Version:  2.0.40 2.2.26 2.4.37 3.1 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

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

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