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>
43 #include <linux/hmm.h>
46 #include <linux/vmacache.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/random.h>
79 #include <linux/tty.h>
80 #include <linux/blkdev.h>
81 #include <linux/fs_struct.h>
82 #include <linux/magic.h>
83 #include <linux/perf_event.h>
84 #include <linux/posix-timers.h>
85 #include <linux/user-return-notifier.h>
86 #include <linux/oom.h>
87 #include <linux/khugepaged.h>
88 #include <linux/signalfd.h>
89 #include <linux/uprobes.h>
90 #include <linux/aio.h>
91 #include <linux/compiler.h>
92 #include <linux/sysctl.h>
93 #include <linux/kcov.h>
94 #include <linux/livepatch.h>
95 #include <linux/thread_info.h>
96 #include <linux/stackleak.h>
98 #include <asm/pgtable.h>
99 #include <asm/pgalloc.h>
100 #include <linux/uaccess.h>
101 #include <asm/mmu_context.h>
102 #include <asm/cacheflush.h>
103 #include <asm/tlbflush.h>
105 #include <trace/events/sched.h>
107 #define CREATE_TRACE_POINTS
108 #include <trace/events/task.h>
111 * Minimum number of threads to boot the kernel
113 #define MIN_THREADS 20
116 * Maximum number of threads
118 #define MAX_THREADS FUTEX_TID_MASK
121 * Protected counters by write_lock_irq(&tasklist_lock)
123 unsigned long total_forks; /* Handle normal Linux uptimes. */
124 int nr_threads; /* The idle threads do not count.. */
126 static int max_threads; /* tunable limit on nr_threads */
128 #define NAMED_ARRAY_INDEX(x) [x] = __stringify(x)
130 static const char * const resident_page_types[] = {
131 NAMED_ARRAY_INDEX(MM_FILEPAGES),
132 NAMED_ARRAY_INDEX(MM_ANONPAGES),
133 NAMED_ARRAY_INDEX(MM_SWAPENTS),
134 NAMED_ARRAY_INDEX(MM_SHMEMPAGES),
137 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
139 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */
141 #ifdef CONFIG_PROVE_RCU
142 int lockdep_tasklist_lock_is_held(void)
144 return lockdep_is_held(&tasklist_lock);
146 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
147 #endif /* #ifdef CONFIG_PROVE_RCU */
149 int nr_processes(void)
154 for_each_possible_cpu(cpu)
155 total += per_cpu(process_counts, cpu);
160 void __weak arch_release_task_struct(struct task_struct *tsk)
164 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
165 static struct kmem_cache *task_struct_cachep;
167 static inline struct task_struct *alloc_task_struct_node(int node)
169 return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node);
172 static inline void free_task_struct(struct task_struct *tsk)
174 kmem_cache_free(task_struct_cachep, tsk);
178 #ifndef CONFIG_ARCH_THREAD_STACK_ALLOCATOR
181 * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
182 * kmemcache based allocator.
184 # if THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK)
186 #ifdef CONFIG_VMAP_STACK
188 * vmalloc() is a bit slow, and calling vfree() enough times will force a TLB
189 * flush. Try to minimize the number of calls by caching stacks.
191 #define NR_CACHED_STACKS 2
192 static DEFINE_PER_CPU(struct vm_struct *, cached_stacks[NR_CACHED_STACKS]);
194 static int free_vm_stack_cache(unsigned int cpu)
196 struct vm_struct **cached_vm_stacks = per_cpu_ptr(cached_stacks, cpu);
199 for (i = 0; i < NR_CACHED_STACKS; i++) {
200 struct vm_struct *vm_stack = cached_vm_stacks[i];
205 vfree(vm_stack->addr);
206 cached_vm_stacks[i] = NULL;
213 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node)
215 #ifdef CONFIG_VMAP_STACK
219 for (i = 0; i < NR_CACHED_STACKS; i++) {
222 s = this_cpu_xchg(cached_stacks[i], NULL);
227 /* Clear stale pointers from reused stack. */
228 memset(s->addr, 0, THREAD_SIZE);
230 tsk->stack_vm_area = s;
231 tsk->stack = s->addr;
236 * Allocated stacks are cached and later reused by new threads,
237 * so memcg accounting is performed manually on assigning/releasing
238 * stacks to tasks. Drop __GFP_ACCOUNT.
240 stack = __vmalloc_node_range(THREAD_SIZE, THREAD_ALIGN,
241 VMALLOC_START, VMALLOC_END,
242 THREADINFO_GFP & ~__GFP_ACCOUNT,
244 0, node, __builtin_return_address(0));
247 * We can't call find_vm_area() in interrupt context, and
248 * free_thread_stack() can be called in interrupt context,
249 * so cache the vm_struct.
252 tsk->stack_vm_area = find_vm_area(stack);
257 struct page *page = alloc_pages_node(node, THREADINFO_GFP,
261 tsk->stack = page_address(page);
268 static inline void free_thread_stack(struct task_struct *tsk)
270 #ifdef CONFIG_VMAP_STACK
271 struct vm_struct *vm = task_stack_vm_area(tsk);
276 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
277 mod_memcg_page_state(vm->pages[i],
278 MEMCG_KERNEL_STACK_KB,
279 -(int)(PAGE_SIZE / 1024));
281 memcg_kmem_uncharge(vm->pages[i], 0);
284 for (i = 0; i < NR_CACHED_STACKS; i++) {
285 if (this_cpu_cmpxchg(cached_stacks[i],
286 NULL, tsk->stack_vm_area) != NULL)
292 vfree_atomic(tsk->stack);
297 __free_pages(virt_to_page(tsk->stack), THREAD_SIZE_ORDER);
300 static struct kmem_cache *thread_stack_cache;
302 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk,
305 unsigned long *stack;
306 stack = kmem_cache_alloc_node(thread_stack_cache, THREADINFO_GFP, node);
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);
360 INIT_LIST_HEAD(&new->anon_vma_chain);
365 void vm_area_free(struct vm_area_struct *vma)
367 kmem_cache_free(vm_area_cachep, vma);
370 static void account_kernel_stack(struct task_struct *tsk, int account)
372 void *stack = task_stack_page(tsk);
373 struct vm_struct *vm = task_stack_vm_area(tsk);
375 BUILD_BUG_ON(IS_ENABLED(CONFIG_VMAP_STACK) && PAGE_SIZE % 1024 != 0);
380 BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE);
382 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
383 mod_zone_page_state(page_zone(vm->pages[i]),
385 PAGE_SIZE / 1024 * account);
389 * All stack pages are in the same zone and belong to the
392 struct page *first_page = virt_to_page(stack);
394 mod_zone_page_state(page_zone(first_page), NR_KERNEL_STACK_KB,
395 THREAD_SIZE / 1024 * account);
397 mod_memcg_page_state(first_page, MEMCG_KERNEL_STACK_KB,
398 account * (THREAD_SIZE / 1024));
402 static int memcg_charge_kernel_stack(struct task_struct *tsk)
404 #ifdef CONFIG_VMAP_STACK
405 struct vm_struct *vm = task_stack_vm_area(tsk);
411 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
413 * If memcg_kmem_charge() fails, page->mem_cgroup
414 * pointer is NULL, and both memcg_kmem_uncharge()
415 * and mod_memcg_page_state() in free_thread_stack()
416 * will ignore this page. So it's safe.
418 ret = memcg_kmem_charge(vm->pages[i], GFP_KERNEL, 0);
422 mod_memcg_page_state(vm->pages[i],
423 MEMCG_KERNEL_STACK_KB,
431 static void release_task_stack(struct task_struct *tsk)
433 if (WARN_ON(tsk->state != TASK_DEAD))
434 return; /* Better to leak the stack than to free prematurely */
436 account_kernel_stack(tsk, -1);
437 free_thread_stack(tsk);
439 #ifdef CONFIG_VMAP_STACK
440 tsk->stack_vm_area = NULL;
444 #ifdef CONFIG_THREAD_INFO_IN_TASK
445 void put_task_stack(struct task_struct *tsk)
447 if (refcount_dec_and_test(&tsk->stack_refcount))
448 release_task_stack(tsk);
452 void free_task(struct task_struct *tsk)
454 #ifndef CONFIG_THREAD_INFO_IN_TASK
456 * The task is finally done with both the stack and thread_info,
459 release_task_stack(tsk);
462 * If the task had a separate stack allocation, it should be gone
465 WARN_ON_ONCE(refcount_read(&tsk->stack_refcount) != 0);
467 rt_mutex_debug_task_free(tsk);
468 ftrace_graph_exit_task(tsk);
469 put_seccomp_filter(tsk);
470 arch_release_task_struct(tsk);
471 if (tsk->flags & PF_KTHREAD)
472 free_kthread_struct(tsk);
473 free_task_struct(tsk);
475 EXPORT_SYMBOL(free_task);
478 static __latent_entropy int dup_mmap(struct mm_struct *mm,
479 struct mm_struct *oldmm)
481 struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
482 struct rb_node **rb_link, *rb_parent;
484 unsigned long charge;
487 uprobe_start_dup_mmap();
488 if (down_write_killable(&oldmm->mmap_sem)) {
490 goto fail_uprobe_end;
492 flush_cache_dup_mm(oldmm);
493 uprobe_dup_mmap(oldmm, mm);
495 * Not linked in yet - no deadlock potential:
497 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
499 /* No ordering required: file already has been exposed. */
500 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
502 mm->total_vm = oldmm->total_vm;
503 mm->data_vm = oldmm->data_vm;
504 mm->exec_vm = oldmm->exec_vm;
505 mm->stack_vm = oldmm->stack_vm;
507 rb_link = &mm->mm_rb.rb_node;
510 retval = ksm_fork(mm, oldmm);
513 retval = khugepaged_fork(mm, oldmm);
518 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
521 if (mpnt->vm_flags & VM_DONTCOPY) {
522 vm_stat_account(mm, mpnt->vm_flags, -vma_pages(mpnt));
527 * Don't duplicate many vmas if we've been oom-killed (for
530 if (fatal_signal_pending(current)) {
534 if (mpnt->vm_flags & VM_ACCOUNT) {
535 unsigned long len = vma_pages(mpnt);
537 if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
541 tmp = vm_area_dup(mpnt);
544 retval = vma_dup_policy(mpnt, tmp);
546 goto fail_nomem_policy;
548 retval = dup_userfaultfd(tmp, &uf);
550 goto fail_nomem_anon_vma_fork;
551 if (tmp->vm_flags & VM_WIPEONFORK) {
552 /* VM_WIPEONFORK gets a clean slate in the child. */
553 tmp->anon_vma = NULL;
554 if (anon_vma_prepare(tmp))
555 goto fail_nomem_anon_vma_fork;
556 } else if (anon_vma_fork(tmp, mpnt))
557 goto fail_nomem_anon_vma_fork;
558 tmp->vm_flags &= ~(VM_LOCKED | VM_LOCKONFAULT);
559 tmp->vm_next = tmp->vm_prev = NULL;
562 struct inode *inode = file_inode(file);
563 struct address_space *mapping = file->f_mapping;
566 if (tmp->vm_flags & VM_DENYWRITE)
567 atomic_dec(&inode->i_writecount);
568 i_mmap_lock_write(mapping);
569 if (tmp->vm_flags & VM_SHARED)
570 atomic_inc(&mapping->i_mmap_writable);
571 flush_dcache_mmap_lock(mapping);
572 /* insert tmp into the share list, just after mpnt */
573 vma_interval_tree_insert_after(tmp, mpnt,
575 flush_dcache_mmap_unlock(mapping);
576 i_mmap_unlock_write(mapping);
580 * Clear hugetlb-related page reserves for children. This only
581 * affects MAP_PRIVATE mappings. Faults generated by the child
582 * are not guaranteed to succeed, even if read-only
584 if (is_vm_hugetlb_page(tmp))
585 reset_vma_resv_huge_pages(tmp);
588 * Link in the new vma and copy the page table entries.
591 pprev = &tmp->vm_next;
595 __vma_link_rb(mm, tmp, rb_link, rb_parent);
596 rb_link = &tmp->vm_rb.rb_right;
597 rb_parent = &tmp->vm_rb;
600 if (!(tmp->vm_flags & VM_WIPEONFORK))
601 retval = copy_page_range(mm, oldmm, mpnt);
603 if (tmp->vm_ops && tmp->vm_ops->open)
604 tmp->vm_ops->open(tmp);
609 /* a new mm has just been created */
610 retval = arch_dup_mmap(oldmm, mm);
612 up_write(&mm->mmap_sem);
614 up_write(&oldmm->mmap_sem);
615 dup_userfaultfd_complete(&uf);
617 uprobe_end_dup_mmap();
619 fail_nomem_anon_vma_fork:
620 mpol_put(vma_policy(tmp));
625 vm_unacct_memory(charge);
629 static inline int mm_alloc_pgd(struct mm_struct *mm)
631 mm->pgd = pgd_alloc(mm);
632 if (unlikely(!mm->pgd))
637 static inline void mm_free_pgd(struct mm_struct *mm)
639 pgd_free(mm, mm->pgd);
642 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
644 down_write(&oldmm->mmap_sem);
645 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
646 up_write(&oldmm->mmap_sem);
649 #define mm_alloc_pgd(mm) (0)
650 #define mm_free_pgd(mm)
651 #endif /* CONFIG_MMU */
653 static void check_mm(struct mm_struct *mm)
657 BUILD_BUG_ON_MSG(ARRAY_SIZE(resident_page_types) != NR_MM_COUNTERS,
658 "Please make sure 'struct resident_page_types[]' is updated as well");
660 for (i = 0; i < NR_MM_COUNTERS; i++) {
661 long x = atomic_long_read(&mm->rss_stat.count[i]);
664 pr_alert("BUG: Bad rss-counter state mm:%p type:%s val:%ld\n",
665 mm, resident_page_types[i], x);
668 if (mm_pgtables_bytes(mm))
669 pr_alert("BUG: non-zero pgtables_bytes on freeing mm: %ld\n",
670 mm_pgtables_bytes(mm));
672 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
673 VM_BUG_ON_MM(mm->pmd_huge_pte, mm);
677 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
678 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm)))
681 * Called when the last reference to the mm
682 * is dropped: either by a lazy thread or by
683 * mmput. Free the page directory and the mm.
685 void __mmdrop(struct mm_struct *mm)
687 BUG_ON(mm == &init_mm);
688 WARN_ON_ONCE(mm == current->mm);
689 WARN_ON_ONCE(mm == current->active_mm);
692 mmu_notifier_mm_destroy(mm);
694 put_user_ns(mm->user_ns);
697 EXPORT_SYMBOL_GPL(__mmdrop);
699 static void mmdrop_async_fn(struct work_struct *work)
701 struct mm_struct *mm;
703 mm = container_of(work, struct mm_struct, async_put_work);
707 static void mmdrop_async(struct mm_struct *mm)
709 if (unlikely(atomic_dec_and_test(&mm->mm_count))) {
710 INIT_WORK(&mm->async_put_work, mmdrop_async_fn);
711 schedule_work(&mm->async_put_work);
715 static inline void free_signal_struct(struct signal_struct *sig)
717 taskstats_tgid_free(sig);
718 sched_autogroup_exit(sig);
720 * __mmdrop is not safe to call from softirq context on x86 due to
721 * pgd_dtor so postpone it to the async context
724 mmdrop_async(sig->oom_mm);
725 kmem_cache_free(signal_cachep, sig);
728 static inline void put_signal_struct(struct signal_struct *sig)
730 if (refcount_dec_and_test(&sig->sigcnt))
731 free_signal_struct(sig);
734 void __put_task_struct(struct task_struct *tsk)
736 WARN_ON(!tsk->exit_state);
737 WARN_ON(refcount_read(&tsk->usage));
738 WARN_ON(tsk == current);
741 task_numa_free(tsk, true);
742 security_task_free(tsk);
744 delayacct_tsk_free(tsk);
745 put_signal_struct(tsk->signal);
747 if (!profile_handoff_task(tsk))
750 EXPORT_SYMBOL_GPL(__put_task_struct);
752 void __init __weak arch_task_cache_init(void) { }
757 static void set_max_threads(unsigned int max_threads_suggested)
760 unsigned long nr_pages = totalram_pages();
763 * The number of threads shall be limited such that the thread
764 * structures may only consume a small part of the available memory.
766 if (fls64(nr_pages) + fls64(PAGE_SIZE) > 64)
767 threads = MAX_THREADS;
769 threads = div64_u64((u64) nr_pages * (u64) PAGE_SIZE,
770 (u64) THREAD_SIZE * 8UL);
772 if (threads > max_threads_suggested)
773 threads = max_threads_suggested;
775 max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS);
778 #ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT
779 /* Initialized by the architecture: */
780 int arch_task_struct_size __read_mostly;
783 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
784 static void task_struct_whitelist(unsigned long *offset, unsigned long *size)
786 /* Fetch thread_struct whitelist for the architecture. */
787 arch_thread_struct_whitelist(offset, size);
790 * Handle zero-sized whitelist or empty thread_struct, otherwise
791 * adjust offset to position of thread_struct in task_struct.
793 if (unlikely(*size == 0))
796 *offset += offsetof(struct task_struct, thread);
798 #endif /* CONFIG_ARCH_TASK_STRUCT_ALLOCATOR */
800 void __init fork_init(void)
803 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
804 #ifndef ARCH_MIN_TASKALIGN
805 #define ARCH_MIN_TASKALIGN 0
807 int align = max_t(int, L1_CACHE_BYTES, ARCH_MIN_TASKALIGN);
808 unsigned long useroffset, usersize;
810 /* create a slab on which task_structs can be allocated */
811 task_struct_whitelist(&useroffset, &usersize);
812 task_struct_cachep = kmem_cache_create_usercopy("task_struct",
813 arch_task_struct_size, align,
814 SLAB_PANIC|SLAB_ACCOUNT,
815 useroffset, usersize, NULL);
818 /* do the arch specific task caches init */
819 arch_task_cache_init();
821 set_max_threads(MAX_THREADS);
823 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
824 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
825 init_task.signal->rlim[RLIMIT_SIGPENDING] =
826 init_task.signal->rlim[RLIMIT_NPROC];
828 for (i = 0; i < UCOUNT_COUNTS; i++) {
829 init_user_ns.ucount_max[i] = max_threads/2;
832 #ifdef CONFIG_VMAP_STACK
833 cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "fork:vm_stack_cache",
834 NULL, free_vm_stack_cache);
837 lockdep_init_task(&init_task);
841 int __weak arch_dup_task_struct(struct task_struct *dst,
842 struct task_struct *src)
848 void set_task_stack_end_magic(struct task_struct *tsk)
850 unsigned long *stackend;
852 stackend = end_of_stack(tsk);
853 *stackend = STACK_END_MAGIC; /* for overflow detection */
856 static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
858 struct task_struct *tsk;
859 unsigned long *stack;
860 struct vm_struct *stack_vm_area __maybe_unused;
863 if (node == NUMA_NO_NODE)
864 node = tsk_fork_get_node(orig);
865 tsk = alloc_task_struct_node(node);
869 stack = alloc_thread_stack_node(tsk, node);
873 if (memcg_charge_kernel_stack(tsk))
876 stack_vm_area = task_stack_vm_area(tsk);
878 err = arch_dup_task_struct(tsk, orig);
881 * arch_dup_task_struct() clobbers the stack-related fields. Make
882 * sure they're properly initialized before using any stack-related
886 #ifdef CONFIG_VMAP_STACK
887 tsk->stack_vm_area = stack_vm_area;
889 #ifdef CONFIG_THREAD_INFO_IN_TASK
890 refcount_set(&tsk->stack_refcount, 1);
896 #ifdef CONFIG_SECCOMP
898 * We must handle setting up seccomp filters once we're under
899 * the sighand lock in case orig has changed between now and
900 * then. Until then, filter must be NULL to avoid messing up
901 * the usage counts on the error path calling free_task.
903 tsk->seccomp.filter = NULL;
906 setup_thread_stack(tsk, orig);
907 clear_user_return_notifier(tsk);
908 clear_tsk_need_resched(tsk);
909 set_task_stack_end_magic(tsk);
911 #ifdef CONFIG_STACKPROTECTOR
912 tsk->stack_canary = get_random_canary();
914 if (orig->cpus_ptr == &orig->cpus_mask)
915 tsk->cpus_ptr = &tsk->cpus_mask;
918 * One for the user space visible state that goes away when reaped.
919 * One for the scheduler.
921 refcount_set(&tsk->rcu_users, 2);
922 /* One for the rcu users */
923 refcount_set(&tsk->usage, 1);
924 #ifdef CONFIG_BLK_DEV_IO_TRACE
927 tsk->splice_pipe = NULL;
928 tsk->task_frag.page = NULL;
929 tsk->wake_q.next = NULL;
931 account_kernel_stack(tsk, 1);
935 #ifdef CONFIG_FAULT_INJECTION
939 #ifdef CONFIG_BLK_CGROUP
940 tsk->throttle_queue = NULL;
941 tsk->use_memdelay = 0;
945 tsk->active_memcg = NULL;
950 free_thread_stack(tsk);
952 free_task_struct(tsk);
956 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
958 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
960 static int __init coredump_filter_setup(char *s)
962 default_dump_filter =
963 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
964 MMF_DUMP_FILTER_MASK;
968 __setup("coredump_filter=", coredump_filter_setup);
970 #include <linux/init_task.h>
972 static void mm_init_aio(struct mm_struct *mm)
975 spin_lock_init(&mm->ioctx_lock);
976 mm->ioctx_table = NULL;
980 static __always_inline void mm_clear_owner(struct mm_struct *mm,
981 struct task_struct *p)
985 WRITE_ONCE(mm->owner, NULL);
989 static void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
996 static void mm_init_uprobes_state(struct mm_struct *mm)
998 #ifdef CONFIG_UPROBES
999 mm->uprobes_state.xol_area = NULL;
1003 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
1004 struct user_namespace *user_ns)
1007 mm->mm_rb = RB_ROOT;
1008 mm->vmacache_seqnum = 0;
1009 atomic_set(&mm->mm_users, 1);
1010 atomic_set(&mm->mm_count, 1);
1011 init_rwsem(&mm->mmap_sem);
1012 INIT_LIST_HEAD(&mm->mmlist);
1013 mm->core_state = NULL;
1014 mm_pgtables_bytes_init(mm);
1017 atomic64_set(&mm->pinned_vm, 0);
1018 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
1019 spin_lock_init(&mm->page_table_lock);
1020 spin_lock_init(&mm->arg_lock);
1021 mm_init_cpumask(mm);
1023 mm_init_owner(mm, p);
1024 RCU_INIT_POINTER(mm->exe_file, NULL);
1025 mmu_notifier_mm_init(mm);
1026 init_tlb_flush_pending(mm);
1027 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
1028 mm->pmd_huge_pte = NULL;
1030 mm_init_uprobes_state(mm);
1033 mm->flags = current->mm->flags & MMF_INIT_MASK;
1034 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK;
1036 mm->flags = default_dump_filter;
1040 if (mm_alloc_pgd(mm))
1043 if (init_new_context(p, mm))
1044 goto fail_nocontext;
1046 mm->user_ns = get_user_ns(user_ns);
1057 * Allocate and initialize an mm_struct.
1059 struct mm_struct *mm_alloc(void)
1061 struct mm_struct *mm;
1067 memset(mm, 0, sizeof(*mm));
1068 return mm_init(mm, current, current_user_ns());
1071 static inline void __mmput(struct mm_struct *mm)
1073 VM_BUG_ON(atomic_read(&mm->mm_users));
1075 uprobe_clear_state(mm);
1078 khugepaged_exit(mm); /* must run before exit_mmap */
1080 mm_put_huge_zero_page(mm);
1081 set_mm_exe_file(mm, NULL);
1082 if (!list_empty(&mm->mmlist)) {
1083 spin_lock(&mmlist_lock);
1084 list_del(&mm->mmlist);
1085 spin_unlock(&mmlist_lock);
1088 module_put(mm->binfmt->module);
1093 * Decrement the use count and release all resources for an mm.
1095 void mmput(struct mm_struct *mm)
1099 if (atomic_dec_and_test(&mm->mm_users))
1102 EXPORT_SYMBOL_GPL(mmput);
1105 static void mmput_async_fn(struct work_struct *work)
1107 struct mm_struct *mm = container_of(work, struct mm_struct,
1113 void mmput_async(struct mm_struct *mm)
1115 if (atomic_dec_and_test(&mm->mm_users)) {
1116 INIT_WORK(&mm->async_put_work, mmput_async_fn);
1117 schedule_work(&mm->async_put_work);
1123 * set_mm_exe_file - change a reference to the mm's executable file
1125 * This changes mm's executable file (shown as symlink /proc/[pid]/exe).
1127 * Main users are mmput() and sys_execve(). Callers prevent concurrent
1128 * invocations: in mmput() nobody alive left, in execve task is single
1129 * threaded. sys_prctl(PR_SET_MM_MAP/EXE_FILE) also needs to set the
1130 * mm->exe_file, but does so without using set_mm_exe_file() in order
1131 * to do avoid the need for any locks.
1133 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
1135 struct file *old_exe_file;
1138 * It is safe to dereference the exe_file without RCU as
1139 * this function is only called if nobody else can access
1140 * this mm -- see comment above for justification.
1142 old_exe_file = rcu_dereference_raw(mm->exe_file);
1145 get_file(new_exe_file);
1146 rcu_assign_pointer(mm->exe_file, new_exe_file);
1152 * get_mm_exe_file - acquire a reference to the mm's executable file
1154 * Returns %NULL if mm has no associated executable file.
1155 * User must release file via fput().
1157 struct file *get_mm_exe_file(struct mm_struct *mm)
1159 struct file *exe_file;
1162 exe_file = rcu_dereference(mm->exe_file);
1163 if (exe_file && !get_file_rcu(exe_file))
1168 EXPORT_SYMBOL(get_mm_exe_file);
1171 * get_task_exe_file - acquire a reference to the task's executable file
1173 * Returns %NULL if task's mm (if any) has no associated executable file or
1174 * this is a kernel thread with borrowed mm (see the comment above get_task_mm).
1175 * User must release file via fput().
1177 struct file *get_task_exe_file(struct task_struct *task)
1179 struct file *exe_file = NULL;
1180 struct mm_struct *mm;
1185 if (!(task->flags & PF_KTHREAD))
1186 exe_file = get_mm_exe_file(mm);
1191 EXPORT_SYMBOL(get_task_exe_file);
1194 * get_task_mm - acquire a reference to the task's mm
1196 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning
1197 * this kernel workthread has transiently adopted a user mm with use_mm,
1198 * to do its AIO) is not set and if so returns a reference to it, after
1199 * bumping up the use count. User must release the mm via mmput()
1200 * after use. Typically used by /proc and ptrace.
1202 struct mm_struct *get_task_mm(struct task_struct *task)
1204 struct mm_struct *mm;
1209 if (task->flags & PF_KTHREAD)
1217 EXPORT_SYMBOL_GPL(get_task_mm);
1219 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
1221 struct mm_struct *mm;
1224 err = mutex_lock_killable(&task->signal->cred_guard_mutex);
1226 return ERR_PTR(err);
1228 mm = get_task_mm(task);
1229 if (mm && mm != current->mm &&
1230 !ptrace_may_access(task, mode)) {
1232 mm = ERR_PTR(-EACCES);
1234 mutex_unlock(&task->signal->cred_guard_mutex);
1239 static void complete_vfork_done(struct task_struct *tsk)
1241 struct completion *vfork;
1244 vfork = tsk->vfork_done;
1245 if (likely(vfork)) {
1246 tsk->vfork_done = NULL;
1252 static int wait_for_vfork_done(struct task_struct *child,
1253 struct completion *vfork)
1257 freezer_do_not_count();
1258 cgroup_enter_frozen();
1259 killed = wait_for_completion_killable(vfork);
1260 cgroup_leave_frozen(false);
1265 child->vfork_done = NULL;
1269 put_task_struct(child);
1273 /* Please note the differences between mmput and mm_release.
1274 * mmput is called whenever we stop holding onto a mm_struct,
1275 * error success whatever.
1277 * mm_release is called after a mm_struct has been removed
1278 * from the current process.
1280 * This difference is important for error handling, when we
1281 * only half set up a mm_struct for a new process and need to restore
1282 * the old one. Because we mmput the new mm_struct before
1283 * restoring the old one. . .
1284 * Eric Biederman 10 January 1998
1286 static void mm_release(struct task_struct *tsk, struct mm_struct *mm)
1288 uprobe_free_utask(tsk);
1290 /* Get rid of any cached register state */
1291 deactivate_mm(tsk, mm);
1294 * Signal userspace if we're not exiting with a core dump
1295 * because we want to leave the value intact for debugging
1298 if (tsk->clear_child_tid) {
1299 if (!(tsk->signal->flags & SIGNAL_GROUP_COREDUMP) &&
1300 atomic_read(&mm->mm_users) > 1) {
1302 * We don't check the error code - if userspace has
1303 * not set up a proper pointer then tough luck.
1305 put_user(0, tsk->clear_child_tid);
1306 do_futex(tsk->clear_child_tid, FUTEX_WAKE,
1307 1, NULL, NULL, 0, 0);
1309 tsk->clear_child_tid = NULL;
1313 * All done, finally we can wake up parent and return this mm to him.
1314 * Also kthread_stop() uses this completion for synchronization.
1316 if (tsk->vfork_done)
1317 complete_vfork_done(tsk);
1320 void exit_mm_release(struct task_struct *tsk, struct mm_struct *mm)
1322 futex_exit_release(tsk);
1323 mm_release(tsk, mm);
1326 void exec_mm_release(struct task_struct *tsk, struct mm_struct *mm)
1328 futex_exec_release(tsk);
1329 mm_release(tsk, mm);
1333 * dup_mm() - duplicates an existing mm structure
1334 * @tsk: the task_struct with which the new mm will be associated.
1335 * @oldmm: the mm to duplicate.
1337 * Allocates a new mm structure and duplicates the provided @oldmm structure
1340 * Return: the duplicated mm or NULL on failure.
1342 static struct mm_struct *dup_mm(struct task_struct *tsk,
1343 struct mm_struct *oldmm)
1345 struct mm_struct *mm;
1352 memcpy(mm, oldmm, sizeof(*mm));
1354 if (!mm_init(mm, tsk, mm->user_ns))
1357 err = dup_mmap(mm, oldmm);
1361 mm->hiwater_rss = get_mm_rss(mm);
1362 mm->hiwater_vm = mm->total_vm;
1364 if (mm->binfmt && !try_module_get(mm->binfmt->module))
1370 /* don't put binfmt in mmput, we haven't got module yet */
1372 mm_init_owner(mm, NULL);
1379 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
1381 struct mm_struct *mm, *oldmm;
1384 tsk->min_flt = tsk->maj_flt = 0;
1385 tsk->nvcsw = tsk->nivcsw = 0;
1386 #ifdef CONFIG_DETECT_HUNG_TASK
1387 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
1388 tsk->last_switch_time = 0;
1392 tsk->active_mm = NULL;
1395 * Are we cloning a kernel thread?
1397 * We need to steal a active VM for that..
1399 oldmm = current->mm;
1403 /* initialize the new vmacache entries */
1404 vmacache_flush(tsk);
1406 if (clone_flags & CLONE_VM) {
1413 mm = dup_mm(tsk, current->mm);
1419 tsk->active_mm = mm;
1426 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
1428 struct fs_struct *fs = current->fs;
1429 if (clone_flags & CLONE_FS) {
1430 /* tsk->fs is already what we want */
1431 spin_lock(&fs->lock);
1433 spin_unlock(&fs->lock);
1437 spin_unlock(&fs->lock);
1440 tsk->fs = copy_fs_struct(fs);
1446 static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
1448 struct files_struct *oldf, *newf;
1452 * A background process may not have any files ...
1454 oldf = current->files;
1458 if (clone_flags & CLONE_FILES) {
1459 atomic_inc(&oldf->count);
1463 newf = dup_fd(oldf, &error);
1473 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
1476 struct io_context *ioc = current->io_context;
1477 struct io_context *new_ioc;
1482 * Share io context with parent, if CLONE_IO is set
1484 if (clone_flags & CLONE_IO) {
1486 tsk->io_context = ioc;
1487 } else if (ioprio_valid(ioc->ioprio)) {
1488 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE);
1489 if (unlikely(!new_ioc))
1492 new_ioc->ioprio = ioc->ioprio;
1493 put_io_context(new_ioc);
1499 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
1501 struct sighand_struct *sig;
1503 if (clone_flags & CLONE_SIGHAND) {
1504 refcount_inc(¤t->sighand->count);
1507 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1508 rcu_assign_pointer(tsk->sighand, sig);
1512 refcount_set(&sig->count, 1);
1513 spin_lock_irq(¤t->sighand->siglock);
1514 memcpy(sig->action, current->sighand->action, sizeof(sig->action));
1515 spin_unlock_irq(¤t->sighand->siglock);
1517 /* Reset all signal handler not set to SIG_IGN to SIG_DFL. */
1518 if (clone_flags & CLONE_CLEAR_SIGHAND)
1519 flush_signal_handlers(tsk, 0);
1524 void __cleanup_sighand(struct sighand_struct *sighand)
1526 if (refcount_dec_and_test(&sighand->count)) {
1527 signalfd_cleanup(sighand);
1529 * sighand_cachep is SLAB_TYPESAFE_BY_RCU so we can free it
1530 * without an RCU grace period, see __lock_task_sighand().
1532 kmem_cache_free(sighand_cachep, sighand);
1537 * Initialize POSIX timer handling for a thread group.
1539 static void posix_cpu_timers_init_group(struct signal_struct *sig)
1541 struct posix_cputimers *pct = &sig->posix_cputimers;
1542 unsigned long cpu_limit;
1544 cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1545 posix_cputimers_group_init(pct, cpu_limit);
1548 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
1550 struct signal_struct *sig;
1552 if (clone_flags & CLONE_THREAD)
1555 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
1560 sig->nr_threads = 1;
1561 atomic_set(&sig->live, 1);
1562 refcount_set(&sig->sigcnt, 1);
1564 /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */
1565 sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node);
1566 tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head);
1568 init_waitqueue_head(&sig->wait_chldexit);
1569 sig->curr_target = tsk;
1570 init_sigpending(&sig->shared_pending);
1571 INIT_HLIST_HEAD(&sig->multiprocess);
1572 seqlock_init(&sig->stats_lock);
1573 prev_cputime_init(&sig->prev_cputime);
1575 #ifdef CONFIG_POSIX_TIMERS
1576 INIT_LIST_HEAD(&sig->posix_timers);
1577 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1578 sig->real_timer.function = it_real_fn;
1581 task_lock(current->group_leader);
1582 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
1583 task_unlock(current->group_leader);
1585 posix_cpu_timers_init_group(sig);
1587 tty_audit_fork(sig);
1588 sched_autogroup_fork(sig);
1590 sig->oom_score_adj = current->signal->oom_score_adj;
1591 sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1593 mutex_init(&sig->cred_guard_mutex);
1598 static void copy_seccomp(struct task_struct *p)
1600 #ifdef CONFIG_SECCOMP
1602 * Must be called with sighand->lock held, which is common to
1603 * all threads in the group. Holding cred_guard_mutex is not
1604 * needed because this new task is not yet running and cannot
1607 assert_spin_locked(¤t->sighand->siglock);
1609 /* Ref-count the new filter user, and assign it. */
1610 get_seccomp_filter(current);
1611 p->seccomp = current->seccomp;
1614 * Explicitly enable no_new_privs here in case it got set
1615 * between the task_struct being duplicated and holding the
1616 * sighand lock. The seccomp state and nnp must be in sync.
1618 if (task_no_new_privs(current))
1619 task_set_no_new_privs(p);
1622 * If the parent gained a seccomp mode after copying thread
1623 * flags and between before we held the sighand lock, we have
1624 * to manually enable the seccomp thread flag here.
1626 if (p->seccomp.mode != SECCOMP_MODE_DISABLED)
1627 set_tsk_thread_flag(p, TIF_SECCOMP);
1631 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1633 current->clear_child_tid = tidptr;
1635 return task_pid_vnr(current);
1638 static void rt_mutex_init_task(struct task_struct *p)
1640 raw_spin_lock_init(&p->pi_lock);
1641 #ifdef CONFIG_RT_MUTEXES
1642 p->pi_waiters = RB_ROOT_CACHED;
1643 p->pi_top_task = NULL;
1644 p->pi_blocked_on = NULL;
1648 static inline void init_task_pid_links(struct task_struct *task)
1652 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
1653 INIT_HLIST_NODE(&task->pid_links[type]);
1658 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid)
1660 if (type == PIDTYPE_PID)
1661 task->thread_pid = pid;
1663 task->signal->pids[type] = pid;
1666 static inline void rcu_copy_process(struct task_struct *p)
1668 #ifdef CONFIG_PREEMPT_RCU
1669 p->rcu_read_lock_nesting = 0;
1670 p->rcu_read_unlock_special.s = 0;
1671 p->rcu_blocked_node = NULL;
1672 INIT_LIST_HEAD(&p->rcu_node_entry);
1673 #endif /* #ifdef CONFIG_PREEMPT_RCU */
1674 #ifdef CONFIG_TASKS_RCU
1675 p->rcu_tasks_holdout = false;
1676 INIT_LIST_HEAD(&p->rcu_tasks_holdout_list);
1677 p->rcu_tasks_idle_cpu = -1;
1678 #endif /* #ifdef CONFIG_TASKS_RCU */
1681 struct pid *pidfd_pid(const struct file *file)
1683 if (file->f_op == &pidfd_fops)
1684 return file->private_data;
1686 return ERR_PTR(-EBADF);
1689 static int pidfd_release(struct inode *inode, struct file *file)
1691 struct pid *pid = file->private_data;
1693 file->private_data = NULL;
1698 #ifdef CONFIG_PROC_FS
1700 * pidfd_show_fdinfo - print information about a pidfd
1701 * @m: proc fdinfo file
1702 * @f: file referencing a pidfd
1705 * This function will print the pid that a given pidfd refers to in the
1706 * pid namespace of the procfs instance.
1707 * If the pid namespace of the process is not a descendant of the pid
1708 * namespace of the procfs instance 0 will be shown as its pid. This is
1709 * similar to calling getppid() on a process whose parent is outside of
1710 * its pid namespace.
1713 * If pid namespaces are supported then this function will also print
1714 * the pid of a given pidfd refers to for all descendant pid namespaces
1715 * starting from the current pid namespace of the instance, i.e. the
1716 * Pid field and the first entry in the NSpid field will be identical.
1717 * If the pid namespace of the process is not a descendant of the pid
1718 * namespace of the procfs instance 0 will be shown as its first NSpid
1719 * entry and no others will be shown.
1720 * Note that this differs from the Pid and NSpid fields in
1721 * /proc/<pid>/status where Pid and NSpid are always shown relative to
1722 * the pid namespace of the procfs instance. The difference becomes
1723 * obvious when sending around a pidfd between pid namespaces from a
1724 * different branch of the tree, i.e. where no ancestoral relation is
1725 * present between the pid namespaces:
1726 * - create two new pid namespaces ns1 and ns2 in the initial pid
1727 * namespace (also take care to create new mount namespaces in the
1728 * new pid namespace and mount procfs)
1729 * - create a process with a pidfd in ns1
1730 * - send pidfd from ns1 to ns2
1731 * - read /proc/self/fdinfo/<pidfd> and observe that both Pid and NSpid
1732 * have exactly one entry, which is 0
1734 static void pidfd_show_fdinfo(struct seq_file *m, struct file *f)
1736 struct pid *pid = f->private_data;
1737 struct pid_namespace *ns;
1740 if (likely(pid_has_task(pid, PIDTYPE_PID))) {
1741 ns = proc_pid_ns(file_inode(m->file));
1742 nr = pid_nr_ns(pid, ns);
1745 seq_put_decimal_ll(m, "Pid:\t", nr);
1747 #ifdef CONFIG_PID_NS
1748 seq_put_decimal_ll(m, "\nNSpid:\t", nr);
1752 /* If nr is non-zero it means that 'pid' is valid and that
1753 * ns, i.e. the pid namespace associated with the procfs
1754 * instance, is in the pid namespace hierarchy of pid.
1755 * Start at one below the already printed level.
1757 for (i = ns->level + 1; i <= pid->level; i++)
1758 seq_put_decimal_ll(m, "\t", pid->numbers[i].nr);
1766 * Poll support for process exit notification.
1768 static __poll_t pidfd_poll(struct file *file, struct poll_table_struct *pts)
1770 struct task_struct *task;
1771 struct pid *pid = file->private_data;
1772 __poll_t poll_flags = 0;
1774 poll_wait(file, &pid->wait_pidfd, pts);
1777 task = pid_task(pid, PIDTYPE_PID);
1779 * Inform pollers only when the whole thread group exits.
1780 * If the thread group leader exits before all other threads in the
1781 * group, then poll(2) should block, similar to the wait(2) family.
1783 if (!task || (task->exit_state && thread_group_empty(task)))
1784 poll_flags = EPOLLIN | EPOLLRDNORM;
1790 const struct file_operations pidfd_fops = {
1791 .release = pidfd_release,
1793 #ifdef CONFIG_PROC_FS
1794 .show_fdinfo = pidfd_show_fdinfo,
1798 static void __delayed_free_task(struct rcu_head *rhp)
1800 struct task_struct *tsk = container_of(rhp, struct task_struct, rcu);
1805 static __always_inline void delayed_free_task(struct task_struct *tsk)
1807 if (IS_ENABLED(CONFIG_MEMCG))
1808 call_rcu(&tsk->rcu, __delayed_free_task);
1814 * This creates a new process as a copy of the old one,
1815 * but does not actually start it yet.
1817 * It copies the registers, and all the appropriate
1818 * parts of the process environment (as per the clone
1819 * flags). The actual kick-off is left to the caller.
1821 static __latent_entropy struct task_struct *copy_process(
1825 struct kernel_clone_args *args)
1827 int pidfd = -1, retval;
1828 struct task_struct *p;
1829 struct multiprocess_signals delayed;
1830 struct file *pidfile = NULL;
1831 u64 clone_flags = args->flags;
1834 * Don't allow sharing the root directory with processes in a different
1837 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1838 return ERR_PTR(-EINVAL);
1840 if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS))
1841 return ERR_PTR(-EINVAL);
1844 * Thread groups must share signals as well, and detached threads
1845 * can only be started up within the thread group.
1847 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1848 return ERR_PTR(-EINVAL);
1851 * Shared signal handlers imply shared VM. By way of the above,
1852 * thread groups also imply shared VM. Blocking this case allows
1853 * for various simplifications in other code.
1855 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1856 return ERR_PTR(-EINVAL);
1859 * Siblings of global init remain as zombies on exit since they are
1860 * not reaped by their parent (swapper). To solve this and to avoid
1861 * multi-rooted process trees, prevent global and container-inits
1862 * from creating siblings.
1864 if ((clone_flags & CLONE_PARENT) &&
1865 current->signal->flags & SIGNAL_UNKILLABLE)
1866 return ERR_PTR(-EINVAL);
1869 * If the new process will be in a different pid or user namespace
1870 * do not allow it to share a thread group with the forking task.
1872 if (clone_flags & CLONE_THREAD) {
1873 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) ||
1874 (task_active_pid_ns(current) !=
1875 current->nsproxy->pid_ns_for_children))
1876 return ERR_PTR(-EINVAL);
1879 if (clone_flags & CLONE_PIDFD) {
1881 * - CLONE_DETACHED is blocked so that we can potentially
1882 * reuse it later for CLONE_PIDFD.
1883 * - CLONE_THREAD is blocked until someone really needs it.
1885 if (clone_flags & (CLONE_DETACHED | CLONE_THREAD))
1886 return ERR_PTR(-EINVAL);
1890 * Force any signals received before this point to be delivered
1891 * before the fork happens. Collect up signals sent to multiple
1892 * processes that happen during the fork and delay them so that
1893 * they appear to happen after the fork.
1895 sigemptyset(&delayed.signal);
1896 INIT_HLIST_NODE(&delayed.node);
1898 spin_lock_irq(¤t->sighand->siglock);
1899 if (!(clone_flags & CLONE_THREAD))
1900 hlist_add_head(&delayed.node, ¤t->signal->multiprocess);
1901 recalc_sigpending();
1902 spin_unlock_irq(¤t->sighand->siglock);
1903 retval = -ERESTARTNOINTR;
1904 if (signal_pending(current))
1908 p = dup_task_struct(current, node);
1913 * This _must_ happen before we call free_task(), i.e. before we jump
1914 * to any of the bad_fork_* labels. This is to avoid freeing
1915 * p->set_child_tid which is (ab)used as a kthread's data pointer for
1916 * kernel threads (PF_KTHREAD).
1918 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? args->child_tid : NULL;
1920 * Clear TID on mm_release()?
1922 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? args->child_tid : NULL;
1924 ftrace_graph_init_task(p);
1926 rt_mutex_init_task(p);
1928 #ifdef CONFIG_PROVE_LOCKING
1929 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1930 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1933 if (atomic_read(&p->real_cred->user->processes) >=
1934 task_rlimit(p, RLIMIT_NPROC)) {
1935 if (p->real_cred->user != INIT_USER &&
1936 !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
1939 current->flags &= ~PF_NPROC_EXCEEDED;
1941 retval = copy_creds(p, clone_flags);
1946 * If multiple threads are within copy_process(), then this check
1947 * triggers too late. This doesn't hurt, the check is only there
1948 * to stop root fork bombs.
1951 if (nr_threads >= max_threads)
1952 goto bad_fork_cleanup_count;
1954 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */
1955 p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER | PF_IDLE);
1956 p->flags |= PF_FORKNOEXEC;
1957 INIT_LIST_HEAD(&p->children);
1958 INIT_LIST_HEAD(&p->sibling);
1959 rcu_copy_process(p);
1960 p->vfork_done = NULL;
1961 spin_lock_init(&p->alloc_lock);
1963 init_sigpending(&p->pending);
1965 p->utime = p->stime = p->gtime = 0;
1966 #ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
1967 p->utimescaled = p->stimescaled = 0;
1969 prev_cputime_init(&p->prev_cputime);
1971 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
1972 seqcount_init(&p->vtime.seqcount);
1973 p->vtime.starttime = 0;
1974 p->vtime.state = VTIME_INACTIVE;
1977 #if defined(SPLIT_RSS_COUNTING)
1978 memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1981 p->default_timer_slack_ns = current->timer_slack_ns;
1987 task_io_accounting_init(&p->ioac);
1988 acct_clear_integrals(p);
1990 posix_cputimers_init(&p->posix_cputimers);
1992 p->io_context = NULL;
1993 audit_set_context(p, NULL);
1996 p->mempolicy = mpol_dup(p->mempolicy);
1997 if (IS_ERR(p->mempolicy)) {
1998 retval = PTR_ERR(p->mempolicy);
1999 p->mempolicy = NULL;
2000 goto bad_fork_cleanup_threadgroup_lock;
2003 #ifdef CONFIG_CPUSETS
2004 p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
2005 p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
2006 seqcount_init(&p->mems_allowed_seq);
2008 #ifdef CONFIG_TRACE_IRQFLAGS
2010 p->hardirqs_enabled = 0;
2011 p->hardirq_enable_ip = 0;
2012 p->hardirq_enable_event = 0;
2013 p->hardirq_disable_ip = _THIS_IP_;
2014 p->hardirq_disable_event = 0;
2015 p->softirqs_enabled = 1;
2016 p->softirq_enable_ip = _THIS_IP_;
2017 p->softirq_enable_event = 0;
2018 p->softirq_disable_ip = 0;
2019 p->softirq_disable_event = 0;
2020 p->hardirq_context = 0;
2021 p->softirq_context = 0;
2024 p->pagefault_disabled = 0;
2026 #ifdef CONFIG_LOCKDEP
2027 lockdep_init_task(p);
2030 #ifdef CONFIG_DEBUG_MUTEXES
2031 p->blocked_on = NULL; /* not blocked yet */
2033 #ifdef CONFIG_BCACHE
2034 p->sequential_io = 0;
2035 p->sequential_io_avg = 0;
2038 /* Perform scheduler related setup. Assign this task to a CPU. */
2039 retval = sched_fork(clone_flags, p);
2041 goto bad_fork_cleanup_policy;
2043 retval = perf_event_init_task(p);
2045 goto bad_fork_cleanup_policy;
2046 retval = audit_alloc(p);
2048 goto bad_fork_cleanup_perf;
2049 /* copy all the process information */
2051 retval = security_task_alloc(p, clone_flags);
2053 goto bad_fork_cleanup_audit;
2054 retval = copy_semundo(clone_flags, p);
2056 goto bad_fork_cleanup_security;
2057 retval = copy_files(clone_flags, p);
2059 goto bad_fork_cleanup_semundo;
2060 retval = copy_fs(clone_flags, p);
2062 goto bad_fork_cleanup_files;
2063 retval = copy_sighand(clone_flags, p);
2065 goto bad_fork_cleanup_fs;
2066 retval = copy_signal(clone_flags, p);
2068 goto bad_fork_cleanup_sighand;
2069 retval = copy_mm(clone_flags, p);
2071 goto bad_fork_cleanup_signal;
2072 retval = copy_namespaces(clone_flags, p);
2074 goto bad_fork_cleanup_mm;
2075 retval = copy_io(clone_flags, p);
2077 goto bad_fork_cleanup_namespaces;
2078 retval = copy_thread_tls(clone_flags, args->stack, args->stack_size, p,
2081 goto bad_fork_cleanup_io;
2083 stackleak_task_init(p);
2085 if (pid != &init_struct_pid) {
2086 pid = alloc_pid(p->nsproxy->pid_ns_for_children, args->set_tid,
2087 args->set_tid_size);
2089 retval = PTR_ERR(pid);
2090 goto bad_fork_cleanup_thread;
2095 * This has to happen after we've potentially unshared the file
2096 * descriptor table (so that the pidfd doesn't leak into the child
2097 * if the fd table isn't shared).
2099 if (clone_flags & CLONE_PIDFD) {
2100 retval = get_unused_fd_flags(O_RDWR | O_CLOEXEC);
2102 goto bad_fork_free_pid;
2106 pidfile = anon_inode_getfile("[pidfd]", &pidfd_fops, pid,
2107 O_RDWR | O_CLOEXEC);
2108 if (IS_ERR(pidfile)) {
2109 put_unused_fd(pidfd);
2110 retval = PTR_ERR(pidfile);
2111 goto bad_fork_free_pid;
2113 get_pid(pid); /* held by pidfile now */
2115 retval = put_user(pidfd, args->pidfd);
2117 goto bad_fork_put_pidfd;
2126 * sigaltstack should be cleared when sharing the same VM
2128 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
2132 * Syscall tracing and stepping should be turned off in the
2133 * child regardless of CLONE_PTRACE.
2135 user_disable_single_step(p);
2136 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
2137 #ifdef TIF_SYSCALL_EMU
2138 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
2140 clear_tsk_latency_tracing(p);
2142 /* ok, now we should be set up.. */
2143 p->pid = pid_nr(pid);
2144 if (clone_flags & CLONE_THREAD) {
2145 p->exit_signal = -1;
2146 p->group_leader = current->group_leader;
2147 p->tgid = current->tgid;
2149 if (clone_flags & CLONE_PARENT)
2150 p->exit_signal = current->group_leader->exit_signal;
2152 p->exit_signal = args->exit_signal;
2153 p->group_leader = p;
2158 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
2159 p->dirty_paused_when = 0;
2161 p->pdeath_signal = 0;
2162 INIT_LIST_HEAD(&p->thread_group);
2163 p->task_works = NULL;
2165 cgroup_threadgroup_change_begin(current);
2167 * Ensure that the cgroup subsystem policies allow the new process to be
2168 * forked. It should be noted the the new process's css_set can be changed
2169 * between here and cgroup_post_fork() if an organisation operation is in
2172 retval = cgroup_can_fork(p);
2174 goto bad_fork_cgroup_threadgroup_change_end;
2177 * From this point on we must avoid any synchronous user-space
2178 * communication until we take the tasklist-lock. In particular, we do
2179 * not want user-space to be able to predict the process start-time by
2180 * stalling fork(2) after we recorded the start_time but before it is
2181 * visible to the system.
2184 p->start_time = ktime_get_ns();
2185 p->real_start_time = ktime_get_boottime_ns();
2188 * Make it visible to the rest of the system, but dont wake it up yet.
2189 * Need tasklist lock for parent etc handling!
2191 write_lock_irq(&tasklist_lock);
2193 /* CLONE_PARENT re-uses the old parent */
2194 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
2195 p->real_parent = current->real_parent;
2196 p->parent_exec_id = current->parent_exec_id;
2198 p->real_parent = current;
2199 p->parent_exec_id = current->self_exec_id;
2202 klp_copy_process(p);
2204 spin_lock(¤t->sighand->siglock);
2207 * Copy seccomp details explicitly here, in case they were changed
2208 * before holding sighand lock.
2212 rseq_fork(p, clone_flags);
2214 /* Don't start children in a dying pid namespace */
2215 if (unlikely(!(ns_of_pid(pid)->pid_allocated & PIDNS_ADDING))) {
2217 goto bad_fork_cancel_cgroup;
2220 /* Let kill terminate clone/fork in the middle */
2221 if (fatal_signal_pending(current)) {
2223 goto bad_fork_cancel_cgroup;
2226 /* past the last point of failure */
2228 fd_install(pidfd, pidfile);
2230 init_task_pid_links(p);
2231 if (likely(p->pid)) {
2232 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
2234 init_task_pid(p, PIDTYPE_PID, pid);
2235 if (thread_group_leader(p)) {
2236 init_task_pid(p, PIDTYPE_TGID, pid);
2237 init_task_pid(p, PIDTYPE_PGID, task_pgrp(current));
2238 init_task_pid(p, PIDTYPE_SID, task_session(current));
2240 if (is_child_reaper(pid)) {
2241 ns_of_pid(pid)->child_reaper = p;
2242 p->signal->flags |= SIGNAL_UNKILLABLE;
2244 p->signal->shared_pending.signal = delayed.signal;
2245 p->signal->tty = tty_kref_get(current->signal->tty);
2247 * Inherit has_child_subreaper flag under the same
2248 * tasklist_lock with adding child to the process tree
2249 * for propagate_has_child_subreaper optimization.
2251 p->signal->has_child_subreaper = p->real_parent->signal->has_child_subreaper ||
2252 p->real_parent->signal->is_child_subreaper;
2253 list_add_tail(&p->sibling, &p->real_parent->children);
2254 list_add_tail_rcu(&p->tasks, &init_task.tasks);
2255 attach_pid(p, PIDTYPE_TGID);
2256 attach_pid(p, PIDTYPE_PGID);
2257 attach_pid(p, PIDTYPE_SID);
2258 __this_cpu_inc(process_counts);
2260 current->signal->nr_threads++;
2261 atomic_inc(¤t->signal->live);
2262 refcount_inc(¤t->signal->sigcnt);
2263 task_join_group_stop(p);
2264 list_add_tail_rcu(&p->thread_group,
2265 &p->group_leader->thread_group);
2266 list_add_tail_rcu(&p->thread_node,
2267 &p->signal->thread_head);
2269 attach_pid(p, PIDTYPE_PID);
2273 hlist_del_init(&delayed.node);
2274 spin_unlock(¤t->sighand->siglock);
2275 syscall_tracepoint_update(p);
2276 write_unlock_irq(&tasklist_lock);
2278 proc_fork_connector(p);
2279 cgroup_post_fork(p);
2280 cgroup_threadgroup_change_end(current);
2283 trace_task_newtask(p, clone_flags);
2284 uprobe_copy_process(p, clone_flags);
2288 bad_fork_cancel_cgroup:
2289 spin_unlock(¤t->sighand->siglock);
2290 write_unlock_irq(&tasklist_lock);
2291 cgroup_cancel_fork(p);
2292 bad_fork_cgroup_threadgroup_change_end:
2293 cgroup_threadgroup_change_end(current);
2295 if (clone_flags & CLONE_PIDFD) {
2297 put_unused_fd(pidfd);
2300 if (pid != &init_struct_pid)
2302 bad_fork_cleanup_thread:
2304 bad_fork_cleanup_io:
2307 bad_fork_cleanup_namespaces:
2308 exit_task_namespaces(p);
2309 bad_fork_cleanup_mm:
2311 mm_clear_owner(p->mm, p);
2314 bad_fork_cleanup_signal:
2315 if (!(clone_flags & CLONE_THREAD))
2316 free_signal_struct(p->signal);
2317 bad_fork_cleanup_sighand:
2318 __cleanup_sighand(p->sighand);
2319 bad_fork_cleanup_fs:
2320 exit_fs(p); /* blocking */
2321 bad_fork_cleanup_files:
2322 exit_files(p); /* blocking */
2323 bad_fork_cleanup_semundo:
2325 bad_fork_cleanup_security:
2326 security_task_free(p);
2327 bad_fork_cleanup_audit:
2329 bad_fork_cleanup_perf:
2330 perf_event_free_task(p);
2331 bad_fork_cleanup_policy:
2332 lockdep_free_task(p);
2334 mpol_put(p->mempolicy);
2335 bad_fork_cleanup_threadgroup_lock:
2337 delayacct_tsk_free(p);
2338 bad_fork_cleanup_count:
2339 atomic_dec(&p->cred->user->processes);
2342 p->state = TASK_DEAD;
2344 delayed_free_task(p);
2346 spin_lock_irq(¤t->sighand->siglock);
2347 hlist_del_init(&delayed.node);
2348 spin_unlock_irq(¤t->sighand->siglock);
2349 return ERR_PTR(retval);
2352 static inline void init_idle_pids(struct task_struct *idle)
2356 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
2357 INIT_HLIST_NODE(&idle->pid_links[type]); /* not really needed */
2358 init_task_pid(idle, type, &init_struct_pid);
2362 struct task_struct *fork_idle(int cpu)
2364 struct task_struct *task;
2365 struct kernel_clone_args args = {
2369 task = copy_process(&init_struct_pid, 0, cpu_to_node(cpu), &args);
2370 if (!IS_ERR(task)) {
2371 init_idle_pids(task);
2372 init_idle(task, cpu);
2378 struct mm_struct *copy_init_mm(void)
2380 return dup_mm(NULL, &init_mm);
2384 * Ok, this is the main fork-routine.
2386 * It copies the process, and if successful kick-starts
2387 * it and waits for it to finish using the VM if required.
2389 * args->exit_signal is expected to be checked for sanity by the caller.
2391 long _do_fork(struct kernel_clone_args *args)
2393 u64 clone_flags = args->flags;
2394 struct completion vfork;
2396 struct task_struct *p;
2401 * Determine whether and which event to report to ptracer. When
2402 * called from kernel_thread or CLONE_UNTRACED is explicitly
2403 * requested, no event is reported; otherwise, report if the event
2404 * for the type of forking is enabled.
2406 if (!(clone_flags & CLONE_UNTRACED)) {
2407 if (clone_flags & CLONE_VFORK)
2408 trace = PTRACE_EVENT_VFORK;
2409 else if (args->exit_signal != SIGCHLD)
2410 trace = PTRACE_EVENT_CLONE;
2412 trace = PTRACE_EVENT_FORK;
2414 if (likely(!ptrace_event_enabled(current, trace)))
2418 p = copy_process(NULL, trace, NUMA_NO_NODE, args);
2419 add_latent_entropy();
2425 * Do this prior waking up the new thread - the thread pointer
2426 * might get invalid after that point, if the thread exits quickly.
2428 trace_sched_process_fork(current, p);
2430 pid = get_task_pid(p, PIDTYPE_PID);
2433 if (clone_flags & CLONE_PARENT_SETTID)
2434 put_user(nr, args->parent_tid);
2436 if (clone_flags & CLONE_VFORK) {
2437 p->vfork_done = &vfork;
2438 init_completion(&vfork);
2442 wake_up_new_task(p);
2444 /* forking complete and child started to run, tell ptracer */
2445 if (unlikely(trace))
2446 ptrace_event_pid(trace, pid);
2448 if (clone_flags & CLONE_VFORK) {
2449 if (!wait_for_vfork_done(p, &vfork))
2450 ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid);
2457 bool legacy_clone_args_valid(const struct kernel_clone_args *kargs)
2459 /* clone(CLONE_PIDFD) uses parent_tidptr to return a pidfd */
2460 if ((kargs->flags & CLONE_PIDFD) &&
2461 (kargs->flags & CLONE_PARENT_SETTID))
2467 #ifndef CONFIG_HAVE_COPY_THREAD_TLS
2468 /* For compatibility with architectures that call do_fork directly rather than
2469 * using the syscall entry points below. */
2470 long do_fork(unsigned long clone_flags,
2471 unsigned long stack_start,
2472 unsigned long stack_size,
2473 int __user *parent_tidptr,
2474 int __user *child_tidptr)
2476 struct kernel_clone_args args = {
2477 .flags = (clone_flags & ~CSIGNAL),
2478 .pidfd = parent_tidptr,
2479 .child_tid = child_tidptr,
2480 .parent_tid = parent_tidptr,
2481 .exit_signal = (clone_flags & CSIGNAL),
2482 .stack = stack_start,
2483 .stack_size = stack_size,
2486 if (!legacy_clone_args_valid(&args))
2489 return _do_fork(&args);
2494 * Create a kernel thread.
2496 pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
2498 struct kernel_clone_args args = {
2499 .flags = ((flags | CLONE_VM | CLONE_UNTRACED) & ~CSIGNAL),
2500 .exit_signal = (flags & CSIGNAL),
2501 .stack = (unsigned long)fn,
2502 .stack_size = (unsigned long)arg,
2505 return _do_fork(&args);
2508 #ifdef __ARCH_WANT_SYS_FORK
2509 SYSCALL_DEFINE0(fork)
2512 struct kernel_clone_args args = {
2513 .exit_signal = SIGCHLD,
2516 return _do_fork(&args);
2518 /* can not support in nommu mode */
2524 #ifdef __ARCH_WANT_SYS_VFORK
2525 SYSCALL_DEFINE0(vfork)
2527 struct kernel_clone_args args = {
2528 .flags = CLONE_VFORK | CLONE_VM,
2529 .exit_signal = SIGCHLD,
2532 return _do_fork(&args);
2536 #ifdef __ARCH_WANT_SYS_CLONE
2537 #ifdef CONFIG_CLONE_BACKWARDS
2538 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2539 int __user *, parent_tidptr,
2541 int __user *, child_tidptr)
2542 #elif defined(CONFIG_CLONE_BACKWARDS2)
2543 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags,
2544 int __user *, parent_tidptr,
2545 int __user *, child_tidptr,
2547 #elif defined(CONFIG_CLONE_BACKWARDS3)
2548 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp,
2550 int __user *, parent_tidptr,
2551 int __user *, child_tidptr,
2554 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2555 int __user *, parent_tidptr,
2556 int __user *, child_tidptr,
2560 struct kernel_clone_args args = {
2561 .flags = (clone_flags & ~CSIGNAL),
2562 .pidfd = parent_tidptr,
2563 .child_tid = child_tidptr,
2564 .parent_tid = parent_tidptr,
2565 .exit_signal = (clone_flags & CSIGNAL),
2570 if (!legacy_clone_args_valid(&args))
2573 return _do_fork(&args);
2577 #ifdef __ARCH_WANT_SYS_CLONE3
2578 noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs,
2579 struct clone_args __user *uargs,
2583 struct clone_args args;
2584 pid_t *kset_tid = kargs->set_tid;
2586 if (unlikely(usize > PAGE_SIZE))
2588 if (unlikely(usize < CLONE_ARGS_SIZE_VER0))
2591 err = copy_struct_from_user(&args, sizeof(args), uargs, usize);
2595 if (unlikely(args.set_tid_size > MAX_PID_NS_LEVEL))
2598 if (unlikely(!args.set_tid && args.set_tid_size > 0))
2601 if (unlikely(args.set_tid && args.set_tid_size == 0))
2605 * Verify that higher 32bits of exit_signal are unset and that
2606 * it is a valid signal
2608 if (unlikely((args.exit_signal & ~((u64)CSIGNAL)) ||
2609 !valid_signal(args.exit_signal)))
2612 *kargs = (struct kernel_clone_args){
2613 .flags = args.flags,
2614 .pidfd = u64_to_user_ptr(args.pidfd),
2615 .child_tid = u64_to_user_ptr(args.child_tid),
2616 .parent_tid = u64_to_user_ptr(args.parent_tid),
2617 .exit_signal = args.exit_signal,
2618 .stack = args.stack,
2619 .stack_size = args.stack_size,
2621 .set_tid_size = args.set_tid_size,
2625 copy_from_user(kset_tid, u64_to_user_ptr(args.set_tid),
2626 (kargs->set_tid_size * sizeof(pid_t))))
2629 kargs->set_tid = kset_tid;
2635 * clone3_stack_valid - check and prepare stack
2636 * @kargs: kernel clone args
2638 * Verify that the stack arguments userspace gave us are sane.
2639 * In addition, set the stack direction for userspace since it's easy for us to
2642 static inline bool clone3_stack_valid(struct kernel_clone_args *kargs)
2644 if (kargs->stack == 0) {
2645 if (kargs->stack_size > 0)
2648 if (kargs->stack_size == 0)
2651 if (!access_ok((void __user *)kargs->stack, kargs->stack_size))
2654 #if !defined(CONFIG_STACK_GROWSUP) && !defined(CONFIG_IA64)
2655 kargs->stack += kargs->stack_size;
2662 static bool clone3_args_valid(struct kernel_clone_args *kargs)
2664 /* Verify that no unknown flags are passed along. */
2665 if (kargs->flags & ~(CLONE_LEGACY_FLAGS | CLONE_CLEAR_SIGHAND))
2669 * - make the CLONE_DETACHED bit reuseable for clone3
2670 * - make the CSIGNAL bits reuseable for clone3
2672 if (kargs->flags & (CLONE_DETACHED | CSIGNAL))
2675 if ((kargs->flags & (CLONE_SIGHAND | CLONE_CLEAR_SIGHAND)) ==
2676 (CLONE_SIGHAND | CLONE_CLEAR_SIGHAND))
2679 if ((kargs->flags & (CLONE_THREAD | CLONE_PARENT)) &&
2683 if (!clone3_stack_valid(kargs))
2690 * clone3 - create a new process with specific properties
2691 * @uargs: argument structure
2692 * @size: size of @uargs
2694 * clone3() is the extensible successor to clone()/clone2().
2695 * It takes a struct as argument that is versioned by its size.
2697 * Return: On success, a positive PID for the child process.
2698 * On error, a negative errno number.
2700 SYSCALL_DEFINE2(clone3, struct clone_args __user *, uargs, size_t, size)
2704 struct kernel_clone_args kargs;
2705 pid_t set_tid[MAX_PID_NS_LEVEL];
2707 kargs.set_tid = set_tid;
2709 err = copy_clone_args_from_user(&kargs, uargs, size);
2713 if (!clone3_args_valid(&kargs))
2716 return _do_fork(&kargs);
2720 void walk_process_tree(struct task_struct *top, proc_visitor visitor, void *data)
2722 struct task_struct *leader, *parent, *child;
2725 read_lock(&tasklist_lock);
2726 leader = top = top->group_leader;
2728 for_each_thread(leader, parent) {
2729 list_for_each_entry(child, &parent->children, sibling) {
2730 res = visitor(child, data);
2742 if (leader != top) {
2744 parent = child->real_parent;
2745 leader = parent->group_leader;
2749 read_unlock(&tasklist_lock);
2752 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
2753 #define ARCH_MIN_MMSTRUCT_ALIGN 0
2756 static void sighand_ctor(void *data)
2758 struct sighand_struct *sighand = data;
2760 spin_lock_init(&sighand->siglock);
2761 init_waitqueue_head(&sighand->signalfd_wqh);
2764 void __init proc_caches_init(void)
2766 unsigned int mm_size;
2768 sighand_cachep = kmem_cache_create("sighand_cache",
2769 sizeof(struct sighand_struct), 0,
2770 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_TYPESAFE_BY_RCU|
2771 SLAB_ACCOUNT, sighand_ctor);
2772 signal_cachep = kmem_cache_create("signal_cache",
2773 sizeof(struct signal_struct), 0,
2774 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2776 files_cachep = kmem_cache_create("files_cache",
2777 sizeof(struct files_struct), 0,
2778 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2780 fs_cachep = kmem_cache_create("fs_cache",
2781 sizeof(struct fs_struct), 0,
2782 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2786 * The mm_cpumask is located at the end of mm_struct, and is
2787 * dynamically sized based on the maximum CPU number this system
2788 * can have, taking hotplug into account (nr_cpu_ids).
2790 mm_size = sizeof(struct mm_struct) + cpumask_size();
2792 mm_cachep = kmem_cache_create_usercopy("mm_struct",
2793 mm_size, ARCH_MIN_MMSTRUCT_ALIGN,
2794 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2795 offsetof(struct mm_struct, saved_auxv),
2796 sizeof_field(struct mm_struct, saved_auxv),
2798 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT);
2800 nsproxy_cache_init();
2804 * Check constraints on flags passed to the unshare system call.
2806 static int check_unshare_flags(unsigned long unshare_flags)
2808 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
2809 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
2810 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET|
2811 CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP))
2814 * Not implemented, but pretend it works if there is nothing
2815 * to unshare. Note that unsharing the address space or the
2816 * signal handlers also need to unshare the signal queues (aka
2819 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
2820 if (!thread_group_empty(current))
2823 if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) {
2824 if (refcount_read(¤t->sighand->count) > 1)
2827 if (unshare_flags & CLONE_VM) {
2828 if (!current_is_single_threaded())
2836 * Unshare the filesystem structure if it is being shared
2838 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
2840 struct fs_struct *fs = current->fs;
2842 if (!(unshare_flags & CLONE_FS) || !fs)
2845 /* don't need lock here; in the worst case we'll do useless copy */
2849 *new_fsp = copy_fs_struct(fs);
2857 * Unshare file descriptor table if it is being shared
2859 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
2861 struct files_struct *fd = current->files;
2864 if ((unshare_flags & CLONE_FILES) &&
2865 (fd && atomic_read(&fd->count) > 1)) {
2866 *new_fdp = dup_fd(fd, &error);
2875 * unshare allows a process to 'unshare' part of the process
2876 * context which was originally shared using clone. copy_*
2877 * functions used by do_fork() cannot be used here directly
2878 * because they modify an inactive task_struct that is being
2879 * constructed. Here we are modifying the current, active,
2882 int ksys_unshare(unsigned long unshare_flags)
2884 struct fs_struct *fs, *new_fs = NULL;
2885 struct files_struct *fd, *new_fd = NULL;
2886 struct cred *new_cred = NULL;
2887 struct nsproxy *new_nsproxy = NULL;
2892 * If unsharing a user namespace must also unshare the thread group
2893 * and unshare the filesystem root and working directories.
2895 if (unshare_flags & CLONE_NEWUSER)
2896 unshare_flags |= CLONE_THREAD | CLONE_FS;
2898 * If unsharing vm, must also unshare signal handlers.
2900 if (unshare_flags & CLONE_VM)
2901 unshare_flags |= CLONE_SIGHAND;
2903 * If unsharing a signal handlers, must also unshare the signal queues.
2905 if (unshare_flags & CLONE_SIGHAND)
2906 unshare_flags |= CLONE_THREAD;
2908 * If unsharing namespace, must also unshare filesystem information.
2910 if (unshare_flags & CLONE_NEWNS)
2911 unshare_flags |= CLONE_FS;
2913 err = check_unshare_flags(unshare_flags);
2915 goto bad_unshare_out;
2917 * CLONE_NEWIPC must also detach from the undolist: after switching
2918 * to a new ipc namespace, the semaphore arrays from the old
2919 * namespace are unreachable.
2921 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
2923 err = unshare_fs(unshare_flags, &new_fs);
2925 goto bad_unshare_out;
2926 err = unshare_fd(unshare_flags, &new_fd);
2928 goto bad_unshare_cleanup_fs;
2929 err = unshare_userns(unshare_flags, &new_cred);
2931 goto bad_unshare_cleanup_fd;
2932 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
2935 goto bad_unshare_cleanup_cred;
2937 if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
2940 * CLONE_SYSVSEM is equivalent to sys_exit().
2944 if (unshare_flags & CLONE_NEWIPC) {
2945 /* Orphan segments in old ns (see sem above). */
2947 shm_init_task(current);
2951 switch_task_namespaces(current, new_nsproxy);
2957 spin_lock(&fs->lock);
2958 current->fs = new_fs;
2963 spin_unlock(&fs->lock);
2967 fd = current->files;
2968 current->files = new_fd;
2972 task_unlock(current);
2975 /* Install the new user namespace */
2976 commit_creds(new_cred);
2981 perf_event_namespaces(current);
2983 bad_unshare_cleanup_cred:
2986 bad_unshare_cleanup_fd:
2988 put_files_struct(new_fd);
2990 bad_unshare_cleanup_fs:
2992 free_fs_struct(new_fs);
2998 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
3000 return ksys_unshare(unshare_flags);
3004 * Helper to unshare the files of the current task.
3005 * We don't want to expose copy_files internals to
3006 * the exec layer of the kernel.
3009 int unshare_files(struct files_struct **displaced)
3011 struct task_struct *task = current;
3012 struct files_struct *copy = NULL;
3015 error = unshare_fd(CLONE_FILES, ©);
3016 if (error || !copy) {
3020 *displaced = task->files;
3027 int sysctl_max_threads(struct ctl_table *table, int write,
3028 void __user *buffer, size_t *lenp, loff_t *ppos)
3032 int threads = max_threads;
3034 int max = MAX_THREADS;
3041 ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
3045 max_threads = threads;