clone(): fix race between copy_process() and de_thread()
[linux-2.6.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/swap.h>
38 #include <linux/syscalls.h>
39 #include <linux/jiffies.h>
40 #include <linux/tracehook.h>
41 #include <linux/futex.h>
42 #include <linux/compat.h>
43 #include <linux/task_io_accounting_ops.h>
44 #include <linux/rcupdate.h>
45 #include <linux/ptrace.h>
46 #include <linux/mount.h>
47 #include <linux/audit.h>
48 #include <linux/memcontrol.h>
49 #include <linux/ftrace.h>
50 #include <linux/profile.h>
51 #include <linux/rmap.h>
52 #include <linux/acct.h>
53 #include <linux/tsacct_kern.h>
54 #include <linux/cn_proc.h>
55 #include <linux/freezer.h>
56 #include <linux/delayacct.h>
57 #include <linux/taskstats_kern.h>
58 #include <linux/random.h>
59 #include <linux/tty.h>
60 #include <linux/proc_fs.h>
61 #include <linux/blkdev.h>
62 #include <linux/fs_struct.h>
63 #include <linux/magic.h>
64 #include <linux/perf_counter.h>
65
66 #include <asm/pgtable.h>
67 #include <asm/pgalloc.h>
68 #include <asm/uaccess.h>
69 #include <asm/mmu_context.h>
70 #include <asm/cacheflush.h>
71 #include <asm/tlbflush.h>
72
73 #include <trace/events/sched.h>
74
75 /*
76  * Protected counters by write_lock_irq(&tasklist_lock)
77  */
78 unsigned long total_forks;      /* Handle normal Linux uptimes. */
79 int nr_threads;                 /* The idle threads do not count.. */
80
81 int max_threads;                /* tunable limit on nr_threads */
82
83 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
84
85 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
86
87 int nr_processes(void)
88 {
89         int cpu;
90         int total = 0;
91
92         for_each_online_cpu(cpu)
93                 total += per_cpu(process_counts, cpu);
94
95         return total;
96 }
97
98 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
99 # define alloc_task_struct()    kmem_cache_alloc(task_struct_cachep, GFP_KERNEL)
100 # define free_task_struct(tsk)  kmem_cache_free(task_struct_cachep, (tsk))
101 static struct kmem_cache *task_struct_cachep;
102 #endif
103
104 #ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR
105 static inline struct thread_info *alloc_thread_info(struct task_struct *tsk)
106 {
107 #ifdef CONFIG_DEBUG_STACK_USAGE
108         gfp_t mask = GFP_KERNEL | __GFP_ZERO;
109 #else
110         gfp_t mask = GFP_KERNEL;
111 #endif
112         return (struct thread_info *)__get_free_pages(mask, THREAD_SIZE_ORDER);
113 }
114
115 static inline void free_thread_info(struct thread_info *ti)
116 {
117         free_pages((unsigned long)ti, THREAD_SIZE_ORDER);
118 }
119 #endif
120
121 /* SLAB cache for signal_struct structures (tsk->signal) */
122 static struct kmem_cache *signal_cachep;
123
124 /* SLAB cache for sighand_struct structures (tsk->sighand) */
125 struct kmem_cache *sighand_cachep;
126
127 /* SLAB cache for files_struct structures (tsk->files) */
128 struct kmem_cache *files_cachep;
129
130 /* SLAB cache for fs_struct structures (tsk->fs) */
131 struct kmem_cache *fs_cachep;
132
133 /* SLAB cache for vm_area_struct structures */
134 struct kmem_cache *vm_area_cachep;
135
136 /* SLAB cache for mm_struct structures (tsk->mm) */
137 static struct kmem_cache *mm_cachep;
138
139 void free_task(struct task_struct *tsk)
140 {
141         prop_local_destroy_single(&tsk->dirties);
142         free_thread_info(tsk->stack);
143         rt_mutex_debug_task_free(tsk);
144         ftrace_graph_exit_task(tsk);
145         free_task_struct(tsk);
146 }
147 EXPORT_SYMBOL(free_task);
148
149 void __put_task_struct(struct task_struct *tsk)
150 {
151         WARN_ON(!tsk->exit_state);
152         WARN_ON(atomic_read(&tsk->usage));
153         WARN_ON(tsk == current);
154
155         put_cred(tsk->real_cred);
156         put_cred(tsk->cred);
157         delayacct_tsk_free(tsk);
158
159         if (!profile_handoff_task(tsk))
160                 free_task(tsk);
161 }
162
163 /*
164  * macro override instead of weak attribute alias, to workaround
165  * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions.
166  */
167 #ifndef arch_task_cache_init
168 #define arch_task_cache_init()
169 #endif
170
171 void __init fork_init(unsigned long mempages)
172 {
173 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
174 #ifndef ARCH_MIN_TASKALIGN
175 #define ARCH_MIN_TASKALIGN      L1_CACHE_BYTES
176 #endif
177         /* create a slab on which task_structs can be allocated */
178         task_struct_cachep =
179                 kmem_cache_create("task_struct", sizeof(struct task_struct),
180                         ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL);
181 #endif
182
183         /* do the arch specific task caches init */
184         arch_task_cache_init();
185
186         /*
187          * The default maximum number of threads is set to a safe
188          * value: the thread structures can take up at most half
189          * of memory.
190          */
191         max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
192
193         /*
194          * we need to allow at least 20 threads to boot a system
195          */
196         if(max_threads < 20)
197                 max_threads = 20;
198
199         init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
200         init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
201         init_task.signal->rlim[RLIMIT_SIGPENDING] =
202                 init_task.signal->rlim[RLIMIT_NPROC];
203 }
204
205 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst,
206                                                struct task_struct *src)
207 {
208         *dst = *src;
209         return 0;
210 }
211
212 static struct task_struct *dup_task_struct(struct task_struct *orig)
213 {
214         struct task_struct *tsk;
215         struct thread_info *ti;
216         unsigned long *stackend;
217
218         int err;
219
220         prepare_to_copy(orig);
221
222         tsk = alloc_task_struct();
223         if (!tsk)
224                 return NULL;
225
226         ti = alloc_thread_info(tsk);
227         if (!ti) {
228                 free_task_struct(tsk);
229                 return NULL;
230         }
231
232         err = arch_dup_task_struct(tsk, orig);
233         if (err)
234                 goto out;
235
236         tsk->stack = ti;
237
238         err = prop_local_init_single(&tsk->dirties);
239         if (err)
240                 goto out;
241
242         setup_thread_stack(tsk, orig);
243         stackend = end_of_stack(tsk);
244         *stackend = STACK_END_MAGIC;    /* for overflow detection */
245
246 #ifdef CONFIG_CC_STACKPROTECTOR
247         tsk->stack_canary = get_random_int();
248 #endif
249
250         /* One for us, one for whoever does the "release_task()" (usually parent) */
251         atomic_set(&tsk->usage,2);
252         atomic_set(&tsk->fs_excl, 0);
253 #ifdef CONFIG_BLK_DEV_IO_TRACE
254         tsk->btrace_seq = 0;
255 #endif
256         tsk->splice_pipe = NULL;
257         return tsk;
258
259 out:
260         free_thread_info(ti);
261         free_task_struct(tsk);
262         return NULL;
263 }
264
265 #ifdef CONFIG_MMU
266 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
267 {
268         struct vm_area_struct *mpnt, *tmp, **pprev;
269         struct rb_node **rb_link, *rb_parent;
270         int retval;
271         unsigned long charge;
272         struct mempolicy *pol;
273
274         down_write(&oldmm->mmap_sem);
275         flush_cache_dup_mm(oldmm);
276         /*
277          * Not linked in yet - no deadlock potential:
278          */
279         down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
280
281         mm->locked_vm = 0;
282         mm->mmap = NULL;
283         mm->mmap_cache = NULL;
284         mm->free_area_cache = oldmm->mmap_base;
285         mm->cached_hole_size = ~0UL;
286         mm->map_count = 0;
287         cpumask_clear(mm_cpumask(mm));
288         mm->mm_rb = RB_ROOT;
289         rb_link = &mm->mm_rb.rb_node;
290         rb_parent = NULL;
291         pprev = &mm->mmap;
292
293         for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
294                 struct file *file;
295
296                 if (mpnt->vm_flags & VM_DONTCOPY) {
297                         long pages = vma_pages(mpnt);
298                         mm->total_vm -= pages;
299                         vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
300                                                                 -pages);
301                         continue;
302                 }
303                 charge = 0;
304                 if (mpnt->vm_flags & VM_ACCOUNT) {
305                         unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
306                         if (security_vm_enough_memory(len))
307                                 goto fail_nomem;
308                         charge = len;
309                 }
310                 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
311                 if (!tmp)
312                         goto fail_nomem;
313                 *tmp = *mpnt;
314                 pol = mpol_dup(vma_policy(mpnt));
315                 retval = PTR_ERR(pol);
316                 if (IS_ERR(pol))
317                         goto fail_nomem_policy;
318                 vma_set_policy(tmp, pol);
319                 tmp->vm_flags &= ~VM_LOCKED;
320                 tmp->vm_mm = mm;
321                 tmp->vm_next = NULL;
322                 anon_vma_link(tmp);
323                 file = tmp->vm_file;
324                 if (file) {
325                         struct inode *inode = file->f_path.dentry->d_inode;
326                         struct address_space *mapping = file->f_mapping;
327
328                         get_file(file);
329                         if (tmp->vm_flags & VM_DENYWRITE)
330                                 atomic_dec(&inode->i_writecount);
331                         spin_lock(&mapping->i_mmap_lock);
332                         if (tmp->vm_flags & VM_SHARED)
333                                 mapping->i_mmap_writable++;
334                         tmp->vm_truncate_count = mpnt->vm_truncate_count;
335                         flush_dcache_mmap_lock(mapping);
336                         /* insert tmp into the share list, just after mpnt */
337                         vma_prio_tree_add(tmp, mpnt);
338                         flush_dcache_mmap_unlock(mapping);
339                         spin_unlock(&mapping->i_mmap_lock);
340                 }
341
342                 /*
343                  * Clear hugetlb-related page reserves for children. This only
344                  * affects MAP_PRIVATE mappings. Faults generated by the child
345                  * are not guaranteed to succeed, even if read-only
346                  */
347                 if (is_vm_hugetlb_page(tmp))
348                         reset_vma_resv_huge_pages(tmp);
349
350                 /*
351                  * Link in the new vma and copy the page table entries.
352                  */
353                 *pprev = tmp;
354                 pprev = &tmp->vm_next;
355
356                 __vma_link_rb(mm, tmp, rb_link, rb_parent);
357                 rb_link = &tmp->vm_rb.rb_right;
358                 rb_parent = &tmp->vm_rb;
359
360                 mm->map_count++;
361                 retval = copy_page_range(mm, oldmm, mpnt);
362
363                 if (tmp->vm_ops && tmp->vm_ops->open)
364                         tmp->vm_ops->open(tmp);
365
366                 if (retval)
367                         goto out;
368         }
369         /* a new mm has just been created */
370         arch_dup_mmap(oldmm, mm);
371         retval = 0;
372 out:
373         up_write(&mm->mmap_sem);
374         flush_tlb_mm(oldmm);
375         up_write(&oldmm->mmap_sem);
376         return retval;
377 fail_nomem_policy:
378         kmem_cache_free(vm_area_cachep, tmp);
379 fail_nomem:
380         retval = -ENOMEM;
381         vm_unacct_memory(charge);
382         goto out;
383 }
384
385 static inline int mm_alloc_pgd(struct mm_struct * mm)
386 {
387         mm->pgd = pgd_alloc(mm);
388         if (unlikely(!mm->pgd))
389                 return -ENOMEM;
390         return 0;
391 }
392
393 static inline void mm_free_pgd(struct mm_struct * mm)
394 {
395         pgd_free(mm, mm->pgd);
396 }
397 #else
398 #define dup_mmap(mm, oldmm)     (0)
399 #define mm_alloc_pgd(mm)        (0)
400 #define mm_free_pgd(mm)
401 #endif /* CONFIG_MMU */
402
403 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
404
405 #define allocate_mm()   (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
406 #define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))
407
408 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
409
410 static int __init coredump_filter_setup(char *s)
411 {
412         default_dump_filter =
413                 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
414                 MMF_DUMP_FILTER_MASK;
415         return 1;
416 }
417
418 __setup("coredump_filter=", coredump_filter_setup);
419
420 #include <linux/init_task.h>
421
422 static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p)
423 {
424         atomic_set(&mm->mm_users, 1);
425         atomic_set(&mm->mm_count, 1);
426         init_rwsem(&mm->mmap_sem);
427         INIT_LIST_HEAD(&mm->mmlist);
428         mm->flags = (current->mm) ? current->mm->flags : default_dump_filter;
429         mm->core_state = NULL;
430         mm->nr_ptes = 0;
431         set_mm_counter(mm, file_rss, 0);
432         set_mm_counter(mm, anon_rss, 0);
433         spin_lock_init(&mm->page_table_lock);
434         spin_lock_init(&mm->ioctx_lock);
435         INIT_HLIST_HEAD(&mm->ioctx_list);
436         mm->free_area_cache = TASK_UNMAPPED_BASE;
437         mm->cached_hole_size = ~0UL;
438         mm_init_owner(mm, p);
439
440         if (likely(!mm_alloc_pgd(mm))) {
441                 mm->def_flags = 0;
442                 mmu_notifier_mm_init(mm);
443                 return mm;
444         }
445
446         free_mm(mm);
447         return NULL;
448 }
449
450 /*
451  * Allocate and initialize an mm_struct.
452  */
453 struct mm_struct * mm_alloc(void)
454 {
455         struct mm_struct * mm;
456
457         mm = allocate_mm();
458         if (mm) {
459                 memset(mm, 0, sizeof(*mm));
460                 mm = mm_init(mm, current);
461         }
462         return mm;
463 }
464
465 /*
466  * Called when the last reference to the mm
467  * is dropped: either by a lazy thread or by
468  * mmput. Free the page directory and the mm.
469  */
470 void __mmdrop(struct mm_struct *mm)
471 {
472         BUG_ON(mm == &init_mm);
473         mm_free_pgd(mm);
474         destroy_context(mm);
475         mmu_notifier_mm_destroy(mm);
476         free_mm(mm);
477 }
478 EXPORT_SYMBOL_GPL(__mmdrop);
479
480 /*
481  * Decrement the use count and release all resources for an mm.
482  */
483 void mmput(struct mm_struct *mm)
484 {
485         might_sleep();
486
487         if (atomic_dec_and_test(&mm->mm_users)) {
488                 exit_aio(mm);
489                 exit_mmap(mm);
490                 set_mm_exe_file(mm, NULL);
491                 if (!list_empty(&mm->mmlist)) {
492                         spin_lock(&mmlist_lock);
493                         list_del(&mm->mmlist);
494                         spin_unlock(&mmlist_lock);
495                 }
496                 put_swap_token(mm);
497                 mmdrop(mm);
498         }
499 }
500 EXPORT_SYMBOL_GPL(mmput);
501
502 /**
503  * get_task_mm - acquire a reference to the task's mm
504  *
505  * Returns %NULL if the task has no mm.  Checks PF_KTHREAD (meaning
506  * this kernel workthread has transiently adopted a user mm with use_mm,
507  * to do its AIO) is not set and if so returns a reference to it, after
508  * bumping up the use count.  User must release the mm via mmput()
509  * after use.  Typically used by /proc and ptrace.
510  */
511 struct mm_struct *get_task_mm(struct task_struct *task)
512 {
513         struct mm_struct *mm;
514
515         task_lock(task);
516         mm = task->mm;
517         if (mm) {
518                 if (task->flags & PF_KTHREAD)
519                         mm = NULL;
520                 else
521                         atomic_inc(&mm->mm_users);
522         }
523         task_unlock(task);
524         return mm;
525 }
526 EXPORT_SYMBOL_GPL(get_task_mm);
527
528 /* Please note the differences between mmput and mm_release.
529  * mmput is called whenever we stop holding onto a mm_struct,
530  * error success whatever.
531  *
532  * mm_release is called after a mm_struct has been removed
533  * from the current process.
534  *
535  * This difference is important for error handling, when we
536  * only half set up a mm_struct for a new process and need to restore
537  * the old one.  Because we mmput the new mm_struct before
538  * restoring the old one. . .
539  * Eric Biederman 10 January 1998
540  */
541 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
542 {
543         struct completion *vfork_done = tsk->vfork_done;
544
545         /* Get rid of any futexes when releasing the mm */
546 #ifdef CONFIG_FUTEX
547         if (unlikely(tsk->robust_list))
548                 exit_robust_list(tsk);
549 #ifdef CONFIG_COMPAT
550         if (unlikely(tsk->compat_robust_list))
551                 compat_exit_robust_list(tsk);
552 #endif
553 #endif
554
555         /* Get rid of any cached register state */
556         deactivate_mm(tsk, mm);
557
558         /* notify parent sleeping on vfork() */
559         if (vfork_done) {
560                 tsk->vfork_done = NULL;
561                 complete(vfork_done);
562         }
563
564         /*
565          * If we're exiting normally, clear a user-space tid field if
566          * requested.  We leave this alone when dying by signal, to leave
567          * the value intact in a core dump, and to save the unnecessary
568          * trouble otherwise.  Userland only wants this done for a sys_exit.
569          */
570         if (tsk->clear_child_tid) {
571                 if (!(tsk->flags & PF_SIGNALED) &&
572                     atomic_read(&mm->mm_users) > 1) {
573                         /*
574                          * We don't check the error code - if userspace has
575                          * not set up a proper pointer then tough luck.
576                          */
577                         put_user(0, tsk->clear_child_tid);
578                         sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
579                                         1, NULL, NULL, 0);
580                 }
581                 tsk->clear_child_tid = NULL;
582         }
583 }
584
585 /*
586  * Allocate a new mm structure and copy contents from the
587  * mm structure of the passed in task structure.
588  */
589 struct mm_struct *dup_mm(struct task_struct *tsk)
590 {
591         struct mm_struct *mm, *oldmm = current->mm;
592         int err;
593
594         if (!oldmm)
595                 return NULL;
596
597         mm = allocate_mm();
598         if (!mm)
599                 goto fail_nomem;
600
601         memcpy(mm, oldmm, sizeof(*mm));
602
603         /* Initializing for Swap token stuff */
604         mm->token_priority = 0;
605         mm->last_interval = 0;
606
607         if (!mm_init(mm, tsk))
608                 goto fail_nomem;
609
610         if (init_new_context(tsk, mm))
611                 goto fail_nocontext;
612
613         dup_mm_exe_file(oldmm, mm);
614
615         err = dup_mmap(mm, oldmm);
616         if (err)
617                 goto free_pt;
618
619         mm->hiwater_rss = get_mm_rss(mm);
620         mm->hiwater_vm = mm->total_vm;
621
622         return mm;
623
624 free_pt:
625         mmput(mm);
626
627 fail_nomem:
628         return NULL;
629
630 fail_nocontext:
631         /*
632          * If init_new_context() failed, we cannot use mmput() to free the mm
633          * because it calls destroy_context()
634          */
635         mm_free_pgd(mm);
636         free_mm(mm);
637         return NULL;
638 }
639
640 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
641 {
642         struct mm_struct * mm, *oldmm;
643         int retval;
644
645         tsk->min_flt = tsk->maj_flt = 0;
646         tsk->nvcsw = tsk->nivcsw = 0;
647 #ifdef CONFIG_DETECT_HUNG_TASK
648         tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
649 #endif
650
651         tsk->mm = NULL;
652         tsk->active_mm = NULL;
653
654         /*
655          * Are we cloning a kernel thread?
656          *
657          * We need to steal a active VM for that..
658          */
659         oldmm = current->mm;
660         if (!oldmm)
661                 return 0;
662
663         if (clone_flags & CLONE_VM) {
664                 atomic_inc(&oldmm->mm_users);
665                 mm = oldmm;
666                 goto good_mm;
667         }
668
669         retval = -ENOMEM;
670         mm = dup_mm(tsk);
671         if (!mm)
672                 goto fail_nomem;
673
674 good_mm:
675         /* Initializing for Swap token stuff */
676         mm->token_priority = 0;
677         mm->last_interval = 0;
678
679         tsk->mm = mm;
680         tsk->active_mm = mm;
681         return 0;
682
683 fail_nomem:
684         return retval;
685 }
686
687 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
688 {
689         struct fs_struct *fs = current->fs;
690         if (clone_flags & CLONE_FS) {
691                 /* tsk->fs is already what we want */
692                 write_lock(&fs->lock);
693                 if (fs->in_exec) {
694                         write_unlock(&fs->lock);
695                         return -EAGAIN;
696                 }
697                 fs->users++;
698                 write_unlock(&fs->lock);
699                 return 0;
700         }
701         tsk->fs = copy_fs_struct(fs);
702         if (!tsk->fs)
703                 return -ENOMEM;
704         return 0;
705 }
706
707 static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
708 {
709         struct files_struct *oldf, *newf;
710         int error = 0;
711
712         /*
713          * A background process may not have any files ...
714          */
715         oldf = current->files;
716         if (!oldf)
717                 goto out;
718
719         if (clone_flags & CLONE_FILES) {
720                 atomic_inc(&oldf->count);
721                 goto out;
722         }
723
724         newf = dup_fd(oldf, &error);
725         if (!newf)
726                 goto out;
727
728         tsk->files = newf;
729         error = 0;
730 out:
731         return error;
732 }
733
734 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
735 {
736 #ifdef CONFIG_BLOCK
737         struct io_context *ioc = current->io_context;
738
739         if (!ioc)
740                 return 0;
741         /*
742          * Share io context with parent, if CLONE_IO is set
743          */
744         if (clone_flags & CLONE_IO) {
745                 tsk->io_context = ioc_task_link(ioc);
746                 if (unlikely(!tsk->io_context))
747                         return -ENOMEM;
748         } else if (ioprio_valid(ioc->ioprio)) {
749                 tsk->io_context = alloc_io_context(GFP_KERNEL, -1);
750                 if (unlikely(!tsk->io_context))
751                         return -ENOMEM;
752
753                 tsk->io_context->ioprio = ioc->ioprio;
754         }
755 #endif
756         return 0;
757 }
758
759 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
760 {
761         struct sighand_struct *sig;
762
763         if (clone_flags & CLONE_SIGHAND) {
764                 atomic_inc(&current->sighand->count);
765                 return 0;
766         }
767         sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
768         rcu_assign_pointer(tsk->sighand, sig);
769         if (!sig)
770                 return -ENOMEM;
771         atomic_set(&sig->count, 1);
772         memcpy(sig->action, current->sighand->action, sizeof(sig->action));
773         return 0;
774 }
775
776 void __cleanup_sighand(struct sighand_struct *sighand)
777 {
778         if (atomic_dec_and_test(&sighand->count))
779                 kmem_cache_free(sighand_cachep, sighand);
780 }
781
782
783 /*
784  * Initialize POSIX timer handling for a thread group.
785  */
786 static void posix_cpu_timers_init_group(struct signal_struct *sig)
787 {
788         /* Thread group counters. */
789         thread_group_cputime_init(sig);
790
791         /* Expiration times and increments. */
792         sig->it_virt_expires = cputime_zero;
793         sig->it_virt_incr = cputime_zero;
794         sig->it_prof_expires = cputime_zero;
795         sig->it_prof_incr = cputime_zero;
796
797         /* Cached expiration times. */
798         sig->cputime_expires.prof_exp = cputime_zero;
799         sig->cputime_expires.virt_exp = cputime_zero;
800         sig->cputime_expires.sched_exp = 0;
801
802         if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) {
803                 sig->cputime_expires.prof_exp =
804                         secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur);
805                 sig->cputimer.running = 1;
806         }
807
808         /* The timer lists. */
809         INIT_LIST_HEAD(&sig->cpu_timers[0]);
810         INIT_LIST_HEAD(&sig->cpu_timers[1]);
811         INIT_LIST_HEAD(&sig->cpu_timers[2]);
812 }
813
814 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
815 {
816         struct signal_struct *sig;
817
818         if (clone_flags & CLONE_THREAD)
819                 return 0;
820
821         sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL);
822         tsk->signal = sig;
823         if (!sig)
824                 return -ENOMEM;
825
826         atomic_set(&sig->count, 1);
827         atomic_set(&sig->live, 1);
828         init_waitqueue_head(&sig->wait_chldexit);
829         sig->flags = 0;
830         if (clone_flags & CLONE_NEWPID)
831                 sig->flags |= SIGNAL_UNKILLABLE;
832         sig->group_exit_code = 0;
833         sig->group_exit_task = NULL;
834         sig->group_stop_count = 0;
835         sig->curr_target = tsk;
836         init_sigpending(&sig->shared_pending);
837         INIT_LIST_HEAD(&sig->posix_timers);
838
839         hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
840         sig->it_real_incr.tv64 = 0;
841         sig->real_timer.function = it_real_fn;
842
843         sig->leader = 0;        /* session leadership doesn't inherit */
844         sig->tty_old_pgrp = NULL;
845         sig->tty = NULL;
846
847         sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero;
848         sig->gtime = cputime_zero;
849         sig->cgtime = cputime_zero;
850         sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0;
851         sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0;
852         sig->inblock = sig->oublock = sig->cinblock = sig->coublock = 0;
853         task_io_accounting_init(&sig->ioac);
854         sig->sum_sched_runtime = 0;
855         taskstats_tgid_init(sig);
856
857         task_lock(current->group_leader);
858         memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
859         task_unlock(current->group_leader);
860
861         posix_cpu_timers_init_group(sig);
862
863         acct_init_pacct(&sig->pacct);
864
865         tty_audit_fork(sig);
866
867         return 0;
868 }
869
870 void __cleanup_signal(struct signal_struct *sig)
871 {
872         thread_group_cputime_free(sig);
873         tty_kref_put(sig->tty);
874         kmem_cache_free(signal_cachep, sig);
875 }
876
877 static void copy_flags(unsigned long clone_flags, struct task_struct *p)
878 {
879         unsigned long new_flags = p->flags;
880
881         new_flags &= ~PF_SUPERPRIV;
882         new_flags |= PF_FORKNOEXEC;
883         new_flags |= PF_STARTING;
884         p->flags = new_flags;
885         clear_freeze_flag(p);
886 }
887
888 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
889 {
890         current->clear_child_tid = tidptr;
891
892         return task_pid_vnr(current);
893 }
894
895 static void rt_mutex_init_task(struct task_struct *p)
896 {
897         spin_lock_init(&p->pi_lock);
898 #ifdef CONFIG_RT_MUTEXES
899         plist_head_init(&p->pi_waiters, &p->pi_lock);
900         p->pi_blocked_on = NULL;
901 #endif
902 }
903
904 #ifdef CONFIG_MM_OWNER
905 void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
906 {
907         mm->owner = p;
908 }
909 #endif /* CONFIG_MM_OWNER */
910
911 /*
912  * Initialize POSIX timer handling for a single task.
913  */
914 static void posix_cpu_timers_init(struct task_struct *tsk)
915 {
916         tsk->cputime_expires.prof_exp = cputime_zero;
917         tsk->cputime_expires.virt_exp = cputime_zero;
918         tsk->cputime_expires.sched_exp = 0;
919         INIT_LIST_HEAD(&tsk->cpu_timers[0]);
920         INIT_LIST_HEAD(&tsk->cpu_timers[1]);
921         INIT_LIST_HEAD(&tsk->cpu_timers[2]);
922 }
923
924 /*
925  * This creates a new process as a copy of the old one,
926  * but does not actually start it yet.
927  *
928  * It copies the registers, and all the appropriate
929  * parts of the process environment (as per the clone
930  * flags). The actual kick-off is left to the caller.
931  */
932 static struct task_struct *copy_process(unsigned long clone_flags,
933                                         unsigned long stack_start,
934                                         struct pt_regs *regs,
935                                         unsigned long stack_size,
936                                         int __user *child_tidptr,
937                                         struct pid *pid,
938                                         int trace)
939 {
940         int retval;
941         struct task_struct *p;
942         int cgroup_callbacks_done = 0;
943
944         if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
945                 return ERR_PTR(-EINVAL);
946
947         /*
948          * Thread groups must share signals as well, and detached threads
949          * can only be started up within the thread group.
950          */
951         if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
952                 return ERR_PTR(-EINVAL);
953
954         /*
955          * Shared signal handlers imply shared VM. By way of the above,
956          * thread groups also imply shared VM. Blocking this case allows
957          * for various simplifications in other code.
958          */
959         if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
960                 return ERR_PTR(-EINVAL);
961
962         retval = security_task_create(clone_flags);
963         if (retval)
964                 goto fork_out;
965
966         retval = -ENOMEM;
967         p = dup_task_struct(current);
968         if (!p)
969                 goto fork_out;
970
971         ftrace_graph_init_task(p);
972
973         rt_mutex_init_task(p);
974
975 #ifdef CONFIG_PROVE_LOCKING
976         DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
977         DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
978 #endif
979         retval = -EAGAIN;
980         if (atomic_read(&p->real_cred->user->processes) >=
981                         p->signal->rlim[RLIMIT_NPROC].rlim_cur) {
982                 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
983                     p->real_cred->user != INIT_USER)
984                         goto bad_fork_free;
985         }
986
987         retval = copy_creds(p, clone_flags);
988         if (retval < 0)
989                 goto bad_fork_free;
990
991         /*
992          * If multiple threads are within copy_process(), then this check
993          * triggers too late. This doesn't hurt, the check is only there
994          * to stop root fork bombs.
995          */
996         retval = -EAGAIN;
997         if (nr_threads >= max_threads)
998                 goto bad_fork_cleanup_count;
999
1000         if (!try_module_get(task_thread_info(p)->exec_domain->module))
1001                 goto bad_fork_cleanup_count;
1002
1003         if (p->binfmt && !try_module_get(p->binfmt->module))
1004                 goto bad_fork_cleanup_put_domain;
1005
1006         p->did_exec = 0;
1007         delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
1008         copy_flags(clone_flags, p);
1009         INIT_LIST_HEAD(&p->children);
1010         INIT_LIST_HEAD(&p->sibling);
1011 #ifdef CONFIG_PREEMPT_RCU
1012         p->rcu_read_lock_nesting = 0;
1013         p->rcu_flipctr_idx = 0;
1014 #endif /* #ifdef CONFIG_PREEMPT_RCU */
1015         p->vfork_done = NULL;
1016         spin_lock_init(&p->alloc_lock);
1017
1018         init_sigpending(&p->pending);
1019
1020         p->utime = cputime_zero;
1021         p->stime = cputime_zero;
1022         p->gtime = cputime_zero;
1023         p->utimescaled = cputime_zero;
1024         p->stimescaled = cputime_zero;
1025         p->prev_utime = cputime_zero;
1026         p->prev_stime = cputime_zero;
1027
1028         p->default_timer_slack_ns = current->timer_slack_ns;
1029
1030         task_io_accounting_init(&p->ioac);
1031         acct_clear_integrals(p);
1032
1033         posix_cpu_timers_init(p);
1034
1035         p->lock_depth = -1;             /* -1 = no lock */
1036         do_posix_clock_monotonic_gettime(&p->start_time);
1037         p->real_start_time = p->start_time;
1038         monotonic_to_bootbased(&p->real_start_time);
1039         p->io_context = NULL;
1040         p->audit_context = NULL;
1041         cgroup_fork(p);
1042 #ifdef CONFIG_NUMA
1043         p->mempolicy = mpol_dup(p->mempolicy);
1044         if (IS_ERR(p->mempolicy)) {
1045                 retval = PTR_ERR(p->mempolicy);
1046                 p->mempolicy = NULL;
1047                 goto bad_fork_cleanup_cgroup;
1048         }
1049         mpol_fix_fork_child_flag(p);
1050 #endif
1051 #ifdef CONFIG_TRACE_IRQFLAGS
1052         p->irq_events = 0;
1053 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
1054         p->hardirqs_enabled = 1;
1055 #else
1056         p->hardirqs_enabled = 0;
1057 #endif
1058         p->hardirq_enable_ip = 0;
1059         p->hardirq_enable_event = 0;
1060         p->hardirq_disable_ip = _THIS_IP_;
1061         p->hardirq_disable_event = 0;
1062         p->softirqs_enabled = 1;
1063         p->softirq_enable_ip = _THIS_IP_;
1064         p->softirq_enable_event = 0;
1065         p->softirq_disable_ip = 0;
1066         p->softirq_disable_event = 0;
1067         p->hardirq_context = 0;
1068         p->softirq_context = 0;
1069 #endif
1070 #ifdef CONFIG_LOCKDEP
1071         p->lockdep_depth = 0; /* no locks held yet */
1072         p->curr_chain_key = 0;
1073         p->lockdep_recursion = 0;
1074 #endif
1075
1076 #ifdef CONFIG_DEBUG_MUTEXES
1077         p->blocked_on = NULL; /* not blocked yet */
1078 #endif
1079
1080         p->bts = NULL;
1081
1082         /* Perform scheduler related setup. Assign this task to a CPU. */
1083         sched_fork(p, clone_flags);
1084
1085         retval = perf_counter_init_task(p);
1086         if (retval)
1087                 goto bad_fork_cleanup_policy;
1088
1089         if ((retval = audit_alloc(p)))
1090                 goto bad_fork_cleanup_policy;
1091         /* copy all the process information */
1092         if ((retval = copy_semundo(clone_flags, p)))
1093                 goto bad_fork_cleanup_audit;
1094         if ((retval = copy_files(clone_flags, p)))
1095                 goto bad_fork_cleanup_semundo;
1096         if ((retval = copy_fs(clone_flags, p)))
1097                 goto bad_fork_cleanup_files;
1098         if ((retval = copy_sighand(clone_flags, p)))
1099                 goto bad_fork_cleanup_fs;
1100         if ((retval = copy_signal(clone_flags, p)))
1101                 goto bad_fork_cleanup_sighand;
1102         if ((retval = copy_mm(clone_flags, p)))
1103                 goto bad_fork_cleanup_signal;
1104         if ((retval = copy_namespaces(clone_flags, p)))
1105                 goto bad_fork_cleanup_mm;
1106         if ((retval = copy_io(clone_flags, p)))
1107                 goto bad_fork_cleanup_namespaces;
1108         retval = copy_thread(clone_flags, stack_start, stack_size, p, regs);
1109         if (retval)
1110                 goto bad_fork_cleanup_io;
1111
1112         if (pid != &init_struct_pid) {
1113                 retval = -ENOMEM;
1114                 pid = alloc_pid(p->nsproxy->pid_ns);
1115                 if (!pid)
1116                         goto bad_fork_cleanup_io;
1117
1118                 if (clone_flags & CLONE_NEWPID) {
1119                         retval = pid_ns_prepare_proc(p->nsproxy->pid_ns);
1120                         if (retval < 0)
1121                                 goto bad_fork_free_pid;
1122                 }
1123         }
1124
1125         p->pid = pid_nr(pid);
1126         p->tgid = p->pid;
1127         if (clone_flags & CLONE_THREAD)
1128                 p->tgid = current->tgid;
1129
1130         if (current->nsproxy != p->nsproxy) {
1131                 retval = ns_cgroup_clone(p, pid);
1132                 if (retval)
1133                         goto bad_fork_free_pid;
1134         }
1135
1136         p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1137         /*
1138          * Clear TID on mm_release()?
1139          */
1140         p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL;
1141 #ifdef CONFIG_FUTEX
1142         p->robust_list = NULL;
1143 #ifdef CONFIG_COMPAT
1144         p->compat_robust_list = NULL;
1145 #endif
1146         INIT_LIST_HEAD(&p->pi_state_list);
1147         p->pi_state_cache = NULL;
1148 #endif
1149         /*
1150          * sigaltstack should be cleared when sharing the same VM
1151          */
1152         if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1153                 p->sas_ss_sp = p->sas_ss_size = 0;
1154
1155         /*
1156          * Syscall tracing should be turned off in the child regardless
1157          * of CLONE_PTRACE.
1158          */
1159         clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1160 #ifdef TIF_SYSCALL_EMU
1161         clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1162 #endif
1163         clear_all_latency_tracing(p);
1164
1165         /* ok, now we should be set up.. */
1166         p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
1167         p->pdeath_signal = 0;
1168         p->exit_state = 0;
1169
1170         /*
1171          * Ok, make it visible to the rest of the system.
1172          * We dont wake it up yet.
1173          */
1174         p->group_leader = p;
1175         INIT_LIST_HEAD(&p->thread_group);
1176
1177         /* Now that the task is set up, run cgroup callbacks if
1178          * necessary. We need to run them before the task is visible
1179          * on the tasklist. */
1180         cgroup_fork_callbacks(p);
1181         cgroup_callbacks_done = 1;
1182
1183         /* Need tasklist lock for parent etc handling! */
1184         write_lock_irq(&tasklist_lock);
1185
1186         /*
1187          * The task hasn't been attached yet, so its cpus_allowed mask will
1188          * not be changed, nor will its assigned CPU.
1189          *
1190          * The cpus_allowed mask of the parent may have changed after it was
1191          * copied first time - so re-copy it here, then check the child's CPU
1192          * to ensure it is on a valid CPU (and if not, just force it back to
1193          * parent's CPU). This avoids alot of nasty races.
1194          */
1195         p->cpus_allowed = current->cpus_allowed;
1196         p->rt.nr_cpus_allowed = current->rt.nr_cpus_allowed;
1197         if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) ||
1198                         !cpu_online(task_cpu(p))))
1199                 set_task_cpu(p, smp_processor_id());
1200
1201         /* CLONE_PARENT re-uses the old parent */
1202         if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1203                 p->real_parent = current->real_parent;
1204                 p->parent_exec_id = current->parent_exec_id;
1205         } else {
1206                 p->real_parent = current;
1207                 p->parent_exec_id = current->self_exec_id;
1208         }
1209
1210         spin_lock(&current->sighand->siglock);
1211
1212         /*
1213          * Process group and session signals need to be delivered to just the
1214          * parent before the fork or both the parent and the child after the
1215          * fork. Restart if a signal comes in before we add the new process to
1216          * it's process group.
1217          * A fatal signal pending means that current will exit, so the new
1218          * thread can't slip out of an OOM kill (or normal SIGKILL).
1219          */
1220         recalc_sigpending();
1221         if (signal_pending(current)) {
1222                 spin_unlock(&current->sighand->siglock);
1223                 write_unlock_irq(&tasklist_lock);
1224                 retval = -ERESTARTNOINTR;
1225                 goto bad_fork_free_pid;
1226         }
1227
1228         if (clone_flags & CLONE_THREAD) {
1229                 atomic_inc(&current->signal->count);
1230                 atomic_inc(&current->signal->live);
1231                 p->group_leader = current->group_leader;
1232                 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1233         }
1234
1235         if (likely(p->pid)) {
1236                 list_add_tail(&p->sibling, &p->real_parent->children);
1237                 tracehook_finish_clone(p, clone_flags, trace);
1238
1239                 if (thread_group_leader(p)) {
1240                         if (clone_flags & CLONE_NEWPID)
1241                                 p->nsproxy->pid_ns->child_reaper = p;
1242
1243                         p->signal->leader_pid = pid;
1244                         tty_kref_put(p->signal->tty);
1245                         p->signal->tty = tty_kref_get(current->signal->tty);
1246                         attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
1247                         attach_pid(p, PIDTYPE_SID, task_session(current));
1248                         list_add_tail_rcu(&p->tasks, &init_task.tasks);
1249                         __get_cpu_var(process_counts)++;
1250                 }
1251                 attach_pid(p, PIDTYPE_PID, pid);
1252                 nr_threads++;
1253         }
1254
1255         total_forks++;
1256         spin_unlock(&current->sighand->siglock);
1257         write_unlock_irq(&tasklist_lock);
1258         proc_fork_connector(p);
1259         cgroup_post_fork(p);
1260         perf_counter_fork(p);
1261         return p;
1262
1263 bad_fork_free_pid:
1264         if (pid != &init_struct_pid)
1265                 free_pid(pid);
1266 bad_fork_cleanup_io:
1267         put_io_context(p->io_context);
1268 bad_fork_cleanup_namespaces:
1269         exit_task_namespaces(p);
1270 bad_fork_cleanup_mm:
1271         if (p->mm)
1272                 mmput(p->mm);
1273 bad_fork_cleanup_signal:
1274         if (!(clone_flags & CLONE_THREAD))
1275                 __cleanup_signal(p->signal);
1276 bad_fork_cleanup_sighand:
1277         __cleanup_sighand(p->sighand);
1278 bad_fork_cleanup_fs:
1279         exit_fs(p); /* blocking */
1280 bad_fork_cleanup_files:
1281         exit_files(p); /* blocking */
1282 bad_fork_cleanup_semundo:
1283         exit_sem(p);
1284 bad_fork_cleanup_audit:
1285         audit_free(p);
1286 bad_fork_cleanup_policy:
1287         perf_counter_free_task(p);
1288 #ifdef CONFIG_NUMA
1289         mpol_put(p->mempolicy);
1290 bad_fork_cleanup_cgroup:
1291 #endif
1292         cgroup_exit(p, cgroup_callbacks_done);
1293         delayacct_tsk_free(p);
1294         if (p->binfmt)
1295                 module_put(p->binfmt->module);
1296 bad_fork_cleanup_put_domain:
1297         module_put(task_thread_info(p)->exec_domain->module);
1298 bad_fork_cleanup_count:
1299         atomic_dec(&p->cred->user->processes);
1300         put_cred(p->real_cred);
1301         put_cred(p->cred);
1302 bad_fork_free:
1303         free_task(p);
1304 fork_out:
1305         return ERR_PTR(retval);
1306 }
1307
1308 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1309 {
1310         memset(regs, 0, sizeof(struct pt_regs));
1311         return regs;
1312 }
1313
1314 struct task_struct * __cpuinit fork_idle(int cpu)
1315 {
1316         struct task_struct *task;
1317         struct pt_regs regs;
1318
1319         task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL,
1320                             &init_struct_pid, 0);
1321         if (!IS_ERR(task))
1322                 init_idle(task, cpu);
1323
1324         return task;
1325 }
1326
1327 /*
1328  *  Ok, this is the main fork-routine.
1329  *
1330  * It copies the process, and if successful kick-starts
1331  * it and waits for it to finish using the VM if required.
1332  */
1333 long do_fork(unsigned long clone_flags,
1334               unsigned long stack_start,
1335               struct pt_regs *regs,
1336               unsigned long stack_size,
1337               int __user *parent_tidptr,
1338               int __user *child_tidptr)
1339 {
1340         struct task_struct *p;
1341         int trace = 0;
1342         long nr;
1343
1344         /*
1345          * Do some preliminary argument and permissions checking before we
1346          * actually start allocating stuff
1347          */
1348         if (clone_flags & CLONE_NEWUSER) {
1349                 if (clone_flags & CLONE_THREAD)
1350                         return -EINVAL;
1351                 /* hopefully this check will go away when userns support is
1352                  * complete
1353                  */
1354                 if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) ||
1355                                 !capable(CAP_SETGID))
1356                         return -EPERM;
1357         }
1358
1359         /*
1360          * We hope to recycle these flags after 2.6.26
1361          */
1362         if (unlikely(clone_flags & CLONE_STOPPED)) {
1363                 static int __read_mostly count = 100;
1364
1365                 if (count > 0 && printk_ratelimit()) {
1366                         char comm[TASK_COMM_LEN];
1367
1368                         count--;
1369                         printk(KERN_INFO "fork(): process `%s' used deprecated "
1370                                         "clone flags 0x%lx\n",
1371                                 get_task_comm(comm, current),
1372                                 clone_flags & CLONE_STOPPED);
1373                 }
1374         }
1375
1376         /*
1377          * When called from kernel_thread, don't do user tracing stuff.
1378          */
1379         if (likely(user_mode(regs)))
1380                 trace = tracehook_prepare_clone(clone_flags);
1381
1382         p = copy_process(clone_flags, stack_start, regs, stack_size,
1383                          child_tidptr, NULL, trace);
1384         /*
1385          * Do this prior waking up the new thread - the thread pointer
1386          * might get invalid after that point, if the thread exits quickly.
1387          */
1388         if (!IS_ERR(p)) {
1389                 struct completion vfork;
1390
1391                 trace_sched_process_fork(current, p);
1392
1393                 nr = task_pid_vnr(p);
1394
1395                 if (clone_flags & CLONE_PARENT_SETTID)
1396                         put_user(nr, parent_tidptr);
1397
1398                 if (clone_flags & CLONE_VFORK) {
1399                         p->vfork_done = &vfork;
1400                         init_completion(&vfork);
1401                 }
1402
1403                 audit_finish_fork(p);
1404                 tracehook_report_clone(regs, clone_flags, nr, p);
1405
1406                 /*
1407                  * We set PF_STARTING at creation in case tracing wants to
1408                  * use this to distinguish a fully live task from one that
1409                  * hasn't gotten to tracehook_report_clone() yet.  Now we
1410                  * clear it and set the child going.
1411                  */
1412                 p->flags &= ~PF_STARTING;
1413
1414                 if (unlikely(clone_flags & CLONE_STOPPED)) {
1415                         /*
1416                          * We'll start up with an immediate SIGSTOP.
1417                          */
1418                         sigaddset(&p->pending.signal, SIGSTOP);
1419                         set_tsk_thread_flag(p, TIF_SIGPENDING);
1420                         __set_task_state(p, TASK_STOPPED);
1421                 } else {
1422                         wake_up_new_task(p, clone_flags);
1423                 }
1424
1425                 tracehook_report_clone_complete(trace, regs,
1426                                                 clone_flags, nr, p);
1427
1428                 if (clone_flags & CLONE_VFORK) {
1429                         freezer_do_not_count();
1430                         wait_for_completion(&vfork);
1431                         freezer_count();
1432                         tracehook_report_vfork_done(p, nr);
1433                 }
1434         } else {
1435                 nr = PTR_ERR(p);
1436         }
1437         return nr;
1438 }
1439
1440 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1441 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1442 #endif
1443
1444 static void sighand_ctor(void *data)
1445 {
1446         struct sighand_struct *sighand = data;
1447
1448         spin_lock_init(&sighand->siglock);
1449         init_waitqueue_head(&sighand->signalfd_wqh);
1450 }
1451
1452 void __init proc_caches_init(void)
1453 {
1454         sighand_cachep = kmem_cache_create("sighand_cache",
1455                         sizeof(struct sighand_struct), 0,
1456                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU|
1457                         SLAB_NOTRACK, sighand_ctor);
1458         signal_cachep = kmem_cache_create("signal_cache",
1459                         sizeof(struct signal_struct), 0,
1460                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1461         files_cachep = kmem_cache_create("files_cache",
1462                         sizeof(struct files_struct), 0,
1463                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1464         fs_cachep = kmem_cache_create("fs_cache",
1465                         sizeof(struct fs_struct), 0,
1466                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1467         mm_cachep = kmem_cache_create("mm_struct",
1468                         sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1469                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1470         vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC);
1471         mmap_init();
1472 }
1473
1474 /*
1475  * Check constraints on flags passed to the unshare system call and
1476  * force unsharing of additional process context as appropriate.
1477  */
1478 static void check_unshare_flags(unsigned long *flags_ptr)
1479 {
1480         /*
1481          * If unsharing a thread from a thread group, must also
1482          * unshare vm.
1483          */
1484         if (*flags_ptr & CLONE_THREAD)
1485                 *flags_ptr |= CLONE_VM;
1486
1487         /*
1488          * If unsharing vm, must also unshare signal handlers.
1489          */
1490         if (*flags_ptr & CLONE_VM)
1491                 *flags_ptr |= CLONE_SIGHAND;
1492
1493         /*
1494          * If unsharing signal handlers and the task was created
1495          * using CLONE_THREAD, then must unshare the thread
1496          */
1497         if ((*flags_ptr & CLONE_SIGHAND) &&
1498             (atomic_read(&current->signal->count) > 1))
1499                 *flags_ptr |= CLONE_THREAD;
1500
1501         /*
1502          * If unsharing namespace, must also unshare filesystem information.
1503          */
1504         if (*flags_ptr & CLONE_NEWNS)
1505                 *flags_ptr |= CLONE_FS;
1506 }
1507
1508 /*
1509  * Unsharing of tasks created with CLONE_THREAD is not supported yet
1510  */
1511 static int unshare_thread(unsigned long unshare_flags)
1512 {
1513         if (unshare_flags & CLONE_THREAD)
1514                 return -EINVAL;
1515
1516         return 0;
1517 }
1518
1519 /*
1520  * Unshare the filesystem structure if it is being shared
1521  */
1522 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1523 {
1524         struct fs_struct *fs = current->fs;
1525
1526         if (!(unshare_flags & CLONE_FS) || !fs)
1527                 return 0;
1528
1529         /* don't need lock here; in the worst case we'll do useless copy */
1530         if (fs->users == 1)
1531                 return 0;
1532
1533         *new_fsp = copy_fs_struct(fs);
1534         if (!*new_fsp)
1535                 return -ENOMEM;
1536
1537         return 0;
1538 }
1539
1540 /*
1541  * Unsharing of sighand is not supported yet
1542  */
1543 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
1544 {
1545         struct sighand_struct *sigh = current->sighand;
1546
1547         if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1)
1548                 return -EINVAL;
1549         else
1550                 return 0;
1551 }
1552
1553 /*
1554  * Unshare vm if it is being shared
1555  */
1556 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
1557 {
1558         struct mm_struct *mm = current->mm;
1559
1560         if ((unshare_flags & CLONE_VM) &&
1561             (mm && atomic_read(&mm->mm_users) > 1)) {
1562                 return -EINVAL;
1563         }
1564
1565         return 0;
1566 }
1567
1568 /*
1569  * Unshare file descriptor table if it is being shared
1570  */
1571 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1572 {
1573         struct files_struct *fd = current->files;
1574         int error = 0;
1575
1576         if ((unshare_flags & CLONE_FILES) &&
1577             (fd && atomic_read(&fd->count) > 1)) {
1578                 *new_fdp = dup_fd(fd, &error);
1579                 if (!*new_fdp)
1580                         return error;
1581         }
1582
1583         return 0;
1584 }
1585
1586 /*
1587  * unshare allows a process to 'unshare' part of the process
1588  * context which was originally shared using clone.  copy_*
1589  * functions used by do_fork() cannot be used here directly
1590  * because they modify an inactive task_struct that is being
1591  * constructed. Here we are modifying the current, active,
1592  * task_struct.
1593  */
1594 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
1595 {
1596         int err = 0;
1597         struct fs_struct *fs, *new_fs = NULL;
1598         struct sighand_struct *new_sigh = NULL;
1599         struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
1600         struct files_struct *fd, *new_fd = NULL;
1601         struct nsproxy *new_nsproxy = NULL;
1602         int do_sysvsem = 0;
1603
1604         check_unshare_flags(&unshare_flags);
1605
1606         /* Return -EINVAL for all unsupported flags */
1607         err = -EINVAL;
1608         if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1609                                 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1610                                 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET))
1611                 goto bad_unshare_out;
1612
1613         /*
1614          * CLONE_NEWIPC must also detach from the undolist: after switching
1615          * to a new ipc namespace, the semaphore arrays from the old
1616          * namespace are unreachable.
1617          */
1618         if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1619                 do_sysvsem = 1;
1620         if ((err = unshare_thread(unshare_flags)))
1621                 goto bad_unshare_out;
1622         if ((err = unshare_fs(unshare_flags, &new_fs)))
1623                 goto bad_unshare_cleanup_thread;
1624         if ((err = unshare_sighand(unshare_flags, &new_sigh)))
1625                 goto bad_unshare_cleanup_fs;
1626         if ((err = unshare_vm(unshare_flags, &new_mm)))
1627                 goto bad_unshare_cleanup_sigh;
1628         if ((err = unshare_fd(unshare_flags, &new_fd)))
1629                 goto bad_unshare_cleanup_vm;
1630         if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
1631                         new_fs)))
1632                 goto bad_unshare_cleanup_fd;
1633
1634         if (new_fs ||  new_mm || new_fd || do_sysvsem || new_nsproxy) {
1635                 if (do_sysvsem) {
1636                         /*
1637                          * CLONE_SYSVSEM is equivalent to sys_exit().
1638                          */
1639                         exit_sem(current);
1640                 }
1641
1642                 if (new_nsproxy) {
1643                         switch_task_namespaces(current, new_nsproxy);
1644                         new_nsproxy = NULL;
1645                 }
1646
1647                 task_lock(current);
1648
1649                 if (new_fs) {
1650                         fs = current->fs;
1651                         write_lock(&fs->lock);
1652                         current->fs = new_fs;
1653                         if (--fs->users)
1654                                 new_fs = NULL;
1655                         else
1656                                 new_fs = fs;
1657                         write_unlock(&fs->lock);
1658                 }
1659
1660                 if (new_mm) {
1661                         mm = current->mm;
1662                         active_mm = current->active_mm;
1663                         current->mm = new_mm;
1664                         current->active_mm = new_mm;
1665                         activate_mm(active_mm, new_mm);
1666                         new_mm = mm;
1667                 }
1668
1669                 if (new_fd) {
1670                         fd = current->files;
1671                         current->files = new_fd;
1672                         new_fd = fd;
1673                 }
1674
1675                 task_unlock(current);
1676         }
1677
1678         if (new_nsproxy)
1679                 put_nsproxy(new_nsproxy);
1680
1681 bad_unshare_cleanup_fd:
1682         if (new_fd)
1683                 put_files_struct(new_fd);
1684
1685 bad_unshare_cleanup_vm:
1686         if (new_mm)
1687                 mmput(new_mm);
1688
1689 bad_unshare_cleanup_sigh:
1690         if (new_sigh)
1691                 if (atomic_dec_and_test(&new_sigh->count))
1692                         kmem_cache_free(sighand_cachep, new_sigh);
1693
1694 bad_unshare_cleanup_fs:
1695         if (new_fs)
1696                 free_fs_struct(new_fs);
1697
1698 bad_unshare_cleanup_thread:
1699 bad_unshare_out:
1700         return err;
1701 }
1702
1703 /*
1704  *      Helper to unshare the files of the current task.
1705  *      We don't want to expose copy_files internals to
1706  *      the exec layer of the kernel.
1707  */
1708
1709 int unshare_files(struct files_struct **displaced)
1710 {
1711         struct task_struct *task = current;
1712         struct files_struct *copy = NULL;
1713         int error;
1714
1715         error = unshare_fd(CLONE_FILES, &copy);
1716         if (error || !copy) {
1717                 *displaced = NULL;
1718                 return error;
1719         }
1720         *displaced = task->files;
1721         task_lock(task);
1722         task->files = copy;
1723         task_unlock(task);
1724         return 0;
1725 }