIRATIME | MS_RELATIME |
3654	MS_STRICTATIME)) == 0)) {
3655	mnt_flags &= ~MNT_ATIME_MASK;
3656	mnt_flags |= path->mnt->mnt_flags & MNT_ATIME_MASK;
3657	}
3658
3659	sb_flags = flags & (SB_RDONLY |
3660	SB_SYNCHRONOUS |
3661	SB_MANDLOCK |
3662	SB_DIRSYNC |
3663	SB_SILENT |
3664	SB_POSIXACL |
3665	SB_LAZYTIME |
3666	SB_I_VERSION);
3667
3668	if ((flags & (MS_REMOUNT | MS_BIND)) == (MS_REMOUNT | MS_BIND))
3669	return do_reconfigure_mnt(path, mnt_flags);
3670	if (flags & MS_REMOUNT)
3671	return do_remount(path, ms_flags: flags, sb_flags, mnt_flags, data: data_page);
3672	if (flags & MS_BIND)
3673	return do_loopback(path, old_name: dev_name, recurse: flags & MS_REC);
3674	if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
3675	return do_change_type(path, ms_flags: flags);
3676	if (flags & MS_MOVE)
3677	return do_move_mount_old(path, old_name: dev_name);
3678
3679	return do_new_mount(path, fstype: type_page, sb_flags, mnt_flags, name: dev_name,
3680	data: data_page);
3681	}
3682
3683	long do_mount(const char *dev_name, const char __user *dir_name,
3684	const char *type_page, unsigned long flags, void *data_page)
3685	{
3686	struct path path;
3687	int ret;
3688
3689	ret = user_path_at(AT_FDCWD, name: dir_name, LOOKUP_FOLLOW, path: &path);
3690	if (ret)
3691	return ret;
3692	ret = path_mount(dev_name, path: &path, type_page, flags, data_page);
3693	path_put(&path);
3694	return ret;
3695	}
3696
3697	static struct ucounts *inc_mnt_namespaces(struct user_namespace *ns)
3698	{
3699	return inc_ucount(ns, current_euid(), type: UCOUNT_MNT_NAMESPACES);
3700	}
3701
3702	static void dec_mnt_namespaces(struct ucounts *ucounts)
3703	{
3704	dec_ucount(ucounts, type: UCOUNT_MNT_NAMESPACES);
3705	}
3706
3707	static void free_mnt_ns(struct mnt_namespace *ns)
3708	{
3709	if (!is_anon_ns(ns))
3710	ns_free_inum(&ns->ns);
3711	dec_mnt_namespaces(ucounts: ns->ucounts);
3712	put_user_ns(ns: ns->user_ns);
3713	kfree(objp: ns);
3714	}
3715
3716	/*
3717	* Assign a sequence number so we can detect when we attempt to bind
3718	* mount a reference to an older mount namespace into the current
3719	* mount namespace, preventing reference counting loops. A 64bit
3720	* number incrementing at 10Ghz will take 12,427 years to wrap which
3721	* is effectively never, so we can ignore the possibility.
3722	*/
3723	static atomic64_t mnt_ns_seq = ATOMIC64_INIT(1);
3724
3725	static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns, bool anon)
3726	{
3727	struct mnt_namespace *new_ns;
3728	struct ucounts *ucounts;
3729	int ret;
3730
3731	ucounts = inc_mnt_namespaces(ns: user_ns);
3732	if (!ucounts)
3733	return ERR_PTR(error: -ENOSPC);
3734
3735	new_ns = kzalloc(size: sizeof(struct mnt_namespace), GFP_KERNEL_ACCOUNT);
3736	if (!new_ns) {
3737	dec_mnt_namespaces(ucounts);
3738	return ERR_PTR(error: -ENOMEM);
3739	}
3740	if (!anon) {
3741	ret = ns_alloc_inum(ns: &new_ns->ns);
3742	if (ret) {
3743	kfree(objp: new_ns);
3744	dec_mnt_namespaces(ucounts);
3745	return ERR_PTR(error: ret);
3746	}
3747	}
3748	new_ns->ns.ops = &mntns_operations;
3749	if (!anon)
3750	new_ns->seq = atomic64_add_return(i: 1, v: &mnt_ns_seq);
3751	refcount_set(r: &new_ns->ns.count, n: 1);
3752	new_ns->mounts = RB_ROOT;
3753	init_waitqueue_head(&new_ns->poll);
3754	new_ns->user_ns = get_user_ns(ns: user_ns);
3755	new_ns->ucounts = ucounts;
3756	return new_ns;
3757	}
3758
3759	__latent_entropy
3760	struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns,
3761	struct user_namespace *user_ns, struct fs_struct *new_fs)
3762	{
3763	struct mnt_namespace *new_ns;
3764	struct vfsmount *rootmnt = NULL, *pwdmnt = NULL;
3765	struct mount *p, *q;
3766	struct mount *old;
3767	struct mount *new;
3768	int copy_flags;
3769
3770	BUG_ON(!ns);
3771
3772	if (likely(!(flags & CLONE_NEWNS))) {
3773	get_mnt_ns(ns);
3774	return ns;
3775	}
3776
3777	old = ns->root;
3778
3779	new_ns = alloc_mnt_ns(user_ns, anon: false);
3780	if (IS_ERR(ptr: new_ns))
3781	return new_ns;
3782
3783	namespace_lock();
3784	/* First pass: copy the tree topology */
3785	copy_flags = CL_COPY_UNBINDABLE | CL_EXPIRE;
3786	if (user_ns != ns->user_ns)
3787	copy_flags |= CL_SHARED_TO_SLAVE;
3788	new = copy_tree(mnt: old, dentry: old->mnt.mnt_root, flag: copy_flags);
3789	if (IS_ERR(ptr: new)) {
3790	namespace_unlock();
3791	free_mnt_ns(ns: new_ns);
3792	return ERR_CAST(ptr: new);
3793	}
3794	if (user_ns != ns->user_ns) {
3795	lock_mount_hash();
3796	lock_mnt_tree(mnt: new);
3797	unlock_mount_hash();
3798	}
3799	new_ns->root = new;
3800
3801	/*
3802	* Second pass: switch the tsk->fs->* elements and mark new vfsmounts
3803	* as belonging to new namespace. We have already acquired a private
3804	* fs_struct, so tsk->fs->lock is not needed.
3805	*/
3806	p = old;
3807	q = new;
3808	while (p) {
3809	mnt_add_to_ns(ns: new_ns, mnt: q);
3810	new_ns->nr_mounts++;
3811	if (new_fs) {
3812	if (&p->mnt == new_fs->root.mnt) {
3813	new_fs->root.mnt = mntget(&q->mnt);
3814	rootmnt = &p->mnt;
3815	}
3816	if (&p->mnt == new_fs->pwd.mnt) {
3817	new_fs->pwd.mnt = mntget(&q->mnt);
3818	pwdmnt = &p->mnt;
3819	}
3820	}
3821	p = next_mnt(p, root: old);
3822	q = next_mnt(p: q, root: new);
3823	if (!q)
3824	break;
3825	// an mntns binding we'd skipped?
3826	while (p->mnt.mnt_root != q->mnt.mnt_root)
3827	p = next_mnt(p: skip_mnt_tree(p), root: old);
3828	}
3829	namespace_unlock();
3830
3831	if (rootmnt)
3832	mntput(rootmnt);
3833	if (pwdmnt)
3834	mntput(pwdmnt);
3835
3836	return new_ns;
3837	}
3838
3839	struct dentry *mount_subtree(struct vfsmount *m, const char *name)
3840	{
3841	struct mount *mnt = real_mount(mnt: m);
3842	struct mnt_namespace *ns;
3843	struct super_block *s;
3844	struct path path;
3845	int err;
3846
3847	ns = alloc_mnt_ns(user_ns: &init_user_ns, anon: true);
3848	if (IS_ERR(ptr: ns)) {
3849	mntput(m);
3850	return ERR_CAST(ptr: ns);
3851	}
3852	ns->root = mnt;
3853	ns->nr_mounts++;
3854	mnt_add_to_ns(ns, mnt);
3855
3856	err = vfs_path_lookup(m->mnt_root, m,
3857	name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &path);
3858
3859	put_mnt_ns(ns);
3860
3861	if (err)
3862	return ERR_PTR(error: err);
3863
3864	/* trade a vfsmount reference for active sb one */
3865	s = path.mnt->mnt_sb;
3866	atomic_inc(v: &s->s_active);
3867	mntput(path.mnt);
3868	/* lock the sucker */
3869	down_write(sem: &s->s_umount);
3870	/* ... and return the root of (sub)tree on it */
3871	return path.dentry;
3872	}
3873	EXPORT_SYMBOL(mount_subtree);
3874
3875	SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name,
3876	char __user *, type, unsigned long, flags, void __user *, data)
3877	{
3878	int ret;
3879	char *kernel_type;
3880	char *kernel_dev;
3881	void *options;
3882
3883	kernel_type = copy_mount_string(data: type);
3884	ret = PTR_ERR(ptr: kernel_type);
3885	if (IS_ERR(ptr: kernel_type))
3886	goto out_type;
3887
3888	kernel_dev = copy_mount_string(data: dev_name);
3889	ret = PTR_ERR(ptr: kernel_dev);
3890	if (IS_ERR(ptr: kernel_dev))
3891	goto out_dev;
3892
3893	options = copy_mount_options(data);
3894	ret = PTR_ERR(ptr: options);
3895	if (IS_ERR(ptr: options))
3896	goto out_data;
3897
3898	ret = do_mount(dev_name: kernel_dev, dir_name, type_page: kernel_type, flags, data_page: options);
3899
3900	kfree(objp: options);
3901	out_data:
3902	kfree(objp: kernel_dev);
3903	out_dev:
3904	kfree(objp: kernel_type);
3905	out_type:
3906	return ret;
3907	}
3908
3909	#define FSMOUNT_VALID_FLAGS \
3910	(MOUNT_ATTR_RDONLY | MOUNT_ATTR_NOSUID | MOUNT_ATTR_NODEV | \
3911	MOUNT_ATTR_NOEXEC | MOUNT_ATTR__ATIME | MOUNT_ATTR_NODIRATIME | \
3912	MOUNT_ATTR_NOSYMFOLLOW)
3913
3914	#define MOUNT_SETATTR_VALID_FLAGS (FSMOUNT_VALID_FLAGS | MOUNT_ATTR_IDMAP)
3915
3916	#define MOUNT_SETATTR_PROPAGATION_FLAGS \
3917	(MS_UNBINDABLE | MS_PRIVATE | MS_SLAVE | MS_SHARED)
3918
3919	static unsigned int attr_flags_to_mnt_flags(u64 attr_flags)
3920	{
3921	unsigned int mnt_flags = 0;
3922
3923	if (attr_flags & MOUNT_ATTR_RDONLY)
3924	mnt_flags |= MNT_READONLY;
3925	if (attr_flags & MOUNT_ATTR_NOSUID)
3926	mnt_flags |= MNT_NOSUID;
3927	if (attr_flags & MOUNT_ATTR_NODEV)
3928	mnt_flags |= MNT_NODEV;
3929	if (attr_flags & MOUNT_ATTR_NOEXEC)
3930	mnt_flags |= MNT_NOEXEC;
3931	if (attr_flags & MOUNT_ATTR_NODIRATIME)
3932	mnt_flags |= MNT_NODIRATIME;
3933	if (attr_flags & MOUNT_ATTR_NOSYMFOLLOW)
3934	mnt_flags |= MNT_NOSYMFOLLOW;
3935
3936	return mnt_flags;
3937	}
3938
3939	/*
3940	* Create a kernel mount representation for a new, prepared superblock
3941	* (specified by fs_fd) and attach to an open_tree-like file descriptor.
3942	*/
3943	SYSCALL_DEFINE3(fsmount, int, fs_fd, unsigned int, flags,
3944	unsigned int, attr_flags)
3945	{
3946	struct mnt_namespace *ns;
3947	struct fs_context *fc;
3948	struct file *file;
3949	struct path newmount;
3950	struct mount *mnt;
3951	struct fd f;
3952	unsigned int mnt_flags = 0;
3953	long ret;
3954
3955	if (!may_mount())
3956	return -EPERM;
3957
3958	if ((flags & ~(FSMOUNT_CLOEXEC)) != 0)
3959	return -EINVAL;
3960
3961	if (attr_flags & ~FSMOUNT_VALID_FLAGS)
3962	return -EINVAL;
3963
3964	mnt_flags = attr_flags_to_mnt_flags(attr_flags);
3965
3966	switch (attr_flags & MOUNT_ATTR__ATIME) {
3967	case MOUNT_ATTR_STRICTATIME:
3968	break;
3969	case MOUNT_ATTR_NOATIME:
3970	mnt_flags |= MNT_NOATIME;
3971	break;
3972	case MOUNT_ATTR_RELATIME:
3973	mnt_flags |= MNT_RELATIME;
3974	break;
3975	default:
3976	return -EINVAL;
3977	}
3978
3979	f = fdget(fd: fs_fd);
3980	if (!f.file)
3981	return -EBADF;
3982
3983	ret = -EINVAL;
3984	if (f.file->f_op != &fscontext_fops)
3985	goto err_fsfd;
3986
3987	fc = f.file->private_data;
3988
3989	ret = mutex_lock_interruptible(&fc->uapi_mutex);
3990	if (ret < 0)
3991	goto err_fsfd;
3992
3993	/* There must be a valid superblock or we can't mount it */
3994	ret = -EINVAL;
3995	if (!fc->root)
3996	goto err_unlock;
3997
3998	ret = -EPERM;
3999	if (mount_too_revealing(sb: fc->root->d_sb, new_mnt_flags: &mnt_flags)) {
4000	pr_warn("VFS: Mount too revealing\n");
4001	goto err_unlock;
4002	}
4003
4004	ret = -EBUSY;
4005	if (fc->phase != FS_CONTEXT_AWAITING_MOUNT)
4006	goto err_unlock;
4007
4008	if (fc->sb_flags & SB_MANDLOCK)
4009	warn_mandlock();
4010
4011	newmount.mnt = vfs_create_mount(fc);
4012	if (IS_ERR(ptr: newmount.mnt)) {
4013	ret = PTR_ERR(ptr: newmount.mnt);
4014	goto err_unlock;
4015	}
4016	newmount.dentry = dget(dentry: fc->root);
4017	newmount.mnt->mnt_flags = mnt_flags;
4018
4019	/* We've done the mount bit - now move the file context into more or
4020	* less the same state as if we'd done an fspick(). We don't want to
4021	* do any memory allocation or anything like that at this point as we
4022	* don't want to have to handle any errors incurred.
4023	*/
4024	vfs_clean_context(fc);
4025
4026	ns = alloc_mnt_ns(current->nsproxy->mnt_ns->user_ns, anon: true);
4027	if (IS_ERR(ptr: ns)) {
4028	ret = PTR_ERR(ptr: ns);
4029	goto err_path;
4030	}
4031	mnt = real_mount(mnt: newmount.mnt);
4032	ns->root = mnt;
4033	ns->nr_mounts = 1;
4034	mnt_add_to_ns(ns, mnt);
4035	mntget(newmount.mnt);
4036
4037	/* Attach to an apparent O_PATH fd with a note that we need to unmount
4038	* it, not just simply put it.
4039	*/
4040	file = dentry_open(path: &newmount, O_PATH, creds: fc->cred);
4041	if (IS_ERR(ptr: file)) {
4042	dissolve_on_fput(mnt: newmount.mnt);
4043	ret = PTR_ERR(ptr: file);
4044	goto err_path;
4045	}
4046	file->f_mode |= FMODE_NEED_UNMOUNT;
4047
4048	ret = get_unused_fd_flags(flags: (flags & FSMOUNT_CLOEXEC) ? O_CLOEXEC : 0);
4049	if (ret >= 0)
4050	fd_install(fd: ret, file);
4051	else
4052	fput(file);
4053
4054	err_path:
4055	path_put(&newmount);
4056	err_unlock:
4057	mutex_unlock(lock: &fc->uapi_mutex);
4058	err_fsfd:
4059	fdput(fd: f);
4060	return ret;
4061	}
4062
4063	/*
4064	* Move a mount from one place to another. In combination with
4065	* fsopen()/fsmount() this is used to install a new mount and in combination
4066	* with open_tree(OPEN_TREE_CLONE [| AT_RECURSIVE]) it can be used to copy
4067	* a mount subtree.
4068	*
4069	* Note the flags value is a combination of MOVE_MOUNT_* flags.
4070	*/
4071	SYSCALL_DEFINE5(move_mount,
4072	int, from_dfd, const char __user *, from_pathname,
4073	int, to_dfd, const char __user *, to_pathname,
4074	unsigned int, flags)
4075	{
4076	struct path from_path, to_path;
4077	unsigned int lflags;
4078	int ret = 0;
4079
4080	if (!may_mount())
4081	return -EPERM;
4082
4083	if (flags & ~MOVE_MOUNT__MASK)
4084	return -EINVAL;
4085
4086	if ((flags & (MOVE_MOUNT_BENEATH | MOVE_MOUNT_SET_GROUP)) ==
4087	(MOVE_MOUNT_BENEATH | MOVE_MOUNT_SET_GROUP))
4088	return -EINVAL;
4089
4090	/* If someone gives a pathname, they aren't permitted to move
4091	* from an fd that requires unmount as we can't get at the flag
4092	* to clear it afterwards.
4093	*/
4094	lflags = 0;
4095	if (flags & MOVE_MOUNT_F_SYMLINKS) lflags |= LOOKUP_FOLLOW;
4096	if (flags & MOVE_MOUNT_F_AUTOMOUNTS) lflags |= LOOKUP_AUTOMOUNT;
4097	if (flags & MOVE_MOUNT_F_EMPTY_PATH) lflags |= LOOKUP_EMPTY;
4098
4099	ret = user_path_at(dfd: from_dfd, name: from_pathname, flags: lflags, path: &from_path);
4100	if (ret < 0)
4101	return ret;
4102
4103	lflags = 0;
4104	if (flags & MOVE_MOUNT_T_SYMLINKS) lflags |= LOOKUP_FOLLOW;
4105	if (flags & MOVE_MOUNT_T_AUTOMOUNTS) lflags |= LOOKUP_AUTOMOUNT;
4106	if (flags & MOVE_MOUNT_T_EMPTY_PATH) lflags |= LOOKUP_EMPTY;
4107
4108	ret = user_path_at(dfd: to_dfd, name: to_pathname, flags: lflags, path: &to_path);
4109	if (ret < 0)
4110	goto out_from;
4111
4112	ret = security_move_mount(from_path: &from_path, to_path: &to_path);
4113	if (ret < 0)
4114	goto out_to;
4115
4116	if (flags & MOVE_MOUNT_SET_GROUP)
4117	ret = do_set_group(from_path: &from_path, to_path: &to_path);
4118	else
4119	ret = do_move_mount(old_path: &from_path, new_path: &to_path,
4120	beneath: (flags & MOVE_MOUNT_BENEATH));
4121
4122	out_to:
4123	path_put(&to_path);
4124	out_from:
4125	path_put(&from_path);
4126	return ret;
4127	}
4128
4129	/*
4130	* Return true if path is reachable from root
4131	*
4132	* namespace_sem or mount_lock is held
4133	*/
4134	bool is_path_reachable(struct mount *mnt, struct dentry *dentry,
4135	const struct path *root)
4136	{
4137	while (&mnt->mnt != root->mnt && mnt_has_parent(mnt)) {
4138	dentry = mnt->mnt_mountpoint;
4139	mnt = mnt->mnt_parent;
4140	}
4141	return &mnt->mnt == root->mnt && is_subdir(dentry, root->dentry);
4142	}
4143
4144	bool path_is_under(const struct path *path1, const struct path *path2)
4145	{
4146	bool res;
4147	read_seqlock_excl(sl: &mount_lock);
4148	res = is_path_reachable(mnt: real_mount(mnt: path1->mnt), dentry: path1->dentry, root: path2);
4149	read_sequnlock_excl(sl: &mount_lock);
4150	return res;
4151	}
4152	EXPORT_SYMBOL(path_is_under);
4153
4154	/*
4155	* pivot_root Semantics:
4156	* Moves the root file system of the current process to the directory put_old,
4157	* makes new_root as the new root file system of the current process, and sets
4158	* root/cwd of all processes which had them on the current root to new_root.
4159	*
4160	* Restrictions:
4161	* The new_root and put_old must be directories, and must not be on the
4162	* same file system as the current process root. The put_old must be
4163	* underneath new_root, i.e. adding a non-zero number of /.. to the string
4164	* pointed to by put_old must yield the same directory as new_root. No other
4165	* file system may be mounted on put_old. After all, new_root is a mountpoint.
4166	*
4167	* Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem.
4168	* See Documentation/filesystems/ramfs-rootfs-initramfs.rst for alternatives
4169	* in this situation.
4170	*
4171	* Notes:
4172	* - we don't move root/cwd if they are not at the root (reason: if something
4173	* cared enough to change them, it's probably wrong to force them elsewhere)
4174	* - it's okay to pick a root that isn't the root of a file system, e.g.
4175	* /nfs/my_root where /nfs is the mount point. It must be a mountpoint,
4176	* though, so you may need to say mount --bind /nfs/my_root /nfs/my_root
4177	* first.
4178	*/
4179	SYSCALL_DEFINE2(pivot_root, const char __user *, new_root,
4180	const char __user *, put_old)
4181	{
4182	struct path new, old, root;
4183	struct mount *new_mnt, *root_mnt, *old_mnt, *root_parent, *ex_parent;
4184	struct mountpoint *old_mp, *root_mp;
4185	int error;
4186
4187	if (!may_mount())
4188	return -EPERM;
4189
4190	error = user_path_at(AT_FDCWD, name: new_root,
4191	LOOKUP_FOLLOW | LOOKUP_DIRECTORY, path: &new);
4192	if (error)
4193	goto out0;
4194
4195	error = user_path_at(AT_FDCWD, name: put_old,
4196	LOOKUP_FOLLOW | LOOKUP_DIRECTORY, path: &old);
4197	if (error)
4198	goto out1;
4199
4200	error = security_sb_pivotroot(old_path: &old, new_path: &new);
4201	if (error)
4202	goto out2;
4203
4204	get_fs_root(current->fs, root: &root);
4205	old_mp = lock_mount(path: &old);
4206	error = PTR_ERR(ptr: old_mp);
4207	if (IS_ERR(ptr: old_mp))
4208	goto out3;
4209
4210	error = -EINVAL;
4211	new_mnt = real_mount(mnt: new.mnt);
4212	root_mnt = real_mount(mnt: root.mnt);
4213	old_mnt = real_mount(mnt: old.mnt);
4214	ex_parent = new_mnt->mnt_parent;
4215	root_parent = root_mnt->mnt_parent;
4216	if (IS_MNT_SHARED(old_mnt) ||
4217	IS_MNT_SHARED(ex_parent) ||
4218	IS_MNT_SHARED(root_parent))
4219	goto out4;
4220	if (!check_mnt(mnt: root_mnt) || !check_mnt(mnt: new_mnt))
4221	goto out4;
4222	if (new_mnt->mnt.mnt_flags & MNT_LOCKED)
4223	goto out4;
4224	error = -ENOENT;
4225	if (d_unlinked(dentry: new.dentry))
4226	goto out4;
4227	error = -EBUSY;
4228	if (new_mnt == root_mnt || old_mnt == root_mnt)
4229	goto out4; /* loop, on the same file system */
4230	error = -EINVAL;
4231	if (!path_mounted(path: &root))
4232	goto out4; /* not a mountpoint */
4233	if (!mnt_has_parent(mnt: root_mnt))
4234	goto out4; /* not attached */
4235	if (!path_mounted(path: &new))
4236	goto out4; /* not a mountpoint */
4237	if (!mnt_has_parent(mnt: new_mnt))
4238	goto out4; /* not attached */
4239	/* make sure we can reach put_old from new_root */
4240	if (!is_path_reachable(mnt: old_mnt, dentry: old.dentry, root: &new))
4241	goto out4;
4242	/* make certain new is below the root */
4243	if (!is_path_reachable(mnt: new_mnt, dentry: new.dentry, root: &root))
4244	goto out4;
4245	lock_mount_hash();
4246	umount_mnt(mnt: new_mnt);
4247	root_mp = unhash_mnt(mnt: root_mnt); /* we'll need its mountpoint */
4248	if (root_mnt->mnt.mnt_flags & MNT_LOCKED) {
4249	new_mnt->mnt.mnt_flags |= MNT_LOCKED;
4250	root_mnt->mnt.mnt_flags &= ~MNT_LOCKED;
4251	}
4252	/* mount old root on put_old */
4253	attach_mnt(mnt: root_mnt, parent: old_mnt, mp: old_mp, beneath: false);
4254	/* mount new_root on / */
4255	attach_mnt(mnt: new_mnt, parent: root_parent, mp: root_mp, beneath: false);
4256	mnt_add_count(mnt: root_parent, n: -1);
4257	touch_mnt_namespace(current->nsproxy->mnt_ns);
4258	/* A moved mount should not expire automatically */
4259	list_del_init(entry: &new_mnt->mnt_expire);
4260	put_mountpoint(mp: root_mp);
4261	unlock_mount_hash();
4262	chroot_fs_refs(&root, &new);
4263	error = 0;
4264	out4:
4265	unlock_mount(where: old_mp);
4266	if (!error)
4267	mntput_no_expire(mnt: ex_parent);
4268	out3:
4269	path_put(&root);
4270	out2:
4271	path_put(&old);
4272	out1:
4273	path_put(&new);
4274	out0:
4275	return error;
4276	}
4277
4278	static unsigned int recalc_flags(struct mount_kattr *kattr, struct mount *mnt)
4279	{
4280	unsigned int flags = mnt->mnt.mnt_flags;
4281
4282	/* flags to clear */
4283	flags &= ~kattr->attr_clr;
4284	/* flags to raise */
4285	flags |= kattr->attr_set;
4286
4287	return flags;
4288	}
4289
4290	static int can_idmap_mount(const struct mount_kattr *kattr, struct mount *mnt)
4291	{
4292	struct vfsmount *m = &mnt->mnt;
4293	struct user_namespace *fs_userns = m->mnt_sb->s_user_ns;
4294
4295	if (!kattr->mnt_idmap)
4296	return 0;
4297
4298	/*
4299	* Creating an idmapped mount with the filesystem wide idmapping
4300	* doesn't make sense so block that. We don't allow mushy semantics.
4301	*/
4302	if (kattr->mnt_userns == m->mnt_sb->s_user_ns)
4303	return -EINVAL;
4304
4305	/*
4306	* Once a mount has been idmapped we don't allow it to change its
4307	* mapping. It makes things simpler and callers can just create
4308	* another bind-mount they can idmap if they want to.
4309	*/
4310	if (is_idmapped_mnt(mnt: m))
4311	return -EPERM;
4312
4313	/* The underlying filesystem doesn't support idmapped mounts yet. */
4314	if (!(m->mnt_sb->s_type->fs_flags & FS_ALLOW_IDMAP))
4315	return -EINVAL;
4316
4317	/* We're not controlling the superblock. */
4318	if (!ns_capable(ns: fs_userns, CAP_SYS_ADMIN))
4319	return -EPERM;
4320
4321	/* Mount has already been visible in the filesystem hierarchy. */
4322	if (!is_anon_ns(ns: mnt->mnt_ns))
4323	return -EINVAL;
4324
4325	return 0;
4326	}
4327
4328	/**
4329	* mnt_allow_writers() - check whether the attribute change allows writers
4330	* @kattr: the new mount attributes
4331	* @mnt: the mount to which @kattr will be applied
4332	*
4333	* Check whether thew new mount attributes in @kattr allow concurrent writers.
4334	*
4335	* Return: true if writers need to be held, false if not
4336	*/
4337	static inline bool mnt_allow_writers(const struct mount_kattr *kattr,
4338	const struct mount *mnt)
4339	{
4340	return (!(kattr->attr_set & MNT_READONLY) ||
4341	(mnt->mnt.mnt_flags & MNT_READONLY)) &&
4342	!kattr->mnt_idmap;
4343	}
4344
4345	static int mount_setattr_prepare(struct mount_kattr *kattr, struct mount *mnt)
4346	{
4347	struct mount *m;
4348	int err;
4349
4350	for (m = mnt; m; m = next_mnt(p: m, root: mnt)) {
4351	if (!can_change_locked_flags(mnt: m, mnt_flags: recalc_flags(kattr, mnt: m))) {
4352	err = -EPERM;
4353	break;
4354	}
4355
4356	err = can_idmap_mount(kattr, mnt: m);
4357	if (err)
4358	break;
4359
4360	if (!mnt_allow_writers(kattr, mnt: m)) {
4361	err = mnt_hold_writers(mnt: m);
4362	if (err)
4363	break;
4364	}
4365
4366	if (!kattr->recurse)
4367	return 0;
4368	}
4369
4370	if (err) {
4371	struct mount *p;
4372
4373	/*
4374	* If we had to call mnt_hold_writers() MNT_WRITE_HOLD will
4375	* be set in @mnt_flags. The loop unsets MNT_WRITE_HOLD for all
4376	* mounts and needs to take care to include the first mount.
4377	*/
4378	for (p = mnt; p; p = next_mnt(p, root: mnt)) {
4379	/* If we had to hold writers unblock them. */
4380	if (p->mnt.mnt_flags & MNT_WRITE_HOLD)
4381	mnt_unhold_writers(mnt: p);
4382
4383	/*
4384	* We're done once the first mount we changed got
4385	* MNT_WRITE_HOLD unset.
4386	*/
4387	if (p == m)
4388	break;
4389	}
4390	}
4391	return err;
4392	}
4393
4394	static void do_idmap_mount(const struct mount_kattr *kattr, struct mount *mnt)
4395	{
4396	if (!kattr->mnt_idmap)
4397	return;
4398
4399	/*
4400	* Pairs with smp_load_acquire() in mnt_idmap().
4401	*
4402	* Since we only allow a mount to change the idmapping once and
4403	* verified this in can_idmap_mount() we know that the mount has
4404	* @nop_mnt_idmap attached to it. So there's no need to drop any
4405	* references.
4406	*/
4407	smp_store_release(&mnt->mnt.mnt_idmap, mnt_idmap_get(kattr->mnt_idmap));
4408	}
4409
4410	static void mount_setattr_commit(struct mount_kattr *kattr, struct mount *mnt)
4411	{
4412	struct mount *m;
4413
4414	for (m = mnt; m; m = next_mnt(p: m, root: mnt)) {
4415	unsigned int flags;
4416
4417	do_idmap_mount(kattr, mnt: m);
4418	flags = recalc_flags(kattr, mnt: m);
4419	WRITE_ONCE(m->mnt.mnt_flags, flags);
4420
4421	/* If we had to hold writers unblock them. */
4422	if (m->mnt.mnt_flags & MNT_WRITE_HOLD)
4423	mnt_unhold_writers(mnt: m);
4424
4425	if (kattr->propagation)
4426	change_mnt_propagation(m, kattr->propagation);
4427	if (!kattr->recurse)
4428	break;
4429	}
4430	touch_mnt_namespace(ns: mnt->mnt_ns);
4431	}
4432
4433	static int do_mount_setattr(struct path *path, struct mount_kattr *kattr)
4434	{
4435	struct mount *mnt = real_mount(mnt: path->mnt);
4436	int err = 0;
4437
4438	if (!path_mounted(path))
4439	return -EINVAL;
4440
4441	if (kattr->mnt_userns) {
4442	struct mnt_idmap *mnt_idmap;
4443
4444	mnt_idmap = alloc_mnt_idmap(mnt_userns: kattr->mnt_userns);
4445	if (IS_ERR(ptr: mnt_idmap))
4446	return PTR_ERR(ptr: mnt_idmap);
4447	kattr->mnt_idmap = mnt_idmap;
4448	}
4449
4450	if (kattr->propagation) {
4451	/*
4452	* Only take namespace_lock() if we're actually changing
4453	* propagation.
4454	*/
4455	namespace_lock();
4456	if (kattr->propagation == MS_SHARED) {
4457	err = invent_group_ids(mnt, recurse: kattr->recurse);
4458	if (err) {
4459	namespace_unlock();
4460	return err;
4461	}
4462	}
4463	}
4464
4465	err = -EINVAL;
4466	lock_mount_hash();
4467
4468	/* Ensure that this isn't anything purely vfs internal. */
4469	if (!is_mounted(mnt: &mnt->mnt))
4470	goto out;
4471
4472	/*
4473	* If this is an attached mount make sure it's located in the callers
4474	* mount namespace. If it's not don't let the caller interact with it.
4475	*
4476	* If this mount doesn't have a parent it's most often simply a
4477	* detached mount with an anonymous mount namespace. IOW, something
4478	* that's simply not attached yet. But there are apparently also users
4479	* that do change mount properties on the rootfs itself. That obviously
4480	* neither has a parent nor is it a detached mount so we cannot
4481	* unconditionally check for detached mounts.
4482	*/
4483	if ((mnt_has_parent(mnt) || !is_anon_ns(ns: mnt->mnt_ns)) && !check_mnt(mnt))
4484	goto out;
4485
4486	/*
4487	* First, we get the mount tree in a shape where we can change mount
4488	* properties without failure. If we succeeded to do so we commit all
4489	* changes and if we failed we clean up.
4490	*/
4491	err = mount_setattr_prepare(kattr, mnt);
4492	if (!err)
4493	mount_setattr_commit(kattr, mnt);
4494
4495	out:
4496	unlock_mount_hash();
4497
4498	if (kattr->propagation) {
4499	if (err)
4500	cleanup_group_ids(mnt, NULL);
4501	namespace_unlock();
4502	}
4503
4504	return err;
4505	}
4506
4507	static int build_mount_idmapped(const struct mount_attr *attr, size_t usize,
4508	struct mount_kattr *kattr, unsigned int flags)
4509	{
4510	int err = 0;
4511	struct ns_common *ns;
4512	struct user_namespace *mnt_userns;
4513	struct fd f;
4514
4515	if (!((attr->attr_set | attr->attr_clr) & MOUNT_ATTR_IDMAP))
4516	return 0;
4517
4518	/*
4519	* We currently do not support clearing an idmapped mount. If this ever
4520	* is a use-case we can revisit this but for now let's keep it simple
4521	* and not allow it.
4522	*/
4523	if (attr->attr_clr & MOUNT_ATTR_IDMAP)
4524	return -EINVAL;
4525
4526	if (attr->userns_fd > INT_MAX)
4527	return -EINVAL;
4528
4529	f = fdget(fd: attr->userns_fd);
4530	if (!f.file)
4531	return -EBADF;
4532
4533	if (!proc_ns_file(file: f.file)) {
4534	err = -EINVAL;
4535	goto out_fput;
4536	}
4537
4538	ns = get_proc_ns(file_inode(f.file));
4539	if (ns->ops->type != CLONE_NEWUSER) {
4540	err = -EINVAL;
4541	goto out_fput;
4542	}
4543
4544	/*
4545	* The initial idmapping cannot be used to create an idmapped
4546	* mount. We use the initial idmapping as an indicator of a mount
4547	* that is not idmapped. It can simply be passed into helpers that
4548	* are aware of idmapped mounts as a convenient shortcut. A user
4549	* can just create a dedicated identity mapping to achieve the same
4550	* result.
4551	*/
4552	mnt_userns = container_of(ns, struct user_namespace, ns);
4553	if (mnt_userns == &init_user_ns) {
4554	err = -EPERM;
4555	goto out_fput;
4556	}
4557
4558	/* We're not controlling the target namespace. */
4559	if (!ns_capable(ns: mnt_userns, CAP_SYS_ADMIN)) {
4560	err = -EPERM;
4561	goto out_fput;
4562	}
4563
4564	kattr->mnt_userns = get_user_ns(ns: mnt_userns);
4565
4566	out_fput:
4567	fdput(fd: f);
4568	return err;
4569	}
4570
4571	static int build_mount_kattr(const struct mount_attr *attr, size_t usize,
4572	struct mount_kattr *kattr, unsigned int flags)
4573	{
4574	unsigned int lookup_flags = LOOKUP_AUTOMOUNT | LOOKUP_FOLLOW;
4575
4576	if (flags & AT_NO_AUTOMOUNT)
4577	lookup_flags &= ~LOOKUP_AUTOMOUNT;
4578	if (flags & AT_SYMLINK_NOFOLLOW)
4579	lookup_flags &= ~LOOKUP_FOLLOW;
4580	if (flags & AT_EMPTY_PATH)
4581	lookup_flags |= LOOKUP_EMPTY;
4582
4583	*kattr = (struct mount_kattr) {
4584	.lookup_flags = lookup_flags,
4585	.recurse = !!(flags & AT_RECURSIVE),
4586	};
4587
4588	if (attr->propagation & ~MOUNT_SETATTR_PROPAGATION_FLAGS)
4589	return -EINVAL;
4590	if (hweight32(attr->propagation & MOUNT_SETATTR_PROPAGATION_FLAGS) > 1)
4591	return -EINVAL;
4592	kattr->propagation = attr->propagation;
4593
4594	if ((attr->attr_set | attr->attr_clr) & ~MOUNT_SETATTR_VALID_FLAGS)
4595	return -EINVAL;
4596
4597	kattr->attr_set = attr_flags_to_mnt_flags(attr_flags: attr->attr_set);
4598	kattr->attr_clr = attr_flags_to_mnt_flags(attr_flags: attr->attr_clr);
4599
4600	/*
4601	* Since the MOUNT_ATTR_<atime> values are an enum, not a bitmap,
4602	* users wanting to transition to a different atime setting cannot
4603	* simply specify the atime setting in @attr_set, but must also
4604	* specify MOUNT_ATTR__ATIME in the @attr_clr field.
4605	* So ensure that MOUNT_ATTR__ATIME can't be partially set in
4606	* @attr_clr and that @attr_set can't have any atime bits set if
4607	* MOUNT_ATTR__ATIME isn't set in @attr_clr.
4608	*/
4609	if (attr->attr_clr & MOUNT_ATTR__ATIME) {
4610	if ((attr->attr_clr & MOUNT_ATTR__ATIME) != MOUNT_ATTR__ATIME)
4611	return -EINVAL;
4612
4613	/*
4614	* Clear all previous time settings as they are mutually
4615	* exclusive.
4616	*/
4617	kattr->attr_clr |= MNT_RELATIME | MNT_NOATIME;
4618	switch (attr->attr_set & MOUNT_ATTR__ATIME) {
4619	case MOUNT_ATTR_RELATIME:
4620	kattr->attr_set |= MNT_RELATIME;
4621	break;
4622	case MOUNT_ATTR_NOATIME:
4623	kattr->attr_set |= MNT_NOATIME;
4624	break;
4625	case MOUNT_ATTR_STRICTATIME:
4626	break;
4627	default:
4628	return -EINVAL;
4629	}
4630	} else {
4631	if (attr->attr_set & MOUNT_ATTR__ATIME)
4632	return -EINVAL;
4633	}
4634
4635	return build_mount_idmapped(attr, usize, kattr, flags);
4636	}
4637
4638	static void finish_mount_kattr(struct mount_kattr *kattr)
4639	{
4640	put_user_ns(ns: kattr->mnt_userns);
4641	kattr->mnt_userns = NULL;
4642
4643	if (kattr->mnt_idmap)
4644	mnt_idmap_put(idmap: kattr->mnt_idmap);
4645	}
4646
4647	SYSCALL_DEFINE5(mount_setattr, int, dfd, const char __user *, path,
4648	unsigned int, flags, struct mount_attr __user *, uattr,
4649	size_t, usize)
4650	{
4651	int err;
4652	struct path target;
4653	struct mount_attr attr;
4654	struct mount_kattr kattr;
4655
4656	BUILD_BUG_ON(sizeof(struct mount_attr) != MOUNT_ATTR_SIZE_VER0);
4657
4658	if (flags & ~(AT_EMPTY_PATH |
4659	AT_RECURSIVE |
4660	AT_SYMLINK_NOFOLLOW |
4661	AT_NO_AUTOMOUNT))
4662	return -EINVAL;
4663
4664	if (unlikely(usize > PAGE_SIZE))
4665	return -E2BIG;
4666	if (unlikely(usize < MOUNT_ATTR_SIZE_VER0))
4667	return -EINVAL;
4668
4669	if (!may_mount())
4670	return -EPERM;
4671
4672	err = copy_struct_from_user(dst: &attr, ksize: sizeof(attr), src: uattr, usize);
4673	if (err)
4674	return err;
4675
4676	/* Don't bother walking through the mounts if this is a nop. */
4677	if (attr.attr_set == 0 &&
4678	attr.attr_clr == 0 &&
4679	attr.propagation == 0)
4680	return 0;
4681
4682	err = build_mount_kattr(attr: &attr, usize, kattr: &kattr, flags);
4683	if (err)
4684	return err;
4685
4686	err = user_path_at(dfd, name: path, flags: kattr.lookup_flags, path: &target);
4687	if (!err) {
4688	err = do_mount_setattr(path: &target, kattr: &kattr);
4689	path_put(&target);
4690	}
4691	finish_mount_kattr(kattr: &kattr);
4692	return err;
4693	}
4694
4695	int show_path(struct seq_file *m, struct dentry *root)
4696	{
4697	if (root->d_sb->s_op->show_path)
4698	return root->d_sb->s_op->show_path(m, root);
4699
4700	seq_dentry(m, root, " \t\n\\");
4701	return 0;
4702	}
4703
4704	static struct vfsmount *lookup_mnt_in_ns(u64 id, struct mnt_namespace *ns)
4705	{
4706	struct mount *mnt = mnt_find_id_at(ns, mnt_id: id);
4707
4708	if (!mnt || mnt->mnt_id_unique != id)
4709	return NULL;
4710
4711	return &mnt->mnt;
4712	}
4713
4714	struct kstatmount {
4715	struct statmount __user *buf;
4716	size_t bufsize;
4717	struct vfsmount *mnt;
4718	u64 mask;
4719	struct path root;
4720	struct statmount sm;
4721	struct seq_file seq;
4722	};
4723
4724	static u64 mnt_to_attr_flags(struct vfsmount *mnt)
4725	{
4726	unsigned int mnt_flags = READ_ONCE(mnt->mnt_flags);
4727	u64 attr_flags = 0;
4728
4729	if (mnt_flags & MNT_READONLY)
4730	attr_flags |= MOUNT_ATTR_RDONLY;
4731	if (mnt_flags & MNT_NOSUID)
4732	attr_flags |= MOUNT_ATTR_NOSUID;
4733	if (mnt_flags & MNT_NODEV)
4734	attr_flags |= MOUNT_ATTR_NODEV;
4735	if (mnt_flags & MNT_NOEXEC)
4736	attr_flags |= MOUNT_ATTR_NOEXEC;
4737	if (mnt_flags & MNT_NODIRATIME)
4738	attr_flags |= MOUNT_ATTR_NODIRATIME;
4739	if (mnt_flags & MNT_NOSYMFOLLOW)
4740	attr_flags |= MOUNT_ATTR_NOSYMFOLLOW;
4741
4742	if (mnt_flags & MNT_NOATIME)
4743	attr_flags |= MOUNT_ATTR_NOATIME;
4744	else if (mnt_flags & MNT_RELATIME)
4745	attr_flags |= MOUNT_ATTR_RELATIME;
4746	else
4747	attr_flags |= MOUNT_ATTR_STRICTATIME;
4748
4749	if (is_idmapped_mnt(mnt))
4750	attr_flags |= MOUNT_ATTR_IDMAP;
4751
4752	return attr_flags;
4753	}
4754
4755	static u64 mnt_to_propagation_flags(struct mount *m)
4756	{
4757	u64 propagation = 0;
4758
4759	if (IS_MNT_SHARED(m))
4760	propagation |= MS_SHARED;
4761	if (IS_MNT_SLAVE(m))
4762	propagation |= MS_SLAVE;
4763	if (IS_MNT_UNBINDABLE(m))
4764	propagation |= MS_UNBINDABLE;
4765	if (!propagation)
4766	propagation |= MS_PRIVATE;
4767
4768	return propagation;
4769	}
4770
4771	static void statmount_sb_basic(struct kstatmount *s)
4772	{
4773	struct super_block *sb = s->mnt->mnt_sb;
4774
4775	s->sm.mask |= STATMOUNT_SB_BASIC;
4776	s->sm.sb_dev_major = MAJOR(sb->s_dev);
4777	s->sm.sb_dev_minor = MINOR(sb->s_dev);
4778	s->sm.sb_magic = sb->s_magic;
4779	s->sm.sb_flags = sb->s_flags & (SB_RDONLY|SB_SYNCHRONOUS|SB_DIRSYNC|SB_LAZYTIME);
4780	}
4781
4782	static void statmount_mnt_basic(struct kstatmount *s)
4783	{
4784	struct mount *m = real_mount(mnt: s->mnt);
4785
4786	s->sm.mask |= STATMOUNT_MNT_BASIC;
4787	s->sm.mnt_id = m->mnt_id_unique;
4788	s->sm.mnt_parent_id = m->mnt_parent->mnt_id_unique;
4789	s->sm.mnt_id_old = m->mnt_id;
4790	s->sm.mnt_parent_id_old = m->mnt_parent->mnt_id;
4791	s->sm.mnt_attr = mnt_to_attr_flags(mnt: &m->mnt);
4792	s->sm.mnt_propagation = mnt_to_propagation_flags(m);
4793	s->sm.mnt_peer_group = IS_MNT_SHARED(m) ? m->mnt_group_id : 0;
4794	s->sm.mnt_master = IS_MNT_SLAVE(m) ? m->mnt_master->mnt_group_id : 0;
4795	}
4796
4797	static void statmount_propagate_from(struct kstatmount *s)
4798	{
4799	struct mount *m = real_mount(mnt: s->mnt);
4800
4801	s->sm.mask |= STATMOUNT_PROPAGATE_FROM;
4802	if (IS_MNT_SLAVE(m))
4803	s->sm.propagate_from = get_dominating_id(mnt: m, root: &current->fs->root);
4804	}
4805
4806	static int statmount_mnt_root(struct kstatmount *s, struct seq_file *seq)
4807	{
4808	int ret;
4809	size_t start = seq->count;
4810
4811	ret = show_path(m: seq, root: s->mnt->mnt_root);
4812	if (ret)
4813	return ret;
4814
4815	if (unlikely(seq_has_overflowed(seq)))
4816	return -EAGAIN;
4817
4818	/*
4819	* Unescape the result. It would be better if supplied string was not
4820	* escaped in the first place, but that's a pretty invasive change.
4821	*/
4822	seq->buf[seq->count] = '\0';
4823	seq->count = start;
4824	seq_commit(m: seq, num: string_unescape_inplace(buf: seq->buf + start, UNESCAPE_OCTAL));
4825	return 0;
4826	}
4827
4828	static int statmount_mnt_point(struct kstatmount *s, struct seq_file *seq)
4829	{
4830	struct vfsmount *mnt = s->mnt;
4831	struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };
4832	int err;
4833
4834	err = seq_path_root(m: seq, path: &mnt_path, root: &s->root, esc: "");
4835	return err == SEQ_SKIP ? 0 : err;
4836	}
4837
4838	static int statmount_fs_type(struct kstatmount *s, struct seq_file *seq)
4839	{
4840	struct super_block *sb = s->mnt->mnt_sb;
4841
4842	seq_puts(m: seq, s: sb->s_type->name);
4843	return 0;
4844	}
4845
4846	static int statmount_string(struct kstatmount *s, u64 flag)
4847	{
4848	int ret;
4849	size_t kbufsize;
4850	struct seq_file *seq = &s->seq;
4851	struct statmount *sm = &s->sm;
4852
4853	switch (flag) {
4854	case STATMOUNT_FS_TYPE:
4855	sm->fs_type = seq->count;
4856	ret = statmount_fs_type(s, seq);
4857	break;
4858	case STATMOUNT_MNT_ROOT:
4859	sm->mnt_root = seq->count;
4860	ret = statmount_mnt_root(s, seq);
4861	break;
4862	case STATMOUNT_MNT_POINT:
4863	sm->mnt_point = seq->count;
4864	ret = statmount_mnt_point(s, seq);
4865	break;
4866	default:
4867	WARN_ON_ONCE(true);
4868	return -EINVAL;
4869	}
4870
4871	if (unlikely(check_add_overflow(sizeof(*sm), seq->count, &kbufsize)))
4872	return -EOVERFLOW;
4873	if (kbufsize >= s->bufsize)
4874	return -EOVERFLOW;
4875
4876	/* signal a retry */
4877	if (unlikely(seq_has_overflowed(seq)))
4878	return -EAGAIN;
4879
4880	if (ret)
4881	return ret;
4882
4883	seq->buf[seq->count++] = '\0';
4884	sm->mask |= flag;
4885	return 0;
4886	}
4887
4888	static int copy_statmount_to_user(struct kstatmount *s)
4889	{
4890	struct statmount *sm = &s->sm;
4891	struct seq_file *seq = &s->seq;
4892	char __user *str = ((char __user *)s->buf) + sizeof(*sm);
4893	size_t copysize = min_t(size_t, s->bufsize, sizeof(*sm));
4894
4895	if (seq->count && copy_to_user(to: str, from: seq->buf, n: seq->count))
4896	return -EFAULT;
4897
4898	/* Return the number of bytes copied to the buffer */
4899	sm->size = copysize + seq->count;
4900	if (copy_to_user(to: s->buf, from: sm, n: copysize))
4901	return -EFAULT;
4902
4903	return 0;
4904	}
4905
4906	static int do_statmount(struct kstatmount *s)
4907	{
4908	struct mount *m = real_mount(mnt: s->mnt);
4909	int err;
4910
4911	/*
4912	* Don't trigger audit denials. We just want to determine what
4913	* mounts to show users.
4914	*/
4915	if (!is_path_reachable(mnt: m, dentry: m->mnt.mnt_root, root: &s->root) &&
4916	!ns_capable_noaudit(ns: &init_user_ns, CAP_SYS_ADMIN))
4917	return -EPERM;
4918
4919	err = security_sb_statfs(dentry: s->mnt->mnt_root);
4920	if (err)
4921	return err;
4922
4923	if (s->mask & STATMOUNT_SB_BASIC)
4924	statmount_sb_basic(s);
4925
4926	if (s->mask & STATMOUNT_MNT_BASIC)
4927	statmount_mnt_basic(s);
4928
4929	if (s->mask & STATMOUNT_PROPAGATE_FROM)
4930	statmount_propagate_from(s);
4931
4932	if (s->mask & STATMOUNT_FS_TYPE)
4933	err = statmount_string(s, STATMOUNT_FS_TYPE);
4934
4935	if (!err && s->mask & STATMOUNT_MNT_ROOT)
4936	err = statmount_string(s, STATMOUNT_MNT_ROOT);
4937
4938	if (!err && s->mask & STATMOUNT_MNT_POINT)
4939	err = statmount_string(s, STATMOUNT_MNT_POINT);
4940
4941	if (err)
4942	return err;
4943
4944	return 0;
4945	}
4946
4947	static inline bool retry_statmount(const long ret, size_t *seq_size)
4948	{
4949	if (likely(ret != -EAGAIN))
4950	return false;
4951	if (unlikely(check_mul_overflow(*seq_size, 2, seq_size)))
4952	return false;
4953	if (unlikely(*seq_size > MAX_RW_COUNT))
4954	return false;
4955	return true;
4956	}
4957
4958	static int prepare_kstatmount(struct kstatmount *ks, struct mnt_id_req *kreq,
4959	struct statmount __user *buf, size_t bufsize,
4960	size_t seq_size)
4961	{
4962	if (!access_ok(buf, bufsize))
4963	return -EFAULT;
4964
4965	memset(ks, 0, sizeof(*ks));
4966	ks->mask = kreq->param;
4967	ks->buf = buf;
4968	ks->bufsize = bufsize;
4969	ks->seq.size = seq_size;
4970	ks->seq.buf = kvmalloc(size: seq_size, GFP_KERNEL_ACCOUNT);
4971	if (!ks->seq.buf)
4972	return -ENOMEM;
4973	return 0;
4974	}
4975
4976	static int copy_mnt_id_req(const struct mnt_id_req __user *req,
4977	struct mnt_id_req *kreq)
4978	{
4979	int ret;
4980	size_t usize;
4981
4982	BUILD_BUG_ON(sizeof(struct mnt_id_req) != MNT_ID_REQ_SIZE_VER0);
4983
4984	ret = get_user(usize, &req->size);
4985	if (ret)
4986	return -EFAULT;
4987	if (unlikely(usize > PAGE_SIZE))
4988	return -E2BIG;
4989	if (unlikely(usize < MNT_ID_REQ_SIZE_VER0))
4990	return -EINVAL;
4991	memset(kreq, 0, sizeof(*kreq));
4992	ret = copy_struct_from_user(dst: kreq, ksize: sizeof(*kreq), src: req, usize);
4993	if (ret)
4994	return ret;
4995	if (kreq->spare != 0)
4996	return -EINVAL;
4997	return 0;
4998	}
4999
5000	SYSCALL_DEFINE4(statmount, const struct mnt_id_req __user *, req,
5001	struct statmount __user *, buf, size_t, bufsize,
5002	unsigned int, flags)
5003	{
5004	struct vfsmount *mnt;
5005	struct mnt_id_req kreq;
5006	struct kstatmount ks;
5007	/* We currently support retrieval of 3 strings. */
5008	size_t seq_size = 3 * PATH_MAX;
5009	int ret;
5010
5011	if (flags)
5012	return -EINVAL;
5013
5014	ret = copy_mnt_id_req(req, kreq: &kreq);
5015	if (ret)
5016	return ret;
5017
5018	retry:
5019	ret = prepare_kstatmount(ks: &ks, kreq: &kreq, buf, bufsize, seq_size);
5020	if (ret)
5021	return ret;
5022
5023	down_read(sem: &namespace_sem);
5024	mnt = lookup_mnt_in_ns(id: kreq.mnt_id, current->nsproxy->mnt_ns);
5025	if (!mnt) {
5026	up_read(sem: &namespace_sem);
5027	kvfree(addr: ks.seq.buf);
5028	return -ENOENT;
5029	}
5030
5031	ks.mnt = mnt;
5032	get_fs_root(current->fs, root: &ks.root);
5033	ret = do_statmount(s: &ks);
5034	path_put(&ks.root);
5035	up_read(sem: &namespace_sem);
5036
5037	if (!ret)
5038	ret = copy_statmount_to_user(s: &ks);
5039	kvfree(addr: ks.seq.buf);
5040	if (retry_statmount(ret, seq_size: &seq_size))
5041	goto retry;
5042	return ret;
5043	}
5044
5045	static struct mount *listmnt_next(struct mount *curr)
5046	{
5047	return node_to_mount(node: rb_next(&curr->mnt_node));
5048	}
5049
5050	static ssize_t do_listmount(struct mount *first, struct path *orig,
5051	u64 mnt_parent_id, u64 __user *mnt_ids,
5052	size_t nr_mnt_ids, const struct path *root)
5053	{
5054	struct mount *r;
5055	ssize_t ret;
5056
5057	/*
5058	* Don't trigger audit denials. We just want to determine what
5059	* mounts to show users.
5060	*/
5061	if (!is_path_reachable(mnt: real_mount(mnt: orig->mnt), dentry: orig->dentry, root) &&
5062	!ns_capable_noaudit(ns: &init_user_ns, CAP_SYS_ADMIN))
5063	return -EPERM;
5064
5065	ret = security_sb_statfs(dentry: orig->dentry);
5066	if (ret)
5067	return ret;
5068
5069	for (ret = 0, r = first; r && nr_mnt_ids; r = listmnt_next(curr: r)) {
5070	if (r->mnt_id_unique == mnt_parent_id)
5071	continue;
5072	if (!is_path_reachable(mnt: r, dentry: r->mnt.mnt_root, root: orig))
5073	continue;
5074	if (put_user(r->mnt_id_unique, mnt_ids))
5075	return -EFAULT;
5076	mnt_ids++;
5077	nr_mnt_ids--;
5078	ret++;
5079	}
5080	return ret;
5081	}
5082
5083	SYSCALL_DEFINE4(listmount, const struct mnt_id_req __user *, req, u64 __user *,
5084	mnt_ids, size_t, nr_mnt_ids, unsigned int, flags)
5085	{
5086	struct mnt_namespace *ns = current->nsproxy->mnt_ns;
5087	struct mnt_id_req kreq;
5088	struct mount *first;
5089	struct path root, orig;
5090	u64 mnt_parent_id, last_mnt_id;
5091	const size_t maxcount = (size_t)-1 >> 3;
5092	ssize_t ret;
5093
5094	if (flags)
5095	return -EINVAL;
5096
5097	if (unlikely(nr_mnt_ids > maxcount))
5098	return -EFAULT;
5099
5100	if (!access_ok(mnt_ids, nr_mnt_ids * sizeof(*mnt_ids)))
5101	return -EFAULT;
5102
5103	ret = copy_mnt_id_req(req, kreq: &kreq);
5104	if (ret)
5105	return ret;
5106	mnt_parent_id = kreq.mnt_id;
5107	last_mnt_id = kreq.param;
5108
5109	down_read(sem: &namespace_sem);
5110	get_fs_root(current->fs, root: &root);
5111	if (mnt_parent_id == LSMT_ROOT) {
5112	orig = root;
5113	} else {
5114	ret = -ENOENT;
5115	orig.mnt = lookup_mnt_in_ns(id: mnt_parent_id, ns);
5116	if (!orig.mnt)
5117	goto err;
5118	orig.dentry = orig.mnt->mnt_root;
5119	}
5120	if (!last_mnt_id)
5121	first = node_to_mount(node: rb_first(&ns->mounts));
5122	else
5123	first = mnt_find_id_at(ns, mnt_id: last_mnt_id + 1);
5124
5125	ret = do_listmount(first, orig: &orig, mnt_parent_id, mnt_ids, nr_mnt_ids, root: &root);
5126	err:
5127	path_put(&root);
5128	up_read(sem: &namespace_sem);
5129	return ret;
5130	}
5131
5132
5133	static void __init init_mount_tree(void)
5134	{
5135	struct vfsmount *mnt;
5136	struct mount *m;
5137	struct mnt_namespace *ns;
5138	struct path root;
5139
5140	mnt = vfs_kern_mount(&rootfs_fs_type, 0, "rootfs", NULL);
5141	if (IS_ERR(ptr: mnt))
5142	panic(fmt: "Can't create rootfs");
5143
5144	ns = alloc_mnt_ns(user_ns: &init_user_ns, anon: false);
5145	if (IS_ERR(ptr: ns))
5146	panic(fmt: "Can't allocate initial namespace");
5147	m = real_mount(mnt);
5148	ns->root = m;
5149	ns->nr_mounts = 1;
5150	mnt_add_to_ns(ns, mnt: m);
5151	init_task.nsproxy->mnt_ns = ns;
5152	get_mnt_ns(ns);
5153
5154	root.mnt = mnt;
5155	root.dentry = mnt->mnt_root;
5156	mnt->mnt_flags |= MNT_LOCKED;
5157
5158	set_fs_pwd(current->fs, &root);
5159	set_fs_root(current->fs, &root);
5160	}
5161
5162	void __init mnt_init(void)
5163	{
5164	int err;
5165
5166	mnt_cache = kmem_cache_create(name: "mnt_cache", size: sizeof(struct mount),
5167	align: 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, NULL);
5168
5169	mount_hashtable = alloc_large_system_hash(tablename: "Mount-cache",
5170	bucketsize: sizeof(struct hlist_head),
5171	numentries: mhash_entries, scale: 19,
5172	HASH_ZERO,
5173	hash_shift: &m_hash_shift, hash_mask: &m_hash_mask, low_limit: 0, high_limit: 0);
5174	mountpoint_hashtable = alloc_large_system_hash(tablename: "Mountpoint-cache",
5175	bucketsize: sizeof(struct hlist_head),
5176	numentries: mphash_entries, scale: 19,
5177	HASH_ZERO,
5178	hash_shift: &mp_hash_shift, hash_mask: &mp_hash_mask, low_limit: 0, high_limit: 0);
5179
5180	if (!mount_hashtable || !mountpoint_hashtable)
5181	panic(fmt: "Failed to allocate mount hash table\n");
5182
5183	kernfs_init();
5184
5185	err = sysfs_init();
5186	if (err)
5187	printk(KERN_WARNING "%s: sysfs_init error: %d\n",
5188	__func__, err);
5189	fs_kobj = kobject_create_and_add(name: "fs", NULL);
5190	if (!fs_kobj)
5191	printk(KERN_WARNING "%s: kobj create error\n", __func__);
5192	shmem_init();
5193	init_rootfs();
5194	init_mount_tree();
5195	}
5196
5197	void put_mnt_ns(struct mnt_namespace *ns)
5198	{
5199	if (!refcount_dec_and_test(r: &ns->ns.count))
5200	return;
5201	drop_collected_mounts(mnt: &ns->root->mnt);
5202	free_mnt_ns(ns);
5203	}
5204
5205	struct vfsmount *kern_mount(struct file_system_type *type)
5206	{
5207	struct vfsmount *mnt;
5208	mnt = vfs_kern_mount(type, SB_KERNMOUNT, type->name, NULL);
5209	if (!IS_ERR(ptr: mnt)) {
5210	/*
5211	* it is a longterm mount, don't release mnt until
5212	* we unmount before file sys is unregistered
5213	*/
5214	real_mount(mnt)->mnt_ns = MNT_NS_INTERNAL;
5215	}
5216	return mnt;
5217	}
5218	EXPORT_SYMBOL_GPL(kern_mount);
5219
5220	void kern_unmount(struct vfsmount *mnt)
5221	{
5222	/* release long term mount so mount point can be released */
5223	if (!IS_ERR(ptr: mnt)) {
5224	mnt_make_shortterm(mnt);
5225	synchronize_rcu(); /* yecchhh... */
5226	mntput(mnt);
5227	}
5228	}
5229	EXPORT_SYMBOL(kern_unmount);
5230
5231	void kern_unmount_array(struct vfsmount *mnt[], unsigned int num)
5232	{
5233	unsigned int i;
5234
5235	for (i = 0; i < num; i++)
5236	mnt_make_shortterm(mnt: mnt[i]);
5237	synchronize_rcu_expedited();
5238	for (i = 0; i < num; i++)
5239	mntput(mnt[i]);
5240	}
5241	EXPORT_SYMBOL(kern_unmount_array);
5242
5243	bool our_mnt(struct vfsmount *mnt)
5244	{
5245	return check_mnt(mnt: real_mount(mnt));
5246	}
5247
5248	bool current_chrooted(void)
5249	{
5250	/* Does the current process have a non-standard root */
5251	struct path ns_root;
5252	struct path fs_root;
5253	bool chrooted;
5254
5255	/* Find the namespace root */
5256	ns_root.mnt = &current->nsproxy->mnt_ns->root->mnt;
5257	ns_root.dentry = ns_root.mnt->mnt_root;
5258	path_get(&ns_root);
5259	while (d_mountpoint(dentry: ns_root.dentry) && follow_down_one(&ns_root))
5260	;
5261
5262	get_fs_root(current->fs, root: &fs_root);
5263
5264	chrooted = !path_equal(path1: &fs_root, path2: &ns_root);
5265
5266	path_put(&fs_root);
5267	path_put(&ns_root);
5268
5269	return chrooted;
5270	}
5271
5272	static bool mnt_already_visible(struct mnt_namespace *ns,
5273	const struct super_block *sb,
5274	int *new_mnt_flags)
5275	{
5276	int new_flags = *new_mnt_flags;
5277	struct mount *mnt, *n;
5278	bool visible = false;
5279
5280	down_read(sem: &namespace_sem);
5281	rbtree_postorder_for_each_entry_safe(mnt, n, &ns->mounts, mnt_node) {
5282	struct mount *child;
5283	int mnt_flags;
5284
5285	if (mnt->mnt.mnt_sb->s_type != sb->s_type)
5286	continue;
5287
5288	/* This mount is not fully visible if it's root directory
5289	* is not the root directory of the filesystem.
5290	*/
5291	if (mnt->mnt.mnt_root != mnt->mnt.mnt_sb->s_root)
5292	continue;
5293
5294	/* A local view of the mount flags */
5295	mnt_flags = mnt->mnt.mnt_flags;
5296
5297	/* Don't miss readonly hidden in the superblock flags */
5298	if (sb_rdonly(sb: mnt->mnt.mnt_sb))
5299	mnt_flags |= MNT_LOCK_READONLY;
5300
5301	/* Verify the mount flags are equal to or more permissive
5302	* than the proposed new mount.
5303	*/
5304	if ((mnt_flags & MNT_LOCK_READONLY) &&
5305	!(new_flags & MNT_READONLY))
5306	continue;
5307	if ((mnt_flags & MNT_LOCK_ATIME) &&
5308	((mnt_flags & MNT_ATIME_MASK) != (new_flags & MNT_ATIME_MASK)))
5309	continue;
5310
5311	/* This mount is not fully visible if there are any
5312	* locked child mounts that cover anything except for
5313	* empty directories.
5314	*/
5315	list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) {
5316	struct inode *inode = child->mnt_mountpoint->d_inode;
5317	/* Only worry about locked mounts */
5318	if (!(child->mnt.mnt_flags & MNT_LOCKED))
5319	continue;
5320	/* Is the directory permanetly empty? */
5321	if (!is_empty_dir_inode(inode))
5322	goto next;
5323	}
5324	/* Preserve the locked attributes */
5325	*new_mnt_flags |= mnt_flags & (MNT_LOCK_READONLY | \
5326	MNT_LOCK_ATIME);
5327	visible = true;
5328	goto found;
5329	next: ;
5330	}
5331	found:
5332	up_read(sem: &namespace_sem);
5333	return visible;
5334	}
5335
5336	static bool mount_too_revealing(const struct super_block *sb, int *new_mnt_flags)
5337	{
5338	const unsigned long required_iflags = SB_I_NOEXEC | SB_I_NODEV;
5339	struct mnt_namespace *ns = current->nsproxy->mnt_ns;
5340	unsigned long s_iflags;
5341
5342	if (ns->user_ns == &init_user_ns)
5343	return false;
5344
5345	/* Can this filesystem be too revealing? */
5346	s_iflags = sb->s_iflags;
5347	if (!(s_iflags & SB_I_USERNS_VISIBLE))
5348	return false;
5349
5350	if ((s_iflags & required_iflags) != required_iflags) {
5351	WARN_ONCE(1, "Expected s_iflags to contain 0x%lx\n",
5352	required_iflags);
5353	return true;
5354	}
5355
5356	return !mnt_already_visible(ns, sb, new_mnt_flags);
5357	}
5358
5359	bool mnt_may_suid(struct vfsmount *mnt)
5360	{
5361	/*
5362	* Foreign mounts (accessed via fchdir or through /proc
5363	* symlinks) are always treated as if they are nosuid. This
5364	* prevents namespaces from trusting potentially unsafe
5365	* suid/sgid bits, file caps, or security labels that originate
5366	* in other namespaces.
5367	*/
5368	return !(mnt->mnt_flags & MNT_NOSUID) && check_mnt(mnt: real_mount(mnt)) &&
5369	current_in_userns(target_ns: mnt->mnt_sb->s_user_ns);
5370	}
5371
5372	static struct ns_common *mntns_get(struct task_struct *task)
5373	{
5374	struct ns_common *ns = NULL;
5375	struct nsproxy *nsproxy;
5376
5377	task_lock(p: task);
5378	nsproxy = task->nsproxy;
5379	if (nsproxy) {
5380	ns = &nsproxy->mnt_ns->ns;
5381	get_mnt_ns(ns: to_mnt_ns(ns));
5382	}
5383	task_unlock(p: task);
5384
5385	return ns;
5386	}
5387
5388	static void mntns_put(struct ns_common *ns)
5389	{
5390	put_mnt_ns(ns: to_mnt_ns(ns));
5391	}
5392
5393	static int mntns_install(struct nsset *nsset, struct ns_common *ns)
5394	{
5395	struct nsproxy *nsproxy = nsset->nsproxy;
5396	struct fs_struct *fs = nsset->fs;
5397	struct mnt_namespace *mnt_ns = to_mnt_ns(ns), *old_mnt_ns;
5398	struct user_namespace *user_ns = nsset->cred->user_ns;
5399	struct path root;
5400	int err;
5401
5402	if (!ns_capable(ns: mnt_ns->user_ns, CAP_SYS_ADMIN) ||
5403	!ns_capable(ns: user_ns, CAP_SYS_CHROOT) ||
5404	!ns_capable(ns: user_ns, CAP_SYS_ADMIN))
5405	return -EPERM;
5406
5407	if (is_anon_ns(ns: mnt_ns))
5408	return -EINVAL;
5409
5410	if (fs->users != 1)
5411	return -EINVAL;
5412
5413	get_mnt_ns(ns: mnt_ns);
5414	old_mnt_ns = nsproxy->mnt_ns;
5415	nsproxy->mnt_ns = mnt_ns;
5416
5417	/* Find the root */
5418	err = vfs_path_lookup(mnt_ns->root->mnt.mnt_root, &mnt_ns->root->mnt,
5419	"/", LOOKUP_DOWN, &root);
5420	if (err) {
5421	/* revert to old namespace */
5422	nsproxy->mnt_ns = old_mnt_ns;
5423	put_mnt_ns(ns: mnt_ns);
5424	return err;
5425	}
5426
5427	put_mnt_ns(ns: old_mnt_ns);
5428
5429	/* Update the pwd and root */
5430	set_fs_pwd(fs, &root);
5431	set_fs_root(fs, &root);
5432
5433	path_put(&root);
5434	return 0;
5435	}
5436
5437	static struct user_namespace *mntns_owner(struct ns_common *ns)
5438	{
5439	return to_mnt_ns(ns)->user_ns;
5440	}
5441
5442	const struct proc_ns_operations mntns_operations = {
5443	.name = "mnt",
5444	.type = CLONE_NEWNS,
5445	.get = mntns_get,
5446	.put = mntns_put,
5447	.install = mntns_install,
5448	.owner = mntns_owner,
5449	};
5450
5451	#ifdef CONFIG_SYSCTL
5452	static struct ctl_table fs_namespace_sysctls[] = {
5453	{
5454	.procname = "mount-max",
5455	.data = &sysctl_mount_max,
5456	.maxlen = sizeof(unsigned int),
5457	.mode = 0644,
5458	.proc_handler = proc_dointvec_minmax,
5459	.extra1 = SYSCTL_ONE,
5460	},
5461	};
5462
5463	static int __init init_fs_namespace_sysctls(void)
5464	{
5465	register_sysctl_init("fs", fs_namespace_sysctls);
5466	return 0;
5467	}
5468	fs_initcall(init_fs_namespace_sysctls);
5469
5470	#endif /* CONFIG_SYSCTL */
5471