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/seccomp.h>
38 #include <linux/swap.h>
39 #include <linux/syscalls.h>
40 #include <linux/jiffies.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/proc_fs.h>
52 #include <linux/profile.h>
53 #include <linux/rmap.h>
54 #include <linux/ksm.h>
55 #include <linux/acct.h>
56 #include <linux/tsacct_kern.h>
57 #include <linux/cn_proc.h>
58 #include <linux/freezer.h>
59 #include <linux/delayacct.h>
60 #include <linux/taskstats_kern.h>
61 #include <linux/random.h>
62 #include <linux/tty.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 #include <linux/signalfd.h>
72 #include <linux/uprobes.h>
73 #include <linux/aio.h>
74
75 #include <asm/pgtable.h>
76 #include <asm/pgalloc.h>
77 #include <asm/uaccess.h>
78 #include <asm/mmu_context.h>
79 #include <asm/cacheflush.h>
80 #include <asm/tlbflush.h>
81
82 #include <trace/events/sched.h>
83
84 #define CREATE_TRACE_POINTS
85 #include <trace/events/task.h>
86
87 /*
88 * Protected counters by write_lock_irq(&tasklist_lock)
89 */
90 unsigned long total_forks; /* Handle normal Linux uptimes. */
91 int nr_threads; /* The idle threads do not count.. */
92
93 int max_threads; /* tunable limit on nr_threads */
94
95 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
96
97 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */
98
99 #ifdef CONFIG_PROVE_RCU
100 int lockdep_tasklist_lock_is_held(void)
101 {
102 return lockdep_is_held(&tasklist_lock);
103 }
104 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
105 #endif /* #ifdef CONFIG_PROVE_RCU */
106
107 int nr_processes(void)
108 {
109 int cpu;
110 int total = 0;
111
112 for_each_possible_cpu(cpu)
113 total += per_cpu(process_counts, cpu);
114
115 return total;
116 }
117
118 void __weak arch_release_task_struct(struct task_struct *tsk)
119 {
120 }
121
122 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
123 static struct kmem_cache *task_struct_cachep;
124
125 static inline struct task_struct *alloc_task_struct_node(int node)
126 {
127 return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node);
128 }
129
130 static inline void free_task_struct(struct task_struct *tsk)
131 {
132 kmem_cache_free(task_struct_cachep, tsk);
133 }
134 #endif
135
136 void __weak arch_release_thread_info(struct thread_info *ti)
137 {
138 }
139
140 #ifndef CONFIG_ARCH_THREAD_INFO_ALLOCATOR
141
142 /*
143 * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
144 * kmemcache based allocator.
145 */
146 # if THREAD_SIZE >= PAGE_SIZE
147 static struct thread_info *alloc_thread_info_node(struct task_struct *tsk,
148 int node)
149 {
150 struct page *page = alloc_pages_node(node, THREADINFO_GFP_ACCOUNTED,
151 THREAD_SIZE_ORDER);
152
153 return page ? page_address(page) : NULL;
154 }
155
156 static inline void free_thread_info(struct thread_info *ti)
157 {
158 free_memcg_kmem_pages((unsigned long)ti, THREAD_SIZE_ORDER);
159 }
160 # else
161 static struct kmem_cache *thread_info_cache;
162
163 static struct thread_info *alloc_thread_info_node(struct task_struct *tsk,
164 int node)
165 {
166 return kmem_cache_alloc_node(thread_info_cache, THREADINFO_GFP, node);
167 }
168
169 static void free_thread_info(struct thread_info *ti)
170 {
171 kmem_cache_free(thread_info_cache, ti);
172 }
173
174 void thread_info_cache_init(void)
175 {
176 thread_info_cache = kmem_cache_create("thread_info", THREAD_SIZE,
177 THREAD_SIZE, 0, NULL);
178 BUG_ON(thread_info_cache == NULL);
179 }
180 # endif
181 #endif
182
183 /* SLAB cache for signal_struct structures (tsk->signal) */
184 static struct kmem_cache *signal_cachep;
185
186 /* SLAB cache for sighand_struct structures (tsk->sighand) */
187 struct kmem_cache *sighand_cachep;
188
189 /* SLAB cache for files_struct structures (tsk->files) */
190 struct kmem_cache *files_cachep;
191
192 /* SLAB cache for fs_struct structures (tsk->fs) */
193 struct kmem_cache *fs_cachep;
194
195 /* SLAB cache for vm_area_struct structures */
196 struct kmem_cache *vm_area_cachep;
197
198 /* SLAB cache for mm_struct structures (tsk->mm) */
199 static struct kmem_cache *mm_cachep;
200
201 static void account_kernel_stack(struct thread_info *ti, int account)
202 {
203 struct zone *zone = page_zone(virt_to_page(ti));
204
205 mod_zone_page_state(zone, NR_KERNEL_STACK, account);
206 }
207
208 void free_task(struct task_struct *tsk)
209 {
210 account_kernel_stack(tsk->stack, -1);
211 arch_release_thread_info(tsk->stack);
212 free_thread_info(tsk->stack);
213 rt_mutex_debug_task_free(tsk);
214 ftrace_graph_exit_task(tsk);
215 put_seccomp_filter(tsk);
216 arch_release_task_struct(tsk);
217 free_task_struct(tsk);
218 }
219 EXPORT_SYMBOL(free_task);
220
221 static inline void free_signal_struct(struct signal_struct *sig)
222 {
223 taskstats_tgid_free(sig);
224 sched_autogroup_exit(sig);
225 kmem_cache_free(signal_cachep, sig);
226 }
227
228 static inline void put_signal_struct(struct signal_struct *sig)
229 {
230 if (atomic_dec_and_test(&sig->sigcnt))
231 free_signal_struct(sig);
232 }
233
234 void __put_task_struct(struct task_struct *tsk)
235 {
236 WARN_ON(!tsk->exit_state);
237 WARN_ON(atomic_read(&tsk->usage));
238 WARN_ON(tsk == current);
239
240 security_task_free(tsk);
241 exit_creds(tsk);
242 delayacct_tsk_free(tsk);
243 put_signal_struct(tsk->signal);
244
245 ccs_free_task_security(tsk);
246 if (!profile_handoff_task(tsk))
247 free_task(tsk);
248 }
249 EXPORT_SYMBOL_GPL(__put_task_struct);
250
251 void __init __weak arch_task_cache_init(void) { }
252
253 void __init fork_init(unsigned long mempages)
254 {
255 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
256 #ifndef ARCH_MIN_TASKALIGN
257 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES
258 #endif
259 /* create a slab on which task_structs can be allocated */
260 task_struct_cachep =
261 kmem_cache_create("task_struct", sizeof(struct task_struct),
262 ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL);
263 #endif
264
265 /* do the arch specific task caches init */
266 arch_task_cache_init();
267
268 /*
269 * The default maximum number of threads is set to a safe
270 * value: the thread structures can take up at most half
271 * of memory.
272 */
273 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
274
275 /*
276 * we need to allow at least 20 threads to boot a system
277 */
278 if (max_threads < 20)
279 max_threads = 20;
280
281 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
282 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
283 init_task.signal->rlim[RLIMIT_SIGPENDING] =
284 init_task.signal->rlim[RLIMIT_NPROC];
285 }
286
287 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst,
288 struct task_struct *src)
289 {
290 *dst = *src;
291 return 0;
292 }
293
294 static struct task_struct *dup_task_struct(struct task_struct *orig)
295 {
296 struct task_struct *tsk;
297 struct thread_info *ti;
298 unsigned long *stackend;
299 int node = tsk_fork_get_node(orig);
300 int err;
301
302 tsk = alloc_task_struct_node(node);
303 if (!tsk)
304 return NULL;
305
306 ti = alloc_thread_info_node(tsk, node);
307 if (!ti)
308 goto free_tsk;
309
310 err = arch_dup_task_struct(tsk, orig);
311 if (err)
312 goto free_ti;
313
314 tsk->stack = ti;
315
316 setup_thread_stack(tsk, orig);
317 clear_user_return_notifier(tsk);
318 clear_tsk_need_resched(tsk);
319 stackend = end_of_stack(tsk);
320 *stackend = STACK_END_MAGIC; /* for overflow detection */
321
322 #ifdef CONFIG_CC_STACKPROTECTOR
323 tsk->stack_canary = get_random_int();
324 #endif
325
326 /*
327 * One for us, one for whoever does the "release_task()" (usually
328 * parent)
329 */
330 atomic_set(&tsk->usage, 2);
331 #ifdef CONFIG_BLK_DEV_IO_TRACE
332 tsk->btrace_seq = 0;
333 #endif
334 tsk->splice_pipe = NULL;
335 tsk->task_frag.page = NULL;
336
337 account_kernel_stack(ti, 1);
338
339 return tsk;
340
341 free_ti:
342 free_thread_info(ti);
343 free_tsk:
344 free_task_struct(tsk);
345 return NULL;
346 }
347
348 #ifdef CONFIG_MMU
349 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
350 {
351 struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
352 struct rb_node **rb_link, *rb_parent;
353 int retval;
354 unsigned long charge;
355
356 uprobe_start_dup_mmap();
357 down_write(&oldmm->mmap_sem);
358 flush_cache_dup_mm(oldmm);
359 uprobe_dup_mmap(oldmm, mm);
360 /*
361 * Not linked in yet - no deadlock potential:
362 */
363 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
364
365 mm->locked_vm = 0;
366 mm->mmap = NULL;
367 mm->mmap_cache = NULL;
368 mm->map_count = 0;
369 cpumask_clear(mm_cpumask(mm));
370 mm->mm_rb = RB_ROOT;
371 rb_link = &mm->mm_rb.rb_node;
372 rb_parent = NULL;
373 pprev = &mm->mmap;
374 retval = ksm_fork(mm, oldmm);
375 if (retval)
376 goto out;
377 retval = khugepaged_fork(mm, oldmm);
378 if (retval)
379 goto out;
380
381 prev = NULL;
382 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
383 struct file *file;
384
385 if (mpnt->vm_flags & VM_DONTCOPY) {
386 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
387 -vma_pages(mpnt));
388 continue;
389 }
390 charge = 0;
391 if (mpnt->vm_flags & VM_ACCOUNT) {
392 unsigned long len = vma_pages(mpnt);
393
394 if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
395 goto fail_nomem;
396 charge = len;
397 }
398 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
399 if (!tmp)
400 goto fail_nomem;
401 *tmp = *mpnt;
402 INIT_LIST_HEAD(&tmp->anon_vma_chain);
403 retval = vma_dup_policy(mpnt, tmp);
404 if (retval)
405 goto fail_nomem_policy;
406 tmp->vm_mm = mm;
407 if (anon_vma_fork(tmp, mpnt))
408 goto fail_nomem_anon_vma_fork;
409 tmp->vm_flags &= ~VM_LOCKED;
410 tmp->vm_next = tmp->vm_prev = NULL;
411 file = tmp->vm_file;
412 if (file) {
413 struct inode *inode = file_inode(file);
414 struct address_space *mapping = file->f_mapping;
415
416 get_file(file);
417 if (tmp->vm_flags & VM_DENYWRITE)
418 atomic_dec(&inode->i_writecount);
419 mutex_lock(&mapping->i_mmap_mutex);
420 if (tmp->vm_flags & VM_SHARED)
421 mapping->i_mmap_writable++;
422 flush_dcache_mmap_lock(mapping);
423 /* insert tmp into the share list, just after mpnt */
424 if (unlikely(tmp->vm_flags & VM_NONLINEAR))
425 vma_nonlinear_insert(tmp,
426 &mapping->i_mmap_nonlinear);
427 else
428 vma_interval_tree_insert_after(tmp, mpnt,
429 &mapping->i_mmap);
430 flush_dcache_mmap_unlock(mapping);
431 mutex_unlock(&mapping->i_mmap_mutex);
432 }
433
434 /*
435 * Clear hugetlb-related page reserves for children. This only
436 * affects MAP_PRIVATE mappings. Faults generated by the child
437 * are not guaranteed to succeed, even if read-only
438 */
439 if (is_vm_hugetlb_page(tmp))
440 reset_vma_resv_huge_pages(tmp);
441
442 /*
443 * Link in the new vma and copy the page table entries.
444 */
445 *pprev = tmp;
446 pprev = &tmp->vm_next;
447 tmp->vm_prev = prev;
448 prev = tmp;
449
450 __vma_link_rb(mm, tmp, rb_link, rb_parent);
451 rb_link = &tmp->vm_rb.rb_right;
452 rb_parent = &tmp->vm_rb;
453
454 mm->map_count++;
455 retval = copy_page_range(mm, oldmm, mpnt);
456
457 if (tmp->vm_ops && tmp->vm_ops->open)
458 tmp->vm_ops->open(tmp);
459
460 if (retval)
461 goto out;
462 }
463 /* a new mm has just been created */
464 arch_dup_mmap(oldmm, mm);
465 retval = 0;
466 out:
467 up_write(&mm->mmap_sem);
468 flush_tlb_mm(oldmm);
469 up_write(&oldmm->mmap_sem);
470 uprobe_end_dup_mmap();
471 return retval;
472 fail_nomem_anon_vma_fork:
473 mpol_put(vma_policy(tmp));
474 fail_nomem_policy:
475 kmem_cache_free(vm_area_cachep, tmp);
476 fail_nomem:
477 retval = -ENOMEM;
478 vm_unacct_memory(charge);
479 goto out;
480 }
481
482 static inline int mm_alloc_pgd(struct mm_struct *mm)
483 {
484 mm->pgd = pgd_alloc(mm);
485 if (unlikely(!mm->pgd))
486 return -ENOMEM;
487 return 0;
488 }
489
490 static inline void mm_free_pgd(struct mm_struct *mm)
491 {
492 pgd_free(mm, mm->pgd);
493 }
494 #else
495 #define dup_mmap(mm, oldmm) (0)
496 #define mm_alloc_pgd(mm) (0)
497 #define mm_free_pgd(mm)
498 #endif /* CONFIG_MMU */
499
500 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
501
502 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
503 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm)))
504
505 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
506
507 static int __init coredump_filter_setup(char *s)
508 {
509 default_dump_filter =
510 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
511 MMF_DUMP_FILTER_MASK;
512 return 1;
513 }
514
515 __setup("coredump_filter=", coredump_filter_setup);
516
517 #include <linux/init_task.h>
518
519 static void mm_init_aio(struct mm_struct *mm)
520 {
521 #ifdef CONFIG_AIO
522 spin_lock_init(&mm->ioctx_lock);
523 mm->ioctx_table = NULL;
524 #endif
525 }
526
527 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p)
528 {
529 atomic_set(&mm->mm_users, 1);
530 atomic_set(&mm->mm_count, 1);
531 init_rwsem(&mm->mmap_sem);
532 INIT_LIST_HEAD(&mm->mmlist);
533 mm->flags = (current->mm) ?
534 (current->mm->flags & MMF_INIT_MASK) : default_dump_filter;
535 mm->core_state = NULL;
536 atomic_long_set(&mm->nr_ptes, 0);
537 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
538 spin_lock_init(&mm->page_table_lock);
539 mm_init_aio(mm);
540 mm_init_owner(mm, p);
541 clear_tlb_flush_pending(mm);
542
543 if (likely(!mm_alloc_pgd(mm))) {
544 mm->def_flags = 0;
545 mmu_notifier_mm_init(mm);
546 return mm;
547 }
548
549 free_mm(mm);
550 return NULL;
551 }
552
553 static void check_mm(struct mm_struct *mm)
554 {
555 int i;
556
557 for (i = 0; i < NR_MM_COUNTERS; i++) {
558 long x = atomic_long_read(&mm->rss_stat.count[i]);
559
560 if (unlikely(x))
561 printk(KERN_ALERT "BUG: Bad rss-counter state "
562 "mm:%p idx:%d val:%ld\n", mm, i, x);
563 }
564
565 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
566 VM_BUG_ON(mm->pmd_huge_pte);
567 #endif
568 }
569
570 /*
571 * Allocate and initialize an mm_struct.
572 */
573 struct mm_struct *mm_alloc(void)
574 {
575 struct mm_struct *mm;
576
577 mm = allocate_mm();
578 if (!mm)
579 return NULL;
580
581 memset(mm, 0, sizeof(*mm));
582 mm_init_cpumask(mm);
583 return mm_init(mm, current);
584 }
585
586 /*
587 * Called when the last reference to the mm
588 * is dropped: either by a lazy thread or by
589 * mmput. Free the page directory and the mm.
590 */
591 void __mmdrop(struct mm_struct *mm)
592 {
593 BUG_ON(mm == &init_mm);
594 mm_free_pgd(mm);
595 destroy_context(mm);
596 mmu_notifier_mm_destroy(mm);
597 check_mm(mm);
598 free_mm(mm);
599 }
600 EXPORT_SYMBOL_GPL(__mmdrop);
601
602 /*
603 * Decrement the use count and release all resources for an mm.
604 */
605 void mmput(struct mm_struct *mm)
606 {
607 might_sleep();
608
609 if (atomic_dec_and_test(&mm->mm_users)) {
610 uprobe_clear_state(mm);
611 exit_aio(mm);
612 ksm_exit(mm);
613 khugepaged_exit(mm); /* must run before exit_mmap */
614 exit_mmap(mm);
615 set_mm_exe_file(mm, NULL);
616 if (!list_empty(&mm->mmlist)) {
617 spin_lock(&mmlist_lock);
618 list_del(&mm->mmlist);
619 spin_unlock(&mmlist_lock);
620 }
621 if (mm->binfmt)
622 module_put(mm->binfmt->module);
623 mmdrop(mm);
624 }
625 }
626 EXPORT_SYMBOL_GPL(mmput);
627
628 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
629 {
630 if (new_exe_file)
631 get_file(new_exe_file);
632 if (mm->exe_file)
633 fput(mm->exe_file);
634 mm->exe_file = new_exe_file;
635 }
636
637 struct file *get_mm_exe_file(struct mm_struct *mm)
638 {
639 struct file *exe_file;
640
641 /* We need mmap_sem to protect against races with removal of exe_file */
642 down_read(&mm->mmap_sem);
643 exe_file = mm->exe_file;
644 if (exe_file)
645 get_file(exe_file);
646 up_read(&mm->mmap_sem);
647 return exe_file;
648 }
649
650 static void dup_mm_exe_file(struct mm_struct *oldmm, struct mm_struct *newmm)
651 {
652 /* It's safe to write the exe_file pointer without exe_file_lock because
653 * this is called during fork when the task is not yet in /proc */
654 newmm->exe_file = get_mm_exe_file(oldmm);
655 }
656
657 /**
658 * get_task_mm - acquire a reference to the task's mm
659 *
660 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning
661 * this kernel workthread has transiently adopted a user mm with use_mm,
662 * to do its AIO) is not set and if so returns a reference to it, after
663 * bumping up the use count. User must release the mm via mmput()
664 * after use. Typically used by /proc and ptrace.
665 */
666 struct mm_struct *get_task_mm(struct task_struct *task)
667 {
668 struct mm_struct *mm;
669
670 task_lock(task);
671 mm = task->mm;
672 if (mm) {
673 if (task->flags & PF_KTHREAD)
674 mm = NULL;
675 else
676 atomic_inc(&mm->mm_users);
677 }
678 task_unlock(task);
679 return mm;
680 }
681 EXPORT_SYMBOL_GPL(get_task_mm);
682
683 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
684 {
685 struct mm_struct *mm;
686 int err;
687
688 err = mutex_lock_killable(&task->signal->cred_guard_mutex);
689 if (err)
690 return ERR_PTR(err);
691
692 mm = get_task_mm(task);
693 if (mm && mm != current->mm &&
694 !ptrace_may_access(task, mode)) {
695 mmput(mm);
696 mm = ERR_PTR(-EACCES);
697 }
698 mutex_unlock(&task->signal->cred_guard_mutex);
699
700 return mm;
701 }
702
703 static void complete_vfork_done(struct task_struct *tsk)
704 {
705 struct completion *vfork;
706
707 task_lock(tsk);
708 vfork = tsk->vfork_done;
709 if (likely(vfork)) {
710 tsk->vfork_done = NULL;
711 complete(vfork);
712 }
713 task_unlock(tsk);
714 }
715
716 static int wait_for_vfork_done(struct task_struct *child,
717 struct completion *vfork)
718 {
719 int killed;
720
721 freezer_do_not_count();
722 killed = wait_for_completion_killable(vfork);
723 freezer_count();
724
725 if (killed) {
726 task_lock(child);
727 child->vfork_done = NULL;
728 task_unlock(child);
729 }
730
731 put_task_struct(child);
732 return killed;
733 }
734
735 /* Please note the differences between mmput and mm_release.
736 * mmput is called whenever we stop holding onto a mm_struct,
737 * error success whatever.
738 *
739 * mm_release is called after a mm_struct has been removed
740 * from the current process.
741 *
742 * This difference is important for error handling, when we
743 * only half set up a mm_struct for a new process and need to restore
744 * the old one. Because we mmput the new mm_struct before
745 * restoring the old one. . .
746 * Eric Biederman 10 January 1998
747 */
748 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
749 {
750 /* Get rid of any futexes when releasing the mm */
751 #ifdef CONFIG_FUTEX
752 if (unlikely(tsk->robust_list)) {
753 exit_robust_list(tsk);
754 tsk->robust_list = NULL;
755 }
756 #ifdef CONFIG_COMPAT
757 if (unlikely(tsk->compat_robust_list)) {
758 compat_exit_robust_list(tsk);
759 tsk->compat_robust_list = NULL;
760 }
761 #endif
762 if (unlikely(!list_empty(&tsk->pi_state_list)))
763 exit_pi_state_list(tsk);
764 #endif
765
766 uprobe_free_utask(tsk);
767
768 /* Get rid of any cached register state */
769 deactivate_mm(tsk, mm);
770
771 /*
772 * If we're exiting normally, clear a user-space tid field if
773 * requested. We leave this alone when dying by signal, to leave
774 * the value intact in a core dump, and to save the unnecessary
775 * trouble, say, a killed vfork parent shouldn't touch this mm.
776 * Userland only wants this done for a sys_exit.
777 */
778 if (tsk->clear_child_tid) {
779 if (!(tsk->flags & PF_SIGNALED) &&
780 atomic_read(&mm->mm_users) > 1) {
781 /*
782 * We don't check the error code - if userspace has
783 * not set up a proper pointer then tough luck.
784 */
785 put_user(0, tsk->clear_child_tid);
786 sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
787 1, NULL, NULL, 0);
788 }
789 tsk->clear_child_tid = NULL;
790 }
791
792 /*
793 * All done, finally we can wake up parent and return this mm to him.
794 * Also kthread_stop() uses this completion for synchronization.
795 */
796 if (tsk->vfork_done)
797 complete_vfork_done(tsk);
798 }
799
800 /*
801 * Allocate a new mm structure and copy contents from the
802 * mm structure of the passed in task structure.
803 */
804 struct mm_struct *dup_mm(struct task_struct *tsk)
805 {
806 struct mm_struct *mm, *oldmm = current->mm;
807 int err;
808
809 if (!oldmm)
810 return NULL;
811
812 mm = allocate_mm();
813 if (!mm)
814 goto fail_nomem;
815
816 memcpy(mm, oldmm, sizeof(*mm));
817 mm_init_cpumask(mm);
818
819 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
820 mm->pmd_huge_pte = NULL;
821 #endif
822 if (!mm_init(mm, tsk))
823 goto fail_nomem;
824
825 if (init_new_context(tsk, mm))
826 goto fail_nocontext;
827
828 dup_mm_exe_file(oldmm, mm);
829
830 err = dup_mmap(mm, oldmm);
831 if (err)
832 goto free_pt;
833
834 mm->hiwater_rss = get_mm_rss(mm);
835 mm->hiwater_vm = mm->total_vm;
836
837 if (mm->binfmt && !try_module_get(mm->binfmt->module))
838 goto free_pt;
839
840 return mm;
841
842 free_pt:
843 /* don't put binfmt in mmput, we haven't got module yet */
844 mm->binfmt = NULL;
845 mmput(mm);
846
847 fail_nomem:
848 return NULL;
849
850 fail_nocontext:
851 /*
852 * If init_new_context() failed, we cannot use mmput() to free the mm
853 * because it calls destroy_context()
854 */
855 mm_free_pgd(mm);
856 free_mm(mm);
857 return NULL;
858 }
859
860 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
861 {
862 struct mm_struct *mm, *oldmm;
863 int retval;
864
865 tsk->min_flt = tsk->maj_flt = 0;
866 tsk->nvcsw = tsk->nivcsw = 0;
867 #ifdef CONFIG_DETECT_HUNG_TASK
868 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
869 #endif
870
871 tsk->mm = NULL;
872 tsk->active_mm = NULL;
873
874 /*
875 * Are we cloning a kernel thread?
876 *
877 * We need to steal a active VM for that..
878 */
879 oldmm = current->mm;
880 if (!oldmm)
881 return 0;
882
883 if (clone_flags & CLONE_VM) {
884 atomic_inc(&oldmm->mm_users);
885 mm = oldmm;
886 goto good_mm;
887 }
888
889 retval = -ENOMEM;
890 mm = dup_mm(tsk);
891 if (!mm)
892 goto fail_nomem;
893
894 good_mm:
895 tsk->mm = mm;
896 tsk->active_mm = mm;
897 return 0;
898
899 fail_nomem:
900 return retval;
901 }
902
903 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
904 {
905 struct fs_struct *fs = current->fs;
906 if (clone_flags & CLONE_FS) {
907 /* tsk->fs is already what we want */
908 spin_lock(&fs->lock);
909 if (fs->in_exec) {
910 spin_unlock(&fs->lock);
911 return -EAGAIN;
912 }
913 fs->users++;
914 spin_unlock(&fs->lock);
915 return 0;
916 }
917 tsk->fs = copy_fs_struct(fs);
918 if (!tsk->fs)
919 return -ENOMEM;
920 return 0;
921 }
922
923 static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
924 {
925 struct files_struct *oldf, *newf;
926 int error = 0;
927
928 /*
929 * A background process may not have any files ...
930 */
931 oldf = current->files;
932 if (!oldf)
933 goto out;
934
935 if (clone_flags & CLONE_FILES) {
936 atomic_inc(&oldf->count);
937 goto out;
938 }
939
940 newf = dup_fd(oldf, &error);
941 if (!newf)
942 goto out;
943
944 tsk->files = newf;
945 error = 0;
946 out:
947 return error;
948 }
949
950 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
951 {
952 #ifdef CONFIG_BLOCK
953 struct io_context *ioc = current->io_context;
954 struct io_context *new_ioc;
955
956 if (!ioc)
957 return 0;
958 /*
959 * Share io context with parent, if CLONE_IO is set
960 */
961 if (clone_flags & CLONE_IO) {
962 ioc_task_link(ioc);
963 tsk->io_context = ioc;
964 } else if (ioprio_valid(ioc->ioprio)) {
965 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE);
966 if (unlikely(!new_ioc))
967 return -ENOMEM;
968
969 new_ioc->ioprio = ioc->ioprio;
970 put_io_context(new_ioc);
971 }
972 #endif
973 return 0;
974 }
975
976 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
977 {
978 struct sighand_struct *sig;
979
980 if (clone_flags & CLONE_SIGHAND) {
981 atomic_inc(¤t->sighand->count);
982 return 0;
983 }
984 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
985 rcu_assign_pointer(tsk->sighand, sig);
986 if (!sig)
987 return -ENOMEM;
988 atomic_set(&sig->count, 1);
989 memcpy(sig->action, current->sighand->action, sizeof(sig->action));
990 return 0;
991 }
992
993 void __cleanup_sighand(struct sighand_struct *sighand)
994 {
995 if (atomic_dec_and_test(&sighand->count)) {
996 signalfd_cleanup(sighand);
997 kmem_cache_free(sighand_cachep, sighand);
998 }
999 }
1000
1001
1002 /*
1003 * Initialize POSIX timer handling for a thread group.
1004 */
1005 static void posix_cpu_timers_init_group(struct signal_struct *sig)
1006 {
1007 unsigned long cpu_limit;
1008
1009 /* Thread group counters. */
1010 thread_group_cputime_init(sig);
1011
1012 cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1013 if (cpu_limit != RLIM_INFINITY) {
1014 sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit);
1015 sig->cputimer.running = 1;
1016 }
1017
1018 /* The timer lists. */
1019 INIT_LIST_HEAD(&sig->cpu_timers[0]);
1020 INIT_LIST_HEAD(&sig->cpu_timers[1]);
1021 INIT_LIST_HEAD(&sig->cpu_timers[2]);
1022 }
1023
1024 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
1025 {
1026 struct signal_struct *sig;
1027
1028 if (clone_flags & CLONE_THREAD)
1029 return 0;
1030
1031 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
1032 tsk->signal = sig;
1033 if (!sig)
1034 return -ENOMEM;
1035
1036 sig->nr_threads = 1;
1037 atomic_set(&sig->live, 1);
1038 atomic_set(&sig->sigcnt, 1);
1039 init_waitqueue_head(&sig->wait_chldexit);
1040 sig->curr_target = tsk;
1041 init_sigpending(&sig->shared_pending);
1042 INIT_LIST_HEAD(&sig->posix_timers);
1043
1044 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1045 sig->real_timer.function = it_real_fn;
1046
1047 task_lock(current->group_leader);
1048 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
1049 task_unlock(current->group_leader);
1050
1051 posix_cpu_timers_init_group(sig);
1052
1053 tty_audit_fork(sig);
1054 sched_autogroup_fork(sig);
1055
1056 #ifdef CONFIG_CGROUPS
1057 init_rwsem(&sig->group_rwsem);
1058 #endif
1059
1060 sig->oom_score_adj = current->signal->oom_score_adj;
1061 sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1062
1063 sig->has_child_subreaper = current->signal->has_child_subreaper ||
1064 current->signal->is_child_subreaper;
1065
1066 mutex_init(&sig->cred_guard_mutex);
1067
1068 return 0;
1069 }
1070
1071 static void copy_flags(unsigned long clone_flags, struct task_struct *p)
1072 {
1073 unsigned long new_flags = p->flags;
1074
1075 new_flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER);
1076 new_flags |= PF_FORKNOEXEC;
1077 p->flags = new_flags;
1078 }
1079
1080 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1081 {
1082 current->clear_child_tid = tidptr;
1083
1084 return task_pid_vnr(current);
1085 }
1086
1087 static void rt_mutex_init_task(struct task_struct *p)
1088 {
1089 raw_spin_lock_init(&p->pi_lock);
1090 #ifdef CONFIG_RT_MUTEXES
1091 plist_head_init(&p->pi_waiters);
1092 p->pi_blocked_on = NULL;
1093 #endif
1094 }
1095
1096 #ifdef CONFIG_MM_OWNER
1097 void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
1098 {
1099 mm->owner = p;
1100 }
1101 #endif /* CONFIG_MM_OWNER */
1102
1103 /*
1104 * Initialize POSIX timer handling for a single task.
1105 */
1106 static void posix_cpu_timers_init(struct task_struct *tsk)
1107 {
1108 tsk->cputime_expires.prof_exp = 0;
1109 tsk->cputime_expires.virt_exp = 0;
1110 tsk->cputime_expires.sched_exp = 0;
1111 INIT_LIST_HEAD(&tsk->cpu_timers[0]);
1112 INIT_LIST_HEAD(&tsk->cpu_timers[1]);
1113 INIT_LIST_HEAD(&tsk->cpu_timers[2]);
1114 }
1115
1116 static inline void
1117 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid)
1118 {
1119 task->pids[type].pid = pid;
1120 }
1121
1122 /*
1123 * This creates a new process as a copy of the old one,
1124 * but does not actually start it yet.
1125 *
1126 * It copies the registers, and all the appropriate
1127 * parts of the process environment (as per the clone
1128 * flags). The actual kick-off is left to the caller.
1129 */
1130 static struct task_struct *copy_process(unsigned long clone_flags,
1131 unsigned long stack_start,
1132 unsigned long stack_size,
1133 int __user *child_tidptr,
1134 struct pid *pid,
1135 int trace)
1136 {
1137 int retval;
1138 struct task_struct *p;
1139
1140 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1141 return ERR_PTR(-EINVAL);
1142
1143 if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS))
1144 return ERR_PTR(-EINVAL);
1145
1146 /*
1147 * Thread groups must share signals as well, and detached threads
1148 * can only be started up within the thread group.
1149 */
1150 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1151 return ERR_PTR(-EINVAL);
1152
1153 /*
1154 * Shared signal handlers imply shared VM. By way of the above,
1155 * thread groups also imply shared VM. Blocking this case allows
1156 * for various simplifications in other code.
1157 */
1158 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1159 return ERR_PTR(-EINVAL);
1160
1161 /*
1162 * Siblings of global init remain as zombies on exit since they are
1163 * not reaped by their parent (swapper). To solve this and to avoid
1164 * multi-rooted process trees, prevent global and container-inits
1165 * from creating siblings.
1166 */
1167 if ((clone_flags & CLONE_PARENT) &&
1168 current->signal->flags & SIGNAL_UNKILLABLE)
1169 return ERR_PTR(-EINVAL);
1170
1171 /*
1172 * If the new process will be in a different pid or user namespace
1173 * do not allow it to share a thread group or signal handlers or
1174 * parent with the forking task.
1175 */
1176 if (clone_flags & CLONE_SIGHAND) {
1177 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) ||
1178 (task_active_pid_ns(current) !=
1179 current->nsproxy->pid_ns_for_children))
1180 return ERR_PTR(-EINVAL);
1181 }
1182
1183 retval = security_task_create(clone_flags);
1184 if (retval)
1185 goto fork_out;
1186
1187 retval = -ENOMEM;
1188 p = dup_task_struct(current);
1189 if (!p)
1190 goto fork_out;
1191
1192 ftrace_graph_init_task(p);
1193 get_seccomp_filter(p);
1194
1195 rt_mutex_init_task(p);
1196
1197 #ifdef CONFIG_PROVE_LOCKING
1198 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1199 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1200 #endif
1201 retval = -EAGAIN;
1202 if (atomic_read(&p->real_cred->user->processes) >=
1203 task_rlimit(p, RLIMIT_NPROC)) {
1204 if (p->real_cred->user != INIT_USER &&
1205 !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
1206 goto bad_fork_free;
1207 }
1208 current->flags &= ~PF_NPROC_EXCEEDED;
1209
1210 retval = copy_creds(p, clone_flags);
1211 if (retval < 0)
1212 goto bad_fork_free;
1213
1214 /*
1215 * If multiple threads are within copy_process(), then this check
1216 * triggers too late. This doesn't hurt, the check is only there
1217 * to stop root fork bombs.
1218 */
1219 retval = -EAGAIN;
1220 if (nr_threads >= max_threads)
1221 goto bad_fork_cleanup_count;
1222
1223 if (!try_module_get(task_thread_info(p)->exec_domain->module))
1224 goto bad_fork_cleanup_count;
1225
1226 p->did_exec = 0;
1227 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */
1228 copy_flags(clone_flags, p);
1229 INIT_LIST_HEAD(&p->children);
1230 INIT_LIST_HEAD(&p->sibling);
1231 rcu_copy_process(p);
1232 p->vfork_done = NULL;
1233 spin_lock_init(&p->alloc_lock);
1234
1235 init_sigpending(&p->pending);
1236
1237 p->utime = p->stime = p->gtime = 0;
1238 p->utimescaled = p->stimescaled = 0;
1239 #ifndef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
1240 p->prev_cputime.utime = p->prev_cputime.stime = 0;
1241 #endif
1242 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
1243 seqlock_init(&p->vtime_seqlock);
1244 p->vtime_snap = 0;
1245 p->vtime_snap_whence = VTIME_SLEEPING;
1246 #endif
1247
1248 #if defined(SPLIT_RSS_COUNTING)
1249 memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1250 #endif
1251
1252 p->default_timer_slack_ns = current->timer_slack_ns;
1253
1254 task_io_accounting_init(&p->ioac);
1255 acct_clear_integrals(p);
1256
1257 posix_cpu_timers_init(p);
1258
1259 do_posix_clock_monotonic_gettime(&p->start_time);
1260 p->real_start_time = p->start_time;
1261 monotonic_to_bootbased(&p->real_start_time);
1262 p->io_context = NULL;
1263 p->audit_context = NULL;
1264 if (clone_flags & CLONE_THREAD)
1265 threadgroup_change_begin(current);
1266 cgroup_fork(p);
1267 #ifdef CONFIG_NUMA
1268 p->mempolicy = mpol_dup(p->mempolicy);
1269 if (IS_ERR(p->mempolicy)) {
1270 retval = PTR_ERR(p->mempolicy);
1271 p->mempolicy = NULL;
1272 goto bad_fork_cleanup_cgroup;
1273 }
1274 mpol_fix_fork_child_flag(p);
1275 #endif
1276 #ifdef CONFIG_CPUSETS
1277 p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
1278 p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
1279 seqcount_init(&p->mems_allowed_seq);
1280 #endif
1281 #ifdef CONFIG_TRACE_IRQFLAGS
1282 p->irq_events = 0;
1283 p->hardirqs_enabled = 0;
1284 p->hardirq_enable_ip = 0;
1285 p->hardirq_enable_event = 0;
1286 p->hardirq_disable_ip = _THIS_IP_;
1287 p->hardirq_disable_event = 0;
1288 p->softirqs_enabled = 1;
1289 p->softirq_enable_ip = _THIS_IP_;
1290 p->softirq_enable_event = 0;
1291 p->softirq_disable_ip = 0;
1292 p->softirq_disable_event = 0;
1293 p->hardirq_context = 0;
1294 p->softirq_context = 0;
1295 #endif
1296 #ifdef CONFIG_LOCKDEP
1297 p->lockdep_depth = 0; /* no locks held yet */
1298 p->curr_chain_key = 0;
1299 p->lockdep_recursion = 0;
1300 #endif
1301
1302 #ifdef CONFIG_DEBUG_MUTEXES
1303 p->blocked_on = NULL; /* not blocked yet */
1304 #endif
1305 #ifdef CONFIG_MEMCG
1306 p->memcg_batch.do_batch = 0;
1307 p->memcg_batch.memcg = NULL;
1308 #endif
1309 #ifdef CONFIG_BCACHE
1310 p->sequential_io = 0;
1311 p->sequential_io_avg = 0;
1312 #endif
1313
1314 /* Perform scheduler related setup. Assign this task to a CPU. */
1315 sched_fork(clone_flags, p);
1316
1317 retval = perf_event_init_task(p);
1318 if (retval)
1319 goto bad_fork_cleanup_policy;
1320 retval = audit_alloc(p);
1321 if (retval)
1322 goto bad_fork_cleanup_policy;
1323 retval = ccs_alloc_task_security(p);
1324 if (retval)
1325 goto bad_fork_cleanup_audit;
1326 /* copy all the process information */
1327 retval = copy_semundo(clone_flags, p);
1328 if (retval)
1329 goto bad_fork_cleanup_audit;
1330 retval = copy_files(clone_flags, p);
1331 if (retval)
1332 goto bad_fork_cleanup_semundo;
1333 retval = copy_fs(clone_flags, p);
1334 if (retval)
1335 goto bad_fork_cleanup_files;
1336 retval = copy_sighand(clone_flags, p);
1337 if (retval)
1338 goto bad_fork_cleanup_fs;
1339 retval = copy_signal(clone_flags, p);
1340 if (retval)
1341 goto bad_fork_cleanup_sighand;
1342 retval = copy_mm(clone_flags, p);
1343 if (retval)
1344 goto bad_fork_cleanup_signal;
1345 retval = copy_namespaces(clone_flags, p);
1346 if (retval)
1347 goto bad_fork_cleanup_mm;
1348 retval = copy_io(clone_flags, p);
1349 if (retval)
1350 goto bad_fork_cleanup_namespaces;
1351 retval = copy_thread(clone_flags, stack_start, stack_size, p);
1352 if (retval)
1353 goto bad_fork_cleanup_io;
1354
1355 if (pid != &init_struct_pid) {
1356 retval = -ENOMEM;
1357 pid = alloc_pid(p->nsproxy->pid_ns_for_children);
1358 if (!pid)
1359 goto bad_fork_cleanup_io;
1360 }
1361
1362 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1363 /*
1364 * Clear TID on mm_release()?
1365 */
1366 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL;
1367 #ifdef CONFIG_BLOCK
1368 p->plug = NULL;
1369 #endif
1370 #ifdef CONFIG_FUTEX
1371 p->robust_list = NULL;
1372 #ifdef CONFIG_COMPAT
1373 p->compat_robust_list = NULL;
1374 #endif
1375 INIT_LIST_HEAD(&p->pi_state_list);
1376 p->pi_state_cache = NULL;
1377 #endif
1378 /*
1379 * sigaltstack should be cleared when sharing the same VM
1380 */
1381 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1382 p->sas_ss_sp = p->sas_ss_size = 0;
1383
1384 /*
1385 * Syscall tracing and stepping should be turned off in the
1386 * child regardless of CLONE_PTRACE.
1387 */
1388 user_disable_single_step(p);
1389 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1390 #ifdef TIF_SYSCALL_EMU
1391 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1392 #endif
1393 clear_all_latency_tracing(p);
1394
1395 /* ok, now we should be set up.. */
1396 p->pid = pid_nr(pid);
1397 if (clone_flags & CLONE_THREAD) {
1398 p->exit_signal = -1;
1399 p->group_leader = current->group_leader;
1400 p->tgid = current->tgid;
1401 } else {
1402 if (clone_flags & CLONE_PARENT)
1403 p->exit_signal = current->group_leader->exit_signal;
1404 else
1405 p->exit_signal = (clone_flags & CSIGNAL);
1406 p->group_leader = p;
1407 p->tgid = p->pid;
1408 }
1409
1410 p->pdeath_signal = 0;
1411 p->exit_state = 0;
1412
1413 p->nr_dirtied = 0;
1414 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
1415 p->dirty_paused_when = 0;
1416
1417 INIT_LIST_HEAD(&p->thread_group);
1418 p->task_works = NULL;
1419
1420 /*
1421 * Make it visible to the rest of the system, but dont wake it up yet.
1422 * Need tasklist lock for parent etc handling!
1423 */
1424 write_lock_irq(&tasklist_lock);
1425
1426 /* CLONE_PARENT re-uses the old parent */
1427 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1428 p->real_parent = current->real_parent;
1429 p->parent_exec_id = current->parent_exec_id;
1430 } else {
1431 p->real_parent = current;
1432 p->parent_exec_id = current->self_exec_id;
1433 }
1434
1435 spin_lock(¤t->sighand->siglock);
1436
1437 /*
1438 * Process group and session signals need to be delivered to just the
1439 * parent before the fork or both the parent and the child after the
1440 * fork. Restart if a signal comes in before we add the new process to
1441 * it's process group.
1442 * A fatal signal pending means that current will exit, so the new
1443 * thread can't slip out of an OOM kill (or normal SIGKILL).
1444 */
1445 recalc_sigpending();
1446 if (signal_pending(current)) {
1447 spin_unlock(¤t->sighand->siglock);
1448 write_unlock_irq(&tasklist_lock);
1449 retval = -ERESTARTNOINTR;
1450 goto bad_fork_free_pid;
1451 }
1452
1453 if (likely(p->pid)) {
1454 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
1455
1456 init_task_pid(p, PIDTYPE_PID, pid);
1457 if (thread_group_leader(p)) {
1458 init_task_pid(p, PIDTYPE_PGID, task_pgrp(current));
1459 init_task_pid(p, PIDTYPE_SID, task_session(current));
1460
1461 if (is_child_reaper(pid)) {
1462 ns_of_pid(pid)->child_reaper = p;
1463 p->signal->flags |= SIGNAL_UNKILLABLE;
1464 }
1465
1466 p->signal->leader_pid = pid;
1467 p->signal->tty = tty_kref_get(current->signal->tty);
1468 list_add_tail(&p->sibling, &p->real_parent->children);
1469 list_add_tail_rcu(&p->tasks, &init_task.tasks);
1470 attach_pid(p, PIDTYPE_PGID);
1471 attach_pid(p, PIDTYPE_SID);
1472 __this_cpu_inc(process_counts);
1473 } else {
1474 current->signal->nr_threads++;
1475 atomic_inc(¤t->signal->live);
1476 atomic_inc(¤t->signal->sigcnt);
1477 list_add_tail_rcu(&p->thread_group,
1478 &p->group_leader->thread_group);
1479 }
1480 attach_pid(p, PIDTYPE_PID);
1481 nr_threads++;
1482 }
1483
1484 total_forks++;
1485 spin_unlock(¤t->sighand->siglock);
1486 write_unlock_irq(&tasklist_lock);
1487 proc_fork_connector(p);
1488 cgroup_post_fork(p);
1489 if (clone_flags & CLONE_THREAD)
1490 threadgroup_change_end(current);
1491 perf_event_fork(p);
1492
1493 trace_task_newtask(p, clone_flags);
1494 uprobe_copy_process(p, clone_flags);
1495
1496 return p;
1497
1498 bad_fork_free_pid:
1499 if (pid != &init_struct_pid)
1500 free_pid(pid);
1501 bad_fork_cleanup_io:
1502 if (p->io_context)
1503 exit_io_context(p);
1504 bad_fork_cleanup_namespaces:
1505 exit_task_namespaces(p);
1506 bad_fork_cleanup_mm:
1507 if (p->mm)
1508 mmput(p->mm);
1509 bad_fork_cleanup_signal:
1510 if (!(clone_flags & CLONE_THREAD))
1511 free_signal_struct(p->signal);
1512 bad_fork_cleanup_sighand:
1513 __cleanup_sighand(p->sighand);
1514 bad_fork_cleanup_fs:
1515 exit_fs(p); /* blocking */
1516 bad_fork_cleanup_files:
1517 exit_files(p); /* blocking */
1518 bad_fork_cleanup_semundo:
1519 exit_sem(p);
1520 bad_fork_cleanup_audit:
1521 audit_free(p);
1522 ccs_free_task_security(p);
1523 bad_fork_cleanup_policy:
1524 perf_event_free_task(p);
1525 #ifdef CONFIG_NUMA
1526 mpol_put(p->mempolicy);
1527 bad_fork_cleanup_cgroup:
1528 #endif
1529 if (clone_flags & CLONE_THREAD)
1530 threadgroup_change_end(current);
1531 cgroup_exit(p, 0);
1532 delayacct_tsk_free(p);
1533 module_put(task_thread_info(p)->exec_domain->module);
1534 bad_fork_cleanup_count:
1535 atomic_dec(&p->cred->user->processes);
1536 exit_creds(p);
1537 bad_fork_free:
1538 free_task(p);
1539 fork_out:
1540 return ERR_PTR(retval);
1541 }
1542
1543 static inline void init_idle_pids(struct pid_link *links)
1544 {
1545 enum pid_type type;
1546
1547 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
1548 INIT_HLIST_NODE(&links[type].node); /* not really needed */
1549 links[type].pid = &init_struct_pid;
1550 }
1551 }
1552
1553 struct task_struct *fork_idle(int cpu)
1554 {
1555 struct task_struct *task;
1556 task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0);
1557 if (!IS_ERR(task)) {
1558 init_idle_pids(task->pids);
1559 init_idle(task, cpu);
1560 }
1561
1562 return task;
1563 }
1564
1565 /*
1566 * Ok, this is the main fork-routine.
1567 *
1568 * It copies the process, and if successful kick-starts
1569 * it and waits for it to finish using the VM if required.
1570 */
1571 long do_fork(unsigned long clone_flags,
1572 unsigned long stack_start,
1573 unsigned long stack_size,
1574 int __user *parent_tidptr,
1575 int __user *child_tidptr)
1576 {
1577 struct task_struct *p;
1578 int trace = 0;
1579 long nr;
1580
1581 /*
1582 * Determine whether and which event to report to ptracer. When
1583 * called from kernel_thread or CLONE_UNTRACED is explicitly
1584 * requested, no event is reported; otherwise, report if the event
1585 * for the type of forking is enabled.
1586 */
1587 if (!(clone_flags & CLONE_UNTRACED)) {
1588 if (clone_flags & CLONE_VFORK)
1589 trace = PTRACE_EVENT_VFORK;
1590 else if ((clone_flags & CSIGNAL) != SIGCHLD)
1591 trace = PTRACE_EVENT_CLONE;
1592 else
1593 trace = PTRACE_EVENT_FORK;
1594
1595 if (likely(!ptrace_event_enabled(current, trace)))
1596 trace = 0;
1597 }
1598
1599 p = copy_process(clone_flags, stack_start, stack_size,
1600 child_tidptr, NULL, trace);
1601 /*
1602 * Do this prior waking up the new thread - the thread pointer
1603 * might get invalid after that point, if the thread exits quickly.
1604 */
1605 if (!IS_ERR(p)) {
1606 struct completion vfork;
1607
1608 trace_sched_process_fork(current, p);
1609
1610 nr = task_pid_vnr(p);
1611
1612 if (clone_flags & CLONE_PARENT_SETTID)
1613 put_user(nr, parent_tidptr);
1614
1615 if (clone_flags & CLONE_VFORK) {
1616 p->vfork_done = &vfork;
1617 init_completion(&vfork);
1618 get_task_struct(p);
1619 }
1620
1621 wake_up_new_task(p);
1622
1623 /* forking complete and child started to run, tell ptracer */
1624 if (unlikely(trace))
1625 ptrace_event(trace, nr);
1626
1627 if (clone_flags & CLONE_VFORK) {
1628 if (!wait_for_vfork_done(p, &vfork))
1629 ptrace_event(PTRACE_EVENT_VFORK_DONE, nr);
1630 }
1631 } else {
1632 nr = PTR_ERR(p);
1633 }
1634 return nr;
1635 }
1636
1637 /*
1638 * Create a kernel thread.
1639 */
1640 pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
1641 {
1642 return do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn,
1643 (unsigned long)arg, NULL, NULL);
1644 }
1645
1646 #ifdef __ARCH_WANT_SYS_FORK
1647 SYSCALL_DEFINE0(fork)
1648 {
1649 #ifdef CONFIG_MMU
1650 return do_fork(SIGCHLD, 0, 0, NULL, NULL);
1651 #else
1652 /* can not support in nommu mode */
1653 return(-EINVAL);
1654 #endif
1655 }
1656 #endif
1657
1658 #ifdef __ARCH_WANT_SYS_VFORK
1659 SYSCALL_DEFINE0(vfork)
1660 {
1661 return do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0,
1662 0, NULL, NULL);
1663 }
1664 #endif
1665
1666 #ifdef __ARCH_WANT_SYS_CLONE
1667 #ifdef CONFIG_CLONE_BACKWARDS
1668 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
1669 int __user *, parent_tidptr,
1670 int, tls_val,
1671 int __user *, child_tidptr)
1672 #elif defined(CONFIG_CLONE_BACKWARDS2)
1673 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags,
1674 int __user *, parent_tidptr,
1675 int __user *, child_tidptr,
1676 int, tls_val)
1677 #elif defined(CONFIG_CLONE_BACKWARDS3)
1678 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp,
1679 int, stack_size,
1680 int __user *, parent_tidptr,
1681 int __user *, child_tidptr,
1682 int, tls_val)
1683 #else
1684 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
1685 int __user *, parent_tidptr,
1686 int __user *, child_tidptr,
1687 int, tls_val)
1688 #endif
1689 {
1690 return do_fork(clone_flags, newsp, 0, parent_tidptr, child_tidptr);
1691 }
1692 #endif
1693
1694 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1695 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1696 #endif
1697
1698 static void sighand_ctor(void *data)
1699 {
1700 struct sighand_struct *sighand = data;
1701
1702 spin_lock_init(&sighand->siglock);
1703 init_waitqueue_head(&sighand->signalfd_wqh);
1704 }
1705
1706 void __init proc_caches_init(void)
1707 {
1708 sighand_cachep = kmem_cache_create("sighand_cache",
1709 sizeof(struct sighand_struct), 0,
1710 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU|
1711 SLAB_NOTRACK, sighand_ctor);
1712 signal_cachep = kmem_cache_create("signal_cache",
1713 sizeof(struct signal_struct), 0,
1714 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1715 files_cachep = kmem_cache_create("files_cache",
1716 sizeof(struct files_struct), 0,
1717 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1718 fs_cachep = kmem_cache_create("fs_cache",
1719 sizeof(struct fs_struct), 0,
1720 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1721 /*
1722 * FIXME! The "sizeof(struct mm_struct)" currently includes the
1723 * whole struct cpumask for the OFFSTACK case. We could change
1724 * this to *only* allocate as much of it as required by the
1725 * maximum number of CPU's we can ever have. The cpumask_allocation
1726 * is at the end of the structure, exactly for that reason.
1727 */
1728 mm_cachep = kmem_cache_create("mm_struct",
1729 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1730 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1731 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC);
1732 mmap_init();
1733 nsproxy_cache_init();
1734 }
1735
1736 /*
1737 * Check constraints on flags passed to the unshare system call.
1738 */
1739 static int check_unshare_flags(unsigned long unshare_flags)
1740 {
1741 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1742 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1743 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET|
1744 CLONE_NEWUSER|CLONE_NEWPID))
1745 return -EINVAL;
1746 /*
1747 * Not implemented, but pretend it works if there is nothing to
1748 * unshare. Note that unsharing CLONE_THREAD or CLONE_SIGHAND
1749 * needs to unshare vm.
1750 */
1751 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
1752 /* FIXME: get_task_mm() increments ->mm_users */
1753 if (atomic_read(¤t->mm->mm_users) > 1)
1754 return -EINVAL;
1755 }
1756
1757 return 0;
1758 }
1759
1760 /*
1761 * Unshare the filesystem structure if it is being shared
1762 */
1763 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1764 {
1765 struct fs_struct *fs = current->fs;
1766
1767 if (!(unshare_flags & CLONE_FS) || !fs)
1768 return 0;
1769
1770 /* don't need lock here; in the worst case we'll do useless copy */
1771 if (fs->users == 1)
1772 return 0;
1773
1774 *new_fsp = copy_fs_struct(fs);
1775 if (!*new_fsp)
1776 return -ENOMEM;
1777
1778 return 0;
1779 }
1780
1781 /*
1782 * Unshare file descriptor table if it is being shared
1783 */
1784 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1785 {
1786 struct files_struct *fd = current->files;
1787 int error = 0;
1788
1789 if ((unshare_flags & CLONE_FILES) &&
1790 (fd && atomic_read(&fd->count) > 1)) {
1791 *new_fdp = dup_fd(fd, &error);
1792 if (!*new_fdp)
1793 return error;
1794 }
1795
1796 return 0;
1797 }
1798
1799 /*
1800 * unshare allows a process to 'unshare' part of the process
1801 * context which was originally shared using clone. copy_*
1802 * functions used by do_fork() cannot be used here directly
1803 * because they modify an inactive task_struct that is being
1804 * constructed. Here we are modifying the current, active,
1805 * task_struct.
1806 */
1807 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
1808 {
1809 struct fs_struct *fs, *new_fs = NULL;
1810 struct files_struct *fd, *new_fd = NULL;
1811 struct cred *new_cred = NULL;
1812 struct nsproxy *new_nsproxy = NULL;
1813 int do_sysvsem = 0;
1814 int err;
1815
1816 /*
1817 * If unsharing a user namespace must also unshare the thread.
1818 */
1819 if (unshare_flags & CLONE_NEWUSER)
1820 unshare_flags |= CLONE_THREAD | CLONE_FS;
1821 /*
1822 * If unsharing a thread from a thread group, must also unshare vm.
1823 */
1824 if (unshare_flags & CLONE_THREAD)
1825 unshare_flags |= CLONE_VM;
1826 /*
1827 * If unsharing vm, must also unshare signal handlers.
1828 */
1829 if (unshare_flags & CLONE_VM)
1830 unshare_flags |= CLONE_SIGHAND;
1831 /*
1832 * If unsharing namespace, must also unshare filesystem information.
1833 */
1834 if (unshare_flags & CLONE_NEWNS)
1835 unshare_flags |= CLONE_FS;
1836
1837 err = check_unshare_flags(unshare_flags);
1838 if (err)
1839 goto bad_unshare_out;
1840 /*
1841 * CLONE_NEWIPC must also detach from the undolist: after switching
1842 * to a new ipc namespace, the semaphore arrays from the old
1843 * namespace are unreachable.
1844 */
1845 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1846 do_sysvsem = 1;
1847 err = unshare_fs(unshare_flags, &new_fs);
1848 if (err)
1849 goto bad_unshare_out;
1850 err = unshare_fd(unshare_flags, &new_fd);
1851 if (err)
1852 goto bad_unshare_cleanup_fs;
1853 err = unshare_userns(unshare_flags, &new_cred);
1854 if (err)
1855 goto bad_unshare_cleanup_fd;
1856 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
1857 new_cred, new_fs);
1858 if (err)
1859 goto bad_unshare_cleanup_cred;
1860
1861 if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
1862 if (do_sysvsem) {
1863 /*
1864 * CLONE_SYSVSEM is equivalent to sys_exit().
1865 */
1866 exit_sem(current);
1867 }
1868
1869 if (new_nsproxy)
1870 switch_task_namespaces(current, new_nsproxy);
1871
1872 task_lock(current);
1873
1874 if (new_fs) {
1875 fs = current->fs;
1876 spin_lock(&fs->lock);
1877 current->fs = new_fs;
1878 if (--fs->users)
1879 new_fs = NULL;
1880 else
1881 new_fs = fs;
1882 spin_unlock(&fs->lock);
1883 }
1884
1885 if (new_fd) {
1886 fd = current->files;
1887 current->files = new_fd;
1888 new_fd = fd;
1889 }
1890
1891 task_unlock(current);
1892
1893 if (new_cred) {
1894 /* Install the new user namespace */
1895 commit_creds(new_cred);
1896 new_cred = NULL;
1897 }
1898 }
1899
1900 bad_unshare_cleanup_cred:
1901 if (new_cred)
1902 put_cred(new_cred);
1903 bad_unshare_cleanup_fd:
1904 if (new_fd)
1905 put_files_struct(new_fd);
1906
1907 bad_unshare_cleanup_fs:
1908 if (new_fs)
1909 free_fs_struct(new_fs);
1910
1911 bad_unshare_out:
1912 return err;
1913 }
1914
1915 /*
1916 * Helper to unshare the files of the current task.
1917 * We don't want to expose copy_files internals to
1918 * the exec layer of the kernel.
1919 */
1920
1921 int unshare_files(struct files_struct **displaced)
1922 {
1923 struct task_struct *task = current;
1924 struct files_struct *copy = NULL;
1925 int error;
1926
1927 error = unshare_fd(CLONE_FILES, ©);
1928 if (error || !copy) {
1929 *displaced = NULL;
1930 return error;
1931 }
1932 *displaced = task->files;
1933 task_lock(task);
1934 task->files = copy;
1935 task_unlock(task);
1936 return 0;
1937 }
1938
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