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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/hmm.h>
44#include <linux/fs.h>
45#include <linux/mm.h>
46#include <linux/vmacache.h>
47#include <linux/nsproxy.h>
48#include <linux/capability.h>
49#include <linux/cpu.h>
50#include <linux/cgroup.h>
51#include <linux/security.h>
52#include <linux/hugetlb.h>
53#include <linux/seccomp.h>
54#include <linux/swap.h>
55#include <linux/syscalls.h>
56#include <linux/jiffies.h>
57#include <linux/futex.h>
58#include <linux/compat.h>
59#include <linux/kthread.h>
60#include <linux/task_io_accounting_ops.h>
61#include <linux/rcupdate.h>
62#include <linux/ptrace.h>
63#include <linux/mount.h>
64#include <linux/audit.h>
65#include <linux/memcontrol.h>
66#include <linux/ftrace.h>
67#include <linux/proc_fs.h>
68#include <linux/profile.h>
69#include <linux/rmap.h>
70#include <linux/ksm.h>
71#include <linux/acct.h>
72#include <linux/userfaultfd_k.h>
73#include <linux/tsacct_kern.h>
74#include <linux/cn_proc.h>
75#include <linux/freezer.h>
76#include <linux/delayacct.h>
77#include <linux/taskstats_kern.h>
78#include <linux/random.h>
79#include <linux/tty.h>
80#include <linux/blkdev.h>
81#include <linux/fs_struct.h>
82#include <linux/magic.h>
83#include <linux/perf_event.h>
84#include <linux/posix-timers.h>
85#include <linux/user-return-notifier.h>
86#include <linux/oom.h>
87#include <linux/khugepaged.h>
88#include <linux/signalfd.h>
89#include <linux/uprobes.h>
90#include <linux/aio.h>
91#include <linux/compiler.h>
92#include <linux/sysctl.h>
93#include <linux/kcov.h>
94#include <linux/livepatch.h>
95#include <linux/thread_info.h>
96#include <linux/stackleak.h>
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 stale pointers from reused stack. */
228 memset(s->addr, 0, THREAD_SIZE);
229
230 tsk->stack_vm_area = s;
231 tsk->stack = s->addr;
232 return s->addr;
233 }
234
235 /*
236 * Allocated stacks are cached and later reused by new threads,
237 * so memcg accounting is performed manually on assigning/releasing
238 * stacks to tasks. Drop __GFP_ACCOUNT.
239 */
240 stack = __vmalloc_node_range(THREAD_SIZE, THREAD_ALIGN,
241 VMALLOC_START, VMALLOC_END,
242 THREADINFO_GFP & ~__GFP_ACCOUNT,
243 PAGE_KERNEL,
244 0, node, __builtin_return_address(0));
245
246 /*
247 * We can't call find_vm_area() in interrupt context, and
248 * free_thread_stack() can be called in interrupt context,
249 * so cache the vm_struct.
250 */
251 if (stack) {
252 tsk->stack_vm_area = find_vm_area(stack);
253 tsk->stack = stack;
254 }
255 return stack;
256#else
257 struct page *page = alloc_pages_node(node, THREADINFO_GFP,
258 THREAD_SIZE_ORDER);
259
260 if (likely(page)) {
261 tsk->stack = page_address(page);
262 return tsk->stack;
263 }
264 return NULL;
265#endif
266}
267
268static inline void free_thread_stack(struct task_struct *tsk)
269{
270#ifdef CONFIG_VMAP_STACK
271 struct vm_struct *vm = task_stack_vm_area(tsk);
272
273 if (vm) {
274 int i;
275
276 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
277 mod_memcg_page_state(vm->pages[i],
278 MEMCG_KERNEL_STACK_KB,
279 -(int)(PAGE_SIZE / 1024));
280
281 memcg_kmem_uncharge(vm->pages[i], 0);
282 }
283
284 for (i = 0; i < NR_CACHED_STACKS; i++) {
285 if (this_cpu_cmpxchg(cached_stacks[i],
286 NULL, tsk->stack_vm_area) != NULL)
287 continue;
288
289 return;
290 }
291
292 vfree_atomic(tsk->stack);
293 return;
294 }
295#endif
296
297 __free_pages(virt_to_page(tsk->stack), THREAD_SIZE_ORDER);
298}
299# else
300static struct kmem_cache *thread_stack_cache;
301
302static unsigned long *alloc_thread_stack_node(struct task_struct *tsk,
303 int node)
304{
305 unsigned long *stack;
306 stack = kmem_cache_alloc_node(thread_stack_cache, THREADINFO_GFP, node);
307 tsk->stack = stack;
308 return stack;
309}
310
311static void free_thread_stack(struct task_struct *tsk)
312{
313 kmem_cache_free(thread_stack_cache, tsk->stack);
314}
315
316void thread_stack_cache_init(void)
317{
318 thread_stack_cache = kmem_cache_create_usercopy("thread_stack",
319 THREAD_SIZE, THREAD_SIZE, 0, 0,
320 THREAD_SIZE, NULL);
321 BUG_ON(thread_stack_cache == NULL);
322}
323# endif
324#endif
325
326/* SLAB cache for signal_struct structures (tsk->signal) */
327static struct kmem_cache *signal_cachep;
328
329/* SLAB cache for sighand_struct structures (tsk->sighand) */
330struct kmem_cache *sighand_cachep;
331
332/* SLAB cache for files_struct structures (tsk->files) */
333struct kmem_cache *files_cachep;
334
335/* SLAB cache for fs_struct structures (tsk->fs) */
336struct kmem_cache *fs_cachep;
337
338/* SLAB cache for vm_area_struct structures */
339static struct kmem_cache *vm_area_cachep;
340
341/* SLAB cache for mm_struct structures (tsk->mm) */
342static struct kmem_cache *mm_cachep;
343
344struct vm_area_struct *vm_area_alloc(struct mm_struct *mm)
345{
346 struct vm_area_struct *vma;
347
348 vma = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
349 if (vma)
350 vma_init(vma, mm);
351 return vma;
352}
353
354struct vm_area_struct *vm_area_dup(struct vm_area_struct *orig)
355{
356 struct vm_area_struct *new = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
357
358 if (new) {
359 *new = *orig;
360 INIT_LIST_HEAD(&new->anon_vma_chain);
361 }
362 return new;
363}
364
365void vm_area_free(struct vm_area_struct *vma)
366{
367 kmem_cache_free(vm_area_cachep, vma);
368}
369
370static void account_kernel_stack(struct task_struct *tsk, int account)
371{
372 void *stack = task_stack_page(tsk);
373 struct vm_struct *vm = task_stack_vm_area(tsk);
374
375 BUILD_BUG_ON(IS_ENABLED(CONFIG_VMAP_STACK) && PAGE_SIZE % 1024 != 0);
376
377 if (vm) {
378 int i;
379
380 BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE);
381
382 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
383 mod_zone_page_state(page_zone(vm->pages[i]),
384 NR_KERNEL_STACK_KB,
385 PAGE_SIZE / 1024 * account);
386 }
387 } else {
388 /*
389 * All stack pages are in the same zone and belong to the
390 * same memcg.
391 */
392 struct page *first_page = virt_to_page(stack);
393
394 mod_zone_page_state(page_zone(first_page), NR_KERNEL_STACK_KB,
395 THREAD_SIZE / 1024 * account);
396
397 mod_memcg_page_state(first_page, MEMCG_KERNEL_STACK_KB,
398 account * (THREAD_SIZE / 1024));
399 }
400}
401
402static int memcg_charge_kernel_stack(struct task_struct *tsk)
403{
404#ifdef CONFIG_VMAP_STACK
405 struct vm_struct *vm = task_stack_vm_area(tsk);
406 int ret;
407
408 if (vm) {
409 int i;
410
411 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
412 /*
413 * If memcg_kmem_charge() fails, page->mem_cgroup
414 * pointer is NULL, and both memcg_kmem_uncharge()
415 * and mod_memcg_page_state() in free_thread_stack()
416 * will ignore this page. So it's safe.
417 */
418 ret = memcg_kmem_charge(vm->pages[i], GFP_KERNEL, 0);
419 if (ret)
420 return ret;
421
422 mod_memcg_page_state(vm->pages[i],
423 MEMCG_KERNEL_STACK_KB,
424 PAGE_SIZE / 1024);
425 }
426 }
427#endif
428 return 0;
429}
430
431static void release_task_stack(struct task_struct *tsk)
432{
433 if (WARN_ON(tsk->state != TASK_DEAD))
434 return; /* Better to leak the stack than to free prematurely */
435
436 account_kernel_stack(tsk, -1);
437 free_thread_stack(tsk);
438 tsk->stack = NULL;
439#ifdef CONFIG_VMAP_STACK
440 tsk->stack_vm_area = NULL;
441#endif
442}
443
444#ifdef CONFIG_THREAD_INFO_IN_TASK
445void put_task_stack(struct task_struct *tsk)
446{
447 if (refcount_dec_and_test(&tsk->stack_refcount))
448 release_task_stack(tsk);
449}
450#endif
451
452void free_task(struct task_struct *tsk)
453{
454#ifndef CONFIG_THREAD_INFO_IN_TASK
455 /*
456 * The task is finally done with both the stack and thread_info,
457 * so free both.
458 */
459 release_task_stack(tsk);
460#else
461 /*
462 * If the task had a separate stack allocation, it should be gone
463 * by now.
464 */
465 WARN_ON_ONCE(refcount_read(&tsk->stack_refcount) != 0);
466#endif
467 rt_mutex_debug_task_free(tsk);
468 ftrace_graph_exit_task(tsk);
469 put_seccomp_filter(tsk);
470 arch_release_task_struct(tsk);
471 if (tsk->flags & PF_KTHREAD)
472 free_kthread_struct(tsk);
473 free_task_struct(tsk);
474}
475EXPORT_SYMBOL(free_task);
476
477#ifdef CONFIG_MMU
478static __latent_entropy int dup_mmap(struct mm_struct *mm,
479 struct mm_struct *oldmm)
480{
481 struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
482 struct rb_node **rb_link, *rb_parent;
483 int retval;
484 unsigned long charge;
485 LIST_HEAD(uf);
486
487 uprobe_start_dup_mmap();
488 if (down_write_killable(&oldmm->mmap_sem)) {
489 retval = -EINTR;
490 goto fail_uprobe_end;
491 }
492 flush_cache_dup_mm(oldmm);
493 uprobe_dup_mmap(oldmm, mm);
494 /*
495 * Not linked in yet - no deadlock potential:
496 */
497 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
498
499 /* No ordering required: file already has been exposed. */
500 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
501
502 mm->total_vm = oldmm->total_vm;
503 mm->data_vm = oldmm->data_vm;
504 mm->exec_vm = oldmm->exec_vm;
505 mm->stack_vm = oldmm->stack_vm;
506
507 rb_link = &mm->mm_rb.rb_node;
508 rb_parent = NULL;
509 pprev = &mm->mmap;
510 retval = ksm_fork(mm, oldmm);
511 if (retval)
512 goto out;
513 retval = khugepaged_fork(mm, oldmm);
514 if (retval)
515 goto out;
516
517 prev = NULL;
518 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
519 struct file *file;
520
521 if (mpnt->vm_flags & VM_DONTCOPY) {
522 vm_stat_account(mm, mpnt->vm_flags, -vma_pages(mpnt));
523 continue;
524 }
525 charge = 0;
526 /*
527 * Don't duplicate many vmas if we've been oom-killed (for
528 * example)
529 */
530 if (fatal_signal_pending(current)) {
531 retval = -EINTR;
532 goto out;
533 }
534 if (mpnt->vm_flags & VM_ACCOUNT) {
535 unsigned long len = vma_pages(mpnt);
536
537 if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
538 goto fail_nomem;
539 charge = len;
540 }
541 tmp = vm_area_dup(mpnt);
542 if (!tmp)
543 goto fail_nomem;
544 retval = vma_dup_policy(mpnt, tmp);
545 if (retval)
546 goto fail_nomem_policy;
547 tmp->vm_mm = mm;
548 retval = dup_userfaultfd(tmp, &uf);
549 if (retval)
550 goto fail_nomem_anon_vma_fork;
551 if (tmp->vm_flags & VM_WIPEONFORK) {
552 /* VM_WIPEONFORK gets a clean slate in the child. */
553 tmp->anon_vma = NULL;
554 if (anon_vma_prepare(tmp))
555 goto fail_nomem_anon_vma_fork;
556 } else if (anon_vma_fork(tmp, mpnt))
557 goto fail_nomem_anon_vma_fork;
558 tmp->vm_flags &= ~(VM_LOCKED | VM_LOCKONFAULT);
559 tmp->vm_next = tmp->vm_prev = NULL;
560 file = tmp->vm_file;
561 if (file) {
562 struct inode *inode = file_inode(file);
563 struct address_space *mapping = file->f_mapping;
564
565 get_file(file);
566 if (tmp->vm_flags & VM_DENYWRITE)
567 atomic_dec(&inode->i_writecount);
568 i_mmap_lock_write(mapping);
569 if (tmp->vm_flags & VM_SHARED)
570 atomic_inc(&mapping->i_mmap_writable);
571 flush_dcache_mmap_lock(mapping);
572 /* insert tmp into the share list, just after mpnt */
573 vma_interval_tree_insert_after(tmp, mpnt,
574 &mapping->i_mmap);
575 flush_dcache_mmap_unlock(mapping);
576 i_mmap_unlock_write(mapping);
577 }
578
579 /*
580 * Clear hugetlb-related page reserves for children. This only
581 * affects MAP_PRIVATE mappings. Faults generated by the child
582 * are not guaranteed to succeed, even if read-only
583 */
584 if (is_vm_hugetlb_page(tmp))
585 reset_vma_resv_huge_pages(tmp);
586
587 /*
588 * Link in the new vma and copy the page table entries.
589 */
590 *pprev = tmp;
591 pprev = &tmp->vm_next;
592 tmp->vm_prev = prev;
593 prev = tmp;
594
595 __vma_link_rb(mm, tmp, rb_link, rb_parent);
596 rb_link = &tmp->vm_rb.rb_right;
597 rb_parent = &tmp->vm_rb;
598
599 mm->map_count++;
600 if (!(tmp->vm_flags & VM_WIPEONFORK))
601 retval = copy_page_range(mm, oldmm, mpnt);
602
603 if (tmp->vm_ops && tmp->vm_ops->open)
604 tmp->vm_ops->open(tmp);
605
606 if (retval)
607 goto out;
608 }
609 /* a new mm has just been created */
610 retval = arch_dup_mmap(oldmm, mm);
611out:
612 up_write(&mm->mmap_sem);
613 flush_tlb_mm(oldmm);
614 up_write(&oldmm->mmap_sem);
615 dup_userfaultfd_complete(&uf);
616fail_uprobe_end:
617 uprobe_end_dup_mmap();
618 return retval;
619fail_nomem_anon_vma_fork:
620 mpol_put(vma_policy(tmp));
621fail_nomem_policy:
622 vm_area_free(tmp);
623fail_nomem:
624 retval = -ENOMEM;
625 vm_unacct_memory(charge);
626 goto out;
627}
628
629static inline int mm_alloc_pgd(struct mm_struct *mm)
630{
631 mm->pgd = pgd_alloc(mm);
632 if (unlikely(!mm->pgd))
633 return -ENOMEM;
634 return 0;
635}
636
637static inline void mm_free_pgd(struct mm_struct *mm)
638{
639 pgd_free(mm, mm->pgd);
640}
641#else
642static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
643{
644 down_write(&oldmm->mmap_sem);
645 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
646 up_write(&oldmm->mmap_sem);
647 return 0;
648}
649#define mm_alloc_pgd(mm) (0)
650#define mm_free_pgd(mm)
651#endif /* CONFIG_MMU */
652
653static void check_mm(struct mm_struct *mm)
654{
655 int i;
656
657 BUILD_BUG_ON_MSG(ARRAY_SIZE(resident_page_types) != NR_MM_COUNTERS,
658 "Please make sure 'struct resident_page_types[]' is updated as well");
659
660 for (i = 0; i < NR_MM_COUNTERS; i++) {
661 long x = atomic_long_read(&mm->rss_stat.count[i]);
662
663 if (unlikely(x))
664 pr_alert("BUG: Bad rss-counter state mm:%p type:%s val:%ld\n",
665 mm, resident_page_types[i], x);
666 }
667
668 if (mm_pgtables_bytes(mm))
669 pr_alert("BUG: non-zero pgtables_bytes on freeing mm: %ld\n",
670 mm_pgtables_bytes(mm));
671
672#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
673 VM_BUG_ON_MM(mm->pmd_huge_pte, mm);
674#endif
675}
676
677#define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
678#define free_mm(mm) (kmem_cache_free(mm_cachep, (mm)))
679
680/*
681 * Called when the last reference to the mm
682 * is dropped: either by a lazy thread or by
683 * mmput. Free the page directory and the mm.
684 */
685void __mmdrop(struct mm_struct *mm)
686{
687 BUG_ON(mm == &init_mm);
688 WARN_ON_ONCE(mm == current->mm);
689 WARN_ON_ONCE(mm == current->active_mm);
690 mm_free_pgd(mm);
691 destroy_context(mm);
692 mmu_notifier_mm_destroy(mm);
693 check_mm(mm);
694 put_user_ns(mm->user_ns);
695 free_mm(mm);
696}
697EXPORT_SYMBOL_GPL(__mmdrop);
698
699static void mmdrop_async_fn(struct work_struct *work)
700{
701 struct mm_struct *mm;
702
703 mm = container_of(work, struct mm_struct, async_put_work);
704 __mmdrop(mm);
705}
706
707static void mmdrop_async(struct mm_struct *mm)
708{
709 if (unlikely(atomic_dec_and_test(&mm->mm_count))) {
710 INIT_WORK(&mm->async_put_work, mmdrop_async_fn);
711 schedule_work(&mm->async_put_work);
712 }
713}
714
715static inline void free_signal_struct(struct signal_struct *sig)
716{
717 taskstats_tgid_free(sig);
718 sched_autogroup_exit(sig);
719 /*
720 * __mmdrop is not safe to call from softirq context on x86 due to
721 * pgd_dtor so postpone it to the async context
722 */
723 if (sig->oom_mm)
724 mmdrop_async(sig->oom_mm);
725 kmem_cache_free(signal_cachep, sig);
726}
727
728static inline void put_signal_struct(struct signal_struct *sig)
729{
730 if (refcount_dec_and_test(&sig->sigcnt))
731 free_signal_struct(sig);
732}
733
734void __put_task_struct(struct task_struct *tsk)
735{
736 WARN_ON(!tsk->exit_state);
737 WARN_ON(refcount_read(&tsk->usage));
738 WARN_ON(tsk == current);
739
740 cgroup_free(tsk);
741 task_numa_free(tsk, true);
742 security_task_free(tsk);
743 exit_creds(tsk);
744 delayacct_tsk_free(tsk);
745 put_signal_struct(tsk->signal);
746
747 if (!profile_handoff_task(tsk))
748 free_task(tsk);
749}
750EXPORT_SYMBOL_GPL(__put_task_struct);
751
752void __init __weak arch_task_cache_init(void) { }
753
754/*
755 * set_max_threads
756 */
757static void set_max_threads(unsigned int max_threads_suggested)
758{
759 u64 threads;
760 unsigned long nr_pages = totalram_pages();
761
762 /*
763 * The number of threads shall be limited such that the thread
764 * structures may only consume a small part of the available memory.
765 */
766 if (fls64(nr_pages) + fls64(PAGE_SIZE) > 64)
767 threads = MAX_THREADS;
768 else
769 threads = div64_u64((u64) nr_pages * (u64) PAGE_SIZE,
770 (u64) THREAD_SIZE * 8UL);
771
772 if (threads > max_threads_suggested)
773 threads = max_threads_suggested;
774
775 max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS);
776}
777
778#ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT
779/* Initialized by the architecture: */
780int arch_task_struct_size __read_mostly;
781#endif
782
783#ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
784static void task_struct_whitelist(unsigned long *offset, unsigned long *size)
785{
786 /* Fetch thread_struct whitelist for the architecture. */
787 arch_thread_struct_whitelist(offset, size);
788
789 /*
790 * Handle zero-sized whitelist or empty thread_struct, otherwise
791 * adjust offset to position of thread_struct in task_struct.
792 */
793 if (unlikely(*size == 0))
794 *offset = 0;
795 else
796 *offset += offsetof(struct task_struct, thread);
797}
798#endif /* CONFIG_ARCH_TASK_STRUCT_ALLOCATOR */
799
800void __init fork_init(void)
801{
802 int i;
803#ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
804#ifndef ARCH_MIN_TASKALIGN
805#define ARCH_MIN_TASKALIGN 0
806#endif
807 int align = max_t(int, L1_CACHE_BYTES, ARCH_MIN_TASKALIGN);
808 unsigned long useroffset, usersize;
809
810 /* create a slab on which task_structs can be allocated */
811 task_struct_whitelist(&useroffset, &usersize);
812 task_struct_cachep = kmem_cache_create_usercopy("task_struct",
813 arch_task_struct_size, align,
814 SLAB_PANIC|SLAB_ACCOUNT,
815 useroffset, usersize, NULL);
816#endif
817
818 /* do the arch specific task caches init */
819 arch_task_cache_init();
820
821 set_max_threads(MAX_THREADS);
822
823 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
824 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
825 init_task.signal->rlim[RLIMIT_SIGPENDING] =
826 init_task.signal->rlim[RLIMIT_NPROC];
827
828 for (i = 0; i < UCOUNT_COUNTS; i++) {
829 init_user_ns.ucount_max[i] = max_threads/2;
830 }
831
832#ifdef CONFIG_VMAP_STACK
833 cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "fork:vm_stack_cache",
834 NULL, free_vm_stack_cache);
835#endif
836
837 lockdep_init_task(&init_task);
838 uprobes_init();
839}
840
841int __weak arch_dup_task_struct(struct task_struct *dst,
842 struct task_struct *src)
843{
844 *dst = *src;
845 return 0;
846}
847
848void set_task_stack_end_magic(struct task_struct *tsk)
849{
850 unsigned long *stackend;
851
852 stackend = end_of_stack(tsk);
853 *stackend = STACK_END_MAGIC; /* for overflow detection */
854}
855
856static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
857{
858 struct task_struct *tsk;
859 unsigned long *stack;
860 struct vm_struct *stack_vm_area __maybe_unused;
861 int err;
862
863 if (node == NUMA_NO_NODE)
864 node = tsk_fork_get_node(orig);
865 tsk = alloc_task_struct_node(node);
866 if (!tsk)
867 return NULL;
868
869 stack = alloc_thread_stack_node(tsk, node);
870 if (!stack)
871 goto free_tsk;
872
873 if (memcg_charge_kernel_stack(tsk))
874 goto free_stack;
875
876 stack_vm_area = task_stack_vm_area(tsk);
877
878 err = arch_dup_task_struct(tsk, orig);
879
880 /*
881 * arch_dup_task_struct() clobbers the stack-related fields. Make
882 * sure they're properly initialized before using any stack-related
883 * functions again.
884 */
885 tsk->stack = stack;
886#ifdef CONFIG_VMAP_STACK
887 tsk->stack_vm_area = stack_vm_area;
888#endif
889#ifdef CONFIG_THREAD_INFO_IN_TASK
890 refcount_set(&tsk->stack_refcount, 1);
891#endif
892
893 if (err)
894 goto free_stack;
895
896#ifdef CONFIG_SECCOMP
897 /*
898 * We must handle setting up seccomp filters once we're under
899 * the sighand lock in case orig has changed between now and
900 * then. Until then, filter must be NULL to avoid messing up
901 * the usage counts on the error path calling free_task.
902 */
903 tsk->seccomp.filter = NULL;
904#endif
905
906 setup_thread_stack(tsk, orig);
907 clear_user_return_notifier(tsk);
908 clear_tsk_need_resched(tsk);
909 set_task_stack_end_magic(tsk);
910
911#ifdef CONFIG_STACKPROTECTOR
912 tsk->stack_canary = get_random_canary();
913#endif
914 if (orig->cpus_ptr == &orig->cpus_mask)
915 tsk->cpus_ptr = &tsk->cpus_mask;
916
917 /*
918 * One for the user space visible state that goes away when reaped.
919 * One for the scheduler.
920 */
921 refcount_set(&tsk->rcu_users, 2);
922 /* One for the rcu users */
923 refcount_set(&tsk->usage, 1);
924#ifdef CONFIG_BLK_DEV_IO_TRACE
925 tsk->btrace_seq = 0;
926#endif
927 tsk->splice_pipe = NULL;
928 tsk->task_frag.page = NULL;
929 tsk->wake_q.next = NULL;
930
931 account_kernel_stack(tsk, 1);
932
933 kcov_task_init(tsk);
934
935#ifdef CONFIG_FAULT_INJECTION
936 tsk->fail_nth = 0;
937#endif
938
939#ifdef CONFIG_BLK_CGROUP
940 tsk->throttle_queue = NULL;
941 tsk->use_memdelay = 0;
942#endif
943
944#ifdef CONFIG_MEMCG
945 tsk->active_memcg = NULL;
946#endif
947 return tsk;
948
949free_stack:
950 free_thread_stack(tsk);
951free_tsk:
952 free_task_struct(tsk);
953 return NULL;
954}
955
956__cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
957
958static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
959
960static int __init coredump_filter_setup(char *s)
961{
962 default_dump_filter =
963 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
964 MMF_DUMP_FILTER_MASK;
965 return 1;
966}
967
968__setup("coredump_filter=", coredump_filter_setup);
969
970#include <linux/init_task.h>
971
972static void mm_init_aio(struct mm_struct *mm)
973{
974#ifdef CONFIG_AIO
975 spin_lock_init(&mm->ioctx_lock);
976 mm->ioctx_table = NULL;
977#endif
978}
979
980static __always_inline void mm_clear_owner(struct mm_struct *mm,
981 struct task_struct *p)
982{
983#ifdef CONFIG_MEMCG
984 if (mm->owner == p)
985 WRITE_ONCE(mm->owner, NULL);
986#endif
987}
988
989static void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
990{
991#ifdef CONFIG_MEMCG
992 mm->owner = p;
993#endif
994}
995
996static void mm_init_uprobes_state(struct mm_struct *mm)
997{
998#ifdef CONFIG_UPROBES
999 mm->uprobes_state.xol_area = NULL;
1000#endif
1001}
1002
1003static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
1004 struct user_namespace *user_ns)
1005{
1006 mm->mmap = NULL;
1007 mm->mm_rb = RB_ROOT;
1008 mm->vmacache_seqnum = 0;
1009 atomic_set(&mm->mm_users, 1);
1010 atomic_set(&mm->mm_count, 1);
1011 init_rwsem(&mm->mmap_sem);
1012 INIT_LIST_HEAD(&mm->mmlist);
1013 mm->core_state = NULL;
1014 mm_pgtables_bytes_init(mm);
1015 mm->map_count = 0;
1016 mm->locked_vm = 0;
1017 atomic64_set(&mm->pinned_vm, 0);
1018 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
1019 spin_lock_init(&mm->page_table_lock);
1020 spin_lock_init(&mm->arg_lock);
1021 mm_init_cpumask(mm);
1022 mm_init_aio(mm);
1023 mm_init_owner(mm, p);
1024 RCU_INIT_POINTER(mm->exe_file, NULL);
1025 mmu_notifier_mm_init(mm);
1026 init_tlb_flush_pending(mm);
1027#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
1028 mm->pmd_huge_pte = NULL;
1029#endif
1030 mm_init_uprobes_state(mm);
1031
1032 if (current->mm) {
1033 mm->flags = current->mm->flags & MMF_INIT_MASK;
1034 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK;
1035 } else {
1036 mm->flags = default_dump_filter;
1037 mm->def_flags = 0;
1038 }
1039
1040 if (mm_alloc_pgd(mm))
1041 goto fail_nopgd;
1042
1043 if (init_new_context(p, mm))
1044 goto fail_nocontext;
1045
1046 mm->user_ns = get_user_ns(user_ns);
1047 return mm;
1048
1049fail_nocontext:
1050 mm_free_pgd(mm);
1051fail_nopgd:
1052 free_mm(mm);
1053 return NULL;
1054}
1055
1056/*
1057 * Allocate and initialize an mm_struct.
1058 */
1059struct mm_struct *mm_alloc(void)
1060{
1061 struct mm_struct *mm;
1062
1063 mm = allocate_mm();
1064 if (!mm)
1065 return NULL;
1066
1067 memset(mm, 0, sizeof(*mm));
1068 return mm_init(mm, current, current_user_ns());
1069}
1070
1071static inline void __mmput(struct mm_struct *mm)
1072{
1073 VM_BUG_ON(atomic_read(&mm->mm_users));
1074
1075 uprobe_clear_state(mm);
1076 exit_aio(mm);
1077 ksm_exit(mm);
1078 khugepaged_exit(mm); /* must run before exit_mmap */
1079 exit_mmap(mm);
1080 mm_put_huge_zero_page(mm);
1081 set_mm_exe_file(mm, NULL);
1082 if (!list_empty(&mm->mmlist)) {
1083 spin_lock(&mmlist_lock);
1084 list_del(&mm->mmlist);
1085 spin_unlock(&mmlist_lock);
1086 }
1087 if (mm->binfmt)
1088 module_put(mm->binfmt->module);
1089 mmdrop(mm);
1090}
1091
1092/*
1093 * Decrement the use count and release all resources for an mm.
1094 */
1095void mmput(struct mm_struct *mm)
1096{
1097 might_sleep();
1098
1099 if (atomic_dec_and_test(&mm->mm_users))
1100 __mmput(mm);
1101}
1102EXPORT_SYMBOL_GPL(mmput);
1103
1104#ifdef CONFIG_MMU
1105static void mmput_async_fn(struct work_struct *work)
1106{
1107 struct mm_struct *mm = container_of(work, struct mm_struct,
1108 async_put_work);
1109
1110 __mmput(mm);
1111}
1112
1113void mmput_async(struct mm_struct *mm)
1114{
1115 if (atomic_dec_and_test(&mm->mm_users)) {
1116 INIT_WORK(&mm->async_put_work, mmput_async_fn);
1117 schedule_work(&mm->async_put_work);
1118 }
1119}
1120#endif
1121
1122/**
1123 * set_mm_exe_file - change a reference to the mm's executable file
1124 *
1125 * This changes mm's executable file (shown as symlink /proc/[pid]/exe).
1126 *
1127 * Main users are mmput() and sys_execve(). Callers prevent concurrent
1128 * invocations: in mmput() nobody alive left, in execve task is single
1129 * threaded. sys_prctl(PR_SET_MM_MAP/EXE_FILE) also needs to set the
1130 * mm->exe_file, but does so without using set_mm_exe_file() in order
1131 * to do avoid the need for any locks.
1132 */
1133void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
1134{
1135 struct file *old_exe_file;
1136
1137 /*
1138 * It is safe to dereference the exe_file without RCU as
1139 * this function is only called if nobody else can access
1140 * this mm -- see comment above for justification.
1141 */
1142 old_exe_file = rcu_dereference_raw(mm->exe_file);
1143
1144 if (new_exe_file)
1145 get_file(new_exe_file);
1146 rcu_assign_pointer(mm->exe_file, new_exe_file);
1147 if (old_exe_file)
1148 fput(old_exe_file);
1149}
1150
1151/**
1152 * get_mm_exe_file - acquire a reference to the mm's executable file
1153 *
1154 * Returns %NULL if mm has no associated executable file.
1155 * User must release file via fput().
1156 */
1157struct file *get_mm_exe_file(struct mm_struct *mm)
1158{
1159 struct file *exe_file;
1160
1161 rcu_read_lock();
1162 exe_file = rcu_dereference(mm->exe_file);
1163 if (exe_file && !get_file_rcu(exe_file))
1164 exe_file = NULL;
1165 rcu_read_unlock();
1166 return exe_file;
1167}
1168EXPORT_SYMBOL(get_mm_exe_file);
1169
1170/**
1171 * get_task_exe_file - acquire a reference to the task's executable file
1172 *
1173 * Returns %NULL if task's mm (if any) has no associated executable file or
1174 * this is a kernel thread with borrowed mm (see the comment above get_task_mm).
1175 * User must release file via fput().
1176 */
1177struct file *get_task_exe_file(struct task_struct *task)
1178{
1179 struct file *exe_file = NULL;
1180 struct mm_struct *mm;
1181
1182 task_lock(task);
1183 mm = task->mm;
1184 if (mm) {
1185 if (!(task->flags & PF_KTHREAD))
1186 exe_file = get_mm_exe_file(mm);
1187 }
1188 task_unlock(task);
1189 return exe_file;
1190}
1191EXPORT_SYMBOL(get_task_exe_file);
1192
1193/**
1194 * get_task_mm - acquire a reference to the task's mm
1195 *
1196 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning
1197 * this kernel workthread has transiently adopted a user mm with use_mm,
1198 * to do its AIO) is not set and if so returns a reference to it, after
1199 * bumping up the use count. User must release the mm via mmput()
1200 * after use. Typically used by /proc and ptrace.
1201 */
1202struct mm_struct *get_task_mm(struct task_struct *task)
1203{
1204 struct mm_struct *mm;
1205
1206 task_lock(task);
1207 mm = task->mm;
1208 if (mm) {
1209 if (task->flags & PF_KTHREAD)
1210 mm = NULL;
1211 else
1212 mmget(mm);
1213 }
1214 task_unlock(task);
1215 return mm;
1216}
1217EXPORT_SYMBOL_GPL(get_task_mm);
1218
1219struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
1220{
1221 struct mm_struct *mm;
1222 int err;
1223
1224 err = mutex_lock_killable(&task->signal->cred_guard_mutex);
1225 if (err)
1226 return ERR_PTR(err);
1227
1228 mm = get_task_mm(task);
1229 if (mm && mm != current->mm &&
1230 !ptrace_may_access(task, mode)) {
1231 mmput(mm);
1232 mm = ERR_PTR(-EACCES);
1233 }
1234 mutex_unlock(&task->signal->cred_guard_mutex);
1235
1236 return mm;
1237}
1238
1239static void complete_vfork_done(struct task_struct *tsk)
1240{
1241 struct completion *vfork;
1242
1243 task_lock(tsk);
1244 vfork = tsk->vfork_done;
1245 if (likely(vfork)) {
1246 tsk->vfork_done = NULL;
1247 complete(vfork);
1248 }
1249 task_unlock(tsk);
1250}
1251
1252static int wait_for_vfork_done(struct task_struct *child,
1253 struct completion *vfork)
1254{
1255 int killed;
1256
1257 freezer_do_not_count();
1258 cgroup_enter_frozen();
1259 killed = wait_for_completion_killable(vfork);
1260 cgroup_leave_frozen(false);
1261 freezer_count();
1262
1263 if (killed) {
1264 task_lock(child);
1265 child->vfork_done = NULL;
1266 task_unlock(child);
1267 }
1268
1269 put_task_struct(child);
1270 return killed;
1271}
1272
1273/* Please note the differences between mmput and mm_release.
1274 * mmput is called whenever we stop holding onto a mm_struct,
1275 * error success whatever.
1276 *
1277 * mm_release is called after a mm_struct has been removed
1278 * from the current process.
1279 *
1280 * This difference is important for error handling, when we
1281 * only half set up a mm_struct for a new process and need to restore
1282 * the old one. Because we mmput the new mm_struct before
1283 * restoring the old one. . .
1284 * Eric Biederman 10 January 1998
1285 */
1286void mm_release(struct task_struct *tsk, struct mm_struct *mm)
1287{
1288 /* Get rid of any futexes when releasing the mm */
1289#ifdef CONFIG_FUTEX
1290 if (unlikely(tsk->robust_list)) {
1291 exit_robust_list(tsk);
1292 tsk->robust_list = NULL;
1293 }
1294#ifdef CONFIG_COMPAT
1295 if (unlikely(tsk->compat_robust_list)) {
1296 compat_exit_robust_list(tsk);
1297 tsk->compat_robust_list = NULL;
1298 }
1299#endif
1300 if (unlikely(!list_empty(&tsk->pi_state_list)))
1301 exit_pi_state_list(tsk);
1302#endif
1303
1304 uprobe_free_utask(tsk);
1305
1306 /* Get rid of any cached register state */
1307 deactivate_mm(tsk, mm);
1308
1309 /*
1310 * Signal userspace if we're not exiting with a core dump
1311 * because we want to leave the value intact for debugging
1312 * purposes.
1313 */
1314 if (tsk->clear_child_tid) {
1315 if (!(tsk->signal->flags & SIGNAL_GROUP_COREDUMP) &&
1316 atomic_read(&mm->mm_users) > 1) {
1317 /*
1318 * We don't check the error code - if userspace has
1319 * not set up a proper pointer then tough luck.
1320 */
1321 put_user(0, tsk->clear_child_tid);
1322 do_futex(tsk->clear_child_tid, FUTEX_WAKE,
1323 1, NULL, NULL, 0, 0);
1324 }
1325 tsk->clear_child_tid = NULL;
1326 }
1327
1328 /*
1329 * All done, finally we can wake up parent and return this mm to him.
1330 * Also kthread_stop() uses this completion for synchronization.
1331 */
1332 if (tsk->vfork_done)
1333 complete_vfork_done(tsk);
1334}
1335
1336/**
1337 * dup_mm() - duplicates an existing mm structure
1338 * @tsk: the task_struct with which the new mm will be associated.
1339 * @oldmm: the mm to duplicate.
1340 *
1341 * Allocates a new mm structure and duplicates the provided @oldmm structure
1342 * content into it.
1343 *
1344 * Return: the duplicated mm or NULL on failure.
1345 */
1346static struct mm_struct *dup_mm(struct task_struct *tsk,
1347 struct mm_struct *oldmm)
1348{
1349 struct mm_struct *mm;
1350 int err;
1351
1352 mm = allocate_mm();
1353 if (!mm)
1354 goto fail_nomem;
1355
1356 memcpy(mm, oldmm, sizeof(*mm));
1357
1358 if (!mm_init(mm, tsk, mm->user_ns))
1359 goto fail_nomem;
1360
1361 err = dup_mmap(mm, oldmm);
1362 if (err)
1363 goto free_pt;
1364
1365 mm->hiwater_rss = get_mm_rss(mm);
1366 mm->hiwater_vm = mm->total_vm;
1367
1368 if (mm->binfmt && !try_module_get(mm->binfmt->module))
1369 goto free_pt;
1370
1371 return mm;
1372
1373free_pt:
1374 /* don't put binfmt in mmput, we haven't got module yet */
1375 mm->binfmt = NULL;
1376 mm_init_owner(mm, NULL);
1377 mmput(mm);
1378
1379fail_nomem:
1380 return NULL;
1381}
1382
1383static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
1384{
1385 struct mm_struct *mm, *oldmm;
1386 int retval;
1387
1388 tsk->min_flt = tsk->maj_flt = 0;
1389 tsk->nvcsw = tsk->nivcsw = 0;
1390#ifdef CONFIG_DETECT_HUNG_TASK
1391 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
1392 tsk->last_switch_time = 0;
1393#endif
1394
1395 tsk->mm = NULL;
1396 tsk->active_mm = NULL;
1397
1398 /*
1399 * Are we cloning a kernel thread?
1400 *
1401 * We need to steal a active VM for that..
1402 */
1403 oldmm = current->mm;
1404 if (!oldmm)
1405 return 0;
1406
1407 /* initialize the new vmacache entries */
1408 vmacache_flush(tsk);
1409
1410 if (clone_flags & CLONE_VM) {
1411 mmget(oldmm);
1412 mm = oldmm;
1413 goto good_mm;
1414 }
1415
1416 retval = -ENOMEM;
1417 mm = dup_mm(tsk, current->mm);
1418 if (!mm)
1419 goto fail_nomem;
1420
1421good_mm:
1422 tsk->mm = mm;
1423 tsk->active_mm = mm;
1424 return 0;
1425
1426fail_nomem:
1427 return retval;
1428}
1429
1430static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
1431{
1432 struct fs_struct *fs = current->fs;
1433 if (clone_flags & CLONE_FS) {
1434 /* tsk->fs is already what we want */
1435 spin_lock(&fs->lock);
1436 if (fs->in_exec) {
1437 spin_unlock(&fs->lock);
1438 return -EAGAIN;
1439 }
1440 fs->users++;
1441 spin_unlock(&fs->lock);
1442 return 0;
1443 }
1444 tsk->fs = copy_fs_struct(fs);
1445 if (!tsk->fs)
1446 return -ENOMEM;
1447 return 0;
1448}
1449
1450static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
1451{
1452 struct files_struct *oldf, *newf;
1453 int error = 0;
1454
1455 /*
1456 * A background process may not have any files ...
1457 */
1458 oldf = current->files;
1459 if (!oldf)
1460 goto out;
1461
1462 if (clone_flags & CLONE_FILES) {
1463 atomic_inc(&oldf->count);
1464 goto out;
1465 }
1466
1467 newf = dup_fd(oldf, &error);
1468 if (!newf)
1469 goto out;
1470
1471 tsk->files = newf;
1472 error = 0;
1473out:
1474 return error;
1475}
1476
1477static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
1478{
1479#ifdef CONFIG_BLOCK
1480 struct io_context *ioc = current->io_context;
1481 struct io_context *new_ioc;
1482
1483 if (!ioc)
1484 return 0;
1485 /*
1486 * Share io context with parent, if CLONE_IO is set
1487 */
1488 if (clone_flags & CLONE_IO) {
1489 ioc_task_link(ioc);
1490 tsk->io_context = ioc;
1491 } else if (ioprio_valid(ioc->ioprio)) {
1492 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE);
1493 if (unlikely(!new_ioc))
1494 return -ENOMEM;
1495
1496 new_ioc->ioprio = ioc->ioprio;
1497 put_io_context(new_ioc);
1498 }
1499#endif
1500 return 0;
1501}
1502
1503static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
1504{
1505 struct sighand_struct *sig;
1506
1507 if (clone_flags & CLONE_SIGHAND) {
1508 refcount_inc(¤t->sighand->count);
1509 return 0;
1510 }
1511 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1512 rcu_assign_pointer(tsk->sighand, sig);
1513 if (!sig)
1514 return -ENOMEM;
1515
1516 refcount_set(&sig->count, 1);
1517 spin_lock_irq(¤t->sighand->siglock);
1518 memcpy(sig->action, current->sighand->action, sizeof(sig->action));
1519 spin_unlock_irq(¤t->sighand->siglock);
1520 return 0;
1521}
1522
1523void __cleanup_sighand(struct sighand_struct *sighand)
1524{
1525 if (refcount_dec_and_test(&sighand->count)) {
1526 signalfd_cleanup(sighand);
1527 /*
1528 * sighand_cachep is SLAB_TYPESAFE_BY_RCU so we can free it
1529 * without an RCU grace period, see __lock_task_sighand().
1530 */
1531 kmem_cache_free(sighand_cachep, sighand);
1532 }
1533}
1534
1535/*
1536 * Initialize POSIX timer handling for a thread group.
1537 */
1538static void posix_cpu_timers_init_group(struct signal_struct *sig)
1539{
1540 struct posix_cputimers *pct = &sig->posix_cputimers;
1541 unsigned long cpu_limit;
1542
1543 cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1544 posix_cputimers_group_init(pct, cpu_limit);
1545}
1546
1547static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
1548{
1549 struct signal_struct *sig;
1550
1551 if (clone_flags & CLONE_THREAD)
1552 return 0;
1553
1554 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
1555 tsk->signal = sig;
1556 if (!sig)
1557 return -ENOMEM;
1558
1559 sig->nr_threads = 1;
1560 atomic_set(&sig->live, 1);
1561 refcount_set(&sig->sigcnt, 1);
1562
1563 /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */
1564 sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node);
1565 tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head);
1566
1567 init_waitqueue_head(&sig->wait_chldexit);
1568 sig->curr_target = tsk;
1569 init_sigpending(&sig->shared_pending);
1570 INIT_HLIST_HEAD(&sig->multiprocess);
1571 seqlock_init(&sig->stats_lock);
1572 prev_cputime_init(&sig->prev_cputime);
1573
1574#ifdef CONFIG_POSIX_TIMERS
1575 INIT_LIST_HEAD(&sig->posix_timers);
1576 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1577 sig->real_timer.function = it_real_fn;
1578#endif
1579
1580 task_lock(current->group_leader);
1581 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
1582 task_unlock(current->group_leader);
1583
1584 posix_cpu_timers_init_group(sig);
1585
1586 tty_audit_fork(sig);
1587 sched_autogroup_fork(sig);
1588
1589 sig->oom_score_adj = current->signal->oom_score_adj;
1590 sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1591
1592 mutex_init(&sig->cred_guard_mutex);
1593
1594 return 0;
1595}
1596
1597static void copy_seccomp(struct task_struct *p)
1598{
1599#ifdef CONFIG_SECCOMP
1600 /*
1601 * Must be called with sighand->lock held, which is common to
1602 * all threads in the group. Holding cred_guard_mutex is not
1603 * needed because this new task is not yet running and cannot
1604 * be racing exec.
1605 */
1606 assert_spin_locked(¤t->sighand->siglock);
1607
1608 /* Ref-count the new filter user, and assign it. */
1609 get_seccomp_filter(current);
1610 p->seccomp = current->seccomp;
1611
1612 /*
1613 * Explicitly enable no_new_privs here in case it got set
1614 * between the task_struct being duplicated and holding the
1615 * sighand lock. The seccomp state and nnp must be in sync.
1616 */
1617 if (task_no_new_privs(current))
1618 task_set_no_new_privs(p);
1619
1620 /*
1621 * If the parent gained a seccomp mode after copying thread
1622 * flags and between before we held the sighand lock, we have
1623 * to manually enable the seccomp thread flag here.
1624 */
1625 if (p->seccomp.mode != SECCOMP_MODE_DISABLED)
1626 set_tsk_thread_flag(p, TIF_SECCOMP);
1627#endif
1628}
1629
1630SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1631{
1632 current->clear_child_tid = tidptr;
1633
1634 return task_pid_vnr(current);
1635}
1636
1637static void rt_mutex_init_task(struct task_struct *p)
1638{
1639 raw_spin_lock_init(&p->pi_lock);
1640#ifdef CONFIG_RT_MUTEXES
1641 p->pi_waiters = RB_ROOT_CACHED;
1642 p->pi_top_task = NULL;
1643 p->pi_blocked_on = NULL;
1644#endif
1645}
1646
1647static inline void init_task_pid_links(struct task_struct *task)
1648{
1649 enum pid_type type;
1650
1651 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
1652 INIT_HLIST_NODE(&task->pid_links[type]);
1653 }
1654}
1655
1656static inline void
1657init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid)
1658{
1659 if (type == PIDTYPE_PID)
1660 task->thread_pid = pid;
1661 else
1662 task->signal->pids[type] = pid;
1663}
1664
1665static inline void rcu_copy_process(struct task_struct *p)
1666{
1667#ifdef CONFIG_PREEMPT_RCU
1668 p->rcu_read_lock_nesting = 0;
1669 p->rcu_read_unlock_special.s = 0;
1670 p->rcu_blocked_node = NULL;
1671 INIT_LIST_HEAD(&p->rcu_node_entry);
1672#endif /* #ifdef CONFIG_PREEMPT_RCU */
1673#ifdef CONFIG_TASKS_RCU
1674 p->rcu_tasks_holdout = false;
1675 INIT_LIST_HEAD(&p->rcu_tasks_holdout_list);
1676 p->rcu_tasks_idle_cpu = -1;
1677#endif /* #ifdef CONFIG_TASKS_RCU */
1678}
1679
1680struct pid *pidfd_pid(const struct file *file)
1681{
1682 if (file->f_op == &pidfd_fops)
1683 return file->private_data;
1684
1685 return ERR_PTR(-EBADF);
1686}
1687
1688static int pidfd_release(struct inode *inode, struct file *file)
1689{
1690 struct pid *pid = file->private_data;
1691
1692 file->private_data = NULL;
1693 put_pid(pid);
1694 return 0;
1695}
1696
1697#ifdef CONFIG_PROC_FS
1698static void pidfd_show_fdinfo(struct seq_file *m, struct file *f)
1699{
1700 struct pid_namespace *ns = proc_pid_ns(file_inode(m->file));
1701 struct pid *pid = f->private_data;
1702
1703 seq_put_decimal_ull(m, "Pid:\t", pid_nr_ns(pid, ns));
1704 seq_putc(m, '\n');
1705}
1706#endif
1707
1708/*
1709 * Poll support for process exit notification.
1710 */
1711static __poll_t pidfd_poll(struct file *file, struct poll_table_struct *pts)
1712{
1713 struct task_struct *task;
1714 struct pid *pid = file->private_data;
1715 __poll_t poll_flags = 0;
1716
1717 poll_wait(file, &pid->wait_pidfd, pts);
1718
1719 rcu_read_lock();
1720 task = pid_task(pid, PIDTYPE_PID);
1721 /*
1722 * Inform pollers only when the whole thread group exits.
1723 * If the thread group leader exits before all other threads in the
1724 * group, then poll(2) should block, similar to the wait(2) family.
1725 */
1726 if (!task || (task->exit_state && thread_group_empty(task)))
1727 poll_flags = EPOLLIN | EPOLLRDNORM;
1728 rcu_read_unlock();
1729
1730 return poll_flags;
1731}
1732
1733const struct file_operations pidfd_fops = {
1734 .release = pidfd_release,
1735 .poll = pidfd_poll,
1736#ifdef CONFIG_PROC_FS
1737 .show_fdinfo = pidfd_show_fdinfo,
1738#endif
1739};
1740
1741static void __delayed_free_task(struct rcu_head *rhp)
1742{
1743 struct task_struct *tsk = container_of(rhp, struct task_struct, rcu);
1744
1745 free_task(tsk);
1746}
1747
1748static __always_inline void delayed_free_task(struct task_struct *tsk)
1749{
1750 if (IS_ENABLED(CONFIG_MEMCG))
1751 call_rcu(&tsk->rcu, __delayed_free_task);
1752 else
1753 free_task(tsk);
1754}
1755
1756/*
1757 * This creates a new process as a copy of the old one,
1758 * but does not actually start it yet.
1759 *
1760 * It copies the registers, and all the appropriate
1761 * parts of the process environment (as per the clone
1762 * flags). The actual kick-off is left to the caller.
1763 */
1764static __latent_entropy struct task_struct *copy_process(
1765 struct pid *pid,
1766 int trace,
1767 int node,
1768 struct kernel_clone_args *args)
1769{
1770 int pidfd = -1, retval;
1771 struct task_struct *p;
1772 struct multiprocess_signals delayed;
1773 struct file *pidfile = NULL;
1774 u64 clone_flags = args->flags;
1775
1776 /*
1777 * Don't allow sharing the root directory with processes in a different
1778 * namespace
1779 */
1780 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1781 return ERR_PTR(-EINVAL);
1782
1783 if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS))
1784 return ERR_PTR(-EINVAL);
1785
1786 /*
1787 * Thread groups must share signals as well, and detached threads
1788 * can only be started up within the thread group.
1789 */
1790 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1791 return ERR_PTR(-EINVAL);
1792
1793 /*
1794 * Shared signal handlers imply shared VM. By way of the above,
1795 * thread groups also imply shared VM. Blocking this case allows
1796 * for various simplifications in other code.
1797 */
1798 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1799 return ERR_PTR(-EINVAL);
1800
1801 /*
1802 * Siblings of global init remain as zombies on exit since they are
1803 * not reaped by their parent (swapper). To solve this and to avoid
1804 * multi-rooted process trees, prevent global and container-inits
1805 * from creating siblings.
1806 */
1807 if ((clone_flags & CLONE_PARENT) &&
1808 current->signal->flags & SIGNAL_UNKILLABLE)
1809 return ERR_PTR(-EINVAL);
1810
1811 /*
1812 * If the new process will be in a different pid or user namespace
1813 * do not allow it to share a thread group with the forking task.
1814 */
1815 if (clone_flags & CLONE_THREAD) {
1816 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) ||
1817 (task_active_pid_ns(current) !=
1818 current->nsproxy->pid_ns_for_children))
1819 return ERR_PTR(-EINVAL);
1820 }
1821
1822 if (clone_flags & CLONE_PIDFD) {
1823 /*
1824 * - CLONE_DETACHED is blocked so that we can potentially
1825 * reuse it later for CLONE_PIDFD.
1826 * - CLONE_THREAD is blocked until someone really needs it.
1827 */
1828 if (clone_flags & (CLONE_DETACHED | CLONE_THREAD))
1829 return ERR_PTR(-EINVAL);
1830 }
1831
1832 /*
1833 * Force any signals received before this point to be delivered
1834 * before the fork happens. Collect up signals sent to multiple
1835 * processes that happen during the fork and delay them so that
1836 * they appear to happen after the fork.
1837 */
1838 sigemptyset(&delayed.signal);
1839 INIT_HLIST_NODE(&delayed.node);
1840
1841 spin_lock_irq(¤t->sighand->siglock);
1842 if (!(clone_flags & CLONE_THREAD))
1843 hlist_add_head(&delayed.node, ¤t->signal->multiprocess);
1844 recalc_sigpending();
1845 spin_unlock_irq(¤t->sighand->siglock);
1846 retval = -ERESTARTNOINTR;
1847 if (signal_pending(current))
1848 goto fork_out;
1849
1850 retval = -ENOMEM;
1851 p = dup_task_struct(current, node);
1852 if (!p)
1853 goto fork_out;
1854
1855 /*
1856 * This _must_ happen before we call free_task(), i.e. before we jump
1857 * to any of the bad_fork_* labels. This is to avoid freeing
1858 * p->set_child_tid which is (ab)used as a kthread's data pointer for
1859 * kernel threads (PF_KTHREAD).
1860 */
1861 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? args->child_tid : NULL;
1862 /*
1863 * Clear TID on mm_release()?
1864 */
1865 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? args->child_tid : NULL;
1866
1867 ftrace_graph_init_task(p);
1868
1869 rt_mutex_init_task(p);
1870
1871#ifdef CONFIG_PROVE_LOCKING
1872 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1873 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1874#endif
1875 retval = -EAGAIN;
1876 if (atomic_read(&p->real_cred->user->processes) >=
1877 task_rlimit(p, RLIMIT_NPROC)) {
1878 if (p->real_cred->user != INIT_USER &&
1879 !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
1880 goto bad_fork_free;
1881 }
1882 current->flags &= ~PF_NPROC_EXCEEDED;
1883
1884 retval = copy_creds(p, clone_flags);
1885 if (retval < 0)
1886 goto bad_fork_free;
1887
1888 /*
1889 * If multiple threads are within copy_process(), then this check
1890 * triggers too late. This doesn't hurt, the check is only there
1891 * to stop root fork bombs.
1892 */
1893 retval = -EAGAIN;
1894 if (nr_threads >= max_threads)
1895 goto bad_fork_cleanup_count;
1896
1897 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */
1898 p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER | PF_IDLE);
1899 p->flags |= PF_FORKNOEXEC;
1900 INIT_LIST_HEAD(&p->children);
1901 INIT_LIST_HEAD(&p->sibling);
1902 rcu_copy_process(p);
1903 p->vfork_done = NULL;
1904 spin_lock_init(&p->alloc_lock);
1905
1906 init_sigpending(&p->pending);
1907
1908 p->utime = p->stime = p->gtime = 0;
1909#ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
1910 p->utimescaled = p->stimescaled = 0;
1911#endif
1912 prev_cputime_init(&p->prev_cputime);
1913
1914#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
1915 seqcount_init(&p->vtime.seqcount);
1916 p->vtime.starttime = 0;
1917 p->vtime.state = VTIME_INACTIVE;
1918#endif
1919
1920#if defined(SPLIT_RSS_COUNTING)
1921 memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1922#endif
1923
1924 p->default_timer_slack_ns = current->timer_slack_ns;
1925
1926#ifdef CONFIG_PSI
1927 p->psi_flags = 0;
1928#endif
1929
1930 task_io_accounting_init(&p->ioac);
1931 acct_clear_integrals(p);
1932
1933 posix_cputimers_init(&p->posix_cputimers);
1934
1935 p->io_context = NULL;
1936 audit_set_context(p, NULL);
1937 cgroup_fork(p);
1938#ifdef CONFIG_NUMA
1939 p->mempolicy = mpol_dup(p->mempolicy);
1940 if (IS_ERR(p->mempolicy)) {
1941 retval = PTR_ERR(p->mempolicy);
1942 p->mempolicy = NULL;
1943 goto bad_fork_cleanup_threadgroup_lock;
1944 }
1945#endif
1946#ifdef CONFIG_CPUSETS
1947 p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
1948 p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
1949 seqcount_init(&p->mems_allowed_seq);
1950#endif
1951#ifdef CONFIG_TRACE_IRQFLAGS
1952 p->irq_events = 0;
1953 p->hardirqs_enabled = 0;
1954 p->hardirq_enable_ip = 0;
1955 p->hardirq_enable_event = 0;
1956 p->hardirq_disable_ip = _THIS_IP_;
1957 p->hardirq_disable_event = 0;
1958 p->softirqs_enabled = 1;
1959 p->softirq_enable_ip = _THIS_IP_;
1960 p->softirq_enable_event = 0;
1961 p->softirq_disable_ip = 0;
1962 p->softirq_disable_event = 0;
1963 p->hardirq_context = 0;
1964 p->softirq_context = 0;
1965#endif
1966
1967 p->pagefault_disabled = 0;
1968
1969#ifdef CONFIG_LOCKDEP
1970 lockdep_init_task(p);
1971#endif
1972
1973#ifdef CONFIG_DEBUG_MUTEXES
1974 p->blocked_on = NULL; /* not blocked yet */
1975#endif
1976#ifdef CONFIG_BCACHE
1977 p->sequential_io = 0;
1978 p->sequential_io_avg = 0;
1979#endif
1980
1981 /* Perform scheduler related setup. Assign this task to a CPU. */
1982 retval = sched_fork(clone_flags, p);
1983 if (retval)
1984 goto bad_fork_cleanup_policy;
1985
1986 retval = perf_event_init_task(p);
1987 if (retval)
1988 goto bad_fork_cleanup_policy;
1989 retval = audit_alloc(p);
1990 if (retval)
1991 goto bad_fork_cleanup_perf;
1992 /* copy all the process information */
1993 shm_init_task(p);
1994 retval = security_task_alloc(p, clone_flags);
1995 if (retval)
1996 goto bad_fork_cleanup_audit;
1997 retval = copy_semundo(clone_flags, p);
1998 if (retval)
1999 goto bad_fork_cleanup_security;
2000 retval = copy_files(clone_flags, p);
2001 if (retval)
2002 goto bad_fork_cleanup_semundo;
2003 retval = copy_fs(clone_flags, p);
2004 if (retval)
2005 goto bad_fork_cleanup_files;
2006 retval = copy_sighand(clone_flags, p);
2007 if (retval)
2008 goto bad_fork_cleanup_fs;
2009 retval = copy_signal(clone_flags, p);
2010 if (retval)
2011 goto bad_fork_cleanup_sighand;
2012 retval = copy_mm(clone_flags, p);
2013 if (retval)
2014 goto bad_fork_cleanup_signal;
2015 retval = copy_namespaces(clone_flags, p);
2016 if (retval)
2017 goto bad_fork_cleanup_mm;
2018 retval = copy_io(clone_flags, p);
2019 if (retval)
2020 goto bad_fork_cleanup_namespaces;
2021 retval = copy_thread_tls(clone_flags, args->stack, args->stack_size, p,
2022 args->tls);
2023 if (retval)
2024 goto bad_fork_cleanup_io;
2025
2026 stackleak_task_init(p);
2027
2028 if (pid != &init_struct_pid) {
2029 pid = alloc_pid(p->nsproxy->pid_ns_for_children);
2030 if (IS_ERR(pid)) {
2031 retval = PTR_ERR(pid);
2032 goto bad_fork_cleanup_thread;
2033 }
2034 }
2035
2036 /*
2037 * This has to happen after we've potentially unshared the file
2038 * descriptor table (so that the pidfd doesn't leak into the child
2039 * if the fd table isn't shared).
2040 */
2041 if (clone_flags & CLONE_PIDFD) {
2042 retval = get_unused_fd_flags(O_RDWR | O_CLOEXEC);
2043 if (retval < 0)
2044 goto bad_fork_free_pid;
2045
2046 pidfd = retval;
2047
2048 pidfile = anon_inode_getfile("[pidfd]", &pidfd_fops, pid,
2049 O_RDWR | O_CLOEXEC);
2050 if (IS_ERR(pidfile)) {
2051 put_unused_fd(pidfd);
2052 retval = PTR_ERR(pidfile);
2053 goto bad_fork_free_pid;
2054 }
2055 get_pid(pid); /* held by pidfile now */
2056
2057 retval = put_user(pidfd, args->pidfd);
2058 if (retval)
2059 goto bad_fork_put_pidfd;
2060 }
2061
2062#ifdef CONFIG_BLOCK
2063 p->plug = NULL;
2064#endif
2065#ifdef CONFIG_FUTEX
2066 p->robust_list = NULL;
2067#ifdef CONFIG_COMPAT
2068 p->compat_robust_list = NULL;
2069#endif
2070 INIT_LIST_HEAD(&p->pi_state_list);
2071 p->pi_state_cache = NULL;
2072#endif
2073 /*
2074 * sigaltstack should be cleared when sharing the same VM
2075 */
2076 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
2077 sas_ss_reset(p);
2078
2079 /*
2080 * Syscall tracing and stepping should be turned off in the
2081 * child regardless of CLONE_PTRACE.
2082 */
2083 user_disable_single_step(p);
2084 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
2085#ifdef TIF_SYSCALL_EMU
2086 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
2087#endif
2088 clear_tsk_latency_tracing(p);
2089
2090 /* ok, now we should be set up.. */
2091 p->pid = pid_nr(pid);
2092 if (clone_flags & CLONE_THREAD) {
2093 p->exit_signal = -1;
2094 p->group_leader = current->group_leader;
2095 p->tgid = current->tgid;
2096 } else {
2097 if (clone_flags & CLONE_PARENT)
2098 p->exit_signal = current->group_leader->exit_signal;
2099 else
2100 p->exit_signal = args->exit_signal;
2101 p->group_leader = p;
2102 p->tgid = p->pid;
2103 }
2104
2105 p->nr_dirtied = 0;
2106 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
2107 p->dirty_paused_when = 0;
2108
2109 p->pdeath_signal = 0;
2110 INIT_LIST_HEAD(&p->thread_group);
2111 p->task_works = NULL;
2112
2113 cgroup_threadgroup_change_begin(current);
2114 /*
2115 * Ensure that the cgroup subsystem policies allow the new process to be
2116 * forked. It should be noted the the new process's css_set can be changed
2117 * between here and cgroup_post_fork() if an organisation operation is in
2118 * progress.
2119 */
2120 retval = cgroup_can_fork(p);
2121 if (retval)
2122 goto bad_fork_cgroup_threadgroup_change_end;
2123
2124 /*
2125 * From this point on we must avoid any synchronous user-space
2126 * communication until we take the tasklist-lock. In particular, we do
2127 * not want user-space to be able to predict the process start-time by
2128 * stalling fork(2) after we recorded the start_time but before it is
2129 * visible to the system.
2130 */
2131
2132 p->start_time = ktime_get_ns();
2133 p->real_start_time = ktime_get_boottime_ns();
2134
2135 /*
2136 * Make it visible to the rest of the system, but dont wake it up yet.
2137 * Need tasklist lock for parent etc handling!
2138 */
2139 write_lock_irq(&tasklist_lock);
2140
2141 /* CLONE_PARENT re-uses the old parent */
2142 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
2143 p->real_parent = current->real_parent;
2144 p->parent_exec_id = current->parent_exec_id;
2145 } else {
2146 p->real_parent = current;
2147 p->parent_exec_id = current->self_exec_id;
2148 }
2149
2150 klp_copy_process(p);
2151
2152 spin_lock(¤t->sighand->siglock);
2153
2154 /*
2155 * Copy seccomp details explicitly here, in case they were changed
2156 * before holding sighand lock.
2157 */
2158 copy_seccomp(p);
2159
2160 rseq_fork(p, clone_flags);
2161
2162 /* Don't start children in a dying pid namespace */
2163 if (unlikely(!(ns_of_pid(pid)->pid_allocated & PIDNS_ADDING))) {
2164 retval = -ENOMEM;
2165 goto bad_fork_cancel_cgroup;
2166 }
2167
2168 /* Let kill terminate clone/fork in the middle */
2169 if (fatal_signal_pending(current)) {
2170 retval = -EINTR;
2171 goto bad_fork_cancel_cgroup;
2172 }
2173
2174 /* past the last point of failure */
2175 if (pidfile)
2176 fd_install(pidfd, pidfile);
2177
2178 init_task_pid_links(p);
2179 if (likely(p->pid)) {
2180 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
2181
2182 init_task_pid(p, PIDTYPE_PID, pid);
2183 if (thread_group_leader(p)) {
2184 init_task_pid(p, PIDTYPE_TGID, pid);
2185 init_task_pid(p, PIDTYPE_PGID, task_pgrp(current));
2186 init_task_pid(p, PIDTYPE_SID, task_session(current));
2187
2188 if (is_child_reaper(pid)) {
2189 ns_of_pid(pid)->child_reaper = p;
2190 p->signal->flags |= SIGNAL_UNKILLABLE;
2191 }
2192 p->signal->shared_pending.signal = delayed.signal;
2193 p->signal->tty = tty_kref_get(current->signal->tty);
2194 /*
2195 * Inherit has_child_subreaper flag under the same
2196 * tasklist_lock with adding child to the process tree
2197 * for propagate_has_child_subreaper optimization.
2198 */
2199 p->signal->has_child_subreaper = p->real_parent->signal->has_child_subreaper ||
2200 p->real_parent->signal->is_child_subreaper;
2201 list_add_tail(&p->sibling, &p->real_parent->children);
2202 list_add_tail_rcu(&p->tasks, &init_task.tasks);
2203 attach_pid(p, PIDTYPE_TGID);
2204 attach_pid(p, PIDTYPE_PGID);
2205 attach_pid(p, PIDTYPE_SID);
2206 __this_cpu_inc(process_counts);
2207 } else {
2208 current->signal->nr_threads++;
2209 atomic_inc(¤t->signal->live);
2210 refcount_inc(¤t->signal->sigcnt);
2211 task_join_group_stop(p);
2212 list_add_tail_rcu(&p->thread_group,
2213 &p->group_leader->thread_group);
2214 list_add_tail_rcu(&p->thread_node,
2215 &p->signal->thread_head);
2216 }
2217 attach_pid(p, PIDTYPE_PID);
2218 nr_threads++;
2219 }
2220 total_forks++;
2221 hlist_del_init(&delayed.node);
2222 spin_unlock(¤t->sighand->siglock);
2223 syscall_tracepoint_update(p);
2224 write_unlock_irq(&tasklist_lock);
2225
2226 proc_fork_connector(p);
2227 cgroup_post_fork(p);
2228 cgroup_threadgroup_change_end(current);
2229 perf_event_fork(p);
2230
2231 trace_task_newtask(p, clone_flags);
2232 uprobe_copy_process(p, clone_flags);
2233
2234 return p;
2235
2236bad_fork_cancel_cgroup:
2237 spin_unlock(¤t->sighand->siglock);
2238 write_unlock_irq(&tasklist_lock);
2239 cgroup_cancel_fork(p);
2240bad_fork_cgroup_threadgroup_change_end:
2241 cgroup_threadgroup_change_end(current);
2242bad_fork_put_pidfd:
2243 if (clone_flags & CLONE_PIDFD) {
2244 fput(pidfile);
2245 put_unused_fd(pidfd);
2246 }
2247bad_fork_free_pid:
2248 if (pid != &init_struct_pid)
2249 free_pid(pid);
2250bad_fork_cleanup_thread:
2251 exit_thread(p);
2252bad_fork_cleanup_io:
2253 if (p->io_context)
2254 exit_io_context(p);
2255bad_fork_cleanup_namespaces:
2256 exit_task_namespaces(p);
2257bad_fork_cleanup_mm:
2258 if (p->mm) {
2259 mm_clear_owner(p->mm, p);
2260 mmput(p->mm);
2261 }
2262bad_fork_cleanup_signal:
2263 if (!(clone_flags & CLONE_THREAD))
2264 free_signal_struct(p->signal);
2265bad_fork_cleanup_sighand:
2266 __cleanup_sighand(p->sighand);
2267bad_fork_cleanup_fs:
2268 exit_fs(p); /* blocking */
2269bad_fork_cleanup_files:
2270 exit_files(p); /* blocking */
2271bad_fork_cleanup_semundo:
2272 exit_sem(p);
2273bad_fork_cleanup_security:
2274 security_task_free(p);
2275bad_fork_cleanup_audit:
2276 audit_free(p);
2277bad_fork_cleanup_perf:
2278 perf_event_free_task(p);
2279bad_fork_cleanup_policy:
2280 lockdep_free_task(p);
2281#ifdef CONFIG_NUMA
2282 mpol_put(p->mempolicy);
2283bad_fork_cleanup_threadgroup_lock:
2284#endif
2285 delayacct_tsk_free(p);
2286bad_fork_cleanup_count:
2287 atomic_dec(&p->cred->user->processes);
2288 exit_creds(p);
2289bad_fork_free:
2290 p->state = TASK_DEAD;
2291 put_task_stack(p);
2292 delayed_free_task(p);
2293fork_out:
2294 spin_lock_irq(¤t->sighand->siglock);
2295 hlist_del_init(&delayed.node);
2296 spin_unlock_irq(¤t->sighand->siglock);
2297 return ERR_PTR(retval);
2298}
2299
2300static inline void init_idle_pids(struct task_struct *idle)
2301{
2302 enum pid_type type;
2303
2304 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
2305 INIT_HLIST_NODE(&idle->pid_links[type]); /* not really needed */
2306 init_task_pid(idle, type, &init_struct_pid);
2307 }
2308}
2309
2310struct task_struct *fork_idle(int cpu)
2311{
2312 struct task_struct *task;
2313 struct kernel_clone_args args = {
2314 .flags = CLONE_VM,
2315 };
2316
2317 task = copy_process(&init_struct_pid, 0, cpu_to_node(cpu), &args);
2318 if (!IS_ERR(task)) {
2319 init_idle_pids(task);
2320 init_idle(task, cpu);
2321 }
2322
2323 return task;
2324}
2325
2326struct mm_struct *copy_init_mm(void)
2327{
2328 return dup_mm(NULL, &init_mm);
2329}
2330
2331/*
2332 * Ok, this is the main fork-routine.
2333 *
2334 * It copies the process, and if successful kick-starts
2335 * it and waits for it to finish using the VM if required.
2336 *
2337 * args->exit_signal is expected to be checked for sanity by the caller.
2338 */
2339long _do_fork(struct kernel_clone_args *args)
2340{
2341 u64 clone_flags = args->flags;
2342 struct completion vfork;
2343 struct pid *pid;
2344 struct task_struct *p;
2345 int trace = 0;
2346 long nr;
2347
2348 /*
2349 * Determine whether and which event to report to ptracer. When
2350 * called from kernel_thread or CLONE_UNTRACED is explicitly
2351 * requested, no event is reported; otherwise, report if the event
2352 * for the type of forking is enabled.
2353 */
2354 if (!(clone_flags & CLONE_UNTRACED)) {
2355 if (clone_flags & CLONE_VFORK)
2356 trace = PTRACE_EVENT_VFORK;
2357 else if (args->exit_signal != SIGCHLD)
2358 trace = PTRACE_EVENT_CLONE;
2359 else
2360 trace = PTRACE_EVENT_FORK;
2361
2362 if (likely(!ptrace_event_enabled(current, trace)))
2363 trace = 0;
2364 }
2365
2366 p = copy_process(NULL, trace, NUMA_NO_NODE, args);
2367 add_latent_entropy();
2368
2369 if (IS_ERR(p))
2370 return PTR_ERR(p);
2371
2372 /*
2373 * Do this prior waking up the new thread - the thread pointer
2374 * might get invalid after that point, if the thread exits quickly.
2375 */
2376 trace_sched_process_fork(current, p);
2377
2378 pid = get_task_pid(p, PIDTYPE_PID);
2379 nr = pid_vnr(pid);
2380
2381 if (clone_flags & CLONE_PARENT_SETTID)
2382 put_user(nr, args->parent_tid);
2383
2384 if (clone_flags & CLONE_VFORK) {
2385 p->vfork_done = &vfork;
2386 init_completion(&vfork);
2387 get_task_struct(p);
2388 }
2389
2390 wake_up_new_task(p);
2391
2392 /* forking complete and child started to run, tell ptracer */
2393 if (unlikely(trace))
2394 ptrace_event_pid(trace, pid);
2395
2396 if (clone_flags & CLONE_VFORK) {
2397 if (!wait_for_vfork_done(p, &vfork))
2398 ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid);
2399 }
2400
2401 put_pid(pid);
2402 return nr;
2403}
2404
2405bool legacy_clone_args_valid(const struct kernel_clone_args *kargs)
2406{
2407 /* clone(CLONE_PIDFD) uses parent_tidptr to return a pidfd */
2408 if ((kargs->flags & CLONE_PIDFD) &&
2409 (kargs->flags & CLONE_PARENT_SETTID))
2410 return false;
2411
2412 return true;
2413}
2414
2415#ifndef CONFIG_HAVE_COPY_THREAD_TLS
2416/* For compatibility with architectures that call do_fork directly rather than
2417 * using the syscall entry points below. */
2418long do_fork(unsigned long clone_flags,
2419 unsigned long stack_start,
2420 unsigned long stack_size,
2421 int __user *parent_tidptr,
2422 int __user *child_tidptr)
2423{
2424 struct kernel_clone_args args = {
2425 .flags = (clone_flags & ~CSIGNAL),
2426 .pidfd = parent_tidptr,
2427 .child_tid = child_tidptr,
2428 .parent_tid = parent_tidptr,
2429 .exit_signal = (clone_flags & CSIGNAL),
2430 .stack = stack_start,
2431 .stack_size = stack_size,
2432 };
2433
2434 if (!legacy_clone_args_valid(&args))
2435 return -EINVAL;
2436
2437 return _do_fork(&args);
2438}
2439#endif
2440
2441/*
2442 * Create a kernel thread.
2443 */
2444pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
2445{
2446 struct kernel_clone_args args = {
2447 .flags = ((flags | CLONE_VM | CLONE_UNTRACED) & ~CSIGNAL),
2448 .exit_signal = (flags & CSIGNAL),
2449 .stack = (unsigned long)fn,
2450 .stack_size = (unsigned long)arg,
2451 };
2452
2453 return _do_fork(&args);
2454}
2455
2456#ifdef __ARCH_WANT_SYS_FORK
2457SYSCALL_DEFINE0(fork)
2458{
2459#ifdef CONFIG_MMU
2460 struct kernel_clone_args args = {
2461 .exit_signal = SIGCHLD,
2462 };
2463
2464 return _do_fork(&args);
2465#else
2466 /* can not support in nommu mode */
2467 return -EINVAL;
2468#endif
2469}
2470#endif
2471
2472#ifdef __ARCH_WANT_SYS_VFORK
2473SYSCALL_DEFINE0(vfork)
2474{
2475 struct kernel_clone_args args = {
2476 .flags = CLONE_VFORK | CLONE_VM,
2477 .exit_signal = SIGCHLD,
2478 };
2479
2480 return _do_fork(&args);
2481}
2482#endif
2483
2484#ifdef __ARCH_WANT_SYS_CLONE
2485#ifdef CONFIG_CLONE_BACKWARDS
2486SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2487 int __user *, parent_tidptr,
2488 unsigned long, tls,
2489 int __user *, child_tidptr)
2490#elif defined(CONFIG_CLONE_BACKWARDS2)
2491SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags,
2492 int __user *, parent_tidptr,
2493 int __user *, child_tidptr,
2494 unsigned long, tls)
2495#elif defined(CONFIG_CLONE_BACKWARDS3)
2496SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp,
2497 int, stack_size,
2498 int __user *, parent_tidptr,
2499 int __user *, child_tidptr,
2500 unsigned long, tls)
2501#else
2502SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2503 int __user *, parent_tidptr,
2504 int __user *, child_tidptr,
2505 unsigned long, tls)
2506#endif
2507{
2508 struct kernel_clone_args args = {
2509 .flags = (clone_flags & ~CSIGNAL),
2510 .pidfd = parent_tidptr,
2511 .child_tid = child_tidptr,
2512 .parent_tid = parent_tidptr,
2513 .exit_signal = (clone_flags & CSIGNAL),
2514 .stack = newsp,
2515 .tls = tls,
2516 };
2517
2518 if (!legacy_clone_args_valid(&args))
2519 return -EINVAL;
2520
2521 return _do_fork(&args);
2522}
2523#endif
2524
2525#ifdef __ARCH_WANT_SYS_CLONE3
2526noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs,
2527 struct clone_args __user *uargs,
2528 size_t usize)
2529{
2530 int err;
2531 struct clone_args args;
2532
2533 if (unlikely(usize > PAGE_SIZE))
2534 return -E2BIG;
2535 if (unlikely(usize < CLONE_ARGS_SIZE_VER0))
2536 return -EINVAL;
2537
2538 err = copy_struct_from_user(&args, sizeof(args), uargs, usize);
2539 if (err)
2540 return err;
2541
2542 /*
2543 * Verify that higher 32bits of exit_signal are unset and that
2544 * it is a valid signal
2545 */
2546 if (unlikely((args.exit_signal & ~((u64)CSIGNAL)) ||
2547 !valid_signal(args.exit_signal)))
2548 return -EINVAL;
2549
2550 *kargs = (struct kernel_clone_args){
2551 .flags = args.flags,
2552 .pidfd = u64_to_user_ptr(args.pidfd),
2553 .child_tid = u64_to_user_ptr(args.child_tid),
2554 .parent_tid = u64_to_user_ptr(args.parent_tid),
2555 .exit_signal = args.exit_signal,
2556 .stack = args.stack,
2557 .stack_size = args.stack_size,
2558 .tls = args.tls,
2559 };
2560
2561 return 0;
2562}
2563
2564/**
2565 * clone3_stack_valid - check and prepare stack
2566 * @kargs: kernel clone args
2567 *
2568 * Verify that the stack arguments userspace gave us are sane.
2569 * In addition, set the stack direction for userspace since it's easy for us to
2570 * determine.
2571 */
2572static inline bool clone3_stack_valid(struct kernel_clone_args *kargs)
2573{
2574 if (kargs->stack == 0) {
2575 if (kargs->stack_size > 0)
2576 return false;
2577 } else {
2578 if (kargs->stack_size == 0)
2579 return false;
2580
2581 if (!access_ok((void __user *)kargs->stack, kargs->stack_size))
2582 return false;
2583
2584#if !defined(CONFIG_STACK_GROWSUP) && !defined(CONFIG_IA64)
2585 kargs->stack += kargs->stack_size;
2586#endif
2587 }
2588
2589 return true;
2590}
2591
2592static bool clone3_args_valid(struct kernel_clone_args *kargs)
2593{
2594 /*
2595 * All lower bits of the flag word are taken.
2596 * Verify that no other unknown flags are passed along.
2597 */
2598 if (kargs->flags & ~CLONE_LEGACY_FLAGS)
2599 return false;
2600
2601 /*
2602 * - make the CLONE_DETACHED bit reuseable for clone3
2603 * - make the CSIGNAL bits reuseable for clone3
2604 */
2605 if (kargs->flags & (CLONE_DETACHED | CSIGNAL))
2606 return false;
2607
2608 if ((kargs->flags & (CLONE_THREAD | CLONE_PARENT)) &&
2609 kargs->exit_signal)
2610 return false;
2611
2612 if (!clone3_stack_valid(kargs))
2613 return false;
2614
2615 return true;
2616}
2617
2618/**
2619 * clone3 - create a new process with specific properties
2620 * @uargs: argument structure
2621 * @size: size of @uargs
2622 *
2623 * clone3() is the extensible successor to clone()/clone2().
2624 * It takes a struct as argument that is versioned by its size.
2625 *
2626 * Return: On success, a positive PID for the child process.
2627 * On error, a negative errno number.
2628 */
2629SYSCALL_DEFINE2(clone3, struct clone_args __user *, uargs, size_t, size)
2630{
2631 int err;
2632
2633 struct kernel_clone_args kargs;
2634
2635 err = copy_clone_args_from_user(&kargs, uargs, size);
2636 if (err)
2637 return err;
2638
2639 if (!clone3_args_valid(&kargs))
2640 return -EINVAL;
2641
2642 return _do_fork(&kargs);
2643}
2644#endif
2645
2646void walk_process_tree(struct task_struct *top, proc_visitor visitor, void *data)
2647{
2648 struct task_struct *leader, *parent, *child;
2649 int res;
2650
2651 read_lock(&tasklist_lock);
2652 leader = top = top->group_leader;
2653down:
2654 for_each_thread(leader, parent) {
2655 list_for_each_entry(child, &parent->children, sibling) {
2656 res = visitor(child, data);
2657 if (res) {
2658 if (res < 0)
2659 goto out;
2660 leader = child;
2661 goto down;
2662 }
2663up:
2664 ;
2665 }
2666 }
2667
2668 if (leader != top) {
2669 child = leader;
2670 parent = child->real_parent;
2671 leader = parent->group_leader;
2672 goto up;
2673 }
2674out:
2675 read_unlock(&tasklist_lock);
2676}
2677
2678#ifndef ARCH_MIN_MMSTRUCT_ALIGN
2679#define ARCH_MIN_MMSTRUCT_ALIGN 0
2680#endif
2681
2682static void sighand_ctor(void *data)
2683{
2684 struct sighand_struct *sighand = data;
2685
2686 spin_lock_init(&sighand->siglock);
2687 init_waitqueue_head(&sighand->signalfd_wqh);
2688}
2689
2690void __init proc_caches_init(void)
2691{
2692 unsigned int mm_size;
2693
2694 sighand_cachep = kmem_cache_create("sighand_cache",
2695 sizeof(struct sighand_struct), 0,
2696 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_TYPESAFE_BY_RCU|
2697 SLAB_ACCOUNT, sighand_ctor);
2698 signal_cachep = kmem_cache_create("signal_cache",
2699 sizeof(struct signal_struct), 0,
2700 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2701 NULL);
2702 files_cachep = kmem_cache_create("files_cache",
2703 sizeof(struct files_struct), 0,
2704 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2705 NULL);
2706 fs_cachep = kmem_cache_create("fs_cache",
2707 sizeof(struct fs_struct), 0,
2708 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2709 NULL);
2710
2711 /*
2712 * The mm_cpumask is located at the end of mm_struct, and is
2713 * dynamically sized based on the maximum CPU number this system
2714 * can have, taking hotplug into account (nr_cpu_ids).
2715 */
2716 mm_size = sizeof(struct mm_struct) + cpumask_size();
2717
2718 mm_cachep = kmem_cache_create_usercopy("mm_struct",
2719 mm_size, ARCH_MIN_MMSTRUCT_ALIGN,
2720 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2721 offsetof(struct mm_struct, saved_auxv),
2722 sizeof_field(struct mm_struct, saved_auxv),
2723 NULL);
2724 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT);
2725 mmap_init();
2726 nsproxy_cache_init();
2727}
2728
2729/*
2730 * Check constraints on flags passed to the unshare system call.
2731 */
2732static int check_unshare_flags(unsigned long unshare_flags)
2733{
2734 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
2735 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
2736 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET|
2737 CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP))
2738 return -EINVAL;
2739 /*
2740 * Not implemented, but pretend it works if there is nothing
2741 * to unshare. Note that unsharing the address space or the
2742 * signal handlers also need to unshare the signal queues (aka
2743 * CLONE_THREAD).
2744 */
2745 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
2746 if (!thread_group_empty(current))
2747 return -EINVAL;
2748 }
2749 if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) {
2750 if (refcount_read(¤t->sighand->count) > 1)
2751 return -EINVAL;
2752 }
2753 if (unshare_flags & CLONE_VM) {
2754 if (!current_is_single_threaded())
2755 return -EINVAL;
2756 }
2757
2758 return 0;
2759}
2760
2761/*
2762 * Unshare the filesystem structure if it is being shared
2763 */
2764static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
2765{
2766 struct fs_struct *fs = current->fs;
2767
2768 if (!(unshare_flags & CLONE_FS) || !fs)
2769 return 0;
2770
2771 /* don't need lock here; in the worst case we'll do useless copy */
2772 if (fs->users == 1)
2773 return 0;
2774
2775 *new_fsp = copy_fs_struct(fs);
2776 if (!*new_fsp)
2777 return -ENOMEM;
2778
2779 return 0;
2780}
2781
2782/*
2783 * Unshare file descriptor table if it is being shared
2784 */
2785static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
2786{
2787 struct files_struct *fd = current->files;
2788 int error = 0;
2789
2790 if ((unshare_flags & CLONE_FILES) &&
2791 (fd && atomic_read(&fd->count) > 1)) {
2792 *new_fdp = dup_fd(fd, &error);
2793 if (!*new_fdp)
2794 return error;
2795 }
2796
2797 return 0;
2798}
2799
2800/*
2801 * unshare allows a process to 'unshare' part of the process
2802 * context which was originally shared using clone. copy_*
2803 * functions used by do_fork() cannot be used here directly
2804 * because they modify an inactive task_struct that is being
2805 * constructed. Here we are modifying the current, active,
2806 * task_struct.
2807 */
2808int ksys_unshare(unsigned long unshare_flags)
2809{
2810 struct fs_struct *fs, *new_fs = NULL;
2811 struct files_struct *fd, *new_fd = NULL;
2812 struct cred *new_cred = NULL;
2813 struct nsproxy *new_nsproxy = NULL;
2814 int do_sysvsem = 0;
2815 int err;
2816
2817 /*
2818 * If unsharing a user namespace must also unshare the thread group
2819 * and unshare the filesystem root and working directories.
2820 */
2821 if (unshare_flags & CLONE_NEWUSER)
2822 unshare_flags |= CLONE_THREAD | CLONE_FS;
2823 /*
2824 * If unsharing vm, must also unshare signal handlers.
2825 */
2826 if (unshare_flags & CLONE_VM)
2827 unshare_flags |= CLONE_SIGHAND;
2828 /*
2829 * If unsharing a signal handlers, must also unshare the signal queues.
2830 */
2831 if (unshare_flags & CLONE_SIGHAND)
2832 unshare_flags |= CLONE_THREAD;
2833 /*
2834 * If unsharing namespace, must also unshare filesystem information.
2835 */
2836 if (unshare_flags & CLONE_NEWNS)
2837 unshare_flags |= CLONE_FS;
2838
2839 err = check_unshare_flags(unshare_flags);
2840 if (err)
2841 goto bad_unshare_out;
2842 /*
2843 * CLONE_NEWIPC must also detach from the undolist: after switching
2844 * to a new ipc namespace, the semaphore arrays from the old
2845 * namespace are unreachable.
2846 */
2847 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
2848 do_sysvsem = 1;
2849 err = unshare_fs(unshare_flags, &new_fs);
2850 if (err)
2851 goto bad_unshare_out;
2852 err = unshare_fd(unshare_flags, &new_fd);
2853 if (err)
2854 goto bad_unshare_cleanup_fs;
2855 err = unshare_userns(unshare_flags, &new_cred);
2856 if (err)
2857 goto bad_unshare_cleanup_fd;
2858 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
2859 new_cred, new_fs);
2860 if (err)
2861 goto bad_unshare_cleanup_cred;
2862
2863 if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
2864 if (do_sysvsem) {
2865 /*
2866 * CLONE_SYSVSEM is equivalent to sys_exit().
2867 */
2868 exit_sem(current);
2869 }
2870 if (unshare_flags & CLONE_NEWIPC) {
2871 /* Orphan segments in old ns (see sem above). */
2872 exit_shm(current);
2873 shm_init_task(current);
2874 }
2875
2876 if (new_nsproxy)
2877 switch_task_namespaces(current, new_nsproxy);
2878
2879 task_lock(current);
2880
2881 if (new_fs) {
2882 fs = current->fs;
2883 spin_lock(&fs->lock);
2884 current->fs = new_fs;
2885 if (--fs->users)
2886 new_fs = NULL;
2887 else
2888 new_fs = fs;
2889 spin_unlock(&fs->lock);
2890 }
2891
2892 if (new_fd) {
2893 fd = current->files;
2894 current->files = new_fd;
2895 new_fd = fd;
2896 }
2897
2898 task_unlock(current);
2899
2900 if (new_cred) {
2901 /* Install the new user namespace */
2902 commit_creds(new_cred);
2903 new_cred = NULL;
2904 }
2905 }
2906
2907 perf_event_namespaces(current);
2908
2909bad_unshare_cleanup_cred:
2910 if (new_cred)
2911 put_cred(new_cred);
2912bad_unshare_cleanup_fd:
2913 if (new_fd)
2914 put_files_struct(new_fd);
2915
2916bad_unshare_cleanup_fs:
2917 if (new_fs)
2918 free_fs_struct(new_fs);
2919
2920bad_unshare_out:
2921 return err;
2922}
2923
2924SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
2925{
2926 return ksys_unshare(unshare_flags);
2927}
2928
2929/*
2930 * Helper to unshare the files of the current task.
2931 * We don't want to expose copy_files internals to
2932 * the exec layer of the kernel.
2933 */
2934
2935int unshare_files(struct files_struct **displaced)
2936{
2937 struct task_struct *task = current;
2938 struct files_struct *copy = NULL;
2939 int error;
2940
2941 error = unshare_fd(CLONE_FILES, ©);
2942 if (error || !copy) {
2943 *displaced = NULL;
2944 return error;
2945 }
2946 *displaced = task->files;
2947 task_lock(task);
2948 task->files = copy;
2949 task_unlock(task);
2950 return 0;
2951}
2952
2953int sysctl_max_threads(struct ctl_table *table, int write,
2954 void __user *buffer, size_t *lenp, loff_t *ppos)
2955{
2956 struct ctl_table t;
2957 int ret;
2958 int threads = max_threads;
2959 int min = 1;
2960 int max = MAX_THREADS;
2961
2962 t = *table;
2963 t.data = &threads;
2964 t.extra1 = &min;
2965 t.extra2 = &max;
2966
2967 ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
2968 if (ret || !write)
2969 return ret;
2970
2971 max_threads = threads;
2972
2973 return 0;
2974}
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/kmsan.h>
41#include <linux/binfmts.h>
42#include <linux/mman.h>
43#include <linux/mmu_notifier.h>
44#include <linux/fs.h>
45#include <linux/mm.h>
46#include <linux/mm_inline.h>
47#include <linux/nsproxy.h>
48#include <linux/capability.h>
49#include <linux/cpu.h>
50#include <linux/cgroup.h>
51#include <linux/security.h>
52#include <linux/hugetlb.h>
53#include <linux/seccomp.h>
54#include <linux/swap.h>
55#include <linux/syscalls.h>
56#include <linux/jiffies.h>
57#include <linux/futex.h>
58#include <linux/compat.h>
59#include <linux/kthread.h>
60#include <linux/task_io_accounting_ops.h>
61#include <linux/rcupdate.h>
62#include <linux/ptrace.h>
63#include <linux/mount.h>
64#include <linux/audit.h>
65#include <linux/memcontrol.h>
66#include <linux/ftrace.h>
67#include <linux/proc_fs.h>
68#include <linux/profile.h>
69#include <linux/rmap.h>
70#include <linux/ksm.h>
71#include <linux/acct.h>
72#include <linux/userfaultfd_k.h>
73#include <linux/tsacct_kern.h>
74#include <linux/cn_proc.h>
75#include <linux/freezer.h>
76#include <linux/delayacct.h>
77#include <linux/taskstats_kern.h>
78#include <linux/tty.h>
79#include <linux/fs_struct.h>
80#include <linux/magic.h>
81#include <linux/perf_event.h>
82#include <linux/posix-timers.h>
83#include <linux/user-return-notifier.h>
84#include <linux/oom.h>
85#include <linux/khugepaged.h>
86#include <linux/signalfd.h>
87#include <linux/uprobes.h>
88#include <linux/aio.h>
89#include <linux/compiler.h>
90#include <linux/sysctl.h>
91#include <linux/kcov.h>
92#include <linux/livepatch.h>
93#include <linux/thread_info.h>
94#include <linux/stackleak.h>
95#include <linux/kasan.h>
96#include <linux/scs.h>
97#include <linux/io_uring.h>
98#include <linux/bpf.h>
99#include <linux/stackprotector.h>
100
101#include <asm/pgalloc.h>
102#include <linux/uaccess.h>
103#include <asm/mmu_context.h>
104#include <asm/cacheflush.h>
105#include <asm/tlbflush.h>
106
107#include <trace/events/sched.h>
108
109#define CREATE_TRACE_POINTS
110#include <trace/events/task.h>
111
112/*
113 * Minimum number of threads to boot the kernel
114 */
115#define MIN_THREADS 20
116
117/*
118 * Maximum number of threads
119 */
120#define MAX_THREADS FUTEX_TID_MASK
121
122/*
123 * Protected counters by write_lock_irq(&tasklist_lock)
124 */
125unsigned long total_forks; /* Handle normal Linux uptimes. */
126int nr_threads; /* The idle threads do not count.. */
127
128static int max_threads; /* tunable limit on nr_threads */
129
130#define NAMED_ARRAY_INDEX(x) [x] = __stringify(x)
131
132static const char * const resident_page_types[] = {
133 NAMED_ARRAY_INDEX(MM_FILEPAGES),
134 NAMED_ARRAY_INDEX(MM_ANONPAGES),
135 NAMED_ARRAY_INDEX(MM_SWAPENTS),
136 NAMED_ARRAY_INDEX(MM_SHMEMPAGES),
137};
138
139DEFINE_PER_CPU(unsigned long, process_counts) = 0;
140
141__cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */
142
143#ifdef CONFIG_PROVE_RCU
144int lockdep_tasklist_lock_is_held(void)
145{
146 return lockdep_is_held(&tasklist_lock);
147}
148EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
149#endif /* #ifdef CONFIG_PROVE_RCU */
150
151int nr_processes(void)
152{
153 int cpu;
154 int total = 0;
155
156 for_each_possible_cpu(cpu)
157 total += per_cpu(process_counts, cpu);
158
159 return total;
160}
161
162void __weak arch_release_task_struct(struct task_struct *tsk)
163{
164}
165
166#ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
167static struct kmem_cache *task_struct_cachep;
168
169static inline struct task_struct *alloc_task_struct_node(int node)
170{
171 return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node);
172}
173
174static inline void free_task_struct(struct task_struct *tsk)
175{
176 kmem_cache_free(task_struct_cachep, tsk);
177}
178#endif
179
180#ifndef CONFIG_ARCH_THREAD_STACK_ALLOCATOR
181
182/*
183 * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
184 * kmemcache based allocator.
185 */
186# if THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK)
187
188# ifdef CONFIG_VMAP_STACK
189/*
190 * vmalloc() is a bit slow, and calling vfree() enough times will force a TLB
191 * flush. Try to minimize the number of calls by caching stacks.
192 */
193#define NR_CACHED_STACKS 2
194static DEFINE_PER_CPU(struct vm_struct *, cached_stacks[NR_CACHED_STACKS]);
195
196struct vm_stack {
197 struct rcu_head rcu;
198 struct vm_struct *stack_vm_area;
199};
200
201static bool try_release_thread_stack_to_cache(struct vm_struct *vm)
202{
203 unsigned int i;
204
205 for (i = 0; i < NR_CACHED_STACKS; i++) {
206 if (this_cpu_cmpxchg(cached_stacks[i], NULL, vm) != NULL)
207 continue;
208 return true;
209 }
210 return false;
211}
212
213static void thread_stack_free_rcu(struct rcu_head *rh)
214{
215 struct vm_stack *vm_stack = container_of(rh, struct vm_stack, rcu);
216
217 if (try_release_thread_stack_to_cache(vm_stack->stack_vm_area))
218 return;
219
220 vfree(vm_stack);
221}
222
223static void thread_stack_delayed_free(struct task_struct *tsk)
224{
225 struct vm_stack *vm_stack = tsk->stack;
226
227 vm_stack->stack_vm_area = tsk->stack_vm_area;
228 call_rcu(&vm_stack->rcu, thread_stack_free_rcu);
229}
230
231static int free_vm_stack_cache(unsigned int cpu)
232{
233 struct vm_struct **cached_vm_stacks = per_cpu_ptr(cached_stacks, cpu);
234 int i;
235
236 for (i = 0; i < NR_CACHED_STACKS; i++) {
237 struct vm_struct *vm_stack = cached_vm_stacks[i];
238
239 if (!vm_stack)
240 continue;
241
242 vfree(vm_stack->addr);
243 cached_vm_stacks[i] = NULL;
244 }
245
246 return 0;
247}
248
249static int memcg_charge_kernel_stack(struct vm_struct *vm)
250{
251 int i;
252 int ret;
253
254 BUILD_BUG_ON(IS_ENABLED(CONFIG_VMAP_STACK) && PAGE_SIZE % 1024 != 0);
255 BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE);
256
257 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
258 ret = memcg_kmem_charge_page(vm->pages[i], GFP_KERNEL, 0);
259 if (ret)
260 goto err;
261 }
262 return 0;
263err:
264 /*
265 * If memcg_kmem_charge_page() fails, page's memory cgroup pointer is
266 * NULL, and memcg_kmem_uncharge_page() in free_thread_stack() will
267 * ignore this page.
268 */
269 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++)
270 memcg_kmem_uncharge_page(vm->pages[i], 0);
271 return ret;
272}
273
274static int alloc_thread_stack_node(struct task_struct *tsk, int node)
275{
276 struct vm_struct *vm;
277 void *stack;
278 int i;
279
280 for (i = 0; i < NR_CACHED_STACKS; i++) {
281 struct vm_struct *s;
282
283 s = this_cpu_xchg(cached_stacks[i], NULL);
284
285 if (!s)
286 continue;
287
288 /* Reset stack metadata. */
289 kasan_unpoison_range(s->addr, THREAD_SIZE);
290
291 stack = kasan_reset_tag(s->addr);
292
293 /* Clear stale pointers from reused stack. */
294 memset(stack, 0, THREAD_SIZE);
295
296 if (memcg_charge_kernel_stack(s)) {
297 vfree(s->addr);
298 return -ENOMEM;
299 }
300
301 tsk->stack_vm_area = s;
302 tsk->stack = stack;
303 return 0;
304 }
305
306 /*
307 * Allocated stacks are cached and later reused by new threads,
308 * so memcg accounting is performed manually on assigning/releasing
309 * stacks to tasks. Drop __GFP_ACCOUNT.
310 */
311 stack = __vmalloc_node_range(THREAD_SIZE, THREAD_ALIGN,
312 VMALLOC_START, VMALLOC_END,
313 THREADINFO_GFP & ~__GFP_ACCOUNT,
314 PAGE_KERNEL,
315 0, node, __builtin_return_address(0));
316 if (!stack)
317 return -ENOMEM;
318
319 vm = find_vm_area(stack);
320 if (memcg_charge_kernel_stack(vm)) {
321 vfree(stack);
322 return -ENOMEM;
323 }
324 /*
325 * We can't call find_vm_area() in interrupt context, and
326 * free_thread_stack() can be called in interrupt context,
327 * so cache the vm_struct.
328 */
329 tsk->stack_vm_area = vm;
330 stack = kasan_reset_tag(stack);
331 tsk->stack = stack;
332 return 0;
333}
334
335static void free_thread_stack(struct task_struct *tsk)
336{
337 if (!try_release_thread_stack_to_cache(tsk->stack_vm_area))
338 thread_stack_delayed_free(tsk);
339
340 tsk->stack = NULL;
341 tsk->stack_vm_area = NULL;
342}
343
344# else /* !CONFIG_VMAP_STACK */
345
346static void thread_stack_free_rcu(struct rcu_head *rh)
347{
348 __free_pages(virt_to_page(rh), THREAD_SIZE_ORDER);
349}
350
351static void thread_stack_delayed_free(struct task_struct *tsk)
352{
353 struct rcu_head *rh = tsk->stack;
354
355 call_rcu(rh, thread_stack_free_rcu);
356}
357
358static int alloc_thread_stack_node(struct task_struct *tsk, int node)
359{
360 struct page *page = alloc_pages_node(node, THREADINFO_GFP,
361 THREAD_SIZE_ORDER);
362
363 if (likely(page)) {
364 tsk->stack = kasan_reset_tag(page_address(page));
365 return 0;
366 }
367 return -ENOMEM;
368}
369
370static void free_thread_stack(struct task_struct *tsk)
371{
372 thread_stack_delayed_free(tsk);
373 tsk->stack = NULL;
374}
375
376# endif /* CONFIG_VMAP_STACK */
377# else /* !(THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK)) */
378
379static struct kmem_cache *thread_stack_cache;
380
381static void thread_stack_free_rcu(struct rcu_head *rh)
382{
383 kmem_cache_free(thread_stack_cache, rh);
384}
385
386static void thread_stack_delayed_free(struct task_struct *tsk)
387{
388 struct rcu_head *rh = tsk->stack;
389
390 call_rcu(rh, thread_stack_free_rcu);
391}
392
393static int alloc_thread_stack_node(struct task_struct *tsk, int node)
394{
395 unsigned long *stack;
396 stack = kmem_cache_alloc_node(thread_stack_cache, THREADINFO_GFP, node);
397 stack = kasan_reset_tag(stack);
398 tsk->stack = stack;
399 return stack ? 0 : -ENOMEM;
400}
401
402static void free_thread_stack(struct task_struct *tsk)
403{
404 thread_stack_delayed_free(tsk);
405 tsk->stack = NULL;
406}
407
408void thread_stack_cache_init(void)
409{
410 thread_stack_cache = kmem_cache_create_usercopy("thread_stack",
411 THREAD_SIZE, THREAD_SIZE, 0, 0,
412 THREAD_SIZE, NULL);
413 BUG_ON(thread_stack_cache == NULL);
414}
415
416# endif /* THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK) */
417#else /* CONFIG_ARCH_THREAD_STACK_ALLOCATOR */
418
419static int alloc_thread_stack_node(struct task_struct *tsk, int node)
420{
421 unsigned long *stack;
422
423 stack = arch_alloc_thread_stack_node(tsk, node);
424 tsk->stack = stack;
425 return stack ? 0 : -ENOMEM;
426}
427
428static void free_thread_stack(struct task_struct *tsk)
429{
430 arch_free_thread_stack(tsk);
431 tsk->stack = NULL;
432}
433
434#endif /* !CONFIG_ARCH_THREAD_STACK_ALLOCATOR */
435
436/* SLAB cache for signal_struct structures (tsk->signal) */
437static struct kmem_cache *signal_cachep;
438
439/* SLAB cache for sighand_struct structures (tsk->sighand) */
440struct kmem_cache *sighand_cachep;
441
442/* SLAB cache for files_struct structures (tsk->files) */
443struct kmem_cache *files_cachep;
444
445/* SLAB cache for fs_struct structures (tsk->fs) */
446struct kmem_cache *fs_cachep;
447
448/* SLAB cache for vm_area_struct structures */
449static struct kmem_cache *vm_area_cachep;
450
451/* SLAB cache for mm_struct structures (tsk->mm) */
452static struct kmem_cache *mm_cachep;
453
454struct vm_area_struct *vm_area_alloc(struct mm_struct *mm)
455{
456 struct vm_area_struct *vma;
457
458 vma = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
459 if (vma)
460 vma_init(vma, mm);
461 return vma;
462}
463
464struct vm_area_struct *vm_area_dup(struct vm_area_struct *orig)
465{
466 struct vm_area_struct *new = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
467
468 if (new) {
469 ASSERT_EXCLUSIVE_WRITER(orig->vm_flags);
470 ASSERT_EXCLUSIVE_WRITER(orig->vm_file);
471 /*
472 * orig->shared.rb may be modified concurrently, but the clone
473 * will be reinitialized.
474 */
475 *new = data_race(*orig);
476 INIT_LIST_HEAD(&new->anon_vma_chain);
477 dup_anon_vma_name(orig, new);
478 }
479 return new;
480}
481
482void vm_area_free(struct vm_area_struct *vma)
483{
484 free_anon_vma_name(vma);
485 kmem_cache_free(vm_area_cachep, vma);
486}
487
488static void account_kernel_stack(struct task_struct *tsk, int account)
489{
490 if (IS_ENABLED(CONFIG_VMAP_STACK)) {
491 struct vm_struct *vm = task_stack_vm_area(tsk);
492 int i;
493
494 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++)
495 mod_lruvec_page_state(vm->pages[i], NR_KERNEL_STACK_KB,
496 account * (PAGE_SIZE / 1024));
497 } else {
498 void *stack = task_stack_page(tsk);
499
500 /* All stack pages are in the same node. */
501 mod_lruvec_kmem_state(stack, NR_KERNEL_STACK_KB,
502 account * (THREAD_SIZE / 1024));
503 }
504}
505
506void exit_task_stack_account(struct task_struct *tsk)
507{
508 account_kernel_stack(tsk, -1);
509
510 if (IS_ENABLED(CONFIG_VMAP_STACK)) {
511 struct vm_struct *vm;
512 int i;
513
514 vm = task_stack_vm_area(tsk);
515 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++)
516 memcg_kmem_uncharge_page(vm->pages[i], 0);
517 }
518}
519
520static void release_task_stack(struct task_struct *tsk)
521{
522 if (WARN_ON(READ_ONCE(tsk->__state) != TASK_DEAD))
523 return; /* Better to leak the stack than to free prematurely */
524
525 free_thread_stack(tsk);
526}
527
528#ifdef CONFIG_THREAD_INFO_IN_TASK
529void put_task_stack(struct task_struct *tsk)
530{
531 if (refcount_dec_and_test(&tsk->stack_refcount))
532 release_task_stack(tsk);
533}
534#endif
535
536void free_task(struct task_struct *tsk)
537{
538#ifdef CONFIG_SECCOMP
539 WARN_ON_ONCE(tsk->seccomp.filter);
540#endif
541 release_user_cpus_ptr(tsk);
542 scs_release(tsk);
543
544#ifndef CONFIG_THREAD_INFO_IN_TASK
545 /*
546 * The task is finally done with both the stack and thread_info,
547 * so free both.
548 */
549 release_task_stack(tsk);
550#else
551 /*
552 * If the task had a separate stack allocation, it should be gone
553 * by now.
554 */
555 WARN_ON_ONCE(refcount_read(&tsk->stack_refcount) != 0);
556#endif
557 rt_mutex_debug_task_free(tsk);
558 ftrace_graph_exit_task(tsk);
559 arch_release_task_struct(tsk);
560 if (tsk->flags & PF_KTHREAD)
561 free_kthread_struct(tsk);
562 free_task_struct(tsk);
563}
564EXPORT_SYMBOL(free_task);
565
566static void dup_mm_exe_file(struct mm_struct *mm, struct mm_struct *oldmm)
567{
568 struct file *exe_file;
569
570 exe_file = get_mm_exe_file(oldmm);
571 RCU_INIT_POINTER(mm->exe_file, exe_file);
572 /*
573 * We depend on the oldmm having properly denied write access to the
574 * exe_file already.
575 */
576 if (exe_file && deny_write_access(exe_file))
577 pr_warn_once("deny_write_access() failed in %s\n", __func__);
578}
579
580#ifdef CONFIG_MMU
581static __latent_entropy int dup_mmap(struct mm_struct *mm,
582 struct mm_struct *oldmm)
583{
584 struct vm_area_struct *mpnt, *tmp;
585 int retval;
586 unsigned long charge = 0;
587 LIST_HEAD(uf);
588 MA_STATE(old_mas, &oldmm->mm_mt, 0, 0);
589 MA_STATE(mas, &mm->mm_mt, 0, 0);
590
591 uprobe_start_dup_mmap();
592 if (mmap_write_lock_killable(oldmm)) {
593 retval = -EINTR;
594 goto fail_uprobe_end;
595 }
596 flush_cache_dup_mm(oldmm);
597 uprobe_dup_mmap(oldmm, mm);
598 /*
599 * Not linked in yet - no deadlock potential:
600 */
601 mmap_write_lock_nested(mm, SINGLE_DEPTH_NESTING);
602
603 /* No ordering required: file already has been exposed. */
604 dup_mm_exe_file(mm, oldmm);
605
606 mm->total_vm = oldmm->total_vm;
607 mm->data_vm = oldmm->data_vm;
608 mm->exec_vm = oldmm->exec_vm;
609 mm->stack_vm = oldmm->stack_vm;
610
611 retval = ksm_fork(mm, oldmm);
612 if (retval)
613 goto out;
614 khugepaged_fork(mm, oldmm);
615
616 retval = mas_expected_entries(&mas, oldmm->map_count);
617 if (retval)
618 goto out;
619
620 mas_for_each(&old_mas, mpnt, ULONG_MAX) {
621 struct file *file;
622
623 if (mpnt->vm_flags & VM_DONTCOPY) {
624 vm_stat_account(mm, mpnt->vm_flags, -vma_pages(mpnt));
625 continue;
626 }
627 charge = 0;
628 /*
629 * Don't duplicate many vmas if we've been oom-killed (for
630 * example)
631 */
632 if (fatal_signal_pending(current)) {
633 retval = -EINTR;
634 goto loop_out;
635 }
636 if (mpnt->vm_flags & VM_ACCOUNT) {
637 unsigned long len = vma_pages(mpnt);
638
639 if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
640 goto fail_nomem;
641 charge = len;
642 }
643 tmp = vm_area_dup(mpnt);
644 if (!tmp)
645 goto fail_nomem;
646 retval = vma_dup_policy(mpnt, tmp);
647 if (retval)
648 goto fail_nomem_policy;
649 tmp->vm_mm = mm;
650 retval = dup_userfaultfd(tmp, &uf);
651 if (retval)
652 goto fail_nomem_anon_vma_fork;
653 if (tmp->vm_flags & VM_WIPEONFORK) {
654 /*
655 * VM_WIPEONFORK gets a clean slate in the child.
656 * Don't prepare anon_vma until fault since we don't
657 * copy page for current vma.
658 */
659 tmp->anon_vma = NULL;
660 } else if (anon_vma_fork(tmp, mpnt))
661 goto fail_nomem_anon_vma_fork;
662 tmp->vm_flags &= ~(VM_LOCKED | VM_LOCKONFAULT);
663 file = tmp->vm_file;
664 if (file) {
665 struct address_space *mapping = file->f_mapping;
666
667 get_file(file);
668 i_mmap_lock_write(mapping);
669 if (tmp->vm_flags & VM_SHARED)
670 mapping_allow_writable(mapping);
671 flush_dcache_mmap_lock(mapping);
672 /* insert tmp into the share list, just after mpnt */
673 vma_interval_tree_insert_after(tmp, mpnt,
674 &mapping->i_mmap);
675 flush_dcache_mmap_unlock(mapping);
676 i_mmap_unlock_write(mapping);
677 }
678
679 /*
680 * Copy/update hugetlb private vma information.
681 */
682 if (is_vm_hugetlb_page(tmp))
683 hugetlb_dup_vma_private(tmp);
684
685 /* Link the vma into the MT */
686 mas.index = tmp->vm_start;
687 mas.last = tmp->vm_end - 1;
688 mas_store(&mas, tmp);
689 if (mas_is_err(&mas))
690 goto fail_nomem_mas_store;
691
692 mm->map_count++;
693 if (!(tmp->vm_flags & VM_WIPEONFORK))
694 retval = copy_page_range(tmp, mpnt);
695
696 if (tmp->vm_ops && tmp->vm_ops->open)
697 tmp->vm_ops->open(tmp);
698
699 if (retval)
700 goto loop_out;
701 }
702 /* a new mm has just been created */
703 retval = arch_dup_mmap(oldmm, mm);
704loop_out:
705 mas_destroy(&mas);
706out:
707 mmap_write_unlock(mm);
708 flush_tlb_mm(oldmm);
709 mmap_write_unlock(oldmm);
710 dup_userfaultfd_complete(&uf);
711fail_uprobe_end:
712 uprobe_end_dup_mmap();
713 return retval;
714
715fail_nomem_mas_store:
716 unlink_anon_vmas(tmp);
717fail_nomem_anon_vma_fork:
718 mpol_put(vma_policy(tmp));
719fail_nomem_policy:
720 vm_area_free(tmp);
721fail_nomem:
722 retval = -ENOMEM;
723 vm_unacct_memory(charge);
724 goto loop_out;
725}
726
727static inline int mm_alloc_pgd(struct mm_struct *mm)
728{
729 mm->pgd = pgd_alloc(mm);
730 if (unlikely(!mm->pgd))
731 return -ENOMEM;
732 return 0;
733}
734
735static inline void mm_free_pgd(struct mm_struct *mm)
736{
737 pgd_free(mm, mm->pgd);
738}
739#else
740static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
741{
742 mmap_write_lock(oldmm);
743 dup_mm_exe_file(mm, oldmm);
744 mmap_write_unlock(oldmm);
745 return 0;
746}
747#define mm_alloc_pgd(mm) (0)
748#define mm_free_pgd(mm)
749#endif /* CONFIG_MMU */
750
751static void check_mm(struct mm_struct *mm)
752{
753 int i;
754
755 BUILD_BUG_ON_MSG(ARRAY_SIZE(resident_page_types) != NR_MM_COUNTERS,
756 "Please make sure 'struct resident_page_types[]' is updated as well");
757
758 for (i = 0; i < NR_MM_COUNTERS; i++) {
759 long x = percpu_counter_sum(&mm->rss_stat[i]);
760
761 if (likely(!x))
762 continue;
763
764 /* Making sure this is not due to race with CPU offlining. */
765 x = percpu_counter_sum_all(&mm->rss_stat[i]);
766 if (unlikely(x))
767 pr_alert("BUG: Bad rss-counter state mm:%p type:%s val:%ld\n",
768 mm, resident_page_types[i], x);
769 }
770
771 if (mm_pgtables_bytes(mm))
772 pr_alert("BUG: non-zero pgtables_bytes on freeing mm: %ld\n",
773 mm_pgtables_bytes(mm));
774
775#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
776 VM_BUG_ON_MM(mm->pmd_huge_pte, mm);
777#endif
778}
779
780#define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
781#define free_mm(mm) (kmem_cache_free(mm_cachep, (mm)))
782
783/*
784 * Called when the last reference to the mm
785 * is dropped: either by a lazy thread or by
786 * mmput. Free the page directory and the mm.
787 */
788void __mmdrop(struct mm_struct *mm)
789{
790 int i;
791
792 BUG_ON(mm == &init_mm);
793 WARN_ON_ONCE(mm == current->mm);
794 WARN_ON_ONCE(mm == current->active_mm);
795 mm_free_pgd(mm);
796 destroy_context(mm);
797 mmu_notifier_subscriptions_destroy(mm);
798 check_mm(mm);
799 put_user_ns(mm->user_ns);
800 mm_pasid_drop(mm);
801
802 for (i = 0; i < NR_MM_COUNTERS; i++)
803 percpu_counter_destroy(&mm->rss_stat[i]);
804 free_mm(mm);
805}
806EXPORT_SYMBOL_GPL(__mmdrop);
807
808static void mmdrop_async_fn(struct work_struct *work)
809{
810 struct mm_struct *mm;
811
812 mm = container_of(work, struct mm_struct, async_put_work);
813 __mmdrop(mm);
814}
815
816static void mmdrop_async(struct mm_struct *mm)
817{
818 if (unlikely(atomic_dec_and_test(&mm->mm_count))) {
819 INIT_WORK(&mm->async_put_work, mmdrop_async_fn);
820 schedule_work(&mm->async_put_work);
821 }
822}
823
824static inline void free_signal_struct(struct signal_struct *sig)
825{
826 taskstats_tgid_free(sig);
827 sched_autogroup_exit(sig);
828 /*
829 * __mmdrop is not safe to call from softirq context on x86 due to
830 * pgd_dtor so postpone it to the async context
831 */
832 if (sig->oom_mm)
833 mmdrop_async(sig->oom_mm);
834 kmem_cache_free(signal_cachep, sig);
835}
836
837static inline void put_signal_struct(struct signal_struct *sig)
838{
839 if (refcount_dec_and_test(&sig->sigcnt))
840 free_signal_struct(sig);
841}
842
843void __put_task_struct(struct task_struct *tsk)
844{
845 WARN_ON(!tsk->exit_state);
846 WARN_ON(refcount_read(&tsk->usage));
847 WARN_ON(tsk == current);
848
849 io_uring_free(tsk);
850 cgroup_free(tsk);
851 task_numa_free(tsk, true);
852 security_task_free(tsk);
853 bpf_task_storage_free(tsk);
854 exit_creds(tsk);
855 delayacct_tsk_free(tsk);
856 put_signal_struct(tsk->signal);
857 sched_core_free(tsk);
858 free_task(tsk);
859}
860EXPORT_SYMBOL_GPL(__put_task_struct);
861
862void __init __weak arch_task_cache_init(void) { }
863
864/*
865 * set_max_threads
866 */
867static void set_max_threads(unsigned int max_threads_suggested)
868{
869 u64 threads;
870 unsigned long nr_pages = totalram_pages();
871
872 /*
873 * The number of threads shall be limited such that the thread
874 * structures may only consume a small part of the available memory.
875 */
876 if (fls64(nr_pages) + fls64(PAGE_SIZE) > 64)
877 threads = MAX_THREADS;
878 else
879 threads = div64_u64((u64) nr_pages * (u64) PAGE_SIZE,
880 (u64) THREAD_SIZE * 8UL);
881
882 if (threads > max_threads_suggested)
883 threads = max_threads_suggested;
884
885 max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS);
886}
887
888#ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT
889/* Initialized by the architecture: */
890int arch_task_struct_size __read_mostly;
891#endif
892
893#ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
894static void task_struct_whitelist(unsigned long *offset, unsigned long *size)
895{
896 /* Fetch thread_struct whitelist for the architecture. */
897 arch_thread_struct_whitelist(offset, size);
898
899 /*
900 * Handle zero-sized whitelist or empty thread_struct, otherwise
901 * adjust offset to position of thread_struct in task_struct.
902 */
903 if (unlikely(*size == 0))
904 *offset = 0;
905 else
906 *offset += offsetof(struct task_struct, thread);
907}
908#endif /* CONFIG_ARCH_TASK_STRUCT_ALLOCATOR */
909
910void __init fork_init(void)
911{
912 int i;
913#ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
914#ifndef ARCH_MIN_TASKALIGN
915#define ARCH_MIN_TASKALIGN 0
916#endif
917 int align = max_t(int, L1_CACHE_BYTES, ARCH_MIN_TASKALIGN);
918 unsigned long useroffset, usersize;
919
920 /* create a slab on which task_structs can be allocated */
921 task_struct_whitelist(&useroffset, &usersize);
922 task_struct_cachep = kmem_cache_create_usercopy("task_struct",
923 arch_task_struct_size, align,
924 SLAB_PANIC|SLAB_ACCOUNT,
925 useroffset, usersize, NULL);
926#endif
927
928 /* do the arch specific task caches init */
929 arch_task_cache_init();
930
931 set_max_threads(MAX_THREADS);
932
933 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
934 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
935 init_task.signal->rlim[RLIMIT_SIGPENDING] =
936 init_task.signal->rlim[RLIMIT_NPROC];
937
938 for (i = 0; i < UCOUNT_COUNTS; i++)
939 init_user_ns.ucount_max[i] = max_threads/2;
940
941 set_userns_rlimit_max(&init_user_ns, UCOUNT_RLIMIT_NPROC, RLIM_INFINITY);
942 set_userns_rlimit_max(&init_user_ns, UCOUNT_RLIMIT_MSGQUEUE, RLIM_INFINITY);
943 set_userns_rlimit_max(&init_user_ns, UCOUNT_RLIMIT_SIGPENDING, RLIM_INFINITY);
944 set_userns_rlimit_max(&init_user_ns, UCOUNT_RLIMIT_MEMLOCK, RLIM_INFINITY);
945
946#ifdef CONFIG_VMAP_STACK
947 cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "fork:vm_stack_cache",
948 NULL, free_vm_stack_cache);
949#endif
950
951 scs_init();
952
953 lockdep_init_task(&init_task);
954 uprobes_init();
955}
956
957int __weak arch_dup_task_struct(struct task_struct *dst,
958 struct task_struct *src)
959{
960 *dst = *src;
961 return 0;
962}
963
964void set_task_stack_end_magic(struct task_struct *tsk)
965{
966 unsigned long *stackend;
967
968 stackend = end_of_stack(tsk);
969 *stackend = STACK_END_MAGIC; /* for overflow detection */
970}
971
972static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
973{
974 struct task_struct *tsk;
975 int err;
976
977 if (node == NUMA_NO_NODE)
978 node = tsk_fork_get_node(orig);
979 tsk = alloc_task_struct_node(node);
980 if (!tsk)
981 return NULL;
982
983 err = arch_dup_task_struct(tsk, orig);
984 if (err)
985 goto free_tsk;
986
987 err = alloc_thread_stack_node(tsk, node);
988 if (err)
989 goto free_tsk;
990
991#ifdef CONFIG_THREAD_INFO_IN_TASK
992 refcount_set(&tsk->stack_refcount, 1);
993#endif
994 account_kernel_stack(tsk, 1);
995
996 err = scs_prepare(tsk, node);
997 if (err)
998 goto free_stack;
999
1000#ifdef CONFIG_SECCOMP
1001 /*
1002 * We must handle setting up seccomp filters once we're under
1003 * the sighand lock in case orig has changed between now and
1004 * then. Until then, filter must be NULL to avoid messing up
1005 * the usage counts on the error path calling free_task.
1006 */
1007 tsk->seccomp.filter = NULL;
1008#endif
1009
1010 setup_thread_stack(tsk, orig);
1011 clear_user_return_notifier(tsk);
1012 clear_tsk_need_resched(tsk);
1013 set_task_stack_end_magic(tsk);
1014 clear_syscall_work_syscall_user_dispatch(tsk);
1015
1016#ifdef CONFIG_STACKPROTECTOR
1017 tsk->stack_canary = get_random_canary();
1018#endif
1019 if (orig->cpus_ptr == &orig->cpus_mask)
1020 tsk->cpus_ptr = &tsk->cpus_mask;
1021 dup_user_cpus_ptr(tsk, orig, node);
1022
1023 /*
1024 * One for the user space visible state that goes away when reaped.
1025 * One for the scheduler.
1026 */
1027 refcount_set(&tsk->rcu_users, 2);
1028 /* One for the rcu users */
1029 refcount_set(&tsk->usage, 1);
1030#ifdef CONFIG_BLK_DEV_IO_TRACE
1031 tsk->btrace_seq = 0;
1032#endif
1033 tsk->splice_pipe = NULL;
1034 tsk->task_frag.page = NULL;
1035 tsk->wake_q.next = NULL;
1036 tsk->worker_private = NULL;
1037
1038 kcov_task_init(tsk);
1039 kmsan_task_create(tsk);
1040 kmap_local_fork(tsk);
1041
1042#ifdef CONFIG_FAULT_INJECTION
1043 tsk->fail_nth = 0;
1044#endif
1045
1046#ifdef CONFIG_BLK_CGROUP
1047 tsk->throttle_queue = NULL;
1048 tsk->use_memdelay = 0;
1049#endif
1050
1051#ifdef CONFIG_IOMMU_SVA
1052 tsk->pasid_activated = 0;
1053#endif
1054
1055#ifdef CONFIG_MEMCG
1056 tsk->active_memcg = NULL;
1057#endif
1058
1059#ifdef CONFIG_CPU_SUP_INTEL
1060 tsk->reported_split_lock = 0;
1061#endif
1062
1063 return tsk;
1064
1065free_stack:
1066 exit_task_stack_account(tsk);
1067 free_thread_stack(tsk);
1068free_tsk:
1069 free_task_struct(tsk);
1070 return NULL;
1071}
1072
1073__cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
1074
1075static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
1076
1077static int __init coredump_filter_setup(char *s)
1078{
1079 default_dump_filter =
1080 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
1081 MMF_DUMP_FILTER_MASK;
1082 return 1;
1083}
1084
1085__setup("coredump_filter=", coredump_filter_setup);
1086
1087#include <linux/init_task.h>
1088
1089static void mm_init_aio(struct mm_struct *mm)
1090{
1091#ifdef CONFIG_AIO
1092 spin_lock_init(&mm->ioctx_lock);
1093 mm->ioctx_table = NULL;
1094#endif
1095}
1096
1097static __always_inline void mm_clear_owner(struct mm_struct *mm,
1098 struct task_struct *p)
1099{
1100#ifdef CONFIG_MEMCG
1101 if (mm->owner == p)
1102 WRITE_ONCE(mm->owner, NULL);
1103#endif
1104}
1105
1106static void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
1107{
1108#ifdef CONFIG_MEMCG
1109 mm->owner = p;
1110#endif
1111}
1112
1113static void mm_init_uprobes_state(struct mm_struct *mm)
1114{
1115#ifdef CONFIG_UPROBES
1116 mm->uprobes_state.xol_area = NULL;
1117#endif
1118}
1119
1120static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
1121 struct user_namespace *user_ns)
1122{
1123 int i;
1124
1125 mt_init_flags(&mm->mm_mt, MM_MT_FLAGS);
1126 mt_set_external_lock(&mm->mm_mt, &mm->mmap_lock);
1127 atomic_set(&mm->mm_users, 1);
1128 atomic_set(&mm->mm_count, 1);
1129 seqcount_init(&mm->write_protect_seq);
1130 mmap_init_lock(mm);
1131 INIT_LIST_HEAD(&mm->mmlist);
1132 mm_pgtables_bytes_init(mm);
1133 mm->map_count = 0;
1134 mm->locked_vm = 0;
1135 atomic64_set(&mm->pinned_vm, 0);
1136 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
1137 spin_lock_init(&mm->page_table_lock);
1138 spin_lock_init(&mm->arg_lock);
1139 mm_init_cpumask(mm);
1140 mm_init_aio(mm);
1141 mm_init_owner(mm, p);
1142 mm_pasid_init(mm);
1143 RCU_INIT_POINTER(mm->exe_file, NULL);
1144 mmu_notifier_subscriptions_init(mm);
1145 init_tlb_flush_pending(mm);
1146#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
1147 mm->pmd_huge_pte = NULL;
1148#endif
1149 mm_init_uprobes_state(mm);
1150 hugetlb_count_init(mm);
1151
1152 if (current->mm) {
1153 mm->flags = current->mm->flags & MMF_INIT_MASK;
1154 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK;
1155 } else {
1156 mm->flags = default_dump_filter;
1157 mm->def_flags = 0;
1158 }
1159
1160 if (mm_alloc_pgd(mm))
1161 goto fail_nopgd;
1162
1163 if (init_new_context(p, mm))
1164 goto fail_nocontext;
1165
1166 for (i = 0; i < NR_MM_COUNTERS; i++)
1167 if (percpu_counter_init(&mm->rss_stat[i], 0, GFP_KERNEL_ACCOUNT))
1168 goto fail_pcpu;
1169
1170 mm->user_ns = get_user_ns(user_ns);
1171 lru_gen_init_mm(mm);
1172 return mm;
1173
1174fail_pcpu:
1175 while (i > 0)
1176 percpu_counter_destroy(&mm->rss_stat[--i]);
1177fail_nocontext:
1178 mm_free_pgd(mm);
1179fail_nopgd:
1180 free_mm(mm);
1181 return NULL;
1182}
1183
1184/*
1185 * Allocate and initialize an mm_struct.
1186 */
1187struct mm_struct *mm_alloc(void)
1188{
1189 struct mm_struct *mm;
1190
1191 mm = allocate_mm();
1192 if (!mm)
1193 return NULL;
1194
1195 memset(mm, 0, sizeof(*mm));
1196 return mm_init(mm, current, current_user_ns());
1197}
1198
1199static inline void __mmput(struct mm_struct *mm)
1200{
1201 VM_BUG_ON(atomic_read(&mm->mm_users));
1202
1203 uprobe_clear_state(mm);
1204 exit_aio(mm);
1205 ksm_exit(mm);
1206 khugepaged_exit(mm); /* must run before exit_mmap */
1207 exit_mmap(mm);
1208 mm_put_huge_zero_page(mm);
1209 set_mm_exe_file(mm, NULL);
1210 if (!list_empty(&mm->mmlist)) {
1211 spin_lock(&mmlist_lock);
1212 list_del(&mm->mmlist);
1213 spin_unlock(&mmlist_lock);
1214 }
1215 if (mm->binfmt)
1216 module_put(mm->binfmt->module);
1217 lru_gen_del_mm(mm);
1218 mmdrop(mm);
1219}
1220
1221/*
1222 * Decrement the use count and release all resources for an mm.
1223 */
1224void mmput(struct mm_struct *mm)
1225{
1226 might_sleep();
1227
1228 if (atomic_dec_and_test(&mm->mm_users))
1229 __mmput(mm);
1230}
1231EXPORT_SYMBOL_GPL(mmput);
1232
1233#ifdef CONFIG_MMU
1234static void mmput_async_fn(struct work_struct *work)
1235{
1236 struct mm_struct *mm = container_of(work, struct mm_struct,
1237 async_put_work);
1238
1239 __mmput(mm);
1240}
1241
1242void mmput_async(struct mm_struct *mm)
1243{
1244 if (atomic_dec_and_test(&mm->mm_users)) {
1245 INIT_WORK(&mm->async_put_work, mmput_async_fn);
1246 schedule_work(&mm->async_put_work);
1247 }
1248}
1249EXPORT_SYMBOL_GPL(mmput_async);
1250#endif
1251
1252/**
1253 * set_mm_exe_file - change a reference to the mm's executable file
1254 *
1255 * This changes mm's executable file (shown as symlink /proc/[pid]/exe).
1256 *
1257 * Main users are mmput() and sys_execve(). Callers prevent concurrent
1258 * invocations: in mmput() nobody alive left, in execve task is single
1259 * threaded.
1260 *
1261 * Can only fail if new_exe_file != NULL.
1262 */
1263int set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
1264{
1265 struct file *old_exe_file;
1266
1267 /*
1268 * It is safe to dereference the exe_file without RCU as
1269 * this function is only called if nobody else can access
1270 * this mm -- see comment above for justification.
1271 */
1272 old_exe_file = rcu_dereference_raw(mm->exe_file);
1273
1274 if (new_exe_file) {
1275 /*
1276 * We expect the caller (i.e., sys_execve) to already denied
1277 * write access, so this is unlikely to fail.
1278 */
1279 if (unlikely(deny_write_access(new_exe_file)))
1280 return -EACCES;
1281 get_file(new_exe_file);
1282 }
1283 rcu_assign_pointer(mm->exe_file, new_exe_file);
1284 if (old_exe_file) {
1285 allow_write_access(old_exe_file);
1286 fput(old_exe_file);
1287 }
1288 return 0;
1289}
1290
1291/**
1292 * replace_mm_exe_file - replace a reference to the mm's executable file
1293 *
1294 * This changes mm's executable file (shown as symlink /proc/[pid]/exe),
1295 * dealing with concurrent invocation and without grabbing the mmap lock in
1296 * write mode.
1297 *
1298 * Main user is sys_prctl(PR_SET_MM_MAP/EXE_FILE).
1299 */
1300int replace_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
1301{
1302 struct vm_area_struct *vma;
1303 struct file *old_exe_file;
1304 int ret = 0;
1305
1306 /* Forbid mm->exe_file change if old file still mapped. */
1307 old_exe_file = get_mm_exe_file(mm);
1308 if (old_exe_file) {
1309 VMA_ITERATOR(vmi, mm, 0);
1310 mmap_read_lock(mm);
1311 for_each_vma(vmi, vma) {
1312 if (!vma->vm_file)
1313 continue;
1314 if (path_equal(&vma->vm_file->f_path,
1315 &old_exe_file->f_path)) {
1316 ret = -EBUSY;
1317 break;
1318 }
1319 }
1320 mmap_read_unlock(mm);
1321 fput(old_exe_file);
1322 if (ret)
1323 return ret;
1324 }
1325
1326 /* set the new file, lockless */
1327 ret = deny_write_access(new_exe_file);
1328 if (ret)
1329 return -EACCES;
1330 get_file(new_exe_file);
1331
1332 old_exe_file = xchg(&mm->exe_file, new_exe_file);
1333 if (old_exe_file) {
1334 /*
1335 * Don't race with dup_mmap() getting the file and disallowing
1336 * write access while someone might open the file writable.
1337 */
1338 mmap_read_lock(mm);
1339 allow_write_access(old_exe_file);
1340 fput(old_exe_file);
1341 mmap_read_unlock(mm);
1342 }
1343 return 0;
1344}
1345
1346/**
1347 * get_mm_exe_file - acquire a reference to the mm's executable file
1348 *
1349 * Returns %NULL if mm has no associated executable file.
1350 * User must release file via fput().
1351 */
1352struct file *get_mm_exe_file(struct mm_struct *mm)
1353{
1354 struct file *exe_file;
1355
1356 rcu_read_lock();
1357 exe_file = rcu_dereference(mm->exe_file);
1358 if (exe_file && !get_file_rcu(exe_file))
1359 exe_file = NULL;
1360 rcu_read_unlock();
1361 return exe_file;
1362}
1363
1364/**
1365 * get_task_exe_file - acquire a reference to the task's executable file
1366 *
1367 * Returns %NULL if task's mm (if any) has no associated executable file or
1368 * this is a kernel thread with borrowed mm (see the comment above get_task_mm).
1369 * User must release file via fput().
1370 */
1371struct file *get_task_exe_file(struct task_struct *task)
1372{
1373 struct file *exe_file = NULL;
1374 struct mm_struct *mm;
1375
1376 task_lock(task);
1377 mm = task->mm;
1378 if (mm) {
1379 if (!(task->flags & PF_KTHREAD))
1380 exe_file = get_mm_exe_file(mm);
1381 }
1382 task_unlock(task);
1383 return exe_file;
1384}
1385
1386/**
1387 * get_task_mm - acquire a reference to the task's mm
1388 *
1389 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning
1390 * this kernel workthread has transiently adopted a user mm with use_mm,
1391 * to do its AIO) is not set and if so returns a reference to it, after
1392 * bumping up the use count. User must release the mm via mmput()
1393 * after use. Typically used by /proc and ptrace.
1394 */
1395struct mm_struct *get_task_mm(struct task_struct *task)
1396{
1397 struct mm_struct *mm;
1398
1399 task_lock(task);
1400 mm = task->mm;
1401 if (mm) {
1402 if (task->flags & PF_KTHREAD)
1403 mm = NULL;
1404 else
1405 mmget(mm);
1406 }
1407 task_unlock(task);
1408 return mm;
1409}
1410EXPORT_SYMBOL_GPL(get_task_mm);
1411
1412struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
1413{
1414 struct mm_struct *mm;
1415 int err;
1416
1417 err = down_read_killable(&task->signal->exec_update_lock);
1418 if (err)
1419 return ERR_PTR(err);
1420
1421 mm = get_task_mm(task);
1422 if (mm && mm != current->mm &&
1423 !ptrace_may_access(task, mode)) {
1424 mmput(mm);
1425 mm = ERR_PTR(-EACCES);
1426 }
1427 up_read(&task->signal->exec_update_lock);
1428
1429 return mm;
1430}
1431
1432static void complete_vfork_done(struct task_struct *tsk)
1433{
1434 struct completion *vfork;
1435
1436 task_lock(tsk);
1437 vfork = tsk->vfork_done;
1438 if (likely(vfork)) {
1439 tsk->vfork_done = NULL;
1440 complete(vfork);
1441 }
1442 task_unlock(tsk);
1443}
1444
1445static int wait_for_vfork_done(struct task_struct *child,
1446 struct completion *vfork)
1447{
1448 unsigned int state = TASK_UNINTERRUPTIBLE|TASK_KILLABLE|TASK_FREEZABLE;
1449 int killed;
1450
1451 cgroup_enter_frozen();
1452 killed = wait_for_completion_state(vfork, state);
1453 cgroup_leave_frozen(false);
1454
1455 if (killed) {
1456 task_lock(child);
1457 child->vfork_done = NULL;
1458 task_unlock(child);
1459 }
1460
1461 put_task_struct(child);
1462 return killed;
1463}
1464
1465/* Please note the differences between mmput and mm_release.
1466 * mmput is called whenever we stop holding onto a mm_struct,
1467 * error success whatever.
1468 *
1469 * mm_release is called after a mm_struct has been removed
1470 * from the current process.
1471 *
1472 * This difference is important for error handling, when we
1473 * only half set up a mm_struct for a new process and need to restore
1474 * the old one. Because we mmput the new mm_struct before
1475 * restoring the old one. . .
1476 * Eric Biederman 10 January 1998
1477 */
1478static void mm_release(struct task_struct *tsk, struct mm_struct *mm)
1479{
1480 uprobe_free_utask(tsk);
1481
1482 /* Get rid of any cached register state */
1483 deactivate_mm(tsk, mm);
1484
1485 /*
1486 * Signal userspace if we're not exiting with a core dump
1487 * because we want to leave the value intact for debugging
1488 * purposes.
1489 */
1490 if (tsk->clear_child_tid) {
1491 if (atomic_read(&mm->mm_users) > 1) {
1492 /*
1493 * We don't check the error code - if userspace has
1494 * not set up a proper pointer then tough luck.
1495 */
1496 put_user(0, tsk->clear_child_tid);
1497 do_futex(tsk->clear_child_tid, FUTEX_WAKE,
1498 1, NULL, NULL, 0, 0);
1499 }
1500 tsk->clear_child_tid = NULL;
1501 }
1502
1503 /*
1504 * All done, finally we can wake up parent and return this mm to him.
1505 * Also kthread_stop() uses this completion for synchronization.
1506 */
1507 if (tsk->vfork_done)
1508 complete_vfork_done(tsk);
1509}
1510
1511void exit_mm_release(struct task_struct *tsk, struct mm_struct *mm)
1512{
1513 futex_exit_release(tsk);
1514 mm_release(tsk, mm);
1515}
1516
1517void exec_mm_release(struct task_struct *tsk, struct mm_struct *mm)
1518{
1519 futex_exec_release(tsk);
1520 mm_release(tsk, mm);
1521}
1522
1523/**
1524 * dup_mm() - duplicates an existing mm structure
1525 * @tsk: the task_struct with which the new mm will be associated.
1526 * @oldmm: the mm to duplicate.
1527 *
1528 * Allocates a new mm structure and duplicates the provided @oldmm structure
1529 * content into it.
1530 *
1531 * Return: the duplicated mm or NULL on failure.
1532 */
1533static struct mm_struct *dup_mm(struct task_struct *tsk,
1534 struct mm_struct *oldmm)
1535{
1536 struct mm_struct *mm;
1537 int err;
1538
1539 mm = allocate_mm();
1540 if (!mm)
1541 goto fail_nomem;
1542
1543 memcpy(mm, oldmm, sizeof(*mm));
1544
1545 if (!mm_init(mm, tsk, mm->user_ns))
1546 goto fail_nomem;
1547
1548 err = dup_mmap(mm, oldmm);
1549 if (err)
1550 goto free_pt;
1551
1552 mm->hiwater_rss = get_mm_rss(mm);
1553 mm->hiwater_vm = mm->total_vm;
1554
1555 if (mm->binfmt && !try_module_get(mm->binfmt->module))
1556 goto free_pt;
1557
1558 return mm;
1559
1560free_pt:
1561 /* don't put binfmt in mmput, we haven't got module yet */
1562 mm->binfmt = NULL;
1563 mm_init_owner(mm, NULL);
1564 mmput(mm);
1565
1566fail_nomem:
1567 return NULL;
1568}
1569
1570static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
1571{
1572 struct mm_struct *mm, *oldmm;
1573
1574 tsk->min_flt = tsk->maj_flt = 0;
1575 tsk->nvcsw = tsk->nivcsw = 0;
1576#ifdef CONFIG_DETECT_HUNG_TASK
1577 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
1578 tsk->last_switch_time = 0;
1579#endif
1580
1581 tsk->mm = NULL;
1582 tsk->active_mm = NULL;
1583
1584 /*
1585 * Are we cloning a kernel thread?
1586 *
1587 * We need to steal a active VM for that..
1588 */
1589 oldmm = current->mm;
1590 if (!oldmm)
1591 return 0;
1592
1593 if (clone_flags & CLONE_VM) {
1594 mmget(oldmm);
1595 mm = oldmm;
1596 } else {
1597 mm = dup_mm(tsk, current->mm);
1598 if (!mm)
1599 return -ENOMEM;
1600 }
1601
1602 tsk->mm = mm;
1603 tsk->active_mm = mm;
1604 return 0;
1605}
1606
1607static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
1608{
1609 struct fs_struct *fs = current->fs;
1610 if (clone_flags & CLONE_FS) {
1611 /* tsk->fs is already what we want */
1612 spin_lock(&fs->lock);
1613 if (fs->in_exec) {
1614 spin_unlock(&fs->lock);
1615 return -EAGAIN;
1616 }
1617 fs->users++;
1618 spin_unlock(&fs->lock);
1619 return 0;
1620 }
1621 tsk->fs = copy_fs_struct(fs);
1622 if (!tsk->fs)
1623 return -ENOMEM;
1624 return 0;
1625}
1626
1627static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
1628{
1629 struct files_struct *oldf, *newf;
1630 int error = 0;
1631
1632 /*
1633 * A background process may not have any files ...
1634 */
1635 oldf = current->files;
1636 if (!oldf)
1637 goto out;
1638
1639 if (clone_flags & CLONE_FILES) {
1640 atomic_inc(&oldf->count);
1641 goto out;
1642 }
1643
1644 newf = dup_fd(oldf, NR_OPEN_MAX, &error);
1645 if (!newf)
1646 goto out;
1647
1648 tsk->files = newf;
1649 error = 0;
1650out:
1651 return error;
1652}
1653
1654static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
1655{
1656 struct sighand_struct *sig;
1657
1658 if (clone_flags & CLONE_SIGHAND) {
1659 refcount_inc(¤t->sighand->count);
1660 return 0;
1661 }
1662 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1663 RCU_INIT_POINTER(tsk->sighand, sig);
1664 if (!sig)
1665 return -ENOMEM;
1666
1667 refcount_set(&sig->count, 1);
1668 spin_lock_irq(¤t->sighand->siglock);
1669 memcpy(sig->action, current->sighand->action, sizeof(sig->action));
1670 spin_unlock_irq(¤t->sighand->siglock);
1671
1672 /* Reset all signal handler not set to SIG_IGN to SIG_DFL. */
1673 if (clone_flags & CLONE_CLEAR_SIGHAND)
1674 flush_signal_handlers(tsk, 0);
1675
1676 return 0;
1677}
1678
1679void __cleanup_sighand(struct sighand_struct *sighand)
1680{
1681 if (refcount_dec_and_test(&sighand->count)) {
1682 signalfd_cleanup(sighand);
1683 /*
1684 * sighand_cachep is SLAB_TYPESAFE_BY_RCU so we can free it
1685 * without an RCU grace period, see __lock_task_sighand().
1686 */
1687 kmem_cache_free(sighand_cachep, sighand);
1688 }
1689}
1690
1691/*
1692 * Initialize POSIX timer handling for a thread group.
1693 */
1694static void posix_cpu_timers_init_group(struct signal_struct *sig)
1695{
1696 struct posix_cputimers *pct = &sig->posix_cputimers;
1697 unsigned long cpu_limit;
1698
1699 cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1700 posix_cputimers_group_init(pct, cpu_limit);
1701}
1702
1703static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
1704{
1705 struct signal_struct *sig;
1706
1707 if (clone_flags & CLONE_THREAD)
1708 return 0;
1709
1710 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
1711 tsk->signal = sig;
1712 if (!sig)
1713 return -ENOMEM;
1714
1715 sig->nr_threads = 1;
1716 sig->quick_threads = 1;
1717 atomic_set(&sig->live, 1);
1718 refcount_set(&sig->sigcnt, 1);
1719
1720 /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */
1721 sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node);
1722 tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head);
1723
1724 init_waitqueue_head(&sig->wait_chldexit);
1725 sig->curr_target = tsk;
1726 init_sigpending(&sig->shared_pending);
1727 INIT_HLIST_HEAD(&sig->multiprocess);
1728 seqlock_init(&sig->stats_lock);
1729 prev_cputime_init(&sig->prev_cputime);
1730
1731#ifdef CONFIG_POSIX_TIMERS
1732 INIT_LIST_HEAD(&sig->posix_timers);
1733 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1734 sig->real_timer.function = it_real_fn;
1735#endif
1736
1737 task_lock(current->group_leader);
1738 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
1739 task_unlock(current->group_leader);
1740
1741 posix_cpu_timers_init_group(sig);
1742
1743 tty_audit_fork(sig);
1744 sched_autogroup_fork(sig);
1745
1746 sig->oom_score_adj = current->signal->oom_score_adj;
1747 sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1748
1749 mutex_init(&sig->cred_guard_mutex);
1750 init_rwsem(&sig->exec_update_lock);
1751
1752 return 0;
1753}
1754
1755static void copy_seccomp(struct task_struct *p)
1756{
1757#ifdef CONFIG_SECCOMP
1758 /*
1759 * Must be called with sighand->lock held, which is common to
1760 * all threads in the group. Holding cred_guard_mutex is not
1761 * needed because this new task is not yet running and cannot
1762 * be racing exec.
1763 */
1764 assert_spin_locked(¤t->sighand->siglock);
1765
1766 /* Ref-count the new filter user, and assign it. */
1767 get_seccomp_filter(current);
1768 p->seccomp = current->seccomp;
1769
1770 /*
1771 * Explicitly enable no_new_privs here in case it got set
1772 * between the task_struct being duplicated and holding the
1773 * sighand lock. The seccomp state and nnp must be in sync.
1774 */
1775 if (task_no_new_privs(current))
1776 task_set_no_new_privs(p);
1777
1778 /*
1779 * If the parent gained a seccomp mode after copying thread
1780 * flags and between before we held the sighand lock, we have
1781 * to manually enable the seccomp thread flag here.
1782 */
1783 if (p->seccomp.mode != SECCOMP_MODE_DISABLED)
1784 set_task_syscall_work(p, SECCOMP);
1785#endif
1786}
1787
1788SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1789{
1790 current->clear_child_tid = tidptr;
1791
1792 return task_pid_vnr(current);
1793}
1794
1795static void rt_mutex_init_task(struct task_struct *p)
1796{
1797 raw_spin_lock_init(&p->pi_lock);
1798#ifdef CONFIG_RT_MUTEXES
1799 p->pi_waiters = RB_ROOT_CACHED;
1800 p->pi_top_task = NULL;
1801 p->pi_blocked_on = NULL;
1802#endif
1803}
1804
1805static inline void init_task_pid_links(struct task_struct *task)
1806{
1807 enum pid_type type;
1808
1809 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type)
1810 INIT_HLIST_NODE(&task->pid_links[type]);
1811}
1812
1813static inline void
1814init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid)
1815{
1816 if (type == PIDTYPE_PID)
1817 task->thread_pid = pid;
1818 else
1819 task->signal->pids[type] = pid;
1820}
1821
1822static inline void rcu_copy_process(struct task_struct *p)
1823{
1824#ifdef CONFIG_PREEMPT_RCU
1825 p->rcu_read_lock_nesting = 0;
1826 p->rcu_read_unlock_special.s = 0;
1827 p->rcu_blocked_node = NULL;
1828 INIT_LIST_HEAD(&p->rcu_node_entry);
1829#endif /* #ifdef CONFIG_PREEMPT_RCU */
1830#ifdef CONFIG_TASKS_RCU
1831 p->rcu_tasks_holdout = false;
1832 INIT_LIST_HEAD(&p->rcu_tasks_holdout_list);
1833 p->rcu_tasks_idle_cpu = -1;
1834#endif /* #ifdef CONFIG_TASKS_RCU */
1835#ifdef CONFIG_TASKS_TRACE_RCU
1836 p->trc_reader_nesting = 0;
1837 p->trc_reader_special.s = 0;
1838 INIT_LIST_HEAD(&p->trc_holdout_list);
1839 INIT_LIST_HEAD(&p->trc_blkd_node);
1840#endif /* #ifdef CONFIG_TASKS_TRACE_RCU */
1841}
1842
1843struct pid *pidfd_pid(const struct file *file)
1844{
1845 if (file->f_op == &pidfd_fops)
1846 return file->private_data;
1847
1848 return ERR_PTR(-EBADF);
1849}
1850
1851static int pidfd_release(struct inode *inode, struct file *file)
1852{
1853 struct pid *pid = file->private_data;
1854
1855 file->private_data = NULL;
1856 put_pid(pid);
1857 return 0;
1858}
1859
1860#ifdef CONFIG_PROC_FS
1861/**
1862 * pidfd_show_fdinfo - print information about a pidfd
1863 * @m: proc fdinfo file
1864 * @f: file referencing a pidfd
1865 *
1866 * Pid:
1867 * This function will print the pid that a given pidfd refers to in the
1868 * pid namespace of the procfs instance.
1869 * If the pid namespace of the process is not a descendant of the pid
1870 * namespace of the procfs instance 0 will be shown as its pid. This is
1871 * similar to calling getppid() on a process whose parent is outside of
1872 * its pid namespace.
1873 *
1874 * NSpid:
1875 * If pid namespaces are supported then this function will also print
1876 * the pid of a given pidfd refers to for all descendant pid namespaces
1877 * starting from the current pid namespace of the instance, i.e. the
1878 * Pid field and the first entry in the NSpid field will be identical.
1879 * If the pid namespace of the process is not a descendant of the pid
1880 * namespace of the procfs instance 0 will be shown as its first NSpid
1881 * entry and no others will be shown.
1882 * Note that this differs from the Pid and NSpid fields in
1883 * /proc/<pid>/status where Pid and NSpid are always shown relative to
1884 * the pid namespace of the procfs instance. The difference becomes
1885 * obvious when sending around a pidfd between pid namespaces from a
1886 * different branch of the tree, i.e. where no ancestral relation is
1887 * present between the pid namespaces:
1888 * - create two new pid namespaces ns1 and ns2 in the initial pid
1889 * namespace (also take care to create new mount namespaces in the
1890 * new pid namespace and mount procfs)
1891 * - create a process with a pidfd in ns1
1892 * - send pidfd from ns1 to ns2
1893 * - read /proc/self/fdinfo/<pidfd> and observe that both Pid and NSpid
1894 * have exactly one entry, which is 0
1895 */
1896static void pidfd_show_fdinfo(struct seq_file *m, struct file *f)
1897{
1898 struct pid *pid = f->private_data;
1899 struct pid_namespace *ns;
1900 pid_t nr = -1;
1901
1902 if (likely(pid_has_task(pid, PIDTYPE_PID))) {
1903 ns = proc_pid_ns(file_inode(m->file)->i_sb);
1904 nr = pid_nr_ns(pid, ns);
1905 }
1906
1907 seq_put_decimal_ll(m, "Pid:\t", nr);
1908
1909#ifdef CONFIG_PID_NS
1910 seq_put_decimal_ll(m, "\nNSpid:\t", nr);
1911 if (nr > 0) {
1912 int i;
1913
1914 /* If nr is non-zero it means that 'pid' is valid and that
1915 * ns, i.e. the pid namespace associated with the procfs
1916 * instance, is in the pid namespace hierarchy of pid.
1917 * Start at one below the already printed level.
1918 */
1919 for (i = ns->level + 1; i <= pid->level; i++)
1920 seq_put_decimal_ll(m, "\t", pid->numbers[i].nr);
1921 }
1922#endif
1923 seq_putc(m, '\n');
1924}
1925#endif
1926
1927/*
1928 * Poll support for process exit notification.
1929 */
1930static __poll_t pidfd_poll(struct file *file, struct poll_table_struct *pts)
1931{
1932 struct pid *pid = file->private_data;
1933 __poll_t poll_flags = 0;
1934
1935 poll_wait(file, &pid->wait_pidfd, pts);
1936
1937 /*
1938 * Inform pollers only when the whole thread group exits.
1939 * If the thread group leader exits before all other threads in the
1940 * group, then poll(2) should block, similar to the wait(2) family.
1941 */
1942 if (thread_group_exited(pid))
1943 poll_flags = EPOLLIN | EPOLLRDNORM;
1944
1945 return poll_flags;
1946}
1947
1948const struct file_operations pidfd_fops = {
1949 .release = pidfd_release,
1950 .poll = pidfd_poll,
1951#ifdef CONFIG_PROC_FS
1952 .show_fdinfo = pidfd_show_fdinfo,
1953#endif
1954};
1955
1956static void __delayed_free_task(struct rcu_head *rhp)
1957{
1958 struct task_struct *tsk = container_of(rhp, struct task_struct, rcu);
1959
1960 free_task(tsk);
1961}
1962
1963static __always_inline void delayed_free_task(struct task_struct *tsk)
1964{
1965 if (IS_ENABLED(CONFIG_MEMCG))
1966 call_rcu(&tsk->rcu, __delayed_free_task);
1967 else
1968 free_task(tsk);
1969}
1970
1971static void copy_oom_score_adj(u64 clone_flags, struct task_struct *tsk)
1972{
1973 /* Skip if kernel thread */
1974 if (!tsk->mm)
1975 return;
1976
1977 /* Skip if spawning a thread or using vfork */
1978 if ((clone_flags & (CLONE_VM | CLONE_THREAD | CLONE_VFORK)) != CLONE_VM)
1979 return;
1980
1981 /* We need to synchronize with __set_oom_adj */
1982 mutex_lock(&oom_adj_mutex);
1983 set_bit(MMF_MULTIPROCESS, &tsk->mm->flags);
1984 /* Update the values in case they were changed after copy_signal */
1985 tsk->signal->oom_score_adj = current->signal->oom_score_adj;
1986 tsk->signal->oom_score_adj_min = current->signal->oom_score_adj_min;
1987 mutex_unlock(&oom_adj_mutex);
1988}
1989
1990#ifdef CONFIG_RV
1991static void rv_task_fork(struct task_struct *p)
1992{
1993 int i;
1994
1995 for (i = 0; i < RV_PER_TASK_MONITORS; i++)
1996 p->rv[i].da_mon.monitoring = false;
1997}
1998#else
1999#define rv_task_fork(p) do {} while (0)
2000#endif
2001
2002/*
2003 * This creates a new process as a copy of the old one,
2004 * but does not actually start it yet.
2005 *
2006 * It copies the registers, and all the appropriate
2007 * parts of the process environment (as per the clone
2008 * flags). The actual kick-off is left to the caller.
2009 */
2010static __latent_entropy struct task_struct *copy_process(
2011 struct pid *pid,
2012 int trace,
2013 int node,
2014 struct kernel_clone_args *args)
2015{
2016 int pidfd = -1, retval;
2017 struct task_struct *p;
2018 struct multiprocess_signals delayed;
2019 struct file *pidfile = NULL;
2020 const u64 clone_flags = args->flags;
2021 struct nsproxy *nsp = current->nsproxy;
2022
2023 /*
2024 * Don't allow sharing the root directory with processes in a different
2025 * namespace
2026 */
2027 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
2028 return ERR_PTR(-EINVAL);
2029
2030 if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS))
2031 return ERR_PTR(-EINVAL);
2032
2033 /*
2034 * Thread groups must share signals as well, and detached threads
2035 * can only be started up within the thread group.
2036 */
2037 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
2038 return ERR_PTR(-EINVAL);
2039
2040 /*
2041 * Shared signal handlers imply shared VM. By way of the above,
2042 * thread groups also imply shared VM. Blocking this case allows
2043 * for various simplifications in other code.
2044 */
2045 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
2046 return ERR_PTR(-EINVAL);
2047
2048 /*
2049 * Siblings of global init remain as zombies on exit since they are
2050 * not reaped by their parent (swapper). To solve this and to avoid
2051 * multi-rooted process trees, prevent global and container-inits
2052 * from creating siblings.
2053 */
2054 if ((clone_flags & CLONE_PARENT) &&
2055 current->signal->flags & SIGNAL_UNKILLABLE)
2056 return ERR_PTR(-EINVAL);
2057
2058 /*
2059 * If the new process will be in a different pid or user namespace
2060 * do not allow it to share a thread group with the forking task.
2061 */
2062 if (clone_flags & CLONE_THREAD) {
2063 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) ||
2064 (task_active_pid_ns(current) != nsp->pid_ns_for_children))
2065 return ERR_PTR(-EINVAL);
2066 }
2067
2068 if (clone_flags & CLONE_PIDFD) {
2069 /*
2070 * - CLONE_DETACHED is blocked so that we can potentially
2071 * reuse it later for CLONE_PIDFD.
2072 * - CLONE_THREAD is blocked until someone really needs it.
2073 */
2074 if (clone_flags & (CLONE_DETACHED | CLONE_THREAD))
2075 return ERR_PTR(-EINVAL);
2076 }
2077
2078 /*
2079 * Force any signals received before this point to be delivered
2080 * before the fork happens. Collect up signals sent to multiple
2081 * processes that happen during the fork and delay them so that
2082 * they appear to happen after the fork.
2083 */
2084 sigemptyset(&delayed.signal);
2085 INIT_HLIST_NODE(&delayed.node);
2086
2087 spin_lock_irq(¤t->sighand->siglock);
2088 if (!(clone_flags & CLONE_THREAD))
2089 hlist_add_head(&delayed.node, ¤t->signal->multiprocess);
2090 recalc_sigpending();
2091 spin_unlock_irq(¤t->sighand->siglock);
2092 retval = -ERESTARTNOINTR;
2093 if (task_sigpending(current))
2094 goto fork_out;
2095
2096 retval = -ENOMEM;
2097 p = dup_task_struct(current, node);
2098 if (!p)
2099 goto fork_out;
2100 p->flags &= ~PF_KTHREAD;
2101 if (args->kthread)
2102 p->flags |= PF_KTHREAD;
2103 if (args->io_thread) {
2104 /*
2105 * Mark us an IO worker, and block any signal that isn't
2106 * fatal or STOP
2107 */
2108 p->flags |= PF_IO_WORKER;
2109 siginitsetinv(&p->blocked, sigmask(SIGKILL)|sigmask(SIGSTOP));
2110 }
2111
2112 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? args->child_tid : NULL;
2113 /*
2114 * Clear TID on mm_release()?
2115 */
2116 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? args->child_tid : NULL;
2117
2118 ftrace_graph_init_task(p);
2119
2120 rt_mutex_init_task(p);
2121
2122 lockdep_assert_irqs_enabled();
2123#ifdef CONFIG_PROVE_LOCKING
2124 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
2125#endif
2126 retval = copy_creds(p, clone_flags);
2127 if (retval < 0)
2128 goto bad_fork_free;
2129
2130 retval = -EAGAIN;
2131 if (is_rlimit_overlimit(task_ucounts(p), UCOUNT_RLIMIT_NPROC, rlimit(RLIMIT_NPROC))) {
2132 if (p->real_cred->user != INIT_USER &&
2133 !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
2134 goto bad_fork_cleanup_count;
2135 }
2136 current->flags &= ~PF_NPROC_EXCEEDED;
2137
2138 /*
2139 * If multiple threads are within copy_process(), then this check
2140 * triggers too late. This doesn't hurt, the check is only there
2141 * to stop root fork bombs.
2142 */
2143 retval = -EAGAIN;
2144 if (data_race(nr_threads >= max_threads))
2145 goto bad_fork_cleanup_count;
2146
2147 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */
2148 p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER | PF_IDLE | PF_NO_SETAFFINITY);
2149 p->flags |= PF_FORKNOEXEC;
2150 INIT_LIST_HEAD(&p->children);
2151 INIT_LIST_HEAD(&p->sibling);
2152 rcu_copy_process(p);
2153 p->vfork_done = NULL;
2154 spin_lock_init(&p->alloc_lock);
2155
2156 init_sigpending(&p->pending);
2157
2158 p->utime = p->stime = p->gtime = 0;
2159#ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
2160 p->utimescaled = p->stimescaled = 0;
2161#endif
2162 prev_cputime_init(&p->prev_cputime);
2163
2164#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
2165 seqcount_init(&p->vtime.seqcount);
2166 p->vtime.starttime = 0;
2167 p->vtime.state = VTIME_INACTIVE;
2168#endif
2169
2170#ifdef CONFIG_IO_URING
2171 p->io_uring = NULL;
2172#endif
2173
2174#if defined(SPLIT_RSS_COUNTING)
2175 memset(&p->rss_stat, 0, sizeof(p->rss_stat));
2176#endif
2177
2178 p->default_timer_slack_ns = current->timer_slack_ns;
2179
2180#ifdef CONFIG_PSI
2181 p->psi_flags = 0;
2182#endif
2183
2184 task_io_accounting_init(&p->ioac);
2185 acct_clear_integrals(p);
2186
2187 posix_cputimers_init(&p->posix_cputimers);
2188
2189 p->io_context = NULL;
2190 audit_set_context(p, NULL);
2191 cgroup_fork(p);
2192 if (args->kthread) {
2193 if (!set_kthread_struct(p))
2194 goto bad_fork_cleanup_delayacct;
2195 }
2196#ifdef CONFIG_NUMA
2197 p->mempolicy = mpol_dup(p->mempolicy);
2198 if (IS_ERR(p->mempolicy)) {
2199 retval = PTR_ERR(p->mempolicy);
2200 p->mempolicy = NULL;
2201 goto bad_fork_cleanup_delayacct;
2202 }
2203#endif
2204#ifdef CONFIG_CPUSETS
2205 p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
2206 p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
2207 seqcount_spinlock_init(&p->mems_allowed_seq, &p->alloc_lock);
2208#endif
2209#ifdef CONFIG_TRACE_IRQFLAGS
2210 memset(&p->irqtrace, 0, sizeof(p->irqtrace));
2211 p->irqtrace.hardirq_disable_ip = _THIS_IP_;
2212 p->irqtrace.softirq_enable_ip = _THIS_IP_;
2213 p->softirqs_enabled = 1;
2214 p->softirq_context = 0;
2215#endif
2216
2217 p->pagefault_disabled = 0;
2218
2219#ifdef CONFIG_LOCKDEP
2220 lockdep_init_task(p);
2221#endif
2222
2223#ifdef CONFIG_DEBUG_MUTEXES
2224 p->blocked_on = NULL; /* not blocked yet */
2225#endif
2226#ifdef CONFIG_BCACHE
2227 p->sequential_io = 0;
2228 p->sequential_io_avg = 0;
2229#endif
2230#ifdef CONFIG_BPF_SYSCALL
2231 RCU_INIT_POINTER(p->bpf_storage, NULL);
2232 p->bpf_ctx = NULL;
2233#endif
2234
2235 /* Perform scheduler related setup. Assign this task to a CPU. */
2236 retval = sched_fork(clone_flags, p);
2237 if (retval)
2238 goto bad_fork_cleanup_policy;
2239
2240 retval = perf_event_init_task(p, clone_flags);
2241 if (retval)
2242 goto bad_fork_cleanup_policy;
2243 retval = audit_alloc(p);
2244 if (retval)
2245 goto bad_fork_cleanup_perf;
2246 /* copy all the process information */
2247 shm_init_task(p);
2248 retval = security_task_alloc(p, clone_flags);
2249 if (retval)
2250 goto bad_fork_cleanup_audit;
2251 retval = copy_semundo(clone_flags, p);
2252 if (retval)
2253 goto bad_fork_cleanup_security;
2254 retval = copy_files(clone_flags, p);
2255 if (retval)
2256 goto bad_fork_cleanup_semundo;
2257 retval = copy_fs(clone_flags, p);
2258 if (retval)
2259 goto bad_fork_cleanup_files;
2260 retval = copy_sighand(clone_flags, p);
2261 if (retval)
2262 goto bad_fork_cleanup_fs;
2263 retval = copy_signal(clone_flags, p);
2264 if (retval)
2265 goto bad_fork_cleanup_sighand;
2266 retval = copy_mm(clone_flags, p);
2267 if (retval)
2268 goto bad_fork_cleanup_signal;
2269 retval = copy_namespaces(clone_flags, p);
2270 if (retval)
2271 goto bad_fork_cleanup_mm;
2272 retval = copy_io(clone_flags, p);
2273 if (retval)
2274 goto bad_fork_cleanup_namespaces;
2275 retval = copy_thread(p, args);
2276 if (retval)
2277 goto bad_fork_cleanup_io;
2278
2279 stackleak_task_init(p);
2280
2281 if (pid != &init_struct_pid) {
2282 pid = alloc_pid(p->nsproxy->pid_ns_for_children, args->set_tid,
2283 args->set_tid_size);
2284 if (IS_ERR(pid)) {
2285 retval = PTR_ERR(pid);
2286 goto bad_fork_cleanup_thread;
2287 }
2288 }
2289
2290 /*
2291 * This has to happen after we've potentially unshared the file
2292 * descriptor table (so that the pidfd doesn't leak into the child
2293 * if the fd table isn't shared).
2294 */
2295 if (clone_flags & CLONE_PIDFD) {
2296 retval = get_unused_fd_flags(O_RDWR | O_CLOEXEC);
2297 if (retval < 0)
2298 goto bad_fork_free_pid;
2299
2300 pidfd = retval;
2301
2302 pidfile = anon_inode_getfile("[pidfd]", &pidfd_fops, pid,
2303 O_RDWR | O_CLOEXEC);
2304 if (IS_ERR(pidfile)) {
2305 put_unused_fd(pidfd);
2306 retval = PTR_ERR(pidfile);
2307 goto bad_fork_free_pid;
2308 }
2309 get_pid(pid); /* held by pidfile now */
2310
2311 retval = put_user(pidfd, args->pidfd);
2312 if (retval)
2313 goto bad_fork_put_pidfd;
2314 }
2315
2316#ifdef CONFIG_BLOCK
2317 p->plug = NULL;
2318#endif
2319 futex_init_task(p);
2320
2321 /*
2322 * sigaltstack should be cleared when sharing the same VM
2323 */
2324 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
2325 sas_ss_reset(p);
2326
2327 /*
2328 * Syscall tracing and stepping should be turned off in the
2329 * child regardless of CLONE_PTRACE.
2330 */
2331 user_disable_single_step(p);
2332 clear_task_syscall_work(p, SYSCALL_TRACE);
2333#if defined(CONFIG_GENERIC_ENTRY) || defined(TIF_SYSCALL_EMU)
2334 clear_task_syscall_work(p, SYSCALL_EMU);
2335#endif
2336 clear_tsk_latency_tracing(p);
2337
2338 /* ok, now we should be set up.. */
2339 p->pid = pid_nr(pid);
2340 if (clone_flags & CLONE_THREAD) {
2341 p->group_leader = current->group_leader;
2342 p->tgid = current->tgid;
2343 } else {
2344 p->group_leader = p;
2345 p->tgid = p->pid;
2346 }
2347
2348 p->nr_dirtied = 0;
2349 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
2350 p->dirty_paused_when = 0;
2351
2352 p->pdeath_signal = 0;
2353 INIT_LIST_HEAD(&p->thread_group);
2354 p->task_works = NULL;
2355 clear_posix_cputimers_work(p);
2356
2357#ifdef CONFIG_KRETPROBES
2358 p->kretprobe_instances.first = NULL;
2359#endif
2360#ifdef CONFIG_RETHOOK
2361 p->rethooks.first = NULL;
2362#endif
2363
2364 /*
2365 * Ensure that the cgroup subsystem policies allow the new process to be
2366 * forked. It should be noted that the new process's css_set can be changed
2367 * between here and cgroup_post_fork() if an organisation operation is in
2368 * progress.
2369 */
2370 retval = cgroup_can_fork(p, args);
2371 if (retval)
2372 goto bad_fork_put_pidfd;
2373
2374 /*
2375 * Now that the cgroups are pinned, re-clone the parent cgroup and put
2376 * the new task on the correct runqueue. All this *before* the task
2377 * becomes visible.
2378 *
2379 * This isn't part of ->can_fork() because while the re-cloning is
2380 * cgroup specific, it unconditionally needs to place the task on a
2381 * runqueue.
2382 */
2383 sched_cgroup_fork(p, args);
2384
2385 /*
2386 * From this point on we must avoid any synchronous user-space
2387 * communication until we take the tasklist-lock. In particular, we do
2388 * not want user-space to be able to predict the process start-time by
2389 * stalling fork(2) after we recorded the start_time but before it is
2390 * visible to the system.
2391 */
2392
2393 p->start_time = ktime_get_ns();
2394 p->start_boottime = ktime_get_boottime_ns();
2395
2396 /*
2397 * Make it visible to the rest of the system, but dont wake it up yet.
2398 * Need tasklist lock for parent etc handling!
2399 */
2400 write_lock_irq(&tasklist_lock);
2401
2402 /* CLONE_PARENT re-uses the old parent */
2403 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
2404 p->real_parent = current->real_parent;
2405 p->parent_exec_id = current->parent_exec_id;
2406 if (clone_flags & CLONE_THREAD)
2407 p->exit_signal = -1;
2408 else
2409 p->exit_signal = current->group_leader->exit_signal;
2410 } else {
2411 p->real_parent = current;
2412 p->parent_exec_id = current->self_exec_id;
2413 p->exit_signal = args->exit_signal;
2414 }
2415
2416 klp_copy_process(p);
2417
2418 sched_core_fork(p);
2419
2420 spin_lock(¤t->sighand->siglock);
2421
2422 rv_task_fork(p);
2423
2424 rseq_fork(p, clone_flags);
2425
2426 /* Don't start children in a dying pid namespace */
2427 if (unlikely(!(ns_of_pid(pid)->pid_allocated & PIDNS_ADDING))) {
2428 retval = -ENOMEM;
2429 goto bad_fork_cancel_cgroup;
2430 }
2431
2432 /* Let kill terminate clone/fork in the middle */
2433 if (fatal_signal_pending(current)) {
2434 retval = -EINTR;
2435 goto bad_fork_cancel_cgroup;
2436 }
2437
2438 /* No more failure paths after this point. */
2439
2440 /*
2441 * Copy seccomp details explicitly here, in case they were changed
2442 * before holding sighand lock.
2443 */
2444 copy_seccomp(p);
2445
2446 init_task_pid_links(p);
2447 if (likely(p->pid)) {
2448 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
2449
2450 init_task_pid(p, PIDTYPE_PID, pid);
2451 if (thread_group_leader(p)) {
2452 init_task_pid(p, PIDTYPE_TGID, pid);
2453 init_task_pid(p, PIDTYPE_PGID, task_pgrp(current));
2454 init_task_pid(p, PIDTYPE_SID, task_session(current));
2455
2456 if (is_child_reaper(pid)) {
2457 ns_of_pid(pid)->child_reaper = p;
2458 p->signal->flags |= SIGNAL_UNKILLABLE;
2459 }
2460 p->signal->shared_pending.signal = delayed.signal;
2461 p->signal->tty = tty_kref_get(current->signal->tty);
2462 /*
2463 * Inherit has_child_subreaper flag under the same
2464 * tasklist_lock with adding child to the process tree
2465 * for propagate_has_child_subreaper optimization.
2466 */
2467 p->signal->has_child_subreaper = p->real_parent->signal->has_child_subreaper ||
2468 p->real_parent->signal->is_child_subreaper;
2469 list_add_tail(&p->sibling, &p->real_parent->children);
2470 list_add_tail_rcu(&p->tasks, &init_task.tasks);
2471 attach_pid(p, PIDTYPE_TGID);
2472 attach_pid(p, PIDTYPE_PGID);
2473 attach_pid(p, PIDTYPE_SID);
2474 __this_cpu_inc(process_counts);
2475 } else {
2476 current->signal->nr_threads++;
2477 current->signal->quick_threads++;
2478 atomic_inc(¤t->signal->live);
2479 refcount_inc(¤t->signal->sigcnt);
2480 task_join_group_stop(p);
2481 list_add_tail_rcu(&p->thread_group,
2482 &p->group_leader->thread_group);
2483 list_add_tail_rcu(&p->thread_node,
2484 &p->signal->thread_head);
2485 }
2486 attach_pid(p, PIDTYPE_PID);
2487 nr_threads++;
2488 }
2489 total_forks++;
2490 hlist_del_init(&delayed.node);
2491 spin_unlock(¤t->sighand->siglock);
2492 syscall_tracepoint_update(p);
2493 write_unlock_irq(&tasklist_lock);
2494
2495 if (pidfile)
2496 fd_install(pidfd, pidfile);
2497
2498 proc_fork_connector(p);
2499 sched_post_fork(p);
2500 cgroup_post_fork(p, args);
2501 perf_event_fork(p);
2502
2503 trace_task_newtask(p, clone_flags);
2504 uprobe_copy_process(p, clone_flags);
2505
2506 copy_oom_score_adj(clone_flags, p);
2507
2508 return p;
2509
2510bad_fork_cancel_cgroup:
2511 sched_core_free(p);
2512 spin_unlock(¤t->sighand->siglock);
2513 write_unlock_irq(&tasklist_lock);
2514 cgroup_cancel_fork(p, args);
2515bad_fork_put_pidfd:
2516 if (clone_flags & CLONE_PIDFD) {
2517 fput(pidfile);
2518 put_unused_fd(pidfd);
2519 }
2520bad_fork_free_pid:
2521 if (pid != &init_struct_pid)
2522 free_pid(pid);
2523bad_fork_cleanup_thread:
2524 exit_thread(p);
2525bad_fork_cleanup_io:
2526 if (p->io_context)
2527 exit_io_context(p);
2528bad_fork_cleanup_namespaces:
2529 exit_task_namespaces(p);
2530bad_fork_cleanup_mm:
2531 if (p->mm) {
2532 mm_clear_owner(p->mm, p);
2533 mmput(p->mm);
2534 }
2535bad_fork_cleanup_signal:
2536 if (!(clone_flags & CLONE_THREAD))
2537 free_signal_struct(p->signal);
2538bad_fork_cleanup_sighand:
2539 __cleanup_sighand(p->sighand);
2540bad_fork_cleanup_fs:
2541 exit_fs(p); /* blocking */
2542bad_fork_cleanup_files:
2543 exit_files(p); /* blocking */
2544bad_fork_cleanup_semundo:
2545 exit_sem(p);
2546bad_fork_cleanup_security:
2547 security_task_free(p);
2548bad_fork_cleanup_audit:
2549 audit_free(p);
2550bad_fork_cleanup_perf:
2551 perf_event_free_task(p);
2552bad_fork_cleanup_policy:
2553 lockdep_free_task(p);
2554#ifdef CONFIG_NUMA
2555 mpol_put(p->mempolicy);
2556#endif
2557bad_fork_cleanup_delayacct:
2558 delayacct_tsk_free(p);
2559bad_fork_cleanup_count:
2560 dec_rlimit_ucounts(task_ucounts(p), UCOUNT_RLIMIT_NPROC, 1);
2561 exit_creds(p);
2562bad_fork_free:
2563 WRITE_ONCE(p->__state, TASK_DEAD);
2564 exit_task_stack_account(p);
2565 put_task_stack(p);
2566 delayed_free_task(p);
2567fork_out:
2568 spin_lock_irq(¤t->sighand->siglock);
2569 hlist_del_init(&delayed.node);
2570 spin_unlock_irq(¤t->sighand->siglock);
2571 return ERR_PTR(retval);
2572}
2573
2574static inline void init_idle_pids(struct task_struct *idle)
2575{
2576 enum pid_type type;
2577
2578 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
2579 INIT_HLIST_NODE(&idle->pid_links[type]); /* not really needed */
2580 init_task_pid(idle, type, &init_struct_pid);
2581 }
2582}
2583
2584static int idle_dummy(void *dummy)
2585{
2586 /* This function is never called */
2587 return 0;
2588}
2589
2590struct task_struct * __init fork_idle(int cpu)
2591{
2592 struct task_struct *task;
2593 struct kernel_clone_args args = {
2594 .flags = CLONE_VM,
2595 .fn = &idle_dummy,
2596 .fn_arg = NULL,
2597 .kthread = 1,
2598 .idle = 1,
2599 };
2600
2601 task = copy_process(&init_struct_pid, 0, cpu_to_node(cpu), &args);
2602 if (!IS_ERR(task)) {
2603 init_idle_pids(task);
2604 init_idle(task, cpu);
2605 }
2606
2607 return task;
2608}
2609
2610/*
2611 * This is like kernel_clone(), but shaved down and tailored to just
2612 * creating io_uring workers. It returns a created task, or an error pointer.
2613 * The returned task is inactive, and the caller must fire it up through
2614 * wake_up_new_task(p). All signals are blocked in the created task.
2615 */
2616struct task_struct *create_io_thread(int (*fn)(void *), void *arg, int node)
2617{
2618 unsigned long flags = CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|
2619 CLONE_IO;
2620 struct kernel_clone_args args = {
2621 .flags = ((lower_32_bits(flags) | CLONE_VM |
2622 CLONE_UNTRACED) & ~CSIGNAL),
2623 .exit_signal = (lower_32_bits(flags) & CSIGNAL),
2624 .fn = fn,
2625 .fn_arg = arg,
2626 .io_thread = 1,
2627 };
2628
2629 return copy_process(NULL, 0, node, &args);
2630}
2631
2632/*
2633 * Ok, this is the main fork-routine.
2634 *
2635 * It copies the process, and if successful kick-starts
2636 * it and waits for it to finish using the VM if required.
2637 *
2638 * args->exit_signal is expected to be checked for sanity by the caller.
2639 */
2640pid_t kernel_clone(struct kernel_clone_args *args)
2641{
2642 u64 clone_flags = args->flags;
2643 struct completion vfork;
2644 struct pid *pid;
2645 struct task_struct *p;
2646 int trace = 0;
2647 pid_t nr;
2648
2649 /*
2650 * For legacy clone() calls, CLONE_PIDFD uses the parent_tid argument
2651 * to return the pidfd. Hence, CLONE_PIDFD and CLONE_PARENT_SETTID are
2652 * mutually exclusive. With clone3() CLONE_PIDFD has grown a separate
2653 * field in struct clone_args and it still doesn't make sense to have
2654 * them both point at the same memory location. Performing this check
2655 * here has the advantage that we don't need to have a separate helper
2656 * to check for legacy clone().
2657 */
2658 if ((args->flags & CLONE_PIDFD) &&
2659 (args->flags & CLONE_PARENT_SETTID) &&
2660 (args->pidfd == args->parent_tid))
2661 return -EINVAL;
2662
2663 /*
2664 * Determine whether and which event to report to ptracer. When
2665 * called from kernel_thread or CLONE_UNTRACED is explicitly
2666 * requested, no event is reported; otherwise, report if the event
2667 * for the type of forking is enabled.
2668 */
2669 if (!(clone_flags & CLONE_UNTRACED)) {
2670 if (clone_flags & CLONE_VFORK)
2671 trace = PTRACE_EVENT_VFORK;
2672 else if (args->exit_signal != SIGCHLD)
2673 trace = PTRACE_EVENT_CLONE;
2674 else
2675 trace = PTRACE_EVENT_FORK;
2676
2677 if (likely(!ptrace_event_enabled(current, trace)))
2678 trace = 0;
2679 }
2680
2681 p = copy_process(NULL, trace, NUMA_NO_NODE, args);
2682 add_latent_entropy();
2683
2684 if (IS_ERR(p))
2685 return PTR_ERR(p);
2686
2687 /*
2688 * Do this prior waking up the new thread - the thread pointer
2689 * might get invalid after that point, if the thread exits quickly.
2690 */
2691 trace_sched_process_fork(current, p);
2692
2693 pid = get_task_pid(p, PIDTYPE_PID);
2694 nr = pid_vnr(pid);
2695
2696 if (clone_flags & CLONE_PARENT_SETTID)
2697 put_user(nr, args->parent_tid);
2698
2699 if (clone_flags & CLONE_VFORK) {
2700 p->vfork_done = &vfork;
2701 init_completion(&vfork);
2702 get_task_struct(p);
2703 }
2704
2705 if (IS_ENABLED(CONFIG_LRU_GEN) && !(clone_flags & CLONE_VM)) {
2706 /* lock the task to synchronize with memcg migration */
2707 task_lock(p);
2708 lru_gen_add_mm(p->mm);
2709 task_unlock(p);
2710 }
2711
2712 wake_up_new_task(p);
2713
2714 /* forking complete and child started to run, tell ptracer */
2715 if (unlikely(trace))
2716 ptrace_event_pid(trace, pid);
2717
2718 if (clone_flags & CLONE_VFORK) {
2719 if (!wait_for_vfork_done(p, &vfork))
2720 ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid);
2721 }
2722
2723 put_pid(pid);
2724 return nr;
2725}
2726
2727/*
2728 * Create a kernel thread.
2729 */
2730pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
2731{
2732 struct kernel_clone_args args = {
2733 .flags = ((lower_32_bits(flags) | CLONE_VM |
2734 CLONE_UNTRACED) & ~CSIGNAL),
2735 .exit_signal = (lower_32_bits(flags) & CSIGNAL),
2736 .fn = fn,
2737 .fn_arg = arg,
2738 .kthread = 1,
2739 };
2740
2741 return kernel_clone(&args);
2742}
2743
2744/*
2745 * Create a user mode thread.
2746 */
2747pid_t user_mode_thread(int (*fn)(void *), void *arg, unsigned long flags)
2748{
2749 struct kernel_clone_args args = {
2750 .flags = ((lower_32_bits(flags) | CLONE_VM |
2751 CLONE_UNTRACED) & ~CSIGNAL),
2752 .exit_signal = (lower_32_bits(flags) & CSIGNAL),
2753 .fn = fn,
2754 .fn_arg = arg,
2755 };
2756
2757 return kernel_clone(&args);
2758}
2759
2760#ifdef __ARCH_WANT_SYS_FORK
2761SYSCALL_DEFINE0(fork)
2762{
2763#ifdef CONFIG_MMU
2764 struct kernel_clone_args args = {
2765 .exit_signal = SIGCHLD,
2766 };
2767
2768 return kernel_clone(&args);
2769#else
2770 /* can not support in nommu mode */
2771 return -EINVAL;
2772#endif
2773}
2774#endif
2775
2776#ifdef __ARCH_WANT_SYS_VFORK
2777SYSCALL_DEFINE0(vfork)
2778{
2779 struct kernel_clone_args args = {
2780 .flags = CLONE_VFORK | CLONE_VM,
2781 .exit_signal = SIGCHLD,
2782 };
2783
2784 return kernel_clone(&args);
2785}
2786#endif
2787
2788#ifdef __ARCH_WANT_SYS_CLONE
2789#ifdef CONFIG_CLONE_BACKWARDS
2790SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2791 int __user *, parent_tidptr,
2792 unsigned long, tls,
2793 int __user *, child_tidptr)
2794#elif defined(CONFIG_CLONE_BACKWARDS2)
2795SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags,
2796 int __user *, parent_tidptr,
2797 int __user *, child_tidptr,
2798 unsigned long, tls)
2799#elif defined(CONFIG_CLONE_BACKWARDS3)
2800SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp,
2801 int, stack_size,
2802 int __user *, parent_tidptr,
2803 int __user *, child_tidptr,
2804 unsigned long, tls)
2805#else
2806SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2807 int __user *, parent_tidptr,
2808 int __user *, child_tidptr,
2809 unsigned long, tls)
2810#endif
2811{
2812 struct kernel_clone_args args = {
2813 .flags = (lower_32_bits(clone_flags) & ~CSIGNAL),
2814 .pidfd = parent_tidptr,
2815 .child_tid = child_tidptr,
2816 .parent_tid = parent_tidptr,
2817 .exit_signal = (lower_32_bits(clone_flags) & CSIGNAL),
2818 .stack = newsp,
2819 .tls = tls,
2820 };
2821
2822 return kernel_clone(&args);
2823}
2824#endif
2825
2826#ifdef __ARCH_WANT_SYS_CLONE3
2827
2828noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs,
2829 struct clone_args __user *uargs,
2830 size_t usize)
2831{
2832 int err;
2833 struct clone_args args;
2834 pid_t *kset_tid = kargs->set_tid;
2835
2836 BUILD_BUG_ON(offsetofend(struct clone_args, tls) !=
2837 CLONE_ARGS_SIZE_VER0);
2838 BUILD_BUG_ON(offsetofend(struct clone_args, set_tid_size) !=
2839 CLONE_ARGS_SIZE_VER1);
2840 BUILD_BUG_ON(offsetofend(struct clone_args, cgroup) !=
2841 CLONE_ARGS_SIZE_VER2);
2842 BUILD_BUG_ON(sizeof(struct clone_args) != CLONE_ARGS_SIZE_VER2);
2843
2844 if (unlikely(usize > PAGE_SIZE))
2845 return -E2BIG;
2846 if (unlikely(usize < CLONE_ARGS_SIZE_VER0))
2847 return -EINVAL;
2848
2849 err = copy_struct_from_user(&args, sizeof(args), uargs, usize);
2850 if (err)
2851 return err;
2852
2853 if (unlikely(args.set_tid_size > MAX_PID_NS_LEVEL))
2854 return -EINVAL;
2855
2856 if (unlikely(!args.set_tid && args.set_tid_size > 0))
2857 return -EINVAL;
2858
2859 if (unlikely(args.set_tid && args.set_tid_size == 0))
2860 return -EINVAL;
2861
2862 /*
2863 * Verify that higher 32bits of exit_signal are unset and that
2864 * it is a valid signal
2865 */
2866 if (unlikely((args.exit_signal & ~((u64)CSIGNAL)) ||
2867 !valid_signal(args.exit_signal)))
2868 return -EINVAL;
2869
2870 if ((args.flags & CLONE_INTO_CGROUP) &&
2871 (args.cgroup > INT_MAX || usize < CLONE_ARGS_SIZE_VER2))
2872 return -EINVAL;
2873
2874 *kargs = (struct kernel_clone_args){
2875 .flags = args.flags,
2876 .pidfd = u64_to_user_ptr(args.pidfd),
2877 .child_tid = u64_to_user_ptr(args.child_tid),
2878 .parent_tid = u64_to_user_ptr(args.parent_tid),
2879 .exit_signal = args.exit_signal,
2880 .stack = args.stack,
2881 .stack_size = args.stack_size,
2882 .tls = args.tls,
2883 .set_tid_size = args.set_tid_size,
2884 .cgroup = args.cgroup,
2885 };
2886
2887 if (args.set_tid &&
2888 copy_from_user(kset_tid, u64_to_user_ptr(args.set_tid),
2889 (kargs->set_tid_size * sizeof(pid_t))))
2890 return -EFAULT;
2891
2892 kargs->set_tid = kset_tid;
2893
2894 return 0;
2895}
2896
2897/**
2898 * clone3_stack_valid - check and prepare stack
2899 * @kargs: kernel clone args
2900 *
2901 * Verify that the stack arguments userspace gave us are sane.
2902 * In addition, set the stack direction for userspace since it's easy for us to
2903 * determine.
2904 */
2905static inline bool clone3_stack_valid(struct kernel_clone_args *kargs)
2906{
2907 if (kargs->stack == 0) {
2908 if (kargs->stack_size > 0)
2909 return false;
2910 } else {
2911 if (kargs->stack_size == 0)
2912 return false;
2913
2914 if (!access_ok((void __user *)kargs->stack, kargs->stack_size))
2915 return false;
2916
2917#if !defined(CONFIG_STACK_GROWSUP) && !defined(CONFIG_IA64)
2918 kargs->stack += kargs->stack_size;
2919#endif
2920 }
2921
2922 return true;
2923}
2924
2925static bool clone3_args_valid(struct kernel_clone_args *kargs)
2926{
2927 /* Verify that no unknown flags are passed along. */
2928 if (kargs->flags &
2929 ~(CLONE_LEGACY_FLAGS | CLONE_CLEAR_SIGHAND | CLONE_INTO_CGROUP))
2930 return false;
2931
2932 /*
2933 * - make the CLONE_DETACHED bit reusable for clone3
2934 * - make the CSIGNAL bits reusable for clone3
2935 */
2936 if (kargs->flags & (CLONE_DETACHED | CSIGNAL))
2937 return false;
2938
2939 if ((kargs->flags & (CLONE_SIGHAND | CLONE_CLEAR_SIGHAND)) ==
2940 (CLONE_SIGHAND | CLONE_CLEAR_SIGHAND))
2941 return false;
2942
2943 if ((kargs->flags & (CLONE_THREAD | CLONE_PARENT)) &&
2944 kargs->exit_signal)
2945 return false;
2946
2947 if (!clone3_stack_valid(kargs))
2948 return false;
2949
2950 return true;
2951}
2952
2953/**
2954 * clone3 - create a new process with specific properties
2955 * @uargs: argument structure
2956 * @size: size of @uargs
2957 *
2958 * clone3() is the extensible successor to clone()/clone2().
2959 * It takes a struct as argument that is versioned by its size.
2960 *
2961 * Return: On success, a positive PID for the child process.
2962 * On error, a negative errno number.
2963 */
2964SYSCALL_DEFINE2(clone3, struct clone_args __user *, uargs, size_t, size)
2965{
2966 int err;
2967
2968 struct kernel_clone_args kargs;
2969 pid_t set_tid[MAX_PID_NS_LEVEL];
2970
2971 kargs.set_tid = set_tid;
2972
2973 err = copy_clone_args_from_user(&kargs, uargs, size);
2974 if (err)
2975 return err;
2976
2977 if (!clone3_args_valid(&kargs))
2978 return -EINVAL;
2979
2980 return kernel_clone(&kargs);
2981}
2982#endif
2983
2984void walk_process_tree(struct task_struct *top, proc_visitor visitor, void *data)
2985{
2986 struct task_struct *leader, *parent, *child;
2987 int res;
2988
2989 read_lock(&tasklist_lock);
2990 leader = top = top->group_leader;
2991down:
2992 for_each_thread(leader, parent) {
2993 list_for_each_entry(child, &parent->children, sibling) {
2994 res = visitor(child, data);
2995 if (res) {
2996 if (res < 0)
2997 goto out;
2998 leader = child;
2999 goto down;
3000 }
3001up:
3002 ;
3003 }
3004 }
3005
3006 if (leader != top) {
3007 child = leader;
3008 parent = child->real_parent;
3009 leader = parent->group_leader;
3010 goto up;
3011 }
3012out:
3013 read_unlock(&tasklist_lock);
3014}
3015
3016#ifndef ARCH_MIN_MMSTRUCT_ALIGN
3017#define ARCH_MIN_MMSTRUCT_ALIGN 0
3018#endif
3019
3020static void sighand_ctor(void *data)
3021{
3022 struct sighand_struct *sighand = data;
3023
3024 spin_lock_init(&sighand->siglock);
3025 init_waitqueue_head(&sighand->signalfd_wqh);
3026}
3027
3028void __init mm_cache_init(void)
3029{
3030 unsigned int mm_size;
3031
3032 /*
3033 * The mm_cpumask is located at the end of mm_struct, and is
3034 * dynamically sized based on the maximum CPU number this system
3035 * can have, taking hotplug into account (nr_cpu_ids).
3036 */
3037 mm_size = sizeof(struct mm_struct) + cpumask_size();
3038
3039 mm_cachep = kmem_cache_create_usercopy("mm_struct",
3040 mm_size, ARCH_MIN_MMSTRUCT_ALIGN,
3041 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
3042 offsetof(struct mm_struct, saved_auxv),
3043 sizeof_field(struct mm_struct, saved_auxv),
3044 NULL);
3045}
3046
3047void __init proc_caches_init(void)
3048{
3049 sighand_cachep = kmem_cache_create("sighand_cache",
3050 sizeof(struct sighand_struct), 0,
3051 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_TYPESAFE_BY_RCU|
3052 SLAB_ACCOUNT, sighand_ctor);
3053 signal_cachep = kmem_cache_create("signal_cache",
3054 sizeof(struct signal_struct), 0,
3055 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
3056 NULL);
3057 files_cachep = kmem_cache_create("files_cache",
3058 sizeof(struct files_struct), 0,
3059 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
3060 NULL);
3061 fs_cachep = kmem_cache_create("fs_cache",
3062 sizeof(struct fs_struct), 0,
3063 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
3064 NULL);
3065
3066 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT);
3067 mmap_init();
3068 nsproxy_cache_init();
3069}
3070
3071/*
3072 * Check constraints on flags passed to the unshare system call.
3073 */
3074static int check_unshare_flags(unsigned long unshare_flags)
3075{
3076 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
3077 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
3078 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET|
3079 CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP|
3080 CLONE_NEWTIME))
3081 return -EINVAL;
3082 /*
3083 * Not implemented, but pretend it works if there is nothing
3084 * to unshare. Note that unsharing the address space or the
3085 * signal handlers also need to unshare the signal queues (aka
3086 * CLONE_THREAD).
3087 */
3088 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
3089 if (!thread_group_empty(current))
3090 return -EINVAL;
3091 }
3092 if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) {
3093 if (refcount_read(¤t->sighand->count) > 1)
3094 return -EINVAL;
3095 }
3096 if (unshare_flags & CLONE_VM) {
3097 if (!current_is_single_threaded())
3098 return -EINVAL;
3099 }
3100
3101 return 0;
3102}
3103
3104/*
3105 * Unshare the filesystem structure if it is being shared
3106 */
3107static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
3108{
3109 struct fs_struct *fs = current->fs;
3110
3111 if (!(unshare_flags & CLONE_FS) || !fs)
3112 return 0;
3113
3114 /* don't need lock here; in the worst case we'll do useless copy */
3115 if (fs->users == 1)
3116 return 0;
3117
3118 *new_fsp = copy_fs_struct(fs);
3119 if (!*new_fsp)
3120 return -ENOMEM;
3121
3122 return 0;
3123}
3124
3125/*
3126 * Unshare file descriptor table if it is being shared
3127 */
3128int unshare_fd(unsigned long unshare_flags, unsigned int max_fds,
3129 struct files_struct **new_fdp)
3130{
3131 struct files_struct *fd = current->files;
3132 int error = 0;
3133
3134 if ((unshare_flags & CLONE_FILES) &&
3135 (fd && atomic_read(&fd->count) > 1)) {
3136 *new_fdp = dup_fd(fd, max_fds, &error);
3137 if (!*new_fdp)
3138 return error;
3139 }
3140
3141 return 0;
3142}
3143
3144/*
3145 * unshare allows a process to 'unshare' part of the process
3146 * context which was originally shared using clone. copy_*
3147 * functions used by kernel_clone() cannot be used here directly
3148 * because they modify an inactive task_struct that is being
3149 * constructed. Here we are modifying the current, active,
3150 * task_struct.
3151 */
3152int ksys_unshare(unsigned long unshare_flags)
3153{
3154 struct fs_struct *fs, *new_fs = NULL;
3155 struct files_struct *new_fd = NULL;
3156 struct cred *new_cred = NULL;
3157 struct nsproxy *new_nsproxy = NULL;
3158 int do_sysvsem = 0;
3159 int err;
3160
3161 /*
3162 * If unsharing a user namespace must also unshare the thread group
3163 * and unshare the filesystem root and working directories.
3164 */
3165 if (unshare_flags & CLONE_NEWUSER)
3166 unshare_flags |= CLONE_THREAD | CLONE_FS;
3167 /*
3168 * If unsharing vm, must also unshare signal handlers.
3169 */
3170 if (unshare_flags & CLONE_VM)
3171 unshare_flags |= CLONE_SIGHAND;
3172 /*
3173 * If unsharing a signal handlers, must also unshare the signal queues.
3174 */
3175 if (unshare_flags & CLONE_SIGHAND)
3176 unshare_flags |= CLONE_THREAD;
3177 /*
3178 * If unsharing namespace, must also unshare filesystem information.
3179 */
3180 if (unshare_flags & CLONE_NEWNS)
3181 unshare_flags |= CLONE_FS;
3182
3183 err = check_unshare_flags(unshare_flags);
3184 if (err)
3185 goto bad_unshare_out;
3186 /*
3187 * CLONE_NEWIPC must also detach from the undolist: after switching
3188 * to a new ipc namespace, the semaphore arrays from the old
3189 * namespace are unreachable.
3190 */
3191 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
3192 do_sysvsem = 1;
3193 err = unshare_fs(unshare_flags, &new_fs);
3194 if (err)
3195 goto bad_unshare_out;
3196 err = unshare_fd(unshare_flags, NR_OPEN_MAX, &new_fd);
3197 if (err)
3198 goto bad_unshare_cleanup_fs;
3199 err = unshare_userns(unshare_flags, &new_cred);
3200 if (err)
3201 goto bad_unshare_cleanup_fd;
3202 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
3203 new_cred, new_fs);
3204 if (err)
3205 goto bad_unshare_cleanup_cred;
3206
3207 if (new_cred) {
3208 err = set_cred_ucounts(new_cred);
3209 if (err)
3210 goto bad_unshare_cleanup_cred;
3211 }
3212
3213 if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
3214 if (do_sysvsem) {
3215 /*
3216 * CLONE_SYSVSEM is equivalent to sys_exit().
3217 */
3218 exit_sem(current);
3219 }
3220 if (unshare_flags & CLONE_NEWIPC) {
3221 /* Orphan segments in old ns (see sem above). */
3222 exit_shm(current);
3223 shm_init_task(current);
3224 }
3225
3226 if (new_nsproxy)
3227 switch_task_namespaces(current, new_nsproxy);
3228
3229 task_lock(current);
3230
3231 if (new_fs) {
3232 fs = current->fs;
3233 spin_lock(&fs->lock);
3234 current->fs = new_fs;
3235 if (--fs->users)
3236 new_fs = NULL;
3237 else
3238 new_fs = fs;
3239 spin_unlock(&fs->lock);
3240 }
3241
3242 if (new_fd)
3243 swap(current->files, new_fd);
3244
3245 task_unlock(current);
3246
3247 if (new_cred) {
3248 /* Install the new user namespace */
3249 commit_creds(new_cred);
3250 new_cred = NULL;
3251 }
3252 }
3253
3254 perf_event_namespaces(current);
3255
3256bad_unshare_cleanup_cred:
3257 if (new_cred)
3258 put_cred(new_cred);
3259bad_unshare_cleanup_fd:
3260 if (new_fd)
3261 put_files_struct(new_fd);
3262
3263bad_unshare_cleanup_fs:
3264 if (new_fs)
3265 free_fs_struct(new_fs);
3266
3267bad_unshare_out:
3268 return err;
3269}
3270
3271SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
3272{
3273 return ksys_unshare(unshare_flags);
3274}
3275
3276/*
3277 * Helper to unshare the files of the current task.
3278 * We don't want to expose copy_files internals to
3279 * the exec layer of the kernel.
3280 */
3281
3282int unshare_files(void)
3283{
3284 struct task_struct *task = current;
3285 struct files_struct *old, *copy = NULL;
3286 int error;
3287
3288 error = unshare_fd(CLONE_FILES, NR_OPEN_MAX, ©);
3289 if (error || !copy)
3290 return error;
3291
3292 old = task->files;
3293 task_lock(task);
3294 task->files = copy;
3295 task_unlock(task);
3296 put_files_struct(old);
3297 return 0;
3298}
3299
3300int sysctl_max_threads(struct ctl_table *table, int write,
3301 void *buffer, size_t *lenp, loff_t *ppos)
3302{
3303 struct ctl_table t;
3304 int ret;
3305 int threads = max_threads;
3306 int min = 1;
3307 int max = MAX_THREADS;
3308
3309 t = *table;
3310 t.data = &threads;
3311 t.extra1 = &min;
3312 t.extra2 = &max;
3313
3314 ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
3315 if (ret || !write)
3316 return ret;
3317
3318 max_threads = threads;
3319
3320 return 0;
3321}