4 * Copyright (C) 1991, 1992 Linus Torvalds
8 * 'fork.c' contains the help-routines for the 'fork' system call
9 * (see also entry.S and others).
10 * Fork is rather simple, once you get the hang of it, but the memory
11 * management can be a bitch. See 'mm/memory.c': 'copy_page_range()'
14 #include <linux/slab.h>
15 #include <linux/init.h>
16 #include <linux/unistd.h>
17 #include <linux/module.h>
18 #include <linux/vmalloc.h>
19 #include <linux/completion.h>
20 #include <linux/personality.h>
21 #include <linux/mempolicy.h>
22 #include <linux/sem.h>
23 #include <linux/file.h>
24 #include <linux/fdtable.h>
25 #include <linux/iocontext.h>
26 #include <linux/key.h>
27 #include <linux/binfmts.h>
28 #include <linux/mman.h>
29 #include <linux/mmu_notifier.h>
32 #include <linux/vmacache.h>
33 #include <linux/nsproxy.h>
34 #include <linux/capability.h>
35 #include <linux/cpu.h>
36 #include <linux/cgroup.h>
37 #include <linux/security.h>
38 #include <linux/hugetlb.h>
39 #include <linux/seccomp.h>
40 #include <linux/swap.h>
41 #include <linux/syscalls.h>
42 #include <linux/jiffies.h>
43 #include <linux/futex.h>
44 #include <linux/compat.h>
45 #include <linux/kthread.h>
46 #include <linux/task_io_accounting_ops.h>
47 #include <linux/rcupdate.h>
48 #include <linux/ptrace.h>
49 #include <linux/mount.h>
50 #include <linux/audit.h>
51 #include <linux/memcontrol.h>
52 #include <linux/ftrace.h>
53 #include <linux/proc_fs.h>
54 #include <linux/profile.h>
55 #include <linux/rmap.h>
56 #include <linux/ksm.h>
57 #include <linux/acct.h>
58 #include <linux/tsacct_kern.h>
59 #include <linux/cn_proc.h>
60 #include <linux/freezer.h>
61 #include <linux/delayacct.h>
62 #include <linux/taskstats_kern.h>
63 #include <linux/random.h>
64 #include <linux/tty.h>
65 #include <linux/blkdev.h>
66 #include <linux/fs_struct.h>
67 #include <linux/magic.h>
68 #include <linux/perf_event.h>
69 #include <linux/posix-timers.h>
70 #include <linux/user-return-notifier.h>
71 #include <linux/oom.h>
72 #include <linux/khugepaged.h>
73 #include <linux/signalfd.h>
74 #include <linux/uprobes.h>
75 #include <linux/aio.h>
76 #include <linux/compiler.h>
77 #include <linux/sysctl.h>
78 #include <linux/kcov.h>
80 #include <asm/pgtable.h>
81 #include <asm/pgalloc.h>
82 #include <linux/uaccess.h>
83 #include <asm/mmu_context.h>
84 #include <asm/cacheflush.h>
85 #include <asm/tlbflush.h>
87 #include <trace/events/sched.h>
89 #define CREATE_TRACE_POINTS
90 #include <trace/events/task.h>
93 * Minimum number of threads to boot the kernel
95 #define MIN_THREADS 20
98 * Maximum number of threads
100 #define MAX_THREADS FUTEX_TID_MASK
103 * Protected counters by write_lock_irq(&tasklist_lock)
105 unsigned long total_forks; /* Handle normal Linux uptimes. */
106 int nr_threads; /* The idle threads do not count.. */
108 int max_threads; /* tunable limit on nr_threads */
110 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
112 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */
114 #ifdef CONFIG_PROVE_RCU
115 int lockdep_tasklist_lock_is_held(void)
117 return lockdep_is_held(&tasklist_lock);
119 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
120 #endif /* #ifdef CONFIG_PROVE_RCU */
122 int nr_processes(void)
127 for_each_possible_cpu(cpu)
128 total += per_cpu(process_counts, cpu);
133 void __weak arch_release_task_struct(struct task_struct *tsk)
137 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
138 static struct kmem_cache *task_struct_cachep;
140 static inline struct task_struct *alloc_task_struct_node(int node)
142 return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node);
145 static inline void free_task_struct(struct task_struct *tsk)
147 kmem_cache_free(task_struct_cachep, tsk);
151 void __weak arch_release_thread_stack(unsigned long *stack)
155 #ifndef CONFIG_ARCH_THREAD_STACK_ALLOCATOR
158 * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
159 * kmemcache based allocator.
161 # if THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK)
163 #ifdef CONFIG_VMAP_STACK
165 * vmalloc() is a bit slow, and calling vfree() enough times will force a TLB
166 * flush. Try to minimize the number of calls by caching stacks.
168 #define NR_CACHED_STACKS 2
169 static DEFINE_PER_CPU(struct vm_struct *, cached_stacks[NR_CACHED_STACKS]);
172 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node)
174 #ifdef CONFIG_VMAP_STACK
179 for (i = 0; i < NR_CACHED_STACKS; i++) {
180 struct vm_struct *s = this_cpu_read(cached_stacks[i]);
184 this_cpu_write(cached_stacks[i], NULL);
186 tsk->stack_vm_area = s;
192 stack = __vmalloc_node_range(THREAD_SIZE, THREAD_SIZE,
193 VMALLOC_START, VMALLOC_END,
194 THREADINFO_GFP | __GFP_HIGHMEM,
196 0, node, __builtin_return_address(0));
199 * We can't call find_vm_area() in interrupt context, and
200 * free_thread_stack() can be called in interrupt context,
201 * so cache the vm_struct.
204 tsk->stack_vm_area = find_vm_area(stack);
207 struct page *page = alloc_pages_node(node, THREADINFO_GFP,
210 return page ? page_address(page) : NULL;
214 static inline void free_thread_stack(struct task_struct *tsk)
216 #ifdef CONFIG_VMAP_STACK
217 if (task_stack_vm_area(tsk)) {
221 local_irq_save(flags);
222 for (i = 0; i < NR_CACHED_STACKS; i++) {
223 if (this_cpu_read(cached_stacks[i]))
226 this_cpu_write(cached_stacks[i], tsk->stack_vm_area);
227 local_irq_restore(flags);
230 local_irq_restore(flags);
232 vfree_atomic(tsk->stack);
237 __free_pages(virt_to_page(tsk->stack), THREAD_SIZE_ORDER);
240 static struct kmem_cache *thread_stack_cache;
242 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk,
245 return kmem_cache_alloc_node(thread_stack_cache, THREADINFO_GFP, node);
248 static void free_thread_stack(struct task_struct *tsk)
250 kmem_cache_free(thread_stack_cache, tsk->stack);
253 void thread_stack_cache_init(void)
255 thread_stack_cache = kmem_cache_create("thread_stack", THREAD_SIZE,
256 THREAD_SIZE, 0, NULL);
257 BUG_ON(thread_stack_cache == NULL);
262 /* SLAB cache for signal_struct structures (tsk->signal) */
263 static struct kmem_cache *signal_cachep;
265 /* SLAB cache for sighand_struct structures (tsk->sighand) */
266 struct kmem_cache *sighand_cachep;
268 /* SLAB cache for files_struct structures (tsk->files) */
269 struct kmem_cache *files_cachep;
271 /* SLAB cache for fs_struct structures (tsk->fs) */
272 struct kmem_cache *fs_cachep;
274 /* SLAB cache for vm_area_struct structures */
275 struct kmem_cache *vm_area_cachep;
277 /* SLAB cache for mm_struct structures (tsk->mm) */
278 static struct kmem_cache *mm_cachep;
280 static void account_kernel_stack(struct task_struct *tsk, int account)
282 void *stack = task_stack_page(tsk);
283 struct vm_struct *vm = task_stack_vm_area(tsk);
285 BUILD_BUG_ON(IS_ENABLED(CONFIG_VMAP_STACK) && PAGE_SIZE % 1024 != 0);
290 BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE);
292 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
293 mod_zone_page_state(page_zone(vm->pages[i]),
295 PAGE_SIZE / 1024 * account);
298 /* All stack pages belong to the same memcg. */
299 memcg_kmem_update_page_stat(vm->pages[0], MEMCG_KERNEL_STACK_KB,
300 account * (THREAD_SIZE / 1024));
303 * All stack pages are in the same zone and belong to the
306 struct page *first_page = virt_to_page(stack);
308 mod_zone_page_state(page_zone(first_page), NR_KERNEL_STACK_KB,
309 THREAD_SIZE / 1024 * account);
311 memcg_kmem_update_page_stat(first_page, MEMCG_KERNEL_STACK_KB,
312 account * (THREAD_SIZE / 1024));
316 static void release_task_stack(struct task_struct *tsk)
318 if (WARN_ON(tsk->state != TASK_DEAD))
319 return; /* Better to leak the stack than to free prematurely */
321 account_kernel_stack(tsk, -1);
322 arch_release_thread_stack(tsk->stack);
323 free_thread_stack(tsk);
325 #ifdef CONFIG_VMAP_STACK
326 tsk->stack_vm_area = NULL;
330 #ifdef CONFIG_THREAD_INFO_IN_TASK
331 void put_task_stack(struct task_struct *tsk)
333 if (atomic_dec_and_test(&tsk->stack_refcount))
334 release_task_stack(tsk);
338 void free_task(struct task_struct *tsk)
340 #ifndef CONFIG_THREAD_INFO_IN_TASK
342 * The task is finally done with both the stack and thread_info,
345 release_task_stack(tsk);
348 * If the task had a separate stack allocation, it should be gone
351 WARN_ON_ONCE(atomic_read(&tsk->stack_refcount) != 0);
353 rt_mutex_debug_task_free(tsk);
354 ftrace_graph_exit_task(tsk);
355 put_seccomp_filter(tsk);
356 arch_release_task_struct(tsk);
357 if (tsk->flags & PF_KTHREAD)
358 free_kthread_struct(tsk);
359 free_task_struct(tsk);
361 EXPORT_SYMBOL(free_task);
363 static inline void free_signal_struct(struct signal_struct *sig)
365 taskstats_tgid_free(sig);
366 sched_autogroup_exit(sig);
368 * __mmdrop is not safe to call from softirq context on x86 due to
369 * pgd_dtor so postpone it to the async context
372 mmdrop_async(sig->oom_mm);
373 kmem_cache_free(signal_cachep, sig);
376 static inline void put_signal_struct(struct signal_struct *sig)
378 if (atomic_dec_and_test(&sig->sigcnt))
379 free_signal_struct(sig);
382 void __put_task_struct(struct task_struct *tsk)
384 WARN_ON(!tsk->exit_state);
385 WARN_ON(atomic_read(&tsk->usage));
386 WARN_ON(tsk == current);
390 security_task_free(tsk);
392 delayacct_tsk_free(tsk);
393 put_signal_struct(tsk->signal);
395 if (!profile_handoff_task(tsk))
398 EXPORT_SYMBOL_GPL(__put_task_struct);
400 void __init __weak arch_task_cache_init(void) { }
405 static void set_max_threads(unsigned int max_threads_suggested)
410 * The number of threads shall be limited such that the thread
411 * structures may only consume a small part of the available memory.
413 if (fls64(totalram_pages) + fls64(PAGE_SIZE) > 64)
414 threads = MAX_THREADS;
416 threads = div64_u64((u64) totalram_pages * (u64) PAGE_SIZE,
417 (u64) THREAD_SIZE * 8UL);
419 if (threads > max_threads_suggested)
420 threads = max_threads_suggested;
422 max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS);
425 #ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT
426 /* Initialized by the architecture: */
427 int arch_task_struct_size __read_mostly;
430 void __init fork_init(void)
433 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
434 #ifndef ARCH_MIN_TASKALIGN
435 #define ARCH_MIN_TASKALIGN 0
437 int align = max_t(int, L1_CACHE_BYTES, ARCH_MIN_TASKALIGN);
439 /* create a slab on which task_structs can be allocated */
440 task_struct_cachep = kmem_cache_create("task_struct",
441 arch_task_struct_size, align,
442 SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, NULL);
445 /* do the arch specific task caches init */
446 arch_task_cache_init();
448 set_max_threads(MAX_THREADS);
450 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
451 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
452 init_task.signal->rlim[RLIMIT_SIGPENDING] =
453 init_task.signal->rlim[RLIMIT_NPROC];
455 for (i = 0; i < UCOUNT_COUNTS; i++) {
456 init_user_ns.ucount_max[i] = max_threads/2;
460 int __weak arch_dup_task_struct(struct task_struct *dst,
461 struct task_struct *src)
467 void set_task_stack_end_magic(struct task_struct *tsk)
469 unsigned long *stackend;
471 stackend = end_of_stack(tsk);
472 *stackend = STACK_END_MAGIC; /* for overflow detection */
475 static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
477 struct task_struct *tsk;
478 unsigned long *stack;
479 struct vm_struct *stack_vm_area;
482 if (node == NUMA_NO_NODE)
483 node = tsk_fork_get_node(orig);
484 tsk = alloc_task_struct_node(node);
488 stack = alloc_thread_stack_node(tsk, node);
492 stack_vm_area = task_stack_vm_area(tsk);
494 err = arch_dup_task_struct(tsk, orig);
497 * arch_dup_task_struct() clobbers the stack-related fields. Make
498 * sure they're properly initialized before using any stack-related
502 #ifdef CONFIG_VMAP_STACK
503 tsk->stack_vm_area = stack_vm_area;
505 #ifdef CONFIG_THREAD_INFO_IN_TASK
506 atomic_set(&tsk->stack_refcount, 1);
512 #ifdef CONFIG_SECCOMP
514 * We must handle setting up seccomp filters once we're under
515 * the sighand lock in case orig has changed between now and
516 * then. Until then, filter must be NULL to avoid messing up
517 * the usage counts on the error path calling free_task.
519 tsk->seccomp.filter = NULL;
522 setup_thread_stack(tsk, orig);
523 clear_user_return_notifier(tsk);
524 clear_tsk_need_resched(tsk);
525 set_task_stack_end_magic(tsk);
527 #ifdef CONFIG_CC_STACKPROTECTOR
528 tsk->stack_canary = get_random_int();
532 * One for us, one for whoever does the "release_task()" (usually
535 atomic_set(&tsk->usage, 2);
536 #ifdef CONFIG_BLK_DEV_IO_TRACE
539 tsk->splice_pipe = NULL;
540 tsk->task_frag.page = NULL;
541 tsk->wake_q.next = NULL;
543 account_kernel_stack(tsk, 1);
550 free_thread_stack(tsk);
552 free_task_struct(tsk);
557 static __latent_entropy int dup_mmap(struct mm_struct *mm,
558 struct mm_struct *oldmm)
560 struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
561 struct rb_node **rb_link, *rb_parent;
563 unsigned long charge;
565 uprobe_start_dup_mmap();
566 if (down_write_killable(&oldmm->mmap_sem)) {
568 goto fail_uprobe_end;
570 flush_cache_dup_mm(oldmm);
571 uprobe_dup_mmap(oldmm, mm);
573 * Not linked in yet - no deadlock potential:
575 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
577 /* No ordering required: file already has been exposed. */
578 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
580 mm->total_vm = oldmm->total_vm;
581 mm->data_vm = oldmm->data_vm;
582 mm->exec_vm = oldmm->exec_vm;
583 mm->stack_vm = oldmm->stack_vm;
585 rb_link = &mm->mm_rb.rb_node;
588 retval = ksm_fork(mm, oldmm);
591 retval = khugepaged_fork(mm, oldmm);
596 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
599 if (mpnt->vm_flags & VM_DONTCOPY) {
600 vm_stat_account(mm, mpnt->vm_flags, -vma_pages(mpnt));
604 if (mpnt->vm_flags & VM_ACCOUNT) {
605 unsigned long len = vma_pages(mpnt);
607 if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
611 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
615 INIT_LIST_HEAD(&tmp->anon_vma_chain);
616 retval = vma_dup_policy(mpnt, tmp);
618 goto fail_nomem_policy;
620 if (anon_vma_fork(tmp, mpnt))
621 goto fail_nomem_anon_vma_fork;
623 ~(VM_LOCKED|VM_LOCKONFAULT|VM_UFFD_MISSING|VM_UFFD_WP);
624 tmp->vm_next = tmp->vm_prev = NULL;
625 tmp->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
628 struct inode *inode = file_inode(file);
629 struct address_space *mapping = file->f_mapping;
632 if (tmp->vm_flags & VM_DENYWRITE)
633 atomic_dec(&inode->i_writecount);
634 i_mmap_lock_write(mapping);
635 if (tmp->vm_flags & VM_SHARED)
636 atomic_inc(&mapping->i_mmap_writable);
637 flush_dcache_mmap_lock(mapping);
638 /* insert tmp into the share list, just after mpnt */
639 vma_interval_tree_insert_after(tmp, mpnt,
641 flush_dcache_mmap_unlock(mapping);
642 i_mmap_unlock_write(mapping);
646 * Clear hugetlb-related page reserves for children. This only
647 * affects MAP_PRIVATE mappings. Faults generated by the child
648 * are not guaranteed to succeed, even if read-only
650 if (is_vm_hugetlb_page(tmp))
651 reset_vma_resv_huge_pages(tmp);
654 * Link in the new vma and copy the page table entries.
657 pprev = &tmp->vm_next;
661 __vma_link_rb(mm, tmp, rb_link, rb_parent);
662 rb_link = &tmp->vm_rb.rb_right;
663 rb_parent = &tmp->vm_rb;
666 retval = copy_page_range(mm, oldmm, mpnt);
668 if (tmp->vm_ops && tmp->vm_ops->open)
669 tmp->vm_ops->open(tmp);
674 /* a new mm has just been created */
675 arch_dup_mmap(oldmm, mm);
678 up_write(&mm->mmap_sem);
680 up_write(&oldmm->mmap_sem);
682 uprobe_end_dup_mmap();
684 fail_nomem_anon_vma_fork:
685 mpol_put(vma_policy(tmp));
687 kmem_cache_free(vm_area_cachep, tmp);
690 vm_unacct_memory(charge);
694 static inline int mm_alloc_pgd(struct mm_struct *mm)
696 mm->pgd = pgd_alloc(mm);
697 if (unlikely(!mm->pgd))
702 static inline void mm_free_pgd(struct mm_struct *mm)
704 pgd_free(mm, mm->pgd);
707 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
709 down_write(&oldmm->mmap_sem);
710 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
711 up_write(&oldmm->mmap_sem);
714 #define mm_alloc_pgd(mm) (0)
715 #define mm_free_pgd(mm)
716 #endif /* CONFIG_MMU */
718 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
720 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
721 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm)))
723 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
725 static int __init coredump_filter_setup(char *s)
727 default_dump_filter =
728 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
729 MMF_DUMP_FILTER_MASK;
733 __setup("coredump_filter=", coredump_filter_setup);
735 #include <linux/init_task.h>
737 static void mm_init_aio(struct mm_struct *mm)
740 spin_lock_init(&mm->ioctx_lock);
741 mm->ioctx_table = NULL;
745 static void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
752 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
753 struct user_namespace *user_ns)
757 mm->vmacache_seqnum = 0;
758 atomic_set(&mm->mm_users, 1);
759 atomic_set(&mm->mm_count, 1);
760 init_rwsem(&mm->mmap_sem);
761 INIT_LIST_HEAD(&mm->mmlist);
762 mm->core_state = NULL;
763 atomic_long_set(&mm->nr_ptes, 0);
768 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
769 spin_lock_init(&mm->page_table_lock);
772 mm_init_owner(mm, p);
773 mmu_notifier_mm_init(mm);
774 clear_tlb_flush_pending(mm);
775 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
776 mm->pmd_huge_pte = NULL;
780 mm->flags = current->mm->flags & MMF_INIT_MASK;
781 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK;
783 mm->flags = default_dump_filter;
787 if (mm_alloc_pgd(mm))
790 if (init_new_context(p, mm))
793 mm->user_ns = get_user_ns(user_ns);
803 static void check_mm(struct mm_struct *mm)
807 for (i = 0; i < NR_MM_COUNTERS; i++) {
808 long x = atomic_long_read(&mm->rss_stat.count[i]);
811 printk(KERN_ALERT "BUG: Bad rss-counter state "
812 "mm:%p idx:%d val:%ld\n", mm, i, x);
815 if (atomic_long_read(&mm->nr_ptes))
816 pr_alert("BUG: non-zero nr_ptes on freeing mm: %ld\n",
817 atomic_long_read(&mm->nr_ptes));
819 pr_alert("BUG: non-zero nr_pmds on freeing mm: %ld\n",
822 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
823 VM_BUG_ON_MM(mm->pmd_huge_pte, mm);
828 * Allocate and initialize an mm_struct.
830 struct mm_struct *mm_alloc(void)
832 struct mm_struct *mm;
838 memset(mm, 0, sizeof(*mm));
839 return mm_init(mm, current, current_user_ns());
843 * Called when the last reference to the mm
844 * is dropped: either by a lazy thread or by
845 * mmput. Free the page directory and the mm.
847 void __mmdrop(struct mm_struct *mm)
849 BUG_ON(mm == &init_mm);
852 mmu_notifier_mm_destroy(mm);
854 put_user_ns(mm->user_ns);
857 EXPORT_SYMBOL_GPL(__mmdrop);
859 static inline void __mmput(struct mm_struct *mm)
861 VM_BUG_ON(atomic_read(&mm->mm_users));
863 uprobe_clear_state(mm);
866 khugepaged_exit(mm); /* must run before exit_mmap */
868 mm_put_huge_zero_page(mm);
869 set_mm_exe_file(mm, NULL);
870 if (!list_empty(&mm->mmlist)) {
871 spin_lock(&mmlist_lock);
872 list_del(&mm->mmlist);
873 spin_unlock(&mmlist_lock);
876 module_put(mm->binfmt->module);
877 set_bit(MMF_OOM_SKIP, &mm->flags);
882 * Decrement the use count and release all resources for an mm.
884 void mmput(struct mm_struct *mm)
888 if (atomic_dec_and_test(&mm->mm_users))
891 EXPORT_SYMBOL_GPL(mmput);
894 static void mmput_async_fn(struct work_struct *work)
896 struct mm_struct *mm = container_of(work, struct mm_struct, async_put_work);
900 void mmput_async(struct mm_struct *mm)
902 if (atomic_dec_and_test(&mm->mm_users)) {
903 INIT_WORK(&mm->async_put_work, mmput_async_fn);
904 schedule_work(&mm->async_put_work);
910 * set_mm_exe_file - change a reference to the mm's executable file
912 * This changes mm's executable file (shown as symlink /proc/[pid]/exe).
914 * Main users are mmput() and sys_execve(). Callers prevent concurrent
915 * invocations: in mmput() nobody alive left, in execve task is single
916 * threaded. sys_prctl(PR_SET_MM_MAP/EXE_FILE) also needs to set the
917 * mm->exe_file, but does so without using set_mm_exe_file() in order
918 * to do avoid the need for any locks.
920 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
922 struct file *old_exe_file;
925 * It is safe to dereference the exe_file without RCU as
926 * this function is only called if nobody else can access
927 * this mm -- see comment above for justification.
929 old_exe_file = rcu_dereference_raw(mm->exe_file);
932 get_file(new_exe_file);
933 rcu_assign_pointer(mm->exe_file, new_exe_file);
939 * get_mm_exe_file - acquire a reference to the mm's executable file
941 * Returns %NULL if mm has no associated executable file.
942 * User must release file via fput().
944 struct file *get_mm_exe_file(struct mm_struct *mm)
946 struct file *exe_file;
949 exe_file = rcu_dereference(mm->exe_file);
950 if (exe_file && !get_file_rcu(exe_file))
955 EXPORT_SYMBOL(get_mm_exe_file);
958 * get_task_exe_file - acquire a reference to the task's executable file
960 * Returns %NULL if task's mm (if any) has no associated executable file or
961 * this is a kernel thread with borrowed mm (see the comment above get_task_mm).
962 * User must release file via fput().
964 struct file *get_task_exe_file(struct task_struct *task)
966 struct file *exe_file = NULL;
967 struct mm_struct *mm;
972 if (!(task->flags & PF_KTHREAD))
973 exe_file = get_mm_exe_file(mm);
978 EXPORT_SYMBOL(get_task_exe_file);
981 * get_task_mm - acquire a reference to the task's mm
983 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning
984 * this kernel workthread has transiently adopted a user mm with use_mm,
985 * to do its AIO) is not set and if so returns a reference to it, after
986 * bumping up the use count. User must release the mm via mmput()
987 * after use. Typically used by /proc and ptrace.
989 struct mm_struct *get_task_mm(struct task_struct *task)
991 struct mm_struct *mm;
996 if (task->flags & PF_KTHREAD)
999 atomic_inc(&mm->mm_users);
1004 EXPORT_SYMBOL_GPL(get_task_mm);
1006 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
1008 struct mm_struct *mm;
1011 err = mutex_lock_killable(&task->signal->cred_guard_mutex);
1013 return ERR_PTR(err);
1015 mm = get_task_mm(task);
1016 if (mm && mm != current->mm &&
1017 !ptrace_may_access(task, mode)) {
1019 mm = ERR_PTR(-EACCES);
1021 mutex_unlock(&task->signal->cred_guard_mutex);
1026 static void complete_vfork_done(struct task_struct *tsk)
1028 struct completion *vfork;
1031 vfork = tsk->vfork_done;
1032 if (likely(vfork)) {
1033 tsk->vfork_done = NULL;
1039 static int wait_for_vfork_done(struct task_struct *child,
1040 struct completion *vfork)
1044 freezer_do_not_count();
1045 killed = wait_for_completion_killable(vfork);
1050 child->vfork_done = NULL;
1054 put_task_struct(child);
1058 /* Please note the differences between mmput and mm_release.
1059 * mmput is called whenever we stop holding onto a mm_struct,
1060 * error success whatever.
1062 * mm_release is called after a mm_struct has been removed
1063 * from the current process.
1065 * This difference is important for error handling, when we
1066 * only half set up a mm_struct for a new process and need to restore
1067 * the old one. Because we mmput the new mm_struct before
1068 * restoring the old one. . .
1069 * Eric Biederman 10 January 1998
1071 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
1073 /* Get rid of any futexes when releasing the mm */
1075 if (unlikely(tsk->robust_list)) {
1076 exit_robust_list(tsk);
1077 tsk->robust_list = NULL;
1079 #ifdef CONFIG_COMPAT
1080 if (unlikely(tsk->compat_robust_list)) {
1081 compat_exit_robust_list(tsk);
1082 tsk->compat_robust_list = NULL;
1085 if (unlikely(!list_empty(&tsk->pi_state_list)))
1086 exit_pi_state_list(tsk);
1089 uprobe_free_utask(tsk);
1091 /* Get rid of any cached register state */
1092 deactivate_mm(tsk, mm);
1095 * Signal userspace if we're not exiting with a core dump
1096 * because we want to leave the value intact for debugging
1099 if (tsk->clear_child_tid) {
1100 if (!(tsk->signal->flags & SIGNAL_GROUP_COREDUMP) &&
1101 atomic_read(&mm->mm_users) > 1) {
1103 * We don't check the error code - if userspace has
1104 * not set up a proper pointer then tough luck.
1106 put_user(0, tsk->clear_child_tid);
1107 sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
1110 tsk->clear_child_tid = NULL;
1114 * All done, finally we can wake up parent and return this mm to him.
1115 * Also kthread_stop() uses this completion for synchronization.
1117 if (tsk->vfork_done)
1118 complete_vfork_done(tsk);
1122 * Allocate a new mm structure and copy contents from the
1123 * mm structure of the passed in task structure.
1125 static struct mm_struct *dup_mm(struct task_struct *tsk)
1127 struct mm_struct *mm, *oldmm = current->mm;
1134 memcpy(mm, oldmm, sizeof(*mm));
1136 if (!mm_init(mm, tsk, mm->user_ns))
1139 err = dup_mmap(mm, oldmm);
1143 mm->hiwater_rss = get_mm_rss(mm);
1144 mm->hiwater_vm = mm->total_vm;
1146 if (mm->binfmt && !try_module_get(mm->binfmt->module))
1152 /* don't put binfmt in mmput, we haven't got module yet */
1160 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
1162 struct mm_struct *mm, *oldmm;
1165 tsk->min_flt = tsk->maj_flt = 0;
1166 tsk->nvcsw = tsk->nivcsw = 0;
1167 #ifdef CONFIG_DETECT_HUNG_TASK
1168 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
1172 tsk->active_mm = NULL;
1175 * Are we cloning a kernel thread?
1177 * We need to steal a active VM for that..
1179 oldmm = current->mm;
1183 /* initialize the new vmacache entries */
1184 vmacache_flush(tsk);
1186 if (clone_flags & CLONE_VM) {
1187 atomic_inc(&oldmm->mm_users);
1199 tsk->active_mm = mm;
1206 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
1208 struct fs_struct *fs = current->fs;
1209 if (clone_flags & CLONE_FS) {
1210 /* tsk->fs is already what we want */
1211 spin_lock(&fs->lock);
1213 spin_unlock(&fs->lock);
1217 spin_unlock(&fs->lock);
1220 tsk->fs = copy_fs_struct(fs);
1226 static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
1228 struct files_struct *oldf, *newf;
1232 * A background process may not have any files ...
1234 oldf = current->files;
1238 if (clone_flags & CLONE_FILES) {
1239 atomic_inc(&oldf->count);
1243 newf = dup_fd(oldf, &error);
1253 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
1256 struct io_context *ioc = current->io_context;
1257 struct io_context *new_ioc;
1262 * Share io context with parent, if CLONE_IO is set
1264 if (clone_flags & CLONE_IO) {
1266 tsk->io_context = ioc;
1267 } else if (ioprio_valid(ioc->ioprio)) {
1268 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE);
1269 if (unlikely(!new_ioc))
1272 new_ioc->ioprio = ioc->ioprio;
1273 put_io_context(new_ioc);
1279 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
1281 struct sighand_struct *sig;
1283 if (clone_flags & CLONE_SIGHAND) {
1284 atomic_inc(¤t->sighand->count);
1287 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1288 rcu_assign_pointer(tsk->sighand, sig);
1292 atomic_set(&sig->count, 1);
1293 memcpy(sig->action, current->sighand->action, sizeof(sig->action));
1297 void __cleanup_sighand(struct sighand_struct *sighand)
1299 if (atomic_dec_and_test(&sighand->count)) {
1300 signalfd_cleanup(sighand);
1302 * sighand_cachep is SLAB_DESTROY_BY_RCU so we can free it
1303 * without an RCU grace period, see __lock_task_sighand().
1305 kmem_cache_free(sighand_cachep, sighand);
1309 #ifdef CONFIG_POSIX_TIMERS
1311 * Initialize POSIX timer handling for a thread group.
1313 static void posix_cpu_timers_init_group(struct signal_struct *sig)
1315 unsigned long cpu_limit;
1317 cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1318 if (cpu_limit != RLIM_INFINITY) {
1319 sig->cputime_expires.prof_exp = cpu_limit * NSEC_PER_SEC;
1320 sig->cputimer.running = true;
1323 /* The timer lists. */
1324 INIT_LIST_HEAD(&sig->cpu_timers[0]);
1325 INIT_LIST_HEAD(&sig->cpu_timers[1]);
1326 INIT_LIST_HEAD(&sig->cpu_timers[2]);
1329 static inline void posix_cpu_timers_init_group(struct signal_struct *sig) { }
1332 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
1334 struct signal_struct *sig;
1336 if (clone_flags & CLONE_THREAD)
1339 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
1344 sig->nr_threads = 1;
1345 atomic_set(&sig->live, 1);
1346 atomic_set(&sig->sigcnt, 1);
1348 /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */
1349 sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node);
1350 tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head);
1352 init_waitqueue_head(&sig->wait_chldexit);
1353 sig->curr_target = tsk;
1354 init_sigpending(&sig->shared_pending);
1355 seqlock_init(&sig->stats_lock);
1356 prev_cputime_init(&sig->prev_cputime);
1358 #ifdef CONFIG_POSIX_TIMERS
1359 INIT_LIST_HEAD(&sig->posix_timers);
1360 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1361 sig->real_timer.function = it_real_fn;
1364 task_lock(current->group_leader);
1365 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
1366 task_unlock(current->group_leader);
1368 posix_cpu_timers_init_group(sig);
1370 tty_audit_fork(sig);
1371 sched_autogroup_fork(sig);
1373 sig->oom_score_adj = current->signal->oom_score_adj;
1374 sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1376 sig->has_child_subreaper = current->signal->has_child_subreaper ||
1377 current->signal->is_child_subreaper;
1379 mutex_init(&sig->cred_guard_mutex);
1384 static void copy_seccomp(struct task_struct *p)
1386 #ifdef CONFIG_SECCOMP
1388 * Must be called with sighand->lock held, which is common to
1389 * all threads in the group. Holding cred_guard_mutex is not
1390 * needed because this new task is not yet running and cannot
1393 assert_spin_locked(¤t->sighand->siglock);
1395 /* Ref-count the new filter user, and assign it. */
1396 get_seccomp_filter(current);
1397 p->seccomp = current->seccomp;
1400 * Explicitly enable no_new_privs here in case it got set
1401 * between the task_struct being duplicated and holding the
1402 * sighand lock. The seccomp state and nnp must be in sync.
1404 if (task_no_new_privs(current))
1405 task_set_no_new_privs(p);
1408 * If the parent gained a seccomp mode after copying thread
1409 * flags and between before we held the sighand lock, we have
1410 * to manually enable the seccomp thread flag here.
1412 if (p->seccomp.mode != SECCOMP_MODE_DISABLED)
1413 set_tsk_thread_flag(p, TIF_SECCOMP);
1417 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1419 current->clear_child_tid = tidptr;
1421 return task_pid_vnr(current);
1424 static void rt_mutex_init_task(struct task_struct *p)
1426 raw_spin_lock_init(&p->pi_lock);
1427 #ifdef CONFIG_RT_MUTEXES
1428 p->pi_waiters = RB_ROOT;
1429 p->pi_waiters_leftmost = NULL;
1430 p->pi_blocked_on = NULL;
1434 #ifdef CONFIG_POSIX_TIMERS
1436 * Initialize POSIX timer handling for a single task.
1438 static void posix_cpu_timers_init(struct task_struct *tsk)
1440 tsk->cputime_expires.prof_exp = 0;
1441 tsk->cputime_expires.virt_exp = 0;
1442 tsk->cputime_expires.sched_exp = 0;
1443 INIT_LIST_HEAD(&tsk->cpu_timers[0]);
1444 INIT_LIST_HEAD(&tsk->cpu_timers[1]);
1445 INIT_LIST_HEAD(&tsk->cpu_timers[2]);
1448 static inline void posix_cpu_timers_init(struct task_struct *tsk) { }
1452 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid)
1454 task->pids[type].pid = pid;
1458 * This creates a new process as a copy of the old one,
1459 * but does not actually start it yet.
1461 * It copies the registers, and all the appropriate
1462 * parts of the process environment (as per the clone
1463 * flags). The actual kick-off is left to the caller.
1465 static __latent_entropy struct task_struct *copy_process(
1466 unsigned long clone_flags,
1467 unsigned long stack_start,
1468 unsigned long stack_size,
1469 int __user *child_tidptr,
1476 struct task_struct *p;
1478 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1479 return ERR_PTR(-EINVAL);
1481 if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS))
1482 return ERR_PTR(-EINVAL);
1485 * Thread groups must share signals as well, and detached threads
1486 * can only be started up within the thread group.
1488 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1489 return ERR_PTR(-EINVAL);
1492 * Shared signal handlers imply shared VM. By way of the above,
1493 * thread groups also imply shared VM. Blocking this case allows
1494 * for various simplifications in other code.
1496 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1497 return ERR_PTR(-EINVAL);
1500 * Siblings of global init remain as zombies on exit since they are
1501 * not reaped by their parent (swapper). To solve this and to avoid
1502 * multi-rooted process trees, prevent global and container-inits
1503 * from creating siblings.
1505 if ((clone_flags & CLONE_PARENT) &&
1506 current->signal->flags & SIGNAL_UNKILLABLE)
1507 return ERR_PTR(-EINVAL);
1510 * If the new process will be in a different pid or user namespace
1511 * do not allow it to share a thread group with the forking task.
1513 if (clone_flags & CLONE_THREAD) {
1514 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) ||
1515 (task_active_pid_ns(current) !=
1516 current->nsproxy->pid_ns_for_children))
1517 return ERR_PTR(-EINVAL);
1520 retval = security_task_create(clone_flags);
1525 p = dup_task_struct(current, node);
1529 ftrace_graph_init_task(p);
1531 rt_mutex_init_task(p);
1533 #ifdef CONFIG_PROVE_LOCKING
1534 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1535 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1538 if (atomic_read(&p->real_cred->user->processes) >=
1539 task_rlimit(p, RLIMIT_NPROC)) {
1540 if (p->real_cred->user != INIT_USER &&
1541 !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
1544 current->flags &= ~PF_NPROC_EXCEEDED;
1546 retval = copy_creds(p, clone_flags);
1551 * If multiple threads are within copy_process(), then this check
1552 * triggers too late. This doesn't hurt, the check is only there
1553 * to stop root fork bombs.
1556 if (nr_threads >= max_threads)
1557 goto bad_fork_cleanup_count;
1559 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */
1560 p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER | PF_IDLE);
1561 p->flags |= PF_FORKNOEXEC;
1562 INIT_LIST_HEAD(&p->children);
1563 INIT_LIST_HEAD(&p->sibling);
1564 rcu_copy_process(p);
1565 p->vfork_done = NULL;
1566 spin_lock_init(&p->alloc_lock);
1568 init_sigpending(&p->pending);
1570 p->utime = p->stime = p->gtime = 0;
1571 #ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
1572 p->utimescaled = p->stimescaled = 0;
1574 prev_cputime_init(&p->prev_cputime);
1576 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
1577 seqcount_init(&p->vtime_seqcount);
1579 p->vtime_snap_whence = VTIME_INACTIVE;
1582 #if defined(SPLIT_RSS_COUNTING)
1583 memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1586 p->default_timer_slack_ns = current->timer_slack_ns;
1588 task_io_accounting_init(&p->ioac);
1589 acct_clear_integrals(p);
1591 posix_cpu_timers_init(p);
1593 p->start_time = ktime_get_ns();
1594 p->real_start_time = ktime_get_boot_ns();
1595 p->io_context = NULL;
1596 p->audit_context = NULL;
1599 p->mempolicy = mpol_dup(p->mempolicy);
1600 if (IS_ERR(p->mempolicy)) {
1601 retval = PTR_ERR(p->mempolicy);
1602 p->mempolicy = NULL;
1603 goto bad_fork_cleanup_threadgroup_lock;
1606 #ifdef CONFIG_CPUSETS
1607 p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
1608 p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
1609 seqcount_init(&p->mems_allowed_seq);
1611 #ifdef CONFIG_TRACE_IRQFLAGS
1613 p->hardirqs_enabled = 0;
1614 p->hardirq_enable_ip = 0;
1615 p->hardirq_enable_event = 0;
1616 p->hardirq_disable_ip = _THIS_IP_;
1617 p->hardirq_disable_event = 0;
1618 p->softirqs_enabled = 1;
1619 p->softirq_enable_ip = _THIS_IP_;
1620 p->softirq_enable_event = 0;
1621 p->softirq_disable_ip = 0;
1622 p->softirq_disable_event = 0;
1623 p->hardirq_context = 0;
1624 p->softirq_context = 0;
1627 p->pagefault_disabled = 0;
1629 #ifdef CONFIG_LOCKDEP
1630 p->lockdep_depth = 0; /* no locks held yet */
1631 p->curr_chain_key = 0;
1632 p->lockdep_recursion = 0;
1635 #ifdef CONFIG_DEBUG_MUTEXES
1636 p->blocked_on = NULL; /* not blocked yet */
1638 #ifdef CONFIG_BCACHE
1639 p->sequential_io = 0;
1640 p->sequential_io_avg = 0;
1643 /* Perform scheduler related setup. Assign this task to a CPU. */
1644 retval = sched_fork(clone_flags, p);
1646 goto bad_fork_cleanup_policy;
1648 retval = perf_event_init_task(p);
1650 goto bad_fork_cleanup_policy;
1651 retval = audit_alloc(p);
1653 goto bad_fork_cleanup_perf;
1654 /* copy all the process information */
1656 retval = copy_semundo(clone_flags, p);
1658 goto bad_fork_cleanup_audit;
1659 retval = copy_files(clone_flags, p);
1661 goto bad_fork_cleanup_semundo;
1662 retval = copy_fs(clone_flags, p);
1664 goto bad_fork_cleanup_files;
1665 retval = copy_sighand(clone_flags, p);
1667 goto bad_fork_cleanup_fs;
1668 retval = copy_signal(clone_flags, p);
1670 goto bad_fork_cleanup_sighand;
1671 retval = copy_mm(clone_flags, p);
1673 goto bad_fork_cleanup_signal;
1674 retval = copy_namespaces(clone_flags, p);
1676 goto bad_fork_cleanup_mm;
1677 retval = copy_io(clone_flags, p);
1679 goto bad_fork_cleanup_namespaces;
1680 retval = copy_thread_tls(clone_flags, stack_start, stack_size, p, tls);
1682 goto bad_fork_cleanup_io;
1684 if (pid != &init_struct_pid) {
1685 pid = alloc_pid(p->nsproxy->pid_ns_for_children);
1687 retval = PTR_ERR(pid);
1688 goto bad_fork_cleanup_thread;
1692 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1694 * Clear TID on mm_release()?
1696 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL;
1701 p->robust_list = NULL;
1702 #ifdef CONFIG_COMPAT
1703 p->compat_robust_list = NULL;
1705 INIT_LIST_HEAD(&p->pi_state_list);
1706 p->pi_state_cache = NULL;
1709 * sigaltstack should be cleared when sharing the same VM
1711 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1715 * Syscall tracing and stepping should be turned off in the
1716 * child regardless of CLONE_PTRACE.
1718 user_disable_single_step(p);
1719 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1720 #ifdef TIF_SYSCALL_EMU
1721 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1723 clear_all_latency_tracing(p);
1725 /* ok, now we should be set up.. */
1726 p->pid = pid_nr(pid);
1727 if (clone_flags & CLONE_THREAD) {
1728 p->exit_signal = -1;
1729 p->group_leader = current->group_leader;
1730 p->tgid = current->tgid;
1732 if (clone_flags & CLONE_PARENT)
1733 p->exit_signal = current->group_leader->exit_signal;
1735 p->exit_signal = (clone_flags & CSIGNAL);
1736 p->group_leader = p;
1741 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
1742 p->dirty_paused_when = 0;
1744 p->pdeath_signal = 0;
1745 INIT_LIST_HEAD(&p->thread_group);
1746 p->task_works = NULL;
1748 threadgroup_change_begin(current);
1750 * Ensure that the cgroup subsystem policies allow the new process to be
1751 * forked. It should be noted the the new process's css_set can be changed
1752 * between here and cgroup_post_fork() if an organisation operation is in
1755 retval = cgroup_can_fork(p);
1757 goto bad_fork_free_pid;
1760 * Make it visible to the rest of the system, but dont wake it up yet.
1761 * Need tasklist lock for parent etc handling!
1763 write_lock_irq(&tasklist_lock);
1765 /* CLONE_PARENT re-uses the old parent */
1766 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1767 p->real_parent = current->real_parent;
1768 p->parent_exec_id = current->parent_exec_id;
1770 p->real_parent = current;
1771 p->parent_exec_id = current->self_exec_id;
1774 spin_lock(¤t->sighand->siglock);
1777 * Copy seccomp details explicitly here, in case they were changed
1778 * before holding sighand lock.
1783 * Process group and session signals need to be delivered to just the
1784 * parent before the fork or both the parent and the child after the
1785 * fork. Restart if a signal comes in before we add the new process to
1786 * it's process group.
1787 * A fatal signal pending means that current will exit, so the new
1788 * thread can't slip out of an OOM kill (or normal SIGKILL).
1790 recalc_sigpending();
1791 if (signal_pending(current)) {
1792 spin_unlock(¤t->sighand->siglock);
1793 write_unlock_irq(&tasklist_lock);
1794 retval = -ERESTARTNOINTR;
1795 goto bad_fork_cancel_cgroup;
1798 if (likely(p->pid)) {
1799 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
1801 init_task_pid(p, PIDTYPE_PID, pid);
1802 if (thread_group_leader(p)) {
1803 init_task_pid(p, PIDTYPE_PGID, task_pgrp(current));
1804 init_task_pid(p, PIDTYPE_SID, task_session(current));
1806 if (is_child_reaper(pid)) {
1807 ns_of_pid(pid)->child_reaper = p;
1808 p->signal->flags |= SIGNAL_UNKILLABLE;
1811 p->signal->leader_pid = pid;
1812 p->signal->tty = tty_kref_get(current->signal->tty);
1813 list_add_tail(&p->sibling, &p->real_parent->children);
1814 list_add_tail_rcu(&p->tasks, &init_task.tasks);
1815 attach_pid(p, PIDTYPE_PGID);
1816 attach_pid(p, PIDTYPE_SID);
1817 __this_cpu_inc(process_counts);
1819 current->signal->nr_threads++;
1820 atomic_inc(¤t->signal->live);
1821 atomic_inc(¤t->signal->sigcnt);
1822 list_add_tail_rcu(&p->thread_group,
1823 &p->group_leader->thread_group);
1824 list_add_tail_rcu(&p->thread_node,
1825 &p->signal->thread_head);
1827 attach_pid(p, PIDTYPE_PID);
1832 spin_unlock(¤t->sighand->siglock);
1833 syscall_tracepoint_update(p);
1834 write_unlock_irq(&tasklist_lock);
1836 proc_fork_connector(p);
1837 cgroup_post_fork(p);
1838 threadgroup_change_end(current);
1841 trace_task_newtask(p, clone_flags);
1842 uprobe_copy_process(p, clone_flags);
1846 bad_fork_cancel_cgroup:
1847 cgroup_cancel_fork(p);
1849 threadgroup_change_end(current);
1850 if (pid != &init_struct_pid)
1852 bad_fork_cleanup_thread:
1854 bad_fork_cleanup_io:
1857 bad_fork_cleanup_namespaces:
1858 exit_task_namespaces(p);
1859 bad_fork_cleanup_mm:
1862 bad_fork_cleanup_signal:
1863 if (!(clone_flags & CLONE_THREAD))
1864 free_signal_struct(p->signal);
1865 bad_fork_cleanup_sighand:
1866 __cleanup_sighand(p->sighand);
1867 bad_fork_cleanup_fs:
1868 exit_fs(p); /* blocking */
1869 bad_fork_cleanup_files:
1870 exit_files(p); /* blocking */
1871 bad_fork_cleanup_semundo:
1873 bad_fork_cleanup_audit:
1875 bad_fork_cleanup_perf:
1876 perf_event_free_task(p);
1877 bad_fork_cleanup_policy:
1879 mpol_put(p->mempolicy);
1880 bad_fork_cleanup_threadgroup_lock:
1882 delayacct_tsk_free(p);
1883 bad_fork_cleanup_count:
1884 atomic_dec(&p->cred->user->processes);
1887 p->state = TASK_DEAD;
1891 return ERR_PTR(retval);
1894 static inline void init_idle_pids(struct pid_link *links)
1898 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
1899 INIT_HLIST_NODE(&links[type].node); /* not really needed */
1900 links[type].pid = &init_struct_pid;
1904 struct task_struct *fork_idle(int cpu)
1906 struct task_struct *task;
1907 task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0, 0,
1909 if (!IS_ERR(task)) {
1910 init_idle_pids(task->pids);
1911 init_idle(task, cpu);
1918 * Ok, this is the main fork-routine.
1920 * It copies the process, and if successful kick-starts
1921 * it and waits for it to finish using the VM if required.
1923 long _do_fork(unsigned long clone_flags,
1924 unsigned long stack_start,
1925 unsigned long stack_size,
1926 int __user *parent_tidptr,
1927 int __user *child_tidptr,
1930 struct task_struct *p;
1935 * Determine whether and which event to report to ptracer. When
1936 * called from kernel_thread or CLONE_UNTRACED is explicitly
1937 * requested, no event is reported; otherwise, report if the event
1938 * for the type of forking is enabled.
1940 if (!(clone_flags & CLONE_UNTRACED)) {
1941 if (clone_flags & CLONE_VFORK)
1942 trace = PTRACE_EVENT_VFORK;
1943 else if ((clone_flags & CSIGNAL) != SIGCHLD)
1944 trace = PTRACE_EVENT_CLONE;
1946 trace = PTRACE_EVENT_FORK;
1948 if (likely(!ptrace_event_enabled(current, trace)))
1952 p = copy_process(clone_flags, stack_start, stack_size,
1953 child_tidptr, NULL, trace, tls, NUMA_NO_NODE);
1954 add_latent_entropy();
1956 * Do this prior waking up the new thread - the thread pointer
1957 * might get invalid after that point, if the thread exits quickly.
1960 struct completion vfork;
1963 trace_sched_process_fork(current, p);
1965 pid = get_task_pid(p, PIDTYPE_PID);
1968 if (clone_flags & CLONE_PARENT_SETTID)
1969 put_user(nr, parent_tidptr);
1971 if (clone_flags & CLONE_VFORK) {
1972 p->vfork_done = &vfork;
1973 init_completion(&vfork);
1977 wake_up_new_task(p);
1979 /* forking complete and child started to run, tell ptracer */
1980 if (unlikely(trace))
1981 ptrace_event_pid(trace, pid);
1983 if (clone_flags & CLONE_VFORK) {
1984 if (!wait_for_vfork_done(p, &vfork))
1985 ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid);
1995 #ifndef CONFIG_HAVE_COPY_THREAD_TLS
1996 /* For compatibility with architectures that call do_fork directly rather than
1997 * using the syscall entry points below. */
1998 long do_fork(unsigned long clone_flags,
1999 unsigned long stack_start,
2000 unsigned long stack_size,
2001 int __user *parent_tidptr,
2002 int __user *child_tidptr)
2004 return _do_fork(clone_flags, stack_start, stack_size,
2005 parent_tidptr, child_tidptr, 0);
2010 * Create a kernel thread.
2012 pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
2014 return _do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn,
2015 (unsigned long)arg, NULL, NULL, 0);
2018 #ifdef __ARCH_WANT_SYS_FORK
2019 SYSCALL_DEFINE0(fork)
2022 return _do_fork(SIGCHLD, 0, 0, NULL, NULL, 0);
2024 /* can not support in nommu mode */
2030 #ifdef __ARCH_WANT_SYS_VFORK
2031 SYSCALL_DEFINE0(vfork)
2033 return _do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0,
2038 #ifdef __ARCH_WANT_SYS_CLONE
2039 #ifdef CONFIG_CLONE_BACKWARDS
2040 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2041 int __user *, parent_tidptr,
2043 int __user *, child_tidptr)
2044 #elif defined(CONFIG_CLONE_BACKWARDS2)
2045 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags,
2046 int __user *, parent_tidptr,
2047 int __user *, child_tidptr,
2049 #elif defined(CONFIG_CLONE_BACKWARDS3)
2050 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp,
2052 int __user *, parent_tidptr,
2053 int __user *, child_tidptr,
2056 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2057 int __user *, parent_tidptr,
2058 int __user *, child_tidptr,
2062 return _do_fork(clone_flags, newsp, 0, parent_tidptr, child_tidptr, tls);
2066 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
2067 #define ARCH_MIN_MMSTRUCT_ALIGN 0
2070 static void sighand_ctor(void *data)
2072 struct sighand_struct *sighand = data;
2074 spin_lock_init(&sighand->siglock);
2075 init_waitqueue_head(&sighand->signalfd_wqh);
2078 void __init proc_caches_init(void)
2080 sighand_cachep = kmem_cache_create("sighand_cache",
2081 sizeof(struct sighand_struct), 0,
2082 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU|
2083 SLAB_NOTRACK|SLAB_ACCOUNT, sighand_ctor);
2084 signal_cachep = kmem_cache_create("signal_cache",
2085 sizeof(struct signal_struct), 0,
2086 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT,
2088 files_cachep = kmem_cache_create("files_cache",
2089 sizeof(struct files_struct), 0,
2090 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT,
2092 fs_cachep = kmem_cache_create("fs_cache",
2093 sizeof(struct fs_struct), 0,
2094 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT,
2097 * FIXME! The "sizeof(struct mm_struct)" currently includes the
2098 * whole struct cpumask for the OFFSTACK case. We could change
2099 * this to *only* allocate as much of it as required by the
2100 * maximum number of CPU's we can ever have. The cpumask_allocation
2101 * is at the end of the structure, exactly for that reason.
2103 mm_cachep = kmem_cache_create("mm_struct",
2104 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
2105 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT,
2107 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT);
2109 nsproxy_cache_init();
2113 * Check constraints on flags passed to the unshare system call.
2115 static int check_unshare_flags(unsigned long unshare_flags)
2117 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
2118 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
2119 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET|
2120 CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP))
2123 * Not implemented, but pretend it works if there is nothing
2124 * to unshare. Note that unsharing the address space or the
2125 * signal handlers also need to unshare the signal queues (aka
2128 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
2129 if (!thread_group_empty(current))
2132 if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) {
2133 if (atomic_read(¤t->sighand->count) > 1)
2136 if (unshare_flags & CLONE_VM) {
2137 if (!current_is_single_threaded())
2145 * Unshare the filesystem structure if it is being shared
2147 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
2149 struct fs_struct *fs = current->fs;
2151 if (!(unshare_flags & CLONE_FS) || !fs)
2154 /* don't need lock here; in the worst case we'll do useless copy */
2158 *new_fsp = copy_fs_struct(fs);
2166 * Unshare file descriptor table if it is being shared
2168 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
2170 struct files_struct *fd = current->files;
2173 if ((unshare_flags & CLONE_FILES) &&
2174 (fd && atomic_read(&fd->count) > 1)) {
2175 *new_fdp = dup_fd(fd, &error);
2184 * unshare allows a process to 'unshare' part of the process
2185 * context which was originally shared using clone. copy_*
2186 * functions used by do_fork() cannot be used here directly
2187 * because they modify an inactive task_struct that is being
2188 * constructed. Here we are modifying the current, active,
2191 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
2193 struct fs_struct *fs, *new_fs = NULL;
2194 struct files_struct *fd, *new_fd = NULL;
2195 struct cred *new_cred = NULL;
2196 struct nsproxy *new_nsproxy = NULL;
2201 * If unsharing a user namespace must also unshare the thread group
2202 * and unshare the filesystem root and working directories.
2204 if (unshare_flags & CLONE_NEWUSER)
2205 unshare_flags |= CLONE_THREAD | CLONE_FS;
2207 * If unsharing vm, must also unshare signal handlers.
2209 if (unshare_flags & CLONE_VM)
2210 unshare_flags |= CLONE_SIGHAND;
2212 * If unsharing a signal handlers, must also unshare the signal queues.
2214 if (unshare_flags & CLONE_SIGHAND)
2215 unshare_flags |= CLONE_THREAD;
2217 * If unsharing namespace, must also unshare filesystem information.
2219 if (unshare_flags & CLONE_NEWNS)
2220 unshare_flags |= CLONE_FS;
2222 err = check_unshare_flags(unshare_flags);
2224 goto bad_unshare_out;
2226 * CLONE_NEWIPC must also detach from the undolist: after switching
2227 * to a new ipc namespace, the semaphore arrays from the old
2228 * namespace are unreachable.
2230 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
2232 err = unshare_fs(unshare_flags, &new_fs);
2234 goto bad_unshare_out;
2235 err = unshare_fd(unshare_flags, &new_fd);
2237 goto bad_unshare_cleanup_fs;
2238 err = unshare_userns(unshare_flags, &new_cred);
2240 goto bad_unshare_cleanup_fd;
2241 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
2244 goto bad_unshare_cleanup_cred;
2246 if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
2249 * CLONE_SYSVSEM is equivalent to sys_exit().
2253 if (unshare_flags & CLONE_NEWIPC) {
2254 /* Orphan segments in old ns (see sem above). */
2256 shm_init_task(current);
2260 switch_task_namespaces(current, new_nsproxy);
2266 spin_lock(&fs->lock);
2267 current->fs = new_fs;
2272 spin_unlock(&fs->lock);
2276 fd = current->files;
2277 current->files = new_fd;
2281 task_unlock(current);
2284 /* Install the new user namespace */
2285 commit_creds(new_cred);
2290 bad_unshare_cleanup_cred:
2293 bad_unshare_cleanup_fd:
2295 put_files_struct(new_fd);
2297 bad_unshare_cleanup_fs:
2299 free_fs_struct(new_fs);
2306 * Helper to unshare the files of the current task.
2307 * We don't want to expose copy_files internals to
2308 * the exec layer of the kernel.
2311 int unshare_files(struct files_struct **displaced)
2313 struct task_struct *task = current;
2314 struct files_struct *copy = NULL;
2317 error = unshare_fd(CLONE_FILES, ©);
2318 if (error || !copy) {
2322 *displaced = task->files;
2329 int sysctl_max_threads(struct ctl_table *table, int write,
2330 void __user *buffer, size_t *lenp, loff_t *ppos)
2334 int threads = max_threads;
2335 int min = MIN_THREADS;
2336 int max = MAX_THREADS;
2343 ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
2347 set_max_threads(threads);