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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/ksm.h> | |
53 | #include <linux/acct.h> | |
54 | #include <linux/tsacct_kern.h> | |
55 | #include <linux/cn_proc.h> | |
56 | #include <linux/freezer.h> | |
57 | #include <linux/delayacct.h> | |
58 | #include <linux/taskstats_kern.h> | |
59 | #include <linux/random.h> | |
60 | #include <linux/tty.h> | |
61 | #include <linux/proc_fs.h> | |
62 | #include <linux/blkdev.h> | |
63 | #include <linux/fs_struct.h> | |
64 | #include <linux/magic.h> | |
65 | #include <linux/perf_event.h> | |
66 | #include <linux/posix-timers.h> | |
67 | #include <linux/user-return-notifier.h> | |
68 | ||
69 | #include <asm/pgtable.h> | |
70 | #include <asm/pgalloc.h> | |
71 | #include <asm/uaccess.h> | |
72 | #include <asm/mmu_context.h> | |
73 | #include <asm/cacheflush.h> | |
74 | #include <asm/tlbflush.h> | |
75 | ||
76 | #include <trace/events/sched.h> | |
77 | ||
78 | /* | |
79 | * Protected counters by write_lock_irq(&tasklist_lock) | |
80 | */ | |
81 | unsigned long total_forks; /* Handle normal Linux uptimes. */ | |
82 | int nr_threads; /* The idle threads do not count.. */ | |
83 | ||
84 | int max_threads; /* tunable limit on nr_threads */ | |
85 | ||
86 | DEFINE_PER_CPU(unsigned long, process_counts) = 0; | |
87 | ||
88 | __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ | |
89 | ||
90 | #ifdef CONFIG_PROVE_RCU | |
91 | int lockdep_tasklist_lock_is_held(void) | |
92 | { | |
93 | return lockdep_is_held(&tasklist_lock); | |
94 | } | |
95 | EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held); | |
96 | #endif /* #ifdef CONFIG_PROVE_RCU */ | |
97 | ||
98 | int nr_processes(void) | |
99 | { | |
100 | int cpu; | |
101 | int total = 0; | |
102 | ||
103 | for_each_possible_cpu(cpu) | |
104 | total += per_cpu(process_counts, cpu); | |
105 | ||
106 | return total; | |
107 | } | |
108 | ||
109 | #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR | |
110 | # define alloc_task_struct() kmem_cache_alloc(task_struct_cachep, GFP_KERNEL) | |
111 | # define free_task_struct(tsk) kmem_cache_free(task_struct_cachep, (tsk)) | |
112 | static struct kmem_cache *task_struct_cachep; | |
113 | #endif | |
114 | ||
115 | #ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR | |
116 | static inline struct thread_info *alloc_thread_info(struct task_struct *tsk) | |
117 | { | |
118 | #ifdef CONFIG_DEBUG_STACK_USAGE | |
119 | gfp_t mask = GFP_KERNEL | __GFP_ZERO; | |
120 | #else | |
121 | gfp_t mask = GFP_KERNEL; | |
122 | #endif | |
123 | return (struct thread_info *)__get_free_pages(mask, THREAD_SIZE_ORDER); | |
124 | } | |
125 | ||
126 | static inline void free_thread_info(struct thread_info *ti) | |
127 | { | |
128 | free_pages((unsigned long)ti, THREAD_SIZE_ORDER); | |
129 | } | |
130 | #endif | |
131 | ||
132 | /* SLAB cache for signal_struct structures (tsk->signal) */ | |
133 | static struct kmem_cache *signal_cachep; | |
134 | ||
135 | /* SLAB cache for sighand_struct structures (tsk->sighand) */ | |
136 | struct kmem_cache *sighand_cachep; | |
137 | ||
138 | /* SLAB cache for files_struct structures (tsk->files) */ | |
139 | struct kmem_cache *files_cachep; | |
140 | ||
141 | /* SLAB cache for fs_struct structures (tsk->fs) */ | |
142 | struct kmem_cache *fs_cachep; | |
143 | ||
144 | /* SLAB cache for vm_area_struct structures */ | |
145 | struct kmem_cache *vm_area_cachep; | |
146 | ||
147 | /* SLAB cache for mm_struct structures (tsk->mm) */ | |
148 | static struct kmem_cache *mm_cachep; | |
149 | ||
150 | static void account_kernel_stack(struct thread_info *ti, int account) | |
151 | { | |
152 | struct zone *zone = page_zone(virt_to_page(ti)); | |
153 | ||
154 | mod_zone_page_state(zone, NR_KERNEL_STACK, account); | |
155 | } | |
156 | ||
157 | void free_task(struct task_struct *tsk) | |
158 | { | |
159 | prop_local_destroy_single(&tsk->dirties); | |
160 | account_kernel_stack(tsk->stack, -1); | |
161 | free_thread_info(tsk->stack); | |
162 | rt_mutex_debug_task_free(tsk); | |
163 | ftrace_graph_exit_task(tsk); | |
164 | free_task_struct(tsk); | |
165 | } | |
166 | EXPORT_SYMBOL(free_task); | |
167 | ||
168 | static inline void free_signal_struct(struct signal_struct *sig) | |
169 | { | |
170 | taskstats_tgid_free(sig); | |
171 | kmem_cache_free(signal_cachep, sig); | |
172 | } | |
173 | ||
174 | static inline void put_signal_struct(struct signal_struct *sig) | |
175 | { | |
176 | if (atomic_dec_and_test(&sig->sigcnt)) | |
177 | free_signal_struct(sig); | |
178 | } | |
179 | ||
180 | void __put_task_struct(struct task_struct *tsk) | |
181 | { | |
182 | WARN_ON(!tsk->exit_state); | |
183 | WARN_ON(atomic_read(&tsk->usage)); | |
184 | WARN_ON(tsk == current); | |
185 | ||
186 | exit_creds(tsk); | |
187 | delayacct_tsk_free(tsk); | |
188 | put_signal_struct(tsk->signal); | |
189 | ||
190 | if (!profile_handoff_task(tsk)) | |
191 | free_task(tsk); | |
192 | } | |
193 | ||
194 | /* | |
195 | * macro override instead of weak attribute alias, to workaround | |
196 | * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions. | |
197 | */ | |
198 | #ifndef arch_task_cache_init | |
199 | #define arch_task_cache_init() | |
200 | #endif | |
201 | ||
202 | void __init fork_init(unsigned long mempages) | |
203 | { | |
204 | #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR | |
205 | #ifndef ARCH_MIN_TASKALIGN | |
206 | #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES | |
207 | #endif | |
208 | /* create a slab on which task_structs can be allocated */ | |
209 | task_struct_cachep = | |
210 | kmem_cache_create("task_struct", sizeof(struct task_struct), | |
211 | ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL); | |
212 | #endif | |
213 | ||
214 | /* do the arch specific task caches init */ | |
215 | arch_task_cache_init(); | |
216 | ||
217 | /* | |
218 | * The default maximum number of threads is set to a safe | |
219 | * value: the thread structures can take up at most half | |
220 | * of memory. | |
221 | */ | |
222 | max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE); | |
223 | ||
224 | /* | |
225 | * we need to allow at least 20 threads to boot a system | |
226 | */ | |
227 | if(max_threads < 20) | |
228 | max_threads = 20; | |
229 | ||
230 | init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; | |
231 | init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; | |
232 | init_task.signal->rlim[RLIMIT_SIGPENDING] = | |
233 | init_task.signal->rlim[RLIMIT_NPROC]; | |
234 | } | |
235 | ||
236 | int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst, | |
237 | struct task_struct *src) | |
238 | { | |
239 | *dst = *src; | |
240 | return 0; | |
241 | } | |
242 | ||
243 | static struct task_struct *dup_task_struct(struct task_struct *orig) | |
244 | { | |
245 | struct task_struct *tsk; | |
246 | struct thread_info *ti; | |
247 | unsigned long *stackend; | |
248 | ||
249 | int err; | |
250 | ||
251 | prepare_to_copy(orig); | |
252 | ||
253 | tsk = alloc_task_struct(); | |
254 | if (!tsk) | |
255 | return NULL; | |
256 | ||
257 | ti = alloc_thread_info(tsk); | |
258 | if (!ti) { | |
259 | free_task_struct(tsk); | |
260 | return NULL; | |
261 | } | |
262 | ||
263 | err = arch_dup_task_struct(tsk, orig); | |
264 | if (err) | |
265 | goto out; | |
266 | ||
267 | tsk->stack = ti; | |
268 | ||
269 | err = prop_local_init_single(&tsk->dirties); | |
270 | if (err) | |
271 | goto out; | |
272 | ||
273 | setup_thread_stack(tsk, orig); | |
274 | clear_user_return_notifier(tsk); | |
275 | stackend = end_of_stack(tsk); | |
276 | *stackend = STACK_END_MAGIC; /* for overflow detection */ | |
277 | ||
278 | #ifdef CONFIG_CC_STACKPROTECTOR | |
279 | tsk->stack_canary = get_random_int(); | |
280 | #endif | |
281 | ||
282 | /* One for us, one for whoever does the "release_task()" (usually parent) */ | |
283 | atomic_set(&tsk->usage,2); | |
284 | atomic_set(&tsk->fs_excl, 0); | |
285 | #ifdef CONFIG_BLK_DEV_IO_TRACE | |
286 | tsk->btrace_seq = 0; | |
287 | #endif | |
288 | tsk->splice_pipe = NULL; | |
289 | ||
290 | account_kernel_stack(ti, 1); | |
291 | ||
292 | return tsk; | |
293 | ||
294 | out: | |
295 | free_thread_info(ti); | |
296 | free_task_struct(tsk); | |
297 | return NULL; | |
298 | } | |
299 | ||
300 | #ifdef CONFIG_MMU | |
301 | static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) | |
302 | { | |
303 | struct vm_area_struct *mpnt, *tmp, **pprev; | |
304 | struct rb_node **rb_link, *rb_parent; | |
305 | int retval; | |
306 | unsigned long charge; | |
307 | struct mempolicy *pol; | |
308 | ||
309 | down_write(&oldmm->mmap_sem); | |
310 | flush_cache_dup_mm(oldmm); | |
311 | /* | |
312 | * Not linked in yet - no deadlock potential: | |
313 | */ | |
314 | down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); | |
315 | ||
316 | mm->locked_vm = 0; | |
317 | mm->mmap = NULL; | |
318 | mm->mmap_cache = NULL; | |
319 | mm->free_area_cache = oldmm->mmap_base; | |
320 | mm->cached_hole_size = ~0UL; | |
321 | mm->map_count = 0; | |
322 | cpumask_clear(mm_cpumask(mm)); | |
323 | mm->mm_rb = RB_ROOT; | |
324 | rb_link = &mm->mm_rb.rb_node; | |
325 | rb_parent = NULL; | |
326 | pprev = &mm->mmap; | |
327 | retval = ksm_fork(mm, oldmm); | |
328 | if (retval) | |
329 | goto out; | |
330 | ||
331 | for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { | |
332 | struct file *file; | |
333 | ||
334 | if (mpnt->vm_flags & VM_DONTCOPY) { | |
335 | long pages = vma_pages(mpnt); | |
336 | mm->total_vm -= pages; | |
337 | vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file, | |
338 | -pages); | |
339 | continue; | |
340 | } | |
341 | charge = 0; | |
342 | if (mpnt->vm_flags & VM_ACCOUNT) { | |
343 | unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT; | |
344 | if (security_vm_enough_memory(len)) | |
345 | goto fail_nomem; | |
346 | charge = len; | |
347 | } | |
348 | tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); | |
349 | if (!tmp) | |
350 | goto fail_nomem; | |
351 | *tmp = *mpnt; | |
352 | INIT_LIST_HEAD(&tmp->anon_vma_chain); | |
353 | pol = mpol_dup(vma_policy(mpnt)); | |
354 | retval = PTR_ERR(pol); | |
355 | if (IS_ERR(pol)) | |
356 | goto fail_nomem_policy; | |
357 | vma_set_policy(tmp, pol); | |
358 | if (anon_vma_fork(tmp, mpnt)) | |
359 | goto fail_nomem_anon_vma_fork; | |
360 | tmp->vm_flags &= ~VM_LOCKED; | |
361 | tmp->vm_mm = mm; | |
362 | tmp->vm_next = NULL; | |
363 | file = tmp->vm_file; | |
364 | if (file) { | |
365 | struct inode *inode = file->f_path.dentry->d_inode; | |
366 | struct address_space *mapping = file->f_mapping; | |
367 | ||
368 | get_file(file); | |
369 | if (tmp->vm_flags & VM_DENYWRITE) | |
370 | atomic_dec(&inode->i_writecount); | |
371 | spin_lock(&mapping->i_mmap_lock); | |
372 | if (tmp->vm_flags & VM_SHARED) | |
373 | mapping->i_mmap_writable++; | |
374 | tmp->vm_truncate_count = mpnt->vm_truncate_count; | |
375 | flush_dcache_mmap_lock(mapping); | |
376 | /* insert tmp into the share list, just after mpnt */ | |
377 | vma_prio_tree_add(tmp, mpnt); | |
378 | flush_dcache_mmap_unlock(mapping); | |
379 | spin_unlock(&mapping->i_mmap_lock); | |
380 | } | |
381 | ||
382 | /* | |
383 | * Clear hugetlb-related page reserves for children. This only | |
384 | * affects MAP_PRIVATE mappings. Faults generated by the child | |
385 | * are not guaranteed to succeed, even if read-only | |
386 | */ | |
387 | if (is_vm_hugetlb_page(tmp)) | |
388 | reset_vma_resv_huge_pages(tmp); | |
389 | ||
390 | /* | |
391 | * Link in the new vma and copy the page table entries. | |
392 | */ | |
393 | *pprev = tmp; | |
394 | pprev = &tmp->vm_next; | |
395 | ||
396 | __vma_link_rb(mm, tmp, rb_link, rb_parent); | |
397 | rb_link = &tmp->vm_rb.rb_right; | |
398 | rb_parent = &tmp->vm_rb; | |
399 | ||
400 | mm->map_count++; | |
401 | retval = copy_page_range(mm, oldmm, mpnt); | |
402 | ||
403 | if (tmp->vm_ops && tmp->vm_ops->open) | |
404 | tmp->vm_ops->open(tmp); | |
405 | ||
406 | if (retval) | |
407 | goto out; | |
408 | } | |
409 | /* a new mm has just been created */ | |
410 | arch_dup_mmap(oldmm, mm); | |
411 | retval = 0; | |
412 | out: | |
413 | up_write(&mm->mmap_sem); | |
414 | flush_tlb_mm(oldmm); | |
415 | up_write(&oldmm->mmap_sem); | |
416 | return retval; | |
417 | fail_nomem_anon_vma_fork: | |
418 | mpol_put(pol); | |
419 | fail_nomem_policy: | |
420 | kmem_cache_free(vm_area_cachep, tmp); | |
421 | fail_nomem: | |
422 | retval = -ENOMEM; | |
423 | vm_unacct_memory(charge); | |
424 | goto out; | |
425 | } | |
426 | ||
427 | static inline int mm_alloc_pgd(struct mm_struct * mm) | |
428 | { | |
429 | mm->pgd = pgd_alloc(mm); | |
430 | if (unlikely(!mm->pgd)) | |
431 | return -ENOMEM; | |
432 | return 0; | |
433 | } | |
434 | ||
435 | static inline void mm_free_pgd(struct mm_struct * mm) | |
436 | { | |
437 | pgd_free(mm, mm->pgd); | |
438 | } | |
439 | #else | |
440 | #define dup_mmap(mm, oldmm) (0) | |
441 | #define mm_alloc_pgd(mm) (0) | |
442 | #define mm_free_pgd(mm) | |
443 | #endif /* CONFIG_MMU */ | |
444 | ||
445 | __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); | |
446 | ||
447 | #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL)) | |
448 | #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) | |
449 | ||
450 | static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT; | |
451 | ||
452 | static int __init coredump_filter_setup(char *s) | |
453 | { | |
454 | default_dump_filter = | |
455 | (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) & | |
456 | MMF_DUMP_FILTER_MASK; | |
457 | return 1; | |
458 | } | |
459 | ||
460 | __setup("coredump_filter=", coredump_filter_setup); | |
461 | ||
462 | #include <linux/init_task.h> | |
463 | ||
464 | static void mm_init_aio(struct mm_struct *mm) | |
465 | { | |
466 | #ifdef CONFIG_AIO | |
467 | spin_lock_init(&mm->ioctx_lock); | |
468 | INIT_HLIST_HEAD(&mm->ioctx_list); | |
469 | #endif | |
470 | } | |
471 | ||
472 | static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p) | |
473 | { | |
474 | atomic_set(&mm->mm_users, 1); | |
475 | atomic_set(&mm->mm_count, 1); | |
476 | init_rwsem(&mm->mmap_sem); | |
477 | INIT_LIST_HEAD(&mm->mmlist); | |
478 | mm->flags = (current->mm) ? | |
479 | (current->mm->flags & MMF_INIT_MASK) : default_dump_filter; | |
480 | mm->core_state = NULL; | |
481 | mm->nr_ptes = 0; | |
482 | memset(&mm->rss_stat, 0, sizeof(mm->rss_stat)); | |
483 | spin_lock_init(&mm->page_table_lock); | |
484 | mm->free_area_cache = TASK_UNMAPPED_BASE; | |
485 | mm->cached_hole_size = ~0UL; | |
486 | mm_init_aio(mm); | |
487 | mm_init_owner(mm, p); | |
488 | ||
489 | if (likely(!mm_alloc_pgd(mm))) { | |
490 | mm->def_flags = 0; | |
491 | mmu_notifier_mm_init(mm); | |
492 | return mm; | |
493 | } | |
494 | ||
495 | free_mm(mm); | |
496 | return NULL; | |
497 | } | |
498 | ||
499 | /* | |
500 | * Allocate and initialize an mm_struct. | |
501 | */ | |
502 | struct mm_struct * mm_alloc(void) | |
503 | { | |
504 | struct mm_struct * mm; | |
505 | ||
506 | mm = allocate_mm(); | |
507 | if (mm) { | |
508 | memset(mm, 0, sizeof(*mm)); | |
509 | mm = mm_init(mm, current); | |
510 | } | |
511 | return mm; | |
512 | } | |
513 | ||
514 | /* | |
515 | * Called when the last reference to the mm | |
516 | * is dropped: either by a lazy thread or by | |
517 | * mmput. Free the page directory and the mm. | |
518 | */ | |
519 | void __mmdrop(struct mm_struct *mm) | |
520 | { | |
521 | BUG_ON(mm == &init_mm); | |
522 | mm_free_pgd(mm); | |
523 | destroy_context(mm); | |
524 | mmu_notifier_mm_destroy(mm); | |
525 | free_mm(mm); | |
526 | } | |
527 | EXPORT_SYMBOL_GPL(__mmdrop); | |
528 | ||
529 | /* | |
530 | * Decrement the use count and release all resources for an mm. | |
531 | */ | |
532 | void mmput(struct mm_struct *mm) | |
533 | { | |
534 | might_sleep(); | |
535 | ||
536 | if (atomic_dec_and_test(&mm->mm_users)) { | |
537 | exit_aio(mm); | |
538 | ksm_exit(mm); | |
539 | exit_mmap(mm); | |
540 | set_mm_exe_file(mm, NULL); | |
541 | if (!list_empty(&mm->mmlist)) { | |
542 | spin_lock(&mmlist_lock); | |
543 | list_del(&mm->mmlist); | |
544 | spin_unlock(&mmlist_lock); | |
545 | } | |
546 | put_swap_token(mm); | |
547 | if (mm->binfmt) | |
548 | module_put(mm->binfmt->module); | |
549 | mmdrop(mm); | |
550 | } | |
551 | } | |
552 | EXPORT_SYMBOL_GPL(mmput); | |
553 | ||
554 | /** | |
555 | * get_task_mm - acquire a reference to the task's mm | |
556 | * | |
557 | * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning | |
558 | * this kernel workthread has transiently adopted a user mm with use_mm, | |
559 | * to do its AIO) is not set and if so returns a reference to it, after | |
560 | * bumping up the use count. User must release the mm via mmput() | |
561 | * after use. Typically used by /proc and ptrace. | |
562 | */ | |
563 | struct mm_struct *get_task_mm(struct task_struct *task) | |
564 | { | |
565 | struct mm_struct *mm; | |
566 | ||
567 | task_lock(task); | |
568 | mm = task->mm; | |
569 | if (mm) { | |
570 | if (task->flags & PF_KTHREAD) | |
571 | mm = NULL; | |
572 | else | |
573 | atomic_inc(&mm->mm_users); | |
574 | } | |
575 | task_unlock(task); | |
576 | return mm; | |
577 | } | |
578 | EXPORT_SYMBOL_GPL(get_task_mm); | |
579 | ||
580 | /* Please note the differences between mmput and mm_release. | |
581 | * mmput is called whenever we stop holding onto a mm_struct, | |
582 | * error success whatever. | |
583 | * | |
584 | * mm_release is called after a mm_struct has been removed | |
585 | * from the current process. | |
586 | * | |
587 | * This difference is important for error handling, when we | |
588 | * only half set up a mm_struct for a new process and need to restore | |
589 | * the old one. Because we mmput the new mm_struct before | |
590 | * restoring the old one. . . | |
591 | * Eric Biederman 10 January 1998 | |
592 | */ | |
593 | void mm_release(struct task_struct *tsk, struct mm_struct *mm) | |
594 | { | |
595 | struct completion *vfork_done = tsk->vfork_done; | |
596 | ||
597 | /* Get rid of any futexes when releasing the mm */ | |
598 | #ifdef CONFIG_FUTEX | |
599 | if (unlikely(tsk->robust_list)) { | |
600 | exit_robust_list(tsk); | |
601 | tsk->robust_list = NULL; | |
602 | } | |
603 | #ifdef CONFIG_COMPAT | |
604 | if (unlikely(tsk->compat_robust_list)) { | |
605 | compat_exit_robust_list(tsk); | |
606 | tsk->compat_robust_list = NULL; | |
607 | } | |
608 | #endif | |
609 | if (unlikely(!list_empty(&tsk->pi_state_list))) | |
610 | exit_pi_state_list(tsk); | |
611 | #endif | |
612 | ||
613 | /* Get rid of any cached register state */ | |
614 | deactivate_mm(tsk, mm); | |
615 | ||
616 | /* notify parent sleeping on vfork() */ | |
617 | if (vfork_done) { | |
618 | tsk->vfork_done = NULL; | |
619 | complete(vfork_done); | |
620 | } | |
621 | ||
622 | /* | |
623 | * If we're exiting normally, clear a user-space tid field if | |
624 | * requested. We leave this alone when dying by signal, to leave | |
625 | * the value intact in a core dump, and to save the unnecessary | |
626 | * trouble otherwise. Userland only wants this done for a sys_exit. | |
627 | */ | |
628 | if (tsk->clear_child_tid) { | |
629 | if (!(tsk->flags & PF_SIGNALED) && | |
630 | atomic_read(&mm->mm_users) > 1) { | |
631 | /* | |
632 | * We don't check the error code - if userspace has | |
633 | * not set up a proper pointer then tough luck. | |
634 | */ | |
635 | put_user(0, tsk->clear_child_tid); | |
636 | sys_futex(tsk->clear_child_tid, FUTEX_WAKE, | |
637 | 1, NULL, NULL, 0); | |
638 | } | |
639 | tsk->clear_child_tid = NULL; | |
640 | } | |
641 | } | |
642 | ||
643 | /* | |
644 | * Allocate a new mm structure and copy contents from the | |
645 | * mm structure of the passed in task structure. | |
646 | */ | |
647 | struct mm_struct *dup_mm(struct task_struct *tsk) | |
648 | { | |
649 | struct mm_struct *mm, *oldmm = current->mm; | |
650 | int err; | |
651 | ||
652 | if (!oldmm) | |
653 | return NULL; | |
654 | ||
655 | mm = allocate_mm(); | |
656 | if (!mm) | |
657 | goto fail_nomem; | |
658 | ||
659 | memcpy(mm, oldmm, sizeof(*mm)); | |
660 | ||
661 | /* Initializing for Swap token stuff */ | |
662 | mm->token_priority = 0; | |
663 | mm->last_interval = 0; | |
664 | ||
665 | if (!mm_init(mm, tsk)) | |
666 | goto fail_nomem; | |
667 | ||
668 | if (init_new_context(tsk, mm)) | |
669 | goto fail_nocontext; | |
670 | ||
671 | dup_mm_exe_file(oldmm, mm); | |
672 | ||
673 | err = dup_mmap(mm, oldmm); | |
674 | if (err) | |
675 | goto free_pt; | |
676 | ||
677 | mm->hiwater_rss = get_mm_rss(mm); | |
678 | mm->hiwater_vm = mm->total_vm; | |
679 | ||
680 | if (mm->binfmt && !try_module_get(mm->binfmt->module)) | |
681 | goto free_pt; | |
682 | ||
683 | return mm; | |
684 | ||
685 | free_pt: | |
686 | /* don't put binfmt in mmput, we haven't got module yet */ | |
687 | mm->binfmt = NULL; | |
688 | mmput(mm); | |
689 | ||
690 | fail_nomem: | |
691 | return NULL; | |
692 | ||
693 | fail_nocontext: | |
694 | /* | |
695 | * If init_new_context() failed, we cannot use mmput() to free the mm | |
696 | * because it calls destroy_context() | |
697 | */ | |
698 | mm_free_pgd(mm); | |
699 | free_mm(mm); | |
700 | return NULL; | |
701 | } | |
702 | ||
703 | static int copy_mm(unsigned long clone_flags, struct task_struct * tsk) | |
704 | { | |
705 | struct mm_struct * mm, *oldmm; | |
706 | int retval; | |
707 | ||
708 | tsk->min_flt = tsk->maj_flt = 0; | |
709 | tsk->nvcsw = tsk->nivcsw = 0; | |
710 | #ifdef CONFIG_DETECT_HUNG_TASK | |
711 | tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw; | |
712 | #endif | |
713 | ||
714 | tsk->mm = NULL; | |
715 | tsk->active_mm = NULL; | |
716 | ||
717 | /* | |
718 | * Are we cloning a kernel thread? | |
719 | * | |
720 | * We need to steal a active VM for that.. | |
721 | */ | |
722 | oldmm = current->mm; | |
723 | if (!oldmm) | |
724 | return 0; | |
725 | ||
726 | if (clone_flags & CLONE_VM) { | |
727 | atomic_inc(&oldmm->mm_users); | |
728 | mm = oldmm; | |
729 | goto good_mm; | |
730 | } | |
731 | ||
732 | retval = -ENOMEM; | |
733 | mm = dup_mm(tsk); | |
734 | if (!mm) | |
735 | goto fail_nomem; | |
736 | ||
737 | good_mm: | |
738 | /* Initializing for Swap token stuff */ | |
739 | mm->token_priority = 0; | |
740 | mm->last_interval = 0; | |
741 | ||
742 | tsk->mm = mm; | |
743 | tsk->active_mm = mm; | |
744 | return 0; | |
745 | ||
746 | fail_nomem: | |
747 | return retval; | |
748 | } | |
749 | ||
750 | static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) | |
751 | { | |
752 | struct fs_struct *fs = current->fs; | |
753 | if (clone_flags & CLONE_FS) { | |
754 | /* tsk->fs is already what we want */ | |
755 | write_lock(&fs->lock); | |
756 | if (fs->in_exec) { | |
757 | write_unlock(&fs->lock); | |
758 | return -EAGAIN; | |
759 | } | |
760 | fs->users++; | |
761 | write_unlock(&fs->lock); | |
762 | return 0; | |
763 | } | |
764 | tsk->fs = copy_fs_struct(fs); | |
765 | if (!tsk->fs) | |
766 | return -ENOMEM; | |
767 | return 0; | |
768 | } | |
769 | ||
770 | static int copy_files(unsigned long clone_flags, struct task_struct * tsk) | |
771 | { | |
772 | struct files_struct *oldf, *newf; | |
773 | int error = 0; | |
774 | ||
775 | /* | |
776 | * A background process may not have any files ... | |
777 | */ | |
778 | oldf = current->files; | |
779 | if (!oldf) | |
780 | goto out; | |
781 | ||
782 | if (clone_flags & CLONE_FILES) { | |
783 | atomic_inc(&oldf->count); | |
784 | goto out; | |
785 | } | |
786 | ||
787 | newf = dup_fd(oldf, &error); | |
788 | if (!newf) | |
789 | goto out; | |
790 | ||
791 | tsk->files = newf; | |
792 | error = 0; | |
793 | out: | |
794 | return error; | |
795 | } | |
796 | ||
797 | static int copy_io(unsigned long clone_flags, struct task_struct *tsk) | |
798 | { | |
799 | #ifdef CONFIG_BLOCK | |
800 | struct io_context *ioc = current->io_context; | |
801 | ||
802 | if (!ioc) | |
803 | return 0; | |
804 | /* | |
805 | * Share io context with parent, if CLONE_IO is set | |
806 | */ | |
807 | if (clone_flags & CLONE_IO) { | |
808 | tsk->io_context = ioc_task_link(ioc); | |
809 | if (unlikely(!tsk->io_context)) | |
810 | return -ENOMEM; | |
811 | } else if (ioprio_valid(ioc->ioprio)) { | |
812 | tsk->io_context = alloc_io_context(GFP_KERNEL, -1); | |
813 | if (unlikely(!tsk->io_context)) | |
814 | return -ENOMEM; | |
815 | ||
816 | tsk->io_context->ioprio = ioc->ioprio; | |
817 | } | |
818 | #endif | |
819 | return 0; | |
820 | } | |
821 | ||
822 | static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) | |
823 | { | |
824 | struct sighand_struct *sig; | |
825 | ||
826 | if (clone_flags & CLONE_SIGHAND) { | |
827 | atomic_inc(¤t->sighand->count); | |
828 | return 0; | |
829 | } | |
830 | sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); | |
831 | rcu_assign_pointer(tsk->sighand, sig); | |
832 | if (!sig) | |
833 | return -ENOMEM; | |
834 | atomic_set(&sig->count, 1); | |
835 | memcpy(sig->action, current->sighand->action, sizeof(sig->action)); | |
836 | return 0; | |
837 | } | |
838 | ||
839 | void __cleanup_sighand(struct sighand_struct *sighand) | |
840 | { | |
841 | if (atomic_dec_and_test(&sighand->count)) | |
842 | kmem_cache_free(sighand_cachep, sighand); | |
843 | } | |
844 | ||
845 | ||
846 | /* | |
847 | * Initialize POSIX timer handling for a thread group. | |
848 | */ | |
849 | static void posix_cpu_timers_init_group(struct signal_struct *sig) | |
850 | { | |
851 | unsigned long cpu_limit; | |
852 | ||
853 | /* Thread group counters. */ | |
854 | thread_group_cputime_init(sig); | |
855 | ||
856 | cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur); | |
857 | if (cpu_limit != RLIM_INFINITY) { | |
858 | sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit); | |
859 | sig->cputimer.running = 1; | |
860 | } | |
861 | ||
862 | /* The timer lists. */ | |
863 | INIT_LIST_HEAD(&sig->cpu_timers[0]); | |
864 | INIT_LIST_HEAD(&sig->cpu_timers[1]); | |
865 | INIT_LIST_HEAD(&sig->cpu_timers[2]); | |
866 | } | |
867 | ||
868 | static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) | |
869 | { | |
870 | struct signal_struct *sig; | |
871 | ||
872 | if (clone_flags & CLONE_THREAD) | |
873 | return 0; | |
874 | ||
875 | sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL); | |
876 | tsk->signal = sig; | |
877 | if (!sig) | |
878 | return -ENOMEM; | |
879 | ||
880 | sig->nr_threads = 1; | |
881 | atomic_set(&sig->live, 1); | |
882 | atomic_set(&sig->sigcnt, 1); | |
883 | init_waitqueue_head(&sig->wait_chldexit); | |
884 | if (clone_flags & CLONE_NEWPID) | |
885 | sig->flags |= SIGNAL_UNKILLABLE; | |
886 | sig->curr_target = tsk; | |
887 | init_sigpending(&sig->shared_pending); | |
888 | INIT_LIST_HEAD(&sig->posix_timers); | |
889 | ||
890 | hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); | |
891 | sig->real_timer.function = it_real_fn; | |
892 | ||
893 | task_lock(current->group_leader); | |
894 | memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); | |
895 | task_unlock(current->group_leader); | |
896 | ||
897 | posix_cpu_timers_init_group(sig); | |
898 | ||
899 | tty_audit_fork(sig); | |
900 | ||
901 | sig->oom_adj = current->signal->oom_adj; | |
902 | ||
903 | return 0; | |
904 | } | |
905 | ||
906 | static void copy_flags(unsigned long clone_flags, struct task_struct *p) | |
907 | { | |
908 | unsigned long new_flags = p->flags; | |
909 | ||
910 | new_flags &= ~PF_SUPERPRIV; | |
911 | new_flags |= PF_FORKNOEXEC; | |
912 | new_flags |= PF_STARTING; | |
913 | p->flags = new_flags; | |
914 | clear_freeze_flag(p); | |
915 | } | |
916 | ||
917 | SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr) | |
918 | { | |
919 | current->clear_child_tid = tidptr; | |
920 | ||
921 | return task_pid_vnr(current); | |
922 | } | |
923 | ||
924 | static void rt_mutex_init_task(struct task_struct *p) | |
925 | { | |
926 | raw_spin_lock_init(&p->pi_lock); | |
927 | #ifdef CONFIG_RT_MUTEXES | |
928 | plist_head_init_raw(&p->pi_waiters, &p->pi_lock); | |
929 | p->pi_blocked_on = NULL; | |
930 | #endif | |
931 | } | |
932 | ||
933 | #ifdef CONFIG_MM_OWNER | |
934 | void mm_init_owner(struct mm_struct *mm, struct task_struct *p) | |
935 | { | |
936 | mm->owner = p; | |
937 | } | |
938 | #endif /* CONFIG_MM_OWNER */ | |
939 | ||
940 | /* | |
941 | * Initialize POSIX timer handling for a single task. | |
942 | */ | |
943 | static void posix_cpu_timers_init(struct task_struct *tsk) | |
944 | { | |
945 | tsk->cputime_expires.prof_exp = cputime_zero; | |
946 | tsk->cputime_expires.virt_exp = cputime_zero; | |
947 | tsk->cputime_expires.sched_exp = 0; | |
948 | INIT_LIST_HEAD(&tsk->cpu_timers[0]); | |
949 | INIT_LIST_HEAD(&tsk->cpu_timers[1]); | |
950 | INIT_LIST_HEAD(&tsk->cpu_timers[2]); | |
951 | } | |
952 | ||
953 | /* | |
954 | * This creates a new process as a copy of the old one, | |
955 | * but does not actually start it yet. | |
956 | * | |
957 | * It copies the registers, and all the appropriate | |
958 | * parts of the process environment (as per the clone | |
959 | * flags). The actual kick-off is left to the caller. | |
960 | */ | |
961 | static struct task_struct *copy_process(unsigned long clone_flags, | |
962 | unsigned long stack_start, | |
963 | struct pt_regs *regs, | |
964 | unsigned long stack_size, | |
965 | int __user *child_tidptr, | |
966 | struct pid *pid, | |
967 | int trace) | |
968 | { | |
969 | int retval; | |
970 | struct task_struct *p; | |
971 | int cgroup_callbacks_done = 0; | |
972 | ||
973 | if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) | |
974 | return ERR_PTR(-EINVAL); | |
975 | ||
976 | /* | |
977 | * Thread groups must share signals as well, and detached threads | |
978 | * can only be started up within the thread group. | |
979 | */ | |
980 | if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) | |
981 | return ERR_PTR(-EINVAL); | |
982 | ||
983 | /* | |
984 | * Shared signal handlers imply shared VM. By way of the above, | |
985 | * thread groups also imply shared VM. Blocking this case allows | |
986 | * for various simplifications in other code. | |
987 | */ | |
988 | if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) | |
989 | return ERR_PTR(-EINVAL); | |
990 | ||
991 | /* | |
992 | * Siblings of global init remain as zombies on exit since they are | |
993 | * not reaped by their parent (swapper). To solve this and to avoid | |
994 | * multi-rooted process trees, prevent global and container-inits | |
995 | * from creating siblings. | |
996 | */ | |
997 | if ((clone_flags & CLONE_PARENT) && | |
998 | current->signal->flags & SIGNAL_UNKILLABLE) | |
999 | return ERR_PTR(-EINVAL); | |
1000 | ||
1001 | retval = security_task_create(clone_flags); | |
1002 | if (retval) | |
1003 | goto fork_out; | |
1004 | ||
1005 | retval = -ENOMEM; | |
1006 | p = dup_task_struct(current); | |
1007 | if (!p) | |
1008 | goto fork_out; | |
1009 | ||
1010 | ftrace_graph_init_task(p); | |
1011 | ||
1012 | rt_mutex_init_task(p); | |
1013 | ||
1014 | #ifdef CONFIG_PROVE_LOCKING | |
1015 | DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); | |
1016 | DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); | |
1017 | #endif | |
1018 | retval = -EAGAIN; | |
1019 | if (atomic_read(&p->real_cred->user->processes) >= | |
1020 | task_rlimit(p, RLIMIT_NPROC)) { | |
1021 | if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) && | |
1022 | p->real_cred->user != INIT_USER) | |
1023 | goto bad_fork_free; | |
1024 | } | |
1025 | ||
1026 | retval = copy_creds(p, clone_flags); | |
1027 | if (retval < 0) | |
1028 | goto bad_fork_free; | |
1029 | ||
1030 | /* | |
1031 | * If multiple threads are within copy_process(), then this check | |
1032 | * triggers too late. This doesn't hurt, the check is only there | |
1033 | * to stop root fork bombs. | |
1034 | */ | |
1035 | retval = -EAGAIN; | |
1036 | if (nr_threads >= max_threads) | |
1037 | goto bad_fork_cleanup_count; | |
1038 | ||
1039 | if (!try_module_get(task_thread_info(p)->exec_domain->module)) | |
1040 | goto bad_fork_cleanup_count; | |
1041 | ||
1042 | p->did_exec = 0; | |
1043 | delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ | |
1044 | copy_flags(clone_flags, p); | |
1045 | INIT_LIST_HEAD(&p->children); | |
1046 | INIT_LIST_HEAD(&p->sibling); | |
1047 | rcu_copy_process(p); | |
1048 | p->vfork_done = NULL; | |
1049 | spin_lock_init(&p->alloc_lock); | |
1050 | ||
1051 | init_sigpending(&p->pending); | |
1052 | ||
1053 | p->utime = cputime_zero; | |
1054 | p->stime = cputime_zero; | |
1055 | p->gtime = cputime_zero; | |
1056 | p->utimescaled = cputime_zero; | |
1057 | p->stimescaled = cputime_zero; | |
1058 | #ifndef CONFIG_VIRT_CPU_ACCOUNTING | |
1059 | p->prev_utime = cputime_zero; | |
1060 | p->prev_stime = cputime_zero; | |
1061 | #endif | |
1062 | #if defined(SPLIT_RSS_COUNTING) | |
1063 | memset(&p->rss_stat, 0, sizeof(p->rss_stat)); | |
1064 | #endif | |
1065 | ||
1066 | p->default_timer_slack_ns = current->timer_slack_ns; | |
1067 | ||
1068 | task_io_accounting_init(&p->ioac); | |
1069 | acct_clear_integrals(p); | |
1070 | ||
1071 | posix_cpu_timers_init(p); | |
1072 | ||
1073 | p->lock_depth = -1; /* -1 = no lock */ | |
1074 | do_posix_clock_monotonic_gettime(&p->start_time); | |
1075 | p->real_start_time = p->start_time; | |
1076 | monotonic_to_bootbased(&p->real_start_time); | |
1077 | p->io_context = NULL; | |
1078 | p->audit_context = NULL; | |
1079 | cgroup_fork(p); | |
1080 | #ifdef CONFIG_NUMA | |
1081 | p->mempolicy = mpol_dup(p->mempolicy); | |
1082 | if (IS_ERR(p->mempolicy)) { | |
1083 | retval = PTR_ERR(p->mempolicy); | |
1084 | p->mempolicy = NULL; | |
1085 | goto bad_fork_cleanup_cgroup; | |
1086 | } | |
1087 | mpol_fix_fork_child_flag(p); | |
1088 | #endif | |
1089 | #ifdef CONFIG_TRACE_IRQFLAGS | |
1090 | p->irq_events = 0; | |
1091 | #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW | |
1092 | p->hardirqs_enabled = 1; | |
1093 | #else | |
1094 | p->hardirqs_enabled = 0; | |
1095 | #endif | |
1096 | p->hardirq_enable_ip = 0; | |
1097 | p->hardirq_enable_event = 0; | |
1098 | p->hardirq_disable_ip = _THIS_IP_; | |
1099 | p->hardirq_disable_event = 0; | |
1100 | p->softirqs_enabled = 1; | |
1101 | p->softirq_enable_ip = _THIS_IP_; | |
1102 | p->softirq_enable_event = 0; | |
1103 | p->softirq_disable_ip = 0; | |
1104 | p->softirq_disable_event = 0; | |
1105 | p->hardirq_context = 0; | |
1106 | p->softirq_context = 0; | |
1107 | #endif | |
1108 | #ifdef CONFIG_LOCKDEP | |
1109 | p->lockdep_depth = 0; /* no locks held yet */ | |
1110 | p->curr_chain_key = 0; | |
1111 | p->lockdep_recursion = 0; | |
1112 | #endif | |
1113 | ||
1114 | #ifdef CONFIG_DEBUG_MUTEXES | |
1115 | p->blocked_on = NULL; /* not blocked yet */ | |
1116 | #endif | |
1117 | #ifdef CONFIG_CGROUP_MEM_RES_CTLR | |
1118 | p->memcg_batch.do_batch = 0; | |
1119 | p->memcg_batch.memcg = NULL; | |
1120 | #endif | |
1121 | ||
1122 | /* Perform scheduler related setup. Assign this task to a CPU. */ | |
1123 | sched_fork(p, clone_flags); | |
1124 | ||
1125 | retval = perf_event_init_task(p); | |
1126 | if (retval) | |
1127 | goto bad_fork_cleanup_policy; | |
1128 | ||
1129 | if ((retval = audit_alloc(p))) | |
1130 | goto bad_fork_cleanup_policy; | |
1131 | /* copy all the process information */ | |
1132 | if ((retval = copy_semundo(clone_flags, p))) | |
1133 | goto bad_fork_cleanup_audit; | |
1134 | if ((retval = copy_files(clone_flags, p))) | |
1135 | goto bad_fork_cleanup_semundo; | |
1136 | if ((retval = copy_fs(clone_flags, p))) | |
1137 | goto bad_fork_cleanup_files; | |
1138 | if ((retval = copy_sighand(clone_flags, p))) | |
1139 | goto bad_fork_cleanup_fs; | |
1140 | if ((retval = copy_signal(clone_flags, p))) | |
1141 | goto bad_fork_cleanup_sighand; | |
1142 | if ((retval = copy_mm(clone_flags, p))) | |
1143 | goto bad_fork_cleanup_signal; | |
1144 | if ((retval = copy_namespaces(clone_flags, p))) | |
1145 | goto bad_fork_cleanup_mm; | |
1146 | if ((retval = copy_io(clone_flags, p))) | |
1147 | goto bad_fork_cleanup_namespaces; | |
1148 | retval = copy_thread(clone_flags, stack_start, stack_size, p, regs); | |
1149 | if (retval) | |
1150 | goto bad_fork_cleanup_io; | |
1151 | ||
1152 | if (pid != &init_struct_pid) { | |
1153 | retval = -ENOMEM; | |
1154 | pid = alloc_pid(p->nsproxy->pid_ns); | |
1155 | if (!pid) | |
1156 | goto bad_fork_cleanup_io; | |
1157 | ||
1158 | if (clone_flags & CLONE_NEWPID) { | |
1159 | retval = pid_ns_prepare_proc(p->nsproxy->pid_ns); | |
1160 | if (retval < 0) | |
1161 | goto bad_fork_free_pid; | |
1162 | } | |
1163 | } | |
1164 | ||
1165 | p->pid = pid_nr(pid); | |
1166 | p->tgid = p->pid; | |
1167 | if (clone_flags & CLONE_THREAD) | |
1168 | p->tgid = current->tgid; | |
1169 | ||
1170 | if (current->nsproxy != p->nsproxy) { | |
1171 | retval = ns_cgroup_clone(p, pid); | |
1172 | if (retval) | |
1173 | goto bad_fork_free_pid; | |
1174 | } | |
1175 | ||
1176 | p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; | |
1177 | /* | |
1178 | * Clear TID on mm_release()? | |
1179 | */ | |
1180 | p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL; | |
1181 | #ifdef CONFIG_FUTEX | |
1182 | p->robust_list = NULL; | |
1183 | #ifdef CONFIG_COMPAT | |
1184 | p->compat_robust_list = NULL; | |
1185 | #endif | |
1186 | INIT_LIST_HEAD(&p->pi_state_list); | |
1187 | p->pi_state_cache = NULL; | |
1188 | #endif | |
1189 | /* | |
1190 | * sigaltstack should be cleared when sharing the same VM | |
1191 | */ | |
1192 | if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) | |
1193 | p->sas_ss_sp = p->sas_ss_size = 0; | |
1194 | ||
1195 | /* | |
1196 | * Syscall tracing and stepping should be turned off in the | |
1197 | * child regardless of CLONE_PTRACE. | |
1198 | */ | |
1199 | user_disable_single_step(p); | |
1200 | clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); | |
1201 | #ifdef TIF_SYSCALL_EMU | |
1202 | clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); | |
1203 | #endif | |
1204 | clear_all_latency_tracing(p); | |
1205 | ||
1206 | /* ok, now we should be set up.. */ | |
1207 | p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL); | |
1208 | p->pdeath_signal = 0; | |
1209 | p->exit_state = 0; | |
1210 | ||
1211 | /* | |
1212 | * Ok, make it visible to the rest of the system. | |
1213 | * We dont wake it up yet. | |
1214 | */ | |
1215 | p->group_leader = p; | |
1216 | INIT_LIST_HEAD(&p->thread_group); | |
1217 | ||
1218 | /* Now that the task is set up, run cgroup callbacks if | |
1219 | * necessary. We need to run them before the task is visible | |
1220 | * on the tasklist. */ | |
1221 | cgroup_fork_callbacks(p); | |
1222 | cgroup_callbacks_done = 1; | |
1223 | ||
1224 | /* Need tasklist lock for parent etc handling! */ | |
1225 | write_lock_irq(&tasklist_lock); | |
1226 | ||
1227 | /* CLONE_PARENT re-uses the old parent */ | |
1228 | if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) { | |
1229 | p->real_parent = current->real_parent; | |
1230 | p->parent_exec_id = current->parent_exec_id; | |
1231 | } else { | |
1232 | p->real_parent = current; | |
1233 | p->parent_exec_id = current->self_exec_id; | |
1234 | } | |
1235 | ||
1236 | spin_lock(¤t->sighand->siglock); | |
1237 | ||
1238 | /* | |
1239 | * Process group and session signals need to be delivered to just the | |
1240 | * parent before the fork or both the parent and the child after the | |
1241 | * fork. Restart if a signal comes in before we add the new process to | |
1242 | * it's process group. | |
1243 | * A fatal signal pending means that current will exit, so the new | |
1244 | * thread can't slip out of an OOM kill (or normal SIGKILL). | |
1245 | */ | |
1246 | recalc_sigpending(); | |
1247 | if (signal_pending(current)) { | |
1248 | spin_unlock(¤t->sighand->siglock); | |
1249 | write_unlock_irq(&tasklist_lock); | |
1250 | retval = -ERESTARTNOINTR; | |
1251 | goto bad_fork_free_pid; | |
1252 | } | |
1253 | ||
1254 | if (clone_flags & CLONE_THREAD) { | |
1255 | current->signal->nr_threads++; | |
1256 | atomic_inc(¤t->signal->live); | |
1257 | atomic_inc(¤t->signal->sigcnt); | |
1258 | p->group_leader = current->group_leader; | |
1259 | list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group); | |
1260 | } | |
1261 | ||
1262 | if (likely(p->pid)) { | |
1263 | tracehook_finish_clone(p, clone_flags, trace); | |
1264 | ||
1265 | if (thread_group_leader(p)) { | |
1266 | if (clone_flags & CLONE_NEWPID) | |
1267 | p->nsproxy->pid_ns->child_reaper = p; | |
1268 | ||
1269 | p->signal->leader_pid = pid; | |
1270 | p->signal->tty = tty_kref_get(current->signal->tty); | |
1271 | attach_pid(p, PIDTYPE_PGID, task_pgrp(current)); | |
1272 | attach_pid(p, PIDTYPE_SID, task_session(current)); | |
1273 | list_add_tail(&p->sibling, &p->real_parent->children); | |
1274 | list_add_tail_rcu(&p->tasks, &init_task.tasks); | |
1275 | __get_cpu_var(process_counts)++; | |
1276 | } | |
1277 | attach_pid(p, PIDTYPE_PID, pid); | |
1278 | nr_threads++; | |
1279 | } | |
1280 | ||
1281 | total_forks++; | |
1282 | spin_unlock(¤t->sighand->siglock); | |
1283 | write_unlock_irq(&tasklist_lock); | |
1284 | proc_fork_connector(p); | |
1285 | cgroup_post_fork(p); | |
1286 | perf_event_fork(p); | |
1287 | return p; | |
1288 | ||
1289 | bad_fork_free_pid: | |
1290 | if (pid != &init_struct_pid) | |
1291 | free_pid(pid); | |
1292 | bad_fork_cleanup_io: | |
1293 | if (p->io_context) | |
1294 | exit_io_context(p); | |
1295 | bad_fork_cleanup_namespaces: | |
1296 | exit_task_namespaces(p); | |
1297 | bad_fork_cleanup_mm: | |
1298 | if (p->mm) | |
1299 | mmput(p->mm); | |
1300 | bad_fork_cleanup_signal: | |
1301 | if (!(clone_flags & CLONE_THREAD)) | |
1302 | free_signal_struct(p->signal); | |
1303 | bad_fork_cleanup_sighand: | |
1304 | __cleanup_sighand(p->sighand); | |
1305 | bad_fork_cleanup_fs: | |
1306 | exit_fs(p); /* blocking */ | |
1307 | bad_fork_cleanup_files: | |
1308 | exit_files(p); /* blocking */ | |
1309 | bad_fork_cleanup_semundo: | |
1310 | exit_sem(p); | |
1311 | bad_fork_cleanup_audit: | |
1312 | audit_free(p); | |
1313 | bad_fork_cleanup_policy: | |
1314 | perf_event_free_task(p); | |
1315 | #ifdef CONFIG_NUMA | |
1316 | mpol_put(p->mempolicy); | |
1317 | bad_fork_cleanup_cgroup: | |
1318 | #endif | |
1319 | cgroup_exit(p, cgroup_callbacks_done); | |
1320 | delayacct_tsk_free(p); | |
1321 | module_put(task_thread_info(p)->exec_domain->module); | |
1322 | bad_fork_cleanup_count: | |
1323 | atomic_dec(&p->cred->user->processes); | |
1324 | exit_creds(p); | |
1325 | bad_fork_free: | |
1326 | free_task(p); | |
1327 | fork_out: | |
1328 | return ERR_PTR(retval); | |
1329 | } | |
1330 | ||
1331 | noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs) | |
1332 | { | |
1333 | memset(regs, 0, sizeof(struct pt_regs)); | |
1334 | return regs; | |
1335 | } | |
1336 | ||
1337 | static inline void init_idle_pids(struct pid_link *links) | |
1338 | { | |
1339 | enum pid_type type; | |
1340 | ||
1341 | for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) { | |
1342 | INIT_HLIST_NODE(&links[type].node); /* not really needed */ | |
1343 | links[type].pid = &init_struct_pid; | |
1344 | } | |
1345 | } | |
1346 | ||
1347 | struct task_struct * __cpuinit fork_idle(int cpu) | |
1348 | { | |
1349 | struct task_struct *task; | |
1350 | struct pt_regs regs; | |
1351 | ||
1352 | task = copy_process(CLONE_VM, 0, idle_regs(®s), 0, NULL, | |
1353 | &init_struct_pid, 0); | |
1354 | if (!IS_ERR(task)) { | |
1355 | init_idle_pids(task->pids); | |
1356 | init_idle(task, cpu); | |
1357 | } | |
1358 | ||
1359 | return task; | |
1360 | } | |
1361 | ||
1362 | /* | |
1363 | * Ok, this is the main fork-routine. | |
1364 | * | |
1365 | * It copies the process, and if successful kick-starts | |
1366 | * it and waits for it to finish using the VM if required. | |
1367 | */ | |
1368 | long do_fork(unsigned long clone_flags, | |
1369 | unsigned long stack_start, | |
1370 | struct pt_regs *regs, | |
1371 | unsigned long stack_size, | |
1372 | int __user *parent_tidptr, | |
1373 | int __user *child_tidptr) | |
1374 | { | |
1375 | struct task_struct *p; | |
1376 | int trace = 0; | |
1377 | long nr; | |
1378 | ||
1379 | /* | |
1380 | * Do some preliminary argument and permissions checking before we | |
1381 | * actually start allocating stuff | |
1382 | */ | |
1383 | if (clone_flags & CLONE_NEWUSER) { | |
1384 | if (clone_flags & CLONE_THREAD) | |
1385 | return -EINVAL; | |
1386 | /* hopefully this check will go away when userns support is | |
1387 | * complete | |
1388 | */ | |
1389 | if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) || | |
1390 | !capable(CAP_SETGID)) | |
1391 | return -EPERM; | |
1392 | } | |
1393 | ||
1394 | /* | |
1395 | * We hope to recycle these flags after 2.6.26 | |
1396 | */ | |
1397 | if (unlikely(clone_flags & CLONE_STOPPED)) { | |
1398 | static int __read_mostly count = 100; | |
1399 | ||
1400 | if (count > 0 && printk_ratelimit()) { | |
1401 | char comm[TASK_COMM_LEN]; | |
1402 | ||
1403 | count--; | |
1404 | printk(KERN_INFO "fork(): process `%s' used deprecated " | |
1405 | "clone flags 0x%lx\n", | |
1406 | get_task_comm(comm, current), | |
1407 | clone_flags & CLONE_STOPPED); | |
1408 | } | |
1409 | } | |
1410 | ||
1411 | /* | |
1412 | * When called from kernel_thread, don't do user tracing stuff. | |
1413 | */ | |
1414 | if (likely(user_mode(regs))) | |
1415 | trace = tracehook_prepare_clone(clone_flags); | |
1416 | ||
1417 | p = copy_process(clone_flags, stack_start, regs, stack_size, | |
1418 | child_tidptr, NULL, trace); | |
1419 | /* | |
1420 | * Do this prior waking up the new thread - the thread pointer | |
1421 | * might get invalid after that point, if the thread exits quickly. | |
1422 | */ | |
1423 | if (!IS_ERR(p)) { | |
1424 | struct completion vfork; | |
1425 | ||
1426 | trace_sched_process_fork(current, p); | |
1427 | ||
1428 | nr = task_pid_vnr(p); | |
1429 | ||
1430 | if (clone_flags & CLONE_PARENT_SETTID) | |
1431 | put_user(nr, parent_tidptr); | |
1432 | ||
1433 | if (clone_flags & CLONE_VFORK) { | |
1434 | p->vfork_done = &vfork; | |
1435 | init_completion(&vfork); | |
1436 | } | |
1437 | ||
1438 | audit_finish_fork(p); | |
1439 | tracehook_report_clone(regs, clone_flags, nr, p); | |
1440 | ||
1441 | /* | |
1442 | * We set PF_STARTING at creation in case tracing wants to | |
1443 | * use this to distinguish a fully live task from one that | |
1444 | * hasn't gotten to tracehook_report_clone() yet. Now we | |
1445 | * clear it and set the child going. | |
1446 | */ | |
1447 | p->flags &= ~PF_STARTING; | |
1448 | ||
1449 | if (unlikely(clone_flags & CLONE_STOPPED)) { | |
1450 | /* | |
1451 | * We'll start up with an immediate SIGSTOP. | |
1452 | */ | |
1453 | sigaddset(&p->pending.signal, SIGSTOP); | |
1454 | set_tsk_thread_flag(p, TIF_SIGPENDING); | |
1455 | __set_task_state(p, TASK_STOPPED); | |
1456 | } else { | |
1457 | wake_up_new_task(p, clone_flags); | |
1458 | } | |
1459 | ||
1460 | tracehook_report_clone_complete(trace, regs, | |
1461 | clone_flags, nr, p); | |
1462 | ||
1463 | if (clone_flags & CLONE_VFORK) { | |
1464 | freezer_do_not_count(); | |
1465 | wait_for_completion(&vfork); | |
1466 | freezer_count(); | |
1467 | tracehook_report_vfork_done(p, nr); | |
1468 | } | |
1469 | } else { | |
1470 | nr = PTR_ERR(p); | |
1471 | } | |
1472 | return nr; | |
1473 | } | |
1474 | ||
1475 | #ifndef ARCH_MIN_MMSTRUCT_ALIGN | |
1476 | #define ARCH_MIN_MMSTRUCT_ALIGN 0 | |
1477 | #endif | |
1478 | ||
1479 | static void sighand_ctor(void *data) | |
1480 | { | |
1481 | struct sighand_struct *sighand = data; | |
1482 | ||
1483 | spin_lock_init(&sighand->siglock); | |
1484 | init_waitqueue_head(&sighand->signalfd_wqh); | |
1485 | } | |
1486 | ||
1487 | void __init proc_caches_init(void) | |
1488 | { | |
1489 | sighand_cachep = kmem_cache_create("sighand_cache", | |
1490 | sizeof(struct sighand_struct), 0, | |
1491 | SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU| | |
1492 | SLAB_NOTRACK, sighand_ctor); | |
1493 | signal_cachep = kmem_cache_create("signal_cache", | |
1494 | sizeof(struct signal_struct), 0, | |
1495 | SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); | |
1496 | files_cachep = kmem_cache_create("files_cache", | |
1497 | sizeof(struct files_struct), 0, | |
1498 | SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); | |
1499 | fs_cachep = kmem_cache_create("fs_cache", | |
1500 | sizeof(struct fs_struct), 0, | |
1501 | SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); | |
1502 | mm_cachep = kmem_cache_create("mm_struct", | |
1503 | sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, | |
1504 | SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); | |
1505 | vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC); | |
1506 | mmap_init(); | |
1507 | } | |
1508 | ||
1509 | /* | |
1510 | * Check constraints on flags passed to the unshare system call and | |
1511 | * force unsharing of additional process context as appropriate. | |
1512 | */ | |
1513 | static void check_unshare_flags(unsigned long *flags_ptr) | |
1514 | { | |
1515 | /* | |
1516 | * If unsharing a thread from a thread group, must also | |
1517 | * unshare vm. | |
1518 | */ | |
1519 | if (*flags_ptr & CLONE_THREAD) | |
1520 | *flags_ptr |= CLONE_VM; | |
1521 | ||
1522 | /* | |
1523 | * If unsharing vm, must also unshare signal handlers. | |
1524 | */ | |
1525 | if (*flags_ptr & CLONE_VM) | |
1526 | *flags_ptr |= CLONE_SIGHAND; | |
1527 | ||
1528 | /* | |
1529 | * If unsharing namespace, must also unshare filesystem information. | |
1530 | */ | |
1531 | if (*flags_ptr & CLONE_NEWNS) | |
1532 | *flags_ptr |= CLONE_FS; | |
1533 | } | |
1534 | ||
1535 | /* | |
1536 | * Unsharing of tasks created with CLONE_THREAD is not supported yet | |
1537 | */ | |
1538 | static int unshare_thread(unsigned long unshare_flags) | |
1539 | { | |
1540 | if (unshare_flags & CLONE_THREAD) | |
1541 | return -EINVAL; | |
1542 | ||
1543 | return 0; | |
1544 | } | |
1545 | ||
1546 | /* | |
1547 | * Unshare the filesystem structure if it is being shared | |
1548 | */ | |
1549 | static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) | |
1550 | { | |
1551 | struct fs_struct *fs = current->fs; | |
1552 | ||
1553 | if (!(unshare_flags & CLONE_FS) || !fs) | |
1554 | return 0; | |
1555 | ||
1556 | /* don't need lock here; in the worst case we'll do useless copy */ | |
1557 | if (fs->users == 1) | |
1558 | return 0; | |
1559 | ||
1560 | *new_fsp = copy_fs_struct(fs); | |
1561 | if (!*new_fsp) | |
1562 | return -ENOMEM; | |
1563 | ||
1564 | return 0; | |
1565 | } | |
1566 | ||
1567 | /* | |
1568 | * Unsharing of sighand is not supported yet | |
1569 | */ | |
1570 | static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp) | |
1571 | { | |
1572 | struct sighand_struct *sigh = current->sighand; | |
1573 | ||
1574 | if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1) | |
1575 | return -EINVAL; | |
1576 | else | |
1577 | return 0; | |
1578 | } | |
1579 | ||
1580 | /* | |
1581 | * Unshare vm if it is being shared | |
1582 | */ | |
1583 | static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp) | |
1584 | { | |
1585 | struct mm_struct *mm = current->mm; | |
1586 | ||
1587 | if ((unshare_flags & CLONE_VM) && | |
1588 | (mm && atomic_read(&mm->mm_users) > 1)) { | |
1589 | return -EINVAL; | |
1590 | } | |
1591 | ||
1592 | return 0; | |
1593 | } | |
1594 | ||
1595 | /* | |
1596 | * Unshare file descriptor table if it is being shared | |
1597 | */ | |
1598 | static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) | |
1599 | { | |
1600 | struct files_struct *fd = current->files; | |
1601 | int error = 0; | |
1602 | ||
1603 | if ((unshare_flags & CLONE_FILES) && | |
1604 | (fd && atomic_read(&fd->count) > 1)) { | |
1605 | *new_fdp = dup_fd(fd, &error); | |
1606 | if (!*new_fdp) | |
1607 | return error; | |
1608 | } | |
1609 | ||
1610 | return 0; | |
1611 | } | |
1612 | ||
1613 | /* | |
1614 | * unshare allows a process to 'unshare' part of the process | |
1615 | * context which was originally shared using clone. copy_* | |
1616 | * functions used by do_fork() cannot be used here directly | |
1617 | * because they modify an inactive task_struct that is being | |
1618 | * constructed. Here we are modifying the current, active, | |
1619 | * task_struct. | |
1620 | */ | |
1621 | SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) | |
1622 | { | |
1623 | int err = 0; | |
1624 | struct fs_struct *fs, *new_fs = NULL; | |
1625 | struct sighand_struct *new_sigh = NULL; | |
1626 | struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL; | |
1627 | struct files_struct *fd, *new_fd = NULL; | |
1628 | struct nsproxy *new_nsproxy = NULL; | |
1629 | int do_sysvsem = 0; | |
1630 | ||
1631 | check_unshare_flags(&unshare_flags); | |
1632 | ||
1633 | /* Return -EINVAL for all unsupported flags */ | |
1634 | err = -EINVAL; | |
1635 | if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| | |
1636 | CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| | |
1637 | CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET)) | |
1638 | goto bad_unshare_out; | |
1639 | ||
1640 | /* | |
1641 | * CLONE_NEWIPC must also detach from the undolist: after switching | |
1642 | * to a new ipc namespace, the semaphore arrays from the old | |
1643 | * namespace are unreachable. | |
1644 | */ | |
1645 | if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) | |
1646 | do_sysvsem = 1; | |
1647 | if ((err = unshare_thread(unshare_flags))) | |
1648 | goto bad_unshare_out; | |
1649 | if ((err = unshare_fs(unshare_flags, &new_fs))) | |
1650 | goto bad_unshare_cleanup_thread; | |
1651 | if ((err = unshare_sighand(unshare_flags, &new_sigh))) | |
1652 | goto bad_unshare_cleanup_fs; | |
1653 | if ((err = unshare_vm(unshare_flags, &new_mm))) | |
1654 | goto bad_unshare_cleanup_sigh; | |
1655 | if ((err = unshare_fd(unshare_flags, &new_fd))) | |
1656 | goto bad_unshare_cleanup_vm; | |
1657 | if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, | |
1658 | new_fs))) | |
1659 | goto bad_unshare_cleanup_fd; | |
1660 | ||
1661 | if (new_fs || new_mm || new_fd || do_sysvsem || new_nsproxy) { | |
1662 | if (do_sysvsem) { | |
1663 | /* | |
1664 | * CLONE_SYSVSEM is equivalent to sys_exit(). | |
1665 | */ | |
1666 | exit_sem(current); | |
1667 | } | |
1668 | ||
1669 | if (new_nsproxy) { | |
1670 | switch_task_namespaces(current, new_nsproxy); | |
1671 | new_nsproxy = NULL; | |
1672 | } | |
1673 | ||
1674 | task_lock(current); | |
1675 | ||
1676 | if (new_fs) { | |
1677 | fs = current->fs; | |
1678 | write_lock(&fs->lock); | |
1679 | current->fs = new_fs; | |
1680 | if (--fs->users) | |
1681 | new_fs = NULL; | |
1682 | else | |
1683 | new_fs = fs; | |
1684 | write_unlock(&fs->lock); | |
1685 | } | |
1686 | ||
1687 | if (new_mm) { | |
1688 | mm = current->mm; | |
1689 | active_mm = current->active_mm; | |
1690 | current->mm = new_mm; | |
1691 | current->active_mm = new_mm; | |
1692 | activate_mm(active_mm, new_mm); | |
1693 | new_mm = mm; | |
1694 | } | |
1695 | ||
1696 | if (new_fd) { | |
1697 | fd = current->files; | |
1698 | current->files = new_fd; | |
1699 | new_fd = fd; | |
1700 | } | |
1701 | ||
1702 | task_unlock(current); | |
1703 | } | |
1704 | ||
1705 | if (new_nsproxy) | |
1706 | put_nsproxy(new_nsproxy); | |
1707 | ||
1708 | bad_unshare_cleanup_fd: | |
1709 | if (new_fd) | |
1710 | put_files_struct(new_fd); | |
1711 | ||
1712 | bad_unshare_cleanup_vm: | |
1713 | if (new_mm) | |
1714 | mmput(new_mm); | |
1715 | ||
1716 | bad_unshare_cleanup_sigh: | |
1717 | if (new_sigh) | |
1718 | if (atomic_dec_and_test(&new_sigh->count)) | |
1719 | kmem_cache_free(sighand_cachep, new_sigh); | |
1720 | ||
1721 | bad_unshare_cleanup_fs: | |
1722 | if (new_fs) | |
1723 | free_fs_struct(new_fs); | |
1724 | ||
1725 | bad_unshare_cleanup_thread: | |
1726 | bad_unshare_out: | |
1727 | return err; | |
1728 | } | |
1729 | ||
1730 | /* | |
1731 | * Helper to unshare the files of the current task. | |
1732 | * We don't want to expose copy_files internals to | |
1733 | * the exec layer of the kernel. | |
1734 | */ | |
1735 | ||
1736 | int unshare_files(struct files_struct **displaced) | |
1737 | { | |
1738 | struct task_struct *task = current; | |
1739 | struct files_struct *copy = NULL; | |
1740 | int error; | |
1741 | ||
1742 | error = unshare_fd(CLONE_FILES, ©); | |
1743 | if (error || !copy) { | |
1744 | *displaced = NULL; | |
1745 | return error; | |
1746 | } | |
1747 | *displaced = task->files; | |
1748 | task_lock(task); | |
1749 | task->files = copy; | |
1750 | task_unlock(task); | |
1751 | return 0; | |
1752 | } |