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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 | void __put_task_struct(struct task_struct *tsk) |
169 | { |
170 | WARN_ON(!tsk->exit_state); |
171 | WARN_ON(atomic_read(&tsk->usage)); |
172 | WARN_ON(tsk == current); |
173 | |
174 | exit_creds(tsk); |
175 | delayacct_tsk_free(tsk); |
176 | |
177 | if (!profile_handoff_task(tsk)) |
178 | free_task(tsk); |
179 | } |
180 | |
181 | /* |
182 | * macro override instead of weak attribute alias, to workaround |
183 | * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions. |
184 | */ |
185 | #ifndef arch_task_cache_init |
186 | #define arch_task_cache_init() |
187 | #endif |
188 | |
189 | void __init fork_init(unsigned long mempages) |
190 | { |
191 | #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR |
192 | #ifndef ARCH_MIN_TASKALIGN |
193 | #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES |
194 | #endif |
195 | /* create a slab on which task_structs can be allocated */ |
196 | task_struct_cachep = |
197 | kmem_cache_create("task_struct", sizeof(struct task_struct), |
198 | ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL); |
199 | #endif |
200 | |
201 | /* do the arch specific task caches init */ |
202 | arch_task_cache_init(); |
203 | |
204 | /* |
205 | * The default maximum number of threads is set to a safe |
206 | * value: the thread structures can take up at most half |
207 | * of memory. |
208 | */ |
209 | max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE); |
210 | |
211 | /* |
212 | * we need to allow at least 20 threads to boot a system |
213 | */ |
214 | if(max_threads < 20) |
215 | max_threads = 20; |
216 | |
217 | init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; |
218 | init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; |
219 | init_task.signal->rlim[RLIMIT_SIGPENDING] = |
220 | init_task.signal->rlim[RLIMIT_NPROC]; |
221 | } |
222 | |
223 | int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst, |
224 | struct task_struct *src) |
225 | { |
226 | *dst = *src; |
227 | return 0; |
228 | } |
229 | |
230 | static struct task_struct *dup_task_struct(struct task_struct *orig) |
231 | { |
232 | struct task_struct *tsk; |
233 | struct thread_info *ti; |
234 | unsigned long *stackend; |
235 | |
236 | int err; |
237 | |
238 | prepare_to_copy(orig); |
239 | |
240 | tsk = alloc_task_struct(); |
241 | if (!tsk) |
242 | return NULL; |
243 | |
244 | ti = alloc_thread_info(tsk); |
245 | if (!ti) { |
246 | free_task_struct(tsk); |
247 | return NULL; |
248 | } |
249 | |
250 | err = arch_dup_task_struct(tsk, orig); |
251 | if (err) |
252 | goto out; |
253 | |
254 | tsk->stack = ti; |
255 | |
256 | err = prop_local_init_single(&tsk->dirties); |
257 | if (err) |
258 | goto out; |
259 | |
260 | setup_thread_stack(tsk, orig); |
261 | clear_user_return_notifier(tsk); |
262 | stackend = end_of_stack(tsk); |
263 | *stackend = STACK_END_MAGIC; /* for overflow detection */ |
264 | |
265 | #ifdef CONFIG_CC_STACKPROTECTOR |
266 | tsk->stack_canary = get_random_int(); |
267 | #endif |
268 | |
269 | /* One for us, one for whoever does the "release_task()" (usually parent) */ |
270 | atomic_set(&tsk->usage,2); |
271 | atomic_set(&tsk->fs_excl, 0); |
272 | #ifdef CONFIG_BLK_DEV_IO_TRACE |
273 | tsk->btrace_seq = 0; |
274 | #endif |
275 | tsk->splice_pipe = NULL; |
276 | |
277 | account_kernel_stack(ti, 1); |
278 | |
279 | return tsk; |
280 | |
281 | out: |
282 | free_thread_info(ti); |
283 | free_task_struct(tsk); |
284 | return NULL; |
285 | } |
286 | |
287 | #ifdef CONFIG_MMU |
288 | static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) |
289 | { |
290 | struct vm_area_struct *mpnt, *tmp, **pprev; |
291 | struct rb_node **rb_link, *rb_parent; |
292 | int retval; |
293 | unsigned long charge; |
294 | struct mempolicy *pol; |
295 | |
296 | down_write(&oldmm->mmap_sem); |
297 | flush_cache_dup_mm(oldmm); |
298 | /* |
299 | * Not linked in yet - no deadlock potential: |
300 | */ |
301 | down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); |
302 | |
303 | mm->locked_vm = 0; |
304 | mm->mmap = NULL; |
305 | mm->mmap_cache = NULL; |
306 | mm->free_area_cache = oldmm->mmap_base; |
307 | mm->cached_hole_size = ~0UL; |
308 | mm->map_count = 0; |
309 | cpumask_clear(mm_cpumask(mm)); |
310 | mm->mm_rb = RB_ROOT; |
311 | rb_link = &mm->mm_rb.rb_node; |
312 | rb_parent = NULL; |
313 | pprev = &mm->mmap; |
314 | retval = ksm_fork(mm, oldmm); |
315 | if (retval) |
316 | goto out; |
317 | |
318 | for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { |
319 | struct file *file; |
320 | |
321 | if (mpnt->vm_flags & VM_DONTCOPY) { |
322 | long pages = vma_pages(mpnt); |
323 | mm->total_vm -= pages; |
324 | vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file, |
325 | -pages); |
326 | continue; |
327 | } |
328 | charge = 0; |
329 | if (mpnt->vm_flags & VM_ACCOUNT) { |
330 | unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT; |
331 | if (security_vm_enough_memory(len)) |
332 | goto fail_nomem; |
333 | charge = len; |
334 | } |
335 | tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); |
336 | if (!tmp) |
337 | goto fail_nomem; |
338 | *tmp = *mpnt; |
339 | INIT_LIST_HEAD(&tmp->anon_vma_chain); |
340 | pol = mpol_dup(vma_policy(mpnt)); |
341 | retval = PTR_ERR(pol); |
342 | if (IS_ERR(pol)) |
343 | goto fail_nomem_policy; |
344 | vma_set_policy(tmp, pol); |
345 | if (anon_vma_fork(tmp, mpnt)) |
346 | goto fail_nomem_anon_vma_fork; |
347 | tmp->vm_flags &= ~VM_LOCKED; |
348 | tmp->vm_mm = mm; |
349 | tmp->vm_next = NULL; |
350 | file = tmp->vm_file; |
351 | if (file) { |
352 | struct inode *inode = file->f_path.dentry->d_inode; |
353 | struct address_space *mapping = file->f_mapping; |
354 | |
355 | get_file(file); |
356 | if (tmp->vm_flags & VM_DENYWRITE) |
357 | atomic_dec(&inode->i_writecount); |
358 | spin_lock(&mapping->i_mmap_lock); |
359 | if (tmp->vm_flags & VM_SHARED) |
360 | mapping->i_mmap_writable++; |
361 | tmp->vm_truncate_count = mpnt->vm_truncate_count; |
362 | flush_dcache_mmap_lock(mapping); |
363 | /* insert tmp into the share list, just after mpnt */ |
364 | vma_prio_tree_add(tmp, mpnt); |
365 | flush_dcache_mmap_unlock(mapping); |
366 | spin_unlock(&mapping->i_mmap_lock); |
367 | } |
368 | |
369 | /* |
370 | * Clear hugetlb-related page reserves for children. This only |
371 | * affects MAP_PRIVATE mappings. Faults generated by the child |
372 | * are not guaranteed to succeed, even if read-only |
373 | */ |
374 | if (is_vm_hugetlb_page(tmp)) |
375 | reset_vma_resv_huge_pages(tmp); |
376 | |
377 | /* |
378 | * Link in the new vma and copy the page table entries. |
379 | */ |
380 | *pprev = tmp; |
381 | pprev = &tmp->vm_next; |
382 | |
383 | __vma_link_rb(mm, tmp, rb_link, rb_parent); |
384 | rb_link = &tmp->vm_rb.rb_right; |
385 | rb_parent = &tmp->vm_rb; |
386 | |
387 | mm->map_count++; |
388 | retval = copy_page_range(mm, oldmm, mpnt); |
389 | |
390 | if (tmp->vm_ops && tmp->vm_ops->open) |
391 | tmp->vm_ops->open(tmp); |
392 | |
393 | if (retval) |
394 | goto out; |
395 | } |
396 | /* a new mm has just been created */ |
397 | arch_dup_mmap(oldmm, mm); |
398 | retval = 0; |
399 | out: |
400 | up_write(&mm->mmap_sem); |
401 | flush_tlb_mm(oldmm); |
402 | up_write(&oldmm->mmap_sem); |
403 | return retval; |
404 | fail_nomem_anon_vma_fork: |
405 | mpol_put(pol); |
406 | fail_nomem_policy: |
407 | kmem_cache_free(vm_area_cachep, tmp); |
408 | fail_nomem: |
409 | retval = -ENOMEM; |
410 | vm_unacct_memory(charge); |
411 | goto out; |
412 | } |
413 | |
414 | static inline int mm_alloc_pgd(struct mm_struct * mm) |
415 | { |
416 | mm->pgd = pgd_alloc(mm); |
417 | if (unlikely(!mm->pgd)) |
418 | return -ENOMEM; |
419 | return 0; |
420 | } |
421 | |
422 | static inline void mm_free_pgd(struct mm_struct * mm) |
423 | { |
424 | pgd_free(mm, mm->pgd); |
425 | } |
426 | #else |
427 | #define dup_mmap(mm, oldmm) (0) |
428 | #define mm_alloc_pgd(mm) (0) |
429 | #define mm_free_pgd(mm) |
430 | #endif /* CONFIG_MMU */ |
431 | |
432 | __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); |
433 | |
434 | #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL)) |
435 | #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) |
436 | |
437 | static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT; |
438 | |
439 | static int __init coredump_filter_setup(char *s) |
440 | { |
441 | default_dump_filter = |
442 | (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) & |
443 | MMF_DUMP_FILTER_MASK; |
444 | return 1; |
445 | } |
446 | |
447 | __setup("coredump_filter=", coredump_filter_setup); |
448 | |
449 | #include <linux/init_task.h> |
450 | |
451 | static void mm_init_aio(struct mm_struct *mm) |
452 | { |
453 | #ifdef CONFIG_AIO |
454 | spin_lock_init(&mm->ioctx_lock); |
455 | INIT_HLIST_HEAD(&mm->ioctx_list); |
456 | #endif |
457 | } |
458 | |
459 | static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p) |
460 | { |
461 | atomic_set(&mm->mm_users, 1); |
462 | atomic_set(&mm->mm_count, 1); |
463 | init_rwsem(&mm->mmap_sem); |
464 | INIT_LIST_HEAD(&mm->mmlist); |
465 | mm->flags = (current->mm) ? |
466 | (current->mm->flags & MMF_INIT_MASK) : default_dump_filter; |
467 | mm->core_state = NULL; |
468 | mm->nr_ptes = 0; |
469 | memset(&mm->rss_stat, 0, sizeof(mm->rss_stat)); |
470 | spin_lock_init(&mm->page_table_lock); |
471 | mm->free_area_cache = TASK_UNMAPPED_BASE; |
472 | mm->cached_hole_size = ~0UL; |
473 | mm_init_aio(mm); |
474 | mm_init_owner(mm, p); |
475 | |
476 | if (likely(!mm_alloc_pgd(mm))) { |
477 | mm->def_flags = 0; |
478 | mmu_notifier_mm_init(mm); |
479 | return mm; |
480 | } |
481 | |
482 | free_mm(mm); |
483 | return NULL; |
484 | } |
485 | |
486 | /* |
487 | * Allocate and initialize an mm_struct. |
488 | */ |
489 | struct mm_struct * mm_alloc(void) |
490 | { |
491 | struct mm_struct * mm; |
492 | |
493 | mm = allocate_mm(); |
494 | if (mm) { |
495 | memset(mm, 0, sizeof(*mm)); |
496 | mm = mm_init(mm, current); |
497 | } |
498 | return mm; |
499 | } |
500 | |
501 | /* |
502 | * Called when the last reference to the mm |
503 | * is dropped: either by a lazy thread or by |
504 | * mmput. Free the page directory and the mm. |
505 | */ |
506 | void __mmdrop(struct mm_struct *mm) |
507 | { |
508 | BUG_ON(mm == &init_mm); |
509 | mm_free_pgd(mm); |
510 | destroy_context(mm); |
511 | mmu_notifier_mm_destroy(mm); |
512 | free_mm(mm); |
513 | } |
514 | EXPORT_SYMBOL_GPL(__mmdrop); |
515 | |
516 | /* |
517 | * Decrement the use count and release all resources for an mm. |
518 | */ |
519 | void mmput(struct mm_struct *mm) |
520 | { |
521 | might_sleep(); |
522 | |
523 | if (atomic_dec_and_test(&mm->mm_users)) { |
524 | exit_aio(mm); |
525 | ksm_exit(mm); |
526 | exit_mmap(mm); |
527 | set_mm_exe_file(mm, NULL); |
528 | if (!list_empty(&mm->mmlist)) { |
529 | spin_lock(&mmlist_lock); |
530 | list_del(&mm->mmlist); |
531 | spin_unlock(&mmlist_lock); |
532 | } |
533 | put_swap_token(mm); |
534 | if (mm->binfmt) |
535 | module_put(mm->binfmt->module); |
536 | mmdrop(mm); |
537 | } |
538 | } |
539 | EXPORT_SYMBOL_GPL(mmput); |
540 | |
541 | /** |
542 | * get_task_mm - acquire a reference to the task's mm |
543 | * |
544 | * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning |
545 | * this kernel workthread has transiently adopted a user mm with use_mm, |
546 | * to do its AIO) is not set and if so returns a reference to it, after |
547 | * bumping up the use count. User must release the mm via mmput() |
548 | * after use. Typically used by /proc and ptrace. |
549 | */ |
550 | struct mm_struct *get_task_mm(struct task_struct *task) |
551 | { |
552 | struct mm_struct *mm; |
553 | |
554 | task_lock(task); |
555 | mm = task->mm; |
556 | if (mm) { |
557 | if (task->flags & PF_KTHREAD) |
558 | mm = NULL; |
559 | else |
560 | atomic_inc(&mm->mm_users); |
561 | } |
562 | task_unlock(task); |
563 | return mm; |
564 | } |
565 | EXPORT_SYMBOL_GPL(get_task_mm); |
566 | |
567 | /* Please note the differences between mmput and mm_release. |
568 | * mmput is called whenever we stop holding onto a mm_struct, |
569 | * error success whatever. |
570 | * |
571 | * mm_release is called after a mm_struct has been removed |
572 | * from the current process. |
573 | * |
574 | * This difference is important for error handling, when we |
575 | * only half set up a mm_struct for a new process and need to restore |
576 | * the old one. Because we mmput the new mm_struct before |
577 | * restoring the old one. . . |
578 | * Eric Biederman 10 January 1998 |
579 | */ |
580 | void mm_release(struct task_struct *tsk, struct mm_struct *mm) |
581 | { |
582 | struct completion *vfork_done = tsk->vfork_done; |
583 | |
584 | /* Get rid of any futexes when releasing the mm */ |
585 | #ifdef CONFIG_FUTEX |
586 | if (unlikely(tsk->robust_list)) { |
587 | exit_robust_list(tsk); |
588 | tsk->robust_list = NULL; |
589 | } |
590 | #ifdef CONFIG_COMPAT |
591 | if (unlikely(tsk->compat_robust_list)) { |
592 | compat_exit_robust_list(tsk); |
593 | tsk->compat_robust_list = NULL; |
594 | } |
595 | #endif |
596 | if (unlikely(!list_empty(&tsk->pi_state_list))) |
597 | exit_pi_state_list(tsk); |
598 | #endif |
599 | |
600 | /* Get rid of any cached register state */ |
601 | deactivate_mm(tsk, mm); |
602 | |
603 | /* notify parent sleeping on vfork() */ |
604 | if (vfork_done) { |
605 | tsk->vfork_done = NULL; |
606 | complete(vfork_done); |
607 | } |
608 | |
609 | /* |
610 | * If we're exiting normally, clear a user-space tid field if |
611 | * requested. We leave this alone when dying by signal, to leave |
612 | * the value intact in a core dump, and to save the unnecessary |
613 | * trouble otherwise. Userland only wants this done for a sys_exit. |
614 | */ |
615 | if (tsk->clear_child_tid) { |
616 | if (!(tsk->flags & PF_SIGNALED) && |
617 | atomic_read(&mm->mm_users) > 1) { |
618 | /* |
619 | * We don't check the error code - if userspace has |
620 | * not set up a proper pointer then tough luck. |
621 | */ |
622 | put_user(0, tsk->clear_child_tid); |
623 | sys_futex(tsk->clear_child_tid, FUTEX_WAKE, |
624 | 1, NULL, NULL, 0); |
625 | } |
626 | tsk->clear_child_tid = NULL; |
627 | } |
628 | } |
629 | |
630 | /* |
631 | * Allocate a new mm structure and copy contents from the |
632 | * mm structure of the passed in task structure. |
633 | */ |
634 | struct mm_struct *dup_mm(struct task_struct *tsk) |
635 | { |
636 | struct mm_struct *mm, *oldmm = current->mm; |
637 | int err; |
638 | |
639 | if (!oldmm) |
640 | return NULL; |
641 | |
642 | mm = allocate_mm(); |
643 | if (!mm) |
644 | goto fail_nomem; |
645 | |
646 | memcpy(mm, oldmm, sizeof(*mm)); |
647 | |
648 | /* Initializing for Swap token stuff */ |
649 | mm->token_priority = 0; |
650 | mm->last_interval = 0; |
651 | |
652 | if (!mm_init(mm, tsk)) |
653 | goto fail_nomem; |
654 | |
655 | if (init_new_context(tsk, mm)) |
656 | goto fail_nocontext; |
657 | |
658 | dup_mm_exe_file(oldmm, mm); |
659 | |
660 | err = dup_mmap(mm, oldmm); |
661 | if (err) |
662 | goto free_pt; |
663 | |
664 | mm->hiwater_rss = get_mm_rss(mm); |
665 | mm->hiwater_vm = mm->total_vm; |
666 | |
667 | if (mm->binfmt && !try_module_get(mm->binfmt->module)) |
668 | goto free_pt; |
669 | |
670 | return mm; |
671 | |
672 | free_pt: |
673 | /* don't put binfmt in mmput, we haven't got module yet */ |
674 | mm->binfmt = NULL; |
675 | mmput(mm); |
676 | |
677 | fail_nomem: |
678 | return NULL; |
679 | |
680 | fail_nocontext: |
681 | /* |
682 | * If init_new_context() failed, we cannot use mmput() to free the mm |
683 | * because it calls destroy_context() |
684 | */ |
685 | mm_free_pgd(mm); |
686 | free_mm(mm); |
687 | return NULL; |
688 | } |
689 | |
690 | static int copy_mm(unsigned long clone_flags, struct task_struct * tsk) |
691 | { |
692 | struct mm_struct * mm, *oldmm; |
693 | int retval; |
694 | |
695 | tsk->min_flt = tsk->maj_flt = 0; |
696 | tsk->nvcsw = tsk->nivcsw = 0; |
697 | #ifdef CONFIG_DETECT_HUNG_TASK |
698 | tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw; |
699 | #endif |
700 | |
701 | tsk->mm = NULL; |
702 | tsk->active_mm = NULL; |
703 | |
704 | /* |
705 | * Are we cloning a kernel thread? |
706 | * |
707 | * We need to steal a active VM for that.. |
708 | */ |
709 | oldmm = current->mm; |
710 | if (!oldmm) |
711 | return 0; |
712 | |
713 | if (clone_flags & CLONE_VM) { |
714 | atomic_inc(&oldmm->mm_users); |
715 | mm = oldmm; |
716 | goto good_mm; |
717 | } |
718 | |
719 | retval = -ENOMEM; |
720 | mm = dup_mm(tsk); |
721 | if (!mm) |
722 | goto fail_nomem; |
723 | |
724 | good_mm: |
725 | /* Initializing for Swap token stuff */ |
726 | mm->token_priority = 0; |
727 | mm->last_interval = 0; |
728 | |
729 | tsk->mm = mm; |
730 | tsk->active_mm = mm; |
731 | return 0; |
732 | |
733 | fail_nomem: |
734 | return retval; |
735 | } |
736 | |
737 | static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) |
738 | { |
739 | struct fs_struct *fs = current->fs; |
740 | if (clone_flags & CLONE_FS) { |
741 | /* tsk->fs is already what we want */ |
742 | write_lock(&fs->lock); |
743 | if (fs->in_exec) { |
744 | write_unlock(&fs->lock); |
745 | return -EAGAIN; |
746 | } |
747 | fs->users++; |
748 | write_unlock(&fs->lock); |
749 | return 0; |
750 | } |
751 | tsk->fs = copy_fs_struct(fs); |
752 | if (!tsk->fs) |
753 | return -ENOMEM; |
754 | return 0; |
755 | } |
756 | |
757 | static int copy_files(unsigned long clone_flags, struct task_struct * tsk) |
758 | { |
759 | struct files_struct *oldf, *newf; |
760 | int error = 0; |
761 | |
762 | /* |
763 | * A background process may not have any files ... |
764 | */ |
765 | oldf = current->files; |
766 | if (!oldf) |
767 | goto out; |
768 | |
769 | if (clone_flags & CLONE_FILES) { |
770 | atomic_inc(&oldf->count); |
771 | goto out; |
772 | } |
773 | |
774 | newf = dup_fd(oldf, &error); |
775 | if (!newf) |
776 | goto out; |
777 | |
778 | tsk->files = newf; |
779 | error = 0; |
780 | out: |
781 | return error; |
782 | } |
783 | |
784 | static int copy_io(unsigned long clone_flags, struct task_struct *tsk) |
785 | { |
786 | #ifdef CONFIG_BLOCK |
787 | struct io_context *ioc = current->io_context; |
788 | |
789 | if (!ioc) |
790 | return 0; |
791 | /* |
792 | * Share io context with parent, if CLONE_IO is set |
793 | */ |
794 | if (clone_flags & CLONE_IO) { |
795 | tsk->io_context = ioc_task_link(ioc); |
796 | if (unlikely(!tsk->io_context)) |
797 | return -ENOMEM; |
798 | } else if (ioprio_valid(ioc->ioprio)) { |
799 | tsk->io_context = alloc_io_context(GFP_KERNEL, -1); |
800 | if (unlikely(!tsk->io_context)) |
801 | return -ENOMEM; |
802 | |
803 | tsk->io_context->ioprio = ioc->ioprio; |
804 | } |
805 | #endif |
806 | return 0; |
807 | } |
808 | |
809 | static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) |
810 | { |
811 | struct sighand_struct *sig; |
812 | |
813 | if (clone_flags & CLONE_SIGHAND) { |
814 | atomic_inc(¤t->sighand->count); |
815 | return 0; |
816 | } |
817 | sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); |
818 | rcu_assign_pointer(tsk->sighand, sig); |
819 | if (!sig) |
820 | return -ENOMEM; |
821 | atomic_set(&sig->count, 1); |
822 | memcpy(sig->action, current->sighand->action, sizeof(sig->action)); |
823 | return 0; |
824 | } |
825 | |
826 | void __cleanup_sighand(struct sighand_struct *sighand) |
827 | { |
828 | if (atomic_dec_and_test(&sighand->count)) |
829 | kmem_cache_free(sighand_cachep, sighand); |
830 | } |
831 | |
832 | |
833 | /* |
834 | * Initialize POSIX timer handling for a thread group. |
835 | */ |
836 | static void posix_cpu_timers_init_group(struct signal_struct *sig) |
837 | { |
838 | unsigned long cpu_limit; |
839 | |
840 | /* Thread group counters. */ |
841 | thread_group_cputime_init(sig); |
842 | |
843 | cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur); |
844 | if (cpu_limit != RLIM_INFINITY) { |
845 | sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit); |
846 | sig->cputimer.running = 1; |
847 | } |
848 | |
849 | /* The timer lists. */ |
850 | INIT_LIST_HEAD(&sig->cpu_timers[0]); |
851 | INIT_LIST_HEAD(&sig->cpu_timers[1]); |
852 | INIT_LIST_HEAD(&sig->cpu_timers[2]); |
853 | } |
854 | |
855 | static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) |
856 | { |
857 | struct signal_struct *sig; |
858 | |
859 | if (clone_flags & CLONE_THREAD) |
860 | return 0; |
861 | |
862 | sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL); |
863 | tsk->signal = sig; |
864 | if (!sig) |
865 | return -ENOMEM; |
866 | |
867 | atomic_set(&sig->count, 1); |
868 | atomic_set(&sig->live, 1); |
869 | init_waitqueue_head(&sig->wait_chldexit); |
870 | if (clone_flags & CLONE_NEWPID) |
871 | sig->flags |= SIGNAL_UNKILLABLE; |
872 | sig->curr_target = tsk; |
873 | init_sigpending(&sig->shared_pending); |
874 | INIT_LIST_HEAD(&sig->posix_timers); |
875 | |
876 | hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); |
877 | sig->real_timer.function = it_real_fn; |
878 | |
879 | task_lock(current->group_leader); |
880 | memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); |
881 | task_unlock(current->group_leader); |
882 | |
883 | posix_cpu_timers_init_group(sig); |
884 | |
885 | tty_audit_fork(sig); |
886 | |
887 | sig->oom_adj = current->signal->oom_adj; |
888 | |
889 | return 0; |
890 | } |
891 | |
892 | void __cleanup_signal(struct signal_struct *sig) |
893 | { |
894 | thread_group_cputime_free(sig); |
895 | tty_kref_put(sig->tty); |
896 | kmem_cache_free(signal_cachep, sig); |
897 | } |
898 | |
899 | static void copy_flags(unsigned long clone_flags, struct task_struct *p) |
900 | { |
901 | unsigned long new_flags = p->flags; |
902 | |
903 | new_flags &= ~PF_SUPERPRIV; |
904 | new_flags |= PF_FORKNOEXEC; |
905 | new_flags |= PF_STARTING; |
906 | p->flags = new_flags; |
907 | clear_freeze_flag(p); |
908 | } |
909 | |
910 | SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr) |
911 | { |
912 | current->clear_child_tid = tidptr; |
913 | |
914 | return task_pid_vnr(current); |
915 | } |
916 | |
917 | static void rt_mutex_init_task(struct task_struct *p) |
918 | { |
919 | raw_spin_lock_init(&p->pi_lock); |
920 | #ifdef CONFIG_RT_MUTEXES |
921 | plist_head_init_raw(&p->pi_waiters, &p->pi_lock); |
922 | p->pi_blocked_on = NULL; |
923 | #endif |
924 | } |
925 | |
926 | #ifdef CONFIG_MM_OWNER |
927 | void mm_init_owner(struct mm_struct *mm, struct task_struct *p) |
928 | { |
929 | mm->owner = p; |
930 | } |
931 | #endif /* CONFIG_MM_OWNER */ |
932 | |
933 | /* |
934 | * Initialize POSIX timer handling for a single task. |
935 | */ |
936 | static void posix_cpu_timers_init(struct task_struct *tsk) |
937 | { |
938 | tsk->cputime_expires.prof_exp = cputime_zero; |
939 | tsk->cputime_expires.virt_exp = cputime_zero; |
940 | tsk->cputime_expires.sched_exp = 0; |
941 | INIT_LIST_HEAD(&tsk->cpu_timers[0]); |
942 | INIT_LIST_HEAD(&tsk->cpu_timers[1]); |
943 | INIT_LIST_HEAD(&tsk->cpu_timers[2]); |
944 | } |
945 | |
946 | /* |
947 | * This creates a new process as a copy of the old one, |
948 | * but does not actually start it yet. |
949 | * |
950 | * It copies the registers, and all the appropriate |
951 | * parts of the process environment (as per the clone |
952 | * flags). The actual kick-off is left to the caller. |
953 | */ |
954 | static struct task_struct *copy_process(unsigned long clone_flags, |
955 | unsigned long stack_start, |
956 | struct pt_regs *regs, |
957 | unsigned long stack_size, |
958 | int __user *child_tidptr, |
959 | struct pid *pid, |
960 | int trace) |
961 | { |
962 | int retval; |
963 | struct task_struct *p; |
964 | int cgroup_callbacks_done = 0; |
965 | |
966 | if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) |
967 | return ERR_PTR(-EINVAL); |
968 | |
969 | /* |
970 | * Thread groups must share signals as well, and detached threads |
971 | * can only be started up within the thread group. |
972 | */ |
973 | if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) |
974 | return ERR_PTR(-EINVAL); |
975 | |
976 | /* |
977 | * Shared signal handlers imply shared VM. By way of the above, |
978 | * thread groups also imply shared VM. Blocking this case allows |
979 | * for various simplifications in other code. |
980 | */ |
981 | if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) |
982 | return ERR_PTR(-EINVAL); |
983 | |
984 | /* |
985 | * Siblings of global init remain as zombies on exit since they are |
986 | * not reaped by their parent (swapper). To solve this and to avoid |
987 | * multi-rooted process trees, prevent global and container-inits |
988 | * from creating siblings. |
989 | */ |
990 | if ((clone_flags & CLONE_PARENT) && |
991 | current->signal->flags & SIGNAL_UNKILLABLE) |
992 | return ERR_PTR(-EINVAL); |
993 | |
994 | retval = security_task_create(clone_flags); |
995 | if (retval) |
996 | goto fork_out; |
997 | |
998 | retval = -ENOMEM; |
999 | p = dup_task_struct(current); |
1000 | if (!p) |
1001 | goto fork_out; |
1002 | |
1003 | ftrace_graph_init_task(p); |
1004 | |
1005 | rt_mutex_init_task(p); |
1006 | |
1007 | #ifdef CONFIG_PROVE_LOCKING |
1008 | DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); |
1009 | DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); |
1010 | #endif |
1011 | retval = -EAGAIN; |
1012 | if (atomic_read(&p->real_cred->user->processes) >= |
1013 | task_rlimit(p, RLIMIT_NPROC)) { |
1014 | if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) && |
1015 | p->real_cred->user != INIT_USER) |
1016 | goto bad_fork_free; |
1017 | } |
1018 | |
1019 | retval = copy_creds(p, clone_flags); |
1020 | if (retval < 0) |
1021 | goto bad_fork_free; |
1022 | |
1023 | /* |
1024 | * If multiple threads are within copy_process(), then this check |
1025 | * triggers too late. This doesn't hurt, the check is only there |
1026 | * to stop root fork bombs. |
1027 | */ |
1028 | retval = -EAGAIN; |
1029 | if (nr_threads >= max_threads) |
1030 | goto bad_fork_cleanup_count; |
1031 | |
1032 | if (!try_module_get(task_thread_info(p)->exec_domain->module)) |
1033 | goto bad_fork_cleanup_count; |
1034 | |
1035 | p->did_exec = 0; |
1036 | delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ |
1037 | copy_flags(clone_flags, p); |
1038 | INIT_LIST_HEAD(&p->children); |
1039 | INIT_LIST_HEAD(&p->sibling); |
1040 | rcu_copy_process(p); |
1041 | p->vfork_done = NULL; |
1042 | spin_lock_init(&p->alloc_lock); |
1043 | |
1044 | init_sigpending(&p->pending); |
1045 | |
1046 | p->utime = cputime_zero; |
1047 | p->stime = cputime_zero; |
1048 | p->gtime = cputime_zero; |
1049 | p->utimescaled = cputime_zero; |
1050 | p->stimescaled = cputime_zero; |
1051 | #ifndef CONFIG_VIRT_CPU_ACCOUNTING |
1052 | p->prev_utime = cputime_zero; |
1053 | p->prev_stime = cputime_zero; |
1054 | #endif |
1055 | #if defined(SPLIT_RSS_COUNTING) |
1056 | memset(&p->rss_stat, 0, sizeof(p->rss_stat)); |
1057 | #endif |
1058 | |
1059 | p->default_timer_slack_ns = current->timer_slack_ns; |
1060 | |
1061 | task_io_accounting_init(&p->ioac); |
1062 | acct_clear_integrals(p); |
1063 | |
1064 | posix_cpu_timers_init(p); |
1065 | |
1066 | p->lock_depth = -1; /* -1 = no lock */ |
1067 | do_posix_clock_monotonic_gettime(&p->start_time); |
1068 | p->real_start_time = p->start_time; |
1069 | monotonic_to_bootbased(&p->real_start_time); |
1070 | p->io_context = NULL; |
1071 | p->audit_context = NULL; |
1072 | cgroup_fork(p); |
1073 | #ifdef CONFIG_NUMA |
1074 | p->mempolicy = mpol_dup(p->mempolicy); |
1075 | if (IS_ERR(p->mempolicy)) { |
1076 | retval = PTR_ERR(p->mempolicy); |
1077 | p->mempolicy = NULL; |
1078 | goto bad_fork_cleanup_cgroup; |
1079 | } |
1080 | mpol_fix_fork_child_flag(p); |
1081 | #endif |
1082 | #ifdef CONFIG_TRACE_IRQFLAGS |
1083 | p->irq_events = 0; |
1084 | #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW |
1085 | p->hardirqs_enabled = 1; |
1086 | #else |
1087 | p->hardirqs_enabled = 0; |
1088 | #endif |
1089 | p->hardirq_enable_ip = 0; |
1090 | p->hardirq_enable_event = 0; |
1091 | p->hardirq_disable_ip = _THIS_IP_; |
1092 | p->hardirq_disable_event = 0; |
1093 | p->softirqs_enabled = 1; |
1094 | p->softirq_enable_ip = _THIS_IP_; |
1095 | p->softirq_enable_event = 0; |
1096 | p->softirq_disable_ip = 0; |
1097 | p->softirq_disable_event = 0; |
1098 | p->hardirq_context = 0; |
1099 | p->softirq_context = 0; |
1100 | #endif |
1101 | #ifdef CONFIG_LOCKDEP |
1102 | p->lockdep_depth = 0; /* no locks held yet */ |
1103 | p->curr_chain_key = 0; |
1104 | p->lockdep_recursion = 0; |
1105 | #endif |
1106 | |
1107 | #ifdef CONFIG_DEBUG_MUTEXES |
1108 | p->blocked_on = NULL; /* not blocked yet */ |
1109 | #endif |
1110 | #ifdef CONFIG_CGROUP_MEM_RES_CTLR |
1111 | p->memcg_batch.do_batch = 0; |
1112 | p->memcg_batch.memcg = NULL; |
1113 | #endif |
1114 | |
1115 | p->bts = NULL; |
1116 | |
1117 | p->stack_start = stack_start; |
1118 | |
1119 | /* Perform scheduler related setup. Assign this task to a CPU. */ |
1120 | sched_fork(p, clone_flags); |
1121 | |
1122 | retval = perf_event_init_task(p); |
1123 | if (retval) |
1124 | goto bad_fork_cleanup_policy; |
1125 | |
1126 | if ((retval = audit_alloc(p))) |
1127 | goto bad_fork_cleanup_policy; |
1128 | /* copy all the process information */ |
1129 | if ((retval = copy_semundo(clone_flags, p))) |
1130 | goto bad_fork_cleanup_audit; |
1131 | if ((retval = copy_files(clone_flags, p))) |
1132 | goto bad_fork_cleanup_semundo; |
1133 | if ((retval = copy_fs(clone_flags, p))) |
1134 | goto bad_fork_cleanup_files; |
1135 | if ((retval = copy_sighand(clone_flags, p))) |
1136 | goto bad_fork_cleanup_fs; |
1137 | if ((retval = copy_signal(clone_flags, p))) |
1138 | goto bad_fork_cleanup_sighand; |
1139 | if ((retval = copy_mm(clone_flags, p))) |
1140 | goto bad_fork_cleanup_signal; |
1141 | if ((retval = copy_namespaces(clone_flags, p))) |
1142 | goto bad_fork_cleanup_mm; |
1143 | if ((retval = copy_io(clone_flags, p))) |
1144 | goto bad_fork_cleanup_namespaces; |
1145 | retval = copy_thread(clone_flags, stack_start, stack_size, p, regs); |
1146 | if (retval) |
1147 | goto bad_fork_cleanup_io; |
1148 | |
1149 | if (pid != &init_struct_pid) { |
1150 | retval = -ENOMEM; |
1151 | pid = alloc_pid(p->nsproxy->pid_ns); |
1152 | if (!pid) |
1153 | goto bad_fork_cleanup_io; |
1154 | |
1155 | if (clone_flags & CLONE_NEWPID) { |
1156 | retval = pid_ns_prepare_proc(p->nsproxy->pid_ns); |
1157 | if (retval < 0) |
1158 | goto bad_fork_free_pid; |
1159 | } |
1160 | } |
1161 | |
1162 | p->pid = pid_nr(pid); |
1163 | p->tgid = p->pid; |
1164 | if (clone_flags & CLONE_THREAD) |
1165 | p->tgid = current->tgid; |
1166 | |
1167 | if (current->nsproxy != p->nsproxy) { |
1168 | retval = ns_cgroup_clone(p, pid); |
1169 | if (retval) |
1170 | goto bad_fork_free_pid; |
1171 | } |
1172 | |
1173 | p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; |
1174 | /* |
1175 | * Clear TID on mm_release()? |
1176 | */ |
1177 | p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL; |
1178 | #ifdef CONFIG_FUTEX |
1179 | p->robust_list = NULL; |
1180 | #ifdef CONFIG_COMPAT |
1181 | p->compat_robust_list = NULL; |
1182 | #endif |
1183 | INIT_LIST_HEAD(&p->pi_state_list); |
1184 | p->pi_state_cache = NULL; |
1185 | #endif |
1186 | /* |
1187 | * sigaltstack should be cleared when sharing the same VM |
1188 | */ |
1189 | if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) |
1190 | p->sas_ss_sp = p->sas_ss_size = 0; |
1191 | |
1192 | /* |
1193 | * Syscall tracing and stepping should be turned off in the |
1194 | * child regardless of CLONE_PTRACE. |
1195 | */ |
1196 | user_disable_single_step(p); |
1197 | clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); |
1198 | #ifdef TIF_SYSCALL_EMU |
1199 | clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); |
1200 | #endif |
1201 | clear_all_latency_tracing(p); |
1202 | |
1203 | /* ok, now we should be set up.. */ |
1204 | p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL); |
1205 | p->pdeath_signal = 0; |
1206 | p->exit_state = 0; |
1207 | |
1208 | /* |
1209 | * Ok, make it visible to the rest of the system. |
1210 | * We dont wake it up yet. |
1211 | */ |
1212 | p->group_leader = p; |
1213 | INIT_LIST_HEAD(&p->thread_group); |
1214 | |
1215 | /* Now that the task is set up, run cgroup callbacks if |
1216 | * necessary. We need to run them before the task is visible |
1217 | * on the tasklist. */ |
1218 | cgroup_fork_callbacks(p); |
1219 | cgroup_callbacks_done = 1; |
1220 | |
1221 | /* Need tasklist lock for parent etc handling! */ |
1222 | write_lock_irq(&tasklist_lock); |
1223 | |
1224 | /* CLONE_PARENT re-uses the old parent */ |
1225 | if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) { |
1226 | p->real_parent = current->real_parent; |
1227 | p->parent_exec_id = current->parent_exec_id; |
1228 | } else { |
1229 | p->real_parent = current; |
1230 | p->parent_exec_id = current->self_exec_id; |
1231 | } |
1232 | |
1233 | spin_lock(¤t->sighand->siglock); |
1234 | |
1235 | /* |
1236 | * Process group and session signals need to be delivered to just the |
1237 | * parent before the fork or both the parent and the child after the |
1238 | * fork. Restart if a signal comes in before we add the new process to |
1239 | * it's process group. |
1240 | * A fatal signal pending means that current will exit, so the new |
1241 | * thread can't slip out of an OOM kill (or normal SIGKILL). |
1242 | */ |
1243 | recalc_sigpending(); |
1244 | if (signal_pending(current)) { |
1245 | spin_unlock(¤t->sighand->siglock); |
1246 | write_unlock_irq(&tasklist_lock); |
1247 | retval = -ERESTARTNOINTR; |
1248 | goto bad_fork_free_pid; |
1249 | } |
1250 | |
1251 | if (clone_flags & CLONE_THREAD) { |
1252 | atomic_inc(¤t->signal->count); |
1253 | atomic_inc(¤t->signal->live); |
1254 | p->group_leader = current->group_leader; |
1255 | list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group); |
1256 | } |
1257 | |
1258 | if (likely(p->pid)) { |
1259 | tracehook_finish_clone(p, clone_flags, trace); |
1260 | |
1261 | if (thread_group_leader(p)) { |
1262 | if (clone_flags & CLONE_NEWPID) |
1263 | p->nsproxy->pid_ns->child_reaper = p; |
1264 | |
1265 | p->signal->leader_pid = pid; |
1266 | tty_kref_put(p->signal->tty); |
1267 | p->signal->tty = tty_kref_get(current->signal->tty); |
1268 | attach_pid(p, PIDTYPE_PGID, task_pgrp(current)); |
1269 | attach_pid(p, PIDTYPE_SID, task_session(current)); |
1270 | list_add_tail(&p->sibling, &p->real_parent->children); |
1271 | list_add_tail_rcu(&p->tasks, &init_task.tasks); |
1272 | __get_cpu_var(process_counts)++; |
1273 | } |
1274 | attach_pid(p, PIDTYPE_PID, pid); |
1275 | nr_threads++; |
1276 | } |
1277 | |
1278 | total_forks++; |
1279 | spin_unlock(¤t->sighand->siglock); |
1280 | write_unlock_irq(&tasklist_lock); |
1281 | proc_fork_connector(p); |
1282 | cgroup_post_fork(p); |
1283 | perf_event_fork(p); |
1284 | return p; |
1285 | |
1286 | bad_fork_free_pid: |
1287 | if (pid != &init_struct_pid) |
1288 | free_pid(pid); |
1289 | bad_fork_cleanup_io: |
1290 | if (p->io_context) |
1291 | exit_io_context(p); |
1292 | bad_fork_cleanup_namespaces: |
1293 | exit_task_namespaces(p); |
1294 | bad_fork_cleanup_mm: |
1295 | if (p->mm) |
1296 | mmput(p->mm); |
1297 | bad_fork_cleanup_signal: |
1298 | if (!(clone_flags & CLONE_THREAD)) |
1299 | __cleanup_signal(p->signal); |
1300 | bad_fork_cleanup_sighand: |
1301 | __cleanup_sighand(p->sighand); |
1302 | bad_fork_cleanup_fs: |
1303 | exit_fs(p); /* blocking */ |
1304 | bad_fork_cleanup_files: |
1305 | exit_files(p); /* blocking */ |
1306 | bad_fork_cleanup_semundo: |
1307 | exit_sem(p); |
1308 | bad_fork_cleanup_audit: |
1309 | audit_free(p); |
1310 | bad_fork_cleanup_policy: |
1311 | perf_event_free_task(p); |
1312 | #ifdef CONFIG_NUMA |
1313 | mpol_put(p->mempolicy); |
1314 | bad_fork_cleanup_cgroup: |
1315 | #endif |
1316 | cgroup_exit(p, cgroup_callbacks_done); |
1317 | delayacct_tsk_free(p); |
1318 | module_put(task_thread_info(p)->exec_domain->module); |
1319 | bad_fork_cleanup_count: |
1320 | atomic_dec(&p->cred->user->processes); |
1321 | exit_creds(p); |
1322 | bad_fork_free: |
1323 | free_task(p); |
1324 | fork_out: |
1325 | return ERR_PTR(retval); |
1326 | } |
1327 | |
1328 | noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs) |
1329 | { |
1330 | memset(regs, 0, sizeof(struct pt_regs)); |
1331 | return regs; |
1332 | } |
1333 | |
1334 | struct task_struct * __cpuinit fork_idle(int cpu) |
1335 | { |
1336 | struct task_struct *task; |
1337 | struct pt_regs regs; |
1338 | |
1339 | task = copy_process(CLONE_VM, 0, idle_regs(®s), 0, NULL, |
1340 | &init_struct_pid, 0); |
1341 | if (!IS_ERR(task)) |
1342 | init_idle(task, cpu); |
1343 | |
1344 | return task; |
1345 | } |
1346 | |
1347 | /* |
1348 | * Ok, this is the main fork-routine. |
1349 | * |
1350 | * It copies the process, and if successful kick-starts |
1351 | * it and waits for it to finish using the VM if required. |
1352 | */ |
1353 | long do_fork(unsigned long clone_flags, |
1354 | unsigned long stack_start, |
1355 | struct pt_regs *regs, |
1356 | unsigned long stack_size, |
1357 | int __user *parent_tidptr, |
1358 | int __user *child_tidptr) |
1359 | { |
1360 | struct task_struct *p; |
1361 | int trace = 0; |
1362 | long nr; |
1363 | |
1364 | /* |
1365 | * Do some preliminary argument and permissions checking before we |
1366 | * actually start allocating stuff |
1367 | */ |
1368 | if (clone_flags & CLONE_NEWUSER) { |
1369 | if (clone_flags & CLONE_THREAD) |
1370 | return -EINVAL; |
1371 | /* hopefully this check will go away when userns support is |
1372 | * complete |
1373 | */ |
1374 | if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) || |
1375 | !capable(CAP_SETGID)) |
1376 | return -EPERM; |
1377 | } |
1378 | |
1379 | /* |
1380 | * We hope to recycle these flags after 2.6.26 |
1381 | */ |
1382 | if (unlikely(clone_flags & CLONE_STOPPED)) { |
1383 | static int __read_mostly count = 100; |
1384 | |
1385 | if (count > 0 && printk_ratelimit()) { |
1386 | char comm[TASK_COMM_LEN]; |
1387 | |
1388 | count--; |
1389 | printk(KERN_INFO "fork(): process `%s' used deprecated " |
1390 | "clone flags 0x%lx\n", |
1391 | get_task_comm(comm, current), |
1392 | clone_flags & CLONE_STOPPED); |
1393 | } |
1394 | } |
1395 | |
1396 | /* |
1397 | * When called from kernel_thread, don't do user tracing stuff. |
1398 | */ |
1399 | if (likely(user_mode(regs))) |
1400 | trace = tracehook_prepare_clone(clone_flags); |
1401 | |
1402 | p = copy_process(clone_flags, stack_start, regs, stack_size, |
1403 | child_tidptr, NULL, trace); |
1404 | /* |
1405 | * Do this prior waking up the new thread - the thread pointer |
1406 | * might get invalid after that point, if the thread exits quickly. |
1407 | */ |
1408 | if (!IS_ERR(p)) { |
1409 | struct completion vfork; |
1410 | |
1411 | trace_sched_process_fork(current, p); |
1412 | |
1413 | nr = task_pid_vnr(p); |
1414 | |
1415 | if (clone_flags & CLONE_PARENT_SETTID) |
1416 | put_user(nr, parent_tidptr); |
1417 | |
1418 | if (clone_flags & CLONE_VFORK) { |
1419 | p->vfork_done = &vfork; |
1420 | init_completion(&vfork); |
1421 | } |
1422 | |
1423 | audit_finish_fork(p); |
1424 | tracehook_report_clone(regs, clone_flags, nr, p); |
1425 | |
1426 | /* |
1427 | * We set PF_STARTING at creation in case tracing wants to |
1428 | * use this to distinguish a fully live task from one that |
1429 | * hasn't gotten to tracehook_report_clone() yet. Now we |
1430 | * clear it and set the child going. |
1431 | */ |
1432 | p->flags &= ~PF_STARTING; |
1433 | |
1434 | if (unlikely(clone_flags & CLONE_STOPPED)) { |
1435 | /* |
1436 | * We'll start up with an immediate SIGSTOP. |
1437 | */ |
1438 | sigaddset(&p->pending.signal, SIGSTOP); |
1439 | set_tsk_thread_flag(p, TIF_SIGPENDING); |
1440 | __set_task_state(p, TASK_STOPPED); |
1441 | } else { |
1442 | wake_up_new_task(p, clone_flags); |
1443 | } |
1444 | |
1445 | tracehook_report_clone_complete(trace, regs, |
1446 | clone_flags, nr, p); |
1447 | |
1448 | if (clone_flags & CLONE_VFORK) { |
1449 | freezer_do_not_count(); |
1450 | wait_for_completion(&vfork); |
1451 | freezer_count(); |
1452 | tracehook_report_vfork_done(p, nr); |
1453 | } |
1454 | } else { |
1455 | nr = PTR_ERR(p); |
1456 | } |
1457 | return nr; |
1458 | } |
1459 | |
1460 | #ifndef ARCH_MIN_MMSTRUCT_ALIGN |
1461 | #define ARCH_MIN_MMSTRUCT_ALIGN 0 |
1462 | #endif |
1463 | |
1464 | static void sighand_ctor(void *data) |
1465 | { |
1466 | struct sighand_struct *sighand = data; |
1467 | |
1468 | spin_lock_init(&sighand->siglock); |
1469 | init_waitqueue_head(&sighand->signalfd_wqh); |
1470 | } |
1471 | |
1472 | void __init proc_caches_init(void) |
1473 | { |
1474 | sighand_cachep = kmem_cache_create("sighand_cache", |
1475 | sizeof(struct sighand_struct), 0, |
1476 | SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU| |
1477 | SLAB_NOTRACK, sighand_ctor); |
1478 | signal_cachep = kmem_cache_create("signal_cache", |
1479 | sizeof(struct signal_struct), 0, |
1480 | SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); |
1481 | files_cachep = kmem_cache_create("files_cache", |
1482 | sizeof(struct files_struct), 0, |
1483 | SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); |
1484 | fs_cachep = kmem_cache_create("fs_cache", |
1485 | sizeof(struct fs_struct), 0, |
1486 | SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); |
1487 | mm_cachep = kmem_cache_create("mm_struct", |
1488 | sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, |
1489 | SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); |
1490 | vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC); |
1491 | mmap_init(); |
1492 | } |
1493 | |
1494 | /* |
1495 | * Check constraints on flags passed to the unshare system call and |
1496 | * force unsharing of additional process context as appropriate. |
1497 | */ |
1498 | static void check_unshare_flags(unsigned long *flags_ptr) |
1499 | { |
1500 | /* |
1501 | * If unsharing a thread from a thread group, must also |
1502 | * unshare vm. |
1503 | */ |
1504 | if (*flags_ptr & CLONE_THREAD) |
1505 | *flags_ptr |= CLONE_VM; |
1506 | |
1507 | /* |
1508 | * If unsharing vm, must also unshare signal handlers. |
1509 | */ |
1510 | if (*flags_ptr & CLONE_VM) |
1511 | *flags_ptr |= CLONE_SIGHAND; |
1512 | |
1513 | /* |
1514 | * If unsharing signal handlers and the task was created |
1515 | * using CLONE_THREAD, then must unshare the thread |
1516 | */ |
1517 | if ((*flags_ptr & CLONE_SIGHAND) && |
1518 | (atomic_read(¤t->signal->count) > 1)) |
1519 | *flags_ptr |= CLONE_THREAD; |
1520 | |
1521 | /* |
1522 | * If unsharing namespace, must also unshare filesystem information. |
1523 | */ |
1524 | if (*flags_ptr & CLONE_NEWNS) |
1525 | *flags_ptr |= CLONE_FS; |
1526 | } |
1527 | |
1528 | /* |
1529 | * Unsharing of tasks created with CLONE_THREAD is not supported yet |
1530 | */ |
1531 | static int unshare_thread(unsigned long unshare_flags) |
1532 | { |
1533 | if (unshare_flags & CLONE_THREAD) |
1534 | return -EINVAL; |
1535 | |
1536 | return 0; |
1537 | } |
1538 | |
1539 | /* |
1540 | * Unshare the filesystem structure if it is being shared |
1541 | */ |
1542 | static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) |
1543 | { |
1544 | struct fs_struct *fs = current->fs; |
1545 | |
1546 | if (!(unshare_flags & CLONE_FS) || !fs) |
1547 | return 0; |
1548 | |
1549 | /* don't need lock here; in the worst case we'll do useless copy */ |
1550 | if (fs->users == 1) |
1551 | return 0; |
1552 | |
1553 | *new_fsp = copy_fs_struct(fs); |
1554 | if (!*new_fsp) |
1555 | return -ENOMEM; |
1556 | |
1557 | return 0; |
1558 | } |
1559 | |
1560 | /* |
1561 | * Unsharing of sighand is not supported yet |
1562 | */ |
1563 | static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp) |
1564 | { |
1565 | struct sighand_struct *sigh = current->sighand; |
1566 | |
1567 | if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1) |
1568 | return -EINVAL; |
1569 | else |
1570 | return 0; |
1571 | } |
1572 | |
1573 | /* |
1574 | * Unshare vm if it is being shared |
1575 | */ |
1576 | static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp) |
1577 | { |
1578 | struct mm_struct *mm = current->mm; |
1579 | |
1580 | if ((unshare_flags & CLONE_VM) && |
1581 | (mm && atomic_read(&mm->mm_users) > 1)) { |
1582 | return -EINVAL; |
1583 | } |
1584 | |
1585 | return 0; |
1586 | } |
1587 | |
1588 | /* |
1589 | * Unshare file descriptor table if it is being shared |
1590 | */ |
1591 | static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) |
1592 | { |
1593 | struct files_struct *fd = current->files; |
1594 | int error = 0; |
1595 | |
1596 | if ((unshare_flags & CLONE_FILES) && |
1597 | (fd && atomic_read(&fd->count) > 1)) { |
1598 | *new_fdp = dup_fd(fd, &error); |
1599 | if (!*new_fdp) |
1600 | return error; |
1601 | } |
1602 | |
1603 | return 0; |
1604 | } |
1605 | |
1606 | /* |
1607 | * unshare allows a process to 'unshare' part of the process |
1608 | * context which was originally shared using clone. copy_* |
1609 | * functions used by do_fork() cannot be used here directly |
1610 | * because they modify an inactive task_struct that is being |
1611 | * constructed. Here we are modifying the current, active, |
1612 | * task_struct. |
1613 | */ |
1614 | SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) |
1615 | { |
1616 | int err = 0; |
1617 | struct fs_struct *fs, *new_fs = NULL; |
1618 | struct sighand_struct *new_sigh = NULL; |
1619 | struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL; |
1620 | struct files_struct *fd, *new_fd = NULL; |
1621 | struct nsproxy *new_nsproxy = NULL; |
1622 | int do_sysvsem = 0; |
1623 | |
1624 | check_unshare_flags(&unshare_flags); |
1625 | |
1626 | /* Return -EINVAL for all unsupported flags */ |
1627 | err = -EINVAL; |
1628 | if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| |
1629 | CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| |
1630 | CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET)) |
1631 | goto bad_unshare_out; |
1632 | |
1633 | /* |
1634 | * CLONE_NEWIPC must also detach from the undolist: after switching |
1635 | * to a new ipc namespace, the semaphore arrays from the old |
1636 | * namespace are unreachable. |
1637 | */ |
1638 | if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) |
1639 | do_sysvsem = 1; |
1640 | if ((err = unshare_thread(unshare_flags))) |
1641 | goto bad_unshare_out; |
1642 | if ((err = unshare_fs(unshare_flags, &new_fs))) |
1643 | goto bad_unshare_cleanup_thread; |
1644 | if ((err = unshare_sighand(unshare_flags, &new_sigh))) |
1645 | goto bad_unshare_cleanup_fs; |
1646 | if ((err = unshare_vm(unshare_flags, &new_mm))) |
1647 | goto bad_unshare_cleanup_sigh; |
1648 | if ((err = unshare_fd(unshare_flags, &new_fd))) |
1649 | goto bad_unshare_cleanup_vm; |
1650 | if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, |
1651 | new_fs))) |
1652 | goto bad_unshare_cleanup_fd; |
1653 | |
1654 | if (new_fs || new_mm || new_fd || do_sysvsem || new_nsproxy) { |
1655 | if (do_sysvsem) { |
1656 | /* |
1657 | * CLONE_SYSVSEM is equivalent to sys_exit(). |
1658 | */ |
1659 | exit_sem(current); |
1660 | } |
1661 | |
1662 | if (new_nsproxy) { |
1663 | switch_task_namespaces(current, new_nsproxy); |
1664 | new_nsproxy = NULL; |
1665 | } |
1666 | |
1667 | task_lock(current); |
1668 | |
1669 | if (new_fs) { |
1670 | fs = current->fs; |
1671 | write_lock(&fs->lock); |
1672 | current->fs = new_fs; |
1673 | if (--fs->users) |
1674 | new_fs = NULL; |
1675 | else |
1676 | new_fs = fs; |
1677 | write_unlock(&fs->lock); |
1678 | } |
1679 | |
1680 | if (new_mm) { |
1681 | mm = current->mm; |
1682 | active_mm = current->active_mm; |
1683 | current->mm = new_mm; |
1684 | current->active_mm = new_mm; |
1685 | activate_mm(active_mm, new_mm); |
1686 | new_mm = mm; |
1687 | } |
1688 | |
1689 | if (new_fd) { |
1690 | fd = current->files; |
1691 | current->files = new_fd; |
1692 | new_fd = fd; |
1693 | } |
1694 | |
1695 | task_unlock(current); |
1696 | } |
1697 | |
1698 | if (new_nsproxy) |
1699 | put_nsproxy(new_nsproxy); |
1700 | |
1701 | bad_unshare_cleanup_fd: |
1702 | if (new_fd) |
1703 | put_files_struct(new_fd); |
1704 | |
1705 | bad_unshare_cleanup_vm: |
1706 | if (new_mm) |
1707 | mmput(new_mm); |
1708 | |
1709 | bad_unshare_cleanup_sigh: |
1710 | if (new_sigh) |
1711 | if (atomic_dec_and_test(&new_sigh->count)) |
1712 | kmem_cache_free(sighand_cachep, new_sigh); |
1713 | |
1714 | bad_unshare_cleanup_fs: |
1715 | if (new_fs) |
1716 | free_fs_struct(new_fs); |
1717 | |
1718 | bad_unshare_cleanup_thread: |
1719 | bad_unshare_out: |
1720 | return err; |
1721 | } |
1722 | |
1723 | /* |
1724 | * Helper to unshare the files of the current task. |
1725 | * We don't want to expose copy_files internals to |
1726 | * the exec layer of the kernel. |
1727 | */ |
1728 | |
1729 | int unshare_files(struct files_struct **displaced) |
1730 | { |
1731 | struct task_struct *task = current; |
1732 | struct files_struct *copy = NULL; |
1733 | int error; |
1734 | |
1735 | error = unshare_fd(CLONE_FILES, ©); |
1736 | if (error || !copy) { |
1737 | *displaced = NULL; |
1738 | return error; |
1739 | } |
1740 | *displaced = task->files; |
1741 | task_lock(task); |
1742 | task->files = copy; |
1743 | task_unlock(task); |
1744 | return 0; |
1745 | } |
1746 |
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Tags:
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v2.6.34-rc5
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