]> git.proxmox.com Git - mirror_ubuntu-bionic-kernel.git/blob - kernel/fork.c
ebpf: add sched_cls_type and map it to sk_filter's verifier ops
[mirror_ubuntu-bionic-kernel.git] / kernel / fork.c
1 /*
2 * linux/kernel/fork.c
3 *
4 * Copyright (C) 1991, 1992 Linus Torvalds
5 */
6
7 /*
8 * 'fork.c' contains the help-routines for the 'fork' system call
9 * (see also entry.S and others).
10 * Fork is rather simple, once you get the hang of it, but the memory
11 * management can be a bitch. See 'mm/memory.c': 'copy_page_range()'
12 */
13
14 #include <linux/slab.h>
15 #include <linux/init.h>
16 #include <linux/unistd.h>
17 #include <linux/module.h>
18 #include <linux/vmalloc.h>
19 #include <linux/completion.h>
20 #include <linux/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/mm.h>
32 #include <linux/vmacache.h>
33 #include <linux/nsproxy.h>
34 #include <linux/capability.h>
35 #include <linux/cpu.h>
36 #include <linux/cgroup.h>
37 #include <linux/security.h>
38 #include <linux/hugetlb.h>
39 #include <linux/seccomp.h>
40 #include <linux/swap.h>
41 #include <linux/syscalls.h>
42 #include <linux/jiffies.h>
43 #include <linux/futex.h>
44 #include <linux/compat.h>
45 #include <linux/kthread.h>
46 #include <linux/task_io_accounting_ops.h>
47 #include <linux/rcupdate.h>
48 #include <linux/ptrace.h>
49 #include <linux/mount.h>
50 #include <linux/audit.h>
51 #include <linux/memcontrol.h>
52 #include <linux/ftrace.h>
53 #include <linux/proc_fs.h>
54 #include <linux/profile.h>
55 #include <linux/rmap.h>
56 #include <linux/ksm.h>
57 #include <linux/acct.h>
58 #include <linux/tsacct_kern.h>
59 #include <linux/cn_proc.h>
60 #include <linux/freezer.h>
61 #include <linux/delayacct.h>
62 #include <linux/taskstats_kern.h>
63 #include <linux/random.h>
64 #include <linux/tty.h>
65 #include <linux/blkdev.h>
66 #include <linux/fs_struct.h>
67 #include <linux/magic.h>
68 #include <linux/perf_event.h>
69 #include <linux/posix-timers.h>
70 #include <linux/user-return-notifier.h>
71 #include <linux/oom.h>
72 #include <linux/khugepaged.h>
73 #include <linux/signalfd.h>
74 #include <linux/uprobes.h>
75 #include <linux/aio.h>
76 #include <linux/compiler.h>
77
78 #include <asm/pgtable.h>
79 #include <asm/pgalloc.h>
80 #include <asm/uaccess.h>
81 #include <asm/mmu_context.h>
82 #include <asm/cacheflush.h>
83 #include <asm/tlbflush.h>
84
85 #include <trace/events/sched.h>
86
87 #define CREATE_TRACE_POINTS
88 #include <trace/events/task.h>
89
90 /*
91 * Protected counters by write_lock_irq(&tasklist_lock)
92 */
93 unsigned long total_forks; /* Handle normal Linux uptimes. */
94 int nr_threads; /* The idle threads do not count.. */
95
96 int max_threads; /* tunable limit on nr_threads */
97
98 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
99
100 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */
101
102 #ifdef CONFIG_PROVE_RCU
103 int lockdep_tasklist_lock_is_held(void)
104 {
105 return lockdep_is_held(&tasklist_lock);
106 }
107 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
108 #endif /* #ifdef CONFIG_PROVE_RCU */
109
110 int nr_processes(void)
111 {
112 int cpu;
113 int total = 0;
114
115 for_each_possible_cpu(cpu)
116 total += per_cpu(process_counts, cpu);
117
118 return total;
119 }
120
121 void __weak arch_release_task_struct(struct task_struct *tsk)
122 {
123 }
124
125 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
126 static struct kmem_cache *task_struct_cachep;
127
128 static inline struct task_struct *alloc_task_struct_node(int node)
129 {
130 return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node);
131 }
132
133 static inline void free_task_struct(struct task_struct *tsk)
134 {
135 kmem_cache_free(task_struct_cachep, tsk);
136 }
137 #endif
138
139 void __weak arch_release_thread_info(struct thread_info *ti)
140 {
141 }
142
143 #ifndef CONFIG_ARCH_THREAD_INFO_ALLOCATOR
144
145 /*
146 * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
147 * kmemcache based allocator.
148 */
149 # if THREAD_SIZE >= PAGE_SIZE
150 static struct thread_info *alloc_thread_info_node(struct task_struct *tsk,
151 int node)
152 {
153 struct page *page = alloc_kmem_pages_node(node, THREADINFO_GFP,
154 THREAD_SIZE_ORDER);
155
156 return page ? page_address(page) : NULL;
157 }
158
159 static inline void free_thread_info(struct thread_info *ti)
160 {
161 free_kmem_pages((unsigned long)ti, THREAD_SIZE_ORDER);
162 }
163 # else
164 static struct kmem_cache *thread_info_cache;
165
166 static struct thread_info *alloc_thread_info_node(struct task_struct *tsk,
167 int node)
168 {
169 return kmem_cache_alloc_node(thread_info_cache, THREADINFO_GFP, node);
170 }
171
172 static void free_thread_info(struct thread_info *ti)
173 {
174 kmem_cache_free(thread_info_cache, ti);
175 }
176
177 void thread_info_cache_init(void)
178 {
179 thread_info_cache = kmem_cache_create("thread_info", THREAD_SIZE,
180 THREAD_SIZE, 0, NULL);
181 BUG_ON(thread_info_cache == NULL);
182 }
183 # endif
184 #endif
185
186 /* SLAB cache for signal_struct structures (tsk->signal) */
187 static struct kmem_cache *signal_cachep;
188
189 /* SLAB cache for sighand_struct structures (tsk->sighand) */
190 struct kmem_cache *sighand_cachep;
191
192 /* SLAB cache for files_struct structures (tsk->files) */
193 struct kmem_cache *files_cachep;
194
195 /* SLAB cache for fs_struct structures (tsk->fs) */
196 struct kmem_cache *fs_cachep;
197
198 /* SLAB cache for vm_area_struct structures */
199 struct kmem_cache *vm_area_cachep;
200
201 /* SLAB cache for mm_struct structures (tsk->mm) */
202 static struct kmem_cache *mm_cachep;
203
204 static void account_kernel_stack(struct thread_info *ti, int account)
205 {
206 struct zone *zone = page_zone(virt_to_page(ti));
207
208 mod_zone_page_state(zone, NR_KERNEL_STACK, account);
209 }
210
211 void free_task(struct task_struct *tsk)
212 {
213 account_kernel_stack(tsk->stack, -1);
214 arch_release_thread_info(tsk->stack);
215 free_thread_info(tsk->stack);
216 rt_mutex_debug_task_free(tsk);
217 ftrace_graph_exit_task(tsk);
218 put_seccomp_filter(tsk);
219 arch_release_task_struct(tsk);
220 free_task_struct(tsk);
221 }
222 EXPORT_SYMBOL(free_task);
223
224 static inline void free_signal_struct(struct signal_struct *sig)
225 {
226 taskstats_tgid_free(sig);
227 sched_autogroup_exit(sig);
228 kmem_cache_free(signal_cachep, sig);
229 }
230
231 static inline void put_signal_struct(struct signal_struct *sig)
232 {
233 if (atomic_dec_and_test(&sig->sigcnt))
234 free_signal_struct(sig);
235 }
236
237 void __put_task_struct(struct task_struct *tsk)
238 {
239 WARN_ON(!tsk->exit_state);
240 WARN_ON(atomic_read(&tsk->usage));
241 WARN_ON(tsk == current);
242
243 task_numa_free(tsk);
244 security_task_free(tsk);
245 exit_creds(tsk);
246 delayacct_tsk_free(tsk);
247 put_signal_struct(tsk->signal);
248
249 if (!profile_handoff_task(tsk))
250 free_task(tsk);
251 }
252 EXPORT_SYMBOL_GPL(__put_task_struct);
253
254 void __init __weak arch_task_cache_init(void) { }
255
256 void __init fork_init(unsigned long mempages)
257 {
258 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
259 #ifndef ARCH_MIN_TASKALIGN
260 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES
261 #endif
262 /* create a slab on which task_structs can be allocated */
263 task_struct_cachep =
264 kmem_cache_create("task_struct", sizeof(struct task_struct),
265 ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL);
266 #endif
267
268 /* do the arch specific task caches init */
269 arch_task_cache_init();
270
271 /*
272 * The default maximum number of threads is set to a safe
273 * value: the thread structures can take up at most half
274 * of memory.
275 */
276 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
277
278 /*
279 * we need to allow at least 20 threads to boot a system
280 */
281 if (max_threads < 20)
282 max_threads = 20;
283
284 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
285 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
286 init_task.signal->rlim[RLIMIT_SIGPENDING] =
287 init_task.signal->rlim[RLIMIT_NPROC];
288 }
289
290 int __weak arch_dup_task_struct(struct task_struct *dst,
291 struct task_struct *src)
292 {
293 *dst = *src;
294 return 0;
295 }
296
297 void set_task_stack_end_magic(struct task_struct *tsk)
298 {
299 unsigned long *stackend;
300
301 stackend = end_of_stack(tsk);
302 *stackend = STACK_END_MAGIC; /* for overflow detection */
303 }
304
305 static struct task_struct *dup_task_struct(struct task_struct *orig)
306 {
307 struct task_struct *tsk;
308 struct thread_info *ti;
309 int node = tsk_fork_get_node(orig);
310 int err;
311
312 tsk = alloc_task_struct_node(node);
313 if (!tsk)
314 return NULL;
315
316 ti = alloc_thread_info_node(tsk, node);
317 if (!ti)
318 goto free_tsk;
319
320 err = arch_dup_task_struct(tsk, orig);
321 if (err)
322 goto free_ti;
323
324 tsk->stack = ti;
325 #ifdef CONFIG_SECCOMP
326 /*
327 * We must handle setting up seccomp filters once we're under
328 * the sighand lock in case orig has changed between now and
329 * then. Until then, filter must be NULL to avoid messing up
330 * the usage counts on the error path calling free_task.
331 */
332 tsk->seccomp.filter = NULL;
333 #endif
334
335 setup_thread_stack(tsk, orig);
336 clear_user_return_notifier(tsk);
337 clear_tsk_need_resched(tsk);
338 set_task_stack_end_magic(tsk);
339
340 #ifdef CONFIG_CC_STACKPROTECTOR
341 tsk->stack_canary = get_random_int();
342 #endif
343
344 /*
345 * One for us, one for whoever does the "release_task()" (usually
346 * parent)
347 */
348 atomic_set(&tsk->usage, 2);
349 #ifdef CONFIG_BLK_DEV_IO_TRACE
350 tsk->btrace_seq = 0;
351 #endif
352 tsk->splice_pipe = NULL;
353 tsk->task_frag.page = NULL;
354
355 account_kernel_stack(ti, 1);
356
357 return tsk;
358
359 free_ti:
360 free_thread_info(ti);
361 free_tsk:
362 free_task_struct(tsk);
363 return NULL;
364 }
365
366 #ifdef CONFIG_MMU
367 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
368 {
369 struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
370 struct rb_node **rb_link, *rb_parent;
371 int retval;
372 unsigned long charge;
373
374 uprobe_start_dup_mmap();
375 down_write(&oldmm->mmap_sem);
376 flush_cache_dup_mm(oldmm);
377 uprobe_dup_mmap(oldmm, mm);
378 /*
379 * Not linked in yet - no deadlock potential:
380 */
381 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
382
383 mm->total_vm = oldmm->total_vm;
384 mm->shared_vm = oldmm->shared_vm;
385 mm->exec_vm = oldmm->exec_vm;
386 mm->stack_vm = oldmm->stack_vm;
387
388 rb_link = &mm->mm_rb.rb_node;
389 rb_parent = NULL;
390 pprev = &mm->mmap;
391 retval = ksm_fork(mm, oldmm);
392 if (retval)
393 goto out;
394 retval = khugepaged_fork(mm, oldmm);
395 if (retval)
396 goto out;
397
398 prev = NULL;
399 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
400 struct file *file;
401
402 if (mpnt->vm_flags & VM_DONTCOPY) {
403 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
404 -vma_pages(mpnt));
405 continue;
406 }
407 charge = 0;
408 if (mpnt->vm_flags & VM_ACCOUNT) {
409 unsigned long len = vma_pages(mpnt);
410
411 if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
412 goto fail_nomem;
413 charge = len;
414 }
415 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
416 if (!tmp)
417 goto fail_nomem;
418 *tmp = *mpnt;
419 INIT_LIST_HEAD(&tmp->anon_vma_chain);
420 retval = vma_dup_policy(mpnt, tmp);
421 if (retval)
422 goto fail_nomem_policy;
423 tmp->vm_mm = mm;
424 if (anon_vma_fork(tmp, mpnt))
425 goto fail_nomem_anon_vma_fork;
426 tmp->vm_flags &= ~VM_LOCKED;
427 tmp->vm_next = tmp->vm_prev = NULL;
428 file = tmp->vm_file;
429 if (file) {
430 struct inode *inode = file_inode(file);
431 struct address_space *mapping = file->f_mapping;
432
433 get_file(file);
434 if (tmp->vm_flags & VM_DENYWRITE)
435 atomic_dec(&inode->i_writecount);
436 i_mmap_lock_write(mapping);
437 if (tmp->vm_flags & VM_SHARED)
438 atomic_inc(&mapping->i_mmap_writable);
439 flush_dcache_mmap_lock(mapping);
440 /* insert tmp into the share list, just after mpnt */
441 vma_interval_tree_insert_after(tmp, mpnt,
442 &mapping->i_mmap);
443 flush_dcache_mmap_unlock(mapping);
444 i_mmap_unlock_write(mapping);
445 }
446
447 /*
448 * Clear hugetlb-related page reserves for children. This only
449 * affects MAP_PRIVATE mappings. Faults generated by the child
450 * are not guaranteed to succeed, even if read-only
451 */
452 if (is_vm_hugetlb_page(tmp))
453 reset_vma_resv_huge_pages(tmp);
454
455 /*
456 * Link in the new vma and copy the page table entries.
457 */
458 *pprev = tmp;
459 pprev = &tmp->vm_next;
460 tmp->vm_prev = prev;
461 prev = tmp;
462
463 __vma_link_rb(mm, tmp, rb_link, rb_parent);
464 rb_link = &tmp->vm_rb.rb_right;
465 rb_parent = &tmp->vm_rb;
466
467 mm->map_count++;
468 retval = copy_page_range(mm, oldmm, mpnt);
469
470 if (tmp->vm_ops && tmp->vm_ops->open)
471 tmp->vm_ops->open(tmp);
472
473 if (retval)
474 goto out;
475 }
476 /* a new mm has just been created */
477 arch_dup_mmap(oldmm, mm);
478 retval = 0;
479 out:
480 up_write(&mm->mmap_sem);
481 flush_tlb_mm(oldmm);
482 up_write(&oldmm->mmap_sem);
483 uprobe_end_dup_mmap();
484 return retval;
485 fail_nomem_anon_vma_fork:
486 mpol_put(vma_policy(tmp));
487 fail_nomem_policy:
488 kmem_cache_free(vm_area_cachep, tmp);
489 fail_nomem:
490 retval = -ENOMEM;
491 vm_unacct_memory(charge);
492 goto out;
493 }
494
495 static inline int mm_alloc_pgd(struct mm_struct *mm)
496 {
497 mm->pgd = pgd_alloc(mm);
498 if (unlikely(!mm->pgd))
499 return -ENOMEM;
500 return 0;
501 }
502
503 static inline void mm_free_pgd(struct mm_struct *mm)
504 {
505 pgd_free(mm, mm->pgd);
506 }
507 #else
508 #define dup_mmap(mm, oldmm) (0)
509 #define mm_alloc_pgd(mm) (0)
510 #define mm_free_pgd(mm)
511 #endif /* CONFIG_MMU */
512
513 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
514
515 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
516 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm)))
517
518 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
519
520 static int __init coredump_filter_setup(char *s)
521 {
522 default_dump_filter =
523 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
524 MMF_DUMP_FILTER_MASK;
525 return 1;
526 }
527
528 __setup("coredump_filter=", coredump_filter_setup);
529
530 #include <linux/init_task.h>
531
532 static void mm_init_aio(struct mm_struct *mm)
533 {
534 #ifdef CONFIG_AIO
535 spin_lock_init(&mm->ioctx_lock);
536 mm->ioctx_table = NULL;
537 #endif
538 }
539
540 static void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
541 {
542 #ifdef CONFIG_MEMCG
543 mm->owner = p;
544 #endif
545 }
546
547 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p)
548 {
549 mm->mmap = NULL;
550 mm->mm_rb = RB_ROOT;
551 mm->vmacache_seqnum = 0;
552 atomic_set(&mm->mm_users, 1);
553 atomic_set(&mm->mm_count, 1);
554 init_rwsem(&mm->mmap_sem);
555 INIT_LIST_HEAD(&mm->mmlist);
556 mm->core_state = NULL;
557 atomic_long_set(&mm->nr_ptes, 0);
558 mm_nr_pmds_init(mm);
559 mm->map_count = 0;
560 mm->locked_vm = 0;
561 mm->pinned_vm = 0;
562 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
563 spin_lock_init(&mm->page_table_lock);
564 mm_init_cpumask(mm);
565 mm_init_aio(mm);
566 mm_init_owner(mm, p);
567 mmu_notifier_mm_init(mm);
568 clear_tlb_flush_pending(mm);
569 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
570 mm->pmd_huge_pte = NULL;
571 #endif
572
573 if (current->mm) {
574 mm->flags = current->mm->flags & MMF_INIT_MASK;
575 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK;
576 } else {
577 mm->flags = default_dump_filter;
578 mm->def_flags = 0;
579 }
580
581 if (mm_alloc_pgd(mm))
582 goto fail_nopgd;
583
584 if (init_new_context(p, mm))
585 goto fail_nocontext;
586
587 return mm;
588
589 fail_nocontext:
590 mm_free_pgd(mm);
591 fail_nopgd:
592 free_mm(mm);
593 return NULL;
594 }
595
596 static void check_mm(struct mm_struct *mm)
597 {
598 int i;
599
600 for (i = 0; i < NR_MM_COUNTERS; i++) {
601 long x = atomic_long_read(&mm->rss_stat.count[i]);
602
603 if (unlikely(x))
604 printk(KERN_ALERT "BUG: Bad rss-counter state "
605 "mm:%p idx:%d val:%ld\n", mm, i, x);
606 }
607
608 if (atomic_long_read(&mm->nr_ptes))
609 pr_alert("BUG: non-zero nr_ptes on freeing mm: %ld\n",
610 atomic_long_read(&mm->nr_ptes));
611 if (mm_nr_pmds(mm))
612 pr_alert("BUG: non-zero nr_pmds on freeing mm: %ld\n",
613 mm_nr_pmds(mm));
614
615 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
616 VM_BUG_ON_MM(mm->pmd_huge_pte, mm);
617 #endif
618 }
619
620 /*
621 * Allocate and initialize an mm_struct.
622 */
623 struct mm_struct *mm_alloc(void)
624 {
625 struct mm_struct *mm;
626
627 mm = allocate_mm();
628 if (!mm)
629 return NULL;
630
631 memset(mm, 0, sizeof(*mm));
632 return mm_init(mm, current);
633 }
634
635 /*
636 * Called when the last reference to the mm
637 * is dropped: either by a lazy thread or by
638 * mmput. Free the page directory and the mm.
639 */
640 void __mmdrop(struct mm_struct *mm)
641 {
642 BUG_ON(mm == &init_mm);
643 mm_free_pgd(mm);
644 destroy_context(mm);
645 mmu_notifier_mm_destroy(mm);
646 check_mm(mm);
647 free_mm(mm);
648 }
649 EXPORT_SYMBOL_GPL(__mmdrop);
650
651 /*
652 * Decrement the use count and release all resources for an mm.
653 */
654 void mmput(struct mm_struct *mm)
655 {
656 might_sleep();
657
658 if (atomic_dec_and_test(&mm->mm_users)) {
659 uprobe_clear_state(mm);
660 exit_aio(mm);
661 ksm_exit(mm);
662 khugepaged_exit(mm); /* must run before exit_mmap */
663 exit_mmap(mm);
664 set_mm_exe_file(mm, NULL);
665 if (!list_empty(&mm->mmlist)) {
666 spin_lock(&mmlist_lock);
667 list_del(&mm->mmlist);
668 spin_unlock(&mmlist_lock);
669 }
670 if (mm->binfmt)
671 module_put(mm->binfmt->module);
672 mmdrop(mm);
673 }
674 }
675 EXPORT_SYMBOL_GPL(mmput);
676
677 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
678 {
679 if (new_exe_file)
680 get_file(new_exe_file);
681 if (mm->exe_file)
682 fput(mm->exe_file);
683 mm->exe_file = new_exe_file;
684 }
685
686 struct file *get_mm_exe_file(struct mm_struct *mm)
687 {
688 struct file *exe_file;
689
690 /* We need mmap_sem to protect against races with removal of exe_file */
691 down_read(&mm->mmap_sem);
692 exe_file = mm->exe_file;
693 if (exe_file)
694 get_file(exe_file);
695 up_read(&mm->mmap_sem);
696 return exe_file;
697 }
698
699 static void dup_mm_exe_file(struct mm_struct *oldmm, struct mm_struct *newmm)
700 {
701 /* It's safe to write the exe_file pointer without exe_file_lock because
702 * this is called during fork when the task is not yet in /proc */
703 newmm->exe_file = get_mm_exe_file(oldmm);
704 }
705
706 /**
707 * get_task_mm - acquire a reference to the task's mm
708 *
709 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning
710 * this kernel workthread has transiently adopted a user mm with use_mm,
711 * to do its AIO) is not set and if so returns a reference to it, after
712 * bumping up the use count. User must release the mm via mmput()
713 * after use. Typically used by /proc and ptrace.
714 */
715 struct mm_struct *get_task_mm(struct task_struct *task)
716 {
717 struct mm_struct *mm;
718
719 task_lock(task);
720 mm = task->mm;
721 if (mm) {
722 if (task->flags & PF_KTHREAD)
723 mm = NULL;
724 else
725 atomic_inc(&mm->mm_users);
726 }
727 task_unlock(task);
728 return mm;
729 }
730 EXPORT_SYMBOL_GPL(get_task_mm);
731
732 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
733 {
734 struct mm_struct *mm;
735 int err;
736
737 err = mutex_lock_killable(&task->signal->cred_guard_mutex);
738 if (err)
739 return ERR_PTR(err);
740
741 mm = get_task_mm(task);
742 if (mm && mm != current->mm &&
743 !ptrace_may_access(task, mode)) {
744 mmput(mm);
745 mm = ERR_PTR(-EACCES);
746 }
747 mutex_unlock(&task->signal->cred_guard_mutex);
748
749 return mm;
750 }
751
752 static void complete_vfork_done(struct task_struct *tsk)
753 {
754 struct completion *vfork;
755
756 task_lock(tsk);
757 vfork = tsk->vfork_done;
758 if (likely(vfork)) {
759 tsk->vfork_done = NULL;
760 complete(vfork);
761 }
762 task_unlock(tsk);
763 }
764
765 static int wait_for_vfork_done(struct task_struct *child,
766 struct completion *vfork)
767 {
768 int killed;
769
770 freezer_do_not_count();
771 killed = wait_for_completion_killable(vfork);
772 freezer_count();
773
774 if (killed) {
775 task_lock(child);
776 child->vfork_done = NULL;
777 task_unlock(child);
778 }
779
780 put_task_struct(child);
781 return killed;
782 }
783
784 /* Please note the differences between mmput and mm_release.
785 * mmput is called whenever we stop holding onto a mm_struct,
786 * error success whatever.
787 *
788 * mm_release is called after a mm_struct has been removed
789 * from the current process.
790 *
791 * This difference is important for error handling, when we
792 * only half set up a mm_struct for a new process and need to restore
793 * the old one. Because we mmput the new mm_struct before
794 * restoring the old one. . .
795 * Eric Biederman 10 January 1998
796 */
797 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
798 {
799 /* Get rid of any futexes when releasing the mm */
800 #ifdef CONFIG_FUTEX
801 if (unlikely(tsk->robust_list)) {
802 exit_robust_list(tsk);
803 tsk->robust_list = NULL;
804 }
805 #ifdef CONFIG_COMPAT
806 if (unlikely(tsk->compat_robust_list)) {
807 compat_exit_robust_list(tsk);
808 tsk->compat_robust_list = NULL;
809 }
810 #endif
811 if (unlikely(!list_empty(&tsk->pi_state_list)))
812 exit_pi_state_list(tsk);
813 #endif
814
815 uprobe_free_utask(tsk);
816
817 /* Get rid of any cached register state */
818 deactivate_mm(tsk, mm);
819
820 /*
821 * If we're exiting normally, clear a user-space tid field if
822 * requested. We leave this alone when dying by signal, to leave
823 * the value intact in a core dump, and to save the unnecessary
824 * trouble, say, a killed vfork parent shouldn't touch this mm.
825 * Userland only wants this done for a sys_exit.
826 */
827 if (tsk->clear_child_tid) {
828 if (!(tsk->flags & PF_SIGNALED) &&
829 atomic_read(&mm->mm_users) > 1) {
830 /*
831 * We don't check the error code - if userspace has
832 * not set up a proper pointer then tough luck.
833 */
834 put_user(0, tsk->clear_child_tid);
835 sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
836 1, NULL, NULL, 0);
837 }
838 tsk->clear_child_tid = NULL;
839 }
840
841 /*
842 * All done, finally we can wake up parent and return this mm to him.
843 * Also kthread_stop() uses this completion for synchronization.
844 */
845 if (tsk->vfork_done)
846 complete_vfork_done(tsk);
847 }
848
849 /*
850 * Allocate a new mm structure and copy contents from the
851 * mm structure of the passed in task structure.
852 */
853 static struct mm_struct *dup_mm(struct task_struct *tsk)
854 {
855 struct mm_struct *mm, *oldmm = current->mm;
856 int err;
857
858 mm = allocate_mm();
859 if (!mm)
860 goto fail_nomem;
861
862 memcpy(mm, oldmm, sizeof(*mm));
863
864 if (!mm_init(mm, tsk))
865 goto fail_nomem;
866
867 dup_mm_exe_file(oldmm, mm);
868
869 err = dup_mmap(mm, oldmm);
870 if (err)
871 goto free_pt;
872
873 mm->hiwater_rss = get_mm_rss(mm);
874 mm->hiwater_vm = mm->total_vm;
875
876 if (mm->binfmt && !try_module_get(mm->binfmt->module))
877 goto free_pt;
878
879 return mm;
880
881 free_pt:
882 /* don't put binfmt in mmput, we haven't got module yet */
883 mm->binfmt = NULL;
884 mmput(mm);
885
886 fail_nomem:
887 return NULL;
888 }
889
890 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
891 {
892 struct mm_struct *mm, *oldmm;
893 int retval;
894
895 tsk->min_flt = tsk->maj_flt = 0;
896 tsk->nvcsw = tsk->nivcsw = 0;
897 #ifdef CONFIG_DETECT_HUNG_TASK
898 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
899 #endif
900
901 tsk->mm = NULL;
902 tsk->active_mm = NULL;
903
904 /*
905 * Are we cloning a kernel thread?
906 *
907 * We need to steal a active VM for that..
908 */
909 oldmm = current->mm;
910 if (!oldmm)
911 return 0;
912
913 /* initialize the new vmacache entries */
914 vmacache_flush(tsk);
915
916 if (clone_flags & CLONE_VM) {
917 atomic_inc(&oldmm->mm_users);
918 mm = oldmm;
919 goto good_mm;
920 }
921
922 retval = -ENOMEM;
923 mm = dup_mm(tsk);
924 if (!mm)
925 goto fail_nomem;
926
927 good_mm:
928 tsk->mm = mm;
929 tsk->active_mm = mm;
930 return 0;
931
932 fail_nomem:
933 return retval;
934 }
935
936 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
937 {
938 struct fs_struct *fs = current->fs;
939 if (clone_flags & CLONE_FS) {
940 /* tsk->fs is already what we want */
941 spin_lock(&fs->lock);
942 if (fs->in_exec) {
943 spin_unlock(&fs->lock);
944 return -EAGAIN;
945 }
946 fs->users++;
947 spin_unlock(&fs->lock);
948 return 0;
949 }
950 tsk->fs = copy_fs_struct(fs);
951 if (!tsk->fs)
952 return -ENOMEM;
953 return 0;
954 }
955
956 static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
957 {
958 struct files_struct *oldf, *newf;
959 int error = 0;
960
961 /*
962 * A background process may not have any files ...
963 */
964 oldf = current->files;
965 if (!oldf)
966 goto out;
967
968 if (clone_flags & CLONE_FILES) {
969 atomic_inc(&oldf->count);
970 goto out;
971 }
972
973 newf = dup_fd(oldf, &error);
974 if (!newf)
975 goto out;
976
977 tsk->files = newf;
978 error = 0;
979 out:
980 return error;
981 }
982
983 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
984 {
985 #ifdef CONFIG_BLOCK
986 struct io_context *ioc = current->io_context;
987 struct io_context *new_ioc;
988
989 if (!ioc)
990 return 0;
991 /*
992 * Share io context with parent, if CLONE_IO is set
993 */
994 if (clone_flags & CLONE_IO) {
995 ioc_task_link(ioc);
996 tsk->io_context = ioc;
997 } else if (ioprio_valid(ioc->ioprio)) {
998 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE);
999 if (unlikely(!new_ioc))
1000 return -ENOMEM;
1001
1002 new_ioc->ioprio = ioc->ioprio;
1003 put_io_context(new_ioc);
1004 }
1005 #endif
1006 return 0;
1007 }
1008
1009 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
1010 {
1011 struct sighand_struct *sig;
1012
1013 if (clone_flags & CLONE_SIGHAND) {
1014 atomic_inc(&current->sighand->count);
1015 return 0;
1016 }
1017 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1018 rcu_assign_pointer(tsk->sighand, sig);
1019 if (!sig)
1020 return -ENOMEM;
1021 atomic_set(&sig->count, 1);
1022 memcpy(sig->action, current->sighand->action, sizeof(sig->action));
1023 return 0;
1024 }
1025
1026 void __cleanup_sighand(struct sighand_struct *sighand)
1027 {
1028 if (atomic_dec_and_test(&sighand->count)) {
1029 signalfd_cleanup(sighand);
1030 /*
1031 * sighand_cachep is SLAB_DESTROY_BY_RCU so we can free it
1032 * without an RCU grace period, see __lock_task_sighand().
1033 */
1034 kmem_cache_free(sighand_cachep, sighand);
1035 }
1036 }
1037
1038 /*
1039 * Initialize POSIX timer handling for a thread group.
1040 */
1041 static void posix_cpu_timers_init_group(struct signal_struct *sig)
1042 {
1043 unsigned long cpu_limit;
1044
1045 /* Thread group counters. */
1046 thread_group_cputime_init(sig);
1047
1048 cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1049 if (cpu_limit != RLIM_INFINITY) {
1050 sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit);
1051 sig->cputimer.running = 1;
1052 }
1053
1054 /* The timer lists. */
1055 INIT_LIST_HEAD(&sig->cpu_timers[0]);
1056 INIT_LIST_HEAD(&sig->cpu_timers[1]);
1057 INIT_LIST_HEAD(&sig->cpu_timers[2]);
1058 }
1059
1060 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
1061 {
1062 struct signal_struct *sig;
1063
1064 if (clone_flags & CLONE_THREAD)
1065 return 0;
1066
1067 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
1068 tsk->signal = sig;
1069 if (!sig)
1070 return -ENOMEM;
1071
1072 sig->nr_threads = 1;
1073 atomic_set(&sig->live, 1);
1074 atomic_set(&sig->sigcnt, 1);
1075
1076 /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */
1077 sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node);
1078 tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head);
1079
1080 init_waitqueue_head(&sig->wait_chldexit);
1081 sig->curr_target = tsk;
1082 init_sigpending(&sig->shared_pending);
1083 INIT_LIST_HEAD(&sig->posix_timers);
1084 seqlock_init(&sig->stats_lock);
1085
1086 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1087 sig->real_timer.function = it_real_fn;
1088
1089 task_lock(current->group_leader);
1090 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
1091 task_unlock(current->group_leader);
1092
1093 posix_cpu_timers_init_group(sig);
1094
1095 tty_audit_fork(sig);
1096 sched_autogroup_fork(sig);
1097
1098 #ifdef CONFIG_CGROUPS
1099 init_rwsem(&sig->group_rwsem);
1100 #endif
1101
1102 sig->oom_score_adj = current->signal->oom_score_adj;
1103 sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1104
1105 sig->has_child_subreaper = current->signal->has_child_subreaper ||
1106 current->signal->is_child_subreaper;
1107
1108 mutex_init(&sig->cred_guard_mutex);
1109
1110 return 0;
1111 }
1112
1113 static void copy_seccomp(struct task_struct *p)
1114 {
1115 #ifdef CONFIG_SECCOMP
1116 /*
1117 * Must be called with sighand->lock held, which is common to
1118 * all threads in the group. Holding cred_guard_mutex is not
1119 * needed because this new task is not yet running and cannot
1120 * be racing exec.
1121 */
1122 assert_spin_locked(&current->sighand->siglock);
1123
1124 /* Ref-count the new filter user, and assign it. */
1125 get_seccomp_filter(current);
1126 p->seccomp = current->seccomp;
1127
1128 /*
1129 * Explicitly enable no_new_privs here in case it got set
1130 * between the task_struct being duplicated and holding the
1131 * sighand lock. The seccomp state and nnp must be in sync.
1132 */
1133 if (task_no_new_privs(current))
1134 task_set_no_new_privs(p);
1135
1136 /*
1137 * If the parent gained a seccomp mode after copying thread
1138 * flags and between before we held the sighand lock, we have
1139 * to manually enable the seccomp thread flag here.
1140 */
1141 if (p->seccomp.mode != SECCOMP_MODE_DISABLED)
1142 set_tsk_thread_flag(p, TIF_SECCOMP);
1143 #endif
1144 }
1145
1146 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1147 {
1148 current->clear_child_tid = tidptr;
1149
1150 return task_pid_vnr(current);
1151 }
1152
1153 static void rt_mutex_init_task(struct task_struct *p)
1154 {
1155 raw_spin_lock_init(&p->pi_lock);
1156 #ifdef CONFIG_RT_MUTEXES
1157 p->pi_waiters = RB_ROOT;
1158 p->pi_waiters_leftmost = NULL;
1159 p->pi_blocked_on = NULL;
1160 #endif
1161 }
1162
1163 /*
1164 * Initialize POSIX timer handling for a single task.
1165 */
1166 static void posix_cpu_timers_init(struct task_struct *tsk)
1167 {
1168 tsk->cputime_expires.prof_exp = 0;
1169 tsk->cputime_expires.virt_exp = 0;
1170 tsk->cputime_expires.sched_exp = 0;
1171 INIT_LIST_HEAD(&tsk->cpu_timers[0]);
1172 INIT_LIST_HEAD(&tsk->cpu_timers[1]);
1173 INIT_LIST_HEAD(&tsk->cpu_timers[2]);
1174 }
1175
1176 static inline void
1177 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid)
1178 {
1179 task->pids[type].pid = pid;
1180 }
1181
1182 /*
1183 * This creates a new process as a copy of the old one,
1184 * but does not actually start it yet.
1185 *
1186 * It copies the registers, and all the appropriate
1187 * parts of the process environment (as per the clone
1188 * flags). The actual kick-off is left to the caller.
1189 */
1190 static struct task_struct *copy_process(unsigned long clone_flags,
1191 unsigned long stack_start,
1192 unsigned long stack_size,
1193 int __user *child_tidptr,
1194 struct pid *pid,
1195 int trace)
1196 {
1197 int retval;
1198 struct task_struct *p;
1199
1200 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1201 return ERR_PTR(-EINVAL);
1202
1203 if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS))
1204 return ERR_PTR(-EINVAL);
1205
1206 /*
1207 * Thread groups must share signals as well, and detached threads
1208 * can only be started up within the thread group.
1209 */
1210 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1211 return ERR_PTR(-EINVAL);
1212
1213 /*
1214 * Shared signal handlers imply shared VM. By way of the above,
1215 * thread groups also imply shared VM. Blocking this case allows
1216 * for various simplifications in other code.
1217 */
1218 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1219 return ERR_PTR(-EINVAL);
1220
1221 /*
1222 * Siblings of global init remain as zombies on exit since they are
1223 * not reaped by their parent (swapper). To solve this and to avoid
1224 * multi-rooted process trees, prevent global and container-inits
1225 * from creating siblings.
1226 */
1227 if ((clone_flags & CLONE_PARENT) &&
1228 current->signal->flags & SIGNAL_UNKILLABLE)
1229 return ERR_PTR(-EINVAL);
1230
1231 /*
1232 * If the new process will be in a different pid or user namespace
1233 * do not allow it to share a thread group or signal handlers or
1234 * parent with the forking task.
1235 */
1236 if (clone_flags & CLONE_SIGHAND) {
1237 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) ||
1238 (task_active_pid_ns(current) !=
1239 current->nsproxy->pid_ns_for_children))
1240 return ERR_PTR(-EINVAL);
1241 }
1242
1243 retval = security_task_create(clone_flags);
1244 if (retval)
1245 goto fork_out;
1246
1247 retval = -ENOMEM;
1248 p = dup_task_struct(current);
1249 if (!p)
1250 goto fork_out;
1251
1252 ftrace_graph_init_task(p);
1253
1254 rt_mutex_init_task(p);
1255
1256 #ifdef CONFIG_PROVE_LOCKING
1257 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1258 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1259 #endif
1260 retval = -EAGAIN;
1261 if (atomic_read(&p->real_cred->user->processes) >=
1262 task_rlimit(p, RLIMIT_NPROC)) {
1263 if (p->real_cred->user != INIT_USER &&
1264 !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
1265 goto bad_fork_free;
1266 }
1267 current->flags &= ~PF_NPROC_EXCEEDED;
1268
1269 retval = copy_creds(p, clone_flags);
1270 if (retval < 0)
1271 goto bad_fork_free;
1272
1273 /*
1274 * If multiple threads are within copy_process(), then this check
1275 * triggers too late. This doesn't hurt, the check is only there
1276 * to stop root fork bombs.
1277 */
1278 retval = -EAGAIN;
1279 if (nr_threads >= max_threads)
1280 goto bad_fork_cleanup_count;
1281
1282 if (!try_module_get(task_thread_info(p)->exec_domain->module))
1283 goto bad_fork_cleanup_count;
1284
1285 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */
1286 p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER);
1287 p->flags |= PF_FORKNOEXEC;
1288 INIT_LIST_HEAD(&p->children);
1289 INIT_LIST_HEAD(&p->sibling);
1290 rcu_copy_process(p);
1291 p->vfork_done = NULL;
1292 spin_lock_init(&p->alloc_lock);
1293
1294 init_sigpending(&p->pending);
1295
1296 p->utime = p->stime = p->gtime = 0;
1297 p->utimescaled = p->stimescaled = 0;
1298 #ifndef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
1299 p->prev_cputime.utime = p->prev_cputime.stime = 0;
1300 #endif
1301 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
1302 seqlock_init(&p->vtime_seqlock);
1303 p->vtime_snap = 0;
1304 p->vtime_snap_whence = VTIME_SLEEPING;
1305 #endif
1306
1307 #if defined(SPLIT_RSS_COUNTING)
1308 memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1309 #endif
1310
1311 p->default_timer_slack_ns = current->timer_slack_ns;
1312
1313 task_io_accounting_init(&p->ioac);
1314 acct_clear_integrals(p);
1315
1316 posix_cpu_timers_init(p);
1317
1318 p->start_time = ktime_get_ns();
1319 p->real_start_time = ktime_get_boot_ns();
1320 p->io_context = NULL;
1321 p->audit_context = NULL;
1322 if (clone_flags & CLONE_THREAD)
1323 threadgroup_change_begin(current);
1324 cgroup_fork(p);
1325 #ifdef CONFIG_NUMA
1326 p->mempolicy = mpol_dup(p->mempolicy);
1327 if (IS_ERR(p->mempolicy)) {
1328 retval = PTR_ERR(p->mempolicy);
1329 p->mempolicy = NULL;
1330 goto bad_fork_cleanup_threadgroup_lock;
1331 }
1332 #endif
1333 #ifdef CONFIG_CPUSETS
1334 p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
1335 p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
1336 seqcount_init(&p->mems_allowed_seq);
1337 #endif
1338 #ifdef CONFIG_TRACE_IRQFLAGS
1339 p->irq_events = 0;
1340 p->hardirqs_enabled = 0;
1341 p->hardirq_enable_ip = 0;
1342 p->hardirq_enable_event = 0;
1343 p->hardirq_disable_ip = _THIS_IP_;
1344 p->hardirq_disable_event = 0;
1345 p->softirqs_enabled = 1;
1346 p->softirq_enable_ip = _THIS_IP_;
1347 p->softirq_enable_event = 0;
1348 p->softirq_disable_ip = 0;
1349 p->softirq_disable_event = 0;
1350 p->hardirq_context = 0;
1351 p->softirq_context = 0;
1352 #endif
1353 #ifdef CONFIG_LOCKDEP
1354 p->lockdep_depth = 0; /* no locks held yet */
1355 p->curr_chain_key = 0;
1356 p->lockdep_recursion = 0;
1357 #endif
1358
1359 #ifdef CONFIG_DEBUG_MUTEXES
1360 p->blocked_on = NULL; /* not blocked yet */
1361 #endif
1362 #ifdef CONFIG_BCACHE
1363 p->sequential_io = 0;
1364 p->sequential_io_avg = 0;
1365 #endif
1366
1367 /* Perform scheduler related setup. Assign this task to a CPU. */
1368 retval = sched_fork(clone_flags, p);
1369 if (retval)
1370 goto bad_fork_cleanup_policy;
1371
1372 retval = perf_event_init_task(p);
1373 if (retval)
1374 goto bad_fork_cleanup_policy;
1375 retval = audit_alloc(p);
1376 if (retval)
1377 goto bad_fork_cleanup_perf;
1378 /* copy all the process information */
1379 shm_init_task(p);
1380 retval = copy_semundo(clone_flags, p);
1381 if (retval)
1382 goto bad_fork_cleanup_audit;
1383 retval = copy_files(clone_flags, p);
1384 if (retval)
1385 goto bad_fork_cleanup_semundo;
1386 retval = copy_fs(clone_flags, p);
1387 if (retval)
1388 goto bad_fork_cleanup_files;
1389 retval = copy_sighand(clone_flags, p);
1390 if (retval)
1391 goto bad_fork_cleanup_fs;
1392 retval = copy_signal(clone_flags, p);
1393 if (retval)
1394 goto bad_fork_cleanup_sighand;
1395 retval = copy_mm(clone_flags, p);
1396 if (retval)
1397 goto bad_fork_cleanup_signal;
1398 retval = copy_namespaces(clone_flags, p);
1399 if (retval)
1400 goto bad_fork_cleanup_mm;
1401 retval = copy_io(clone_flags, p);
1402 if (retval)
1403 goto bad_fork_cleanup_namespaces;
1404 retval = copy_thread(clone_flags, stack_start, stack_size, p);
1405 if (retval)
1406 goto bad_fork_cleanup_io;
1407
1408 if (pid != &init_struct_pid) {
1409 retval = -ENOMEM;
1410 pid = alloc_pid(p->nsproxy->pid_ns_for_children);
1411 if (!pid)
1412 goto bad_fork_cleanup_io;
1413 }
1414
1415 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1416 /*
1417 * Clear TID on mm_release()?
1418 */
1419 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL;
1420 #ifdef CONFIG_BLOCK
1421 p->plug = NULL;
1422 #endif
1423 #ifdef CONFIG_FUTEX
1424 p->robust_list = NULL;
1425 #ifdef CONFIG_COMPAT
1426 p->compat_robust_list = NULL;
1427 #endif
1428 INIT_LIST_HEAD(&p->pi_state_list);
1429 p->pi_state_cache = NULL;
1430 #endif
1431 /*
1432 * sigaltstack should be cleared when sharing the same VM
1433 */
1434 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1435 p->sas_ss_sp = p->sas_ss_size = 0;
1436
1437 /*
1438 * Syscall tracing and stepping should be turned off in the
1439 * child regardless of CLONE_PTRACE.
1440 */
1441 user_disable_single_step(p);
1442 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1443 #ifdef TIF_SYSCALL_EMU
1444 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1445 #endif
1446 clear_all_latency_tracing(p);
1447
1448 /* ok, now we should be set up.. */
1449 p->pid = pid_nr(pid);
1450 if (clone_flags & CLONE_THREAD) {
1451 p->exit_signal = -1;
1452 p->group_leader = current->group_leader;
1453 p->tgid = current->tgid;
1454 } else {
1455 if (clone_flags & CLONE_PARENT)
1456 p->exit_signal = current->group_leader->exit_signal;
1457 else
1458 p->exit_signal = (clone_flags & CSIGNAL);
1459 p->group_leader = p;
1460 p->tgid = p->pid;
1461 }
1462
1463 p->nr_dirtied = 0;
1464 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
1465 p->dirty_paused_when = 0;
1466
1467 p->pdeath_signal = 0;
1468 INIT_LIST_HEAD(&p->thread_group);
1469 p->task_works = NULL;
1470
1471 /*
1472 * Make it visible to the rest of the system, but dont wake it up yet.
1473 * Need tasklist lock for parent etc handling!
1474 */
1475 write_lock_irq(&tasklist_lock);
1476
1477 /* CLONE_PARENT re-uses the old parent */
1478 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1479 p->real_parent = current->real_parent;
1480 p->parent_exec_id = current->parent_exec_id;
1481 } else {
1482 p->real_parent = current;
1483 p->parent_exec_id = current->self_exec_id;
1484 }
1485
1486 spin_lock(&current->sighand->siglock);
1487
1488 /*
1489 * Copy seccomp details explicitly here, in case they were changed
1490 * before holding sighand lock.
1491 */
1492 copy_seccomp(p);
1493
1494 /*
1495 * Process group and session signals need to be delivered to just the
1496 * parent before the fork or both the parent and the child after the
1497 * fork. Restart if a signal comes in before we add the new process to
1498 * it's process group.
1499 * A fatal signal pending means that current will exit, so the new
1500 * thread can't slip out of an OOM kill (or normal SIGKILL).
1501 */
1502 recalc_sigpending();
1503 if (signal_pending(current)) {
1504 spin_unlock(&current->sighand->siglock);
1505 write_unlock_irq(&tasklist_lock);
1506 retval = -ERESTARTNOINTR;
1507 goto bad_fork_free_pid;
1508 }
1509
1510 if (likely(p->pid)) {
1511 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
1512
1513 init_task_pid(p, PIDTYPE_PID, pid);
1514 if (thread_group_leader(p)) {
1515 init_task_pid(p, PIDTYPE_PGID, task_pgrp(current));
1516 init_task_pid(p, PIDTYPE_SID, task_session(current));
1517
1518 if (is_child_reaper(pid)) {
1519 ns_of_pid(pid)->child_reaper = p;
1520 p->signal->flags |= SIGNAL_UNKILLABLE;
1521 }
1522
1523 p->signal->leader_pid = pid;
1524 p->signal->tty = tty_kref_get(current->signal->tty);
1525 list_add_tail(&p->sibling, &p->real_parent->children);
1526 list_add_tail_rcu(&p->tasks, &init_task.tasks);
1527 attach_pid(p, PIDTYPE_PGID);
1528 attach_pid(p, PIDTYPE_SID);
1529 __this_cpu_inc(process_counts);
1530 } else {
1531 current->signal->nr_threads++;
1532 atomic_inc(&current->signal->live);
1533 atomic_inc(&current->signal->sigcnt);
1534 list_add_tail_rcu(&p->thread_group,
1535 &p->group_leader->thread_group);
1536 list_add_tail_rcu(&p->thread_node,
1537 &p->signal->thread_head);
1538 }
1539 attach_pid(p, PIDTYPE_PID);
1540 nr_threads++;
1541 }
1542
1543 total_forks++;
1544 spin_unlock(&current->sighand->siglock);
1545 syscall_tracepoint_update(p);
1546 write_unlock_irq(&tasklist_lock);
1547
1548 proc_fork_connector(p);
1549 cgroup_post_fork(p);
1550 if (clone_flags & CLONE_THREAD)
1551 threadgroup_change_end(current);
1552 perf_event_fork(p);
1553
1554 trace_task_newtask(p, clone_flags);
1555 uprobe_copy_process(p, clone_flags);
1556
1557 return p;
1558
1559 bad_fork_free_pid:
1560 if (pid != &init_struct_pid)
1561 free_pid(pid);
1562 bad_fork_cleanup_io:
1563 if (p->io_context)
1564 exit_io_context(p);
1565 bad_fork_cleanup_namespaces:
1566 exit_task_namespaces(p);
1567 bad_fork_cleanup_mm:
1568 if (p->mm)
1569 mmput(p->mm);
1570 bad_fork_cleanup_signal:
1571 if (!(clone_flags & CLONE_THREAD))
1572 free_signal_struct(p->signal);
1573 bad_fork_cleanup_sighand:
1574 __cleanup_sighand(p->sighand);
1575 bad_fork_cleanup_fs:
1576 exit_fs(p); /* blocking */
1577 bad_fork_cleanup_files:
1578 exit_files(p); /* blocking */
1579 bad_fork_cleanup_semundo:
1580 exit_sem(p);
1581 bad_fork_cleanup_audit:
1582 audit_free(p);
1583 bad_fork_cleanup_perf:
1584 perf_event_free_task(p);
1585 bad_fork_cleanup_policy:
1586 #ifdef CONFIG_NUMA
1587 mpol_put(p->mempolicy);
1588 bad_fork_cleanup_threadgroup_lock:
1589 #endif
1590 if (clone_flags & CLONE_THREAD)
1591 threadgroup_change_end(current);
1592 delayacct_tsk_free(p);
1593 module_put(task_thread_info(p)->exec_domain->module);
1594 bad_fork_cleanup_count:
1595 atomic_dec(&p->cred->user->processes);
1596 exit_creds(p);
1597 bad_fork_free:
1598 free_task(p);
1599 fork_out:
1600 return ERR_PTR(retval);
1601 }
1602
1603 static inline void init_idle_pids(struct pid_link *links)
1604 {
1605 enum pid_type type;
1606
1607 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
1608 INIT_HLIST_NODE(&links[type].node); /* not really needed */
1609 links[type].pid = &init_struct_pid;
1610 }
1611 }
1612
1613 struct task_struct *fork_idle(int cpu)
1614 {
1615 struct task_struct *task;
1616 task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0);
1617 if (!IS_ERR(task)) {
1618 init_idle_pids(task->pids);
1619 init_idle(task, cpu);
1620 }
1621
1622 return task;
1623 }
1624
1625 /*
1626 * Ok, this is the main fork-routine.
1627 *
1628 * It copies the process, and if successful kick-starts
1629 * it and waits for it to finish using the VM if required.
1630 */
1631 long do_fork(unsigned long clone_flags,
1632 unsigned long stack_start,
1633 unsigned long stack_size,
1634 int __user *parent_tidptr,
1635 int __user *child_tidptr)
1636 {
1637 struct task_struct *p;
1638 int trace = 0;
1639 long nr;
1640
1641 /*
1642 * Determine whether and which event to report to ptracer. When
1643 * called from kernel_thread or CLONE_UNTRACED is explicitly
1644 * requested, no event is reported; otherwise, report if the event
1645 * for the type of forking is enabled.
1646 */
1647 if (!(clone_flags & CLONE_UNTRACED)) {
1648 if (clone_flags & CLONE_VFORK)
1649 trace = PTRACE_EVENT_VFORK;
1650 else if ((clone_flags & CSIGNAL) != SIGCHLD)
1651 trace = PTRACE_EVENT_CLONE;
1652 else
1653 trace = PTRACE_EVENT_FORK;
1654
1655 if (likely(!ptrace_event_enabled(current, trace)))
1656 trace = 0;
1657 }
1658
1659 p = copy_process(clone_flags, stack_start, stack_size,
1660 child_tidptr, NULL, trace);
1661 /*
1662 * Do this prior waking up the new thread - the thread pointer
1663 * might get invalid after that point, if the thread exits quickly.
1664 */
1665 if (!IS_ERR(p)) {
1666 struct completion vfork;
1667 struct pid *pid;
1668
1669 trace_sched_process_fork(current, p);
1670
1671 pid = get_task_pid(p, PIDTYPE_PID);
1672 nr = pid_vnr(pid);
1673
1674 if (clone_flags & CLONE_PARENT_SETTID)
1675 put_user(nr, parent_tidptr);
1676
1677 if (clone_flags & CLONE_VFORK) {
1678 p->vfork_done = &vfork;
1679 init_completion(&vfork);
1680 get_task_struct(p);
1681 }
1682
1683 wake_up_new_task(p);
1684
1685 /* forking complete and child started to run, tell ptracer */
1686 if (unlikely(trace))
1687 ptrace_event_pid(trace, pid);
1688
1689 if (clone_flags & CLONE_VFORK) {
1690 if (!wait_for_vfork_done(p, &vfork))
1691 ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid);
1692 }
1693
1694 put_pid(pid);
1695 } else {
1696 nr = PTR_ERR(p);
1697 }
1698 return nr;
1699 }
1700
1701 /*
1702 * Create a kernel thread.
1703 */
1704 pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
1705 {
1706 return do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn,
1707 (unsigned long)arg, NULL, NULL);
1708 }
1709
1710 #ifdef __ARCH_WANT_SYS_FORK
1711 SYSCALL_DEFINE0(fork)
1712 {
1713 #ifdef CONFIG_MMU
1714 return do_fork(SIGCHLD, 0, 0, NULL, NULL);
1715 #else
1716 /* can not support in nommu mode */
1717 return -EINVAL;
1718 #endif
1719 }
1720 #endif
1721
1722 #ifdef __ARCH_WANT_SYS_VFORK
1723 SYSCALL_DEFINE0(vfork)
1724 {
1725 return do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0,
1726 0, NULL, NULL);
1727 }
1728 #endif
1729
1730 #ifdef __ARCH_WANT_SYS_CLONE
1731 #ifdef CONFIG_CLONE_BACKWARDS
1732 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
1733 int __user *, parent_tidptr,
1734 int, tls_val,
1735 int __user *, child_tidptr)
1736 #elif defined(CONFIG_CLONE_BACKWARDS2)
1737 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags,
1738 int __user *, parent_tidptr,
1739 int __user *, child_tidptr,
1740 int, tls_val)
1741 #elif defined(CONFIG_CLONE_BACKWARDS3)
1742 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp,
1743 int, stack_size,
1744 int __user *, parent_tidptr,
1745 int __user *, child_tidptr,
1746 int, tls_val)
1747 #else
1748 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
1749 int __user *, parent_tidptr,
1750 int __user *, child_tidptr,
1751 int, tls_val)
1752 #endif
1753 {
1754 return do_fork(clone_flags, newsp, 0, parent_tidptr, child_tidptr);
1755 }
1756 #endif
1757
1758 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1759 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1760 #endif
1761
1762 static void sighand_ctor(void *data)
1763 {
1764 struct sighand_struct *sighand = data;
1765
1766 spin_lock_init(&sighand->siglock);
1767 init_waitqueue_head(&sighand->signalfd_wqh);
1768 }
1769
1770 void __init proc_caches_init(void)
1771 {
1772 sighand_cachep = kmem_cache_create("sighand_cache",
1773 sizeof(struct sighand_struct), 0,
1774 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU|
1775 SLAB_NOTRACK, sighand_ctor);
1776 signal_cachep = kmem_cache_create("signal_cache",
1777 sizeof(struct signal_struct), 0,
1778 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1779 files_cachep = kmem_cache_create("files_cache",
1780 sizeof(struct files_struct), 0,
1781 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1782 fs_cachep = kmem_cache_create("fs_cache",
1783 sizeof(struct fs_struct), 0,
1784 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1785 /*
1786 * FIXME! The "sizeof(struct mm_struct)" currently includes the
1787 * whole struct cpumask for the OFFSTACK case. We could change
1788 * this to *only* allocate as much of it as required by the
1789 * maximum number of CPU's we can ever have. The cpumask_allocation
1790 * is at the end of the structure, exactly for that reason.
1791 */
1792 mm_cachep = kmem_cache_create("mm_struct",
1793 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1794 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1795 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC);
1796 mmap_init();
1797 nsproxy_cache_init();
1798 }
1799
1800 /*
1801 * Check constraints on flags passed to the unshare system call.
1802 */
1803 static int check_unshare_flags(unsigned long unshare_flags)
1804 {
1805 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1806 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1807 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET|
1808 CLONE_NEWUSER|CLONE_NEWPID))
1809 return -EINVAL;
1810 /*
1811 * Not implemented, but pretend it works if there is nothing to
1812 * unshare. Note that unsharing CLONE_THREAD or CLONE_SIGHAND
1813 * needs to unshare vm.
1814 */
1815 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
1816 /* FIXME: get_task_mm() increments ->mm_users */
1817 if (atomic_read(&current->mm->mm_users) > 1)
1818 return -EINVAL;
1819 }
1820
1821 return 0;
1822 }
1823
1824 /*
1825 * Unshare the filesystem structure if it is being shared
1826 */
1827 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1828 {
1829 struct fs_struct *fs = current->fs;
1830
1831 if (!(unshare_flags & CLONE_FS) || !fs)
1832 return 0;
1833
1834 /* don't need lock here; in the worst case we'll do useless copy */
1835 if (fs->users == 1)
1836 return 0;
1837
1838 *new_fsp = copy_fs_struct(fs);
1839 if (!*new_fsp)
1840 return -ENOMEM;
1841
1842 return 0;
1843 }
1844
1845 /*
1846 * Unshare file descriptor table if it is being shared
1847 */
1848 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1849 {
1850 struct files_struct *fd = current->files;
1851 int error = 0;
1852
1853 if ((unshare_flags & CLONE_FILES) &&
1854 (fd && atomic_read(&fd->count) > 1)) {
1855 *new_fdp = dup_fd(fd, &error);
1856 if (!*new_fdp)
1857 return error;
1858 }
1859
1860 return 0;
1861 }
1862
1863 /*
1864 * unshare allows a process to 'unshare' part of the process
1865 * context which was originally shared using clone. copy_*
1866 * functions used by do_fork() cannot be used here directly
1867 * because they modify an inactive task_struct that is being
1868 * constructed. Here we are modifying the current, active,
1869 * task_struct.
1870 */
1871 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
1872 {
1873 struct fs_struct *fs, *new_fs = NULL;
1874 struct files_struct *fd, *new_fd = NULL;
1875 struct cred *new_cred = NULL;
1876 struct nsproxy *new_nsproxy = NULL;
1877 int do_sysvsem = 0;
1878 int err;
1879
1880 /*
1881 * If unsharing a user namespace must also unshare the thread.
1882 */
1883 if (unshare_flags & CLONE_NEWUSER)
1884 unshare_flags |= CLONE_THREAD | CLONE_FS;
1885 /*
1886 * If unsharing a thread from a thread group, must also unshare vm.
1887 */
1888 if (unshare_flags & CLONE_THREAD)
1889 unshare_flags |= CLONE_VM;
1890 /*
1891 * If unsharing vm, must also unshare signal handlers.
1892 */
1893 if (unshare_flags & CLONE_VM)
1894 unshare_flags |= CLONE_SIGHAND;
1895 /*
1896 * If unsharing namespace, must also unshare filesystem information.
1897 */
1898 if (unshare_flags & CLONE_NEWNS)
1899 unshare_flags |= CLONE_FS;
1900
1901 err = check_unshare_flags(unshare_flags);
1902 if (err)
1903 goto bad_unshare_out;
1904 /*
1905 * CLONE_NEWIPC must also detach from the undolist: after switching
1906 * to a new ipc namespace, the semaphore arrays from the old
1907 * namespace are unreachable.
1908 */
1909 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1910 do_sysvsem = 1;
1911 err = unshare_fs(unshare_flags, &new_fs);
1912 if (err)
1913 goto bad_unshare_out;
1914 err = unshare_fd(unshare_flags, &new_fd);
1915 if (err)
1916 goto bad_unshare_cleanup_fs;
1917 err = unshare_userns(unshare_flags, &new_cred);
1918 if (err)
1919 goto bad_unshare_cleanup_fd;
1920 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
1921 new_cred, new_fs);
1922 if (err)
1923 goto bad_unshare_cleanup_cred;
1924
1925 if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
1926 if (do_sysvsem) {
1927 /*
1928 * CLONE_SYSVSEM is equivalent to sys_exit().
1929 */
1930 exit_sem(current);
1931 }
1932 if (unshare_flags & CLONE_NEWIPC) {
1933 /* Orphan segments in old ns (see sem above). */
1934 exit_shm(current);
1935 shm_init_task(current);
1936 }
1937
1938 if (new_nsproxy)
1939 switch_task_namespaces(current, new_nsproxy);
1940
1941 task_lock(current);
1942
1943 if (new_fs) {
1944 fs = current->fs;
1945 spin_lock(&fs->lock);
1946 current->fs = new_fs;
1947 if (--fs->users)
1948 new_fs = NULL;
1949 else
1950 new_fs = fs;
1951 spin_unlock(&fs->lock);
1952 }
1953
1954 if (new_fd) {
1955 fd = current->files;
1956 current->files = new_fd;
1957 new_fd = fd;
1958 }
1959
1960 task_unlock(current);
1961
1962 if (new_cred) {
1963 /* Install the new user namespace */
1964 commit_creds(new_cred);
1965 new_cred = NULL;
1966 }
1967 }
1968
1969 bad_unshare_cleanup_cred:
1970 if (new_cred)
1971 put_cred(new_cred);
1972 bad_unshare_cleanup_fd:
1973 if (new_fd)
1974 put_files_struct(new_fd);
1975
1976 bad_unshare_cleanup_fs:
1977 if (new_fs)
1978 free_fs_struct(new_fs);
1979
1980 bad_unshare_out:
1981 return err;
1982 }
1983
1984 /*
1985 * Helper to unshare the files of the current task.
1986 * We don't want to expose copy_files internals to
1987 * the exec layer of the kernel.
1988 */
1989
1990 int unshare_files(struct files_struct **displaced)
1991 {
1992 struct task_struct *task = current;
1993 struct files_struct *copy = NULL;
1994 int error;
1995
1996 error = unshare_fd(CLONE_FILES, &copy);
1997 if (error || !copy) {
1998 *displaced = NULL;
1999 return error;
2000 }
2001 *displaced = task->files;
2002 task_lock(task);
2003 task->files = copy;
2004 task_unlock(task);
2005 return 0;
2006 }