Version:  2.0.40 2.2.26 2.4.37 3.5 3.6 3.7 3.8 3.9 3.10 3.11 3.12 3.13 3.14 3.15 3.16 3.17 3.18 3.19 4.0 4.1

Linux/kernel/fork.c

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

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