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>
98 #include <linux/io_uring.h>
99 #include <linux/bpf.h>
101 #include <asm/pgalloc.h>
102 #include <linux/uaccess.h>
103 #include <asm/mmu_context.h>
104 #include <asm/cacheflush.h>
105 #include <asm/tlbflush.h>
107 #include <trace/events/sched.h>
109 #define CREATE_TRACE_POINTS
110 #include <trace/events/task.h>
113 * Minimum number of threads to boot the kernel
115 #define MIN_THREADS 20
118 * Maximum number of threads
120 #define MAX_THREADS FUTEX_TID_MASK
123 * Protected counters by write_lock_irq(&tasklist_lock)
125 unsigned long total_forks; /* Handle normal Linux uptimes. */
126 int nr_threads; /* The idle threads do not count.. */
128 static int max_threads; /* tunable limit on nr_threads */
130 #define NAMED_ARRAY_INDEX(x) [x] = __stringify(x)
132 static const char * const resident_page_types[] = {
133 NAMED_ARRAY_INDEX(MM_FILEPAGES),
134 NAMED_ARRAY_INDEX(MM_ANONPAGES),
135 NAMED_ARRAY_INDEX(MM_SWAPENTS),
136 NAMED_ARRAY_INDEX(MM_SHMEMPAGES),
139 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
141 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */
143 #ifdef CONFIG_PROVE_RCU
144 int lockdep_tasklist_lock_is_held(void)
146 return lockdep_is_held(&tasklist_lock);
148 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
149 #endif /* #ifdef CONFIG_PROVE_RCU */
151 int nr_processes(void)
156 for_each_possible_cpu(cpu)
157 total += per_cpu(process_counts, cpu);
162 void __weak arch_release_task_struct(struct task_struct *tsk)
166 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
167 static struct kmem_cache *task_struct_cachep;
169 static inline struct task_struct *alloc_task_struct_node(int node)
171 return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node);
174 static inline void free_task_struct(struct task_struct *tsk)
176 kmem_cache_free(task_struct_cachep, tsk);
180 #ifndef CONFIG_ARCH_THREAD_STACK_ALLOCATOR
183 * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
184 * kmemcache based allocator.
186 # if THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK)
188 #ifdef CONFIG_VMAP_STACK
190 * vmalloc() is a bit slow, and calling vfree() enough times will force a TLB
191 * flush. Try to minimize the number of calls by caching stacks.
193 #define NR_CACHED_STACKS 2
194 static DEFINE_PER_CPU(struct vm_struct *, cached_stacks[NR_CACHED_STACKS]);
196 static int free_vm_stack_cache(unsigned int cpu)
198 struct vm_struct **cached_vm_stacks = per_cpu_ptr(cached_stacks, cpu);
201 for (i = 0; i < NR_CACHED_STACKS; i++) {
202 struct vm_struct *vm_stack = cached_vm_stacks[i];
207 vfree(vm_stack->addr);
208 cached_vm_stacks[i] = NULL;
215 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node)
217 #ifdef CONFIG_VMAP_STACK
221 for (i = 0; i < NR_CACHED_STACKS; i++) {
224 s = this_cpu_xchg(cached_stacks[i], NULL);
229 /* Mark stack accessible for KASAN. */
230 kasan_unpoison_range(s->addr, THREAD_SIZE);
232 /* Clear stale pointers from reused stack. */
233 memset(s->addr, 0, THREAD_SIZE);
235 tsk->stack_vm_area = s;
236 tsk->stack = s->addr;
241 * Allocated stacks are cached and later reused by new threads,
242 * so memcg accounting is performed manually on assigning/releasing
243 * stacks to tasks. Drop __GFP_ACCOUNT.
245 stack = __vmalloc_node_range(THREAD_SIZE, THREAD_ALIGN,
246 VMALLOC_START, VMALLOC_END,
247 THREADINFO_GFP & ~__GFP_ACCOUNT,
249 0, node, __builtin_return_address(0));
252 * We can't call find_vm_area() in interrupt context, and
253 * free_thread_stack() can be called in interrupt context,
254 * so cache the vm_struct.
257 tsk->stack_vm_area = find_vm_area(stack);
262 struct page *page = alloc_pages_node(node, THREADINFO_GFP,
266 tsk->stack = kasan_reset_tag(page_address(page));
273 static inline void free_thread_stack(struct task_struct *tsk)
275 #ifdef CONFIG_VMAP_STACK
276 struct vm_struct *vm = task_stack_vm_area(tsk);
281 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++)
282 memcg_kmem_uncharge_page(vm->pages[i], 0);
284 for (i = 0; i < NR_CACHED_STACKS; i++) {
285 if (this_cpu_cmpxchg(cached_stacks[i],
286 NULL, tsk->stack_vm_area) != NULL)
292 if (!IS_ENABLED(CONFIG_PREEMPT_RT))
293 vfree_atomic(tsk->stack);
300 __free_pages(virt_to_page(tsk->stack), THREAD_SIZE_ORDER);
303 static struct kmem_cache *thread_stack_cache;
305 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk,
308 unsigned long *stack;
309 stack = kmem_cache_alloc_node(thread_stack_cache, THREADINFO_GFP, node);
310 stack = kasan_reset_tag(stack);
315 static void free_thread_stack(struct task_struct *tsk)
317 kmem_cache_free(thread_stack_cache, tsk->stack);
320 void thread_stack_cache_init(void)
322 thread_stack_cache = kmem_cache_create_usercopy("thread_stack",
323 THREAD_SIZE, THREAD_SIZE, 0, 0,
325 BUG_ON(thread_stack_cache == NULL);
330 /* SLAB cache for signal_struct structures (tsk->signal) */
331 static struct kmem_cache *signal_cachep;
333 /* SLAB cache for sighand_struct structures (tsk->sighand) */
334 struct kmem_cache *sighand_cachep;
336 /* SLAB cache for files_struct structures (tsk->files) */
337 struct kmem_cache *files_cachep;
339 /* SLAB cache for fs_struct structures (tsk->fs) */
340 struct kmem_cache *fs_cachep;
342 /* SLAB cache for vm_area_struct structures */
343 static struct kmem_cache *vm_area_cachep;
345 /* SLAB cache for mm_struct structures (tsk->mm) */
346 static struct kmem_cache *mm_cachep;
348 struct vm_area_struct *vm_area_alloc(struct mm_struct *mm)
350 struct vm_area_struct *vma;
352 vma = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
358 struct vm_area_struct *vm_area_dup(struct vm_area_struct *orig)
360 struct vm_area_struct *new = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
363 ASSERT_EXCLUSIVE_WRITER(orig->vm_flags);
364 ASSERT_EXCLUSIVE_WRITER(orig->vm_file);
366 * orig->shared.rb may be modified concurrently, but the clone
367 * will be reinitialized.
369 *new = data_race(*orig);
370 INIT_LIST_HEAD(&new->anon_vma_chain);
371 new->vm_next = new->vm_prev = NULL;
376 void vm_area_free(struct vm_area_struct *vma)
378 kmem_cache_free(vm_area_cachep, vma);
381 static void account_kernel_stack(struct task_struct *tsk, int account)
383 void *stack = task_stack_page(tsk);
384 struct vm_struct *vm = task_stack_vm_area(tsk);
389 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++)
390 mod_lruvec_page_state(vm->pages[i], NR_KERNEL_STACK_KB,
391 account * (PAGE_SIZE / 1024));
393 /* All stack pages are in the same node. */
394 mod_lruvec_kmem_state(stack, NR_KERNEL_STACK_KB,
395 account * (THREAD_SIZE / 1024));
399 static int memcg_charge_kernel_stack(struct task_struct *tsk)
401 #ifdef CONFIG_VMAP_STACK
402 struct vm_struct *vm = task_stack_vm_area(tsk);
405 BUILD_BUG_ON(IS_ENABLED(CONFIG_VMAP_STACK) && PAGE_SIZE % 1024 != 0);
410 BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE);
412 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
414 * If memcg_kmem_charge_page() fails, page's
415 * memory cgroup pointer is NULL, and
416 * memcg_kmem_uncharge_page() in free_thread_stack()
417 * will ignore this page.
419 ret = memcg_kmem_charge_page(vm->pages[i], GFP_KERNEL,
429 static void release_task_stack(struct task_struct *tsk)
431 if (WARN_ON(READ_ONCE(tsk->__state) != TASK_DEAD))
432 return; /* Better to leak the stack than to free prematurely */
434 account_kernel_stack(tsk, -1);
435 free_thread_stack(tsk);
437 #ifdef CONFIG_VMAP_STACK
438 tsk->stack_vm_area = NULL;
442 #ifdef CONFIG_THREAD_INFO_IN_TASK
443 void put_task_stack(struct task_struct *tsk)
445 if (refcount_dec_and_test(&tsk->stack_refcount))
446 release_task_stack(tsk);
450 void free_task(struct task_struct *tsk)
452 release_user_cpus_ptr(tsk);
455 #ifndef CONFIG_THREAD_INFO_IN_TASK
457 * The task is finally done with both the stack and thread_info,
460 release_task_stack(tsk);
463 * If the task had a separate stack allocation, it should be gone
466 WARN_ON_ONCE(refcount_read(&tsk->stack_refcount) != 0);
468 rt_mutex_debug_task_free(tsk);
469 ftrace_graph_exit_task(tsk);
470 arch_release_task_struct(tsk);
471 if (tsk->flags & PF_KTHREAD)
472 free_kthread_struct(tsk);
473 free_task_struct(tsk);
475 EXPORT_SYMBOL(free_task);
477 static void dup_mm_exe_file(struct mm_struct *mm, struct mm_struct *oldmm)
479 struct file *exe_file;
481 exe_file = get_mm_exe_file(oldmm);
482 RCU_INIT_POINTER(mm->exe_file, exe_file);
484 * We depend on the oldmm having properly denied write access to the
487 if (exe_file && deny_write_access(exe_file))
488 pr_warn_once("deny_write_access() failed in %s\n", __func__);
492 static __latent_entropy int dup_mmap(struct mm_struct *mm,
493 struct mm_struct *oldmm)
495 struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
496 struct rb_node **rb_link, *rb_parent;
498 unsigned long charge;
501 uprobe_start_dup_mmap();
502 if (mmap_write_lock_killable(oldmm)) {
504 goto fail_uprobe_end;
506 flush_cache_dup_mm(oldmm);
507 uprobe_dup_mmap(oldmm, mm);
509 * Not linked in yet - no deadlock potential:
511 mmap_write_lock_nested(mm, SINGLE_DEPTH_NESTING);
513 /* No ordering required: file already has been exposed. */
514 dup_mm_exe_file(mm, oldmm);
516 mm->total_vm = oldmm->total_vm;
517 mm->data_vm = oldmm->data_vm;
518 mm->exec_vm = oldmm->exec_vm;
519 mm->stack_vm = oldmm->stack_vm;
521 rb_link = &mm->mm_rb.rb_node;
524 retval = ksm_fork(mm, oldmm);
527 retval = khugepaged_fork(mm, oldmm);
532 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
535 if (mpnt->vm_flags & VM_DONTCOPY) {
536 vm_stat_account(mm, mpnt->vm_flags, -vma_pages(mpnt));
541 * Don't duplicate many vmas if we've been oom-killed (for
544 if (fatal_signal_pending(current)) {
548 if (mpnt->vm_flags & VM_ACCOUNT) {
549 unsigned long len = vma_pages(mpnt);
551 if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
555 tmp = vm_area_dup(mpnt);
558 retval = vma_dup_policy(mpnt, tmp);
560 goto fail_nomem_policy;
562 retval = dup_userfaultfd(tmp, &uf);
564 goto fail_nomem_anon_vma_fork;
565 if (tmp->vm_flags & VM_WIPEONFORK) {
567 * VM_WIPEONFORK gets a clean slate in the child.
568 * Don't prepare anon_vma until fault since we don't
569 * copy page for current vma.
571 tmp->anon_vma = NULL;
572 } else if (anon_vma_fork(tmp, mpnt))
573 goto fail_nomem_anon_vma_fork;
574 tmp->vm_flags &= ~(VM_LOCKED | VM_LOCKONFAULT);
577 struct address_space *mapping = file->f_mapping;
580 i_mmap_lock_write(mapping);
581 if (tmp->vm_flags & VM_SHARED)
582 mapping_allow_writable(mapping);
583 flush_dcache_mmap_lock(mapping);
584 /* insert tmp into the share list, just after mpnt */
585 vma_interval_tree_insert_after(tmp, mpnt,
587 flush_dcache_mmap_unlock(mapping);
588 i_mmap_unlock_write(mapping);
592 * Clear hugetlb-related page reserves for children. This only
593 * affects MAP_PRIVATE mappings. Faults generated by the child
594 * are not guaranteed to succeed, even if read-only
596 if (is_vm_hugetlb_page(tmp))
597 reset_vma_resv_huge_pages(tmp);
600 * Link in the new vma and copy the page table entries.
603 pprev = &tmp->vm_next;
607 __vma_link_rb(mm, tmp, rb_link, rb_parent);
608 rb_link = &tmp->vm_rb.rb_right;
609 rb_parent = &tmp->vm_rb;
612 if (!(tmp->vm_flags & VM_WIPEONFORK))
613 retval = copy_page_range(tmp, mpnt);
615 if (tmp->vm_ops && tmp->vm_ops->open)
616 tmp->vm_ops->open(tmp);
621 /* a new mm has just been created */
622 retval = arch_dup_mmap(oldmm, mm);
624 mmap_write_unlock(mm);
626 mmap_write_unlock(oldmm);
627 dup_userfaultfd_complete(&uf);
629 uprobe_end_dup_mmap();
631 fail_nomem_anon_vma_fork:
632 mpol_put(vma_policy(tmp));
637 vm_unacct_memory(charge);
641 static inline int mm_alloc_pgd(struct mm_struct *mm)
643 mm->pgd = pgd_alloc(mm);
644 if (unlikely(!mm->pgd))
649 static inline void mm_free_pgd(struct mm_struct *mm)
651 pgd_free(mm, mm->pgd);
654 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
656 mmap_write_lock(oldmm);
657 dup_mm_exe_file(mm, oldmm);
658 mmap_write_unlock(oldmm);
661 #define mm_alloc_pgd(mm) (0)
662 #define mm_free_pgd(mm)
663 #endif /* CONFIG_MMU */
665 static void check_mm(struct mm_struct *mm)
669 BUILD_BUG_ON_MSG(ARRAY_SIZE(resident_page_types) != NR_MM_COUNTERS,
670 "Please make sure 'struct resident_page_types[]' is updated as well");
672 for (i = 0; i < NR_MM_COUNTERS; i++) {
673 long x = atomic_long_read(&mm->rss_stat.count[i]);
676 pr_alert("BUG: Bad rss-counter state mm:%p type:%s val:%ld\n",
677 mm, resident_page_types[i], x);
680 if (mm_pgtables_bytes(mm))
681 pr_alert("BUG: non-zero pgtables_bytes on freeing mm: %ld\n",
682 mm_pgtables_bytes(mm));
684 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
685 VM_BUG_ON_MM(mm->pmd_huge_pte, mm);
689 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
690 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm)))
693 * Called when the last reference to the mm
694 * is dropped: either by a lazy thread or by
695 * mmput. Free the page directory and the mm.
697 void __mmdrop(struct mm_struct *mm)
699 BUG_ON(mm == &init_mm);
700 WARN_ON_ONCE(mm == current->mm);
701 WARN_ON_ONCE(mm == current->active_mm);
704 mmu_notifier_subscriptions_destroy(mm);
706 put_user_ns(mm->user_ns);
709 EXPORT_SYMBOL_GPL(__mmdrop);
711 #ifdef CONFIG_PREEMPT_RT
713 * RCU callback for delayed mm drop. Not strictly RCU, but call_rcu() is
714 * by far the least expensive way to do that.
716 void __mmdrop_delayed(struct rcu_head *rhp)
718 struct mm_struct *mm = container_of(rhp, struct mm_struct, delayed_drop);
724 static void mmdrop_async_fn(struct work_struct *work)
726 struct mm_struct *mm;
728 mm = container_of(work, struct mm_struct, async_put_work);
732 static void mmdrop_async(struct mm_struct *mm)
734 if (unlikely(atomic_dec_and_test(&mm->mm_count))) {
735 INIT_WORK(&mm->async_put_work, mmdrop_async_fn);
736 schedule_work(&mm->async_put_work);
740 static inline void free_signal_struct(struct signal_struct *sig)
742 taskstats_tgid_free(sig);
743 sched_autogroup_exit(sig);
745 * __mmdrop is not safe to call from softirq context on x86 due to
746 * pgd_dtor so postpone it to the async context
749 mmdrop_async(sig->oom_mm);
750 kmem_cache_free(signal_cachep, sig);
753 static inline void put_signal_struct(struct signal_struct *sig)
755 if (refcount_dec_and_test(&sig->sigcnt))
756 free_signal_struct(sig);
759 void __put_task_struct(struct task_struct *tsk)
761 WARN_ON(!tsk->exit_state);
762 WARN_ON(refcount_read(&tsk->usage));
763 WARN_ON(tsk == current);
767 task_numa_free(tsk, true);
768 security_task_free(tsk);
769 bpf_task_storage_free(tsk);
771 delayacct_tsk_free(tsk);
772 put_signal_struct(tsk->signal);
773 sched_core_free(tsk);
775 if (!profile_handoff_task(tsk))
778 EXPORT_SYMBOL_GPL(__put_task_struct);
780 void __init __weak arch_task_cache_init(void) { }
785 static void set_max_threads(unsigned int max_threads_suggested)
788 unsigned long nr_pages = totalram_pages();
791 * The number of threads shall be limited such that the thread
792 * structures may only consume a small part of the available memory.
794 if (fls64(nr_pages) + fls64(PAGE_SIZE) > 64)
795 threads = MAX_THREADS;
797 threads = div64_u64((u64) nr_pages * (u64) PAGE_SIZE,
798 (u64) THREAD_SIZE * 8UL);
800 if (threads > max_threads_suggested)
801 threads = max_threads_suggested;
803 max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS);
806 #ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT
807 /* Initialized by the architecture: */
808 int arch_task_struct_size __read_mostly;
811 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
812 static void task_struct_whitelist(unsigned long *offset, unsigned long *size)
814 /* Fetch thread_struct whitelist for the architecture. */
815 arch_thread_struct_whitelist(offset, size);
818 * Handle zero-sized whitelist or empty thread_struct, otherwise
819 * adjust offset to position of thread_struct in task_struct.
821 if (unlikely(*size == 0))
824 *offset += offsetof(struct task_struct, thread);
826 #endif /* CONFIG_ARCH_TASK_STRUCT_ALLOCATOR */
828 void __init fork_init(void)
831 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
832 #ifndef ARCH_MIN_TASKALIGN
833 #define ARCH_MIN_TASKALIGN 0
835 int align = max_t(int, L1_CACHE_BYTES, ARCH_MIN_TASKALIGN);
836 unsigned long useroffset, usersize;
838 /* create a slab on which task_structs can be allocated */
839 task_struct_whitelist(&useroffset, &usersize);
840 task_struct_cachep = kmem_cache_create_usercopy("task_struct",
841 arch_task_struct_size, align,
842 SLAB_PANIC|SLAB_ACCOUNT,
843 useroffset, usersize, NULL);
846 /* do the arch specific task caches init */
847 arch_task_cache_init();
849 set_max_threads(MAX_THREADS);
851 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
852 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
853 init_task.signal->rlim[RLIMIT_SIGPENDING] =
854 init_task.signal->rlim[RLIMIT_NPROC];
856 for (i = 0; i < MAX_PER_NAMESPACE_UCOUNTS; i++)
857 init_user_ns.ucount_max[i] = max_threads/2;
859 set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_NPROC, RLIM_INFINITY);
860 set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_MSGQUEUE, RLIM_INFINITY);
861 set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_SIGPENDING, RLIM_INFINITY);
862 set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_MEMLOCK, RLIM_INFINITY);
864 #ifdef CONFIG_VMAP_STACK
865 cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "fork:vm_stack_cache",
866 NULL, free_vm_stack_cache);
871 lockdep_init_task(&init_task);
875 int __weak arch_dup_task_struct(struct task_struct *dst,
876 struct task_struct *src)
882 void set_task_stack_end_magic(struct task_struct *tsk)
884 unsigned long *stackend;
886 stackend = end_of_stack(tsk);
887 *stackend = STACK_END_MAGIC; /* for overflow detection */
890 static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
892 struct task_struct *tsk;
893 unsigned long *stack;
894 struct vm_struct *stack_vm_area __maybe_unused;
897 if (node == NUMA_NO_NODE)
898 node = tsk_fork_get_node(orig);
899 tsk = alloc_task_struct_node(node);
903 stack = alloc_thread_stack_node(tsk, node);
907 if (memcg_charge_kernel_stack(tsk))
910 stack_vm_area = task_stack_vm_area(tsk);
912 err = arch_dup_task_struct(tsk, orig);
915 * arch_dup_task_struct() clobbers the stack-related fields. Make
916 * sure they're properly initialized before using any stack-related
920 #ifdef CONFIG_VMAP_STACK
921 tsk->stack_vm_area = stack_vm_area;
923 #ifdef CONFIG_THREAD_INFO_IN_TASK
924 refcount_set(&tsk->stack_refcount, 1);
930 err = scs_prepare(tsk, node);
934 #ifdef CONFIG_SECCOMP
936 * We must handle setting up seccomp filters once we're under
937 * the sighand lock in case orig has changed between now and
938 * then. Until then, filter must be NULL to avoid messing up
939 * the usage counts on the error path calling free_task.
941 tsk->seccomp.filter = NULL;
944 setup_thread_stack(tsk, orig);
945 clear_user_return_notifier(tsk);
946 clear_tsk_need_resched(tsk);
947 set_task_stack_end_magic(tsk);
948 clear_syscall_work_syscall_user_dispatch(tsk);
950 #ifdef CONFIG_STACKPROTECTOR
951 tsk->stack_canary = get_random_canary();
953 if (orig->cpus_ptr == &orig->cpus_mask)
954 tsk->cpus_ptr = &tsk->cpus_mask;
955 dup_user_cpus_ptr(tsk, orig, node);
958 * One for the user space visible state that goes away when reaped.
959 * One for the scheduler.
961 refcount_set(&tsk->rcu_users, 2);
962 /* One for the rcu users */
963 refcount_set(&tsk->usage, 1);
964 #ifdef CONFIG_BLK_DEV_IO_TRACE
967 tsk->splice_pipe = NULL;
968 tsk->task_frag.page = NULL;
969 tsk->wake_q.next = NULL;
970 tsk->pf_io_worker = NULL;
972 account_kernel_stack(tsk, 1);
975 kmap_local_fork(tsk);
977 #ifdef CONFIG_FAULT_INJECTION
981 #ifdef CONFIG_BLK_CGROUP
982 tsk->throttle_queue = NULL;
983 tsk->use_memdelay = 0;
987 tsk->active_memcg = NULL;
992 free_thread_stack(tsk);
994 free_task_struct(tsk);
998 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
1000 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
1002 static int __init coredump_filter_setup(char *s)
1004 default_dump_filter =
1005 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
1006 MMF_DUMP_FILTER_MASK;
1010 __setup("coredump_filter=", coredump_filter_setup);
1012 #include <linux/init_task.h>
1014 static void mm_init_aio(struct mm_struct *mm)
1017 spin_lock_init(&mm->ioctx_lock);
1018 mm->ioctx_table = NULL;
1022 static __always_inline void mm_clear_owner(struct mm_struct *mm,
1023 struct task_struct *p)
1027 WRITE_ONCE(mm->owner, NULL);
1031 static void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
1038 static void mm_init_pasid(struct mm_struct *mm)
1040 #ifdef CONFIG_IOMMU_SUPPORT
1041 mm->pasid = INIT_PASID;
1045 static void mm_init_uprobes_state(struct mm_struct *mm)
1047 #ifdef CONFIG_UPROBES
1048 mm->uprobes_state.xol_area = NULL;
1052 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
1053 struct user_namespace *user_ns)
1056 mm->mm_rb = RB_ROOT;
1057 mm->vmacache_seqnum = 0;
1058 atomic_set(&mm->mm_users, 1);
1059 atomic_set(&mm->mm_count, 1);
1060 seqcount_init(&mm->write_protect_seq);
1062 INIT_LIST_HEAD(&mm->mmlist);
1063 mm->core_state = NULL;
1064 mm_pgtables_bytes_init(mm);
1067 atomic64_set(&mm->pinned_vm, 0);
1068 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
1069 spin_lock_init(&mm->page_table_lock);
1070 spin_lock_init(&mm->arg_lock);
1071 mm_init_cpumask(mm);
1073 mm_init_owner(mm, p);
1075 RCU_INIT_POINTER(mm->exe_file, NULL);
1076 mmu_notifier_subscriptions_init(mm);
1077 init_tlb_flush_pending(mm);
1078 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
1079 mm->pmd_huge_pte = NULL;
1081 mm_init_uprobes_state(mm);
1082 hugetlb_count_init(mm);
1085 mm->flags = current->mm->flags & MMF_INIT_MASK;
1086 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK;
1088 mm->flags = default_dump_filter;
1092 if (mm_alloc_pgd(mm))
1095 if (init_new_context(p, mm))
1096 goto fail_nocontext;
1098 mm->user_ns = get_user_ns(user_ns);
1109 * Allocate and initialize an mm_struct.
1111 struct mm_struct *mm_alloc(void)
1113 struct mm_struct *mm;
1119 memset(mm, 0, sizeof(*mm));
1120 return mm_init(mm, current, current_user_ns());
1123 static inline void __mmput(struct mm_struct *mm)
1125 VM_BUG_ON(atomic_read(&mm->mm_users));
1127 uprobe_clear_state(mm);
1130 khugepaged_exit(mm); /* must run before exit_mmap */
1132 mm_put_huge_zero_page(mm);
1133 set_mm_exe_file(mm, NULL);
1134 if (!list_empty(&mm->mmlist)) {
1135 spin_lock(&mmlist_lock);
1136 list_del(&mm->mmlist);
1137 spin_unlock(&mmlist_lock);
1140 module_put(mm->binfmt->module);
1145 * Decrement the use count and release all resources for an mm.
1147 void mmput(struct mm_struct *mm)
1151 if (atomic_dec_and_test(&mm->mm_users))
1154 EXPORT_SYMBOL_GPL(mmput);
1157 static void mmput_async_fn(struct work_struct *work)
1159 struct mm_struct *mm = container_of(work, struct mm_struct,
1165 void mmput_async(struct mm_struct *mm)
1167 if (atomic_dec_and_test(&mm->mm_users)) {
1168 INIT_WORK(&mm->async_put_work, mmput_async_fn);
1169 schedule_work(&mm->async_put_work);
1172 EXPORT_SYMBOL_GPL(mmput_async);
1176 * set_mm_exe_file - change a reference to the mm's executable file
1178 * This changes mm's executable file (shown as symlink /proc/[pid]/exe).
1180 * Main users are mmput() and sys_execve(). Callers prevent concurrent
1181 * invocations: in mmput() nobody alive left, in execve task is single
1184 * Can only fail if new_exe_file != NULL.
1186 int set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
1188 struct file *old_exe_file;
1191 * It is safe to dereference the exe_file without RCU as
1192 * this function is only called if nobody else can access
1193 * this mm -- see comment above for justification.
1195 old_exe_file = rcu_dereference_raw(mm->exe_file);
1199 * We expect the caller (i.e., sys_execve) to already denied
1200 * write access, so this is unlikely to fail.
1202 if (unlikely(deny_write_access(new_exe_file)))
1204 get_file(new_exe_file);
1206 rcu_assign_pointer(mm->exe_file, new_exe_file);
1208 allow_write_access(old_exe_file);
1215 * replace_mm_exe_file - replace a reference to the mm's executable file
1217 * This changes mm's executable file (shown as symlink /proc/[pid]/exe),
1218 * dealing with concurrent invocation and without grabbing the mmap lock in
1221 * Main user is sys_prctl(PR_SET_MM_MAP/EXE_FILE).
1223 int replace_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
1225 struct vm_area_struct *vma;
1226 struct file *old_exe_file;
1229 /* Forbid mm->exe_file change if old file still mapped. */
1230 old_exe_file = get_mm_exe_file(mm);
1233 for (vma = mm->mmap; vma && !ret; vma = vma->vm_next) {
1236 if (path_equal(&vma->vm_file->f_path,
1237 &old_exe_file->f_path))
1240 mmap_read_unlock(mm);
1246 /* set the new file, lockless */
1247 ret = deny_write_access(new_exe_file);
1250 get_file(new_exe_file);
1252 old_exe_file = xchg(&mm->exe_file, new_exe_file);
1255 * Don't race with dup_mmap() getting the file and disallowing
1256 * write access while someone might open the file writable.
1259 allow_write_access(old_exe_file);
1261 mmap_read_unlock(mm);
1267 * get_mm_exe_file - acquire a reference to the mm's executable file
1269 * Returns %NULL if mm has no associated executable file.
1270 * User must release file via fput().
1272 struct file *get_mm_exe_file(struct mm_struct *mm)
1274 struct file *exe_file;
1277 exe_file = rcu_dereference(mm->exe_file);
1278 if (exe_file && !get_file_rcu(exe_file))
1285 * get_task_exe_file - acquire a reference to the task's executable file
1287 * Returns %NULL if task's mm (if any) has no associated executable file or
1288 * this is a kernel thread with borrowed mm (see the comment above get_task_mm).
1289 * User must release file via fput().
1291 struct file *get_task_exe_file(struct task_struct *task)
1293 struct file *exe_file = NULL;
1294 struct mm_struct *mm;
1299 if (!(task->flags & PF_KTHREAD))
1300 exe_file = get_mm_exe_file(mm);
1307 * get_task_mm - acquire a reference to the task's mm
1309 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning
1310 * this kernel workthread has transiently adopted a user mm with use_mm,
1311 * to do its AIO) is not set and if so returns a reference to it, after
1312 * bumping up the use count. User must release the mm via mmput()
1313 * after use. Typically used by /proc and ptrace.
1315 struct mm_struct *get_task_mm(struct task_struct *task)
1317 struct mm_struct *mm;
1322 if (task->flags & PF_KTHREAD)
1330 EXPORT_SYMBOL_GPL(get_task_mm);
1332 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
1334 struct mm_struct *mm;
1337 err = down_read_killable(&task->signal->exec_update_lock);
1339 return ERR_PTR(err);
1341 mm = get_task_mm(task);
1342 if (mm && mm != current->mm &&
1343 !ptrace_may_access(task, mode)) {
1345 mm = ERR_PTR(-EACCES);
1347 up_read(&task->signal->exec_update_lock);
1352 static void complete_vfork_done(struct task_struct *tsk)
1354 struct completion *vfork;
1357 vfork = tsk->vfork_done;
1358 if (likely(vfork)) {
1359 tsk->vfork_done = NULL;
1365 static int wait_for_vfork_done(struct task_struct *child,
1366 struct completion *vfork)
1370 freezer_do_not_count();
1371 cgroup_enter_frozen();
1372 killed = wait_for_completion_killable(vfork);
1373 cgroup_leave_frozen(false);
1378 child->vfork_done = NULL;
1382 put_task_struct(child);
1386 /* Please note the differences between mmput and mm_release.
1387 * mmput is called whenever we stop holding onto a mm_struct,
1388 * error success whatever.
1390 * mm_release is called after a mm_struct has been removed
1391 * from the current process.
1393 * This difference is important for error handling, when we
1394 * only half set up a mm_struct for a new process and need to restore
1395 * the old one. Because we mmput the new mm_struct before
1396 * restoring the old one. . .
1397 * Eric Biederman 10 January 1998
1399 static void mm_release(struct task_struct *tsk, struct mm_struct *mm)
1401 uprobe_free_utask(tsk);
1403 /* Get rid of any cached register state */
1404 deactivate_mm(tsk, mm);
1407 * Signal userspace if we're not exiting with a core dump
1408 * because we want to leave the value intact for debugging
1411 if (tsk->clear_child_tid) {
1412 if (!(tsk->signal->flags & SIGNAL_GROUP_COREDUMP) &&
1413 atomic_read(&mm->mm_users) > 1) {
1415 * We don't check the error code - if userspace has
1416 * not set up a proper pointer then tough luck.
1418 put_user(0, tsk->clear_child_tid);
1419 do_futex(tsk->clear_child_tid, FUTEX_WAKE,
1420 1, NULL, NULL, 0, 0);
1422 tsk->clear_child_tid = NULL;
1426 * All done, finally we can wake up parent and return this mm to him.
1427 * Also kthread_stop() uses this completion for synchronization.
1429 if (tsk->vfork_done)
1430 complete_vfork_done(tsk);
1433 void exit_mm_release(struct task_struct *tsk, struct mm_struct *mm)
1435 futex_exit_release(tsk);
1436 mm_release(tsk, mm);
1439 void exec_mm_release(struct task_struct *tsk, struct mm_struct *mm)
1441 futex_exec_release(tsk);
1442 mm_release(tsk, mm);
1446 * dup_mm() - duplicates an existing mm structure
1447 * @tsk: the task_struct with which the new mm will be associated.
1448 * @oldmm: the mm to duplicate.
1450 * Allocates a new mm structure and duplicates the provided @oldmm structure
1453 * Return: the duplicated mm or NULL on failure.
1455 static struct mm_struct *dup_mm(struct task_struct *tsk,
1456 struct mm_struct *oldmm)
1458 struct mm_struct *mm;
1465 memcpy(mm, oldmm, sizeof(*mm));
1467 if (!mm_init(mm, tsk, mm->user_ns))
1470 err = dup_mmap(mm, oldmm);
1474 mm->hiwater_rss = get_mm_rss(mm);
1475 mm->hiwater_vm = mm->total_vm;
1477 if (mm->binfmt && !try_module_get(mm->binfmt->module))
1483 /* don't put binfmt in mmput, we haven't got module yet */
1485 mm_init_owner(mm, NULL);
1492 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
1494 struct mm_struct *mm, *oldmm;
1496 tsk->min_flt = tsk->maj_flt = 0;
1497 tsk->nvcsw = tsk->nivcsw = 0;
1498 #ifdef CONFIG_DETECT_HUNG_TASK
1499 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
1500 tsk->last_switch_time = 0;
1504 tsk->active_mm = NULL;
1507 * Are we cloning a kernel thread?
1509 * We need to steal a active VM for that..
1511 oldmm = current->mm;
1515 /* initialize the new vmacache entries */
1516 vmacache_flush(tsk);
1518 if (clone_flags & CLONE_VM) {
1522 mm = dup_mm(tsk, current->mm);
1528 tsk->active_mm = mm;
1532 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
1534 struct fs_struct *fs = current->fs;
1535 if (clone_flags & CLONE_FS) {
1536 /* tsk->fs is already what we want */
1537 spin_lock(&fs->lock);
1539 spin_unlock(&fs->lock);
1543 spin_unlock(&fs->lock);
1546 tsk->fs = copy_fs_struct(fs);
1552 static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
1554 struct files_struct *oldf, *newf;
1558 * A background process may not have any files ...
1560 oldf = current->files;
1564 if (clone_flags & CLONE_FILES) {
1565 atomic_inc(&oldf->count);
1569 newf = dup_fd(oldf, NR_OPEN_MAX, &error);
1579 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
1582 struct io_context *ioc = current->io_context;
1583 struct io_context *new_ioc;
1588 * Share io context with parent, if CLONE_IO is set
1590 if (clone_flags & CLONE_IO) {
1592 tsk->io_context = ioc;
1593 } else if (ioprio_valid(ioc->ioprio)) {
1594 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE);
1595 if (unlikely(!new_ioc))
1598 new_ioc->ioprio = ioc->ioprio;
1599 put_io_context(new_ioc);
1605 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
1607 struct sighand_struct *sig;
1609 if (clone_flags & CLONE_SIGHAND) {
1610 refcount_inc(¤t->sighand->count);
1613 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1614 RCU_INIT_POINTER(tsk->sighand, sig);
1618 refcount_set(&sig->count, 1);
1619 spin_lock_irq(¤t->sighand->siglock);
1620 memcpy(sig->action, current->sighand->action, sizeof(sig->action));
1621 spin_unlock_irq(¤t->sighand->siglock);
1623 /* Reset all signal handler not set to SIG_IGN to SIG_DFL. */
1624 if (clone_flags & CLONE_CLEAR_SIGHAND)
1625 flush_signal_handlers(tsk, 0);
1630 void __cleanup_sighand(struct sighand_struct *sighand)
1632 if (refcount_dec_and_test(&sighand->count)) {
1633 signalfd_cleanup(sighand);
1635 * sighand_cachep is SLAB_TYPESAFE_BY_RCU so we can free it
1636 * without an RCU grace period, see __lock_task_sighand().
1638 kmem_cache_free(sighand_cachep, sighand);
1643 * Initialize POSIX timer handling for a thread group.
1645 static void posix_cpu_timers_init_group(struct signal_struct *sig)
1647 struct posix_cputimers *pct = &sig->posix_cputimers;
1648 unsigned long cpu_limit;
1650 cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1651 posix_cputimers_group_init(pct, cpu_limit);
1654 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
1656 struct signal_struct *sig;
1658 if (clone_flags & CLONE_THREAD)
1661 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
1666 sig->nr_threads = 1;
1667 atomic_set(&sig->live, 1);
1668 refcount_set(&sig->sigcnt, 1);
1670 /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */
1671 sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node);
1672 tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head);
1674 init_waitqueue_head(&sig->wait_chldexit);
1675 sig->curr_target = tsk;
1676 init_sigpending(&sig->shared_pending);
1677 INIT_HLIST_HEAD(&sig->multiprocess);
1678 seqlock_init(&sig->stats_lock);
1679 prev_cputime_init(&sig->prev_cputime);
1681 #ifdef CONFIG_POSIX_TIMERS
1682 INIT_LIST_HEAD(&sig->posix_timers);
1683 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1684 sig->real_timer.function = it_real_fn;
1687 task_lock(current->group_leader);
1688 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
1689 task_unlock(current->group_leader);
1691 posix_cpu_timers_init_group(sig);
1693 tty_audit_fork(sig);
1694 sched_autogroup_fork(sig);
1696 sig->oom_score_adj = current->signal->oom_score_adj;
1697 sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1699 mutex_init(&sig->cred_guard_mutex);
1700 init_rwsem(&sig->exec_update_lock);
1705 static void copy_seccomp(struct task_struct *p)
1707 #ifdef CONFIG_SECCOMP
1709 * Must be called with sighand->lock held, which is common to
1710 * all threads in the group. Holding cred_guard_mutex is not
1711 * needed because this new task is not yet running and cannot
1714 assert_spin_locked(¤t->sighand->siglock);
1716 /* Ref-count the new filter user, and assign it. */
1717 get_seccomp_filter(current);
1718 p->seccomp = current->seccomp;
1721 * Explicitly enable no_new_privs here in case it got set
1722 * between the task_struct being duplicated and holding the
1723 * sighand lock. The seccomp state and nnp must be in sync.
1725 if (task_no_new_privs(current))
1726 task_set_no_new_privs(p);
1729 * If the parent gained a seccomp mode after copying thread
1730 * flags and between before we held the sighand lock, we have
1731 * to manually enable the seccomp thread flag here.
1733 if (p->seccomp.mode != SECCOMP_MODE_DISABLED)
1734 set_task_syscall_work(p, SECCOMP);
1738 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1740 current->clear_child_tid = tidptr;
1742 return task_pid_vnr(current);
1745 static void rt_mutex_init_task(struct task_struct *p)
1747 raw_spin_lock_init(&p->pi_lock);
1748 #ifdef CONFIG_RT_MUTEXES
1749 p->pi_waiters = RB_ROOT_CACHED;
1750 p->pi_top_task = NULL;
1751 p->pi_blocked_on = NULL;
1755 static inline void init_task_pid_links(struct task_struct *task)
1759 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type)
1760 INIT_HLIST_NODE(&task->pid_links[type]);
1764 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid)
1766 if (type == PIDTYPE_PID)
1767 task->thread_pid = pid;
1769 task->signal->pids[type] = pid;
1772 static inline void rcu_copy_process(struct task_struct *p)
1774 #ifdef CONFIG_PREEMPT_RCU
1775 p->rcu_read_lock_nesting = 0;
1776 p->rcu_read_unlock_special.s = 0;
1777 p->rcu_blocked_node = NULL;
1778 INIT_LIST_HEAD(&p->rcu_node_entry);
1779 #endif /* #ifdef CONFIG_PREEMPT_RCU */
1780 #ifdef CONFIG_TASKS_RCU
1781 p->rcu_tasks_holdout = false;
1782 INIT_LIST_HEAD(&p->rcu_tasks_holdout_list);
1783 p->rcu_tasks_idle_cpu = -1;
1784 #endif /* #ifdef CONFIG_TASKS_RCU */
1785 #ifdef CONFIG_TASKS_TRACE_RCU
1786 p->trc_reader_nesting = 0;
1787 p->trc_reader_special.s = 0;
1788 INIT_LIST_HEAD(&p->trc_holdout_list);
1789 #endif /* #ifdef CONFIG_TASKS_TRACE_RCU */
1792 struct pid *pidfd_pid(const struct file *file)
1794 if (file->f_op == &pidfd_fops)
1795 return file->private_data;
1797 return ERR_PTR(-EBADF);
1800 static int pidfd_release(struct inode *inode, struct file *file)
1802 struct pid *pid = file->private_data;
1804 file->private_data = NULL;
1809 #ifdef CONFIG_PROC_FS
1811 * pidfd_show_fdinfo - print information about a pidfd
1812 * @m: proc fdinfo file
1813 * @f: file referencing a pidfd
1816 * This function will print the pid that a given pidfd refers to in the
1817 * pid namespace of the procfs instance.
1818 * If the pid namespace of the process is not a descendant of the pid
1819 * namespace of the procfs instance 0 will be shown as its pid. This is
1820 * similar to calling getppid() on a process whose parent is outside of
1821 * its pid namespace.
1824 * If pid namespaces are supported then this function will also print
1825 * the pid of a given pidfd refers to for all descendant pid namespaces
1826 * starting from the current pid namespace of the instance, i.e. the
1827 * Pid field and the first entry in the NSpid field will be identical.
1828 * If the pid namespace of the process is not a descendant of the pid
1829 * namespace of the procfs instance 0 will be shown as its first NSpid
1830 * entry and no others will be shown.
1831 * Note that this differs from the Pid and NSpid fields in
1832 * /proc/<pid>/status where Pid and NSpid are always shown relative to
1833 * the pid namespace of the procfs instance. The difference becomes
1834 * obvious when sending around a pidfd between pid namespaces from a
1835 * different branch of the tree, i.e. where no ancestral relation is
1836 * present between the pid namespaces:
1837 * - create two new pid namespaces ns1 and ns2 in the initial pid
1838 * namespace (also take care to create new mount namespaces in the
1839 * new pid namespace and mount procfs)
1840 * - create a process with a pidfd in ns1
1841 * - send pidfd from ns1 to ns2
1842 * - read /proc/self/fdinfo/<pidfd> and observe that both Pid and NSpid
1843 * have exactly one entry, which is 0
1845 static void pidfd_show_fdinfo(struct seq_file *m, struct file *f)
1847 struct pid *pid = f->private_data;
1848 struct pid_namespace *ns;
1851 if (likely(pid_has_task(pid, PIDTYPE_PID))) {
1852 ns = proc_pid_ns(file_inode(m->file)->i_sb);
1853 nr = pid_nr_ns(pid, ns);
1856 seq_put_decimal_ll(m, "Pid:\t", nr);
1858 #ifdef CONFIG_PID_NS
1859 seq_put_decimal_ll(m, "\nNSpid:\t", nr);
1863 /* If nr is non-zero it means that 'pid' is valid and that
1864 * ns, i.e. the pid namespace associated with the procfs
1865 * instance, is in the pid namespace hierarchy of pid.
1866 * Start at one below the already printed level.
1868 for (i = ns->level + 1; i <= pid->level; i++)
1869 seq_put_decimal_ll(m, "\t", pid->numbers[i].nr);
1877 * Poll support for process exit notification.
1879 static __poll_t pidfd_poll(struct file *file, struct poll_table_struct *pts)
1881 struct pid *pid = file->private_data;
1882 __poll_t poll_flags = 0;
1884 poll_wait(file, &pid->wait_pidfd, pts);
1887 * Inform pollers only when the whole thread group exits.
1888 * If the thread group leader exits before all other threads in the
1889 * group, then poll(2) should block, similar to the wait(2) family.
1891 if (thread_group_exited(pid))
1892 poll_flags = EPOLLIN | EPOLLRDNORM;
1897 const struct file_operations pidfd_fops = {
1898 .release = pidfd_release,
1900 #ifdef CONFIG_PROC_FS
1901 .show_fdinfo = pidfd_show_fdinfo,
1905 static void __delayed_free_task(struct rcu_head *rhp)
1907 struct task_struct *tsk = container_of(rhp, struct task_struct, rcu);
1912 static __always_inline void delayed_free_task(struct task_struct *tsk)
1914 if (IS_ENABLED(CONFIG_MEMCG))
1915 call_rcu(&tsk->rcu, __delayed_free_task);
1920 static void copy_oom_score_adj(u64 clone_flags, struct task_struct *tsk)
1922 /* Skip if kernel thread */
1926 /* Skip if spawning a thread or using vfork */
1927 if ((clone_flags & (CLONE_VM | CLONE_THREAD | CLONE_VFORK)) != CLONE_VM)
1930 /* We need to synchronize with __set_oom_adj */
1931 mutex_lock(&oom_adj_mutex);
1932 set_bit(MMF_MULTIPROCESS, &tsk->mm->flags);
1933 /* Update the values in case they were changed after copy_signal */
1934 tsk->signal->oom_score_adj = current->signal->oom_score_adj;
1935 tsk->signal->oom_score_adj_min = current->signal->oom_score_adj_min;
1936 mutex_unlock(&oom_adj_mutex);
1940 * This creates a new process as a copy of the old one,
1941 * but does not actually start it yet.
1943 * It copies the registers, and all the appropriate
1944 * parts of the process environment (as per the clone
1945 * flags). The actual kick-off is left to the caller.
1947 static __latent_entropy struct task_struct *copy_process(
1951 struct kernel_clone_args *args)
1953 int pidfd = -1, retval;
1954 struct task_struct *p;
1955 struct multiprocess_signals delayed;
1956 struct file *pidfile = NULL;
1957 u64 clone_flags = args->flags;
1958 struct nsproxy *nsp = current->nsproxy;
1961 * Don't allow sharing the root directory with processes in a different
1964 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1965 return ERR_PTR(-EINVAL);
1967 if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS))
1968 return ERR_PTR(-EINVAL);
1971 * Thread groups must share signals as well, and detached threads
1972 * can only be started up within the thread group.
1974 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1975 return ERR_PTR(-EINVAL);
1978 * Shared signal handlers imply shared VM. By way of the above,
1979 * thread groups also imply shared VM. Blocking this case allows
1980 * for various simplifications in other code.
1982 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1983 return ERR_PTR(-EINVAL);
1986 * Siblings of global init remain as zombies on exit since they are
1987 * not reaped by their parent (swapper). To solve this and to avoid
1988 * multi-rooted process trees, prevent global and container-inits
1989 * from creating siblings.
1991 if ((clone_flags & CLONE_PARENT) &&
1992 current->signal->flags & SIGNAL_UNKILLABLE)
1993 return ERR_PTR(-EINVAL);
1996 * If the new process will be in a different pid or user namespace
1997 * do not allow it to share a thread group with the forking task.
1999 if (clone_flags & CLONE_THREAD) {
2000 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) ||
2001 (task_active_pid_ns(current) != nsp->pid_ns_for_children))
2002 return ERR_PTR(-EINVAL);
2006 * If the new process will be in a different time namespace
2007 * do not allow it to share VM or a thread group with the forking task.
2009 if (clone_flags & (CLONE_THREAD | CLONE_VM)) {
2010 if (nsp->time_ns != nsp->time_ns_for_children)
2011 return ERR_PTR(-EINVAL);
2014 if (clone_flags & CLONE_PIDFD) {
2016 * - CLONE_DETACHED is blocked so that we can potentially
2017 * reuse it later for CLONE_PIDFD.
2018 * - CLONE_THREAD is blocked until someone really needs it.
2020 if (clone_flags & (CLONE_DETACHED | CLONE_THREAD))
2021 return ERR_PTR(-EINVAL);
2025 * Force any signals received before this point to be delivered
2026 * before the fork happens. Collect up signals sent to multiple
2027 * processes that happen during the fork and delay them so that
2028 * they appear to happen after the fork.
2030 sigemptyset(&delayed.signal);
2031 INIT_HLIST_NODE(&delayed.node);
2033 spin_lock_irq(¤t->sighand->siglock);
2034 if (!(clone_flags & CLONE_THREAD))
2035 hlist_add_head(&delayed.node, ¤t->signal->multiprocess);
2036 recalc_sigpending();
2037 spin_unlock_irq(¤t->sighand->siglock);
2038 retval = -ERESTARTNOINTR;
2039 if (task_sigpending(current))
2043 p = dup_task_struct(current, node);
2046 if (args->io_thread) {
2048 * Mark us an IO worker, and block any signal that isn't
2051 p->flags |= PF_IO_WORKER;
2052 siginitsetinv(&p->blocked, sigmask(SIGKILL)|sigmask(SIGSTOP));
2056 * This _must_ happen before we call free_task(), i.e. before we jump
2057 * to any of the bad_fork_* labels. This is to avoid freeing
2058 * p->set_child_tid which is (ab)used as a kthread's data pointer for
2059 * kernel threads (PF_KTHREAD).
2061 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? args->child_tid : NULL;
2063 * Clear TID on mm_release()?
2065 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? args->child_tid : NULL;
2067 ftrace_graph_init_task(p);
2069 rt_mutex_init_task(p);
2071 lockdep_assert_irqs_enabled();
2072 #ifdef CONFIG_PROVE_LOCKING
2073 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
2075 retval = copy_creds(p, clone_flags);
2080 if (is_ucounts_overlimit(task_ucounts(p), UCOUNT_RLIMIT_NPROC, rlimit(RLIMIT_NPROC))) {
2081 if (p->real_cred->user != INIT_USER &&
2082 !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
2083 goto bad_fork_cleanup_count;
2085 current->flags &= ~PF_NPROC_EXCEEDED;
2088 * If multiple threads are within copy_process(), then this check
2089 * triggers too late. This doesn't hurt, the check is only there
2090 * to stop root fork bombs.
2093 if (data_race(nr_threads >= max_threads))
2094 goto bad_fork_cleanup_count;
2096 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */
2097 p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER | PF_IDLE | PF_NO_SETAFFINITY);
2098 p->flags |= PF_FORKNOEXEC;
2099 INIT_LIST_HEAD(&p->children);
2100 INIT_LIST_HEAD(&p->sibling);
2101 rcu_copy_process(p);
2102 p->vfork_done = NULL;
2103 spin_lock_init(&p->alloc_lock);
2105 init_sigpending(&p->pending);
2107 p->utime = p->stime = p->gtime = 0;
2108 #ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
2109 p->utimescaled = p->stimescaled = 0;
2111 prev_cputime_init(&p->prev_cputime);
2113 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
2114 seqcount_init(&p->vtime.seqcount);
2115 p->vtime.starttime = 0;
2116 p->vtime.state = VTIME_INACTIVE;
2119 #ifdef CONFIG_IO_URING
2123 #if defined(SPLIT_RSS_COUNTING)
2124 memset(&p->rss_stat, 0, sizeof(p->rss_stat));
2127 p->default_timer_slack_ns = current->timer_slack_ns;
2133 task_io_accounting_init(&p->ioac);
2134 acct_clear_integrals(p);
2136 posix_cputimers_init(&p->posix_cputimers);
2138 p->io_context = NULL;
2139 audit_set_context(p, NULL);
2142 p->mempolicy = mpol_dup(p->mempolicy);
2143 if (IS_ERR(p->mempolicy)) {
2144 retval = PTR_ERR(p->mempolicy);
2145 p->mempolicy = NULL;
2146 goto bad_fork_cleanup_threadgroup_lock;
2149 #ifdef CONFIG_CPUSETS
2150 p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
2151 p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
2152 seqcount_spinlock_init(&p->mems_allowed_seq, &p->alloc_lock);
2154 #ifdef CONFIG_TRACE_IRQFLAGS
2155 memset(&p->irqtrace, 0, sizeof(p->irqtrace));
2156 p->irqtrace.hardirq_disable_ip = _THIS_IP_;
2157 p->irqtrace.softirq_enable_ip = _THIS_IP_;
2158 p->softirqs_enabled = 1;
2159 p->softirq_context = 0;
2162 p->pagefault_disabled = 0;
2164 #ifdef CONFIG_LOCKDEP
2165 lockdep_init_task(p);
2168 #ifdef CONFIG_DEBUG_MUTEXES
2169 p->blocked_on = NULL; /* not blocked yet */
2171 #ifdef CONFIG_BCACHE
2172 p->sequential_io = 0;
2173 p->sequential_io_avg = 0;
2175 #ifdef CONFIG_BPF_SYSCALL
2176 RCU_INIT_POINTER(p->bpf_storage, NULL);
2180 /* Perform scheduler related setup. Assign this task to a CPU. */
2181 retval = sched_fork(clone_flags, p);
2183 goto bad_fork_cleanup_policy;
2185 retval = perf_event_init_task(p, clone_flags);
2187 goto bad_fork_cleanup_policy;
2188 retval = audit_alloc(p);
2190 goto bad_fork_cleanup_perf;
2191 /* copy all the process information */
2193 retval = security_task_alloc(p, clone_flags);
2195 goto bad_fork_cleanup_audit;
2196 retval = copy_semundo(clone_flags, p);
2198 goto bad_fork_cleanup_security;
2199 retval = copy_files(clone_flags, p);
2201 goto bad_fork_cleanup_semundo;
2202 retval = copy_fs(clone_flags, p);
2204 goto bad_fork_cleanup_files;
2205 retval = copy_sighand(clone_flags, p);
2207 goto bad_fork_cleanup_fs;
2208 retval = copy_signal(clone_flags, p);
2210 goto bad_fork_cleanup_sighand;
2211 retval = copy_mm(clone_flags, p);
2213 goto bad_fork_cleanup_signal;
2214 retval = copy_namespaces(clone_flags, p);
2216 goto bad_fork_cleanup_mm;
2217 retval = copy_io(clone_flags, p);
2219 goto bad_fork_cleanup_namespaces;
2220 retval = copy_thread(clone_flags, args->stack, args->stack_size, p, args->tls);
2222 goto bad_fork_cleanup_io;
2224 stackleak_task_init(p);
2226 if (pid != &init_struct_pid) {
2227 pid = alloc_pid(p->nsproxy->pid_ns_for_children, args->set_tid,
2228 args->set_tid_size);
2230 retval = PTR_ERR(pid);
2231 goto bad_fork_cleanup_thread;
2236 * This has to happen after we've potentially unshared the file
2237 * descriptor table (so that the pidfd doesn't leak into the child
2238 * if the fd table isn't shared).
2240 if (clone_flags & CLONE_PIDFD) {
2241 retval = get_unused_fd_flags(O_RDWR | O_CLOEXEC);
2243 goto bad_fork_free_pid;
2247 pidfile = anon_inode_getfile("[pidfd]", &pidfd_fops, pid,
2248 O_RDWR | O_CLOEXEC);
2249 if (IS_ERR(pidfile)) {
2250 put_unused_fd(pidfd);
2251 retval = PTR_ERR(pidfile);
2252 goto bad_fork_free_pid;
2254 get_pid(pid); /* held by pidfile now */
2256 retval = put_user(pidfd, args->pidfd);
2258 goto bad_fork_put_pidfd;
2267 * sigaltstack should be cleared when sharing the same VM
2269 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
2273 * Syscall tracing and stepping should be turned off in the
2274 * child regardless of CLONE_PTRACE.
2276 user_disable_single_step(p);
2277 clear_task_syscall_work(p, SYSCALL_TRACE);
2278 #if defined(CONFIG_GENERIC_ENTRY) || defined(TIF_SYSCALL_EMU)
2279 clear_task_syscall_work(p, SYSCALL_EMU);
2281 clear_tsk_latency_tracing(p);
2283 /* ok, now we should be set up.. */
2284 p->pid = pid_nr(pid);
2285 if (clone_flags & CLONE_THREAD) {
2286 p->group_leader = current->group_leader;
2287 p->tgid = current->tgid;
2289 p->group_leader = p;
2294 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
2295 p->dirty_paused_when = 0;
2297 p->pdeath_signal = 0;
2298 INIT_LIST_HEAD(&p->thread_group);
2299 p->task_works = NULL;
2300 clear_posix_cputimers_work(p);
2302 #ifdef CONFIG_KRETPROBES
2303 p->kretprobe_instances.first = NULL;
2307 * Ensure that the cgroup subsystem policies allow the new process to be
2308 * forked. It should be noted that the new process's css_set can be changed
2309 * between here and cgroup_post_fork() if an organisation operation is in
2312 retval = cgroup_can_fork(p, args);
2314 goto bad_fork_put_pidfd;
2317 * Now that the cgroups are pinned, re-clone the parent cgroup and put
2318 * the new task on the correct runqueue. All this *before* the task
2321 * This isn't part of ->can_fork() because while the re-cloning is
2322 * cgroup specific, it unconditionally needs to place the task on a
2325 sched_cgroup_fork(p, args);
2328 * From this point on we must avoid any synchronous user-space
2329 * communication until we take the tasklist-lock. In particular, we do
2330 * not want user-space to be able to predict the process start-time by
2331 * stalling fork(2) after we recorded the start_time but before it is
2332 * visible to the system.
2335 p->start_time = ktime_get_ns();
2336 p->start_boottime = ktime_get_boottime_ns();
2339 * Make it visible to the rest of the system, but dont wake it up yet.
2340 * Need tasklist lock for parent etc handling!
2342 write_lock_irq(&tasklist_lock);
2344 /* CLONE_PARENT re-uses the old parent */
2345 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
2346 p->real_parent = current->real_parent;
2347 p->parent_exec_id = current->parent_exec_id;
2348 if (clone_flags & CLONE_THREAD)
2349 p->exit_signal = -1;
2351 p->exit_signal = current->group_leader->exit_signal;
2353 p->real_parent = current;
2354 p->parent_exec_id = current->self_exec_id;
2355 p->exit_signal = args->exit_signal;
2358 klp_copy_process(p);
2362 spin_lock(¤t->sighand->siglock);
2365 * Copy seccomp details explicitly here, in case they were changed
2366 * before holding sighand lock.
2370 rseq_fork(p, clone_flags);
2372 /* Don't start children in a dying pid namespace */
2373 if (unlikely(!(ns_of_pid(pid)->pid_allocated & PIDNS_ADDING))) {
2375 goto bad_fork_cancel_cgroup;
2378 /* Let kill terminate clone/fork in the middle */
2379 if (fatal_signal_pending(current)) {
2381 goto bad_fork_cancel_cgroup;
2384 init_task_pid_links(p);
2385 if (likely(p->pid)) {
2386 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
2388 init_task_pid(p, PIDTYPE_PID, pid);
2389 if (thread_group_leader(p)) {
2390 init_task_pid(p, PIDTYPE_TGID, pid);
2391 init_task_pid(p, PIDTYPE_PGID, task_pgrp(current));
2392 init_task_pid(p, PIDTYPE_SID, task_session(current));
2394 if (is_child_reaper(pid)) {
2395 ns_of_pid(pid)->child_reaper = p;
2396 p->signal->flags |= SIGNAL_UNKILLABLE;
2398 p->signal->shared_pending.signal = delayed.signal;
2399 p->signal->tty = tty_kref_get(current->signal->tty);
2401 * Inherit has_child_subreaper flag under the same
2402 * tasklist_lock with adding child to the process tree
2403 * for propagate_has_child_subreaper optimization.
2405 p->signal->has_child_subreaper = p->real_parent->signal->has_child_subreaper ||
2406 p->real_parent->signal->is_child_subreaper;
2407 list_add_tail(&p->sibling, &p->real_parent->children);
2408 list_add_tail_rcu(&p->tasks, &init_task.tasks);
2409 attach_pid(p, PIDTYPE_TGID);
2410 attach_pid(p, PIDTYPE_PGID);
2411 attach_pid(p, PIDTYPE_SID);
2412 __this_cpu_inc(process_counts);
2414 current->signal->nr_threads++;
2415 atomic_inc(¤t->signal->live);
2416 refcount_inc(¤t->signal->sigcnt);
2417 task_join_group_stop(p);
2418 list_add_tail_rcu(&p->thread_group,
2419 &p->group_leader->thread_group);
2420 list_add_tail_rcu(&p->thread_node,
2421 &p->signal->thread_head);
2423 attach_pid(p, PIDTYPE_PID);
2427 hlist_del_init(&delayed.node);
2428 spin_unlock(¤t->sighand->siglock);
2429 syscall_tracepoint_update(p);
2430 write_unlock_irq(&tasklist_lock);
2433 fd_install(pidfd, pidfile);
2435 proc_fork_connector(p);
2437 cgroup_post_fork(p, args);
2440 trace_task_newtask(p, clone_flags);
2441 uprobe_copy_process(p, clone_flags);
2443 copy_oom_score_adj(clone_flags, p);
2447 bad_fork_cancel_cgroup:
2449 spin_unlock(¤t->sighand->siglock);
2450 write_unlock_irq(&tasklist_lock);
2451 cgroup_cancel_fork(p, args);
2453 if (clone_flags & CLONE_PIDFD) {
2455 put_unused_fd(pidfd);
2458 if (pid != &init_struct_pid)
2460 bad_fork_cleanup_thread:
2462 bad_fork_cleanup_io:
2465 bad_fork_cleanup_namespaces:
2466 exit_task_namespaces(p);
2467 bad_fork_cleanup_mm:
2469 mm_clear_owner(p->mm, p);
2472 bad_fork_cleanup_signal:
2473 if (!(clone_flags & CLONE_THREAD))
2474 free_signal_struct(p->signal);
2475 bad_fork_cleanup_sighand:
2476 __cleanup_sighand(p->sighand);
2477 bad_fork_cleanup_fs:
2478 exit_fs(p); /* blocking */
2479 bad_fork_cleanup_files:
2480 exit_files(p); /* blocking */
2481 bad_fork_cleanup_semundo:
2483 bad_fork_cleanup_security:
2484 security_task_free(p);
2485 bad_fork_cleanup_audit:
2487 bad_fork_cleanup_perf:
2488 perf_event_free_task(p);
2489 bad_fork_cleanup_policy:
2490 lockdep_free_task(p);
2492 mpol_put(p->mempolicy);
2493 bad_fork_cleanup_threadgroup_lock:
2495 delayacct_tsk_free(p);
2496 bad_fork_cleanup_count:
2497 dec_rlimit_ucounts(task_ucounts(p), UCOUNT_RLIMIT_NPROC, 1);
2500 WRITE_ONCE(p->__state, TASK_DEAD);
2502 delayed_free_task(p);
2504 spin_lock_irq(¤t->sighand->siglock);
2505 hlist_del_init(&delayed.node);
2506 spin_unlock_irq(¤t->sighand->siglock);
2507 return ERR_PTR(retval);
2510 static inline void init_idle_pids(struct task_struct *idle)
2514 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
2515 INIT_HLIST_NODE(&idle->pid_links[type]); /* not really needed */
2516 init_task_pid(idle, type, &init_struct_pid);
2520 struct task_struct * __init fork_idle(int cpu)
2522 struct task_struct *task;
2523 struct kernel_clone_args args = {
2527 task = copy_process(&init_struct_pid, 0, cpu_to_node(cpu), &args);
2528 if (!IS_ERR(task)) {
2529 init_idle_pids(task);
2530 init_idle(task, cpu);
2536 struct mm_struct *copy_init_mm(void)
2538 return dup_mm(NULL, &init_mm);
2542 * This is like kernel_clone(), but shaved down and tailored to just
2543 * creating io_uring workers. It returns a created task, or an error pointer.
2544 * The returned task is inactive, and the caller must fire it up through
2545 * wake_up_new_task(p). All signals are blocked in the created task.
2547 struct task_struct *create_io_thread(int (*fn)(void *), void *arg, int node)
2549 unsigned long flags = CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|
2551 struct kernel_clone_args args = {
2552 .flags = ((lower_32_bits(flags) | CLONE_VM |
2553 CLONE_UNTRACED) & ~CSIGNAL),
2554 .exit_signal = (lower_32_bits(flags) & CSIGNAL),
2555 .stack = (unsigned long)fn,
2556 .stack_size = (unsigned long)arg,
2560 return copy_process(NULL, 0, node, &args);
2564 * Ok, this is the main fork-routine.
2566 * It copies the process, and if successful kick-starts
2567 * it and waits for it to finish using the VM if required.
2569 * args->exit_signal is expected to be checked for sanity by the caller.
2571 pid_t kernel_clone(struct kernel_clone_args *args)
2573 u64 clone_flags = args->flags;
2574 struct completion vfork;
2576 struct task_struct *p;
2581 * For legacy clone() calls, CLONE_PIDFD uses the parent_tid argument
2582 * to return the pidfd. Hence, CLONE_PIDFD and CLONE_PARENT_SETTID are
2583 * mutually exclusive. With clone3() CLONE_PIDFD has grown a separate
2584 * field in struct clone_args and it still doesn't make sense to have
2585 * them both point at the same memory location. Performing this check
2586 * here has the advantage that we don't need to have a separate helper
2587 * to check for legacy clone().
2589 if ((args->flags & CLONE_PIDFD) &&
2590 (args->flags & CLONE_PARENT_SETTID) &&
2591 (args->pidfd == args->parent_tid))
2595 * Determine whether and which event to report to ptracer. When
2596 * called from kernel_thread or CLONE_UNTRACED is explicitly
2597 * requested, no event is reported; otherwise, report if the event
2598 * for the type of forking is enabled.
2600 if (!(clone_flags & CLONE_UNTRACED)) {
2601 if (clone_flags & CLONE_VFORK)
2602 trace = PTRACE_EVENT_VFORK;
2603 else if (args->exit_signal != SIGCHLD)
2604 trace = PTRACE_EVENT_CLONE;
2606 trace = PTRACE_EVENT_FORK;
2608 if (likely(!ptrace_event_enabled(current, trace)))
2612 p = copy_process(NULL, trace, NUMA_NO_NODE, args);
2613 add_latent_entropy();
2619 * Do this prior waking up the new thread - the thread pointer
2620 * might get invalid after that point, if the thread exits quickly.
2622 trace_sched_process_fork(current, p);
2624 pid = get_task_pid(p, PIDTYPE_PID);
2627 if (clone_flags & CLONE_PARENT_SETTID)
2628 put_user(nr, args->parent_tid);
2630 if (clone_flags & CLONE_VFORK) {
2631 p->vfork_done = &vfork;
2632 init_completion(&vfork);
2636 wake_up_new_task(p);
2638 /* forking complete and child started to run, tell ptracer */
2639 if (unlikely(trace))
2640 ptrace_event_pid(trace, pid);
2642 if (clone_flags & CLONE_VFORK) {
2643 if (!wait_for_vfork_done(p, &vfork))
2644 ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid);
2652 * Create a kernel thread.
2654 pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
2656 struct kernel_clone_args args = {
2657 .flags = ((lower_32_bits(flags) | CLONE_VM |
2658 CLONE_UNTRACED) & ~CSIGNAL),
2659 .exit_signal = (lower_32_bits(flags) & CSIGNAL),
2660 .stack = (unsigned long)fn,
2661 .stack_size = (unsigned long)arg,
2664 return kernel_clone(&args);
2667 #ifdef __ARCH_WANT_SYS_FORK
2668 SYSCALL_DEFINE0(fork)
2671 struct kernel_clone_args args = {
2672 .exit_signal = SIGCHLD,
2675 return kernel_clone(&args);
2677 /* can not support in nommu mode */
2683 #ifdef __ARCH_WANT_SYS_VFORK
2684 SYSCALL_DEFINE0(vfork)
2686 struct kernel_clone_args args = {
2687 .flags = CLONE_VFORK | CLONE_VM,
2688 .exit_signal = SIGCHLD,
2691 return kernel_clone(&args);
2695 #ifdef __ARCH_WANT_SYS_CLONE
2696 #ifdef CONFIG_CLONE_BACKWARDS
2697 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2698 int __user *, parent_tidptr,
2700 int __user *, child_tidptr)
2701 #elif defined(CONFIG_CLONE_BACKWARDS2)
2702 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags,
2703 int __user *, parent_tidptr,
2704 int __user *, child_tidptr,
2706 #elif defined(CONFIG_CLONE_BACKWARDS3)
2707 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp,
2709 int __user *, parent_tidptr,
2710 int __user *, child_tidptr,
2713 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2714 int __user *, parent_tidptr,
2715 int __user *, child_tidptr,
2719 struct kernel_clone_args args = {
2720 .flags = (lower_32_bits(clone_flags) & ~CSIGNAL),
2721 .pidfd = parent_tidptr,
2722 .child_tid = child_tidptr,
2723 .parent_tid = parent_tidptr,
2724 .exit_signal = (lower_32_bits(clone_flags) & CSIGNAL),
2729 return kernel_clone(&args);
2733 #ifdef __ARCH_WANT_SYS_CLONE3
2735 noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs,
2736 struct clone_args __user *uargs,
2740 struct clone_args args;
2741 pid_t *kset_tid = kargs->set_tid;
2743 BUILD_BUG_ON(offsetofend(struct clone_args, tls) !=
2744 CLONE_ARGS_SIZE_VER0);
2745 BUILD_BUG_ON(offsetofend(struct clone_args, set_tid_size) !=
2746 CLONE_ARGS_SIZE_VER1);
2747 BUILD_BUG_ON(offsetofend(struct clone_args, cgroup) !=
2748 CLONE_ARGS_SIZE_VER2);
2749 BUILD_BUG_ON(sizeof(struct clone_args) != CLONE_ARGS_SIZE_VER2);
2751 if (unlikely(usize > PAGE_SIZE))
2753 if (unlikely(usize < CLONE_ARGS_SIZE_VER0))
2756 err = copy_struct_from_user(&args, sizeof(args), uargs, usize);
2760 if (unlikely(args.set_tid_size > MAX_PID_NS_LEVEL))
2763 if (unlikely(!args.set_tid && args.set_tid_size > 0))
2766 if (unlikely(args.set_tid && args.set_tid_size == 0))
2770 * Verify that higher 32bits of exit_signal are unset and that
2771 * it is a valid signal
2773 if (unlikely((args.exit_signal & ~((u64)CSIGNAL)) ||
2774 !valid_signal(args.exit_signal)))
2777 if ((args.flags & CLONE_INTO_CGROUP) &&
2778 (args.cgroup > INT_MAX || usize < CLONE_ARGS_SIZE_VER2))
2781 *kargs = (struct kernel_clone_args){
2782 .flags = args.flags,
2783 .pidfd = u64_to_user_ptr(args.pidfd),
2784 .child_tid = u64_to_user_ptr(args.child_tid),
2785 .parent_tid = u64_to_user_ptr(args.parent_tid),
2786 .exit_signal = args.exit_signal,
2787 .stack = args.stack,
2788 .stack_size = args.stack_size,
2790 .set_tid_size = args.set_tid_size,
2791 .cgroup = args.cgroup,
2795 copy_from_user(kset_tid, u64_to_user_ptr(args.set_tid),
2796 (kargs->set_tid_size * sizeof(pid_t))))
2799 kargs->set_tid = kset_tid;
2805 * clone3_stack_valid - check and prepare stack
2806 * @kargs: kernel clone args
2808 * Verify that the stack arguments userspace gave us are sane.
2809 * In addition, set the stack direction for userspace since it's easy for us to
2812 static inline bool clone3_stack_valid(struct kernel_clone_args *kargs)
2814 if (kargs->stack == 0) {
2815 if (kargs->stack_size > 0)
2818 if (kargs->stack_size == 0)
2821 if (!access_ok((void __user *)kargs->stack, kargs->stack_size))
2824 #if !defined(CONFIG_STACK_GROWSUP) && !defined(CONFIG_IA64)
2825 kargs->stack += kargs->stack_size;
2832 static bool clone3_args_valid(struct kernel_clone_args *kargs)
2834 /* Verify that no unknown flags are passed along. */
2836 ~(CLONE_LEGACY_FLAGS | CLONE_CLEAR_SIGHAND | CLONE_INTO_CGROUP))
2840 * - make the CLONE_DETACHED bit reusable for clone3
2841 * - make the CSIGNAL bits reusable for clone3
2843 if (kargs->flags & (CLONE_DETACHED | CSIGNAL))
2846 if ((kargs->flags & (CLONE_SIGHAND | CLONE_CLEAR_SIGHAND)) ==
2847 (CLONE_SIGHAND | CLONE_CLEAR_SIGHAND))
2850 if ((kargs->flags & (CLONE_THREAD | CLONE_PARENT)) &&
2854 if (!clone3_stack_valid(kargs))
2861 * clone3 - create a new process with specific properties
2862 * @uargs: argument structure
2863 * @size: size of @uargs
2865 * clone3() is the extensible successor to clone()/clone2().
2866 * It takes a struct as argument that is versioned by its size.
2868 * Return: On success, a positive PID for the child process.
2869 * On error, a negative errno number.
2871 SYSCALL_DEFINE2(clone3, struct clone_args __user *, uargs, size_t, size)
2875 struct kernel_clone_args kargs;
2876 pid_t set_tid[MAX_PID_NS_LEVEL];
2878 kargs.set_tid = set_tid;
2880 err = copy_clone_args_from_user(&kargs, uargs, size);
2884 if (!clone3_args_valid(&kargs))
2887 return kernel_clone(&kargs);
2891 void walk_process_tree(struct task_struct *top, proc_visitor visitor, void *data)
2893 struct task_struct *leader, *parent, *child;
2896 read_lock(&tasklist_lock);
2897 leader = top = top->group_leader;
2899 for_each_thread(leader, parent) {
2900 list_for_each_entry(child, &parent->children, sibling) {
2901 res = visitor(child, data);
2913 if (leader != top) {
2915 parent = child->real_parent;
2916 leader = parent->group_leader;
2920 read_unlock(&tasklist_lock);
2923 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
2924 #define ARCH_MIN_MMSTRUCT_ALIGN 0
2927 static void sighand_ctor(void *data)
2929 struct sighand_struct *sighand = data;
2931 spin_lock_init(&sighand->siglock);
2932 init_waitqueue_head(&sighand->signalfd_wqh);
2935 void __init proc_caches_init(void)
2937 unsigned int mm_size;
2939 sighand_cachep = kmem_cache_create("sighand_cache",
2940 sizeof(struct sighand_struct), 0,
2941 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_TYPESAFE_BY_RCU|
2942 SLAB_ACCOUNT, sighand_ctor);
2943 signal_cachep = kmem_cache_create("signal_cache",
2944 sizeof(struct signal_struct), 0,
2945 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2947 files_cachep = kmem_cache_create("files_cache",
2948 sizeof(struct files_struct), 0,
2949 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2951 fs_cachep = kmem_cache_create("fs_cache",
2952 sizeof(struct fs_struct), 0,
2953 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2957 * The mm_cpumask is located at the end of mm_struct, and is
2958 * dynamically sized based on the maximum CPU number this system
2959 * can have, taking hotplug into account (nr_cpu_ids).
2961 mm_size = sizeof(struct mm_struct) + cpumask_size();
2963 mm_cachep = kmem_cache_create_usercopy("mm_struct",
2964 mm_size, ARCH_MIN_MMSTRUCT_ALIGN,
2965 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2966 offsetof(struct mm_struct, saved_auxv),
2967 sizeof_field(struct mm_struct, saved_auxv),
2969 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT);
2971 nsproxy_cache_init();
2975 * Check constraints on flags passed to the unshare system call.
2977 static int check_unshare_flags(unsigned long unshare_flags)
2979 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
2980 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
2981 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET|
2982 CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP|
2986 * Not implemented, but pretend it works if there is nothing
2987 * to unshare. Note that unsharing the address space or the
2988 * signal handlers also need to unshare the signal queues (aka
2991 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
2992 if (!thread_group_empty(current))
2995 if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) {
2996 if (refcount_read(¤t->sighand->count) > 1)
2999 if (unshare_flags & CLONE_VM) {
3000 if (!current_is_single_threaded())
3008 * Unshare the filesystem structure if it is being shared
3010 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
3012 struct fs_struct *fs = current->fs;
3014 if (!(unshare_flags & CLONE_FS) || !fs)
3017 /* don't need lock here; in the worst case we'll do useless copy */
3021 *new_fsp = copy_fs_struct(fs);
3029 * Unshare file descriptor table if it is being shared
3031 int unshare_fd(unsigned long unshare_flags, unsigned int max_fds,
3032 struct files_struct **new_fdp)
3034 struct files_struct *fd = current->files;
3037 if ((unshare_flags & CLONE_FILES) &&
3038 (fd && atomic_read(&fd->count) > 1)) {
3039 *new_fdp = dup_fd(fd, max_fds, &error);
3048 * unshare allows a process to 'unshare' part of the process
3049 * context which was originally shared using clone. copy_*
3050 * functions used by kernel_clone() cannot be used here directly
3051 * because they modify an inactive task_struct that is being
3052 * constructed. Here we are modifying the current, active,
3055 int ksys_unshare(unsigned long unshare_flags)
3057 struct fs_struct *fs, *new_fs = NULL;
3058 struct files_struct *fd, *new_fd = NULL;
3059 struct cred *new_cred = NULL;
3060 struct nsproxy *new_nsproxy = NULL;
3065 * If unsharing a user namespace must also unshare the thread group
3066 * and unshare the filesystem root and working directories.
3068 if (unshare_flags & CLONE_NEWUSER)
3069 unshare_flags |= CLONE_THREAD | CLONE_FS;
3071 * If unsharing vm, must also unshare signal handlers.
3073 if (unshare_flags & CLONE_VM)
3074 unshare_flags |= CLONE_SIGHAND;
3076 * If unsharing a signal handlers, must also unshare the signal queues.
3078 if (unshare_flags & CLONE_SIGHAND)
3079 unshare_flags |= CLONE_THREAD;
3081 * If unsharing namespace, must also unshare filesystem information.
3083 if (unshare_flags & CLONE_NEWNS)
3084 unshare_flags |= CLONE_FS;
3086 err = check_unshare_flags(unshare_flags);
3088 goto bad_unshare_out;
3090 * CLONE_NEWIPC must also detach from the undolist: after switching
3091 * to a new ipc namespace, the semaphore arrays from the old
3092 * namespace are unreachable.
3094 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
3096 err = unshare_fs(unshare_flags, &new_fs);
3098 goto bad_unshare_out;
3099 err = unshare_fd(unshare_flags, NR_OPEN_MAX, &new_fd);
3101 goto bad_unshare_cleanup_fs;
3102 err = unshare_userns(unshare_flags, &new_cred);
3104 goto bad_unshare_cleanup_fd;
3105 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
3108 goto bad_unshare_cleanup_cred;
3111 err = set_cred_ucounts(new_cred);
3113 goto bad_unshare_cleanup_cred;
3116 if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
3119 * CLONE_SYSVSEM is equivalent to sys_exit().
3123 if (unshare_flags & CLONE_NEWIPC) {
3124 /* Orphan segments in old ns (see sem above). */
3126 shm_init_task(current);
3130 switch_task_namespaces(current, new_nsproxy);
3136 spin_lock(&fs->lock);
3137 current->fs = new_fs;
3142 spin_unlock(&fs->lock);
3146 fd = current->files;
3147 current->files = new_fd;
3151 task_unlock(current);
3154 /* Install the new user namespace */
3155 commit_creds(new_cred);
3160 perf_event_namespaces(current);
3162 bad_unshare_cleanup_cred:
3165 bad_unshare_cleanup_fd:
3167 put_files_struct(new_fd);
3169 bad_unshare_cleanup_fs:
3171 free_fs_struct(new_fs);
3177 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
3179 return ksys_unshare(unshare_flags);
3183 * Helper to unshare the files of the current task.
3184 * We don't want to expose copy_files internals to
3185 * the exec layer of the kernel.
3188 int unshare_files(void)
3190 struct task_struct *task = current;
3191 struct files_struct *old, *copy = NULL;
3194 error = unshare_fd(CLONE_FILES, NR_OPEN_MAX, ©);
3202 put_files_struct(old);
3206 int sysctl_max_threads(struct ctl_table *table, int write,
3207 void *buffer, size_t *lenp, loff_t *ppos)
3211 int threads = max_threads;
3213 int max = MAX_THREADS;
3220 ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
3224 max_threads = threads;