sched: Remove __ARCH_WANT_INTERRUPTS_ON_CTXSW
[linux-3.10.git] / 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/nsproxy.h>
32 #include <linux/capability.h>
33 #include <linux/cpu.h>
34 #include <linux/cgroup.h>
35 #include <linux/security.h>
36 #include <linux/hugetlb.h>
37 #include <linux/seccomp.h>
38 #include <linux/swap.h>
39 #include <linux/syscalls.h>
40 #include <linux/jiffies.h>
41 #include <linux/futex.h>
42 #include <linux/compat.h>
43 #include <linux/kthread.h>
44 #include <linux/task_io_accounting_ops.h>
45 #include <linux/rcupdate.h>
46 #include <linux/ptrace.h>
47 #include <linux/mount.h>
48 #include <linux/audit.h>
49 #include <linux/memcontrol.h>
50 #include <linux/ftrace.h>
51 #include <linux/proc_fs.h>
52 #include <linux/profile.h>
53 #include <linux/rmap.h>
54 #include <linux/ksm.h>
55 #include <linux/acct.h>
56 #include <linux/tsacct_kern.h>
57 #include <linux/cn_proc.h>
58 #include <linux/freezer.h>
59 #include <linux/delayacct.h>
60 #include <linux/taskstats_kern.h>
61 #include <linux/random.h>
62 #include <linux/tty.h>
63 #include <linux/blkdev.h>
64 #include <linux/fs_struct.h>
65 #include <linux/magic.h>
66 #include <linux/perf_event.h>
67 #include <linux/posix-timers.h>
68 #include <linux/user-return-notifier.h>
69 #include <linux/oom.h>
70 #include <linux/khugepaged.h>
71 #include <linux/signalfd.h>
72 #include <linux/uprobes.h>
73
74 #include <asm/pgtable.h>
75 #include <asm/pgalloc.h>
76 #include <asm/uaccess.h>
77 #include <asm/mmu_context.h>
78 #include <asm/cacheflush.h>
79 #include <asm/tlbflush.h>
80
81 #include <trace/events/sched.h>
82
83 #define CREATE_TRACE_POINTS
84 #include <trace/events/task.h>
85
86 /*
87  * Protected counters by write_lock_irq(&tasklist_lock)
88  */
89 unsigned long total_forks;      /* Handle normal Linux uptimes. */
90 int nr_threads;                 /* The idle threads do not count.. */
91
92 int max_threads;                /* tunable limit on nr_threads */
93
94 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
95
96 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
97
98 #ifdef CONFIG_PROVE_RCU
99 int lockdep_tasklist_lock_is_held(void)
100 {
101         return lockdep_is_held(&tasklist_lock);
102 }
103 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
104 #endif /* #ifdef CONFIG_PROVE_RCU */
105
106 int nr_processes(void)
107 {
108         int cpu;
109         int total = 0;
110
111         for_each_possible_cpu(cpu)
112                 total += per_cpu(process_counts, cpu);
113
114         return total;
115 }
116
117 void __weak arch_release_task_struct(struct task_struct *tsk)
118 {
119 }
120
121 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
122 static struct kmem_cache *task_struct_cachep;
123
124 static inline struct task_struct *alloc_task_struct_node(int node)
125 {
126         return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node);
127 }
128
129 static inline void free_task_struct(struct task_struct *tsk)
130 {
131         kmem_cache_free(task_struct_cachep, tsk);
132 }
133 #endif
134
135 void __weak arch_release_thread_info(struct thread_info *ti)
136 {
137 }
138
139 #ifndef CONFIG_ARCH_THREAD_INFO_ALLOCATOR
140
141 /*
142  * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
143  * kmemcache based allocator.
144  */
145 # if THREAD_SIZE >= PAGE_SIZE
146 static struct thread_info *alloc_thread_info_node(struct task_struct *tsk,
147                                                   int node)
148 {
149         struct page *page = alloc_pages_node(node, THREADINFO_GFP,
150                                              THREAD_SIZE_ORDER);
151
152         return page ? page_address(page) : NULL;
153 }
154
155 static inline void free_thread_info(struct thread_info *ti)
156 {
157         free_pages((unsigned long)ti, THREAD_SIZE_ORDER);
158 }
159 # else
160 static struct kmem_cache *thread_info_cache;
161
162 static struct thread_info *alloc_thread_info_node(struct task_struct *tsk,
163                                                   int node)
164 {
165         return kmem_cache_alloc_node(thread_info_cache, THREADINFO_GFP, node);
166 }
167
168 static void free_thread_info(struct thread_info *ti)
169 {
170         kmem_cache_free(thread_info_cache, ti);
171 }
172
173 void thread_info_cache_init(void)
174 {
175         thread_info_cache = kmem_cache_create("thread_info", THREAD_SIZE,
176                                               THREAD_SIZE, 0, NULL);
177         BUG_ON(thread_info_cache == NULL);
178 }
179 # endif
180 #endif
181
182 /* SLAB cache for signal_struct structures (tsk->signal) */
183 static struct kmem_cache *signal_cachep;
184
185 /* SLAB cache for sighand_struct structures (tsk->sighand) */
186 struct kmem_cache *sighand_cachep;
187
188 /* SLAB cache for files_struct structures (tsk->files) */
189 struct kmem_cache *files_cachep;
190
191 /* SLAB cache for fs_struct structures (tsk->fs) */
192 struct kmem_cache *fs_cachep;
193
194 /* SLAB cache for vm_area_struct structures */
195 struct kmem_cache *vm_area_cachep;
196
197 /* SLAB cache for mm_struct structures (tsk->mm) */
198 static struct kmem_cache *mm_cachep;
199
200 static void account_kernel_stack(struct thread_info *ti, int account)
201 {
202         struct zone *zone = page_zone(virt_to_page(ti));
203
204         mod_zone_page_state(zone, NR_KERNEL_STACK, account);
205 }
206
207 void free_task(struct task_struct *tsk)
208 {
209         account_kernel_stack(tsk->stack, -1);
210         arch_release_thread_info(tsk->stack);
211         free_thread_info(tsk->stack);
212         rt_mutex_debug_task_free(tsk);
213         ftrace_graph_exit_task(tsk);
214         put_seccomp_filter(tsk);
215         arch_release_task_struct(tsk);
216         free_task_struct(tsk);
217 }
218 EXPORT_SYMBOL(free_task);
219
220 static inline void free_signal_struct(struct signal_struct *sig)
221 {
222         taskstats_tgid_free(sig);
223         sched_autogroup_exit(sig);
224         kmem_cache_free(signal_cachep, sig);
225 }
226
227 static inline void put_signal_struct(struct signal_struct *sig)
228 {
229         if (atomic_dec_and_test(&sig->sigcnt))
230                 free_signal_struct(sig);
231 }
232
233 void __put_task_struct(struct task_struct *tsk)
234 {
235         WARN_ON(!tsk->exit_state);
236         WARN_ON(atomic_read(&tsk->usage));
237         WARN_ON(tsk == current);
238
239         security_task_free(tsk);
240         exit_creds(tsk);
241         delayacct_tsk_free(tsk);
242         put_signal_struct(tsk->signal);
243
244         if (!profile_handoff_task(tsk))
245                 free_task(tsk);
246 }
247 EXPORT_SYMBOL_GPL(__put_task_struct);
248
249 void __init __weak arch_task_cache_init(void) { }
250
251 void __init fork_init(unsigned long mempages)
252 {
253 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
254 #ifndef ARCH_MIN_TASKALIGN
255 #define ARCH_MIN_TASKALIGN      L1_CACHE_BYTES
256 #endif
257         /* create a slab on which task_structs can be allocated */
258         task_struct_cachep =
259                 kmem_cache_create("task_struct", sizeof(struct task_struct),
260                         ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL);
261 #endif
262
263         /* do the arch specific task caches init */
264         arch_task_cache_init();
265
266         /*
267          * The default maximum number of threads is set to a safe
268          * value: the thread structures can take up at most half
269          * of memory.
270          */
271         max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
272
273         /*
274          * we need to allow at least 20 threads to boot a system
275          */
276         if (max_threads < 20)
277                 max_threads = 20;
278
279         init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
280         init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
281         init_task.signal->rlim[RLIMIT_SIGPENDING] =
282                 init_task.signal->rlim[RLIMIT_NPROC];
283 }
284
285 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst,
286                                                struct task_struct *src)
287 {
288         *dst = *src;
289         return 0;
290 }
291
292 static struct task_struct *dup_task_struct(struct task_struct *orig)
293 {
294         struct task_struct *tsk;
295         struct thread_info *ti;
296         unsigned long *stackend;
297         int node = tsk_fork_get_node(orig);
298         int err;
299
300         tsk = alloc_task_struct_node(node);
301         if (!tsk)
302                 return NULL;
303
304         ti = alloc_thread_info_node(tsk, node);
305         if (!ti)
306                 goto free_tsk;
307
308         err = arch_dup_task_struct(tsk, orig);
309         if (err)
310                 goto free_ti;
311
312         tsk->stack = ti;
313
314         setup_thread_stack(tsk, orig);
315         clear_user_return_notifier(tsk);
316         clear_tsk_need_resched(tsk);
317         stackend = end_of_stack(tsk);
318         *stackend = STACK_END_MAGIC;    /* for overflow detection */
319
320 #ifdef CONFIG_CC_STACKPROTECTOR
321         tsk->stack_canary = get_random_int();
322 #endif
323
324         /*
325          * One for us, one for whoever does the "release_task()" (usually
326          * parent)
327          */
328         atomic_set(&tsk->usage, 2);
329 #ifdef CONFIG_BLK_DEV_IO_TRACE
330         tsk->btrace_seq = 0;
331 #endif
332         tsk->splice_pipe = NULL;
333
334         account_kernel_stack(ti, 1);
335
336         return tsk;
337
338 free_ti:
339         free_thread_info(ti);
340 free_tsk:
341         free_task_struct(tsk);
342         return NULL;
343 }
344
345 #ifdef CONFIG_MMU
346 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
347 {
348         struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
349         struct rb_node **rb_link, *rb_parent;
350         int retval;
351         unsigned long charge;
352         struct mempolicy *pol;
353
354         down_write(&oldmm->mmap_sem);
355         flush_cache_dup_mm(oldmm);
356         /*
357          * Not linked in yet - no deadlock potential:
358          */
359         down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
360
361         mm->locked_vm = 0;
362         mm->mmap = NULL;
363         mm->mmap_cache = NULL;
364         mm->free_area_cache = oldmm->mmap_base;
365         mm->cached_hole_size = ~0UL;
366         mm->map_count = 0;
367         cpumask_clear(mm_cpumask(mm));
368         mm->mm_rb = RB_ROOT;
369         rb_link = &mm->mm_rb.rb_node;
370         rb_parent = NULL;
371         pprev = &mm->mmap;
372         retval = ksm_fork(mm, oldmm);
373         if (retval)
374                 goto out;
375         retval = khugepaged_fork(mm, oldmm);
376         if (retval)
377                 goto out;
378
379         prev = NULL;
380         for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
381                 struct file *file;
382
383                 if (mpnt->vm_flags & VM_DONTCOPY) {
384                         vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
385                                                         -vma_pages(mpnt));
386                         continue;
387                 }
388                 charge = 0;
389                 if (mpnt->vm_flags & VM_ACCOUNT) {
390                         unsigned long len = vma_pages(mpnt);
391
392                         if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
393                                 goto fail_nomem;
394                         charge = len;
395                 }
396                 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
397                 if (!tmp)
398                         goto fail_nomem;
399                 *tmp = *mpnt;
400                 INIT_LIST_HEAD(&tmp->anon_vma_chain);
401                 pol = mpol_dup(vma_policy(mpnt));
402                 retval = PTR_ERR(pol);
403                 if (IS_ERR(pol))
404                         goto fail_nomem_policy;
405                 vma_set_policy(tmp, pol);
406                 tmp->vm_mm = mm;
407                 if (anon_vma_fork(tmp, mpnt))
408                         goto fail_nomem_anon_vma_fork;
409                 tmp->vm_flags &= ~VM_LOCKED;
410                 tmp->vm_next = tmp->vm_prev = NULL;
411                 file = tmp->vm_file;
412                 if (file) {
413                         struct inode *inode = file->f_path.dentry->d_inode;
414                         struct address_space *mapping = file->f_mapping;
415
416                         get_file(file);
417                         if (tmp->vm_flags & VM_DENYWRITE)
418                                 atomic_dec(&inode->i_writecount);
419                         mutex_lock(&mapping->i_mmap_mutex);
420                         if (tmp->vm_flags & VM_SHARED)
421                                 mapping->i_mmap_writable++;
422                         flush_dcache_mmap_lock(mapping);
423                         /* insert tmp into the share list, just after mpnt */
424                         vma_prio_tree_add(tmp, mpnt);
425                         flush_dcache_mmap_unlock(mapping);
426                         mutex_unlock(&mapping->i_mmap_mutex);
427                 }
428
429                 /*
430                  * Clear hugetlb-related page reserves for children. This only
431                  * affects MAP_PRIVATE mappings. Faults generated by the child
432                  * are not guaranteed to succeed, even if read-only
433                  */
434                 if (is_vm_hugetlb_page(tmp))
435                         reset_vma_resv_huge_pages(tmp);
436
437                 /*
438                  * Link in the new vma and copy the page table entries.
439                  */
440                 *pprev = tmp;
441                 pprev = &tmp->vm_next;
442                 tmp->vm_prev = prev;
443                 prev = tmp;
444
445                 __vma_link_rb(mm, tmp, rb_link, rb_parent);
446                 rb_link = &tmp->vm_rb.rb_right;
447                 rb_parent = &tmp->vm_rb;
448
449                 mm->map_count++;
450                 retval = copy_page_range(mm, oldmm, mpnt);
451
452                 if (tmp->vm_ops && tmp->vm_ops->open)
453                         tmp->vm_ops->open(tmp);
454
455                 if (retval)
456                         goto out;
457
458                 if (file)
459                         uprobe_mmap(tmp);
460         }
461         /* a new mm has just been created */
462         arch_dup_mmap(oldmm, mm);
463         retval = 0;
464 out:
465         up_write(&mm->mmap_sem);
466         flush_tlb_mm(oldmm);
467         up_write(&oldmm->mmap_sem);
468         return retval;
469 fail_nomem_anon_vma_fork:
470         mpol_put(pol);
471 fail_nomem_policy:
472         kmem_cache_free(vm_area_cachep, tmp);
473 fail_nomem:
474         retval = -ENOMEM;
475         vm_unacct_memory(charge);
476         goto out;
477 }
478
479 static inline int mm_alloc_pgd(struct mm_struct *mm)
480 {
481         mm->pgd = pgd_alloc(mm);
482         if (unlikely(!mm->pgd))
483                 return -ENOMEM;
484         return 0;
485 }
486
487 static inline void mm_free_pgd(struct mm_struct *mm)
488 {
489         pgd_free(mm, mm->pgd);
490 }
491 #else
492 #define dup_mmap(mm, oldmm)     (0)
493 #define mm_alloc_pgd(mm)        (0)
494 #define mm_free_pgd(mm)
495 #endif /* CONFIG_MMU */
496
497 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
498
499 #define allocate_mm()   (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
500 #define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))
501
502 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
503
504 static int __init coredump_filter_setup(char *s)
505 {
506         default_dump_filter =
507                 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
508                 MMF_DUMP_FILTER_MASK;
509         return 1;
510 }
511
512 __setup("coredump_filter=", coredump_filter_setup);
513
514 #include <linux/init_task.h>
515
516 static void mm_init_aio(struct mm_struct *mm)
517 {
518 #ifdef CONFIG_AIO
519         spin_lock_init(&mm->ioctx_lock);
520         INIT_HLIST_HEAD(&mm->ioctx_list);
521 #endif
522 }
523
524 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p)
525 {
526         atomic_set(&mm->mm_users, 1);
527         atomic_set(&mm->mm_count, 1);
528         init_rwsem(&mm->mmap_sem);
529         INIT_LIST_HEAD(&mm->mmlist);
530         mm->flags = (current->mm) ?
531                 (current->mm->flags & MMF_INIT_MASK) : default_dump_filter;
532         mm->core_state = NULL;
533         mm->nr_ptes = 0;
534         memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
535         spin_lock_init(&mm->page_table_lock);
536         mm->free_area_cache = TASK_UNMAPPED_BASE;
537         mm->cached_hole_size = ~0UL;
538         mm_init_aio(mm);
539         mm_init_owner(mm, p);
540
541         if (likely(!mm_alloc_pgd(mm))) {
542                 mm->def_flags = 0;
543                 mmu_notifier_mm_init(mm);
544                 return mm;
545         }
546
547         free_mm(mm);
548         return NULL;
549 }
550
551 static void check_mm(struct mm_struct *mm)
552 {
553         int i;
554
555         for (i = 0; i < NR_MM_COUNTERS; i++) {
556                 long x = atomic_long_read(&mm->rss_stat.count[i]);
557
558                 if (unlikely(x))
559                         printk(KERN_ALERT "BUG: Bad rss-counter state "
560                                           "mm:%p idx:%d val:%ld\n", mm, i, x);
561         }
562
563 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
564         VM_BUG_ON(mm->pmd_huge_pte);
565 #endif
566 }
567
568 /*
569  * Allocate and initialize an mm_struct.
570  */
571 struct mm_struct *mm_alloc(void)
572 {
573         struct mm_struct *mm;
574
575         mm = allocate_mm();
576         if (!mm)
577                 return NULL;
578
579         memset(mm, 0, sizeof(*mm));
580         mm_init_cpumask(mm);
581         return mm_init(mm, current);
582 }
583
584 /*
585  * Called when the last reference to the mm
586  * is dropped: either by a lazy thread or by
587  * mmput. Free the page directory and the mm.
588  */
589 void __mmdrop(struct mm_struct *mm)
590 {
591         BUG_ON(mm == &init_mm);
592         mm_free_pgd(mm);
593         destroy_context(mm);
594         mmu_notifier_mm_destroy(mm);
595         check_mm(mm);
596         free_mm(mm);
597 }
598 EXPORT_SYMBOL_GPL(__mmdrop);
599
600 /*
601  * Decrement the use count and release all resources for an mm.
602  */
603 void mmput(struct mm_struct *mm)
604 {
605         might_sleep();
606
607         if (atomic_dec_and_test(&mm->mm_users)) {
608                 uprobe_clear_state(mm);
609                 exit_aio(mm);
610                 ksm_exit(mm);
611                 khugepaged_exit(mm); /* must run before exit_mmap */
612                 exit_mmap(mm);
613                 set_mm_exe_file(mm, NULL);
614                 if (!list_empty(&mm->mmlist)) {
615                         spin_lock(&mmlist_lock);
616                         list_del(&mm->mmlist);
617                         spin_unlock(&mmlist_lock);
618                 }
619                 if (mm->binfmt)
620                         module_put(mm->binfmt->module);
621                 mmdrop(mm);
622         }
623 }
624 EXPORT_SYMBOL_GPL(mmput);
625
626 /*
627  * We added or removed a vma mapping the executable. The vmas are only mapped
628  * during exec and are not mapped with the mmap system call.
629  * Callers must hold down_write() on the mm's mmap_sem for these
630  */
631 void added_exe_file_vma(struct mm_struct *mm)
632 {
633         mm->num_exe_file_vmas++;
634 }
635
636 void removed_exe_file_vma(struct mm_struct *mm)
637 {
638         mm->num_exe_file_vmas--;
639         if ((mm->num_exe_file_vmas == 0) && mm->exe_file) {
640                 fput(mm->exe_file);
641                 mm->exe_file = NULL;
642         }
643
644 }
645
646 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
647 {
648         if (new_exe_file)
649                 get_file(new_exe_file);
650         if (mm->exe_file)
651                 fput(mm->exe_file);
652         mm->exe_file = new_exe_file;
653         mm->num_exe_file_vmas = 0;
654 }
655
656 struct file *get_mm_exe_file(struct mm_struct *mm)
657 {
658         struct file *exe_file;
659
660         /* We need mmap_sem to protect against races with removal of
661          * VM_EXECUTABLE vmas */
662         down_read(&mm->mmap_sem);
663         exe_file = mm->exe_file;
664         if (exe_file)
665                 get_file(exe_file);
666         up_read(&mm->mmap_sem);
667         return exe_file;
668 }
669
670 static void dup_mm_exe_file(struct mm_struct *oldmm, struct mm_struct *newmm)
671 {
672         /* It's safe to write the exe_file pointer without exe_file_lock because
673          * this is called during fork when the task is not yet in /proc */
674         newmm->exe_file = get_mm_exe_file(oldmm);
675 }
676
677 /**
678  * get_task_mm - acquire a reference to the task's mm
679  *
680  * Returns %NULL if the task has no mm.  Checks PF_KTHREAD (meaning
681  * this kernel workthread has transiently adopted a user mm with use_mm,
682  * to do its AIO) is not set and if so returns a reference to it, after
683  * bumping up the use count.  User must release the mm via mmput()
684  * after use.  Typically used by /proc and ptrace.
685  */
686 struct mm_struct *get_task_mm(struct task_struct *task)
687 {
688         struct mm_struct *mm;
689
690         task_lock(task);
691         mm = task->mm;
692         if (mm) {
693                 if (task->flags & PF_KTHREAD)
694                         mm = NULL;
695                 else
696                         atomic_inc(&mm->mm_users);
697         }
698         task_unlock(task);
699         return mm;
700 }
701 EXPORT_SYMBOL_GPL(get_task_mm);
702
703 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
704 {
705         struct mm_struct *mm;
706         int err;
707
708         err =  mutex_lock_killable(&task->signal->cred_guard_mutex);
709         if (err)
710                 return ERR_PTR(err);
711
712         mm = get_task_mm(task);
713         if (mm && mm != current->mm &&
714                         !ptrace_may_access(task, mode)) {
715                 mmput(mm);
716                 mm = ERR_PTR(-EACCES);
717         }
718         mutex_unlock(&task->signal->cred_guard_mutex);
719
720         return mm;
721 }
722
723 static void complete_vfork_done(struct task_struct *tsk)
724 {
725         struct completion *vfork;
726
727         task_lock(tsk);
728         vfork = tsk->vfork_done;
729         if (likely(vfork)) {
730                 tsk->vfork_done = NULL;
731                 complete(vfork);
732         }
733         task_unlock(tsk);
734 }
735
736 static int wait_for_vfork_done(struct task_struct *child,
737                                 struct completion *vfork)
738 {
739         int killed;
740
741         freezer_do_not_count();
742         killed = wait_for_completion_killable(vfork);
743         freezer_count();
744
745         if (killed) {
746                 task_lock(child);
747                 child->vfork_done = NULL;
748                 task_unlock(child);
749         }
750
751         put_task_struct(child);
752         return killed;
753 }
754
755 /* Please note the differences between mmput and mm_release.
756  * mmput is called whenever we stop holding onto a mm_struct,
757  * error success whatever.
758  *
759  * mm_release is called after a mm_struct has been removed
760  * from the current process.
761  *
762  * This difference is important for error handling, when we
763  * only half set up a mm_struct for a new process and need to restore
764  * the old one.  Because we mmput the new mm_struct before
765  * restoring the old one. . .
766  * Eric Biederman 10 January 1998
767  */
768 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
769 {
770         /* Get rid of any futexes when releasing the mm */
771 #ifdef CONFIG_FUTEX
772         if (unlikely(tsk->robust_list)) {
773                 exit_robust_list(tsk);
774                 tsk->robust_list = NULL;
775         }
776 #ifdef CONFIG_COMPAT
777         if (unlikely(tsk->compat_robust_list)) {
778                 compat_exit_robust_list(tsk);
779                 tsk->compat_robust_list = NULL;
780         }
781 #endif
782         if (unlikely(!list_empty(&tsk->pi_state_list)))
783                 exit_pi_state_list(tsk);
784 #endif
785
786         uprobe_free_utask(tsk);
787
788         /* Get rid of any cached register state */
789         deactivate_mm(tsk, mm);
790
791         /*
792          * If we're exiting normally, clear a user-space tid field if
793          * requested.  We leave this alone when dying by signal, to leave
794          * the value intact in a core dump, and to save the unnecessary
795          * trouble, say, a killed vfork parent shouldn't touch this mm.
796          * Userland only wants this done for a sys_exit.
797          */
798         if (tsk->clear_child_tid) {
799                 if (!(tsk->flags & PF_SIGNALED) &&
800                     atomic_read(&mm->mm_users) > 1) {
801                         /*
802                          * We don't check the error code - if userspace has
803                          * not set up a proper pointer then tough luck.
804                          */
805                         put_user(0, tsk->clear_child_tid);
806                         sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
807                                         1, NULL, NULL, 0);
808                 }
809                 tsk->clear_child_tid = NULL;
810         }
811
812         /*
813          * All done, finally we can wake up parent and return this mm to him.
814          * Also kthread_stop() uses this completion for synchronization.
815          */
816         if (tsk->vfork_done)
817                 complete_vfork_done(tsk);
818 }
819
820 /*
821  * Allocate a new mm structure and copy contents from the
822  * mm structure of the passed in task structure.
823  */
824 struct mm_struct *dup_mm(struct task_struct *tsk)
825 {
826         struct mm_struct *mm, *oldmm = current->mm;
827         int err;
828
829         if (!oldmm)
830                 return NULL;
831
832         mm = allocate_mm();
833         if (!mm)
834                 goto fail_nomem;
835
836         memcpy(mm, oldmm, sizeof(*mm));
837         mm_init_cpumask(mm);
838
839 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
840         mm->pmd_huge_pte = NULL;
841 #endif
842         uprobe_reset_state(mm);
843
844         if (!mm_init(mm, tsk))
845                 goto fail_nomem;
846
847         if (init_new_context(tsk, mm))
848                 goto fail_nocontext;
849
850         dup_mm_exe_file(oldmm, mm);
851
852         err = dup_mmap(mm, oldmm);
853         if (err)
854                 goto free_pt;
855
856         mm->hiwater_rss = get_mm_rss(mm);
857         mm->hiwater_vm = mm->total_vm;
858
859         if (mm->binfmt && !try_module_get(mm->binfmt->module))
860                 goto free_pt;
861
862         return mm;
863
864 free_pt:
865         /* don't put binfmt in mmput, we haven't got module yet */
866         mm->binfmt = NULL;
867         mmput(mm);
868
869 fail_nomem:
870         return NULL;
871
872 fail_nocontext:
873         /*
874          * If init_new_context() failed, we cannot use mmput() to free the mm
875          * because it calls destroy_context()
876          */
877         mm_free_pgd(mm);
878         free_mm(mm);
879         return NULL;
880 }
881
882 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
883 {
884         struct mm_struct *mm, *oldmm;
885         int retval;
886
887         tsk->min_flt = tsk->maj_flt = 0;
888         tsk->nvcsw = tsk->nivcsw = 0;
889 #ifdef CONFIG_DETECT_HUNG_TASK
890         tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
891 #endif
892
893         tsk->mm = NULL;
894         tsk->active_mm = NULL;
895
896         /*
897          * Are we cloning a kernel thread?
898          *
899          * We need to steal a active VM for that..
900          */
901         oldmm = current->mm;
902         if (!oldmm)
903                 return 0;
904
905         if (clone_flags & CLONE_VM) {
906                 atomic_inc(&oldmm->mm_users);
907                 mm = oldmm;
908                 goto good_mm;
909         }
910
911         retval = -ENOMEM;
912         mm = dup_mm(tsk);
913         if (!mm)
914                 goto fail_nomem;
915
916 good_mm:
917         tsk->mm = mm;
918         tsk->active_mm = mm;
919         return 0;
920
921 fail_nomem:
922         return retval;
923 }
924
925 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
926 {
927         struct fs_struct *fs = current->fs;
928         if (clone_flags & CLONE_FS) {
929                 /* tsk->fs is already what we want */
930                 spin_lock(&fs->lock);
931                 if (fs->in_exec) {
932                         spin_unlock(&fs->lock);
933                         return -EAGAIN;
934                 }
935                 fs->users++;
936                 spin_unlock(&fs->lock);
937                 return 0;
938         }
939         tsk->fs = copy_fs_struct(fs);
940         if (!tsk->fs)
941                 return -ENOMEM;
942         return 0;
943 }
944
945 static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
946 {
947         struct files_struct *oldf, *newf;
948         int error = 0;
949
950         /*
951          * A background process may not have any files ...
952          */
953         oldf = current->files;
954         if (!oldf)
955                 goto out;
956
957         if (clone_flags & CLONE_FILES) {
958                 atomic_inc(&oldf->count);
959                 goto out;
960         }
961
962         newf = dup_fd(oldf, &error);
963         if (!newf)
964                 goto out;
965
966         tsk->files = newf;
967         error = 0;
968 out:
969         return error;
970 }
971
972 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
973 {
974 #ifdef CONFIG_BLOCK
975         struct io_context *ioc = current->io_context;
976         struct io_context *new_ioc;
977
978         if (!ioc)
979                 return 0;
980         /*
981          * Share io context with parent, if CLONE_IO is set
982          */
983         if (clone_flags & CLONE_IO) {
984                 ioc_task_link(ioc);
985                 tsk->io_context = ioc;
986         } else if (ioprio_valid(ioc->ioprio)) {
987                 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE);
988                 if (unlikely(!new_ioc))
989                         return -ENOMEM;
990
991                 new_ioc->ioprio = ioc->ioprio;
992                 put_io_context(new_ioc);
993         }
994 #endif
995         return 0;
996 }
997
998 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
999 {
1000         struct sighand_struct *sig;
1001
1002         if (clone_flags & CLONE_SIGHAND) {
1003                 atomic_inc(&current->sighand->count);
1004                 return 0;
1005         }
1006         sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1007         rcu_assign_pointer(tsk->sighand, sig);
1008         if (!sig)
1009                 return -ENOMEM;
1010         atomic_set(&sig->count, 1);
1011         memcpy(sig->action, current->sighand->action, sizeof(sig->action));
1012         return 0;
1013 }
1014
1015 void __cleanup_sighand(struct sighand_struct *sighand)
1016 {
1017         if (atomic_dec_and_test(&sighand->count)) {
1018                 signalfd_cleanup(sighand);
1019                 kmem_cache_free(sighand_cachep, sighand);
1020         }
1021 }
1022
1023
1024 /*
1025  * Initialize POSIX timer handling for a thread group.
1026  */
1027 static void posix_cpu_timers_init_group(struct signal_struct *sig)
1028 {
1029         unsigned long cpu_limit;
1030
1031         /* Thread group counters. */
1032         thread_group_cputime_init(sig);
1033
1034         cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1035         if (cpu_limit != RLIM_INFINITY) {
1036                 sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit);
1037                 sig->cputimer.running = 1;
1038         }
1039
1040         /* The timer lists. */
1041         INIT_LIST_HEAD(&sig->cpu_timers[0]);
1042         INIT_LIST_HEAD(&sig->cpu_timers[1]);
1043         INIT_LIST_HEAD(&sig->cpu_timers[2]);
1044 }
1045
1046 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
1047 {
1048         struct signal_struct *sig;
1049
1050         if (clone_flags & CLONE_THREAD)
1051                 return 0;
1052
1053         sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
1054         tsk->signal = sig;
1055         if (!sig)
1056                 return -ENOMEM;
1057
1058         sig->nr_threads = 1;
1059         atomic_set(&sig->live, 1);
1060         atomic_set(&sig->sigcnt, 1);
1061         init_waitqueue_head(&sig->wait_chldexit);
1062         if (clone_flags & CLONE_NEWPID)
1063                 sig->flags |= SIGNAL_UNKILLABLE;
1064         sig->curr_target = tsk;
1065         init_sigpending(&sig->shared_pending);
1066         INIT_LIST_HEAD(&sig->posix_timers);
1067
1068         hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1069         sig->real_timer.function = it_real_fn;
1070
1071         task_lock(current->group_leader);
1072         memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
1073         task_unlock(current->group_leader);
1074
1075         posix_cpu_timers_init_group(sig);
1076
1077         tty_audit_fork(sig);
1078         sched_autogroup_fork(sig);
1079
1080 #ifdef CONFIG_CGROUPS
1081         init_rwsem(&sig->group_rwsem);
1082 #endif
1083
1084         sig->oom_adj = current->signal->oom_adj;
1085         sig->oom_score_adj = current->signal->oom_score_adj;
1086         sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1087
1088         sig->has_child_subreaper = current->signal->has_child_subreaper ||
1089                                    current->signal->is_child_subreaper;
1090
1091         mutex_init(&sig->cred_guard_mutex);
1092
1093         return 0;
1094 }
1095
1096 static void copy_flags(unsigned long clone_flags, struct task_struct *p)
1097 {
1098         unsigned long new_flags = p->flags;
1099
1100         new_flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER);
1101         new_flags |= PF_FORKNOEXEC;
1102         p->flags = new_flags;
1103 }
1104
1105 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1106 {
1107         current->clear_child_tid = tidptr;
1108
1109         return task_pid_vnr(current);
1110 }
1111
1112 static void rt_mutex_init_task(struct task_struct *p)
1113 {
1114         raw_spin_lock_init(&p->pi_lock);
1115 #ifdef CONFIG_RT_MUTEXES
1116         plist_head_init(&p->pi_waiters);
1117         p->pi_blocked_on = NULL;
1118 #endif
1119 }
1120
1121 #ifdef CONFIG_MM_OWNER
1122 void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
1123 {
1124         mm->owner = p;
1125 }
1126 #endif /* CONFIG_MM_OWNER */
1127
1128 /*
1129  * Initialize POSIX timer handling for a single task.
1130  */
1131 static void posix_cpu_timers_init(struct task_struct *tsk)
1132 {
1133         tsk->cputime_expires.prof_exp = 0;
1134         tsk->cputime_expires.virt_exp = 0;
1135         tsk->cputime_expires.sched_exp = 0;
1136         INIT_LIST_HEAD(&tsk->cpu_timers[0]);
1137         INIT_LIST_HEAD(&tsk->cpu_timers[1]);
1138         INIT_LIST_HEAD(&tsk->cpu_timers[2]);
1139 }
1140
1141 /*
1142  * This creates a new process as a copy of the old one,
1143  * but does not actually start it yet.
1144  *
1145  * It copies the registers, and all the appropriate
1146  * parts of the process environment (as per the clone
1147  * flags). The actual kick-off is left to the caller.
1148  */
1149 static struct task_struct *copy_process(unsigned long clone_flags,
1150                                         unsigned long stack_start,
1151                                         struct pt_regs *regs,
1152                                         unsigned long stack_size,
1153                                         int __user *child_tidptr,
1154                                         struct pid *pid,
1155                                         int trace)
1156 {
1157         int retval;
1158         struct task_struct *p;
1159         int cgroup_callbacks_done = 0;
1160
1161         if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1162                 return ERR_PTR(-EINVAL);
1163
1164         /*
1165          * Thread groups must share signals as well, and detached threads
1166          * can only be started up within the thread group.
1167          */
1168         if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1169                 return ERR_PTR(-EINVAL);
1170
1171         /*
1172          * Shared signal handlers imply shared VM. By way of the above,
1173          * thread groups also imply shared VM. Blocking this case allows
1174          * for various simplifications in other code.
1175          */
1176         if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1177                 return ERR_PTR(-EINVAL);
1178
1179         /*
1180          * Siblings of global init remain as zombies on exit since they are
1181          * not reaped by their parent (swapper). To solve this and to avoid
1182          * multi-rooted process trees, prevent global and container-inits
1183          * from creating siblings.
1184          */
1185         if ((clone_flags & CLONE_PARENT) &&
1186                                 current->signal->flags & SIGNAL_UNKILLABLE)
1187                 return ERR_PTR(-EINVAL);
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 (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
1211                     p->real_cred->user != INIT_USER)
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         p->did_exec = 0;
1233         delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
1234         copy_flags(clone_flags, p);
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
1246         p->prev_utime = p->prev_stime = 0;
1247 #endif
1248 #if defined(SPLIT_RSS_COUNTING)
1249         memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1250 #endif
1251
1252         p->default_timer_slack_ns = current->timer_slack_ns;
1253
1254         task_io_accounting_init(&p->ioac);
1255         acct_clear_integrals(p);
1256
1257         posix_cpu_timers_init(p);
1258
1259         do_posix_clock_monotonic_gettime(&p->start_time);
1260         p->real_start_time = p->start_time;
1261         monotonic_to_bootbased(&p->real_start_time);
1262         p->io_context = NULL;
1263         p->audit_context = NULL;
1264         if (clone_flags & CLONE_THREAD)
1265                 threadgroup_change_begin(current);
1266         cgroup_fork(p);
1267 #ifdef CONFIG_NUMA
1268         p->mempolicy = mpol_dup(p->mempolicy);
1269         if (IS_ERR(p->mempolicy)) {
1270                 retval = PTR_ERR(p->mempolicy);
1271                 p->mempolicy = NULL;
1272                 goto bad_fork_cleanup_cgroup;
1273         }
1274         mpol_fix_fork_child_flag(p);
1275 #endif
1276 #ifdef CONFIG_CPUSETS
1277         p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
1278         p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
1279         seqcount_init(&p->mems_allowed_seq);
1280 #endif
1281 #ifdef CONFIG_TRACE_IRQFLAGS
1282         p->irq_events = 0;
1283         p->hardirqs_enabled = 0;
1284         p->hardirq_enable_ip = 0;
1285         p->hardirq_enable_event = 0;
1286         p->hardirq_disable_ip = _THIS_IP_;
1287         p->hardirq_disable_event = 0;
1288         p->softirqs_enabled = 1;
1289         p->softirq_enable_ip = _THIS_IP_;
1290         p->softirq_enable_event = 0;
1291         p->softirq_disable_ip = 0;
1292         p->softirq_disable_event = 0;
1293         p->hardirq_context = 0;
1294         p->softirq_context = 0;
1295 #endif
1296 #ifdef CONFIG_LOCKDEP
1297         p->lockdep_depth = 0; /* no locks held yet */
1298         p->curr_chain_key = 0;
1299         p->lockdep_recursion = 0;
1300 #endif
1301
1302 #ifdef CONFIG_DEBUG_MUTEXES
1303         p->blocked_on = NULL; /* not blocked yet */
1304 #endif
1305 #ifdef CONFIG_MEMCG
1306         p->memcg_batch.do_batch = 0;
1307         p->memcg_batch.memcg = NULL;
1308 #endif
1309
1310         /* Perform scheduler related setup. Assign this task to a CPU. */
1311         sched_fork(p);
1312
1313         retval = perf_event_init_task(p);
1314         if (retval)
1315                 goto bad_fork_cleanup_policy;
1316         retval = audit_alloc(p);
1317         if (retval)
1318                 goto bad_fork_cleanup_policy;
1319         /* copy all the process information */
1320         retval = copy_semundo(clone_flags, p);
1321         if (retval)
1322                 goto bad_fork_cleanup_audit;
1323         retval = copy_files(clone_flags, p);
1324         if (retval)
1325                 goto bad_fork_cleanup_semundo;
1326         retval = copy_fs(clone_flags, p);
1327         if (retval)
1328                 goto bad_fork_cleanup_files;
1329         retval = copy_sighand(clone_flags, p);
1330         if (retval)
1331                 goto bad_fork_cleanup_fs;
1332         retval = copy_signal(clone_flags, p);
1333         if (retval)
1334                 goto bad_fork_cleanup_sighand;
1335         retval = copy_mm(clone_flags, p);
1336         if (retval)
1337                 goto bad_fork_cleanup_signal;
1338         retval = copy_namespaces(clone_flags, p);
1339         if (retval)
1340                 goto bad_fork_cleanup_mm;
1341         retval = copy_io(clone_flags, p);
1342         if (retval)
1343                 goto bad_fork_cleanup_namespaces;
1344         retval = copy_thread(clone_flags, stack_start, stack_size, p, regs);
1345         if (retval)
1346                 goto bad_fork_cleanup_io;
1347
1348         if (pid != &init_struct_pid) {
1349                 retval = -ENOMEM;
1350                 pid = alloc_pid(p->nsproxy->pid_ns);
1351                 if (!pid)
1352                         goto bad_fork_cleanup_io;
1353         }
1354
1355         p->pid = pid_nr(pid);
1356         p->tgid = p->pid;
1357         if (clone_flags & CLONE_THREAD)
1358                 p->tgid = current->tgid;
1359
1360         p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1361         /*
1362          * Clear TID on mm_release()?
1363          */
1364         p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL;
1365 #ifdef CONFIG_BLOCK
1366         p->plug = NULL;
1367 #endif
1368 #ifdef CONFIG_FUTEX
1369         p->robust_list = NULL;
1370 #ifdef CONFIG_COMPAT
1371         p->compat_robust_list = NULL;
1372 #endif
1373         INIT_LIST_HEAD(&p->pi_state_list);
1374         p->pi_state_cache = NULL;
1375 #endif
1376         uprobe_copy_process(p);
1377         /*
1378          * sigaltstack should be cleared when sharing the same VM
1379          */
1380         if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1381                 p->sas_ss_sp = p->sas_ss_size = 0;
1382
1383         /*
1384          * Syscall tracing and stepping should be turned off in the
1385          * child regardless of CLONE_PTRACE.
1386          */
1387         user_disable_single_step(p);
1388         clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1389 #ifdef TIF_SYSCALL_EMU
1390         clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1391 #endif
1392         clear_all_latency_tracing(p);
1393
1394         /* ok, now we should be set up.. */
1395         if (clone_flags & CLONE_THREAD)
1396                 p->exit_signal = -1;
1397         else if (clone_flags & CLONE_PARENT)
1398                 p->exit_signal = current->group_leader->exit_signal;
1399         else
1400                 p->exit_signal = (clone_flags & CSIGNAL);
1401
1402         p->pdeath_signal = 0;
1403         p->exit_state = 0;
1404
1405         p->nr_dirtied = 0;
1406         p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
1407         p->dirty_paused_when = 0;
1408
1409         /*
1410          * Ok, make it visible to the rest of the system.
1411          * We dont wake it up yet.
1412          */
1413         p->group_leader = p;
1414         INIT_LIST_HEAD(&p->thread_group);
1415         p->task_works = NULL;
1416
1417         /* Now that the task is set up, run cgroup callbacks if
1418          * necessary. We need to run them before the task is visible
1419          * on the tasklist. */
1420         cgroup_fork_callbacks(p);
1421         cgroup_callbacks_done = 1;
1422
1423         /* Need tasklist lock for parent etc handling! */
1424         write_lock_irq(&tasklist_lock);
1425
1426         /* CLONE_PARENT re-uses the old parent */
1427         if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1428                 p->real_parent = current->real_parent;
1429                 p->parent_exec_id = current->parent_exec_id;
1430         } else {
1431                 p->real_parent = current;
1432                 p->parent_exec_id = current->self_exec_id;
1433         }
1434
1435         spin_lock(&current->sighand->siglock);
1436
1437         /*
1438          * Process group and session signals need to be delivered to just the
1439          * parent before the fork or both the parent and the child after the
1440          * fork. Restart if a signal comes in before we add the new process to
1441          * it's process group.
1442          * A fatal signal pending means that current will exit, so the new
1443          * thread can't slip out of an OOM kill (or normal SIGKILL).
1444         */
1445         recalc_sigpending();
1446         if (signal_pending(current)) {
1447                 spin_unlock(&current->sighand->siglock);
1448                 write_unlock_irq(&tasklist_lock);
1449                 retval = -ERESTARTNOINTR;
1450                 goto bad_fork_free_pid;
1451         }
1452
1453         if (clone_flags & CLONE_THREAD) {
1454                 current->signal->nr_threads++;
1455                 atomic_inc(&current->signal->live);
1456                 atomic_inc(&current->signal->sigcnt);
1457                 p->group_leader = current->group_leader;
1458                 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1459         }
1460
1461         if (likely(p->pid)) {
1462                 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
1463
1464                 if (thread_group_leader(p)) {
1465                         if (is_child_reaper(pid))
1466                                 p->nsproxy->pid_ns->child_reaper = p;
1467
1468                         p->signal->leader_pid = pid;
1469                         p->signal->tty = tty_kref_get(current->signal->tty);
1470                         attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
1471                         attach_pid(p, PIDTYPE_SID, task_session(current));
1472                         list_add_tail(&p->sibling, &p->real_parent->children);
1473                         list_add_tail_rcu(&p->tasks, &init_task.tasks);
1474                         __this_cpu_inc(process_counts);
1475                 }
1476                 attach_pid(p, PIDTYPE_PID, pid);
1477                 nr_threads++;
1478         }
1479
1480         total_forks++;
1481         spin_unlock(&current->sighand->siglock);
1482         write_unlock_irq(&tasklist_lock);
1483         proc_fork_connector(p);
1484         cgroup_post_fork(p);
1485         if (clone_flags & CLONE_THREAD)
1486                 threadgroup_change_end(current);
1487         perf_event_fork(p);
1488
1489         trace_task_newtask(p, clone_flags);
1490
1491         return p;
1492
1493 bad_fork_free_pid:
1494         if (pid != &init_struct_pid)
1495                 free_pid(pid);
1496 bad_fork_cleanup_io:
1497         if (p->io_context)
1498                 exit_io_context(p);
1499 bad_fork_cleanup_namespaces:
1500         if (unlikely(clone_flags & CLONE_NEWPID))
1501                 pid_ns_release_proc(p->nsproxy->pid_ns);
1502         exit_task_namespaces(p);
1503 bad_fork_cleanup_mm:
1504         if (p->mm)
1505                 mmput(p->mm);
1506 bad_fork_cleanup_signal:
1507         if (!(clone_flags & CLONE_THREAD))
1508                 free_signal_struct(p->signal);
1509 bad_fork_cleanup_sighand:
1510         __cleanup_sighand(p->sighand);
1511 bad_fork_cleanup_fs:
1512         exit_fs(p); /* blocking */
1513 bad_fork_cleanup_files:
1514         exit_files(p); /* blocking */
1515 bad_fork_cleanup_semundo:
1516         exit_sem(p);
1517 bad_fork_cleanup_audit:
1518         audit_free(p);
1519 bad_fork_cleanup_policy:
1520         perf_event_free_task(p);
1521 #ifdef CONFIG_NUMA
1522         mpol_put(p->mempolicy);
1523 bad_fork_cleanup_cgroup:
1524 #endif
1525         if (clone_flags & CLONE_THREAD)
1526                 threadgroup_change_end(current);
1527         cgroup_exit(p, cgroup_callbacks_done);
1528         delayacct_tsk_free(p);
1529         module_put(task_thread_info(p)->exec_domain->module);
1530 bad_fork_cleanup_count:
1531         atomic_dec(&p->cred->user->processes);
1532         exit_creds(p);
1533 bad_fork_free:
1534         free_task(p);
1535 fork_out:
1536         return ERR_PTR(retval);
1537 }
1538
1539 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1540 {
1541         memset(regs, 0, sizeof(struct pt_regs));
1542         return regs;
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 * __cpuinit fork_idle(int cpu)
1556 {
1557         struct task_struct *task;
1558         struct pt_regs regs;
1559
1560         task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL,
1561                             &init_struct_pid, 0);
1562         if (!IS_ERR(task)) {
1563                 init_idle_pids(task->pids);
1564                 init_idle(task, cpu);
1565         }
1566
1567         return task;
1568 }
1569
1570 /*
1571  *  Ok, this is the main fork-routine.
1572  *
1573  * It copies the process, and if successful kick-starts
1574  * it and waits for it to finish using the VM if required.
1575  */
1576 long do_fork(unsigned long clone_flags,
1577               unsigned long stack_start,
1578               struct pt_regs *regs,
1579               unsigned long stack_size,
1580               int __user *parent_tidptr,
1581               int __user *child_tidptr)
1582 {
1583         struct task_struct *p;
1584         int trace = 0;
1585         long nr;
1586
1587         /*
1588          * Do some preliminary argument and permissions checking before we
1589          * actually start allocating stuff
1590          */
1591         if (clone_flags & CLONE_NEWUSER) {
1592                 if (clone_flags & CLONE_THREAD)
1593                         return -EINVAL;
1594                 /* hopefully this check will go away when userns support is
1595                  * complete
1596                  */
1597                 if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) ||
1598                                 !capable(CAP_SETGID))
1599                         return -EPERM;
1600         }
1601
1602         /*
1603          * Determine whether and which event to report to ptracer.  When
1604          * called from kernel_thread or CLONE_UNTRACED is explicitly
1605          * requested, no event is reported; otherwise, report if the event
1606          * for the type of forking is enabled.
1607          */
1608         if (likely(user_mode(regs)) && !(clone_flags & CLONE_UNTRACED)) {
1609                 if (clone_flags & CLONE_VFORK)
1610                         trace = PTRACE_EVENT_VFORK;
1611                 else if ((clone_flags & CSIGNAL) != SIGCHLD)
1612                         trace = PTRACE_EVENT_CLONE;
1613                 else
1614                         trace = PTRACE_EVENT_FORK;
1615
1616                 if (likely(!ptrace_event_enabled(current, trace)))
1617                         trace = 0;
1618         }
1619
1620         p = copy_process(clone_flags, stack_start, regs, stack_size,
1621                          child_tidptr, NULL, trace);
1622         /*
1623          * Do this prior waking up the new thread - the thread pointer
1624          * might get invalid after that point, if the thread exits quickly.
1625          */
1626         if (!IS_ERR(p)) {
1627                 struct completion vfork;
1628
1629                 trace_sched_process_fork(current, p);
1630
1631                 nr = task_pid_vnr(p);
1632
1633                 if (clone_flags & CLONE_PARENT_SETTID)
1634                         put_user(nr, parent_tidptr);
1635
1636                 if (clone_flags & CLONE_VFORK) {
1637                         p->vfork_done = &vfork;
1638                         init_completion(&vfork);
1639                         get_task_struct(p);
1640                 }
1641
1642                 wake_up_new_task(p);
1643
1644                 /* forking complete and child started to run, tell ptracer */
1645                 if (unlikely(trace))
1646                         ptrace_event(trace, nr);
1647
1648                 if (clone_flags & CLONE_VFORK) {
1649                         if (!wait_for_vfork_done(p, &vfork))
1650                                 ptrace_event(PTRACE_EVENT_VFORK_DONE, nr);
1651                 }
1652         } else {
1653                 nr = PTR_ERR(p);
1654         }
1655         return nr;
1656 }
1657
1658 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1659 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1660 #endif
1661
1662 static void sighand_ctor(void *data)
1663 {
1664         struct sighand_struct *sighand = data;
1665
1666         spin_lock_init(&sighand->siglock);
1667         init_waitqueue_head(&sighand->signalfd_wqh);
1668 }
1669
1670 void __init proc_caches_init(void)
1671 {
1672         sighand_cachep = kmem_cache_create("sighand_cache",
1673                         sizeof(struct sighand_struct), 0,
1674                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU|
1675                         SLAB_NOTRACK, sighand_ctor);
1676         signal_cachep = kmem_cache_create("signal_cache",
1677                         sizeof(struct signal_struct), 0,
1678                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1679         files_cachep = kmem_cache_create("files_cache",
1680                         sizeof(struct files_struct), 0,
1681                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1682         fs_cachep = kmem_cache_create("fs_cache",
1683                         sizeof(struct fs_struct), 0,
1684                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1685         /*
1686          * FIXME! The "sizeof(struct mm_struct)" currently includes the
1687          * whole struct cpumask for the OFFSTACK case. We could change
1688          * this to *only* allocate as much of it as required by the
1689          * maximum number of CPU's we can ever have.  The cpumask_allocation
1690          * is at the end of the structure, exactly for that reason.
1691          */
1692         mm_cachep = kmem_cache_create("mm_struct",
1693                         sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1694                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1695         vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC);
1696         mmap_init();
1697         nsproxy_cache_init();
1698 }
1699
1700 /*
1701  * Check constraints on flags passed to the unshare system call.
1702  */
1703 static int check_unshare_flags(unsigned long unshare_flags)
1704 {
1705         if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1706                                 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1707                                 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET))
1708                 return -EINVAL;
1709         /*
1710          * Not implemented, but pretend it works if there is nothing to
1711          * unshare. Note that unsharing CLONE_THREAD or CLONE_SIGHAND
1712          * needs to unshare vm.
1713          */
1714         if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
1715                 /* FIXME: get_task_mm() increments ->mm_users */
1716                 if (atomic_read(&current->mm->mm_users) > 1)
1717                         return -EINVAL;
1718         }
1719
1720         return 0;
1721 }
1722
1723 /*
1724  * Unshare the filesystem structure if it is being shared
1725  */
1726 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1727 {
1728         struct fs_struct *fs = current->fs;
1729
1730         if (!(unshare_flags & CLONE_FS) || !fs)
1731                 return 0;
1732
1733         /* don't need lock here; in the worst case we'll do useless copy */
1734         if (fs->users == 1)
1735                 return 0;
1736
1737         *new_fsp = copy_fs_struct(fs);
1738         if (!*new_fsp)
1739                 return -ENOMEM;
1740
1741         return 0;
1742 }
1743
1744 /*
1745  * Unshare file descriptor table if it is being shared
1746  */
1747 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1748 {
1749         struct files_struct *fd = current->files;
1750         int error = 0;
1751
1752         if ((unshare_flags & CLONE_FILES) &&
1753             (fd && atomic_read(&fd->count) > 1)) {
1754                 *new_fdp = dup_fd(fd, &error);
1755                 if (!*new_fdp)
1756                         return error;
1757         }
1758
1759         return 0;
1760 }
1761
1762 /*
1763  * unshare allows a process to 'unshare' part of the process
1764  * context which was originally shared using clone.  copy_*
1765  * functions used by do_fork() cannot be used here directly
1766  * because they modify an inactive task_struct that is being
1767  * constructed. Here we are modifying the current, active,
1768  * task_struct.
1769  */
1770 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
1771 {
1772         struct fs_struct *fs, *new_fs = NULL;
1773         struct files_struct *fd, *new_fd = NULL;
1774         struct nsproxy *new_nsproxy = NULL;
1775         int do_sysvsem = 0;
1776         int err;
1777
1778         err = check_unshare_flags(unshare_flags);
1779         if (err)
1780                 goto bad_unshare_out;
1781
1782         /*
1783          * If unsharing namespace, must also unshare filesystem information.
1784          */
1785         if (unshare_flags & CLONE_NEWNS)
1786                 unshare_flags |= CLONE_FS;
1787         /*
1788          * CLONE_NEWIPC must also detach from the undolist: after switching
1789          * to a new ipc namespace, the semaphore arrays from the old
1790          * namespace are unreachable.
1791          */
1792         if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1793                 do_sysvsem = 1;
1794         err = unshare_fs(unshare_flags, &new_fs);
1795         if (err)
1796                 goto bad_unshare_out;
1797         err = unshare_fd(unshare_flags, &new_fd);
1798         if (err)
1799                 goto bad_unshare_cleanup_fs;
1800         err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, new_fs);
1801         if (err)
1802                 goto bad_unshare_cleanup_fd;
1803
1804         if (new_fs || new_fd || do_sysvsem || new_nsproxy) {
1805                 if (do_sysvsem) {
1806                         /*
1807                          * CLONE_SYSVSEM is equivalent to sys_exit().
1808                          */
1809                         exit_sem(current);
1810                 }
1811
1812                 if (new_nsproxy) {
1813                         switch_task_namespaces(current, new_nsproxy);
1814                         new_nsproxy = NULL;
1815                 }
1816
1817                 task_lock(current);
1818
1819                 if (new_fs) {
1820                         fs = current->fs;
1821                         spin_lock(&fs->lock);
1822                         current->fs = new_fs;
1823                         if (--fs->users)
1824                                 new_fs = NULL;
1825                         else
1826                                 new_fs = fs;
1827                         spin_unlock(&fs->lock);
1828                 }
1829
1830                 if (new_fd) {
1831                         fd = current->files;
1832                         current->files = new_fd;
1833                         new_fd = fd;
1834                 }
1835
1836                 task_unlock(current);
1837         }
1838
1839         if (new_nsproxy)
1840                 put_nsproxy(new_nsproxy);
1841
1842 bad_unshare_cleanup_fd:
1843         if (new_fd)
1844                 put_files_struct(new_fd);
1845
1846 bad_unshare_cleanup_fs:
1847         if (new_fs)
1848                 free_fs_struct(new_fs);
1849
1850 bad_unshare_out:
1851         return err;
1852 }
1853
1854 /*
1855  *      Helper to unshare the files of the current task.
1856  *      We don't want to expose copy_files internals to
1857  *      the exec layer of the kernel.
1858  */
1859
1860 int unshare_files(struct files_struct **displaced)
1861 {
1862         struct task_struct *task = current;
1863         struct files_struct *copy = NULL;
1864         int error;
1865
1866         error = unshare_fd(CLONE_FILES, &copy);
1867         if (error || !copy) {
1868                 *displaced = NULL;
1869                 return error;
1870         }
1871         *displaced = task->files;
1872         task_lock(task);
1873         task->files = copy;
1874         task_unlock(task);
1875         return 0;
1876 }