projects/linux·blob v5.3-rc6 · refs

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