1 // SPDX-License-Identifier: GPL-2.0-only
5 * Copyright (C) 1991, 1992 Linus Torvalds
9 * 'fork.c' contains the help-routines for the 'fork' system call
10 * (see also entry.S and others).
11 * Fork is rather simple, once you get the hang of it, but the memory
12 * management can be a bitch. See 'mm/memory.c': 'copy_page_range()'
15 #include <linux/anon_inodes.h>
16 #include <linux/slab.h>
17 #include <linux/sched/autogroup.h>
18 #include <linux/sched/mm.h>
19 #include <linux/sched/coredump.h>
20 #include <linux/sched/user.h>
21 #include <linux/sched/numa_balancing.h>
22 #include <linux/sched/stat.h>
23 #include <linux/sched/task.h>
24 #include <linux/sched/task_stack.h>
25 #include <linux/sched/cputime.h>
26 #include <linux/seq_file.h>
27 #include <linux/rtmutex.h>
28 #include <linux/init.h>
29 #include <linux/unistd.h>
30 #include <linux/module.h>
31 #include <linux/vmalloc.h>
32 #include <linux/completion.h>
33 #include <linux/personality.h>
34 #include <linux/mempolicy.h>
35 #include <linux/sem.h>
36 #include <linux/file.h>
37 #include <linux/fdtable.h>
38 #include <linux/iocontext.h>
39 #include <linux/key.h>
40 #include <linux/binfmts.h>
41 #include <linux/mman.h>
42 #include <linux/mmu_notifier.h>
45 #include <linux/vmacache.h>
46 #include <linux/nsproxy.h>
47 #include <linux/capability.h>
48 #include <linux/cpu.h>
49 #include <linux/cgroup.h>
50 #include <linux/security.h>
51 #include <linux/hugetlb.h>
52 #include <linux/seccomp.h>
53 #include <linux/swap.h>
54 #include <linux/syscalls.h>
55 #include <linux/jiffies.h>
56 #include <linux/futex.h>
57 #include <linux/compat.h>
58 #include <linux/kthread.h>
59 #include <linux/task_io_accounting_ops.h>
60 #include <linux/rcupdate.h>
61 #include <linux/ptrace.h>
62 #include <linux/mount.h>
63 #include <linux/audit.h>
64 #include <linux/memcontrol.h>
65 #include <linux/ftrace.h>
66 #include <linux/proc_fs.h>
67 #include <linux/profile.h>
68 #include <linux/rmap.h>
69 #include <linux/ksm.h>
70 #include <linux/acct.h>
71 #include <linux/userfaultfd_k.h>
72 #include <linux/tsacct_kern.h>
73 #include <linux/cn_proc.h>
74 #include <linux/freezer.h>
75 #include <linux/delayacct.h>
76 #include <linux/taskstats_kern.h>
77 #include <linux/random.h>
78 #include <linux/tty.h>
79 #include <linux/blkdev.h>
80 #include <linux/fs_struct.h>
81 #include <linux/magic.h>
82 #include <linux/perf_event.h>
83 #include <linux/posix-timers.h>
84 #include <linux/user-return-notifier.h>
85 #include <linux/oom.h>
86 #include <linux/khugepaged.h>
87 #include <linux/signalfd.h>
88 #include <linux/uprobes.h>
89 #include <linux/aio.h>
90 #include <linux/compiler.h>
91 #include <linux/sysctl.h>
92 #include <linux/kcov.h>
93 #include <linux/livepatch.h>
94 #include <linux/thread_info.h>
95 #include <linux/stackleak.h>
96 #include <linux/kasan.h>
97 #include <linux/scs.h>
99 #include <asm/pgalloc.h>
100 #include <linux/uaccess.h>
101 #include <asm/mmu_context.h>
102 #include <asm/cacheflush.h>
103 #include <asm/tlbflush.h>
105 #include <trace/events/sched.h>
107 #define CREATE_TRACE_POINTS
108 #include <trace/events/task.h>
111 * Minimum number of threads to boot the kernel
113 #define MIN_THREADS 20
116 * Maximum number of threads
118 #define MAX_THREADS FUTEX_TID_MASK
121 * Protected counters by write_lock_irq(&tasklist_lock)
123 unsigned long total_forks; /* Handle normal Linux uptimes. */
124 int nr_threads; /* The idle threads do not count.. */
126 static int max_threads; /* tunable limit on nr_threads */
128 #define NAMED_ARRAY_INDEX(x) [x] = __stringify(x)
130 static const char * const resident_page_types[] = {
131 NAMED_ARRAY_INDEX(MM_FILEPAGES),
132 NAMED_ARRAY_INDEX(MM_ANONPAGES),
133 NAMED_ARRAY_INDEX(MM_SWAPENTS),
134 NAMED_ARRAY_INDEX(MM_SHMEMPAGES),
137 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
139 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */
141 #ifdef CONFIG_PROVE_RCU
142 int lockdep_tasklist_lock_is_held(void)
144 return lockdep_is_held(&tasklist_lock);
146 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
147 #endif /* #ifdef CONFIG_PROVE_RCU */
149 int nr_processes(void)
154 for_each_possible_cpu(cpu)
155 total += per_cpu(process_counts, cpu);
160 void __weak arch_release_task_struct(struct task_struct *tsk)
164 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
165 static struct kmem_cache *task_struct_cachep;
167 static inline struct task_struct *alloc_task_struct_node(int node)
169 return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node);
172 static inline void free_task_struct(struct task_struct *tsk)
174 kmem_cache_free(task_struct_cachep, tsk);
178 #ifndef CONFIG_ARCH_THREAD_STACK_ALLOCATOR
181 * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
182 * kmemcache based allocator.
184 # if THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK)
186 #ifdef CONFIG_VMAP_STACK
188 * vmalloc() is a bit slow, and calling vfree() enough times will force a TLB
189 * flush. Try to minimize the number of calls by caching stacks.
191 #define NR_CACHED_STACKS 2
192 static DEFINE_PER_CPU(struct vm_struct *, cached_stacks[NR_CACHED_STACKS]);
194 static int free_vm_stack_cache(unsigned int cpu)
196 struct vm_struct **cached_vm_stacks = per_cpu_ptr(cached_stacks, cpu);
199 for (i = 0; i < NR_CACHED_STACKS; i++) {
200 struct vm_struct *vm_stack = cached_vm_stacks[i];
205 vfree(vm_stack->addr);
206 cached_vm_stacks[i] = NULL;
213 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node)
215 #ifdef CONFIG_VMAP_STACK
219 for (i = 0; i < NR_CACHED_STACKS; i++) {
222 s = this_cpu_xchg(cached_stacks[i], NULL);
227 /* Clear the KASAN shadow of the stack. */
228 kasan_unpoison_shadow(s->addr, THREAD_SIZE);
230 /* Clear stale pointers from reused stack. */
231 memset(s->addr, 0, THREAD_SIZE);
233 tsk->stack_vm_area = s;
234 tsk->stack = s->addr;
239 * Allocated stacks are cached and later reused by new threads,
240 * so memcg accounting is performed manually on assigning/releasing
241 * stacks to tasks. Drop __GFP_ACCOUNT.
243 stack = __vmalloc_node_range(THREAD_SIZE, THREAD_ALIGN,
244 VMALLOC_START, VMALLOC_END,
245 THREADINFO_GFP & ~__GFP_ACCOUNT,
247 0, node, __builtin_return_address(0));
250 * We can't call find_vm_area() in interrupt context, and
251 * free_thread_stack() can be called in interrupt context,
252 * so cache the vm_struct.
255 tsk->stack_vm_area = find_vm_area(stack);
260 struct page *page = alloc_pages_node(node, THREADINFO_GFP,
264 tsk->stack = kasan_reset_tag(page_address(page));
271 static inline void free_thread_stack(struct task_struct *tsk)
273 #ifdef CONFIG_VMAP_STACK
274 struct vm_struct *vm = task_stack_vm_area(tsk);
279 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++)
280 memcg_kmem_uncharge_page(vm->pages[i], 0);
282 for (i = 0; i < NR_CACHED_STACKS; i++) {
283 if (this_cpu_cmpxchg(cached_stacks[i],
284 NULL, tsk->stack_vm_area) != NULL)
290 vfree_atomic(tsk->stack);
295 __free_pages(virt_to_page(tsk->stack), THREAD_SIZE_ORDER);
298 static struct kmem_cache *thread_stack_cache;
300 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk,
303 unsigned long *stack;
304 stack = kmem_cache_alloc_node(thread_stack_cache, THREADINFO_GFP, node);
305 stack = kasan_reset_tag(stack);
310 static void free_thread_stack(struct task_struct *tsk)
312 kmem_cache_free(thread_stack_cache, tsk->stack);
315 void thread_stack_cache_init(void)
317 thread_stack_cache = kmem_cache_create_usercopy("thread_stack",
318 THREAD_SIZE, THREAD_SIZE, 0, 0,
320 BUG_ON(thread_stack_cache == NULL);
325 /* SLAB cache for signal_struct structures (tsk->signal) */
326 static struct kmem_cache *signal_cachep;
328 /* SLAB cache for sighand_struct structures (tsk->sighand) */
329 struct kmem_cache *sighand_cachep;
331 /* SLAB cache for files_struct structures (tsk->files) */
332 struct kmem_cache *files_cachep;
334 /* SLAB cache for fs_struct structures (tsk->fs) */
335 struct kmem_cache *fs_cachep;
337 /* SLAB cache for vm_area_struct structures */
338 static struct kmem_cache *vm_area_cachep;
340 /* SLAB cache for mm_struct structures (tsk->mm) */
341 static struct kmem_cache *mm_cachep;
343 struct vm_area_struct *vm_area_alloc(struct mm_struct *mm)
345 struct vm_area_struct *vma;
347 vma = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
353 struct vm_area_struct *vm_area_dup(struct vm_area_struct *orig)
355 struct vm_area_struct *new = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
358 ASSERT_EXCLUSIVE_WRITER(orig->vm_flags);
359 ASSERT_EXCLUSIVE_WRITER(orig->vm_file);
361 * orig->shared.rb may be modified concurrently, but the clone
362 * will be reinitialized.
364 *new = data_race(*orig);
365 INIT_LIST_HEAD(&new->anon_vma_chain);
366 new->vm_next = new->vm_prev = NULL;
371 void vm_area_free(struct vm_area_struct *vma)
373 kmem_cache_free(vm_area_cachep, vma);
376 static void account_kernel_stack(struct task_struct *tsk, int account)
378 void *stack = task_stack_page(tsk);
379 struct vm_struct *vm = task_stack_vm_area(tsk);
382 /* All stack pages are in the same node. */
384 mod_lruvec_page_state(vm->pages[0], NR_KERNEL_STACK_KB,
385 account * (THREAD_SIZE / 1024));
387 mod_lruvec_slab_state(stack, NR_KERNEL_STACK_KB,
388 account * (THREAD_SIZE / 1024));
391 static int memcg_charge_kernel_stack(struct task_struct *tsk)
393 #ifdef CONFIG_VMAP_STACK
394 struct vm_struct *vm = task_stack_vm_area(tsk);
397 BUILD_BUG_ON(IS_ENABLED(CONFIG_VMAP_STACK) && PAGE_SIZE % 1024 != 0);
402 BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE);
404 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
406 * If memcg_kmem_charge_page() fails, page->mem_cgroup
407 * pointer is NULL, and memcg_kmem_uncharge_page() in
408 * free_thread_stack() will ignore this page.
410 ret = memcg_kmem_charge_page(vm->pages[i], GFP_KERNEL,
420 static void release_task_stack(struct task_struct *tsk)
422 if (WARN_ON(tsk->state != TASK_DEAD))
423 return; /* Better to leak the stack than to free prematurely */
425 account_kernel_stack(tsk, -1);
426 free_thread_stack(tsk);
428 #ifdef CONFIG_VMAP_STACK
429 tsk->stack_vm_area = NULL;
433 #ifdef CONFIG_THREAD_INFO_IN_TASK
434 void put_task_stack(struct task_struct *tsk)
436 if (refcount_dec_and_test(&tsk->stack_refcount))
437 release_task_stack(tsk);
441 void free_task(struct task_struct *tsk)
445 #ifndef CONFIG_THREAD_INFO_IN_TASK
447 * The task is finally done with both the stack and thread_info,
450 release_task_stack(tsk);
453 * If the task had a separate stack allocation, it should be gone
456 WARN_ON_ONCE(refcount_read(&tsk->stack_refcount) != 0);
458 rt_mutex_debug_task_free(tsk);
459 ftrace_graph_exit_task(tsk);
460 arch_release_task_struct(tsk);
461 if (tsk->flags & PF_KTHREAD)
462 free_kthread_struct(tsk);
463 free_task_struct(tsk);
465 EXPORT_SYMBOL(free_task);
468 static __latent_entropy int dup_mmap(struct mm_struct *mm,
469 struct mm_struct *oldmm)
471 struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
472 struct rb_node **rb_link, *rb_parent;
474 unsigned long charge;
477 uprobe_start_dup_mmap();
478 if (mmap_write_lock_killable(oldmm)) {
480 goto fail_uprobe_end;
482 flush_cache_dup_mm(oldmm);
483 uprobe_dup_mmap(oldmm, mm);
485 * Not linked in yet - no deadlock potential:
487 mmap_write_lock_nested(mm, SINGLE_DEPTH_NESTING);
489 /* No ordering required: file already has been exposed. */
490 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
492 mm->total_vm = oldmm->total_vm;
493 mm->data_vm = oldmm->data_vm;
494 mm->exec_vm = oldmm->exec_vm;
495 mm->stack_vm = oldmm->stack_vm;
497 rb_link = &mm->mm_rb.rb_node;
500 retval = ksm_fork(mm, oldmm);
503 retval = khugepaged_fork(mm, oldmm);
508 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
511 if (mpnt->vm_flags & VM_DONTCOPY) {
512 vm_stat_account(mm, mpnt->vm_flags, -vma_pages(mpnt));
517 * Don't duplicate many vmas if we've been oom-killed (for
520 if (fatal_signal_pending(current)) {
524 if (mpnt->vm_flags & VM_ACCOUNT) {
525 unsigned long len = vma_pages(mpnt);
527 if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
531 tmp = vm_area_dup(mpnt);
534 retval = vma_dup_policy(mpnt, tmp);
536 goto fail_nomem_policy;
538 retval = dup_userfaultfd(tmp, &uf);
540 goto fail_nomem_anon_vma_fork;
541 if (tmp->vm_flags & VM_WIPEONFORK) {
543 * VM_WIPEONFORK gets a clean slate in the child.
544 * Don't prepare anon_vma until fault since we don't
545 * copy page for current vma.
547 tmp->anon_vma = NULL;
548 } else if (anon_vma_fork(tmp, mpnt))
549 goto fail_nomem_anon_vma_fork;
550 tmp->vm_flags &= ~(VM_LOCKED | VM_LOCKONFAULT);
553 struct inode *inode = file_inode(file);
554 struct address_space *mapping = file->f_mapping;
557 if (tmp->vm_flags & VM_DENYWRITE)
558 atomic_dec(&inode->i_writecount);
559 i_mmap_lock_write(mapping);
560 if (tmp->vm_flags & VM_SHARED)
561 atomic_inc(&mapping->i_mmap_writable);
562 flush_dcache_mmap_lock(mapping);
563 /* insert tmp into the share list, just after mpnt */
564 vma_interval_tree_insert_after(tmp, mpnt,
566 flush_dcache_mmap_unlock(mapping);
567 i_mmap_unlock_write(mapping);
571 * Clear hugetlb-related page reserves for children. This only
572 * affects MAP_PRIVATE mappings. Faults generated by the child
573 * are not guaranteed to succeed, even if read-only
575 if (is_vm_hugetlb_page(tmp))
576 reset_vma_resv_huge_pages(tmp);
579 * Link in the new vma and copy the page table entries.
582 pprev = &tmp->vm_next;
586 __vma_link_rb(mm, tmp, rb_link, rb_parent);
587 rb_link = &tmp->vm_rb.rb_right;
588 rb_parent = &tmp->vm_rb;
591 if (!(tmp->vm_flags & VM_WIPEONFORK))
592 retval = copy_page_range(mm, oldmm, mpnt, tmp);
594 if (tmp->vm_ops && tmp->vm_ops->open)
595 tmp->vm_ops->open(tmp);
600 /* a new mm has just been created */
601 retval = arch_dup_mmap(oldmm, mm);
603 mmap_write_unlock(mm);
605 mmap_write_unlock(oldmm);
606 dup_userfaultfd_complete(&uf);
608 uprobe_end_dup_mmap();
610 fail_nomem_anon_vma_fork:
611 mpol_put(vma_policy(tmp));
616 vm_unacct_memory(charge);
620 static inline int mm_alloc_pgd(struct mm_struct *mm)
622 mm->pgd = pgd_alloc(mm);
623 if (unlikely(!mm->pgd))
628 static inline void mm_free_pgd(struct mm_struct *mm)
630 pgd_free(mm, mm->pgd);
633 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
635 mmap_write_lock(oldmm);
636 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
637 mmap_write_unlock(oldmm);
640 #define mm_alloc_pgd(mm) (0)
641 #define mm_free_pgd(mm)
642 #endif /* CONFIG_MMU */
644 static void check_mm(struct mm_struct *mm)
648 BUILD_BUG_ON_MSG(ARRAY_SIZE(resident_page_types) != NR_MM_COUNTERS,
649 "Please make sure 'struct resident_page_types[]' is updated as well");
651 for (i = 0; i < NR_MM_COUNTERS; i++) {
652 long x = atomic_long_read(&mm->rss_stat.count[i]);
655 pr_alert("BUG: Bad rss-counter state mm:%p type:%s val:%ld\n",
656 mm, resident_page_types[i], x);
659 if (mm_pgtables_bytes(mm))
660 pr_alert("BUG: non-zero pgtables_bytes on freeing mm: %ld\n",
661 mm_pgtables_bytes(mm));
663 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
664 VM_BUG_ON_MM(mm->pmd_huge_pte, mm);
668 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
669 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm)))
672 * Called when the last reference to the mm
673 * is dropped: either by a lazy thread or by
674 * mmput. Free the page directory and the mm.
676 void __mmdrop(struct mm_struct *mm)
678 BUG_ON(mm == &init_mm);
679 WARN_ON_ONCE(mm == current->mm);
680 WARN_ON_ONCE(mm == current->active_mm);
683 mmu_notifier_subscriptions_destroy(mm);
685 put_user_ns(mm->user_ns);
688 EXPORT_SYMBOL_GPL(__mmdrop);
690 static void mmdrop_async_fn(struct work_struct *work)
692 struct mm_struct *mm;
694 mm = container_of(work, struct mm_struct, async_put_work);
698 static void mmdrop_async(struct mm_struct *mm)
700 if (unlikely(atomic_dec_and_test(&mm->mm_count))) {
701 INIT_WORK(&mm->async_put_work, mmdrop_async_fn);
702 schedule_work(&mm->async_put_work);
706 static inline void free_signal_struct(struct signal_struct *sig)
708 taskstats_tgid_free(sig);
709 sched_autogroup_exit(sig);
711 * __mmdrop is not safe to call from softirq context on x86 due to
712 * pgd_dtor so postpone it to the async context
715 mmdrop_async(sig->oom_mm);
716 kmem_cache_free(signal_cachep, sig);
719 static inline void put_signal_struct(struct signal_struct *sig)
721 if (refcount_dec_and_test(&sig->sigcnt))
722 free_signal_struct(sig);
725 void __put_task_struct(struct task_struct *tsk)
727 WARN_ON(!tsk->exit_state);
728 WARN_ON(refcount_read(&tsk->usage));
729 WARN_ON(tsk == current);
732 task_numa_free(tsk, true);
733 security_task_free(tsk);
735 delayacct_tsk_free(tsk);
736 put_signal_struct(tsk->signal);
738 if (!profile_handoff_task(tsk))
741 EXPORT_SYMBOL_GPL(__put_task_struct);
743 void __init __weak arch_task_cache_init(void) { }
748 static void set_max_threads(unsigned int max_threads_suggested)
751 unsigned long nr_pages = totalram_pages();
754 * The number of threads shall be limited such that the thread
755 * structures may only consume a small part of the available memory.
757 if (fls64(nr_pages) + fls64(PAGE_SIZE) > 64)
758 threads = MAX_THREADS;
760 threads = div64_u64((u64) nr_pages * (u64) PAGE_SIZE,
761 (u64) THREAD_SIZE * 8UL);
763 if (threads > max_threads_suggested)
764 threads = max_threads_suggested;
766 max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS);
769 #ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT
770 /* Initialized by the architecture: */
771 int arch_task_struct_size __read_mostly;
774 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
775 static void task_struct_whitelist(unsigned long *offset, unsigned long *size)
777 /* Fetch thread_struct whitelist for the architecture. */
778 arch_thread_struct_whitelist(offset, size);
781 * Handle zero-sized whitelist or empty thread_struct, otherwise
782 * adjust offset to position of thread_struct in task_struct.
784 if (unlikely(*size == 0))
787 *offset += offsetof(struct task_struct, thread);
789 #endif /* CONFIG_ARCH_TASK_STRUCT_ALLOCATOR */
791 void __init fork_init(void)
794 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
795 #ifndef ARCH_MIN_TASKALIGN
796 #define ARCH_MIN_TASKALIGN 0
798 int align = max_t(int, L1_CACHE_BYTES, ARCH_MIN_TASKALIGN);
799 unsigned long useroffset, usersize;
801 /* create a slab on which task_structs can be allocated */
802 task_struct_whitelist(&useroffset, &usersize);
803 task_struct_cachep = kmem_cache_create_usercopy("task_struct",
804 arch_task_struct_size, align,
805 SLAB_PANIC|SLAB_ACCOUNT,
806 useroffset, usersize, NULL);
809 /* do the arch specific task caches init */
810 arch_task_cache_init();
812 set_max_threads(MAX_THREADS);
814 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
815 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
816 init_task.signal->rlim[RLIMIT_SIGPENDING] =
817 init_task.signal->rlim[RLIMIT_NPROC];
819 for (i = 0; i < UCOUNT_COUNTS; i++) {
820 init_user_ns.ucount_max[i] = max_threads/2;
823 #ifdef CONFIG_VMAP_STACK
824 cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "fork:vm_stack_cache",
825 NULL, free_vm_stack_cache);
830 lockdep_init_task(&init_task);
834 int __weak arch_dup_task_struct(struct task_struct *dst,
835 struct task_struct *src)
841 void set_task_stack_end_magic(struct task_struct *tsk)
843 unsigned long *stackend;
845 stackend = end_of_stack(tsk);
846 *stackend = STACK_END_MAGIC; /* for overflow detection */
849 static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
851 struct task_struct *tsk;
852 unsigned long *stack;
853 struct vm_struct *stack_vm_area __maybe_unused;
856 if (node == NUMA_NO_NODE)
857 node = tsk_fork_get_node(orig);
858 tsk = alloc_task_struct_node(node);
862 stack = alloc_thread_stack_node(tsk, node);
866 if (memcg_charge_kernel_stack(tsk))
869 stack_vm_area = task_stack_vm_area(tsk);
871 err = arch_dup_task_struct(tsk, orig);
874 * arch_dup_task_struct() clobbers the stack-related fields. Make
875 * sure they're properly initialized before using any stack-related
879 #ifdef CONFIG_VMAP_STACK
880 tsk->stack_vm_area = stack_vm_area;
882 #ifdef CONFIG_THREAD_INFO_IN_TASK
883 refcount_set(&tsk->stack_refcount, 1);
889 err = scs_prepare(tsk, node);
893 #ifdef CONFIG_SECCOMP
895 * We must handle setting up seccomp filters once we're under
896 * the sighand lock in case orig has changed between now and
897 * then. Until then, filter must be NULL to avoid messing up
898 * the usage counts on the error path calling free_task.
900 tsk->seccomp.filter = NULL;
903 setup_thread_stack(tsk, orig);
904 clear_user_return_notifier(tsk);
905 clear_tsk_need_resched(tsk);
906 set_task_stack_end_magic(tsk);
908 #ifdef CONFIG_STACKPROTECTOR
909 tsk->stack_canary = get_random_canary();
911 if (orig->cpus_ptr == &orig->cpus_mask)
912 tsk->cpus_ptr = &tsk->cpus_mask;
915 * One for the user space visible state that goes away when reaped.
916 * One for the scheduler.
918 refcount_set(&tsk->rcu_users, 2);
919 /* One for the rcu users */
920 refcount_set(&tsk->usage, 1);
921 #ifdef CONFIG_BLK_DEV_IO_TRACE
924 tsk->splice_pipe = NULL;
925 tsk->task_frag.page = NULL;
926 tsk->wake_q.next = NULL;
928 account_kernel_stack(tsk, 1);
932 #ifdef CONFIG_FAULT_INJECTION
936 #ifdef CONFIG_BLK_CGROUP
937 tsk->throttle_queue = NULL;
938 tsk->use_memdelay = 0;
942 tsk->active_memcg = NULL;
947 free_thread_stack(tsk);
949 free_task_struct(tsk);
953 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
955 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
957 static int __init coredump_filter_setup(char *s)
959 default_dump_filter =
960 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
961 MMF_DUMP_FILTER_MASK;
965 __setup("coredump_filter=", coredump_filter_setup);
967 #include <linux/init_task.h>
969 static void mm_init_aio(struct mm_struct *mm)
972 spin_lock_init(&mm->ioctx_lock);
973 mm->ioctx_table = NULL;
977 static __always_inline void mm_clear_owner(struct mm_struct *mm,
978 struct task_struct *p)
982 WRITE_ONCE(mm->owner, NULL);
986 static void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
993 static void mm_init_uprobes_state(struct mm_struct *mm)
995 #ifdef CONFIG_UPROBES
996 mm->uprobes_state.xol_area = NULL;
1000 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
1001 struct user_namespace *user_ns)
1004 mm->mm_rb = RB_ROOT;
1005 mm->vmacache_seqnum = 0;
1006 atomic_set(&mm->mm_users, 1);
1007 atomic_set(&mm->mm_count, 1);
1009 INIT_LIST_HEAD(&mm->mmlist);
1010 mm->core_state = NULL;
1011 mm_pgtables_bytes_init(mm);
1014 atomic_set(&mm->has_pinned, 0);
1015 atomic64_set(&mm->pinned_vm, 0);
1016 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
1017 spin_lock_init(&mm->page_table_lock);
1018 spin_lock_init(&mm->arg_lock);
1019 mm_init_cpumask(mm);
1021 mm_init_owner(mm, p);
1022 RCU_INIT_POINTER(mm->exe_file, NULL);
1023 mmu_notifier_subscriptions_init(mm);
1024 init_tlb_flush_pending(mm);
1025 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
1026 mm->pmd_huge_pte = NULL;
1028 mm_init_uprobes_state(mm);
1031 mm->flags = current->mm->flags & MMF_INIT_MASK;
1032 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK;
1034 mm->flags = default_dump_filter;
1038 if (mm_alloc_pgd(mm))
1041 if (init_new_context(p, mm))
1042 goto fail_nocontext;
1044 mm->user_ns = get_user_ns(user_ns);
1055 * Allocate and initialize an mm_struct.
1057 struct mm_struct *mm_alloc(void)
1059 struct mm_struct *mm;
1065 memset(mm, 0, sizeof(*mm));
1066 return mm_init(mm, current, current_user_ns());
1069 static inline void __mmput(struct mm_struct *mm)
1071 VM_BUG_ON(atomic_read(&mm->mm_users));
1073 uprobe_clear_state(mm);
1076 khugepaged_exit(mm); /* must run before exit_mmap */
1078 mm_put_huge_zero_page(mm);
1079 set_mm_exe_file(mm, NULL);
1080 if (!list_empty(&mm->mmlist)) {
1081 spin_lock(&mmlist_lock);
1082 list_del(&mm->mmlist);
1083 spin_unlock(&mmlist_lock);
1086 module_put(mm->binfmt->module);
1091 * Decrement the use count and release all resources for an mm.
1093 void mmput(struct mm_struct *mm)
1097 if (atomic_dec_and_test(&mm->mm_users))
1100 EXPORT_SYMBOL_GPL(mmput);
1103 static void mmput_async_fn(struct work_struct *work)
1105 struct mm_struct *mm = container_of(work, struct mm_struct,
1111 void mmput_async(struct mm_struct *mm)
1113 if (atomic_dec_and_test(&mm->mm_users)) {
1114 INIT_WORK(&mm->async_put_work, mmput_async_fn);
1115 schedule_work(&mm->async_put_work);
1121 * set_mm_exe_file - change a reference to the mm's executable file
1123 * This changes mm's executable file (shown as symlink /proc/[pid]/exe).
1125 * Main users are mmput() and sys_execve(). Callers prevent concurrent
1126 * invocations: in mmput() nobody alive left, in execve task is single
1127 * threaded. sys_prctl(PR_SET_MM_MAP/EXE_FILE) also needs to set the
1128 * mm->exe_file, but does so without using set_mm_exe_file() in order
1129 * to do avoid the need for any locks.
1131 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
1133 struct file *old_exe_file;
1136 * It is safe to dereference the exe_file without RCU as
1137 * this function is only called if nobody else can access
1138 * this mm -- see comment above for justification.
1140 old_exe_file = rcu_dereference_raw(mm->exe_file);
1143 get_file(new_exe_file);
1144 rcu_assign_pointer(mm->exe_file, new_exe_file);
1150 * get_mm_exe_file - acquire a reference to the mm's executable file
1152 * Returns %NULL if mm has no associated executable file.
1153 * User must release file via fput().
1155 struct file *get_mm_exe_file(struct mm_struct *mm)
1157 struct file *exe_file;
1160 exe_file = rcu_dereference(mm->exe_file);
1161 if (exe_file && !get_file_rcu(exe_file))
1166 EXPORT_SYMBOL(get_mm_exe_file);
1169 * get_task_exe_file - acquire a reference to the task's executable file
1171 * Returns %NULL if task's mm (if any) has no associated executable file or
1172 * this is a kernel thread with borrowed mm (see the comment above get_task_mm).
1173 * User must release file via fput().
1175 struct file *get_task_exe_file(struct task_struct *task)
1177 struct file *exe_file = NULL;
1178 struct mm_struct *mm;
1183 if (!(task->flags & PF_KTHREAD))
1184 exe_file = get_mm_exe_file(mm);
1189 EXPORT_SYMBOL(get_task_exe_file);
1192 * get_task_mm - acquire a reference to the task's mm
1194 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning
1195 * this kernel workthread has transiently adopted a user mm with use_mm,
1196 * to do its AIO) is not set and if so returns a reference to it, after
1197 * bumping up the use count. User must release the mm via mmput()
1198 * after use. Typically used by /proc and ptrace.
1200 struct mm_struct *get_task_mm(struct task_struct *task)
1202 struct mm_struct *mm;
1207 if (task->flags & PF_KTHREAD)
1215 EXPORT_SYMBOL_GPL(get_task_mm);
1217 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
1219 struct mm_struct *mm;
1222 err = mutex_lock_killable(&task->signal->exec_update_mutex);
1224 return ERR_PTR(err);
1226 mm = get_task_mm(task);
1227 if (mm && mm != current->mm &&
1228 !ptrace_may_access(task, mode)) {
1230 mm = ERR_PTR(-EACCES);
1232 mutex_unlock(&task->signal->exec_update_mutex);
1237 static void complete_vfork_done(struct task_struct *tsk)
1239 struct completion *vfork;
1242 vfork = tsk->vfork_done;
1243 if (likely(vfork)) {
1244 tsk->vfork_done = NULL;
1250 static int wait_for_vfork_done(struct task_struct *child,
1251 struct completion *vfork)
1255 freezer_do_not_count();
1256 cgroup_enter_frozen();
1257 killed = wait_for_completion_killable(vfork);
1258 cgroup_leave_frozen(false);
1263 child->vfork_done = NULL;
1267 put_task_struct(child);
1271 /* Please note the differences between mmput and mm_release.
1272 * mmput is called whenever we stop holding onto a mm_struct,
1273 * error success whatever.
1275 * mm_release is called after a mm_struct has been removed
1276 * from the current process.
1278 * This difference is important for error handling, when we
1279 * only half set up a mm_struct for a new process and need to restore
1280 * the old one. Because we mmput the new mm_struct before
1281 * restoring the old one. . .
1282 * Eric Biederman 10 January 1998
1284 static void mm_release(struct task_struct *tsk, struct mm_struct *mm)
1286 uprobe_free_utask(tsk);
1288 /* Get rid of any cached register state */
1289 deactivate_mm(tsk, mm);
1292 * Signal userspace if we're not exiting with a core dump
1293 * because we want to leave the value intact for debugging
1296 if (tsk->clear_child_tid) {
1297 if (!(tsk->signal->flags & SIGNAL_GROUP_COREDUMP) &&
1298 atomic_read(&mm->mm_users) > 1) {
1300 * We don't check the error code - if userspace has
1301 * not set up a proper pointer then tough luck.
1303 put_user(0, tsk->clear_child_tid);
1304 do_futex(tsk->clear_child_tid, FUTEX_WAKE,
1305 1, NULL, NULL, 0, 0);
1307 tsk->clear_child_tid = NULL;
1311 * All done, finally we can wake up parent and return this mm to him.
1312 * Also kthread_stop() uses this completion for synchronization.
1314 if (tsk->vfork_done)
1315 complete_vfork_done(tsk);
1318 void exit_mm_release(struct task_struct *tsk, struct mm_struct *mm)
1320 futex_exit_release(tsk);
1321 mm_release(tsk, mm);
1324 void exec_mm_release(struct task_struct *tsk, struct mm_struct *mm)
1326 futex_exec_release(tsk);
1327 mm_release(tsk, mm);
1331 * dup_mm() - duplicates an existing mm structure
1332 * @tsk: the task_struct with which the new mm will be associated.
1333 * @oldmm: the mm to duplicate.
1335 * Allocates a new mm structure and duplicates the provided @oldmm structure
1338 * Return: the duplicated mm or NULL on failure.
1340 static struct mm_struct *dup_mm(struct task_struct *tsk,
1341 struct mm_struct *oldmm)
1343 struct mm_struct *mm;
1350 memcpy(mm, oldmm, sizeof(*mm));
1352 if (!mm_init(mm, tsk, mm->user_ns))
1355 err = dup_mmap(mm, oldmm);
1359 mm->hiwater_rss = get_mm_rss(mm);
1360 mm->hiwater_vm = mm->total_vm;
1362 if (mm->binfmt && !try_module_get(mm->binfmt->module))
1368 /* don't put binfmt in mmput, we haven't got module yet */
1370 mm_init_owner(mm, NULL);
1377 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
1379 struct mm_struct *mm, *oldmm;
1382 tsk->min_flt = tsk->maj_flt = 0;
1383 tsk->nvcsw = tsk->nivcsw = 0;
1384 #ifdef CONFIG_DETECT_HUNG_TASK
1385 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
1386 tsk->last_switch_time = 0;
1390 tsk->active_mm = NULL;
1393 * Are we cloning a kernel thread?
1395 * We need to steal a active VM for that..
1397 oldmm = current->mm;
1401 /* initialize the new vmacache entries */
1402 vmacache_flush(tsk);
1404 if (clone_flags & CLONE_VM) {
1411 mm = dup_mm(tsk, current->mm);
1417 tsk->active_mm = mm;
1424 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
1426 struct fs_struct *fs = current->fs;
1427 if (clone_flags & CLONE_FS) {
1428 /* tsk->fs is already what we want */
1429 spin_lock(&fs->lock);
1431 spin_unlock(&fs->lock);
1435 spin_unlock(&fs->lock);
1438 tsk->fs = copy_fs_struct(fs);
1444 static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
1446 struct files_struct *oldf, *newf;
1450 * A background process may not have any files ...
1452 oldf = current->files;
1456 if (clone_flags & CLONE_FILES) {
1457 atomic_inc(&oldf->count);
1461 newf = dup_fd(oldf, NR_OPEN_MAX, &error);
1471 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
1474 struct io_context *ioc = current->io_context;
1475 struct io_context *new_ioc;
1480 * Share io context with parent, if CLONE_IO is set
1482 if (clone_flags & CLONE_IO) {
1484 tsk->io_context = ioc;
1485 } else if (ioprio_valid(ioc->ioprio)) {
1486 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE);
1487 if (unlikely(!new_ioc))
1490 new_ioc->ioprio = ioc->ioprio;
1491 put_io_context(new_ioc);
1497 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
1499 struct sighand_struct *sig;
1501 if (clone_flags & CLONE_SIGHAND) {
1502 refcount_inc(¤t->sighand->count);
1505 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1506 RCU_INIT_POINTER(tsk->sighand, sig);
1510 refcount_set(&sig->count, 1);
1511 spin_lock_irq(¤t->sighand->siglock);
1512 memcpy(sig->action, current->sighand->action, sizeof(sig->action));
1513 spin_unlock_irq(¤t->sighand->siglock);
1515 /* Reset all signal handler not set to SIG_IGN to SIG_DFL. */
1516 if (clone_flags & CLONE_CLEAR_SIGHAND)
1517 flush_signal_handlers(tsk, 0);
1522 void __cleanup_sighand(struct sighand_struct *sighand)
1524 if (refcount_dec_and_test(&sighand->count)) {
1525 signalfd_cleanup(sighand);
1527 * sighand_cachep is SLAB_TYPESAFE_BY_RCU so we can free it
1528 * without an RCU grace period, see __lock_task_sighand().
1530 kmem_cache_free(sighand_cachep, sighand);
1535 * Initialize POSIX timer handling for a thread group.
1537 static void posix_cpu_timers_init_group(struct signal_struct *sig)
1539 struct posix_cputimers *pct = &sig->posix_cputimers;
1540 unsigned long cpu_limit;
1542 cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1543 posix_cputimers_group_init(pct, cpu_limit);
1546 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
1548 struct signal_struct *sig;
1550 if (clone_flags & CLONE_THREAD)
1553 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
1558 sig->nr_threads = 1;
1559 atomic_set(&sig->live, 1);
1560 refcount_set(&sig->sigcnt, 1);
1562 /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */
1563 sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node);
1564 tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head);
1566 init_waitqueue_head(&sig->wait_chldexit);
1567 sig->curr_target = tsk;
1568 init_sigpending(&sig->shared_pending);
1569 INIT_HLIST_HEAD(&sig->multiprocess);
1570 seqlock_init(&sig->stats_lock);
1571 prev_cputime_init(&sig->prev_cputime);
1573 #ifdef CONFIG_POSIX_TIMERS
1574 INIT_LIST_HEAD(&sig->posix_timers);
1575 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1576 sig->real_timer.function = it_real_fn;
1579 task_lock(current->group_leader);
1580 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
1581 task_unlock(current->group_leader);
1583 posix_cpu_timers_init_group(sig);
1585 tty_audit_fork(sig);
1586 sched_autogroup_fork(sig);
1588 sig->oom_score_adj = current->signal->oom_score_adj;
1589 sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1591 mutex_init(&sig->cred_guard_mutex);
1592 mutex_init(&sig->exec_update_mutex);
1597 static void copy_seccomp(struct task_struct *p)
1599 #ifdef CONFIG_SECCOMP
1601 * Must be called with sighand->lock held, which is common to
1602 * all threads in the group. Holding cred_guard_mutex is not
1603 * needed because this new task is not yet running and cannot
1606 assert_spin_locked(¤t->sighand->siglock);
1608 /* Ref-count the new filter user, and assign it. */
1609 get_seccomp_filter(current);
1610 p->seccomp = current->seccomp;
1613 * Explicitly enable no_new_privs here in case it got set
1614 * between the task_struct being duplicated and holding the
1615 * sighand lock. The seccomp state and nnp must be in sync.
1617 if (task_no_new_privs(current))
1618 task_set_no_new_privs(p);
1621 * If the parent gained a seccomp mode after copying thread
1622 * flags and between before we held the sighand lock, we have
1623 * to manually enable the seccomp thread flag here.
1625 if (p->seccomp.mode != SECCOMP_MODE_DISABLED)
1626 set_tsk_thread_flag(p, TIF_SECCOMP);
1630 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1632 current->clear_child_tid = tidptr;
1634 return task_pid_vnr(current);
1637 static void rt_mutex_init_task(struct task_struct *p)
1639 raw_spin_lock_init(&p->pi_lock);
1640 #ifdef CONFIG_RT_MUTEXES
1641 p->pi_waiters = RB_ROOT_CACHED;
1642 p->pi_top_task = NULL;
1643 p->pi_blocked_on = NULL;
1647 static inline void init_task_pid_links(struct task_struct *task)
1651 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
1652 INIT_HLIST_NODE(&task->pid_links[type]);
1657 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid)
1659 if (type == PIDTYPE_PID)
1660 task->thread_pid = pid;
1662 task->signal->pids[type] = pid;
1665 static inline void rcu_copy_process(struct task_struct *p)
1667 #ifdef CONFIG_PREEMPT_RCU
1668 p->rcu_read_lock_nesting = 0;
1669 p->rcu_read_unlock_special.s = 0;
1670 p->rcu_blocked_node = NULL;
1671 INIT_LIST_HEAD(&p->rcu_node_entry);
1672 #endif /* #ifdef CONFIG_PREEMPT_RCU */
1673 #ifdef CONFIG_TASKS_RCU
1674 p->rcu_tasks_holdout = false;
1675 INIT_LIST_HEAD(&p->rcu_tasks_holdout_list);
1676 p->rcu_tasks_idle_cpu = -1;
1677 #endif /* #ifdef CONFIG_TASKS_RCU */
1678 #ifdef CONFIG_TASKS_TRACE_RCU
1679 p->trc_reader_nesting = 0;
1680 p->trc_reader_special.s = 0;
1681 INIT_LIST_HEAD(&p->trc_holdout_list);
1682 #endif /* #ifdef CONFIG_TASKS_TRACE_RCU */
1685 struct pid *pidfd_pid(const struct file *file)
1687 if (file->f_op == &pidfd_fops)
1688 return file->private_data;
1690 return ERR_PTR(-EBADF);
1693 static int pidfd_release(struct inode *inode, struct file *file)
1695 struct pid *pid = file->private_data;
1697 file->private_data = NULL;
1702 #ifdef CONFIG_PROC_FS
1704 * pidfd_show_fdinfo - print information about a pidfd
1705 * @m: proc fdinfo file
1706 * @f: file referencing a pidfd
1709 * This function will print the pid that a given pidfd refers to in the
1710 * pid namespace of the procfs instance.
1711 * If the pid namespace of the process is not a descendant of the pid
1712 * namespace of the procfs instance 0 will be shown as its pid. This is
1713 * similar to calling getppid() on a process whose parent is outside of
1714 * its pid namespace.
1717 * If pid namespaces are supported then this function will also print
1718 * the pid of a given pidfd refers to for all descendant pid namespaces
1719 * starting from the current pid namespace of the instance, i.e. the
1720 * Pid field and the first entry in the NSpid field will be identical.
1721 * If the pid namespace of the process is not a descendant of the pid
1722 * namespace of the procfs instance 0 will be shown as its first NSpid
1723 * entry and no others will be shown.
1724 * Note that this differs from the Pid and NSpid fields in
1725 * /proc/<pid>/status where Pid and NSpid are always shown relative to
1726 * the pid namespace of the procfs instance. The difference becomes
1727 * obvious when sending around a pidfd between pid namespaces from a
1728 * different branch of the tree, i.e. where no ancestoral relation is
1729 * present between the pid namespaces:
1730 * - create two new pid namespaces ns1 and ns2 in the initial pid
1731 * namespace (also take care to create new mount namespaces in the
1732 * new pid namespace and mount procfs)
1733 * - create a process with a pidfd in ns1
1734 * - send pidfd from ns1 to ns2
1735 * - read /proc/self/fdinfo/<pidfd> and observe that both Pid and NSpid
1736 * have exactly one entry, which is 0
1738 static void pidfd_show_fdinfo(struct seq_file *m, struct file *f)
1740 struct pid *pid = f->private_data;
1741 struct pid_namespace *ns;
1744 if (likely(pid_has_task(pid, PIDTYPE_PID))) {
1745 ns = proc_pid_ns(file_inode(m->file)->i_sb);
1746 nr = pid_nr_ns(pid, ns);
1749 seq_put_decimal_ll(m, "Pid:\t", nr);
1751 #ifdef CONFIG_PID_NS
1752 seq_put_decimal_ll(m, "\nNSpid:\t", nr);
1756 /* If nr is non-zero it means that 'pid' is valid and that
1757 * ns, i.e. the pid namespace associated with the procfs
1758 * instance, is in the pid namespace hierarchy of pid.
1759 * Start at one below the already printed level.
1761 for (i = ns->level + 1; i <= pid->level; i++)
1762 seq_put_decimal_ll(m, "\t", pid->numbers[i].nr);
1770 * Poll support for process exit notification.
1772 static __poll_t pidfd_poll(struct file *file, struct poll_table_struct *pts)
1774 struct pid *pid = file->private_data;
1775 __poll_t poll_flags = 0;
1777 poll_wait(file, &pid->wait_pidfd, pts);
1780 * Inform pollers only when the whole thread group exits.
1781 * If the thread group leader exits before all other threads in the
1782 * group, then poll(2) should block, similar to the wait(2) family.
1784 if (thread_group_exited(pid))
1785 poll_flags = EPOLLIN | EPOLLRDNORM;
1790 const struct file_operations pidfd_fops = {
1791 .release = pidfd_release,
1793 #ifdef CONFIG_PROC_FS
1794 .show_fdinfo = pidfd_show_fdinfo,
1798 static void __delayed_free_task(struct rcu_head *rhp)
1800 struct task_struct *tsk = container_of(rhp, struct task_struct, rcu);
1805 static __always_inline void delayed_free_task(struct task_struct *tsk)
1807 if (IS_ENABLED(CONFIG_MEMCG))
1808 call_rcu(&tsk->rcu, __delayed_free_task);
1814 * This creates a new process as a copy of the old one,
1815 * but does not actually start it yet.
1817 * It copies the registers, and all the appropriate
1818 * parts of the process environment (as per the clone
1819 * flags). The actual kick-off is left to the caller.
1821 static __latent_entropy struct task_struct *copy_process(
1825 struct kernel_clone_args *args)
1827 int pidfd = -1, retval;
1828 struct task_struct *p;
1829 struct multiprocess_signals delayed;
1830 struct file *pidfile = NULL;
1831 u64 clone_flags = args->flags;
1832 struct nsproxy *nsp = current->nsproxy;
1835 * Don't allow sharing the root directory with processes in a different
1838 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1839 return ERR_PTR(-EINVAL);
1841 if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS))
1842 return ERR_PTR(-EINVAL);
1845 * Thread groups must share signals as well, and detached threads
1846 * can only be started up within the thread group.
1848 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1849 return ERR_PTR(-EINVAL);
1852 * Shared signal handlers imply shared VM. By way of the above,
1853 * thread groups also imply shared VM. Blocking this case allows
1854 * for various simplifications in other code.
1856 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1857 return ERR_PTR(-EINVAL);
1860 * Siblings of global init remain as zombies on exit since they are
1861 * not reaped by their parent (swapper). To solve this and to avoid
1862 * multi-rooted process trees, prevent global and container-inits
1863 * from creating siblings.
1865 if ((clone_flags & CLONE_PARENT) &&
1866 current->signal->flags & SIGNAL_UNKILLABLE)
1867 return ERR_PTR(-EINVAL);
1870 * If the new process will be in a different pid or user namespace
1871 * do not allow it to share a thread group with the forking task.
1873 if (clone_flags & CLONE_THREAD) {
1874 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) ||
1875 (task_active_pid_ns(current) != nsp->pid_ns_for_children))
1876 return ERR_PTR(-EINVAL);
1880 * If the new process will be in a different time namespace
1881 * do not allow it to share VM or a thread group with the forking task.
1883 if (clone_flags & (CLONE_THREAD | CLONE_VM)) {
1884 if (nsp->time_ns != nsp->time_ns_for_children)
1885 return ERR_PTR(-EINVAL);
1888 if (clone_flags & CLONE_PIDFD) {
1890 * - CLONE_DETACHED is blocked so that we can potentially
1891 * reuse it later for CLONE_PIDFD.
1892 * - CLONE_THREAD is blocked until someone really needs it.
1894 if (clone_flags & (CLONE_DETACHED | CLONE_THREAD))
1895 return ERR_PTR(-EINVAL);
1899 * Force any signals received before this point to be delivered
1900 * before the fork happens. Collect up signals sent to multiple
1901 * processes that happen during the fork and delay them so that
1902 * they appear to happen after the fork.
1904 sigemptyset(&delayed.signal);
1905 INIT_HLIST_NODE(&delayed.node);
1907 spin_lock_irq(¤t->sighand->siglock);
1908 if (!(clone_flags & CLONE_THREAD))
1909 hlist_add_head(&delayed.node, ¤t->signal->multiprocess);
1910 recalc_sigpending();
1911 spin_unlock_irq(¤t->sighand->siglock);
1912 retval = -ERESTARTNOINTR;
1913 if (signal_pending(current))
1917 p = dup_task_struct(current, node);
1922 * This _must_ happen before we call free_task(), i.e. before we jump
1923 * to any of the bad_fork_* labels. This is to avoid freeing
1924 * p->set_child_tid which is (ab)used as a kthread's data pointer for
1925 * kernel threads (PF_KTHREAD).
1927 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? args->child_tid : NULL;
1929 * Clear TID on mm_release()?
1931 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? args->child_tid : NULL;
1933 ftrace_graph_init_task(p);
1935 rt_mutex_init_task(p);
1937 lockdep_assert_irqs_enabled();
1938 #ifdef CONFIG_PROVE_LOCKING
1939 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1942 if (atomic_read(&p->real_cred->user->processes) >=
1943 task_rlimit(p, RLIMIT_NPROC)) {
1944 if (p->real_cred->user != INIT_USER &&
1945 !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
1948 current->flags &= ~PF_NPROC_EXCEEDED;
1950 retval = copy_creds(p, clone_flags);
1955 * If multiple threads are within copy_process(), then this check
1956 * triggers too late. This doesn't hurt, the check is only there
1957 * to stop root fork bombs.
1960 if (data_race(nr_threads >= max_threads))
1961 goto bad_fork_cleanup_count;
1963 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */
1964 p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER | PF_IDLE);
1965 p->flags |= PF_FORKNOEXEC;
1966 INIT_LIST_HEAD(&p->children);
1967 INIT_LIST_HEAD(&p->sibling);
1968 rcu_copy_process(p);
1969 p->vfork_done = NULL;
1970 spin_lock_init(&p->alloc_lock);
1972 init_sigpending(&p->pending);
1974 p->utime = p->stime = p->gtime = 0;
1975 #ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
1976 p->utimescaled = p->stimescaled = 0;
1978 prev_cputime_init(&p->prev_cputime);
1980 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
1981 seqcount_init(&p->vtime.seqcount);
1982 p->vtime.starttime = 0;
1983 p->vtime.state = VTIME_INACTIVE;
1986 #if defined(SPLIT_RSS_COUNTING)
1987 memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1990 p->default_timer_slack_ns = current->timer_slack_ns;
1996 task_io_accounting_init(&p->ioac);
1997 acct_clear_integrals(p);
1999 posix_cputimers_init(&p->posix_cputimers);
2001 p->io_context = NULL;
2002 audit_set_context(p, NULL);
2005 p->mempolicy = mpol_dup(p->mempolicy);
2006 if (IS_ERR(p->mempolicy)) {
2007 retval = PTR_ERR(p->mempolicy);
2008 p->mempolicy = NULL;
2009 goto bad_fork_cleanup_threadgroup_lock;
2012 #ifdef CONFIG_CPUSETS
2013 p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
2014 p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
2015 seqcount_spinlock_init(&p->mems_allowed_seq, &p->alloc_lock);
2017 #ifdef CONFIG_TRACE_IRQFLAGS
2018 memset(&p->irqtrace, 0, sizeof(p->irqtrace));
2019 p->irqtrace.hardirq_disable_ip = _THIS_IP_;
2020 p->irqtrace.softirq_enable_ip = _THIS_IP_;
2021 p->softirqs_enabled = 1;
2022 p->softirq_context = 0;
2025 p->pagefault_disabled = 0;
2027 #ifdef CONFIG_LOCKDEP
2028 lockdep_init_task(p);
2031 #ifdef CONFIG_DEBUG_MUTEXES
2032 p->blocked_on = NULL; /* not blocked yet */
2034 #ifdef CONFIG_BCACHE
2035 p->sequential_io = 0;
2036 p->sequential_io_avg = 0;
2039 /* Perform scheduler related setup. Assign this task to a CPU. */
2040 retval = sched_fork(clone_flags, p);
2042 goto bad_fork_cleanup_policy;
2044 retval = perf_event_init_task(p);
2046 goto bad_fork_cleanup_policy;
2047 retval = audit_alloc(p);
2049 goto bad_fork_cleanup_perf;
2050 /* copy all the process information */
2052 retval = security_task_alloc(p, clone_flags);
2054 goto bad_fork_cleanup_audit;
2055 retval = copy_semundo(clone_flags, p);
2057 goto bad_fork_cleanup_security;
2058 retval = copy_files(clone_flags, p);
2060 goto bad_fork_cleanup_semundo;
2061 retval = copy_fs(clone_flags, p);
2063 goto bad_fork_cleanup_files;
2064 retval = copy_sighand(clone_flags, p);
2066 goto bad_fork_cleanup_fs;
2067 retval = copy_signal(clone_flags, p);
2069 goto bad_fork_cleanup_sighand;
2070 retval = copy_mm(clone_flags, p);
2072 goto bad_fork_cleanup_signal;
2073 retval = copy_namespaces(clone_flags, p);
2075 goto bad_fork_cleanup_mm;
2076 retval = copy_io(clone_flags, p);
2078 goto bad_fork_cleanup_namespaces;
2079 retval = copy_thread(clone_flags, args->stack, args->stack_size, p, args->tls);
2081 goto bad_fork_cleanup_io;
2083 stackleak_task_init(p);
2085 if (pid != &init_struct_pid) {
2086 pid = alloc_pid(p->nsproxy->pid_ns_for_children, args->set_tid,
2087 args->set_tid_size);
2089 retval = PTR_ERR(pid);
2090 goto bad_fork_cleanup_thread;
2095 * This has to happen after we've potentially unshared the file
2096 * descriptor table (so that the pidfd doesn't leak into the child
2097 * if the fd table isn't shared).
2099 if (clone_flags & CLONE_PIDFD) {
2100 retval = get_unused_fd_flags(O_RDWR | O_CLOEXEC);
2102 goto bad_fork_free_pid;
2106 pidfile = anon_inode_getfile("[pidfd]", &pidfd_fops, pid,
2107 O_RDWR | O_CLOEXEC);
2108 if (IS_ERR(pidfile)) {
2109 put_unused_fd(pidfd);
2110 retval = PTR_ERR(pidfile);
2111 goto bad_fork_free_pid;
2113 get_pid(pid); /* held by pidfile now */
2115 retval = put_user(pidfd, args->pidfd);
2117 goto bad_fork_put_pidfd;
2126 * sigaltstack should be cleared when sharing the same VM
2128 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
2132 * Syscall tracing and stepping should be turned off in the
2133 * child regardless of CLONE_PTRACE.
2135 user_disable_single_step(p);
2136 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
2137 #ifdef TIF_SYSCALL_EMU
2138 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
2140 clear_tsk_latency_tracing(p);
2142 /* ok, now we should be set up.. */
2143 p->pid = pid_nr(pid);
2144 if (clone_flags & CLONE_THREAD) {
2145 p->exit_signal = -1;
2146 p->group_leader = current->group_leader;
2147 p->tgid = current->tgid;
2149 if (clone_flags & CLONE_PARENT)
2150 p->exit_signal = current->group_leader->exit_signal;
2152 p->exit_signal = args->exit_signal;
2153 p->group_leader = p;
2158 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
2159 p->dirty_paused_when = 0;
2161 p->pdeath_signal = 0;
2162 INIT_LIST_HEAD(&p->thread_group);
2163 p->task_works = NULL;
2166 * Ensure that the cgroup subsystem policies allow the new process to be
2167 * forked. It should be noted the the new process's css_set can be changed
2168 * between here and cgroup_post_fork() if an organisation operation is in
2171 retval = cgroup_can_fork(p, args);
2173 goto bad_fork_put_pidfd;
2176 * From this point on we must avoid any synchronous user-space
2177 * communication until we take the tasklist-lock. In particular, we do
2178 * not want user-space to be able to predict the process start-time by
2179 * stalling fork(2) after we recorded the start_time but before it is
2180 * visible to the system.
2183 p->start_time = ktime_get_ns();
2184 p->start_boottime = ktime_get_boottime_ns();
2187 * Make it visible to the rest of the system, but dont wake it up yet.
2188 * Need tasklist lock for parent etc handling!
2190 write_lock_irq(&tasklist_lock);
2192 /* CLONE_PARENT re-uses the old parent */
2193 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
2194 p->real_parent = current->real_parent;
2195 p->parent_exec_id = current->parent_exec_id;
2197 p->real_parent = current;
2198 p->parent_exec_id = current->self_exec_id;
2201 klp_copy_process(p);
2203 spin_lock(¤t->sighand->siglock);
2206 * Copy seccomp details explicitly here, in case they were changed
2207 * before holding sighand lock.
2211 rseq_fork(p, clone_flags);
2213 /* Don't start children in a dying pid namespace */
2214 if (unlikely(!(ns_of_pid(pid)->pid_allocated & PIDNS_ADDING))) {
2216 goto bad_fork_cancel_cgroup;
2219 /* Let kill terminate clone/fork in the middle */
2220 if (fatal_signal_pending(current)) {
2222 goto bad_fork_cancel_cgroup;
2225 /* past the last point of failure */
2227 fd_install(pidfd, pidfile);
2229 init_task_pid_links(p);
2230 if (likely(p->pid)) {
2231 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
2233 init_task_pid(p, PIDTYPE_PID, pid);
2234 if (thread_group_leader(p)) {
2235 init_task_pid(p, PIDTYPE_TGID, pid);
2236 init_task_pid(p, PIDTYPE_PGID, task_pgrp(current));
2237 init_task_pid(p, PIDTYPE_SID, task_session(current));
2239 if (is_child_reaper(pid)) {
2240 ns_of_pid(pid)->child_reaper = p;
2241 p->signal->flags |= SIGNAL_UNKILLABLE;
2243 p->signal->shared_pending.signal = delayed.signal;
2244 p->signal->tty = tty_kref_get(current->signal->tty);
2246 * Inherit has_child_subreaper flag under the same
2247 * tasklist_lock with adding child to the process tree
2248 * for propagate_has_child_subreaper optimization.
2250 p->signal->has_child_subreaper = p->real_parent->signal->has_child_subreaper ||
2251 p->real_parent->signal->is_child_subreaper;
2252 list_add_tail(&p->sibling, &p->real_parent->children);
2253 list_add_tail_rcu(&p->tasks, &init_task.tasks);
2254 attach_pid(p, PIDTYPE_TGID);
2255 attach_pid(p, PIDTYPE_PGID);
2256 attach_pid(p, PIDTYPE_SID);
2257 __this_cpu_inc(process_counts);
2259 current->signal->nr_threads++;
2260 atomic_inc(¤t->signal->live);
2261 refcount_inc(¤t->signal->sigcnt);
2262 task_join_group_stop(p);
2263 list_add_tail_rcu(&p->thread_group,
2264 &p->group_leader->thread_group);
2265 list_add_tail_rcu(&p->thread_node,
2266 &p->signal->thread_head);
2268 attach_pid(p, PIDTYPE_PID);
2272 hlist_del_init(&delayed.node);
2273 spin_unlock(¤t->sighand->siglock);
2274 syscall_tracepoint_update(p);
2275 write_unlock_irq(&tasklist_lock);
2277 proc_fork_connector(p);
2279 cgroup_post_fork(p, args);
2282 trace_task_newtask(p, clone_flags);
2283 uprobe_copy_process(p, clone_flags);
2287 bad_fork_cancel_cgroup:
2288 spin_unlock(¤t->sighand->siglock);
2289 write_unlock_irq(&tasklist_lock);
2290 cgroup_cancel_fork(p, args);
2292 if (clone_flags & CLONE_PIDFD) {
2294 put_unused_fd(pidfd);
2297 if (pid != &init_struct_pid)
2299 bad_fork_cleanup_thread:
2301 bad_fork_cleanup_io:
2304 bad_fork_cleanup_namespaces:
2305 exit_task_namespaces(p);
2306 bad_fork_cleanup_mm:
2308 mm_clear_owner(p->mm, p);
2311 bad_fork_cleanup_signal:
2312 if (!(clone_flags & CLONE_THREAD))
2313 free_signal_struct(p->signal);
2314 bad_fork_cleanup_sighand:
2315 __cleanup_sighand(p->sighand);
2316 bad_fork_cleanup_fs:
2317 exit_fs(p); /* blocking */
2318 bad_fork_cleanup_files:
2319 exit_files(p); /* blocking */
2320 bad_fork_cleanup_semundo:
2322 bad_fork_cleanup_security:
2323 security_task_free(p);
2324 bad_fork_cleanup_audit:
2326 bad_fork_cleanup_perf:
2327 perf_event_free_task(p);
2328 bad_fork_cleanup_policy:
2329 lockdep_free_task(p);
2331 mpol_put(p->mempolicy);
2332 bad_fork_cleanup_threadgroup_lock:
2334 delayacct_tsk_free(p);
2335 bad_fork_cleanup_count:
2336 atomic_dec(&p->cred->user->processes);
2339 p->state = TASK_DEAD;
2341 delayed_free_task(p);
2343 spin_lock_irq(¤t->sighand->siglock);
2344 hlist_del_init(&delayed.node);
2345 spin_unlock_irq(¤t->sighand->siglock);
2346 return ERR_PTR(retval);
2349 static inline void init_idle_pids(struct task_struct *idle)
2353 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
2354 INIT_HLIST_NODE(&idle->pid_links[type]); /* not really needed */
2355 init_task_pid(idle, type, &init_struct_pid);
2359 struct task_struct *fork_idle(int cpu)
2361 struct task_struct *task;
2362 struct kernel_clone_args args = {
2366 task = copy_process(&init_struct_pid, 0, cpu_to_node(cpu), &args);
2367 if (!IS_ERR(task)) {
2368 init_idle_pids(task);
2369 init_idle(task, cpu);
2375 struct mm_struct *copy_init_mm(void)
2377 return dup_mm(NULL, &init_mm);
2381 * Ok, this is the main fork-routine.
2383 * It copies the process, and if successful kick-starts
2384 * it and waits for it to finish using the VM if required.
2386 * args->exit_signal is expected to be checked for sanity by the caller.
2388 long _do_fork(struct kernel_clone_args *args)
2390 u64 clone_flags = args->flags;
2391 struct completion vfork;
2393 struct task_struct *p;
2398 * For legacy clone() calls, CLONE_PIDFD uses the parent_tid argument
2399 * to return the pidfd. Hence, CLONE_PIDFD and CLONE_PARENT_SETTID are
2400 * mutually exclusive. With clone3() CLONE_PIDFD has grown a separate
2401 * field in struct clone_args and it still doesn't make sense to have
2402 * them both point at the same memory location. Performing this check
2403 * here has the advantage that we don't need to have a separate helper
2404 * to check for legacy clone().
2406 if ((args->flags & CLONE_PIDFD) &&
2407 (args->flags & CLONE_PARENT_SETTID) &&
2408 (args->pidfd == args->parent_tid))
2412 * Determine whether and which event to report to ptracer. When
2413 * called from kernel_thread or CLONE_UNTRACED is explicitly
2414 * requested, no event is reported; otherwise, report if the event
2415 * for the type of forking is enabled.
2417 if (!(clone_flags & CLONE_UNTRACED)) {
2418 if (clone_flags & CLONE_VFORK)
2419 trace = PTRACE_EVENT_VFORK;
2420 else if (args->exit_signal != SIGCHLD)
2421 trace = PTRACE_EVENT_CLONE;
2423 trace = PTRACE_EVENT_FORK;
2425 if (likely(!ptrace_event_enabled(current, trace)))
2429 p = copy_process(NULL, trace, NUMA_NO_NODE, args);
2430 add_latent_entropy();
2436 * Do this prior waking up the new thread - the thread pointer
2437 * might get invalid after that point, if the thread exits quickly.
2439 trace_sched_process_fork(current, p);
2441 pid = get_task_pid(p, PIDTYPE_PID);
2444 if (clone_flags & CLONE_PARENT_SETTID)
2445 put_user(nr, args->parent_tid);
2447 if (clone_flags & CLONE_VFORK) {
2448 p->vfork_done = &vfork;
2449 init_completion(&vfork);
2453 wake_up_new_task(p);
2455 /* forking complete and child started to run, tell ptracer */
2456 if (unlikely(trace))
2457 ptrace_event_pid(trace, pid);
2459 if (clone_flags & CLONE_VFORK) {
2460 if (!wait_for_vfork_done(p, &vfork))
2461 ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid);
2469 * Create a kernel thread.
2471 pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
2473 struct kernel_clone_args args = {
2474 .flags = ((lower_32_bits(flags) | CLONE_VM |
2475 CLONE_UNTRACED) & ~CSIGNAL),
2476 .exit_signal = (lower_32_bits(flags) & CSIGNAL),
2477 .stack = (unsigned long)fn,
2478 .stack_size = (unsigned long)arg,
2481 return _do_fork(&args);
2484 #ifdef __ARCH_WANT_SYS_FORK
2485 SYSCALL_DEFINE0(fork)
2488 struct kernel_clone_args args = {
2489 .exit_signal = SIGCHLD,
2492 return _do_fork(&args);
2494 /* can not support in nommu mode */
2500 #ifdef __ARCH_WANT_SYS_VFORK
2501 SYSCALL_DEFINE0(vfork)
2503 struct kernel_clone_args args = {
2504 .flags = CLONE_VFORK | CLONE_VM,
2505 .exit_signal = SIGCHLD,
2508 return _do_fork(&args);
2512 #ifdef __ARCH_WANT_SYS_CLONE
2513 #ifdef CONFIG_CLONE_BACKWARDS
2514 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2515 int __user *, parent_tidptr,
2517 int __user *, child_tidptr)
2518 #elif defined(CONFIG_CLONE_BACKWARDS2)
2519 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags,
2520 int __user *, parent_tidptr,
2521 int __user *, child_tidptr,
2523 #elif defined(CONFIG_CLONE_BACKWARDS3)
2524 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp,
2526 int __user *, parent_tidptr,
2527 int __user *, child_tidptr,
2530 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2531 int __user *, parent_tidptr,
2532 int __user *, child_tidptr,
2536 struct kernel_clone_args args = {
2537 .flags = (lower_32_bits(clone_flags) & ~CSIGNAL),
2538 .pidfd = parent_tidptr,
2539 .child_tid = child_tidptr,
2540 .parent_tid = parent_tidptr,
2541 .exit_signal = (lower_32_bits(clone_flags) & CSIGNAL),
2546 return _do_fork(&args);
2550 #ifdef __ARCH_WANT_SYS_CLONE3
2552 noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs,
2553 struct clone_args __user *uargs,
2557 struct clone_args args;
2558 pid_t *kset_tid = kargs->set_tid;
2560 BUILD_BUG_ON(offsetofend(struct clone_args, tls) !=
2561 CLONE_ARGS_SIZE_VER0);
2562 BUILD_BUG_ON(offsetofend(struct clone_args, set_tid_size) !=
2563 CLONE_ARGS_SIZE_VER1);
2564 BUILD_BUG_ON(offsetofend(struct clone_args, cgroup) !=
2565 CLONE_ARGS_SIZE_VER2);
2566 BUILD_BUG_ON(sizeof(struct clone_args) != CLONE_ARGS_SIZE_VER2);
2568 if (unlikely(usize > PAGE_SIZE))
2570 if (unlikely(usize < CLONE_ARGS_SIZE_VER0))
2573 err = copy_struct_from_user(&args, sizeof(args), uargs, usize);
2577 if (unlikely(args.set_tid_size > MAX_PID_NS_LEVEL))
2580 if (unlikely(!args.set_tid && args.set_tid_size > 0))
2583 if (unlikely(args.set_tid && args.set_tid_size == 0))
2587 * Verify that higher 32bits of exit_signal are unset and that
2588 * it is a valid signal
2590 if (unlikely((args.exit_signal & ~((u64)CSIGNAL)) ||
2591 !valid_signal(args.exit_signal)))
2594 if ((args.flags & CLONE_INTO_CGROUP) &&
2595 (args.cgroup > INT_MAX || usize < CLONE_ARGS_SIZE_VER2))
2598 *kargs = (struct kernel_clone_args){
2599 .flags = args.flags,
2600 .pidfd = u64_to_user_ptr(args.pidfd),
2601 .child_tid = u64_to_user_ptr(args.child_tid),
2602 .parent_tid = u64_to_user_ptr(args.parent_tid),
2603 .exit_signal = args.exit_signal,
2604 .stack = args.stack,
2605 .stack_size = args.stack_size,
2607 .set_tid_size = args.set_tid_size,
2608 .cgroup = args.cgroup,
2612 copy_from_user(kset_tid, u64_to_user_ptr(args.set_tid),
2613 (kargs->set_tid_size * sizeof(pid_t))))
2616 kargs->set_tid = kset_tid;
2622 * clone3_stack_valid - check and prepare stack
2623 * @kargs: kernel clone args
2625 * Verify that the stack arguments userspace gave us are sane.
2626 * In addition, set the stack direction for userspace since it's easy for us to
2629 static inline bool clone3_stack_valid(struct kernel_clone_args *kargs)
2631 if (kargs->stack == 0) {
2632 if (kargs->stack_size > 0)
2635 if (kargs->stack_size == 0)
2638 if (!access_ok((void __user *)kargs->stack, kargs->stack_size))
2641 #if !defined(CONFIG_STACK_GROWSUP) && !defined(CONFIG_IA64)
2642 kargs->stack += kargs->stack_size;
2649 static bool clone3_args_valid(struct kernel_clone_args *kargs)
2651 /* Verify that no unknown flags are passed along. */
2653 ~(CLONE_LEGACY_FLAGS | CLONE_CLEAR_SIGHAND | CLONE_INTO_CGROUP))
2657 * - make the CLONE_DETACHED bit reuseable for clone3
2658 * - make the CSIGNAL bits reuseable for clone3
2660 if (kargs->flags & (CLONE_DETACHED | CSIGNAL))
2663 if ((kargs->flags & (CLONE_SIGHAND | CLONE_CLEAR_SIGHAND)) ==
2664 (CLONE_SIGHAND | CLONE_CLEAR_SIGHAND))
2667 if ((kargs->flags & (CLONE_THREAD | CLONE_PARENT)) &&
2671 if (!clone3_stack_valid(kargs))
2678 * clone3 - create a new process with specific properties
2679 * @uargs: argument structure
2680 * @size: size of @uargs
2682 * clone3() is the extensible successor to clone()/clone2().
2683 * It takes a struct as argument that is versioned by its size.
2685 * Return: On success, a positive PID for the child process.
2686 * On error, a negative errno number.
2688 SYSCALL_DEFINE2(clone3, struct clone_args __user *, uargs, size_t, size)
2692 struct kernel_clone_args kargs;
2693 pid_t set_tid[MAX_PID_NS_LEVEL];
2695 kargs.set_tid = set_tid;
2697 err = copy_clone_args_from_user(&kargs, uargs, size);
2701 if (!clone3_args_valid(&kargs))
2704 return _do_fork(&kargs);
2708 void walk_process_tree(struct task_struct *top, proc_visitor visitor, void *data)
2710 struct task_struct *leader, *parent, *child;
2713 read_lock(&tasklist_lock);
2714 leader = top = top->group_leader;
2716 for_each_thread(leader, parent) {
2717 list_for_each_entry(child, &parent->children, sibling) {
2718 res = visitor(child, data);
2730 if (leader != top) {
2732 parent = child->real_parent;
2733 leader = parent->group_leader;
2737 read_unlock(&tasklist_lock);
2740 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
2741 #define ARCH_MIN_MMSTRUCT_ALIGN 0
2744 static void sighand_ctor(void *data)
2746 struct sighand_struct *sighand = data;
2748 spin_lock_init(&sighand->siglock);
2749 init_waitqueue_head(&sighand->signalfd_wqh);
2752 void __init proc_caches_init(void)
2754 unsigned int mm_size;
2756 sighand_cachep = kmem_cache_create("sighand_cache",
2757 sizeof(struct sighand_struct), 0,
2758 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_TYPESAFE_BY_RCU|
2759 SLAB_ACCOUNT, sighand_ctor);
2760 signal_cachep = kmem_cache_create("signal_cache",
2761 sizeof(struct signal_struct), 0,
2762 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2764 files_cachep = kmem_cache_create("files_cache",
2765 sizeof(struct files_struct), 0,
2766 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2768 fs_cachep = kmem_cache_create("fs_cache",
2769 sizeof(struct fs_struct), 0,
2770 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2774 * The mm_cpumask is located at the end of mm_struct, and is
2775 * dynamically sized based on the maximum CPU number this system
2776 * can have, taking hotplug into account (nr_cpu_ids).
2778 mm_size = sizeof(struct mm_struct) + cpumask_size();
2780 mm_cachep = kmem_cache_create_usercopy("mm_struct",
2781 mm_size, ARCH_MIN_MMSTRUCT_ALIGN,
2782 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2783 offsetof(struct mm_struct, saved_auxv),
2784 sizeof_field(struct mm_struct, saved_auxv),
2786 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT);
2788 nsproxy_cache_init();
2792 * Check constraints on flags passed to the unshare system call.
2794 static int check_unshare_flags(unsigned long unshare_flags)
2796 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
2797 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
2798 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET|
2799 CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP|
2803 * Not implemented, but pretend it works if there is nothing
2804 * to unshare. Note that unsharing the address space or the
2805 * signal handlers also need to unshare the signal queues (aka
2808 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
2809 if (!thread_group_empty(current))
2812 if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) {
2813 if (refcount_read(¤t->sighand->count) > 1)
2816 if (unshare_flags & CLONE_VM) {
2817 if (!current_is_single_threaded())
2825 * Unshare the filesystem structure if it is being shared
2827 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
2829 struct fs_struct *fs = current->fs;
2831 if (!(unshare_flags & CLONE_FS) || !fs)
2834 /* don't need lock here; in the worst case we'll do useless copy */
2838 *new_fsp = copy_fs_struct(fs);
2846 * Unshare file descriptor table if it is being shared
2848 int unshare_fd(unsigned long unshare_flags, unsigned int max_fds,
2849 struct files_struct **new_fdp)
2851 struct files_struct *fd = current->files;
2854 if ((unshare_flags & CLONE_FILES) &&
2855 (fd && atomic_read(&fd->count) > 1)) {
2856 *new_fdp = dup_fd(fd, max_fds, &error);
2865 * unshare allows a process to 'unshare' part of the process
2866 * context which was originally shared using clone. copy_*
2867 * functions used by _do_fork() cannot be used here directly
2868 * because they modify an inactive task_struct that is being
2869 * constructed. Here we are modifying the current, active,
2872 int ksys_unshare(unsigned long unshare_flags)
2874 struct fs_struct *fs, *new_fs = NULL;
2875 struct files_struct *fd, *new_fd = NULL;
2876 struct cred *new_cred = NULL;
2877 struct nsproxy *new_nsproxy = NULL;
2882 * If unsharing a user namespace must also unshare the thread group
2883 * and unshare the filesystem root and working directories.
2885 if (unshare_flags & CLONE_NEWUSER)
2886 unshare_flags |= CLONE_THREAD | CLONE_FS;
2888 * If unsharing vm, must also unshare signal handlers.
2890 if (unshare_flags & CLONE_VM)
2891 unshare_flags |= CLONE_SIGHAND;
2893 * If unsharing a signal handlers, must also unshare the signal queues.
2895 if (unshare_flags & CLONE_SIGHAND)
2896 unshare_flags |= CLONE_THREAD;
2898 * If unsharing namespace, must also unshare filesystem information.
2900 if (unshare_flags & CLONE_NEWNS)
2901 unshare_flags |= CLONE_FS;
2903 err = check_unshare_flags(unshare_flags);
2905 goto bad_unshare_out;
2907 * CLONE_NEWIPC must also detach from the undolist: after switching
2908 * to a new ipc namespace, the semaphore arrays from the old
2909 * namespace are unreachable.
2911 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
2913 err = unshare_fs(unshare_flags, &new_fs);
2915 goto bad_unshare_out;
2916 err = unshare_fd(unshare_flags, NR_OPEN_MAX, &new_fd);
2918 goto bad_unshare_cleanup_fs;
2919 err = unshare_userns(unshare_flags, &new_cred);
2921 goto bad_unshare_cleanup_fd;
2922 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
2925 goto bad_unshare_cleanup_cred;
2927 if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
2930 * CLONE_SYSVSEM is equivalent to sys_exit().
2934 if (unshare_flags & CLONE_NEWIPC) {
2935 /* Orphan segments in old ns (see sem above). */
2937 shm_init_task(current);
2941 switch_task_namespaces(current, new_nsproxy);
2947 spin_lock(&fs->lock);
2948 current->fs = new_fs;
2953 spin_unlock(&fs->lock);
2957 fd = current->files;
2958 current->files = new_fd;
2962 task_unlock(current);
2965 /* Install the new user namespace */
2966 commit_creds(new_cred);
2971 perf_event_namespaces(current);
2973 bad_unshare_cleanup_cred:
2976 bad_unshare_cleanup_fd:
2978 put_files_struct(new_fd);
2980 bad_unshare_cleanup_fs:
2982 free_fs_struct(new_fs);
2988 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
2990 return ksys_unshare(unshare_flags);
2994 * Helper to unshare the files of the current task.
2995 * We don't want to expose copy_files internals to
2996 * the exec layer of the kernel.
2999 int unshare_files(struct files_struct **displaced)
3001 struct task_struct *task = current;
3002 struct files_struct *copy = NULL;
3005 error = unshare_fd(CLONE_FILES, NR_OPEN_MAX, ©);
3006 if (error || !copy) {
3010 *displaced = task->files;
3017 int sysctl_max_threads(struct ctl_table *table, int write,
3018 void *buffer, size_t *lenp, loff_t *ppos)
3022 int threads = max_threads;
3024 int max = MAX_THREADS;
3031 ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
3035 max_threads = threads;