1/*
2 * linux/kernel/fork.c
3 *
4 * Copyright (C) 1991, 1992 Linus Torvalds
5 */
6
7/*
8 * 'fork.c' contains the help-routines for the 'fork' system call
9 * (see also entry.S and others).
10 * Fork is rather simple, once you get the hang of it, but the memory
11 * management can be a bitch. See 'mm/memory.c': 'copy_page_range()'
12 */
13
14#include <linux/slab.h>
15#include <linux/init.h>
16#include <linux/unistd.h>
17#include <linux/module.h>
18#include <linux/vmalloc.h>
19#include <linux/completion.h>
20#include <linux/personality.h>
21#include <linux/mempolicy.h>
22#include <linux/sem.h>
23#include <linux/file.h>
24#include <linux/fdtable.h>
25#include <linux/iocontext.h>
26#include <linux/key.h>
27#include <linux/binfmts.h>
28#include <linux/mman.h>
29#include <linux/mmu_notifier.h>
30#include <linux/fs.h>
31#include <linux/mm.h>
32#include <linux/vmacache.h>
33#include <linux/nsproxy.h>
34#include <linux/capability.h>
35#include <linux/cpu.h>
36#include <linux/cgroup.h>
37#include <linux/security.h>
38#include <linux/hugetlb.h>
39#include <linux/seccomp.h>
40#include <linux/swap.h>
41#include <linux/syscalls.h>
42#include <linux/jiffies.h>
43#include <linux/futex.h>
44#include <linux/compat.h>
45#include <linux/kthread.h>
46#include <linux/task_io_accounting_ops.h>
47#include <linux/rcupdate.h>
48#include <linux/ptrace.h>
49#include <linux/mount.h>
50#include <linux/audit.h>
51#include <linux/memcontrol.h>
52#include <linux/ftrace.h>
53#include <linux/proc_fs.h>
54#include <linux/profile.h>
55#include <linux/rmap.h>
56#include <linux/ksm.h>
57#include <linux/acct.h>
58#include <linux/tsacct_kern.h>
59#include <linux/cn_proc.h>
60#include <linux/freezer.h>
61#include <linux/delayacct.h>
62#include <linux/taskstats_kern.h>
63#include <linux/random.h>
64#include <linux/tty.h>
65#include <linux/blkdev.h>
66#include <linux/fs_struct.h>
67#include <linux/magic.h>
68#include <linux/perf_event.h>
69#include <linux/posix-timers.h>
70#include <linux/user-return-notifier.h>
71#include <linux/oom.h>
72#include <linux/khugepaged.h>
73#include <linux/signalfd.h>
74#include <linux/uprobes.h>
75#include <linux/aio.h>
76#include <linux/compiler.h>
77#include <linux/sysctl.h>
78#include <linux/kcov.h>
79
80#include <asm/pgtable.h>
81#include <asm/pgalloc.h>
82#include <linux/uaccess.h>
83#include <asm/mmu_context.h>
84#include <asm/cacheflush.h>
85#include <asm/tlbflush.h>
86
87#include <trace/events/sched.h>
88
89#define CREATE_TRACE_POINTS
90#include <trace/events/task.h>
91
92/*
93 * Minimum number of threads to boot the kernel
94 */
95#define MIN_THREADS 20
96
97/*
98 * Maximum number of threads
99 */
100#define MAX_THREADS FUTEX_TID_MASK
101
102/*
103 * Protected counters by write_lock_irq(&tasklist_lock)
104 */
105unsigned long total_forks; /* Handle normal Linux uptimes. */
106int nr_threads; /* The idle threads do not count.. */
107
108int max_threads; /* tunable limit on nr_threads */
109
110DEFINE_PER_CPU(unsigned long, process_counts) = 0;
111
112__cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */
113
114#ifdef CONFIG_PROVE_RCU
115int lockdep_tasklist_lock_is_held(void)
116{
117 return lockdep_is_held(&tasklist_lock);
118}
119EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
120#endif /* #ifdef CONFIG_PROVE_RCU */
121
122int nr_processes(void)
123{
124 int cpu;
125 int total = 0;
126
127 for_each_possible_cpu(cpu)
128 total += per_cpu(process_counts, cpu);
129
130 return total;
131}
132
133void __weak arch_release_task_struct(struct task_struct *tsk)
134{
135}
136
137#ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
138static struct kmem_cache *task_struct_cachep;
139
140static inline struct task_struct *alloc_task_struct_node(int node)
141{
142 return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node);
143}
144
145static inline void free_task_struct(struct task_struct *tsk)
146{
147 kmem_cache_free(task_struct_cachep, tsk);
148}
149#endif
150
151void __weak arch_release_thread_stack(unsigned long *stack)
152{
153}
154
155#ifndef CONFIG_ARCH_THREAD_STACK_ALLOCATOR
156
157/*
158 * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
159 * kmemcache based allocator.
160 */
161# if THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK)
162
163#ifdef CONFIG_VMAP_STACK
164/*
165 * vmalloc() is a bit slow, and calling vfree() enough times will force a TLB
166 * flush. Try to minimize the number of calls by caching stacks.
167 */
168#define NR_CACHED_STACKS 2
169static DEFINE_PER_CPU(struct vm_struct *, cached_stacks[NR_CACHED_STACKS]);
170#endif
171
172static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node)
173{
174#ifdef CONFIG_VMAP_STACK
175 void *stack;
176 int i;
177
178 local_irq_disable();
179 for (i = 0; i < NR_CACHED_STACKS; i++) {
180 struct vm_struct *s = this_cpu_read(cached_stacks[i]);
181
182 if (!s)
183 continue;
184 this_cpu_write(cached_stacks[i], NULL);
185
186 tsk->stack_vm_area = s;
187 local_irq_enable();
188 return s->addr;
189 }
190 local_irq_enable();
191
192 stack = __vmalloc_node_range(THREAD_SIZE, THREAD_SIZE,
193 VMALLOC_START, VMALLOC_END,
194 THREADINFO_GFP | __GFP_HIGHMEM,
195 PAGE_KERNEL,
196 0, node, __builtin_return_address(0));
197
198 /*
199 * We can't call find_vm_area() in interrupt context, and
200 * free_thread_stack() can be called in interrupt context,
201 * so cache the vm_struct.
202 */
203 if (stack)
204 tsk->stack_vm_area = find_vm_area(stack);
205 return stack;
206#else
207 struct page *page = alloc_pages_node(node, THREADINFO_GFP,
208 THREAD_SIZE_ORDER);
209
210 return page ? page_address(page) : NULL;
211#endif
212}
213
214static inline void free_thread_stack(struct task_struct *tsk)
215{
216#ifdef CONFIG_VMAP_STACK
217 if (task_stack_vm_area(tsk)) {
218 unsigned long flags;
219 int i;
220
221 local_irq_save(flags);
222 for (i = 0; i < NR_CACHED_STACKS; i++) {
223 if (this_cpu_read(cached_stacks[i]))
224 continue;
225
226 this_cpu_write(cached_stacks[i], tsk->stack_vm_area);
227 local_irq_restore(flags);
228 return;
229 }
230 local_irq_restore(flags);
231
232 vfree_atomic(tsk->stack);
233 return;
234 }
235#endif
236
237 __free_pages(virt_to_page(tsk->stack), THREAD_SIZE_ORDER);
238}
239# else
240static struct kmem_cache *thread_stack_cache;
241
242static unsigned long *alloc_thread_stack_node(struct task_struct *tsk,
243 int node)
244{
245 return kmem_cache_alloc_node(thread_stack_cache, THREADINFO_GFP, node);
246}
247
248static void free_thread_stack(struct task_struct *tsk)
249{
250 kmem_cache_free(thread_stack_cache, tsk->stack);
251}
252
253void thread_stack_cache_init(void)
254{
255 thread_stack_cache = kmem_cache_create("thread_stack", THREAD_SIZE,
256 THREAD_SIZE, 0, NULL);
257 BUG_ON(thread_stack_cache == NULL);
258}
259# endif
260#endif
261
262/* SLAB cache for signal_struct structures (tsk->signal) */
263static struct kmem_cache *signal_cachep;
264
265/* SLAB cache for sighand_struct structures (tsk->sighand) */
266struct kmem_cache *sighand_cachep;
267
268/* SLAB cache for files_struct structures (tsk->files) */
269struct kmem_cache *files_cachep;
270
271/* SLAB cache for fs_struct structures (tsk->fs) */
272struct kmem_cache *fs_cachep;
273
274/* SLAB cache for vm_area_struct structures */
275struct kmem_cache *vm_area_cachep;
276
277/* SLAB cache for mm_struct structures (tsk->mm) */
278static struct kmem_cache *mm_cachep;
279
280static void account_kernel_stack(struct task_struct *tsk, int account)
281{
282 void *stack = task_stack_page(tsk);
283 struct vm_struct *vm = task_stack_vm_area(tsk);
284
285 BUILD_BUG_ON(IS_ENABLED(CONFIG_VMAP_STACK) && PAGE_SIZE % 1024 != 0);
286
287 if (vm) {
288 int i;
289
290 BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE);
291
292 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
293 mod_zone_page_state(page_zone(vm->pages[i]),
294 NR_KERNEL_STACK_KB,
295 PAGE_SIZE / 1024 * account);
296 }
297
298 /* All stack pages belong to the same memcg. */
299 memcg_kmem_update_page_stat(vm->pages[0], MEMCG_KERNEL_STACK_KB,
300 account * (THREAD_SIZE / 1024));
301 } else {
302 /*
303 * All stack pages are in the same zone and belong to the
304 * same memcg.
305 */
306 struct page *first_page = virt_to_page(stack);
307
308 mod_zone_page_state(page_zone(first_page), NR_KERNEL_STACK_KB,
309 THREAD_SIZE / 1024 * account);
310
311 memcg_kmem_update_page_stat(first_page, MEMCG_KERNEL_STACK_KB,
312 account * (THREAD_SIZE / 1024));
313 }
314}
315
316static void release_task_stack(struct task_struct *tsk)
317{
318 if (WARN_ON(tsk->state != TASK_DEAD))
319 return; /* Better to leak the stack than to free prematurely */
320
321 account_kernel_stack(tsk, -1);
322 arch_release_thread_stack(tsk->stack);
323 free_thread_stack(tsk);
324 tsk->stack = NULL;
325#ifdef CONFIG_VMAP_STACK
326 tsk->stack_vm_area = NULL;
327#endif
328}
329
330#ifdef CONFIG_THREAD_INFO_IN_TASK
331void put_task_stack(struct task_struct *tsk)
332{
333 if (atomic_dec_and_test(&tsk->stack_refcount))
334 release_task_stack(tsk);
335}
336#endif
337
338void free_task(struct task_struct *tsk)
339{
340#ifndef CONFIG_THREAD_INFO_IN_TASK
341 /*
342 * The task is finally done with both the stack and thread_info,
343 * so free both.
344 */
345 release_task_stack(tsk);
346#else
347 /*
348 * If the task had a separate stack allocation, it should be gone
349 * by now.
350 */
351 WARN_ON_ONCE(atomic_read(&tsk->stack_refcount) != 0);
352#endif
353 rt_mutex_debug_task_free(tsk);
354 ftrace_graph_exit_task(tsk);
355 put_seccomp_filter(tsk);
356 arch_release_task_struct(tsk);
357 if (tsk->flags & PF_KTHREAD)
358 free_kthread_struct(tsk);
359 free_task_struct(tsk);
360}
361EXPORT_SYMBOL(free_task);
362
363static inline void free_signal_struct(struct signal_struct *sig)
364{
365 taskstats_tgid_free(sig);
366 sched_autogroup_exit(sig);
367 /*
368 * __mmdrop is not safe to call from softirq context on x86 due to
369 * pgd_dtor so postpone it to the async context
370 */
371 if (sig->oom_mm)
372 mmdrop_async(sig->oom_mm);
373 kmem_cache_free(signal_cachep, sig);
374}
375
376static inline void put_signal_struct(struct signal_struct *sig)
377{
378 if (atomic_dec_and_test(&sig->sigcnt))
379 free_signal_struct(sig);
380}
381
382void __put_task_struct(struct task_struct *tsk)
383{
384 WARN_ON(!tsk->exit_state);
385 WARN_ON(atomic_read(&tsk->usage));
386 WARN_ON(tsk == current);
387
388 cgroup_free(tsk);
389 task_numa_free(tsk);
390 security_task_free(tsk);
391 exit_creds(tsk);
392 delayacct_tsk_free(tsk);
393 put_signal_struct(tsk->signal);
394
395 if (!profile_handoff_task(tsk))
396 free_task(tsk);
397}
398EXPORT_SYMBOL_GPL(__put_task_struct);
399
400void __init __weak arch_task_cache_init(void) { }
401
402/*
403 * set_max_threads
404 */
405static void set_max_threads(unsigned int max_threads_suggested)
406{
407 u64 threads;
408
409 /*
410 * The number of threads shall be limited such that the thread
411 * structures may only consume a small part of the available memory.
412 */
413 if (fls64(totalram_pages) + fls64(PAGE_SIZE) > 64)
414 threads = MAX_THREADS;
415 else
416 threads = div64_u64((u64) totalram_pages * (u64) PAGE_SIZE,
417 (u64) THREAD_SIZE * 8UL);
418
419 if (threads > max_threads_suggested)
420 threads = max_threads_suggested;
421
422 max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS);
423}
424
425#ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT
426/* Initialized by the architecture: */
427int arch_task_struct_size __read_mostly;
428#endif
429
430void __init fork_init(void)
431{
432 int i;
433#ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
434#ifndef ARCH_MIN_TASKALIGN
435#define ARCH_MIN_TASKALIGN L1_CACHE_BYTES
436#endif
437 /* create a slab on which task_structs can be allocated */
438 task_struct_cachep = kmem_cache_create("task_struct",
439 arch_task_struct_size, ARCH_MIN_TASKALIGN,
440 SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, NULL);
441#endif
442
443 /* do the arch specific task caches init */
444 arch_task_cache_init();
445
446 set_max_threads(MAX_THREADS);
447
448 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
449 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
450 init_task.signal->rlim[RLIMIT_SIGPENDING] =
451 init_task.signal->rlim[RLIMIT_NPROC];
452
453 for (i = 0; i < UCOUNT_COUNTS; i++) {
454 init_user_ns.ucount_max[i] = max_threads/2;
455 }
456}
457
458int __weak arch_dup_task_struct(struct task_struct *dst,
459 struct task_struct *src)
460{
461 *dst = *src;
462 return 0;
463}
464
465void set_task_stack_end_magic(struct task_struct *tsk)
466{
467 unsigned long *stackend;
468
469 stackend = end_of_stack(tsk);
470 *stackend = STACK_END_MAGIC; /* for overflow detection */
471}
472
473static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
474{
475 struct task_struct *tsk;
476 unsigned long *stack;
477 struct vm_struct *stack_vm_area;
478 int err;
479
480 if (node == NUMA_NO_NODE)
481 node = tsk_fork_get_node(orig);
482 tsk = alloc_task_struct_node(node);
483 if (!tsk)
484 return NULL;
485
486 stack = alloc_thread_stack_node(tsk, node);
487 if (!stack)
488 goto free_tsk;
489
490 stack_vm_area = task_stack_vm_area(tsk);
491
492 err = arch_dup_task_struct(tsk, orig);
493
494 /*
495 * arch_dup_task_struct() clobbers the stack-related fields. Make
496 * sure they're properly initialized before using any stack-related
497 * functions again.
498 */
499 tsk->stack = stack;
500#ifdef CONFIG_VMAP_STACK
501 tsk->stack_vm_area = stack_vm_area;
502#endif
503#ifdef CONFIG_THREAD_INFO_IN_TASK
504 atomic_set(&tsk->stack_refcount, 1);
505#endif
506
507 if (err)
508 goto free_stack;
509
510#ifdef CONFIG_SECCOMP
511 /*
512 * We must handle setting up seccomp filters once we're under
513 * the sighand lock in case orig has changed between now and
514 * then. Until then, filter must be NULL to avoid messing up
515 * the usage counts on the error path calling free_task.
516 */
517 tsk->seccomp.filter = NULL;
518#endif
519
520 setup_thread_stack(tsk, orig);
521 clear_user_return_notifier(tsk);
522 clear_tsk_need_resched(tsk);
523 set_task_stack_end_magic(tsk);
524
525#ifdef CONFIG_CC_STACKPROTECTOR
526 tsk->stack_canary = get_random_int();
527#endif
528
529 /*
530 * One for us, one for whoever does the "release_task()" (usually
531 * parent)
532 */
533 atomic_set(&tsk->usage, 2);
534#ifdef CONFIG_BLK_DEV_IO_TRACE
535 tsk->btrace_seq = 0;
536#endif
537 tsk->splice_pipe = NULL;
538 tsk->task_frag.page = NULL;
539 tsk->wake_q.next = NULL;
540
541 account_kernel_stack(tsk, 1);
542
543 kcov_task_init(tsk);
544
545 return tsk;
546
547free_stack:
548 free_thread_stack(tsk);
549free_tsk:
550 free_task_struct(tsk);
551 return NULL;
552}
553
554#ifdef CONFIG_MMU
555static __latent_entropy int dup_mmap(struct mm_struct *mm,
556 struct mm_struct *oldmm)
557{
558 struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
559 struct rb_node **rb_link, *rb_parent;
560 int retval;
561 unsigned long charge;
562
563 uprobe_start_dup_mmap();
564 if (down_write_killable(&oldmm->mmap_sem)) {
565 retval = -EINTR;
566 goto fail_uprobe_end;
567 }
568 flush_cache_dup_mm(oldmm);
569 uprobe_dup_mmap(oldmm, mm);
570 /*
571 * Not linked in yet - no deadlock potential:
572 */
573 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
574
575 /* No ordering required: file already has been exposed. */
576 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
577
578 mm->total_vm = oldmm->total_vm;
579 mm->data_vm = oldmm->data_vm;
580 mm->exec_vm = oldmm->exec_vm;
581 mm->stack_vm = oldmm->stack_vm;
582
583 rb_link = &mm->mm_rb.rb_node;
584 rb_parent = NULL;
585 pprev = &mm->mmap;
586 retval = ksm_fork(mm, oldmm);
587 if (retval)
588 goto out;
589 retval = khugepaged_fork(mm, oldmm);
590 if (retval)
591 goto out;
592
593 prev = NULL;
594 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
595 struct file *file;
596
597 if (mpnt->vm_flags & VM_DONTCOPY) {
598 vm_stat_account(mm, mpnt->vm_flags, -vma_pages(mpnt));
599 continue;
600 }
601 charge = 0;
602 if (mpnt->vm_flags & VM_ACCOUNT) {
603 unsigned long len = vma_pages(mpnt);
604
605 if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
606 goto fail_nomem;
607 charge = len;
608 }
609 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
610 if (!tmp)
611 goto fail_nomem;
612 *tmp = *mpnt;
613 INIT_LIST_HEAD(&tmp->anon_vma_chain);
614 retval = vma_dup_policy(mpnt, tmp);
615 if (retval)
616 goto fail_nomem_policy;
617 tmp->vm_mm = mm;
618 if (anon_vma_fork(tmp, mpnt))
619 goto fail_nomem_anon_vma_fork;
620 tmp->vm_flags &=
621 ~(VM_LOCKED|VM_LOCKONFAULT|VM_UFFD_MISSING|VM_UFFD_WP);
622 tmp->vm_next = tmp->vm_prev = NULL;
623 tmp->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
624 file = tmp->vm_file;
625 if (file) {
626 struct inode *inode = file_inode(file);
627 struct address_space *mapping = file->f_mapping;
628
629 get_file(file);
630 if (tmp->vm_flags & VM_DENYWRITE)
631 atomic_dec(&inode->i_writecount);
632 i_mmap_lock_write(mapping);
633 if (tmp->vm_flags & VM_SHARED)
634 atomic_inc(&mapping->i_mmap_writable);
635 flush_dcache_mmap_lock(mapping);
636 /* insert tmp into the share list, just after mpnt */
637 vma_interval_tree_insert_after(tmp, mpnt,
638 &mapping->i_mmap);
639 flush_dcache_mmap_unlock(mapping);
640 i_mmap_unlock_write(mapping);
641 }
642
643 /*
644 * Clear hugetlb-related page reserves for children. This only
645 * affects MAP_PRIVATE mappings. Faults generated by the child
646 * are not guaranteed to succeed, even if read-only
647 */
648 if (is_vm_hugetlb_page(tmp))
649 reset_vma_resv_huge_pages(tmp);
650
651 /*
652 * Link in the new vma and copy the page table entries.
653 */
654 *pprev = tmp;
655 pprev = &tmp->vm_next;
656 tmp->vm_prev = prev;
657 prev = tmp;
658
659 __vma_link_rb(mm, tmp, rb_link, rb_parent);
660 rb_link = &tmp->vm_rb.rb_right;
661 rb_parent = &tmp->vm_rb;
662
663 mm->map_count++;
664 retval = copy_page_range(mm, oldmm, mpnt);
665
666 if (tmp->vm_ops && tmp->vm_ops->open)
667 tmp->vm_ops->open(tmp);
668
669 if (retval)
670 goto out;
671 }
672 /* a new mm has just been created */
673 arch_dup_mmap(oldmm, mm);
674 retval = 0;
675out:
676 up_write(&mm->mmap_sem);
677 flush_tlb_mm(oldmm);
678 up_write(&oldmm->mmap_sem);
679fail_uprobe_end:
680 uprobe_end_dup_mmap();
681 return retval;
682fail_nomem_anon_vma_fork:
683 mpol_put(vma_policy(tmp));
684fail_nomem_policy:
685 kmem_cache_free(vm_area_cachep, tmp);
686fail_nomem:
687 retval = -ENOMEM;
688 vm_unacct_memory(charge);
689 goto out;
690}
691
692static inline int mm_alloc_pgd(struct mm_struct *mm)
693{
694 mm->pgd = pgd_alloc(mm);
695 if (unlikely(!mm->pgd))
696 return -ENOMEM;
697 return 0;
698}
699
700static inline void mm_free_pgd(struct mm_struct *mm)
701{
702 pgd_free(mm, mm->pgd);
703}
704#else
705static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
706{
707 down_write(&oldmm->mmap_sem);
708 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
709 up_write(&oldmm->mmap_sem);
710 return 0;
711}
712#define mm_alloc_pgd(mm) (0)
713#define mm_free_pgd(mm)
714#endif /* CONFIG_MMU */
715
716__cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
717
718#define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
719#define free_mm(mm) (kmem_cache_free(mm_cachep, (mm)))
720
721static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
722
723static int __init coredump_filter_setup(char *s)
724{
725 default_dump_filter =
726 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
727 MMF_DUMP_FILTER_MASK;
728 return 1;
729}
730
731__setup("coredump_filter=", coredump_filter_setup);
732
733#include <linux/init_task.h>
734
735static void mm_init_aio(struct mm_struct *mm)
736{
737#ifdef CONFIG_AIO
738 spin_lock_init(&mm->ioctx_lock);
739 mm->ioctx_table = NULL;
740#endif
741}
742
743static void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
744{
745#ifdef CONFIG_MEMCG
746 mm->owner = p;
747#endif
748}
749
750static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
751 struct user_namespace *user_ns)
752{
753 mm->mmap = NULL;
754 mm->mm_rb = RB_ROOT;
755 mm->vmacache_seqnum = 0;
756 atomic_set(&mm->mm_users, 1);
757 atomic_set(&mm->mm_count, 1);
758 init_rwsem(&mm->mmap_sem);
759 INIT_LIST_HEAD(&mm->mmlist);
760 mm->core_state = NULL;
761 atomic_long_set(&mm->nr_ptes, 0);
762 mm_nr_pmds_init(mm);
763 mm->map_count = 0;
764 mm->locked_vm = 0;
765 mm->pinned_vm = 0;
766 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
767 spin_lock_init(&mm->page_table_lock);
768 mm_init_cpumask(mm);
769 mm_init_aio(mm);
770 mm_init_owner(mm, p);
771 mmu_notifier_mm_init(mm);
772 clear_tlb_flush_pending(mm);
773#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
774 mm->pmd_huge_pte = NULL;
775#endif
776
777 if (current->mm) {
778 mm->flags = current->mm->flags & MMF_INIT_MASK;
779 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK;
780 } else {
781 mm->flags = default_dump_filter;
782 mm->def_flags = 0;
783 }
784
785 if (mm_alloc_pgd(mm))
786 goto fail_nopgd;
787
788 if (init_new_context(p, mm))
789 goto fail_nocontext;
790
791 mm->user_ns = get_user_ns(user_ns);
792 return mm;
793
794fail_nocontext:
795 mm_free_pgd(mm);
796fail_nopgd:
797 free_mm(mm);
798 return NULL;
799}
800
801static void check_mm(struct mm_struct *mm)
802{
803 int i;
804
805 for (i = 0; i < NR_MM_COUNTERS; i++) {
806 long x = atomic_long_read(&mm->rss_stat.count[i]);
807
808 if (unlikely(x))
809 printk(KERN_ALERT "BUG: Bad rss-counter state "
810 "mm:%p idx:%d val:%ld\n", mm, i, x);
811 }
812
813 if (atomic_long_read(&mm->nr_ptes))
814 pr_alert("BUG: non-zero nr_ptes on freeing mm: %ld\n",
815 atomic_long_read(&mm->nr_ptes));
816 if (mm_nr_pmds(mm))
817 pr_alert("BUG: non-zero nr_pmds on freeing mm: %ld\n",
818 mm_nr_pmds(mm));
819
820#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
821 VM_BUG_ON_MM(mm->pmd_huge_pte, mm);
822#endif
823}
824
825/*
826 * Allocate and initialize an mm_struct.
827 */
828struct mm_struct *mm_alloc(void)
829{
830 struct mm_struct *mm;
831
832 mm = allocate_mm();
833 if (!mm)
834 return NULL;
835
836 memset(mm, 0, sizeof(*mm));
837 return mm_init(mm, current, current_user_ns());
838}
839
840/*
841 * Called when the last reference to the mm
842 * is dropped: either by a lazy thread or by
843 * mmput. Free the page directory and the mm.
844 */
845void __mmdrop(struct mm_struct *mm)
846{
847 BUG_ON(mm == &init_mm);
848 mm_free_pgd(mm);
849 destroy_context(mm);
850 mmu_notifier_mm_destroy(mm);
851 check_mm(mm);
852 put_user_ns(mm->user_ns);
853 free_mm(mm);
854}
855EXPORT_SYMBOL_GPL(__mmdrop);
856
857static inline void __mmput(struct mm_struct *mm)
858{
859 VM_BUG_ON(atomic_read(&mm->mm_users));
860
861 uprobe_clear_state(mm);
862 exit_aio(mm);
863 ksm_exit(mm);
864 khugepaged_exit(mm); /* must run before exit_mmap */
865 exit_mmap(mm);
866 mm_put_huge_zero_page(mm);
867 set_mm_exe_file(mm, NULL);
868 if (!list_empty(&mm->mmlist)) {
869 spin_lock(&mmlist_lock);
870 list_del(&mm->mmlist);
871 spin_unlock(&mmlist_lock);
872 }
873 if (mm->binfmt)
874 module_put(mm->binfmt->module);
875 set_bit(MMF_OOM_SKIP, &mm->flags);
876 mmdrop(mm);
877}
878
879/*
880 * Decrement the use count and release all resources for an mm.
881 */
882void mmput(struct mm_struct *mm)
883{
884 might_sleep();
885
886 if (atomic_dec_and_test(&mm->mm_users))
887 __mmput(mm);
888}
889EXPORT_SYMBOL_GPL(mmput);
890
891#ifdef CONFIG_MMU
892static void mmput_async_fn(struct work_struct *work)
893{
894 struct mm_struct *mm = container_of(work, struct mm_struct, async_put_work);
895 __mmput(mm);
896}
897
898void mmput_async(struct mm_struct *mm)
899{
900 if (atomic_dec_and_test(&mm->mm_users)) {
901 INIT_WORK(&mm->async_put_work, mmput_async_fn);
902 schedule_work(&mm->async_put_work);
903 }
904}
905#endif
906
907/**
908 * set_mm_exe_file - change a reference to the mm's executable file
909 *
910 * This changes mm's executable file (shown as symlink /proc/[pid]/exe).
911 *
912 * Main users are mmput() and sys_execve(). Callers prevent concurrent
913 * invocations: in mmput() nobody alive left, in execve task is single
914 * threaded. sys_prctl(PR_SET_MM_MAP/EXE_FILE) also needs to set the
915 * mm->exe_file, but does so without using set_mm_exe_file() in order
916 * to do avoid the need for any locks.
917 */
918void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
919{
920 struct file *old_exe_file;
921
922 /*
923 * It is safe to dereference the exe_file without RCU as
924 * this function is only called if nobody else can access
925 * this mm -- see comment above for justification.
926 */
927 old_exe_file = rcu_dereference_raw(mm->exe_file);
928
929 if (new_exe_file)
930 get_file(new_exe_file);
931 rcu_assign_pointer(mm->exe_file, new_exe_file);
932 if (old_exe_file)
933 fput(old_exe_file);
934}
935
936/**
937 * get_mm_exe_file - acquire a reference to the mm's executable file
938 *
939 * Returns %NULL if mm has no associated executable file.
940 * User must release file via fput().
941 */
942struct file *get_mm_exe_file(struct mm_struct *mm)
943{
944 struct file *exe_file;
945
946 rcu_read_lock();
947 exe_file = rcu_dereference(mm->exe_file);
948 if (exe_file && !get_file_rcu(exe_file))
949 exe_file = NULL;
950 rcu_read_unlock();
951 return exe_file;
952}
953EXPORT_SYMBOL(get_mm_exe_file);
954
955/**
956 * get_task_exe_file - acquire a reference to the task's executable file
957 *
958 * Returns %NULL if task's mm (if any) has no associated executable file or
959 * this is a kernel thread with borrowed mm (see the comment above get_task_mm).
960 * User must release file via fput().
961 */
962struct file *get_task_exe_file(struct task_struct *task)
963{
964 struct file *exe_file = NULL;
965 struct mm_struct *mm;
966
967 task_lock(task);
968 mm = task->mm;
969 if (mm) {
970 if (!(task->flags & PF_KTHREAD))
971 exe_file = get_mm_exe_file(mm);
972 }
973 task_unlock(task);
974 return exe_file;
975}
976EXPORT_SYMBOL(get_task_exe_file);
977
978/**
979 * get_task_mm - acquire a reference to the task's mm
980 *
981 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning
982 * this kernel workthread has transiently adopted a user mm with use_mm,
983 * to do its AIO) is not set and if so returns a reference to it, after
984 * bumping up the use count. User must release the mm via mmput()
985 * after use. Typically used by /proc and ptrace.
986 */
987struct mm_struct *get_task_mm(struct task_struct *task)
988{
989 struct mm_struct *mm;
990
991 task_lock(task);
992 mm = task->mm;
993 if (mm) {
994 if (task->flags & PF_KTHREAD)
995 mm = NULL;
996 else
997 atomic_inc(&mm->mm_users);
998 }
999 task_unlock(task);
1000 return mm;
1001}
1002EXPORT_SYMBOL_GPL(get_task_mm);
1003
1004struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
1005{
1006 struct mm_struct *mm;
1007 int err;
1008
1009 err = mutex_lock_killable(&task->signal->cred_guard_mutex);
1010 if (err)
1011 return ERR_PTR(err);
1012
1013 mm = get_task_mm(task);
1014 if (mm && mm != current->mm &&
1015 !ptrace_may_access(task, mode)) {
1016 mmput(mm);
1017 mm = ERR_PTR(-EACCES);
1018 }
1019 mutex_unlock(&task->signal->cred_guard_mutex);
1020
1021 return mm;
1022}
1023
1024static void complete_vfork_done(struct task_struct *tsk)
1025{
1026 struct completion *vfork;
1027
1028 task_lock(tsk);
1029 vfork = tsk->vfork_done;
1030 if (likely(vfork)) {
1031 tsk->vfork_done = NULL;
1032 complete(vfork);
1033 }
1034 task_unlock(tsk);
1035}
1036
1037static int wait_for_vfork_done(struct task_struct *child,
1038 struct completion *vfork)
1039{
1040 int killed;
1041
1042 freezer_do_not_count();
1043 killed = wait_for_completion_killable(vfork);
1044 freezer_count();
1045
1046 if (killed) {
1047 task_lock(child);
1048 child->vfork_done = NULL;
1049 task_unlock(child);
1050 }
1051
1052 put_task_struct(child);
1053 return killed;
1054}
1055
1056/* Please note the differences between mmput and mm_release.
1057 * mmput is called whenever we stop holding onto a mm_struct,
1058 * error success whatever.
1059 *
1060 * mm_release is called after a mm_struct has been removed
1061 * from the current process.
1062 *
1063 * This difference is important for error handling, when we
1064 * only half set up a mm_struct for a new process and need to restore
1065 * the old one. Because we mmput the new mm_struct before
1066 * restoring the old one. . .
1067 * Eric Biederman 10 January 1998
1068 */
1069void mm_release(struct task_struct *tsk, struct mm_struct *mm)
1070{
1071 /* Get rid of any futexes when releasing the mm */
1072#ifdef CONFIG_FUTEX
1073 if (unlikely(tsk->robust_list)) {
1074 exit_robust_list(tsk);
1075 tsk->robust_list = NULL;
1076 }
1077#ifdef CONFIG_COMPAT
1078 if (unlikely(tsk->compat_robust_list)) {
1079 compat_exit_robust_list(tsk);
1080 tsk->compat_robust_list = NULL;
1081 }
1082#endif
1083 if (unlikely(!list_empty(&tsk->pi_state_list)))
1084 exit_pi_state_list(tsk);
1085#endif
1086
1087 uprobe_free_utask(tsk);
1088
1089 /* Get rid of any cached register state */
1090 deactivate_mm(tsk, mm);
1091
1092 /*
1093 * Signal userspace if we're not exiting with a core dump
1094 * because we want to leave the value intact for debugging
1095 * purposes.
1096 */
1097 if (tsk->clear_child_tid) {
1098 if (!(tsk->signal->flags & SIGNAL_GROUP_COREDUMP) &&
1099 atomic_read(&mm->mm_users) > 1) {
1100 /*
1101 * We don't check the error code - if userspace has
1102 * not set up a proper pointer then tough luck.
1103 */
1104 put_user(0, tsk->clear_child_tid);
1105 sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
1106 1, NULL, NULL, 0);
1107 }
1108 tsk->clear_child_tid = NULL;
1109 }
1110
1111 /*
1112 * All done, finally we can wake up parent and return this mm to him.
1113 * Also kthread_stop() uses this completion for synchronization.
1114 */
1115 if (tsk->vfork_done)
1116 complete_vfork_done(tsk);
1117}
1118
1119/*
1120 * Allocate a new mm structure and copy contents from the
1121 * mm structure of the passed in task structure.
1122 */
1123static struct mm_struct *dup_mm(struct task_struct *tsk)
1124{
1125 struct mm_struct *mm, *oldmm = current->mm;
1126 int err;
1127
1128 mm = allocate_mm();
1129 if (!mm)
1130 goto fail_nomem;
1131
1132 memcpy(mm, oldmm, sizeof(*mm));
1133
1134 if (!mm_init(mm, tsk, mm->user_ns))
1135 goto fail_nomem;
1136
1137 err = dup_mmap(mm, oldmm);
1138 if (err)
1139 goto free_pt;
1140
1141 mm->hiwater_rss = get_mm_rss(mm);
1142 mm->hiwater_vm = mm->total_vm;
1143
1144 if (mm->binfmt && !try_module_get(mm->binfmt->module))
1145 goto free_pt;
1146
1147 return mm;
1148
1149free_pt:
1150 /* don't put binfmt in mmput, we haven't got module yet */
1151 mm->binfmt = NULL;
1152 mmput(mm);
1153
1154fail_nomem:
1155 return NULL;
1156}
1157
1158static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
1159{
1160 struct mm_struct *mm, *oldmm;
1161 int retval;
1162
1163 tsk->min_flt = tsk->maj_flt = 0;
1164 tsk->nvcsw = tsk->nivcsw = 0;
1165#ifdef CONFIG_DETECT_HUNG_TASK
1166 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
1167#endif
1168
1169 tsk->mm = NULL;
1170 tsk->active_mm = NULL;
1171
1172 /*
1173 * Are we cloning a kernel thread?
1174 *
1175 * We need to steal a active VM for that..
1176 */
1177 oldmm = current->mm;
1178 if (!oldmm)
1179 return 0;
1180
1181 /* initialize the new vmacache entries */
1182 vmacache_flush(tsk);
1183
1184 if (clone_flags & CLONE_VM) {
1185 atomic_inc(&oldmm->mm_users);
1186 mm = oldmm;
1187 goto good_mm;
1188 }
1189
1190 retval = -ENOMEM;
1191 mm = dup_mm(tsk);
1192 if (!mm)
1193 goto fail_nomem;
1194
1195good_mm:
1196 tsk->mm = mm;
1197 tsk->active_mm = mm;
1198 return 0;
1199
1200fail_nomem:
1201 return retval;
1202}
1203
1204static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
1205{
1206 struct fs_struct *fs = current->fs;
1207 if (clone_flags & CLONE_FS) {
1208 /* tsk->fs is already what we want */
1209 spin_lock(&fs->lock);
1210 if (fs->in_exec) {
1211 spin_unlock(&fs->lock);
1212 return -EAGAIN;
1213 }
1214 fs->users++;
1215 spin_unlock(&fs->lock);
1216 return 0;
1217 }
1218 tsk->fs = copy_fs_struct(fs);
1219 if (!tsk->fs)
1220 return -ENOMEM;
1221 return 0;
1222}
1223
1224static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
1225{
1226 struct files_struct *oldf, *newf;
1227 int error = 0;
1228
1229 /*
1230 * A background process may not have any files ...
1231 */
1232 oldf = current->files;
1233 if (!oldf)
1234 goto out;
1235
1236 if (clone_flags & CLONE_FILES) {
1237 atomic_inc(&oldf->count);
1238 goto out;
1239 }
1240
1241 newf = dup_fd(oldf, &error);
1242 if (!newf)
1243 goto out;
1244
1245 tsk->files = newf;
1246 error = 0;
1247out:
1248 return error;
1249}
1250
1251static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
1252{
1253#ifdef CONFIG_BLOCK
1254 struct io_context *ioc = current->io_context;
1255 struct io_context *new_ioc;
1256
1257 if (!ioc)
1258 return 0;
1259 /*
1260 * Share io context with parent, if CLONE_IO is set
1261 */
1262 if (clone_flags & CLONE_IO) {
1263 ioc_task_link(ioc);
1264 tsk->io_context = ioc;
1265 } else if (ioprio_valid(ioc->ioprio)) {
1266 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE);
1267 if (unlikely(!new_ioc))
1268 return -ENOMEM;
1269
1270 new_ioc->ioprio = ioc->ioprio;
1271 put_io_context(new_ioc);
1272 }
1273#endif
1274 return 0;
1275}
1276
1277static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
1278{
1279 struct sighand_struct *sig;
1280
1281 if (clone_flags & CLONE_SIGHAND) {
1282 atomic_inc(&current->sighand->count);
1283 return 0;
1284 }
1285 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1286 rcu_assign_pointer(tsk->sighand, sig);
1287 if (!sig)
1288 return -ENOMEM;
1289
1290 atomic_set(&sig->count, 1);
1291 memcpy(sig->action, current->sighand->action, sizeof(sig->action));
1292 return 0;
1293}
1294
1295void __cleanup_sighand(struct sighand_struct *sighand)
1296{
1297 if (atomic_dec_and_test(&sighand->count)) {
1298 signalfd_cleanup(sighand);
1299 /*
1300 * sighand_cachep is SLAB_DESTROY_BY_RCU so we can free it
1301 * without an RCU grace period, see __lock_task_sighand().
1302 */
1303 kmem_cache_free(sighand_cachep, sighand);
1304 }
1305}
1306
1307/*
1308 * Initialize POSIX timer handling for a thread group.
1309 */
1310static void posix_cpu_timers_init_group(struct signal_struct *sig)
1311{
1312 unsigned long cpu_limit;
1313
1314 cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1315 if (cpu_limit != RLIM_INFINITY) {
1316 sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit);
1317 sig->cputimer.running = true;
1318 }
1319
1320 /* The timer lists. */
1321 INIT_LIST_HEAD(&sig->cpu_timers[0]);
1322 INIT_LIST_HEAD(&sig->cpu_timers[1]);
1323 INIT_LIST_HEAD(&sig->cpu_timers[2]);
1324}
1325
1326static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
1327{
1328 struct signal_struct *sig;
1329
1330 if (clone_flags & CLONE_THREAD)
1331 return 0;
1332
1333 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
1334 tsk->signal = sig;
1335 if (!sig)
1336 return -ENOMEM;
1337
1338 sig->nr_threads = 1;
1339 atomic_set(&sig->live, 1);
1340 atomic_set(&sig->sigcnt, 1);
1341
1342 /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */
1343 sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node);
1344 tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head);
1345
1346 init_waitqueue_head(&sig->wait_chldexit);
1347 sig->curr_target = tsk;
1348 init_sigpending(&sig->shared_pending);
1349 INIT_LIST_HEAD(&sig->posix_timers);
1350 seqlock_init(&sig->stats_lock);
1351 prev_cputime_init(&sig->prev_cputime);
1352
1353#ifdef CONFIG_POSIX_TIMERS
1354 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1355 sig->real_timer.function = it_real_fn;
1356#endif
1357
1358 task_lock(current->group_leader);
1359 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
1360 task_unlock(current->group_leader);
1361
1362 posix_cpu_timers_init_group(sig);
1363
1364 tty_audit_fork(sig);
1365 sched_autogroup_fork(sig);
1366
1367 sig->oom_score_adj = current->signal->oom_score_adj;
1368 sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1369
1370 sig->has_child_subreaper = current->signal->has_child_subreaper ||
1371 current->signal->is_child_subreaper;
1372
1373 mutex_init(&sig->cred_guard_mutex);
1374
1375 return 0;
1376}
1377
1378static void copy_seccomp(struct task_struct *p)
1379{
1380#ifdef CONFIG_SECCOMP
1381 /*
1382 * Must be called with sighand->lock held, which is common to
1383 * all threads in the group. Holding cred_guard_mutex is not
1384 * needed because this new task is not yet running and cannot
1385 * be racing exec.
1386 */
1387 assert_spin_locked(&current->sighand->siglock);
1388
1389 /* Ref-count the new filter user, and assign it. */
1390 get_seccomp_filter(current);
1391 p->seccomp = current->seccomp;
1392
1393 /*
1394 * Explicitly enable no_new_privs here in case it got set
1395 * between the task_struct being duplicated and holding the
1396 * sighand lock. The seccomp state and nnp must be in sync.
1397 */
1398 if (task_no_new_privs(current))
1399 task_set_no_new_privs(p);
1400
1401 /*
1402 * If the parent gained a seccomp mode after copying thread
1403 * flags and between before we held the sighand lock, we have
1404 * to manually enable the seccomp thread flag here.
1405 */
1406 if (p->seccomp.mode != SECCOMP_MODE_DISABLED)
1407 set_tsk_thread_flag(p, TIF_SECCOMP);
1408#endif
1409}
1410
1411SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1412{
1413 current->clear_child_tid = tidptr;
1414
1415 return task_pid_vnr(current);
1416}
1417
1418static void rt_mutex_init_task(struct task_struct *p)
1419{
1420 raw_spin_lock_init(&p->pi_lock);
1421#ifdef CONFIG_RT_MUTEXES
1422 p->pi_waiters = RB_ROOT;
1423 p->pi_waiters_leftmost = NULL;
1424 p->pi_blocked_on = NULL;
1425#endif
1426}
1427
1428/*
1429 * Initialize POSIX timer handling for a single task.
1430 */
1431static void posix_cpu_timers_init(struct task_struct *tsk)
1432{
1433 tsk->cputime_expires.prof_exp = 0;
1434 tsk->cputime_expires.virt_exp = 0;
1435 tsk->cputime_expires.sched_exp = 0;
1436 INIT_LIST_HEAD(&tsk->cpu_timers[0]);
1437 INIT_LIST_HEAD(&tsk->cpu_timers[1]);
1438 INIT_LIST_HEAD(&tsk->cpu_timers[2]);
1439}
1440
1441static inline void
1442init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid)
1443{
1444 task->pids[type].pid = pid;
1445}
1446
1447/*
1448 * This creates a new process as a copy of the old one,
1449 * but does not actually start it yet.
1450 *
1451 * It copies the registers, and all the appropriate
1452 * parts of the process environment (as per the clone
1453 * flags). The actual kick-off is left to the caller.
1454 */
1455static __latent_entropy struct task_struct *copy_process(
1456 unsigned long clone_flags,
1457 unsigned long stack_start,
1458 unsigned long stack_size,
1459 int __user *child_tidptr,
1460 struct pid *pid,
1461 int trace,
1462 unsigned long tls,
1463 int node)
1464{
1465 int retval;
1466 struct task_struct *p;
1467
1468 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1469 return ERR_PTR(-EINVAL);
1470
1471 if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS))
1472 return ERR_PTR(-EINVAL);
1473
1474 /*
1475 * Thread groups must share signals as well, and detached threads
1476 * can only be started up within the thread group.
1477 */
1478 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1479 return ERR_PTR(-EINVAL);
1480
1481 /*
1482 * Shared signal handlers imply shared VM. By way of the above,
1483 * thread groups also imply shared VM. Blocking this case allows
1484 * for various simplifications in other code.
1485 */
1486 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1487 return ERR_PTR(-EINVAL);
1488
1489 /*
1490 * Siblings of global init remain as zombies on exit since they are
1491 * not reaped by their parent (swapper). To solve this and to avoid
1492 * multi-rooted process trees, prevent global and container-inits
1493 * from creating siblings.
1494 */
1495 if ((clone_flags & CLONE_PARENT) &&
1496 current->signal->flags & SIGNAL_UNKILLABLE)
1497 return ERR_PTR(-EINVAL);
1498
1499 /*
1500 * If the new process will be in a different pid or user namespace
1501 * do not allow it to share a thread group with the forking task.
1502 */
1503 if (clone_flags & CLONE_THREAD) {
1504 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) ||
1505 (task_active_pid_ns(current) !=
1506 current->nsproxy->pid_ns_for_children))
1507 return ERR_PTR(-EINVAL);
1508 }
1509
1510 retval = security_task_create(clone_flags);
1511 if (retval)
1512 goto fork_out;
1513
1514 retval = -ENOMEM;
1515 p = dup_task_struct(current, node);
1516 if (!p)
1517 goto fork_out;
1518
1519 ftrace_graph_init_task(p);
1520
1521 rt_mutex_init_task(p);
1522
1523#ifdef CONFIG_PROVE_LOCKING
1524 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1525 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1526#endif
1527 retval = -EAGAIN;
1528 if (atomic_read(&p->real_cred->user->processes) >=
1529 task_rlimit(p, RLIMIT_NPROC)) {
1530 if (p->real_cred->user != INIT_USER &&
1531 !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
1532 goto bad_fork_free;
1533 }
1534 current->flags &= ~PF_NPROC_EXCEEDED;
1535
1536 retval = copy_creds(p, clone_flags);
1537 if (retval < 0)
1538 goto bad_fork_free;
1539
1540 /*
1541 * If multiple threads are within copy_process(), then this check
1542 * triggers too late. This doesn't hurt, the check is only there
1543 * to stop root fork bombs.
1544 */
1545 retval = -EAGAIN;
1546 if (nr_threads >= max_threads)
1547 goto bad_fork_cleanup_count;
1548
1549 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */
1550 p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER | PF_IDLE);
1551 p->flags |= PF_FORKNOEXEC;
1552 INIT_LIST_HEAD(&p->children);
1553 INIT_LIST_HEAD(&p->sibling);
1554 rcu_copy_process(p);
1555 p->vfork_done = NULL;
1556 spin_lock_init(&p->alloc_lock);
1557
1558 init_sigpending(&p->pending);
1559
1560 p->utime = p->stime = p->gtime = 0;
1561#ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
1562 p->utimescaled = p->stimescaled = 0;
1563#endif
1564 prev_cputime_init(&p->prev_cputime);
1565
1566#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
1567 seqcount_init(&p->vtime_seqcount);
1568 p->vtime_snap = 0;
1569 p->vtime_snap_whence = VTIME_INACTIVE;
1570#endif
1571
1572#if defined(SPLIT_RSS_COUNTING)
1573 memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1574#endif
1575
1576 p->default_timer_slack_ns = current->timer_slack_ns;
1577
1578 task_io_accounting_init(&p->ioac);
1579 acct_clear_integrals(p);
1580
1581 posix_cpu_timers_init(p);
1582
1583 p->start_time = ktime_get_ns();
1584 p->real_start_time = ktime_get_boot_ns();
1585 p->io_context = NULL;
1586 p->audit_context = NULL;
1587 cgroup_fork(p);
1588#ifdef CONFIG_NUMA
1589 p->mempolicy = mpol_dup(p->mempolicy);
1590 if (IS_ERR(p->mempolicy)) {
1591 retval = PTR_ERR(p->mempolicy);
1592 p->mempolicy = NULL;
1593 goto bad_fork_cleanup_threadgroup_lock;
1594 }
1595#endif
1596#ifdef CONFIG_CPUSETS
1597 p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
1598 p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
1599 seqcount_init(&p->mems_allowed_seq);
1600#endif
1601#ifdef CONFIG_TRACE_IRQFLAGS
1602 p->irq_events = 0;
1603 p->hardirqs_enabled = 0;
1604 p->hardirq_enable_ip = 0;
1605 p->hardirq_enable_event = 0;
1606 p->hardirq_disable_ip = _THIS_IP_;
1607 p->hardirq_disable_event = 0;
1608 p->softirqs_enabled = 1;
1609 p->softirq_enable_ip = _THIS_IP_;
1610 p->softirq_enable_event = 0;
1611 p->softirq_disable_ip = 0;
1612 p->softirq_disable_event = 0;
1613 p->hardirq_context = 0;
1614 p->softirq_context = 0;
1615#endif
1616
1617 p->pagefault_disabled = 0;
1618
1619#ifdef CONFIG_LOCKDEP
1620 p->lockdep_depth = 0; /* no locks held yet */
1621 p->curr_chain_key = 0;
1622 p->lockdep_recursion = 0;
1623#endif
1624
1625#ifdef CONFIG_DEBUG_MUTEXES
1626 p->blocked_on = NULL; /* not blocked yet */
1627#endif
1628#ifdef CONFIG_BCACHE
1629 p->sequential_io = 0;
1630 p->sequential_io_avg = 0;
1631#endif
1632
1633 /* Perform scheduler related setup. Assign this task to a CPU. */
1634 retval = sched_fork(clone_flags, p);
1635 if (retval)
1636 goto bad_fork_cleanup_policy;
1637
1638 retval = perf_event_init_task(p);
1639 if (retval)
1640 goto bad_fork_cleanup_policy;
1641 retval = audit_alloc(p);
1642 if (retval)
1643 goto bad_fork_cleanup_perf;
1644 /* copy all the process information */
1645 shm_init_task(p);
1646 retval = copy_semundo(clone_flags, p);
1647 if (retval)
1648 goto bad_fork_cleanup_audit;
1649 retval = copy_files(clone_flags, p);
1650 if (retval)
1651 goto bad_fork_cleanup_semundo;
1652 retval = copy_fs(clone_flags, p);
1653 if (retval)
1654 goto bad_fork_cleanup_files;
1655 retval = copy_sighand(clone_flags, p);
1656 if (retval)
1657 goto bad_fork_cleanup_fs;
1658 retval = copy_signal(clone_flags, p);
1659 if (retval)
1660 goto bad_fork_cleanup_sighand;
1661 retval = copy_mm(clone_flags, p);
1662 if (retval)
1663 goto bad_fork_cleanup_signal;
1664 retval = copy_namespaces(clone_flags, p);
1665 if (retval)
1666 goto bad_fork_cleanup_mm;
1667 retval = copy_io(clone_flags, p);
1668 if (retval)
1669 goto bad_fork_cleanup_namespaces;
1670 retval = copy_thread_tls(clone_flags, stack_start, stack_size, p, tls);
1671 if (retval)
1672 goto bad_fork_cleanup_io;
1673
1674 if (pid != &init_struct_pid) {
1675 pid = alloc_pid(p->nsproxy->pid_ns_for_children);
1676 if (IS_ERR(pid)) {
1677 retval = PTR_ERR(pid);
1678 goto bad_fork_cleanup_thread;
1679 }
1680 }
1681
1682 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1683 /*
1684 * Clear TID on mm_release()?
1685 */
1686 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL;
1687#ifdef CONFIG_BLOCK
1688 p->plug = NULL;
1689#endif
1690#ifdef CONFIG_FUTEX
1691 p->robust_list = NULL;
1692#ifdef CONFIG_COMPAT
1693 p->compat_robust_list = NULL;
1694#endif
1695 INIT_LIST_HEAD(&p->pi_state_list);
1696 p->pi_state_cache = NULL;
1697#endif
1698 /*
1699 * sigaltstack should be cleared when sharing the same VM
1700 */
1701 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1702 sas_ss_reset(p);
1703
1704 /*
1705 * Syscall tracing and stepping should be turned off in the
1706 * child regardless of CLONE_PTRACE.
1707 */
1708 user_disable_single_step(p);
1709 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1710#ifdef TIF_SYSCALL_EMU
1711 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1712#endif
1713 clear_all_latency_tracing(p);
1714
1715 /* ok, now we should be set up.. */
1716 p->pid = pid_nr(pid);
1717 if (clone_flags & CLONE_THREAD) {
1718 p->exit_signal = -1;
1719 p->group_leader = current->group_leader;
1720 p->tgid = current->tgid;
1721 } else {
1722 if (clone_flags & CLONE_PARENT)
1723 p->exit_signal = current->group_leader->exit_signal;
1724 else
1725 p->exit_signal = (clone_flags & CSIGNAL);
1726 p->group_leader = p;
1727 p->tgid = p->pid;
1728 }
1729
1730 p->nr_dirtied = 0;
1731 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
1732 p->dirty_paused_when = 0;
1733
1734 p->pdeath_signal = 0;
1735 INIT_LIST_HEAD(&p->thread_group);
1736 p->task_works = NULL;
1737
1738 threadgroup_change_begin(current);
1739 /*
1740 * Ensure that the cgroup subsystem policies allow the new process to be
1741 * forked. It should be noted the the new process's css_set can be changed
1742 * between here and cgroup_post_fork() if an organisation operation is in
1743 * progress.
1744 */
1745 retval = cgroup_can_fork(p);
1746 if (retval)
1747 goto bad_fork_free_pid;
1748
1749 /*
1750 * Make it visible to the rest of the system, but dont wake it up yet.
1751 * Need tasklist lock for parent etc handling!
1752 */
1753 write_lock_irq(&tasklist_lock);
1754
1755 /* CLONE_PARENT re-uses the old parent */
1756 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1757 p->real_parent = current->real_parent;
1758 p->parent_exec_id = current->parent_exec_id;
1759 } else {
1760 p->real_parent = current;
1761 p->parent_exec_id = current->self_exec_id;
1762 }
1763
1764 spin_lock(&current->sighand->siglock);
1765
1766 /*
1767 * Copy seccomp details explicitly here, in case they were changed
1768 * before holding sighand lock.
1769 */
1770 copy_seccomp(p);
1771
1772 /*
1773 * Process group and session signals need to be delivered to just the
1774 * parent before the fork or both the parent and the child after the
1775 * fork. Restart if a signal comes in before we add the new process to
1776 * it's process group.
1777 * A fatal signal pending means that current will exit, so the new
1778 * thread can't slip out of an OOM kill (or normal SIGKILL).
1779 */
1780 recalc_sigpending();
1781 if (signal_pending(current)) {
1782 spin_unlock(&current->sighand->siglock);
1783 write_unlock_irq(&tasklist_lock);
1784 retval = -ERESTARTNOINTR;
1785 goto bad_fork_cancel_cgroup;
1786 }
1787
1788 if (likely(p->pid)) {
1789 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
1790
1791 init_task_pid(p, PIDTYPE_PID, pid);
1792 if (thread_group_leader(p)) {
1793 init_task_pid(p, PIDTYPE_PGID, task_pgrp(current));
1794 init_task_pid(p, PIDTYPE_SID, task_session(current));
1795
1796 if (is_child_reaper(pid)) {
1797 ns_of_pid(pid)->child_reaper = p;
1798 p->signal->flags |= SIGNAL_UNKILLABLE;
1799 }
1800
1801 p->signal->leader_pid = pid;
1802 p->signal->tty = tty_kref_get(current->signal->tty);
1803 list_add_tail(&p->sibling, &p->real_parent->children);
1804 list_add_tail_rcu(&p->tasks, &init_task.tasks);
1805 attach_pid(p, PIDTYPE_PGID);
1806 attach_pid(p, PIDTYPE_SID);
1807 __this_cpu_inc(process_counts);
1808 } else {
1809 current->signal->nr_threads++;
1810 atomic_inc(&current->signal->live);
1811 atomic_inc(&current->signal->sigcnt);
1812 list_add_tail_rcu(&p->thread_group,
1813 &p->group_leader->thread_group);
1814 list_add_tail_rcu(&p->thread_node,
1815 &p->signal->thread_head);
1816 }
1817 attach_pid(p, PIDTYPE_PID);
1818 nr_threads++;
1819 }
1820
1821 total_forks++;
1822 spin_unlock(&current->sighand->siglock);
1823 syscall_tracepoint_update(p);
1824 write_unlock_irq(&tasklist_lock);
1825
1826 proc_fork_connector(p);
1827 cgroup_post_fork(p);
1828 threadgroup_change_end(current);
1829 perf_event_fork(p);
1830
1831 trace_task_newtask(p, clone_flags);
1832 uprobe_copy_process(p, clone_flags);
1833
1834 return p;
1835
1836bad_fork_cancel_cgroup:
1837 cgroup_cancel_fork(p);
1838bad_fork_free_pid:
1839 threadgroup_change_end(current);
1840 if (pid != &init_struct_pid)
1841 free_pid(pid);
1842bad_fork_cleanup_thread:
1843 exit_thread(p);
1844bad_fork_cleanup_io:
1845 if (p->io_context)
1846 exit_io_context(p);
1847bad_fork_cleanup_namespaces:
1848 exit_task_namespaces(p);
1849bad_fork_cleanup_mm:
1850 if (p->mm)
1851 mmput(p->mm);
1852bad_fork_cleanup_signal:
1853 if (!(clone_flags & CLONE_THREAD))
1854 free_signal_struct(p->signal);
1855bad_fork_cleanup_sighand:
1856 __cleanup_sighand(p->sighand);
1857bad_fork_cleanup_fs:
1858 exit_fs(p); /* blocking */
1859bad_fork_cleanup_files:
1860 exit_files(p); /* blocking */
1861bad_fork_cleanup_semundo:
1862 exit_sem(p);
1863bad_fork_cleanup_audit:
1864 audit_free(p);
1865bad_fork_cleanup_perf:
1866 perf_event_free_task(p);
1867bad_fork_cleanup_policy:
1868#ifdef CONFIG_NUMA
1869 mpol_put(p->mempolicy);
1870bad_fork_cleanup_threadgroup_lock:
1871#endif
1872 delayacct_tsk_free(p);
1873bad_fork_cleanup_count:
1874 atomic_dec(&p->cred->user->processes);
1875 exit_creds(p);
1876bad_fork_free:
1877 p->state = TASK_DEAD;
1878 put_task_stack(p);
1879 free_task(p);
1880fork_out:
1881 return ERR_PTR(retval);
1882}
1883
1884static inline void init_idle_pids(struct pid_link *links)
1885{
1886 enum pid_type type;
1887
1888 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
1889 INIT_HLIST_NODE(&links[type].node); /* not really needed */
1890 links[type].pid = &init_struct_pid;
1891 }
1892}
1893
1894struct task_struct *fork_idle(int cpu)
1895{
1896 struct task_struct *task;
1897 task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0, 0,
1898 cpu_to_node(cpu));
1899 if (!IS_ERR(task)) {
1900 init_idle_pids(task->pids);
1901 init_idle(task, cpu);
1902 }
1903
1904 return task;
1905}
1906
1907/*
1908 * Ok, this is the main fork-routine.
1909 *
1910 * It copies the process, and if successful kick-starts
1911 * it and waits for it to finish using the VM if required.
1912 */
1913long _do_fork(unsigned long clone_flags,
1914 unsigned long stack_start,
1915 unsigned long stack_size,
1916 int __user *parent_tidptr,
1917 int __user *child_tidptr,
1918 unsigned long tls)
1919{
1920 struct task_struct *p;
1921 int trace = 0;
1922 long nr;
1923
1924 /*
1925 * Determine whether and which event to report to ptracer. When
1926 * called from kernel_thread or CLONE_UNTRACED is explicitly
1927 * requested, no event is reported; otherwise, report if the event
1928 * for the type of forking is enabled.
1929 */
1930 if (!(clone_flags & CLONE_UNTRACED)) {
1931 if (clone_flags & CLONE_VFORK)
1932 trace = PTRACE_EVENT_VFORK;
1933 else if ((clone_flags & CSIGNAL) != SIGCHLD)
1934 trace = PTRACE_EVENT_CLONE;
1935 else
1936 trace = PTRACE_EVENT_FORK;
1937
1938 if (likely(!ptrace_event_enabled(current, trace)))
1939 trace = 0;
1940 }
1941
1942 p = copy_process(clone_flags, stack_start, stack_size,
1943 child_tidptr, NULL, trace, tls, NUMA_NO_NODE);
1944 add_latent_entropy();
1945 /*
1946 * Do this prior waking up the new thread - the thread pointer
1947 * might get invalid after that point, if the thread exits quickly.
1948 */
1949 if (!IS_ERR(p)) {
1950 struct completion vfork;
1951 struct pid *pid;
1952
1953 trace_sched_process_fork(current, p);
1954
1955 pid = get_task_pid(p, PIDTYPE_PID);
1956 nr = pid_vnr(pid);
1957
1958 if (clone_flags & CLONE_PARENT_SETTID)
1959 put_user(nr, parent_tidptr);
1960
1961 if (clone_flags & CLONE_VFORK) {
1962 p->vfork_done = &vfork;
1963 init_completion(&vfork);
1964 get_task_struct(p);
1965 }
1966
1967 wake_up_new_task(p);
1968
1969 /* forking complete and child started to run, tell ptracer */
1970 if (unlikely(trace))
1971 ptrace_event_pid(trace, pid);
1972
1973 if (clone_flags & CLONE_VFORK) {
1974 if (!wait_for_vfork_done(p, &vfork))
1975 ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid);
1976 }
1977
1978 put_pid(pid);
1979 } else {
1980 nr = PTR_ERR(p);
1981 }
1982 return nr;
1983}
1984
1985#ifndef CONFIG_HAVE_COPY_THREAD_TLS
1986/* For compatibility with architectures that call do_fork directly rather than
1987 * using the syscall entry points below. */
1988long do_fork(unsigned long clone_flags,
1989 unsigned long stack_start,
1990 unsigned long stack_size,
1991 int __user *parent_tidptr,
1992 int __user *child_tidptr)
1993{
1994 return _do_fork(clone_flags, stack_start, stack_size,
1995 parent_tidptr, child_tidptr, 0);
1996}
1997#endif
1998
1999/*
2000 * Create a kernel thread.
2001 */
2002pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
2003{
2004 return _do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn,
2005 (unsigned long)arg, NULL, NULL, 0);
2006}
2007
2008#ifdef __ARCH_WANT_SYS_FORK
2009SYSCALL_DEFINE0(fork)
2010{
2011#ifdef CONFIG_MMU
2012 return _do_fork(SIGCHLD, 0, 0, NULL, NULL, 0);
2013#else
2014 /* can not support in nommu mode */
2015 return -EINVAL;
2016#endif
2017}
2018#endif
2019
2020#ifdef __ARCH_WANT_SYS_VFORK
2021SYSCALL_DEFINE0(vfork)
2022{
2023 return _do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0,
2024 0, NULL, NULL, 0);
2025}
2026#endif
2027
2028#ifdef __ARCH_WANT_SYS_CLONE
2029#ifdef CONFIG_CLONE_BACKWARDS
2030SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2031 int __user *, parent_tidptr,
2032 unsigned long, tls,
2033 int __user *, child_tidptr)
2034#elif defined(CONFIG_CLONE_BACKWARDS2)
2035SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags,
2036 int __user *, parent_tidptr,
2037 int __user *, child_tidptr,
2038 unsigned long, tls)
2039#elif defined(CONFIG_CLONE_BACKWARDS3)
2040SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp,
2041 int, stack_size,
2042 int __user *, parent_tidptr,
2043 int __user *, child_tidptr,
2044 unsigned long, tls)
2045#else
2046SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2047 int __user *, parent_tidptr,
2048 int __user *, child_tidptr,
2049 unsigned long, tls)
2050#endif
2051{
2052 return _do_fork(clone_flags, newsp, 0, parent_tidptr, child_tidptr, tls);
2053}
2054#endif
2055
2056#ifndef ARCH_MIN_MMSTRUCT_ALIGN
2057#define ARCH_MIN_MMSTRUCT_ALIGN 0
2058#endif
2059
2060static void sighand_ctor(void *data)
2061{
2062 struct sighand_struct *sighand = data;
2063
2064 spin_lock_init(&sighand->siglock);
2065 init_waitqueue_head(&sighand->signalfd_wqh);
2066}
2067
2068void __init proc_caches_init(void)
2069{
2070 sighand_cachep = kmem_cache_create("sighand_cache",
2071 sizeof(struct sighand_struct), 0,
2072 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU|
2073 SLAB_NOTRACK|SLAB_ACCOUNT, sighand_ctor);
2074 signal_cachep = kmem_cache_create("signal_cache",
2075 sizeof(struct signal_struct), 0,
2076 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT,
2077 NULL);
2078 files_cachep = kmem_cache_create("files_cache",
2079 sizeof(struct files_struct), 0,
2080 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT,
2081 NULL);
2082 fs_cachep = kmem_cache_create("fs_cache",
2083 sizeof(struct fs_struct), 0,
2084 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT,
2085 NULL);
2086 /*
2087 * FIXME! The "sizeof(struct mm_struct)" currently includes the
2088 * whole struct cpumask for the OFFSTACK case. We could change
2089 * this to *only* allocate as much of it as required by the
2090 * maximum number of CPU's we can ever have. The cpumask_allocation
2091 * is at the end of the structure, exactly for that reason.
2092 */
2093 mm_cachep = kmem_cache_create("mm_struct",
2094 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
2095 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT,
2096 NULL);
2097 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT);
2098 mmap_init();
2099 nsproxy_cache_init();
2100}
2101
2102/*
2103 * Check constraints on flags passed to the unshare system call.
2104 */
2105static int check_unshare_flags(unsigned long unshare_flags)
2106{
2107 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
2108 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
2109 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET|
2110 CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP))
2111 return -EINVAL;
2112 /*
2113 * Not implemented, but pretend it works if there is nothing
2114 * to unshare. Note that unsharing the address space or the
2115 * signal handlers also need to unshare the signal queues (aka
2116 * CLONE_THREAD).
2117 */
2118 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
2119 if (!thread_group_empty(current))
2120 return -EINVAL;
2121 }
2122 if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) {
2123 if (atomic_read(&current->sighand->count) > 1)
2124 return -EINVAL;
2125 }
2126 if (unshare_flags & CLONE_VM) {
2127 if (!current_is_single_threaded())
2128 return -EINVAL;
2129 }
2130
2131 return 0;
2132}
2133
2134/*
2135 * Unshare the filesystem structure if it is being shared
2136 */
2137static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
2138{
2139 struct fs_struct *fs = current->fs;
2140
2141 if (!(unshare_flags & CLONE_FS) || !fs)
2142 return 0;
2143
2144 /* don't need lock here; in the worst case we'll do useless copy */
2145 if (fs->users == 1)
2146 return 0;
2147
2148 *new_fsp = copy_fs_struct(fs);
2149 if (!*new_fsp)
2150 return -ENOMEM;
2151
2152 return 0;
2153}
2154
2155/*
2156 * Unshare file descriptor table if it is being shared
2157 */
2158static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
2159{
2160 struct files_struct *fd = current->files;
2161 int error = 0;
2162
2163 if ((unshare_flags & CLONE_FILES) &&
2164 (fd && atomic_read(&fd->count) > 1)) {
2165 *new_fdp = dup_fd(fd, &error);
2166 if (!*new_fdp)
2167 return error;
2168 }
2169
2170 return 0;
2171}
2172
2173/*
2174 * unshare allows a process to 'unshare' part of the process
2175 * context which was originally shared using clone. copy_*
2176 * functions used by do_fork() cannot be used here directly
2177 * because they modify an inactive task_struct that is being
2178 * constructed. Here we are modifying the current, active,
2179 * task_struct.
2180 */
2181SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
2182{
2183 struct fs_struct *fs, *new_fs = NULL;
2184 struct files_struct *fd, *new_fd = NULL;
2185 struct cred *new_cred = NULL;
2186 struct nsproxy *new_nsproxy = NULL;
2187 int do_sysvsem = 0;
2188 int err;
2189
2190 /*
2191 * If unsharing a user namespace must also unshare the thread group
2192 * and unshare the filesystem root and working directories.
2193 */
2194 if (unshare_flags & CLONE_NEWUSER)
2195 unshare_flags |= CLONE_THREAD | CLONE_FS;
2196 /*
2197 * If unsharing vm, must also unshare signal handlers.
2198 */
2199 if (unshare_flags & CLONE_VM)
2200 unshare_flags |= CLONE_SIGHAND;
2201 /*
2202 * If unsharing a signal handlers, must also unshare the signal queues.
2203 */
2204 if (unshare_flags & CLONE_SIGHAND)
2205 unshare_flags |= CLONE_THREAD;
2206 /*
2207 * If unsharing namespace, must also unshare filesystem information.
2208 */
2209 if (unshare_flags & CLONE_NEWNS)
2210 unshare_flags |= CLONE_FS;
2211
2212 err = check_unshare_flags(unshare_flags);
2213 if (err)
2214 goto bad_unshare_out;
2215 /*
2216 * CLONE_NEWIPC must also detach from the undolist: after switching
2217 * to a new ipc namespace, the semaphore arrays from the old
2218 * namespace are unreachable.
2219 */
2220 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
2221 do_sysvsem = 1;
2222 err = unshare_fs(unshare_flags, &new_fs);
2223 if (err)
2224 goto bad_unshare_out;
2225 err = unshare_fd(unshare_flags, &new_fd);
2226 if (err)
2227 goto bad_unshare_cleanup_fs;
2228 err = unshare_userns(unshare_flags, &new_cred);
2229 if (err)
2230 goto bad_unshare_cleanup_fd;
2231 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
2232 new_cred, new_fs);
2233 if (err)
2234 goto bad_unshare_cleanup_cred;
2235
2236 if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
2237 if (do_sysvsem) {
2238 /*
2239 * CLONE_SYSVSEM is equivalent to sys_exit().
2240 */
2241 exit_sem(current);
2242 }
2243 if (unshare_flags & CLONE_NEWIPC) {
2244 /* Orphan segments in old ns (see sem above). */
2245 exit_shm(current);
2246 shm_init_task(current);
2247 }
2248
2249 if (new_nsproxy)
2250 switch_task_namespaces(current, new_nsproxy);
2251
2252 task_lock(current);
2253
2254 if (new_fs) {
2255 fs = current->fs;
2256 spin_lock(&fs->lock);
2257 current->fs = new_fs;
2258 if (--fs->users)
2259 new_fs = NULL;
2260 else
2261 new_fs = fs;
2262 spin_unlock(&fs->lock);
2263 }
2264
2265 if (new_fd) {
2266 fd = current->files;
2267 current->files = new_fd;
2268 new_fd = fd;
2269 }
2270
2271 task_unlock(current);
2272
2273 if (new_cred) {
2274 /* Install the new user namespace */
2275 commit_creds(new_cred);
2276 new_cred = NULL;
2277 }
2278 }
2279
2280bad_unshare_cleanup_cred:
2281 if (new_cred)
2282 put_cred(new_cred);
2283bad_unshare_cleanup_fd:
2284 if (new_fd)
2285 put_files_struct(new_fd);
2286
2287bad_unshare_cleanup_fs:
2288 if (new_fs)
2289 free_fs_struct(new_fs);
2290
2291bad_unshare_out:
2292 return err;
2293}
2294
2295/*
2296 * Helper to unshare the files of the current task.
2297 * We don't want to expose copy_files internals to
2298 * the exec layer of the kernel.
2299 */
2300
2301int unshare_files(struct files_struct **displaced)
2302{
2303 struct task_struct *task = current;
2304 struct files_struct *copy = NULL;
2305 int error;
2306
2307 error = unshare_fd(CLONE_FILES, &copy);
2308 if (error || !copy) {
2309 *displaced = NULL;
2310 return error;
2311 }
2312 *displaced = task->files;
2313 task_lock(task);
2314 task->files = copy;
2315 task_unlock(task);
2316 return 0;
2317}
2318
2319int sysctl_max_threads(struct ctl_table *table, int write,
2320 void __user *buffer, size_t *lenp, loff_t *ppos)
2321{
2322 struct ctl_table t;
2323 int ret;
2324 int threads = max_threads;
2325 int min = MIN_THREADS;
2326 int max = MAX_THREADS;
2327
2328 t = *table;
2329 t.data = &threads;
2330 t.extra1 = &min;
2331 t.extra2 = &max;
2332
2333 ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
2334 if (ret || !write)
2335 return ret;
2336
2337 set_max_threads(threads);
2338
2339 return 0;
2340}
2341