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

source code of linux/kernel/fork.c