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/sched/autogroup.h>
16#include <linux/sched/mm.h>
17#include <linux/sched/coredump.h>
18#include <linux/sched/user.h>
19#include <linux/sched/numa_balancing.h>
20#include <linux/sched/stat.h>
21#include <linux/sched/task.h>
22#include <linux/sched/task_stack.h>
23#include <linux/sched/cputime.h>
24#include <linux/rtmutex.h>
25#include <linux/init.h>
26#include <linux/unistd.h>
27#include <linux/module.h>
28#include <linux/vmalloc.h>
29#include <linux/completion.h>
30#include <linux/personality.h>
31#include <linux/mempolicy.h>
32#include <linux/sem.h>
33#include <linux/file.h>
34#include <linux/fdtable.h>
35#include <linux/iocontext.h>
36#include <linux/key.h>
37#include <linux/binfmts.h>
38#include <linux/mman.h>
39#include <linux/mmu_notifier.h>
40#include <linux/fs.h>
41#include <linux/mm.h>
42#include <linux/vmacache.h>
43#include <linux/nsproxy.h>
44#include <linux/capability.h>
45#include <linux/cpu.h>
46#include <linux/cgroup.h>
47#include <linux/security.h>
48#include <linux/hugetlb.h>
49#include <linux/seccomp.h>
50#include <linux/swap.h>
51#include <linux/syscalls.h>
52#include <linux/jiffies.h>
53#include <linux/futex.h>
54#include <linux/compat.h>
55#include <linux/kthread.h>
56#include <linux/task_io_accounting_ops.h>
57#include <linux/rcupdate.h>
58#include <linux/ptrace.h>
59#include <linux/mount.h>
60#include <linux/audit.h>
61#include <linux/memcontrol.h>
62#include <linux/ftrace.h>
63#include <linux/proc_fs.h>
64#include <linux/profile.h>
65#include <linux/rmap.h>
66#include <linux/ksm.h>
67#include <linux/acct.h>
68#include <linux/userfaultfd_k.h>
69#include <linux/tsacct_kern.h>
70#include <linux/cn_proc.h>
71#include <linux/freezer.h>
72#include <linux/delayacct.h>
73#include <linux/taskstats_kern.h>
74#include <linux/random.h>
75#include <linux/tty.h>
76#include <linux/blkdev.h>
77#include <linux/fs_struct.h>
78#include <linux/magic.h>
79#include <linux/perf_event.h>
80#include <linux/posix-timers.h>
81#include <linux/user-return-notifier.h>
82#include <linux/oom.h>
83#include <linux/khugepaged.h>
84#include <linux/signalfd.h>
85#include <linux/uprobes.h>
86#include <linux/aio.h>
87#include <linux/compiler.h>
88#include <linux/sysctl.h>
89#include <linux/kcov.h>
90
91#include <asm/pgtable.h>
92#include <asm/pgalloc.h>
93#include <linux/uaccess.h>
94#include <asm/mmu_context.h>
95#include <asm/cacheflush.h>
96#include <asm/tlbflush.h>
97
98#include <trace/events/sched.h>
99
100#define CREATE_TRACE_POINTS
101#include <trace/events/task.h>
102
103/*
104 * Minimum number of threads to boot the kernel
105 */
106#define MIN_THREADS 20
107
108/*
109 * Maximum number of threads
110 */
111#define MAX_THREADS FUTEX_TID_MASK
112
113/*
114 * Protected counters by write_lock_irq(&tasklist_lock)
115 */
116unsigned long total_forks; /* Handle normal Linux uptimes. */
117int nr_threads; /* The idle threads do not count.. */
118
119int max_threads; /* tunable limit on nr_threads */
120
121DEFINE_PER_CPU(unsigned long, process_counts) = 0;
122
123__cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */
124
125#ifdef CONFIG_PROVE_RCU
126int lockdep_tasklist_lock_is_held(void)
127{
128 return lockdep_is_held(&tasklist_lock);
129}
130EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
131#endif /* #ifdef CONFIG_PROVE_RCU */
132
133int nr_processes(void)
134{
135 int cpu;
136 int total = 0;
137
138 for_each_possible_cpu(cpu)
139 total += per_cpu(process_counts, cpu);
140
141 return total;
142}
143
144void __weak arch_release_task_struct(struct task_struct *tsk)
145{
146}
147
148#ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
149static struct kmem_cache *task_struct_cachep;
150
151static inline struct task_struct *alloc_task_struct_node(int node)
152{
153 return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node);
154}
155
156static inline void free_task_struct(struct task_struct *tsk)
157{
158 kmem_cache_free(task_struct_cachep, tsk);
159}
160#endif
161
162void __weak arch_release_thread_stack(unsigned long *stack)
163{
164}
165
166#ifndef CONFIG_ARCH_THREAD_STACK_ALLOCATOR
167
168/*
169 * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
170 * kmemcache based allocator.
171 */
172# if THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK)
173
174#ifdef CONFIG_VMAP_STACK
175/*
176 * vmalloc() is a bit slow, and calling vfree() enough times will force a TLB
177 * flush. Try to minimize the number of calls by caching stacks.
178 */
179#define NR_CACHED_STACKS 2
180static DEFINE_PER_CPU(struct vm_struct *, cached_stacks[NR_CACHED_STACKS]);
181#endif
182
183static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node)
184{
185#ifdef CONFIG_VMAP_STACK
186 void *stack;
187 int i;
188
189 local_irq_disable();
190 for (i = 0; i < NR_CACHED_STACKS; i++) {
191 struct vm_struct *s = this_cpu_read(cached_stacks[i]);
192
193 if (!s)
194 continue;
195 this_cpu_write(cached_stacks[i], NULL);
196
197 tsk->stack_vm_area = s;
198 local_irq_enable();
199 return s->addr;
200 }
201 local_irq_enable();
202
203 stack = __vmalloc_node_range(THREAD_SIZE, THREAD_SIZE,
204 VMALLOC_START, VMALLOC_END,
205 THREADINFO_GFP | __GFP_HIGHMEM,
206 PAGE_KERNEL,
207 0, node, __builtin_return_address(0));
208
209 /*
210 * We can't call find_vm_area() in interrupt context, and
211 * free_thread_stack() can be called in interrupt context,
212 * so cache the vm_struct.
213 */
214 if (stack)
215 tsk->stack_vm_area = find_vm_area(stack);
216 return stack;
217#else
218 struct page *page = alloc_pages_node(node, THREADINFO_GFP,
219 THREAD_SIZE_ORDER);
220
221 return page ? page_address(page) : NULL;
222#endif
223}
224
225static inline void free_thread_stack(struct task_struct *tsk)
226{
227#ifdef CONFIG_VMAP_STACK
228 if (task_stack_vm_area(tsk)) {
229 unsigned long flags;
230 int i;
231
232 local_irq_save(flags);
233 for (i = 0; i < NR_CACHED_STACKS; i++) {
234 if (this_cpu_read(cached_stacks[i]))
235 continue;
236
237 this_cpu_write(cached_stacks[i], tsk->stack_vm_area);
238 local_irq_restore(flags);
239 return;
240 }
241 local_irq_restore(flags);
242
243 vfree_atomic(tsk->stack);
244 return;
245 }
246#endif
247
248 __free_pages(virt_to_page(tsk->stack), THREAD_SIZE_ORDER);
249}
250# else
251static struct kmem_cache *thread_stack_cache;
252
253static unsigned long *alloc_thread_stack_node(struct task_struct *tsk,
254 int node)
255{
256 return kmem_cache_alloc_node(thread_stack_cache, THREADINFO_GFP, node);
257}
258
259static void free_thread_stack(struct task_struct *tsk)
260{
261 kmem_cache_free(thread_stack_cache, tsk->stack);
262}
263
264void thread_stack_cache_init(void)
265{
266 thread_stack_cache = kmem_cache_create("thread_stack", THREAD_SIZE,
267 THREAD_SIZE, 0, NULL);
268 BUG_ON(thread_stack_cache == NULL);
269}
270# endif
271#endif
272
273/* SLAB cache for signal_struct structures (tsk->signal) */
274static struct kmem_cache *signal_cachep;
275
276/* SLAB cache for sighand_struct structures (tsk->sighand) */
277struct kmem_cache *sighand_cachep;
278
279/* SLAB cache for files_struct structures (tsk->files) */
280struct kmem_cache *files_cachep;
281
282/* SLAB cache for fs_struct structures (tsk->fs) */
283struct kmem_cache *fs_cachep;
284
285/* SLAB cache for vm_area_struct structures */
286struct kmem_cache *vm_area_cachep;
287
288/* SLAB cache for mm_struct structures (tsk->mm) */
289static struct kmem_cache *mm_cachep;
290
291static void account_kernel_stack(struct task_struct *tsk, int account)
292{
293 void *stack = task_stack_page(tsk);
294 struct vm_struct *vm = task_stack_vm_area(tsk);
295
296 BUILD_BUG_ON(IS_ENABLED(CONFIG_VMAP_STACK) && PAGE_SIZE % 1024 != 0);
297
298 if (vm) {
299 int i;
300
301 BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE);
302
303 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
304 mod_zone_page_state(page_zone(vm->pages[i]),
305 NR_KERNEL_STACK_KB,
306 PAGE_SIZE / 1024 * account);
307 }
308
309 /* All stack pages belong to the same memcg. */
310 memcg_kmem_update_page_stat(vm->pages[0], MEMCG_KERNEL_STACK_KB,
311 account * (THREAD_SIZE / 1024));
312 } else {
313 /*
314 * All stack pages are in the same zone and belong to the
315 * same memcg.
316 */
317 struct page *first_page = virt_to_page(stack);
318
319 mod_zone_page_state(page_zone(first_page), NR_KERNEL_STACK_KB,
320 THREAD_SIZE / 1024 * account);
321
322 memcg_kmem_update_page_stat(first_page, MEMCG_KERNEL_STACK_KB,
323 account * (THREAD_SIZE / 1024));
324 }
325}
326
327static void release_task_stack(struct task_struct *tsk)
328{
329 if (WARN_ON(tsk->state != TASK_DEAD))
330 return; /* Better to leak the stack than to free prematurely */
331
332 account_kernel_stack(tsk, -1);
333 arch_release_thread_stack(tsk->stack);
334 free_thread_stack(tsk);
335 tsk->stack = NULL;
336#ifdef CONFIG_VMAP_STACK
337 tsk->stack_vm_area = NULL;
338#endif
339}
340
341#ifdef CONFIG_THREAD_INFO_IN_TASK
342void put_task_stack(struct task_struct *tsk)
343{
344 if (atomic_dec_and_test(&tsk->stack_refcount))
345 release_task_stack(tsk);
346}
347#endif
348
349void free_task(struct task_struct *tsk)
350{
351#ifndef CONFIG_THREAD_INFO_IN_TASK
352 /*
353 * The task is finally done with both the stack and thread_info,
354 * so free both.
355 */
356 release_task_stack(tsk);
357#else
358 /*
359 * If the task had a separate stack allocation, it should be gone
360 * by now.
361 */
362 WARN_ON_ONCE(atomic_read(&tsk->stack_refcount) != 0);
363#endif
364 rt_mutex_debug_task_free(tsk);
365 ftrace_graph_exit_task(tsk);
366 put_seccomp_filter(tsk);
367 arch_release_task_struct(tsk);
368 if (tsk->flags & PF_KTHREAD)
369 free_kthread_struct(tsk);
370 free_task_struct(tsk);
371}
372EXPORT_SYMBOL(free_task);
373
374static inline void free_signal_struct(struct signal_struct *sig)
375{
376 taskstats_tgid_free(sig);
377 sched_autogroup_exit(sig);
378 /*
379 * __mmdrop is not safe to call from softirq context on x86 due to
380 * pgd_dtor so postpone it to the async context
381 */
382 if (sig->oom_mm)
383 mmdrop_async(sig->oom_mm);
384 kmem_cache_free(signal_cachep, sig);
385}
386
387static inline void put_signal_struct(struct signal_struct *sig)
388{
389 if (atomic_dec_and_test(&sig->sigcnt))
390 free_signal_struct(sig);
391}
392
393void __put_task_struct(struct task_struct *tsk)
394{
395 WARN_ON(!tsk->exit_state);
396 WARN_ON(atomic_read(&tsk->usage));
397 WARN_ON(tsk == current);
398
399 cgroup_free(tsk);
400 task_numa_free(tsk);
401 security_task_free(tsk);
402 exit_creds(tsk);
403 delayacct_tsk_free(tsk);
404 put_signal_struct(tsk->signal);
405
406 if (!profile_handoff_task(tsk))
407 free_task(tsk);
408}
409EXPORT_SYMBOL_GPL(__put_task_struct);
410
411void __init __weak arch_task_cache_init(void) { }
412
413/*
414 * set_max_threads
415 */
416static void set_max_threads(unsigned int max_threads_suggested)
417{
418 u64 threads;
419
420 /*
421 * The number of threads shall be limited such that the thread
422 * structures may only consume a small part of the available memory.
423 */
424 if (fls64(totalram_pages) + fls64(PAGE_SIZE) > 64)
425 threads = MAX_THREADS;
426 else
427 threads = div64_u64((u64) totalram_pages * (u64) PAGE_SIZE,
428 (u64) THREAD_SIZE * 8UL);
429
430 if (threads > max_threads_suggested)
431 threads = max_threads_suggested;
432
433 max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS);
434}
435
436#ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT
437/* Initialized by the architecture: */
438int arch_task_struct_size __read_mostly;
439#endif
440
441void __init fork_init(void)
442{
443 int i;
444#ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
445#ifndef ARCH_MIN_TASKALIGN
446#define ARCH_MIN_TASKALIGN 0
447#endif
448 int align = max_t(int, L1_CACHE_BYTES, ARCH_MIN_TASKALIGN);
449
450 /* create a slab on which task_structs can be allocated */
451 task_struct_cachep = kmem_cache_create("task_struct",
452 arch_task_struct_size, align,
453 SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, NULL);
454#endif
455
456 /* do the arch specific task caches init */
457 arch_task_cache_init();
458
459 set_max_threads(MAX_THREADS);
460
461 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
462 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
463 init_task.signal->rlim[RLIMIT_SIGPENDING] =
464 init_task.signal->rlim[RLIMIT_NPROC];
465
466 for (i = 0; i < UCOUNT_COUNTS; i++) {
467 init_user_ns.ucount_max[i] = max_threads/2;
468 }
469}
470
471int __weak arch_dup_task_struct(struct task_struct *dst,
472 struct task_struct *src)
473{
474 *dst = *src;
475 return 0;
476}
477
478void set_task_stack_end_magic(struct task_struct *tsk)
479{
480 unsigned long *stackend;
481
482 stackend = end_of_stack(tsk);
483 *stackend = STACK_END_MAGIC; /* for overflow detection */
484}
485
486static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
487{
488 struct task_struct *tsk;
489 unsigned long *stack;
490 struct vm_struct *stack_vm_area;
491 int err;
492
493 if (node == NUMA_NO_NODE)
494 node = tsk_fork_get_node(orig);
495 tsk = alloc_task_struct_node(node);
496 if (!tsk)
497 return NULL;
498
499 stack = alloc_thread_stack_node(tsk, node);
500 if (!stack)
501 goto free_tsk;
502
503 stack_vm_area = task_stack_vm_area(tsk);
504
505 err = arch_dup_task_struct(tsk, orig);
506
507 /*
508 * arch_dup_task_struct() clobbers the stack-related fields. Make
509 * sure they're properly initialized before using any stack-related
510 * functions again.
511 */
512 tsk->stack = stack;
513#ifdef CONFIG_VMAP_STACK
514 tsk->stack_vm_area = stack_vm_area;
515#endif
516#ifdef CONFIG_THREAD_INFO_IN_TASK
517 atomic_set(&tsk->stack_refcount, 1);
518#endif
519
520 if (err)
521 goto free_stack;
522
523#ifdef CONFIG_SECCOMP
524 /*
525 * We must handle setting up seccomp filters once we're under
526 * the sighand lock in case orig has changed between now and
527 * then. Until then, filter must be NULL to avoid messing up
528 * the usage counts on the error path calling free_task.
529 */
530 tsk->seccomp.filter = NULL;
531#endif
532
533 setup_thread_stack(tsk, orig);
534 clear_user_return_notifier(tsk);
535 clear_tsk_need_resched(tsk);
536 set_task_stack_end_magic(tsk);
537
538#ifdef CONFIG_CC_STACKPROTECTOR
539 tsk->stack_canary = get_random_int();
540#endif
541
542 /*
543 * One for us, one for whoever does the "release_task()" (usually
544 * parent)
545 */
546 atomic_set(&tsk->usage, 2);
547#ifdef CONFIG_BLK_DEV_IO_TRACE
548 tsk->btrace_seq = 0;
549#endif
550 tsk->splice_pipe = NULL;
551 tsk->task_frag.page = NULL;
552 tsk->wake_q.next = NULL;
553
554 account_kernel_stack(tsk, 1);
555
556 kcov_task_init(tsk);
557
558 return tsk;
559
560free_stack:
561 free_thread_stack(tsk);
562free_tsk:
563 free_task_struct(tsk);
564 return NULL;
565}
566
567#ifdef CONFIG_MMU
568static __latent_entropy int dup_mmap(struct mm_struct *mm,
569 struct mm_struct *oldmm)
570{
571 struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
572 struct rb_node **rb_link, *rb_parent;
573 int retval;
574 unsigned long charge;
575 LIST_HEAD(uf);
576
577 uprobe_start_dup_mmap();
578 if (down_write_killable(&oldmm->mmap_sem)) {
579 retval = -EINTR;
580 goto fail_uprobe_end;
581 }
582 flush_cache_dup_mm(oldmm);
583 uprobe_dup_mmap(oldmm, mm);
584 /*
585 * Not linked in yet - no deadlock potential:
586 */
587 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
588
589 /* No ordering required: file already has been exposed. */
590 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
591
592 mm->total_vm = oldmm->total_vm;
593 mm->data_vm = oldmm->data_vm;
594 mm->exec_vm = oldmm->exec_vm;
595 mm->stack_vm = oldmm->stack_vm;
596
597 rb_link = &mm->mm_rb.rb_node;
598 rb_parent = NULL;
599 pprev = &mm->mmap;
600 retval = ksm_fork(mm, oldmm);
601 if (retval)
602 goto out;
603 retval = khugepaged_fork(mm, oldmm);
604 if (retval)
605 goto out;
606
607 prev = NULL;
608 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
609 struct file *file;
610
611 if (mpnt->vm_flags & VM_DONTCOPY) {
612 vm_stat_account(mm, mpnt->vm_flags, -vma_pages(mpnt));
613 continue;
614 }
615 charge = 0;
616 if (mpnt->vm_flags & VM_ACCOUNT) {
617 unsigned long len = vma_pages(mpnt);
618
619 if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
620 goto fail_nomem;
621 charge = len;
622 }
623 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
624 if (!tmp)
625 goto fail_nomem;
626 *tmp = *mpnt;
627 INIT_LIST_HEAD(&tmp->anon_vma_chain);
628 retval = vma_dup_policy(mpnt, tmp);
629 if (retval)
630 goto fail_nomem_policy;
631 tmp->vm_mm = mm;
632 retval = dup_userfaultfd(tmp, &uf);
633 if (retval)
634 goto fail_nomem_anon_vma_fork;
635 if (anon_vma_fork(tmp, mpnt))
636 goto fail_nomem_anon_vma_fork;
637 tmp->vm_flags &= ~(VM_LOCKED | VM_LOCKONFAULT);
638 tmp->vm_next = tmp->vm_prev = NULL;
639 file = tmp->vm_file;
640 if (file) {
641 struct inode *inode = file_inode(file);
642 struct address_space *mapping = file->f_mapping;
643
644 get_file(file);
645 if (tmp->vm_flags & VM_DENYWRITE)
646 atomic_dec(&inode->i_writecount);
647 i_mmap_lock_write(mapping);
648 if (tmp->vm_flags & VM_SHARED)
649 atomic_inc(&mapping->i_mmap_writable);
650 flush_dcache_mmap_lock(mapping);
651 /* insert tmp into the share list, just after mpnt */
652 vma_interval_tree_insert_after(tmp, mpnt,
653 &mapping->i_mmap);
654 flush_dcache_mmap_unlock(mapping);
655 i_mmap_unlock_write(mapping);
656 }
657
658 /*
659 * Clear hugetlb-related page reserves for children. This only
660 * affects MAP_PRIVATE mappings. Faults generated by the child
661 * are not guaranteed to succeed, even if read-only
662 */
663 if (is_vm_hugetlb_page(tmp))
664 reset_vma_resv_huge_pages(tmp);
665
666 /*
667 * Link in the new vma and copy the page table entries.
668 */
669 *pprev = tmp;
670 pprev = &tmp->vm_next;
671 tmp->vm_prev = prev;
672 prev = tmp;
673
674 __vma_link_rb(mm, tmp, rb_link, rb_parent);
675 rb_link = &tmp->vm_rb.rb_right;
676 rb_parent = &tmp->vm_rb;
677
678 mm->map_count++;
679 retval = copy_page_range(mm, oldmm, mpnt);
680
681 if (tmp->vm_ops && tmp->vm_ops->open)
682 tmp->vm_ops->open(tmp);
683
684 if (retval)
685 goto out;
686 }
687 /* a new mm has just been created */
688 arch_dup_mmap(oldmm, mm);
689 retval = 0;
690out:
691 up_write(&mm->mmap_sem);
692 flush_tlb_mm(oldmm);
693 up_write(&oldmm->mmap_sem);
694 dup_userfaultfd_complete(&uf);
695fail_uprobe_end:
696 uprobe_end_dup_mmap();
697 return retval;
698fail_nomem_anon_vma_fork:
699 mpol_put(vma_policy(tmp));
700fail_nomem_policy:
701 kmem_cache_free(vm_area_cachep, tmp);
702fail_nomem:
703 retval = -ENOMEM;
704 vm_unacct_memory(charge);
705 goto out;
706}
707
708static inline int mm_alloc_pgd(struct mm_struct *mm)
709{
710 mm->pgd = pgd_alloc(mm);
711 if (unlikely(!mm->pgd))
712 return -ENOMEM;
713 return 0;
714}
715
716static inline void mm_free_pgd(struct mm_struct *mm)
717{
718 pgd_free(mm, mm->pgd);
719}
720#else
721static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
722{
723 down_write(&oldmm->mmap_sem);
724 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
725 up_write(&oldmm->mmap_sem);
726 return 0;
727}
728#define mm_alloc_pgd(mm) (0)
729#define mm_free_pgd(mm)
730#endif /* CONFIG_MMU */
731
732__cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
733
734#define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
735#define free_mm(mm) (kmem_cache_free(mm_cachep, (mm)))
736
737static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
738
739static int __init coredump_filter_setup(char *s)
740{
741 default_dump_filter =
742 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
743 MMF_DUMP_FILTER_MASK;
744 return 1;
745}
746
747__setup("coredump_filter=", coredump_filter_setup);
748
749#include <linux/init_task.h>
750
751static void mm_init_aio(struct mm_struct *mm)
752{
753#ifdef CONFIG_AIO
754 spin_lock_init(&mm->ioctx_lock);
755 mm->ioctx_table = NULL;
756#endif
757}
758
759static void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
760{
761#ifdef CONFIG_MEMCG
762 mm->owner = p;
763#endif
764}
765
766static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
767 struct user_namespace *user_ns)
768{
769 mm->mmap = NULL;
770 mm->mm_rb = RB_ROOT;
771 mm->vmacache_seqnum = 0;
772 atomic_set(&mm->mm_users, 1);
773 atomic_set(&mm->mm_count, 1);
774 init_rwsem(&mm->mmap_sem);
775 INIT_LIST_HEAD(&mm->mmlist);
776 mm->core_state = NULL;
777 atomic_long_set(&mm->nr_ptes, 0);
778 mm_nr_pmds_init(mm);
779 mm->map_count = 0;
780 mm->locked_vm = 0;
781 mm->pinned_vm = 0;
782 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
783 spin_lock_init(&mm->page_table_lock);
784 mm_init_cpumask(mm);
785 mm_init_aio(mm);
786 mm_init_owner(mm, p);
787 mmu_notifier_mm_init(mm);
788 clear_tlb_flush_pending(mm);
789#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
790 mm->pmd_huge_pte = NULL;
791#endif
792
793 if (current->mm) {
794 mm->flags = current->mm->flags & MMF_INIT_MASK;
795 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK;
796 } else {
797 mm->flags = default_dump_filter;
798 mm->def_flags = 0;
799 }
800
801 if (mm_alloc_pgd(mm))
802 goto fail_nopgd;
803
804 if (init_new_context(p, mm))
805 goto fail_nocontext;
806
807 mm->user_ns = get_user_ns(user_ns);
808 return mm;
809
810fail_nocontext:
811 mm_free_pgd(mm);
812fail_nopgd:
813 free_mm(mm);
814 return NULL;
815}
816
817static void check_mm(struct mm_struct *mm)
818{
819 int i;
820
821 for (i = 0; i < NR_MM_COUNTERS; i++) {
822 long x = atomic_long_read(&mm->rss_stat.count[i]);
823
824 if (unlikely(x))
825 printk(KERN_ALERT "BUG: Bad rss-counter state "
826 "mm:%p idx:%d val:%ld\n", mm, i, x);
827 }
828
829 if (atomic_long_read(&mm->nr_ptes))
830 pr_alert("BUG: non-zero nr_ptes on freeing mm: %ld\n",
831 atomic_long_read(&mm->nr_ptes));
832 if (mm_nr_pmds(mm))
833 pr_alert("BUG: non-zero nr_pmds on freeing mm: %ld\n",
834 mm_nr_pmds(mm));
835
836#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
837 VM_BUG_ON_MM(mm->pmd_huge_pte, mm);
838#endif
839}
840
841/*
842 * Allocate and initialize an mm_struct.
843 */
844struct mm_struct *mm_alloc(void)
845{
846 struct mm_struct *mm;
847
848 mm = allocate_mm();
849 if (!mm)
850 return NULL;
851
852 memset(mm, 0, sizeof(*mm));
853 return mm_init(mm, current, current_user_ns());
854}
855
856/*
857 * Called when the last reference to the mm
858 * is dropped: either by a lazy thread or by
859 * mmput. Free the page directory and the mm.
860 */
861void __mmdrop(struct mm_struct *mm)
862{
863 BUG_ON(mm == &init_mm);
864 mm_free_pgd(mm);
865 destroy_context(mm);
866 mmu_notifier_mm_destroy(mm);
867 check_mm(mm);
868 put_user_ns(mm->user_ns);
869 free_mm(mm);
870}
871EXPORT_SYMBOL_GPL(__mmdrop);
872
873static inline void __mmput(struct mm_struct *mm)
874{
875 VM_BUG_ON(atomic_read(&mm->mm_users));
876
877 uprobe_clear_state(mm);
878 exit_aio(mm);
879 ksm_exit(mm);
880 khugepaged_exit(mm); /* must run before exit_mmap */
881 exit_mmap(mm);
882 mm_put_huge_zero_page(mm);
883 set_mm_exe_file(mm, NULL);
884 if (!list_empty(&mm->mmlist)) {
885 spin_lock(&mmlist_lock);
886 list_del(&mm->mmlist);
887 spin_unlock(&mmlist_lock);
888 }
889 if (mm->binfmt)
890 module_put(mm->binfmt->module);
891 set_bit(MMF_OOM_SKIP, &mm->flags);
892 mmdrop(mm);
893}
894
895/*
896 * Decrement the use count and release all resources for an mm.
897 */
898void mmput(struct mm_struct *mm)
899{
900 might_sleep();
901
902 if (atomic_dec_and_test(&mm->mm_users))
903 __mmput(mm);
904}
905EXPORT_SYMBOL_GPL(mmput);
906
907#ifdef CONFIG_MMU
908static void mmput_async_fn(struct work_struct *work)
909{
910 struct mm_struct *mm = container_of(work, struct mm_struct, async_put_work);
911 __mmput(mm);
912}
913
914void mmput_async(struct mm_struct *mm)
915{
916 if (atomic_dec_and_test(&mm->mm_users)) {
917 INIT_WORK(&mm->async_put_work, mmput_async_fn);
918 schedule_work(&mm->async_put_work);
919 }
920}
921#endif
922
923/**
924 * set_mm_exe_file - change a reference to the mm's executable file
925 *
926 * This changes mm's executable file (shown as symlink /proc/[pid]/exe).
927 *
928 * Main users are mmput() and sys_execve(). Callers prevent concurrent
929 * invocations: in mmput() nobody alive left, in execve task is single
930 * threaded. sys_prctl(PR_SET_MM_MAP/EXE_FILE) also needs to set the
931 * mm->exe_file, but does so without using set_mm_exe_file() in order
932 * to do avoid the need for any locks.
933 */
934void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
935{
936 struct file *old_exe_file;
937
938 /*
939 * It is safe to dereference the exe_file without RCU as
940 * this function is only called if nobody else can access
941 * this mm -- see comment above for justification.
942 */
943 old_exe_file = rcu_dereference_raw(mm->exe_file);
944
945 if (new_exe_file)
946 get_file(new_exe_file);
947 rcu_assign_pointer(mm->exe_file, new_exe_file);
948 if (old_exe_file)
949 fput(old_exe_file);
950}
951
952/**
953 * get_mm_exe_file - acquire a reference to the mm's executable file
954 *
955 * Returns %NULL if mm has no associated executable file.
956 * User must release file via fput().
957 */
958struct file *get_mm_exe_file(struct mm_struct *mm)
959{
960 struct file *exe_file;
961
962 rcu_read_lock();
963 exe_file = rcu_dereference(mm->exe_file);
964 if (exe_file && !get_file_rcu(exe_file))
965 exe_file = NULL;
966 rcu_read_unlock();
967 return exe_file;
968}
969EXPORT_SYMBOL(get_mm_exe_file);
970
971/**
972 * get_task_exe_file - acquire a reference to the task's executable file
973 *
974 * Returns %NULL if task's mm (if any) has no associated executable file or
975 * this is a kernel thread with borrowed mm (see the comment above get_task_mm).
976 * User must release file via fput().
977 */
978struct file *get_task_exe_file(struct task_struct *task)
979{
980 struct file *exe_file = NULL;
981 struct mm_struct *mm;
982
983 task_lock(task);
984 mm = task->mm;
985 if (mm) {
986 if (!(task->flags & PF_KTHREAD))
987 exe_file = get_mm_exe_file(mm);
988 }
989 task_unlock(task);
990 return exe_file;
991}
992EXPORT_SYMBOL(get_task_exe_file);
993
994/**
995 * get_task_mm - acquire a reference to the task's mm
996 *
997 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning
998 * this kernel workthread has transiently adopted a user mm with use_mm,
999 * to do its AIO) is not set and if so returns a reference to it, after
1000 * bumping up the use count. User must release the mm via mmput()
1001 * after use. Typically used by /proc and ptrace.
1002 */
1003struct mm_struct *get_task_mm(struct task_struct *task)
1004{
1005 struct mm_struct *mm;
1006
1007 task_lock(task);
1008 mm = task->mm;
1009 if (mm) {
1010 if (task->flags & PF_KTHREAD)
1011 mm = NULL;
1012 else
1013 mmget(mm);
1014 }
1015 task_unlock(task);
1016 return mm;
1017}
1018EXPORT_SYMBOL_GPL(get_task_mm);
1019
1020struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
1021{
1022 struct mm_struct *mm;
1023 int err;
1024
1025 err = mutex_lock_killable(&task->signal->cred_guard_mutex);
1026 if (err)
1027 return ERR_PTR(err);
1028
1029 mm = get_task_mm(task);
1030 if (mm && mm != current->mm &&
1031 !ptrace_may_access(task, mode)) {
1032 mmput(mm);
1033 mm = ERR_PTR(-EACCES);
1034 }
1035 mutex_unlock(&task->signal->cred_guard_mutex);
1036
1037 return mm;
1038}
1039
1040static void complete_vfork_done(struct task_struct *tsk)
1041{
1042 struct completion *vfork;
1043
1044 task_lock(tsk);
1045 vfork = tsk->vfork_done;
1046 if (likely(vfork)) {
1047 tsk->vfork_done = NULL;
1048 complete(vfork);
1049 }
1050 task_unlock(tsk);
1051}
1052
1053static int wait_for_vfork_done(struct task_struct *child,
1054 struct completion *vfork)
1055{
1056 int killed;
1057
1058 freezer_do_not_count();
1059 killed = wait_for_completion_killable(vfork);
1060 freezer_count();
1061
1062 if (killed) {
1063 task_lock(child);
1064 child->vfork_done = NULL;
1065 task_unlock(child);
1066 }
1067
1068 put_task_struct(child);
1069 return killed;
1070}
1071
1072/* Please note the differences between mmput and mm_release.
1073 * mmput is called whenever we stop holding onto a mm_struct,
1074 * error success whatever.
1075 *
1076 * mm_release is called after a mm_struct has been removed
1077 * from the current process.
1078 *
1079 * This difference is important for error handling, when we
1080 * only half set up a mm_struct for a new process and need to restore
1081 * the old one. Because we mmput the new mm_struct before
1082 * restoring the old one. . .
1083 * Eric Biederman 10 January 1998
1084 */
1085void mm_release(struct task_struct *tsk, struct mm_struct *mm)
1086{
1087 /* Get rid of any futexes when releasing the mm */
1088#ifdef CONFIG_FUTEX
1089 if (unlikely(tsk->robust_list)) {
1090 exit_robust_list(tsk);
1091 tsk->robust_list = NULL;
1092 }
1093#ifdef CONFIG_COMPAT
1094 if (unlikely(tsk->compat_robust_list)) {
1095 compat_exit_robust_list(tsk);
1096 tsk->compat_robust_list = NULL;
1097 }
1098#endif
1099 if (unlikely(!list_empty(&tsk->pi_state_list)))
1100 exit_pi_state_list(tsk);
1101#endif
1102
1103 uprobe_free_utask(tsk);
1104
1105 /* Get rid of any cached register state */
1106 deactivate_mm(tsk, mm);
1107
1108 /*
1109 * Signal userspace if we're not exiting with a core dump
1110 * because we want to leave the value intact for debugging
1111 * purposes.
1112 */
1113 if (tsk->clear_child_tid) {
1114 if (!(tsk->signal->flags & SIGNAL_GROUP_COREDUMP) &&
1115 atomic_read(&mm->mm_users) > 1) {
1116 /*
1117 * We don't check the error code - if userspace has
1118 * not set up a proper pointer then tough luck.
1119 */
1120 put_user(0, tsk->clear_child_tid);
1121 sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
1122 1, NULL, NULL, 0);
1123 }
1124 tsk->clear_child_tid = NULL;
1125 }
1126
1127 /*
1128 * All done, finally we can wake up parent and return this mm to him.
1129 * Also kthread_stop() uses this completion for synchronization.
1130 */
1131 if (tsk->vfork_done)
1132 complete_vfork_done(tsk);
1133}
1134
1135/*
1136 * Allocate a new mm structure and copy contents from the
1137 * mm structure of the passed in task structure.
1138 */
1139static struct mm_struct *dup_mm(struct task_struct *tsk)
1140{
1141 struct mm_struct *mm, *oldmm = current->mm;
1142 int err;
1143
1144 mm = allocate_mm();
1145 if (!mm)
1146 goto fail_nomem;
1147
1148 memcpy(mm, oldmm, sizeof(*mm));
1149
1150 if (!mm_init(mm, tsk, mm->user_ns))
1151 goto fail_nomem;
1152
1153 err = dup_mmap(mm, oldmm);
1154 if (err)
1155 goto free_pt;
1156
1157 mm->hiwater_rss = get_mm_rss(mm);
1158 mm->hiwater_vm = mm->total_vm;
1159
1160 if (mm->binfmt && !try_module_get(mm->binfmt->module))
1161 goto free_pt;
1162
1163 return mm;
1164
1165free_pt:
1166 /* don't put binfmt in mmput, we haven't got module yet */
1167 mm->binfmt = NULL;
1168 mmput(mm);
1169
1170fail_nomem:
1171 return NULL;
1172}
1173
1174static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
1175{
1176 struct mm_struct *mm, *oldmm;
1177 int retval;
1178
1179 tsk->min_flt = tsk->maj_flt = 0;
1180 tsk->nvcsw = tsk->nivcsw = 0;
1181#ifdef CONFIG_DETECT_HUNG_TASK
1182 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
1183#endif
1184
1185 tsk->mm = NULL;
1186 tsk->active_mm = NULL;
1187
1188 /*
1189 * Are we cloning a kernel thread?
1190 *
1191 * We need to steal a active VM for that..
1192 */
1193 oldmm = current->mm;
1194 if (!oldmm)
1195 return 0;
1196
1197 /* initialize the new vmacache entries */
1198 vmacache_flush(tsk);
1199
1200 if (clone_flags & CLONE_VM) {
1201 mmget(oldmm);
1202 mm = oldmm;
1203 goto good_mm;
1204 }
1205
1206 retval = -ENOMEM;
1207 mm = dup_mm(tsk);
1208 if (!mm)
1209 goto fail_nomem;
1210
1211good_mm:
1212 tsk->mm = mm;
1213 tsk->active_mm = mm;
1214 return 0;
1215
1216fail_nomem:
1217 return retval;
1218}
1219
1220static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
1221{
1222 struct fs_struct *fs = current->fs;
1223 if (clone_flags & CLONE_FS) {
1224 /* tsk->fs is already what we want */
1225 spin_lock(&fs->lock);
1226 if (fs->in_exec) {
1227 spin_unlock(&fs->lock);
1228 return -EAGAIN;
1229 }
1230 fs->users++;
1231 spin_unlock(&fs->lock);
1232 return 0;
1233 }
1234 tsk->fs = copy_fs_struct(fs);
1235 if (!tsk->fs)
1236 return -ENOMEM;
1237 return 0;
1238}
1239
1240static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
1241{
1242 struct files_struct *oldf, *newf;
1243 int error = 0;
1244
1245 /*
1246 * A background process may not have any files ...
1247 */
1248 oldf = current->files;
1249 if (!oldf)
1250 goto out;
1251
1252 if (clone_flags & CLONE_FILES) {
1253 atomic_inc(&oldf->count);
1254 goto out;
1255 }
1256
1257 newf = dup_fd(oldf, &error);
1258 if (!newf)
1259 goto out;
1260
1261 tsk->files = newf;
1262 error = 0;
1263out:
1264 return error;
1265}
1266
1267static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
1268{
1269#ifdef CONFIG_BLOCK
1270 struct io_context *ioc = current->io_context;
1271 struct io_context *new_ioc;
1272
1273 if (!ioc)
1274 return 0;
1275 /*
1276 * Share io context with parent, if CLONE_IO is set
1277 */
1278 if (clone_flags & CLONE_IO) {
1279 ioc_task_link(ioc);
1280 tsk->io_context = ioc;
1281 } else if (ioprio_valid(ioc->ioprio)) {
1282 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE);
1283 if (unlikely(!new_ioc))
1284 return -ENOMEM;
1285
1286 new_ioc->ioprio = ioc->ioprio;
1287 put_io_context(new_ioc);
1288 }
1289#endif
1290 return 0;
1291}
1292
1293static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
1294{
1295 struct sighand_struct *sig;
1296
1297 if (clone_flags & CLONE_SIGHAND) {
1298 atomic_inc(&current->sighand->count);
1299 return 0;
1300 }
1301 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1302 rcu_assign_pointer(tsk->sighand, sig);
1303 if (!sig)
1304 return -ENOMEM;
1305
1306 atomic_set(&sig->count, 1);
1307 memcpy(sig->action, current->sighand->action, sizeof(sig->action));
1308 return 0;
1309}
1310
1311void __cleanup_sighand(struct sighand_struct *sighand)
1312{
1313 if (atomic_dec_and_test(&sighand->count)) {
1314 signalfd_cleanup(sighand);
1315 /*
1316 * sighand_cachep is SLAB_DESTROY_BY_RCU so we can free it
1317 * without an RCU grace period, see __lock_task_sighand().
1318 */
1319 kmem_cache_free(sighand_cachep, sighand);
1320 }
1321}
1322
1323#ifdef CONFIG_POSIX_TIMERS
1324/*
1325 * Initialize POSIX timer handling for a thread group.
1326 */
1327static void posix_cpu_timers_init_group(struct signal_struct *sig)
1328{
1329 unsigned long cpu_limit;
1330
1331 cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1332 if (cpu_limit != RLIM_INFINITY) {
1333 sig->cputime_expires.prof_exp = cpu_limit * NSEC_PER_SEC;
1334 sig->cputimer.running = true;
1335 }
1336
1337 /* The timer lists. */
1338 INIT_LIST_HEAD(&sig->cpu_timers[0]);
1339 INIT_LIST_HEAD(&sig->cpu_timers[1]);
1340 INIT_LIST_HEAD(&sig->cpu_timers[2]);
1341}
1342#else
1343static inline void posix_cpu_timers_init_group(struct signal_struct *sig) { }
1344#endif
1345
1346static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
1347{
1348 struct signal_struct *sig;
1349
1350 if (clone_flags & CLONE_THREAD)
1351 return 0;
1352
1353 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
1354 tsk->signal = sig;
1355 if (!sig)
1356 return -ENOMEM;
1357
1358 sig->nr_threads = 1;
1359 atomic_set(&sig->live, 1);
1360 atomic_set(&sig->sigcnt, 1);
1361
1362 /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */
1363 sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node);
1364 tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head);
1365
1366 init_waitqueue_head(&sig->wait_chldexit);
1367 sig->curr_target = tsk;
1368 init_sigpending(&sig->shared_pending);
1369 seqlock_init(&sig->stats_lock);
1370 prev_cputime_init(&sig->prev_cputime);
1371
1372#ifdef CONFIG_POSIX_TIMERS
1373 INIT_LIST_HEAD(&sig->posix_timers);
1374 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1375 sig->real_timer.function = it_real_fn;
1376#endif
1377
1378 task_lock(current->group_leader);
1379 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
1380 task_unlock(current->group_leader);
1381
1382 posix_cpu_timers_init_group(sig);
1383
1384 tty_audit_fork(sig);
1385 sched_autogroup_fork(sig);
1386
1387 sig->oom_score_adj = current->signal->oom_score_adj;
1388 sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1389
1390 mutex_init(&sig->cred_guard_mutex);
1391
1392 return 0;
1393}
1394
1395static void copy_seccomp(struct task_struct *p)
1396{
1397#ifdef CONFIG_SECCOMP
1398 /*
1399 * Must be called with sighand->lock held, which is common to
1400 * all threads in the group. Holding cred_guard_mutex is not
1401 * needed because this new task is not yet running and cannot
1402 * be racing exec.
1403 */
1404 assert_spin_locked(&current->sighand->siglock);
1405
1406 /* Ref-count the new filter user, and assign it. */
1407 get_seccomp_filter(current);
1408 p->seccomp = current->seccomp;
1409
1410 /*
1411 * Explicitly enable no_new_privs here in case it got set
1412 * between the task_struct being duplicated and holding the
1413 * sighand lock. The seccomp state and nnp must be in sync.
1414 */
1415 if (task_no_new_privs(current))
1416 task_set_no_new_privs(p);
1417
1418 /*
1419 * If the parent gained a seccomp mode after copying thread
1420 * flags and between before we held the sighand lock, we have
1421 * to manually enable the seccomp thread flag here.
1422 */
1423 if (p->seccomp.mode != SECCOMP_MODE_DISABLED)
1424 set_tsk_thread_flag(p, TIF_SECCOMP);
1425#endif
1426}
1427
1428SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1429{
1430 current->clear_child_tid = tidptr;
1431
1432 return task_pid_vnr(current);
1433}
1434
1435static void rt_mutex_init_task(struct task_struct *p)
1436{
1437 raw_spin_lock_init(&p->pi_lock);
1438#ifdef CONFIG_RT_MUTEXES
1439 p->pi_waiters = RB_ROOT;
1440 p->pi_waiters_leftmost = NULL;
1441 p->pi_blocked_on = NULL;
1442#endif
1443}
1444
1445#ifdef CONFIG_POSIX_TIMERS
1446/*
1447 * Initialize POSIX timer handling for a single task.
1448 */
1449static void posix_cpu_timers_init(struct task_struct *tsk)
1450{
1451 tsk->cputime_expires.prof_exp = 0;
1452 tsk->cputime_expires.virt_exp = 0;
1453 tsk->cputime_expires.sched_exp = 0;
1454 INIT_LIST_HEAD(&tsk->cpu_timers[0]);
1455 INIT_LIST_HEAD(&tsk->cpu_timers[1]);
1456 INIT_LIST_HEAD(&tsk->cpu_timers[2]);
1457}
1458#else
1459static inline void posix_cpu_timers_init(struct task_struct *tsk) { }
1460#endif
1461
1462static inline void
1463init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid)
1464{
1465 task->pids[type].pid = pid;
1466}
1467
1468static inline void rcu_copy_process(struct task_struct *p)
1469{
1470#ifdef CONFIG_PREEMPT_RCU
1471 p->rcu_read_lock_nesting = 0;
1472 p->rcu_read_unlock_special.s = 0;
1473 p->rcu_blocked_node = NULL;
1474 INIT_LIST_HEAD(&p->rcu_node_entry);
1475#endif /* #ifdef CONFIG_PREEMPT_RCU */
1476#ifdef CONFIG_TASKS_RCU
1477 p->rcu_tasks_holdout = false;
1478 INIT_LIST_HEAD(&p->rcu_tasks_holdout_list);
1479 p->rcu_tasks_idle_cpu = -1;
1480#endif /* #ifdef CONFIG_TASKS_RCU */
1481}
1482
1483/*
1484 * This creates a new process as a copy of the old one,
1485 * but does not actually start it yet.
1486 *
1487 * It copies the registers, and all the appropriate
1488 * parts of the process environment (as per the clone
1489 * flags). The actual kick-off is left to the caller.
1490 */
1491static __latent_entropy struct task_struct *copy_process(
1492 unsigned long clone_flags,
1493 unsigned long stack_start,
1494 unsigned long stack_size,
1495 int __user *child_tidptr,
1496 struct pid *pid,
1497 int trace,
1498 unsigned long tls,
1499 int node)
1500{
1501 int retval;
1502 struct task_struct *p;
1503
1504 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1505 return ERR_PTR(-EINVAL);
1506
1507 if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS))
1508 return ERR_PTR(-EINVAL);
1509
1510 /*
1511 * Thread groups must share signals as well, and detached threads
1512 * can only be started up within the thread group.
1513 */
1514 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1515 return ERR_PTR(-EINVAL);
1516
1517 /*
1518 * Shared signal handlers imply shared VM. By way of the above,
1519 * thread groups also imply shared VM. Blocking this case allows
1520 * for various simplifications in other code.
1521 */
1522 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1523 return ERR_PTR(-EINVAL);
1524
1525 /*
1526 * Siblings of global init remain as zombies on exit since they are
1527 * not reaped by their parent (swapper). To solve this and to avoid
1528 * multi-rooted process trees, prevent global and container-inits
1529 * from creating siblings.
1530 */
1531 if ((clone_flags & CLONE_PARENT) &&
1532 current->signal->flags & SIGNAL_UNKILLABLE)
1533 return ERR_PTR(-EINVAL);
1534
1535 /*
1536 * If the new process will be in a different pid or user namespace
1537 * do not allow it to share a thread group with the forking task.
1538 */
1539 if (clone_flags & CLONE_THREAD) {
1540 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) ||
1541 (task_active_pid_ns(current) !=
1542 current->nsproxy->pid_ns_for_children))
1543 return ERR_PTR(-EINVAL);
1544 }
1545
1546 retval = security_task_create(clone_flags);
1547 if (retval)
1548 goto fork_out;
1549
1550 retval = -ENOMEM;
1551 p = dup_task_struct(current, node);
1552 if (!p)
1553 goto fork_out;
1554
1555 ftrace_graph_init_task(p);
1556
1557 rt_mutex_init_task(p);
1558
1559#ifdef CONFIG_PROVE_LOCKING
1560 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1561 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1562#endif
1563 retval = -EAGAIN;
1564 if (atomic_read(&p->real_cred->user->processes) >=
1565 task_rlimit(p, RLIMIT_NPROC)) {
1566 if (p->real_cred->user != INIT_USER &&
1567 !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
1568 goto bad_fork_free;
1569 }
1570 current->flags &= ~PF_NPROC_EXCEEDED;
1571
1572 retval = copy_creds(p, clone_flags);
1573 if (retval < 0)
1574 goto bad_fork_free;
1575
1576 /*
1577 * If multiple threads are within copy_process(), then this check
1578 * triggers too late. This doesn't hurt, the check is only there
1579 * to stop root fork bombs.
1580 */
1581 retval = -EAGAIN;
1582 if (nr_threads >= max_threads)
1583 goto bad_fork_cleanup_count;
1584
1585 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */
1586 p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER | PF_IDLE);
1587 p->flags |= PF_FORKNOEXEC;
1588 INIT_LIST_HEAD(&p->children);
1589 INIT_LIST_HEAD(&p->sibling);
1590 rcu_copy_process(p);
1591 p->vfork_done = NULL;
1592 spin_lock_init(&p->alloc_lock);
1593
1594 init_sigpending(&p->pending);
1595
1596 p->utime = p->stime = p->gtime = 0;
1597#ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
1598 p->utimescaled = p->stimescaled = 0;
1599#endif
1600 prev_cputime_init(&p->prev_cputime);
1601
1602#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
1603 seqcount_init(&p->vtime_seqcount);
1604 p->vtime_snap = 0;
1605 p->vtime_snap_whence = VTIME_INACTIVE;
1606#endif
1607
1608#if defined(SPLIT_RSS_COUNTING)
1609 memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1610#endif
1611
1612 p->default_timer_slack_ns = current->timer_slack_ns;
1613
1614 task_io_accounting_init(&p->ioac);
1615 acct_clear_integrals(p);
1616
1617 posix_cpu_timers_init(p);
1618
1619 p->start_time = ktime_get_ns();
1620 p->real_start_time = ktime_get_boot_ns();
1621 p->io_context = NULL;
1622 p->audit_context = NULL;
1623 cgroup_fork(p);
1624#ifdef CONFIG_NUMA
1625 p->mempolicy = mpol_dup(p->mempolicy);
1626 if (IS_ERR(p->mempolicy)) {
1627 retval = PTR_ERR(p->mempolicy);
1628 p->mempolicy = NULL;
1629 goto bad_fork_cleanup_threadgroup_lock;
1630 }
1631#endif
1632#ifdef CONFIG_CPUSETS
1633 p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
1634 p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
1635 seqcount_init(&p->mems_allowed_seq);
1636#endif
1637#ifdef CONFIG_TRACE_IRQFLAGS
1638 p->irq_events = 0;
1639 p->hardirqs_enabled = 0;
1640 p->hardirq_enable_ip = 0;
1641 p->hardirq_enable_event = 0;
1642 p->hardirq_disable_ip = _THIS_IP_;
1643 p->hardirq_disable_event = 0;
1644 p->softirqs_enabled = 1;
1645 p->softirq_enable_ip = _THIS_IP_;
1646 p->softirq_enable_event = 0;
1647 p->softirq_disable_ip = 0;
1648 p->softirq_disable_event = 0;
1649 p->hardirq_context = 0;
1650 p->softirq_context = 0;
1651#endif
1652
1653 p->pagefault_disabled = 0;
1654
1655#ifdef CONFIG_LOCKDEP
1656 p->lockdep_depth = 0; /* no locks held yet */
1657 p->curr_chain_key = 0;
1658 p->lockdep_recursion = 0;
1659#endif
1660
1661#ifdef CONFIG_DEBUG_MUTEXES
1662 p->blocked_on = NULL; /* not blocked yet */
1663#endif
1664#ifdef CONFIG_BCACHE
1665 p->sequential_io = 0;
1666 p->sequential_io_avg = 0;
1667#endif
1668
1669 /* Perform scheduler related setup. Assign this task to a CPU. */
1670 retval = sched_fork(clone_flags, p);
1671 if (retval)
1672 goto bad_fork_cleanup_policy;
1673
1674 retval = perf_event_init_task(p);
1675 if (retval)
1676 goto bad_fork_cleanup_policy;
1677 retval = audit_alloc(p);
1678 if (retval)
1679 goto bad_fork_cleanup_perf;
1680 /* copy all the process information */
1681 shm_init_task(p);
1682 retval = copy_semundo(clone_flags, p);
1683 if (retval)
1684 goto bad_fork_cleanup_audit;
1685 retval = copy_files(clone_flags, p);
1686 if (retval)
1687 goto bad_fork_cleanup_semundo;
1688 retval = copy_fs(clone_flags, p);
1689 if (retval)
1690 goto bad_fork_cleanup_files;
1691 retval = copy_sighand(clone_flags, p);
1692 if (retval)
1693 goto bad_fork_cleanup_fs;
1694 retval = copy_signal(clone_flags, p);
1695 if (retval)
1696 goto bad_fork_cleanup_sighand;
1697 retval = copy_mm(clone_flags, p);
1698 if (retval)
1699 goto bad_fork_cleanup_signal;
1700 retval = copy_namespaces(clone_flags, p);
1701 if (retval)
1702 goto bad_fork_cleanup_mm;
1703 retval = copy_io(clone_flags, p);
1704 if (retval)
1705 goto bad_fork_cleanup_namespaces;
1706 retval = copy_thread_tls(clone_flags, stack_start, stack_size, p, tls);
1707 if (retval)
1708 goto bad_fork_cleanup_io;
1709
1710 if (pid != &init_struct_pid) {
1711 pid = alloc_pid(p->nsproxy->pid_ns_for_children);
1712 if (IS_ERR(pid)) {
1713 retval = PTR_ERR(pid);
1714 goto bad_fork_cleanup_thread;
1715 }
1716 }
1717
1718 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1719 /*
1720 * Clear TID on mm_release()?
1721 */
1722 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL;
1723#ifdef CONFIG_BLOCK
1724 p->plug = NULL;
1725#endif
1726#ifdef CONFIG_FUTEX
1727 p->robust_list = NULL;
1728#ifdef CONFIG_COMPAT
1729 p->compat_robust_list = NULL;
1730#endif
1731 INIT_LIST_HEAD(&p->pi_state_list);
1732 p->pi_state_cache = NULL;
1733#endif
1734 /*
1735 * sigaltstack should be cleared when sharing the same VM
1736 */
1737 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1738 sas_ss_reset(p);
1739
1740 /*
1741 * Syscall tracing and stepping should be turned off in the
1742 * child regardless of CLONE_PTRACE.
1743 */
1744 user_disable_single_step(p);
1745 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1746#ifdef TIF_SYSCALL_EMU
1747 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1748#endif
1749 clear_all_latency_tracing(p);
1750
1751 /* ok, now we should be set up.. */
1752 p->pid = pid_nr(pid);
1753 if (clone_flags & CLONE_THREAD) {
1754 p->exit_signal = -1;
1755 p->group_leader = current->group_leader;
1756 p->tgid = current->tgid;
1757 } else {
1758 if (clone_flags & CLONE_PARENT)
1759 p->exit_signal = current->group_leader->exit_signal;
1760 else
1761 p->exit_signal = (clone_flags & CSIGNAL);
1762 p->group_leader = p;
1763 p->tgid = p->pid;
1764 }
1765
1766 p->nr_dirtied = 0;
1767 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
1768 p->dirty_paused_when = 0;
1769
1770 p->pdeath_signal = 0;
1771 INIT_LIST_HEAD(&p->thread_group);
1772 p->task_works = NULL;
1773
1774 cgroup_threadgroup_change_begin(current);
1775 /*
1776 * Ensure that the cgroup subsystem policies allow the new process to be
1777 * forked. It should be noted the the new process's css_set can be changed
1778 * between here and cgroup_post_fork() if an organisation operation is in
1779 * progress.
1780 */
1781 retval = cgroup_can_fork(p);
1782 if (retval)
1783 goto bad_fork_free_pid;
1784
1785 /*
1786 * Make it visible to the rest of the system, but dont wake it up yet.
1787 * Need tasklist lock for parent etc handling!
1788 */
1789 write_lock_irq(&tasklist_lock);
1790
1791 /* CLONE_PARENT re-uses the old parent */
1792 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1793 p->real_parent = current->real_parent;
1794 p->parent_exec_id = current->parent_exec_id;
1795 } else {
1796 p->real_parent = current;
1797 p->parent_exec_id = current->self_exec_id;
1798 }
1799
1800 spin_lock(&current->sighand->siglock);
1801
1802 /*
1803 * Copy seccomp details explicitly here, in case they were changed
1804 * before holding sighand lock.
1805 */
1806 copy_seccomp(p);
1807
1808 /*
1809 * Process group and session signals need to be delivered to just the
1810 * parent before the fork or both the parent and the child after the
1811 * fork. Restart if a signal comes in before we add the new process to
1812 * it's process group.
1813 * A fatal signal pending means that current will exit, so the new
1814 * thread can't slip out of an OOM kill (or normal SIGKILL).
1815 */
1816 recalc_sigpending();
1817 if (signal_pending(current)) {
1818 spin_unlock(&current->sighand->siglock);
1819 write_unlock_irq(&tasklist_lock);
1820 retval = -ERESTARTNOINTR;
1821 goto bad_fork_cancel_cgroup;
1822 }
1823
1824 if (likely(p->pid)) {
1825 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
1826
1827 init_task_pid(p, PIDTYPE_PID, pid);
1828 if (thread_group_leader(p)) {
1829 init_task_pid(p, PIDTYPE_PGID, task_pgrp(current));
1830 init_task_pid(p, PIDTYPE_SID, task_session(current));
1831
1832 if (is_child_reaper(pid)) {
1833 ns_of_pid(pid)->child_reaper = p;
1834 p->signal->flags |= SIGNAL_UNKILLABLE;
1835 }
1836
1837 p->signal->leader_pid = pid;
1838 p->signal->tty = tty_kref_get(current->signal->tty);
1839 /*
1840 * Inherit has_child_subreaper flag under the same
1841 * tasklist_lock with adding child to the process tree
1842 * for propagate_has_child_subreaper optimization.
1843 */
1844 p->signal->has_child_subreaper = p->real_parent->signal->has_child_subreaper ||
1845 p->real_parent->signal->is_child_subreaper;
1846 list_add_tail(&p->sibling, &p->real_parent->children);
1847 list_add_tail_rcu(&p->tasks, &init_task.tasks);
1848 attach_pid(p, PIDTYPE_PGID);
1849 attach_pid(p, PIDTYPE_SID);
1850 __this_cpu_inc(process_counts);
1851 } else {
1852 current->signal->nr_threads++;
1853 atomic_inc(&current->signal->live);
1854 atomic_inc(&current->signal->sigcnt);
1855 list_add_tail_rcu(&p->thread_group,
1856 &p->group_leader->thread_group);
1857 list_add_tail_rcu(&p->thread_node,
1858 &p->signal->thread_head);
1859 }
1860 attach_pid(p, PIDTYPE_PID);
1861 nr_threads++;
1862 }
1863
1864 total_forks++;
1865 spin_unlock(&current->sighand->siglock);
1866 syscall_tracepoint_update(p);
1867 write_unlock_irq(&tasklist_lock);
1868
1869 proc_fork_connector(p);
1870 cgroup_post_fork(p);
1871 cgroup_threadgroup_change_end(current);
1872 perf_event_fork(p);
1873
1874 trace_task_newtask(p, clone_flags);
1875 uprobe_copy_process(p, clone_flags);
1876
1877 return p;
1878
1879bad_fork_cancel_cgroup:
1880 cgroup_cancel_fork(p);
1881bad_fork_free_pid:
1882 cgroup_threadgroup_change_end(current);
1883 if (pid != &init_struct_pid)
1884 free_pid(pid);
1885bad_fork_cleanup_thread:
1886 exit_thread(p);
1887bad_fork_cleanup_io:
1888 if (p->io_context)
1889 exit_io_context(p);
1890bad_fork_cleanup_namespaces:
1891 exit_task_namespaces(p);
1892bad_fork_cleanup_mm:
1893 if (p->mm)
1894 mmput(p->mm);
1895bad_fork_cleanup_signal:
1896 if (!(clone_flags & CLONE_THREAD))
1897 free_signal_struct(p->signal);
1898bad_fork_cleanup_sighand:
1899 __cleanup_sighand(p->sighand);
1900bad_fork_cleanup_fs:
1901 exit_fs(p); /* blocking */
1902bad_fork_cleanup_files:
1903 exit_files(p); /* blocking */
1904bad_fork_cleanup_semundo:
1905 exit_sem(p);
1906bad_fork_cleanup_audit:
1907 audit_free(p);
1908bad_fork_cleanup_perf:
1909 perf_event_free_task(p);
1910bad_fork_cleanup_policy:
1911#ifdef CONFIG_NUMA
1912 mpol_put(p->mempolicy);
1913bad_fork_cleanup_threadgroup_lock:
1914#endif
1915 delayacct_tsk_free(p);
1916bad_fork_cleanup_count:
1917 atomic_dec(&p->cred->user->processes);
1918 exit_creds(p);
1919bad_fork_free:
1920 p->state = TASK_DEAD;
1921 put_task_stack(p);
1922 free_task(p);
1923fork_out:
1924 return ERR_PTR(retval);
1925}
1926
1927static inline void init_idle_pids(struct pid_link *links)
1928{
1929 enum pid_type type;
1930
1931 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
1932 INIT_HLIST_NODE(&links[type].node); /* not really needed */
1933 links[type].pid = &init_struct_pid;
1934 }
1935}
1936
1937struct task_struct *fork_idle(int cpu)
1938{
1939 struct task_struct *task;
1940 task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0, 0,
1941 cpu_to_node(cpu));
1942 if (!IS_ERR(task)) {
1943 init_idle_pids(task->pids);
1944 init_idle(task, cpu);
1945 }
1946
1947 return task;
1948}
1949
1950/*
1951 * Ok, this is the main fork-routine.
1952 *
1953 * It copies the process, and if successful kick-starts
1954 * it and waits for it to finish using the VM if required.
1955 */
1956long _do_fork(unsigned long clone_flags,
1957 unsigned long stack_start,
1958 unsigned long stack_size,
1959 int __user *parent_tidptr,
1960 int __user *child_tidptr,
1961 unsigned long tls)
1962{
1963 struct task_struct *p;
1964 int trace = 0;
1965 long nr;
1966
1967 /*
1968 * Determine whether and which event to report to ptracer. When
1969 * called from kernel_thread or CLONE_UNTRACED is explicitly
1970 * requested, no event is reported; otherwise, report if the event
1971 * for the type of forking is enabled.
1972 */
1973 if (!(clone_flags & CLONE_UNTRACED)) {
1974 if (clone_flags & CLONE_VFORK)
1975 trace = PTRACE_EVENT_VFORK;
1976 else if ((clone_flags & CSIGNAL) != SIGCHLD)
1977 trace = PTRACE_EVENT_CLONE;
1978 else
1979 trace = PTRACE_EVENT_FORK;
1980
1981 if (likely(!ptrace_event_enabled(current, trace)))
1982 trace = 0;
1983 }
1984
1985 p = copy_process(clone_flags, stack_start, stack_size,
1986 child_tidptr, NULL, trace, tls, NUMA_NO_NODE);
1987 add_latent_entropy();
1988 /*
1989 * Do this prior waking up the new thread - the thread pointer
1990 * might get invalid after that point, if the thread exits quickly.
1991 */
1992 if (!IS_ERR(p)) {
1993 struct completion vfork;
1994 struct pid *pid;
1995
1996 trace_sched_process_fork(current, p);
1997
1998 pid = get_task_pid(p, PIDTYPE_PID);
1999 nr = pid_vnr(pid);
2000
2001 if (clone_flags & CLONE_PARENT_SETTID)
2002 put_user(nr, parent_tidptr);
2003
2004 if (clone_flags & CLONE_VFORK) {
2005 p->vfork_done = &vfork;
2006 init_completion(&vfork);
2007 get_task_struct(p);
2008 }
2009
2010 wake_up_new_task(p);
2011
2012 /* forking complete and child started to run, tell ptracer */
2013 if (unlikely(trace))
2014 ptrace_event_pid(trace, pid);
2015
2016 if (clone_flags & CLONE_VFORK) {
2017 if (!wait_for_vfork_done(p, &vfork))
2018 ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid);
2019 }
2020
2021 put_pid(pid);
2022 } else {
2023 nr = PTR_ERR(p);
2024 }
2025 return nr;
2026}
2027
2028#ifndef CONFIG_HAVE_COPY_THREAD_TLS
2029/* For compatibility with architectures that call do_fork directly rather than
2030 * using the syscall entry points below. */
2031long do_fork(unsigned long clone_flags,
2032 unsigned long stack_start,
2033 unsigned long stack_size,
2034 int __user *parent_tidptr,
2035 int __user *child_tidptr)
2036{
2037 return _do_fork(clone_flags, stack_start, stack_size,
2038 parent_tidptr, child_tidptr, 0);
2039}
2040#endif
2041
2042/*
2043 * Create a kernel thread.
2044 */
2045pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
2046{
2047 return _do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn,
2048 (unsigned long)arg, NULL, NULL, 0);
2049}
2050
2051#ifdef __ARCH_WANT_SYS_FORK
2052SYSCALL_DEFINE0(fork)
2053{
2054#ifdef CONFIG_MMU
2055 return _do_fork(SIGCHLD, 0, 0, NULL, NULL, 0);
2056#else
2057 /* can not support in nommu mode */
2058 return -EINVAL;
2059#endif
2060}
2061#endif
2062
2063#ifdef __ARCH_WANT_SYS_VFORK
2064SYSCALL_DEFINE0(vfork)
2065{
2066 return _do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0,
2067 0, NULL, NULL, 0);
2068}
2069#endif
2070
2071#ifdef __ARCH_WANT_SYS_CLONE
2072#ifdef CONFIG_CLONE_BACKWARDS
2073SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2074 int __user *, parent_tidptr,
2075 unsigned long, tls,
2076 int __user *, child_tidptr)
2077#elif defined(CONFIG_CLONE_BACKWARDS2)
2078SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags,
2079 int __user *, parent_tidptr,
2080 int __user *, child_tidptr,
2081 unsigned long, tls)
2082#elif defined(CONFIG_CLONE_BACKWARDS3)
2083SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp,
2084 int, stack_size,
2085 int __user *, parent_tidptr,
2086 int __user *, child_tidptr,
2087 unsigned long, tls)
2088#else
2089SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2090 int __user *, parent_tidptr,
2091 int __user *, child_tidptr,
2092 unsigned long, tls)
2093#endif
2094{
2095 return _do_fork(clone_flags, newsp, 0, parent_tidptr, child_tidptr, tls);
2096}
2097#endif
2098
2099void walk_process_tree(struct task_struct *top, proc_visitor visitor, void *data)
2100{
2101 struct task_struct *leader, *parent, *child;
2102 int res;
2103
2104 read_lock(&tasklist_lock);
2105 leader = top = top->group_leader;
2106down:
2107 for_each_thread(leader, parent) {
2108 list_for_each_entry(child, &parent->children, sibling) {
2109 res = visitor(child, data);
2110 if (res) {
2111 if (res < 0)
2112 goto out;
2113 leader = child;
2114 goto down;
2115 }
2116up:
2117 ;
2118 }
2119 }
2120
2121 if (leader != top) {
2122 child = leader;
2123 parent = child->real_parent;
2124 leader = parent->group_leader;
2125 goto up;
2126 }
2127out:
2128 read_unlock(&tasklist_lock);
2129}
2130
2131#ifndef ARCH_MIN_MMSTRUCT_ALIGN
2132#define ARCH_MIN_MMSTRUCT_ALIGN 0
2133#endif
2134
2135static void sighand_ctor(void *data)
2136{
2137 struct sighand_struct *sighand = data;
2138
2139 spin_lock_init(&sighand->siglock);
2140 init_waitqueue_head(&sighand->signalfd_wqh);
2141}
2142
2143void __init proc_caches_init(void)
2144{
2145 sighand_cachep = kmem_cache_create("sighand_cache",
2146 sizeof(struct sighand_struct), 0,
2147 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU|
2148 SLAB_NOTRACK|SLAB_ACCOUNT, sighand_ctor);
2149 signal_cachep = kmem_cache_create("signal_cache",
2150 sizeof(struct signal_struct), 0,
2151 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT,
2152 NULL);
2153 files_cachep = kmem_cache_create("files_cache",
2154 sizeof(struct files_struct), 0,
2155 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT,
2156 NULL);
2157 fs_cachep = kmem_cache_create("fs_cache",
2158 sizeof(struct fs_struct), 0,
2159 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT,
2160 NULL);
2161 /*
2162 * FIXME! The "sizeof(struct mm_struct)" currently includes the
2163 * whole struct cpumask for the OFFSTACK case. We could change
2164 * this to *only* allocate as much of it as required by the
2165 * maximum number of CPU's we can ever have. The cpumask_allocation
2166 * is at the end of the structure, exactly for that reason.
2167 */
2168 mm_cachep = kmem_cache_create("mm_struct",
2169 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
2170 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT,
2171 NULL);
2172 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT);
2173 mmap_init();
2174 nsproxy_cache_init();
2175}
2176
2177/*
2178 * Check constraints on flags passed to the unshare system call.
2179 */
2180static int check_unshare_flags(unsigned long unshare_flags)
2181{
2182 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
2183 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
2184 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET|
2185 CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP))
2186 return -EINVAL;
2187 /*
2188 * Not implemented, but pretend it works if there is nothing
2189 * to unshare. Note that unsharing the address space or the
2190 * signal handlers also need to unshare the signal queues (aka
2191 * CLONE_THREAD).
2192 */
2193 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
2194 if (!thread_group_empty(current))
2195 return -EINVAL;
2196 }
2197 if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) {
2198 if (atomic_read(&current->sighand->count) > 1)
2199 return -EINVAL;
2200 }
2201 if (unshare_flags & CLONE_VM) {
2202 if (!current_is_single_threaded())
2203 return -EINVAL;
2204 }
2205
2206 return 0;
2207}
2208
2209/*
2210 * Unshare the filesystem structure if it is being shared
2211 */
2212static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
2213{
2214 struct fs_struct *fs = current->fs;
2215
2216 if (!(unshare_flags & CLONE_FS) || !fs)
2217 return 0;
2218
2219 /* don't need lock here; in the worst case we'll do useless copy */
2220 if (fs->users == 1)
2221 return 0;
2222
2223 *new_fsp = copy_fs_struct(fs);
2224 if (!*new_fsp)
2225 return -ENOMEM;
2226
2227 return 0;
2228}
2229
2230/*
2231 * Unshare file descriptor table if it is being shared
2232 */
2233static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
2234{
2235 struct files_struct *fd = current->files;
2236 int error = 0;
2237
2238 if ((unshare_flags & CLONE_FILES) &&
2239 (fd && atomic_read(&fd->count) > 1)) {
2240 *new_fdp = dup_fd(fd, &error);
2241 if (!*new_fdp)
2242 return error;
2243 }
2244
2245 return 0;
2246}
2247
2248/*
2249 * unshare allows a process to 'unshare' part of the process
2250 * context which was originally shared using clone. copy_*
2251 * functions used by do_fork() cannot be used here directly
2252 * because they modify an inactive task_struct that is being
2253 * constructed. Here we are modifying the current, active,
2254 * task_struct.
2255 */
2256SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
2257{
2258 struct fs_struct *fs, *new_fs = NULL;
2259 struct files_struct *fd, *new_fd = NULL;
2260 struct cred *new_cred = NULL;
2261 struct nsproxy *new_nsproxy = NULL;
2262 int do_sysvsem = 0;
2263 int err;
2264
2265 /*
2266 * If unsharing a user namespace must also unshare the thread group
2267 * and unshare the filesystem root and working directories.
2268 */
2269 if (unshare_flags & CLONE_NEWUSER)
2270 unshare_flags |= CLONE_THREAD | CLONE_FS;
2271 /*
2272 * If unsharing vm, must also unshare signal handlers.
2273 */
2274 if (unshare_flags & CLONE_VM)
2275 unshare_flags |= CLONE_SIGHAND;
2276 /*
2277 * If unsharing a signal handlers, must also unshare the signal queues.
2278 */
2279 if (unshare_flags & CLONE_SIGHAND)
2280 unshare_flags |= CLONE_THREAD;
2281 /*
2282 * If unsharing namespace, must also unshare filesystem information.
2283 */
2284 if (unshare_flags & CLONE_NEWNS)
2285 unshare_flags |= CLONE_FS;
2286
2287 err = check_unshare_flags(unshare_flags);
2288 if (err)
2289 goto bad_unshare_out;
2290 /*
2291 * CLONE_NEWIPC must also detach from the undolist: after switching
2292 * to a new ipc namespace, the semaphore arrays from the old
2293 * namespace are unreachable.
2294 */
2295 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
2296 do_sysvsem = 1;
2297 err = unshare_fs(unshare_flags, &new_fs);
2298 if (err)
2299 goto bad_unshare_out;
2300 err = unshare_fd(unshare_flags, &new_fd);
2301 if (err)
2302 goto bad_unshare_cleanup_fs;
2303 err = unshare_userns(unshare_flags, &new_cred);
2304 if (err)
2305 goto bad_unshare_cleanup_fd;
2306 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
2307 new_cred, new_fs);
2308 if (err)
2309 goto bad_unshare_cleanup_cred;
2310
2311 if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
2312 if (do_sysvsem) {
2313 /*
2314 * CLONE_SYSVSEM is equivalent to sys_exit().
2315 */
2316 exit_sem(current);
2317 }
2318 if (unshare_flags & CLONE_NEWIPC) {
2319 /* Orphan segments in old ns (see sem above). */
2320 exit_shm(current);
2321 shm_init_task(current);
2322 }
2323
2324 if (new_nsproxy)
2325 switch_task_namespaces(current, new_nsproxy);
2326
2327 task_lock(current);
2328
2329 if (new_fs) {
2330 fs = current->fs;
2331 spin_lock(&fs->lock);
2332 current->fs = new_fs;
2333 if (--fs->users)
2334 new_fs = NULL;
2335 else
2336 new_fs = fs;
2337 spin_unlock(&fs->lock);
2338 }
2339
2340 if (new_fd) {
2341 fd = current->files;
2342 current->files = new_fd;
2343 new_fd = fd;
2344 }
2345
2346 task_unlock(current);
2347
2348 if (new_cred) {
2349 /* Install the new user namespace */
2350 commit_creds(new_cred);
2351 new_cred = NULL;
2352 }
2353 }
2354
2355bad_unshare_cleanup_cred:
2356 if (new_cred)
2357 put_cred(new_cred);
2358bad_unshare_cleanup_fd:
2359 if (new_fd)
2360 put_files_struct(new_fd);
2361
2362bad_unshare_cleanup_fs:
2363 if (new_fs)
2364 free_fs_struct(new_fs);
2365
2366bad_unshare_out:
2367 return err;
2368}
2369
2370/*
2371 * Helper to unshare the files of the current task.
2372 * We don't want to expose copy_files internals to
2373 * the exec layer of the kernel.
2374 */
2375
2376int unshare_files(struct files_struct **displaced)
2377{
2378 struct task_struct *task = current;
2379 struct files_struct *copy = NULL;
2380 int error;
2381
2382 error = unshare_fd(CLONE_FILES, &copy);
2383 if (error || !copy) {
2384 *displaced = NULL;
2385 return error;
2386 }
2387 *displaced = task->files;
2388 task_lock(task);
2389 task->files = copy;
2390 task_unlock(task);
2391 return 0;
2392}
2393
2394int sysctl_max_threads(struct ctl_table *table, int write,
2395 void __user *buffer, size_t *lenp, loff_t *ppos)
2396{
2397 struct ctl_table t;
2398 int ret;
2399 int threads = max_threads;
2400 int min = MIN_THREADS;
2401 int max = MAX_THREADS;
2402
2403 t = *table;
2404 t.data = &threads;
2405 t.extra1 = &min;
2406 t.extra2 = &max;
2407
2408 ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
2409 if (ret || !write)
2410 return ret;
2411
2412 set_max_threads(threads);
2413
2414 return 0;
2415}
2416