projects/linux·blob v5.13 · refs

3111 lines · 75.5 KiB

1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * linux/kernel/fork.c
4 *
5 * Copyright (C) 1991, 1992 Linus Torvalds
6 */
7
8/*
9 * 'fork.c' contains the help-routines for the 'fork' system call
10 * (see also entry.S and others).
11 * Fork is rather simple, once you get the hang of it, but the memory
12 * management can be a bitch. See 'mm/memory.c': 'copy_page_range()'
13 */
14
15#include <linux/anon_inodes.h>
16#include <linux/slab.h>
17#include <linux/sched/autogroup.h>
18#include <linux/sched/mm.h>
19#include <linux/sched/coredump.h>
20#include <linux/sched/user.h>
21#include <linux/sched/numa_balancing.h>
22#include <linux/sched/stat.h>
23#include <linux/sched/task.h>
24#include <linux/sched/task_stack.h>
25#include <linux/sched/cputime.h>
26#include <linux/seq_file.h>
27#include <linux/rtmutex.h>
28#include <linux/init.h>
29#include <linux/unistd.h>
30#include <linux/module.h>
31#include <linux/vmalloc.h>
32#include <linux/completion.h>
33#include <linux/personality.h>
34#include <linux/mempolicy.h>
35#include <linux/sem.h>
36#include <linux/file.h>
37#include <linux/fdtable.h>
38#include <linux/iocontext.h>
39#include <linux/key.h>
40#include <linux/binfmts.h>
41#include <linux/mman.h>
42#include <linux/mmu_notifier.h>
43#include <linux/fs.h>
44#include <linux/mm.h>
45#include <linux/vmacache.h>
46#include <linux/nsproxy.h>
47#include <linux/capability.h>
48#include <linux/cpu.h>
49#include <linux/cgroup.h>
50#include <linux/security.h>
51#include <linux/hugetlb.h>
52#include <linux/seccomp.h>
53#include <linux/swap.h>
54#include <linux/syscalls.h>
55#include <linux/jiffies.h>
56#include <linux/futex.h>
57#include <linux/compat.h>
58#include <linux/kthread.h>
59#include <linux/task_io_accounting_ops.h>
60#include <linux/rcupdate.h>
61#include <linux/ptrace.h>
62#include <linux/mount.h>
63#include <linux/audit.h>
64#include <linux/memcontrol.h>
65#include <linux/ftrace.h>
66#include <linux/proc_fs.h>
67#include <linux/profile.h>
68#include <linux/rmap.h>
69#include <linux/ksm.h>
70#include <linux/acct.h>
71#include <linux/userfaultfd_k.h>
72#include <linux/tsacct_kern.h>
73#include <linux/cn_proc.h>
74#include <linux/freezer.h>
75#include <linux/delayacct.h>
76#include <linux/taskstats_kern.h>
77#include <linux/random.h>
78#include <linux/tty.h>
79#include <linux/blkdev.h>
80#include <linux/fs_struct.h>
81#include <linux/magic.h>
82#include <linux/perf_event.h>
83#include <linux/posix-timers.h>
84#include <linux/user-return-notifier.h>
85#include <linux/oom.h>
86#include <linux/khugepaged.h>
87#include <linux/signalfd.h>
88#include <linux/uprobes.h>
89#include <linux/aio.h>
90#include <linux/compiler.h>
91#include <linux/sysctl.h>
92#include <linux/kcov.h>
93#include <linux/livepatch.h>
94#include <linux/thread_info.h>
95#include <linux/stackleak.h>
96#include <linux/kasan.h>
97#include <linux/scs.h>
98#include <linux/io_uring.h>
99#include <linux/bpf.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
196static int free_vm_stack_cache(unsigned int cpu)
197{
198 struct vm_struct **cached_vm_stacks = per_cpu_ptr(cached_stacks, cpu);
199 int i;
200
201 for (i = 0; i < NR_CACHED_STACKS; i++) {
202 struct vm_struct *vm_stack = cached_vm_stacks[i];
203
204 if (!vm_stack)
205 continue;
206
207 vfree(vm_stack->addr);
208 cached_vm_stacks[i] = NULL;
209 }
210
211 return 0;
212}
213#endif
214
215static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node)
216{
217#ifdef CONFIG_VMAP_STACK
218 void *stack;
219 int i;
220
221 for (i = 0; i < NR_CACHED_STACKS; i++) {
222 struct vm_struct *s;
223
224 s = this_cpu_xchg(cached_stacks[i], NULL);
225
226 if (!s)
227 continue;
228
229 /* Mark stack accessible for KASAN. */
230 kasan_unpoison_range(s->addr, THREAD_SIZE);
231
232 /* Clear stale pointers from reused stack. */
233 memset(s->addr, 0, THREAD_SIZE);
234
235 tsk->stack_vm_area = s;
236 tsk->stack = s->addr;
237 return s->addr;
238 }
239
240 /*
241 * Allocated stacks are cached and later reused by new threads,
242 * so memcg accounting is performed manually on assigning/releasing
243 * stacks to tasks. Drop __GFP_ACCOUNT.
244 */
245 stack = __vmalloc_node_range(THREAD_SIZE, THREAD_ALIGN,
246 VMALLOC_START, VMALLOC_END,
247 THREADINFO_GFP & ~__GFP_ACCOUNT,
248 PAGE_KERNEL,
249 0, node, __builtin_return_address(0));
250
251 /*
252 * We can't call find_vm_area() in interrupt context, and
253 * free_thread_stack() can be called in interrupt context,
254 * so cache the vm_struct.
255 */
256 if (stack) {
257 tsk->stack_vm_area = find_vm_area(stack);
258 tsk->stack = stack;
259 }
260 return stack;
261#else
262 struct page *page = alloc_pages_node(node, THREADINFO_GFP,
263 THREAD_SIZE_ORDER);
264
265 if (likely(page)) {
266 tsk->stack = kasan_reset_tag(page_address(page));
267 return tsk->stack;
268 }
269 return NULL;
270#endif
271}
272
273static inline void free_thread_stack(struct task_struct *tsk)
274{
275#ifdef CONFIG_VMAP_STACK
276 struct vm_struct *vm = task_stack_vm_area(tsk);
277
278 if (vm) {
279 int i;
280
281 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++)
282 memcg_kmem_uncharge_page(vm->pages[i], 0);
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 stack = kasan_reset_tag(stack);
308 tsk->stack = stack;
309 return stack;
310}
311
312static void free_thread_stack(struct task_struct *tsk)
313{
314 kmem_cache_free(thread_stack_cache, tsk->stack);
315}
316
317void thread_stack_cache_init(void)
318{
319 thread_stack_cache = kmem_cache_create_usercopy("thread_stack",
320 THREAD_SIZE, THREAD_SIZE, 0, 0,
321 THREAD_SIZE, NULL);
322 BUG_ON(thread_stack_cache == NULL);
323}
324# endif
325#endif
326
327/* SLAB cache for signal_struct structures (tsk->signal) */
328static struct kmem_cache *signal_cachep;
329
330/* SLAB cache for sighand_struct structures (tsk->sighand) */
331struct kmem_cache *sighand_cachep;
332
333/* SLAB cache for files_struct structures (tsk->files) */
334struct kmem_cache *files_cachep;
335
336/* SLAB cache for fs_struct structures (tsk->fs) */
337struct kmem_cache *fs_cachep;
338
339/* SLAB cache for vm_area_struct structures */
340static struct kmem_cache *vm_area_cachep;
341
342/* SLAB cache for mm_struct structures (tsk->mm) */
343static struct kmem_cache *mm_cachep;
344
345struct vm_area_struct *vm_area_alloc(struct mm_struct *mm)
346{
347 struct vm_area_struct *vma;
348
349 vma = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
350 if (vma)
351 vma_init(vma, mm);
352 return vma;
353}
354
355struct vm_area_struct *vm_area_dup(struct vm_area_struct *orig)
356{
357 struct vm_area_struct *new = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
358
359 if (new) {
360 ASSERT_EXCLUSIVE_WRITER(orig->vm_flags);
361 ASSERT_EXCLUSIVE_WRITER(orig->vm_file);
362 /*
363 * orig->shared.rb may be modified concurrently, but the clone
364 * will be reinitialized.
365 */
366 *new = data_race(*orig);
367 INIT_LIST_HEAD(&new->anon_vma_chain);
368 new->vm_next = new->vm_prev = NULL;
369 }
370 return new;
371}
372
373void vm_area_free(struct vm_area_struct *vma)
374{
375 kmem_cache_free(vm_area_cachep, vma);
376}
377
378static void account_kernel_stack(struct task_struct *tsk, int account)
379{
380 void *stack = task_stack_page(tsk);
381 struct vm_struct *vm = task_stack_vm_area(tsk);
382
383 if (vm) {
384 int i;
385
386 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++)
387 mod_lruvec_page_state(vm->pages[i], NR_KERNEL_STACK_KB,
388 account * (PAGE_SIZE / 1024));
389 } else {
390 /* All stack pages are in the same node. */
391 mod_lruvec_kmem_state(stack, NR_KERNEL_STACK_KB,
392 account * (THREAD_SIZE / 1024));
393 }
394}
395
396static int memcg_charge_kernel_stack(struct task_struct *tsk)
397{
398#ifdef CONFIG_VMAP_STACK
399 struct vm_struct *vm = task_stack_vm_area(tsk);
400 int ret;
401
402 BUILD_BUG_ON(IS_ENABLED(CONFIG_VMAP_STACK) && PAGE_SIZE % 1024 != 0);
403
404 if (vm) {
405 int i;
406
407 BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE);
408
409 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
410 /*
411 * If memcg_kmem_charge_page() fails, page's
412 * memory cgroup pointer is NULL, and
413 * memcg_kmem_uncharge_page() in free_thread_stack()
414 * will ignore this page.
415 */
416 ret = memcg_kmem_charge_page(vm->pages[i], GFP_KERNEL,
417 0);
418 if (ret)
419 return ret;
420 }
421 }
422#endif
423 return 0;
424}
425
426static void release_task_stack(struct task_struct *tsk)
427{
428 if (WARN_ON(tsk->state != TASK_DEAD))
429 return; /* Better to leak the stack than to free prematurely */
430
431 account_kernel_stack(tsk, -1);
432 free_thread_stack(tsk);
433 tsk->stack = NULL;
434#ifdef CONFIG_VMAP_STACK
435 tsk->stack_vm_area = NULL;
436#endif
437}
438
439#ifdef CONFIG_THREAD_INFO_IN_TASK
440void put_task_stack(struct task_struct *tsk)
441{
442 if (refcount_dec_and_test(&tsk->stack_refcount))
443 release_task_stack(tsk);
444}
445#endif
446
447void free_task(struct task_struct *tsk)
448{
449 scs_release(tsk);
450
451#ifndef CONFIG_THREAD_INFO_IN_TASK
452 /*
453 * The task is finally done with both the stack and thread_info,
454 * so free both.
455 */
456 release_task_stack(tsk);
457#else
458 /*
459 * If the task had a separate stack allocation, it should be gone
460 * by now.
461 */
462 WARN_ON_ONCE(refcount_read(&tsk->stack_refcount) != 0);
463#endif
464 rt_mutex_debug_task_free(tsk);
465 ftrace_graph_exit_task(tsk);
466 arch_release_task_struct(tsk);
467 if (tsk->flags & PF_KTHREAD)
468 free_kthread_struct(tsk);
469 free_task_struct(tsk);
470}
471EXPORT_SYMBOL(free_task);
472
473#ifdef CONFIG_MMU
474static __latent_entropy int dup_mmap(struct mm_struct *mm,
475 struct mm_struct *oldmm)
476{
477 struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
478 struct rb_node **rb_link, *rb_parent;
479 int retval;
480 unsigned long charge;
481 LIST_HEAD(uf);
482
483 uprobe_start_dup_mmap();
484 if (mmap_write_lock_killable(oldmm)) {
485 retval = -EINTR;
486 goto fail_uprobe_end;
487 }
488 flush_cache_dup_mm(oldmm);
489 uprobe_dup_mmap(oldmm, mm);
490 /*
491 * Not linked in yet - no deadlock potential:
492 */
493 mmap_write_lock_nested(mm, SINGLE_DEPTH_NESTING);
494
495 /* No ordering required: file already has been exposed. */
496 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
497
498 mm->total_vm = oldmm->total_vm;
499 mm->data_vm = oldmm->data_vm;
500 mm->exec_vm = oldmm->exec_vm;
501 mm->stack_vm = oldmm->stack_vm;
502
503 rb_link = &mm->mm_rb.rb_node;
504 rb_parent = NULL;
505 pprev = &mm->mmap;
506 retval = ksm_fork(mm, oldmm);
507 if (retval)
508 goto out;
509 retval = khugepaged_fork(mm, oldmm);
510 if (retval)
511 goto out;
512
513 prev = NULL;
514 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
515 struct file *file;
516
517 if (mpnt->vm_flags & VM_DONTCOPY) {
518 vm_stat_account(mm, mpnt->vm_flags, -vma_pages(mpnt));
519 continue;
520 }
521 charge = 0;
522 /*
523 * Don't duplicate many vmas if we've been oom-killed (for
524 * example)
525 */
526 if (fatal_signal_pending(current)) {
527 retval = -EINTR;
528 goto out;
529 }
530 if (mpnt->vm_flags & VM_ACCOUNT) {
531 unsigned long len = vma_pages(mpnt);
532
533 if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
534 goto fail_nomem;
535 charge = len;
536 }
537 tmp = vm_area_dup(mpnt);
538 if (!tmp)
539 goto fail_nomem;
540 retval = vma_dup_policy(mpnt, tmp);
541 if (retval)
542 goto fail_nomem_policy;
543 tmp->vm_mm = mm;
544 retval = dup_userfaultfd(tmp, &uf);
545 if (retval)
546 goto fail_nomem_anon_vma_fork;
547 if (tmp->vm_flags & VM_WIPEONFORK) {
548 /*
549 * VM_WIPEONFORK gets a clean slate in the child.
550 * Don't prepare anon_vma until fault since we don't
551 * copy page for current vma.
552 */
553 tmp->anon_vma = NULL;
554 } else if (anon_vma_fork(tmp, mpnt))
555 goto fail_nomem_anon_vma_fork;
556 tmp->vm_flags &= ~(VM_LOCKED | VM_LOCKONFAULT);
557 file = tmp->vm_file;
558 if (file) {
559 struct inode *inode = file_inode(file);
560 struct address_space *mapping = file->f_mapping;
561
562 get_file(file);
563 if (tmp->vm_flags & VM_DENYWRITE)
564 put_write_access(inode);
565 i_mmap_lock_write(mapping);
566 if (tmp->vm_flags & VM_SHARED)
567 mapping_allow_writable(mapping);
568 flush_dcache_mmap_lock(mapping);
569 /* insert tmp into the share list, just after mpnt */
570 vma_interval_tree_insert_after(tmp, mpnt,
571 &mapping->i_mmap);
572 flush_dcache_mmap_unlock(mapping);
573 i_mmap_unlock_write(mapping);
574 }
575
576 /*
577 * Clear hugetlb-related page reserves for children. This only
578 * affects MAP_PRIVATE mappings. Faults generated by the child
579 * are not guaranteed to succeed, even if read-only
580 */
581 if (is_vm_hugetlb_page(tmp))
582 reset_vma_resv_huge_pages(tmp);
583
584 /*
585 * Link in the new vma and copy the page table entries.
586 */
587 *pprev = tmp;
588 pprev = &tmp->vm_next;
589 tmp->vm_prev = prev;
590 prev = tmp;
591
592 __vma_link_rb(mm, tmp, rb_link, rb_parent);
593 rb_link = &tmp->vm_rb.rb_right;
594 rb_parent = &tmp->vm_rb;
595
596 mm->map_count++;
597 if (!(tmp->vm_flags & VM_WIPEONFORK))
598 retval = copy_page_range(tmp, mpnt);
599
600 if (tmp->vm_ops && tmp->vm_ops->open)
601 tmp->vm_ops->open(tmp);
602
603 if (retval)
604 goto out;
605 }
606 /* a new mm has just been created */
607 retval = arch_dup_mmap(oldmm, mm);
608out:
609 mmap_write_unlock(mm);
610 flush_tlb_mm(oldmm);
611 mmap_write_unlock(oldmm);
612 dup_userfaultfd_complete(&uf);
613fail_uprobe_end:
614 uprobe_end_dup_mmap();
615 return retval;
616fail_nomem_anon_vma_fork:
617 mpol_put(vma_policy(tmp));
618fail_nomem_policy:
619 vm_area_free(tmp);
620fail_nomem:
621 retval = -ENOMEM;
622 vm_unacct_memory(charge);
623 goto out;
624}
625
626static inline int mm_alloc_pgd(struct mm_struct *mm)
627{
628 mm->pgd = pgd_alloc(mm);
629 if (unlikely(!mm->pgd))
630 return -ENOMEM;
631 return 0;
632}
633
634static inline void mm_free_pgd(struct mm_struct *mm)
635{
636 pgd_free(mm, mm->pgd);
637}
638#else
639static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
640{
641 mmap_write_lock(oldmm);
642 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
643 mmap_write_unlock(oldmm);
644 return 0;
645}
646#define mm_alloc_pgd(mm) (0)
647#define mm_free_pgd(mm)
648#endif /* CONFIG_MMU */
649
650static void check_mm(struct mm_struct *mm)
651{
652 int i;
653
654 BUILD_BUG_ON_MSG(ARRAY_SIZE(resident_page_types) != NR_MM_COUNTERS,
655 "Please make sure 'struct resident_page_types[]' is updated as well");
656
657 for (i = 0; i < NR_MM_COUNTERS; i++) {
658 long x = atomic_long_read(&mm->rss_stat.count[i]);
659
660 if (unlikely(x))
661 pr_alert("BUG: Bad rss-counter state mm:%p type:%s val:%ld\n",
662 mm, resident_page_types[i], x);
663 }
664
665 if (mm_pgtables_bytes(mm))
666 pr_alert("BUG: non-zero pgtables_bytes on freeing mm: %ld\n",
667 mm_pgtables_bytes(mm));
668
669#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
670 VM_BUG_ON_MM(mm->pmd_huge_pte, mm);
671#endif
672}
673
674#define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
675#define free_mm(mm) (kmem_cache_free(mm_cachep, (mm)))
676
677/*
678 * Called when the last reference to the mm
679 * is dropped: either by a lazy thread or by
680 * mmput. Free the page directory and the mm.
681 */
682void __mmdrop(struct mm_struct *mm)
683{
684 BUG_ON(mm == &init_mm);
685 WARN_ON_ONCE(mm == current->mm);
686 WARN_ON_ONCE(mm == current->active_mm);
687 mm_free_pgd(mm);
688 destroy_context(mm);
689 mmu_notifier_subscriptions_destroy(mm);
690 check_mm(mm);
691 put_user_ns(mm->user_ns);
692 free_mm(mm);
693}
694EXPORT_SYMBOL_GPL(__mmdrop);
695
696static void mmdrop_async_fn(struct work_struct *work)
697{
698 struct mm_struct *mm;
699
700 mm = container_of(work, struct mm_struct, async_put_work);
701 __mmdrop(mm);
702}
703
704static void mmdrop_async(struct mm_struct *mm)
705{
706 if (unlikely(atomic_dec_and_test(&mm->mm_count))) {
707 INIT_WORK(&mm->async_put_work, mmdrop_async_fn);
708 schedule_work(&mm->async_put_work);
709 }
710}
711
712static inline void free_signal_struct(struct signal_struct *sig)
713{
714 taskstats_tgid_free(sig);
715 sched_autogroup_exit(sig);
716 /*
717 * __mmdrop is not safe to call from softirq context on x86 due to
718 * pgd_dtor so postpone it to the async context
719 */
720 if (sig->oom_mm)
721 mmdrop_async(sig->oom_mm);
722 kmem_cache_free(signal_cachep, sig);
723}
724
725static inline void put_signal_struct(struct signal_struct *sig)
726{
727 if (refcount_dec_and_test(&sig->sigcnt))
728 free_signal_struct(sig);
729}
730
731void __put_task_struct(struct task_struct *tsk)
732{
733 WARN_ON(!tsk->exit_state);
734 WARN_ON(refcount_read(&tsk->usage));
735 WARN_ON(tsk == current);
736
737 io_uring_free(tsk);
738 cgroup_free(tsk);
739 task_numa_free(tsk, true);
740 security_task_free(tsk);
741 bpf_task_storage_free(tsk);
742 exit_creds(tsk);
743 delayacct_tsk_free(tsk);
744 put_signal_struct(tsk->signal);
745
746 if (!profile_handoff_task(tsk))
747 free_task(tsk);
748}
749EXPORT_SYMBOL_GPL(__put_task_struct);
750
751void __init __weak arch_task_cache_init(void) { }
752
753/*
754 * set_max_threads
755 */
756static void set_max_threads(unsigned int max_threads_suggested)
757{
758 u64 threads;
759 unsigned long nr_pages = totalram_pages();
760
761 /*
762 * The number of threads shall be limited such that the thread
763 * structures may only consume a small part of the available memory.
764 */
765 if (fls64(nr_pages) + fls64(PAGE_SIZE) > 64)
766 threads = MAX_THREADS;
767 else
768 threads = div64_u64((u64) nr_pages * (u64) PAGE_SIZE,
769 (u64) THREAD_SIZE * 8UL);
770
771 if (threads > max_threads_suggested)
772 threads = max_threads_suggested;
773
774 max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS);
775}
776
777#ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT
778/* Initialized by the architecture: */
779int arch_task_struct_size __read_mostly;
780#endif
781
782#ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
783static void task_struct_whitelist(unsigned long *offset, unsigned long *size)
784{
785 /* Fetch thread_struct whitelist for the architecture. */
786 arch_thread_struct_whitelist(offset, size);
787
788 /*
789 * Handle zero-sized whitelist or empty thread_struct, otherwise
790 * adjust offset to position of thread_struct in task_struct.
791 */
792 if (unlikely(*size == 0))
793 *offset = 0;
794 else
795 *offset += offsetof(struct task_struct, thread);
796}
797#endif /* CONFIG_ARCH_TASK_STRUCT_ALLOCATOR */
798
799void __init fork_init(void)
800{
801 int i;
802#ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
803#ifndef ARCH_MIN_TASKALIGN
804#define ARCH_MIN_TASKALIGN 0
805#endif
806 int align = max_t(int, L1_CACHE_BYTES, ARCH_MIN_TASKALIGN);
807 unsigned long useroffset, usersize;
808
809 /* create a slab on which task_structs can be allocated */
810 task_struct_whitelist(&useroffset, &usersize);
811 task_struct_cachep = kmem_cache_create_usercopy("task_struct",
812 arch_task_struct_size, align,
813 SLAB_PANIC|SLAB_ACCOUNT,
814 useroffset, usersize, NULL);
815#endif
816
817 /* do the arch specific task caches init */
818 arch_task_cache_init();
819
820 set_max_threads(MAX_THREADS);
821
822 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
823 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
824 init_task.signal->rlim[RLIMIT_SIGPENDING] =
825 init_task.signal->rlim[RLIMIT_NPROC];
826
827 for (i = 0; i < UCOUNT_COUNTS; i++)
828 init_user_ns.ucount_max[i] = max_threads/2;
829
830#ifdef CONFIG_VMAP_STACK
831 cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "fork:vm_stack_cache",
832 NULL, free_vm_stack_cache);
833#endif
834
835 scs_init();
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 err = scs_prepare(tsk, node);
897 if (err)
898 goto free_stack;
899
900#ifdef CONFIG_SECCOMP
901 /*
902 * We must handle setting up seccomp filters once we're under
903 * the sighand lock in case orig has changed between now and
904 * then. Until then, filter must be NULL to avoid messing up
905 * the usage counts on the error path calling free_task.
906 */
907 tsk->seccomp.filter = NULL;
908#endif
909
910 setup_thread_stack(tsk, orig);
911 clear_user_return_notifier(tsk);
912 clear_tsk_need_resched(tsk);
913 set_task_stack_end_magic(tsk);
914 clear_syscall_work_syscall_user_dispatch(tsk);
915
916#ifdef CONFIG_STACKPROTECTOR
917 tsk->stack_canary = get_random_canary();
918#endif
919 if (orig->cpus_ptr == &orig->cpus_mask)
920 tsk->cpus_ptr = &tsk->cpus_mask;
921
922 /*
923 * One for the user space visible state that goes away when reaped.
924 * One for the scheduler.
925 */
926 refcount_set(&tsk->rcu_users, 2);
927 /* One for the rcu users */
928 refcount_set(&tsk->usage, 1);
929#ifdef CONFIG_BLK_DEV_IO_TRACE
930 tsk->btrace_seq = 0;
931#endif
932 tsk->splice_pipe = NULL;
933 tsk->task_frag.page = NULL;
934 tsk->wake_q.next = NULL;
935 tsk->pf_io_worker = NULL;
936
937 account_kernel_stack(tsk, 1);
938
939 kcov_task_init(tsk);
940 kmap_local_fork(tsk);
941
942#ifdef CONFIG_FAULT_INJECTION
943 tsk->fail_nth = 0;
944#endif
945
946#ifdef CONFIG_BLK_CGROUP
947 tsk->throttle_queue = NULL;
948 tsk->use_memdelay = 0;
949#endif
950
951#ifdef CONFIG_MEMCG
952 tsk->active_memcg = NULL;
953#endif
954 return tsk;
955
956free_stack:
957 free_thread_stack(tsk);
958free_tsk:
959 free_task_struct(tsk);
960 return NULL;
961}
962
963__cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
964
965static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
966
967static int __init coredump_filter_setup(char *s)
968{
969 default_dump_filter =
970 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
971 MMF_DUMP_FILTER_MASK;
972 return 1;
973}
974
975__setup("coredump_filter=", coredump_filter_setup);
976
977#include <linux/init_task.h>
978
979static void mm_init_aio(struct mm_struct *mm)
980{
981#ifdef CONFIG_AIO
982 spin_lock_init(&mm->ioctx_lock);
983 mm->ioctx_table = NULL;
984#endif
985}
986
987static __always_inline void mm_clear_owner(struct mm_struct *mm,
988 struct task_struct *p)
989{
990#ifdef CONFIG_MEMCG
991 if (mm->owner == p)
992 WRITE_ONCE(mm->owner, NULL);
993#endif
994}
995
996static void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
997{
998#ifdef CONFIG_MEMCG
999 mm->owner = p;
1000#endif
1001}
1002
1003static void mm_init_pasid(struct mm_struct *mm)
1004{
1005#ifdef CONFIG_IOMMU_SUPPORT
1006 mm->pasid = INIT_PASID;
1007#endif
1008}
1009
1010static void mm_init_uprobes_state(struct mm_struct *mm)
1011{
1012#ifdef CONFIG_UPROBES
1013 mm->uprobes_state.xol_area = NULL;
1014#endif
1015}
1016
1017static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
1018 struct user_namespace *user_ns)
1019{
1020 mm->mmap = NULL;
1021 mm->mm_rb = RB_ROOT;
1022 mm->vmacache_seqnum = 0;
1023 atomic_set(&mm->mm_users, 1);
1024 atomic_set(&mm->mm_count, 1);
1025 seqcount_init(&mm->write_protect_seq);
1026 mmap_init_lock(mm);
1027 INIT_LIST_HEAD(&mm->mmlist);
1028 mm->core_state = NULL;
1029 mm_pgtables_bytes_init(mm);
1030 mm->map_count = 0;
1031 mm->locked_vm = 0;
1032 atomic_set(&mm->has_pinned, 0);
1033 atomic64_set(&mm->pinned_vm, 0);
1034 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
1035 spin_lock_init(&mm->page_table_lock);
1036 spin_lock_init(&mm->arg_lock);
1037 mm_init_cpumask(mm);
1038 mm_init_aio(mm);
1039 mm_init_owner(mm, p);
1040 mm_init_pasid(mm);
1041 RCU_INIT_POINTER(mm->exe_file, NULL);
1042 mmu_notifier_subscriptions_init(mm);
1043 init_tlb_flush_pending(mm);
1044#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
1045 mm->pmd_huge_pte = NULL;
1046#endif
1047 mm_init_uprobes_state(mm);
1048
1049 if (current->mm) {
1050 mm->flags = current->mm->flags & MMF_INIT_MASK;
1051 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK;
1052 } else {
1053 mm->flags = default_dump_filter;
1054 mm->def_flags = 0;
1055 }
1056
1057 if (mm_alloc_pgd(mm))
1058 goto fail_nopgd;
1059
1060 if (init_new_context(p, mm))
1061 goto fail_nocontext;
1062
1063 mm->user_ns = get_user_ns(user_ns);
1064 return mm;
1065
1066fail_nocontext:
1067 mm_free_pgd(mm);
1068fail_nopgd:
1069 free_mm(mm);
1070 return NULL;
1071}
1072
1073/*
1074 * Allocate and initialize an mm_struct.
1075 */
1076struct mm_struct *mm_alloc(void)
1077{
1078 struct mm_struct *mm;
1079
1080 mm = allocate_mm();
1081 if (!mm)
1082 return NULL;
1083
1084 memset(mm, 0, sizeof(*mm));
1085 return mm_init(mm, current, current_user_ns());
1086}
1087
1088static inline void __mmput(struct mm_struct *mm)
1089{
1090 VM_BUG_ON(atomic_read(&mm->mm_users));
1091
1092 uprobe_clear_state(mm);
1093 exit_aio(mm);
1094 ksm_exit(mm);
1095 khugepaged_exit(mm); /* must run before exit_mmap */
1096 exit_mmap(mm);
1097 mm_put_huge_zero_page(mm);
1098 set_mm_exe_file(mm, NULL);
1099 if (!list_empty(&mm->mmlist)) {
1100 spin_lock(&mmlist_lock);
1101 list_del(&mm->mmlist);
1102 spin_unlock(&mmlist_lock);
1103 }
1104 if (mm->binfmt)
1105 module_put(mm->binfmt->module);
1106 mmdrop(mm);
1107}
1108
1109/*
1110 * Decrement the use count and release all resources for an mm.
1111 */
1112void mmput(struct mm_struct *mm)
1113{
1114 might_sleep();
1115
1116 if (atomic_dec_and_test(&mm->mm_users))
1117 __mmput(mm);
1118}
1119EXPORT_SYMBOL_GPL(mmput);
1120
1121#ifdef CONFIG_MMU
1122static void mmput_async_fn(struct work_struct *work)
1123{
1124 struct mm_struct *mm = container_of(work, struct mm_struct,
1125 async_put_work);
1126
1127 __mmput(mm);
1128}
1129
1130void mmput_async(struct mm_struct *mm)
1131{
1132 if (atomic_dec_and_test(&mm->mm_users)) {
1133 INIT_WORK(&mm->async_put_work, mmput_async_fn);
1134 schedule_work(&mm->async_put_work);
1135 }
1136}
1137#endif
1138
1139/**
1140 * set_mm_exe_file - change a reference to the mm's executable file
1141 *
1142 * This changes mm's executable file (shown as symlink /proc/[pid]/exe).
1143 *
1144 * Main users are mmput() and sys_execve(). Callers prevent concurrent
1145 * invocations: in mmput() nobody alive left, in execve task is single
1146 * threaded. sys_prctl(PR_SET_MM_MAP/EXE_FILE) also needs to set the
1147 * mm->exe_file, but does so without using set_mm_exe_file() in order
1148 * to avoid the need for any locks.
1149 */
1150void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
1151{
1152 struct file *old_exe_file;
1153
1154 /*
1155 * It is safe to dereference the exe_file without RCU as
1156 * this function is only called if nobody else can access
1157 * this mm -- see comment above for justification.
1158 */
1159 old_exe_file = rcu_dereference_raw(mm->exe_file);
1160
1161 if (new_exe_file)
1162 get_file(new_exe_file);
1163 rcu_assign_pointer(mm->exe_file, new_exe_file);
1164 if (old_exe_file)
1165 fput(old_exe_file);
1166}
1167
1168/**
1169 * get_mm_exe_file - acquire a reference to the mm's executable file
1170 *
1171 * Returns %NULL if mm has no associated executable file.
1172 * User must release file via fput().
1173 */
1174struct file *get_mm_exe_file(struct mm_struct *mm)
1175{
1176 struct file *exe_file;
1177
1178 rcu_read_lock();
1179 exe_file = rcu_dereference(mm->exe_file);
1180 if (exe_file && !get_file_rcu(exe_file))
1181 exe_file = NULL;
1182 rcu_read_unlock();
1183 return exe_file;
1184}
1185EXPORT_SYMBOL(get_mm_exe_file);
1186
1187/**
1188 * get_task_exe_file - acquire a reference to the task's executable file
1189 *
1190 * Returns %NULL if task's mm (if any) has no associated executable file or
1191 * this is a kernel thread with borrowed mm (see the comment above get_task_mm).
1192 * User must release file via fput().
1193 */
1194struct file *get_task_exe_file(struct task_struct *task)
1195{
1196 struct file *exe_file = NULL;
1197 struct mm_struct *mm;
1198
1199 task_lock(task);
1200 mm = task->mm;
1201 if (mm) {
1202 if (!(task->flags & PF_KTHREAD))
1203 exe_file = get_mm_exe_file(mm);
1204 }
1205 task_unlock(task);
1206 return exe_file;
1207}
1208EXPORT_SYMBOL(get_task_exe_file);
1209
1210/**
1211 * get_task_mm - acquire a reference to the task's mm
1212 *
1213 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning
1214 * this kernel workthread has transiently adopted a user mm with use_mm,
1215 * to do its AIO) is not set and if so returns a reference to it, after
1216 * bumping up the use count. User must release the mm via mmput()
1217 * after use. Typically used by /proc and ptrace.
1218 */
1219struct mm_struct *get_task_mm(struct task_struct *task)
1220{
1221 struct mm_struct *mm;
1222
1223 task_lock(task);
1224 mm = task->mm;
1225 if (mm) {
1226 if (task->flags & PF_KTHREAD)
1227 mm = NULL;
1228 else
1229 mmget(mm);
1230 }
1231 task_unlock(task);
1232 return mm;
1233}
1234EXPORT_SYMBOL_GPL(get_task_mm);
1235
1236struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
1237{
1238 struct mm_struct *mm;
1239 int err;
1240
1241 err = down_read_killable(&task->signal->exec_update_lock);
1242 if (err)
1243 return ERR_PTR(err);
1244
1245 mm = get_task_mm(task);
1246 if (mm && mm != current->mm &&
1247 !ptrace_may_access(task, mode)) {
1248 mmput(mm);
1249 mm = ERR_PTR(-EACCES);
1250 }
1251 up_read(&task->signal->exec_update_lock);
1252
1253 return mm;
1254}
1255
1256static void complete_vfork_done(struct task_struct *tsk)
1257{
1258 struct completion *vfork;
1259
1260 task_lock(tsk);
1261 vfork = tsk->vfork_done;
1262 if (likely(vfork)) {
1263 tsk->vfork_done = NULL;
1264 complete(vfork);
1265 }
1266 task_unlock(tsk);
1267}
1268
1269static int wait_for_vfork_done(struct task_struct *child,
1270 struct completion *vfork)
1271{
1272 int killed;
1273
1274 freezer_do_not_count();
1275 cgroup_enter_frozen();
1276 killed = wait_for_completion_killable(vfork);
1277 cgroup_leave_frozen(false);
1278 freezer_count();
1279
1280 if (killed) {
1281 task_lock(child);
1282 child->vfork_done = NULL;
1283 task_unlock(child);
1284 }
1285
1286 put_task_struct(child);
1287 return killed;
1288}
1289
1290/* Please note the differences between mmput and mm_release.
1291 * mmput is called whenever we stop holding onto a mm_struct,
1292 * error success whatever.
1293 *
1294 * mm_release is called after a mm_struct has been removed
1295 * from the current process.
1296 *
1297 * This difference is important for error handling, when we
1298 * only half set up a mm_struct for a new process and need to restore
1299 * the old one. Because we mmput the new mm_struct before
1300 * restoring the old one. . .
1301 * Eric Biederman 10 January 1998
1302 */
1303static void mm_release(struct task_struct *tsk, struct mm_struct *mm)
1304{
1305 uprobe_free_utask(tsk);
1306
1307 /* Get rid of any cached register state */
1308 deactivate_mm(tsk, mm);
1309
1310 /*
1311 * Signal userspace if we're not exiting with a core dump
1312 * because we want to leave the value intact for debugging
1313 * purposes.
1314 */
1315 if (tsk->clear_child_tid) {
1316 if (!(tsk->signal->flags & SIGNAL_GROUP_COREDUMP) &&
1317 atomic_read(&mm->mm_users) > 1) {
1318 /*
1319 * We don't check the error code - if userspace has
1320 * not set up a proper pointer then tough luck.
1321 */
1322 put_user(0, tsk->clear_child_tid);
1323 do_futex(tsk->clear_child_tid, FUTEX_WAKE,
1324 1, NULL, NULL, 0, 0);
1325 }
1326 tsk->clear_child_tid = NULL;
1327 }
1328
1329 /*
1330 * All done, finally we can wake up parent and return this mm to him.
1331 * Also kthread_stop() uses this completion for synchronization.
1332 */
1333 if (tsk->vfork_done)
1334 complete_vfork_done(tsk);
1335}
1336
1337void exit_mm_release(struct task_struct *tsk, struct mm_struct *mm)
1338{
1339 futex_exit_release(tsk);
1340 mm_release(tsk, mm);
1341}
1342
1343void exec_mm_release(struct task_struct *tsk, struct mm_struct *mm)
1344{
1345 futex_exec_release(tsk);
1346 mm_release(tsk, mm);
1347}
1348
1349/**
1350 * dup_mm() - duplicates an existing mm structure
1351 * @tsk: the task_struct with which the new mm will be associated.
1352 * @oldmm: the mm to duplicate.
1353 *
1354 * Allocates a new mm structure and duplicates the provided @oldmm structure
1355 * content into it.
1356 *
1357 * Return: the duplicated mm or NULL on failure.
1358 */
1359static struct mm_struct *dup_mm(struct task_struct *tsk,
1360 struct mm_struct *oldmm)
1361{
1362 struct mm_struct *mm;
1363 int err;
1364
1365 mm = allocate_mm();
1366 if (!mm)
1367 goto fail_nomem;
1368
1369 memcpy(mm, oldmm, sizeof(*mm));
1370
1371 if (!mm_init(mm, tsk, mm->user_ns))
1372 goto fail_nomem;
1373
1374 err = dup_mmap(mm, oldmm);
1375 if (err)
1376 goto free_pt;
1377
1378 mm->hiwater_rss = get_mm_rss(mm);
1379 mm->hiwater_vm = mm->total_vm;
1380
1381 if (mm->binfmt && !try_module_get(mm->binfmt->module))
1382 goto free_pt;
1383
1384 return mm;
1385
1386free_pt:
1387 /* don't put binfmt in mmput, we haven't got module yet */
1388 mm->binfmt = NULL;
1389 mm_init_owner(mm, NULL);
1390 mmput(mm);
1391
1392fail_nomem:
1393 return NULL;
1394}
1395
1396static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
1397{
1398 struct mm_struct *mm, *oldmm;
1399
1400 tsk->min_flt = tsk->maj_flt = 0;
1401 tsk->nvcsw = tsk->nivcsw = 0;
1402#ifdef CONFIG_DETECT_HUNG_TASK
1403 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
1404 tsk->last_switch_time = 0;
1405#endif
1406
1407 tsk->mm = NULL;
1408 tsk->active_mm = NULL;
1409
1410 /*
1411 * Are we cloning a kernel thread?
1412 *
1413 * We need to steal a active VM for that..
1414 */
1415 oldmm = current->mm;
1416 if (!oldmm)
1417 return 0;
1418
1419 /* initialize the new vmacache entries */
1420 vmacache_flush(tsk);
1421
1422 if (clone_flags & CLONE_VM) {
1423 mmget(oldmm);
1424 mm = oldmm;
1425 } else {
1426 mm = dup_mm(tsk, current->mm);
1427 if (!mm)
1428 return -ENOMEM;
1429 }
1430
1431 tsk->mm = mm;
1432 tsk->active_mm = mm;
1433 return 0;
1434}
1435
1436static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
1437{
1438 struct fs_struct *fs = current->fs;
1439 if (clone_flags & CLONE_FS) {
1440 /* tsk->fs is already what we want */
1441 spin_lock(&fs->lock);
1442 if (fs->in_exec) {
1443 spin_unlock(&fs->lock);
1444 return -EAGAIN;
1445 }
1446 fs->users++;
1447 spin_unlock(&fs->lock);
1448 return 0;
1449 }
1450 tsk->fs = copy_fs_struct(fs);
1451 if (!tsk->fs)
1452 return -ENOMEM;
1453 return 0;
1454}
1455
1456static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
1457{
1458 struct files_struct *oldf, *newf;
1459 int error = 0;
1460
1461 /*
1462 * A background process may not have any files ...
1463 */
1464 oldf = current->files;
1465 if (!oldf)
1466 goto out;
1467
1468 if (clone_flags & CLONE_FILES) {
1469 atomic_inc(&oldf->count);
1470 goto out;
1471 }
1472
1473 newf = dup_fd(oldf, NR_OPEN_MAX, &error);
1474 if (!newf)
1475 goto out;
1476
1477 tsk->files = newf;
1478 error = 0;
1479out:
1480 return error;
1481}
1482
1483static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
1484{
1485#ifdef CONFIG_BLOCK
1486 struct io_context *ioc = current->io_context;
1487 struct io_context *new_ioc;
1488
1489 if (!ioc)
1490 return 0;
1491 /*
1492 * Share io context with parent, if CLONE_IO is set
1493 */
1494 if (clone_flags & CLONE_IO) {
1495 ioc_task_link(ioc);
1496 tsk->io_context = ioc;
1497 } else if (ioprio_valid(ioc->ioprio)) {
1498 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE);
1499 if (unlikely(!new_ioc))
1500 return -ENOMEM;
1501
1502 new_ioc->ioprio = ioc->ioprio;
1503 put_io_context(new_ioc);
1504 }
1505#endif
1506 return 0;
1507}
1508
1509static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
1510{
1511 struct sighand_struct *sig;
1512
1513 if (clone_flags & CLONE_SIGHAND) {
1514 refcount_inc(&current->sighand->count);
1515 return 0;
1516 }
1517 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1518 RCU_INIT_POINTER(tsk->sighand, sig);
1519 if (!sig)
1520 return -ENOMEM;
1521
1522 refcount_set(&sig->count, 1);
1523 spin_lock_irq(&current->sighand->siglock);
1524 memcpy(sig->action, current->sighand->action, sizeof(sig->action));
1525 spin_unlock_irq(&current->sighand->siglock);
1526
1527 /* Reset all signal handler not set to SIG_IGN to SIG_DFL. */
1528 if (clone_flags & CLONE_CLEAR_SIGHAND)
1529 flush_signal_handlers(tsk, 0);
1530
1531 return 0;
1532}
1533
1534void __cleanup_sighand(struct sighand_struct *sighand)
1535{
1536 if (refcount_dec_and_test(&sighand->count)) {
1537 signalfd_cleanup(sighand);
1538 /*
1539 * sighand_cachep is SLAB_TYPESAFE_BY_RCU so we can free it
1540 * without an RCU grace period, see __lock_task_sighand().
1541 */
1542 kmem_cache_free(sighand_cachep, sighand);
1543 }
1544}
1545
1546/*
1547 * Initialize POSIX timer handling for a thread group.
1548 */
1549static void posix_cpu_timers_init_group(struct signal_struct *sig)
1550{
1551 struct posix_cputimers *pct = &sig->posix_cputimers;
1552 unsigned long cpu_limit;
1553
1554 cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1555 posix_cputimers_group_init(pct, cpu_limit);
1556}
1557
1558static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
1559{
1560 struct signal_struct *sig;
1561
1562 if (clone_flags & CLONE_THREAD)
1563 return 0;
1564
1565 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
1566 tsk->signal = sig;
1567 if (!sig)
1568 return -ENOMEM;
1569
1570 sig->nr_threads = 1;
1571 atomic_set(&sig->live, 1);
1572 refcount_set(&sig->sigcnt, 1);
1573
1574 /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */
1575 sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node);
1576 tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head);
1577
1578 init_waitqueue_head(&sig->wait_chldexit);
1579 sig->curr_target = tsk;
1580 init_sigpending(&sig->shared_pending);
1581 INIT_HLIST_HEAD(&sig->multiprocess);
1582 seqlock_init(&sig->stats_lock);
1583 prev_cputime_init(&sig->prev_cputime);
1584
1585#ifdef CONFIG_POSIX_TIMERS
1586 INIT_LIST_HEAD(&sig->posix_timers);
1587 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1588 sig->real_timer.function = it_real_fn;
1589#endif
1590
1591 task_lock(current->group_leader);
1592 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
1593 task_unlock(current->group_leader);
1594
1595 posix_cpu_timers_init_group(sig);
1596
1597 tty_audit_fork(sig);
1598 sched_autogroup_fork(sig);
1599
1600 sig->oom_score_adj = current->signal->oom_score_adj;
1601 sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1602
1603 mutex_init(&sig->cred_guard_mutex);
1604 init_rwsem(&sig->exec_update_lock);
1605
1606 return 0;
1607}
1608
1609static void copy_seccomp(struct task_struct *p)
1610{
1611#ifdef CONFIG_SECCOMP
1612 /*
1613 * Must be called with sighand->lock held, which is common to
1614 * all threads in the group. Holding cred_guard_mutex is not
1615 * needed because this new task is not yet running and cannot
1616 * be racing exec.
1617 */
1618 assert_spin_locked(&current->sighand->siglock);
1619
1620 /* Ref-count the new filter user, and assign it. */
1621 get_seccomp_filter(current);
1622 p->seccomp = current->seccomp;
1623
1624 /*
1625 * Explicitly enable no_new_privs here in case it got set
1626 * between the task_struct being duplicated and holding the
1627 * sighand lock. The seccomp state and nnp must be in sync.
1628 */
1629 if (task_no_new_privs(current))
1630 task_set_no_new_privs(p);
1631
1632 /*
1633 * If the parent gained a seccomp mode after copying thread
1634 * flags and between before we held the sighand lock, we have
1635 * to manually enable the seccomp thread flag here.
1636 */
1637 if (p->seccomp.mode != SECCOMP_MODE_DISABLED)
1638 set_task_syscall_work(p, SECCOMP);
1639#endif
1640}
1641
1642SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1643{
1644 current->clear_child_tid = tidptr;
1645
1646 return task_pid_vnr(current);
1647}
1648
1649static void rt_mutex_init_task(struct task_struct *p)
1650{
1651 raw_spin_lock_init(&p->pi_lock);
1652#ifdef CONFIG_RT_MUTEXES
1653 p->pi_waiters = RB_ROOT_CACHED;
1654 p->pi_top_task = NULL;
1655 p->pi_blocked_on = NULL;
1656#endif
1657}
1658
1659static inline void init_task_pid_links(struct task_struct *task)
1660{
1661 enum pid_type type;
1662
1663 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type)
1664 INIT_HLIST_NODE(&task->pid_links[type]);
1665}
1666
1667static inline void
1668init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid)
1669{
1670 if (type == PIDTYPE_PID)
1671 task->thread_pid = pid;
1672 else
1673 task->signal->pids[type] = pid;
1674}
1675
1676static inline void rcu_copy_process(struct task_struct *p)
1677{
1678#ifdef CONFIG_PREEMPT_RCU
1679 p->rcu_read_lock_nesting = 0;
1680 p->rcu_read_unlock_special.s = 0;
1681 p->rcu_blocked_node = NULL;
1682 INIT_LIST_HEAD(&p->rcu_node_entry);
1683#endif /* #ifdef CONFIG_PREEMPT_RCU */
1684#ifdef CONFIG_TASKS_RCU
1685 p->rcu_tasks_holdout = false;
1686 INIT_LIST_HEAD(&p->rcu_tasks_holdout_list);
1687 p->rcu_tasks_idle_cpu = -1;
1688#endif /* #ifdef CONFIG_TASKS_RCU */
1689#ifdef CONFIG_TASKS_TRACE_RCU
1690 p->trc_reader_nesting = 0;
1691 p->trc_reader_special.s = 0;
1692 INIT_LIST_HEAD(&p->trc_holdout_list);
1693#endif /* #ifdef CONFIG_TASKS_TRACE_RCU */
1694}
1695
1696struct pid *pidfd_pid(const struct file *file)
1697{
1698 if (file->f_op == &pidfd_fops)
1699 return file->private_data;
1700
1701 return ERR_PTR(-EBADF);
1702}
1703
1704static int pidfd_release(struct inode *inode, struct file *file)
1705{
1706 struct pid *pid = file->private_data;
1707
1708 file->private_data = NULL;
1709 put_pid(pid);
1710 return 0;
1711}
1712
1713#ifdef CONFIG_PROC_FS
1714/**
1715 * pidfd_show_fdinfo - print information about a pidfd
1716 * @m: proc fdinfo file
1717 * @f: file referencing a pidfd
1718 *
1719 * Pid:
1720 * This function will print the pid that a given pidfd refers to in the
1721 * pid namespace of the procfs instance.
1722 * If the pid namespace of the process is not a descendant of the pid
1723 * namespace of the procfs instance 0 will be shown as its pid. This is
1724 * similar to calling getppid() on a process whose parent is outside of
1725 * its pid namespace.
1726 *
1727 * NSpid:
1728 * If pid namespaces are supported then this function will also print
1729 * the pid of a given pidfd refers to for all descendant pid namespaces
1730 * starting from the current pid namespace of the instance, i.e. the
1731 * Pid field and the first entry in the NSpid field will be identical.
1732 * If the pid namespace of the process is not a descendant of the pid
1733 * namespace of the procfs instance 0 will be shown as its first NSpid
1734 * entry and no others will be shown.
1735 * Note that this differs from the Pid and NSpid fields in
1736 * /proc/<pid>/status where Pid and NSpid are always shown relative to
1737 * the pid namespace of the procfs instance. The difference becomes
1738 * obvious when sending around a pidfd between pid namespaces from a
1739 * different branch of the tree, i.e. where no ancestral relation is
1740 * present between the pid namespaces:
1741 * - create two new pid namespaces ns1 and ns2 in the initial pid
1742 * namespace (also take care to create new mount namespaces in the
1743 * new pid namespace and mount procfs)
1744 * - create a process with a pidfd in ns1
1745 * - send pidfd from ns1 to ns2
1746 * - read /proc/self/fdinfo/<pidfd> and observe that both Pid and NSpid
1747 * have exactly one entry, which is 0
1748 */
1749static void pidfd_show_fdinfo(struct seq_file *m, struct file *f)
1750{
1751 struct pid *pid = f->private_data;
1752 struct pid_namespace *ns;
1753 pid_t nr = -1;
1754
1755 if (likely(pid_has_task(pid, PIDTYPE_PID))) {
1756 ns = proc_pid_ns(file_inode(m->file)->i_sb);
1757 nr = pid_nr_ns(pid, ns);
1758 }
1759
1760 seq_put_decimal_ll(m, "Pid:\t", nr);
1761
1762#ifdef CONFIG_PID_NS
1763 seq_put_decimal_ll(m, "\nNSpid:\t", nr);
1764 if (nr > 0) {
1765 int i;
1766
1767 /* If nr is non-zero it means that 'pid' is valid and that
1768 * ns, i.e. the pid namespace associated with the procfs
1769 * instance, is in the pid namespace hierarchy of pid.
1770 * Start at one below the already printed level.
1771 */
1772 for (i = ns->level + 1; i <= pid->level; i++)
1773 seq_put_decimal_ll(m, "\t", pid->numbers[i].nr);
1774 }
1775#endif
1776 seq_putc(m, '\n');
1777}
1778#endif
1779
1780/*
1781 * Poll support for process exit notification.
1782 */
1783static __poll_t pidfd_poll(struct file *file, struct poll_table_struct *pts)
1784{
1785 struct pid *pid = file->private_data;
1786 __poll_t poll_flags = 0;
1787
1788 poll_wait(file, &pid->wait_pidfd, pts);
1789
1790 /*
1791 * Inform pollers only when the whole thread group exits.
1792 * If the thread group leader exits before all other threads in the
1793 * group, then poll(2) should block, similar to the wait(2) family.
1794 */
1795 if (thread_group_exited(pid))
1796 poll_flags = EPOLLIN | EPOLLRDNORM;
1797
1798 return poll_flags;
1799}
1800
1801const struct file_operations pidfd_fops = {
1802 .release = pidfd_release,
1803 .poll = pidfd_poll,
1804#ifdef CONFIG_PROC_FS
1805 .show_fdinfo = pidfd_show_fdinfo,
1806#endif
1807};
1808
1809static void __delayed_free_task(struct rcu_head *rhp)
1810{
1811 struct task_struct *tsk = container_of(rhp, struct task_struct, rcu);
1812
1813 free_task(tsk);
1814}
1815
1816static __always_inline void delayed_free_task(struct task_struct *tsk)
1817{
1818 if (IS_ENABLED(CONFIG_MEMCG))
1819 call_rcu(&tsk->rcu, __delayed_free_task);
1820 else
1821 free_task(tsk);
1822}
1823
1824static void copy_oom_score_adj(u64 clone_flags, struct task_struct *tsk)
1825{
1826 /* Skip if kernel thread */
1827 if (!tsk->mm)
1828 return;
1829
1830 /* Skip if spawning a thread or using vfork */
1831 if ((clone_flags & (CLONE_VM | CLONE_THREAD | CLONE_VFORK)) != CLONE_VM)
1832 return;
1833
1834 /* We need to synchronize with __set_oom_adj */
1835 mutex_lock(&oom_adj_mutex);
1836 set_bit(MMF_MULTIPROCESS, &tsk->mm->flags);
1837 /* Update the values in case they were changed after copy_signal */
1838 tsk->signal->oom_score_adj = current->signal->oom_score_adj;
1839 tsk->signal->oom_score_adj_min = current->signal->oom_score_adj_min;
1840 mutex_unlock(&oom_adj_mutex);
1841}
1842
1843/*
1844 * This creates a new process as a copy of the old one,
1845 * but does not actually start it yet.
1846 *
1847 * It copies the registers, and all the appropriate
1848 * parts of the process environment (as per the clone
1849 * flags). The actual kick-off is left to the caller.
1850 */
1851static __latent_entropy struct task_struct *copy_process(
1852 struct pid *pid,
1853 int trace,
1854 int node,
1855 struct kernel_clone_args *args)
1856{
1857 int pidfd = -1, retval;
1858 struct task_struct *p;
1859 struct multiprocess_signals delayed;
1860 struct file *pidfile = NULL;
1861 u64 clone_flags = args->flags;
1862 struct nsproxy *nsp = current->nsproxy;
1863
1864 /*
1865 * Don't allow sharing the root directory with processes in a different
1866 * namespace
1867 */
1868 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1869 return ERR_PTR(-EINVAL);
1870
1871 if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS))
1872 return ERR_PTR(-EINVAL);
1873
1874 /*
1875 * Thread groups must share signals as well, and detached threads
1876 * can only be started up within the thread group.
1877 */
1878 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1879 return ERR_PTR(-EINVAL);
1880
1881 /*
1882 * Shared signal handlers imply shared VM. By way of the above,
1883 * thread groups also imply shared VM. Blocking this case allows
1884 * for various simplifications in other code.
1885 */
1886 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1887 return ERR_PTR(-EINVAL);
1888
1889 /*
1890 * Siblings of global init remain as zombies on exit since they are
1891 * not reaped by their parent (swapper). To solve this and to avoid
1892 * multi-rooted process trees, prevent global and container-inits
1893 * from creating siblings.
1894 */
1895 if ((clone_flags & CLONE_PARENT) &&
1896 current->signal->flags & SIGNAL_UNKILLABLE)
1897 return ERR_PTR(-EINVAL);
1898
1899 /*
1900 * If the new process will be in a different pid or user namespace
1901 * do not allow it to share a thread group with the forking task.
1902 */
1903 if (clone_flags & CLONE_THREAD) {
1904 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) ||
1905 (task_active_pid_ns(current) != nsp->pid_ns_for_children))
1906 return ERR_PTR(-EINVAL);
1907 }
1908
1909 /*
1910 * If the new process will be in a different time namespace
1911 * do not allow it to share VM or a thread group with the forking task.
1912 */
1913 if (clone_flags & (CLONE_THREAD | CLONE_VM)) {
1914 if (nsp->time_ns != nsp->time_ns_for_children)
1915 return ERR_PTR(-EINVAL);
1916 }
1917
1918 if (clone_flags & CLONE_PIDFD) {
1919 /*
1920 * - CLONE_DETACHED is blocked so that we can potentially
1921 * reuse it later for CLONE_PIDFD.
1922 * - CLONE_THREAD is blocked until someone really needs it.
1923 */
1924 if (clone_flags & (CLONE_DETACHED | CLONE_THREAD))
1925 return ERR_PTR(-EINVAL);
1926 }
1927
1928 /*
1929 * Force any signals received before this point to be delivered
1930 * before the fork happens. Collect up signals sent to multiple
1931 * processes that happen during the fork and delay them so that
1932 * they appear to happen after the fork.
1933 */
1934 sigemptyset(&delayed.signal);
1935 INIT_HLIST_NODE(&delayed.node);
1936
1937 spin_lock_irq(&current->sighand->siglock);
1938 if (!(clone_flags & CLONE_THREAD))
1939 hlist_add_head(&delayed.node, &current->signal->multiprocess);
1940 recalc_sigpending();
1941 spin_unlock_irq(&current->sighand->siglock);
1942 retval = -ERESTARTNOINTR;
1943 if (task_sigpending(current))
1944 goto fork_out;
1945
1946 retval = -ENOMEM;
1947 p = dup_task_struct(current, node);
1948 if (!p)
1949 goto fork_out;
1950 if (args->io_thread) {
1951 /*
1952 * Mark us an IO worker, and block any signal that isn't
1953 * fatal or STOP
1954 */
1955 p->flags |= PF_IO_WORKER;
1956 siginitsetinv(&p->blocked, sigmask(SIGKILL)|sigmask(SIGSTOP));
1957 }
1958
1959 /*
1960 * This _must_ happen before we call free_task(), i.e. before we jump
1961 * to any of the bad_fork_* labels. This is to avoid freeing
1962 * p->set_child_tid which is (ab)used as a kthread's data pointer for
1963 * kernel threads (PF_KTHREAD).
1964 */
1965 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? args->child_tid : NULL;
1966 /*
1967 * Clear TID on mm_release()?
1968 */
1969 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? args->child_tid : NULL;
1970
1971 ftrace_graph_init_task(p);
1972
1973 rt_mutex_init_task(p);
1974
1975 lockdep_assert_irqs_enabled();
1976#ifdef CONFIG_PROVE_LOCKING
1977 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1978#endif
1979 retval = -EAGAIN;
1980 if (atomic_read(&p->real_cred->user->processes) >=
1981 task_rlimit(p, RLIMIT_NPROC)) {
1982 if (p->real_cred->user != INIT_USER &&
1983 !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
1984 goto bad_fork_free;
1985 }
1986 current->flags &= ~PF_NPROC_EXCEEDED;
1987
1988 retval = copy_creds(p, clone_flags);
1989 if (retval < 0)
1990 goto bad_fork_free;
1991
1992 /*
1993 * If multiple threads are within copy_process(), then this check
1994 * triggers too late. This doesn't hurt, the check is only there
1995 * to stop root fork bombs.
1996 */
1997 retval = -EAGAIN;
1998 if (data_race(nr_threads >= max_threads))
1999 goto bad_fork_cleanup_count;
2000
2001 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */
2002 p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER | PF_IDLE);
2003 p->flags |= PF_FORKNOEXEC;
2004 INIT_LIST_HEAD(&p->children);
2005 INIT_LIST_HEAD(&p->sibling);
2006 rcu_copy_process(p);
2007 p->vfork_done = NULL;
2008 spin_lock_init(&p->alloc_lock);
2009
2010 init_sigpending(&p->pending);
2011
2012 p->utime = p->stime = p->gtime = 0;
2013#ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
2014 p->utimescaled = p->stimescaled = 0;
2015#endif
2016 prev_cputime_init(&p->prev_cputime);
2017
2018#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
2019 seqcount_init(&p->vtime.seqcount);
2020 p->vtime.starttime = 0;
2021 p->vtime.state = VTIME_INACTIVE;
2022#endif
2023
2024#ifdef CONFIG_IO_URING
2025 p->io_uring = NULL;
2026#endif
2027
2028#if defined(SPLIT_RSS_COUNTING)
2029 memset(&p->rss_stat, 0, sizeof(p->rss_stat));
2030#endif
2031
2032 p->default_timer_slack_ns = current->timer_slack_ns;
2033
2034#ifdef CONFIG_PSI
2035 p->psi_flags = 0;
2036#endif
2037
2038 task_io_accounting_init(&p->ioac);
2039 acct_clear_integrals(p);
2040
2041 posix_cputimers_init(&p->posix_cputimers);
2042
2043 p->io_context = NULL;
2044 audit_set_context(p, NULL);
2045 cgroup_fork(p);
2046#ifdef CONFIG_NUMA
2047 p->mempolicy = mpol_dup(p->mempolicy);
2048 if (IS_ERR(p->mempolicy)) {
2049 retval = PTR_ERR(p->mempolicy);
2050 p->mempolicy = NULL;
2051 goto bad_fork_cleanup_threadgroup_lock;
2052 }
2053#endif
2054#ifdef CONFIG_CPUSETS
2055 p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
2056 p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
2057 seqcount_spinlock_init(&p->mems_allowed_seq, &p->alloc_lock);
2058#endif
2059#ifdef CONFIG_TRACE_IRQFLAGS
2060 memset(&p->irqtrace, 0, sizeof(p->irqtrace));
2061 p->irqtrace.hardirq_disable_ip = _THIS_IP_;
2062 p->irqtrace.softirq_enable_ip = _THIS_IP_;
2063 p->softirqs_enabled = 1;
2064 p->softirq_context = 0;
2065#endif
2066
2067 p->pagefault_disabled = 0;
2068
2069#ifdef CONFIG_LOCKDEP
2070 lockdep_init_task(p);
2071#endif
2072
2073#ifdef CONFIG_DEBUG_MUTEXES
2074 p->blocked_on = NULL; /* not blocked yet */
2075#endif
2076#ifdef CONFIG_BCACHE
2077 p->sequential_io = 0;
2078 p->sequential_io_avg = 0;
2079#endif
2080#ifdef CONFIG_BPF_SYSCALL
2081 RCU_INIT_POINTER(p->bpf_storage, NULL);
2082#endif
2083
2084 /* Perform scheduler related setup. Assign this task to a CPU. */
2085 retval = sched_fork(clone_flags, p);
2086 if (retval)
2087 goto bad_fork_cleanup_policy;
2088
2089 retval = perf_event_init_task(p, clone_flags);
2090 if (retval)
2091 goto bad_fork_cleanup_policy;
2092 retval = audit_alloc(p);
2093 if (retval)
2094 goto bad_fork_cleanup_perf;
2095 /* copy all the process information */
2096 shm_init_task(p);
2097 retval = security_task_alloc(p, clone_flags);
2098 if (retval)
2099 goto bad_fork_cleanup_audit;
2100 retval = copy_semundo(clone_flags, p);
2101 if (retval)
2102 goto bad_fork_cleanup_security;
2103 retval = copy_files(clone_flags, p);
2104 if (retval)
2105 goto bad_fork_cleanup_semundo;
2106 retval = copy_fs(clone_flags, p);
2107 if (retval)
2108 goto bad_fork_cleanup_files;
2109 retval = copy_sighand(clone_flags, p);
2110 if (retval)
2111 goto bad_fork_cleanup_fs;
2112 retval = copy_signal(clone_flags, p);
2113 if (retval)
2114 goto bad_fork_cleanup_sighand;
2115 retval = copy_mm(clone_flags, p);
2116 if (retval)
2117 goto bad_fork_cleanup_signal;
2118 retval = copy_namespaces(clone_flags, p);
2119 if (retval)
2120 goto bad_fork_cleanup_mm;
2121 retval = copy_io(clone_flags, p);
2122 if (retval)
2123 goto bad_fork_cleanup_namespaces;
2124 retval = copy_thread(clone_flags, args->stack, args->stack_size, p, args->tls);
2125 if (retval)
2126 goto bad_fork_cleanup_io;
2127
2128 stackleak_task_init(p);
2129
2130 if (pid != &init_struct_pid) {
2131 pid = alloc_pid(p->nsproxy->pid_ns_for_children, args->set_tid,
2132 args->set_tid_size);
2133 if (IS_ERR(pid)) {
2134 retval = PTR_ERR(pid);
2135 goto bad_fork_cleanup_thread;
2136 }
2137 }
2138
2139 /*
2140 * This has to happen after we've potentially unshared the file
2141 * descriptor table (so that the pidfd doesn't leak into the child
2142 * if the fd table isn't shared).
2143 */
2144 if (clone_flags & CLONE_PIDFD) {
2145 retval = get_unused_fd_flags(O_RDWR | O_CLOEXEC);
2146 if (retval < 0)
2147 goto bad_fork_free_pid;
2148
2149 pidfd = retval;
2150
2151 pidfile = anon_inode_getfile("[pidfd]", &pidfd_fops, pid,
2152 O_RDWR | O_CLOEXEC);
2153 if (IS_ERR(pidfile)) {
2154 put_unused_fd(pidfd);
2155 retval = PTR_ERR(pidfile);
2156 goto bad_fork_free_pid;
2157 }
2158 get_pid(pid); /* held by pidfile now */
2159
2160 retval = put_user(pidfd, args->pidfd);
2161 if (retval)
2162 goto bad_fork_put_pidfd;
2163 }
2164
2165#ifdef CONFIG_BLOCK
2166 p->plug = NULL;
2167#endif
2168 futex_init_task(p);
2169
2170 /*
2171 * sigaltstack should be cleared when sharing the same VM
2172 */
2173 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
2174 sas_ss_reset(p);
2175
2176 /*
2177 * Syscall tracing and stepping should be turned off in the
2178 * child regardless of CLONE_PTRACE.
2179 */
2180 user_disable_single_step(p);
2181 clear_task_syscall_work(p, SYSCALL_TRACE);
2182#if defined(CONFIG_GENERIC_ENTRY) || defined(TIF_SYSCALL_EMU)
2183 clear_task_syscall_work(p, SYSCALL_EMU);
2184#endif
2185 clear_tsk_latency_tracing(p);
2186
2187 /* ok, now we should be set up.. */
2188 p->pid = pid_nr(pid);
2189 if (clone_flags & CLONE_THREAD) {
2190 p->group_leader = current->group_leader;
2191 p->tgid = current->tgid;
2192 } else {
2193 p->group_leader = p;
2194 p->tgid = p->pid;
2195 }
2196
2197 p->nr_dirtied = 0;
2198 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
2199 p->dirty_paused_when = 0;
2200
2201 p->pdeath_signal = 0;
2202 INIT_LIST_HEAD(&p->thread_group);
2203 p->task_works = NULL;
2204
2205#ifdef CONFIG_KRETPROBES
2206 p->kretprobe_instances.first = NULL;
2207#endif
2208
2209 /*
2210 * Ensure that the cgroup subsystem policies allow the new process to be
2211 * forked. It should be noted that the new process's css_set can be changed
2212 * between here and cgroup_post_fork() if an organisation operation is in
2213 * progress.
2214 */
2215 retval = cgroup_can_fork(p, args);
2216 if (retval)
2217 goto bad_fork_put_pidfd;
2218
2219 /*
2220 * From this point on we must avoid any synchronous user-space
2221 * communication until we take the tasklist-lock. In particular, we do
2222 * not want user-space to be able to predict the process start-time by
2223 * stalling fork(2) after we recorded the start_time but before it is
2224 * visible to the system.
2225 */
2226
2227 p->start_time = ktime_get_ns();
2228 p->start_boottime = ktime_get_boottime_ns();
2229
2230 /*
2231 * Make it visible to the rest of the system, but dont wake it up yet.
2232 * Need tasklist lock for parent etc handling!
2233 */
2234 write_lock_irq(&tasklist_lock);
2235
2236 /* CLONE_PARENT re-uses the old parent */
2237 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
2238 p->real_parent = current->real_parent;
2239 p->parent_exec_id = current->parent_exec_id;
2240 if (clone_flags & CLONE_THREAD)
2241 p->exit_signal = -1;
2242 else
2243 p->exit_signal = current->group_leader->exit_signal;
2244 } else {
2245 p->real_parent = current;
2246 p->parent_exec_id = current->self_exec_id;
2247 p->exit_signal = args->exit_signal;
2248 }
2249
2250 klp_copy_process(p);
2251
2252 spin_lock(&current->sighand->siglock);
2253
2254 /*
2255 * Copy seccomp details explicitly here, in case they were changed
2256 * before holding sighand lock.
2257 */
2258 copy_seccomp(p);
2259
2260 rseq_fork(p, clone_flags);
2261
2262 /* Don't start children in a dying pid namespace */
2263 if (unlikely(!(ns_of_pid(pid)->pid_allocated & PIDNS_ADDING))) {
2264 retval = -ENOMEM;
2265 goto bad_fork_cancel_cgroup;
2266 }
2267
2268 /* Let kill terminate clone/fork in the middle */
2269 if (fatal_signal_pending(current)) {
2270 retval = -EINTR;
2271 goto bad_fork_cancel_cgroup;
2272 }
2273
2274 /* past the last point of failure */
2275 if (pidfile)
2276 fd_install(pidfd, pidfile);
2277
2278 init_task_pid_links(p);
2279 if (likely(p->pid)) {
2280 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
2281
2282 init_task_pid(p, PIDTYPE_PID, pid);
2283 if (thread_group_leader(p)) {
2284 init_task_pid(p, PIDTYPE_TGID, pid);
2285 init_task_pid(p, PIDTYPE_PGID, task_pgrp(current));
2286 init_task_pid(p, PIDTYPE_SID, task_session(current));
2287
2288 if (is_child_reaper(pid)) {
2289 ns_of_pid(pid)->child_reaper = p;
2290 p->signal->flags |= SIGNAL_UNKILLABLE;
2291 }
2292 p->signal->shared_pending.signal = delayed.signal;
2293 p->signal->tty = tty_kref_get(current->signal->tty);
2294 /*
2295 * Inherit has_child_subreaper flag under the same
2296 * tasklist_lock with adding child to the process tree
2297 * for propagate_has_child_subreaper optimization.
2298 */
2299 p->signal->has_child_subreaper = p->real_parent->signal->has_child_subreaper ||
2300 p->real_parent->signal->is_child_subreaper;
2301 list_add_tail(&p->sibling, &p->real_parent->children);
2302 list_add_tail_rcu(&p->tasks, &init_task.tasks);
2303 attach_pid(p, PIDTYPE_TGID);
2304 attach_pid(p, PIDTYPE_PGID);
2305 attach_pid(p, PIDTYPE_SID);
2306 __this_cpu_inc(process_counts);
2307 } else {
2308 current->signal->nr_threads++;
2309 atomic_inc(&current->signal->live);
2310 refcount_inc(&current->signal->sigcnt);
2311 task_join_group_stop(p);
2312 list_add_tail_rcu(&p->thread_group,
2313 &p->group_leader->thread_group);
2314 list_add_tail_rcu(&p->thread_node,
2315 &p->signal->thread_head);
2316 }
2317 attach_pid(p, PIDTYPE_PID);
2318 nr_threads++;
2319 }
2320 total_forks++;
2321 hlist_del_init(&delayed.node);
2322 spin_unlock(&current->sighand->siglock);
2323 syscall_tracepoint_update(p);
2324 write_unlock_irq(&tasklist_lock);
2325
2326 proc_fork_connector(p);
2327 sched_post_fork(p);
2328 cgroup_post_fork(p, args);
2329 perf_event_fork(p);
2330
2331 trace_task_newtask(p, clone_flags);
2332 uprobe_copy_process(p, clone_flags);
2333
2334 copy_oom_score_adj(clone_flags, p);
2335
2336 return p;
2337
2338bad_fork_cancel_cgroup:
2339 spin_unlock(&current->sighand->siglock);
2340 write_unlock_irq(&tasklist_lock);
2341 cgroup_cancel_fork(p, args);
2342bad_fork_put_pidfd:
2343 if (clone_flags & CLONE_PIDFD) {
2344 fput(pidfile);
2345 put_unused_fd(pidfd);
2346 }
2347bad_fork_free_pid:
2348 if (pid != &init_struct_pid)
2349 free_pid(pid);
2350bad_fork_cleanup_thread:
2351 exit_thread(p);
2352bad_fork_cleanup_io:
2353 if (p->io_context)
2354 exit_io_context(p);
2355bad_fork_cleanup_namespaces:
2356 exit_task_namespaces(p);
2357bad_fork_cleanup_mm:
2358 if (p->mm) {
2359 mm_clear_owner(p->mm, p);
2360 mmput(p->mm);
2361 }
2362bad_fork_cleanup_signal:
2363 if (!(clone_flags & CLONE_THREAD))
2364 free_signal_struct(p->signal);
2365bad_fork_cleanup_sighand:
2366 __cleanup_sighand(p->sighand);
2367bad_fork_cleanup_fs:
2368 exit_fs(p); /* blocking */
2369bad_fork_cleanup_files:
2370 exit_files(p); /* blocking */
2371bad_fork_cleanup_semundo:
2372 exit_sem(p);
2373bad_fork_cleanup_security:
2374 security_task_free(p);
2375bad_fork_cleanup_audit:
2376 audit_free(p);
2377bad_fork_cleanup_perf:
2378 perf_event_free_task(p);
2379bad_fork_cleanup_policy:
2380 lockdep_free_task(p);
2381#ifdef CONFIG_NUMA
2382 mpol_put(p->mempolicy);
2383bad_fork_cleanup_threadgroup_lock:
2384#endif
2385 delayacct_tsk_free(p);
2386bad_fork_cleanup_count:
2387 atomic_dec(&p->cred->user->processes);
2388 exit_creds(p);
2389bad_fork_free:
2390 p->state = TASK_DEAD;
2391 put_task_stack(p);
2392 delayed_free_task(p);
2393fork_out:
2394 spin_lock_irq(&current->sighand->siglock);
2395 hlist_del_init(&delayed.node);
2396 spin_unlock_irq(&current->sighand->siglock);
2397 return ERR_PTR(retval);
2398}
2399
2400static inline void init_idle_pids(struct task_struct *idle)
2401{
2402 enum pid_type type;
2403
2404 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
2405 INIT_HLIST_NODE(&idle->pid_links[type]); /* not really needed */
2406 init_task_pid(idle, type, &init_struct_pid);
2407 }
2408}
2409
2410struct task_struct *fork_idle(int cpu)
2411{
2412 struct task_struct *task;
2413 struct kernel_clone_args args = {
2414 .flags = CLONE_VM,
2415 };
2416
2417 task = copy_process(&init_struct_pid, 0, cpu_to_node(cpu), &args);
2418 if (!IS_ERR(task)) {
2419 init_idle_pids(task);
2420 init_idle(task, cpu);
2421 }
2422
2423 return task;
2424}
2425
2426struct mm_struct *copy_init_mm(void)
2427{
2428 return dup_mm(NULL, &init_mm);
2429}
2430
2431/*
2432 * This is like kernel_clone(), but shaved down and tailored to just
2433 * creating io_uring workers. It returns a created task, or an error pointer.
2434 * The returned task is inactive, and the caller must fire it up through
2435 * wake_up_new_task(p). All signals are blocked in the created task.
2436 */
2437struct task_struct *create_io_thread(int (*fn)(void *), void *arg, int node)
2438{
2439 unsigned long flags = CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|
2440 CLONE_IO;
2441 struct kernel_clone_args args = {
2442 .flags = ((lower_32_bits(flags) | CLONE_VM |
2443 CLONE_UNTRACED) & ~CSIGNAL),
2444 .exit_signal = (lower_32_bits(flags) & CSIGNAL),
2445 .stack = (unsigned long)fn,
2446 .stack_size = (unsigned long)arg,
2447 .io_thread = 1,
2448 };
2449
2450 return copy_process(NULL, 0, node, &args);
2451}
2452
2453/*
2454 * Ok, this is the main fork-routine.
2455 *
2456 * It copies the process, and if successful kick-starts
2457 * it and waits for it to finish using the VM if required.
2458 *
2459 * args->exit_signal is expected to be checked for sanity by the caller.
2460 */
2461pid_t kernel_clone(struct kernel_clone_args *args)
2462{
2463 u64 clone_flags = args->flags;
2464 struct completion vfork;
2465 struct pid *pid;
2466 struct task_struct *p;
2467 int trace = 0;
2468 pid_t nr;
2469
2470 /*
2471 * For legacy clone() calls, CLONE_PIDFD uses the parent_tid argument
2472 * to return the pidfd. Hence, CLONE_PIDFD and CLONE_PARENT_SETTID are
2473 * mutually exclusive. With clone3() CLONE_PIDFD has grown a separate
2474 * field in struct clone_args and it still doesn't make sense to have
2475 * them both point at the same memory location. Performing this check
2476 * here has the advantage that we don't need to have a separate helper
2477 * to check for legacy clone().
2478 */
2479 if ((args->flags & CLONE_PIDFD) &&
2480 (args->flags & CLONE_PARENT_SETTID) &&
2481 (args->pidfd == args->parent_tid))
2482 return -EINVAL;
2483
2484 /*
2485 * Determine whether and which event to report to ptracer. When
2486 * called from kernel_thread or CLONE_UNTRACED is explicitly
2487 * requested, no event is reported; otherwise, report if the event
2488 * for the type of forking is enabled.
2489 */
2490 if (!(clone_flags & CLONE_UNTRACED)) {
2491 if (clone_flags & CLONE_VFORK)
2492 trace = PTRACE_EVENT_VFORK;
2493 else if (args->exit_signal != SIGCHLD)
2494 trace = PTRACE_EVENT_CLONE;
2495 else
2496 trace = PTRACE_EVENT_FORK;
2497
2498 if (likely(!ptrace_event_enabled(current, trace)))
2499 trace = 0;
2500 }
2501
2502 p = copy_process(NULL, trace, NUMA_NO_NODE, args);
2503 add_latent_entropy();
2504
2505 if (IS_ERR(p))
2506 return PTR_ERR(p);
2507
2508 /*
2509 * Do this prior waking up the new thread - the thread pointer
2510 * might get invalid after that point, if the thread exits quickly.
2511 */
2512 trace_sched_process_fork(current, p);
2513
2514 pid = get_task_pid(p, PIDTYPE_PID);
2515 nr = pid_vnr(pid);
2516
2517 if (clone_flags & CLONE_PARENT_SETTID)
2518 put_user(nr, args->parent_tid);
2519
2520 if (clone_flags & CLONE_VFORK) {
2521 p->vfork_done = &vfork;
2522 init_completion(&vfork);
2523 get_task_struct(p);
2524 }
2525
2526 wake_up_new_task(p);
2527
2528 /* forking complete and child started to run, tell ptracer */
2529 if (unlikely(trace))
2530 ptrace_event_pid(trace, pid);
2531
2532 if (clone_flags & CLONE_VFORK) {
2533 if (!wait_for_vfork_done(p, &vfork))
2534 ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid);
2535 }
2536
2537 put_pid(pid);
2538 return nr;
2539}
2540
2541/*
2542 * Create a kernel thread.
2543 */
2544pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
2545{
2546 struct kernel_clone_args args = {
2547 .flags = ((lower_32_bits(flags) | CLONE_VM |
2548 CLONE_UNTRACED) & ~CSIGNAL),
2549 .exit_signal = (lower_32_bits(flags) & CSIGNAL),
2550 .stack = (unsigned long)fn,
2551 .stack_size = (unsigned long)arg,
2552 };
2553
2554 return kernel_clone(&args);
2555}
2556
2557#ifdef __ARCH_WANT_SYS_FORK
2558SYSCALL_DEFINE0(fork)
2559{
2560#ifdef CONFIG_MMU
2561 struct kernel_clone_args args = {
2562 .exit_signal = SIGCHLD,
2563 };
2564
2565 return kernel_clone(&args);
2566#else
2567 /* can not support in nommu mode */
2568 return -EINVAL;
2569#endif
2570}
2571#endif
2572
2573#ifdef __ARCH_WANT_SYS_VFORK
2574SYSCALL_DEFINE0(vfork)
2575{
2576 struct kernel_clone_args args = {
2577 .flags = CLONE_VFORK | CLONE_VM,
2578 .exit_signal = SIGCHLD,
2579 };
2580
2581 return kernel_clone(&args);
2582}
2583#endif
2584
2585#ifdef __ARCH_WANT_SYS_CLONE
2586#ifdef CONFIG_CLONE_BACKWARDS
2587SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2588 int __user *, parent_tidptr,
2589 unsigned long, tls,
2590 int __user *, child_tidptr)
2591#elif defined(CONFIG_CLONE_BACKWARDS2)
2592SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags,
2593 int __user *, parent_tidptr,
2594 int __user *, child_tidptr,
2595 unsigned long, tls)
2596#elif defined(CONFIG_CLONE_BACKWARDS3)
2597SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp,
2598 int, stack_size,
2599 int __user *, parent_tidptr,
2600 int __user *, child_tidptr,
2601 unsigned long, tls)
2602#else
2603SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2604 int __user *, parent_tidptr,
2605 int __user *, child_tidptr,
2606 unsigned long, tls)
2607#endif
2608{
2609 struct kernel_clone_args args = {
2610 .flags = (lower_32_bits(clone_flags) & ~CSIGNAL),
2611 .pidfd = parent_tidptr,
2612 .child_tid = child_tidptr,
2613 .parent_tid = parent_tidptr,
2614 .exit_signal = (lower_32_bits(clone_flags) & CSIGNAL),
2615 .stack = newsp,
2616 .tls = tls,
2617 };
2618
2619 return kernel_clone(&args);
2620}
2621#endif
2622
2623#ifdef __ARCH_WANT_SYS_CLONE3
2624
2625noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs,
2626 struct clone_args __user *uargs,
2627 size_t usize)
2628{
2629 int err;
2630 struct clone_args args;
2631 pid_t *kset_tid = kargs->set_tid;
2632
2633 BUILD_BUG_ON(offsetofend(struct clone_args, tls) !=
2634 CLONE_ARGS_SIZE_VER0);
2635 BUILD_BUG_ON(offsetofend(struct clone_args, set_tid_size) !=
2636 CLONE_ARGS_SIZE_VER1);
2637 BUILD_BUG_ON(offsetofend(struct clone_args, cgroup) !=
2638 CLONE_ARGS_SIZE_VER2);
2639 BUILD_BUG_ON(sizeof(struct clone_args) != CLONE_ARGS_SIZE_VER2);
2640
2641 if (unlikely(usize > PAGE_SIZE))
2642 return -E2BIG;
2643 if (unlikely(usize < CLONE_ARGS_SIZE_VER0))
2644 return -EINVAL;
2645
2646 err = copy_struct_from_user(&args, sizeof(args), uargs, usize);
2647 if (err)
2648 return err;
2649
2650 if (unlikely(args.set_tid_size > MAX_PID_NS_LEVEL))
2651 return -EINVAL;
2652
2653 if (unlikely(!args.set_tid && args.set_tid_size > 0))
2654 return -EINVAL;
2655
2656 if (unlikely(args.set_tid && args.set_tid_size == 0))
2657 return -EINVAL;
2658
2659 /*
2660 * Verify that higher 32bits of exit_signal are unset and that
2661 * it is a valid signal
2662 */
2663 if (unlikely((args.exit_signal & ~((u64)CSIGNAL)) ||
2664 !valid_signal(args.exit_signal)))
2665 return -EINVAL;
2666
2667 if ((args.flags & CLONE_INTO_CGROUP) &&
2668 (args.cgroup > INT_MAX || usize < CLONE_ARGS_SIZE_VER2))
2669 return -EINVAL;
2670
2671 *kargs = (struct kernel_clone_args){
2672 .flags = args.flags,
2673 .pidfd = u64_to_user_ptr(args.pidfd),
2674 .child_tid = u64_to_user_ptr(args.child_tid),
2675 .parent_tid = u64_to_user_ptr(args.parent_tid),
2676 .exit_signal = args.exit_signal,
2677 .stack = args.stack,
2678 .stack_size = args.stack_size,
2679 .tls = args.tls,
2680 .set_tid_size = args.set_tid_size,
2681 .cgroup = args.cgroup,
2682 };
2683
2684 if (args.set_tid &&
2685 copy_from_user(kset_tid, u64_to_user_ptr(args.set_tid),
2686 (kargs->set_tid_size * sizeof(pid_t))))
2687 return -EFAULT;
2688
2689 kargs->set_tid = kset_tid;
2690
2691 return 0;
2692}
2693
2694/**
2695 * clone3_stack_valid - check and prepare stack
2696 * @kargs: kernel clone args
2697 *
2698 * Verify that the stack arguments userspace gave us are sane.
2699 * In addition, set the stack direction for userspace since it's easy for us to
2700 * determine.
2701 */
2702static inline bool clone3_stack_valid(struct kernel_clone_args *kargs)
2703{
2704 if (kargs->stack == 0) {
2705 if (kargs->stack_size > 0)
2706 return false;
2707 } else {
2708 if (kargs->stack_size == 0)
2709 return false;
2710
2711 if (!access_ok((void __user *)kargs->stack, kargs->stack_size))
2712 return false;
2713
2714#if !defined(CONFIG_STACK_GROWSUP) && !defined(CONFIG_IA64)
2715 kargs->stack += kargs->stack_size;
2716#endif
2717 }
2718
2719 return true;
2720}
2721
2722static bool clone3_args_valid(struct kernel_clone_args *kargs)
2723{
2724 /* Verify that no unknown flags are passed along. */
2725 if (kargs->flags &
2726 ~(CLONE_LEGACY_FLAGS | CLONE_CLEAR_SIGHAND | CLONE_INTO_CGROUP))
2727 return false;
2728
2729 /*
2730 * - make the CLONE_DETACHED bit reusable for clone3
2731 * - make the CSIGNAL bits reusable for clone3
2732 */
2733 if (kargs->flags & (CLONE_DETACHED | CSIGNAL))
2734 return false;
2735
2736 if ((kargs->flags & (CLONE_SIGHAND | CLONE_CLEAR_SIGHAND)) ==
2737 (CLONE_SIGHAND | CLONE_CLEAR_SIGHAND))
2738 return false;
2739
2740 if ((kargs->flags & (CLONE_THREAD | CLONE_PARENT)) &&
2741 kargs->exit_signal)
2742 return false;
2743
2744 if (!clone3_stack_valid(kargs))
2745 return false;
2746
2747 return true;
2748}
2749
2750/**
2751 * clone3 - create a new process with specific properties
2752 * @uargs: argument structure
2753 * @size: size of @uargs
2754 *
2755 * clone3() is the extensible successor to clone()/clone2().
2756 * It takes a struct as argument that is versioned by its size.
2757 *
2758 * Return: On success, a positive PID for the child process.
2759 * On error, a negative errno number.
2760 */
2761SYSCALL_DEFINE2(clone3, struct clone_args __user *, uargs, size_t, size)
2762{
2763 int err;
2764
2765 struct kernel_clone_args kargs;
2766 pid_t set_tid[MAX_PID_NS_LEVEL];
2767
2768 kargs.set_tid = set_tid;
2769
2770 err = copy_clone_args_from_user(&kargs, uargs, size);
2771 if (err)
2772 return err;
2773
2774 if (!clone3_args_valid(&kargs))
2775 return -EINVAL;
2776
2777 return kernel_clone(&kargs);
2778}
2779#endif
2780
2781void walk_process_tree(struct task_struct *top, proc_visitor visitor, void *data)
2782{
2783 struct task_struct *leader, *parent, *child;
2784 int res;
2785
2786 read_lock(&tasklist_lock);
2787 leader = top = top->group_leader;
2788down:
2789 for_each_thread(leader, parent) {
2790 list_for_each_entry(child, &parent->children, sibling) {
2791 res = visitor(child, data);
2792 if (res) {
2793 if (res < 0)
2794 goto out;
2795 leader = child;
2796 goto down;
2797 }
2798up:
2799 ;
2800 }
2801 }
2802
2803 if (leader != top) {
2804 child = leader;
2805 parent = child->real_parent;
2806 leader = parent->group_leader;
2807 goto up;
2808 }
2809out:
2810 read_unlock(&tasklist_lock);
2811}
2812
2813#ifndef ARCH_MIN_MMSTRUCT_ALIGN
2814#define ARCH_MIN_MMSTRUCT_ALIGN 0
2815#endif
2816
2817static void sighand_ctor(void *data)
2818{
2819 struct sighand_struct *sighand = data;
2820
2821 spin_lock_init(&sighand->siglock);
2822 init_waitqueue_head(&sighand->signalfd_wqh);
2823}
2824
2825void __init proc_caches_init(void)
2826{
2827 unsigned int mm_size;
2828
2829 sighand_cachep = kmem_cache_create("sighand_cache",
2830 sizeof(struct sighand_struct), 0,
2831 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_TYPESAFE_BY_RCU|
2832 SLAB_ACCOUNT, sighand_ctor);
2833 signal_cachep = kmem_cache_create("signal_cache",
2834 sizeof(struct signal_struct), 0,
2835 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2836 NULL);
2837 files_cachep = kmem_cache_create("files_cache",
2838 sizeof(struct files_struct), 0,
2839 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2840 NULL);
2841 fs_cachep = kmem_cache_create("fs_cache",
2842 sizeof(struct fs_struct), 0,
2843 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2844 NULL);
2845
2846 /*
2847 * The mm_cpumask is located at the end of mm_struct, and is
2848 * dynamically sized based on the maximum CPU number this system
2849 * can have, taking hotplug into account (nr_cpu_ids).
2850 */
2851 mm_size = sizeof(struct mm_struct) + cpumask_size();
2852
2853 mm_cachep = kmem_cache_create_usercopy("mm_struct",
2854 mm_size, ARCH_MIN_MMSTRUCT_ALIGN,
2855 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2856 offsetof(struct mm_struct, saved_auxv),
2857 sizeof_field(struct mm_struct, saved_auxv),
2858 NULL);
2859 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT);
2860 mmap_init();
2861 nsproxy_cache_init();
2862}
2863
2864/*
2865 * Check constraints on flags passed to the unshare system call.
2866 */
2867static int check_unshare_flags(unsigned long unshare_flags)
2868{
2869 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
2870 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
2871 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET|
2872 CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP|
2873 CLONE_NEWTIME))
2874 return -EINVAL;
2875 /*
2876 * Not implemented, but pretend it works if there is nothing
2877 * to unshare. Note that unsharing the address space or the
2878 * signal handlers also need to unshare the signal queues (aka
2879 * CLONE_THREAD).
2880 */
2881 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
2882 if (!thread_group_empty(current))
2883 return -EINVAL;
2884 }
2885 if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) {
2886 if (refcount_read(&current->sighand->count) > 1)
2887 return -EINVAL;
2888 }
2889 if (unshare_flags & CLONE_VM) {
2890 if (!current_is_single_threaded())
2891 return -EINVAL;
2892 }
2893
2894 return 0;
2895}
2896
2897/*
2898 * Unshare the filesystem structure if it is being shared
2899 */
2900static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
2901{
2902 struct fs_struct *fs = current->fs;
2903
2904 if (!(unshare_flags & CLONE_FS) || !fs)
2905 return 0;
2906
2907 /* don't need lock here; in the worst case we'll do useless copy */
2908 if (fs->users == 1)
2909 return 0;
2910
2911 *new_fsp = copy_fs_struct(fs);
2912 if (!*new_fsp)
2913 return -ENOMEM;
2914
2915 return 0;
2916}
2917
2918/*
2919 * Unshare file descriptor table if it is being shared
2920 */
2921int unshare_fd(unsigned long unshare_flags, unsigned int max_fds,
2922 struct files_struct **new_fdp)
2923{
2924 struct files_struct *fd = current->files;
2925 int error = 0;
2926
2927 if ((unshare_flags & CLONE_FILES) &&
2928 (fd && atomic_read(&fd->count) > 1)) {
2929 *new_fdp = dup_fd(fd, max_fds, &error);
2930 if (!*new_fdp)
2931 return error;
2932 }
2933
2934 return 0;
2935}
2936
2937/*
2938 * unshare allows a process to 'unshare' part of the process
2939 * context which was originally shared using clone. copy_*
2940 * functions used by kernel_clone() cannot be used here directly
2941 * because they modify an inactive task_struct that is being
2942 * constructed. Here we are modifying the current, active,
2943 * task_struct.
2944 */
2945int ksys_unshare(unsigned long unshare_flags)
2946{
2947 struct fs_struct *fs, *new_fs = NULL;
2948 struct files_struct *fd, *new_fd = NULL;
2949 struct cred *new_cred = NULL;
2950 struct nsproxy *new_nsproxy = NULL;
2951 int do_sysvsem = 0;
2952 int err;
2953
2954 /*
2955 * If unsharing a user namespace must also unshare the thread group
2956 * and unshare the filesystem root and working directories.
2957 */
2958 if (unshare_flags & CLONE_NEWUSER)
2959 unshare_flags |= CLONE_THREAD | CLONE_FS;
2960 /*
2961 * If unsharing vm, must also unshare signal handlers.
2962 */
2963 if (unshare_flags & CLONE_VM)
2964 unshare_flags |= CLONE_SIGHAND;
2965 /*
2966 * If unsharing a signal handlers, must also unshare the signal queues.
2967 */
2968 if (unshare_flags & CLONE_SIGHAND)
2969 unshare_flags |= CLONE_THREAD;
2970 /*
2971 * If unsharing namespace, must also unshare filesystem information.
2972 */
2973 if (unshare_flags & CLONE_NEWNS)
2974 unshare_flags |= CLONE_FS;
2975
2976 err = check_unshare_flags(unshare_flags);
2977 if (err)
2978 goto bad_unshare_out;
2979 /*
2980 * CLONE_NEWIPC must also detach from the undolist: after switching
2981 * to a new ipc namespace, the semaphore arrays from the old
2982 * namespace are unreachable.
2983 */
2984 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
2985 do_sysvsem = 1;
2986 err = unshare_fs(unshare_flags, &new_fs);
2987 if (err)
2988 goto bad_unshare_out;
2989 err = unshare_fd(unshare_flags, NR_OPEN_MAX, &new_fd);
2990 if (err)
2991 goto bad_unshare_cleanup_fs;
2992 err = unshare_userns(unshare_flags, &new_cred);
2993 if (err)
2994 goto bad_unshare_cleanup_fd;
2995 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
2996 new_cred, new_fs);
2997 if (err)
2998 goto bad_unshare_cleanup_cred;
2999
3000 if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
3001 if (do_sysvsem) {
3002 /*
3003 * CLONE_SYSVSEM is equivalent to sys_exit().
3004 */
3005 exit_sem(current);
3006 }
3007 if (unshare_flags & CLONE_NEWIPC) {
3008 /* Orphan segments in old ns (see sem above). */
3009 exit_shm(current);
3010 shm_init_task(current);
3011 }
3012
3013 if (new_nsproxy)
3014 switch_task_namespaces(current, new_nsproxy);
3015
3016 task_lock(current);
3017
3018 if (new_fs) {
3019 fs = current->fs;
3020 spin_lock(&fs->lock);
3021 current->fs = new_fs;
3022 if (--fs->users)
3023 new_fs = NULL;
3024 else
3025 new_fs = fs;
3026 spin_unlock(&fs->lock);
3027 }
3028
3029 if (new_fd) {
3030 fd = current->files;
3031 current->files = new_fd;
3032 new_fd = fd;
3033 }
3034
3035 task_unlock(current);
3036
3037 if (new_cred) {
3038 /* Install the new user namespace */
3039 commit_creds(new_cred);
3040 new_cred = NULL;
3041 }
3042 }
3043
3044 perf_event_namespaces(current);
3045
3046bad_unshare_cleanup_cred:
3047 if (new_cred)
3048 put_cred(new_cred);
3049bad_unshare_cleanup_fd:
3050 if (new_fd)
3051 put_files_struct(new_fd);
3052
3053bad_unshare_cleanup_fs:
3054 if (new_fs)
3055 free_fs_struct(new_fs);
3056
3057bad_unshare_out:
3058 return err;
3059}
3060
3061SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
3062{
3063 return ksys_unshare(unshare_flags);
3064}
3065
3066/*
3067 * Helper to unshare the files of the current task.
3068 * We don't want to expose copy_files internals to
3069 * the exec layer of the kernel.
3070 */
3071
3072int unshare_files(void)
3073{
3074 struct task_struct *task = current;
3075 struct files_struct *old, *copy = NULL;
3076 int error;
3077
3078 error = unshare_fd(CLONE_FILES, NR_OPEN_MAX, &copy);
3079 if (error || !copy)
3080 return error;
3081
3082 old = task->files;
3083 task_lock(task);
3084 task->files = copy;
3085 task_unlock(task);
3086 put_files_struct(old);
3087 return 0;
3088}
3089
3090int sysctl_max_threads(struct ctl_table *table, int write,
3091 void *buffer, size_t *lenp, loff_t *ppos)
3092{
3093 struct ctl_table t;
3094 int ret;
3095 int threads = max_threads;
3096 int min = 1;
3097 int max = MAX_THREADS;
3098
3099 t = *table;
3100 t.data = &threads;
3101 t.extra1 = &min;
3102 t.extra2 = &max;
3103
3104 ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
3105 if (ret || !write)
3106 return ret;
3107
3108 max_threads = threads;
3109
3110 return 0;
3111}