Version:  2.0.40 2.2.26 2.4.37 3.2 3.3 3.4 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

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

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