4 * Copyright (C) 1991, 1992 Linus Torvalds
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()'
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/hmm.h>
43 #include <linux/vmacache.h>
44 #include <linux/nsproxy.h>
45 #include <linux/capability.h>
46 #include <linux/cpu.h>
47 #include <linux/cgroup.h>
48 #include <linux/security.h>
49 #include <linux/hugetlb.h>
50 #include <linux/seccomp.h>
51 #include <linux/swap.h>
52 #include <linux/syscalls.h>
53 #include <linux/jiffies.h>
54 #include <linux/futex.h>
55 #include <linux/compat.h>
56 #include <linux/kthread.h>
57 #include <linux/task_io_accounting_ops.h>
58 #include <linux/rcupdate.h>
59 #include <linux/ptrace.h>
60 #include <linux/mount.h>
61 #include <linux/audit.h>
62 #include <linux/memcontrol.h>
63 #include <linux/ftrace.h>
64 #include <linux/proc_fs.h>
65 #include <linux/profile.h>
66 #include <linux/rmap.h>
67 #include <linux/ksm.h>
68 #include <linux/acct.h>
69 #include <linux/userfaultfd_k.h>
70 #include <linux/tsacct_kern.h>
71 #include <linux/cn_proc.h>
72 #include <linux/freezer.h>
73 #include <linux/delayacct.h>
74 #include <linux/taskstats_kern.h>
75 #include <linux/random.h>
76 #include <linux/tty.h>
77 #include <linux/blkdev.h>
78 #include <linux/fs_struct.h>
79 #include <linux/magic.h>
80 #include <linux/sched/mm.h>
81 #include <linux/perf_event.h>
82 #include <linux/posix-timers.h>
83 #include <linux/user-return-notifier.h>
84 #include <linux/oom.h>
85 #include <linux/khugepaged.h>
86 #include <linux/signalfd.h>
87 #include <linux/uprobes.h>
88 #include <linux/aio.h>
89 #include <linux/compiler.h>
90 #include <linux/sysctl.h>
91 #include <linux/kcov.h>
92 #include <linux/livepatch.h>
93 #include <linux/thread_info.h>
95 #include <asm/pgtable.h>
96 #include <asm/pgalloc.h>
97 #include <linux/uaccess.h>
98 #include <asm/mmu_context.h>
99 #include <asm/cacheflush.h>
100 #include <asm/tlbflush.h>
102 #include <trace/events/sched.h>
104 #define CREATE_TRACE_POINTS
105 #include <trace/events/task.h>
108 * Minimum number of threads to boot the kernel
110 #define MIN_THREADS 20
113 * Maximum number of threads
115 #define MAX_THREADS FUTEX_TID_MASK
118 * Protected counters by write_lock_irq(&tasklist_lock)
120 unsigned long total_forks; /* Handle normal Linux uptimes. */
121 int nr_threads; /* The idle threads do not count.. */
123 int max_threads; /* tunable limit on nr_threads */
125 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
127 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */
129 #ifdef CONFIG_PROVE_RCU
130 int lockdep_tasklist_lock_is_held(void)
132 return lockdep_is_held(&tasklist_lock);
134 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
135 #endif /* #ifdef CONFIG_PROVE_RCU */
137 int nr_processes(void)
142 for_each_possible_cpu(cpu)
143 total += per_cpu(process_counts, cpu);
148 void __weak arch_release_task_struct(struct task_struct *tsk)
152 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
153 static struct kmem_cache *task_struct_cachep;
155 static inline struct task_struct *alloc_task_struct_node(int node)
157 return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node);
160 static inline void free_task_struct(struct task_struct *tsk)
162 kmem_cache_free(task_struct_cachep, tsk);
166 #ifndef CONFIG_ARCH_THREAD_STACK_ALLOCATOR
169 * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
170 * kmemcache based allocator.
172 # if THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK)
174 #ifdef CONFIG_VMAP_STACK
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.
179 #define NR_CACHED_STACKS 2
180 static DEFINE_PER_CPU(struct vm_struct *, cached_stacks[NR_CACHED_STACKS]);
182 static int free_vm_stack_cache(unsigned int cpu)
184 struct vm_struct **cached_vm_stacks = per_cpu_ptr(cached_stacks, cpu);
187 for (i = 0; i < NR_CACHED_STACKS; i++) {
188 struct vm_struct *vm_stack = cached_vm_stacks[i];
193 vfree(vm_stack->addr);
194 cached_vm_stacks[i] = NULL;
201 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node)
203 #ifdef CONFIG_VMAP_STACK
207 for (i = 0; i < NR_CACHED_STACKS; i++) {
210 s = this_cpu_xchg(cached_stacks[i], NULL);
215 /* Clear stale pointers from reused stack. */
216 memset(s->addr, 0, THREAD_SIZE);
218 tsk->stack_vm_area = s;
222 stack = __vmalloc_node_range(THREAD_SIZE, THREAD_ALIGN,
223 VMALLOC_START, VMALLOC_END,
226 0, node, __builtin_return_address(0));
229 * We can't call find_vm_area() in interrupt context, and
230 * free_thread_stack() can be called in interrupt context,
231 * so cache the vm_struct.
234 tsk->stack_vm_area = find_vm_area(stack);
237 struct page *page = alloc_pages_node(node, THREADINFO_GFP,
240 return page ? page_address(page) : NULL;
244 static inline void free_thread_stack(struct task_struct *tsk)
246 #ifdef CONFIG_VMAP_STACK
247 if (task_stack_vm_area(tsk)) {
250 for (i = 0; i < NR_CACHED_STACKS; i++) {
251 if (this_cpu_cmpxchg(cached_stacks[i],
252 NULL, tsk->stack_vm_area) != NULL)
258 vfree_atomic(tsk->stack);
263 __free_pages(virt_to_page(tsk->stack), THREAD_SIZE_ORDER);
266 static struct kmem_cache *thread_stack_cache;
268 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk,
271 return kmem_cache_alloc_node(thread_stack_cache, THREADINFO_GFP, node);
274 static void free_thread_stack(struct task_struct *tsk)
276 kmem_cache_free(thread_stack_cache, tsk->stack);
279 void thread_stack_cache_init(void)
281 thread_stack_cache = kmem_cache_create_usercopy("thread_stack",
282 THREAD_SIZE, THREAD_SIZE, 0, 0,
284 BUG_ON(thread_stack_cache == NULL);
289 /* SLAB cache for signal_struct structures (tsk->signal) */
290 static struct kmem_cache *signal_cachep;
292 /* SLAB cache for sighand_struct structures (tsk->sighand) */
293 struct kmem_cache *sighand_cachep;
295 /* SLAB cache for files_struct structures (tsk->files) */
296 struct kmem_cache *files_cachep;
298 /* SLAB cache for fs_struct structures (tsk->fs) */
299 struct kmem_cache *fs_cachep;
301 /* SLAB cache for vm_area_struct structures */
302 static struct kmem_cache *vm_area_cachep;
304 /* SLAB cache for mm_struct structures (tsk->mm) */
305 static struct kmem_cache *mm_cachep;
307 struct vm_area_struct *vm_area_alloc(struct mm_struct *mm)
309 struct vm_area_struct *vma;
311 vma = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
317 struct vm_area_struct *vm_area_dup(struct vm_area_struct *orig)
319 struct vm_area_struct *new = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
323 INIT_LIST_HEAD(&new->anon_vma_chain);
328 void vm_area_free(struct vm_area_struct *vma)
330 kmem_cache_free(vm_area_cachep, vma);
333 static void account_kernel_stack(struct task_struct *tsk, int account)
335 void *stack = task_stack_page(tsk);
336 struct vm_struct *vm = task_stack_vm_area(tsk);
338 BUILD_BUG_ON(IS_ENABLED(CONFIG_VMAP_STACK) && PAGE_SIZE % 1024 != 0);
343 BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE);
345 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
346 mod_zone_page_state(page_zone(vm->pages[i]),
348 PAGE_SIZE / 1024 * account);
351 /* All stack pages belong to the same memcg. */
352 mod_memcg_page_state(vm->pages[0], MEMCG_KERNEL_STACK_KB,
353 account * (THREAD_SIZE / 1024));
356 * All stack pages are in the same zone and belong to the
359 struct page *first_page = virt_to_page(stack);
361 mod_zone_page_state(page_zone(first_page), NR_KERNEL_STACK_KB,
362 THREAD_SIZE / 1024 * account);
364 mod_memcg_page_state(first_page, MEMCG_KERNEL_STACK_KB,
365 account * (THREAD_SIZE / 1024));
369 static void release_task_stack(struct task_struct *tsk)
371 if (WARN_ON(tsk->state != TASK_DEAD))
372 return; /* Better to leak the stack than to free prematurely */
374 account_kernel_stack(tsk, -1);
375 free_thread_stack(tsk);
377 #ifdef CONFIG_VMAP_STACK
378 tsk->stack_vm_area = NULL;
382 #ifdef CONFIG_THREAD_INFO_IN_TASK
383 void put_task_stack(struct task_struct *tsk)
385 if (atomic_dec_and_test(&tsk->stack_refcount))
386 release_task_stack(tsk);
390 void free_task(struct task_struct *tsk)
392 #ifndef CONFIG_THREAD_INFO_IN_TASK
394 * The task is finally done with both the stack and thread_info,
397 release_task_stack(tsk);
400 * If the task had a separate stack allocation, it should be gone
403 WARN_ON_ONCE(atomic_read(&tsk->stack_refcount) != 0);
405 rt_mutex_debug_task_free(tsk);
406 ftrace_graph_exit_task(tsk);
407 put_seccomp_filter(tsk);
408 arch_release_task_struct(tsk);
409 if (tsk->flags & PF_KTHREAD)
410 free_kthread_struct(tsk);
411 free_task_struct(tsk);
413 EXPORT_SYMBOL(free_task);
416 static __latent_entropy int dup_mmap(struct mm_struct *mm,
417 struct mm_struct *oldmm)
419 struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
420 struct rb_node **rb_link, *rb_parent;
422 unsigned long charge;
425 uprobe_start_dup_mmap();
426 if (down_write_killable(&oldmm->mmap_sem)) {
428 goto fail_uprobe_end;
430 flush_cache_dup_mm(oldmm);
431 uprobe_dup_mmap(oldmm, mm);
433 * Not linked in yet - no deadlock potential:
435 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
437 /* No ordering required: file already has been exposed. */
438 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
440 mm->total_vm = oldmm->total_vm;
441 mm->data_vm = oldmm->data_vm;
442 mm->exec_vm = oldmm->exec_vm;
443 mm->stack_vm = oldmm->stack_vm;
445 rb_link = &mm->mm_rb.rb_node;
448 retval = ksm_fork(mm, oldmm);
451 retval = khugepaged_fork(mm, oldmm);
456 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
459 if (mpnt->vm_flags & VM_DONTCOPY) {
460 vm_stat_account(mm, mpnt->vm_flags, -vma_pages(mpnt));
465 * Don't duplicate many vmas if we've been oom-killed (for
468 if (fatal_signal_pending(current)) {
472 if (mpnt->vm_flags & VM_ACCOUNT) {
473 unsigned long len = vma_pages(mpnt);
475 if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
479 tmp = vm_area_dup(mpnt);
482 retval = vma_dup_policy(mpnt, tmp);
484 goto fail_nomem_policy;
486 retval = dup_userfaultfd(tmp, &uf);
488 goto fail_nomem_anon_vma_fork;
489 if (tmp->vm_flags & VM_WIPEONFORK) {
490 /* VM_WIPEONFORK gets a clean slate in the child. */
491 tmp->anon_vma = NULL;
492 if (anon_vma_prepare(tmp))
493 goto fail_nomem_anon_vma_fork;
494 } else if (anon_vma_fork(tmp, mpnt))
495 goto fail_nomem_anon_vma_fork;
496 tmp->vm_flags &= ~(VM_LOCKED | VM_LOCKONFAULT);
497 tmp->vm_next = tmp->vm_prev = NULL;
500 struct inode *inode = file_inode(file);
501 struct address_space *mapping = file->f_mapping;
504 if (tmp->vm_flags & VM_DENYWRITE)
505 atomic_dec(&inode->i_writecount);
506 i_mmap_lock_write(mapping);
507 if (tmp->vm_flags & VM_SHARED)
508 atomic_inc(&mapping->i_mmap_writable);
509 flush_dcache_mmap_lock(mapping);
510 /* insert tmp into the share list, just after mpnt */
511 vma_interval_tree_insert_after(tmp, mpnt,
513 flush_dcache_mmap_unlock(mapping);
514 i_mmap_unlock_write(mapping);
518 * Clear hugetlb-related page reserves for children. This only
519 * affects MAP_PRIVATE mappings. Faults generated by the child
520 * are not guaranteed to succeed, even if read-only
522 if (is_vm_hugetlb_page(tmp))
523 reset_vma_resv_huge_pages(tmp);
526 * Link in the new vma and copy the page table entries.
529 pprev = &tmp->vm_next;
533 __vma_link_rb(mm, tmp, rb_link, rb_parent);
534 rb_link = &tmp->vm_rb.rb_right;
535 rb_parent = &tmp->vm_rb;
538 if (!(tmp->vm_flags & VM_WIPEONFORK))
539 retval = copy_page_range(mm, oldmm, mpnt);
541 if (tmp->vm_ops && tmp->vm_ops->open)
542 tmp->vm_ops->open(tmp);
547 /* a new mm has just been created */
548 retval = arch_dup_mmap(oldmm, mm);
550 up_write(&mm->mmap_sem);
552 up_write(&oldmm->mmap_sem);
553 dup_userfaultfd_complete(&uf);
555 uprobe_end_dup_mmap();
557 fail_nomem_anon_vma_fork:
558 mpol_put(vma_policy(tmp));
563 vm_unacct_memory(charge);
567 static inline int mm_alloc_pgd(struct mm_struct *mm)
569 mm->pgd = pgd_alloc(mm);
570 if (unlikely(!mm->pgd))
575 static inline void mm_free_pgd(struct mm_struct *mm)
577 pgd_free(mm, mm->pgd);
580 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
582 down_write(&oldmm->mmap_sem);
583 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
584 up_write(&oldmm->mmap_sem);
587 #define mm_alloc_pgd(mm) (0)
588 #define mm_free_pgd(mm)
589 #endif /* CONFIG_MMU */
591 static void check_mm(struct mm_struct *mm)
595 for (i = 0; i < NR_MM_COUNTERS; i++) {
596 long x = atomic_long_read(&mm->rss_stat.count[i]);
599 printk(KERN_ALERT "BUG: Bad rss-counter state "
600 "mm:%p idx:%d val:%ld\n", mm, i, x);
603 if (mm_pgtables_bytes(mm))
604 pr_alert("BUG: non-zero pgtables_bytes on freeing mm: %ld\n",
605 mm_pgtables_bytes(mm));
607 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
608 VM_BUG_ON_MM(mm->pmd_huge_pte, mm);
612 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
613 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm)))
616 * Called when the last reference to the mm
617 * is dropped: either by a lazy thread or by
618 * mmput. Free the page directory and the mm.
620 void __mmdrop(struct mm_struct *mm)
622 BUG_ON(mm == &init_mm);
623 WARN_ON_ONCE(mm == current->mm);
624 WARN_ON_ONCE(mm == current->active_mm);
628 mmu_notifier_mm_destroy(mm);
630 put_user_ns(mm->user_ns);
633 EXPORT_SYMBOL_GPL(__mmdrop);
635 static void mmdrop_async_fn(struct work_struct *work)
637 struct mm_struct *mm;
639 mm = container_of(work, struct mm_struct, async_put_work);
643 static void mmdrop_async(struct mm_struct *mm)
645 if (unlikely(atomic_dec_and_test(&mm->mm_count))) {
646 INIT_WORK(&mm->async_put_work, mmdrop_async_fn);
647 schedule_work(&mm->async_put_work);
651 static inline void free_signal_struct(struct signal_struct *sig)
653 taskstats_tgid_free(sig);
654 sched_autogroup_exit(sig);
656 * __mmdrop is not safe to call from softirq context on x86 due to
657 * pgd_dtor so postpone it to the async context
660 mmdrop_async(sig->oom_mm);
661 kmem_cache_free(signal_cachep, sig);
664 static inline void put_signal_struct(struct signal_struct *sig)
666 if (atomic_dec_and_test(&sig->sigcnt))
667 free_signal_struct(sig);
670 void __put_task_struct(struct task_struct *tsk)
672 WARN_ON(!tsk->exit_state);
673 WARN_ON(atomic_read(&tsk->usage));
674 WARN_ON(tsk == current);
677 task_numa_free(tsk, true);
678 security_task_free(tsk);
680 delayacct_tsk_free(tsk);
681 put_signal_struct(tsk->signal);
683 if (!profile_handoff_task(tsk))
686 EXPORT_SYMBOL_GPL(__put_task_struct);
688 void __init __weak arch_task_cache_init(void) { }
693 static void set_max_threads(unsigned int max_threads_suggested)
698 * The number of threads shall be limited such that the thread
699 * structures may only consume a small part of the available memory.
701 if (fls64(totalram_pages) + fls64(PAGE_SIZE) > 64)
702 threads = MAX_THREADS;
704 threads = div64_u64((u64) totalram_pages * (u64) PAGE_SIZE,
705 (u64) THREAD_SIZE * 8UL);
707 if (threads > max_threads_suggested)
708 threads = max_threads_suggested;
710 max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS);
713 #ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT
714 /* Initialized by the architecture: */
715 int arch_task_struct_size __read_mostly;
718 static void task_struct_whitelist(unsigned long *offset, unsigned long *size)
720 /* Fetch thread_struct whitelist for the architecture. */
721 arch_thread_struct_whitelist(offset, size);
724 * Handle zero-sized whitelist or empty thread_struct, otherwise
725 * adjust offset to position of thread_struct in task_struct.
727 if (unlikely(*size == 0))
730 *offset += offsetof(struct task_struct, thread);
733 void __init fork_init(void)
736 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
737 #ifndef ARCH_MIN_TASKALIGN
738 #define ARCH_MIN_TASKALIGN 0
740 int align = max_t(int, L1_CACHE_BYTES, ARCH_MIN_TASKALIGN);
741 unsigned long useroffset, usersize;
743 /* create a slab on which task_structs can be allocated */
744 task_struct_whitelist(&useroffset, &usersize);
745 task_struct_cachep = kmem_cache_create_usercopy("task_struct",
746 arch_task_struct_size, align,
747 SLAB_PANIC|SLAB_ACCOUNT,
748 useroffset, usersize, NULL);
751 /* do the arch specific task caches init */
752 arch_task_cache_init();
754 set_max_threads(MAX_THREADS);
756 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
757 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
758 init_task.signal->rlim[RLIMIT_SIGPENDING] =
759 init_task.signal->rlim[RLIMIT_NPROC];
761 for (i = 0; i < UCOUNT_COUNTS; i++) {
762 init_user_ns.ucount_max[i] = max_threads/2;
765 #ifdef CONFIG_VMAP_STACK
766 cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "fork:vm_stack_cache",
767 NULL, free_vm_stack_cache);
770 lockdep_init_task(&init_task);
773 int __weak arch_dup_task_struct(struct task_struct *dst,
774 struct task_struct *src)
780 void set_task_stack_end_magic(struct task_struct *tsk)
782 unsigned long *stackend;
784 stackend = end_of_stack(tsk);
785 *stackend = STACK_END_MAGIC; /* for overflow detection */
788 static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
790 struct task_struct *tsk;
791 unsigned long *stack;
792 struct vm_struct *stack_vm_area;
795 if (node == NUMA_NO_NODE)
796 node = tsk_fork_get_node(orig);
797 tsk = alloc_task_struct_node(node);
801 stack = alloc_thread_stack_node(tsk, node);
805 stack_vm_area = task_stack_vm_area(tsk);
807 err = arch_dup_task_struct(tsk, orig);
810 * arch_dup_task_struct() clobbers the stack-related fields. Make
811 * sure they're properly initialized before using any stack-related
815 #ifdef CONFIG_VMAP_STACK
816 tsk->stack_vm_area = stack_vm_area;
818 #ifdef CONFIG_THREAD_INFO_IN_TASK
819 atomic_set(&tsk->stack_refcount, 1);
825 #ifdef CONFIG_SECCOMP
827 * We must handle setting up seccomp filters once we're under
828 * the sighand lock in case orig has changed between now and
829 * then. Until then, filter must be NULL to avoid messing up
830 * the usage counts on the error path calling free_task.
832 tsk->seccomp.filter = NULL;
835 setup_thread_stack(tsk, orig);
836 clear_user_return_notifier(tsk);
837 clear_tsk_need_resched(tsk);
838 set_task_stack_end_magic(tsk);
840 #ifdef CONFIG_STACKPROTECTOR
841 tsk->stack_canary = get_random_canary();
845 * One for us, one for whoever does the "release_task()" (usually
848 atomic_set(&tsk->usage, 2);
849 #ifdef CONFIG_BLK_DEV_IO_TRACE
852 tsk->splice_pipe = NULL;
853 tsk->task_frag.page = NULL;
854 tsk->wake_q.next = NULL;
856 account_kernel_stack(tsk, 1);
860 #ifdef CONFIG_FAULT_INJECTION
864 #ifdef CONFIG_BLK_CGROUP
865 tsk->throttle_queue = NULL;
866 tsk->use_memdelay = 0;
870 tsk->active_memcg = NULL;
875 free_thread_stack(tsk);
877 free_task_struct(tsk);
881 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
883 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
885 static int __init coredump_filter_setup(char *s)
887 default_dump_filter =
888 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
889 MMF_DUMP_FILTER_MASK;
893 __setup("coredump_filter=", coredump_filter_setup);
895 #include <linux/init_task.h>
897 static void mm_init_aio(struct mm_struct *mm)
900 spin_lock_init(&mm->ioctx_lock);
901 mm->ioctx_table = NULL;
905 static __always_inline void mm_clear_owner(struct mm_struct *mm,
906 struct task_struct *p)
910 WRITE_ONCE(mm->owner, NULL);
914 static void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
921 static void mm_init_uprobes_state(struct mm_struct *mm)
923 #ifdef CONFIG_UPROBES
924 mm->uprobes_state.xol_area = NULL;
928 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
929 struct user_namespace *user_ns)
933 mm->vmacache_seqnum = 0;
934 atomic_set(&mm->mm_users, 1);
935 atomic_set(&mm->mm_count, 1);
936 init_rwsem(&mm->mmap_sem);
937 INIT_LIST_HEAD(&mm->mmlist);
938 mm->core_state = NULL;
939 mm_pgtables_bytes_init(mm);
943 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
944 spin_lock_init(&mm->page_table_lock);
945 spin_lock_init(&mm->arg_lock);
948 mm_init_owner(mm, p);
949 RCU_INIT_POINTER(mm->exe_file, NULL);
950 mmu_notifier_mm_init(mm);
952 init_tlb_flush_pending(mm);
953 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
954 mm->pmd_huge_pte = NULL;
956 mm_init_uprobes_state(mm);
959 mm->flags = current->mm->flags & MMF_INIT_MASK;
960 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK;
962 mm->flags = default_dump_filter;
966 if (mm_alloc_pgd(mm))
969 if (init_new_context(p, mm))
972 mm->user_ns = get_user_ns(user_ns);
983 * Allocate and initialize an mm_struct.
985 struct mm_struct *mm_alloc(void)
987 struct mm_struct *mm;
993 memset(mm, 0, sizeof(*mm));
994 return mm_init(mm, current, current_user_ns());
997 static inline void __mmput(struct mm_struct *mm)
999 VM_BUG_ON(atomic_read(&mm->mm_users));
1001 uprobe_clear_state(mm);
1004 khugepaged_exit(mm); /* must run before exit_mmap */
1006 mm_put_huge_zero_page(mm);
1007 set_mm_exe_file(mm, NULL);
1008 if (!list_empty(&mm->mmlist)) {
1009 spin_lock(&mmlist_lock);
1010 list_del(&mm->mmlist);
1011 spin_unlock(&mmlist_lock);
1014 module_put(mm->binfmt->module);
1019 * Decrement the use count and release all resources for an mm.
1021 void mmput(struct mm_struct *mm)
1025 if (atomic_dec_and_test(&mm->mm_users))
1028 EXPORT_SYMBOL_GPL(mmput);
1031 static void mmput_async_fn(struct work_struct *work)
1033 struct mm_struct *mm = container_of(work, struct mm_struct,
1039 void mmput_async(struct mm_struct *mm)
1041 if (atomic_dec_and_test(&mm->mm_users)) {
1042 INIT_WORK(&mm->async_put_work, mmput_async_fn);
1043 schedule_work(&mm->async_put_work);
1049 * set_mm_exe_file - change a reference to the mm's executable file
1051 * This changes mm's executable file (shown as symlink /proc/[pid]/exe).
1053 * Main users are mmput() and sys_execve(). Callers prevent concurrent
1054 * invocations: in mmput() nobody alive left, in execve task is single
1055 * threaded. sys_prctl(PR_SET_MM_MAP/EXE_FILE) also needs to set the
1056 * mm->exe_file, but does so without using set_mm_exe_file() in order
1057 * to do avoid the need for any locks.
1059 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
1061 struct file *old_exe_file;
1064 * It is safe to dereference the exe_file without RCU as
1065 * this function is only called if nobody else can access
1066 * this mm -- see comment above for justification.
1068 old_exe_file = rcu_dereference_raw(mm->exe_file);
1071 get_file(new_exe_file);
1072 rcu_assign_pointer(mm->exe_file, new_exe_file);
1078 * get_mm_exe_file - acquire a reference to the mm's executable file
1080 * Returns %NULL if mm has no associated executable file.
1081 * User must release file via fput().
1083 struct file *get_mm_exe_file(struct mm_struct *mm)
1085 struct file *exe_file;
1088 exe_file = rcu_dereference(mm->exe_file);
1089 if (exe_file && !get_file_rcu(exe_file))
1094 EXPORT_SYMBOL(get_mm_exe_file);
1097 * get_task_exe_file - acquire a reference to the task's executable file
1099 * Returns %NULL if task's mm (if any) has no associated executable file or
1100 * this is a kernel thread with borrowed mm (see the comment above get_task_mm).
1101 * User must release file via fput().
1103 struct file *get_task_exe_file(struct task_struct *task)
1105 struct file *exe_file = NULL;
1106 struct mm_struct *mm;
1111 if (!(task->flags & PF_KTHREAD))
1112 exe_file = get_mm_exe_file(mm);
1117 EXPORT_SYMBOL(get_task_exe_file);
1120 * get_task_mm - acquire a reference to the task's mm
1122 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning
1123 * this kernel workthread has transiently adopted a user mm with use_mm,
1124 * to do its AIO) is not set and if so returns a reference to it, after
1125 * bumping up the use count. User must release the mm via mmput()
1126 * after use. Typically used by /proc and ptrace.
1128 struct mm_struct *get_task_mm(struct task_struct *task)
1130 struct mm_struct *mm;
1135 if (task->flags & PF_KTHREAD)
1143 EXPORT_SYMBOL_GPL(get_task_mm);
1145 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
1147 struct mm_struct *mm;
1150 err = mutex_lock_killable(&task->signal->cred_guard_mutex);
1152 return ERR_PTR(err);
1154 mm = get_task_mm(task);
1155 if (mm && mm != current->mm &&
1156 !ptrace_may_access(task, mode)) {
1158 mm = ERR_PTR(-EACCES);
1160 mutex_unlock(&task->signal->cred_guard_mutex);
1165 static void complete_vfork_done(struct task_struct *tsk)
1167 struct completion *vfork;
1170 vfork = tsk->vfork_done;
1171 if (likely(vfork)) {
1172 tsk->vfork_done = NULL;
1178 static int wait_for_vfork_done(struct task_struct *child,
1179 struct completion *vfork)
1183 freezer_do_not_count();
1184 killed = wait_for_completion_killable(vfork);
1189 child->vfork_done = NULL;
1193 put_task_struct(child);
1197 /* Please note the differences between mmput and mm_release.
1198 * mmput is called whenever we stop holding onto a mm_struct,
1199 * error success whatever.
1201 * mm_release is called after a mm_struct has been removed
1202 * from the current process.
1204 * This difference is important for error handling, when we
1205 * only half set up a mm_struct for a new process and need to restore
1206 * the old one. Because we mmput the new mm_struct before
1207 * restoring the old one. . .
1208 * Eric Biederman 10 January 1998
1210 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
1212 /* Get rid of any futexes when releasing the mm */
1214 if (unlikely(tsk->robust_list)) {
1215 exit_robust_list(tsk);
1216 tsk->robust_list = NULL;
1218 #ifdef CONFIG_COMPAT
1219 if (unlikely(tsk->compat_robust_list)) {
1220 compat_exit_robust_list(tsk);
1221 tsk->compat_robust_list = NULL;
1224 if (unlikely(!list_empty(&tsk->pi_state_list)))
1225 exit_pi_state_list(tsk);
1228 uprobe_free_utask(tsk);
1230 /* Get rid of any cached register state */
1231 deactivate_mm(tsk, mm);
1234 * Signal userspace if we're not exiting with a core dump
1235 * because we want to leave the value intact for debugging
1238 if (tsk->clear_child_tid) {
1239 if (!(tsk->signal->flags & SIGNAL_GROUP_COREDUMP) &&
1240 atomic_read(&mm->mm_users) > 1) {
1242 * We don't check the error code - if userspace has
1243 * not set up a proper pointer then tough luck.
1245 put_user(0, tsk->clear_child_tid);
1246 do_futex(tsk->clear_child_tid, FUTEX_WAKE,
1247 1, NULL, NULL, 0, 0);
1249 tsk->clear_child_tid = NULL;
1253 * All done, finally we can wake up parent and return this mm to him.
1254 * Also kthread_stop() uses this completion for synchronization.
1256 if (tsk->vfork_done)
1257 complete_vfork_done(tsk);
1261 * Allocate a new mm structure and copy contents from the
1262 * mm structure of the passed in task structure.
1264 static struct mm_struct *dup_mm(struct task_struct *tsk)
1266 struct mm_struct *mm, *oldmm = current->mm;
1273 memcpy(mm, oldmm, sizeof(*mm));
1275 if (!mm_init(mm, tsk, mm->user_ns))
1278 err = dup_mmap(mm, oldmm);
1282 mm->hiwater_rss = get_mm_rss(mm);
1283 mm->hiwater_vm = mm->total_vm;
1285 if (mm->binfmt && !try_module_get(mm->binfmt->module))
1291 /* don't put binfmt in mmput, we haven't got module yet */
1293 mm_init_owner(mm, NULL);
1300 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
1302 struct mm_struct *mm, *oldmm;
1305 tsk->min_flt = tsk->maj_flt = 0;
1306 tsk->nvcsw = tsk->nivcsw = 0;
1307 #ifdef CONFIG_DETECT_HUNG_TASK
1308 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
1309 tsk->last_switch_time = 0;
1313 tsk->active_mm = NULL;
1316 * Are we cloning a kernel thread?
1318 * We need to steal a active VM for that..
1320 oldmm = current->mm;
1324 /* initialize the new vmacache entries */
1325 vmacache_flush(tsk);
1327 if (clone_flags & CLONE_VM) {
1340 tsk->active_mm = mm;
1347 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
1349 struct fs_struct *fs = current->fs;
1350 if (clone_flags & CLONE_FS) {
1351 /* tsk->fs is already what we want */
1352 spin_lock(&fs->lock);
1354 spin_unlock(&fs->lock);
1358 spin_unlock(&fs->lock);
1361 tsk->fs = copy_fs_struct(fs);
1367 static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
1369 struct files_struct *oldf, *newf;
1373 * A background process may not have any files ...
1375 oldf = current->files;
1379 if (clone_flags & CLONE_FILES) {
1380 atomic_inc(&oldf->count);
1384 newf = dup_fd(oldf, &error);
1394 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
1397 struct io_context *ioc = current->io_context;
1398 struct io_context *new_ioc;
1403 * Share io context with parent, if CLONE_IO is set
1405 if (clone_flags & CLONE_IO) {
1407 tsk->io_context = ioc;
1408 } else if (ioprio_valid(ioc->ioprio)) {
1409 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE);
1410 if (unlikely(!new_ioc))
1413 new_ioc->ioprio = ioc->ioprio;
1414 put_io_context(new_ioc);
1420 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
1422 struct sighand_struct *sig;
1424 if (clone_flags & CLONE_SIGHAND) {
1425 atomic_inc(¤t->sighand->count);
1428 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1429 rcu_assign_pointer(tsk->sighand, sig);
1433 atomic_set(&sig->count, 1);
1434 spin_lock_irq(¤t->sighand->siglock);
1435 memcpy(sig->action, current->sighand->action, sizeof(sig->action));
1436 spin_unlock_irq(¤t->sighand->siglock);
1440 void __cleanup_sighand(struct sighand_struct *sighand)
1442 if (atomic_dec_and_test(&sighand->count)) {
1443 signalfd_cleanup(sighand);
1445 * sighand_cachep is SLAB_TYPESAFE_BY_RCU so we can free it
1446 * without an RCU grace period, see __lock_task_sighand().
1448 kmem_cache_free(sighand_cachep, sighand);
1452 #ifdef CONFIG_POSIX_TIMERS
1454 * Initialize POSIX timer handling for a thread group.
1456 static void posix_cpu_timers_init_group(struct signal_struct *sig)
1458 unsigned long cpu_limit;
1460 cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1461 if (cpu_limit != RLIM_INFINITY) {
1462 sig->cputime_expires.prof_exp = cpu_limit * NSEC_PER_SEC;
1463 sig->cputimer.running = true;
1466 /* The timer lists. */
1467 INIT_LIST_HEAD(&sig->cpu_timers[0]);
1468 INIT_LIST_HEAD(&sig->cpu_timers[1]);
1469 INIT_LIST_HEAD(&sig->cpu_timers[2]);
1472 static inline void posix_cpu_timers_init_group(struct signal_struct *sig) { }
1475 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
1477 struct signal_struct *sig;
1479 if (clone_flags & CLONE_THREAD)
1482 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
1487 sig->nr_threads = 1;
1488 atomic_set(&sig->live, 1);
1489 atomic_set(&sig->sigcnt, 1);
1491 /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */
1492 sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node);
1493 tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head);
1495 init_waitqueue_head(&sig->wait_chldexit);
1496 sig->curr_target = tsk;
1497 init_sigpending(&sig->shared_pending);
1498 INIT_HLIST_HEAD(&sig->multiprocess);
1499 seqlock_init(&sig->stats_lock);
1500 prev_cputime_init(&sig->prev_cputime);
1502 #ifdef CONFIG_POSIX_TIMERS
1503 INIT_LIST_HEAD(&sig->posix_timers);
1504 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1505 sig->real_timer.function = it_real_fn;
1508 task_lock(current->group_leader);
1509 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
1510 task_unlock(current->group_leader);
1512 posix_cpu_timers_init_group(sig);
1514 tty_audit_fork(sig);
1515 sched_autogroup_fork(sig);
1517 sig->oom_score_adj = current->signal->oom_score_adj;
1518 sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1520 mutex_init(&sig->cred_guard_mutex);
1525 static void copy_seccomp(struct task_struct *p)
1527 #ifdef CONFIG_SECCOMP
1529 * Must be called with sighand->lock held, which is common to
1530 * all threads in the group. Holding cred_guard_mutex is not
1531 * needed because this new task is not yet running and cannot
1534 assert_spin_locked(¤t->sighand->siglock);
1536 /* Ref-count the new filter user, and assign it. */
1537 get_seccomp_filter(current);
1538 p->seccomp = current->seccomp;
1541 * Explicitly enable no_new_privs here in case it got set
1542 * between the task_struct being duplicated and holding the
1543 * sighand lock. The seccomp state and nnp must be in sync.
1545 if (task_no_new_privs(current))
1546 task_set_no_new_privs(p);
1549 * If the parent gained a seccomp mode after copying thread
1550 * flags and between before we held the sighand lock, we have
1551 * to manually enable the seccomp thread flag here.
1553 if (p->seccomp.mode != SECCOMP_MODE_DISABLED)
1554 set_tsk_thread_flag(p, TIF_SECCOMP);
1558 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1560 current->clear_child_tid = tidptr;
1562 return task_pid_vnr(current);
1565 static void rt_mutex_init_task(struct task_struct *p)
1567 raw_spin_lock_init(&p->pi_lock);
1568 #ifdef CONFIG_RT_MUTEXES
1569 p->pi_waiters = RB_ROOT_CACHED;
1570 p->pi_top_task = NULL;
1571 p->pi_blocked_on = NULL;
1575 #ifdef CONFIG_POSIX_TIMERS
1577 * Initialize POSIX timer handling for a single task.
1579 static void posix_cpu_timers_init(struct task_struct *tsk)
1581 tsk->cputime_expires.prof_exp = 0;
1582 tsk->cputime_expires.virt_exp = 0;
1583 tsk->cputime_expires.sched_exp = 0;
1584 INIT_LIST_HEAD(&tsk->cpu_timers[0]);
1585 INIT_LIST_HEAD(&tsk->cpu_timers[1]);
1586 INIT_LIST_HEAD(&tsk->cpu_timers[2]);
1589 static inline void posix_cpu_timers_init(struct task_struct *tsk) { }
1592 static inline void init_task_pid_links(struct task_struct *task)
1596 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
1597 INIT_HLIST_NODE(&task->pid_links[type]);
1602 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid)
1604 if (type == PIDTYPE_PID)
1605 task->thread_pid = pid;
1607 task->signal->pids[type] = pid;
1610 static inline void rcu_copy_process(struct task_struct *p)
1612 #ifdef CONFIG_PREEMPT_RCU
1613 p->rcu_read_lock_nesting = 0;
1614 p->rcu_read_unlock_special.s = 0;
1615 p->rcu_blocked_node = NULL;
1616 INIT_LIST_HEAD(&p->rcu_node_entry);
1617 #endif /* #ifdef CONFIG_PREEMPT_RCU */
1618 #ifdef CONFIG_TASKS_RCU
1619 p->rcu_tasks_holdout = false;
1620 INIT_LIST_HEAD(&p->rcu_tasks_holdout_list);
1621 p->rcu_tasks_idle_cpu = -1;
1622 #endif /* #ifdef CONFIG_TASKS_RCU */
1625 static void __delayed_free_task(struct rcu_head *rhp)
1627 struct task_struct *tsk = container_of(rhp, struct task_struct, rcu);
1632 static __always_inline void delayed_free_task(struct task_struct *tsk)
1634 if (IS_ENABLED(CONFIG_MEMCG))
1635 call_rcu(&tsk->rcu, __delayed_free_task);
1641 * This creates a new process as a copy of the old one,
1642 * but does not actually start it yet.
1644 * It copies the registers, and all the appropriate
1645 * parts of the process environment (as per the clone
1646 * flags). The actual kick-off is left to the caller.
1648 static __latent_entropy struct task_struct *copy_process(
1649 unsigned long clone_flags,
1650 unsigned long stack_start,
1651 unsigned long stack_size,
1652 int __user *child_tidptr,
1659 struct task_struct *p;
1660 struct multiprocess_signals delayed;
1663 * Don't allow sharing the root directory with processes in a different
1666 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1667 return ERR_PTR(-EINVAL);
1669 if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS))
1670 return ERR_PTR(-EINVAL);
1673 * Thread groups must share signals as well, and detached threads
1674 * can only be started up within the thread group.
1676 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1677 return ERR_PTR(-EINVAL);
1680 * Shared signal handlers imply shared VM. By way of the above,
1681 * thread groups also imply shared VM. Blocking this case allows
1682 * for various simplifications in other code.
1684 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1685 return ERR_PTR(-EINVAL);
1688 * Siblings of global init remain as zombies on exit since they are
1689 * not reaped by their parent (swapper). To solve this and to avoid
1690 * multi-rooted process trees, prevent global and container-inits
1691 * from creating siblings.
1693 if ((clone_flags & CLONE_PARENT) &&
1694 current->signal->flags & SIGNAL_UNKILLABLE)
1695 return ERR_PTR(-EINVAL);
1698 * If the new process will be in a different pid or user namespace
1699 * do not allow it to share a thread group with the forking task.
1701 if (clone_flags & CLONE_THREAD) {
1702 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) ||
1703 (task_active_pid_ns(current) !=
1704 current->nsproxy->pid_ns_for_children))
1705 return ERR_PTR(-EINVAL);
1709 * Force any signals received before this point to be delivered
1710 * before the fork happens. Collect up signals sent to multiple
1711 * processes that happen during the fork and delay them so that
1712 * they appear to happen after the fork.
1714 sigemptyset(&delayed.signal);
1715 INIT_HLIST_NODE(&delayed.node);
1717 spin_lock_irq(¤t->sighand->siglock);
1718 if (!(clone_flags & CLONE_THREAD))
1719 hlist_add_head(&delayed.node, ¤t->signal->multiprocess);
1720 recalc_sigpending();
1721 spin_unlock_irq(¤t->sighand->siglock);
1722 retval = -ERESTARTNOINTR;
1723 if (signal_pending(current))
1727 p = dup_task_struct(current, node);
1732 * This _must_ happen before we call free_task(), i.e. before we jump
1733 * to any of the bad_fork_* labels. This is to avoid freeing
1734 * p->set_child_tid which is (ab)used as a kthread's data pointer for
1735 * kernel threads (PF_KTHREAD).
1737 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1739 * Clear TID on mm_release()?
1741 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL;
1743 ftrace_graph_init_task(p);
1745 rt_mutex_init_task(p);
1747 #ifdef CONFIG_PROVE_LOCKING
1748 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1749 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1752 if (atomic_read(&p->real_cred->user->processes) >=
1753 task_rlimit(p, RLIMIT_NPROC)) {
1754 if (p->real_cred->user != INIT_USER &&
1755 !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
1758 current->flags &= ~PF_NPROC_EXCEEDED;
1760 retval = copy_creds(p, clone_flags);
1765 * If multiple threads are within copy_process(), then this check
1766 * triggers too late. This doesn't hurt, the check is only there
1767 * to stop root fork bombs.
1770 if (nr_threads >= max_threads)
1771 goto bad_fork_cleanup_count;
1773 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */
1774 p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER | PF_IDLE);
1775 p->flags |= PF_FORKNOEXEC;
1776 INIT_LIST_HEAD(&p->children);
1777 INIT_LIST_HEAD(&p->sibling);
1778 rcu_copy_process(p);
1779 p->vfork_done = NULL;
1780 spin_lock_init(&p->alloc_lock);
1782 init_sigpending(&p->pending);
1784 p->utime = p->stime = p->gtime = 0;
1785 #ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
1786 p->utimescaled = p->stimescaled = 0;
1788 prev_cputime_init(&p->prev_cputime);
1790 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
1791 seqcount_init(&p->vtime.seqcount);
1792 p->vtime.starttime = 0;
1793 p->vtime.state = VTIME_INACTIVE;
1796 #if defined(SPLIT_RSS_COUNTING)
1797 memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1800 p->default_timer_slack_ns = current->timer_slack_ns;
1802 task_io_accounting_init(&p->ioac);
1803 acct_clear_integrals(p);
1805 posix_cpu_timers_init(p);
1807 p->io_context = NULL;
1808 audit_set_context(p, NULL);
1811 p->mempolicy = mpol_dup(p->mempolicy);
1812 if (IS_ERR(p->mempolicy)) {
1813 retval = PTR_ERR(p->mempolicy);
1814 p->mempolicy = NULL;
1815 goto bad_fork_cleanup_threadgroup_lock;
1818 #ifdef CONFIG_CPUSETS
1819 p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
1820 p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
1821 seqcount_init(&p->mems_allowed_seq);
1823 #ifdef CONFIG_TRACE_IRQFLAGS
1825 p->hardirqs_enabled = 0;
1826 p->hardirq_enable_ip = 0;
1827 p->hardirq_enable_event = 0;
1828 p->hardirq_disable_ip = _THIS_IP_;
1829 p->hardirq_disable_event = 0;
1830 p->softirqs_enabled = 1;
1831 p->softirq_enable_ip = _THIS_IP_;
1832 p->softirq_enable_event = 0;
1833 p->softirq_disable_ip = 0;
1834 p->softirq_disable_event = 0;
1835 p->hardirq_context = 0;
1836 p->softirq_context = 0;
1839 p->pagefault_disabled = 0;
1841 #ifdef CONFIG_LOCKDEP
1842 p->lockdep_depth = 0; /* no locks held yet */
1843 p->curr_chain_key = 0;
1844 p->lockdep_recursion = 0;
1845 lockdep_init_task(p);
1848 #ifdef CONFIG_DEBUG_MUTEXES
1849 p->blocked_on = NULL; /* not blocked yet */
1851 #ifdef CONFIG_BCACHE
1852 p->sequential_io = 0;
1853 p->sequential_io_avg = 0;
1856 /* Perform scheduler related setup. Assign this task to a CPU. */
1857 retval = sched_fork(clone_flags, p);
1859 goto bad_fork_cleanup_policy;
1861 retval = perf_event_init_task(p);
1863 goto bad_fork_cleanup_policy;
1864 retval = audit_alloc(p);
1866 goto bad_fork_cleanup_perf;
1867 /* copy all the process information */
1869 retval = security_task_alloc(p, clone_flags);
1871 goto bad_fork_cleanup_audit;
1872 retval = copy_semundo(clone_flags, p);
1874 goto bad_fork_cleanup_security;
1875 retval = copy_files(clone_flags, p);
1877 goto bad_fork_cleanup_semundo;
1878 retval = copy_fs(clone_flags, p);
1880 goto bad_fork_cleanup_files;
1881 retval = copy_sighand(clone_flags, p);
1883 goto bad_fork_cleanup_fs;
1884 retval = copy_signal(clone_flags, p);
1886 goto bad_fork_cleanup_sighand;
1887 retval = copy_mm(clone_flags, p);
1889 goto bad_fork_cleanup_signal;
1890 retval = copy_namespaces(clone_flags, p);
1892 goto bad_fork_cleanup_mm;
1893 retval = copy_io(clone_flags, p);
1895 goto bad_fork_cleanup_namespaces;
1896 retval = copy_thread_tls(clone_flags, stack_start, stack_size, p, tls);
1898 goto bad_fork_cleanup_io;
1900 if (pid != &init_struct_pid) {
1901 pid = alloc_pid(p->nsproxy->pid_ns_for_children);
1903 retval = PTR_ERR(pid);
1904 goto bad_fork_cleanup_thread;
1912 p->robust_list = NULL;
1913 #ifdef CONFIG_COMPAT
1914 p->compat_robust_list = NULL;
1916 INIT_LIST_HEAD(&p->pi_state_list);
1917 p->pi_state_cache = NULL;
1920 * sigaltstack should be cleared when sharing the same VM
1922 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1926 * Syscall tracing and stepping should be turned off in the
1927 * child regardless of CLONE_PTRACE.
1929 user_disable_single_step(p);
1930 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1931 #ifdef TIF_SYSCALL_EMU
1932 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1934 clear_all_latency_tracing(p);
1936 /* ok, now we should be set up.. */
1937 p->pid = pid_nr(pid);
1938 if (clone_flags & CLONE_THREAD) {
1939 p->exit_signal = -1;
1940 p->group_leader = current->group_leader;
1941 p->tgid = current->tgid;
1943 if (clone_flags & CLONE_PARENT)
1944 p->exit_signal = current->group_leader->exit_signal;
1946 p->exit_signal = (clone_flags & CSIGNAL);
1947 p->group_leader = p;
1952 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
1953 p->dirty_paused_when = 0;
1955 p->pdeath_signal = 0;
1956 INIT_LIST_HEAD(&p->thread_group);
1957 p->task_works = NULL;
1959 cgroup_threadgroup_change_begin(current);
1961 * Ensure that the cgroup subsystem policies allow the new process to be
1962 * forked. It should be noted the the new process's css_set can be changed
1963 * between here and cgroup_post_fork() if an organisation operation is in
1966 retval = cgroup_can_fork(p);
1968 goto bad_fork_free_pid;
1971 * From this point on we must avoid any synchronous user-space
1972 * communication until we take the tasklist-lock. In particular, we do
1973 * not want user-space to be able to predict the process start-time by
1974 * stalling fork(2) after we recorded the start_time but before it is
1975 * visible to the system.
1978 p->start_time = ktime_get_ns();
1979 p->real_start_time = ktime_get_boot_ns();
1982 * Make it visible to the rest of the system, but dont wake it up yet.
1983 * Need tasklist lock for parent etc handling!
1985 write_lock_irq(&tasklist_lock);
1987 /* CLONE_PARENT re-uses the old parent */
1988 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1989 p->real_parent = current->real_parent;
1990 p->parent_exec_id = current->parent_exec_id;
1992 p->real_parent = current;
1993 p->parent_exec_id = current->self_exec_id;
1996 klp_copy_process(p);
1998 spin_lock(¤t->sighand->siglock);
2001 * Copy seccomp details explicitly here, in case they were changed
2002 * before holding sighand lock.
2006 rseq_fork(p, clone_flags);
2008 /* Don't start children in a dying pid namespace */
2009 if (unlikely(!(ns_of_pid(pid)->pid_allocated & PIDNS_ADDING))) {
2011 goto bad_fork_cancel_cgroup;
2014 /* Let kill terminate clone/fork in the middle */
2015 if (fatal_signal_pending(current)) {
2017 goto bad_fork_cancel_cgroup;
2021 init_task_pid_links(p);
2022 if (likely(p->pid)) {
2023 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
2025 init_task_pid(p, PIDTYPE_PID, pid);
2026 if (thread_group_leader(p)) {
2027 init_task_pid(p, PIDTYPE_TGID, pid);
2028 init_task_pid(p, PIDTYPE_PGID, task_pgrp(current));
2029 init_task_pid(p, PIDTYPE_SID, task_session(current));
2031 if (is_child_reaper(pid)) {
2032 ns_of_pid(pid)->child_reaper = p;
2033 p->signal->flags |= SIGNAL_UNKILLABLE;
2035 p->signal->shared_pending.signal = delayed.signal;
2036 p->signal->tty = tty_kref_get(current->signal->tty);
2038 * Inherit has_child_subreaper flag under the same
2039 * tasklist_lock with adding child to the process tree
2040 * for propagate_has_child_subreaper optimization.
2042 p->signal->has_child_subreaper = p->real_parent->signal->has_child_subreaper ||
2043 p->real_parent->signal->is_child_subreaper;
2044 list_add_tail(&p->sibling, &p->real_parent->children);
2045 list_add_tail_rcu(&p->tasks, &init_task.tasks);
2046 attach_pid(p, PIDTYPE_TGID);
2047 attach_pid(p, PIDTYPE_PGID);
2048 attach_pid(p, PIDTYPE_SID);
2049 __this_cpu_inc(process_counts);
2051 current->signal->nr_threads++;
2052 atomic_inc(¤t->signal->live);
2053 atomic_inc(¤t->signal->sigcnt);
2054 task_join_group_stop(p);
2055 list_add_tail_rcu(&p->thread_group,
2056 &p->group_leader->thread_group);
2057 list_add_tail_rcu(&p->thread_node,
2058 &p->signal->thread_head);
2060 attach_pid(p, PIDTYPE_PID);
2064 hlist_del_init(&delayed.node);
2065 spin_unlock(¤t->sighand->siglock);
2066 syscall_tracepoint_update(p);
2067 write_unlock_irq(&tasklist_lock);
2069 proc_fork_connector(p);
2070 cgroup_post_fork(p);
2071 cgroup_threadgroup_change_end(current);
2074 trace_task_newtask(p, clone_flags);
2075 uprobe_copy_process(p, clone_flags);
2079 bad_fork_cancel_cgroup:
2080 spin_unlock(¤t->sighand->siglock);
2081 write_unlock_irq(&tasklist_lock);
2082 cgroup_cancel_fork(p);
2084 cgroup_threadgroup_change_end(current);
2085 if (pid != &init_struct_pid)
2087 bad_fork_cleanup_thread:
2089 bad_fork_cleanup_io:
2092 bad_fork_cleanup_namespaces:
2093 exit_task_namespaces(p);
2094 bad_fork_cleanup_mm:
2096 mm_clear_owner(p->mm, p);
2099 bad_fork_cleanup_signal:
2100 if (!(clone_flags & CLONE_THREAD))
2101 free_signal_struct(p->signal);
2102 bad_fork_cleanup_sighand:
2103 __cleanup_sighand(p->sighand);
2104 bad_fork_cleanup_fs:
2105 exit_fs(p); /* blocking */
2106 bad_fork_cleanup_files:
2107 exit_files(p); /* blocking */
2108 bad_fork_cleanup_semundo:
2110 bad_fork_cleanup_security:
2111 security_task_free(p);
2112 bad_fork_cleanup_audit:
2114 bad_fork_cleanup_perf:
2115 perf_event_free_task(p);
2116 bad_fork_cleanup_policy:
2117 lockdep_free_task(p);
2119 mpol_put(p->mempolicy);
2120 bad_fork_cleanup_threadgroup_lock:
2122 delayacct_tsk_free(p);
2123 bad_fork_cleanup_count:
2124 atomic_dec(&p->cred->user->processes);
2127 p->state = TASK_DEAD;
2129 delayed_free_task(p);
2131 spin_lock_irq(¤t->sighand->siglock);
2132 hlist_del_init(&delayed.node);
2133 spin_unlock_irq(¤t->sighand->siglock);
2134 return ERR_PTR(retval);
2137 static inline void init_idle_pids(struct task_struct *idle)
2141 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
2142 INIT_HLIST_NODE(&idle->pid_links[type]); /* not really needed */
2143 init_task_pid(idle, type, &init_struct_pid);
2147 struct task_struct *fork_idle(int cpu)
2149 struct task_struct *task;
2150 task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0, 0,
2152 if (!IS_ERR(task)) {
2153 init_idle_pids(task);
2154 init_idle(task, cpu);
2161 * Ok, this is the main fork-routine.
2163 * It copies the process, and if successful kick-starts
2164 * it and waits for it to finish using the VM if required.
2166 long _do_fork(unsigned long clone_flags,
2167 unsigned long stack_start,
2168 unsigned long stack_size,
2169 int __user *parent_tidptr,
2170 int __user *child_tidptr,
2173 struct completion vfork;
2175 struct task_struct *p;
2180 * Determine whether and which event to report to ptracer. When
2181 * called from kernel_thread or CLONE_UNTRACED is explicitly
2182 * requested, no event is reported; otherwise, report if the event
2183 * for the type of forking is enabled.
2185 if (!(clone_flags & CLONE_UNTRACED)) {
2186 if (clone_flags & CLONE_VFORK)
2187 trace = PTRACE_EVENT_VFORK;
2188 else if ((clone_flags & CSIGNAL) != SIGCHLD)
2189 trace = PTRACE_EVENT_CLONE;
2191 trace = PTRACE_EVENT_FORK;
2193 if (likely(!ptrace_event_enabled(current, trace)))
2197 p = copy_process(clone_flags, stack_start, stack_size,
2198 child_tidptr, NULL, trace, tls, NUMA_NO_NODE);
2199 add_latent_entropy();
2205 * Do this prior waking up the new thread - the thread pointer
2206 * might get invalid after that point, if the thread exits quickly.
2208 trace_sched_process_fork(current, p);
2210 pid = get_task_pid(p, PIDTYPE_PID);
2213 if (clone_flags & CLONE_PARENT_SETTID)
2214 put_user(nr, parent_tidptr);
2216 if (clone_flags & CLONE_VFORK) {
2217 p->vfork_done = &vfork;
2218 init_completion(&vfork);
2222 wake_up_new_task(p);
2224 /* forking complete and child started to run, tell ptracer */
2225 if (unlikely(trace))
2226 ptrace_event_pid(trace, pid);
2228 if (clone_flags & CLONE_VFORK) {
2229 if (!wait_for_vfork_done(p, &vfork))
2230 ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid);
2237 #ifndef CONFIG_HAVE_COPY_THREAD_TLS
2238 /* For compatibility with architectures that call do_fork directly rather than
2239 * using the syscall entry points below. */
2240 long do_fork(unsigned long clone_flags,
2241 unsigned long stack_start,
2242 unsigned long stack_size,
2243 int __user *parent_tidptr,
2244 int __user *child_tidptr)
2246 return _do_fork(clone_flags, stack_start, stack_size,
2247 parent_tidptr, child_tidptr, 0);
2252 * Create a kernel thread.
2254 pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
2256 return _do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn,
2257 (unsigned long)arg, NULL, NULL, 0);
2260 #ifdef __ARCH_WANT_SYS_FORK
2261 SYSCALL_DEFINE0(fork)
2264 return _do_fork(SIGCHLD, 0, 0, NULL, NULL, 0);
2266 /* can not support in nommu mode */
2272 #ifdef __ARCH_WANT_SYS_VFORK
2273 SYSCALL_DEFINE0(vfork)
2275 return _do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0,
2280 #ifdef __ARCH_WANT_SYS_CLONE
2281 #ifdef CONFIG_CLONE_BACKWARDS
2282 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2283 int __user *, parent_tidptr,
2285 int __user *, child_tidptr)
2286 #elif defined(CONFIG_CLONE_BACKWARDS2)
2287 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags,
2288 int __user *, parent_tidptr,
2289 int __user *, child_tidptr,
2291 #elif defined(CONFIG_CLONE_BACKWARDS3)
2292 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp,
2294 int __user *, parent_tidptr,
2295 int __user *, child_tidptr,
2298 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2299 int __user *, parent_tidptr,
2300 int __user *, child_tidptr,
2304 return _do_fork(clone_flags, newsp, 0, parent_tidptr, child_tidptr, tls);
2308 void walk_process_tree(struct task_struct *top, proc_visitor visitor, void *data)
2310 struct task_struct *leader, *parent, *child;
2313 read_lock(&tasklist_lock);
2314 leader = top = top->group_leader;
2316 for_each_thread(leader, parent) {
2317 list_for_each_entry(child, &parent->children, sibling) {
2318 res = visitor(child, data);
2330 if (leader != top) {
2332 parent = child->real_parent;
2333 leader = parent->group_leader;
2337 read_unlock(&tasklist_lock);
2340 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
2341 #define ARCH_MIN_MMSTRUCT_ALIGN 0
2344 static void sighand_ctor(void *data)
2346 struct sighand_struct *sighand = data;
2348 spin_lock_init(&sighand->siglock);
2349 init_waitqueue_head(&sighand->signalfd_wqh);
2352 void __init proc_caches_init(void)
2354 unsigned int mm_size;
2356 sighand_cachep = kmem_cache_create("sighand_cache",
2357 sizeof(struct sighand_struct), 0,
2358 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_TYPESAFE_BY_RCU|
2359 SLAB_ACCOUNT, sighand_ctor);
2360 signal_cachep = kmem_cache_create("signal_cache",
2361 sizeof(struct signal_struct), 0,
2362 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2364 files_cachep = kmem_cache_create("files_cache",
2365 sizeof(struct files_struct), 0,
2366 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2368 fs_cachep = kmem_cache_create("fs_cache",
2369 sizeof(struct fs_struct), 0,
2370 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2374 * The mm_cpumask is located at the end of mm_struct, and is
2375 * dynamically sized based on the maximum CPU number this system
2376 * can have, taking hotplug into account (nr_cpu_ids).
2378 mm_size = sizeof(struct mm_struct) + cpumask_size();
2380 mm_cachep = kmem_cache_create_usercopy("mm_struct",
2381 mm_size, ARCH_MIN_MMSTRUCT_ALIGN,
2382 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2383 offsetof(struct mm_struct, saved_auxv),
2384 sizeof_field(struct mm_struct, saved_auxv),
2386 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT);
2388 nsproxy_cache_init();
2392 * Check constraints on flags passed to the unshare system call.
2394 static int check_unshare_flags(unsigned long unshare_flags)
2396 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
2397 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
2398 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET|
2399 CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP))
2402 * Not implemented, but pretend it works if there is nothing
2403 * to unshare. Note that unsharing the address space or the
2404 * signal handlers also need to unshare the signal queues (aka
2407 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
2408 if (!thread_group_empty(current))
2411 if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) {
2412 if (atomic_read(¤t->sighand->count) > 1)
2415 if (unshare_flags & CLONE_VM) {
2416 if (!current_is_single_threaded())
2424 * Unshare the filesystem structure if it is being shared
2426 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
2428 struct fs_struct *fs = current->fs;
2430 if (!(unshare_flags & CLONE_FS) || !fs)
2433 /* don't need lock here; in the worst case we'll do useless copy */
2437 *new_fsp = copy_fs_struct(fs);
2445 * Unshare file descriptor table if it is being shared
2447 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
2449 struct files_struct *fd = current->files;
2452 if ((unshare_flags & CLONE_FILES) &&
2453 (fd && atomic_read(&fd->count) > 1)) {
2454 *new_fdp = dup_fd(fd, &error);
2463 * unshare allows a process to 'unshare' part of the process
2464 * context which was originally shared using clone. copy_*
2465 * functions used by do_fork() cannot be used here directly
2466 * because they modify an inactive task_struct that is being
2467 * constructed. Here we are modifying the current, active,
2470 int ksys_unshare(unsigned long unshare_flags)
2472 struct fs_struct *fs, *new_fs = NULL;
2473 struct files_struct *fd, *new_fd = NULL;
2474 struct cred *new_cred = NULL;
2475 struct nsproxy *new_nsproxy = NULL;
2480 * If unsharing a user namespace must also unshare the thread group
2481 * and unshare the filesystem root and working directories.
2483 if (unshare_flags & CLONE_NEWUSER)
2484 unshare_flags |= CLONE_THREAD | CLONE_FS;
2486 * If unsharing vm, must also unshare signal handlers.
2488 if (unshare_flags & CLONE_VM)
2489 unshare_flags |= CLONE_SIGHAND;
2491 * If unsharing a signal handlers, must also unshare the signal queues.
2493 if (unshare_flags & CLONE_SIGHAND)
2494 unshare_flags |= CLONE_THREAD;
2496 * If unsharing namespace, must also unshare filesystem information.
2498 if (unshare_flags & CLONE_NEWNS)
2499 unshare_flags |= CLONE_FS;
2501 err = check_unshare_flags(unshare_flags);
2503 goto bad_unshare_out;
2505 * CLONE_NEWIPC must also detach from the undolist: after switching
2506 * to a new ipc namespace, the semaphore arrays from the old
2507 * namespace are unreachable.
2509 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
2511 err = unshare_fs(unshare_flags, &new_fs);
2513 goto bad_unshare_out;
2514 err = unshare_fd(unshare_flags, &new_fd);
2516 goto bad_unshare_cleanup_fs;
2517 err = unshare_userns(unshare_flags, &new_cred);
2519 goto bad_unshare_cleanup_fd;
2520 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
2523 goto bad_unshare_cleanup_cred;
2525 if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
2528 * CLONE_SYSVSEM is equivalent to sys_exit().
2532 if (unshare_flags & CLONE_NEWIPC) {
2533 /* Orphan segments in old ns (see sem above). */
2535 shm_init_task(current);
2539 switch_task_namespaces(current, new_nsproxy);
2545 spin_lock(&fs->lock);
2546 current->fs = new_fs;
2551 spin_unlock(&fs->lock);
2555 fd = current->files;
2556 current->files = new_fd;
2560 task_unlock(current);
2563 /* Install the new user namespace */
2564 commit_creds(new_cred);
2569 perf_event_namespaces(current);
2571 bad_unshare_cleanup_cred:
2574 bad_unshare_cleanup_fd:
2576 put_files_struct(new_fd);
2578 bad_unshare_cleanup_fs:
2580 free_fs_struct(new_fs);
2586 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
2588 return ksys_unshare(unshare_flags);
2592 * Helper to unshare the files of the current task.
2593 * We don't want to expose copy_files internals to
2594 * the exec layer of the kernel.
2597 int unshare_files(struct files_struct **displaced)
2599 struct task_struct *task = current;
2600 struct files_struct *copy = NULL;
2603 error = unshare_fd(CLONE_FILES, ©);
2604 if (error || !copy) {
2608 *displaced = task->files;
2615 int sysctl_max_threads(struct ctl_table *table, int write,
2616 void __user *buffer, size_t *lenp, loff_t *ppos)
2620 int threads = max_threads;
2622 int max = MAX_THREADS;
2629 ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
2633 max_threads = threads;