projects/linux·blob v5.5-rc7 · refs

3061 lines · 73.5 KiB

1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * linux/kernel/fork.c
4 *
5 * Copyright (C) 1991, 1992 Linus Torvalds
6 */
7
8/*
9 * 'fork.c' contains the help-routines for the 'fork' system call
10 * (see also entry.S and others).
11 * Fork is rather simple, once you get the hang of it, but the memory
12 * management can be a bitch. See 'mm/memory.c': 'copy_page_range()'
13 */
14
15#include <linux/anon_inodes.h>
16#include <linux/slab.h>
17#include <linux/sched/autogroup.h>
18#include <linux/sched/mm.h>
19#include <linux/sched/coredump.h>
20#include <linux/sched/user.h>
21#include <linux/sched/numa_balancing.h>
22#include <linux/sched/stat.h>
23#include <linux/sched/task.h>
24#include <linux/sched/task_stack.h>
25#include <linux/sched/cputime.h>
26#include <linux/seq_file.h>
27#include <linux/rtmutex.h>
28#include <linux/init.h>
29#include <linux/unistd.h>
30#include <linux/module.h>
31#include <linux/vmalloc.h>
32#include <linux/completion.h>
33#include <linux/personality.h>
34#include <linux/mempolicy.h>
35#include <linux/sem.h>
36#include <linux/file.h>
37#include <linux/fdtable.h>
38#include <linux/iocontext.h>
39#include <linux/key.h>
40#include <linux/binfmts.h>
41#include <linux/mman.h>
42#include <linux/mmu_notifier.h>
43#include <linux/fs.h>
44#include <linux/mm.h>
45#include <linux/vmacache.h>
46#include <linux/nsproxy.h>
47#include <linux/capability.h>
48#include <linux/cpu.h>
49#include <linux/cgroup.h>
50#include <linux/security.h>
51#include <linux/hugetlb.h>
52#include <linux/seccomp.h>
53#include <linux/swap.h>
54#include <linux/syscalls.h>
55#include <linux/jiffies.h>
56#include <linux/futex.h>
57#include <linux/compat.h>
58#include <linux/kthread.h>
59#include <linux/task_io_accounting_ops.h>
60#include <linux/rcupdate.h>
61#include <linux/ptrace.h>
62#include <linux/mount.h>
63#include <linux/audit.h>
64#include <linux/memcontrol.h>
65#include <linux/ftrace.h>
66#include <linux/proc_fs.h>
67#include <linux/profile.h>
68#include <linux/rmap.h>
69#include <linux/ksm.h>
70#include <linux/acct.h>
71#include <linux/userfaultfd_k.h>
72#include <linux/tsacct_kern.h>
73#include <linux/cn_proc.h>
74#include <linux/freezer.h>
75#include <linux/delayacct.h>
76#include <linux/taskstats_kern.h>
77#include <linux/random.h>
78#include <linux/tty.h>
79#include <linux/blkdev.h>
80#include <linux/fs_struct.h>
81#include <linux/magic.h>
82#include <linux/perf_event.h>
83#include <linux/posix-timers.h>
84#include <linux/user-return-notifier.h>
85#include <linux/oom.h>
86#include <linux/khugepaged.h>
87#include <linux/signalfd.h>
88#include <linux/uprobes.h>
89#include <linux/aio.h>
90#include <linux/compiler.h>
91#include <linux/sysctl.h>
92#include <linux/kcov.h>
93#include <linux/livepatch.h>
94#include <linux/thread_info.h>
95#include <linux/stackleak.h>
96#include <linux/kasan.h>
97
98#include <asm/pgtable.h>
99#include <asm/pgalloc.h>
100#include <linux/uaccess.h>
101#include <asm/mmu_context.h>
102#include <asm/cacheflush.h>
103#include <asm/tlbflush.h>
104
105#include <trace/events/sched.h>
106
107#define CREATE_TRACE_POINTS
108#include <trace/events/task.h>
109
110/*
111 * Minimum number of threads to boot the kernel
112 */
113#define MIN_THREADS 20
114
115/*
116 * Maximum number of threads
117 */
118#define MAX_THREADS FUTEX_TID_MASK
119
120/*
121 * Protected counters by write_lock_irq(&tasklist_lock)
122 */
123unsigned long total_forks; /* Handle normal Linux uptimes. */
124int nr_threads; /* The idle threads do not count.. */
125
126static int max_threads; /* tunable limit on nr_threads */
127
128#define NAMED_ARRAY_INDEX(x) [x] = __stringify(x)
129
130static const char * const resident_page_types[] = {
131 NAMED_ARRAY_INDEX(MM_FILEPAGES),
132 NAMED_ARRAY_INDEX(MM_ANONPAGES),
133 NAMED_ARRAY_INDEX(MM_SWAPENTS),
134 NAMED_ARRAY_INDEX(MM_SHMEMPAGES),
135};
136
137DEFINE_PER_CPU(unsigned long, process_counts) = 0;
138
139__cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */
140
141#ifdef CONFIG_PROVE_RCU
142int lockdep_tasklist_lock_is_held(void)
143{
144 return lockdep_is_held(&tasklist_lock);
145}
146EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
147#endif /* #ifdef CONFIG_PROVE_RCU */
148
149int nr_processes(void)
150{
151 int cpu;
152 int total = 0;
153
154 for_each_possible_cpu(cpu)
155 total += per_cpu(process_counts, cpu);
156
157 return total;
158}
159
160void __weak arch_release_task_struct(struct task_struct *tsk)
161{
162}
163
164#ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
165static struct kmem_cache *task_struct_cachep;
166
167static inline struct task_struct *alloc_task_struct_node(int node)
168{
169 return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node);
170}
171
172static inline void free_task_struct(struct task_struct *tsk)
173{
174 kmem_cache_free(task_struct_cachep, tsk);
175}
176#endif
177
178#ifndef CONFIG_ARCH_THREAD_STACK_ALLOCATOR
179
180/*
181 * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
182 * kmemcache based allocator.
183 */
184# if THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK)
185
186#ifdef CONFIG_VMAP_STACK
187/*
188 * vmalloc() is a bit slow, and calling vfree() enough times will force a TLB
189 * flush. Try to minimize the number of calls by caching stacks.
190 */
191#define NR_CACHED_STACKS 2
192static DEFINE_PER_CPU(struct vm_struct *, cached_stacks[NR_CACHED_STACKS]);
193
194static int free_vm_stack_cache(unsigned int cpu)
195{
196 struct vm_struct **cached_vm_stacks = per_cpu_ptr(cached_stacks, cpu);
197 int i;
198
199 for (i = 0; i < NR_CACHED_STACKS; i++) {
200 struct vm_struct *vm_stack = cached_vm_stacks[i];
201
202 if (!vm_stack)
203 continue;
204
205 vfree(vm_stack->addr);
206 cached_vm_stacks[i] = NULL;
207 }
208
209 return 0;
210}
211#endif
212
213static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node)
214{
215#ifdef CONFIG_VMAP_STACK
216 void *stack;
217 int i;
218
219 for (i = 0; i < NR_CACHED_STACKS; i++) {
220 struct vm_struct *s;
221
222 s = this_cpu_xchg(cached_stacks[i], NULL);
223
224 if (!s)
225 continue;
226
227 /* Clear the KASAN shadow of the stack. */
228 kasan_unpoison_shadow(s->addr, THREAD_SIZE);
229
230 /* Clear stale pointers from reused stack. */
231 memset(s->addr, 0, THREAD_SIZE);
232
233 tsk->stack_vm_area = s;
234 tsk->stack = s->addr;
235 return s->addr;
236 }
237
238 /*
239 * Allocated stacks are cached and later reused by new threads,
240 * so memcg accounting is performed manually on assigning/releasing
241 * stacks to tasks. Drop __GFP_ACCOUNT.
242 */
243 stack = __vmalloc_node_range(THREAD_SIZE, THREAD_ALIGN,
244 VMALLOC_START, VMALLOC_END,
245 THREADINFO_GFP & ~__GFP_ACCOUNT,
246 PAGE_KERNEL,
247 0, node, __builtin_return_address(0));
248
249 /*
250 * We can't call find_vm_area() in interrupt context, and
251 * free_thread_stack() can be called in interrupt context,
252 * so cache the vm_struct.
253 */
254 if (stack) {
255 tsk->stack_vm_area = find_vm_area(stack);
256 tsk->stack = stack;
257 }
258 return stack;
259#else
260 struct page *page = alloc_pages_node(node, THREADINFO_GFP,
261 THREAD_SIZE_ORDER);
262
263 if (likely(page)) {
264 tsk->stack = page_address(page);
265 return tsk->stack;
266 }
267 return NULL;
268#endif
269}
270
271static inline void free_thread_stack(struct task_struct *tsk)
272{
273#ifdef CONFIG_VMAP_STACK
274 struct vm_struct *vm = task_stack_vm_area(tsk);
275
276 if (vm) {
277 int i;
278
279 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
280 mod_memcg_page_state(vm->pages[i],
281 MEMCG_KERNEL_STACK_KB,
282 -(int)(PAGE_SIZE / 1024));
283
284 memcg_kmem_uncharge(vm->pages[i], 0);
285 }
286
287 for (i = 0; i < NR_CACHED_STACKS; i++) {
288 if (this_cpu_cmpxchg(cached_stacks[i],
289 NULL, tsk->stack_vm_area) != NULL)
290 continue;
291
292 return;
293 }
294
295 vfree_atomic(tsk->stack);
296 return;
297 }
298#endif
299
300 __free_pages(virt_to_page(tsk->stack), THREAD_SIZE_ORDER);
301}
302# else
303static struct kmem_cache *thread_stack_cache;
304
305static unsigned long *alloc_thread_stack_node(struct task_struct *tsk,
306 int node)
307{
308 unsigned long *stack;
309 stack = kmem_cache_alloc_node(thread_stack_cache, THREADINFO_GFP, node);
310 tsk->stack = stack;
311 return stack;
312}
313
314static void free_thread_stack(struct task_struct *tsk)
315{
316 kmem_cache_free(thread_stack_cache, tsk->stack);
317}
318
319void thread_stack_cache_init(void)
320{
321 thread_stack_cache = kmem_cache_create_usercopy("thread_stack",
322 THREAD_SIZE, THREAD_SIZE, 0, 0,
323 THREAD_SIZE, NULL);
324 BUG_ON(thread_stack_cache == NULL);
325}
326# endif
327#endif
328
329/* SLAB cache for signal_struct structures (tsk->signal) */
330static struct kmem_cache *signal_cachep;
331
332/* SLAB cache for sighand_struct structures (tsk->sighand) */
333struct kmem_cache *sighand_cachep;
334
335/* SLAB cache for files_struct structures (tsk->files) */
336struct kmem_cache *files_cachep;
337
338/* SLAB cache for fs_struct structures (tsk->fs) */
339struct kmem_cache *fs_cachep;
340
341/* SLAB cache for vm_area_struct structures */
342static struct kmem_cache *vm_area_cachep;
343
344/* SLAB cache for mm_struct structures (tsk->mm) */
345static struct kmem_cache *mm_cachep;
346
347struct vm_area_struct *vm_area_alloc(struct mm_struct *mm)
348{
349 struct vm_area_struct *vma;
350
351 vma = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
352 if (vma)
353 vma_init(vma, mm);
354 return vma;
355}
356
357struct vm_area_struct *vm_area_dup(struct vm_area_struct *orig)
358{
359 struct vm_area_struct *new = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
360
361 if (new) {
362 *new = *orig;
363 INIT_LIST_HEAD(&new->anon_vma_chain);
364 }
365 return new;
366}
367
368void vm_area_free(struct vm_area_struct *vma)
369{
370 kmem_cache_free(vm_area_cachep, vma);
371}
372
373static void account_kernel_stack(struct task_struct *tsk, int account)
374{
375 void *stack = task_stack_page(tsk);
376 struct vm_struct *vm = task_stack_vm_area(tsk);
377
378 BUILD_BUG_ON(IS_ENABLED(CONFIG_VMAP_STACK) && PAGE_SIZE % 1024 != 0);
379
380 if (vm) {
381 int i;
382
383 BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE);
384
385 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
386 mod_zone_page_state(page_zone(vm->pages[i]),
387 NR_KERNEL_STACK_KB,
388 PAGE_SIZE / 1024 * account);
389 }
390 } else {
391 /*
392 * All stack pages are in the same zone and belong to the
393 * same memcg.
394 */
395 struct page *first_page = virt_to_page(stack);
396
397 mod_zone_page_state(page_zone(first_page), NR_KERNEL_STACK_KB,
398 THREAD_SIZE / 1024 * account);
399
400 mod_memcg_page_state(first_page, MEMCG_KERNEL_STACK_KB,
401 account * (THREAD_SIZE / 1024));
402 }
403}
404
405static int memcg_charge_kernel_stack(struct task_struct *tsk)
406{
407#ifdef CONFIG_VMAP_STACK
408 struct vm_struct *vm = task_stack_vm_area(tsk);
409 int ret;
410
411 if (vm) {
412 int i;
413
414 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
415 /*
416 * If memcg_kmem_charge() fails, page->mem_cgroup
417 * pointer is NULL, and both memcg_kmem_uncharge()
418 * and mod_memcg_page_state() in free_thread_stack()
419 * will ignore this page. So it's safe.
420 */
421 ret = memcg_kmem_charge(vm->pages[i], GFP_KERNEL, 0);
422 if (ret)
423 return ret;
424
425 mod_memcg_page_state(vm->pages[i],
426 MEMCG_KERNEL_STACK_KB,
427 PAGE_SIZE / 1024);
428 }
429 }
430#endif
431 return 0;
432}
433
434static void release_task_stack(struct task_struct *tsk)
435{
436 if (WARN_ON(tsk->state != TASK_DEAD))
437 return; /* Better to leak the stack than to free prematurely */
438
439 account_kernel_stack(tsk, -1);
440 free_thread_stack(tsk);
441 tsk->stack = NULL;
442#ifdef CONFIG_VMAP_STACK
443 tsk->stack_vm_area = NULL;
444#endif
445}
446
447#ifdef CONFIG_THREAD_INFO_IN_TASK
448void put_task_stack(struct task_struct *tsk)
449{
450 if (refcount_dec_and_test(&tsk->stack_refcount))
451 release_task_stack(tsk);
452}
453#endif
454
455void free_task(struct task_struct *tsk)
456{
457#ifndef CONFIG_THREAD_INFO_IN_TASK
458 /*
459 * The task is finally done with both the stack and thread_info,
460 * so free both.
461 */
462 release_task_stack(tsk);
463#else
464 /*
465 * If the task had a separate stack allocation, it should be gone
466 * by now.
467 */
468 WARN_ON_ONCE(refcount_read(&tsk->stack_refcount) != 0);
469#endif
470 rt_mutex_debug_task_free(tsk);
471 ftrace_graph_exit_task(tsk);
472 put_seccomp_filter(tsk);
473 arch_release_task_struct(tsk);
474 if (tsk->flags & PF_KTHREAD)
475 free_kthread_struct(tsk);
476 free_task_struct(tsk);
477}
478EXPORT_SYMBOL(free_task);
479
480#ifdef CONFIG_MMU
481static __latent_entropy int dup_mmap(struct mm_struct *mm,
482 struct mm_struct *oldmm)
483{
484 struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
485 struct rb_node **rb_link, *rb_parent;
486 int retval;
487 unsigned long charge;
488 LIST_HEAD(uf);
489
490 uprobe_start_dup_mmap();
491 if (down_write_killable(&oldmm->mmap_sem)) {
492 retval = -EINTR;
493 goto fail_uprobe_end;
494 }
495 flush_cache_dup_mm(oldmm);
496 uprobe_dup_mmap(oldmm, mm);
497 /*
498 * Not linked in yet - no deadlock potential:
499 */
500 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
501
502 /* No ordering required: file already has been exposed. */
503 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
504
505 mm->total_vm = oldmm->total_vm;
506 mm->data_vm = oldmm->data_vm;
507 mm->exec_vm = oldmm->exec_vm;
508 mm->stack_vm = oldmm->stack_vm;
509
510 rb_link = &mm->mm_rb.rb_node;
511 rb_parent = NULL;
512 pprev = &mm->mmap;
513 retval = ksm_fork(mm, oldmm);
514 if (retval)
515 goto out;
516 retval = khugepaged_fork(mm, oldmm);
517 if (retval)
518 goto out;
519
520 prev = NULL;
521 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
522 struct file *file;
523
524 if (mpnt->vm_flags & VM_DONTCOPY) {
525 vm_stat_account(mm, mpnt->vm_flags, -vma_pages(mpnt));
526 continue;
527 }
528 charge = 0;
529 /*
530 * Don't duplicate many vmas if we've been oom-killed (for
531 * example)
532 */
533 if (fatal_signal_pending(current)) {
534 retval = -EINTR;
535 goto out;
536 }
537 if (mpnt->vm_flags & VM_ACCOUNT) {
538 unsigned long len = vma_pages(mpnt);
539
540 if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
541 goto fail_nomem;
542 charge = len;
543 }
544 tmp = vm_area_dup(mpnt);
545 if (!tmp)
546 goto fail_nomem;
547 retval = vma_dup_policy(mpnt, tmp);
548 if (retval)
549 goto fail_nomem_policy;
550 tmp->vm_mm = mm;
551 retval = dup_userfaultfd(tmp, &uf);
552 if (retval)
553 goto fail_nomem_anon_vma_fork;
554 if (tmp->vm_flags & VM_WIPEONFORK) {
555 /* VM_WIPEONFORK gets a clean slate in the child. */
556 tmp->anon_vma = NULL;
557 if (anon_vma_prepare(tmp))
558 goto fail_nomem_anon_vma_fork;
559 } else if (anon_vma_fork(tmp, mpnt))
560 goto fail_nomem_anon_vma_fork;
561 tmp->vm_flags &= ~(VM_LOCKED | VM_LOCKONFAULT);
562 tmp->vm_next = tmp->vm_prev = NULL;
563 file = tmp->vm_file;
564 if (file) {
565 struct inode *inode = file_inode(file);
566 struct address_space *mapping = file->f_mapping;
567
568 get_file(file);
569 if (tmp->vm_flags & VM_DENYWRITE)
570 atomic_dec(&inode->i_writecount);
571 i_mmap_lock_write(mapping);
572 if (tmp->vm_flags & VM_SHARED)
573 atomic_inc(&mapping->i_mmap_writable);
574 flush_dcache_mmap_lock(mapping);
575 /* insert tmp into the share list, just after mpnt */
576 vma_interval_tree_insert_after(tmp, mpnt,
577 &mapping->i_mmap);
578 flush_dcache_mmap_unlock(mapping);
579 i_mmap_unlock_write(mapping);
580 }
581
582 /*
583 * Clear hugetlb-related page reserves for children. This only
584 * affects MAP_PRIVATE mappings. Faults generated by the child
585 * are not guaranteed to succeed, even if read-only
586 */
587 if (is_vm_hugetlb_page(tmp))
588 reset_vma_resv_huge_pages(tmp);
589
590 /*
591 * Link in the new vma and copy the page table entries.
592 */
593 *pprev = tmp;
594 pprev = &tmp->vm_next;
595 tmp->vm_prev = prev;
596 prev = tmp;
597
598 __vma_link_rb(mm, tmp, rb_link, rb_parent);
599 rb_link = &tmp->vm_rb.rb_right;
600 rb_parent = &tmp->vm_rb;
601
602 mm->map_count++;
603 if (!(tmp->vm_flags & VM_WIPEONFORK))
604 retval = copy_page_range(mm, oldmm, mpnt);
605
606 if (tmp->vm_ops && tmp->vm_ops->open)
607 tmp->vm_ops->open(tmp);
608
609 if (retval)
610 goto out;
611 }
612 /* a new mm has just been created */
613 retval = arch_dup_mmap(oldmm, mm);
614out:
615 up_write(&mm->mmap_sem);
616 flush_tlb_mm(oldmm);
617 up_write(&oldmm->mmap_sem);
618 dup_userfaultfd_complete(&uf);
619fail_uprobe_end:
620 uprobe_end_dup_mmap();
621 return retval;
622fail_nomem_anon_vma_fork:
623 mpol_put(vma_policy(tmp));
624fail_nomem_policy:
625 vm_area_free(tmp);
626fail_nomem:
627 retval = -ENOMEM;
628 vm_unacct_memory(charge);
629 goto out;
630}
631
632static inline int mm_alloc_pgd(struct mm_struct *mm)
633{
634 mm->pgd = pgd_alloc(mm);
635 if (unlikely(!mm->pgd))
636 return -ENOMEM;
637 return 0;
638}
639
640static inline void mm_free_pgd(struct mm_struct *mm)
641{
642 pgd_free(mm, mm->pgd);
643}
644#else
645static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
646{
647 down_write(&oldmm->mmap_sem);
648 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
649 up_write(&oldmm->mmap_sem);
650 return 0;
651}
652#define mm_alloc_pgd(mm) (0)
653#define mm_free_pgd(mm)
654#endif /* CONFIG_MMU */
655
656static void check_mm(struct mm_struct *mm)
657{
658 int i;
659
660 BUILD_BUG_ON_MSG(ARRAY_SIZE(resident_page_types) != NR_MM_COUNTERS,
661 "Please make sure 'struct resident_page_types[]' is updated as well");
662
663 for (i = 0; i < NR_MM_COUNTERS; i++) {
664 long x = atomic_long_read(&mm->rss_stat.count[i]);
665
666 if (unlikely(x))
667 pr_alert("BUG: Bad rss-counter state mm:%p type:%s val:%ld\n",
668 mm, resident_page_types[i], x);
669 }
670
671 if (mm_pgtables_bytes(mm))
672 pr_alert("BUG: non-zero pgtables_bytes on freeing mm: %ld\n",
673 mm_pgtables_bytes(mm));
674
675#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
676 VM_BUG_ON_MM(mm->pmd_huge_pte, mm);
677#endif
678}
679
680#define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
681#define free_mm(mm) (kmem_cache_free(mm_cachep, (mm)))
682
683/*
684 * Called when the last reference to the mm
685 * is dropped: either by a lazy thread or by
686 * mmput. Free the page directory and the mm.
687 */
688void __mmdrop(struct mm_struct *mm)
689{
690 BUG_ON(mm == &init_mm);
691 WARN_ON_ONCE(mm == current->mm);
692 WARN_ON_ONCE(mm == current->active_mm);
693 mm_free_pgd(mm);
694 destroy_context(mm);
695 mmu_notifier_mm_destroy(mm);
696 check_mm(mm);
697 put_user_ns(mm->user_ns);
698 free_mm(mm);
699}
700EXPORT_SYMBOL_GPL(__mmdrop);
701
702static void mmdrop_async_fn(struct work_struct *work)
703{
704 struct mm_struct *mm;
705
706 mm = container_of(work, struct mm_struct, async_put_work);
707 __mmdrop(mm);
708}
709
710static void mmdrop_async(struct mm_struct *mm)
711{
712 if (unlikely(atomic_dec_and_test(&mm->mm_count))) {
713 INIT_WORK(&mm->async_put_work, mmdrop_async_fn);
714 schedule_work(&mm->async_put_work);
715 }
716}
717
718static inline void free_signal_struct(struct signal_struct *sig)
719{
720 taskstats_tgid_free(sig);
721 sched_autogroup_exit(sig);
722 /*
723 * __mmdrop is not safe to call from softirq context on x86 due to
724 * pgd_dtor so postpone it to the async context
725 */
726 if (sig->oom_mm)
727 mmdrop_async(sig->oom_mm);
728 kmem_cache_free(signal_cachep, sig);
729}
730
731static inline void put_signal_struct(struct signal_struct *sig)
732{
733 if (refcount_dec_and_test(&sig->sigcnt))
734 free_signal_struct(sig);
735}
736
737void __put_task_struct(struct task_struct *tsk)
738{
739 WARN_ON(!tsk->exit_state);
740 WARN_ON(refcount_read(&tsk->usage));
741 WARN_ON(tsk == current);
742
743 cgroup_free(tsk);
744 task_numa_free(tsk, true);
745 security_task_free(tsk);
746 exit_creds(tsk);
747 delayacct_tsk_free(tsk);
748 put_signal_struct(tsk->signal);
749
750 if (!profile_handoff_task(tsk))
751 free_task(tsk);
752}
753EXPORT_SYMBOL_GPL(__put_task_struct);
754
755void __init __weak arch_task_cache_init(void) { }
756
757/*
758 * set_max_threads
759 */
760static void set_max_threads(unsigned int max_threads_suggested)
761{
762 u64 threads;
763 unsigned long nr_pages = totalram_pages();
764
765 /*
766 * The number of threads shall be limited such that the thread
767 * structures may only consume a small part of the available memory.
768 */
769 if (fls64(nr_pages) + fls64(PAGE_SIZE) > 64)
770 threads = MAX_THREADS;
771 else
772 threads = div64_u64((u64) nr_pages * (u64) PAGE_SIZE,
773 (u64) THREAD_SIZE * 8UL);
774
775 if (threads > max_threads_suggested)
776 threads = max_threads_suggested;
777
778 max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS);
779}
780
781#ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT
782/* Initialized by the architecture: */
783int arch_task_struct_size __read_mostly;
784#endif
785
786#ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
787static void task_struct_whitelist(unsigned long *offset, unsigned long *size)
788{
789 /* Fetch thread_struct whitelist for the architecture. */
790 arch_thread_struct_whitelist(offset, size);
791
792 /*
793 * Handle zero-sized whitelist or empty thread_struct, otherwise
794 * adjust offset to position of thread_struct in task_struct.
795 */
796 if (unlikely(*size == 0))
797 *offset = 0;
798 else
799 *offset += offsetof(struct task_struct, thread);
800}
801#endif /* CONFIG_ARCH_TASK_STRUCT_ALLOCATOR */
802
803void __init fork_init(void)
804{
805 int i;
806#ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
807#ifndef ARCH_MIN_TASKALIGN
808#define ARCH_MIN_TASKALIGN 0
809#endif
810 int align = max_t(int, L1_CACHE_BYTES, ARCH_MIN_TASKALIGN);
811 unsigned long useroffset, usersize;
812
813 /* create a slab on which task_structs can be allocated */
814 task_struct_whitelist(&useroffset, &usersize);
815 task_struct_cachep = kmem_cache_create_usercopy("task_struct",
816 arch_task_struct_size, align,
817 SLAB_PANIC|SLAB_ACCOUNT,
818 useroffset, usersize, NULL);
819#endif
820
821 /* do the arch specific task caches init */
822 arch_task_cache_init();
823
824 set_max_threads(MAX_THREADS);
825
826 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
827 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
828 init_task.signal->rlim[RLIMIT_SIGPENDING] =
829 init_task.signal->rlim[RLIMIT_NPROC];
830
831 for (i = 0; i < UCOUNT_COUNTS; i++) {
832 init_user_ns.ucount_max[i] = max_threads/2;
833 }
834
835#ifdef CONFIG_VMAP_STACK
836 cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "fork:vm_stack_cache",
837 NULL, free_vm_stack_cache);
838#endif
839
840 lockdep_init_task(&init_task);
841 uprobes_init();
842}
843
844int __weak arch_dup_task_struct(struct task_struct *dst,
845 struct task_struct *src)
846{
847 *dst = *src;
848 return 0;
849}
850
851void set_task_stack_end_magic(struct task_struct *tsk)
852{
853 unsigned long *stackend;
854
855 stackend = end_of_stack(tsk);
856 *stackend = STACK_END_MAGIC; /* for overflow detection */
857}
858
859static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
860{
861 struct task_struct *tsk;
862 unsigned long *stack;
863 struct vm_struct *stack_vm_area __maybe_unused;
864 int err;
865
866 if (node == NUMA_NO_NODE)
867 node = tsk_fork_get_node(orig);
868 tsk = alloc_task_struct_node(node);
869 if (!tsk)
870 return NULL;
871
872 stack = alloc_thread_stack_node(tsk, node);
873 if (!stack)
874 goto free_tsk;
875
876 if (memcg_charge_kernel_stack(tsk))
877 goto free_stack;
878
879 stack_vm_area = task_stack_vm_area(tsk);
880
881 err = arch_dup_task_struct(tsk, orig);
882
883 /*
884 * arch_dup_task_struct() clobbers the stack-related fields. Make
885 * sure they're properly initialized before using any stack-related
886 * functions again.
887 */
888 tsk->stack = stack;
889#ifdef CONFIG_VMAP_STACK
890 tsk->stack_vm_area = stack_vm_area;
891#endif
892#ifdef CONFIG_THREAD_INFO_IN_TASK
893 refcount_set(&tsk->stack_refcount, 1);
894#endif
895
896 if (err)
897 goto free_stack;
898
899#ifdef CONFIG_SECCOMP
900 /*
901 * We must handle setting up seccomp filters once we're under
902 * the sighand lock in case orig has changed between now and
903 * then. Until then, filter must be NULL to avoid messing up
904 * the usage counts on the error path calling free_task.
905 */
906 tsk->seccomp.filter = NULL;
907#endif
908
909 setup_thread_stack(tsk, orig);
910 clear_user_return_notifier(tsk);
911 clear_tsk_need_resched(tsk);
912 set_task_stack_end_magic(tsk);
913
914#ifdef CONFIG_STACKPROTECTOR
915 tsk->stack_canary = get_random_canary();
916#endif
917 if (orig->cpus_ptr == &orig->cpus_mask)
918 tsk->cpus_ptr = &tsk->cpus_mask;
919
920 /*
921 * One for the user space visible state that goes away when reaped.
922 * One for the scheduler.
923 */
924 refcount_set(&tsk->rcu_users, 2);
925 /* One for the rcu users */
926 refcount_set(&tsk->usage, 1);
927#ifdef CONFIG_BLK_DEV_IO_TRACE
928 tsk->btrace_seq = 0;
929#endif
930 tsk->splice_pipe = NULL;
931 tsk->task_frag.page = NULL;
932 tsk->wake_q.next = NULL;
933
934 account_kernel_stack(tsk, 1);
935
936 kcov_task_init(tsk);
937
938#ifdef CONFIG_FAULT_INJECTION
939 tsk->fail_nth = 0;
940#endif
941
942#ifdef CONFIG_BLK_CGROUP
943 tsk->throttle_queue = NULL;
944 tsk->use_memdelay = 0;
945#endif
946
947#ifdef CONFIG_MEMCG
948 tsk->active_memcg = NULL;
949#endif
950 return tsk;
951
952free_stack:
953 free_thread_stack(tsk);
954free_tsk:
955 free_task_struct(tsk);
956 return NULL;
957}
958
959__cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
960
961static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
962
963static int __init coredump_filter_setup(char *s)
964{
965 default_dump_filter =
966 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
967 MMF_DUMP_FILTER_MASK;
968 return 1;
969}
970
971__setup("coredump_filter=", coredump_filter_setup);
972
973#include <linux/init_task.h>
974
975static void mm_init_aio(struct mm_struct *mm)
976{
977#ifdef CONFIG_AIO
978 spin_lock_init(&mm->ioctx_lock);
979 mm->ioctx_table = NULL;
980#endif
981}
982
983static __always_inline void mm_clear_owner(struct mm_struct *mm,
984 struct task_struct *p)
985{
986#ifdef CONFIG_MEMCG
987 if (mm->owner == p)
988 WRITE_ONCE(mm->owner, NULL);
989#endif
990}
991
992static void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
993{
994#ifdef CONFIG_MEMCG
995 mm->owner = p;
996#endif
997}
998
999static void mm_init_uprobes_state(struct mm_struct *mm)
1000{
1001#ifdef CONFIG_UPROBES
1002 mm->uprobes_state.xol_area = NULL;
1003#endif
1004}
1005
1006static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
1007 struct user_namespace *user_ns)
1008{
1009 mm->mmap = NULL;
1010 mm->mm_rb = RB_ROOT;
1011 mm->vmacache_seqnum = 0;
1012 atomic_set(&mm->mm_users, 1);
1013 atomic_set(&mm->mm_count, 1);
1014 init_rwsem(&mm->mmap_sem);
1015 INIT_LIST_HEAD(&mm->mmlist);
1016 mm->core_state = NULL;
1017 mm_pgtables_bytes_init(mm);
1018 mm->map_count = 0;
1019 mm->locked_vm = 0;
1020 atomic64_set(&mm->pinned_vm, 0);
1021 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
1022 spin_lock_init(&mm->page_table_lock);
1023 spin_lock_init(&mm->arg_lock);
1024 mm_init_cpumask(mm);
1025 mm_init_aio(mm);
1026 mm_init_owner(mm, p);
1027 RCU_INIT_POINTER(mm->exe_file, NULL);
1028 mmu_notifier_mm_init(mm);
1029 init_tlb_flush_pending(mm);
1030#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
1031 mm->pmd_huge_pte = NULL;
1032#endif
1033 mm_init_uprobes_state(mm);
1034
1035 if (current->mm) {
1036 mm->flags = current->mm->flags & MMF_INIT_MASK;
1037 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK;
1038 } else {
1039 mm->flags = default_dump_filter;
1040 mm->def_flags = 0;
1041 }
1042
1043 if (mm_alloc_pgd(mm))
1044 goto fail_nopgd;
1045
1046 if (init_new_context(p, mm))
1047 goto fail_nocontext;
1048
1049 mm->user_ns = get_user_ns(user_ns);
1050 return mm;
1051
1052fail_nocontext:
1053 mm_free_pgd(mm);
1054fail_nopgd:
1055 free_mm(mm);
1056 return NULL;
1057}
1058
1059/*
1060 * Allocate and initialize an mm_struct.
1061 */
1062struct mm_struct *mm_alloc(void)
1063{
1064 struct mm_struct *mm;
1065
1066 mm = allocate_mm();
1067 if (!mm)
1068 return NULL;
1069
1070 memset(mm, 0, sizeof(*mm));
1071 return mm_init(mm, current, current_user_ns());
1072}
1073
1074static inline void __mmput(struct mm_struct *mm)
1075{
1076 VM_BUG_ON(atomic_read(&mm->mm_users));
1077
1078 uprobe_clear_state(mm);
1079 exit_aio(mm);
1080 ksm_exit(mm);
1081 khugepaged_exit(mm); /* must run before exit_mmap */
1082 exit_mmap(mm);
1083 mm_put_huge_zero_page(mm);
1084 set_mm_exe_file(mm, NULL);
1085 if (!list_empty(&mm->mmlist)) {
1086 spin_lock(&mmlist_lock);
1087 list_del(&mm->mmlist);
1088 spin_unlock(&mmlist_lock);
1089 }
1090 if (mm->binfmt)
1091 module_put(mm->binfmt->module);
1092 mmdrop(mm);
1093}
1094
1095/*
1096 * Decrement the use count and release all resources for an mm.
1097 */
1098void mmput(struct mm_struct *mm)
1099{
1100 might_sleep();
1101
1102 if (atomic_dec_and_test(&mm->mm_users))
1103 __mmput(mm);
1104}
1105EXPORT_SYMBOL_GPL(mmput);
1106
1107#ifdef CONFIG_MMU
1108static void mmput_async_fn(struct work_struct *work)
1109{
1110 struct mm_struct *mm = container_of(work, struct mm_struct,
1111 async_put_work);
1112
1113 __mmput(mm);
1114}
1115
1116void mmput_async(struct mm_struct *mm)
1117{
1118 if (atomic_dec_and_test(&mm->mm_users)) {
1119 INIT_WORK(&mm->async_put_work, mmput_async_fn);
1120 schedule_work(&mm->async_put_work);
1121 }
1122}
1123#endif
1124
1125/**
1126 * set_mm_exe_file - change a reference to the mm's executable file
1127 *
1128 * This changes mm's executable file (shown as symlink /proc/[pid]/exe).
1129 *
1130 * Main users are mmput() and sys_execve(). Callers prevent concurrent
1131 * invocations: in mmput() nobody alive left, in execve task is single
1132 * threaded. sys_prctl(PR_SET_MM_MAP/EXE_FILE) also needs to set the
1133 * mm->exe_file, but does so without using set_mm_exe_file() in order
1134 * to do avoid the need for any locks.
1135 */
1136void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
1137{
1138 struct file *old_exe_file;
1139
1140 /*
1141 * It is safe to dereference the exe_file without RCU as
1142 * this function is only called if nobody else can access
1143 * this mm -- see comment above for justification.
1144 */
1145 old_exe_file = rcu_dereference_raw(mm->exe_file);
1146
1147 if (new_exe_file)
1148 get_file(new_exe_file);
1149 rcu_assign_pointer(mm->exe_file, new_exe_file);
1150 if (old_exe_file)
1151 fput(old_exe_file);
1152}
1153
1154/**
1155 * get_mm_exe_file - acquire a reference to the mm's executable file
1156 *
1157 * Returns %NULL if mm has no associated executable file.
1158 * User must release file via fput().
1159 */
1160struct file *get_mm_exe_file(struct mm_struct *mm)
1161{
1162 struct file *exe_file;
1163
1164 rcu_read_lock();
1165 exe_file = rcu_dereference(mm->exe_file);
1166 if (exe_file && !get_file_rcu(exe_file))
1167 exe_file = NULL;
1168 rcu_read_unlock();
1169 return exe_file;
1170}
1171EXPORT_SYMBOL(get_mm_exe_file);
1172
1173/**
1174 * get_task_exe_file - acquire a reference to the task's executable file
1175 *
1176 * Returns %NULL if task's mm (if any) has no associated executable file or
1177 * this is a kernel thread with borrowed mm (see the comment above get_task_mm).
1178 * User must release file via fput().
1179 */
1180struct file *get_task_exe_file(struct task_struct *task)
1181{
1182 struct file *exe_file = NULL;
1183 struct mm_struct *mm;
1184
1185 task_lock(task);
1186 mm = task->mm;
1187 if (mm) {
1188 if (!(task->flags & PF_KTHREAD))
1189 exe_file = get_mm_exe_file(mm);
1190 }
1191 task_unlock(task);
1192 return exe_file;
1193}
1194EXPORT_SYMBOL(get_task_exe_file);
1195
1196/**
1197 * get_task_mm - acquire a reference to the task's mm
1198 *
1199 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning
1200 * this kernel workthread has transiently adopted a user mm with use_mm,
1201 * to do its AIO) is not set and if so returns a reference to it, after
1202 * bumping up the use count. User must release the mm via mmput()
1203 * after use. Typically used by /proc and ptrace.
1204 */
1205struct mm_struct *get_task_mm(struct task_struct *task)
1206{
1207 struct mm_struct *mm;
1208
1209 task_lock(task);
1210 mm = task->mm;
1211 if (mm) {
1212 if (task->flags & PF_KTHREAD)
1213 mm = NULL;
1214 else
1215 mmget(mm);
1216 }
1217 task_unlock(task);
1218 return mm;
1219}
1220EXPORT_SYMBOL_GPL(get_task_mm);
1221
1222struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
1223{
1224 struct mm_struct *mm;
1225 int err;
1226
1227 err = mutex_lock_killable(&task->signal->cred_guard_mutex);
1228 if (err)
1229 return ERR_PTR(err);
1230
1231 mm = get_task_mm(task);
1232 if (mm && mm != current->mm &&
1233 !ptrace_may_access(task, mode)) {
1234 mmput(mm);
1235 mm = ERR_PTR(-EACCES);
1236 }
1237 mutex_unlock(&task->signal->cred_guard_mutex);
1238
1239 return mm;
1240}
1241
1242static void complete_vfork_done(struct task_struct *tsk)
1243{
1244 struct completion *vfork;
1245
1246 task_lock(tsk);
1247 vfork = tsk->vfork_done;
1248 if (likely(vfork)) {
1249 tsk->vfork_done = NULL;
1250 complete(vfork);
1251 }
1252 task_unlock(tsk);
1253}
1254
1255static int wait_for_vfork_done(struct task_struct *child,
1256 struct completion *vfork)
1257{
1258 int killed;
1259
1260 freezer_do_not_count();
1261 cgroup_enter_frozen();
1262 killed = wait_for_completion_killable(vfork);
1263 cgroup_leave_frozen(false);
1264 freezer_count();
1265
1266 if (killed) {
1267 task_lock(child);
1268 child->vfork_done = NULL;
1269 task_unlock(child);
1270 }
1271
1272 put_task_struct(child);
1273 return killed;
1274}
1275
1276/* Please note the differences between mmput and mm_release.
1277 * mmput is called whenever we stop holding onto a mm_struct,
1278 * error success whatever.
1279 *
1280 * mm_release is called after a mm_struct has been removed
1281 * from the current process.
1282 *
1283 * This difference is important for error handling, when we
1284 * only half set up a mm_struct for a new process and need to restore
1285 * the old one. Because we mmput the new mm_struct before
1286 * restoring the old one. . .
1287 * Eric Biederman 10 January 1998
1288 */
1289static void mm_release(struct task_struct *tsk, struct mm_struct *mm)
1290{
1291 uprobe_free_utask(tsk);
1292
1293 /* Get rid of any cached register state */
1294 deactivate_mm(tsk, mm);
1295
1296 /*
1297 * Signal userspace if we're not exiting with a core dump
1298 * because we want to leave the value intact for debugging
1299 * purposes.
1300 */
1301 if (tsk->clear_child_tid) {
1302 if (!(tsk->signal->flags & SIGNAL_GROUP_COREDUMP) &&
1303 atomic_read(&mm->mm_users) > 1) {
1304 /*
1305 * We don't check the error code - if userspace has
1306 * not set up a proper pointer then tough luck.
1307 */
1308 put_user(0, tsk->clear_child_tid);
1309 do_futex(tsk->clear_child_tid, FUTEX_WAKE,
1310 1, NULL, NULL, 0, 0);
1311 }
1312 tsk->clear_child_tid = NULL;
1313 }
1314
1315 /*
1316 * All done, finally we can wake up parent and return this mm to him.
1317 * Also kthread_stop() uses this completion for synchronization.
1318 */
1319 if (tsk->vfork_done)
1320 complete_vfork_done(tsk);
1321}
1322
1323void exit_mm_release(struct task_struct *tsk, struct mm_struct *mm)
1324{
1325 futex_exit_release(tsk);
1326 mm_release(tsk, mm);
1327}
1328
1329void exec_mm_release(struct task_struct *tsk, struct mm_struct *mm)
1330{
1331 futex_exec_release(tsk);
1332 mm_release(tsk, mm);
1333}
1334
1335/**
1336 * dup_mm() - duplicates an existing mm structure
1337 * @tsk: the task_struct with which the new mm will be associated.
1338 * @oldmm: the mm to duplicate.
1339 *
1340 * Allocates a new mm structure and duplicates the provided @oldmm structure
1341 * content into it.
1342 *
1343 * Return: the duplicated mm or NULL on failure.
1344 */
1345static struct mm_struct *dup_mm(struct task_struct *tsk,
1346 struct mm_struct *oldmm)
1347{
1348 struct mm_struct *mm;
1349 int err;
1350
1351 mm = allocate_mm();
1352 if (!mm)
1353 goto fail_nomem;
1354
1355 memcpy(mm, oldmm, sizeof(*mm));
1356
1357 if (!mm_init(mm, tsk, mm->user_ns))
1358 goto fail_nomem;
1359
1360 err = dup_mmap(mm, oldmm);
1361 if (err)
1362 goto free_pt;
1363
1364 mm->hiwater_rss = get_mm_rss(mm);
1365 mm->hiwater_vm = mm->total_vm;
1366
1367 if (mm->binfmt && !try_module_get(mm->binfmt->module))
1368 goto free_pt;
1369
1370 return mm;
1371
1372free_pt:
1373 /* don't put binfmt in mmput, we haven't got module yet */
1374 mm->binfmt = NULL;
1375 mm_init_owner(mm, NULL);
1376 mmput(mm);
1377
1378fail_nomem:
1379 return NULL;
1380}
1381
1382static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
1383{
1384 struct mm_struct *mm, *oldmm;
1385 int retval;
1386
1387 tsk->min_flt = tsk->maj_flt = 0;
1388 tsk->nvcsw = tsk->nivcsw = 0;
1389#ifdef CONFIG_DETECT_HUNG_TASK
1390 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
1391 tsk->last_switch_time = 0;
1392#endif
1393
1394 tsk->mm = NULL;
1395 tsk->active_mm = NULL;
1396
1397 /*
1398 * Are we cloning a kernel thread?
1399 *
1400 * We need to steal a active VM for that..
1401 */
1402 oldmm = current->mm;
1403 if (!oldmm)
1404 return 0;
1405
1406 /* initialize the new vmacache entries */
1407 vmacache_flush(tsk);
1408
1409 if (clone_flags & CLONE_VM) {
1410 mmget(oldmm);
1411 mm = oldmm;
1412 goto good_mm;
1413 }
1414
1415 retval = -ENOMEM;
1416 mm = dup_mm(tsk, current->mm);
1417 if (!mm)
1418 goto fail_nomem;
1419
1420good_mm:
1421 tsk->mm = mm;
1422 tsk->active_mm = mm;
1423 return 0;
1424
1425fail_nomem:
1426 return retval;
1427}
1428
1429static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
1430{
1431 struct fs_struct *fs = current->fs;
1432 if (clone_flags & CLONE_FS) {
1433 /* tsk->fs is already what we want */
1434 spin_lock(&fs->lock);
1435 if (fs->in_exec) {
1436 spin_unlock(&fs->lock);
1437 return -EAGAIN;
1438 }
1439 fs->users++;
1440 spin_unlock(&fs->lock);
1441 return 0;
1442 }
1443 tsk->fs = copy_fs_struct(fs);
1444 if (!tsk->fs)
1445 return -ENOMEM;
1446 return 0;
1447}
1448
1449static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
1450{
1451 struct files_struct *oldf, *newf;
1452 int error = 0;
1453
1454 /*
1455 * A background process may not have any files ...
1456 */
1457 oldf = current->files;
1458 if (!oldf)
1459 goto out;
1460
1461 if (clone_flags & CLONE_FILES) {
1462 atomic_inc(&oldf->count);
1463 goto out;
1464 }
1465
1466 newf = dup_fd(oldf, &error);
1467 if (!newf)
1468 goto out;
1469
1470 tsk->files = newf;
1471 error = 0;
1472out:
1473 return error;
1474}
1475
1476static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
1477{
1478#ifdef CONFIG_BLOCK
1479 struct io_context *ioc = current->io_context;
1480 struct io_context *new_ioc;
1481
1482 if (!ioc)
1483 return 0;
1484 /*
1485 * Share io context with parent, if CLONE_IO is set
1486 */
1487 if (clone_flags & CLONE_IO) {
1488 ioc_task_link(ioc);
1489 tsk->io_context = ioc;
1490 } else if (ioprio_valid(ioc->ioprio)) {
1491 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE);
1492 if (unlikely(!new_ioc))
1493 return -ENOMEM;
1494
1495 new_ioc->ioprio = ioc->ioprio;
1496 put_io_context(new_ioc);
1497 }
1498#endif
1499 return 0;
1500}
1501
1502static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
1503{
1504 struct sighand_struct *sig;
1505
1506 if (clone_flags & CLONE_SIGHAND) {
1507 refcount_inc(&current->sighand->count);
1508 return 0;
1509 }
1510 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1511 rcu_assign_pointer(tsk->sighand, sig);
1512 if (!sig)
1513 return -ENOMEM;
1514
1515 refcount_set(&sig->count, 1);
1516 spin_lock_irq(&current->sighand->siglock);
1517 memcpy(sig->action, current->sighand->action, sizeof(sig->action));
1518 spin_unlock_irq(&current->sighand->siglock);
1519
1520 /* Reset all signal handler not set to SIG_IGN to SIG_DFL. */
1521 if (clone_flags & CLONE_CLEAR_SIGHAND)
1522 flush_signal_handlers(tsk, 0);
1523
1524 return 0;
1525}
1526
1527void __cleanup_sighand(struct sighand_struct *sighand)
1528{
1529 if (refcount_dec_and_test(&sighand->count)) {
1530 signalfd_cleanup(sighand);
1531 /*
1532 * sighand_cachep is SLAB_TYPESAFE_BY_RCU so we can free it
1533 * without an RCU grace period, see __lock_task_sighand().
1534 */
1535 kmem_cache_free(sighand_cachep, sighand);
1536 }
1537}
1538
1539/*
1540 * Initialize POSIX timer handling for a thread group.
1541 */
1542static void posix_cpu_timers_init_group(struct signal_struct *sig)
1543{
1544 struct posix_cputimers *pct = &sig->posix_cputimers;
1545 unsigned long cpu_limit;
1546
1547 cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1548 posix_cputimers_group_init(pct, cpu_limit);
1549}
1550
1551static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
1552{
1553 struct signal_struct *sig;
1554
1555 if (clone_flags & CLONE_THREAD)
1556 return 0;
1557
1558 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
1559 tsk->signal = sig;
1560 if (!sig)
1561 return -ENOMEM;
1562
1563 sig->nr_threads = 1;
1564 atomic_set(&sig->live, 1);
1565 refcount_set(&sig->sigcnt, 1);
1566
1567 /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */
1568 sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node);
1569 tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head);
1570
1571 init_waitqueue_head(&sig->wait_chldexit);
1572 sig->curr_target = tsk;
1573 init_sigpending(&sig->shared_pending);
1574 INIT_HLIST_HEAD(&sig->multiprocess);
1575 seqlock_init(&sig->stats_lock);
1576 prev_cputime_init(&sig->prev_cputime);
1577
1578#ifdef CONFIG_POSIX_TIMERS
1579 INIT_LIST_HEAD(&sig->posix_timers);
1580 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1581 sig->real_timer.function = it_real_fn;
1582#endif
1583
1584 task_lock(current->group_leader);
1585 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
1586 task_unlock(current->group_leader);
1587
1588 posix_cpu_timers_init_group(sig);
1589
1590 tty_audit_fork(sig);
1591 sched_autogroup_fork(sig);
1592
1593 sig->oom_score_adj = current->signal->oom_score_adj;
1594 sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1595
1596 mutex_init(&sig->cred_guard_mutex);
1597
1598 return 0;
1599}
1600
1601static void copy_seccomp(struct task_struct *p)
1602{
1603#ifdef CONFIG_SECCOMP
1604 /*
1605 * Must be called with sighand->lock held, which is common to
1606 * all threads in the group. Holding cred_guard_mutex is not
1607 * needed because this new task is not yet running and cannot
1608 * be racing exec.
1609 */
1610 assert_spin_locked(&current->sighand->siglock);
1611
1612 /* Ref-count the new filter user, and assign it. */
1613 get_seccomp_filter(current);
1614 p->seccomp = current->seccomp;
1615
1616 /*
1617 * Explicitly enable no_new_privs here in case it got set
1618 * between the task_struct being duplicated and holding the
1619 * sighand lock. The seccomp state and nnp must be in sync.
1620 */
1621 if (task_no_new_privs(current))
1622 task_set_no_new_privs(p);
1623
1624 /*
1625 * If the parent gained a seccomp mode after copying thread
1626 * flags and between before we held the sighand lock, we have
1627 * to manually enable the seccomp thread flag here.
1628 */
1629 if (p->seccomp.mode != SECCOMP_MODE_DISABLED)
1630 set_tsk_thread_flag(p, TIF_SECCOMP);
1631#endif
1632}
1633
1634SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1635{
1636 current->clear_child_tid = tidptr;
1637
1638 return task_pid_vnr(current);
1639}
1640
1641static void rt_mutex_init_task(struct task_struct *p)
1642{
1643 raw_spin_lock_init(&p->pi_lock);
1644#ifdef CONFIG_RT_MUTEXES
1645 p->pi_waiters = RB_ROOT_CACHED;
1646 p->pi_top_task = NULL;
1647 p->pi_blocked_on = NULL;
1648#endif
1649}
1650
1651static inline void init_task_pid_links(struct task_struct *task)
1652{
1653 enum pid_type type;
1654
1655 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
1656 INIT_HLIST_NODE(&task->pid_links[type]);
1657 }
1658}
1659
1660static inline void
1661init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid)
1662{
1663 if (type == PIDTYPE_PID)
1664 task->thread_pid = pid;
1665 else
1666 task->signal->pids[type] = pid;
1667}
1668
1669static inline void rcu_copy_process(struct task_struct *p)
1670{
1671#ifdef CONFIG_PREEMPT_RCU
1672 p->rcu_read_lock_nesting = 0;
1673 p->rcu_read_unlock_special.s = 0;
1674 p->rcu_blocked_node = NULL;
1675 INIT_LIST_HEAD(&p->rcu_node_entry);
1676#endif /* #ifdef CONFIG_PREEMPT_RCU */
1677#ifdef CONFIG_TASKS_RCU
1678 p->rcu_tasks_holdout = false;
1679 INIT_LIST_HEAD(&p->rcu_tasks_holdout_list);
1680 p->rcu_tasks_idle_cpu = -1;
1681#endif /* #ifdef CONFIG_TASKS_RCU */
1682}
1683
1684struct pid *pidfd_pid(const struct file *file)
1685{
1686 if (file->f_op == &pidfd_fops)
1687 return file->private_data;
1688
1689 return ERR_PTR(-EBADF);
1690}
1691
1692static int pidfd_release(struct inode *inode, struct file *file)
1693{
1694 struct pid *pid = file->private_data;
1695
1696 file->private_data = NULL;
1697 put_pid(pid);
1698 return 0;
1699}
1700
1701#ifdef CONFIG_PROC_FS
1702/**
1703 * pidfd_show_fdinfo - print information about a pidfd
1704 * @m: proc fdinfo file
1705 * @f: file referencing a pidfd
1706 *
1707 * Pid:
1708 * This function will print the pid that a given pidfd refers to in the
1709 * pid namespace of the procfs instance.
1710 * If the pid namespace of the process is not a descendant of the pid
1711 * namespace of the procfs instance 0 will be shown as its pid. This is
1712 * similar to calling getppid() on a process whose parent is outside of
1713 * its pid namespace.
1714 *
1715 * NSpid:
1716 * If pid namespaces are supported then this function will also print
1717 * the pid of a given pidfd refers to for all descendant pid namespaces
1718 * starting from the current pid namespace of the instance, i.e. the
1719 * Pid field and the first entry in the NSpid field will be identical.
1720 * If the pid namespace of the process is not a descendant of the pid
1721 * namespace of the procfs instance 0 will be shown as its first NSpid
1722 * entry and no others will be shown.
1723 * Note that this differs from the Pid and NSpid fields in
1724 * /proc/<pid>/status where Pid and NSpid are always shown relative to
1725 * the pid namespace of the procfs instance. The difference becomes
1726 * obvious when sending around a pidfd between pid namespaces from a
1727 * different branch of the tree, i.e. where no ancestoral relation is
1728 * present between the pid namespaces:
1729 * - create two new pid namespaces ns1 and ns2 in the initial pid
1730 * namespace (also take care to create new mount namespaces in the
1731 * new pid namespace and mount procfs)
1732 * - create a process with a pidfd in ns1
1733 * - send pidfd from ns1 to ns2
1734 * - read /proc/self/fdinfo/<pidfd> and observe that both Pid and NSpid
1735 * have exactly one entry, which is 0
1736 */
1737static void pidfd_show_fdinfo(struct seq_file *m, struct file *f)
1738{
1739 struct pid *pid = f->private_data;
1740 struct pid_namespace *ns;
1741 pid_t nr = -1;
1742
1743 if (likely(pid_has_task(pid, PIDTYPE_PID))) {
1744 ns = proc_pid_ns(file_inode(m->file));
1745 nr = pid_nr_ns(pid, ns);
1746 }
1747
1748 seq_put_decimal_ll(m, "Pid:\t", nr);
1749
1750#ifdef CONFIG_PID_NS
1751 seq_put_decimal_ll(m, "\nNSpid:\t", nr);
1752 if (nr > 0) {
1753 int i;
1754
1755 /* If nr is non-zero it means that 'pid' is valid and that
1756 * ns, i.e. the pid namespace associated with the procfs
1757 * instance, is in the pid namespace hierarchy of pid.
1758 * Start at one below the already printed level.
1759 */
1760 for (i = ns->level + 1; i <= pid->level; i++)
1761 seq_put_decimal_ll(m, "\t", pid->numbers[i].nr);
1762 }
1763#endif
1764 seq_putc(m, '\n');
1765}
1766#endif
1767
1768/*
1769 * Poll support for process exit notification.
1770 */
1771static __poll_t pidfd_poll(struct file *file, struct poll_table_struct *pts)
1772{
1773 struct task_struct *task;
1774 struct pid *pid = file->private_data;
1775 __poll_t poll_flags = 0;
1776
1777 poll_wait(file, &pid->wait_pidfd, pts);
1778
1779 rcu_read_lock();
1780 task = pid_task(pid, PIDTYPE_PID);
1781 /*
1782 * Inform pollers only when the whole thread group exits.
1783 * If the thread group leader exits before all other threads in the
1784 * group, then poll(2) should block, similar to the wait(2) family.
1785 */
1786 if (!task || (task->exit_state && thread_group_empty(task)))
1787 poll_flags = EPOLLIN | EPOLLRDNORM;
1788 rcu_read_unlock();
1789
1790 return poll_flags;
1791}
1792
1793const struct file_operations pidfd_fops = {
1794 .release = pidfd_release,
1795 .poll = pidfd_poll,
1796#ifdef CONFIG_PROC_FS
1797 .show_fdinfo = pidfd_show_fdinfo,
1798#endif
1799};
1800
1801static void __delayed_free_task(struct rcu_head *rhp)
1802{
1803 struct task_struct *tsk = container_of(rhp, struct task_struct, rcu);
1804
1805 free_task(tsk);
1806}
1807
1808static __always_inline void delayed_free_task(struct task_struct *tsk)
1809{
1810 if (IS_ENABLED(CONFIG_MEMCG))
1811 call_rcu(&tsk->rcu, __delayed_free_task);
1812 else
1813 free_task(tsk);
1814}
1815
1816/*
1817 * This creates a new process as a copy of the old one,
1818 * but does not actually start it yet.
1819 *
1820 * It copies the registers, and all the appropriate
1821 * parts of the process environment (as per the clone
1822 * flags). The actual kick-off is left to the caller.
1823 */
1824static __latent_entropy struct task_struct *copy_process(
1825 struct pid *pid,
1826 int trace,
1827 int node,
1828 struct kernel_clone_args *args)
1829{
1830 int pidfd = -1, retval;
1831 struct task_struct *p;
1832 struct multiprocess_signals delayed;
1833 struct file *pidfile = NULL;
1834 u64 clone_flags = args->flags;
1835
1836 /*
1837 * Don't allow sharing the root directory with processes in a different
1838 * namespace
1839 */
1840 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1841 return ERR_PTR(-EINVAL);
1842
1843 if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS))
1844 return ERR_PTR(-EINVAL);
1845
1846 /*
1847 * Thread groups must share signals as well, and detached threads
1848 * can only be started up within the thread group.
1849 */
1850 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1851 return ERR_PTR(-EINVAL);
1852
1853 /*
1854 * Shared signal handlers imply shared VM. By way of the above,
1855 * thread groups also imply shared VM. Blocking this case allows
1856 * for various simplifications in other code.
1857 */
1858 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1859 return ERR_PTR(-EINVAL);
1860
1861 /*
1862 * Siblings of global init remain as zombies on exit since they are
1863 * not reaped by their parent (swapper). To solve this and to avoid
1864 * multi-rooted process trees, prevent global and container-inits
1865 * from creating siblings.
1866 */
1867 if ((clone_flags & CLONE_PARENT) &&
1868 current->signal->flags & SIGNAL_UNKILLABLE)
1869 return ERR_PTR(-EINVAL);
1870
1871 /*
1872 * If the new process will be in a different pid or user namespace
1873 * do not allow it to share a thread group with the forking task.
1874 */
1875 if (clone_flags & CLONE_THREAD) {
1876 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) ||
1877 (task_active_pid_ns(current) !=
1878 current->nsproxy->pid_ns_for_children))
1879 return ERR_PTR(-EINVAL);
1880 }
1881
1882 if (clone_flags & CLONE_PIDFD) {
1883 /*
1884 * - CLONE_DETACHED is blocked so that we can potentially
1885 * reuse it later for CLONE_PIDFD.
1886 * - CLONE_THREAD is blocked until someone really needs it.
1887 */
1888 if (clone_flags & (CLONE_DETACHED | CLONE_THREAD))
1889 return ERR_PTR(-EINVAL);
1890 }
1891
1892 /*
1893 * Force any signals received before this point to be delivered
1894 * before the fork happens. Collect up signals sent to multiple
1895 * processes that happen during the fork and delay them so that
1896 * they appear to happen after the fork.
1897 */
1898 sigemptyset(&delayed.signal);
1899 INIT_HLIST_NODE(&delayed.node);
1900
1901 spin_lock_irq(&current->sighand->siglock);
1902 if (!(clone_flags & CLONE_THREAD))
1903 hlist_add_head(&delayed.node, &current->signal->multiprocess);
1904 recalc_sigpending();
1905 spin_unlock_irq(&current->sighand->siglock);
1906 retval = -ERESTARTNOINTR;
1907 if (signal_pending(current))
1908 goto fork_out;
1909
1910 retval = -ENOMEM;
1911 p = dup_task_struct(current, node);
1912 if (!p)
1913 goto fork_out;
1914
1915 /*
1916 * This _must_ happen before we call free_task(), i.e. before we jump
1917 * to any of the bad_fork_* labels. This is to avoid freeing
1918 * p->set_child_tid which is (ab)used as a kthread's data pointer for
1919 * kernel threads (PF_KTHREAD).
1920 */
1921 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? args->child_tid : NULL;
1922 /*
1923 * Clear TID on mm_release()?
1924 */
1925 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? args->child_tid : NULL;
1926
1927 ftrace_graph_init_task(p);
1928
1929 rt_mutex_init_task(p);
1930
1931#ifdef CONFIG_PROVE_LOCKING
1932 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1933 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1934#endif
1935 retval = -EAGAIN;
1936 if (atomic_read(&p->real_cred->user->processes) >=
1937 task_rlimit(p, RLIMIT_NPROC)) {
1938 if (p->real_cred->user != INIT_USER &&
1939 !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
1940 goto bad_fork_free;
1941 }
1942 current->flags &= ~PF_NPROC_EXCEEDED;
1943
1944 retval = copy_creds(p, clone_flags);
1945 if (retval < 0)
1946 goto bad_fork_free;
1947
1948 /*
1949 * If multiple threads are within copy_process(), then this check
1950 * triggers too late. This doesn't hurt, the check is only there
1951 * to stop root fork bombs.
1952 */
1953 retval = -EAGAIN;
1954 if (nr_threads >= max_threads)
1955 goto bad_fork_cleanup_count;
1956
1957 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */
1958 p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER | PF_IDLE);
1959 p->flags |= PF_FORKNOEXEC;
1960 INIT_LIST_HEAD(&p->children);
1961 INIT_LIST_HEAD(&p->sibling);
1962 rcu_copy_process(p);
1963 p->vfork_done = NULL;
1964 spin_lock_init(&p->alloc_lock);
1965
1966 init_sigpending(&p->pending);
1967
1968 p->utime = p->stime = p->gtime = 0;
1969#ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
1970 p->utimescaled = p->stimescaled = 0;
1971#endif
1972 prev_cputime_init(&p->prev_cputime);
1973
1974#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
1975 seqcount_init(&p->vtime.seqcount);
1976 p->vtime.starttime = 0;
1977 p->vtime.state = VTIME_INACTIVE;
1978#endif
1979
1980#if defined(SPLIT_RSS_COUNTING)
1981 memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1982#endif
1983
1984 p->default_timer_slack_ns = current->timer_slack_ns;
1985
1986#ifdef CONFIG_PSI
1987 p->psi_flags = 0;
1988#endif
1989
1990 task_io_accounting_init(&p->ioac);
1991 acct_clear_integrals(p);
1992
1993 posix_cputimers_init(&p->posix_cputimers);
1994
1995 p->io_context = NULL;
1996 audit_set_context(p, NULL);
1997 cgroup_fork(p);
1998#ifdef CONFIG_NUMA
1999 p->mempolicy = mpol_dup(p->mempolicy);
2000 if (IS_ERR(p->mempolicy)) {
2001 retval = PTR_ERR(p->mempolicy);
2002 p->mempolicy = NULL;
2003 goto bad_fork_cleanup_threadgroup_lock;
2004 }
2005#endif
2006#ifdef CONFIG_CPUSETS
2007 p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
2008 p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
2009 seqcount_init(&p->mems_allowed_seq);
2010#endif
2011#ifdef CONFIG_TRACE_IRQFLAGS
2012 p->irq_events = 0;
2013 p->hardirqs_enabled = 0;
2014 p->hardirq_enable_ip = 0;
2015 p->hardirq_enable_event = 0;
2016 p->hardirq_disable_ip = _THIS_IP_;
2017 p->hardirq_disable_event = 0;
2018 p->softirqs_enabled = 1;
2019 p->softirq_enable_ip = _THIS_IP_;
2020 p->softirq_enable_event = 0;
2021 p->softirq_disable_ip = 0;
2022 p->softirq_disable_event = 0;
2023 p->hardirq_context = 0;
2024 p->softirq_context = 0;
2025#endif
2026
2027 p->pagefault_disabled = 0;
2028
2029#ifdef CONFIG_LOCKDEP
2030 lockdep_init_task(p);
2031#endif
2032
2033#ifdef CONFIG_DEBUG_MUTEXES
2034 p->blocked_on = NULL; /* not blocked yet */
2035#endif
2036#ifdef CONFIG_BCACHE
2037 p->sequential_io = 0;
2038 p->sequential_io_avg = 0;
2039#endif
2040
2041 /* Perform scheduler related setup. Assign this task to a CPU. */
2042 retval = sched_fork(clone_flags, p);
2043 if (retval)
2044 goto bad_fork_cleanup_policy;
2045
2046 retval = perf_event_init_task(p);
2047 if (retval)
2048 goto bad_fork_cleanup_policy;
2049 retval = audit_alloc(p);
2050 if (retval)
2051 goto bad_fork_cleanup_perf;
2052 /* copy all the process information */
2053 shm_init_task(p);
2054 retval = security_task_alloc(p, clone_flags);
2055 if (retval)
2056 goto bad_fork_cleanup_audit;
2057 retval = copy_semundo(clone_flags, p);
2058 if (retval)
2059 goto bad_fork_cleanup_security;
2060 retval = copy_files(clone_flags, p);
2061 if (retval)
2062 goto bad_fork_cleanup_semundo;
2063 retval = copy_fs(clone_flags, p);
2064 if (retval)
2065 goto bad_fork_cleanup_files;
2066 retval = copy_sighand(clone_flags, p);
2067 if (retval)
2068 goto bad_fork_cleanup_fs;
2069 retval = copy_signal(clone_flags, p);
2070 if (retval)
2071 goto bad_fork_cleanup_sighand;
2072 retval = copy_mm(clone_flags, p);
2073 if (retval)
2074 goto bad_fork_cleanup_signal;
2075 retval = copy_namespaces(clone_flags, p);
2076 if (retval)
2077 goto bad_fork_cleanup_mm;
2078 retval = copy_io(clone_flags, p);
2079 if (retval)
2080 goto bad_fork_cleanup_namespaces;
2081 retval = copy_thread_tls(clone_flags, args->stack, args->stack_size, p,
2082 args->tls);
2083 if (retval)
2084 goto bad_fork_cleanup_io;
2085
2086 stackleak_task_init(p);
2087
2088 if (pid != &init_struct_pid) {
2089 pid = alloc_pid(p->nsproxy->pid_ns_for_children, args->set_tid,
2090 args->set_tid_size);
2091 if (IS_ERR(pid)) {
2092 retval = PTR_ERR(pid);
2093 goto bad_fork_cleanup_thread;
2094 }
2095 }
2096
2097 /*
2098 * This has to happen after we've potentially unshared the file
2099 * descriptor table (so that the pidfd doesn't leak into the child
2100 * if the fd table isn't shared).
2101 */
2102 if (clone_flags & CLONE_PIDFD) {
2103 retval = get_unused_fd_flags(O_RDWR | O_CLOEXEC);
2104 if (retval < 0)
2105 goto bad_fork_free_pid;
2106
2107 pidfd = retval;
2108
2109 pidfile = anon_inode_getfile("[pidfd]", &pidfd_fops, pid,
2110 O_RDWR | O_CLOEXEC);
2111 if (IS_ERR(pidfile)) {
2112 put_unused_fd(pidfd);
2113 retval = PTR_ERR(pidfile);
2114 goto bad_fork_free_pid;
2115 }
2116 get_pid(pid); /* held by pidfile now */
2117
2118 retval = put_user(pidfd, args->pidfd);
2119 if (retval)
2120 goto bad_fork_put_pidfd;
2121 }
2122
2123#ifdef CONFIG_BLOCK
2124 p->plug = NULL;
2125#endif
2126 futex_init_task(p);
2127
2128 /*
2129 * sigaltstack should be cleared when sharing the same VM
2130 */
2131 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
2132 sas_ss_reset(p);
2133
2134 /*
2135 * Syscall tracing and stepping should be turned off in the
2136 * child regardless of CLONE_PTRACE.
2137 */
2138 user_disable_single_step(p);
2139 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
2140#ifdef TIF_SYSCALL_EMU
2141 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
2142#endif
2143 clear_tsk_latency_tracing(p);
2144
2145 /* ok, now we should be set up.. */
2146 p->pid = pid_nr(pid);
2147 if (clone_flags & CLONE_THREAD) {
2148 p->exit_signal = -1;
2149 p->group_leader = current->group_leader;
2150 p->tgid = current->tgid;
2151 } else {
2152 if (clone_flags & CLONE_PARENT)
2153 p->exit_signal = current->group_leader->exit_signal;
2154 else
2155 p->exit_signal = args->exit_signal;
2156 p->group_leader = p;
2157 p->tgid = p->pid;
2158 }
2159
2160 p->nr_dirtied = 0;
2161 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
2162 p->dirty_paused_when = 0;
2163
2164 p->pdeath_signal = 0;
2165 INIT_LIST_HEAD(&p->thread_group);
2166 p->task_works = NULL;
2167
2168 cgroup_threadgroup_change_begin(current);
2169 /*
2170 * Ensure that the cgroup subsystem policies allow the new process to be
2171 * forked. It should be noted the the new process's css_set can be changed
2172 * between here and cgroup_post_fork() if an organisation operation is in
2173 * progress.
2174 */
2175 retval = cgroup_can_fork(p);
2176 if (retval)
2177 goto bad_fork_cgroup_threadgroup_change_end;
2178
2179 /*
2180 * From this point on we must avoid any synchronous user-space
2181 * communication until we take the tasklist-lock. In particular, we do
2182 * not want user-space to be able to predict the process start-time by
2183 * stalling fork(2) after we recorded the start_time but before it is
2184 * visible to the system.
2185 */
2186
2187 p->start_time = ktime_get_ns();
2188 p->start_boottime = ktime_get_boottime_ns();
2189
2190 /*
2191 * Make it visible to the rest of the system, but dont wake it up yet.
2192 * Need tasklist lock for parent etc handling!
2193 */
2194 write_lock_irq(&tasklist_lock);
2195
2196 /* CLONE_PARENT re-uses the old parent */
2197 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
2198 p->real_parent = current->real_parent;
2199 p->parent_exec_id = current->parent_exec_id;
2200 } else {
2201 p->real_parent = current;
2202 p->parent_exec_id = current->self_exec_id;
2203 }
2204
2205 klp_copy_process(p);
2206
2207 spin_lock(&current->sighand->siglock);
2208
2209 /*
2210 * Copy seccomp details explicitly here, in case they were changed
2211 * before holding sighand lock.
2212 */
2213 copy_seccomp(p);
2214
2215 rseq_fork(p, clone_flags);
2216
2217 /* Don't start children in a dying pid namespace */
2218 if (unlikely(!(ns_of_pid(pid)->pid_allocated & PIDNS_ADDING))) {
2219 retval = -ENOMEM;
2220 goto bad_fork_cancel_cgroup;
2221 }
2222
2223 /* Let kill terminate clone/fork in the middle */
2224 if (fatal_signal_pending(current)) {
2225 retval = -EINTR;
2226 goto bad_fork_cancel_cgroup;
2227 }
2228
2229 /* past the last point of failure */
2230 if (pidfile)
2231 fd_install(pidfd, pidfile);
2232
2233 init_task_pid_links(p);
2234 if (likely(p->pid)) {
2235 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
2236
2237 init_task_pid(p, PIDTYPE_PID, pid);
2238 if (thread_group_leader(p)) {
2239 init_task_pid(p, PIDTYPE_TGID, pid);
2240 init_task_pid(p, PIDTYPE_PGID, task_pgrp(current));
2241 init_task_pid(p, PIDTYPE_SID, task_session(current));
2242
2243 if (is_child_reaper(pid)) {
2244 ns_of_pid(pid)->child_reaper = p;
2245 p->signal->flags |= SIGNAL_UNKILLABLE;
2246 }
2247 p->signal->shared_pending.signal = delayed.signal;
2248 p->signal->tty = tty_kref_get(current->signal->tty);
2249 /*
2250 * Inherit has_child_subreaper flag under the same
2251 * tasklist_lock with adding child to the process tree
2252 * for propagate_has_child_subreaper optimization.
2253 */
2254 p->signal->has_child_subreaper = p->real_parent->signal->has_child_subreaper ||
2255 p->real_parent->signal->is_child_subreaper;
2256 list_add_tail(&p->sibling, &p->real_parent->children);
2257 list_add_tail_rcu(&p->tasks, &init_task.tasks);
2258 attach_pid(p, PIDTYPE_TGID);
2259 attach_pid(p, PIDTYPE_PGID);
2260 attach_pid(p, PIDTYPE_SID);
2261 __this_cpu_inc(process_counts);
2262 } else {
2263 current->signal->nr_threads++;
2264 atomic_inc(&current->signal->live);
2265 refcount_inc(&current->signal->sigcnt);
2266 task_join_group_stop(p);
2267 list_add_tail_rcu(&p->thread_group,
2268 &p->group_leader->thread_group);
2269 list_add_tail_rcu(&p->thread_node,
2270 &p->signal->thread_head);
2271 }
2272 attach_pid(p, PIDTYPE_PID);
2273 nr_threads++;
2274 }
2275 total_forks++;
2276 hlist_del_init(&delayed.node);
2277 spin_unlock(&current->sighand->siglock);
2278 syscall_tracepoint_update(p);
2279 write_unlock_irq(&tasklist_lock);
2280
2281 proc_fork_connector(p);
2282 cgroup_post_fork(p);
2283 cgroup_threadgroup_change_end(current);
2284 perf_event_fork(p);
2285
2286 trace_task_newtask(p, clone_flags);
2287 uprobe_copy_process(p, clone_flags);
2288
2289 return p;
2290
2291bad_fork_cancel_cgroup:
2292 spin_unlock(&current->sighand->siglock);
2293 write_unlock_irq(&tasklist_lock);
2294 cgroup_cancel_fork(p);
2295bad_fork_cgroup_threadgroup_change_end:
2296 cgroup_threadgroup_change_end(current);
2297bad_fork_put_pidfd:
2298 if (clone_flags & CLONE_PIDFD) {
2299 fput(pidfile);
2300 put_unused_fd(pidfd);
2301 }
2302bad_fork_free_pid:
2303 if (pid != &init_struct_pid)
2304 free_pid(pid);
2305bad_fork_cleanup_thread:
2306 exit_thread(p);
2307bad_fork_cleanup_io:
2308 if (p->io_context)
2309 exit_io_context(p);
2310bad_fork_cleanup_namespaces:
2311 exit_task_namespaces(p);
2312bad_fork_cleanup_mm:
2313 if (p->mm) {
2314 mm_clear_owner(p->mm, p);
2315 mmput(p->mm);
2316 }
2317bad_fork_cleanup_signal:
2318 if (!(clone_flags & CLONE_THREAD))
2319 free_signal_struct(p->signal);
2320bad_fork_cleanup_sighand:
2321 __cleanup_sighand(p->sighand);
2322bad_fork_cleanup_fs:
2323 exit_fs(p); /* blocking */
2324bad_fork_cleanup_files:
2325 exit_files(p); /* blocking */
2326bad_fork_cleanup_semundo:
2327 exit_sem(p);
2328bad_fork_cleanup_security:
2329 security_task_free(p);
2330bad_fork_cleanup_audit:
2331 audit_free(p);
2332bad_fork_cleanup_perf:
2333 perf_event_free_task(p);
2334bad_fork_cleanup_policy:
2335 lockdep_free_task(p);
2336#ifdef CONFIG_NUMA
2337 mpol_put(p->mempolicy);
2338bad_fork_cleanup_threadgroup_lock:
2339#endif
2340 delayacct_tsk_free(p);
2341bad_fork_cleanup_count:
2342 atomic_dec(&p->cred->user->processes);
2343 exit_creds(p);
2344bad_fork_free:
2345 p->state = TASK_DEAD;
2346 put_task_stack(p);
2347 delayed_free_task(p);
2348fork_out:
2349 spin_lock_irq(&current->sighand->siglock);
2350 hlist_del_init(&delayed.node);
2351 spin_unlock_irq(&current->sighand->siglock);
2352 return ERR_PTR(retval);
2353}
2354
2355static inline void init_idle_pids(struct task_struct *idle)
2356{
2357 enum pid_type type;
2358
2359 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
2360 INIT_HLIST_NODE(&idle->pid_links[type]); /* not really needed */
2361 init_task_pid(idle, type, &init_struct_pid);
2362 }
2363}
2364
2365struct task_struct *fork_idle(int cpu)
2366{
2367 struct task_struct *task;
2368 struct kernel_clone_args args = {
2369 .flags = CLONE_VM,
2370 };
2371
2372 task = copy_process(&init_struct_pid, 0, cpu_to_node(cpu), &args);
2373 if (!IS_ERR(task)) {
2374 init_idle_pids(task);
2375 init_idle(task, cpu);
2376 }
2377
2378 return task;
2379}
2380
2381struct mm_struct *copy_init_mm(void)
2382{
2383 return dup_mm(NULL, &init_mm);
2384}
2385
2386/*
2387 * Ok, this is the main fork-routine.
2388 *
2389 * It copies the process, and if successful kick-starts
2390 * it and waits for it to finish using the VM if required.
2391 *
2392 * args->exit_signal is expected to be checked for sanity by the caller.
2393 */
2394long _do_fork(struct kernel_clone_args *args)
2395{
2396 u64 clone_flags = args->flags;
2397 struct completion vfork;
2398 struct pid *pid;
2399 struct task_struct *p;
2400 int trace = 0;
2401 long nr;
2402
2403 /*
2404 * Determine whether and which event to report to ptracer. When
2405 * called from kernel_thread or CLONE_UNTRACED is explicitly
2406 * requested, no event is reported; otherwise, report if the event
2407 * for the type of forking is enabled.
2408 */
2409 if (!(clone_flags & CLONE_UNTRACED)) {
2410 if (clone_flags & CLONE_VFORK)
2411 trace = PTRACE_EVENT_VFORK;
2412 else if (args->exit_signal != SIGCHLD)
2413 trace = PTRACE_EVENT_CLONE;
2414 else
2415 trace = PTRACE_EVENT_FORK;
2416
2417 if (likely(!ptrace_event_enabled(current, trace)))
2418 trace = 0;
2419 }
2420
2421 p = copy_process(NULL, trace, NUMA_NO_NODE, args);
2422 add_latent_entropy();
2423
2424 if (IS_ERR(p))
2425 return PTR_ERR(p);
2426
2427 /*
2428 * Do this prior waking up the new thread - the thread pointer
2429 * might get invalid after that point, if the thread exits quickly.
2430 */
2431 trace_sched_process_fork(current, p);
2432
2433 pid = get_task_pid(p, PIDTYPE_PID);
2434 nr = pid_vnr(pid);
2435
2436 if (clone_flags & CLONE_PARENT_SETTID)
2437 put_user(nr, args->parent_tid);
2438
2439 if (clone_flags & CLONE_VFORK) {
2440 p->vfork_done = &vfork;
2441 init_completion(&vfork);
2442 get_task_struct(p);
2443 }
2444
2445 wake_up_new_task(p);
2446
2447 /* forking complete and child started to run, tell ptracer */
2448 if (unlikely(trace))
2449 ptrace_event_pid(trace, pid);
2450
2451 if (clone_flags & CLONE_VFORK) {
2452 if (!wait_for_vfork_done(p, &vfork))
2453 ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid);
2454 }
2455
2456 put_pid(pid);
2457 return nr;
2458}
2459
2460bool legacy_clone_args_valid(const struct kernel_clone_args *kargs)
2461{
2462 /* clone(CLONE_PIDFD) uses parent_tidptr to return a pidfd */
2463 if ((kargs->flags & CLONE_PIDFD) &&
2464 (kargs->flags & CLONE_PARENT_SETTID))
2465 return false;
2466
2467 return true;
2468}
2469
2470#ifndef CONFIG_HAVE_COPY_THREAD_TLS
2471/* For compatibility with architectures that call do_fork directly rather than
2472 * using the syscall entry points below. */
2473long do_fork(unsigned long clone_flags,
2474 unsigned long stack_start,
2475 unsigned long stack_size,
2476 int __user *parent_tidptr,
2477 int __user *child_tidptr)
2478{
2479 struct kernel_clone_args args = {
2480 .flags = (clone_flags & ~CSIGNAL),
2481 .pidfd = parent_tidptr,
2482 .child_tid = child_tidptr,
2483 .parent_tid = parent_tidptr,
2484 .exit_signal = (clone_flags & CSIGNAL),
2485 .stack = stack_start,
2486 .stack_size = stack_size,
2487 };
2488
2489 if (!legacy_clone_args_valid(&args))
2490 return -EINVAL;
2491
2492 return _do_fork(&args);
2493}
2494#endif
2495
2496/*
2497 * Create a kernel thread.
2498 */
2499pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
2500{
2501 struct kernel_clone_args args = {
2502 .flags = ((flags | CLONE_VM | CLONE_UNTRACED) & ~CSIGNAL),
2503 .exit_signal = (flags & CSIGNAL),
2504 .stack = (unsigned long)fn,
2505 .stack_size = (unsigned long)arg,
2506 };
2507
2508 return _do_fork(&args);
2509}
2510
2511#ifdef __ARCH_WANT_SYS_FORK
2512SYSCALL_DEFINE0(fork)
2513{
2514#ifdef CONFIG_MMU
2515 struct kernel_clone_args args = {
2516 .exit_signal = SIGCHLD,
2517 };
2518
2519 return _do_fork(&args);
2520#else
2521 /* can not support in nommu mode */
2522 return -EINVAL;
2523#endif
2524}
2525#endif
2526
2527#ifdef __ARCH_WANT_SYS_VFORK
2528SYSCALL_DEFINE0(vfork)
2529{
2530 struct kernel_clone_args args = {
2531 .flags = CLONE_VFORK | CLONE_VM,
2532 .exit_signal = SIGCHLD,
2533 };
2534
2535 return _do_fork(&args);
2536}
2537#endif
2538
2539#ifdef __ARCH_WANT_SYS_CLONE
2540#ifdef CONFIG_CLONE_BACKWARDS
2541SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2542 int __user *, parent_tidptr,
2543 unsigned long, tls,
2544 int __user *, child_tidptr)
2545#elif defined(CONFIG_CLONE_BACKWARDS2)
2546SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags,
2547 int __user *, parent_tidptr,
2548 int __user *, child_tidptr,
2549 unsigned long, tls)
2550#elif defined(CONFIG_CLONE_BACKWARDS3)
2551SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp,
2552 int, stack_size,
2553 int __user *, parent_tidptr,
2554 int __user *, child_tidptr,
2555 unsigned long, tls)
2556#else
2557SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2558 int __user *, parent_tidptr,
2559 int __user *, child_tidptr,
2560 unsigned long, tls)
2561#endif
2562{
2563 struct kernel_clone_args args = {
2564 .flags = (clone_flags & ~CSIGNAL),
2565 .pidfd = parent_tidptr,
2566 .child_tid = child_tidptr,
2567 .parent_tid = parent_tidptr,
2568 .exit_signal = (clone_flags & CSIGNAL),
2569 .stack = newsp,
2570 .tls = tls,
2571 };
2572
2573 if (!legacy_clone_args_valid(&args))
2574 return -EINVAL;
2575
2576 return _do_fork(&args);
2577}
2578#endif
2579
2580#ifdef __ARCH_WANT_SYS_CLONE3
2581
2582/*
2583 * copy_thread implementations handle CLONE_SETTLS by reading the TLS value from
2584 * the registers containing the syscall arguments for clone. This doesn't work
2585 * with clone3 since the TLS value is passed in clone_args instead.
2586 */
2587#ifndef CONFIG_HAVE_COPY_THREAD_TLS
2588#error clone3 requires copy_thread_tls support in arch
2589#endif
2590
2591noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs,
2592 struct clone_args __user *uargs,
2593 size_t usize)
2594{
2595 int err;
2596 struct clone_args args;
2597 pid_t *kset_tid = kargs->set_tid;
2598
2599 if (unlikely(usize > PAGE_SIZE))
2600 return -E2BIG;
2601 if (unlikely(usize < CLONE_ARGS_SIZE_VER0))
2602 return -EINVAL;
2603
2604 err = copy_struct_from_user(&args, sizeof(args), uargs, usize);
2605 if (err)
2606 return err;
2607
2608 if (unlikely(args.set_tid_size > MAX_PID_NS_LEVEL))
2609 return -EINVAL;
2610
2611 if (unlikely(!args.set_tid && args.set_tid_size > 0))
2612 return -EINVAL;
2613
2614 if (unlikely(args.set_tid && args.set_tid_size == 0))
2615 return -EINVAL;
2616
2617 /*
2618 * Verify that higher 32bits of exit_signal are unset and that
2619 * it is a valid signal
2620 */
2621 if (unlikely((args.exit_signal & ~((u64)CSIGNAL)) ||
2622 !valid_signal(args.exit_signal)))
2623 return -EINVAL;
2624
2625 *kargs = (struct kernel_clone_args){
2626 .flags = args.flags,
2627 .pidfd = u64_to_user_ptr(args.pidfd),
2628 .child_tid = u64_to_user_ptr(args.child_tid),
2629 .parent_tid = u64_to_user_ptr(args.parent_tid),
2630 .exit_signal = args.exit_signal,
2631 .stack = args.stack,
2632 .stack_size = args.stack_size,
2633 .tls = args.tls,
2634 .set_tid_size = args.set_tid_size,
2635 };
2636
2637 if (args.set_tid &&
2638 copy_from_user(kset_tid, u64_to_user_ptr(args.set_tid),
2639 (kargs->set_tid_size * sizeof(pid_t))))
2640 return -EFAULT;
2641
2642 kargs->set_tid = kset_tid;
2643
2644 return 0;
2645}
2646
2647/**
2648 * clone3_stack_valid - check and prepare stack
2649 * @kargs: kernel clone args
2650 *
2651 * Verify that the stack arguments userspace gave us are sane.
2652 * In addition, set the stack direction for userspace since it's easy for us to
2653 * determine.
2654 */
2655static inline bool clone3_stack_valid(struct kernel_clone_args *kargs)
2656{
2657 if (kargs->stack == 0) {
2658 if (kargs->stack_size > 0)
2659 return false;
2660 } else {
2661 if (kargs->stack_size == 0)
2662 return false;
2663
2664 if (!access_ok((void __user *)kargs->stack, kargs->stack_size))
2665 return false;
2666
2667#if !defined(CONFIG_STACK_GROWSUP) && !defined(CONFIG_IA64)
2668 kargs->stack += kargs->stack_size;
2669#endif
2670 }
2671
2672 return true;
2673}
2674
2675static bool clone3_args_valid(struct kernel_clone_args *kargs)
2676{
2677 /* Verify that no unknown flags are passed along. */
2678 if (kargs->flags & ~(CLONE_LEGACY_FLAGS | CLONE_CLEAR_SIGHAND))
2679 return false;
2680
2681 /*
2682 * - make the CLONE_DETACHED bit reuseable for clone3
2683 * - make the CSIGNAL bits reuseable for clone3
2684 */
2685 if (kargs->flags & (CLONE_DETACHED | CSIGNAL))
2686 return false;
2687
2688 if ((kargs->flags & (CLONE_SIGHAND | CLONE_CLEAR_SIGHAND)) ==
2689 (CLONE_SIGHAND | CLONE_CLEAR_SIGHAND))
2690 return false;
2691
2692 if ((kargs->flags & (CLONE_THREAD | CLONE_PARENT)) &&
2693 kargs->exit_signal)
2694 return false;
2695
2696 if (!clone3_stack_valid(kargs))
2697 return false;
2698
2699 return true;
2700}
2701
2702/**
2703 * clone3 - create a new process with specific properties
2704 * @uargs: argument structure
2705 * @size: size of @uargs
2706 *
2707 * clone3() is the extensible successor to clone()/clone2().
2708 * It takes a struct as argument that is versioned by its size.
2709 *
2710 * Return: On success, a positive PID for the child process.
2711 * On error, a negative errno number.
2712 */
2713SYSCALL_DEFINE2(clone3, struct clone_args __user *, uargs, size_t, size)
2714{
2715 int err;
2716
2717 struct kernel_clone_args kargs;
2718 pid_t set_tid[MAX_PID_NS_LEVEL];
2719
2720 kargs.set_tid = set_tid;
2721
2722 err = copy_clone_args_from_user(&kargs, uargs, size);
2723 if (err)
2724 return err;
2725
2726 if (!clone3_args_valid(&kargs))
2727 return -EINVAL;
2728
2729 return _do_fork(&kargs);
2730}
2731#endif
2732
2733void walk_process_tree(struct task_struct *top, proc_visitor visitor, void *data)
2734{
2735 struct task_struct *leader, *parent, *child;
2736 int res;
2737
2738 read_lock(&tasklist_lock);
2739 leader = top = top->group_leader;
2740down:
2741 for_each_thread(leader, parent) {
2742 list_for_each_entry(child, &parent->children, sibling) {
2743 res = visitor(child, data);
2744 if (res) {
2745 if (res < 0)
2746 goto out;
2747 leader = child;
2748 goto down;
2749 }
2750up:
2751 ;
2752 }
2753 }
2754
2755 if (leader != top) {
2756 child = leader;
2757 parent = child->real_parent;
2758 leader = parent->group_leader;
2759 goto up;
2760 }
2761out:
2762 read_unlock(&tasklist_lock);
2763}
2764
2765#ifndef ARCH_MIN_MMSTRUCT_ALIGN
2766#define ARCH_MIN_MMSTRUCT_ALIGN 0
2767#endif
2768
2769static void sighand_ctor(void *data)
2770{
2771 struct sighand_struct *sighand = data;
2772
2773 spin_lock_init(&sighand->siglock);
2774 init_waitqueue_head(&sighand->signalfd_wqh);
2775}
2776
2777void __init proc_caches_init(void)
2778{
2779 unsigned int mm_size;
2780
2781 sighand_cachep = kmem_cache_create("sighand_cache",
2782 sizeof(struct sighand_struct), 0,
2783 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_TYPESAFE_BY_RCU|
2784 SLAB_ACCOUNT, sighand_ctor);
2785 signal_cachep = kmem_cache_create("signal_cache",
2786 sizeof(struct signal_struct), 0,
2787 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2788 NULL);
2789 files_cachep = kmem_cache_create("files_cache",
2790 sizeof(struct files_struct), 0,
2791 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2792 NULL);
2793 fs_cachep = kmem_cache_create("fs_cache",
2794 sizeof(struct fs_struct), 0,
2795 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2796 NULL);
2797
2798 /*
2799 * The mm_cpumask is located at the end of mm_struct, and is
2800 * dynamically sized based on the maximum CPU number this system
2801 * can have, taking hotplug into account (nr_cpu_ids).
2802 */
2803 mm_size = sizeof(struct mm_struct) + cpumask_size();
2804
2805 mm_cachep = kmem_cache_create_usercopy("mm_struct",
2806 mm_size, ARCH_MIN_MMSTRUCT_ALIGN,
2807 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2808 offsetof(struct mm_struct, saved_auxv),
2809 sizeof_field(struct mm_struct, saved_auxv),
2810 NULL);
2811 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT);
2812 mmap_init();
2813 nsproxy_cache_init();
2814}
2815
2816/*
2817 * Check constraints on flags passed to the unshare system call.
2818 */
2819static int check_unshare_flags(unsigned long unshare_flags)
2820{
2821 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
2822 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
2823 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET|
2824 CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP))
2825 return -EINVAL;
2826 /*
2827 * Not implemented, but pretend it works if there is nothing
2828 * to unshare. Note that unsharing the address space or the
2829 * signal handlers also need to unshare the signal queues (aka
2830 * CLONE_THREAD).
2831 */
2832 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
2833 if (!thread_group_empty(current))
2834 return -EINVAL;
2835 }
2836 if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) {
2837 if (refcount_read(&current->sighand->count) > 1)
2838 return -EINVAL;
2839 }
2840 if (unshare_flags & CLONE_VM) {
2841 if (!current_is_single_threaded())
2842 return -EINVAL;
2843 }
2844
2845 return 0;
2846}
2847
2848/*
2849 * Unshare the filesystem structure if it is being shared
2850 */
2851static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
2852{
2853 struct fs_struct *fs = current->fs;
2854
2855 if (!(unshare_flags & CLONE_FS) || !fs)
2856 return 0;
2857
2858 /* don't need lock here; in the worst case we'll do useless copy */
2859 if (fs->users == 1)
2860 return 0;
2861
2862 *new_fsp = copy_fs_struct(fs);
2863 if (!*new_fsp)
2864 return -ENOMEM;
2865
2866 return 0;
2867}
2868
2869/*
2870 * Unshare file descriptor table if it is being shared
2871 */
2872static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
2873{
2874 struct files_struct *fd = current->files;
2875 int error = 0;
2876
2877 if ((unshare_flags & CLONE_FILES) &&
2878 (fd && atomic_read(&fd->count) > 1)) {
2879 *new_fdp = dup_fd(fd, &error);
2880 if (!*new_fdp)
2881 return error;
2882 }
2883
2884 return 0;
2885}
2886
2887/*
2888 * unshare allows a process to 'unshare' part of the process
2889 * context which was originally shared using clone. copy_*
2890 * functions used by do_fork() cannot be used here directly
2891 * because they modify an inactive task_struct that is being
2892 * constructed. Here we are modifying the current, active,
2893 * task_struct.
2894 */
2895int ksys_unshare(unsigned long unshare_flags)
2896{
2897 struct fs_struct *fs, *new_fs = NULL;
2898 struct files_struct *fd, *new_fd = NULL;
2899 struct cred *new_cred = NULL;
2900 struct nsproxy *new_nsproxy = NULL;
2901 int do_sysvsem = 0;
2902 int err;
2903
2904 /*
2905 * If unsharing a user namespace must also unshare the thread group
2906 * and unshare the filesystem root and working directories.
2907 */
2908 if (unshare_flags & CLONE_NEWUSER)
2909 unshare_flags |= CLONE_THREAD | CLONE_FS;
2910 /*
2911 * If unsharing vm, must also unshare signal handlers.
2912 */
2913 if (unshare_flags & CLONE_VM)
2914 unshare_flags |= CLONE_SIGHAND;
2915 /*
2916 * If unsharing a signal handlers, must also unshare the signal queues.
2917 */
2918 if (unshare_flags & CLONE_SIGHAND)
2919 unshare_flags |= CLONE_THREAD;
2920 /*
2921 * If unsharing namespace, must also unshare filesystem information.
2922 */
2923 if (unshare_flags & CLONE_NEWNS)
2924 unshare_flags |= CLONE_FS;
2925
2926 err = check_unshare_flags(unshare_flags);
2927 if (err)
2928 goto bad_unshare_out;
2929 /*
2930 * CLONE_NEWIPC must also detach from the undolist: after switching
2931 * to a new ipc namespace, the semaphore arrays from the old
2932 * namespace are unreachable.
2933 */
2934 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
2935 do_sysvsem = 1;
2936 err = unshare_fs(unshare_flags, &new_fs);
2937 if (err)
2938 goto bad_unshare_out;
2939 err = unshare_fd(unshare_flags, &new_fd);
2940 if (err)
2941 goto bad_unshare_cleanup_fs;
2942 err = unshare_userns(unshare_flags, &new_cred);
2943 if (err)
2944 goto bad_unshare_cleanup_fd;
2945 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
2946 new_cred, new_fs);
2947 if (err)
2948 goto bad_unshare_cleanup_cred;
2949
2950 if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
2951 if (do_sysvsem) {
2952 /*
2953 * CLONE_SYSVSEM is equivalent to sys_exit().
2954 */
2955 exit_sem(current);
2956 }
2957 if (unshare_flags & CLONE_NEWIPC) {
2958 /* Orphan segments in old ns (see sem above). */
2959 exit_shm(current);
2960 shm_init_task(current);
2961 }
2962
2963 if (new_nsproxy)
2964 switch_task_namespaces(current, new_nsproxy);
2965
2966 task_lock(current);
2967
2968 if (new_fs) {
2969 fs = current->fs;
2970 spin_lock(&fs->lock);
2971 current->fs = new_fs;
2972 if (--fs->users)
2973 new_fs = NULL;
2974 else
2975 new_fs = fs;
2976 spin_unlock(&fs->lock);
2977 }
2978
2979 if (new_fd) {
2980 fd = current->files;
2981 current->files = new_fd;
2982 new_fd = fd;
2983 }
2984
2985 task_unlock(current);
2986
2987 if (new_cred) {
2988 /* Install the new user namespace */
2989 commit_creds(new_cred);
2990 new_cred = NULL;
2991 }
2992 }
2993
2994 perf_event_namespaces(current);
2995
2996bad_unshare_cleanup_cred:
2997 if (new_cred)
2998 put_cred(new_cred);
2999bad_unshare_cleanup_fd:
3000 if (new_fd)
3001 put_files_struct(new_fd);
3002
3003bad_unshare_cleanup_fs:
3004 if (new_fs)
3005 free_fs_struct(new_fs);
3006
3007bad_unshare_out:
3008 return err;
3009}
3010
3011SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
3012{
3013 return ksys_unshare(unshare_flags);
3014}
3015
3016/*
3017 * Helper to unshare the files of the current task.
3018 * We don't want to expose copy_files internals to
3019 * the exec layer of the kernel.
3020 */
3021
3022int unshare_files(struct files_struct **displaced)
3023{
3024 struct task_struct *task = current;
3025 struct files_struct *copy = NULL;
3026 int error;
3027
3028 error = unshare_fd(CLONE_FILES, &copy);
3029 if (error || !copy) {
3030 *displaced = NULL;
3031 return error;
3032 }
3033 *displaced = task->files;
3034 task_lock(task);
3035 task->files = copy;
3036 task_unlock(task);
3037 return 0;
3038}
3039
3040int sysctl_max_threads(struct ctl_table *table, int write,
3041 void __user *buffer, size_t *lenp, loff_t *ppos)
3042{
3043 struct ctl_table t;
3044 int ret;
3045 int threads = max_threads;
3046 int min = 1;
3047 int max = MAX_THREADS;
3048
3049 t = *table;
3050 t.data = &threads;
3051 t.extra1 = &min;
3052 t.extra2 = &max;
3053
3054 ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
3055 if (ret || !write)
3056 return ret;
3057
3058 max_threads = threads;
3059
3060 return 0;
3061}