Version:  2.0.40 2.2.26 2.4.37 2.6.39 3.0 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

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

This page was automatically generated by LXR 0.3.1 (source).  •  Linux is a registered trademark of Linus Torvalds  •  Contact us