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/fs_struct.h>
80 #include <linux/magic.h>
81 #include <linux/perf_event.h>
82 #include <linux/posix-timers.h>
83 #include <linux/user-return-notifier.h>
84 #include <linux/oom.h>
85 #include <linux/khugepaged.h>
86 #include <linux/signalfd.h>
87 #include <linux/uprobes.h>
88 #include <linux/aio.h>
89 #include <linux/compiler.h>
90 #include <linux/sysctl.h>
91 #include <linux/kcov.h>
92 #include <linux/livepatch.h>
93 #include <linux/thread_info.h>
94 #include <linux/stackleak.h>
95 #include <linux/kasan.h>
96 #include <linux/scs.h>
97 #include <linux/io_uring.h>
98 #include <linux/bpf.h>
100 #include <asm/pgalloc.h>
101 #include <linux/uaccess.h>
102 #include <asm/mmu_context.h>
103 #include <asm/cacheflush.h>
104 #include <asm/tlbflush.h>
106 #include <trace/events/sched.h>
108 #define CREATE_TRACE_POINTS
109 #include <trace/events/task.h>
112 * Minimum number of threads to boot the kernel
114 #define MIN_THREADS 20
117 * Maximum number of threads
119 #define MAX_THREADS FUTEX_TID_MASK
122 * Protected counters by write_lock_irq(&tasklist_lock)
124 unsigned long total_forks; /* Handle normal Linux uptimes. */
125 int nr_threads; /* The idle threads do not count.. */
127 static int max_threads; /* tunable limit on nr_threads */
129 #define NAMED_ARRAY_INDEX(x) [x] = __stringify(x)
131 static const char * const resident_page_types[] = {
132 NAMED_ARRAY_INDEX(MM_FILEPAGES),
133 NAMED_ARRAY_INDEX(MM_ANONPAGES),
134 NAMED_ARRAY_INDEX(MM_SWAPENTS),
135 NAMED_ARRAY_INDEX(MM_SHMEMPAGES),
138 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
140 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */
142 #ifdef CONFIG_PROVE_RCU
143 int lockdep_tasklist_lock_is_held(void)
145 return lockdep_is_held(&tasklist_lock);
147 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
148 #endif /* #ifdef CONFIG_PROVE_RCU */
150 int nr_processes(void)
155 for_each_possible_cpu(cpu)
156 total += per_cpu(process_counts, cpu);
161 void __weak arch_release_task_struct(struct task_struct *tsk)
165 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
166 static struct kmem_cache *task_struct_cachep;
168 static inline struct task_struct *alloc_task_struct_node(int node)
170 return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node);
173 static inline void free_task_struct(struct task_struct *tsk)
175 kmem_cache_free(task_struct_cachep, tsk);
179 #ifndef CONFIG_ARCH_THREAD_STACK_ALLOCATOR
182 * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
183 * kmemcache based allocator.
185 # if THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK)
187 #ifdef CONFIG_VMAP_STACK
189 * vmalloc() is a bit slow, and calling vfree() enough times will force a TLB
190 * flush. Try to minimize the number of calls by caching stacks.
192 #define NR_CACHED_STACKS 2
193 static DEFINE_PER_CPU(struct vm_struct *, cached_stacks[NR_CACHED_STACKS]);
195 static int free_vm_stack_cache(unsigned int cpu)
197 struct vm_struct **cached_vm_stacks = per_cpu_ptr(cached_stacks, cpu);
200 for (i = 0; i < NR_CACHED_STACKS; i++) {
201 struct vm_struct *vm_stack = cached_vm_stacks[i];
206 vfree(vm_stack->addr);
207 cached_vm_stacks[i] = NULL;
214 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node)
216 #ifdef CONFIG_VMAP_STACK
220 for (i = 0; i < NR_CACHED_STACKS; i++) {
223 s = this_cpu_xchg(cached_stacks[i], NULL);
228 /* Mark stack accessible for KASAN. */
229 kasan_unpoison_range(s->addr, THREAD_SIZE);
231 /* Clear stale pointers from reused stack. */
232 memset(s->addr, 0, THREAD_SIZE);
234 tsk->stack_vm_area = s;
235 tsk->stack = s->addr;
240 * Allocated stacks are cached and later reused by new threads,
241 * so memcg accounting is performed manually on assigning/releasing
242 * stacks to tasks. Drop __GFP_ACCOUNT.
244 stack = __vmalloc_node_range(THREAD_SIZE, THREAD_ALIGN,
245 VMALLOC_START, VMALLOC_END,
246 THREADINFO_GFP & ~__GFP_ACCOUNT,
248 0, node, __builtin_return_address(0));
251 * We can't call find_vm_area() in interrupt context, and
252 * free_thread_stack() can be called in interrupt context,
253 * so cache the vm_struct.
256 tsk->stack_vm_area = find_vm_area(stack);
261 struct page *page = alloc_pages_node(node, THREADINFO_GFP,
265 tsk->stack = kasan_reset_tag(page_address(page));
272 static inline void free_thread_stack(struct task_struct *tsk)
274 #ifdef CONFIG_VMAP_STACK
275 struct vm_struct *vm = task_stack_vm_area(tsk);
280 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++)
281 memcg_kmem_uncharge_page(vm->pages[i], 0);
283 for (i = 0; i < NR_CACHED_STACKS; i++) {
284 if (this_cpu_cmpxchg(cached_stacks[i],
285 NULL, tsk->stack_vm_area) != NULL)
291 vfree_atomic(tsk->stack);
296 __free_pages(virt_to_page(tsk->stack), THREAD_SIZE_ORDER);
299 static struct kmem_cache *thread_stack_cache;
301 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk,
304 unsigned long *stack;
305 stack = kmem_cache_alloc_node(thread_stack_cache, THREADINFO_GFP, node);
306 stack = kasan_reset_tag(stack);
311 static void free_thread_stack(struct task_struct *tsk)
313 kmem_cache_free(thread_stack_cache, tsk->stack);
316 void thread_stack_cache_init(void)
318 thread_stack_cache = kmem_cache_create_usercopy("thread_stack",
319 THREAD_SIZE, THREAD_SIZE, 0, 0,
321 BUG_ON(thread_stack_cache == NULL);
326 /* SLAB cache for signal_struct structures (tsk->signal) */
327 static struct kmem_cache *signal_cachep;
329 /* SLAB cache for sighand_struct structures (tsk->sighand) */
330 struct kmem_cache *sighand_cachep;
332 /* SLAB cache for files_struct structures (tsk->files) */
333 struct kmem_cache *files_cachep;
335 /* SLAB cache for fs_struct structures (tsk->fs) */
336 struct kmem_cache *fs_cachep;
338 /* SLAB cache for vm_area_struct structures */
339 static struct kmem_cache *vm_area_cachep;
341 /* SLAB cache for mm_struct structures (tsk->mm) */
342 static struct kmem_cache *mm_cachep;
344 struct vm_area_struct *vm_area_alloc(struct mm_struct *mm)
346 struct vm_area_struct *vma;
348 vma = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
354 struct vm_area_struct *vm_area_dup(struct vm_area_struct *orig)
356 struct vm_area_struct *new = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
359 ASSERT_EXCLUSIVE_WRITER(orig->vm_flags);
360 ASSERT_EXCLUSIVE_WRITER(orig->vm_file);
362 * orig->shared.rb may be modified concurrently, but the clone
363 * will be reinitialized.
365 *new = data_race(*orig);
366 INIT_LIST_HEAD(&new->anon_vma_chain);
367 new->vm_next = new->vm_prev = NULL;
372 void vm_area_free(struct vm_area_struct *vma)
374 kmem_cache_free(vm_area_cachep, vma);
377 static void account_kernel_stack(struct task_struct *tsk, int account)
379 void *stack = task_stack_page(tsk);
380 struct vm_struct *vm = task_stack_vm_area(tsk);
385 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++)
386 mod_lruvec_page_state(vm->pages[i], NR_KERNEL_STACK_KB,
387 account * (PAGE_SIZE / 1024));
389 /* All stack pages are in the same node. */
390 mod_lruvec_kmem_state(stack, NR_KERNEL_STACK_KB,
391 account * (THREAD_SIZE / 1024));
395 static int memcg_charge_kernel_stack(struct task_struct *tsk)
397 #ifdef CONFIG_VMAP_STACK
398 struct vm_struct *vm = task_stack_vm_area(tsk);
401 BUILD_BUG_ON(IS_ENABLED(CONFIG_VMAP_STACK) && PAGE_SIZE % 1024 != 0);
406 BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE);
408 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
410 * If memcg_kmem_charge_page() fails, page's
411 * memory cgroup pointer is NULL, and
412 * memcg_kmem_uncharge_page() in free_thread_stack()
413 * will ignore this page.
415 ret = memcg_kmem_charge_page(vm->pages[i], GFP_KERNEL,
425 static void release_task_stack(struct task_struct *tsk)
427 if (WARN_ON(READ_ONCE(tsk->__state) != TASK_DEAD))
428 return; /* Better to leak the stack than to free prematurely */
430 account_kernel_stack(tsk, -1);
431 free_thread_stack(tsk);
433 #ifdef CONFIG_VMAP_STACK
434 tsk->stack_vm_area = NULL;
438 #ifdef CONFIG_THREAD_INFO_IN_TASK
439 void put_task_stack(struct task_struct *tsk)
441 if (refcount_dec_and_test(&tsk->stack_refcount))
442 release_task_stack(tsk);
446 void free_task(struct task_struct *tsk)
448 release_user_cpus_ptr(tsk);
451 #ifndef CONFIG_THREAD_INFO_IN_TASK
453 * The task is finally done with both the stack and thread_info,
456 release_task_stack(tsk);
459 * If the task had a separate stack allocation, it should be gone
462 WARN_ON_ONCE(refcount_read(&tsk->stack_refcount) != 0);
464 rt_mutex_debug_task_free(tsk);
465 ftrace_graph_exit_task(tsk);
466 arch_release_task_struct(tsk);
467 if (tsk->flags & PF_KTHREAD)
468 free_kthread_struct(tsk);
469 free_task_struct(tsk);
471 EXPORT_SYMBOL(free_task);
473 static void dup_mm_exe_file(struct mm_struct *mm, struct mm_struct *oldmm)
475 struct file *exe_file;
477 exe_file = get_mm_exe_file(oldmm);
478 RCU_INIT_POINTER(mm->exe_file, exe_file);
480 * We depend on the oldmm having properly denied write access to the
483 if (exe_file && deny_write_access(exe_file))
484 pr_warn_once("deny_write_access() failed in %s\n", __func__);
488 static __latent_entropy int dup_mmap(struct mm_struct *mm,
489 struct mm_struct *oldmm)
491 struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
492 struct rb_node **rb_link, *rb_parent;
494 unsigned long charge;
497 uprobe_start_dup_mmap();
498 if (mmap_write_lock_killable(oldmm)) {
500 goto fail_uprobe_end;
502 flush_cache_dup_mm(oldmm);
503 uprobe_dup_mmap(oldmm, mm);
505 * Not linked in yet - no deadlock potential:
507 mmap_write_lock_nested(mm, SINGLE_DEPTH_NESTING);
509 /* No ordering required: file already has been exposed. */
510 dup_mm_exe_file(mm, oldmm);
512 mm->total_vm = oldmm->total_vm;
513 mm->data_vm = oldmm->data_vm;
514 mm->exec_vm = oldmm->exec_vm;
515 mm->stack_vm = oldmm->stack_vm;
517 rb_link = &mm->mm_rb.rb_node;
520 retval = ksm_fork(mm, oldmm);
523 retval = khugepaged_fork(mm, oldmm);
528 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
531 if (mpnt->vm_flags & VM_DONTCOPY) {
532 vm_stat_account(mm, mpnt->vm_flags, -vma_pages(mpnt));
537 * Don't duplicate many vmas if we've been oom-killed (for
540 if (fatal_signal_pending(current)) {
544 if (mpnt->vm_flags & VM_ACCOUNT) {
545 unsigned long len = vma_pages(mpnt);
547 if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
551 tmp = vm_area_dup(mpnt);
554 retval = vma_dup_policy(mpnt, tmp);
556 goto fail_nomem_policy;
558 retval = dup_userfaultfd(tmp, &uf);
560 goto fail_nomem_anon_vma_fork;
561 if (tmp->vm_flags & VM_WIPEONFORK) {
563 * VM_WIPEONFORK gets a clean slate in the child.
564 * Don't prepare anon_vma until fault since we don't
565 * copy page for current vma.
567 tmp->anon_vma = NULL;
568 } else if (anon_vma_fork(tmp, mpnt))
569 goto fail_nomem_anon_vma_fork;
570 tmp->vm_flags &= ~(VM_LOCKED | VM_LOCKONFAULT);
573 struct address_space *mapping = file->f_mapping;
576 i_mmap_lock_write(mapping);
577 if (tmp->vm_flags & VM_SHARED)
578 mapping_allow_writable(mapping);
579 flush_dcache_mmap_lock(mapping);
580 /* insert tmp into the share list, just after mpnt */
581 vma_interval_tree_insert_after(tmp, mpnt,
583 flush_dcache_mmap_unlock(mapping);
584 i_mmap_unlock_write(mapping);
588 * Clear hugetlb-related page reserves for children. This only
589 * affects MAP_PRIVATE mappings. Faults generated by the child
590 * are not guaranteed to succeed, even if read-only
592 if (is_vm_hugetlb_page(tmp))
593 reset_vma_resv_huge_pages(tmp);
596 * Link in the new vma and copy the page table entries.
599 pprev = &tmp->vm_next;
603 __vma_link_rb(mm, tmp, rb_link, rb_parent);
604 rb_link = &tmp->vm_rb.rb_right;
605 rb_parent = &tmp->vm_rb;
608 if (!(tmp->vm_flags & VM_WIPEONFORK))
609 retval = copy_page_range(tmp, mpnt);
611 if (tmp->vm_ops && tmp->vm_ops->open)
612 tmp->vm_ops->open(tmp);
617 /* a new mm has just been created */
618 retval = arch_dup_mmap(oldmm, mm);
620 mmap_write_unlock(mm);
622 mmap_write_unlock(oldmm);
623 dup_userfaultfd_complete(&uf);
625 uprobe_end_dup_mmap();
627 fail_nomem_anon_vma_fork:
628 mpol_put(vma_policy(tmp));
633 vm_unacct_memory(charge);
637 static inline int mm_alloc_pgd(struct mm_struct *mm)
639 mm->pgd = pgd_alloc(mm);
640 if (unlikely(!mm->pgd))
645 static inline void mm_free_pgd(struct mm_struct *mm)
647 pgd_free(mm, mm->pgd);
650 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
652 mmap_write_lock(oldmm);
653 dup_mm_exe_file(mm, oldmm);
654 mmap_write_unlock(oldmm);
657 #define mm_alloc_pgd(mm) (0)
658 #define mm_free_pgd(mm)
659 #endif /* CONFIG_MMU */
661 static void check_mm(struct mm_struct *mm)
665 BUILD_BUG_ON_MSG(ARRAY_SIZE(resident_page_types) != NR_MM_COUNTERS,
666 "Please make sure 'struct resident_page_types[]' is updated as well");
668 for (i = 0; i < NR_MM_COUNTERS; i++) {
669 long x = atomic_long_read(&mm->rss_stat.count[i]);
672 pr_alert("BUG: Bad rss-counter state mm:%p type:%s val:%ld\n",
673 mm, resident_page_types[i], x);
676 if (mm_pgtables_bytes(mm))
677 pr_alert("BUG: non-zero pgtables_bytes on freeing mm: %ld\n",
678 mm_pgtables_bytes(mm));
680 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
681 VM_BUG_ON_MM(mm->pmd_huge_pte, mm);
685 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
686 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm)))
689 * Called when the last reference to the mm
690 * is dropped: either by a lazy thread or by
691 * mmput. Free the page directory and the mm.
693 void __mmdrop(struct mm_struct *mm)
695 BUG_ON(mm == &init_mm);
696 WARN_ON_ONCE(mm == current->mm);
697 WARN_ON_ONCE(mm == current->active_mm);
700 mmu_notifier_subscriptions_destroy(mm);
702 put_user_ns(mm->user_ns);
705 EXPORT_SYMBOL_GPL(__mmdrop);
707 static void mmdrop_async_fn(struct work_struct *work)
709 struct mm_struct *mm;
711 mm = container_of(work, struct mm_struct, async_put_work);
715 static void mmdrop_async(struct mm_struct *mm)
717 if (unlikely(atomic_dec_and_test(&mm->mm_count))) {
718 INIT_WORK(&mm->async_put_work, mmdrop_async_fn);
719 schedule_work(&mm->async_put_work);
723 static inline void free_signal_struct(struct signal_struct *sig)
725 taskstats_tgid_free(sig);
726 sched_autogroup_exit(sig);
728 * __mmdrop is not safe to call from softirq context on x86 due to
729 * pgd_dtor so postpone it to the async context
732 mmdrop_async(sig->oom_mm);
733 kmem_cache_free(signal_cachep, sig);
736 static inline void put_signal_struct(struct signal_struct *sig)
738 if (refcount_dec_and_test(&sig->sigcnt))
739 free_signal_struct(sig);
742 void __put_task_struct(struct task_struct *tsk)
744 WARN_ON(!tsk->exit_state);
745 WARN_ON(refcount_read(&tsk->usage));
746 WARN_ON(tsk == current);
750 task_numa_free(tsk, true);
751 security_task_free(tsk);
752 bpf_task_storage_free(tsk);
754 delayacct_tsk_free(tsk);
755 put_signal_struct(tsk->signal);
756 sched_core_free(tsk);
758 if (!profile_handoff_task(tsk))
761 EXPORT_SYMBOL_GPL(__put_task_struct);
763 void __init __weak arch_task_cache_init(void) { }
768 static void set_max_threads(unsigned int max_threads_suggested)
771 unsigned long nr_pages = totalram_pages();
774 * The number of threads shall be limited such that the thread
775 * structures may only consume a small part of the available memory.
777 if (fls64(nr_pages) + fls64(PAGE_SIZE) > 64)
778 threads = MAX_THREADS;
780 threads = div64_u64((u64) nr_pages * (u64) PAGE_SIZE,
781 (u64) THREAD_SIZE * 8UL);
783 if (threads > max_threads_suggested)
784 threads = max_threads_suggested;
786 max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS);
789 #ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT
790 /* Initialized by the architecture: */
791 int arch_task_struct_size __read_mostly;
794 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
795 static void task_struct_whitelist(unsigned long *offset, unsigned long *size)
797 /* Fetch thread_struct whitelist for the architecture. */
798 arch_thread_struct_whitelist(offset, size);
801 * Handle zero-sized whitelist or empty thread_struct, otherwise
802 * adjust offset to position of thread_struct in task_struct.
804 if (unlikely(*size == 0))
807 *offset += offsetof(struct task_struct, thread);
809 #endif /* CONFIG_ARCH_TASK_STRUCT_ALLOCATOR */
811 void __init fork_init(void)
814 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
815 #ifndef ARCH_MIN_TASKALIGN
816 #define ARCH_MIN_TASKALIGN 0
818 int align = max_t(int, L1_CACHE_BYTES, ARCH_MIN_TASKALIGN);
819 unsigned long useroffset, usersize;
821 /* create a slab on which task_structs can be allocated */
822 task_struct_whitelist(&useroffset, &usersize);
823 task_struct_cachep = kmem_cache_create_usercopy("task_struct",
824 arch_task_struct_size, align,
825 SLAB_PANIC|SLAB_ACCOUNT,
826 useroffset, usersize, NULL);
829 /* do the arch specific task caches init */
830 arch_task_cache_init();
832 set_max_threads(MAX_THREADS);
834 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
835 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
836 init_task.signal->rlim[RLIMIT_SIGPENDING] =
837 init_task.signal->rlim[RLIMIT_NPROC];
839 for (i = 0; i < MAX_PER_NAMESPACE_UCOUNTS; i++)
840 init_user_ns.ucount_max[i] = max_threads/2;
842 set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_NPROC, RLIM_INFINITY);
843 set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_MSGQUEUE, RLIM_INFINITY);
844 set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_SIGPENDING, RLIM_INFINITY);
845 set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_MEMLOCK, RLIM_INFINITY);
847 #ifdef CONFIG_VMAP_STACK
848 cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "fork:vm_stack_cache",
849 NULL, free_vm_stack_cache);
854 lockdep_init_task(&init_task);
858 int __weak arch_dup_task_struct(struct task_struct *dst,
859 struct task_struct *src)
865 void set_task_stack_end_magic(struct task_struct *tsk)
867 unsigned long *stackend;
869 stackend = end_of_stack(tsk);
870 *stackend = STACK_END_MAGIC; /* for overflow detection */
873 static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
875 struct task_struct *tsk;
876 unsigned long *stack;
877 struct vm_struct *stack_vm_area __maybe_unused;
880 if (node == NUMA_NO_NODE)
881 node = tsk_fork_get_node(orig);
882 tsk = alloc_task_struct_node(node);
886 stack = alloc_thread_stack_node(tsk, node);
890 if (memcg_charge_kernel_stack(tsk))
893 stack_vm_area = task_stack_vm_area(tsk);
895 err = arch_dup_task_struct(tsk, orig);
898 * arch_dup_task_struct() clobbers the stack-related fields. Make
899 * sure they're properly initialized before using any stack-related
903 #ifdef CONFIG_VMAP_STACK
904 tsk->stack_vm_area = stack_vm_area;
906 #ifdef CONFIG_THREAD_INFO_IN_TASK
907 refcount_set(&tsk->stack_refcount, 1);
913 err = scs_prepare(tsk, node);
917 #ifdef CONFIG_SECCOMP
919 * We must handle setting up seccomp filters once we're under
920 * the sighand lock in case orig has changed between now and
921 * then. Until then, filter must be NULL to avoid messing up
922 * the usage counts on the error path calling free_task.
924 tsk->seccomp.filter = NULL;
927 setup_thread_stack(tsk, orig);
928 clear_user_return_notifier(tsk);
929 clear_tsk_need_resched(tsk);
930 set_task_stack_end_magic(tsk);
931 clear_syscall_work_syscall_user_dispatch(tsk);
933 #ifdef CONFIG_STACKPROTECTOR
934 tsk->stack_canary = get_random_canary();
936 if (orig->cpus_ptr == &orig->cpus_mask)
937 tsk->cpus_ptr = &tsk->cpus_mask;
938 dup_user_cpus_ptr(tsk, orig, node);
941 * One for the user space visible state that goes away when reaped.
942 * One for the scheduler.
944 refcount_set(&tsk->rcu_users, 2);
945 /* One for the rcu users */
946 refcount_set(&tsk->usage, 1);
947 #ifdef CONFIG_BLK_DEV_IO_TRACE
950 tsk->splice_pipe = NULL;
951 tsk->task_frag.page = NULL;
952 tsk->wake_q.next = NULL;
953 tsk->pf_io_worker = NULL;
955 account_kernel_stack(tsk, 1);
958 kmap_local_fork(tsk);
960 #ifdef CONFIG_FAULT_INJECTION
964 #ifdef CONFIG_BLK_CGROUP
965 tsk->throttle_queue = NULL;
966 tsk->use_memdelay = 0;
970 tsk->active_memcg = NULL;
975 free_thread_stack(tsk);
977 free_task_struct(tsk);
981 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
983 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
985 static int __init coredump_filter_setup(char *s)
987 default_dump_filter =
988 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
989 MMF_DUMP_FILTER_MASK;
993 __setup("coredump_filter=", coredump_filter_setup);
995 #include <linux/init_task.h>
997 static void mm_init_aio(struct mm_struct *mm)
1000 spin_lock_init(&mm->ioctx_lock);
1001 mm->ioctx_table = NULL;
1005 static __always_inline void mm_clear_owner(struct mm_struct *mm,
1006 struct task_struct *p)
1010 WRITE_ONCE(mm->owner, NULL);
1014 static void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
1021 static void mm_init_pasid(struct mm_struct *mm)
1023 #ifdef CONFIG_IOMMU_SUPPORT
1024 mm->pasid = INIT_PASID;
1028 static void mm_init_uprobes_state(struct mm_struct *mm)
1030 #ifdef CONFIG_UPROBES
1031 mm->uprobes_state.xol_area = NULL;
1035 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
1036 struct user_namespace *user_ns)
1039 mm->mm_rb = RB_ROOT;
1040 mm->vmacache_seqnum = 0;
1041 atomic_set(&mm->mm_users, 1);
1042 atomic_set(&mm->mm_count, 1);
1043 seqcount_init(&mm->write_protect_seq);
1045 INIT_LIST_HEAD(&mm->mmlist);
1046 mm_pgtables_bytes_init(mm);
1049 atomic64_set(&mm->pinned_vm, 0);
1050 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
1051 spin_lock_init(&mm->page_table_lock);
1052 spin_lock_init(&mm->arg_lock);
1053 mm_init_cpumask(mm);
1055 mm_init_owner(mm, p);
1057 RCU_INIT_POINTER(mm->exe_file, NULL);
1058 mmu_notifier_subscriptions_init(mm);
1059 init_tlb_flush_pending(mm);
1060 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
1061 mm->pmd_huge_pte = NULL;
1063 mm_init_uprobes_state(mm);
1064 hugetlb_count_init(mm);
1067 mm->flags = current->mm->flags & MMF_INIT_MASK;
1068 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK;
1070 mm->flags = default_dump_filter;
1074 if (mm_alloc_pgd(mm))
1077 if (init_new_context(p, mm))
1078 goto fail_nocontext;
1080 mm->user_ns = get_user_ns(user_ns);
1091 * Allocate and initialize an mm_struct.
1093 struct mm_struct *mm_alloc(void)
1095 struct mm_struct *mm;
1101 memset(mm, 0, sizeof(*mm));
1102 return mm_init(mm, current, current_user_ns());
1105 static inline void __mmput(struct mm_struct *mm)
1107 VM_BUG_ON(atomic_read(&mm->mm_users));
1109 uprobe_clear_state(mm);
1112 khugepaged_exit(mm); /* must run before exit_mmap */
1114 mm_put_huge_zero_page(mm);
1115 set_mm_exe_file(mm, NULL);
1116 if (!list_empty(&mm->mmlist)) {
1117 spin_lock(&mmlist_lock);
1118 list_del(&mm->mmlist);
1119 spin_unlock(&mmlist_lock);
1122 module_put(mm->binfmt->module);
1127 * Decrement the use count and release all resources for an mm.
1129 void mmput(struct mm_struct *mm)
1133 if (atomic_dec_and_test(&mm->mm_users))
1136 EXPORT_SYMBOL_GPL(mmput);
1139 static void mmput_async_fn(struct work_struct *work)
1141 struct mm_struct *mm = container_of(work, struct mm_struct,
1147 void mmput_async(struct mm_struct *mm)
1149 if (atomic_dec_and_test(&mm->mm_users)) {
1150 INIT_WORK(&mm->async_put_work, mmput_async_fn);
1151 schedule_work(&mm->async_put_work);
1157 * set_mm_exe_file - change a reference to the mm's executable file
1159 * This changes mm's executable file (shown as symlink /proc/[pid]/exe).
1161 * Main users are mmput() and sys_execve(). Callers prevent concurrent
1162 * invocations: in mmput() nobody alive left, in execve task is single
1165 * Can only fail if new_exe_file != NULL.
1167 int set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
1169 struct file *old_exe_file;
1172 * It is safe to dereference the exe_file without RCU as
1173 * this function is only called if nobody else can access
1174 * this mm -- see comment above for justification.
1176 old_exe_file = rcu_dereference_raw(mm->exe_file);
1180 * We expect the caller (i.e., sys_execve) to already denied
1181 * write access, so this is unlikely to fail.
1183 if (unlikely(deny_write_access(new_exe_file)))
1185 get_file(new_exe_file);
1187 rcu_assign_pointer(mm->exe_file, new_exe_file);
1189 allow_write_access(old_exe_file);
1196 * replace_mm_exe_file - replace a reference to the mm's executable file
1198 * This changes mm's executable file (shown as symlink /proc/[pid]/exe),
1199 * dealing with concurrent invocation and without grabbing the mmap lock in
1202 * Main user is sys_prctl(PR_SET_MM_MAP/EXE_FILE).
1204 int replace_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
1206 struct vm_area_struct *vma;
1207 struct file *old_exe_file;
1210 /* Forbid mm->exe_file change if old file still mapped. */
1211 old_exe_file = get_mm_exe_file(mm);
1214 for (vma = mm->mmap; vma && !ret; vma = vma->vm_next) {
1217 if (path_equal(&vma->vm_file->f_path,
1218 &old_exe_file->f_path))
1221 mmap_read_unlock(mm);
1227 /* set the new file, lockless */
1228 ret = deny_write_access(new_exe_file);
1231 get_file(new_exe_file);
1233 old_exe_file = xchg(&mm->exe_file, new_exe_file);
1236 * Don't race with dup_mmap() getting the file and disallowing
1237 * write access while someone might open the file writable.
1240 allow_write_access(old_exe_file);
1242 mmap_read_unlock(mm);
1248 * get_mm_exe_file - acquire a reference to the mm's executable file
1250 * Returns %NULL if mm has no associated executable file.
1251 * User must release file via fput().
1253 struct file *get_mm_exe_file(struct mm_struct *mm)
1255 struct file *exe_file;
1258 exe_file = rcu_dereference(mm->exe_file);
1259 if (exe_file && !get_file_rcu(exe_file))
1266 * get_task_exe_file - acquire a reference to the task's executable file
1268 * Returns %NULL if task's mm (if any) has no associated executable file or
1269 * this is a kernel thread with borrowed mm (see the comment above get_task_mm).
1270 * User must release file via fput().
1272 struct file *get_task_exe_file(struct task_struct *task)
1274 struct file *exe_file = NULL;
1275 struct mm_struct *mm;
1280 if (!(task->flags & PF_KTHREAD))
1281 exe_file = get_mm_exe_file(mm);
1288 * get_task_mm - acquire a reference to the task's mm
1290 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning
1291 * this kernel workthread has transiently adopted a user mm with use_mm,
1292 * to do its AIO) is not set and if so returns a reference to it, after
1293 * bumping up the use count. User must release the mm via mmput()
1294 * after use. Typically used by /proc and ptrace.
1296 struct mm_struct *get_task_mm(struct task_struct *task)
1298 struct mm_struct *mm;
1303 if (task->flags & PF_KTHREAD)
1311 EXPORT_SYMBOL_GPL(get_task_mm);
1313 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
1315 struct mm_struct *mm;
1318 err = down_read_killable(&task->signal->exec_update_lock);
1320 return ERR_PTR(err);
1322 mm = get_task_mm(task);
1323 if (mm && mm != current->mm &&
1324 !ptrace_may_access(task, mode)) {
1326 mm = ERR_PTR(-EACCES);
1328 up_read(&task->signal->exec_update_lock);
1333 static void complete_vfork_done(struct task_struct *tsk)
1335 struct completion *vfork;
1338 vfork = tsk->vfork_done;
1339 if (likely(vfork)) {
1340 tsk->vfork_done = NULL;
1346 static int wait_for_vfork_done(struct task_struct *child,
1347 struct completion *vfork)
1351 freezer_do_not_count();
1352 cgroup_enter_frozen();
1353 killed = wait_for_completion_killable(vfork);
1354 cgroup_leave_frozen(false);
1359 child->vfork_done = NULL;
1363 put_task_struct(child);
1367 /* Please note the differences between mmput and mm_release.
1368 * mmput is called whenever we stop holding onto a mm_struct,
1369 * error success whatever.
1371 * mm_release is called after a mm_struct has been removed
1372 * from the current process.
1374 * This difference is important for error handling, when we
1375 * only half set up a mm_struct for a new process and need to restore
1376 * the old one. Because we mmput the new mm_struct before
1377 * restoring the old one. . .
1378 * Eric Biederman 10 January 1998
1380 static void mm_release(struct task_struct *tsk, struct mm_struct *mm)
1382 uprobe_free_utask(tsk);
1384 /* Get rid of any cached register state */
1385 deactivate_mm(tsk, mm);
1388 * Signal userspace if we're not exiting with a core dump
1389 * because we want to leave the value intact for debugging
1392 if (tsk->clear_child_tid) {
1393 if (atomic_read(&mm->mm_users) > 1) {
1395 * We don't check the error code - if userspace has
1396 * not set up a proper pointer then tough luck.
1398 put_user(0, tsk->clear_child_tid);
1399 do_futex(tsk->clear_child_tid, FUTEX_WAKE,
1400 1, NULL, NULL, 0, 0);
1402 tsk->clear_child_tid = NULL;
1406 * All done, finally we can wake up parent and return this mm to him.
1407 * Also kthread_stop() uses this completion for synchronization.
1409 if (tsk->vfork_done)
1410 complete_vfork_done(tsk);
1413 void exit_mm_release(struct task_struct *tsk, struct mm_struct *mm)
1415 futex_exit_release(tsk);
1416 mm_release(tsk, mm);
1419 void exec_mm_release(struct task_struct *tsk, struct mm_struct *mm)
1421 futex_exec_release(tsk);
1422 mm_release(tsk, mm);
1426 * dup_mm() - duplicates an existing mm structure
1427 * @tsk: the task_struct with which the new mm will be associated.
1428 * @oldmm: the mm to duplicate.
1430 * Allocates a new mm structure and duplicates the provided @oldmm structure
1433 * Return: the duplicated mm or NULL on failure.
1435 static struct mm_struct *dup_mm(struct task_struct *tsk,
1436 struct mm_struct *oldmm)
1438 struct mm_struct *mm;
1445 memcpy(mm, oldmm, sizeof(*mm));
1447 if (!mm_init(mm, tsk, mm->user_ns))
1450 err = dup_mmap(mm, oldmm);
1454 mm->hiwater_rss = get_mm_rss(mm);
1455 mm->hiwater_vm = mm->total_vm;
1457 if (mm->binfmt && !try_module_get(mm->binfmt->module))
1463 /* don't put binfmt in mmput, we haven't got module yet */
1465 mm_init_owner(mm, NULL);
1472 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
1474 struct mm_struct *mm, *oldmm;
1476 tsk->min_flt = tsk->maj_flt = 0;
1477 tsk->nvcsw = tsk->nivcsw = 0;
1478 #ifdef CONFIG_DETECT_HUNG_TASK
1479 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
1480 tsk->last_switch_time = 0;
1484 tsk->active_mm = NULL;
1487 * Are we cloning a kernel thread?
1489 * We need to steal a active VM for that..
1491 oldmm = current->mm;
1495 /* initialize the new vmacache entries */
1496 vmacache_flush(tsk);
1498 if (clone_flags & CLONE_VM) {
1502 mm = dup_mm(tsk, current->mm);
1508 tsk->active_mm = mm;
1512 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
1514 struct fs_struct *fs = current->fs;
1515 if (clone_flags & CLONE_FS) {
1516 /* tsk->fs is already what we want */
1517 spin_lock(&fs->lock);
1519 spin_unlock(&fs->lock);
1523 spin_unlock(&fs->lock);
1526 tsk->fs = copy_fs_struct(fs);
1532 static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
1534 struct files_struct *oldf, *newf;
1538 * A background process may not have any files ...
1540 oldf = current->files;
1544 if (clone_flags & CLONE_FILES) {
1545 atomic_inc(&oldf->count);
1549 newf = dup_fd(oldf, NR_OPEN_MAX, &error);
1559 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
1562 struct io_context *ioc = current->io_context;
1563 struct io_context *new_ioc;
1568 * Share io context with parent, if CLONE_IO is set
1570 if (clone_flags & CLONE_IO) {
1572 tsk->io_context = ioc;
1573 } else if (ioprio_valid(ioc->ioprio)) {
1574 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE);
1575 if (unlikely(!new_ioc))
1578 new_ioc->ioprio = ioc->ioprio;
1579 put_io_context(new_ioc);
1585 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
1587 struct sighand_struct *sig;
1589 if (clone_flags & CLONE_SIGHAND) {
1590 refcount_inc(¤t->sighand->count);
1593 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1594 RCU_INIT_POINTER(tsk->sighand, sig);
1598 refcount_set(&sig->count, 1);
1599 spin_lock_irq(¤t->sighand->siglock);
1600 memcpy(sig->action, current->sighand->action, sizeof(sig->action));
1601 spin_unlock_irq(¤t->sighand->siglock);
1603 /* Reset all signal handler not set to SIG_IGN to SIG_DFL. */
1604 if (clone_flags & CLONE_CLEAR_SIGHAND)
1605 flush_signal_handlers(tsk, 0);
1610 void __cleanup_sighand(struct sighand_struct *sighand)
1612 if (refcount_dec_and_test(&sighand->count)) {
1613 signalfd_cleanup(sighand);
1615 * sighand_cachep is SLAB_TYPESAFE_BY_RCU so we can free it
1616 * without an RCU grace period, see __lock_task_sighand().
1618 kmem_cache_free(sighand_cachep, sighand);
1623 * Initialize POSIX timer handling for a thread group.
1625 static void posix_cpu_timers_init_group(struct signal_struct *sig)
1627 struct posix_cputimers *pct = &sig->posix_cputimers;
1628 unsigned long cpu_limit;
1630 cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1631 posix_cputimers_group_init(pct, cpu_limit);
1634 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
1636 struct signal_struct *sig;
1638 if (clone_flags & CLONE_THREAD)
1641 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
1646 sig->nr_threads = 1;
1647 atomic_set(&sig->live, 1);
1648 refcount_set(&sig->sigcnt, 1);
1650 /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */
1651 sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node);
1652 tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head);
1654 init_waitqueue_head(&sig->wait_chldexit);
1655 sig->curr_target = tsk;
1656 init_sigpending(&sig->shared_pending);
1657 INIT_HLIST_HEAD(&sig->multiprocess);
1658 seqlock_init(&sig->stats_lock);
1659 prev_cputime_init(&sig->prev_cputime);
1661 #ifdef CONFIG_POSIX_TIMERS
1662 INIT_LIST_HEAD(&sig->posix_timers);
1663 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1664 sig->real_timer.function = it_real_fn;
1667 task_lock(current->group_leader);
1668 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
1669 task_unlock(current->group_leader);
1671 posix_cpu_timers_init_group(sig);
1673 tty_audit_fork(sig);
1674 sched_autogroup_fork(sig);
1676 sig->oom_score_adj = current->signal->oom_score_adj;
1677 sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1679 mutex_init(&sig->cred_guard_mutex);
1680 init_rwsem(&sig->exec_update_lock);
1685 static void copy_seccomp(struct task_struct *p)
1687 #ifdef CONFIG_SECCOMP
1689 * Must be called with sighand->lock held, which is common to
1690 * all threads in the group. Holding cred_guard_mutex is not
1691 * needed because this new task is not yet running and cannot
1694 assert_spin_locked(¤t->sighand->siglock);
1696 /* Ref-count the new filter user, and assign it. */
1697 get_seccomp_filter(current);
1698 p->seccomp = current->seccomp;
1701 * Explicitly enable no_new_privs here in case it got set
1702 * between the task_struct being duplicated and holding the
1703 * sighand lock. The seccomp state and nnp must be in sync.
1705 if (task_no_new_privs(current))
1706 task_set_no_new_privs(p);
1709 * If the parent gained a seccomp mode after copying thread
1710 * flags and between before we held the sighand lock, we have
1711 * to manually enable the seccomp thread flag here.
1713 if (p->seccomp.mode != SECCOMP_MODE_DISABLED)
1714 set_task_syscall_work(p, SECCOMP);
1718 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1720 current->clear_child_tid = tidptr;
1722 return task_pid_vnr(current);
1725 static void rt_mutex_init_task(struct task_struct *p)
1727 raw_spin_lock_init(&p->pi_lock);
1728 #ifdef CONFIG_RT_MUTEXES
1729 p->pi_waiters = RB_ROOT_CACHED;
1730 p->pi_top_task = NULL;
1731 p->pi_blocked_on = NULL;
1735 static inline void init_task_pid_links(struct task_struct *task)
1739 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type)
1740 INIT_HLIST_NODE(&task->pid_links[type]);
1744 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid)
1746 if (type == PIDTYPE_PID)
1747 task->thread_pid = pid;
1749 task->signal->pids[type] = pid;
1752 static inline void rcu_copy_process(struct task_struct *p)
1754 #ifdef CONFIG_PREEMPT_RCU
1755 p->rcu_read_lock_nesting = 0;
1756 p->rcu_read_unlock_special.s = 0;
1757 p->rcu_blocked_node = NULL;
1758 INIT_LIST_HEAD(&p->rcu_node_entry);
1759 #endif /* #ifdef CONFIG_PREEMPT_RCU */
1760 #ifdef CONFIG_TASKS_RCU
1761 p->rcu_tasks_holdout = false;
1762 INIT_LIST_HEAD(&p->rcu_tasks_holdout_list);
1763 p->rcu_tasks_idle_cpu = -1;
1764 #endif /* #ifdef CONFIG_TASKS_RCU */
1765 #ifdef CONFIG_TASKS_TRACE_RCU
1766 p->trc_reader_nesting = 0;
1767 p->trc_reader_special.s = 0;
1768 INIT_LIST_HEAD(&p->trc_holdout_list);
1769 #endif /* #ifdef CONFIG_TASKS_TRACE_RCU */
1772 struct pid *pidfd_pid(const struct file *file)
1774 if (file->f_op == &pidfd_fops)
1775 return file->private_data;
1777 return ERR_PTR(-EBADF);
1780 static int pidfd_release(struct inode *inode, struct file *file)
1782 struct pid *pid = file->private_data;
1784 file->private_data = NULL;
1789 #ifdef CONFIG_PROC_FS
1791 * pidfd_show_fdinfo - print information about a pidfd
1792 * @m: proc fdinfo file
1793 * @f: file referencing a pidfd
1796 * This function will print the pid that a given pidfd refers to in the
1797 * pid namespace of the procfs instance.
1798 * If the pid namespace of the process is not a descendant of the pid
1799 * namespace of the procfs instance 0 will be shown as its pid. This is
1800 * similar to calling getppid() on a process whose parent is outside of
1801 * its pid namespace.
1804 * If pid namespaces are supported then this function will also print
1805 * the pid of a given pidfd refers to for all descendant pid namespaces
1806 * starting from the current pid namespace of the instance, i.e. the
1807 * Pid field and the first entry in the NSpid field will be identical.
1808 * If the pid namespace of the process is not a descendant of the pid
1809 * namespace of the procfs instance 0 will be shown as its first NSpid
1810 * entry and no others will be shown.
1811 * Note that this differs from the Pid and NSpid fields in
1812 * /proc/<pid>/status where Pid and NSpid are always shown relative to
1813 * the pid namespace of the procfs instance. The difference becomes
1814 * obvious when sending around a pidfd between pid namespaces from a
1815 * different branch of the tree, i.e. where no ancestral relation is
1816 * present between the pid namespaces:
1817 * - create two new pid namespaces ns1 and ns2 in the initial pid
1818 * namespace (also take care to create new mount namespaces in the
1819 * new pid namespace and mount procfs)
1820 * - create a process with a pidfd in ns1
1821 * - send pidfd from ns1 to ns2
1822 * - read /proc/self/fdinfo/<pidfd> and observe that both Pid and NSpid
1823 * have exactly one entry, which is 0
1825 static void pidfd_show_fdinfo(struct seq_file *m, struct file *f)
1827 struct pid *pid = f->private_data;
1828 struct pid_namespace *ns;
1831 if (likely(pid_has_task(pid, PIDTYPE_PID))) {
1832 ns = proc_pid_ns(file_inode(m->file)->i_sb);
1833 nr = pid_nr_ns(pid, ns);
1836 seq_put_decimal_ll(m, "Pid:\t", nr);
1838 #ifdef CONFIG_PID_NS
1839 seq_put_decimal_ll(m, "\nNSpid:\t", nr);
1843 /* If nr is non-zero it means that 'pid' is valid and that
1844 * ns, i.e. the pid namespace associated with the procfs
1845 * instance, is in the pid namespace hierarchy of pid.
1846 * Start at one below the already printed level.
1848 for (i = ns->level + 1; i <= pid->level; i++)
1849 seq_put_decimal_ll(m, "\t", pid->numbers[i].nr);
1857 * Poll support for process exit notification.
1859 static __poll_t pidfd_poll(struct file *file, struct poll_table_struct *pts)
1861 struct pid *pid = file->private_data;
1862 __poll_t poll_flags = 0;
1864 poll_wait(file, &pid->wait_pidfd, pts);
1867 * Inform pollers only when the whole thread group exits.
1868 * If the thread group leader exits before all other threads in the
1869 * group, then poll(2) should block, similar to the wait(2) family.
1871 if (thread_group_exited(pid))
1872 poll_flags = EPOLLIN | EPOLLRDNORM;
1877 const struct file_operations pidfd_fops = {
1878 .release = pidfd_release,
1880 #ifdef CONFIG_PROC_FS
1881 .show_fdinfo = pidfd_show_fdinfo,
1885 static void __delayed_free_task(struct rcu_head *rhp)
1887 struct task_struct *tsk = container_of(rhp, struct task_struct, rcu);
1892 static __always_inline void delayed_free_task(struct task_struct *tsk)
1894 if (IS_ENABLED(CONFIG_MEMCG))
1895 call_rcu(&tsk->rcu, __delayed_free_task);
1900 static void copy_oom_score_adj(u64 clone_flags, struct task_struct *tsk)
1902 /* Skip if kernel thread */
1906 /* Skip if spawning a thread or using vfork */
1907 if ((clone_flags & (CLONE_VM | CLONE_THREAD | CLONE_VFORK)) != CLONE_VM)
1910 /* We need to synchronize with __set_oom_adj */
1911 mutex_lock(&oom_adj_mutex);
1912 set_bit(MMF_MULTIPROCESS, &tsk->mm->flags);
1913 /* Update the values in case they were changed after copy_signal */
1914 tsk->signal->oom_score_adj = current->signal->oom_score_adj;
1915 tsk->signal->oom_score_adj_min = current->signal->oom_score_adj_min;
1916 mutex_unlock(&oom_adj_mutex);
1920 * This creates a new process as a copy of the old one,
1921 * but does not actually start it yet.
1923 * It copies the registers, and all the appropriate
1924 * parts of the process environment (as per the clone
1925 * flags). The actual kick-off is left to the caller.
1927 static __latent_entropy struct task_struct *copy_process(
1931 struct kernel_clone_args *args)
1933 int pidfd = -1, retval;
1934 struct task_struct *p;
1935 struct multiprocess_signals delayed;
1936 struct file *pidfile = NULL;
1937 u64 clone_flags = args->flags;
1938 struct nsproxy *nsp = current->nsproxy;
1941 * Don't allow sharing the root directory with processes in a different
1944 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1945 return ERR_PTR(-EINVAL);
1947 if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS))
1948 return ERR_PTR(-EINVAL);
1951 * Thread groups must share signals as well, and detached threads
1952 * can only be started up within the thread group.
1954 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1955 return ERR_PTR(-EINVAL);
1958 * Shared signal handlers imply shared VM. By way of the above,
1959 * thread groups also imply shared VM. Blocking this case allows
1960 * for various simplifications in other code.
1962 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1963 return ERR_PTR(-EINVAL);
1966 * Siblings of global init remain as zombies on exit since they are
1967 * not reaped by their parent (swapper). To solve this and to avoid
1968 * multi-rooted process trees, prevent global and container-inits
1969 * from creating siblings.
1971 if ((clone_flags & CLONE_PARENT) &&
1972 current->signal->flags & SIGNAL_UNKILLABLE)
1973 return ERR_PTR(-EINVAL);
1976 * If the new process will be in a different pid or user namespace
1977 * do not allow it to share a thread group with the forking task.
1979 if (clone_flags & CLONE_THREAD) {
1980 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) ||
1981 (task_active_pid_ns(current) != nsp->pid_ns_for_children))
1982 return ERR_PTR(-EINVAL);
1986 * If the new process will be in a different time namespace
1987 * do not allow it to share VM or a thread group with the forking task.
1989 if (clone_flags & (CLONE_THREAD | CLONE_VM)) {
1990 if (nsp->time_ns != nsp->time_ns_for_children)
1991 return ERR_PTR(-EINVAL);
1994 if (clone_flags & CLONE_PIDFD) {
1996 * - CLONE_DETACHED is blocked so that we can potentially
1997 * reuse it later for CLONE_PIDFD.
1998 * - CLONE_THREAD is blocked until someone really needs it.
2000 if (clone_flags & (CLONE_DETACHED | CLONE_THREAD))
2001 return ERR_PTR(-EINVAL);
2005 * Force any signals received before this point to be delivered
2006 * before the fork happens. Collect up signals sent to multiple
2007 * processes that happen during the fork and delay them so that
2008 * they appear to happen after the fork.
2010 sigemptyset(&delayed.signal);
2011 INIT_HLIST_NODE(&delayed.node);
2013 spin_lock_irq(¤t->sighand->siglock);
2014 if (!(clone_flags & CLONE_THREAD))
2015 hlist_add_head(&delayed.node, ¤t->signal->multiprocess);
2016 recalc_sigpending();
2017 spin_unlock_irq(¤t->sighand->siglock);
2018 retval = -ERESTARTNOINTR;
2019 if (task_sigpending(current))
2023 p = dup_task_struct(current, node);
2026 if (args->io_thread) {
2028 * Mark us an IO worker, and block any signal that isn't
2031 p->flags |= PF_IO_WORKER;
2032 siginitsetinv(&p->blocked, sigmask(SIGKILL)|sigmask(SIGSTOP));
2036 * This _must_ happen before we call free_task(), i.e. before we jump
2037 * to any of the bad_fork_* labels. This is to avoid freeing
2038 * p->set_child_tid which is (ab)used as a kthread's data pointer for
2039 * kernel threads (PF_KTHREAD).
2041 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? args->child_tid : NULL;
2043 * Clear TID on mm_release()?
2045 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? args->child_tid : NULL;
2047 ftrace_graph_init_task(p);
2049 rt_mutex_init_task(p);
2051 lockdep_assert_irqs_enabled();
2052 #ifdef CONFIG_PROVE_LOCKING
2053 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
2056 if (is_ucounts_overlimit(task_ucounts(p), UCOUNT_RLIMIT_NPROC, rlimit(RLIMIT_NPROC))) {
2057 if (p->real_cred->user != INIT_USER &&
2058 !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
2061 current->flags &= ~PF_NPROC_EXCEEDED;
2063 retval = copy_creds(p, clone_flags);
2068 * If multiple threads are within copy_process(), then this check
2069 * triggers too late. This doesn't hurt, the check is only there
2070 * to stop root fork bombs.
2073 if (data_race(nr_threads >= max_threads))
2074 goto bad_fork_cleanup_count;
2076 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */
2077 p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER | PF_IDLE | PF_NO_SETAFFINITY);
2078 p->flags |= PF_FORKNOEXEC;
2079 INIT_LIST_HEAD(&p->children);
2080 INIT_LIST_HEAD(&p->sibling);
2081 rcu_copy_process(p);
2082 p->vfork_done = NULL;
2083 spin_lock_init(&p->alloc_lock);
2085 init_sigpending(&p->pending);
2087 p->utime = p->stime = p->gtime = 0;
2088 #ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
2089 p->utimescaled = p->stimescaled = 0;
2091 prev_cputime_init(&p->prev_cputime);
2093 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
2094 seqcount_init(&p->vtime.seqcount);
2095 p->vtime.starttime = 0;
2096 p->vtime.state = VTIME_INACTIVE;
2099 #ifdef CONFIG_IO_URING
2103 #if defined(SPLIT_RSS_COUNTING)
2104 memset(&p->rss_stat, 0, sizeof(p->rss_stat));
2107 p->default_timer_slack_ns = current->timer_slack_ns;
2113 task_io_accounting_init(&p->ioac);
2114 acct_clear_integrals(p);
2116 posix_cputimers_init(&p->posix_cputimers);
2118 p->io_context = NULL;
2119 audit_set_context(p, NULL);
2122 p->mempolicy = mpol_dup(p->mempolicy);
2123 if (IS_ERR(p->mempolicy)) {
2124 retval = PTR_ERR(p->mempolicy);
2125 p->mempolicy = NULL;
2126 goto bad_fork_cleanup_threadgroup_lock;
2129 #ifdef CONFIG_CPUSETS
2130 p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
2131 p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
2132 seqcount_spinlock_init(&p->mems_allowed_seq, &p->alloc_lock);
2134 #ifdef CONFIG_TRACE_IRQFLAGS
2135 memset(&p->irqtrace, 0, sizeof(p->irqtrace));
2136 p->irqtrace.hardirq_disable_ip = _THIS_IP_;
2137 p->irqtrace.softirq_enable_ip = _THIS_IP_;
2138 p->softirqs_enabled = 1;
2139 p->softirq_context = 0;
2142 p->pagefault_disabled = 0;
2144 #ifdef CONFIG_LOCKDEP
2145 lockdep_init_task(p);
2148 #ifdef CONFIG_DEBUG_MUTEXES
2149 p->blocked_on = NULL; /* not blocked yet */
2151 #ifdef CONFIG_BCACHE
2152 p->sequential_io = 0;
2153 p->sequential_io_avg = 0;
2155 #ifdef CONFIG_BPF_SYSCALL
2156 RCU_INIT_POINTER(p->bpf_storage, NULL);
2160 /* Perform scheduler related setup. Assign this task to a CPU. */
2161 retval = sched_fork(clone_flags, p);
2163 goto bad_fork_cleanup_policy;
2165 retval = perf_event_init_task(p, clone_flags);
2167 goto bad_fork_cleanup_policy;
2168 retval = audit_alloc(p);
2170 goto bad_fork_cleanup_perf;
2171 /* copy all the process information */
2173 retval = security_task_alloc(p, clone_flags);
2175 goto bad_fork_cleanup_audit;
2176 retval = copy_semundo(clone_flags, p);
2178 goto bad_fork_cleanup_security;
2179 retval = copy_files(clone_flags, p);
2181 goto bad_fork_cleanup_semundo;
2182 retval = copy_fs(clone_flags, p);
2184 goto bad_fork_cleanup_files;
2185 retval = copy_sighand(clone_flags, p);
2187 goto bad_fork_cleanup_fs;
2188 retval = copy_signal(clone_flags, p);
2190 goto bad_fork_cleanup_sighand;
2191 retval = copy_mm(clone_flags, p);
2193 goto bad_fork_cleanup_signal;
2194 retval = copy_namespaces(clone_flags, p);
2196 goto bad_fork_cleanup_mm;
2197 retval = copy_io(clone_flags, p);
2199 goto bad_fork_cleanup_namespaces;
2200 retval = copy_thread(clone_flags, args->stack, args->stack_size, p, args->tls);
2202 goto bad_fork_cleanup_io;
2204 stackleak_task_init(p);
2206 if (pid != &init_struct_pid) {
2207 pid = alloc_pid(p->nsproxy->pid_ns_for_children, args->set_tid,
2208 args->set_tid_size);
2210 retval = PTR_ERR(pid);
2211 goto bad_fork_cleanup_thread;
2216 * This has to happen after we've potentially unshared the file
2217 * descriptor table (so that the pidfd doesn't leak into the child
2218 * if the fd table isn't shared).
2220 if (clone_flags & CLONE_PIDFD) {
2221 retval = get_unused_fd_flags(O_RDWR | O_CLOEXEC);
2223 goto bad_fork_free_pid;
2227 pidfile = anon_inode_getfile("[pidfd]", &pidfd_fops, pid,
2228 O_RDWR | O_CLOEXEC);
2229 if (IS_ERR(pidfile)) {
2230 put_unused_fd(pidfd);
2231 retval = PTR_ERR(pidfile);
2232 goto bad_fork_free_pid;
2234 get_pid(pid); /* held by pidfile now */
2236 retval = put_user(pidfd, args->pidfd);
2238 goto bad_fork_put_pidfd;
2247 * sigaltstack should be cleared when sharing the same VM
2249 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
2253 * Syscall tracing and stepping should be turned off in the
2254 * child regardless of CLONE_PTRACE.
2256 user_disable_single_step(p);
2257 clear_task_syscall_work(p, SYSCALL_TRACE);
2258 #if defined(CONFIG_GENERIC_ENTRY) || defined(TIF_SYSCALL_EMU)
2259 clear_task_syscall_work(p, SYSCALL_EMU);
2261 clear_tsk_latency_tracing(p);
2263 /* ok, now we should be set up.. */
2264 p->pid = pid_nr(pid);
2265 if (clone_flags & CLONE_THREAD) {
2266 p->group_leader = current->group_leader;
2267 p->tgid = current->tgid;
2269 p->group_leader = p;
2274 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
2275 p->dirty_paused_when = 0;
2277 p->pdeath_signal = 0;
2278 INIT_LIST_HEAD(&p->thread_group);
2279 p->task_works = NULL;
2281 #ifdef CONFIG_KRETPROBES
2282 p->kretprobe_instances.first = NULL;
2286 * Ensure that the cgroup subsystem policies allow the new process to be
2287 * forked. It should be noted that the new process's css_set can be changed
2288 * between here and cgroup_post_fork() if an organisation operation is in
2291 retval = cgroup_can_fork(p, args);
2293 goto bad_fork_put_pidfd;
2296 * From this point on we must avoid any synchronous user-space
2297 * communication until we take the tasklist-lock. In particular, we do
2298 * not want user-space to be able to predict the process start-time by
2299 * stalling fork(2) after we recorded the start_time but before it is
2300 * visible to the system.
2303 p->start_time = ktime_get_ns();
2304 p->start_boottime = ktime_get_boottime_ns();
2307 * Make it visible to the rest of the system, but dont wake it up yet.
2308 * Need tasklist lock for parent etc handling!
2310 write_lock_irq(&tasklist_lock);
2312 /* CLONE_PARENT re-uses the old parent */
2313 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
2314 p->real_parent = current->real_parent;
2315 p->parent_exec_id = current->parent_exec_id;
2316 if (clone_flags & CLONE_THREAD)
2317 p->exit_signal = -1;
2319 p->exit_signal = current->group_leader->exit_signal;
2321 p->real_parent = current;
2322 p->parent_exec_id = current->self_exec_id;
2323 p->exit_signal = args->exit_signal;
2326 klp_copy_process(p);
2330 spin_lock(¤t->sighand->siglock);
2333 * Copy seccomp details explicitly here, in case they were changed
2334 * before holding sighand lock.
2338 rseq_fork(p, clone_flags);
2340 /* Don't start children in a dying pid namespace */
2341 if (unlikely(!(ns_of_pid(pid)->pid_allocated & PIDNS_ADDING))) {
2343 goto bad_fork_cancel_cgroup;
2346 /* Let kill terminate clone/fork in the middle */
2347 if (fatal_signal_pending(current)) {
2349 goto bad_fork_cancel_cgroup;
2352 /* past the last point of failure */
2354 fd_install(pidfd, pidfile);
2356 init_task_pid_links(p);
2357 if (likely(p->pid)) {
2358 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
2360 init_task_pid(p, PIDTYPE_PID, pid);
2361 if (thread_group_leader(p)) {
2362 init_task_pid(p, PIDTYPE_TGID, pid);
2363 init_task_pid(p, PIDTYPE_PGID, task_pgrp(current));
2364 init_task_pid(p, PIDTYPE_SID, task_session(current));
2366 if (is_child_reaper(pid)) {
2367 ns_of_pid(pid)->child_reaper = p;
2368 p->signal->flags |= SIGNAL_UNKILLABLE;
2370 p->signal->shared_pending.signal = delayed.signal;
2371 p->signal->tty = tty_kref_get(current->signal->tty);
2373 * Inherit has_child_subreaper flag under the same
2374 * tasklist_lock with adding child to the process tree
2375 * for propagate_has_child_subreaper optimization.
2377 p->signal->has_child_subreaper = p->real_parent->signal->has_child_subreaper ||
2378 p->real_parent->signal->is_child_subreaper;
2379 list_add_tail(&p->sibling, &p->real_parent->children);
2380 list_add_tail_rcu(&p->tasks, &init_task.tasks);
2381 attach_pid(p, PIDTYPE_TGID);
2382 attach_pid(p, PIDTYPE_PGID);
2383 attach_pid(p, PIDTYPE_SID);
2384 __this_cpu_inc(process_counts);
2386 current->signal->nr_threads++;
2387 atomic_inc(¤t->signal->live);
2388 refcount_inc(¤t->signal->sigcnt);
2389 task_join_group_stop(p);
2390 list_add_tail_rcu(&p->thread_group,
2391 &p->group_leader->thread_group);
2392 list_add_tail_rcu(&p->thread_node,
2393 &p->signal->thread_head);
2395 attach_pid(p, PIDTYPE_PID);
2399 hlist_del_init(&delayed.node);
2400 spin_unlock(¤t->sighand->siglock);
2401 syscall_tracepoint_update(p);
2402 write_unlock_irq(&tasklist_lock);
2404 proc_fork_connector(p);
2405 sched_post_fork(p, args);
2406 cgroup_post_fork(p, args);
2409 trace_task_newtask(p, clone_flags);
2410 uprobe_copy_process(p, clone_flags);
2412 copy_oom_score_adj(clone_flags, p);
2416 bad_fork_cancel_cgroup:
2418 spin_unlock(¤t->sighand->siglock);
2419 write_unlock_irq(&tasklist_lock);
2420 cgroup_cancel_fork(p, args);
2422 if (clone_flags & CLONE_PIDFD) {
2424 put_unused_fd(pidfd);
2427 if (pid != &init_struct_pid)
2429 bad_fork_cleanup_thread:
2431 bad_fork_cleanup_io:
2434 bad_fork_cleanup_namespaces:
2435 exit_task_namespaces(p);
2436 bad_fork_cleanup_mm:
2438 mm_clear_owner(p->mm, p);
2441 bad_fork_cleanup_signal:
2442 if (!(clone_flags & CLONE_THREAD))
2443 free_signal_struct(p->signal);
2444 bad_fork_cleanup_sighand:
2445 __cleanup_sighand(p->sighand);
2446 bad_fork_cleanup_fs:
2447 exit_fs(p); /* blocking */
2448 bad_fork_cleanup_files:
2449 exit_files(p); /* blocking */
2450 bad_fork_cleanup_semundo:
2452 bad_fork_cleanup_security:
2453 security_task_free(p);
2454 bad_fork_cleanup_audit:
2456 bad_fork_cleanup_perf:
2457 perf_event_free_task(p);
2458 bad_fork_cleanup_policy:
2459 lockdep_free_task(p);
2461 mpol_put(p->mempolicy);
2462 bad_fork_cleanup_threadgroup_lock:
2464 delayacct_tsk_free(p);
2465 bad_fork_cleanup_count:
2466 dec_rlimit_ucounts(task_ucounts(p), UCOUNT_RLIMIT_NPROC, 1);
2469 WRITE_ONCE(p->__state, TASK_DEAD);
2471 delayed_free_task(p);
2473 spin_lock_irq(¤t->sighand->siglock);
2474 hlist_del_init(&delayed.node);
2475 spin_unlock_irq(¤t->sighand->siglock);
2476 return ERR_PTR(retval);
2479 static inline void init_idle_pids(struct task_struct *idle)
2483 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
2484 INIT_HLIST_NODE(&idle->pid_links[type]); /* not really needed */
2485 init_task_pid(idle, type, &init_struct_pid);
2489 struct task_struct * __init fork_idle(int cpu)
2491 struct task_struct *task;
2492 struct kernel_clone_args args = {
2496 task = copy_process(&init_struct_pid, 0, cpu_to_node(cpu), &args);
2497 if (!IS_ERR(task)) {
2498 init_idle_pids(task);
2499 init_idle(task, cpu);
2505 struct mm_struct *copy_init_mm(void)
2507 return dup_mm(NULL, &init_mm);
2511 * This is like kernel_clone(), but shaved down and tailored to just
2512 * creating io_uring workers. It returns a created task, or an error pointer.
2513 * The returned task is inactive, and the caller must fire it up through
2514 * wake_up_new_task(p). All signals are blocked in the created task.
2516 struct task_struct *create_io_thread(int (*fn)(void *), void *arg, int node)
2518 unsigned long flags = CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|
2520 struct kernel_clone_args args = {
2521 .flags = ((lower_32_bits(flags) | CLONE_VM |
2522 CLONE_UNTRACED) & ~CSIGNAL),
2523 .exit_signal = (lower_32_bits(flags) & CSIGNAL),
2524 .stack = (unsigned long)fn,
2525 .stack_size = (unsigned long)arg,
2529 return copy_process(NULL, 0, node, &args);
2533 * Ok, this is the main fork-routine.
2535 * It copies the process, and if successful kick-starts
2536 * it and waits for it to finish using the VM if required.
2538 * args->exit_signal is expected to be checked for sanity by the caller.
2540 pid_t kernel_clone(struct kernel_clone_args *args)
2542 u64 clone_flags = args->flags;
2543 struct completion vfork;
2545 struct task_struct *p;
2550 * For legacy clone() calls, CLONE_PIDFD uses the parent_tid argument
2551 * to return the pidfd. Hence, CLONE_PIDFD and CLONE_PARENT_SETTID are
2552 * mutually exclusive. With clone3() CLONE_PIDFD has grown a separate
2553 * field in struct clone_args and it still doesn't make sense to have
2554 * them both point at the same memory location. Performing this check
2555 * here has the advantage that we don't need to have a separate helper
2556 * to check for legacy clone().
2558 if ((args->flags & CLONE_PIDFD) &&
2559 (args->flags & CLONE_PARENT_SETTID) &&
2560 (args->pidfd == args->parent_tid))
2564 * Determine whether and which event to report to ptracer. When
2565 * called from kernel_thread or CLONE_UNTRACED is explicitly
2566 * requested, no event is reported; otherwise, report if the event
2567 * for the type of forking is enabled.
2569 if (!(clone_flags & CLONE_UNTRACED)) {
2570 if (clone_flags & CLONE_VFORK)
2571 trace = PTRACE_EVENT_VFORK;
2572 else if (args->exit_signal != SIGCHLD)
2573 trace = PTRACE_EVENT_CLONE;
2575 trace = PTRACE_EVENT_FORK;
2577 if (likely(!ptrace_event_enabled(current, trace)))
2581 p = copy_process(NULL, trace, NUMA_NO_NODE, args);
2582 add_latent_entropy();
2588 * Do this prior waking up the new thread - the thread pointer
2589 * might get invalid after that point, if the thread exits quickly.
2591 trace_sched_process_fork(current, p);
2593 pid = get_task_pid(p, PIDTYPE_PID);
2596 if (clone_flags & CLONE_PARENT_SETTID)
2597 put_user(nr, args->parent_tid);
2599 if (clone_flags & CLONE_VFORK) {
2600 p->vfork_done = &vfork;
2601 init_completion(&vfork);
2605 wake_up_new_task(p);
2607 /* forking complete and child started to run, tell ptracer */
2608 if (unlikely(trace))
2609 ptrace_event_pid(trace, pid);
2611 if (clone_flags & CLONE_VFORK) {
2612 if (!wait_for_vfork_done(p, &vfork))
2613 ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid);
2621 * Create a kernel thread.
2623 pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
2625 struct kernel_clone_args args = {
2626 .flags = ((lower_32_bits(flags) | CLONE_VM |
2627 CLONE_UNTRACED) & ~CSIGNAL),
2628 .exit_signal = (lower_32_bits(flags) & CSIGNAL),
2629 .stack = (unsigned long)fn,
2630 .stack_size = (unsigned long)arg,
2633 return kernel_clone(&args);
2636 #ifdef __ARCH_WANT_SYS_FORK
2637 SYSCALL_DEFINE0(fork)
2640 struct kernel_clone_args args = {
2641 .exit_signal = SIGCHLD,
2644 return kernel_clone(&args);
2646 /* can not support in nommu mode */
2652 #ifdef __ARCH_WANT_SYS_VFORK
2653 SYSCALL_DEFINE0(vfork)
2655 struct kernel_clone_args args = {
2656 .flags = CLONE_VFORK | CLONE_VM,
2657 .exit_signal = SIGCHLD,
2660 return kernel_clone(&args);
2664 #ifdef __ARCH_WANT_SYS_CLONE
2665 #ifdef CONFIG_CLONE_BACKWARDS
2666 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2667 int __user *, parent_tidptr,
2669 int __user *, child_tidptr)
2670 #elif defined(CONFIG_CLONE_BACKWARDS2)
2671 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags,
2672 int __user *, parent_tidptr,
2673 int __user *, child_tidptr,
2675 #elif defined(CONFIG_CLONE_BACKWARDS3)
2676 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp,
2678 int __user *, parent_tidptr,
2679 int __user *, child_tidptr,
2682 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2683 int __user *, parent_tidptr,
2684 int __user *, child_tidptr,
2688 struct kernel_clone_args args = {
2689 .flags = (lower_32_bits(clone_flags) & ~CSIGNAL),
2690 .pidfd = parent_tidptr,
2691 .child_tid = child_tidptr,
2692 .parent_tid = parent_tidptr,
2693 .exit_signal = (lower_32_bits(clone_flags) & CSIGNAL),
2698 return kernel_clone(&args);
2702 #ifdef __ARCH_WANT_SYS_CLONE3
2704 noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs,
2705 struct clone_args __user *uargs,
2709 struct clone_args args;
2710 pid_t *kset_tid = kargs->set_tid;
2712 BUILD_BUG_ON(offsetofend(struct clone_args, tls) !=
2713 CLONE_ARGS_SIZE_VER0);
2714 BUILD_BUG_ON(offsetofend(struct clone_args, set_tid_size) !=
2715 CLONE_ARGS_SIZE_VER1);
2716 BUILD_BUG_ON(offsetofend(struct clone_args, cgroup) !=
2717 CLONE_ARGS_SIZE_VER2);
2718 BUILD_BUG_ON(sizeof(struct clone_args) != CLONE_ARGS_SIZE_VER2);
2720 if (unlikely(usize > PAGE_SIZE))
2722 if (unlikely(usize < CLONE_ARGS_SIZE_VER0))
2725 err = copy_struct_from_user(&args, sizeof(args), uargs, usize);
2729 if (unlikely(args.set_tid_size > MAX_PID_NS_LEVEL))
2732 if (unlikely(!args.set_tid && args.set_tid_size > 0))
2735 if (unlikely(args.set_tid && args.set_tid_size == 0))
2739 * Verify that higher 32bits of exit_signal are unset and that
2740 * it is a valid signal
2742 if (unlikely((args.exit_signal & ~((u64)CSIGNAL)) ||
2743 !valid_signal(args.exit_signal)))
2746 if ((args.flags & CLONE_INTO_CGROUP) &&
2747 (args.cgroup > INT_MAX || usize < CLONE_ARGS_SIZE_VER2))
2750 *kargs = (struct kernel_clone_args){
2751 .flags = args.flags,
2752 .pidfd = u64_to_user_ptr(args.pidfd),
2753 .child_tid = u64_to_user_ptr(args.child_tid),
2754 .parent_tid = u64_to_user_ptr(args.parent_tid),
2755 .exit_signal = args.exit_signal,
2756 .stack = args.stack,
2757 .stack_size = args.stack_size,
2759 .set_tid_size = args.set_tid_size,
2760 .cgroup = args.cgroup,
2764 copy_from_user(kset_tid, u64_to_user_ptr(args.set_tid),
2765 (kargs->set_tid_size * sizeof(pid_t))))
2768 kargs->set_tid = kset_tid;
2774 * clone3_stack_valid - check and prepare stack
2775 * @kargs: kernel clone args
2777 * Verify that the stack arguments userspace gave us are sane.
2778 * In addition, set the stack direction for userspace since it's easy for us to
2781 static inline bool clone3_stack_valid(struct kernel_clone_args *kargs)
2783 if (kargs->stack == 0) {
2784 if (kargs->stack_size > 0)
2787 if (kargs->stack_size == 0)
2790 if (!access_ok((void __user *)kargs->stack, kargs->stack_size))
2793 #if !defined(CONFIG_STACK_GROWSUP) && !defined(CONFIG_IA64)
2794 kargs->stack += kargs->stack_size;
2801 static bool clone3_args_valid(struct kernel_clone_args *kargs)
2803 /* Verify that no unknown flags are passed along. */
2805 ~(CLONE_LEGACY_FLAGS | CLONE_CLEAR_SIGHAND | CLONE_INTO_CGROUP))
2809 * - make the CLONE_DETACHED bit reusable for clone3
2810 * - make the CSIGNAL bits reusable for clone3
2812 if (kargs->flags & (CLONE_DETACHED | CSIGNAL))
2815 if ((kargs->flags & (CLONE_SIGHAND | CLONE_CLEAR_SIGHAND)) ==
2816 (CLONE_SIGHAND | CLONE_CLEAR_SIGHAND))
2819 if ((kargs->flags & (CLONE_THREAD | CLONE_PARENT)) &&
2823 if (!clone3_stack_valid(kargs))
2830 * clone3 - create a new process with specific properties
2831 * @uargs: argument structure
2832 * @size: size of @uargs
2834 * clone3() is the extensible successor to clone()/clone2().
2835 * It takes a struct as argument that is versioned by its size.
2837 * Return: On success, a positive PID for the child process.
2838 * On error, a negative errno number.
2840 SYSCALL_DEFINE2(clone3, struct clone_args __user *, uargs, size_t, size)
2844 struct kernel_clone_args kargs;
2845 pid_t set_tid[MAX_PID_NS_LEVEL];
2847 kargs.set_tid = set_tid;
2849 err = copy_clone_args_from_user(&kargs, uargs, size);
2853 if (!clone3_args_valid(&kargs))
2856 return kernel_clone(&kargs);
2860 void walk_process_tree(struct task_struct *top, proc_visitor visitor, void *data)
2862 struct task_struct *leader, *parent, *child;
2865 read_lock(&tasklist_lock);
2866 leader = top = top->group_leader;
2868 for_each_thread(leader, parent) {
2869 list_for_each_entry(child, &parent->children, sibling) {
2870 res = visitor(child, data);
2882 if (leader != top) {
2884 parent = child->real_parent;
2885 leader = parent->group_leader;
2889 read_unlock(&tasklist_lock);
2892 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
2893 #define ARCH_MIN_MMSTRUCT_ALIGN 0
2896 static void sighand_ctor(void *data)
2898 struct sighand_struct *sighand = data;
2900 spin_lock_init(&sighand->siglock);
2901 init_waitqueue_head(&sighand->signalfd_wqh);
2904 void __init proc_caches_init(void)
2906 unsigned int mm_size;
2908 sighand_cachep = kmem_cache_create("sighand_cache",
2909 sizeof(struct sighand_struct), 0,
2910 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_TYPESAFE_BY_RCU|
2911 SLAB_ACCOUNT, sighand_ctor);
2912 signal_cachep = kmem_cache_create("signal_cache",
2913 sizeof(struct signal_struct), 0,
2914 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2916 files_cachep = kmem_cache_create("files_cache",
2917 sizeof(struct files_struct), 0,
2918 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2920 fs_cachep = kmem_cache_create("fs_cache",
2921 sizeof(struct fs_struct), 0,
2922 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2926 * The mm_cpumask is located at the end of mm_struct, and is
2927 * dynamically sized based on the maximum CPU number this system
2928 * can have, taking hotplug into account (nr_cpu_ids).
2930 mm_size = sizeof(struct mm_struct) + cpumask_size();
2932 mm_cachep = kmem_cache_create_usercopy("mm_struct",
2933 mm_size, ARCH_MIN_MMSTRUCT_ALIGN,
2934 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2935 offsetof(struct mm_struct, saved_auxv),
2936 sizeof_field(struct mm_struct, saved_auxv),
2938 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT);
2940 nsproxy_cache_init();
2944 * Check constraints on flags passed to the unshare system call.
2946 static int check_unshare_flags(unsigned long unshare_flags)
2948 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
2949 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
2950 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET|
2951 CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP|
2955 * Not implemented, but pretend it works if there is nothing
2956 * to unshare. Note that unsharing the address space or the
2957 * signal handlers also need to unshare the signal queues (aka
2960 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
2961 if (!thread_group_empty(current))
2964 if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) {
2965 if (refcount_read(¤t->sighand->count) > 1)
2968 if (unshare_flags & CLONE_VM) {
2969 if (!current_is_single_threaded())
2977 * Unshare the filesystem structure if it is being shared
2979 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
2981 struct fs_struct *fs = current->fs;
2983 if (!(unshare_flags & CLONE_FS) || !fs)
2986 /* don't need lock here; in the worst case we'll do useless copy */
2990 *new_fsp = copy_fs_struct(fs);
2998 * Unshare file descriptor table if it is being shared
3000 int unshare_fd(unsigned long unshare_flags, unsigned int max_fds,
3001 struct files_struct **new_fdp)
3003 struct files_struct *fd = current->files;
3006 if ((unshare_flags & CLONE_FILES) &&
3007 (fd && atomic_read(&fd->count) > 1)) {
3008 *new_fdp = dup_fd(fd, max_fds, &error);
3017 * unshare allows a process to 'unshare' part of the process
3018 * context which was originally shared using clone. copy_*
3019 * functions used by kernel_clone() cannot be used here directly
3020 * because they modify an inactive task_struct that is being
3021 * constructed. Here we are modifying the current, active,
3024 int ksys_unshare(unsigned long unshare_flags)
3026 struct fs_struct *fs, *new_fs = NULL;
3027 struct files_struct *new_fd = NULL;
3028 struct cred *new_cred = NULL;
3029 struct nsproxy *new_nsproxy = NULL;
3034 * If unsharing a user namespace must also unshare the thread group
3035 * and unshare the filesystem root and working directories.
3037 if (unshare_flags & CLONE_NEWUSER)
3038 unshare_flags |= CLONE_THREAD | CLONE_FS;
3040 * If unsharing vm, must also unshare signal handlers.
3042 if (unshare_flags & CLONE_VM)
3043 unshare_flags |= CLONE_SIGHAND;
3045 * If unsharing a signal handlers, must also unshare the signal queues.
3047 if (unshare_flags & CLONE_SIGHAND)
3048 unshare_flags |= CLONE_THREAD;
3050 * If unsharing namespace, must also unshare filesystem information.
3052 if (unshare_flags & CLONE_NEWNS)
3053 unshare_flags |= CLONE_FS;
3055 err = check_unshare_flags(unshare_flags);
3057 goto bad_unshare_out;
3059 * CLONE_NEWIPC must also detach from the undolist: after switching
3060 * to a new ipc namespace, the semaphore arrays from the old
3061 * namespace are unreachable.
3063 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
3065 err = unshare_fs(unshare_flags, &new_fs);
3067 goto bad_unshare_out;
3068 err = unshare_fd(unshare_flags, NR_OPEN_MAX, &new_fd);
3070 goto bad_unshare_cleanup_fs;
3071 err = unshare_userns(unshare_flags, &new_cred);
3073 goto bad_unshare_cleanup_fd;
3074 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
3077 goto bad_unshare_cleanup_cred;
3080 err = set_cred_ucounts(new_cred);
3082 goto bad_unshare_cleanup_cred;
3085 if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
3088 * CLONE_SYSVSEM is equivalent to sys_exit().
3092 if (unshare_flags & CLONE_NEWIPC) {
3093 /* Orphan segments in old ns (see sem above). */
3095 shm_init_task(current);
3099 switch_task_namespaces(current, new_nsproxy);
3105 spin_lock(&fs->lock);
3106 current->fs = new_fs;
3111 spin_unlock(&fs->lock);
3115 swap(current->files, new_fd);
3117 task_unlock(current);
3120 /* Install the new user namespace */
3121 commit_creds(new_cred);
3126 perf_event_namespaces(current);
3128 bad_unshare_cleanup_cred:
3131 bad_unshare_cleanup_fd:
3133 put_files_struct(new_fd);
3135 bad_unshare_cleanup_fs:
3137 free_fs_struct(new_fs);
3143 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
3145 return ksys_unshare(unshare_flags);
3149 * Helper to unshare the files of the current task.
3150 * We don't want to expose copy_files internals to
3151 * the exec layer of the kernel.
3154 int unshare_files(void)
3156 struct task_struct *task = current;
3157 struct files_struct *old, *copy = NULL;
3160 error = unshare_fd(CLONE_FILES, NR_OPEN_MAX, ©);
3168 put_files_struct(old);
3172 int sysctl_max_threads(struct ctl_table *table, int write,
3173 void *buffer, size_t *lenp, loff_t *ppos)
3177 int threads = max_threads;
3179 int max = MAX_THREADS;
3186 ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
3190 max_threads = threads;