CRED: Detach the credentials from task_struct
[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/mnt_namespace.h>
21 #include <linux/personality.h>
22 #include <linux/mempolicy.h>
23 #include <linux/sem.h>
24 #include <linux/file.h>
25 #include <linux/fdtable.h>
26 #include <linux/iocontext.h>
27 #include <linux/key.h>
28 #include <linux/binfmts.h>
29 #include <linux/mman.h>
30 #include <linux/mmu_notifier.h>
31 #include <linux/fs.h>
32 #include <linux/nsproxy.h>
33 #include <linux/capability.h>
34 #include <linux/cpu.h>
35 #include <linux/cgroup.h>
36 #include <linux/security.h>
37 #include <linux/hugetlb.h>
38 #include <linux/swap.h>
39 #include <linux/syscalls.h>
40 #include <linux/jiffies.h>
41 #include <linux/tracehook.h>
42 #include <linux/futex.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/profile.h>
50 #include <linux/rmap.h>
51 #include <linux/acct.h>
52 #include <linux/tsacct_kern.h>
53 #include <linux/cn_proc.h>
54 #include <linux/freezer.h>
55 #include <linux/delayacct.h>
56 #include <linux/taskstats_kern.h>
57 #include <linux/random.h>
58 #include <linux/tty.h>
59 #include <linux/proc_fs.h>
60 #include <linux/blkdev.h>
61 #include <trace/sched.h>
62
63 #include <asm/pgtable.h>
64 #include <asm/pgalloc.h>
65 #include <asm/uaccess.h>
66 #include <asm/mmu_context.h>
67 #include <asm/cacheflush.h>
68 #include <asm/tlbflush.h>
69
70 /*
71  * Protected counters by write_lock_irq(&tasklist_lock)
72  */
73 unsigned long total_forks;      /* Handle normal Linux uptimes. */
74 int nr_threads;                 /* The idle threads do not count.. */
75
76 int max_threads;                /* tunable limit on nr_threads */
77
78 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
79
80 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
81
82 int nr_processes(void)
83 {
84         int cpu;
85         int total = 0;
86
87         for_each_online_cpu(cpu)
88                 total += per_cpu(process_counts, cpu);
89
90         return total;
91 }
92
93 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
94 # define alloc_task_struct()    kmem_cache_alloc(task_struct_cachep, GFP_KERNEL)
95 # define free_task_struct(tsk)  kmem_cache_free(task_struct_cachep, (tsk))
96 static struct kmem_cache *task_struct_cachep;
97 #endif
98
99 #ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR
100 static inline struct thread_info *alloc_thread_info(struct task_struct *tsk)
101 {
102 #ifdef CONFIG_DEBUG_STACK_USAGE
103         gfp_t mask = GFP_KERNEL | __GFP_ZERO;
104 #else
105         gfp_t mask = GFP_KERNEL;
106 #endif
107         return (struct thread_info *)__get_free_pages(mask, THREAD_SIZE_ORDER);
108 }
109
110 static inline void free_thread_info(struct thread_info *ti)
111 {
112         free_pages((unsigned long)ti, THREAD_SIZE_ORDER);
113 }
114 #endif
115
116 /* SLAB cache for signal_struct structures (tsk->signal) */
117 static struct kmem_cache *signal_cachep;
118
119 /* SLAB cache for sighand_struct structures (tsk->sighand) */
120 struct kmem_cache *sighand_cachep;
121
122 /* SLAB cache for files_struct structures (tsk->files) */
123 struct kmem_cache *files_cachep;
124
125 /* SLAB cache for fs_struct structures (tsk->fs) */
126 struct kmem_cache *fs_cachep;
127
128 /* SLAB cache for vm_area_struct structures */
129 struct kmem_cache *vm_area_cachep;
130
131 /* SLAB cache for mm_struct structures (tsk->mm) */
132 static struct kmem_cache *mm_cachep;
133
134 void free_task(struct task_struct *tsk)
135 {
136         prop_local_destroy_single(&tsk->dirties);
137         free_thread_info(tsk->stack);
138         rt_mutex_debug_task_free(tsk);
139         free_task_struct(tsk);
140 }
141 EXPORT_SYMBOL(free_task);
142
143 void __put_task_struct(struct task_struct *tsk)
144 {
145         WARN_ON(!tsk->exit_state);
146         WARN_ON(atomic_read(&tsk->usage));
147         WARN_ON(tsk == current);
148
149         put_cred(tsk->cred);
150         delayacct_tsk_free(tsk);
151
152         if (!profile_handoff_task(tsk))
153                 free_task(tsk);
154 }
155
156 /*
157  * macro override instead of weak attribute alias, to workaround
158  * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions.
159  */
160 #ifndef arch_task_cache_init
161 #define arch_task_cache_init()
162 #endif
163
164 void __init fork_init(unsigned long mempages)
165 {
166 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
167 #ifndef ARCH_MIN_TASKALIGN
168 #define ARCH_MIN_TASKALIGN      L1_CACHE_BYTES
169 #endif
170         /* create a slab on which task_structs can be allocated */
171         task_struct_cachep =
172                 kmem_cache_create("task_struct", sizeof(struct task_struct),
173                         ARCH_MIN_TASKALIGN, SLAB_PANIC, NULL);
174 #endif
175
176         /* do the arch specific task caches init */
177         arch_task_cache_init();
178
179         /*
180          * The default maximum number of threads is set to a safe
181          * value: the thread structures can take up at most half
182          * of memory.
183          */
184         max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
185
186         /*
187          * we need to allow at least 20 threads to boot a system
188          */
189         if(max_threads < 20)
190                 max_threads = 20;
191
192         init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
193         init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
194         init_task.signal->rlim[RLIMIT_SIGPENDING] =
195                 init_task.signal->rlim[RLIMIT_NPROC];
196 }
197
198 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst,
199                                                struct task_struct *src)
200 {
201         *dst = *src;
202         return 0;
203 }
204
205 static struct task_struct *dup_task_struct(struct task_struct *orig)
206 {
207         struct task_struct *tsk;
208         struct thread_info *ti;
209         int err;
210
211         prepare_to_copy(orig);
212
213         tsk = alloc_task_struct();
214         if (!tsk)
215                 return NULL;
216
217         ti = alloc_thread_info(tsk);
218         if (!ti) {
219                 free_task_struct(tsk);
220                 return NULL;
221         }
222
223         err = arch_dup_task_struct(tsk, orig);
224         if (err)
225                 goto out;
226
227         tsk->stack = ti;
228
229         err = prop_local_init_single(&tsk->dirties);
230         if (err)
231                 goto out;
232
233         setup_thread_stack(tsk, orig);
234
235 #ifdef CONFIG_CC_STACKPROTECTOR
236         tsk->stack_canary = get_random_int();
237 #endif
238
239         /* One for us, one for whoever does the "release_task()" (usually parent) */
240         atomic_set(&tsk->usage,2);
241         atomic_set(&tsk->fs_excl, 0);
242 #ifdef CONFIG_BLK_DEV_IO_TRACE
243         tsk->btrace_seq = 0;
244 #endif
245         tsk->splice_pipe = NULL;
246         return tsk;
247
248 out:
249         free_thread_info(ti);
250         free_task_struct(tsk);
251         return NULL;
252 }
253
254 #ifdef CONFIG_MMU
255 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
256 {
257         struct vm_area_struct *mpnt, *tmp, **pprev;
258         struct rb_node **rb_link, *rb_parent;
259         int retval;
260         unsigned long charge;
261         struct mempolicy *pol;
262
263         down_write(&oldmm->mmap_sem);
264         flush_cache_dup_mm(oldmm);
265         /*
266          * Not linked in yet - no deadlock potential:
267          */
268         down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
269
270         mm->locked_vm = 0;
271         mm->mmap = NULL;
272         mm->mmap_cache = NULL;
273         mm->free_area_cache = oldmm->mmap_base;
274         mm->cached_hole_size = ~0UL;
275         mm->map_count = 0;
276         cpus_clear(mm->cpu_vm_mask);
277         mm->mm_rb = RB_ROOT;
278         rb_link = &mm->mm_rb.rb_node;
279         rb_parent = NULL;
280         pprev = &mm->mmap;
281
282         for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
283                 struct file *file;
284
285                 if (mpnt->vm_flags & VM_DONTCOPY) {
286                         long pages = vma_pages(mpnt);
287                         mm->total_vm -= pages;
288                         vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
289                                                                 -pages);
290                         continue;
291                 }
292                 charge = 0;
293                 if (mpnt->vm_flags & VM_ACCOUNT) {
294                         unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
295                         if (security_vm_enough_memory(len))
296                                 goto fail_nomem;
297                         charge = len;
298                 }
299                 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
300                 if (!tmp)
301                         goto fail_nomem;
302                 *tmp = *mpnt;
303                 pol = mpol_dup(vma_policy(mpnt));
304                 retval = PTR_ERR(pol);
305                 if (IS_ERR(pol))
306                         goto fail_nomem_policy;
307                 vma_set_policy(tmp, pol);
308                 tmp->vm_flags &= ~VM_LOCKED;
309                 tmp->vm_mm = mm;
310                 tmp->vm_next = NULL;
311                 anon_vma_link(tmp);
312                 file = tmp->vm_file;
313                 if (file) {
314                         struct inode *inode = file->f_path.dentry->d_inode;
315                         get_file(file);
316                         if (tmp->vm_flags & VM_DENYWRITE)
317                                 atomic_dec(&inode->i_writecount);
318
319                         /* insert tmp into the share list, just after mpnt */
320                         spin_lock(&file->f_mapping->i_mmap_lock);
321                         tmp->vm_truncate_count = mpnt->vm_truncate_count;
322                         flush_dcache_mmap_lock(file->f_mapping);
323                         vma_prio_tree_add(tmp, mpnt);
324                         flush_dcache_mmap_unlock(file->f_mapping);
325                         spin_unlock(&file->f_mapping->i_mmap_lock);
326                 }
327
328                 /*
329                  * Clear hugetlb-related page reserves for children. This only
330                  * affects MAP_PRIVATE mappings. Faults generated by the child
331                  * are not guaranteed to succeed, even if read-only
332                  */
333                 if (is_vm_hugetlb_page(tmp))
334                         reset_vma_resv_huge_pages(tmp);
335
336                 /*
337                  * Link in the new vma and copy the page table entries.
338                  */
339                 *pprev = tmp;
340                 pprev = &tmp->vm_next;
341
342                 __vma_link_rb(mm, tmp, rb_link, rb_parent);
343                 rb_link = &tmp->vm_rb.rb_right;
344                 rb_parent = &tmp->vm_rb;
345
346                 mm->map_count++;
347                 retval = copy_page_range(mm, oldmm, mpnt);
348
349                 if (tmp->vm_ops && tmp->vm_ops->open)
350                         tmp->vm_ops->open(tmp);
351
352                 if (retval)
353                         goto out;
354         }
355         /* a new mm has just been created */
356         arch_dup_mmap(oldmm, mm);
357         retval = 0;
358 out:
359         up_write(&mm->mmap_sem);
360         flush_tlb_mm(oldmm);
361         up_write(&oldmm->mmap_sem);
362         return retval;
363 fail_nomem_policy:
364         kmem_cache_free(vm_area_cachep, tmp);
365 fail_nomem:
366         retval = -ENOMEM;
367         vm_unacct_memory(charge);
368         goto out;
369 }
370
371 static inline int mm_alloc_pgd(struct mm_struct * mm)
372 {
373         mm->pgd = pgd_alloc(mm);
374         if (unlikely(!mm->pgd))
375                 return -ENOMEM;
376         return 0;
377 }
378
379 static inline void mm_free_pgd(struct mm_struct * mm)
380 {
381         pgd_free(mm, mm->pgd);
382 }
383 #else
384 #define dup_mmap(mm, oldmm)     (0)
385 #define mm_alloc_pgd(mm)        (0)
386 #define mm_free_pgd(mm)
387 #endif /* CONFIG_MMU */
388
389 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
390
391 #define allocate_mm()   (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
392 #define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))
393
394 #include <linux/init_task.h>
395
396 static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p)
397 {
398         atomic_set(&mm->mm_users, 1);
399         atomic_set(&mm->mm_count, 1);
400         init_rwsem(&mm->mmap_sem);
401         INIT_LIST_HEAD(&mm->mmlist);
402         mm->flags = (current->mm) ? current->mm->flags
403                                   : MMF_DUMP_FILTER_DEFAULT;
404         mm->core_state = NULL;
405         mm->nr_ptes = 0;
406         set_mm_counter(mm, file_rss, 0);
407         set_mm_counter(mm, anon_rss, 0);
408         spin_lock_init(&mm->page_table_lock);
409         rwlock_init(&mm->ioctx_list_lock);
410         mm->ioctx_list = NULL;
411         mm->free_area_cache = TASK_UNMAPPED_BASE;
412         mm->cached_hole_size = ~0UL;
413         mm_init_owner(mm, p);
414
415         if (likely(!mm_alloc_pgd(mm))) {
416                 mm->def_flags = 0;
417                 mmu_notifier_mm_init(mm);
418                 return mm;
419         }
420
421         free_mm(mm);
422         return NULL;
423 }
424
425 /*
426  * Allocate and initialize an mm_struct.
427  */
428 struct mm_struct * mm_alloc(void)
429 {
430         struct mm_struct * mm;
431
432         mm = allocate_mm();
433         if (mm) {
434                 memset(mm, 0, sizeof(*mm));
435                 mm = mm_init(mm, current);
436         }
437         return mm;
438 }
439
440 /*
441  * Called when the last reference to the mm
442  * is dropped: either by a lazy thread or by
443  * mmput. Free the page directory and the mm.
444  */
445 void __mmdrop(struct mm_struct *mm)
446 {
447         BUG_ON(mm == &init_mm);
448         mm_free_pgd(mm);
449         destroy_context(mm);
450         mmu_notifier_mm_destroy(mm);
451         free_mm(mm);
452 }
453 EXPORT_SYMBOL_GPL(__mmdrop);
454
455 /*
456  * Decrement the use count and release all resources for an mm.
457  */
458 void mmput(struct mm_struct *mm)
459 {
460         might_sleep();
461
462         if (atomic_dec_and_test(&mm->mm_users)) {
463                 exit_aio(mm);
464                 exit_mmap(mm);
465                 set_mm_exe_file(mm, NULL);
466                 if (!list_empty(&mm->mmlist)) {
467                         spin_lock(&mmlist_lock);
468                         list_del(&mm->mmlist);
469                         spin_unlock(&mmlist_lock);
470                 }
471                 put_swap_token(mm);
472                 mmdrop(mm);
473         }
474 }
475 EXPORT_SYMBOL_GPL(mmput);
476
477 /**
478  * get_task_mm - acquire a reference to the task's mm
479  *
480  * Returns %NULL if the task has no mm.  Checks PF_KTHREAD (meaning
481  * this kernel workthread has transiently adopted a user mm with use_mm,
482  * to do its AIO) is not set and if so returns a reference to it, after
483  * bumping up the use count.  User must release the mm via mmput()
484  * after use.  Typically used by /proc and ptrace.
485  */
486 struct mm_struct *get_task_mm(struct task_struct *task)
487 {
488         struct mm_struct *mm;
489
490         task_lock(task);
491         mm = task->mm;
492         if (mm) {
493                 if (task->flags & PF_KTHREAD)
494                         mm = NULL;
495                 else
496                         atomic_inc(&mm->mm_users);
497         }
498         task_unlock(task);
499         return mm;
500 }
501 EXPORT_SYMBOL_GPL(get_task_mm);
502
503 /* Please note the differences between mmput and mm_release.
504  * mmput is called whenever we stop holding onto a mm_struct,
505  * error success whatever.
506  *
507  * mm_release is called after a mm_struct has been removed
508  * from the current process.
509  *
510  * This difference is important for error handling, when we
511  * only half set up a mm_struct for a new process and need to restore
512  * the old one.  Because we mmput the new mm_struct before
513  * restoring the old one. . .
514  * Eric Biederman 10 January 1998
515  */
516 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
517 {
518         struct completion *vfork_done = tsk->vfork_done;
519
520         /* Get rid of any cached register state */
521         deactivate_mm(tsk, mm);
522
523         /* notify parent sleeping on vfork() */
524         if (vfork_done) {
525                 tsk->vfork_done = NULL;
526                 complete(vfork_done);
527         }
528
529         /*
530          * If we're exiting normally, clear a user-space tid field if
531          * requested.  We leave this alone when dying by signal, to leave
532          * the value intact in a core dump, and to save the unnecessary
533          * trouble otherwise.  Userland only wants this done for a sys_exit.
534          */
535         if (tsk->clear_child_tid
536             && !(tsk->flags & PF_SIGNALED)
537             && atomic_read(&mm->mm_users) > 1) {
538                 u32 __user * tidptr = tsk->clear_child_tid;
539                 tsk->clear_child_tid = NULL;
540
541                 /*
542                  * We don't check the error code - if userspace has
543                  * not set up a proper pointer then tough luck.
544                  */
545                 put_user(0, tidptr);
546                 sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0);
547         }
548 }
549
550 /*
551  * Allocate a new mm structure and copy contents from the
552  * mm structure of the passed in task structure.
553  */
554 struct mm_struct *dup_mm(struct task_struct *tsk)
555 {
556         struct mm_struct *mm, *oldmm = current->mm;
557         int err;
558
559         if (!oldmm)
560                 return NULL;
561
562         mm = allocate_mm();
563         if (!mm)
564                 goto fail_nomem;
565
566         memcpy(mm, oldmm, sizeof(*mm));
567
568         /* Initializing for Swap token stuff */
569         mm->token_priority = 0;
570         mm->last_interval = 0;
571
572         if (!mm_init(mm, tsk))
573                 goto fail_nomem;
574
575         if (init_new_context(tsk, mm))
576                 goto fail_nocontext;
577
578         dup_mm_exe_file(oldmm, mm);
579
580         err = dup_mmap(mm, oldmm);
581         if (err)
582                 goto free_pt;
583
584         mm->hiwater_rss = get_mm_rss(mm);
585         mm->hiwater_vm = mm->total_vm;
586
587         return mm;
588
589 free_pt:
590         mmput(mm);
591
592 fail_nomem:
593         return NULL;
594
595 fail_nocontext:
596         /*
597          * If init_new_context() failed, we cannot use mmput() to free the mm
598          * because it calls destroy_context()
599          */
600         mm_free_pgd(mm);
601         free_mm(mm);
602         return NULL;
603 }
604
605 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
606 {
607         struct mm_struct * mm, *oldmm;
608         int retval;
609
610         tsk->min_flt = tsk->maj_flt = 0;
611         tsk->nvcsw = tsk->nivcsw = 0;
612
613         tsk->mm = NULL;
614         tsk->active_mm = NULL;
615
616         /*
617          * Are we cloning a kernel thread?
618          *
619          * We need to steal a active VM for that..
620          */
621         oldmm = current->mm;
622         if (!oldmm)
623                 return 0;
624
625         if (clone_flags & CLONE_VM) {
626                 atomic_inc(&oldmm->mm_users);
627                 mm = oldmm;
628                 goto good_mm;
629         }
630
631         retval = -ENOMEM;
632         mm = dup_mm(tsk);
633         if (!mm)
634                 goto fail_nomem;
635
636 good_mm:
637         /* Initializing for Swap token stuff */
638         mm->token_priority = 0;
639         mm->last_interval = 0;
640
641         tsk->mm = mm;
642         tsk->active_mm = mm;
643         return 0;
644
645 fail_nomem:
646         return retval;
647 }
648
649 static struct fs_struct *__copy_fs_struct(struct fs_struct *old)
650 {
651         struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL);
652         /* We don't need to lock fs - think why ;-) */
653         if (fs) {
654                 atomic_set(&fs->count, 1);
655                 rwlock_init(&fs->lock);
656                 fs->umask = old->umask;
657                 read_lock(&old->lock);
658                 fs->root = old->root;
659                 path_get(&old->root);
660                 fs->pwd = old->pwd;
661                 path_get(&old->pwd);
662                 read_unlock(&old->lock);
663         }
664         return fs;
665 }
666
667 struct fs_struct *copy_fs_struct(struct fs_struct *old)
668 {
669         return __copy_fs_struct(old);
670 }
671
672 EXPORT_SYMBOL_GPL(copy_fs_struct);
673
674 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
675 {
676         if (clone_flags & CLONE_FS) {
677                 atomic_inc(&current->fs->count);
678                 return 0;
679         }
680         tsk->fs = __copy_fs_struct(current->fs);
681         if (!tsk->fs)
682                 return -ENOMEM;
683         return 0;
684 }
685
686 static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
687 {
688         struct files_struct *oldf, *newf;
689         int error = 0;
690
691         /*
692          * A background process may not have any files ...
693          */
694         oldf = current->files;
695         if (!oldf)
696                 goto out;
697
698         if (clone_flags & CLONE_FILES) {
699                 atomic_inc(&oldf->count);
700                 goto out;
701         }
702
703         newf = dup_fd(oldf, &error);
704         if (!newf)
705                 goto out;
706
707         tsk->files = newf;
708         error = 0;
709 out:
710         return error;
711 }
712
713 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
714 {
715 #ifdef CONFIG_BLOCK
716         struct io_context *ioc = current->io_context;
717
718         if (!ioc)
719                 return 0;
720         /*
721          * Share io context with parent, if CLONE_IO is set
722          */
723         if (clone_flags & CLONE_IO) {
724                 tsk->io_context = ioc_task_link(ioc);
725                 if (unlikely(!tsk->io_context))
726                         return -ENOMEM;
727         } else if (ioprio_valid(ioc->ioprio)) {
728                 tsk->io_context = alloc_io_context(GFP_KERNEL, -1);
729                 if (unlikely(!tsk->io_context))
730                         return -ENOMEM;
731
732                 tsk->io_context->ioprio = ioc->ioprio;
733         }
734 #endif
735         return 0;
736 }
737
738 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
739 {
740         struct sighand_struct *sig;
741
742         if (clone_flags & (CLONE_SIGHAND | CLONE_THREAD)) {
743                 atomic_inc(&current->sighand->count);
744                 return 0;
745         }
746         sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
747         rcu_assign_pointer(tsk->sighand, sig);
748         if (!sig)
749                 return -ENOMEM;
750         atomic_set(&sig->count, 1);
751         memcpy(sig->action, current->sighand->action, sizeof(sig->action));
752         return 0;
753 }
754
755 void __cleanup_sighand(struct sighand_struct *sighand)
756 {
757         if (atomic_dec_and_test(&sighand->count))
758                 kmem_cache_free(sighand_cachep, sighand);
759 }
760
761
762 /*
763  * Initialize POSIX timer handling for a thread group.
764  */
765 static void posix_cpu_timers_init_group(struct signal_struct *sig)
766 {
767         /* Thread group counters. */
768         thread_group_cputime_init(sig);
769
770         /* Expiration times and increments. */
771         sig->it_virt_expires = cputime_zero;
772         sig->it_virt_incr = cputime_zero;
773         sig->it_prof_expires = cputime_zero;
774         sig->it_prof_incr = cputime_zero;
775
776         /* Cached expiration times. */
777         sig->cputime_expires.prof_exp = cputime_zero;
778         sig->cputime_expires.virt_exp = cputime_zero;
779         sig->cputime_expires.sched_exp = 0;
780
781         /* The timer lists. */
782         INIT_LIST_HEAD(&sig->cpu_timers[0]);
783         INIT_LIST_HEAD(&sig->cpu_timers[1]);
784         INIT_LIST_HEAD(&sig->cpu_timers[2]);
785 }
786
787 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
788 {
789         struct signal_struct *sig;
790         int ret;
791
792         if (clone_flags & CLONE_THREAD) {
793                 ret = thread_group_cputime_clone_thread(current);
794                 if (likely(!ret)) {
795                         atomic_inc(&current->signal->count);
796                         atomic_inc(&current->signal->live);
797                 }
798                 return ret;
799         }
800         sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL);
801         tsk->signal = sig;
802         if (!sig)
803                 return -ENOMEM;
804
805         ret = copy_thread_group_keys(tsk);
806         if (ret < 0) {
807                 kmem_cache_free(signal_cachep, sig);
808                 return ret;
809         }
810
811         atomic_set(&sig->count, 1);
812         atomic_set(&sig->live, 1);
813         init_waitqueue_head(&sig->wait_chldexit);
814         sig->flags = 0;
815         sig->group_exit_code = 0;
816         sig->group_exit_task = NULL;
817         sig->group_stop_count = 0;
818         sig->curr_target = tsk;
819         init_sigpending(&sig->shared_pending);
820         INIT_LIST_HEAD(&sig->posix_timers);
821
822         hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
823         sig->it_real_incr.tv64 = 0;
824         sig->real_timer.function = it_real_fn;
825
826         sig->leader = 0;        /* session leadership doesn't inherit */
827         sig->tty_old_pgrp = NULL;
828         sig->tty = NULL;
829
830         sig->cutime = sig->cstime = cputime_zero;
831         sig->gtime = cputime_zero;
832         sig->cgtime = cputime_zero;
833         sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0;
834         sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0;
835         sig->inblock = sig->oublock = sig->cinblock = sig->coublock = 0;
836         task_io_accounting_init(&sig->ioac);
837         taskstats_tgid_init(sig);
838
839         task_lock(current->group_leader);
840         memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
841         task_unlock(current->group_leader);
842
843         posix_cpu_timers_init_group(sig);
844
845         acct_init_pacct(&sig->pacct);
846
847         tty_audit_fork(sig);
848
849         return 0;
850 }
851
852 void __cleanup_signal(struct signal_struct *sig)
853 {
854         thread_group_cputime_free(sig);
855         exit_thread_group_keys(sig);
856         tty_kref_put(sig->tty);
857         kmem_cache_free(signal_cachep, sig);
858 }
859
860 static void cleanup_signal(struct task_struct *tsk)
861 {
862         struct signal_struct *sig = tsk->signal;
863
864         atomic_dec(&sig->live);
865
866         if (atomic_dec_and_test(&sig->count))
867                 __cleanup_signal(sig);
868 }
869
870 static void copy_flags(unsigned long clone_flags, struct task_struct *p)
871 {
872         unsigned long new_flags = p->flags;
873
874         new_flags &= ~PF_SUPERPRIV;
875         new_flags |= PF_FORKNOEXEC;
876         new_flags |= PF_STARTING;
877         p->flags = new_flags;
878         clear_freeze_flag(p);
879 }
880
881 asmlinkage long sys_set_tid_address(int __user *tidptr)
882 {
883         current->clear_child_tid = tidptr;
884
885         return task_pid_vnr(current);
886 }
887
888 static void rt_mutex_init_task(struct task_struct *p)
889 {
890         spin_lock_init(&p->pi_lock);
891 #ifdef CONFIG_RT_MUTEXES
892         plist_head_init(&p->pi_waiters, &p->pi_lock);
893         p->pi_blocked_on = NULL;
894 #endif
895 }
896
897 #ifdef CONFIG_MM_OWNER
898 void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
899 {
900         mm->owner = p;
901 }
902 #endif /* CONFIG_MM_OWNER */
903
904 /*
905  * Initialize POSIX timer handling for a single task.
906  */
907 static void posix_cpu_timers_init(struct task_struct *tsk)
908 {
909         tsk->cputime_expires.prof_exp = cputime_zero;
910         tsk->cputime_expires.virt_exp = cputime_zero;
911         tsk->cputime_expires.sched_exp = 0;
912         INIT_LIST_HEAD(&tsk->cpu_timers[0]);
913         INIT_LIST_HEAD(&tsk->cpu_timers[1]);
914         INIT_LIST_HEAD(&tsk->cpu_timers[2]);
915 }
916
917 /*
918  * This creates a new process as a copy of the old one,
919  * but does not actually start it yet.
920  *
921  * It copies the registers, and all the appropriate
922  * parts of the process environment (as per the clone
923  * flags). The actual kick-off is left to the caller.
924  */
925 static struct task_struct *copy_process(unsigned long clone_flags,
926                                         unsigned long stack_start,
927                                         struct pt_regs *regs,
928                                         unsigned long stack_size,
929                                         int __user *child_tidptr,
930                                         struct pid *pid,
931                                         int trace)
932 {
933         int retval;
934         struct task_struct *p;
935         int cgroup_callbacks_done = 0;
936
937         if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
938                 return ERR_PTR(-EINVAL);
939
940         /*
941          * Thread groups must share signals as well, and detached threads
942          * can only be started up within the thread group.
943          */
944         if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
945                 return ERR_PTR(-EINVAL);
946
947         /*
948          * Shared signal handlers imply shared VM. By way of the above,
949          * thread groups also imply shared VM. Blocking this case allows
950          * for various simplifications in other code.
951          */
952         if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
953                 return ERR_PTR(-EINVAL);
954
955         retval = security_task_create(clone_flags);
956         if (retval)
957                 goto fork_out;
958
959         retval = -ENOMEM;
960         p = dup_task_struct(current);
961         if (!p)
962                 goto fork_out;
963
964         rt_mutex_init_task(p);
965
966 #ifdef CONFIG_PROVE_LOCKING
967         DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
968         DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
969 #endif
970         retval = -EAGAIN;
971         if (atomic_read(&p->cred->user->processes) >=
972                         p->signal->rlim[RLIMIT_NPROC].rlim_cur) {
973                 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
974                     p->cred->user != current->nsproxy->user_ns->root_user)
975                         goto bad_fork_free;
976         }
977
978         retval = copy_creds(p, clone_flags);
979         if (retval < 0)
980                 goto bad_fork_free;
981
982         /*
983          * If multiple threads are within copy_process(), then this check
984          * triggers too late. This doesn't hurt, the check is only there
985          * to stop root fork bombs.
986          */
987         if (nr_threads >= max_threads)
988                 goto bad_fork_cleanup_count;
989
990         if (!try_module_get(task_thread_info(p)->exec_domain->module))
991                 goto bad_fork_cleanup_count;
992
993         if (p->binfmt && !try_module_get(p->binfmt->module))
994                 goto bad_fork_cleanup_put_domain;
995
996         p->did_exec = 0;
997         delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
998         copy_flags(clone_flags, p);
999         INIT_LIST_HEAD(&p->children);
1000         INIT_LIST_HEAD(&p->sibling);
1001 #ifdef CONFIG_PREEMPT_RCU
1002         p->rcu_read_lock_nesting = 0;
1003         p->rcu_flipctr_idx = 0;
1004 #endif /* #ifdef CONFIG_PREEMPT_RCU */
1005         p->vfork_done = NULL;
1006         spin_lock_init(&p->alloc_lock);
1007
1008         clear_tsk_thread_flag(p, TIF_SIGPENDING);
1009         init_sigpending(&p->pending);
1010
1011         p->utime = cputime_zero;
1012         p->stime = cputime_zero;
1013         p->gtime = cputime_zero;
1014         p->utimescaled = cputime_zero;
1015         p->stimescaled = cputime_zero;
1016         p->prev_utime = cputime_zero;
1017         p->prev_stime = cputime_zero;
1018
1019         p->default_timer_slack_ns = current->timer_slack_ns;
1020
1021 #ifdef CONFIG_DETECT_SOFTLOCKUP
1022         p->last_switch_count = 0;
1023         p->last_switch_timestamp = 0;
1024 #endif
1025
1026         task_io_accounting_init(&p->ioac);
1027         acct_clear_integrals(p);
1028
1029         posix_cpu_timers_init(p);
1030
1031         p->lock_depth = -1;             /* -1 = no lock */
1032         do_posix_clock_monotonic_gettime(&p->start_time);
1033         p->real_start_time = p->start_time;
1034         monotonic_to_bootbased(&p->real_start_time);
1035         p->io_context = NULL;
1036         p->audit_context = NULL;
1037         cgroup_fork(p);
1038 #ifdef CONFIG_NUMA
1039         p->mempolicy = mpol_dup(p->mempolicy);
1040         if (IS_ERR(p->mempolicy)) {
1041                 retval = PTR_ERR(p->mempolicy);
1042                 p->mempolicy = NULL;
1043                 goto bad_fork_cleanup_cgroup;
1044         }
1045         mpol_fix_fork_child_flag(p);
1046 #endif
1047 #ifdef CONFIG_TRACE_IRQFLAGS
1048         p->irq_events = 0;
1049 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
1050         p->hardirqs_enabled = 1;
1051 #else
1052         p->hardirqs_enabled = 0;
1053 #endif
1054         p->hardirq_enable_ip = 0;
1055         p->hardirq_enable_event = 0;
1056         p->hardirq_disable_ip = _THIS_IP_;
1057         p->hardirq_disable_event = 0;
1058         p->softirqs_enabled = 1;
1059         p->softirq_enable_ip = _THIS_IP_;
1060         p->softirq_enable_event = 0;
1061         p->softirq_disable_ip = 0;
1062         p->softirq_disable_event = 0;
1063         p->hardirq_context = 0;
1064         p->softirq_context = 0;
1065 #endif
1066 #ifdef CONFIG_LOCKDEP
1067         p->lockdep_depth = 0; /* no locks held yet */
1068         p->curr_chain_key = 0;
1069         p->lockdep_recursion = 0;
1070 #endif
1071
1072 #ifdef CONFIG_DEBUG_MUTEXES
1073         p->blocked_on = NULL; /* not blocked yet */
1074 #endif
1075
1076         /* Perform scheduler related setup. Assign this task to a CPU. */
1077         sched_fork(p, clone_flags);
1078
1079         if ((retval = audit_alloc(p)))
1080                 goto bad_fork_cleanup_policy;
1081         /* copy all the process information */
1082         if ((retval = copy_semundo(clone_flags, p)))
1083                 goto bad_fork_cleanup_audit;
1084         if ((retval = copy_files(clone_flags, p)))
1085                 goto bad_fork_cleanup_semundo;
1086         if ((retval = copy_fs(clone_flags, p)))
1087                 goto bad_fork_cleanup_files;
1088         if ((retval = copy_sighand(clone_flags, p)))
1089                 goto bad_fork_cleanup_fs;
1090         if ((retval = copy_signal(clone_flags, p)))
1091                 goto bad_fork_cleanup_sighand;
1092         if ((retval = copy_mm(clone_flags, p)))
1093                 goto bad_fork_cleanup_signal;
1094         if ((retval = copy_keys(clone_flags, p)))
1095                 goto bad_fork_cleanup_mm;
1096         if ((retval = copy_namespaces(clone_flags, p)))
1097                 goto bad_fork_cleanup_keys;
1098         if ((retval = copy_io(clone_flags, p)))
1099                 goto bad_fork_cleanup_namespaces;
1100         retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs);
1101         if (retval)
1102                 goto bad_fork_cleanup_io;
1103
1104         if (pid != &init_struct_pid) {
1105                 retval = -ENOMEM;
1106                 pid = alloc_pid(task_active_pid_ns(p));
1107                 if (!pid)
1108                         goto bad_fork_cleanup_io;
1109
1110                 if (clone_flags & CLONE_NEWPID) {
1111                         retval = pid_ns_prepare_proc(task_active_pid_ns(p));
1112                         if (retval < 0)
1113                                 goto bad_fork_free_pid;
1114                 }
1115         }
1116
1117         p->pid = pid_nr(pid);
1118         p->tgid = p->pid;
1119         if (clone_flags & CLONE_THREAD)
1120                 p->tgid = current->tgid;
1121
1122         if (current->nsproxy != p->nsproxy) {
1123                 retval = ns_cgroup_clone(p, pid);
1124                 if (retval)
1125                         goto bad_fork_free_pid;
1126         }
1127
1128         p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1129         /*
1130          * Clear TID on mm_release()?
1131          */
1132         p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL;
1133 #ifdef CONFIG_FUTEX
1134         p->robust_list = NULL;
1135 #ifdef CONFIG_COMPAT
1136         p->compat_robust_list = NULL;
1137 #endif
1138         INIT_LIST_HEAD(&p->pi_state_list);
1139         p->pi_state_cache = NULL;
1140 #endif
1141         /*
1142          * sigaltstack should be cleared when sharing the same VM
1143          */
1144         if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1145                 p->sas_ss_sp = p->sas_ss_size = 0;
1146
1147         /*
1148          * Syscall tracing should be turned off in the child regardless
1149          * of CLONE_PTRACE.
1150          */
1151         clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1152 #ifdef TIF_SYSCALL_EMU
1153         clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1154 #endif
1155         clear_all_latency_tracing(p);
1156
1157         /* Our parent execution domain becomes current domain
1158            These must match for thread signalling to apply */
1159         p->parent_exec_id = p->self_exec_id;
1160
1161         /* ok, now we should be set up.. */
1162         p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
1163         p->pdeath_signal = 0;
1164         p->exit_state = 0;
1165
1166         /*
1167          * Ok, make it visible to the rest of the system.
1168          * We dont wake it up yet.
1169          */
1170         p->group_leader = p;
1171         INIT_LIST_HEAD(&p->thread_group);
1172
1173         /* Now that the task is set up, run cgroup callbacks if
1174          * necessary. We need to run them before the task is visible
1175          * on the tasklist. */
1176         cgroup_fork_callbacks(p);
1177         cgroup_callbacks_done = 1;
1178
1179         /* Need tasklist lock for parent etc handling! */
1180         write_lock_irq(&tasklist_lock);
1181
1182         /*
1183          * The task hasn't been attached yet, so its cpus_allowed mask will
1184          * not be changed, nor will its assigned CPU.
1185          *
1186          * The cpus_allowed mask of the parent may have changed after it was
1187          * copied first time - so re-copy it here, then check the child's CPU
1188          * to ensure it is on a valid CPU (and if not, just force it back to
1189          * parent's CPU). This avoids alot of nasty races.
1190          */
1191         p->cpus_allowed = current->cpus_allowed;
1192         p->rt.nr_cpus_allowed = current->rt.nr_cpus_allowed;
1193         if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) ||
1194                         !cpu_online(task_cpu(p))))
1195                 set_task_cpu(p, smp_processor_id());
1196
1197         /* CLONE_PARENT re-uses the old parent */
1198         if (clone_flags & (CLONE_PARENT|CLONE_THREAD))
1199                 p->real_parent = current->real_parent;
1200         else
1201                 p->real_parent = current;
1202
1203         spin_lock(&current->sighand->siglock);
1204
1205         /*
1206          * Process group and session signals need to be delivered to just the
1207          * parent before the fork or both the parent and the child after the
1208          * fork. Restart if a signal comes in before we add the new process to
1209          * it's process group.
1210          * A fatal signal pending means that current will exit, so the new
1211          * thread can't slip out of an OOM kill (or normal SIGKILL).
1212          */
1213         recalc_sigpending();
1214         if (signal_pending(current)) {
1215                 spin_unlock(&current->sighand->siglock);
1216                 write_unlock_irq(&tasklist_lock);
1217                 retval = -ERESTARTNOINTR;
1218                 goto bad_fork_free_pid;
1219         }
1220
1221         if (clone_flags & CLONE_THREAD) {
1222                 p->group_leader = current->group_leader;
1223                 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1224         }
1225
1226         if (likely(p->pid)) {
1227                 list_add_tail(&p->sibling, &p->real_parent->children);
1228                 tracehook_finish_clone(p, clone_flags, trace);
1229
1230                 if (thread_group_leader(p)) {
1231                         if (clone_flags & CLONE_NEWPID)
1232                                 p->nsproxy->pid_ns->child_reaper = p;
1233
1234                         p->signal->leader_pid = pid;
1235                         tty_kref_put(p->signal->tty);
1236                         p->signal->tty = tty_kref_get(current->signal->tty);
1237                         set_task_pgrp(p, task_pgrp_nr(current));
1238                         set_task_session(p, task_session_nr(current));
1239                         attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
1240                         attach_pid(p, PIDTYPE_SID, task_session(current));
1241                         list_add_tail_rcu(&p->tasks, &init_task.tasks);
1242                         __get_cpu_var(process_counts)++;
1243                 }
1244                 attach_pid(p, PIDTYPE_PID, pid);
1245                 nr_threads++;
1246         }
1247
1248         total_forks++;
1249         spin_unlock(&current->sighand->siglock);
1250         write_unlock_irq(&tasklist_lock);
1251         proc_fork_connector(p);
1252         cgroup_post_fork(p);
1253         return p;
1254
1255 bad_fork_free_pid:
1256         if (pid != &init_struct_pid)
1257                 free_pid(pid);
1258 bad_fork_cleanup_io:
1259         put_io_context(p->io_context);
1260 bad_fork_cleanup_namespaces:
1261         exit_task_namespaces(p);
1262 bad_fork_cleanup_keys:
1263         exit_keys(p);
1264 bad_fork_cleanup_mm:
1265         if (p->mm)
1266                 mmput(p->mm);
1267 bad_fork_cleanup_signal:
1268         cleanup_signal(p);
1269 bad_fork_cleanup_sighand:
1270         __cleanup_sighand(p->sighand);
1271 bad_fork_cleanup_fs:
1272         exit_fs(p); /* blocking */
1273 bad_fork_cleanup_files:
1274         exit_files(p); /* blocking */
1275 bad_fork_cleanup_semundo:
1276         exit_sem(p);
1277 bad_fork_cleanup_audit:
1278         audit_free(p);
1279 bad_fork_cleanup_policy:
1280 #ifdef CONFIG_NUMA
1281         mpol_put(p->mempolicy);
1282 bad_fork_cleanup_cgroup:
1283 #endif
1284         cgroup_exit(p, cgroup_callbacks_done);
1285         delayacct_tsk_free(p);
1286         if (p->binfmt)
1287                 module_put(p->binfmt->module);
1288 bad_fork_cleanup_put_domain:
1289         module_put(task_thread_info(p)->exec_domain->module);
1290 bad_fork_cleanup_count:
1291         put_cred(p->cred);
1292 bad_fork_free:
1293         free_task(p);
1294 fork_out:
1295         return ERR_PTR(retval);
1296 }
1297
1298 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1299 {
1300         memset(regs, 0, sizeof(struct pt_regs));
1301         return regs;
1302 }
1303
1304 struct task_struct * __cpuinit fork_idle(int cpu)
1305 {
1306         struct task_struct *task;
1307         struct pt_regs regs;
1308
1309         task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL,
1310                             &init_struct_pid, 0);
1311         if (!IS_ERR(task))
1312                 init_idle(task, cpu);
1313
1314         return task;
1315 }
1316
1317 /*
1318  *  Ok, this is the main fork-routine.
1319  *
1320  * It copies the process, and if successful kick-starts
1321  * it and waits for it to finish using the VM if required.
1322  */
1323 long do_fork(unsigned long clone_flags,
1324               unsigned long stack_start,
1325               struct pt_regs *regs,
1326               unsigned long stack_size,
1327               int __user *parent_tidptr,
1328               int __user *child_tidptr)
1329 {
1330         struct task_struct *p;
1331         int trace = 0;
1332         long nr;
1333
1334         /*
1335          * We hope to recycle these flags after 2.6.26
1336          */
1337         if (unlikely(clone_flags & CLONE_STOPPED)) {
1338                 static int __read_mostly count = 100;
1339
1340                 if (count > 0 && printk_ratelimit()) {
1341                         char comm[TASK_COMM_LEN];
1342
1343                         count--;
1344                         printk(KERN_INFO "fork(): process `%s' used deprecated "
1345                                         "clone flags 0x%lx\n",
1346                                 get_task_comm(comm, current),
1347                                 clone_flags & CLONE_STOPPED);
1348                 }
1349         }
1350
1351         /*
1352          * When called from kernel_thread, don't do user tracing stuff.
1353          */
1354         if (likely(user_mode(regs)))
1355                 trace = tracehook_prepare_clone(clone_flags);
1356
1357         p = copy_process(clone_flags, stack_start, regs, stack_size,
1358                          child_tidptr, NULL, trace);
1359         /*
1360          * Do this prior waking up the new thread - the thread pointer
1361          * might get invalid after that point, if the thread exits quickly.
1362          */
1363         if (!IS_ERR(p)) {
1364                 struct completion vfork;
1365
1366                 trace_sched_process_fork(current, p);
1367
1368                 nr = task_pid_vnr(p);
1369
1370                 if (clone_flags & CLONE_PARENT_SETTID)
1371                         put_user(nr, parent_tidptr);
1372
1373                 if (clone_flags & CLONE_VFORK) {
1374                         p->vfork_done = &vfork;
1375                         init_completion(&vfork);
1376                 }
1377
1378                 tracehook_report_clone(trace, regs, clone_flags, nr, p);
1379
1380                 /*
1381                  * We set PF_STARTING at creation in case tracing wants to
1382                  * use this to distinguish a fully live task from one that
1383                  * hasn't gotten to tracehook_report_clone() yet.  Now we
1384                  * clear it and set the child going.
1385                  */
1386                 p->flags &= ~PF_STARTING;
1387
1388                 if (unlikely(clone_flags & CLONE_STOPPED)) {
1389                         /*
1390                          * We'll start up with an immediate SIGSTOP.
1391                          */
1392                         sigaddset(&p->pending.signal, SIGSTOP);
1393                         set_tsk_thread_flag(p, TIF_SIGPENDING);
1394                         __set_task_state(p, TASK_STOPPED);
1395                 } else {
1396                         wake_up_new_task(p, clone_flags);
1397                 }
1398
1399                 tracehook_report_clone_complete(trace, regs,
1400                                                 clone_flags, nr, p);
1401
1402                 if (clone_flags & CLONE_VFORK) {
1403                         freezer_do_not_count();
1404                         wait_for_completion(&vfork);
1405                         freezer_count();
1406                         tracehook_report_vfork_done(p, nr);
1407                 }
1408         } else {
1409                 nr = PTR_ERR(p);
1410         }
1411         return nr;
1412 }
1413
1414 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1415 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1416 #endif
1417
1418 static void sighand_ctor(void *data)
1419 {
1420         struct sighand_struct *sighand = data;
1421
1422         spin_lock_init(&sighand->siglock);
1423         init_waitqueue_head(&sighand->signalfd_wqh);
1424 }
1425
1426 void __init proc_caches_init(void)
1427 {
1428         sighand_cachep = kmem_cache_create("sighand_cache",
1429                         sizeof(struct sighand_struct), 0,
1430                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU,
1431                         sighand_ctor);
1432         signal_cachep = kmem_cache_create("signal_cache",
1433                         sizeof(struct signal_struct), 0,
1434                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1435         files_cachep = kmem_cache_create("files_cache",
1436                         sizeof(struct files_struct), 0,
1437                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1438         fs_cachep = kmem_cache_create("fs_cache",
1439                         sizeof(struct fs_struct), 0,
1440                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1441         vm_area_cachep = kmem_cache_create("vm_area_struct",
1442                         sizeof(struct vm_area_struct), 0,
1443                         SLAB_PANIC, NULL);
1444         mm_cachep = kmem_cache_create("mm_struct",
1445                         sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1446                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1447 }
1448
1449 /*
1450  * Check constraints on flags passed to the unshare system call and
1451  * force unsharing of additional process context as appropriate.
1452  */
1453 static void check_unshare_flags(unsigned long *flags_ptr)
1454 {
1455         /*
1456          * If unsharing a thread from a thread group, must also
1457          * unshare vm.
1458          */
1459         if (*flags_ptr & CLONE_THREAD)
1460                 *flags_ptr |= CLONE_VM;
1461
1462         /*
1463          * If unsharing vm, must also unshare signal handlers.
1464          */
1465         if (*flags_ptr & CLONE_VM)
1466                 *flags_ptr |= CLONE_SIGHAND;
1467
1468         /*
1469          * If unsharing signal handlers and the task was created
1470          * using CLONE_THREAD, then must unshare the thread
1471          */
1472         if ((*flags_ptr & CLONE_SIGHAND) &&
1473             (atomic_read(&current->signal->count) > 1))
1474                 *flags_ptr |= CLONE_THREAD;
1475
1476         /*
1477          * If unsharing namespace, must also unshare filesystem information.
1478          */
1479         if (*flags_ptr & CLONE_NEWNS)
1480                 *flags_ptr |= CLONE_FS;
1481 }
1482
1483 /*
1484  * Unsharing of tasks created with CLONE_THREAD is not supported yet
1485  */
1486 static int unshare_thread(unsigned long unshare_flags)
1487 {
1488         if (unshare_flags & CLONE_THREAD)
1489                 return -EINVAL;
1490
1491         return 0;
1492 }
1493
1494 /*
1495  * Unshare the filesystem structure if it is being shared
1496  */
1497 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1498 {
1499         struct fs_struct *fs = current->fs;
1500
1501         if ((unshare_flags & CLONE_FS) &&
1502             (fs && atomic_read(&fs->count) > 1)) {
1503                 *new_fsp = __copy_fs_struct(current->fs);
1504                 if (!*new_fsp)
1505                         return -ENOMEM;
1506         }
1507
1508         return 0;
1509 }
1510
1511 /*
1512  * Unsharing of sighand is not supported yet
1513  */
1514 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
1515 {
1516         struct sighand_struct *sigh = current->sighand;
1517
1518         if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1)
1519                 return -EINVAL;
1520         else
1521                 return 0;
1522 }
1523
1524 /*
1525  * Unshare vm if it is being shared
1526  */
1527 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
1528 {
1529         struct mm_struct *mm = current->mm;
1530
1531         if ((unshare_flags & CLONE_VM) &&
1532             (mm && atomic_read(&mm->mm_users) > 1)) {
1533                 return -EINVAL;
1534         }
1535
1536         return 0;
1537 }
1538
1539 /*
1540  * Unshare file descriptor table if it is being shared
1541  */
1542 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1543 {
1544         struct files_struct *fd = current->files;
1545         int error = 0;
1546
1547         if ((unshare_flags & CLONE_FILES) &&
1548             (fd && atomic_read(&fd->count) > 1)) {
1549                 *new_fdp = dup_fd(fd, &error);
1550                 if (!*new_fdp)
1551                         return error;
1552         }
1553
1554         return 0;
1555 }
1556
1557 /*
1558  * unshare allows a process to 'unshare' part of the process
1559  * context which was originally shared using clone.  copy_*
1560  * functions used by do_fork() cannot be used here directly
1561  * because they modify an inactive task_struct that is being
1562  * constructed. Here we are modifying the current, active,
1563  * task_struct.
1564  */
1565 asmlinkage long sys_unshare(unsigned long unshare_flags)
1566 {
1567         int err = 0;
1568         struct fs_struct *fs, *new_fs = NULL;
1569         struct sighand_struct *new_sigh = NULL;
1570         struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
1571         struct files_struct *fd, *new_fd = NULL;
1572         struct nsproxy *new_nsproxy = NULL;
1573         int do_sysvsem = 0;
1574
1575         check_unshare_flags(&unshare_flags);
1576
1577         /* Return -EINVAL for all unsupported flags */
1578         err = -EINVAL;
1579         if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1580                                 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1581                                 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWUSER|
1582                                 CLONE_NEWNET))
1583                 goto bad_unshare_out;
1584
1585         /*
1586          * CLONE_NEWIPC must also detach from the undolist: after switching
1587          * to a new ipc namespace, the semaphore arrays from the old
1588          * namespace are unreachable.
1589          */
1590         if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1591                 do_sysvsem = 1;
1592         if ((err = unshare_thread(unshare_flags)))
1593                 goto bad_unshare_out;
1594         if ((err = unshare_fs(unshare_flags, &new_fs)))
1595                 goto bad_unshare_cleanup_thread;
1596         if ((err = unshare_sighand(unshare_flags, &new_sigh)))
1597                 goto bad_unshare_cleanup_fs;
1598         if ((err = unshare_vm(unshare_flags, &new_mm)))
1599                 goto bad_unshare_cleanup_sigh;
1600         if ((err = unshare_fd(unshare_flags, &new_fd)))
1601                 goto bad_unshare_cleanup_vm;
1602         if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
1603                         new_fs)))
1604                 goto bad_unshare_cleanup_fd;
1605
1606         if (new_fs ||  new_mm || new_fd || do_sysvsem || new_nsproxy) {
1607                 if (do_sysvsem) {
1608                         /*
1609                          * CLONE_SYSVSEM is equivalent to sys_exit().
1610                          */
1611                         exit_sem(current);
1612                 }
1613
1614                 if (new_nsproxy) {
1615                         switch_task_namespaces(current, new_nsproxy);
1616                         new_nsproxy = NULL;
1617                 }
1618
1619                 task_lock(current);
1620
1621                 if (new_fs) {
1622                         fs = current->fs;
1623                         current->fs = new_fs;
1624                         new_fs = fs;
1625                 }
1626
1627                 if (new_mm) {
1628                         mm = current->mm;
1629                         active_mm = current->active_mm;
1630                         current->mm = new_mm;
1631                         current->active_mm = new_mm;
1632                         activate_mm(active_mm, new_mm);
1633                         new_mm = mm;
1634                 }
1635
1636                 if (new_fd) {
1637                         fd = current->files;
1638                         current->files = new_fd;
1639                         new_fd = fd;
1640                 }
1641
1642                 task_unlock(current);
1643         }
1644
1645         if (new_nsproxy)
1646                 put_nsproxy(new_nsproxy);
1647
1648 bad_unshare_cleanup_fd:
1649         if (new_fd)
1650                 put_files_struct(new_fd);
1651
1652 bad_unshare_cleanup_vm:
1653         if (new_mm)
1654                 mmput(new_mm);
1655
1656 bad_unshare_cleanup_sigh:
1657         if (new_sigh)
1658                 if (atomic_dec_and_test(&new_sigh->count))
1659                         kmem_cache_free(sighand_cachep, new_sigh);
1660
1661 bad_unshare_cleanup_fs:
1662         if (new_fs)
1663                 put_fs_struct(new_fs);
1664
1665 bad_unshare_cleanup_thread:
1666 bad_unshare_out:
1667         return err;
1668 }
1669
1670 /*
1671  *      Helper to unshare the files of the current task.
1672  *      We don't want to expose copy_files internals to
1673  *      the exec layer of the kernel.
1674  */
1675
1676 int unshare_files(struct files_struct **displaced)
1677 {
1678         struct task_struct *task = current;
1679         struct files_struct *copy = NULL;
1680         int error;
1681
1682         error = unshare_fd(CLONE_FILES, &copy);
1683         if (error || !copy) {
1684                 *displaced = NULL;
1685                 return error;
1686         }
1687         *displaced = task->files;
1688         task_lock(task);
1689         task->files = copy;
1690         task_unlock(task);
1691         return 0;
1692 }