projects/linux·blob v4.7 · refs

2159 lines · 51.7 KiB

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