projects/linux·blob v4.17 · refs

2524 lines · 60.2 KiB

1/*
2 * linux/kernel/fork.c
3 *
4 * Copyright (C) 1991, 1992 Linus Torvalds
5 */
6
7/*
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()'
12 */
13
14#include <linux/slab.h>
15#include <linux/sched/autogroup.h>
16#include <linux/sched/mm.h>
17#include <linux/sched/coredump.h>
18#include <linux/sched/user.h>
19#include <linux/sched/numa_balancing.h>
20#include <linux/sched/stat.h>
21#include <linux/sched/task.h>
22#include <linux/sched/task_stack.h>
23#include <linux/sched/cputime.h>
24#include <linux/rtmutex.h>
25#include <linux/init.h>
26#include <linux/unistd.h>
27#include <linux/module.h>
28#include <linux/vmalloc.h>
29#include <linux/completion.h>
30#include <linux/personality.h>
31#include <linux/mempolicy.h>
32#include <linux/sem.h>
33#include <linux/file.h>
34#include <linux/fdtable.h>
35#include <linux/iocontext.h>
36#include <linux/key.h>
37#include <linux/binfmts.h>
38#include <linux/mman.h>
39#include <linux/mmu_notifier.h>
40#include <linux/hmm.h>
41#include <linux/fs.h>
42#include <linux/mm.h>
43#include <linux/vmacache.h>
44#include <linux/nsproxy.h>
45#include <linux/capability.h>
46#include <linux/cpu.h>
47#include <linux/cgroup.h>
48#include <linux/security.h>
49#include <linux/hugetlb.h>
50#include <linux/seccomp.h>
51#include <linux/swap.h>
52#include <linux/syscalls.h>
53#include <linux/jiffies.h>
54#include <linux/futex.h>
55#include <linux/compat.h>
56#include <linux/kthread.h>
57#include <linux/task_io_accounting_ops.h>
58#include <linux/rcupdate.h>
59#include <linux/ptrace.h>
60#include <linux/mount.h>
61#include <linux/audit.h>
62#include <linux/memcontrol.h>
63#include <linux/ftrace.h>
64#include <linux/proc_fs.h>
65#include <linux/profile.h>
66#include <linux/rmap.h>
67#include <linux/ksm.h>
68#include <linux/acct.h>
69#include <linux/userfaultfd_k.h>
70#include <linux/tsacct_kern.h>
71#include <linux/cn_proc.h>
72#include <linux/freezer.h>
73#include <linux/delayacct.h>
74#include <linux/taskstats_kern.h>
75#include <linux/random.h>
76#include <linux/tty.h>
77#include <linux/blkdev.h>
78#include <linux/fs_struct.h>
79#include <linux/magic.h>
80#include <linux/sched/mm.h>
81#include <linux/perf_event.h>
82#include <linux/posix-timers.h>
83#include <linux/user-return-notifier.h>
84#include <linux/oom.h>
85#include <linux/khugepaged.h>
86#include <linux/signalfd.h>
87#include <linux/uprobes.h>
88#include <linux/aio.h>
89#include <linux/compiler.h>
90#include <linux/sysctl.h>
91#include <linux/kcov.h>
92#include <linux/livepatch.h>
93#include <linux/thread_info.h>
94
95#include <asm/pgtable.h>
96#include <asm/pgalloc.h>
97#include <linux/uaccess.h>
98#include <asm/mmu_context.h>
99#include <asm/cacheflush.h>
100#include <asm/tlbflush.h>
101
102#include <trace/events/sched.h>
103
104#define CREATE_TRACE_POINTS
105#include <trace/events/task.h>
106
107/*
108 * Minimum number of threads to boot the kernel
109 */
110#define MIN_THREADS 20
111
112/*
113 * Maximum number of threads
114 */
115#define MAX_THREADS FUTEX_TID_MASK
116
117/*
118 * Protected counters by write_lock_irq(&tasklist_lock)
119 */
120unsigned long total_forks; /* Handle normal Linux uptimes. */
121int nr_threads; /* The idle threads do not count.. */
122
123int max_threads; /* tunable limit on nr_threads */
124
125DEFINE_PER_CPU(unsigned long, process_counts) = 0;
126
127__cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */
128
129#ifdef CONFIG_PROVE_RCU
130int lockdep_tasklist_lock_is_held(void)
131{
132 return lockdep_is_held(&tasklist_lock);
133}
134EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
135#endif /* #ifdef CONFIG_PROVE_RCU */
136
137int nr_processes(void)
138{
139 int cpu;
140 int total = 0;
141
142 for_each_possible_cpu(cpu)
143 total += per_cpu(process_counts, cpu);
144
145 return total;
146}
147
148void __weak arch_release_task_struct(struct task_struct *tsk)
149{
150}
151
152#ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
153static struct kmem_cache *task_struct_cachep;
154
155static inline struct task_struct *alloc_task_struct_node(int node)
156{
157 return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node);
158}
159
160static inline void free_task_struct(struct task_struct *tsk)
161{
162 kmem_cache_free(task_struct_cachep, tsk);
163}
164#endif
165
166void __weak arch_release_thread_stack(unsigned long *stack)
167{
168}
169
170#ifndef CONFIG_ARCH_THREAD_STACK_ALLOCATOR
171
172/*
173 * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
174 * kmemcache based allocator.
175 */
176# if THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK)
177
178#ifdef CONFIG_VMAP_STACK
179/*
180 * vmalloc() is a bit slow, and calling vfree() enough times will force a TLB
181 * flush. Try to minimize the number of calls by caching stacks.
182 */
183#define NR_CACHED_STACKS 2
184static DEFINE_PER_CPU(struct vm_struct *, cached_stacks[NR_CACHED_STACKS]);
185
186static int free_vm_stack_cache(unsigned int cpu)
187{
188 struct vm_struct **cached_vm_stacks = per_cpu_ptr(cached_stacks, cpu);
189 int i;
190
191 for (i = 0; i < NR_CACHED_STACKS; i++) {
192 struct vm_struct *vm_stack = cached_vm_stacks[i];
193
194 if (!vm_stack)
195 continue;
196
197 vfree(vm_stack->addr);
198 cached_vm_stacks[i] = NULL;
199 }
200
201 return 0;
202}
203#endif
204
205static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node)
206{
207#ifdef CONFIG_VMAP_STACK
208 void *stack;
209 int i;
210
211 for (i = 0; i < NR_CACHED_STACKS; i++) {
212 struct vm_struct *s;
213
214 s = this_cpu_xchg(cached_stacks[i], NULL);
215
216 if (!s)
217 continue;
218
219 /* Clear stale pointers from reused stack. */
220 memset(s->addr, 0, THREAD_SIZE);
221
222 tsk->stack_vm_area = s;
223 return s->addr;
224 }
225
226 stack = __vmalloc_node_range(THREAD_SIZE, THREAD_ALIGN,
227 VMALLOC_START, VMALLOC_END,
228 THREADINFO_GFP,
229 PAGE_KERNEL,
230 0, node, __builtin_return_address(0));
231
232 /*
233 * We can't call find_vm_area() in interrupt context, and
234 * free_thread_stack() can be called in interrupt context,
235 * so cache the vm_struct.
236 */
237 if (stack)
238 tsk->stack_vm_area = find_vm_area(stack);
239 return stack;
240#else
241 struct page *page = alloc_pages_node(node, THREADINFO_GFP,
242 THREAD_SIZE_ORDER);
243
244 return page ? page_address(page) : NULL;
245#endif
246}
247
248static inline void free_thread_stack(struct task_struct *tsk)
249{
250#ifdef CONFIG_VMAP_STACK
251 if (task_stack_vm_area(tsk)) {
252 int i;
253
254 for (i = 0; i < NR_CACHED_STACKS; i++) {
255 if (this_cpu_cmpxchg(cached_stacks[i],
256 NULL, tsk->stack_vm_area) != NULL)
257 continue;
258
259 return;
260 }
261
262 vfree_atomic(tsk->stack);
263 return;
264 }
265#endif
266
267 __free_pages(virt_to_page(tsk->stack), THREAD_SIZE_ORDER);
268}
269# else
270static struct kmem_cache *thread_stack_cache;
271
272static unsigned long *alloc_thread_stack_node(struct task_struct *tsk,
273 int node)
274{
275 return kmem_cache_alloc_node(thread_stack_cache, THREADINFO_GFP, node);
276}
277
278static void free_thread_stack(struct task_struct *tsk)
279{
280 kmem_cache_free(thread_stack_cache, tsk->stack);
281}
282
283void thread_stack_cache_init(void)
284{
285 thread_stack_cache = kmem_cache_create_usercopy("thread_stack",
286 THREAD_SIZE, THREAD_SIZE, 0, 0,
287 THREAD_SIZE, NULL);
288 BUG_ON(thread_stack_cache == NULL);
289}
290# endif
291#endif
292
293/* SLAB cache for signal_struct structures (tsk->signal) */
294static struct kmem_cache *signal_cachep;
295
296/* SLAB cache for sighand_struct structures (tsk->sighand) */
297struct kmem_cache *sighand_cachep;
298
299/* SLAB cache for files_struct structures (tsk->files) */
300struct kmem_cache *files_cachep;
301
302/* SLAB cache for fs_struct structures (tsk->fs) */
303struct kmem_cache *fs_cachep;
304
305/* SLAB cache for vm_area_struct structures */
306struct kmem_cache *vm_area_cachep;
307
308/* SLAB cache for mm_struct structures (tsk->mm) */
309static struct kmem_cache *mm_cachep;
310
311static void account_kernel_stack(struct task_struct *tsk, int account)
312{
313 void *stack = task_stack_page(tsk);
314 struct vm_struct *vm = task_stack_vm_area(tsk);
315
316 BUILD_BUG_ON(IS_ENABLED(CONFIG_VMAP_STACK) && PAGE_SIZE % 1024 != 0);
317
318 if (vm) {
319 int i;
320
321 BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE);
322
323 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
324 mod_zone_page_state(page_zone(vm->pages[i]),
325 NR_KERNEL_STACK_KB,
326 PAGE_SIZE / 1024 * account);
327 }
328
329 /* All stack pages belong to the same memcg. */
330 mod_memcg_page_state(vm->pages[0], MEMCG_KERNEL_STACK_KB,
331 account * (THREAD_SIZE / 1024));
332 } else {
333 /*
334 * All stack pages are in the same zone and belong to the
335 * same memcg.
336 */
337 struct page *first_page = virt_to_page(stack);
338
339 mod_zone_page_state(page_zone(first_page), NR_KERNEL_STACK_KB,
340 THREAD_SIZE / 1024 * account);
341
342 mod_memcg_page_state(first_page, MEMCG_KERNEL_STACK_KB,
343 account * (THREAD_SIZE / 1024));
344 }
345}
346
347static void release_task_stack(struct task_struct *tsk)
348{
349 if (WARN_ON(tsk->state != TASK_DEAD))
350 return; /* Better to leak the stack than to free prematurely */
351
352 account_kernel_stack(tsk, -1);
353 arch_release_thread_stack(tsk->stack);
354 free_thread_stack(tsk);
355 tsk->stack = NULL;
356#ifdef CONFIG_VMAP_STACK
357 tsk->stack_vm_area = NULL;
358#endif
359}
360
361#ifdef CONFIG_THREAD_INFO_IN_TASK
362void put_task_stack(struct task_struct *tsk)
363{
364 if (atomic_dec_and_test(&tsk->stack_refcount))
365 release_task_stack(tsk);
366}
367#endif
368
369void free_task(struct task_struct *tsk)
370{
371#ifndef CONFIG_THREAD_INFO_IN_TASK
372 /*
373 * The task is finally done with both the stack and thread_info,
374 * so free both.
375 */
376 release_task_stack(tsk);
377#else
378 /*
379 * If the task had a separate stack allocation, it should be gone
380 * by now.
381 */
382 WARN_ON_ONCE(atomic_read(&tsk->stack_refcount) != 0);
383#endif
384 rt_mutex_debug_task_free(tsk);
385 ftrace_graph_exit_task(tsk);
386 put_seccomp_filter(tsk);
387 arch_release_task_struct(tsk);
388 if (tsk->flags & PF_KTHREAD)
389 free_kthread_struct(tsk);
390 free_task_struct(tsk);
391}
392EXPORT_SYMBOL(free_task);
393
394#ifdef CONFIG_MMU
395static __latent_entropy int dup_mmap(struct mm_struct *mm,
396 struct mm_struct *oldmm)
397{
398 struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
399 struct rb_node **rb_link, *rb_parent;
400 int retval;
401 unsigned long charge;
402 LIST_HEAD(uf);
403
404 uprobe_start_dup_mmap();
405 if (down_write_killable(&oldmm->mmap_sem)) {
406 retval = -EINTR;
407 goto fail_uprobe_end;
408 }
409 flush_cache_dup_mm(oldmm);
410 uprobe_dup_mmap(oldmm, mm);
411 /*
412 * Not linked in yet - no deadlock potential:
413 */
414 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
415
416 /* No ordering required: file already has been exposed. */
417 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
418
419 mm->total_vm = oldmm->total_vm;
420 mm->data_vm = oldmm->data_vm;
421 mm->exec_vm = oldmm->exec_vm;
422 mm->stack_vm = oldmm->stack_vm;
423
424 rb_link = &mm->mm_rb.rb_node;
425 rb_parent = NULL;
426 pprev = &mm->mmap;
427 retval = ksm_fork(mm, oldmm);
428 if (retval)
429 goto out;
430 retval = khugepaged_fork(mm, oldmm);
431 if (retval)
432 goto out;
433
434 prev = NULL;
435 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
436 struct file *file;
437
438 if (mpnt->vm_flags & VM_DONTCOPY) {
439 vm_stat_account(mm, mpnt->vm_flags, -vma_pages(mpnt));
440 continue;
441 }
442 charge = 0;
443 if (mpnt->vm_flags & VM_ACCOUNT) {
444 unsigned long len = vma_pages(mpnt);
445
446 if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
447 goto fail_nomem;
448 charge = len;
449 }
450 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
451 if (!tmp)
452 goto fail_nomem;
453 *tmp = *mpnt;
454 INIT_LIST_HEAD(&tmp->anon_vma_chain);
455 retval = vma_dup_policy(mpnt, tmp);
456 if (retval)
457 goto fail_nomem_policy;
458 tmp->vm_mm = mm;
459 retval = dup_userfaultfd(tmp, &uf);
460 if (retval)
461 goto fail_nomem_anon_vma_fork;
462 if (tmp->vm_flags & VM_WIPEONFORK) {
463 /* VM_WIPEONFORK gets a clean slate in the child. */
464 tmp->anon_vma = NULL;
465 if (anon_vma_prepare(tmp))
466 goto fail_nomem_anon_vma_fork;
467 } else if (anon_vma_fork(tmp, mpnt))
468 goto fail_nomem_anon_vma_fork;
469 tmp->vm_flags &= ~(VM_LOCKED | VM_LOCKONFAULT);
470 tmp->vm_next = tmp->vm_prev = NULL;
471 file = tmp->vm_file;
472 if (file) {
473 struct inode *inode = file_inode(file);
474 struct address_space *mapping = file->f_mapping;
475
476 get_file(file);
477 if (tmp->vm_flags & VM_DENYWRITE)
478 atomic_dec(&inode->i_writecount);
479 i_mmap_lock_write(mapping);
480 if (tmp->vm_flags & VM_SHARED)
481 atomic_inc(&mapping->i_mmap_writable);
482 flush_dcache_mmap_lock(mapping);
483 /* insert tmp into the share list, just after mpnt */
484 vma_interval_tree_insert_after(tmp, mpnt,
485 &mapping->i_mmap);
486 flush_dcache_mmap_unlock(mapping);
487 i_mmap_unlock_write(mapping);
488 }
489
490 /*
491 * Clear hugetlb-related page reserves for children. This only
492 * affects MAP_PRIVATE mappings. Faults generated by the child
493 * are not guaranteed to succeed, even if read-only
494 */
495 if (is_vm_hugetlb_page(tmp))
496 reset_vma_resv_huge_pages(tmp);
497
498 /*
499 * Link in the new vma and copy the page table entries.
500 */
501 *pprev = tmp;
502 pprev = &tmp->vm_next;
503 tmp->vm_prev = prev;
504 prev = tmp;
505
506 __vma_link_rb(mm, tmp, rb_link, rb_parent);
507 rb_link = &tmp->vm_rb.rb_right;
508 rb_parent = &tmp->vm_rb;
509
510 mm->map_count++;
511 if (!(tmp->vm_flags & VM_WIPEONFORK))
512 retval = copy_page_range(mm, oldmm, mpnt);
513
514 if (tmp->vm_ops && tmp->vm_ops->open)
515 tmp->vm_ops->open(tmp);
516
517 if (retval)
518 goto out;
519 }
520 /* a new mm has just been created */
521 arch_dup_mmap(oldmm, mm);
522 retval = 0;
523out:
524 up_write(&mm->mmap_sem);
525 flush_tlb_mm(oldmm);
526 up_write(&oldmm->mmap_sem);
527 dup_userfaultfd_complete(&uf);
528fail_uprobe_end:
529 uprobe_end_dup_mmap();
530 return retval;
531fail_nomem_anon_vma_fork:
532 mpol_put(vma_policy(tmp));
533fail_nomem_policy:
534 kmem_cache_free(vm_area_cachep, tmp);
535fail_nomem:
536 retval = -ENOMEM;
537 vm_unacct_memory(charge);
538 goto out;
539}
540
541static inline int mm_alloc_pgd(struct mm_struct *mm)
542{
543 mm->pgd = pgd_alloc(mm);
544 if (unlikely(!mm->pgd))
545 return -ENOMEM;
546 return 0;
547}
548
549static inline void mm_free_pgd(struct mm_struct *mm)
550{
551 pgd_free(mm, mm->pgd);
552}
553#else
554static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
555{
556 down_write(&oldmm->mmap_sem);
557 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
558 up_write(&oldmm->mmap_sem);
559 return 0;
560}
561#define mm_alloc_pgd(mm) (0)
562#define mm_free_pgd(mm)
563#endif /* CONFIG_MMU */
564
565static void check_mm(struct mm_struct *mm)
566{
567 int i;
568
569 for (i = 0; i < NR_MM_COUNTERS; i++) {
570 long x = atomic_long_read(&mm->rss_stat.count[i]);
571
572 if (unlikely(x))
573 printk(KERN_ALERT "BUG: Bad rss-counter state "
574 "mm:%p idx:%d val:%ld\n", mm, i, x);
575 }
576
577 if (mm_pgtables_bytes(mm))
578 pr_alert("BUG: non-zero pgtables_bytes on freeing mm: %ld\n",
579 mm_pgtables_bytes(mm));
580
581#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
582 VM_BUG_ON_MM(mm->pmd_huge_pte, mm);
583#endif
584}
585
586#define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
587#define free_mm(mm) (kmem_cache_free(mm_cachep, (mm)))
588
589/*
590 * Called when the last reference to the mm
591 * is dropped: either by a lazy thread or by
592 * mmput. Free the page directory and the mm.
593 */
594void __mmdrop(struct mm_struct *mm)
595{
596 BUG_ON(mm == &init_mm);
597 WARN_ON_ONCE(mm == current->mm);
598 WARN_ON_ONCE(mm == current->active_mm);
599 mm_free_pgd(mm);
600 destroy_context(mm);
601 hmm_mm_destroy(mm);
602 mmu_notifier_mm_destroy(mm);
603 check_mm(mm);
604 put_user_ns(mm->user_ns);
605 free_mm(mm);
606}
607EXPORT_SYMBOL_GPL(__mmdrop);
608
609static void mmdrop_async_fn(struct work_struct *work)
610{
611 struct mm_struct *mm;
612
613 mm = container_of(work, struct mm_struct, async_put_work);
614 __mmdrop(mm);
615}
616
617static void mmdrop_async(struct mm_struct *mm)
618{
619 if (unlikely(atomic_dec_and_test(&mm->mm_count))) {
620 INIT_WORK(&mm->async_put_work, mmdrop_async_fn);
621 schedule_work(&mm->async_put_work);
622 }
623}
624
625static inline void free_signal_struct(struct signal_struct *sig)
626{
627 taskstats_tgid_free(sig);
628 sched_autogroup_exit(sig);
629 /*
630 * __mmdrop is not safe to call from softirq context on x86 due to
631 * pgd_dtor so postpone it to the async context
632 */
633 if (sig->oom_mm)
634 mmdrop_async(sig->oom_mm);
635 kmem_cache_free(signal_cachep, sig);
636}
637
638static inline void put_signal_struct(struct signal_struct *sig)
639{
640 if (atomic_dec_and_test(&sig->sigcnt))
641 free_signal_struct(sig);
642}
643
644void __put_task_struct(struct task_struct *tsk)
645{
646 WARN_ON(!tsk->exit_state);
647 WARN_ON(atomic_read(&tsk->usage));
648 WARN_ON(tsk == current);
649
650 cgroup_free(tsk);
651 task_numa_free(tsk);
652 security_task_free(tsk);
653 exit_creds(tsk);
654 delayacct_tsk_free(tsk);
655 put_signal_struct(tsk->signal);
656
657 if (!profile_handoff_task(tsk))
658 free_task(tsk);
659}
660EXPORT_SYMBOL_GPL(__put_task_struct);
661
662void __init __weak arch_task_cache_init(void) { }
663
664/*
665 * set_max_threads
666 */
667static void set_max_threads(unsigned int max_threads_suggested)
668{
669 u64 threads;
670
671 /*
672 * The number of threads shall be limited such that the thread
673 * structures may only consume a small part of the available memory.
674 */
675 if (fls64(totalram_pages) + fls64(PAGE_SIZE) > 64)
676 threads = MAX_THREADS;
677 else
678 threads = div64_u64((u64) totalram_pages * (u64) PAGE_SIZE,
679 (u64) THREAD_SIZE * 8UL);
680
681 if (threads > max_threads_suggested)
682 threads = max_threads_suggested;
683
684 max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS);
685}
686
687#ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT
688/* Initialized by the architecture: */
689int arch_task_struct_size __read_mostly;
690#endif
691
692static void task_struct_whitelist(unsigned long *offset, unsigned long *size)
693{
694 /* Fetch thread_struct whitelist for the architecture. */
695 arch_thread_struct_whitelist(offset, size);
696
697 /*
698 * Handle zero-sized whitelist or empty thread_struct, otherwise
699 * adjust offset to position of thread_struct in task_struct.
700 */
701 if (unlikely(*size == 0))
702 *offset = 0;
703 else
704 *offset += offsetof(struct task_struct, thread);
705}
706
707void __init fork_init(void)
708{
709 int i;
710#ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
711#ifndef ARCH_MIN_TASKALIGN
712#define ARCH_MIN_TASKALIGN 0
713#endif
714 int align = max_t(int, L1_CACHE_BYTES, ARCH_MIN_TASKALIGN);
715 unsigned long useroffset, usersize;
716
717 /* create a slab on which task_structs can be allocated */
718 task_struct_whitelist(&useroffset, &usersize);
719 task_struct_cachep = kmem_cache_create_usercopy("task_struct",
720 arch_task_struct_size, align,
721 SLAB_PANIC|SLAB_ACCOUNT,
722 useroffset, usersize, NULL);
723#endif
724
725 /* do the arch specific task caches init */
726 arch_task_cache_init();
727
728 set_max_threads(MAX_THREADS);
729
730 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
731 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
732 init_task.signal->rlim[RLIMIT_SIGPENDING] =
733 init_task.signal->rlim[RLIMIT_NPROC];
734
735 for (i = 0; i < UCOUNT_COUNTS; i++) {
736 init_user_ns.ucount_max[i] = max_threads/2;
737 }
738
739#ifdef CONFIG_VMAP_STACK
740 cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "fork:vm_stack_cache",
741 NULL, free_vm_stack_cache);
742#endif
743
744 lockdep_init_task(&init_task);
745}
746
747int __weak arch_dup_task_struct(struct task_struct *dst,
748 struct task_struct *src)
749{
750 *dst = *src;
751 return 0;
752}
753
754void set_task_stack_end_magic(struct task_struct *tsk)
755{
756 unsigned long *stackend;
757
758 stackend = end_of_stack(tsk);
759 *stackend = STACK_END_MAGIC; /* for overflow detection */
760}
761
762static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
763{
764 struct task_struct *tsk;
765 unsigned long *stack;
766 struct vm_struct *stack_vm_area;
767 int err;
768
769 if (node == NUMA_NO_NODE)
770 node = tsk_fork_get_node(orig);
771 tsk = alloc_task_struct_node(node);
772 if (!tsk)
773 return NULL;
774
775 stack = alloc_thread_stack_node(tsk, node);
776 if (!stack)
777 goto free_tsk;
778
779 stack_vm_area = task_stack_vm_area(tsk);
780
781 err = arch_dup_task_struct(tsk, orig);
782
783 /*
784 * arch_dup_task_struct() clobbers the stack-related fields. Make
785 * sure they're properly initialized before using any stack-related
786 * functions again.
787 */
788 tsk->stack = stack;
789#ifdef CONFIG_VMAP_STACK
790 tsk->stack_vm_area = stack_vm_area;
791#endif
792#ifdef CONFIG_THREAD_INFO_IN_TASK
793 atomic_set(&tsk->stack_refcount, 1);
794#endif
795
796 if (err)
797 goto free_stack;
798
799#ifdef CONFIG_SECCOMP
800 /*
801 * We must handle setting up seccomp filters once we're under
802 * the sighand lock in case orig has changed between now and
803 * then. Until then, filter must be NULL to avoid messing up
804 * the usage counts on the error path calling free_task.
805 */
806 tsk->seccomp.filter = NULL;
807#endif
808
809 setup_thread_stack(tsk, orig);
810 clear_user_return_notifier(tsk);
811 clear_tsk_need_resched(tsk);
812 set_task_stack_end_magic(tsk);
813
814#ifdef CONFIG_CC_STACKPROTECTOR
815 tsk->stack_canary = get_random_canary();
816#endif
817
818 /*
819 * One for us, one for whoever does the "release_task()" (usually
820 * parent)
821 */
822 atomic_set(&tsk->usage, 2);
823#ifdef CONFIG_BLK_DEV_IO_TRACE
824 tsk->btrace_seq = 0;
825#endif
826 tsk->splice_pipe = NULL;
827 tsk->task_frag.page = NULL;
828 tsk->wake_q.next = NULL;
829
830 account_kernel_stack(tsk, 1);
831
832 kcov_task_init(tsk);
833
834#ifdef CONFIG_FAULT_INJECTION
835 tsk->fail_nth = 0;
836#endif
837
838 return tsk;
839
840free_stack:
841 free_thread_stack(tsk);
842free_tsk:
843 free_task_struct(tsk);
844 return NULL;
845}
846
847__cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
848
849static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
850
851static int __init coredump_filter_setup(char *s)
852{
853 default_dump_filter =
854 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
855 MMF_DUMP_FILTER_MASK;
856 return 1;
857}
858
859__setup("coredump_filter=", coredump_filter_setup);
860
861#include <linux/init_task.h>
862
863static void mm_init_aio(struct mm_struct *mm)
864{
865#ifdef CONFIG_AIO
866 spin_lock_init(&mm->ioctx_lock);
867 mm->ioctx_table = NULL;
868#endif
869}
870
871static void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
872{
873#ifdef CONFIG_MEMCG
874 mm->owner = p;
875#endif
876}
877
878static void mm_init_uprobes_state(struct mm_struct *mm)
879{
880#ifdef CONFIG_UPROBES
881 mm->uprobes_state.xol_area = NULL;
882#endif
883}
884
885static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
886 struct user_namespace *user_ns)
887{
888 mm->mmap = NULL;
889 mm->mm_rb = RB_ROOT;
890 mm->vmacache_seqnum = 0;
891 atomic_set(&mm->mm_users, 1);
892 atomic_set(&mm->mm_count, 1);
893 init_rwsem(&mm->mmap_sem);
894 INIT_LIST_HEAD(&mm->mmlist);
895 mm->core_state = NULL;
896 mm_pgtables_bytes_init(mm);
897 mm->map_count = 0;
898 mm->locked_vm = 0;
899 mm->pinned_vm = 0;
900 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
901 spin_lock_init(&mm->page_table_lock);
902 mm_init_cpumask(mm);
903 mm_init_aio(mm);
904 mm_init_owner(mm, p);
905 RCU_INIT_POINTER(mm->exe_file, NULL);
906 mmu_notifier_mm_init(mm);
907 hmm_mm_init(mm);
908 init_tlb_flush_pending(mm);
909#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
910 mm->pmd_huge_pte = NULL;
911#endif
912 mm_init_uprobes_state(mm);
913
914 if (current->mm) {
915 mm->flags = current->mm->flags & MMF_INIT_MASK;
916 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK;
917 } else {
918 mm->flags = default_dump_filter;
919 mm->def_flags = 0;
920 }
921
922 if (mm_alloc_pgd(mm))
923 goto fail_nopgd;
924
925 if (init_new_context(p, mm))
926 goto fail_nocontext;
927
928 mm->user_ns = get_user_ns(user_ns);
929 return mm;
930
931fail_nocontext:
932 mm_free_pgd(mm);
933fail_nopgd:
934 free_mm(mm);
935 return NULL;
936}
937
938/*
939 * Allocate and initialize an mm_struct.
940 */
941struct mm_struct *mm_alloc(void)
942{
943 struct mm_struct *mm;
944
945 mm = allocate_mm();
946 if (!mm)
947 return NULL;
948
949 memset(mm, 0, sizeof(*mm));
950 return mm_init(mm, current, current_user_ns());
951}
952
953static inline void __mmput(struct mm_struct *mm)
954{
955 VM_BUG_ON(atomic_read(&mm->mm_users));
956
957 uprobe_clear_state(mm);
958 exit_aio(mm);
959 ksm_exit(mm);
960 khugepaged_exit(mm); /* must run before exit_mmap */
961 exit_mmap(mm);
962 mm_put_huge_zero_page(mm);
963 set_mm_exe_file(mm, NULL);
964 if (!list_empty(&mm->mmlist)) {
965 spin_lock(&mmlist_lock);
966 list_del(&mm->mmlist);
967 spin_unlock(&mmlist_lock);
968 }
969 if (mm->binfmt)
970 module_put(mm->binfmt->module);
971 mmdrop(mm);
972}
973
974/*
975 * Decrement the use count and release all resources for an mm.
976 */
977void mmput(struct mm_struct *mm)
978{
979 might_sleep();
980
981 if (atomic_dec_and_test(&mm->mm_users))
982 __mmput(mm);
983}
984EXPORT_SYMBOL_GPL(mmput);
985
986#ifdef CONFIG_MMU
987static void mmput_async_fn(struct work_struct *work)
988{
989 struct mm_struct *mm = container_of(work, struct mm_struct,
990 async_put_work);
991
992 __mmput(mm);
993}
994
995void mmput_async(struct mm_struct *mm)
996{
997 if (atomic_dec_and_test(&mm->mm_users)) {
998 INIT_WORK(&mm->async_put_work, mmput_async_fn);
999 schedule_work(&mm->async_put_work);
1000 }
1001}
1002#endif
1003
1004/**
1005 * set_mm_exe_file - change a reference to the mm's executable file
1006 *
1007 * This changes mm's executable file (shown as symlink /proc/[pid]/exe).
1008 *
1009 * Main users are mmput() and sys_execve(). Callers prevent concurrent
1010 * invocations: in mmput() nobody alive left, in execve task is single
1011 * threaded. sys_prctl(PR_SET_MM_MAP/EXE_FILE) also needs to set the
1012 * mm->exe_file, but does so without using set_mm_exe_file() in order
1013 * to do avoid the need for any locks.
1014 */
1015void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
1016{
1017 struct file *old_exe_file;
1018
1019 /*
1020 * It is safe to dereference the exe_file without RCU as
1021 * this function is only called if nobody else can access
1022 * this mm -- see comment above for justification.
1023 */
1024 old_exe_file = rcu_dereference_raw(mm->exe_file);
1025
1026 if (new_exe_file)
1027 get_file(new_exe_file);
1028 rcu_assign_pointer(mm->exe_file, new_exe_file);
1029 if (old_exe_file)
1030 fput(old_exe_file);
1031}
1032
1033/**
1034 * get_mm_exe_file - acquire a reference to the mm's executable file
1035 *
1036 * Returns %NULL if mm has no associated executable file.
1037 * User must release file via fput().
1038 */
1039struct file *get_mm_exe_file(struct mm_struct *mm)
1040{
1041 struct file *exe_file;
1042
1043 rcu_read_lock();
1044 exe_file = rcu_dereference(mm->exe_file);
1045 if (exe_file && !get_file_rcu(exe_file))
1046 exe_file = NULL;
1047 rcu_read_unlock();
1048 return exe_file;
1049}
1050EXPORT_SYMBOL(get_mm_exe_file);
1051
1052/**
1053 * get_task_exe_file - acquire a reference to the task's executable file
1054 *
1055 * Returns %NULL if task's mm (if any) has no associated executable file or
1056 * this is a kernel thread with borrowed mm (see the comment above get_task_mm).
1057 * User must release file via fput().
1058 */
1059struct file *get_task_exe_file(struct task_struct *task)
1060{
1061 struct file *exe_file = NULL;
1062 struct mm_struct *mm;
1063
1064 task_lock(task);
1065 mm = task->mm;
1066 if (mm) {
1067 if (!(task->flags & PF_KTHREAD))
1068 exe_file = get_mm_exe_file(mm);
1069 }
1070 task_unlock(task);
1071 return exe_file;
1072}
1073EXPORT_SYMBOL(get_task_exe_file);
1074
1075/**
1076 * get_task_mm - acquire a reference to the task's mm
1077 *
1078 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning
1079 * this kernel workthread has transiently adopted a user mm with use_mm,
1080 * to do its AIO) is not set and if so returns a reference to it, after
1081 * bumping up the use count. User must release the mm via mmput()
1082 * after use. Typically used by /proc and ptrace.
1083 */
1084struct mm_struct *get_task_mm(struct task_struct *task)
1085{
1086 struct mm_struct *mm;
1087
1088 task_lock(task);
1089 mm = task->mm;
1090 if (mm) {
1091 if (task->flags & PF_KTHREAD)
1092 mm = NULL;
1093 else
1094 mmget(mm);
1095 }
1096 task_unlock(task);
1097 return mm;
1098}
1099EXPORT_SYMBOL_GPL(get_task_mm);
1100
1101struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
1102{
1103 struct mm_struct *mm;
1104 int err;
1105
1106 err = mutex_lock_killable(&task->signal->cred_guard_mutex);
1107 if (err)
1108 return ERR_PTR(err);
1109
1110 mm = get_task_mm(task);
1111 if (mm && mm != current->mm &&
1112 !ptrace_may_access(task, mode)) {
1113 mmput(mm);
1114 mm = ERR_PTR(-EACCES);
1115 }
1116 mutex_unlock(&task->signal->cred_guard_mutex);
1117
1118 return mm;
1119}
1120
1121static void complete_vfork_done(struct task_struct *tsk)
1122{
1123 struct completion *vfork;
1124
1125 task_lock(tsk);
1126 vfork = tsk->vfork_done;
1127 if (likely(vfork)) {
1128 tsk->vfork_done = NULL;
1129 complete(vfork);
1130 }
1131 task_unlock(tsk);
1132}
1133
1134static int wait_for_vfork_done(struct task_struct *child,
1135 struct completion *vfork)
1136{
1137 int killed;
1138
1139 freezer_do_not_count();
1140 killed = wait_for_completion_killable(vfork);
1141 freezer_count();
1142
1143 if (killed) {
1144 task_lock(child);
1145 child->vfork_done = NULL;
1146 task_unlock(child);
1147 }
1148
1149 put_task_struct(child);
1150 return killed;
1151}
1152
1153/* Please note the differences between mmput and mm_release.
1154 * mmput is called whenever we stop holding onto a mm_struct,
1155 * error success whatever.
1156 *
1157 * mm_release is called after a mm_struct has been removed
1158 * from the current process.
1159 *
1160 * This difference is important for error handling, when we
1161 * only half set up a mm_struct for a new process and need to restore
1162 * the old one. Because we mmput the new mm_struct before
1163 * restoring the old one. . .
1164 * Eric Biederman 10 January 1998
1165 */
1166void mm_release(struct task_struct *tsk, struct mm_struct *mm)
1167{
1168 /* Get rid of any futexes when releasing the mm */
1169#ifdef CONFIG_FUTEX
1170 if (unlikely(tsk->robust_list)) {
1171 exit_robust_list(tsk);
1172 tsk->robust_list = NULL;
1173 }
1174#ifdef CONFIG_COMPAT
1175 if (unlikely(tsk->compat_robust_list)) {
1176 compat_exit_robust_list(tsk);
1177 tsk->compat_robust_list = NULL;
1178 }
1179#endif
1180 if (unlikely(!list_empty(&tsk->pi_state_list)))
1181 exit_pi_state_list(tsk);
1182#endif
1183
1184 uprobe_free_utask(tsk);
1185
1186 /* Get rid of any cached register state */
1187 deactivate_mm(tsk, mm);
1188
1189 /*
1190 * Signal userspace if we're not exiting with a core dump
1191 * because we want to leave the value intact for debugging
1192 * purposes.
1193 */
1194 if (tsk->clear_child_tid) {
1195 if (!(tsk->signal->flags & SIGNAL_GROUP_COREDUMP) &&
1196 atomic_read(&mm->mm_users) > 1) {
1197 /*
1198 * We don't check the error code - if userspace has
1199 * not set up a proper pointer then tough luck.
1200 */
1201 put_user(0, tsk->clear_child_tid);
1202 do_futex(tsk->clear_child_tid, FUTEX_WAKE,
1203 1, NULL, NULL, 0, 0);
1204 }
1205 tsk->clear_child_tid = NULL;
1206 }
1207
1208 /*
1209 * All done, finally we can wake up parent and return this mm to him.
1210 * Also kthread_stop() uses this completion for synchronization.
1211 */
1212 if (tsk->vfork_done)
1213 complete_vfork_done(tsk);
1214}
1215
1216/*
1217 * Allocate a new mm structure and copy contents from the
1218 * mm structure of the passed in task structure.
1219 */
1220static struct mm_struct *dup_mm(struct task_struct *tsk)
1221{
1222 struct mm_struct *mm, *oldmm = current->mm;
1223 int err;
1224
1225 mm = allocate_mm();
1226 if (!mm)
1227 goto fail_nomem;
1228
1229 memcpy(mm, oldmm, sizeof(*mm));
1230
1231 if (!mm_init(mm, tsk, mm->user_ns))
1232 goto fail_nomem;
1233
1234 err = dup_mmap(mm, oldmm);
1235 if (err)
1236 goto free_pt;
1237
1238 mm->hiwater_rss = get_mm_rss(mm);
1239 mm->hiwater_vm = mm->total_vm;
1240
1241 if (mm->binfmt && !try_module_get(mm->binfmt->module))
1242 goto free_pt;
1243
1244 return mm;
1245
1246free_pt:
1247 /* don't put binfmt in mmput, we haven't got module yet */
1248 mm->binfmt = NULL;
1249 mmput(mm);
1250
1251fail_nomem:
1252 return NULL;
1253}
1254
1255static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
1256{
1257 struct mm_struct *mm, *oldmm;
1258 int retval;
1259
1260 tsk->min_flt = tsk->maj_flt = 0;
1261 tsk->nvcsw = tsk->nivcsw = 0;
1262#ifdef CONFIG_DETECT_HUNG_TASK
1263 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
1264#endif
1265
1266 tsk->mm = NULL;
1267 tsk->active_mm = NULL;
1268
1269 /*
1270 * Are we cloning a kernel thread?
1271 *
1272 * We need to steal a active VM for that..
1273 */
1274 oldmm = current->mm;
1275 if (!oldmm)
1276 return 0;
1277
1278 /* initialize the new vmacache entries */
1279 vmacache_flush(tsk);
1280
1281 if (clone_flags & CLONE_VM) {
1282 mmget(oldmm);
1283 mm = oldmm;
1284 goto good_mm;
1285 }
1286
1287 retval = -ENOMEM;
1288 mm = dup_mm(tsk);
1289 if (!mm)
1290 goto fail_nomem;
1291
1292good_mm:
1293 tsk->mm = mm;
1294 tsk->active_mm = mm;
1295 return 0;
1296
1297fail_nomem:
1298 return retval;
1299}
1300
1301static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
1302{
1303 struct fs_struct *fs = current->fs;
1304 if (clone_flags & CLONE_FS) {
1305 /* tsk->fs is already what we want */
1306 spin_lock(&fs->lock);
1307 if (fs->in_exec) {
1308 spin_unlock(&fs->lock);
1309 return -EAGAIN;
1310 }
1311 fs->users++;
1312 spin_unlock(&fs->lock);
1313 return 0;
1314 }
1315 tsk->fs = copy_fs_struct(fs);
1316 if (!tsk->fs)
1317 return -ENOMEM;
1318 return 0;
1319}
1320
1321static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
1322{
1323 struct files_struct *oldf, *newf;
1324 int error = 0;
1325
1326 /*
1327 * A background process may not have any files ...
1328 */
1329 oldf = current->files;
1330 if (!oldf)
1331 goto out;
1332
1333 if (clone_flags & CLONE_FILES) {
1334 atomic_inc(&oldf->count);
1335 goto out;
1336 }
1337
1338 newf = dup_fd(oldf, &error);
1339 if (!newf)
1340 goto out;
1341
1342 tsk->files = newf;
1343 error = 0;
1344out:
1345 return error;
1346}
1347
1348static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
1349{
1350#ifdef CONFIG_BLOCK
1351 struct io_context *ioc = current->io_context;
1352 struct io_context *new_ioc;
1353
1354 if (!ioc)
1355 return 0;
1356 /*
1357 * Share io context with parent, if CLONE_IO is set
1358 */
1359 if (clone_flags & CLONE_IO) {
1360 ioc_task_link(ioc);
1361 tsk->io_context = ioc;
1362 } else if (ioprio_valid(ioc->ioprio)) {
1363 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE);
1364 if (unlikely(!new_ioc))
1365 return -ENOMEM;
1366
1367 new_ioc->ioprio = ioc->ioprio;
1368 put_io_context(new_ioc);
1369 }
1370#endif
1371 return 0;
1372}
1373
1374static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
1375{
1376 struct sighand_struct *sig;
1377
1378 if (clone_flags & CLONE_SIGHAND) {
1379 atomic_inc(&current->sighand->count);
1380 return 0;
1381 }
1382 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1383 rcu_assign_pointer(tsk->sighand, sig);
1384 if (!sig)
1385 return -ENOMEM;
1386
1387 atomic_set(&sig->count, 1);
1388 memcpy(sig->action, current->sighand->action, sizeof(sig->action));
1389 return 0;
1390}
1391
1392void __cleanup_sighand(struct sighand_struct *sighand)
1393{
1394 if (atomic_dec_and_test(&sighand->count)) {
1395 signalfd_cleanup(sighand);
1396 /*
1397 * sighand_cachep is SLAB_TYPESAFE_BY_RCU so we can free it
1398 * without an RCU grace period, see __lock_task_sighand().
1399 */
1400 kmem_cache_free(sighand_cachep, sighand);
1401 }
1402}
1403
1404#ifdef CONFIG_POSIX_TIMERS
1405/*
1406 * Initialize POSIX timer handling for a thread group.
1407 */
1408static void posix_cpu_timers_init_group(struct signal_struct *sig)
1409{
1410 unsigned long cpu_limit;
1411
1412 cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1413 if (cpu_limit != RLIM_INFINITY) {
1414 sig->cputime_expires.prof_exp = cpu_limit * NSEC_PER_SEC;
1415 sig->cputimer.running = true;
1416 }
1417
1418 /* The timer lists. */
1419 INIT_LIST_HEAD(&sig->cpu_timers[0]);
1420 INIT_LIST_HEAD(&sig->cpu_timers[1]);
1421 INIT_LIST_HEAD(&sig->cpu_timers[2]);
1422}
1423#else
1424static inline void posix_cpu_timers_init_group(struct signal_struct *sig) { }
1425#endif
1426
1427static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
1428{
1429 struct signal_struct *sig;
1430
1431 if (clone_flags & CLONE_THREAD)
1432 return 0;
1433
1434 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
1435 tsk->signal = sig;
1436 if (!sig)
1437 return -ENOMEM;
1438
1439 sig->nr_threads = 1;
1440 atomic_set(&sig->live, 1);
1441 atomic_set(&sig->sigcnt, 1);
1442
1443 /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */
1444 sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node);
1445 tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head);
1446
1447 init_waitqueue_head(&sig->wait_chldexit);
1448 sig->curr_target = tsk;
1449 init_sigpending(&sig->shared_pending);
1450 seqlock_init(&sig->stats_lock);
1451 prev_cputime_init(&sig->prev_cputime);
1452
1453#ifdef CONFIG_POSIX_TIMERS
1454 INIT_LIST_HEAD(&sig->posix_timers);
1455 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1456 sig->real_timer.function = it_real_fn;
1457#endif
1458
1459 task_lock(current->group_leader);
1460 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
1461 task_unlock(current->group_leader);
1462
1463 posix_cpu_timers_init_group(sig);
1464
1465 tty_audit_fork(sig);
1466 sched_autogroup_fork(sig);
1467
1468 sig->oom_score_adj = current->signal->oom_score_adj;
1469 sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1470
1471 mutex_init(&sig->cred_guard_mutex);
1472
1473 return 0;
1474}
1475
1476static void copy_seccomp(struct task_struct *p)
1477{
1478#ifdef CONFIG_SECCOMP
1479 /*
1480 * Must be called with sighand->lock held, which is common to
1481 * all threads in the group. Holding cred_guard_mutex is not
1482 * needed because this new task is not yet running and cannot
1483 * be racing exec.
1484 */
1485 assert_spin_locked(&current->sighand->siglock);
1486
1487 /* Ref-count the new filter user, and assign it. */
1488 get_seccomp_filter(current);
1489 p->seccomp = current->seccomp;
1490
1491 /*
1492 * Explicitly enable no_new_privs here in case it got set
1493 * between the task_struct being duplicated and holding the
1494 * sighand lock. The seccomp state and nnp must be in sync.
1495 */
1496 if (task_no_new_privs(current))
1497 task_set_no_new_privs(p);
1498
1499 /*
1500 * If the parent gained a seccomp mode after copying thread
1501 * flags and between before we held the sighand lock, we have
1502 * to manually enable the seccomp thread flag here.
1503 */
1504 if (p->seccomp.mode != SECCOMP_MODE_DISABLED)
1505 set_tsk_thread_flag(p, TIF_SECCOMP);
1506#endif
1507}
1508
1509SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1510{
1511 current->clear_child_tid = tidptr;
1512
1513 return task_pid_vnr(current);
1514}
1515
1516static void rt_mutex_init_task(struct task_struct *p)
1517{
1518 raw_spin_lock_init(&p->pi_lock);
1519#ifdef CONFIG_RT_MUTEXES
1520 p->pi_waiters = RB_ROOT_CACHED;
1521 p->pi_top_task = NULL;
1522 p->pi_blocked_on = NULL;
1523#endif
1524}
1525
1526#ifdef CONFIG_POSIX_TIMERS
1527/*
1528 * Initialize POSIX timer handling for a single task.
1529 */
1530static void posix_cpu_timers_init(struct task_struct *tsk)
1531{
1532 tsk->cputime_expires.prof_exp = 0;
1533 tsk->cputime_expires.virt_exp = 0;
1534 tsk->cputime_expires.sched_exp = 0;
1535 INIT_LIST_HEAD(&tsk->cpu_timers[0]);
1536 INIT_LIST_HEAD(&tsk->cpu_timers[1]);
1537 INIT_LIST_HEAD(&tsk->cpu_timers[2]);
1538}
1539#else
1540static inline void posix_cpu_timers_init(struct task_struct *tsk) { }
1541#endif
1542
1543static inline void
1544init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid)
1545{
1546 task->pids[type].pid = pid;
1547}
1548
1549static inline void rcu_copy_process(struct task_struct *p)
1550{
1551#ifdef CONFIG_PREEMPT_RCU
1552 p->rcu_read_lock_nesting = 0;
1553 p->rcu_read_unlock_special.s = 0;
1554 p->rcu_blocked_node = NULL;
1555 INIT_LIST_HEAD(&p->rcu_node_entry);
1556#endif /* #ifdef CONFIG_PREEMPT_RCU */
1557#ifdef CONFIG_TASKS_RCU
1558 p->rcu_tasks_holdout = false;
1559 INIT_LIST_HEAD(&p->rcu_tasks_holdout_list);
1560 p->rcu_tasks_idle_cpu = -1;
1561#endif /* #ifdef CONFIG_TASKS_RCU */
1562}
1563
1564/*
1565 * This creates a new process as a copy of the old one,
1566 * but does not actually start it yet.
1567 *
1568 * It copies the registers, and all the appropriate
1569 * parts of the process environment (as per the clone
1570 * flags). The actual kick-off is left to the caller.
1571 */
1572static __latent_entropy struct task_struct *copy_process(
1573 unsigned long clone_flags,
1574 unsigned long stack_start,
1575 unsigned long stack_size,
1576 int __user *child_tidptr,
1577 struct pid *pid,
1578 int trace,
1579 unsigned long tls,
1580 int node)
1581{
1582 int retval;
1583 struct task_struct *p;
1584
1585 /*
1586 * Don't allow sharing the root directory with processes in a different
1587 * namespace
1588 */
1589 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1590 return ERR_PTR(-EINVAL);
1591
1592 if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS))
1593 return ERR_PTR(-EINVAL);
1594
1595 /*
1596 * Thread groups must share signals as well, and detached threads
1597 * can only be started up within the thread group.
1598 */
1599 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1600 return ERR_PTR(-EINVAL);
1601
1602 /*
1603 * Shared signal handlers imply shared VM. By way of the above,
1604 * thread groups also imply shared VM. Blocking this case allows
1605 * for various simplifications in other code.
1606 */
1607 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1608 return ERR_PTR(-EINVAL);
1609
1610 /*
1611 * Siblings of global init remain as zombies on exit since they are
1612 * not reaped by their parent (swapper). To solve this and to avoid
1613 * multi-rooted process trees, prevent global and container-inits
1614 * from creating siblings.
1615 */
1616 if ((clone_flags & CLONE_PARENT) &&
1617 current->signal->flags & SIGNAL_UNKILLABLE)
1618 return ERR_PTR(-EINVAL);
1619
1620 /*
1621 * If the new process will be in a different pid or user namespace
1622 * do not allow it to share a thread group with the forking task.
1623 */
1624 if (clone_flags & CLONE_THREAD) {
1625 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) ||
1626 (task_active_pid_ns(current) !=
1627 current->nsproxy->pid_ns_for_children))
1628 return ERR_PTR(-EINVAL);
1629 }
1630
1631 retval = -ENOMEM;
1632 p = dup_task_struct(current, node);
1633 if (!p)
1634 goto fork_out;
1635
1636 /*
1637 * This _must_ happen before we call free_task(), i.e. before we jump
1638 * to any of the bad_fork_* labels. This is to avoid freeing
1639 * p->set_child_tid which is (ab)used as a kthread's data pointer for
1640 * kernel threads (PF_KTHREAD).
1641 */
1642 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1643 /*
1644 * Clear TID on mm_release()?
1645 */
1646 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL;
1647
1648 ftrace_graph_init_task(p);
1649
1650 rt_mutex_init_task(p);
1651
1652#ifdef CONFIG_PROVE_LOCKING
1653 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1654 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1655#endif
1656 retval = -EAGAIN;
1657 if (atomic_read(&p->real_cred->user->processes) >=
1658 task_rlimit(p, RLIMIT_NPROC)) {
1659 if (p->real_cred->user != INIT_USER &&
1660 !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
1661 goto bad_fork_free;
1662 }
1663 current->flags &= ~PF_NPROC_EXCEEDED;
1664
1665 retval = copy_creds(p, clone_flags);
1666 if (retval < 0)
1667 goto bad_fork_free;
1668
1669 /*
1670 * If multiple threads are within copy_process(), then this check
1671 * triggers too late. This doesn't hurt, the check is only there
1672 * to stop root fork bombs.
1673 */
1674 retval = -EAGAIN;
1675 if (nr_threads >= max_threads)
1676 goto bad_fork_cleanup_count;
1677
1678 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */
1679 p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER | PF_IDLE);
1680 p->flags |= PF_FORKNOEXEC;
1681 INIT_LIST_HEAD(&p->children);
1682 INIT_LIST_HEAD(&p->sibling);
1683 rcu_copy_process(p);
1684 p->vfork_done = NULL;
1685 spin_lock_init(&p->alloc_lock);
1686
1687 init_sigpending(&p->pending);
1688
1689 p->utime = p->stime = p->gtime = 0;
1690#ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
1691 p->utimescaled = p->stimescaled = 0;
1692#endif
1693 prev_cputime_init(&p->prev_cputime);
1694
1695#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
1696 seqcount_init(&p->vtime.seqcount);
1697 p->vtime.starttime = 0;
1698 p->vtime.state = VTIME_INACTIVE;
1699#endif
1700
1701#if defined(SPLIT_RSS_COUNTING)
1702 memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1703#endif
1704
1705 p->default_timer_slack_ns = current->timer_slack_ns;
1706
1707 task_io_accounting_init(&p->ioac);
1708 acct_clear_integrals(p);
1709
1710 posix_cpu_timers_init(p);
1711
1712 p->start_time = ktime_get_ns();
1713 p->real_start_time = ktime_get_boot_ns();
1714 p->io_context = NULL;
1715 p->audit_context = NULL;
1716 cgroup_fork(p);
1717#ifdef CONFIG_NUMA
1718 p->mempolicy = mpol_dup(p->mempolicy);
1719 if (IS_ERR(p->mempolicy)) {
1720 retval = PTR_ERR(p->mempolicy);
1721 p->mempolicy = NULL;
1722 goto bad_fork_cleanup_threadgroup_lock;
1723 }
1724#endif
1725#ifdef CONFIG_CPUSETS
1726 p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
1727 p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
1728 seqcount_init(&p->mems_allowed_seq);
1729#endif
1730#ifdef CONFIG_TRACE_IRQFLAGS
1731 p->irq_events = 0;
1732 p->hardirqs_enabled = 0;
1733 p->hardirq_enable_ip = 0;
1734 p->hardirq_enable_event = 0;
1735 p->hardirq_disable_ip = _THIS_IP_;
1736 p->hardirq_disable_event = 0;
1737 p->softirqs_enabled = 1;
1738 p->softirq_enable_ip = _THIS_IP_;
1739 p->softirq_enable_event = 0;
1740 p->softirq_disable_ip = 0;
1741 p->softirq_disable_event = 0;
1742 p->hardirq_context = 0;
1743 p->softirq_context = 0;
1744#endif
1745
1746 p->pagefault_disabled = 0;
1747
1748#ifdef CONFIG_LOCKDEP
1749 p->lockdep_depth = 0; /* no locks held yet */
1750 p->curr_chain_key = 0;
1751 p->lockdep_recursion = 0;
1752 lockdep_init_task(p);
1753#endif
1754
1755#ifdef CONFIG_DEBUG_MUTEXES
1756 p->blocked_on = NULL; /* not blocked yet */
1757#endif
1758#ifdef CONFIG_BCACHE
1759 p->sequential_io = 0;
1760 p->sequential_io_avg = 0;
1761#endif
1762
1763 /* Perform scheduler related setup. Assign this task to a CPU. */
1764 retval = sched_fork(clone_flags, p);
1765 if (retval)
1766 goto bad_fork_cleanup_policy;
1767
1768 retval = perf_event_init_task(p);
1769 if (retval)
1770 goto bad_fork_cleanup_policy;
1771 retval = audit_alloc(p);
1772 if (retval)
1773 goto bad_fork_cleanup_perf;
1774 /* copy all the process information */
1775 shm_init_task(p);
1776 retval = security_task_alloc(p, clone_flags);
1777 if (retval)
1778 goto bad_fork_cleanup_audit;
1779 retval = copy_semundo(clone_flags, p);
1780 if (retval)
1781 goto bad_fork_cleanup_security;
1782 retval = copy_files(clone_flags, p);
1783 if (retval)
1784 goto bad_fork_cleanup_semundo;
1785 retval = copy_fs(clone_flags, p);
1786 if (retval)
1787 goto bad_fork_cleanup_files;
1788 retval = copy_sighand(clone_flags, p);
1789 if (retval)
1790 goto bad_fork_cleanup_fs;
1791 retval = copy_signal(clone_flags, p);
1792 if (retval)
1793 goto bad_fork_cleanup_sighand;
1794 retval = copy_mm(clone_flags, p);
1795 if (retval)
1796 goto bad_fork_cleanup_signal;
1797 retval = copy_namespaces(clone_flags, p);
1798 if (retval)
1799 goto bad_fork_cleanup_mm;
1800 retval = copy_io(clone_flags, p);
1801 if (retval)
1802 goto bad_fork_cleanup_namespaces;
1803 retval = copy_thread_tls(clone_flags, stack_start, stack_size, p, tls);
1804 if (retval)
1805 goto bad_fork_cleanup_io;
1806
1807 if (pid != &init_struct_pid) {
1808 pid = alloc_pid(p->nsproxy->pid_ns_for_children);
1809 if (IS_ERR(pid)) {
1810 retval = PTR_ERR(pid);
1811 goto bad_fork_cleanup_thread;
1812 }
1813 }
1814
1815#ifdef CONFIG_BLOCK
1816 p->plug = NULL;
1817#endif
1818#ifdef CONFIG_FUTEX
1819 p->robust_list = NULL;
1820#ifdef CONFIG_COMPAT
1821 p->compat_robust_list = NULL;
1822#endif
1823 INIT_LIST_HEAD(&p->pi_state_list);
1824 p->pi_state_cache = NULL;
1825#endif
1826 /*
1827 * sigaltstack should be cleared when sharing the same VM
1828 */
1829 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1830 sas_ss_reset(p);
1831
1832 /*
1833 * Syscall tracing and stepping should be turned off in the
1834 * child regardless of CLONE_PTRACE.
1835 */
1836 user_disable_single_step(p);
1837 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1838#ifdef TIF_SYSCALL_EMU
1839 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1840#endif
1841 clear_all_latency_tracing(p);
1842
1843 /* ok, now we should be set up.. */
1844 p->pid = pid_nr(pid);
1845 if (clone_flags & CLONE_THREAD) {
1846 p->exit_signal = -1;
1847 p->group_leader = current->group_leader;
1848 p->tgid = current->tgid;
1849 } else {
1850 if (clone_flags & CLONE_PARENT)
1851 p->exit_signal = current->group_leader->exit_signal;
1852 else
1853 p->exit_signal = (clone_flags & CSIGNAL);
1854 p->group_leader = p;
1855 p->tgid = p->pid;
1856 }
1857
1858 p->nr_dirtied = 0;
1859 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
1860 p->dirty_paused_when = 0;
1861
1862 p->pdeath_signal = 0;
1863 INIT_LIST_HEAD(&p->thread_group);
1864 p->task_works = NULL;
1865
1866 cgroup_threadgroup_change_begin(current);
1867 /*
1868 * Ensure that the cgroup subsystem policies allow the new process to be
1869 * forked. It should be noted the the new process's css_set can be changed
1870 * between here and cgroup_post_fork() if an organisation operation is in
1871 * progress.
1872 */
1873 retval = cgroup_can_fork(p);
1874 if (retval)
1875 goto bad_fork_free_pid;
1876
1877 /*
1878 * Make it visible to the rest of the system, but dont wake it up yet.
1879 * Need tasklist lock for parent etc handling!
1880 */
1881 write_lock_irq(&tasklist_lock);
1882
1883 /* CLONE_PARENT re-uses the old parent */
1884 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1885 p->real_parent = current->real_parent;
1886 p->parent_exec_id = current->parent_exec_id;
1887 } else {
1888 p->real_parent = current;
1889 p->parent_exec_id = current->self_exec_id;
1890 }
1891
1892 klp_copy_process(p);
1893
1894 spin_lock(&current->sighand->siglock);
1895
1896 /*
1897 * Copy seccomp details explicitly here, in case they were changed
1898 * before holding sighand lock.
1899 */
1900 copy_seccomp(p);
1901
1902 /*
1903 * Process group and session signals need to be delivered to just the
1904 * parent before the fork or both the parent and the child after the
1905 * fork. Restart if a signal comes in before we add the new process to
1906 * it's process group.
1907 * A fatal signal pending means that current will exit, so the new
1908 * thread can't slip out of an OOM kill (or normal SIGKILL).
1909 */
1910 recalc_sigpending();
1911 if (signal_pending(current)) {
1912 retval = -ERESTARTNOINTR;
1913 goto bad_fork_cancel_cgroup;
1914 }
1915 if (unlikely(!(ns_of_pid(pid)->pid_allocated & PIDNS_ADDING))) {
1916 retval = -ENOMEM;
1917 goto bad_fork_cancel_cgroup;
1918 }
1919
1920 if (likely(p->pid)) {
1921 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
1922
1923 init_task_pid(p, PIDTYPE_PID, pid);
1924 if (thread_group_leader(p)) {
1925 init_task_pid(p, PIDTYPE_PGID, task_pgrp(current));
1926 init_task_pid(p, PIDTYPE_SID, task_session(current));
1927
1928 if (is_child_reaper(pid)) {
1929 ns_of_pid(pid)->child_reaper = p;
1930 p->signal->flags |= SIGNAL_UNKILLABLE;
1931 }
1932
1933 p->signal->leader_pid = pid;
1934 p->signal->tty = tty_kref_get(current->signal->tty);
1935 /*
1936 * Inherit has_child_subreaper flag under the same
1937 * tasklist_lock with adding child to the process tree
1938 * for propagate_has_child_subreaper optimization.
1939 */
1940 p->signal->has_child_subreaper = p->real_parent->signal->has_child_subreaper ||
1941 p->real_parent->signal->is_child_subreaper;
1942 list_add_tail(&p->sibling, &p->real_parent->children);
1943 list_add_tail_rcu(&p->tasks, &init_task.tasks);
1944 attach_pid(p, PIDTYPE_PGID);
1945 attach_pid(p, PIDTYPE_SID);
1946 __this_cpu_inc(process_counts);
1947 } else {
1948 current->signal->nr_threads++;
1949 atomic_inc(&current->signal->live);
1950 atomic_inc(&current->signal->sigcnt);
1951 list_add_tail_rcu(&p->thread_group,
1952 &p->group_leader->thread_group);
1953 list_add_tail_rcu(&p->thread_node,
1954 &p->signal->thread_head);
1955 }
1956 attach_pid(p, PIDTYPE_PID);
1957 nr_threads++;
1958 }
1959
1960 total_forks++;
1961 spin_unlock(&current->sighand->siglock);
1962 syscall_tracepoint_update(p);
1963 write_unlock_irq(&tasklist_lock);
1964
1965 proc_fork_connector(p);
1966 cgroup_post_fork(p);
1967 cgroup_threadgroup_change_end(current);
1968 perf_event_fork(p);
1969
1970 trace_task_newtask(p, clone_flags);
1971 uprobe_copy_process(p, clone_flags);
1972
1973 return p;
1974
1975bad_fork_cancel_cgroup:
1976 spin_unlock(&current->sighand->siglock);
1977 write_unlock_irq(&tasklist_lock);
1978 cgroup_cancel_fork(p);
1979bad_fork_free_pid:
1980 cgroup_threadgroup_change_end(current);
1981 if (pid != &init_struct_pid)
1982 free_pid(pid);
1983bad_fork_cleanup_thread:
1984 exit_thread(p);
1985bad_fork_cleanup_io:
1986 if (p->io_context)
1987 exit_io_context(p);
1988bad_fork_cleanup_namespaces:
1989 exit_task_namespaces(p);
1990bad_fork_cleanup_mm:
1991 if (p->mm)
1992 mmput(p->mm);
1993bad_fork_cleanup_signal:
1994 if (!(clone_flags & CLONE_THREAD))
1995 free_signal_struct(p->signal);
1996bad_fork_cleanup_sighand:
1997 __cleanup_sighand(p->sighand);
1998bad_fork_cleanup_fs:
1999 exit_fs(p); /* blocking */
2000bad_fork_cleanup_files:
2001 exit_files(p); /* blocking */
2002bad_fork_cleanup_semundo:
2003 exit_sem(p);
2004bad_fork_cleanup_security:
2005 security_task_free(p);
2006bad_fork_cleanup_audit:
2007 audit_free(p);
2008bad_fork_cleanup_perf:
2009 perf_event_free_task(p);
2010bad_fork_cleanup_policy:
2011 lockdep_free_task(p);
2012#ifdef CONFIG_NUMA
2013 mpol_put(p->mempolicy);
2014bad_fork_cleanup_threadgroup_lock:
2015#endif
2016 delayacct_tsk_free(p);
2017bad_fork_cleanup_count:
2018 atomic_dec(&p->cred->user->processes);
2019 exit_creds(p);
2020bad_fork_free:
2021 p->state = TASK_DEAD;
2022 put_task_stack(p);
2023 free_task(p);
2024fork_out:
2025 return ERR_PTR(retval);
2026}
2027
2028static inline void init_idle_pids(struct pid_link *links)
2029{
2030 enum pid_type type;
2031
2032 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
2033 INIT_HLIST_NODE(&links[type].node); /* not really needed */
2034 links[type].pid = &init_struct_pid;
2035 }
2036}
2037
2038struct task_struct *fork_idle(int cpu)
2039{
2040 struct task_struct *task;
2041 task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0, 0,
2042 cpu_to_node(cpu));
2043 if (!IS_ERR(task)) {
2044 init_idle_pids(task->pids);
2045 init_idle(task, cpu);
2046 }
2047
2048 return task;
2049}
2050
2051/*
2052 * Ok, this is the main fork-routine.
2053 *
2054 * It copies the process, and if successful kick-starts
2055 * it and waits for it to finish using the VM if required.
2056 */
2057long _do_fork(unsigned long clone_flags,
2058 unsigned long stack_start,
2059 unsigned long stack_size,
2060 int __user *parent_tidptr,
2061 int __user *child_tidptr,
2062 unsigned long tls)
2063{
2064 struct completion vfork;
2065 struct pid *pid;
2066 struct task_struct *p;
2067 int trace = 0;
2068 long nr;
2069
2070 /*
2071 * Determine whether and which event to report to ptracer. When
2072 * called from kernel_thread or CLONE_UNTRACED is explicitly
2073 * requested, no event is reported; otherwise, report if the event
2074 * for the type of forking is enabled.
2075 */
2076 if (!(clone_flags & CLONE_UNTRACED)) {
2077 if (clone_flags & CLONE_VFORK)
2078 trace = PTRACE_EVENT_VFORK;
2079 else if ((clone_flags & CSIGNAL) != SIGCHLD)
2080 trace = PTRACE_EVENT_CLONE;
2081 else
2082 trace = PTRACE_EVENT_FORK;
2083
2084 if (likely(!ptrace_event_enabled(current, trace)))
2085 trace = 0;
2086 }
2087
2088 p = copy_process(clone_flags, stack_start, stack_size,
2089 child_tidptr, NULL, trace, tls, NUMA_NO_NODE);
2090 add_latent_entropy();
2091
2092 if (IS_ERR(p))
2093 return PTR_ERR(p);
2094
2095 /*
2096 * Do this prior waking up the new thread - the thread pointer
2097 * might get invalid after that point, if the thread exits quickly.
2098 */
2099 trace_sched_process_fork(current, p);
2100
2101 pid = get_task_pid(p, PIDTYPE_PID);
2102 nr = pid_vnr(pid);
2103
2104 if (clone_flags & CLONE_PARENT_SETTID)
2105 put_user(nr, parent_tidptr);
2106
2107 if (clone_flags & CLONE_VFORK) {
2108 p->vfork_done = &vfork;
2109 init_completion(&vfork);
2110 get_task_struct(p);
2111 }
2112
2113 wake_up_new_task(p);
2114
2115 /* forking complete and child started to run, tell ptracer */
2116 if (unlikely(trace))
2117 ptrace_event_pid(trace, pid);
2118
2119 if (clone_flags & CLONE_VFORK) {
2120 if (!wait_for_vfork_done(p, &vfork))
2121 ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid);
2122 }
2123
2124 put_pid(pid);
2125 return nr;
2126}
2127
2128#ifndef CONFIG_HAVE_COPY_THREAD_TLS
2129/* For compatibility with architectures that call do_fork directly rather than
2130 * using the syscall entry points below. */
2131long do_fork(unsigned long clone_flags,
2132 unsigned long stack_start,
2133 unsigned long stack_size,
2134 int __user *parent_tidptr,
2135 int __user *child_tidptr)
2136{
2137 return _do_fork(clone_flags, stack_start, stack_size,
2138 parent_tidptr, child_tidptr, 0);
2139}
2140#endif
2141
2142/*
2143 * Create a kernel thread.
2144 */
2145pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
2146{
2147 return _do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn,
2148 (unsigned long)arg, NULL, NULL, 0);
2149}
2150
2151#ifdef __ARCH_WANT_SYS_FORK
2152SYSCALL_DEFINE0(fork)
2153{
2154#ifdef CONFIG_MMU
2155 return _do_fork(SIGCHLD, 0, 0, NULL, NULL, 0);
2156#else
2157 /* can not support in nommu mode */
2158 return -EINVAL;
2159#endif
2160}
2161#endif
2162
2163#ifdef __ARCH_WANT_SYS_VFORK
2164SYSCALL_DEFINE0(vfork)
2165{
2166 return _do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0,
2167 0, NULL, NULL, 0);
2168}
2169#endif
2170
2171#ifdef __ARCH_WANT_SYS_CLONE
2172#ifdef CONFIG_CLONE_BACKWARDS
2173SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2174 int __user *, parent_tidptr,
2175 unsigned long, tls,
2176 int __user *, child_tidptr)
2177#elif defined(CONFIG_CLONE_BACKWARDS2)
2178SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags,
2179 int __user *, parent_tidptr,
2180 int __user *, child_tidptr,
2181 unsigned long, tls)
2182#elif defined(CONFIG_CLONE_BACKWARDS3)
2183SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp,
2184 int, stack_size,
2185 int __user *, parent_tidptr,
2186 int __user *, child_tidptr,
2187 unsigned long, tls)
2188#else
2189SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2190 int __user *, parent_tidptr,
2191 int __user *, child_tidptr,
2192 unsigned long, tls)
2193#endif
2194{
2195 return _do_fork(clone_flags, newsp, 0, parent_tidptr, child_tidptr, tls);
2196}
2197#endif
2198
2199void walk_process_tree(struct task_struct *top, proc_visitor visitor, void *data)
2200{
2201 struct task_struct *leader, *parent, *child;
2202 int res;
2203
2204 read_lock(&tasklist_lock);
2205 leader = top = top->group_leader;
2206down:
2207 for_each_thread(leader, parent) {
2208 list_for_each_entry(child, &parent->children, sibling) {
2209 res = visitor(child, data);
2210 if (res) {
2211 if (res < 0)
2212 goto out;
2213 leader = child;
2214 goto down;
2215 }
2216up:
2217 ;
2218 }
2219 }
2220
2221 if (leader != top) {
2222 child = leader;
2223 parent = child->real_parent;
2224 leader = parent->group_leader;
2225 goto up;
2226 }
2227out:
2228 read_unlock(&tasklist_lock);
2229}
2230
2231#ifndef ARCH_MIN_MMSTRUCT_ALIGN
2232#define ARCH_MIN_MMSTRUCT_ALIGN 0
2233#endif
2234
2235static void sighand_ctor(void *data)
2236{
2237 struct sighand_struct *sighand = data;
2238
2239 spin_lock_init(&sighand->siglock);
2240 init_waitqueue_head(&sighand->signalfd_wqh);
2241}
2242
2243void __init proc_caches_init(void)
2244{
2245 sighand_cachep = kmem_cache_create("sighand_cache",
2246 sizeof(struct sighand_struct), 0,
2247 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_TYPESAFE_BY_RCU|
2248 SLAB_ACCOUNT, sighand_ctor);
2249 signal_cachep = kmem_cache_create("signal_cache",
2250 sizeof(struct signal_struct), 0,
2251 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2252 NULL);
2253 files_cachep = kmem_cache_create("files_cache",
2254 sizeof(struct files_struct), 0,
2255 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2256 NULL);
2257 fs_cachep = kmem_cache_create("fs_cache",
2258 sizeof(struct fs_struct), 0,
2259 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2260 NULL);
2261 /*
2262 * FIXME! The "sizeof(struct mm_struct)" currently includes the
2263 * whole struct cpumask for the OFFSTACK case. We could change
2264 * this to *only* allocate as much of it as required by the
2265 * maximum number of CPU's we can ever have. The cpumask_allocation
2266 * is at the end of the structure, exactly for that reason.
2267 */
2268 mm_cachep = kmem_cache_create_usercopy("mm_struct",
2269 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
2270 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2271 offsetof(struct mm_struct, saved_auxv),
2272 sizeof_field(struct mm_struct, saved_auxv),
2273 NULL);
2274 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT);
2275 mmap_init();
2276 nsproxy_cache_init();
2277}
2278
2279/*
2280 * Check constraints on flags passed to the unshare system call.
2281 */
2282static int check_unshare_flags(unsigned long unshare_flags)
2283{
2284 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
2285 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
2286 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET|
2287 CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP))
2288 return -EINVAL;
2289 /*
2290 * Not implemented, but pretend it works if there is nothing
2291 * to unshare. Note that unsharing the address space or the
2292 * signal handlers also need to unshare the signal queues (aka
2293 * CLONE_THREAD).
2294 */
2295 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
2296 if (!thread_group_empty(current))
2297 return -EINVAL;
2298 }
2299 if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) {
2300 if (atomic_read(&current->sighand->count) > 1)
2301 return -EINVAL;
2302 }
2303 if (unshare_flags & CLONE_VM) {
2304 if (!current_is_single_threaded())
2305 return -EINVAL;
2306 }
2307
2308 return 0;
2309}
2310
2311/*
2312 * Unshare the filesystem structure if it is being shared
2313 */
2314static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
2315{
2316 struct fs_struct *fs = current->fs;
2317
2318 if (!(unshare_flags & CLONE_FS) || !fs)
2319 return 0;
2320
2321 /* don't need lock here; in the worst case we'll do useless copy */
2322 if (fs->users == 1)
2323 return 0;
2324
2325 *new_fsp = copy_fs_struct(fs);
2326 if (!*new_fsp)
2327 return -ENOMEM;
2328
2329 return 0;
2330}
2331
2332/*
2333 * Unshare file descriptor table if it is being shared
2334 */
2335static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
2336{
2337 struct files_struct *fd = current->files;
2338 int error = 0;
2339
2340 if ((unshare_flags & CLONE_FILES) &&
2341 (fd && atomic_read(&fd->count) > 1)) {
2342 *new_fdp = dup_fd(fd, &error);
2343 if (!*new_fdp)
2344 return error;
2345 }
2346
2347 return 0;
2348}
2349
2350/*
2351 * unshare allows a process to 'unshare' part of the process
2352 * context which was originally shared using clone. copy_*
2353 * functions used by do_fork() cannot be used here directly
2354 * because they modify an inactive task_struct that is being
2355 * constructed. Here we are modifying the current, active,
2356 * task_struct.
2357 */
2358int ksys_unshare(unsigned long unshare_flags)
2359{
2360 struct fs_struct *fs, *new_fs = NULL;
2361 struct files_struct *fd, *new_fd = NULL;
2362 struct cred *new_cred = NULL;
2363 struct nsproxy *new_nsproxy = NULL;
2364 int do_sysvsem = 0;
2365 int err;
2366
2367 /*
2368 * If unsharing a user namespace must also unshare the thread group
2369 * and unshare the filesystem root and working directories.
2370 */
2371 if (unshare_flags & CLONE_NEWUSER)
2372 unshare_flags |= CLONE_THREAD | CLONE_FS;
2373 /*
2374 * If unsharing vm, must also unshare signal handlers.
2375 */
2376 if (unshare_flags & CLONE_VM)
2377 unshare_flags |= CLONE_SIGHAND;
2378 /*
2379 * If unsharing a signal handlers, must also unshare the signal queues.
2380 */
2381 if (unshare_flags & CLONE_SIGHAND)
2382 unshare_flags |= CLONE_THREAD;
2383 /*
2384 * If unsharing namespace, must also unshare filesystem information.
2385 */
2386 if (unshare_flags & CLONE_NEWNS)
2387 unshare_flags |= CLONE_FS;
2388
2389 err = check_unshare_flags(unshare_flags);
2390 if (err)
2391 goto bad_unshare_out;
2392 /*
2393 * CLONE_NEWIPC must also detach from the undolist: after switching
2394 * to a new ipc namespace, the semaphore arrays from the old
2395 * namespace are unreachable.
2396 */
2397 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
2398 do_sysvsem = 1;
2399 err = unshare_fs(unshare_flags, &new_fs);
2400 if (err)
2401 goto bad_unshare_out;
2402 err = unshare_fd(unshare_flags, &new_fd);
2403 if (err)
2404 goto bad_unshare_cleanup_fs;
2405 err = unshare_userns(unshare_flags, &new_cred);
2406 if (err)
2407 goto bad_unshare_cleanup_fd;
2408 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
2409 new_cred, new_fs);
2410 if (err)
2411 goto bad_unshare_cleanup_cred;
2412
2413 if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
2414 if (do_sysvsem) {
2415 /*
2416 * CLONE_SYSVSEM is equivalent to sys_exit().
2417 */
2418 exit_sem(current);
2419 }
2420 if (unshare_flags & CLONE_NEWIPC) {
2421 /* Orphan segments in old ns (see sem above). */
2422 exit_shm(current);
2423 shm_init_task(current);
2424 }
2425
2426 if (new_nsproxy)
2427 switch_task_namespaces(current, new_nsproxy);
2428
2429 task_lock(current);
2430
2431 if (new_fs) {
2432 fs = current->fs;
2433 spin_lock(&fs->lock);
2434 current->fs = new_fs;
2435 if (--fs->users)
2436 new_fs = NULL;
2437 else
2438 new_fs = fs;
2439 spin_unlock(&fs->lock);
2440 }
2441
2442 if (new_fd) {
2443 fd = current->files;
2444 current->files = new_fd;
2445 new_fd = fd;
2446 }
2447
2448 task_unlock(current);
2449
2450 if (new_cred) {
2451 /* Install the new user namespace */
2452 commit_creds(new_cred);
2453 new_cred = NULL;
2454 }
2455 }
2456
2457 perf_event_namespaces(current);
2458
2459bad_unshare_cleanup_cred:
2460 if (new_cred)
2461 put_cred(new_cred);
2462bad_unshare_cleanup_fd:
2463 if (new_fd)
2464 put_files_struct(new_fd);
2465
2466bad_unshare_cleanup_fs:
2467 if (new_fs)
2468 free_fs_struct(new_fs);
2469
2470bad_unshare_out:
2471 return err;
2472}
2473
2474SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
2475{
2476 return ksys_unshare(unshare_flags);
2477}
2478
2479/*
2480 * Helper to unshare the files of the current task.
2481 * We don't want to expose copy_files internals to
2482 * the exec layer of the kernel.
2483 */
2484
2485int unshare_files(struct files_struct **displaced)
2486{
2487 struct task_struct *task = current;
2488 struct files_struct *copy = NULL;
2489 int error;
2490
2491 error = unshare_fd(CLONE_FILES, &copy);
2492 if (error || !copy) {
2493 *displaced = NULL;
2494 return error;
2495 }
2496 *displaced = task->files;
2497 task_lock(task);
2498 task->files = copy;
2499 task_unlock(task);
2500 return 0;
2501}
2502
2503int sysctl_max_threads(struct ctl_table *table, int write,
2504 void __user *buffer, size_t *lenp, loff_t *ppos)
2505{
2506 struct ctl_table t;
2507 int ret;
2508 int threads = max_threads;
2509 int min = MIN_THREADS;
2510 int max = MAX_THREADS;
2511
2512 t = *table;
2513 t.data = &threads;
2514 t.extra1 = &min;
2515 t.extra2 = &max;
2516
2517 ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
2518 if (ret || !write)
2519 return ret;
2520
2521 set_max_threads(threads);
2522
2523 return 0;
2524}