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