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/kmsan.h>
41 #include <linux/binfmts.h>
42 #include <linux/mman.h>
43 #include <linux/mmu_notifier.h>
46 #include <linux/mm_inline.h>
47 #include <linux/nsproxy.h>
48 #include <linux/capability.h>
49 #include <linux/cpu.h>
50 #include <linux/cgroup.h>
51 #include <linux/security.h>
52 #include <linux/hugetlb.h>
53 #include <linux/seccomp.h>
54 #include <linux/swap.h>
55 #include <linux/syscalls.h>
56 #include <linux/jiffies.h>
57 #include <linux/futex.h>
58 #include <linux/compat.h>
59 #include <linux/kthread.h>
60 #include <linux/task_io_accounting_ops.h>
61 #include <linux/rcupdate.h>
62 #include <linux/ptrace.h>
63 #include <linux/mount.h>
64 #include <linux/audit.h>
65 #include <linux/memcontrol.h>
66 #include <linux/ftrace.h>
67 #include <linux/proc_fs.h>
68 #include <linux/profile.h>
69 #include <linux/rmap.h>
70 #include <linux/ksm.h>
71 #include <linux/acct.h>
72 #include <linux/userfaultfd_k.h>
73 #include <linux/tsacct_kern.h>
74 #include <linux/cn_proc.h>
75 #include <linux/freezer.h>
76 #include <linux/delayacct.h>
77 #include <linux/taskstats_kern.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>
99 #include <linux/stackprotector.h>
100 #include <linux/user_events.h>
101 #include <linux/iommu.h>
103 #include <asm/pgalloc.h>
104 #include <linux/uaccess.h>
105 #include <asm/mmu_context.h>
106 #include <asm/cacheflush.h>
107 #include <asm/tlbflush.h>
109 #include <trace/events/sched.h>
111 #define CREATE_TRACE_POINTS
112 #include <trace/events/task.h>
115 * Minimum number of threads to boot the kernel
117 #define MIN_THREADS 20
120 * Maximum number of threads
122 #define MAX_THREADS FUTEX_TID_MASK
125 * Protected counters by write_lock_irq(&tasklist_lock)
127 unsigned long total_forks; /* Handle normal Linux uptimes. */
128 int nr_threads; /* The idle threads do not count.. */
130 static int max_threads; /* tunable limit on nr_threads */
132 #define NAMED_ARRAY_INDEX(x) [x] = __stringify(x)
134 static const char * const resident_page_types[] = {
135 NAMED_ARRAY_INDEX(MM_FILEPAGES),
136 NAMED_ARRAY_INDEX(MM_ANONPAGES),
137 NAMED_ARRAY_INDEX(MM_SWAPENTS),
138 NAMED_ARRAY_INDEX(MM_SHMEMPAGES),
141 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
143 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */
145 #ifdef CONFIG_PROVE_RCU
146 int lockdep_tasklist_lock_is_held(void)
148 return lockdep_is_held(&tasklist_lock);
150 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
151 #endif /* #ifdef CONFIG_PROVE_RCU */
153 int nr_processes(void)
158 for_each_possible_cpu(cpu)
159 total += per_cpu(process_counts, cpu);
164 void __weak arch_release_task_struct(struct task_struct *tsk)
168 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
169 static struct kmem_cache *task_struct_cachep;
171 static inline struct task_struct *alloc_task_struct_node(int node)
173 return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node);
176 static inline void free_task_struct(struct task_struct *tsk)
178 kmem_cache_free(task_struct_cachep, tsk);
182 #ifndef CONFIG_ARCH_THREAD_STACK_ALLOCATOR
185 * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
186 * kmemcache based allocator.
188 # if THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK)
190 # ifdef CONFIG_VMAP_STACK
192 * vmalloc() is a bit slow, and calling vfree() enough times will force a TLB
193 * flush. Try to minimize the number of calls by caching stacks.
195 #define NR_CACHED_STACKS 2
196 static DEFINE_PER_CPU(struct vm_struct *, cached_stacks[NR_CACHED_STACKS]);
200 struct vm_struct *stack_vm_area;
203 static bool try_release_thread_stack_to_cache(struct vm_struct *vm)
207 for (i = 0; i < NR_CACHED_STACKS; i++) {
208 if (this_cpu_cmpxchg(cached_stacks[i], NULL, vm) != NULL)
215 static void thread_stack_free_rcu(struct rcu_head *rh)
217 struct vm_stack *vm_stack = container_of(rh, struct vm_stack, rcu);
219 if (try_release_thread_stack_to_cache(vm_stack->stack_vm_area))
225 static void thread_stack_delayed_free(struct task_struct *tsk)
227 struct vm_stack *vm_stack = tsk->stack;
229 vm_stack->stack_vm_area = tsk->stack_vm_area;
230 call_rcu(&vm_stack->rcu, thread_stack_free_rcu);
233 static int free_vm_stack_cache(unsigned int cpu)
235 struct vm_struct **cached_vm_stacks = per_cpu_ptr(cached_stacks, cpu);
238 for (i = 0; i < NR_CACHED_STACKS; i++) {
239 struct vm_struct *vm_stack = cached_vm_stacks[i];
244 vfree(vm_stack->addr);
245 cached_vm_stacks[i] = NULL;
251 static int memcg_charge_kernel_stack(struct vm_struct *vm)
257 BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE);
259 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
260 ret = memcg_kmem_charge_page(vm->pages[i], GFP_KERNEL, 0);
267 for (i = 0; i < nr_charged; i++)
268 memcg_kmem_uncharge_page(vm->pages[i], 0);
272 static int alloc_thread_stack_node(struct task_struct *tsk, int node)
274 struct vm_struct *vm;
278 for (i = 0; i < NR_CACHED_STACKS; i++) {
281 s = this_cpu_xchg(cached_stacks[i], NULL);
286 /* Reset stack metadata. */
287 kasan_unpoison_range(s->addr, THREAD_SIZE);
289 stack = kasan_reset_tag(s->addr);
291 /* Clear stale pointers from reused stack. */
292 memset(stack, 0, THREAD_SIZE);
294 if (memcg_charge_kernel_stack(s)) {
299 tsk->stack_vm_area = s;
305 * Allocated stacks are cached and later reused by new threads,
306 * so memcg accounting is performed manually on assigning/releasing
307 * stacks to tasks. Drop __GFP_ACCOUNT.
309 stack = __vmalloc_node_range(THREAD_SIZE, THREAD_ALIGN,
310 VMALLOC_START, VMALLOC_END,
311 THREADINFO_GFP & ~__GFP_ACCOUNT,
313 0, node, __builtin_return_address(0));
317 vm = find_vm_area(stack);
318 if (memcg_charge_kernel_stack(vm)) {
323 * We can't call find_vm_area() in interrupt context, and
324 * free_thread_stack() can be called in interrupt context,
325 * so cache the vm_struct.
327 tsk->stack_vm_area = vm;
328 stack = kasan_reset_tag(stack);
333 static void free_thread_stack(struct task_struct *tsk)
335 if (!try_release_thread_stack_to_cache(tsk->stack_vm_area))
336 thread_stack_delayed_free(tsk);
339 tsk->stack_vm_area = NULL;
342 # else /* !CONFIG_VMAP_STACK */
344 static void thread_stack_free_rcu(struct rcu_head *rh)
346 __free_pages(virt_to_page(rh), THREAD_SIZE_ORDER);
349 static void thread_stack_delayed_free(struct task_struct *tsk)
351 struct rcu_head *rh = tsk->stack;
353 call_rcu(rh, thread_stack_free_rcu);
356 static int alloc_thread_stack_node(struct task_struct *tsk, int node)
358 struct page *page = alloc_pages_node(node, THREADINFO_GFP,
362 tsk->stack = kasan_reset_tag(page_address(page));
368 static void free_thread_stack(struct task_struct *tsk)
370 thread_stack_delayed_free(tsk);
374 # endif /* CONFIG_VMAP_STACK */
375 # else /* !(THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK)) */
377 static struct kmem_cache *thread_stack_cache;
379 static void thread_stack_free_rcu(struct rcu_head *rh)
381 kmem_cache_free(thread_stack_cache, rh);
384 static void thread_stack_delayed_free(struct task_struct *tsk)
386 struct rcu_head *rh = tsk->stack;
388 call_rcu(rh, thread_stack_free_rcu);
391 static int alloc_thread_stack_node(struct task_struct *tsk, int node)
393 unsigned long *stack;
394 stack = kmem_cache_alloc_node(thread_stack_cache, THREADINFO_GFP, node);
395 stack = kasan_reset_tag(stack);
397 return stack ? 0 : -ENOMEM;
400 static void free_thread_stack(struct task_struct *tsk)
402 thread_stack_delayed_free(tsk);
406 void thread_stack_cache_init(void)
408 thread_stack_cache = kmem_cache_create_usercopy("thread_stack",
409 THREAD_SIZE, THREAD_SIZE, 0, 0,
411 BUG_ON(thread_stack_cache == NULL);
414 # endif /* THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK) */
415 #else /* CONFIG_ARCH_THREAD_STACK_ALLOCATOR */
417 static int alloc_thread_stack_node(struct task_struct *tsk, int node)
419 unsigned long *stack;
421 stack = arch_alloc_thread_stack_node(tsk, node);
423 return stack ? 0 : -ENOMEM;
426 static void free_thread_stack(struct task_struct *tsk)
428 arch_free_thread_stack(tsk);
432 #endif /* !CONFIG_ARCH_THREAD_STACK_ALLOCATOR */
434 /* SLAB cache for signal_struct structures (tsk->signal) */
435 static struct kmem_cache *signal_cachep;
437 /* SLAB cache for sighand_struct structures (tsk->sighand) */
438 struct kmem_cache *sighand_cachep;
440 /* SLAB cache for files_struct structures (tsk->files) */
441 struct kmem_cache *files_cachep;
443 /* SLAB cache for fs_struct structures (tsk->fs) */
444 struct kmem_cache *fs_cachep;
446 /* SLAB cache for vm_area_struct structures */
447 static struct kmem_cache *vm_area_cachep;
449 /* SLAB cache for mm_struct structures (tsk->mm) */
450 static struct kmem_cache *mm_cachep;
452 #ifdef CONFIG_PER_VMA_LOCK
454 /* SLAB cache for vm_area_struct.lock */
455 static struct kmem_cache *vma_lock_cachep;
457 static bool vma_lock_alloc(struct vm_area_struct *vma)
459 vma->vm_lock = kmem_cache_alloc(vma_lock_cachep, GFP_KERNEL);
463 init_rwsem(&vma->vm_lock->lock);
464 vma->vm_lock_seq = -1;
469 static inline void vma_lock_free(struct vm_area_struct *vma)
471 kmem_cache_free(vma_lock_cachep, vma->vm_lock);
474 #else /* CONFIG_PER_VMA_LOCK */
476 static inline bool vma_lock_alloc(struct vm_area_struct *vma) { return true; }
477 static inline void vma_lock_free(struct vm_area_struct *vma) {}
479 #endif /* CONFIG_PER_VMA_LOCK */
481 struct vm_area_struct *vm_area_alloc(struct mm_struct *mm)
483 struct vm_area_struct *vma;
485 vma = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
490 if (!vma_lock_alloc(vma)) {
491 kmem_cache_free(vm_area_cachep, vma);
498 struct vm_area_struct *vm_area_dup(struct vm_area_struct *orig)
500 struct vm_area_struct *new = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
505 ASSERT_EXCLUSIVE_WRITER(orig->vm_flags);
506 ASSERT_EXCLUSIVE_WRITER(orig->vm_file);
508 * orig->shared.rb may be modified concurrently, but the clone
509 * will be reinitialized.
511 data_race(memcpy(new, orig, sizeof(*new)));
512 if (!vma_lock_alloc(new)) {
513 kmem_cache_free(vm_area_cachep, new);
516 INIT_LIST_HEAD(&new->anon_vma_chain);
517 vma_numab_state_init(new);
518 dup_anon_vma_name(orig, new);
523 void __vm_area_free(struct vm_area_struct *vma)
525 vma_numab_state_free(vma);
526 free_anon_vma_name(vma);
528 kmem_cache_free(vm_area_cachep, vma);
531 #ifdef CONFIG_PER_VMA_LOCK
532 static void vm_area_free_rcu_cb(struct rcu_head *head)
534 struct vm_area_struct *vma = container_of(head, struct vm_area_struct,
537 /* The vma should not be locked while being destroyed. */
538 VM_BUG_ON_VMA(rwsem_is_locked(&vma->vm_lock->lock), vma);
543 void vm_area_free(struct vm_area_struct *vma)
545 #ifdef CONFIG_PER_VMA_LOCK
546 call_rcu(&vma->vm_rcu, vm_area_free_rcu_cb);
552 static void account_kernel_stack(struct task_struct *tsk, int account)
554 if (IS_ENABLED(CONFIG_VMAP_STACK)) {
555 struct vm_struct *vm = task_stack_vm_area(tsk);
558 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++)
559 mod_lruvec_page_state(vm->pages[i], NR_KERNEL_STACK_KB,
560 account * (PAGE_SIZE / 1024));
562 void *stack = task_stack_page(tsk);
564 /* All stack pages are in the same node. */
565 mod_lruvec_kmem_state(stack, NR_KERNEL_STACK_KB,
566 account * (THREAD_SIZE / 1024));
570 void exit_task_stack_account(struct task_struct *tsk)
572 account_kernel_stack(tsk, -1);
574 if (IS_ENABLED(CONFIG_VMAP_STACK)) {
575 struct vm_struct *vm;
578 vm = task_stack_vm_area(tsk);
579 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++)
580 memcg_kmem_uncharge_page(vm->pages[i], 0);
584 static void release_task_stack(struct task_struct *tsk)
586 if (WARN_ON(READ_ONCE(tsk->__state) != TASK_DEAD))
587 return; /* Better to leak the stack than to free prematurely */
589 free_thread_stack(tsk);
592 #ifdef CONFIG_THREAD_INFO_IN_TASK
593 void put_task_stack(struct task_struct *tsk)
595 if (refcount_dec_and_test(&tsk->stack_refcount))
596 release_task_stack(tsk);
600 void free_task(struct task_struct *tsk)
602 #ifdef CONFIG_SECCOMP
603 WARN_ON_ONCE(tsk->seccomp.filter);
605 release_user_cpus_ptr(tsk);
608 #ifndef CONFIG_THREAD_INFO_IN_TASK
610 * The task is finally done with both the stack and thread_info,
613 release_task_stack(tsk);
616 * If the task had a separate stack allocation, it should be gone
619 WARN_ON_ONCE(refcount_read(&tsk->stack_refcount) != 0);
621 rt_mutex_debug_task_free(tsk);
622 ftrace_graph_exit_task(tsk);
623 arch_release_task_struct(tsk);
624 if (tsk->flags & PF_KTHREAD)
625 free_kthread_struct(tsk);
626 bpf_task_storage_free(tsk);
627 free_task_struct(tsk);
629 EXPORT_SYMBOL(free_task);
631 static void dup_mm_exe_file(struct mm_struct *mm, struct mm_struct *oldmm)
633 struct file *exe_file;
635 exe_file = get_mm_exe_file(oldmm);
636 RCU_INIT_POINTER(mm->exe_file, exe_file);
638 * We depend on the oldmm having properly denied write access to the
641 if (exe_file && deny_write_access(exe_file))
642 pr_warn_once("deny_write_access() failed in %s\n", __func__);
646 static __latent_entropy int dup_mmap(struct mm_struct *mm,
647 struct mm_struct *oldmm)
649 struct vm_area_struct *mpnt, *tmp;
651 unsigned long charge = 0;
653 VMA_ITERATOR(old_vmi, oldmm, 0);
654 VMA_ITERATOR(vmi, mm, 0);
656 uprobe_start_dup_mmap();
657 if (mmap_write_lock_killable(oldmm)) {
659 goto fail_uprobe_end;
661 flush_cache_dup_mm(oldmm);
662 uprobe_dup_mmap(oldmm, mm);
664 * Not linked in yet - no deadlock potential:
666 mmap_write_lock_nested(mm, SINGLE_DEPTH_NESTING);
668 /* No ordering required: file already has been exposed. */
669 dup_mm_exe_file(mm, oldmm);
671 mm->total_vm = oldmm->total_vm;
672 mm->data_vm = oldmm->data_vm;
673 mm->exec_vm = oldmm->exec_vm;
674 mm->stack_vm = oldmm->stack_vm;
676 retval = ksm_fork(mm, oldmm);
679 khugepaged_fork(mm, oldmm);
681 retval = vma_iter_bulk_alloc(&vmi, oldmm->map_count);
685 mt_clear_in_rcu(vmi.mas.tree);
686 for_each_vma(old_vmi, mpnt) {
689 vma_start_write(mpnt);
690 if (mpnt->vm_flags & VM_DONTCOPY) {
691 vm_stat_account(mm, mpnt->vm_flags, -vma_pages(mpnt));
696 * Don't duplicate many vmas if we've been oom-killed (for
699 if (fatal_signal_pending(current)) {
703 if (mpnt->vm_flags & VM_ACCOUNT) {
704 unsigned long len = vma_pages(mpnt);
706 if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
710 tmp = vm_area_dup(mpnt);
713 retval = vma_dup_policy(mpnt, tmp);
715 goto fail_nomem_policy;
717 retval = dup_userfaultfd(tmp, &uf);
719 goto fail_nomem_anon_vma_fork;
720 if (tmp->vm_flags & VM_WIPEONFORK) {
722 * VM_WIPEONFORK gets a clean slate in the child.
723 * Don't prepare anon_vma until fault since we don't
724 * copy page for current vma.
726 tmp->anon_vma = NULL;
727 } else if (anon_vma_fork(tmp, mpnt))
728 goto fail_nomem_anon_vma_fork;
729 vm_flags_clear(tmp, VM_LOCKED_MASK);
732 struct address_space *mapping = file->f_mapping;
735 i_mmap_lock_write(mapping);
736 if (tmp->vm_flags & VM_SHARED)
737 mapping_allow_writable(mapping);
738 flush_dcache_mmap_lock(mapping);
739 /* insert tmp into the share list, just after mpnt */
740 vma_interval_tree_insert_after(tmp, mpnt,
742 flush_dcache_mmap_unlock(mapping);
743 i_mmap_unlock_write(mapping);
747 * Copy/update hugetlb private vma information.
749 if (is_vm_hugetlb_page(tmp))
750 hugetlb_dup_vma_private(tmp);
752 /* Link the vma into the MT */
753 if (vma_iter_bulk_store(&vmi, tmp))
754 goto fail_nomem_vmi_store;
757 if (!(tmp->vm_flags & VM_WIPEONFORK))
758 retval = copy_page_range(tmp, mpnt);
760 if (tmp->vm_ops && tmp->vm_ops->open)
761 tmp->vm_ops->open(tmp);
766 /* a new mm has just been created */
767 retval = arch_dup_mmap(oldmm, mm);
771 mt_set_in_rcu(vmi.mas.tree);
773 mmap_write_unlock(mm);
775 mmap_write_unlock(oldmm);
776 dup_userfaultfd_complete(&uf);
778 uprobe_end_dup_mmap();
781 fail_nomem_vmi_store:
782 unlink_anon_vmas(tmp);
783 fail_nomem_anon_vma_fork:
784 mpol_put(vma_policy(tmp));
789 vm_unacct_memory(charge);
793 static inline int mm_alloc_pgd(struct mm_struct *mm)
795 mm->pgd = pgd_alloc(mm);
796 if (unlikely(!mm->pgd))
801 static inline void mm_free_pgd(struct mm_struct *mm)
803 pgd_free(mm, mm->pgd);
806 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
808 mmap_write_lock(oldmm);
809 dup_mm_exe_file(mm, oldmm);
810 mmap_write_unlock(oldmm);
813 #define mm_alloc_pgd(mm) (0)
814 #define mm_free_pgd(mm)
815 #endif /* CONFIG_MMU */
817 static void check_mm(struct mm_struct *mm)
821 BUILD_BUG_ON_MSG(ARRAY_SIZE(resident_page_types) != NR_MM_COUNTERS,
822 "Please make sure 'struct resident_page_types[]' is updated as well");
824 for (i = 0; i < NR_MM_COUNTERS; i++) {
825 long x = percpu_counter_sum(&mm->rss_stat[i]);
828 pr_alert("BUG: Bad rss-counter state mm:%p type:%s val:%ld\n",
829 mm, resident_page_types[i], x);
832 if (mm_pgtables_bytes(mm))
833 pr_alert("BUG: non-zero pgtables_bytes on freeing mm: %ld\n",
834 mm_pgtables_bytes(mm));
836 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
837 VM_BUG_ON_MM(mm->pmd_huge_pte, mm);
841 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
842 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm)))
844 static void do_check_lazy_tlb(void *arg)
846 struct mm_struct *mm = arg;
848 WARN_ON_ONCE(current->active_mm == mm);
851 static void do_shoot_lazy_tlb(void *arg)
853 struct mm_struct *mm = arg;
855 if (current->active_mm == mm) {
856 WARN_ON_ONCE(current->mm);
857 current->active_mm = &init_mm;
858 switch_mm(mm, &init_mm, current);
862 static void cleanup_lazy_tlbs(struct mm_struct *mm)
864 if (!IS_ENABLED(CONFIG_MMU_LAZY_TLB_SHOOTDOWN)) {
866 * In this case, lazy tlb mms are refounted and would not reach
867 * __mmdrop until all CPUs have switched away and mmdrop()ed.
873 * Lazy mm shootdown does not refcount "lazy tlb mm" usage, rather it
874 * requires lazy mm users to switch to another mm when the refcount
875 * drops to zero, before the mm is freed. This requires IPIs here to
876 * switch kernel threads to init_mm.
878 * archs that use IPIs to flush TLBs can piggy-back that lazy tlb mm
879 * switch with the final userspace teardown TLB flush which leaves the
880 * mm lazy on this CPU but no others, reducing the need for additional
881 * IPIs here. There are cases where a final IPI is still required here,
882 * such as the final mmdrop being performed on a different CPU than the
883 * one exiting, or kernel threads using the mm when userspace exits.
885 * IPI overheads have not found to be expensive, but they could be
886 * reduced in a number of possible ways, for example (roughly
887 * increasing order of complexity):
888 * - The last lazy reference created by exit_mm() could instead switch
889 * to init_mm, however it's probable this will run on the same CPU
890 * immediately afterwards, so this may not reduce IPIs much.
891 * - A batch of mms requiring IPIs could be gathered and freed at once.
892 * - CPUs store active_mm where it can be remotely checked without a
893 * lock, to filter out false-positives in the cpumask.
894 * - After mm_users or mm_count reaches zero, switching away from the
895 * mm could clear mm_cpumask to reduce some IPIs, perhaps together
896 * with some batching or delaying of the final IPIs.
897 * - A delayed freeing and RCU-like quiescing sequence based on mm
898 * switching to avoid IPIs completely.
900 on_each_cpu_mask(mm_cpumask(mm), do_shoot_lazy_tlb, (void *)mm, 1);
901 if (IS_ENABLED(CONFIG_DEBUG_VM_SHOOT_LAZIES))
902 on_each_cpu(do_check_lazy_tlb, (void *)mm, 1);
906 * Called when the last reference to the mm
907 * is dropped: either by a lazy thread or by
908 * mmput. Free the page directory and the mm.
910 void __mmdrop(struct mm_struct *mm)
914 BUG_ON(mm == &init_mm);
915 WARN_ON_ONCE(mm == current->mm);
917 /* Ensure no CPUs are using this as their lazy tlb mm */
918 cleanup_lazy_tlbs(mm);
920 WARN_ON_ONCE(mm == current->active_mm);
923 mmu_notifier_subscriptions_destroy(mm);
925 put_user_ns(mm->user_ns);
929 for (i = 0; i < NR_MM_COUNTERS; i++)
930 percpu_counter_destroy(&mm->rss_stat[i]);
933 EXPORT_SYMBOL_GPL(__mmdrop);
935 static void mmdrop_async_fn(struct work_struct *work)
937 struct mm_struct *mm;
939 mm = container_of(work, struct mm_struct, async_put_work);
943 static void mmdrop_async(struct mm_struct *mm)
945 if (unlikely(atomic_dec_and_test(&mm->mm_count))) {
946 INIT_WORK(&mm->async_put_work, mmdrop_async_fn);
947 schedule_work(&mm->async_put_work);
951 static inline void free_signal_struct(struct signal_struct *sig)
953 taskstats_tgid_free(sig);
954 sched_autogroup_exit(sig);
956 * __mmdrop is not safe to call from softirq context on x86 due to
957 * pgd_dtor so postpone it to the async context
960 mmdrop_async(sig->oom_mm);
961 kmem_cache_free(signal_cachep, sig);
964 static inline void put_signal_struct(struct signal_struct *sig)
966 if (refcount_dec_and_test(&sig->sigcnt))
967 free_signal_struct(sig);
970 void __put_task_struct(struct task_struct *tsk)
972 WARN_ON(!tsk->exit_state);
973 WARN_ON(refcount_read(&tsk->usage));
974 WARN_ON(tsk == current);
978 task_numa_free(tsk, true);
979 security_task_free(tsk);
981 delayacct_tsk_free(tsk);
982 put_signal_struct(tsk->signal);
983 sched_core_free(tsk);
986 EXPORT_SYMBOL_GPL(__put_task_struct);
988 void __put_task_struct_rcu_cb(struct rcu_head *rhp)
990 struct task_struct *task = container_of(rhp, struct task_struct, rcu);
992 __put_task_struct(task);
994 EXPORT_SYMBOL_GPL(__put_task_struct_rcu_cb);
996 void __init __weak arch_task_cache_init(void) { }
1001 static void set_max_threads(unsigned int max_threads_suggested)
1004 unsigned long nr_pages = totalram_pages();
1007 * The number of threads shall be limited such that the thread
1008 * structures may only consume a small part of the available memory.
1010 if (fls64(nr_pages) + fls64(PAGE_SIZE) > 64)
1011 threads = MAX_THREADS;
1013 threads = div64_u64((u64) nr_pages * (u64) PAGE_SIZE,
1014 (u64) THREAD_SIZE * 8UL);
1016 if (threads > max_threads_suggested)
1017 threads = max_threads_suggested;
1019 max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS);
1022 #ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT
1023 /* Initialized by the architecture: */
1024 int arch_task_struct_size __read_mostly;
1027 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
1028 static void task_struct_whitelist(unsigned long *offset, unsigned long *size)
1030 /* Fetch thread_struct whitelist for the architecture. */
1031 arch_thread_struct_whitelist(offset, size);
1034 * Handle zero-sized whitelist or empty thread_struct, otherwise
1035 * adjust offset to position of thread_struct in task_struct.
1037 if (unlikely(*size == 0))
1040 *offset += offsetof(struct task_struct, thread);
1042 #endif /* CONFIG_ARCH_TASK_STRUCT_ALLOCATOR */
1044 void __init fork_init(void)
1047 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
1048 #ifndef ARCH_MIN_TASKALIGN
1049 #define ARCH_MIN_TASKALIGN 0
1051 int align = max_t(int, L1_CACHE_BYTES, ARCH_MIN_TASKALIGN);
1052 unsigned long useroffset, usersize;
1054 /* create a slab on which task_structs can be allocated */
1055 task_struct_whitelist(&useroffset, &usersize);
1056 task_struct_cachep = kmem_cache_create_usercopy("task_struct",
1057 arch_task_struct_size, align,
1058 SLAB_PANIC|SLAB_ACCOUNT,
1059 useroffset, usersize, NULL);
1062 /* do the arch specific task caches init */
1063 arch_task_cache_init();
1065 set_max_threads(MAX_THREADS);
1067 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
1068 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
1069 init_task.signal->rlim[RLIMIT_SIGPENDING] =
1070 init_task.signal->rlim[RLIMIT_NPROC];
1072 for (i = 0; i < UCOUNT_COUNTS; i++)
1073 init_user_ns.ucount_max[i] = max_threads/2;
1075 set_userns_rlimit_max(&init_user_ns, UCOUNT_RLIMIT_NPROC, RLIM_INFINITY);
1076 set_userns_rlimit_max(&init_user_ns, UCOUNT_RLIMIT_MSGQUEUE, RLIM_INFINITY);
1077 set_userns_rlimit_max(&init_user_ns, UCOUNT_RLIMIT_SIGPENDING, RLIM_INFINITY);
1078 set_userns_rlimit_max(&init_user_ns, UCOUNT_RLIMIT_MEMLOCK, RLIM_INFINITY);
1080 #ifdef CONFIG_VMAP_STACK
1081 cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "fork:vm_stack_cache",
1082 NULL, free_vm_stack_cache);
1087 lockdep_init_task(&init_task);
1091 int __weak arch_dup_task_struct(struct task_struct *dst,
1092 struct task_struct *src)
1098 void set_task_stack_end_magic(struct task_struct *tsk)
1100 unsigned long *stackend;
1102 stackend = end_of_stack(tsk);
1103 *stackend = STACK_END_MAGIC; /* for overflow detection */
1106 static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
1108 struct task_struct *tsk;
1111 if (node == NUMA_NO_NODE)
1112 node = tsk_fork_get_node(orig);
1113 tsk = alloc_task_struct_node(node);
1117 err = arch_dup_task_struct(tsk, orig);
1121 err = alloc_thread_stack_node(tsk, node);
1125 #ifdef CONFIG_THREAD_INFO_IN_TASK
1126 refcount_set(&tsk->stack_refcount, 1);
1128 account_kernel_stack(tsk, 1);
1130 err = scs_prepare(tsk, node);
1134 #ifdef CONFIG_SECCOMP
1136 * We must handle setting up seccomp filters once we're under
1137 * the sighand lock in case orig has changed between now and
1138 * then. Until then, filter must be NULL to avoid messing up
1139 * the usage counts on the error path calling free_task.
1141 tsk->seccomp.filter = NULL;
1144 setup_thread_stack(tsk, orig);
1145 clear_user_return_notifier(tsk);
1146 clear_tsk_need_resched(tsk);
1147 set_task_stack_end_magic(tsk);
1148 clear_syscall_work_syscall_user_dispatch(tsk);
1150 #ifdef CONFIG_STACKPROTECTOR
1151 tsk->stack_canary = get_random_canary();
1153 if (orig->cpus_ptr == &orig->cpus_mask)
1154 tsk->cpus_ptr = &tsk->cpus_mask;
1155 dup_user_cpus_ptr(tsk, orig, node);
1158 * One for the user space visible state that goes away when reaped.
1159 * One for the scheduler.
1161 refcount_set(&tsk->rcu_users, 2);
1162 /* One for the rcu users */
1163 refcount_set(&tsk->usage, 1);
1164 #ifdef CONFIG_BLK_DEV_IO_TRACE
1165 tsk->btrace_seq = 0;
1167 tsk->splice_pipe = NULL;
1168 tsk->task_frag.page = NULL;
1169 tsk->wake_q.next = NULL;
1170 tsk->worker_private = NULL;
1172 kcov_task_init(tsk);
1173 kmsan_task_create(tsk);
1174 kmap_local_fork(tsk);
1176 #ifdef CONFIG_FAULT_INJECTION
1180 #ifdef CONFIG_BLK_CGROUP
1181 tsk->throttle_disk = NULL;
1182 tsk->use_memdelay = 0;
1185 #ifdef CONFIG_IOMMU_SVA
1186 tsk->pasid_activated = 0;
1190 tsk->active_memcg = NULL;
1193 #ifdef CONFIG_CPU_SUP_INTEL
1194 tsk->reported_split_lock = 0;
1197 #ifdef CONFIG_SCHED_MM_CID
1199 tsk->last_mm_cid = -1;
1200 tsk->mm_cid_active = 0;
1201 tsk->migrate_from_cpu = -1;
1206 exit_task_stack_account(tsk);
1207 free_thread_stack(tsk);
1209 free_task_struct(tsk);
1213 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
1215 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
1217 static int __init coredump_filter_setup(char *s)
1219 default_dump_filter =
1220 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
1221 MMF_DUMP_FILTER_MASK;
1225 __setup("coredump_filter=", coredump_filter_setup);
1227 #include <linux/init_task.h>
1229 static void mm_init_aio(struct mm_struct *mm)
1232 spin_lock_init(&mm->ioctx_lock);
1233 mm->ioctx_table = NULL;
1237 static __always_inline void mm_clear_owner(struct mm_struct *mm,
1238 struct task_struct *p)
1242 WRITE_ONCE(mm->owner, NULL);
1246 static void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
1253 static void mm_init_uprobes_state(struct mm_struct *mm)
1255 #ifdef CONFIG_UPROBES
1256 mm->uprobes_state.xol_area = NULL;
1260 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
1261 struct user_namespace *user_ns)
1265 mt_init_flags(&mm->mm_mt, MM_MT_FLAGS);
1266 mt_set_external_lock(&mm->mm_mt, &mm->mmap_lock);
1267 atomic_set(&mm->mm_users, 1);
1268 atomic_set(&mm->mm_count, 1);
1269 seqcount_init(&mm->write_protect_seq);
1271 INIT_LIST_HEAD(&mm->mmlist);
1272 #ifdef CONFIG_PER_VMA_LOCK
1273 mm->mm_lock_seq = 0;
1275 mm_pgtables_bytes_init(mm);
1278 atomic64_set(&mm->pinned_vm, 0);
1279 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
1280 spin_lock_init(&mm->page_table_lock);
1281 spin_lock_init(&mm->arg_lock);
1282 mm_init_cpumask(mm);
1284 mm_init_owner(mm, p);
1286 RCU_INIT_POINTER(mm->exe_file, NULL);
1287 mmu_notifier_subscriptions_init(mm);
1288 init_tlb_flush_pending(mm);
1289 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
1290 mm->pmd_huge_pte = NULL;
1292 mm_init_uprobes_state(mm);
1293 hugetlb_count_init(mm);
1296 mm->flags = current->mm->flags & MMF_INIT_MASK;
1297 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK;
1299 mm->flags = default_dump_filter;
1303 if (mm_alloc_pgd(mm))
1306 if (init_new_context(p, mm))
1307 goto fail_nocontext;
1309 if (mm_alloc_cid(mm))
1312 for (i = 0; i < NR_MM_COUNTERS; i++)
1313 if (percpu_counter_init(&mm->rss_stat[i], 0, GFP_KERNEL_ACCOUNT))
1316 mm->user_ns = get_user_ns(user_ns);
1317 lru_gen_init_mm(mm);
1322 percpu_counter_destroy(&mm->rss_stat[--i]);
1325 destroy_context(mm);
1334 * Allocate and initialize an mm_struct.
1336 struct mm_struct *mm_alloc(void)
1338 struct mm_struct *mm;
1344 memset(mm, 0, sizeof(*mm));
1345 return mm_init(mm, current, current_user_ns());
1348 static inline void __mmput(struct mm_struct *mm)
1350 VM_BUG_ON(atomic_read(&mm->mm_users));
1352 uprobe_clear_state(mm);
1355 khugepaged_exit(mm); /* must run before exit_mmap */
1357 mm_put_huge_zero_page(mm);
1358 set_mm_exe_file(mm, NULL);
1359 if (!list_empty(&mm->mmlist)) {
1360 spin_lock(&mmlist_lock);
1361 list_del(&mm->mmlist);
1362 spin_unlock(&mmlist_lock);
1365 module_put(mm->binfmt->module);
1371 * Decrement the use count and release all resources for an mm.
1373 void mmput(struct mm_struct *mm)
1377 if (atomic_dec_and_test(&mm->mm_users))
1380 EXPORT_SYMBOL_GPL(mmput);
1383 static void mmput_async_fn(struct work_struct *work)
1385 struct mm_struct *mm = container_of(work, struct mm_struct,
1391 void mmput_async(struct mm_struct *mm)
1393 if (atomic_dec_and_test(&mm->mm_users)) {
1394 INIT_WORK(&mm->async_put_work, mmput_async_fn);
1395 schedule_work(&mm->async_put_work);
1398 EXPORT_SYMBOL_GPL(mmput_async);
1402 * set_mm_exe_file - change a reference to the mm's executable file
1404 * This changes mm's executable file (shown as symlink /proc/[pid]/exe).
1406 * Main users are mmput() and sys_execve(). Callers prevent concurrent
1407 * invocations: in mmput() nobody alive left, in execve task is single
1410 * Can only fail if new_exe_file != NULL.
1412 int set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
1414 struct file *old_exe_file;
1417 * It is safe to dereference the exe_file without RCU as
1418 * this function is only called if nobody else can access
1419 * this mm -- see comment above for justification.
1421 old_exe_file = rcu_dereference_raw(mm->exe_file);
1425 * We expect the caller (i.e., sys_execve) to already denied
1426 * write access, so this is unlikely to fail.
1428 if (unlikely(deny_write_access(new_exe_file)))
1430 get_file(new_exe_file);
1432 rcu_assign_pointer(mm->exe_file, new_exe_file);
1434 allow_write_access(old_exe_file);
1441 * replace_mm_exe_file - replace a reference to the mm's executable file
1443 * This changes mm's executable file (shown as symlink /proc/[pid]/exe),
1444 * dealing with concurrent invocation and without grabbing the mmap lock in
1447 * Main user is sys_prctl(PR_SET_MM_MAP/EXE_FILE).
1449 int replace_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
1451 struct vm_area_struct *vma;
1452 struct file *old_exe_file;
1455 /* Forbid mm->exe_file change if old file still mapped. */
1456 old_exe_file = get_mm_exe_file(mm);
1458 VMA_ITERATOR(vmi, mm, 0);
1460 for_each_vma(vmi, vma) {
1463 if (path_equal(&vma->vm_file->f_path,
1464 &old_exe_file->f_path)) {
1469 mmap_read_unlock(mm);
1475 /* set the new file, lockless */
1476 ret = deny_write_access(new_exe_file);
1479 get_file(new_exe_file);
1481 old_exe_file = xchg(&mm->exe_file, new_exe_file);
1484 * Don't race with dup_mmap() getting the file and disallowing
1485 * write access while someone might open the file writable.
1488 allow_write_access(old_exe_file);
1490 mmap_read_unlock(mm);
1496 * get_mm_exe_file - acquire a reference to the mm's executable file
1498 * Returns %NULL if mm has no associated executable file.
1499 * User must release file via fput().
1501 struct file *get_mm_exe_file(struct mm_struct *mm)
1503 struct file *exe_file;
1506 exe_file = rcu_dereference(mm->exe_file);
1507 if (exe_file && !get_file_rcu(exe_file))
1514 * get_task_exe_file - acquire a reference to the task's executable file
1516 * Returns %NULL if task's mm (if any) has no associated executable file or
1517 * this is a kernel thread with borrowed mm (see the comment above get_task_mm).
1518 * User must release file via fput().
1520 struct file *get_task_exe_file(struct task_struct *task)
1522 struct file *exe_file = NULL;
1523 struct mm_struct *mm;
1528 if (!(task->flags & PF_KTHREAD))
1529 exe_file = get_mm_exe_file(mm);
1536 * get_task_mm - acquire a reference to the task's mm
1538 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning
1539 * this kernel workthread has transiently adopted a user mm with use_mm,
1540 * to do its AIO) is not set and if so returns a reference to it, after
1541 * bumping up the use count. User must release the mm via mmput()
1542 * after use. Typically used by /proc and ptrace.
1544 struct mm_struct *get_task_mm(struct task_struct *task)
1546 struct mm_struct *mm;
1551 if (task->flags & PF_KTHREAD)
1559 EXPORT_SYMBOL_GPL(get_task_mm);
1561 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
1563 struct mm_struct *mm;
1566 err = down_read_killable(&task->signal->exec_update_lock);
1568 return ERR_PTR(err);
1570 mm = get_task_mm(task);
1571 if (mm && mm != current->mm &&
1572 !ptrace_may_access(task, mode)) {
1574 mm = ERR_PTR(-EACCES);
1576 up_read(&task->signal->exec_update_lock);
1581 static void complete_vfork_done(struct task_struct *tsk)
1583 struct completion *vfork;
1586 vfork = tsk->vfork_done;
1587 if (likely(vfork)) {
1588 tsk->vfork_done = NULL;
1594 static int wait_for_vfork_done(struct task_struct *child,
1595 struct completion *vfork)
1597 unsigned int state = TASK_UNINTERRUPTIBLE|TASK_KILLABLE|TASK_FREEZABLE;
1600 cgroup_enter_frozen();
1601 killed = wait_for_completion_state(vfork, state);
1602 cgroup_leave_frozen(false);
1606 child->vfork_done = NULL;
1610 put_task_struct(child);
1614 /* Please note the differences between mmput and mm_release.
1615 * mmput is called whenever we stop holding onto a mm_struct,
1616 * error success whatever.
1618 * mm_release is called after a mm_struct has been removed
1619 * from the current process.
1621 * This difference is important for error handling, when we
1622 * only half set up a mm_struct for a new process and need to restore
1623 * the old one. Because we mmput the new mm_struct before
1624 * restoring the old one. . .
1625 * Eric Biederman 10 January 1998
1627 static void mm_release(struct task_struct *tsk, struct mm_struct *mm)
1629 uprobe_free_utask(tsk);
1631 /* Get rid of any cached register state */
1632 deactivate_mm(tsk, mm);
1635 * Signal userspace if we're not exiting with a core dump
1636 * because we want to leave the value intact for debugging
1639 if (tsk->clear_child_tid) {
1640 if (atomic_read(&mm->mm_users) > 1) {
1642 * We don't check the error code - if userspace has
1643 * not set up a proper pointer then tough luck.
1645 put_user(0, tsk->clear_child_tid);
1646 do_futex(tsk->clear_child_tid, FUTEX_WAKE,
1647 1, NULL, NULL, 0, 0);
1649 tsk->clear_child_tid = NULL;
1653 * All done, finally we can wake up parent and return this mm to him.
1654 * Also kthread_stop() uses this completion for synchronization.
1656 if (tsk->vfork_done)
1657 complete_vfork_done(tsk);
1660 void exit_mm_release(struct task_struct *tsk, struct mm_struct *mm)
1662 futex_exit_release(tsk);
1663 mm_release(tsk, mm);
1666 void exec_mm_release(struct task_struct *tsk, struct mm_struct *mm)
1668 futex_exec_release(tsk);
1669 mm_release(tsk, mm);
1673 * dup_mm() - duplicates an existing mm structure
1674 * @tsk: the task_struct with which the new mm will be associated.
1675 * @oldmm: the mm to duplicate.
1677 * Allocates a new mm structure and duplicates the provided @oldmm structure
1680 * Return: the duplicated mm or NULL on failure.
1682 static struct mm_struct *dup_mm(struct task_struct *tsk,
1683 struct mm_struct *oldmm)
1685 struct mm_struct *mm;
1692 memcpy(mm, oldmm, sizeof(*mm));
1694 if (!mm_init(mm, tsk, mm->user_ns))
1697 err = dup_mmap(mm, oldmm);
1701 mm->hiwater_rss = get_mm_rss(mm);
1702 mm->hiwater_vm = mm->total_vm;
1704 if (mm->binfmt && !try_module_get(mm->binfmt->module))
1710 /* don't put binfmt in mmput, we haven't got module yet */
1712 mm_init_owner(mm, NULL);
1719 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
1721 struct mm_struct *mm, *oldmm;
1723 tsk->min_flt = tsk->maj_flt = 0;
1724 tsk->nvcsw = tsk->nivcsw = 0;
1725 #ifdef CONFIG_DETECT_HUNG_TASK
1726 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
1727 tsk->last_switch_time = 0;
1731 tsk->active_mm = NULL;
1734 * Are we cloning a kernel thread?
1736 * We need to steal a active VM for that..
1738 oldmm = current->mm;
1742 if (clone_flags & CLONE_VM) {
1746 mm = dup_mm(tsk, current->mm);
1752 tsk->active_mm = mm;
1753 sched_mm_cid_fork(tsk);
1757 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
1759 struct fs_struct *fs = current->fs;
1760 if (clone_flags & CLONE_FS) {
1761 /* tsk->fs is already what we want */
1762 spin_lock(&fs->lock);
1764 spin_unlock(&fs->lock);
1768 spin_unlock(&fs->lock);
1771 tsk->fs = copy_fs_struct(fs);
1777 static int copy_files(unsigned long clone_flags, struct task_struct *tsk,
1780 struct files_struct *oldf, *newf;
1784 * A background process may not have any files ...
1786 oldf = current->files;
1795 if (clone_flags & CLONE_FILES) {
1796 atomic_inc(&oldf->count);
1800 newf = dup_fd(oldf, NR_OPEN_MAX, &error);
1810 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
1812 struct sighand_struct *sig;
1814 if (clone_flags & CLONE_SIGHAND) {
1815 refcount_inc(¤t->sighand->count);
1818 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1819 RCU_INIT_POINTER(tsk->sighand, sig);
1823 refcount_set(&sig->count, 1);
1824 spin_lock_irq(¤t->sighand->siglock);
1825 memcpy(sig->action, current->sighand->action, sizeof(sig->action));
1826 spin_unlock_irq(¤t->sighand->siglock);
1828 /* Reset all signal handler not set to SIG_IGN to SIG_DFL. */
1829 if (clone_flags & CLONE_CLEAR_SIGHAND)
1830 flush_signal_handlers(tsk, 0);
1835 void __cleanup_sighand(struct sighand_struct *sighand)
1837 if (refcount_dec_and_test(&sighand->count)) {
1838 signalfd_cleanup(sighand);
1840 * sighand_cachep is SLAB_TYPESAFE_BY_RCU so we can free it
1841 * without an RCU grace period, see __lock_task_sighand().
1843 kmem_cache_free(sighand_cachep, sighand);
1848 * Initialize POSIX timer handling for a thread group.
1850 static void posix_cpu_timers_init_group(struct signal_struct *sig)
1852 struct posix_cputimers *pct = &sig->posix_cputimers;
1853 unsigned long cpu_limit;
1855 cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1856 posix_cputimers_group_init(pct, cpu_limit);
1859 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
1861 struct signal_struct *sig;
1863 if (clone_flags & CLONE_THREAD)
1866 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
1871 sig->nr_threads = 1;
1872 sig->quick_threads = 1;
1873 atomic_set(&sig->live, 1);
1874 refcount_set(&sig->sigcnt, 1);
1876 /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */
1877 sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node);
1878 tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head);
1880 init_waitqueue_head(&sig->wait_chldexit);
1881 sig->curr_target = tsk;
1882 init_sigpending(&sig->shared_pending);
1883 INIT_HLIST_HEAD(&sig->multiprocess);
1884 seqlock_init(&sig->stats_lock);
1885 prev_cputime_init(&sig->prev_cputime);
1887 #ifdef CONFIG_POSIX_TIMERS
1888 INIT_LIST_HEAD(&sig->posix_timers);
1889 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1890 sig->real_timer.function = it_real_fn;
1893 task_lock(current->group_leader);
1894 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
1895 task_unlock(current->group_leader);
1897 posix_cpu_timers_init_group(sig);
1899 tty_audit_fork(sig);
1900 sched_autogroup_fork(sig);
1902 sig->oom_score_adj = current->signal->oom_score_adj;
1903 sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1905 mutex_init(&sig->cred_guard_mutex);
1906 init_rwsem(&sig->exec_update_lock);
1911 static void copy_seccomp(struct task_struct *p)
1913 #ifdef CONFIG_SECCOMP
1915 * Must be called with sighand->lock held, which is common to
1916 * all threads in the group. Holding cred_guard_mutex is not
1917 * needed because this new task is not yet running and cannot
1920 assert_spin_locked(¤t->sighand->siglock);
1922 /* Ref-count the new filter user, and assign it. */
1923 get_seccomp_filter(current);
1924 p->seccomp = current->seccomp;
1927 * Explicitly enable no_new_privs here in case it got set
1928 * between the task_struct being duplicated and holding the
1929 * sighand lock. The seccomp state and nnp must be in sync.
1931 if (task_no_new_privs(current))
1932 task_set_no_new_privs(p);
1935 * If the parent gained a seccomp mode after copying thread
1936 * flags and between before we held the sighand lock, we have
1937 * to manually enable the seccomp thread flag here.
1939 if (p->seccomp.mode != SECCOMP_MODE_DISABLED)
1940 set_task_syscall_work(p, SECCOMP);
1944 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1946 current->clear_child_tid = tidptr;
1948 return task_pid_vnr(current);
1951 static void rt_mutex_init_task(struct task_struct *p)
1953 raw_spin_lock_init(&p->pi_lock);
1954 #ifdef CONFIG_RT_MUTEXES
1955 p->pi_waiters = RB_ROOT_CACHED;
1956 p->pi_top_task = NULL;
1957 p->pi_blocked_on = NULL;
1961 static inline void init_task_pid_links(struct task_struct *task)
1965 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type)
1966 INIT_HLIST_NODE(&task->pid_links[type]);
1970 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid)
1972 if (type == PIDTYPE_PID)
1973 task->thread_pid = pid;
1975 task->signal->pids[type] = pid;
1978 static inline void rcu_copy_process(struct task_struct *p)
1980 #ifdef CONFIG_PREEMPT_RCU
1981 p->rcu_read_lock_nesting = 0;
1982 p->rcu_read_unlock_special.s = 0;
1983 p->rcu_blocked_node = NULL;
1984 INIT_LIST_HEAD(&p->rcu_node_entry);
1985 #endif /* #ifdef CONFIG_PREEMPT_RCU */
1986 #ifdef CONFIG_TASKS_RCU
1987 p->rcu_tasks_holdout = false;
1988 INIT_LIST_HEAD(&p->rcu_tasks_holdout_list);
1989 p->rcu_tasks_idle_cpu = -1;
1990 #endif /* #ifdef CONFIG_TASKS_RCU */
1991 #ifdef CONFIG_TASKS_TRACE_RCU
1992 p->trc_reader_nesting = 0;
1993 p->trc_reader_special.s = 0;
1994 INIT_LIST_HEAD(&p->trc_holdout_list);
1995 INIT_LIST_HEAD(&p->trc_blkd_node);
1996 #endif /* #ifdef CONFIG_TASKS_TRACE_RCU */
1999 struct pid *pidfd_pid(const struct file *file)
2001 if (file->f_op == &pidfd_fops)
2002 return file->private_data;
2004 return ERR_PTR(-EBADF);
2007 static int pidfd_release(struct inode *inode, struct file *file)
2009 struct pid *pid = file->private_data;
2011 file->private_data = NULL;
2016 #ifdef CONFIG_PROC_FS
2018 * pidfd_show_fdinfo - print information about a pidfd
2019 * @m: proc fdinfo file
2020 * @f: file referencing a pidfd
2023 * This function will print the pid that a given pidfd refers to in the
2024 * pid namespace of the procfs instance.
2025 * If the pid namespace of the process is not a descendant of the pid
2026 * namespace of the procfs instance 0 will be shown as its pid. This is
2027 * similar to calling getppid() on a process whose parent is outside of
2028 * its pid namespace.
2031 * If pid namespaces are supported then this function will also print
2032 * the pid of a given pidfd refers to for all descendant pid namespaces
2033 * starting from the current pid namespace of the instance, i.e. the
2034 * Pid field and the first entry in the NSpid field will be identical.
2035 * If the pid namespace of the process is not a descendant of the pid
2036 * namespace of the procfs instance 0 will be shown as its first NSpid
2037 * entry and no others will be shown.
2038 * Note that this differs from the Pid and NSpid fields in
2039 * /proc/<pid>/status where Pid and NSpid are always shown relative to
2040 * the pid namespace of the procfs instance. The difference becomes
2041 * obvious when sending around a pidfd between pid namespaces from a
2042 * different branch of the tree, i.e. where no ancestral relation is
2043 * present between the pid namespaces:
2044 * - create two new pid namespaces ns1 and ns2 in the initial pid
2045 * namespace (also take care to create new mount namespaces in the
2046 * new pid namespace and mount procfs)
2047 * - create a process with a pidfd in ns1
2048 * - send pidfd from ns1 to ns2
2049 * - read /proc/self/fdinfo/<pidfd> and observe that both Pid and NSpid
2050 * have exactly one entry, which is 0
2052 static void pidfd_show_fdinfo(struct seq_file *m, struct file *f)
2054 struct pid *pid = f->private_data;
2055 struct pid_namespace *ns;
2058 if (likely(pid_has_task(pid, PIDTYPE_PID))) {
2059 ns = proc_pid_ns(file_inode(m->file)->i_sb);
2060 nr = pid_nr_ns(pid, ns);
2063 seq_put_decimal_ll(m, "Pid:\t", nr);
2065 #ifdef CONFIG_PID_NS
2066 seq_put_decimal_ll(m, "\nNSpid:\t", nr);
2070 /* If nr is non-zero it means that 'pid' is valid and that
2071 * ns, i.e. the pid namespace associated with the procfs
2072 * instance, is in the pid namespace hierarchy of pid.
2073 * Start at one below the already printed level.
2075 for (i = ns->level + 1; i <= pid->level; i++)
2076 seq_put_decimal_ll(m, "\t", pid->numbers[i].nr);
2084 * Poll support for process exit notification.
2086 static __poll_t pidfd_poll(struct file *file, struct poll_table_struct *pts)
2088 struct pid *pid = file->private_data;
2089 __poll_t poll_flags = 0;
2091 poll_wait(file, &pid->wait_pidfd, pts);
2094 * Inform pollers only when the whole thread group exits.
2095 * If the thread group leader exits before all other threads in the
2096 * group, then poll(2) should block, similar to the wait(2) family.
2098 if (thread_group_exited(pid))
2099 poll_flags = EPOLLIN | EPOLLRDNORM;
2104 const struct file_operations pidfd_fops = {
2105 .release = pidfd_release,
2107 #ifdef CONFIG_PROC_FS
2108 .show_fdinfo = pidfd_show_fdinfo,
2113 * __pidfd_prepare - allocate a new pidfd_file and reserve a pidfd
2114 * @pid: the struct pid for which to create a pidfd
2115 * @flags: flags of the new @pidfd
2116 * @pidfd: the pidfd to return
2118 * Allocate a new file that stashes @pid and reserve a new pidfd number in the
2119 * caller's file descriptor table. The pidfd is reserved but not installed yet.
2121 * The helper doesn't perform checks on @pid which makes it useful for pidfds
2122 * created via CLONE_PIDFD where @pid has no task attached when the pidfd and
2123 * pidfd file are prepared.
2125 * If this function returns successfully the caller is responsible to either
2126 * call fd_install() passing the returned pidfd and pidfd file as arguments in
2127 * order to install the pidfd into its file descriptor table or they must use
2128 * put_unused_fd() and fput() on the returned pidfd and pidfd file
2131 * This function is useful when a pidfd must already be reserved but there
2132 * might still be points of failure afterwards and the caller wants to ensure
2133 * that no pidfd is leaked into its file descriptor table.
2135 * Return: On success, a reserved pidfd is returned from the function and a new
2136 * pidfd file is returned in the last argument to the function. On
2137 * error, a negative error code is returned from the function and the
2138 * last argument remains unchanged.
2140 static int __pidfd_prepare(struct pid *pid, unsigned int flags, struct file **ret)
2143 struct file *pidfd_file;
2145 if (flags & ~(O_NONBLOCK | O_RDWR | O_CLOEXEC))
2148 pidfd = get_unused_fd_flags(O_RDWR | O_CLOEXEC);
2152 pidfd_file = anon_inode_getfile("[pidfd]", &pidfd_fops, pid,
2153 flags | O_RDWR | O_CLOEXEC);
2154 if (IS_ERR(pidfd_file)) {
2155 put_unused_fd(pidfd);
2156 return PTR_ERR(pidfd_file);
2158 get_pid(pid); /* held by pidfd_file now */
2164 * pidfd_prepare - allocate a new pidfd_file and reserve a pidfd
2165 * @pid: the struct pid for which to create a pidfd
2166 * @flags: flags of the new @pidfd
2167 * @pidfd: the pidfd to return
2169 * Allocate a new file that stashes @pid and reserve a new pidfd number in the
2170 * caller's file descriptor table. The pidfd is reserved but not installed yet.
2172 * The helper verifies that @pid is used as a thread group leader.
2174 * If this function returns successfully the caller is responsible to either
2175 * call fd_install() passing the returned pidfd and pidfd file as arguments in
2176 * order to install the pidfd into its file descriptor table or they must use
2177 * put_unused_fd() and fput() on the returned pidfd and pidfd file
2180 * This function is useful when a pidfd must already be reserved but there
2181 * might still be points of failure afterwards and the caller wants to ensure
2182 * that no pidfd is leaked into its file descriptor table.
2184 * Return: On success, a reserved pidfd is returned from the function and a new
2185 * pidfd file is returned in the last argument to the function. On
2186 * error, a negative error code is returned from the function and the
2187 * last argument remains unchanged.
2189 int pidfd_prepare(struct pid *pid, unsigned int flags, struct file **ret)
2191 if (!pid || !pid_has_task(pid, PIDTYPE_TGID))
2194 return __pidfd_prepare(pid, flags, ret);
2197 static void __delayed_free_task(struct rcu_head *rhp)
2199 struct task_struct *tsk = container_of(rhp, struct task_struct, rcu);
2204 static __always_inline void delayed_free_task(struct task_struct *tsk)
2206 if (IS_ENABLED(CONFIG_MEMCG))
2207 call_rcu(&tsk->rcu, __delayed_free_task);
2212 static void copy_oom_score_adj(u64 clone_flags, struct task_struct *tsk)
2214 /* Skip if kernel thread */
2218 /* Skip if spawning a thread or using vfork */
2219 if ((clone_flags & (CLONE_VM | CLONE_THREAD | CLONE_VFORK)) != CLONE_VM)
2222 /* We need to synchronize with __set_oom_adj */
2223 mutex_lock(&oom_adj_mutex);
2224 set_bit(MMF_MULTIPROCESS, &tsk->mm->flags);
2225 /* Update the values in case they were changed after copy_signal */
2226 tsk->signal->oom_score_adj = current->signal->oom_score_adj;
2227 tsk->signal->oom_score_adj_min = current->signal->oom_score_adj_min;
2228 mutex_unlock(&oom_adj_mutex);
2232 static void rv_task_fork(struct task_struct *p)
2236 for (i = 0; i < RV_PER_TASK_MONITORS; i++)
2237 p->rv[i].da_mon.monitoring = false;
2240 #define rv_task_fork(p) do {} while (0)
2244 * This creates a new process as a copy of the old one,
2245 * but does not actually start it yet.
2247 * It copies the registers, and all the appropriate
2248 * parts of the process environment (as per the clone
2249 * flags). The actual kick-off is left to the caller.
2251 __latent_entropy struct task_struct *copy_process(
2255 struct kernel_clone_args *args)
2257 int pidfd = -1, retval;
2258 struct task_struct *p;
2259 struct multiprocess_signals delayed;
2260 struct file *pidfile = NULL;
2261 const u64 clone_flags = args->flags;
2262 struct nsproxy *nsp = current->nsproxy;
2265 * Don't allow sharing the root directory with processes in a different
2268 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
2269 return ERR_PTR(-EINVAL);
2271 if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS))
2272 return ERR_PTR(-EINVAL);
2275 * Thread groups must share signals as well, and detached threads
2276 * can only be started up within the thread group.
2278 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
2279 return ERR_PTR(-EINVAL);
2282 * Shared signal handlers imply shared VM. By way of the above,
2283 * thread groups also imply shared VM. Blocking this case allows
2284 * for various simplifications in other code.
2286 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
2287 return ERR_PTR(-EINVAL);
2290 * Siblings of global init remain as zombies on exit since they are
2291 * not reaped by their parent (swapper). To solve this and to avoid
2292 * multi-rooted process trees, prevent global and container-inits
2293 * from creating siblings.
2295 if ((clone_flags & CLONE_PARENT) &&
2296 current->signal->flags & SIGNAL_UNKILLABLE)
2297 return ERR_PTR(-EINVAL);
2300 * If the new process will be in a different pid or user namespace
2301 * do not allow it to share a thread group with the forking task.
2303 if (clone_flags & CLONE_THREAD) {
2304 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) ||
2305 (task_active_pid_ns(current) != nsp->pid_ns_for_children))
2306 return ERR_PTR(-EINVAL);
2309 if (clone_flags & CLONE_PIDFD) {
2311 * - CLONE_DETACHED is blocked so that we can potentially
2312 * reuse it later for CLONE_PIDFD.
2313 * - CLONE_THREAD is blocked until someone really needs it.
2315 if (clone_flags & (CLONE_DETACHED | CLONE_THREAD))
2316 return ERR_PTR(-EINVAL);
2320 * Force any signals received before this point to be delivered
2321 * before the fork happens. Collect up signals sent to multiple
2322 * processes that happen during the fork and delay them so that
2323 * they appear to happen after the fork.
2325 sigemptyset(&delayed.signal);
2326 INIT_HLIST_NODE(&delayed.node);
2328 spin_lock_irq(¤t->sighand->siglock);
2329 if (!(clone_flags & CLONE_THREAD))
2330 hlist_add_head(&delayed.node, ¤t->signal->multiprocess);
2331 recalc_sigpending();
2332 spin_unlock_irq(¤t->sighand->siglock);
2333 retval = -ERESTARTNOINTR;
2334 if (task_sigpending(current))
2338 p = dup_task_struct(current, node);
2341 p->flags &= ~PF_KTHREAD;
2343 p->flags |= PF_KTHREAD;
2344 if (args->user_worker) {
2346 * Mark us a user worker, and block any signal that isn't
2349 p->flags |= PF_USER_WORKER;
2350 siginitsetinv(&p->blocked, sigmask(SIGKILL)|sigmask(SIGSTOP));
2352 if (args->io_thread)
2353 p->flags |= PF_IO_WORKER;
2356 strscpy_pad(p->comm, args->name, sizeof(p->comm));
2358 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? args->child_tid : NULL;
2360 * Clear TID on mm_release()?
2362 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? args->child_tid : NULL;
2364 ftrace_graph_init_task(p);
2366 rt_mutex_init_task(p);
2368 lockdep_assert_irqs_enabled();
2369 #ifdef CONFIG_PROVE_LOCKING
2370 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
2372 retval = copy_creds(p, clone_flags);
2377 if (is_rlimit_overlimit(task_ucounts(p), UCOUNT_RLIMIT_NPROC, rlimit(RLIMIT_NPROC))) {
2378 if (p->real_cred->user != INIT_USER &&
2379 !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
2380 goto bad_fork_cleanup_count;
2382 current->flags &= ~PF_NPROC_EXCEEDED;
2385 * If multiple threads are within copy_process(), then this check
2386 * triggers too late. This doesn't hurt, the check is only there
2387 * to stop root fork bombs.
2390 if (data_race(nr_threads >= max_threads))
2391 goto bad_fork_cleanup_count;
2393 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */
2394 p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER | PF_IDLE | PF_NO_SETAFFINITY);
2395 p->flags |= PF_FORKNOEXEC;
2396 INIT_LIST_HEAD(&p->children);
2397 INIT_LIST_HEAD(&p->sibling);
2398 rcu_copy_process(p);
2399 p->vfork_done = NULL;
2400 spin_lock_init(&p->alloc_lock);
2402 init_sigpending(&p->pending);
2404 p->utime = p->stime = p->gtime = 0;
2405 #ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
2406 p->utimescaled = p->stimescaled = 0;
2408 prev_cputime_init(&p->prev_cputime);
2410 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
2411 seqcount_init(&p->vtime.seqcount);
2412 p->vtime.starttime = 0;
2413 p->vtime.state = VTIME_INACTIVE;
2416 #ifdef CONFIG_IO_URING
2420 #if defined(SPLIT_RSS_COUNTING)
2421 memset(&p->rss_stat, 0, sizeof(p->rss_stat));
2424 p->default_timer_slack_ns = current->timer_slack_ns;
2430 task_io_accounting_init(&p->ioac);
2431 acct_clear_integrals(p);
2433 posix_cputimers_init(&p->posix_cputimers);
2435 p->io_context = NULL;
2436 audit_set_context(p, NULL);
2438 if (args->kthread) {
2439 if (!set_kthread_struct(p))
2440 goto bad_fork_cleanup_delayacct;
2443 p->mempolicy = mpol_dup(p->mempolicy);
2444 if (IS_ERR(p->mempolicy)) {
2445 retval = PTR_ERR(p->mempolicy);
2446 p->mempolicy = NULL;
2447 goto bad_fork_cleanup_delayacct;
2450 #ifdef CONFIG_CPUSETS
2451 p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
2452 p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
2453 seqcount_spinlock_init(&p->mems_allowed_seq, &p->alloc_lock);
2455 #ifdef CONFIG_TRACE_IRQFLAGS
2456 memset(&p->irqtrace, 0, sizeof(p->irqtrace));
2457 p->irqtrace.hardirq_disable_ip = _THIS_IP_;
2458 p->irqtrace.softirq_enable_ip = _THIS_IP_;
2459 p->softirqs_enabled = 1;
2460 p->softirq_context = 0;
2463 p->pagefault_disabled = 0;
2465 #ifdef CONFIG_LOCKDEP
2466 lockdep_init_task(p);
2469 #ifdef CONFIG_DEBUG_MUTEXES
2470 p->blocked_on = NULL; /* not blocked yet */
2472 #ifdef CONFIG_BCACHE
2473 p->sequential_io = 0;
2474 p->sequential_io_avg = 0;
2476 #ifdef CONFIG_BPF_SYSCALL
2477 RCU_INIT_POINTER(p->bpf_storage, NULL);
2481 /* Perform scheduler related setup. Assign this task to a CPU. */
2482 retval = sched_fork(clone_flags, p);
2484 goto bad_fork_cleanup_policy;
2486 retval = perf_event_init_task(p, clone_flags);
2488 goto bad_fork_cleanup_policy;
2489 retval = audit_alloc(p);
2491 goto bad_fork_cleanup_perf;
2492 /* copy all the process information */
2494 retval = security_task_alloc(p, clone_flags);
2496 goto bad_fork_cleanup_audit;
2497 retval = copy_semundo(clone_flags, p);
2499 goto bad_fork_cleanup_security;
2500 retval = copy_files(clone_flags, p, args->no_files);
2502 goto bad_fork_cleanup_semundo;
2503 retval = copy_fs(clone_flags, p);
2505 goto bad_fork_cleanup_files;
2506 retval = copy_sighand(clone_flags, p);
2508 goto bad_fork_cleanup_fs;
2509 retval = copy_signal(clone_flags, p);
2511 goto bad_fork_cleanup_sighand;
2512 retval = copy_mm(clone_flags, p);
2514 goto bad_fork_cleanup_signal;
2515 retval = copy_namespaces(clone_flags, p);
2517 goto bad_fork_cleanup_mm;
2518 retval = copy_io(clone_flags, p);
2520 goto bad_fork_cleanup_namespaces;
2521 retval = copy_thread(p, args);
2523 goto bad_fork_cleanup_io;
2525 stackleak_task_init(p);
2527 if (pid != &init_struct_pid) {
2528 pid = alloc_pid(p->nsproxy->pid_ns_for_children, args->set_tid,
2529 args->set_tid_size);
2531 retval = PTR_ERR(pid);
2532 goto bad_fork_cleanup_thread;
2537 * This has to happen after we've potentially unshared the file
2538 * descriptor table (so that the pidfd doesn't leak into the child
2539 * if the fd table isn't shared).
2541 if (clone_flags & CLONE_PIDFD) {
2542 /* Note that no task has been attached to @pid yet. */
2543 retval = __pidfd_prepare(pid, O_RDWR | O_CLOEXEC, &pidfile);
2545 goto bad_fork_free_pid;
2548 retval = put_user(pidfd, args->pidfd);
2550 goto bad_fork_put_pidfd;
2559 * sigaltstack should be cleared when sharing the same VM
2561 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
2565 * Syscall tracing and stepping should be turned off in the
2566 * child regardless of CLONE_PTRACE.
2568 user_disable_single_step(p);
2569 clear_task_syscall_work(p, SYSCALL_TRACE);
2570 #if defined(CONFIG_GENERIC_ENTRY) || defined(TIF_SYSCALL_EMU)
2571 clear_task_syscall_work(p, SYSCALL_EMU);
2573 clear_tsk_latency_tracing(p);
2575 /* ok, now we should be set up.. */
2576 p->pid = pid_nr(pid);
2577 if (clone_flags & CLONE_THREAD) {
2578 p->group_leader = current->group_leader;
2579 p->tgid = current->tgid;
2581 p->group_leader = p;
2586 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
2587 p->dirty_paused_when = 0;
2589 p->pdeath_signal = 0;
2590 INIT_LIST_HEAD(&p->thread_group);
2591 p->task_works = NULL;
2592 clear_posix_cputimers_work(p);
2594 #ifdef CONFIG_KRETPROBES
2595 p->kretprobe_instances.first = NULL;
2597 #ifdef CONFIG_RETHOOK
2598 p->rethooks.first = NULL;
2602 * Ensure that the cgroup subsystem policies allow the new process to be
2603 * forked. It should be noted that the new process's css_set can be changed
2604 * between here and cgroup_post_fork() if an organisation operation is in
2607 retval = cgroup_can_fork(p, args);
2609 goto bad_fork_put_pidfd;
2612 * Now that the cgroups are pinned, re-clone the parent cgroup and put
2613 * the new task on the correct runqueue. All this *before* the task
2616 * This isn't part of ->can_fork() because while the re-cloning is
2617 * cgroup specific, it unconditionally needs to place the task on a
2620 sched_cgroup_fork(p, args);
2623 * From this point on we must avoid any synchronous user-space
2624 * communication until we take the tasklist-lock. In particular, we do
2625 * not want user-space to be able to predict the process start-time by
2626 * stalling fork(2) after we recorded the start_time but before it is
2627 * visible to the system.
2630 p->start_time = ktime_get_ns();
2631 p->start_boottime = ktime_get_boottime_ns();
2634 * Make it visible to the rest of the system, but dont wake it up yet.
2635 * Need tasklist lock for parent etc handling!
2637 write_lock_irq(&tasklist_lock);
2639 /* CLONE_PARENT re-uses the old parent */
2640 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
2641 p->real_parent = current->real_parent;
2642 p->parent_exec_id = current->parent_exec_id;
2643 if (clone_flags & CLONE_THREAD)
2644 p->exit_signal = -1;
2646 p->exit_signal = current->group_leader->exit_signal;
2648 p->real_parent = current;
2649 p->parent_exec_id = current->self_exec_id;
2650 p->exit_signal = args->exit_signal;
2653 klp_copy_process(p);
2657 spin_lock(¤t->sighand->siglock);
2661 rseq_fork(p, clone_flags);
2663 /* Don't start children in a dying pid namespace */
2664 if (unlikely(!(ns_of_pid(pid)->pid_allocated & PIDNS_ADDING))) {
2666 goto bad_fork_cancel_cgroup;
2669 /* Let kill terminate clone/fork in the middle */
2670 if (fatal_signal_pending(current)) {
2672 goto bad_fork_cancel_cgroup;
2675 /* No more failure paths after this point. */
2678 * Copy seccomp details explicitly here, in case they were changed
2679 * before holding sighand lock.
2683 init_task_pid_links(p);
2684 if (likely(p->pid)) {
2685 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
2687 init_task_pid(p, PIDTYPE_PID, pid);
2688 if (thread_group_leader(p)) {
2689 init_task_pid(p, PIDTYPE_TGID, pid);
2690 init_task_pid(p, PIDTYPE_PGID, task_pgrp(current));
2691 init_task_pid(p, PIDTYPE_SID, task_session(current));
2693 if (is_child_reaper(pid)) {
2694 ns_of_pid(pid)->child_reaper = p;
2695 p->signal->flags |= SIGNAL_UNKILLABLE;
2697 p->signal->shared_pending.signal = delayed.signal;
2698 p->signal->tty = tty_kref_get(current->signal->tty);
2700 * Inherit has_child_subreaper flag under the same
2701 * tasklist_lock with adding child to the process tree
2702 * for propagate_has_child_subreaper optimization.
2704 p->signal->has_child_subreaper = p->real_parent->signal->has_child_subreaper ||
2705 p->real_parent->signal->is_child_subreaper;
2706 list_add_tail(&p->sibling, &p->real_parent->children);
2707 list_add_tail_rcu(&p->tasks, &init_task.tasks);
2708 attach_pid(p, PIDTYPE_TGID);
2709 attach_pid(p, PIDTYPE_PGID);
2710 attach_pid(p, PIDTYPE_SID);
2711 __this_cpu_inc(process_counts);
2713 current->signal->nr_threads++;
2714 current->signal->quick_threads++;
2715 atomic_inc(¤t->signal->live);
2716 refcount_inc(¤t->signal->sigcnt);
2717 task_join_group_stop(p);
2718 list_add_tail_rcu(&p->thread_group,
2719 &p->group_leader->thread_group);
2720 list_add_tail_rcu(&p->thread_node,
2721 &p->signal->thread_head);
2723 attach_pid(p, PIDTYPE_PID);
2727 hlist_del_init(&delayed.node);
2728 spin_unlock(¤t->sighand->siglock);
2729 syscall_tracepoint_update(p);
2730 write_unlock_irq(&tasklist_lock);
2733 fd_install(pidfd, pidfile);
2735 proc_fork_connector(p);
2737 cgroup_post_fork(p, args);
2740 trace_task_newtask(p, clone_flags);
2741 uprobe_copy_process(p, clone_flags);
2742 user_events_fork(p, clone_flags);
2744 copy_oom_score_adj(clone_flags, p);
2748 bad_fork_cancel_cgroup:
2750 spin_unlock(¤t->sighand->siglock);
2751 write_unlock_irq(&tasklist_lock);
2752 cgroup_cancel_fork(p, args);
2754 if (clone_flags & CLONE_PIDFD) {
2756 put_unused_fd(pidfd);
2759 if (pid != &init_struct_pid)
2761 bad_fork_cleanup_thread:
2763 bad_fork_cleanup_io:
2766 bad_fork_cleanup_namespaces:
2767 exit_task_namespaces(p);
2768 bad_fork_cleanup_mm:
2770 mm_clear_owner(p->mm, p);
2773 bad_fork_cleanup_signal:
2774 if (!(clone_flags & CLONE_THREAD))
2775 free_signal_struct(p->signal);
2776 bad_fork_cleanup_sighand:
2777 __cleanup_sighand(p->sighand);
2778 bad_fork_cleanup_fs:
2779 exit_fs(p); /* blocking */
2780 bad_fork_cleanup_files:
2781 exit_files(p); /* blocking */
2782 bad_fork_cleanup_semundo:
2784 bad_fork_cleanup_security:
2785 security_task_free(p);
2786 bad_fork_cleanup_audit:
2788 bad_fork_cleanup_perf:
2789 perf_event_free_task(p);
2790 bad_fork_cleanup_policy:
2791 lockdep_free_task(p);
2793 mpol_put(p->mempolicy);
2795 bad_fork_cleanup_delayacct:
2796 delayacct_tsk_free(p);
2797 bad_fork_cleanup_count:
2798 dec_rlimit_ucounts(task_ucounts(p), UCOUNT_RLIMIT_NPROC, 1);
2801 WRITE_ONCE(p->__state, TASK_DEAD);
2802 exit_task_stack_account(p);
2804 delayed_free_task(p);
2806 spin_lock_irq(¤t->sighand->siglock);
2807 hlist_del_init(&delayed.node);
2808 spin_unlock_irq(¤t->sighand->siglock);
2809 return ERR_PTR(retval);
2812 static inline void init_idle_pids(struct task_struct *idle)
2816 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
2817 INIT_HLIST_NODE(&idle->pid_links[type]); /* not really needed */
2818 init_task_pid(idle, type, &init_struct_pid);
2822 static int idle_dummy(void *dummy)
2824 /* This function is never called */
2828 struct task_struct * __init fork_idle(int cpu)
2830 struct task_struct *task;
2831 struct kernel_clone_args args = {
2839 task = copy_process(&init_struct_pid, 0, cpu_to_node(cpu), &args);
2840 if (!IS_ERR(task)) {
2841 init_idle_pids(task);
2842 init_idle(task, cpu);
2849 * This is like kernel_clone(), but shaved down and tailored to just
2850 * creating io_uring workers. It returns a created task, or an error pointer.
2851 * The returned task is inactive, and the caller must fire it up through
2852 * wake_up_new_task(p). All signals are blocked in the created task.
2854 struct task_struct *create_io_thread(int (*fn)(void *), void *arg, int node)
2856 unsigned long flags = CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|
2858 struct kernel_clone_args args = {
2859 .flags = ((lower_32_bits(flags) | CLONE_VM |
2860 CLONE_UNTRACED) & ~CSIGNAL),
2861 .exit_signal = (lower_32_bits(flags) & CSIGNAL),
2868 return copy_process(NULL, 0, node, &args);
2872 * Ok, this is the main fork-routine.
2874 * It copies the process, and if successful kick-starts
2875 * it and waits for it to finish using the VM if required.
2877 * args->exit_signal is expected to be checked for sanity by the caller.
2879 pid_t kernel_clone(struct kernel_clone_args *args)
2881 u64 clone_flags = args->flags;
2882 struct completion vfork;
2884 struct task_struct *p;
2889 * For legacy clone() calls, CLONE_PIDFD uses the parent_tid argument
2890 * to return the pidfd. Hence, CLONE_PIDFD and CLONE_PARENT_SETTID are
2891 * mutually exclusive. With clone3() CLONE_PIDFD has grown a separate
2892 * field in struct clone_args and it still doesn't make sense to have
2893 * them both point at the same memory location. Performing this check
2894 * here has the advantage that we don't need to have a separate helper
2895 * to check for legacy clone().
2897 if ((args->flags & CLONE_PIDFD) &&
2898 (args->flags & CLONE_PARENT_SETTID) &&
2899 (args->pidfd == args->parent_tid))
2903 * Determine whether and which event to report to ptracer. When
2904 * called from kernel_thread or CLONE_UNTRACED is explicitly
2905 * requested, no event is reported; otherwise, report if the event
2906 * for the type of forking is enabled.
2908 if (!(clone_flags & CLONE_UNTRACED)) {
2909 if (clone_flags & CLONE_VFORK)
2910 trace = PTRACE_EVENT_VFORK;
2911 else if (args->exit_signal != SIGCHLD)
2912 trace = PTRACE_EVENT_CLONE;
2914 trace = PTRACE_EVENT_FORK;
2916 if (likely(!ptrace_event_enabled(current, trace)))
2920 p = copy_process(NULL, trace, NUMA_NO_NODE, args);
2921 add_latent_entropy();
2927 * Do this prior waking up the new thread - the thread pointer
2928 * might get invalid after that point, if the thread exits quickly.
2930 trace_sched_process_fork(current, p);
2932 pid = get_task_pid(p, PIDTYPE_PID);
2935 if (clone_flags & CLONE_PARENT_SETTID)
2936 put_user(nr, args->parent_tid);
2938 if (clone_flags & CLONE_VFORK) {
2939 p->vfork_done = &vfork;
2940 init_completion(&vfork);
2944 if (IS_ENABLED(CONFIG_LRU_GEN) && !(clone_flags & CLONE_VM)) {
2945 /* lock the task to synchronize with memcg migration */
2947 lru_gen_add_mm(p->mm);
2951 wake_up_new_task(p);
2953 /* forking complete and child started to run, tell ptracer */
2954 if (unlikely(trace))
2955 ptrace_event_pid(trace, pid);
2957 if (clone_flags & CLONE_VFORK) {
2958 if (!wait_for_vfork_done(p, &vfork))
2959 ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid);
2967 * Create a kernel thread.
2969 pid_t kernel_thread(int (*fn)(void *), void *arg, const char *name,
2970 unsigned long flags)
2972 struct kernel_clone_args args = {
2973 .flags = ((lower_32_bits(flags) | CLONE_VM |
2974 CLONE_UNTRACED) & ~CSIGNAL),
2975 .exit_signal = (lower_32_bits(flags) & CSIGNAL),
2982 return kernel_clone(&args);
2986 * Create a user mode thread.
2988 pid_t user_mode_thread(int (*fn)(void *), void *arg, unsigned long flags)
2990 struct kernel_clone_args args = {
2991 .flags = ((lower_32_bits(flags) | CLONE_VM |
2992 CLONE_UNTRACED) & ~CSIGNAL),
2993 .exit_signal = (lower_32_bits(flags) & CSIGNAL),
2998 return kernel_clone(&args);
3001 #ifdef __ARCH_WANT_SYS_FORK
3002 SYSCALL_DEFINE0(fork)
3005 struct kernel_clone_args args = {
3006 .exit_signal = SIGCHLD,
3009 return kernel_clone(&args);
3011 /* can not support in nommu mode */
3017 #ifdef __ARCH_WANT_SYS_VFORK
3018 SYSCALL_DEFINE0(vfork)
3020 struct kernel_clone_args args = {
3021 .flags = CLONE_VFORK | CLONE_VM,
3022 .exit_signal = SIGCHLD,
3025 return kernel_clone(&args);
3029 #ifdef __ARCH_WANT_SYS_CLONE
3030 #ifdef CONFIG_CLONE_BACKWARDS
3031 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
3032 int __user *, parent_tidptr,
3034 int __user *, child_tidptr)
3035 #elif defined(CONFIG_CLONE_BACKWARDS2)
3036 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags,
3037 int __user *, parent_tidptr,
3038 int __user *, child_tidptr,
3040 #elif defined(CONFIG_CLONE_BACKWARDS3)
3041 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp,
3043 int __user *, parent_tidptr,
3044 int __user *, child_tidptr,
3047 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
3048 int __user *, parent_tidptr,
3049 int __user *, child_tidptr,
3053 struct kernel_clone_args args = {
3054 .flags = (lower_32_bits(clone_flags) & ~CSIGNAL),
3055 .pidfd = parent_tidptr,
3056 .child_tid = child_tidptr,
3057 .parent_tid = parent_tidptr,
3058 .exit_signal = (lower_32_bits(clone_flags) & CSIGNAL),
3063 return kernel_clone(&args);
3067 #ifdef __ARCH_WANT_SYS_CLONE3
3069 noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs,
3070 struct clone_args __user *uargs,
3074 struct clone_args args;
3075 pid_t *kset_tid = kargs->set_tid;
3077 BUILD_BUG_ON(offsetofend(struct clone_args, tls) !=
3078 CLONE_ARGS_SIZE_VER0);
3079 BUILD_BUG_ON(offsetofend(struct clone_args, set_tid_size) !=
3080 CLONE_ARGS_SIZE_VER1);
3081 BUILD_BUG_ON(offsetofend(struct clone_args, cgroup) !=
3082 CLONE_ARGS_SIZE_VER2);
3083 BUILD_BUG_ON(sizeof(struct clone_args) != CLONE_ARGS_SIZE_VER2);
3085 if (unlikely(usize > PAGE_SIZE))
3087 if (unlikely(usize < CLONE_ARGS_SIZE_VER0))
3090 err = copy_struct_from_user(&args, sizeof(args), uargs, usize);
3094 if (unlikely(args.set_tid_size > MAX_PID_NS_LEVEL))
3097 if (unlikely(!args.set_tid && args.set_tid_size > 0))
3100 if (unlikely(args.set_tid && args.set_tid_size == 0))
3104 * Verify that higher 32bits of exit_signal are unset and that
3105 * it is a valid signal
3107 if (unlikely((args.exit_signal & ~((u64)CSIGNAL)) ||
3108 !valid_signal(args.exit_signal)))
3111 if ((args.flags & CLONE_INTO_CGROUP) &&
3112 (args.cgroup > INT_MAX || usize < CLONE_ARGS_SIZE_VER2))
3115 *kargs = (struct kernel_clone_args){
3116 .flags = args.flags,
3117 .pidfd = u64_to_user_ptr(args.pidfd),
3118 .child_tid = u64_to_user_ptr(args.child_tid),
3119 .parent_tid = u64_to_user_ptr(args.parent_tid),
3120 .exit_signal = args.exit_signal,
3121 .stack = args.stack,
3122 .stack_size = args.stack_size,
3124 .set_tid_size = args.set_tid_size,
3125 .cgroup = args.cgroup,
3129 copy_from_user(kset_tid, u64_to_user_ptr(args.set_tid),
3130 (kargs->set_tid_size * sizeof(pid_t))))
3133 kargs->set_tid = kset_tid;
3139 * clone3_stack_valid - check and prepare stack
3140 * @kargs: kernel clone args
3142 * Verify that the stack arguments userspace gave us are sane.
3143 * In addition, set the stack direction for userspace since it's easy for us to
3146 static inline bool clone3_stack_valid(struct kernel_clone_args *kargs)
3148 if (kargs->stack == 0) {
3149 if (kargs->stack_size > 0)
3152 if (kargs->stack_size == 0)
3155 if (!access_ok((void __user *)kargs->stack, kargs->stack_size))
3158 #if !defined(CONFIG_STACK_GROWSUP) && !defined(CONFIG_IA64)
3159 kargs->stack += kargs->stack_size;
3166 static bool clone3_args_valid(struct kernel_clone_args *kargs)
3168 /* Verify that no unknown flags are passed along. */
3170 ~(CLONE_LEGACY_FLAGS | CLONE_CLEAR_SIGHAND | CLONE_INTO_CGROUP))
3174 * - make the CLONE_DETACHED bit reusable for clone3
3175 * - make the CSIGNAL bits reusable for clone3
3177 if (kargs->flags & (CLONE_DETACHED | (CSIGNAL & (~CLONE_NEWTIME))))
3180 if ((kargs->flags & (CLONE_SIGHAND | CLONE_CLEAR_SIGHAND)) ==
3181 (CLONE_SIGHAND | CLONE_CLEAR_SIGHAND))
3184 if ((kargs->flags & (CLONE_THREAD | CLONE_PARENT)) &&
3188 if (!clone3_stack_valid(kargs))
3195 * clone3 - create a new process with specific properties
3196 * @uargs: argument structure
3197 * @size: size of @uargs
3199 * clone3() is the extensible successor to clone()/clone2().
3200 * It takes a struct as argument that is versioned by its size.
3202 * Return: On success, a positive PID for the child process.
3203 * On error, a negative errno number.
3205 SYSCALL_DEFINE2(clone3, struct clone_args __user *, uargs, size_t, size)
3209 struct kernel_clone_args kargs;
3210 pid_t set_tid[MAX_PID_NS_LEVEL];
3212 kargs.set_tid = set_tid;
3214 err = copy_clone_args_from_user(&kargs, uargs, size);
3218 if (!clone3_args_valid(&kargs))
3221 return kernel_clone(&kargs);
3225 void walk_process_tree(struct task_struct *top, proc_visitor visitor, void *data)
3227 struct task_struct *leader, *parent, *child;
3230 read_lock(&tasklist_lock);
3231 leader = top = top->group_leader;
3233 for_each_thread(leader, parent) {
3234 list_for_each_entry(child, &parent->children, sibling) {
3235 res = visitor(child, data);
3247 if (leader != top) {
3249 parent = child->real_parent;
3250 leader = parent->group_leader;
3254 read_unlock(&tasklist_lock);
3257 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
3258 #define ARCH_MIN_MMSTRUCT_ALIGN 0
3261 static void sighand_ctor(void *data)
3263 struct sighand_struct *sighand = data;
3265 spin_lock_init(&sighand->siglock);
3266 init_waitqueue_head(&sighand->signalfd_wqh);
3269 void __init mm_cache_init(void)
3271 unsigned int mm_size;
3274 * The mm_cpumask is located at the end of mm_struct, and is
3275 * dynamically sized based on the maximum CPU number this system
3276 * can have, taking hotplug into account (nr_cpu_ids).
3278 mm_size = sizeof(struct mm_struct) + cpumask_size() + mm_cid_size();
3280 mm_cachep = kmem_cache_create_usercopy("mm_struct",
3281 mm_size, ARCH_MIN_MMSTRUCT_ALIGN,
3282 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
3283 offsetof(struct mm_struct, saved_auxv),
3284 sizeof_field(struct mm_struct, saved_auxv),
3288 void __init proc_caches_init(void)
3290 sighand_cachep = kmem_cache_create("sighand_cache",
3291 sizeof(struct sighand_struct), 0,
3292 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_TYPESAFE_BY_RCU|
3293 SLAB_ACCOUNT, sighand_ctor);
3294 signal_cachep = kmem_cache_create("signal_cache",
3295 sizeof(struct signal_struct), 0,
3296 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
3298 files_cachep = kmem_cache_create("files_cache",
3299 sizeof(struct files_struct), 0,
3300 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
3302 fs_cachep = kmem_cache_create("fs_cache",
3303 sizeof(struct fs_struct), 0,
3304 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
3307 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT);
3308 #ifdef CONFIG_PER_VMA_LOCK
3309 vma_lock_cachep = KMEM_CACHE(vma_lock, SLAB_PANIC|SLAB_ACCOUNT);
3312 nsproxy_cache_init();
3316 * Check constraints on flags passed to the unshare system call.
3318 static int check_unshare_flags(unsigned long unshare_flags)
3320 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
3321 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
3322 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET|
3323 CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP|
3327 * Not implemented, but pretend it works if there is nothing
3328 * to unshare. Note that unsharing the address space or the
3329 * signal handlers also need to unshare the signal queues (aka
3332 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
3333 if (!thread_group_empty(current))
3336 if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) {
3337 if (refcount_read(¤t->sighand->count) > 1)
3340 if (unshare_flags & CLONE_VM) {
3341 if (!current_is_single_threaded())
3349 * Unshare the filesystem structure if it is being shared
3351 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
3353 struct fs_struct *fs = current->fs;
3355 if (!(unshare_flags & CLONE_FS) || !fs)
3358 /* don't need lock here; in the worst case we'll do useless copy */
3362 *new_fsp = copy_fs_struct(fs);
3370 * Unshare file descriptor table if it is being shared
3372 int unshare_fd(unsigned long unshare_flags, unsigned int max_fds,
3373 struct files_struct **new_fdp)
3375 struct files_struct *fd = current->files;
3378 if ((unshare_flags & CLONE_FILES) &&
3379 (fd && atomic_read(&fd->count) > 1)) {
3380 *new_fdp = dup_fd(fd, max_fds, &error);
3389 * unshare allows a process to 'unshare' part of the process
3390 * context which was originally shared using clone. copy_*
3391 * functions used by kernel_clone() cannot be used here directly
3392 * because they modify an inactive task_struct that is being
3393 * constructed. Here we are modifying the current, active,
3396 int ksys_unshare(unsigned long unshare_flags)
3398 struct fs_struct *fs, *new_fs = NULL;
3399 struct files_struct *new_fd = NULL;
3400 struct cred *new_cred = NULL;
3401 struct nsproxy *new_nsproxy = NULL;
3406 * If unsharing a user namespace must also unshare the thread group
3407 * and unshare the filesystem root and working directories.
3409 if (unshare_flags & CLONE_NEWUSER)
3410 unshare_flags |= CLONE_THREAD | CLONE_FS;
3412 * If unsharing vm, must also unshare signal handlers.
3414 if (unshare_flags & CLONE_VM)
3415 unshare_flags |= CLONE_SIGHAND;
3417 * If unsharing a signal handlers, must also unshare the signal queues.
3419 if (unshare_flags & CLONE_SIGHAND)
3420 unshare_flags |= CLONE_THREAD;
3422 * If unsharing namespace, must also unshare filesystem information.
3424 if (unshare_flags & CLONE_NEWNS)
3425 unshare_flags |= CLONE_FS;
3427 err = check_unshare_flags(unshare_flags);
3429 goto bad_unshare_out;
3431 * CLONE_NEWIPC must also detach from the undolist: after switching
3432 * to a new ipc namespace, the semaphore arrays from the old
3433 * namespace are unreachable.
3435 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
3437 err = unshare_fs(unshare_flags, &new_fs);
3439 goto bad_unshare_out;
3440 err = unshare_fd(unshare_flags, NR_OPEN_MAX, &new_fd);
3442 goto bad_unshare_cleanup_fs;
3443 err = unshare_userns(unshare_flags, &new_cred);
3445 goto bad_unshare_cleanup_fd;
3446 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
3449 goto bad_unshare_cleanup_cred;
3452 err = set_cred_ucounts(new_cred);
3454 goto bad_unshare_cleanup_cred;
3457 if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
3460 * CLONE_SYSVSEM is equivalent to sys_exit().
3464 if (unshare_flags & CLONE_NEWIPC) {
3465 /* Orphan segments in old ns (see sem above). */
3467 shm_init_task(current);
3471 switch_task_namespaces(current, new_nsproxy);
3477 spin_lock(&fs->lock);
3478 current->fs = new_fs;
3483 spin_unlock(&fs->lock);
3487 swap(current->files, new_fd);
3489 task_unlock(current);
3492 /* Install the new user namespace */
3493 commit_creds(new_cred);
3498 perf_event_namespaces(current);
3500 bad_unshare_cleanup_cred:
3503 bad_unshare_cleanup_fd:
3505 put_files_struct(new_fd);
3507 bad_unshare_cleanup_fs:
3509 free_fs_struct(new_fs);
3515 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
3517 return ksys_unshare(unshare_flags);
3521 * Helper to unshare the files of the current task.
3522 * We don't want to expose copy_files internals to
3523 * the exec layer of the kernel.
3526 int unshare_files(void)
3528 struct task_struct *task = current;
3529 struct files_struct *old, *copy = NULL;
3532 error = unshare_fd(CLONE_FILES, NR_OPEN_MAX, ©);
3540 put_files_struct(old);
3544 int sysctl_max_threads(struct ctl_table *table, int write,
3545 void *buffer, size_t *lenp, loff_t *ppos)
3549 int threads = max_threads;
3551 int max = MAX_THREADS;
3558 ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
3562 max_threads = threads;