projects/linux·blob v4.5 · refs

2117 lines · 50.7 KiB

1/*
2 * linux/kernel/fork.c
3 *
4 * Copyright (C) 1991, 1992 Linus Torvalds
5 */
6
7/*
8 * 'fork.c' contains the help-routines for the 'fork' system call
9 * (see also entry.S and others).
10 * Fork is rather simple, once you get the hang of it, but the memory
11 * management can be a bitch. See 'mm/memory.c': 'copy_page_range()'
12 */
13
14#include <linux/slab.h>
15#include <linux/init.h>
16#include <linux/unistd.h>
17#include <linux/module.h>
18#include <linux/vmalloc.h>
19#include <linux/completion.h>
20#include <linux/personality.h>
21#include <linux/mempolicy.h>
22#include <linux/sem.h>
23#include <linux/file.h>
24#include <linux/fdtable.h>
25#include <linux/iocontext.h>
26#include <linux/key.h>
27#include <linux/binfmts.h>
28#include <linux/mman.h>
29#include <linux/mmu_notifier.h>
30#include <linux/fs.h>
31#include <linux/mm.h>
32#include <linux/vmacache.h>
33#include <linux/nsproxy.h>
34#include <linux/capability.h>
35#include <linux/cpu.h>
36#include <linux/cgroup.h>
37#include <linux/security.h>
38#include <linux/hugetlb.h>
39#include <linux/seccomp.h>
40#include <linux/swap.h>
41#include <linux/syscalls.h>
42#include <linux/jiffies.h>
43#include <linux/futex.h>
44#include <linux/compat.h>
45#include <linux/kthread.h>
46#include <linux/task_io_accounting_ops.h>
47#include <linux/rcupdate.h>
48#include <linux/ptrace.h>
49#include <linux/mount.h>
50#include <linux/audit.h>
51#include <linux/memcontrol.h>
52#include <linux/ftrace.h>
53#include <linux/proc_fs.h>
54#include <linux/profile.h>
55#include <linux/rmap.h>
56#include <linux/ksm.h>
57#include <linux/acct.h>
58#include <linux/tsacct_kern.h>
59#include <linux/cn_proc.h>
60#include <linux/freezer.h>
61#include <linux/delayacct.h>
62#include <linux/taskstats_kern.h>
63#include <linux/random.h>
64#include <linux/tty.h>
65#include <linux/blkdev.h>
66#include <linux/fs_struct.h>
67#include <linux/magic.h>
68#include <linux/perf_event.h>
69#include <linux/posix-timers.h>
70#include <linux/user-return-notifier.h>
71#include <linux/oom.h>
72#include <linux/khugepaged.h>
73#include <linux/signalfd.h>
74#include <linux/uprobes.h>
75#include <linux/aio.h>
76#include <linux/compiler.h>
77#include <linux/sysctl.h>
78
79#include <asm/pgtable.h>
80#include <asm/pgalloc.h>
81#include <asm/uaccess.h>
82#include <asm/mmu_context.h>
83#include <asm/cacheflush.h>
84#include <asm/tlbflush.h>
85
86#include <trace/events/sched.h>
87
88#define CREATE_TRACE_POINTS
89#include <trace/events/task.h>
90
91/*
92 * Minimum number of threads to boot the kernel
93 */
94#define MIN_THREADS 20
95
96/*
97 * Maximum number of threads
98 */
99#define MAX_THREADS FUTEX_TID_MASK
100
101/*
102 * Protected counters by write_lock_irq(&tasklist_lock)
103 */
104unsigned long total_forks; /* Handle normal Linux uptimes. */
105int nr_threads; /* The idle threads do not count.. */
106
107int max_threads; /* tunable limit on nr_threads */
108
109DEFINE_PER_CPU(unsigned long, process_counts) = 0;
110
111__cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */
112
113#ifdef CONFIG_PROVE_RCU
114int lockdep_tasklist_lock_is_held(void)
115{
116 return lockdep_is_held(&tasklist_lock);
117}
118EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
119#endif /* #ifdef CONFIG_PROVE_RCU */
120
121int nr_processes(void)
122{
123 int cpu;
124 int total = 0;
125
126 for_each_possible_cpu(cpu)
127 total += per_cpu(process_counts, cpu);
128
129 return total;
130}
131
132void __weak arch_release_task_struct(struct task_struct *tsk)
133{
134}
135
136#ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
137static struct kmem_cache *task_struct_cachep;
138
139static inline struct task_struct *alloc_task_struct_node(int node)
140{
141 return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node);
142}
143
144static inline void free_task_struct(struct task_struct *tsk)
145{
146 kmem_cache_free(task_struct_cachep, tsk);
147}
148#endif
149
150void __weak arch_release_thread_info(struct thread_info *ti)
151{
152}
153
154#ifndef CONFIG_ARCH_THREAD_INFO_ALLOCATOR
155
156/*
157 * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
158 * kmemcache based allocator.
159 */
160# if THREAD_SIZE >= PAGE_SIZE
161static struct thread_info *alloc_thread_info_node(struct task_struct *tsk,
162 int node)
163{
164 struct page *page = alloc_kmem_pages_node(node, THREADINFO_GFP,
165 THREAD_SIZE_ORDER);
166
167 return page ? page_address(page) : NULL;
168}
169
170static inline void free_thread_info(struct thread_info *ti)
171{
172 free_kmem_pages((unsigned long)ti, THREAD_SIZE_ORDER);
173}
174# else
175static struct kmem_cache *thread_info_cache;
176
177static struct thread_info *alloc_thread_info_node(struct task_struct *tsk,
178 int node)
179{
180 return kmem_cache_alloc_node(thread_info_cache, THREADINFO_GFP, node);
181}
182
183static void free_thread_info(struct thread_info *ti)
184{
185 kmem_cache_free(thread_info_cache, ti);
186}
187
188void thread_info_cache_init(void)
189{
190 thread_info_cache = kmem_cache_create("thread_info", THREAD_SIZE,
191 THREAD_SIZE, 0, NULL);
192 BUG_ON(thread_info_cache == NULL);
193}
194# endif
195#endif
196
197/* SLAB cache for signal_struct structures (tsk->signal) */
198static struct kmem_cache *signal_cachep;
199
200/* SLAB cache for sighand_struct structures (tsk->sighand) */
201struct kmem_cache *sighand_cachep;
202
203/* SLAB cache for files_struct structures (tsk->files) */
204struct kmem_cache *files_cachep;
205
206/* SLAB cache for fs_struct structures (tsk->fs) */
207struct kmem_cache *fs_cachep;
208
209/* SLAB cache for vm_area_struct structures */
210struct kmem_cache *vm_area_cachep;
211
212/* SLAB cache for mm_struct structures (tsk->mm) */
213static struct kmem_cache *mm_cachep;
214
215static void account_kernel_stack(struct thread_info *ti, int account)
216{
217 struct zone *zone = page_zone(virt_to_page(ti));
218
219 mod_zone_page_state(zone, NR_KERNEL_STACK, account);
220}
221
222void free_task(struct task_struct *tsk)
223{
224 account_kernel_stack(tsk->stack, -1);
225 arch_release_thread_info(tsk->stack);
226 free_thread_info(tsk->stack);
227 rt_mutex_debug_task_free(tsk);
228 ftrace_graph_exit_task(tsk);
229 put_seccomp_filter(tsk);
230 arch_release_task_struct(tsk);
231 free_task_struct(tsk);
232}
233EXPORT_SYMBOL(free_task);
234
235static inline void free_signal_struct(struct signal_struct *sig)
236{
237 taskstats_tgid_free(sig);
238 sched_autogroup_exit(sig);
239 kmem_cache_free(signal_cachep, sig);
240}
241
242static inline void put_signal_struct(struct signal_struct *sig)
243{
244 if (atomic_dec_and_test(&sig->sigcnt))
245 free_signal_struct(sig);
246}
247
248void __put_task_struct(struct task_struct *tsk)
249{
250 WARN_ON(!tsk->exit_state);
251 WARN_ON(atomic_read(&tsk->usage));
252 WARN_ON(tsk == current);
253
254 cgroup_free(tsk);
255 task_numa_free(tsk);
256 security_task_free(tsk);
257 exit_creds(tsk);
258 delayacct_tsk_free(tsk);
259 put_signal_struct(tsk->signal);
260
261 if (!profile_handoff_task(tsk))
262 free_task(tsk);
263}
264EXPORT_SYMBOL_GPL(__put_task_struct);
265
266void __init __weak arch_task_cache_init(void) { }
267
268/*
269 * set_max_threads
270 */
271static void set_max_threads(unsigned int max_threads_suggested)
272{
273 u64 threads;
274
275 /*
276 * The number of threads shall be limited such that the thread
277 * structures may only consume a small part of the available memory.
278 */
279 if (fls64(totalram_pages) + fls64(PAGE_SIZE) > 64)
280 threads = MAX_THREADS;
281 else
282 threads = div64_u64((u64) totalram_pages * (u64) PAGE_SIZE,
283 (u64) THREAD_SIZE * 8UL);
284
285 if (threads > max_threads_suggested)
286 threads = max_threads_suggested;
287
288 max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS);
289}
290
291#ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT
292/* Initialized by the architecture: */
293int arch_task_struct_size __read_mostly;
294#endif
295
296void __init fork_init(void)
297{
298#ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
299#ifndef ARCH_MIN_TASKALIGN
300#define ARCH_MIN_TASKALIGN L1_CACHE_BYTES
301#endif
302 /* create a slab on which task_structs can be allocated */
303 task_struct_cachep = kmem_cache_create("task_struct",
304 arch_task_struct_size, ARCH_MIN_TASKALIGN,
305 SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, NULL);
306#endif
307
308 /* do the arch specific task caches init */
309 arch_task_cache_init();
310
311 set_max_threads(MAX_THREADS);
312
313 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
314 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
315 init_task.signal->rlim[RLIMIT_SIGPENDING] =
316 init_task.signal->rlim[RLIMIT_NPROC];
317}
318
319int __weak arch_dup_task_struct(struct task_struct *dst,
320 struct task_struct *src)
321{
322 *dst = *src;
323 return 0;
324}
325
326void set_task_stack_end_magic(struct task_struct *tsk)
327{
328 unsigned long *stackend;
329
330 stackend = end_of_stack(tsk);
331 *stackend = STACK_END_MAGIC; /* for overflow detection */
332}
333
334static struct task_struct *dup_task_struct(struct task_struct *orig)
335{
336 struct task_struct *tsk;
337 struct thread_info *ti;
338 int node = tsk_fork_get_node(orig);
339 int err;
340
341 tsk = alloc_task_struct_node(node);
342 if (!tsk)
343 return NULL;
344
345 ti = alloc_thread_info_node(tsk, node);
346 if (!ti)
347 goto free_tsk;
348
349 err = arch_dup_task_struct(tsk, orig);
350 if (err)
351 goto free_ti;
352
353 tsk->stack = ti;
354#ifdef CONFIG_SECCOMP
355 /*
356 * We must handle setting up seccomp filters once we're under
357 * the sighand lock in case orig has changed between now and
358 * then. Until then, filter must be NULL to avoid messing up
359 * the usage counts on the error path calling free_task.
360 */
361 tsk->seccomp.filter = NULL;
362#endif
363
364 setup_thread_stack(tsk, orig);
365 clear_user_return_notifier(tsk);
366 clear_tsk_need_resched(tsk);
367 set_task_stack_end_magic(tsk);
368
369#ifdef CONFIG_CC_STACKPROTECTOR
370 tsk->stack_canary = get_random_int();
371#endif
372
373 /*
374 * One for us, one for whoever does the "release_task()" (usually
375 * parent)
376 */
377 atomic_set(&tsk->usage, 2);
378#ifdef CONFIG_BLK_DEV_IO_TRACE
379 tsk->btrace_seq = 0;
380#endif
381 tsk->splice_pipe = NULL;
382 tsk->task_frag.page = NULL;
383 tsk->wake_q.next = NULL;
384
385 account_kernel_stack(ti, 1);
386
387 return tsk;
388
389free_ti:
390 free_thread_info(ti);
391free_tsk:
392 free_task_struct(tsk);
393 return NULL;
394}
395
396#ifdef CONFIG_MMU
397static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
398{
399 struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
400 struct rb_node **rb_link, *rb_parent;
401 int retval;
402 unsigned long charge;
403
404 uprobe_start_dup_mmap();
405 down_write(&oldmm->mmap_sem);
406 flush_cache_dup_mm(oldmm);
407 uprobe_dup_mmap(oldmm, mm);
408 /*
409 * Not linked in yet - no deadlock potential:
410 */
411 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
412
413 /* No ordering required: file already has been exposed. */
414 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
415
416 mm->total_vm = oldmm->total_vm;
417 mm->data_vm = oldmm->data_vm;
418 mm->exec_vm = oldmm->exec_vm;
419 mm->stack_vm = oldmm->stack_vm;
420
421 rb_link = &mm->mm_rb.rb_node;
422 rb_parent = NULL;
423 pprev = &mm->mmap;
424 retval = ksm_fork(mm, oldmm);
425 if (retval)
426 goto out;
427 retval = khugepaged_fork(mm, oldmm);
428 if (retval)
429 goto out;
430
431 prev = NULL;
432 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
433 struct file *file;
434
435 if (mpnt->vm_flags & VM_DONTCOPY) {
436 vm_stat_account(mm, mpnt->vm_flags, -vma_pages(mpnt));
437 continue;
438 }
439 charge = 0;
440 if (mpnt->vm_flags & VM_ACCOUNT) {
441 unsigned long len = vma_pages(mpnt);
442
443 if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
444 goto fail_nomem;
445 charge = len;
446 }
447 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
448 if (!tmp)
449 goto fail_nomem;
450 *tmp = *mpnt;
451 INIT_LIST_HEAD(&tmp->anon_vma_chain);
452 retval = vma_dup_policy(mpnt, tmp);
453 if (retval)
454 goto fail_nomem_policy;
455 tmp->vm_mm = mm;
456 if (anon_vma_fork(tmp, mpnt))
457 goto fail_nomem_anon_vma_fork;
458 tmp->vm_flags &=
459 ~(VM_LOCKED|VM_LOCKONFAULT|VM_UFFD_MISSING|VM_UFFD_WP);
460 tmp->vm_next = tmp->vm_prev = NULL;
461 tmp->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
462 file = tmp->vm_file;
463 if (file) {
464 struct inode *inode = file_inode(file);
465 struct address_space *mapping = file->f_mapping;
466
467 get_file(file);
468 if (tmp->vm_flags & VM_DENYWRITE)
469 atomic_dec(&inode->i_writecount);
470 i_mmap_lock_write(mapping);
471 if (tmp->vm_flags & VM_SHARED)
472 atomic_inc(&mapping->i_mmap_writable);
473 flush_dcache_mmap_lock(mapping);
474 /* insert tmp into the share list, just after mpnt */
475 vma_interval_tree_insert_after(tmp, mpnt,
476 &mapping->i_mmap);
477 flush_dcache_mmap_unlock(mapping);
478 i_mmap_unlock_write(mapping);
479 }
480
481 /*
482 * Clear hugetlb-related page reserves for children. This only
483 * affects MAP_PRIVATE mappings. Faults generated by the child
484 * are not guaranteed to succeed, even if read-only
485 */
486 if (is_vm_hugetlb_page(tmp))
487 reset_vma_resv_huge_pages(tmp);
488
489 /*
490 * Link in the new vma and copy the page table entries.
491 */
492 *pprev = tmp;
493 pprev = &tmp->vm_next;
494 tmp->vm_prev = prev;
495 prev = tmp;
496
497 __vma_link_rb(mm, tmp, rb_link, rb_parent);
498 rb_link = &tmp->vm_rb.rb_right;
499 rb_parent = &tmp->vm_rb;
500
501 mm->map_count++;
502 retval = copy_page_range(mm, oldmm, mpnt);
503
504 if (tmp->vm_ops && tmp->vm_ops->open)
505 tmp->vm_ops->open(tmp);
506
507 if (retval)
508 goto out;
509 }
510 /* a new mm has just been created */
511 arch_dup_mmap(oldmm, mm);
512 retval = 0;
513out:
514 up_write(&mm->mmap_sem);
515 flush_tlb_mm(oldmm);
516 up_write(&oldmm->mmap_sem);
517 uprobe_end_dup_mmap();
518 return retval;
519fail_nomem_anon_vma_fork:
520 mpol_put(vma_policy(tmp));
521fail_nomem_policy:
522 kmem_cache_free(vm_area_cachep, tmp);
523fail_nomem:
524 retval = -ENOMEM;
525 vm_unacct_memory(charge);
526 goto out;
527}
528
529static inline int mm_alloc_pgd(struct mm_struct *mm)
530{
531 mm->pgd = pgd_alloc(mm);
532 if (unlikely(!mm->pgd))
533 return -ENOMEM;
534 return 0;
535}
536
537static inline void mm_free_pgd(struct mm_struct *mm)
538{
539 pgd_free(mm, mm->pgd);
540}
541#else
542static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
543{
544 down_write(&oldmm->mmap_sem);
545 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
546 up_write(&oldmm->mmap_sem);
547 return 0;
548}
549#define mm_alloc_pgd(mm) (0)
550#define mm_free_pgd(mm)
551#endif /* CONFIG_MMU */
552
553__cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
554
555#define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
556#define free_mm(mm) (kmem_cache_free(mm_cachep, (mm)))
557
558static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
559
560static int __init coredump_filter_setup(char *s)
561{
562 default_dump_filter =
563 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
564 MMF_DUMP_FILTER_MASK;
565 return 1;
566}
567
568__setup("coredump_filter=", coredump_filter_setup);
569
570#include <linux/init_task.h>
571
572static void mm_init_aio(struct mm_struct *mm)
573{
574#ifdef CONFIG_AIO
575 spin_lock_init(&mm->ioctx_lock);
576 mm->ioctx_table = NULL;
577#endif
578}
579
580static void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
581{
582#ifdef CONFIG_MEMCG
583 mm->owner = p;
584#endif
585}
586
587static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p)
588{
589 mm->mmap = NULL;
590 mm->mm_rb = RB_ROOT;
591 mm->vmacache_seqnum = 0;
592 atomic_set(&mm->mm_users, 1);
593 atomic_set(&mm->mm_count, 1);
594 init_rwsem(&mm->mmap_sem);
595 INIT_LIST_HEAD(&mm->mmlist);
596 mm->core_state = NULL;
597 atomic_long_set(&mm->nr_ptes, 0);
598 mm_nr_pmds_init(mm);
599 mm->map_count = 0;
600 mm->locked_vm = 0;
601 mm->pinned_vm = 0;
602 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
603 spin_lock_init(&mm->page_table_lock);
604 mm_init_cpumask(mm);
605 mm_init_aio(mm);
606 mm_init_owner(mm, p);
607 mmu_notifier_mm_init(mm);
608 clear_tlb_flush_pending(mm);
609#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
610 mm->pmd_huge_pte = NULL;
611#endif
612
613 if (current->mm) {
614 mm->flags = current->mm->flags & MMF_INIT_MASK;
615 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK;
616 } else {
617 mm->flags = default_dump_filter;
618 mm->def_flags = 0;
619 }
620
621 if (mm_alloc_pgd(mm))
622 goto fail_nopgd;
623
624 if (init_new_context(p, mm))
625 goto fail_nocontext;
626
627 return mm;
628
629fail_nocontext:
630 mm_free_pgd(mm);
631fail_nopgd:
632 free_mm(mm);
633 return NULL;
634}
635
636static void check_mm(struct mm_struct *mm)
637{
638 int i;
639
640 for (i = 0; i < NR_MM_COUNTERS; i++) {
641 long x = atomic_long_read(&mm->rss_stat.count[i]);
642
643 if (unlikely(x))
644 printk(KERN_ALERT "BUG: Bad rss-counter state "
645 "mm:%p idx:%d val:%ld\n", mm, i, x);
646 }
647
648 if (atomic_long_read(&mm->nr_ptes))
649 pr_alert("BUG: non-zero nr_ptes on freeing mm: %ld\n",
650 atomic_long_read(&mm->nr_ptes));
651 if (mm_nr_pmds(mm))
652 pr_alert("BUG: non-zero nr_pmds on freeing mm: %ld\n",
653 mm_nr_pmds(mm));
654
655#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
656 VM_BUG_ON_MM(mm->pmd_huge_pte, mm);
657#endif
658}
659
660/*
661 * Allocate and initialize an mm_struct.
662 */
663struct mm_struct *mm_alloc(void)
664{
665 struct mm_struct *mm;
666
667 mm = allocate_mm();
668 if (!mm)
669 return NULL;
670
671 memset(mm, 0, sizeof(*mm));
672 return mm_init(mm, current);
673}
674
675/*
676 * Called when the last reference to the mm
677 * is dropped: either by a lazy thread or by
678 * mmput. Free the page directory and the mm.
679 */
680void __mmdrop(struct mm_struct *mm)
681{
682 BUG_ON(mm == &init_mm);
683 mm_free_pgd(mm);
684 destroy_context(mm);
685 mmu_notifier_mm_destroy(mm);
686 check_mm(mm);
687 free_mm(mm);
688}
689EXPORT_SYMBOL_GPL(__mmdrop);
690
691/*
692 * Decrement the use count and release all resources for an mm.
693 */
694void mmput(struct mm_struct *mm)
695{
696 might_sleep();
697
698 if (atomic_dec_and_test(&mm->mm_users)) {
699 uprobe_clear_state(mm);
700 exit_aio(mm);
701 ksm_exit(mm);
702 khugepaged_exit(mm); /* must run before exit_mmap */
703 exit_mmap(mm);
704 set_mm_exe_file(mm, NULL);
705 if (!list_empty(&mm->mmlist)) {
706 spin_lock(&mmlist_lock);
707 list_del(&mm->mmlist);
708 spin_unlock(&mmlist_lock);
709 }
710 if (mm->binfmt)
711 module_put(mm->binfmt->module);
712 mmdrop(mm);
713 }
714}
715EXPORT_SYMBOL_GPL(mmput);
716
717/**
718 * set_mm_exe_file - change a reference to the mm's executable file
719 *
720 * This changes mm's executable file (shown as symlink /proc/[pid]/exe).
721 *
722 * Main users are mmput() and sys_execve(). Callers prevent concurrent
723 * invocations: in mmput() nobody alive left, in execve task is single
724 * threaded. sys_prctl(PR_SET_MM_MAP/EXE_FILE) also needs to set the
725 * mm->exe_file, but does so without using set_mm_exe_file() in order
726 * to do avoid the need for any locks.
727 */
728void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
729{
730 struct file *old_exe_file;
731
732 /*
733 * It is safe to dereference the exe_file without RCU as
734 * this function is only called if nobody else can access
735 * this mm -- see comment above for justification.
736 */
737 old_exe_file = rcu_dereference_raw(mm->exe_file);
738
739 if (new_exe_file)
740 get_file(new_exe_file);
741 rcu_assign_pointer(mm->exe_file, new_exe_file);
742 if (old_exe_file)
743 fput(old_exe_file);
744}
745
746/**
747 * get_mm_exe_file - acquire a reference to the mm's executable file
748 *
749 * Returns %NULL if mm has no associated executable file.
750 * User must release file via fput().
751 */
752struct file *get_mm_exe_file(struct mm_struct *mm)
753{
754 struct file *exe_file;
755
756 rcu_read_lock();
757 exe_file = rcu_dereference(mm->exe_file);
758 if (exe_file && !get_file_rcu(exe_file))
759 exe_file = NULL;
760 rcu_read_unlock();
761 return exe_file;
762}
763EXPORT_SYMBOL(get_mm_exe_file);
764
765/**
766 * get_task_mm - acquire a reference to the task's mm
767 *
768 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning
769 * this kernel workthread has transiently adopted a user mm with use_mm,
770 * to do its AIO) is not set and if so returns a reference to it, after
771 * bumping up the use count. User must release the mm via mmput()
772 * after use. Typically used by /proc and ptrace.
773 */
774struct mm_struct *get_task_mm(struct task_struct *task)
775{
776 struct mm_struct *mm;
777
778 task_lock(task);
779 mm = task->mm;
780 if (mm) {
781 if (task->flags & PF_KTHREAD)
782 mm = NULL;
783 else
784 atomic_inc(&mm->mm_users);
785 }
786 task_unlock(task);
787 return mm;
788}
789EXPORT_SYMBOL_GPL(get_task_mm);
790
791struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
792{
793 struct mm_struct *mm;
794 int err;
795
796 err = mutex_lock_killable(&task->signal->cred_guard_mutex);
797 if (err)
798 return ERR_PTR(err);
799
800 mm = get_task_mm(task);
801 if (mm && mm != current->mm &&
802 !ptrace_may_access(task, mode)) {
803 mmput(mm);
804 mm = ERR_PTR(-EACCES);
805 }
806 mutex_unlock(&task->signal->cred_guard_mutex);
807
808 return mm;
809}
810
811static void complete_vfork_done(struct task_struct *tsk)
812{
813 struct completion *vfork;
814
815 task_lock(tsk);
816 vfork = tsk->vfork_done;
817 if (likely(vfork)) {
818 tsk->vfork_done = NULL;
819 complete(vfork);
820 }
821 task_unlock(tsk);
822}
823
824static int wait_for_vfork_done(struct task_struct *child,
825 struct completion *vfork)
826{
827 int killed;
828
829 freezer_do_not_count();
830 killed = wait_for_completion_killable(vfork);
831 freezer_count();
832
833 if (killed) {
834 task_lock(child);
835 child->vfork_done = NULL;
836 task_unlock(child);
837 }
838
839 put_task_struct(child);
840 return killed;
841}
842
843/* Please note the differences between mmput and mm_release.
844 * mmput is called whenever we stop holding onto a mm_struct,
845 * error success whatever.
846 *
847 * mm_release is called after a mm_struct has been removed
848 * from the current process.
849 *
850 * This difference is important for error handling, when we
851 * only half set up a mm_struct for a new process and need to restore
852 * the old one. Because we mmput the new mm_struct before
853 * restoring the old one. . .
854 * Eric Biederman 10 January 1998
855 */
856void mm_release(struct task_struct *tsk, struct mm_struct *mm)
857{
858 /* Get rid of any futexes when releasing the mm */
859#ifdef CONFIG_FUTEX
860 if (unlikely(tsk->robust_list)) {
861 exit_robust_list(tsk);
862 tsk->robust_list = NULL;
863 }
864#ifdef CONFIG_COMPAT
865 if (unlikely(tsk->compat_robust_list)) {
866 compat_exit_robust_list(tsk);
867 tsk->compat_robust_list = NULL;
868 }
869#endif
870 if (unlikely(!list_empty(&tsk->pi_state_list)))
871 exit_pi_state_list(tsk);
872#endif
873
874 uprobe_free_utask(tsk);
875
876 /* Get rid of any cached register state */
877 deactivate_mm(tsk, mm);
878
879 /*
880 * If we're exiting normally, clear a user-space tid field if
881 * requested. We leave this alone when dying by signal, to leave
882 * the value intact in a core dump, and to save the unnecessary
883 * trouble, say, a killed vfork parent shouldn't touch this mm.
884 * Userland only wants this done for a sys_exit.
885 */
886 if (tsk->clear_child_tid) {
887 if (!(tsk->flags & PF_SIGNALED) &&
888 atomic_read(&mm->mm_users) > 1) {
889 /*
890 * We don't check the error code - if userspace has
891 * not set up a proper pointer then tough luck.
892 */
893 put_user(0, tsk->clear_child_tid);
894 sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
895 1, NULL, NULL, 0);
896 }
897 tsk->clear_child_tid = NULL;
898 }
899
900 /*
901 * All done, finally we can wake up parent and return this mm to him.
902 * Also kthread_stop() uses this completion for synchronization.
903 */
904 if (tsk->vfork_done)
905 complete_vfork_done(tsk);
906}
907
908/*
909 * Allocate a new mm structure and copy contents from the
910 * mm structure of the passed in task structure.
911 */
912static struct mm_struct *dup_mm(struct task_struct *tsk)
913{
914 struct mm_struct *mm, *oldmm = current->mm;
915 int err;
916
917 mm = allocate_mm();
918 if (!mm)
919 goto fail_nomem;
920
921 memcpy(mm, oldmm, sizeof(*mm));
922
923 if (!mm_init(mm, tsk))
924 goto fail_nomem;
925
926 err = dup_mmap(mm, oldmm);
927 if (err)
928 goto free_pt;
929
930 mm->hiwater_rss = get_mm_rss(mm);
931 mm->hiwater_vm = mm->total_vm;
932
933 if (mm->binfmt && !try_module_get(mm->binfmt->module))
934 goto free_pt;
935
936 return mm;
937
938free_pt:
939 /* don't put binfmt in mmput, we haven't got module yet */
940 mm->binfmt = NULL;
941 mmput(mm);
942
943fail_nomem:
944 return NULL;
945}
946
947static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
948{
949 struct mm_struct *mm, *oldmm;
950 int retval;
951
952 tsk->min_flt = tsk->maj_flt = 0;
953 tsk->nvcsw = tsk->nivcsw = 0;
954#ifdef CONFIG_DETECT_HUNG_TASK
955 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
956#endif
957
958 tsk->mm = NULL;
959 tsk->active_mm = NULL;
960
961 /*
962 * Are we cloning a kernel thread?
963 *
964 * We need to steal a active VM for that..
965 */
966 oldmm = current->mm;
967 if (!oldmm)
968 return 0;
969
970 /* initialize the new vmacache entries */
971 vmacache_flush(tsk);
972
973 if (clone_flags & CLONE_VM) {
974 atomic_inc(&oldmm->mm_users);
975 mm = oldmm;
976 goto good_mm;
977 }
978
979 retval = -ENOMEM;
980 mm = dup_mm(tsk);
981 if (!mm)
982 goto fail_nomem;
983
984good_mm:
985 tsk->mm = mm;
986 tsk->active_mm = mm;
987 return 0;
988
989fail_nomem:
990 return retval;
991}
992
993static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
994{
995 struct fs_struct *fs = current->fs;
996 if (clone_flags & CLONE_FS) {
997 /* tsk->fs is already what we want */
998 spin_lock(&fs->lock);
999 if (fs->in_exec) {
1000 spin_unlock(&fs->lock);
1001 return -EAGAIN;
1002 }
1003 fs->users++;
1004 spin_unlock(&fs->lock);
1005 return 0;
1006 }
1007 tsk->fs = copy_fs_struct(fs);
1008 if (!tsk->fs)
1009 return -ENOMEM;
1010 return 0;
1011}
1012
1013static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
1014{
1015 struct files_struct *oldf, *newf;
1016 int error = 0;
1017
1018 /*
1019 * A background process may not have any files ...
1020 */
1021 oldf = current->files;
1022 if (!oldf)
1023 goto out;
1024
1025 if (clone_flags & CLONE_FILES) {
1026 atomic_inc(&oldf->count);
1027 goto out;
1028 }
1029
1030 newf = dup_fd(oldf, &error);
1031 if (!newf)
1032 goto out;
1033
1034 tsk->files = newf;
1035 error = 0;
1036out:
1037 return error;
1038}
1039
1040static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
1041{
1042#ifdef CONFIG_BLOCK
1043 struct io_context *ioc = current->io_context;
1044 struct io_context *new_ioc;
1045
1046 if (!ioc)
1047 return 0;
1048 /*
1049 * Share io context with parent, if CLONE_IO is set
1050 */
1051 if (clone_flags & CLONE_IO) {
1052 ioc_task_link(ioc);
1053 tsk->io_context = ioc;
1054 } else if (ioprio_valid(ioc->ioprio)) {
1055 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE);
1056 if (unlikely(!new_ioc))
1057 return -ENOMEM;
1058
1059 new_ioc->ioprio = ioc->ioprio;
1060 put_io_context(new_ioc);
1061 }
1062#endif
1063 return 0;
1064}
1065
1066static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
1067{
1068 struct sighand_struct *sig;
1069
1070 if (clone_flags & CLONE_SIGHAND) {
1071 atomic_inc(&current->sighand->count);
1072 return 0;
1073 }
1074 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1075 rcu_assign_pointer(tsk->sighand, sig);
1076 if (!sig)
1077 return -ENOMEM;
1078
1079 atomic_set(&sig->count, 1);
1080 memcpy(sig->action, current->sighand->action, sizeof(sig->action));
1081 return 0;
1082}
1083
1084void __cleanup_sighand(struct sighand_struct *sighand)
1085{
1086 if (atomic_dec_and_test(&sighand->count)) {
1087 signalfd_cleanup(sighand);
1088 /*
1089 * sighand_cachep is SLAB_DESTROY_BY_RCU so we can free it
1090 * without an RCU grace period, see __lock_task_sighand().
1091 */
1092 kmem_cache_free(sighand_cachep, sighand);
1093 }
1094}
1095
1096/*
1097 * Initialize POSIX timer handling for a thread group.
1098 */
1099static void posix_cpu_timers_init_group(struct signal_struct *sig)
1100{
1101 unsigned long cpu_limit;
1102
1103 cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1104 if (cpu_limit != RLIM_INFINITY) {
1105 sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit);
1106 sig->cputimer.running = true;
1107 }
1108
1109 /* The timer lists. */
1110 INIT_LIST_HEAD(&sig->cpu_timers[0]);
1111 INIT_LIST_HEAD(&sig->cpu_timers[1]);
1112 INIT_LIST_HEAD(&sig->cpu_timers[2]);
1113}
1114
1115static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
1116{
1117 struct signal_struct *sig;
1118
1119 if (clone_flags & CLONE_THREAD)
1120 return 0;
1121
1122 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
1123 tsk->signal = sig;
1124 if (!sig)
1125 return -ENOMEM;
1126
1127 sig->nr_threads = 1;
1128 atomic_set(&sig->live, 1);
1129 atomic_set(&sig->sigcnt, 1);
1130
1131 /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */
1132 sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node);
1133 tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head);
1134
1135 init_waitqueue_head(&sig->wait_chldexit);
1136 sig->curr_target = tsk;
1137 init_sigpending(&sig->shared_pending);
1138 INIT_LIST_HEAD(&sig->posix_timers);
1139 seqlock_init(&sig->stats_lock);
1140 prev_cputime_init(&sig->prev_cputime);
1141
1142 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1143 sig->real_timer.function = it_real_fn;
1144
1145 task_lock(current->group_leader);
1146 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
1147 task_unlock(current->group_leader);
1148
1149 posix_cpu_timers_init_group(sig);
1150
1151 tty_audit_fork(sig);
1152 sched_autogroup_fork(sig);
1153
1154 sig->oom_score_adj = current->signal->oom_score_adj;
1155 sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1156
1157 sig->has_child_subreaper = current->signal->has_child_subreaper ||
1158 current->signal->is_child_subreaper;
1159
1160 mutex_init(&sig->cred_guard_mutex);
1161
1162 return 0;
1163}
1164
1165static void copy_seccomp(struct task_struct *p)
1166{
1167#ifdef CONFIG_SECCOMP
1168 /*
1169 * Must be called with sighand->lock held, which is common to
1170 * all threads in the group. Holding cred_guard_mutex is not
1171 * needed because this new task is not yet running and cannot
1172 * be racing exec.
1173 */
1174 assert_spin_locked(&current->sighand->siglock);
1175
1176 /* Ref-count the new filter user, and assign it. */
1177 get_seccomp_filter(current);
1178 p->seccomp = current->seccomp;
1179
1180 /*
1181 * Explicitly enable no_new_privs here in case it got set
1182 * between the task_struct being duplicated and holding the
1183 * sighand lock. The seccomp state and nnp must be in sync.
1184 */
1185 if (task_no_new_privs(current))
1186 task_set_no_new_privs(p);
1187
1188 /*
1189 * If the parent gained a seccomp mode after copying thread
1190 * flags and between before we held the sighand lock, we have
1191 * to manually enable the seccomp thread flag here.
1192 */
1193 if (p->seccomp.mode != SECCOMP_MODE_DISABLED)
1194 set_tsk_thread_flag(p, TIF_SECCOMP);
1195#endif
1196}
1197
1198SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1199{
1200 current->clear_child_tid = tidptr;
1201
1202 return task_pid_vnr(current);
1203}
1204
1205static void rt_mutex_init_task(struct task_struct *p)
1206{
1207 raw_spin_lock_init(&p->pi_lock);
1208#ifdef CONFIG_RT_MUTEXES
1209 p->pi_waiters = RB_ROOT;
1210 p->pi_waiters_leftmost = NULL;
1211 p->pi_blocked_on = NULL;
1212#endif
1213}
1214
1215/*
1216 * Initialize POSIX timer handling for a single task.
1217 */
1218static void posix_cpu_timers_init(struct task_struct *tsk)
1219{
1220 tsk->cputime_expires.prof_exp = 0;
1221 tsk->cputime_expires.virt_exp = 0;
1222 tsk->cputime_expires.sched_exp = 0;
1223 INIT_LIST_HEAD(&tsk->cpu_timers[0]);
1224 INIT_LIST_HEAD(&tsk->cpu_timers[1]);
1225 INIT_LIST_HEAD(&tsk->cpu_timers[2]);
1226}
1227
1228static inline void
1229init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid)
1230{
1231 task->pids[type].pid = pid;
1232}
1233
1234/*
1235 * This creates a new process as a copy of the old one,
1236 * but does not actually start it yet.
1237 *
1238 * It copies the registers, and all the appropriate
1239 * parts of the process environment (as per the clone
1240 * flags). The actual kick-off is left to the caller.
1241 */
1242static struct task_struct *copy_process(unsigned long clone_flags,
1243 unsigned long stack_start,
1244 unsigned long stack_size,
1245 int __user *child_tidptr,
1246 struct pid *pid,
1247 int trace,
1248 unsigned long tls)
1249{
1250 int retval;
1251 struct task_struct *p;
1252
1253 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1254 return ERR_PTR(-EINVAL);
1255
1256 if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS))
1257 return ERR_PTR(-EINVAL);
1258
1259 /*
1260 * Thread groups must share signals as well, and detached threads
1261 * can only be started up within the thread group.
1262 */
1263 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1264 return ERR_PTR(-EINVAL);
1265
1266 /*
1267 * Shared signal handlers imply shared VM. By way of the above,
1268 * thread groups also imply shared VM. Blocking this case allows
1269 * for various simplifications in other code.
1270 */
1271 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1272 return ERR_PTR(-EINVAL);
1273
1274 /*
1275 * Siblings of global init remain as zombies on exit since they are
1276 * not reaped by their parent (swapper). To solve this and to avoid
1277 * multi-rooted process trees, prevent global and container-inits
1278 * from creating siblings.
1279 */
1280 if ((clone_flags & CLONE_PARENT) &&
1281 current->signal->flags & SIGNAL_UNKILLABLE)
1282 return ERR_PTR(-EINVAL);
1283
1284 /*
1285 * If the new process will be in a different pid or user namespace
1286 * do not allow it to share a thread group with the forking task.
1287 */
1288 if (clone_flags & CLONE_THREAD) {
1289 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) ||
1290 (task_active_pid_ns(current) !=
1291 current->nsproxy->pid_ns_for_children))
1292 return ERR_PTR(-EINVAL);
1293 }
1294
1295 retval = security_task_create(clone_flags);
1296 if (retval)
1297 goto fork_out;
1298
1299 retval = -ENOMEM;
1300 p = dup_task_struct(current);
1301 if (!p)
1302 goto fork_out;
1303
1304 ftrace_graph_init_task(p);
1305
1306 rt_mutex_init_task(p);
1307
1308#ifdef CONFIG_PROVE_LOCKING
1309 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1310 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1311#endif
1312 retval = -EAGAIN;
1313 if (atomic_read(&p->real_cred->user->processes) >=
1314 task_rlimit(p, RLIMIT_NPROC)) {
1315 if (p->real_cred->user != INIT_USER &&
1316 !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
1317 goto bad_fork_free;
1318 }
1319 current->flags &= ~PF_NPROC_EXCEEDED;
1320
1321 retval = copy_creds(p, clone_flags);
1322 if (retval < 0)
1323 goto bad_fork_free;
1324
1325 /*
1326 * If multiple threads are within copy_process(), then this check
1327 * triggers too late. This doesn't hurt, the check is only there
1328 * to stop root fork bombs.
1329 */
1330 retval = -EAGAIN;
1331 if (nr_threads >= max_threads)
1332 goto bad_fork_cleanup_count;
1333
1334 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */
1335 p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER);
1336 p->flags |= PF_FORKNOEXEC;
1337 INIT_LIST_HEAD(&p->children);
1338 INIT_LIST_HEAD(&p->sibling);
1339 rcu_copy_process(p);
1340 p->vfork_done = NULL;
1341 spin_lock_init(&p->alloc_lock);
1342
1343 init_sigpending(&p->pending);
1344
1345 p->utime = p->stime = p->gtime = 0;
1346 p->utimescaled = p->stimescaled = 0;
1347 prev_cputime_init(&p->prev_cputime);
1348
1349#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
1350 seqcount_init(&p->vtime_seqcount);
1351 p->vtime_snap = 0;
1352 p->vtime_snap_whence = VTIME_INACTIVE;
1353#endif
1354
1355#if defined(SPLIT_RSS_COUNTING)
1356 memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1357#endif
1358
1359 p->default_timer_slack_ns = current->timer_slack_ns;
1360
1361 task_io_accounting_init(&p->ioac);
1362 acct_clear_integrals(p);
1363
1364 posix_cpu_timers_init(p);
1365
1366 p->start_time = ktime_get_ns();
1367 p->real_start_time = ktime_get_boot_ns();
1368 p->io_context = NULL;
1369 p->audit_context = NULL;
1370 threadgroup_change_begin(current);
1371 cgroup_fork(p);
1372#ifdef CONFIG_NUMA
1373 p->mempolicy = mpol_dup(p->mempolicy);
1374 if (IS_ERR(p->mempolicy)) {
1375 retval = PTR_ERR(p->mempolicy);
1376 p->mempolicy = NULL;
1377 goto bad_fork_cleanup_threadgroup_lock;
1378 }
1379#endif
1380#ifdef CONFIG_CPUSETS
1381 p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
1382 p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
1383 seqcount_init(&p->mems_allowed_seq);
1384#endif
1385#ifdef CONFIG_TRACE_IRQFLAGS
1386 p->irq_events = 0;
1387 p->hardirqs_enabled = 0;
1388 p->hardirq_enable_ip = 0;
1389 p->hardirq_enable_event = 0;
1390 p->hardirq_disable_ip = _THIS_IP_;
1391 p->hardirq_disable_event = 0;
1392 p->softirqs_enabled = 1;
1393 p->softirq_enable_ip = _THIS_IP_;
1394 p->softirq_enable_event = 0;
1395 p->softirq_disable_ip = 0;
1396 p->softirq_disable_event = 0;
1397 p->hardirq_context = 0;
1398 p->softirq_context = 0;
1399#endif
1400
1401 p->pagefault_disabled = 0;
1402
1403#ifdef CONFIG_LOCKDEP
1404 p->lockdep_depth = 0; /* no locks held yet */
1405 p->curr_chain_key = 0;
1406 p->lockdep_recursion = 0;
1407#endif
1408
1409#ifdef CONFIG_DEBUG_MUTEXES
1410 p->blocked_on = NULL; /* not blocked yet */
1411#endif
1412#ifdef CONFIG_BCACHE
1413 p->sequential_io = 0;
1414 p->sequential_io_avg = 0;
1415#endif
1416
1417 /* Perform scheduler related setup. Assign this task to a CPU. */
1418 retval = sched_fork(clone_flags, p);
1419 if (retval)
1420 goto bad_fork_cleanup_policy;
1421
1422 retval = perf_event_init_task(p);
1423 if (retval)
1424 goto bad_fork_cleanup_policy;
1425 retval = audit_alloc(p);
1426 if (retval)
1427 goto bad_fork_cleanup_perf;
1428 /* copy all the process information */
1429 shm_init_task(p);
1430 retval = copy_semundo(clone_flags, p);
1431 if (retval)
1432 goto bad_fork_cleanup_audit;
1433 retval = copy_files(clone_flags, p);
1434 if (retval)
1435 goto bad_fork_cleanup_semundo;
1436 retval = copy_fs(clone_flags, p);
1437 if (retval)
1438 goto bad_fork_cleanup_files;
1439 retval = copy_sighand(clone_flags, p);
1440 if (retval)
1441 goto bad_fork_cleanup_fs;
1442 retval = copy_signal(clone_flags, p);
1443 if (retval)
1444 goto bad_fork_cleanup_sighand;
1445 retval = copy_mm(clone_flags, p);
1446 if (retval)
1447 goto bad_fork_cleanup_signal;
1448 retval = copy_namespaces(clone_flags, p);
1449 if (retval)
1450 goto bad_fork_cleanup_mm;
1451 retval = copy_io(clone_flags, p);
1452 if (retval)
1453 goto bad_fork_cleanup_namespaces;
1454 retval = copy_thread_tls(clone_flags, stack_start, stack_size, p, tls);
1455 if (retval)
1456 goto bad_fork_cleanup_io;
1457
1458 if (pid != &init_struct_pid) {
1459 pid = alloc_pid(p->nsproxy->pid_ns_for_children);
1460 if (IS_ERR(pid)) {
1461 retval = PTR_ERR(pid);
1462 goto bad_fork_cleanup_io;
1463 }
1464 }
1465
1466 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1467 /*
1468 * Clear TID on mm_release()?
1469 */
1470 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL;
1471#ifdef CONFIG_BLOCK
1472 p->plug = NULL;
1473#endif
1474#ifdef CONFIG_FUTEX
1475 p->robust_list = NULL;
1476#ifdef CONFIG_COMPAT
1477 p->compat_robust_list = NULL;
1478#endif
1479 INIT_LIST_HEAD(&p->pi_state_list);
1480 p->pi_state_cache = NULL;
1481#endif
1482 /*
1483 * sigaltstack should be cleared when sharing the same VM
1484 */
1485 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1486 p->sas_ss_sp = p->sas_ss_size = 0;
1487
1488 /*
1489 * Syscall tracing and stepping should be turned off in the
1490 * child regardless of CLONE_PTRACE.
1491 */
1492 user_disable_single_step(p);
1493 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1494#ifdef TIF_SYSCALL_EMU
1495 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1496#endif
1497 clear_all_latency_tracing(p);
1498
1499 /* ok, now we should be set up.. */
1500 p->pid = pid_nr(pid);
1501 if (clone_flags & CLONE_THREAD) {
1502 p->exit_signal = -1;
1503 p->group_leader = current->group_leader;
1504 p->tgid = current->tgid;
1505 } else {
1506 if (clone_flags & CLONE_PARENT)
1507 p->exit_signal = current->group_leader->exit_signal;
1508 else
1509 p->exit_signal = (clone_flags & CSIGNAL);
1510 p->group_leader = p;
1511 p->tgid = p->pid;
1512 }
1513
1514 p->nr_dirtied = 0;
1515 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
1516 p->dirty_paused_when = 0;
1517
1518 p->pdeath_signal = 0;
1519 INIT_LIST_HEAD(&p->thread_group);
1520 p->task_works = NULL;
1521
1522 /*
1523 * Ensure that the cgroup subsystem policies allow the new process to be
1524 * forked. It should be noted the the new process's css_set can be changed
1525 * between here and cgroup_post_fork() if an organisation operation is in
1526 * progress.
1527 */
1528 retval = cgroup_can_fork(p);
1529 if (retval)
1530 goto bad_fork_free_pid;
1531
1532 /*
1533 * Make it visible to the rest of the system, but dont wake it up yet.
1534 * Need tasklist lock for parent etc handling!
1535 */
1536 write_lock_irq(&tasklist_lock);
1537
1538 /* CLONE_PARENT re-uses the old parent */
1539 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1540 p->real_parent = current->real_parent;
1541 p->parent_exec_id = current->parent_exec_id;
1542 } else {
1543 p->real_parent = current;
1544 p->parent_exec_id = current->self_exec_id;
1545 }
1546
1547 spin_lock(&current->sighand->siglock);
1548
1549 /*
1550 * Copy seccomp details explicitly here, in case they were changed
1551 * before holding sighand lock.
1552 */
1553 copy_seccomp(p);
1554
1555 /*
1556 * Process group and session signals need to be delivered to just the
1557 * parent before the fork or both the parent and the child after the
1558 * fork. Restart if a signal comes in before we add the new process to
1559 * it's process group.
1560 * A fatal signal pending means that current will exit, so the new
1561 * thread can't slip out of an OOM kill (or normal SIGKILL).
1562 */
1563 recalc_sigpending();
1564 if (signal_pending(current)) {
1565 spin_unlock(&current->sighand->siglock);
1566 write_unlock_irq(&tasklist_lock);
1567 retval = -ERESTARTNOINTR;
1568 goto bad_fork_cancel_cgroup;
1569 }
1570
1571 if (likely(p->pid)) {
1572 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
1573
1574 init_task_pid(p, PIDTYPE_PID, pid);
1575 if (thread_group_leader(p)) {
1576 init_task_pid(p, PIDTYPE_PGID, task_pgrp(current));
1577 init_task_pid(p, PIDTYPE_SID, task_session(current));
1578
1579 if (is_child_reaper(pid)) {
1580 ns_of_pid(pid)->child_reaper = p;
1581 p->signal->flags |= SIGNAL_UNKILLABLE;
1582 }
1583
1584 p->signal->leader_pid = pid;
1585 p->signal->tty = tty_kref_get(current->signal->tty);
1586 list_add_tail(&p->sibling, &p->real_parent->children);
1587 list_add_tail_rcu(&p->tasks, &init_task.tasks);
1588 attach_pid(p, PIDTYPE_PGID);
1589 attach_pid(p, PIDTYPE_SID);
1590 __this_cpu_inc(process_counts);
1591 } else {
1592 current->signal->nr_threads++;
1593 atomic_inc(&current->signal->live);
1594 atomic_inc(&current->signal->sigcnt);
1595 list_add_tail_rcu(&p->thread_group,
1596 &p->group_leader->thread_group);
1597 list_add_tail_rcu(&p->thread_node,
1598 &p->signal->thread_head);
1599 }
1600 attach_pid(p, PIDTYPE_PID);
1601 nr_threads++;
1602 }
1603
1604 total_forks++;
1605 spin_unlock(&current->sighand->siglock);
1606 syscall_tracepoint_update(p);
1607 write_unlock_irq(&tasklist_lock);
1608
1609 proc_fork_connector(p);
1610 cgroup_post_fork(p);
1611 threadgroup_change_end(current);
1612 perf_event_fork(p);
1613
1614 trace_task_newtask(p, clone_flags);
1615 uprobe_copy_process(p, clone_flags);
1616
1617 return p;
1618
1619bad_fork_cancel_cgroup:
1620 cgroup_cancel_fork(p);
1621bad_fork_free_pid:
1622 if (pid != &init_struct_pid)
1623 free_pid(pid);
1624bad_fork_cleanup_io:
1625 if (p->io_context)
1626 exit_io_context(p);
1627bad_fork_cleanup_namespaces:
1628 exit_task_namespaces(p);
1629bad_fork_cleanup_mm:
1630 if (p->mm)
1631 mmput(p->mm);
1632bad_fork_cleanup_signal:
1633 if (!(clone_flags & CLONE_THREAD))
1634 free_signal_struct(p->signal);
1635bad_fork_cleanup_sighand:
1636 __cleanup_sighand(p->sighand);
1637bad_fork_cleanup_fs:
1638 exit_fs(p); /* blocking */
1639bad_fork_cleanup_files:
1640 exit_files(p); /* blocking */
1641bad_fork_cleanup_semundo:
1642 exit_sem(p);
1643bad_fork_cleanup_audit:
1644 audit_free(p);
1645bad_fork_cleanup_perf:
1646 perf_event_free_task(p);
1647bad_fork_cleanup_policy:
1648#ifdef CONFIG_NUMA
1649 mpol_put(p->mempolicy);
1650bad_fork_cleanup_threadgroup_lock:
1651#endif
1652 threadgroup_change_end(current);
1653 delayacct_tsk_free(p);
1654bad_fork_cleanup_count:
1655 atomic_dec(&p->cred->user->processes);
1656 exit_creds(p);
1657bad_fork_free:
1658 free_task(p);
1659fork_out:
1660 return ERR_PTR(retval);
1661}
1662
1663static inline void init_idle_pids(struct pid_link *links)
1664{
1665 enum pid_type type;
1666
1667 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
1668 INIT_HLIST_NODE(&links[type].node); /* not really needed */
1669 links[type].pid = &init_struct_pid;
1670 }
1671}
1672
1673struct task_struct *fork_idle(int cpu)
1674{
1675 struct task_struct *task;
1676 task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0, 0);
1677 if (!IS_ERR(task)) {
1678 init_idle_pids(task->pids);
1679 init_idle(task, cpu);
1680 }
1681
1682 return task;
1683}
1684
1685/*
1686 * Ok, this is the main fork-routine.
1687 *
1688 * It copies the process, and if successful kick-starts
1689 * it and waits for it to finish using the VM if required.
1690 */
1691long _do_fork(unsigned long clone_flags,
1692 unsigned long stack_start,
1693 unsigned long stack_size,
1694 int __user *parent_tidptr,
1695 int __user *child_tidptr,
1696 unsigned long tls)
1697{
1698 struct task_struct *p;
1699 int trace = 0;
1700 long nr;
1701
1702 /*
1703 * Determine whether and which event to report to ptracer. When
1704 * called from kernel_thread or CLONE_UNTRACED is explicitly
1705 * requested, no event is reported; otherwise, report if the event
1706 * for the type of forking is enabled.
1707 */
1708 if (!(clone_flags & CLONE_UNTRACED)) {
1709 if (clone_flags & CLONE_VFORK)
1710 trace = PTRACE_EVENT_VFORK;
1711 else if ((clone_flags & CSIGNAL) != SIGCHLD)
1712 trace = PTRACE_EVENT_CLONE;
1713 else
1714 trace = PTRACE_EVENT_FORK;
1715
1716 if (likely(!ptrace_event_enabled(current, trace)))
1717 trace = 0;
1718 }
1719
1720 p = copy_process(clone_flags, stack_start, stack_size,
1721 child_tidptr, NULL, trace, tls);
1722 /*
1723 * Do this prior waking up the new thread - the thread pointer
1724 * might get invalid after that point, if the thread exits quickly.
1725 */
1726 if (!IS_ERR(p)) {
1727 struct completion vfork;
1728 struct pid *pid;
1729
1730 trace_sched_process_fork(current, p);
1731
1732 pid = get_task_pid(p, PIDTYPE_PID);
1733 nr = pid_vnr(pid);
1734
1735 if (clone_flags & CLONE_PARENT_SETTID)
1736 put_user(nr, parent_tidptr);
1737
1738 if (clone_flags & CLONE_VFORK) {
1739 p->vfork_done = &vfork;
1740 init_completion(&vfork);
1741 get_task_struct(p);
1742 }
1743
1744 wake_up_new_task(p);
1745
1746 /* forking complete and child started to run, tell ptracer */
1747 if (unlikely(trace))
1748 ptrace_event_pid(trace, pid);
1749
1750 if (clone_flags & CLONE_VFORK) {
1751 if (!wait_for_vfork_done(p, &vfork))
1752 ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid);
1753 }
1754
1755 put_pid(pid);
1756 } else {
1757 nr = PTR_ERR(p);
1758 }
1759 return nr;
1760}
1761
1762#ifndef CONFIG_HAVE_COPY_THREAD_TLS
1763/* For compatibility with architectures that call do_fork directly rather than
1764 * using the syscall entry points below. */
1765long do_fork(unsigned long clone_flags,
1766 unsigned long stack_start,
1767 unsigned long stack_size,
1768 int __user *parent_tidptr,
1769 int __user *child_tidptr)
1770{
1771 return _do_fork(clone_flags, stack_start, stack_size,
1772 parent_tidptr, child_tidptr, 0);
1773}
1774#endif
1775
1776/*
1777 * Create a kernel thread.
1778 */
1779pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
1780{
1781 return _do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn,
1782 (unsigned long)arg, NULL, NULL, 0);
1783}
1784
1785#ifdef __ARCH_WANT_SYS_FORK
1786SYSCALL_DEFINE0(fork)
1787{
1788#ifdef CONFIG_MMU
1789 return _do_fork(SIGCHLD, 0, 0, NULL, NULL, 0);
1790#else
1791 /* can not support in nommu mode */
1792 return -EINVAL;
1793#endif
1794}
1795#endif
1796
1797#ifdef __ARCH_WANT_SYS_VFORK
1798SYSCALL_DEFINE0(vfork)
1799{
1800 return _do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0,
1801 0, NULL, NULL, 0);
1802}
1803#endif
1804
1805#ifdef __ARCH_WANT_SYS_CLONE
1806#ifdef CONFIG_CLONE_BACKWARDS
1807SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
1808 int __user *, parent_tidptr,
1809 unsigned long, tls,
1810 int __user *, child_tidptr)
1811#elif defined(CONFIG_CLONE_BACKWARDS2)
1812SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags,
1813 int __user *, parent_tidptr,
1814 int __user *, child_tidptr,
1815 unsigned long, tls)
1816#elif defined(CONFIG_CLONE_BACKWARDS3)
1817SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp,
1818 int, stack_size,
1819 int __user *, parent_tidptr,
1820 int __user *, child_tidptr,
1821 unsigned long, tls)
1822#else
1823SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
1824 int __user *, parent_tidptr,
1825 int __user *, child_tidptr,
1826 unsigned long, tls)
1827#endif
1828{
1829 return _do_fork(clone_flags, newsp, 0, parent_tidptr, child_tidptr, tls);
1830}
1831#endif
1832
1833#ifndef ARCH_MIN_MMSTRUCT_ALIGN
1834#define ARCH_MIN_MMSTRUCT_ALIGN 0
1835#endif
1836
1837static void sighand_ctor(void *data)
1838{
1839 struct sighand_struct *sighand = data;
1840
1841 spin_lock_init(&sighand->siglock);
1842 init_waitqueue_head(&sighand->signalfd_wqh);
1843}
1844
1845void __init proc_caches_init(void)
1846{
1847 sighand_cachep = kmem_cache_create("sighand_cache",
1848 sizeof(struct sighand_struct), 0,
1849 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU|
1850 SLAB_NOTRACK|SLAB_ACCOUNT, sighand_ctor);
1851 signal_cachep = kmem_cache_create("signal_cache",
1852 sizeof(struct signal_struct), 0,
1853 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT,
1854 NULL);
1855 files_cachep = kmem_cache_create("files_cache",
1856 sizeof(struct files_struct), 0,
1857 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT,
1858 NULL);
1859 fs_cachep = kmem_cache_create("fs_cache",
1860 sizeof(struct fs_struct), 0,
1861 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT,
1862 NULL);
1863 /*
1864 * FIXME! The "sizeof(struct mm_struct)" currently includes the
1865 * whole struct cpumask for the OFFSTACK case. We could change
1866 * this to *only* allocate as much of it as required by the
1867 * maximum number of CPU's we can ever have. The cpumask_allocation
1868 * is at the end of the structure, exactly for that reason.
1869 */
1870 mm_cachep = kmem_cache_create("mm_struct",
1871 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1872 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT,
1873 NULL);
1874 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT);
1875 mmap_init();
1876 nsproxy_cache_init();
1877}
1878
1879/*
1880 * Check constraints on flags passed to the unshare system call.
1881 */
1882static int check_unshare_flags(unsigned long unshare_flags)
1883{
1884 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1885 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1886 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET|
1887 CLONE_NEWUSER|CLONE_NEWPID))
1888 return -EINVAL;
1889 /*
1890 * Not implemented, but pretend it works if there is nothing
1891 * to unshare. Note that unsharing the address space or the
1892 * signal handlers also need to unshare the signal queues (aka
1893 * CLONE_THREAD).
1894 */
1895 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
1896 if (!thread_group_empty(current))
1897 return -EINVAL;
1898 }
1899 if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) {
1900 if (atomic_read(&current->sighand->count) > 1)
1901 return -EINVAL;
1902 }
1903 if (unshare_flags & CLONE_VM) {
1904 if (!current_is_single_threaded())
1905 return -EINVAL;
1906 }
1907
1908 return 0;
1909}
1910
1911/*
1912 * Unshare the filesystem structure if it is being shared
1913 */
1914static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1915{
1916 struct fs_struct *fs = current->fs;
1917
1918 if (!(unshare_flags & CLONE_FS) || !fs)
1919 return 0;
1920
1921 /* don't need lock here; in the worst case we'll do useless copy */
1922 if (fs->users == 1)
1923 return 0;
1924
1925 *new_fsp = copy_fs_struct(fs);
1926 if (!*new_fsp)
1927 return -ENOMEM;
1928
1929 return 0;
1930}
1931
1932/*
1933 * Unshare file descriptor table if it is being shared
1934 */
1935static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1936{
1937 struct files_struct *fd = current->files;
1938 int error = 0;
1939
1940 if ((unshare_flags & CLONE_FILES) &&
1941 (fd && atomic_read(&fd->count) > 1)) {
1942 *new_fdp = dup_fd(fd, &error);
1943 if (!*new_fdp)
1944 return error;
1945 }
1946
1947 return 0;
1948}
1949
1950/*
1951 * unshare allows a process to 'unshare' part of the process
1952 * context which was originally shared using clone. copy_*
1953 * functions used by do_fork() cannot be used here directly
1954 * because they modify an inactive task_struct that is being
1955 * constructed. Here we are modifying the current, active,
1956 * task_struct.
1957 */
1958SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
1959{
1960 struct fs_struct *fs, *new_fs = NULL;
1961 struct files_struct *fd, *new_fd = NULL;
1962 struct cred *new_cred = NULL;
1963 struct nsproxy *new_nsproxy = NULL;
1964 int do_sysvsem = 0;
1965 int err;
1966
1967 /*
1968 * If unsharing a user namespace must also unshare the thread group
1969 * and unshare the filesystem root and working directories.
1970 */
1971 if (unshare_flags & CLONE_NEWUSER)
1972 unshare_flags |= CLONE_THREAD | CLONE_FS;
1973 /*
1974 * If unsharing vm, must also unshare signal handlers.
1975 */
1976 if (unshare_flags & CLONE_VM)
1977 unshare_flags |= CLONE_SIGHAND;
1978 /*
1979 * If unsharing a signal handlers, must also unshare the signal queues.
1980 */
1981 if (unshare_flags & CLONE_SIGHAND)
1982 unshare_flags |= CLONE_THREAD;
1983 /*
1984 * If unsharing namespace, must also unshare filesystem information.
1985 */
1986 if (unshare_flags & CLONE_NEWNS)
1987 unshare_flags |= CLONE_FS;
1988
1989 err = check_unshare_flags(unshare_flags);
1990 if (err)
1991 goto bad_unshare_out;
1992 /*
1993 * CLONE_NEWIPC must also detach from the undolist: after switching
1994 * to a new ipc namespace, the semaphore arrays from the old
1995 * namespace are unreachable.
1996 */
1997 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1998 do_sysvsem = 1;
1999 err = unshare_fs(unshare_flags, &new_fs);
2000 if (err)
2001 goto bad_unshare_out;
2002 err = unshare_fd(unshare_flags, &new_fd);
2003 if (err)
2004 goto bad_unshare_cleanup_fs;
2005 err = unshare_userns(unshare_flags, &new_cred);
2006 if (err)
2007 goto bad_unshare_cleanup_fd;
2008 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
2009 new_cred, new_fs);
2010 if (err)
2011 goto bad_unshare_cleanup_cred;
2012
2013 if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
2014 if (do_sysvsem) {
2015 /*
2016 * CLONE_SYSVSEM is equivalent to sys_exit().
2017 */
2018 exit_sem(current);
2019 }
2020 if (unshare_flags & CLONE_NEWIPC) {
2021 /* Orphan segments in old ns (see sem above). */
2022 exit_shm(current);
2023 shm_init_task(current);
2024 }
2025
2026 if (new_nsproxy)
2027 switch_task_namespaces(current, new_nsproxy);
2028
2029 task_lock(current);
2030
2031 if (new_fs) {
2032 fs = current->fs;
2033 spin_lock(&fs->lock);
2034 current->fs = new_fs;
2035 if (--fs->users)
2036 new_fs = NULL;
2037 else
2038 new_fs = fs;
2039 spin_unlock(&fs->lock);
2040 }
2041
2042 if (new_fd) {
2043 fd = current->files;
2044 current->files = new_fd;
2045 new_fd = fd;
2046 }
2047
2048 task_unlock(current);
2049
2050 if (new_cred) {
2051 /* Install the new user namespace */
2052 commit_creds(new_cred);
2053 new_cred = NULL;
2054 }
2055 }
2056
2057bad_unshare_cleanup_cred:
2058 if (new_cred)
2059 put_cred(new_cred);
2060bad_unshare_cleanup_fd:
2061 if (new_fd)
2062 put_files_struct(new_fd);
2063
2064bad_unshare_cleanup_fs:
2065 if (new_fs)
2066 free_fs_struct(new_fs);
2067
2068bad_unshare_out:
2069 return err;
2070}
2071
2072/*
2073 * Helper to unshare the files of the current task.
2074 * We don't want to expose copy_files internals to
2075 * the exec layer of the kernel.
2076 */
2077
2078int unshare_files(struct files_struct **displaced)
2079{
2080 struct task_struct *task = current;
2081 struct files_struct *copy = NULL;
2082 int error;
2083
2084 error = unshare_fd(CLONE_FILES, &copy);
2085 if (error || !copy) {
2086 *displaced = NULL;
2087 return error;
2088 }
2089 *displaced = task->files;
2090 task_lock(task);
2091 task->files = copy;
2092 task_unlock(task);
2093 return 0;
2094}
2095
2096int sysctl_max_threads(struct ctl_table *table, int write,
2097 void __user *buffer, size_t *lenp, loff_t *ppos)
2098{
2099 struct ctl_table t;
2100 int ret;
2101 int threads = max_threads;
2102 int min = MIN_THREADS;
2103 int max = MAX_THREADS;
2104
2105 t = *table;
2106 t.data = &threads;
2107 t.extra1 = &min;
2108 t.extra2 = &max;
2109
2110 ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
2111 if (ret || !write)
2112 return ret;
2113
2114 set_max_threads(threads);
2115
2116 return 0;
2117}