Line data Source code
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 15 : int nr_processes(void)
111 : {
112 : int cpu;
113 : int total = 0;
114 :
115 30 : for_each_possible_cpu(cpu)
116 15 : total += per_cpu(process_counts, cpu);
117 :
118 15 : return total;
119 : }
120 :
121 2915 : void __weak arch_release_task_struct(struct task_struct *tsk)
122 : {
123 2915 : }
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 2993 : 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 2915 : kmem_cache_free(task_struct_cachep, tsk);
136 : }
137 : #endif
138 :
139 2915 : void __weak arch_release_thread_info(struct thread_info *ti)
140 : {
141 2915 : }
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 2993 : static struct thread_info *alloc_thread_info_node(struct task_struct *tsk,
151 : int node)
152 : {
153 2993 : struct page *page = alloc_kmem_pages_node(node, THREADINFO_GFP,
154 : THREAD_SIZE_ORDER);
155 :
156 5986 : return page ? page_address(page) : NULL;
157 : }
158 :
159 : static inline void free_thread_info(struct thread_info *ti)
160 : {
161 2915 : 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 5908 : static void account_kernel_stack(struct thread_info *ti, int account)
205 : {
206 11816 : struct zone *zone = page_zone(virt_to_page(ti));
207 :
208 : mod_zone_page_state(zone, NR_KERNEL_STACK, account);
209 5908 : }
210 :
211 2915 : void free_task(struct task_struct *tsk)
212 : {
213 2915 : account_kernel_stack(tsk->stack, -1);
214 2915 : arch_release_thread_info(tsk->stack);
215 2915 : free_thread_info(tsk->stack);
216 : rt_mutex_debug_task_free(tsk);
217 : ftrace_graph_exit_task(tsk);
218 2915 : put_seccomp_filter(tsk);
219 2915 : arch_release_task_struct(tsk);
220 : free_task_struct(tsk);
221 2915 : }
222 : EXPORT_SYMBOL(free_task);
223 :
224 2915 : static inline void free_signal_struct(struct signal_struct *sig)
225 : {
226 : taskstats_tgid_free(sig);
227 2915 : sched_autogroup_exit(sig);
228 2915 : kmem_cache_free(signal_cachep, sig);
229 : }
230 :
231 : static inline void put_signal_struct(struct signal_struct *sig)
232 : {
233 5828 : if (atomic_dec_and_test(&sig->sigcnt))
234 : free_signal_struct(sig);
235 : }
236 :
237 2914 : void __put_task_struct(struct task_struct *tsk)
238 : {
239 : WARN_ON(!tsk->exit_state);
240 2914 : WARN_ON(atomic_read(&tsk->usage));
241 : WARN_ON(tsk == current);
242 :
243 : task_numa_free(tsk);
244 : security_task_free(tsk);
245 2914 : exit_creds(tsk);
246 : delayacct_tsk_free(tsk);
247 2914 : put_signal_struct(tsk->signal);
248 :
249 : if (!profile_handoff_task(tsk))
250 2914 : free_task(tsk);
251 2914 : }
252 : EXPORT_SYMBOL_GPL(__put_task_struct);
253 :
254 1 : void __init __weak arch_task_cache_init(void) { }
255 :
256 1 : 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 1 : task_struct_cachep =
264 1 : 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 1 : 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 1 : 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 1 : if (max_threads < 20)
282 0 : max_threads = 20;
283 :
284 1 : init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
285 1 : init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
286 1 : init_task.signal->rlim[RLIMIT_SIGPENDING] =
287 1 : init_task.signal->rlim[RLIMIT_NPROC];
288 1 : }
289 :
290 2993 : int __weak arch_dup_task_struct(struct task_struct *dst,
291 : struct task_struct *src)
292 : {
293 2993 : *dst = *src;
294 2993 : return 0;
295 : }
296 :
297 1 : void set_task_stack_end_magic(struct task_struct *tsk)
298 : {
299 : unsigned long *stackend;
300 :
301 : stackend = end_of_stack(tsk);
302 2994 : *stackend = STACK_END_MAGIC; /* for overflow detection */
303 1 : }
304 :
305 2993 : static struct task_struct *dup_task_struct(struct task_struct *orig)
306 : {
307 : struct task_struct *tsk;
308 : struct thread_info *ti;
309 2993 : int node = tsk_fork_get_node(orig);
310 : int err;
311 :
312 : tsk = alloc_task_struct_node(node);
313 2993 : if (!tsk)
314 : return NULL;
315 :
316 2993 : ti = alloc_thread_info_node(tsk, node);
317 2993 : if (!ti)
318 : goto free_tsk;
319 :
320 2993 : err = arch_dup_task_struct(tsk, orig);
321 2993 : if (err)
322 : goto free_ti;
323 :
324 2993 : 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 2993 : 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 2993 : atomic_set(&tsk->usage, 2);
349 : #ifdef CONFIG_BLK_DEV_IO_TRACE
350 : tsk->btrace_seq = 0;
351 : #endif
352 2993 : tsk->splice_pipe = NULL;
353 2993 : tsk->task_frag.page = NULL;
354 :
355 2993 : account_kernel_stack(ti, 1);
356 :
357 2993 : return tsk;
358 :
359 : free_ti:
360 : free_thread_info(ti);
361 : free_tsk:
362 : free_task_struct(tsk);
363 0 : return NULL;
364 : }
365 :
366 : #ifdef CONFIG_MMU
367 2895 : static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
368 : {
369 45204 : 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 2895 : down_write(&oldmm->mmap_sem);
376 2895 : flush_cache_dup_mm(oldmm);
377 : uprobe_dup_mmap(oldmm, mm);
378 : /*
379 : * Not linked in yet - no deadlock potential:
380 : */
381 2895 : down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
382 :
383 2895 : mm->total_vm = oldmm->total_vm;
384 2895 : mm->shared_vm = oldmm->shared_vm;
385 2895 : mm->exec_vm = oldmm->exec_vm;
386 2895 : mm->stack_vm = oldmm->stack_vm;
387 :
388 2895 : rb_link = &mm->mm_rb.rb_node;
389 : rb_parent = NULL;
390 2895 : 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 81610 : for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
400 60132 : struct file *file;
401 :
402 78715 : if (mpnt->vm_flags & VM_DONTCOPY) {
403 0 : vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
404 0 : -vma_pages(mpnt));
405 0 : continue;
406 : }
407 : charge = 0;
408 78715 : if (mpnt->vm_flags & VM_ACCOUNT) {
409 : unsigned long len = vma_pages(mpnt);
410 :
411 90408 : if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
412 : goto fail_nomem;
413 : charge = len;
414 : }
415 78715 : tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
416 78715 : if (!tmp)
417 : goto fail_nomem;
418 78715 : *tmp = *mpnt;
419 78715 : INIT_LIST_HEAD(&tmp->anon_vma_chain);
420 : retval = vma_dup_policy(mpnt, tmp);
421 : if (retval)
422 : goto fail_nomem_policy;
423 78715 : tmp->vm_mm = mm;
424 78715 : if (anon_vma_fork(tmp, mpnt))
425 : goto fail_nomem_anon_vma_fork;
426 78715 : tmp->vm_flags &= ~VM_LOCKED;
427 78715 : tmp->vm_next = tmp->vm_prev = NULL;
428 78715 : file = tmp->vm_file;
429 78715 : if (file) {
430 : struct inode *inode = file_inode(file);
431 60132 : struct address_space *mapping = file->f_mapping;
432 :
433 : get_file(file);
434 60132 : if (tmp->vm_flags & VM_DENYWRITE)
435 15156 : atomic_dec(&inode->i_writecount);
436 : i_mmap_lock_write(mapping);
437 60132 : if (tmp->vm_flags & VM_SHARED)
438 141 : atomic_inc(&mapping->i_mmap_writable);
439 : flush_dcache_mmap_lock(mapping);
440 : /* insert tmp into the share list, just after mpnt */
441 60132 : if (unlikely(tmp->vm_flags & VM_NONLINEAR))
442 0 : vma_nonlinear_insert(tmp,
443 : &mapping->i_mmap_nonlinear);
444 : else
445 60132 : vma_interval_tree_insert_after(tmp, mpnt,
446 : &mapping->i_mmap);
447 : flush_dcache_mmap_unlock(mapping);
448 : i_mmap_unlock_write(mapping);
449 : }
450 :
451 : /*
452 : * Clear hugetlb-related page reserves for children. This only
453 : * affects MAP_PRIVATE mappings. Faults generated by the child
454 : * are not guaranteed to succeed, even if read-only
455 : */
456 : if (is_vm_hugetlb_page(tmp))
457 : reset_vma_resv_huge_pages(tmp);
458 :
459 : /*
460 : * Link in the new vma and copy the page table entries.
461 : */
462 78715 : *pprev = tmp;
463 78715 : pprev = &tmp->vm_next;
464 78715 : tmp->vm_prev = prev;
465 : prev = tmp;
466 :
467 78715 : __vma_link_rb(mm, tmp, rb_link, rb_parent);
468 78715 : rb_link = &tmp->vm_rb.rb_right;
469 78715 : rb_parent = &tmp->vm_rb;
470 :
471 78715 : mm->map_count++;
472 78715 : retval = copy_page_range(mm, oldmm, mpnt);
473 :
474 78715 : if (tmp->vm_ops && tmp->vm_ops->open)
475 0 : tmp->vm_ops->open(tmp);
476 :
477 78715 : if (retval)
478 : goto out;
479 : }
480 : /* a new mm has just been created */
481 : arch_dup_mmap(oldmm, mm);
482 : retval = 0;
483 : out:
484 2895 : up_write(&mm->mmap_sem);
485 : flush_tlb_mm(oldmm);
486 2895 : up_write(&oldmm->mmap_sem);
487 : uprobe_end_dup_mmap();
488 2895 : return retval;
489 : fail_nomem_anon_vma_fork:
490 : mpol_put(vma_policy(tmp));
491 : fail_nomem_policy:
492 0 : kmem_cache_free(vm_area_cachep, tmp);
493 : fail_nomem:
494 : retval = -ENOMEM;
495 0 : vm_unacct_memory(charge);
496 : goto out;
497 : }
498 :
499 : static inline int mm_alloc_pgd(struct mm_struct *mm)
500 : {
501 5044 : mm->pgd = pgd_alloc(mm);
502 5044 : if (unlikely(!mm->pgd))
503 : return -ENOMEM;
504 : return 0;
505 : }
506 :
507 : static inline void mm_free_pgd(struct mm_struct *mm)
508 : {
509 5008 : pgd_free(mm, mm->pgd);
510 : }
511 : #else
512 : #define dup_mmap(mm, oldmm) (0)
513 : #define mm_alloc_pgd(mm) (0)
514 : #define mm_free_pgd(mm)
515 : #endif /* CONFIG_MMU */
516 :
517 : __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
518 :
519 : #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
520 : #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm)))
521 :
522 : static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
523 :
524 0 : static int __init coredump_filter_setup(char *s)
525 : {
526 0 : default_dump_filter =
527 0 : (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
528 : MMF_DUMP_FILTER_MASK;
529 0 : return 1;
530 : }
531 :
532 : __setup("coredump_filter=", coredump_filter_setup);
533 :
534 : #include <linux/init_task.h>
535 :
536 : static void mm_init_aio(struct mm_struct *mm)
537 : {
538 : #ifdef CONFIG_AIO
539 : spin_lock_init(&mm->ioctx_lock);
540 5044 : mm->ioctx_table = NULL;
541 : #endif
542 : }
543 :
544 : static void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
545 : {
546 : #ifdef CONFIG_MEMCG
547 5044 : mm->owner = p;
548 : #endif
549 : }
550 :
551 5044 : static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p)
552 : {
553 5044 : mm->mmap = NULL;
554 5044 : mm->mm_rb = RB_ROOT;
555 5044 : mm->vmacache_seqnum = 0;
556 5044 : atomic_set(&mm->mm_users, 1);
557 5044 : atomic_set(&mm->mm_count, 1);
558 5044 : init_rwsem(&mm->mmap_sem);
559 5044 : INIT_LIST_HEAD(&mm->mmlist);
560 5044 : mm->core_state = NULL;
561 : atomic_long_set(&mm->nr_ptes, 0);
562 5044 : mm->map_count = 0;
563 5044 : mm->locked_vm = 0;
564 5044 : mm->pinned_vm = 0;
565 5044 : memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
566 : spin_lock_init(&mm->page_table_lock);
567 : mm_init_cpumask(mm);
568 : mm_init_aio(mm);
569 : mm_init_owner(mm, p);
570 : mmu_notifier_mm_init(mm);
571 : clear_tlb_flush_pending(mm);
572 : #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
573 : mm->pmd_huge_pte = NULL;
574 : #endif
575 :
576 5044 : if (current->mm) {
577 5021 : mm->flags = current->mm->flags & MMF_INIT_MASK;
578 5021 : mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK;
579 : } else {
580 23 : mm->flags = default_dump_filter;
581 23 : mm->def_flags = 0;
582 : }
583 :
584 5044 : if (mm_alloc_pgd(mm))
585 : goto fail_nopgd;
586 :
587 5044 : if (init_new_context(p, mm))
588 : goto fail_nocontext;
589 :
590 5044 : return mm;
591 :
592 : fail_nocontext:
593 : mm_free_pgd(mm);
594 : fail_nopgd:
595 0 : free_mm(mm);
596 0 : return NULL;
597 : }
598 :
599 5008 : static void check_mm(struct mm_struct *mm)
600 : {
601 : int i;
602 :
603 20032 : for (i = 0; i < NR_MM_COUNTERS; i++) {
604 15024 : long x = atomic_long_read(&mm->rss_stat.count[i]);
605 :
606 15024 : if (unlikely(x))
607 0 : printk(KERN_ALERT "BUG: Bad rss-counter state "
608 : "mm:%p idx:%d val:%ld\n", mm, i, x);
609 : }
610 : #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
611 : VM_BUG_ON_MM(mm->pmd_huge_pte, mm);
612 : #endif
613 5008 : }
614 :
615 : /*
616 : * Allocate and initialize an mm_struct.
617 : */
618 2149 : struct mm_struct *mm_alloc(void)
619 : {
620 : struct mm_struct *mm;
621 :
622 2149 : mm = allocate_mm();
623 2149 : if (!mm)
624 : return NULL;
625 :
626 2149 : memset(mm, 0, sizeof(*mm));
627 2149 : return mm_init(mm, current);
628 : }
629 :
630 : /*
631 : * Called when the last reference to the mm
632 : * is dropped: either by a lazy thread or by
633 : * mmput. Free the page directory and the mm.
634 : */
635 5008 : void __mmdrop(struct mm_struct *mm)
636 : {
637 : BUG_ON(mm == &init_mm);
638 : mm_free_pgd(mm);
639 : destroy_context(mm);
640 : mmu_notifier_mm_destroy(mm);
641 5008 : check_mm(mm);
642 5008 : free_mm(mm);
643 5008 : }
644 : EXPORT_SYMBOL_GPL(__mmdrop);
645 :
646 : /*
647 : * Decrement the use count and release all resources for an mm.
648 : */
649 6093 : void mmput(struct mm_struct *mm)
650 : {
651 : might_sleep();
652 :
653 12186 : if (atomic_dec_and_test(&mm->mm_users)) {
654 : uprobe_clear_state(mm);
655 5008 : exit_aio(mm);
656 : ksm_exit(mm);
657 : khugepaged_exit(mm); /* must run before exit_mmap */
658 5008 : exit_mmap(mm);
659 5008 : set_mm_exe_file(mm, NULL);
660 10016 : if (!list_empty(&mm->mmlist)) {
661 : spin_lock(&mmlist_lock);
662 : list_del(&mm->mmlist);
663 : spin_unlock(&mmlist_lock);
664 : }
665 5008 : if (mm->binfmt)
666 5008 : module_put(mm->binfmt->module);
667 : mmdrop(mm);
668 : }
669 6093 : }
670 : EXPORT_SYMBOL_GPL(mmput);
671 :
672 7157 : void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
673 : {
674 7157 : if (new_exe_file)
675 : get_file(new_exe_file);
676 7157 : if (mm->exe_file)
677 5008 : fput(mm->exe_file);
678 7157 : mm->exe_file = new_exe_file;
679 7157 : }
680 :
681 3065 : struct file *get_mm_exe_file(struct mm_struct *mm)
682 : {
683 : struct file *exe_file;
684 :
685 : /* We need mmap_sem to protect against races with removal of exe_file */
686 3065 : down_read(&mm->mmap_sem);
687 3065 : exe_file = mm->exe_file;
688 3065 : if (exe_file)
689 : get_file(exe_file);
690 3065 : up_read(&mm->mmap_sem);
691 3065 : return exe_file;
692 : }
693 :
694 : static void dup_mm_exe_file(struct mm_struct *oldmm, struct mm_struct *newmm)
695 : {
696 : /* It's safe to write the exe_file pointer without exe_file_lock because
697 : * this is called during fork when the task is not yet in /proc */
698 2895 : newmm->exe_file = get_mm_exe_file(oldmm);
699 : }
700 :
701 : /**
702 : * get_task_mm - acquire a reference to the task's mm
703 : *
704 : * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning
705 : * this kernel workthread has transiently adopted a user mm with use_mm,
706 : * to do its AIO) is not set and if so returns a reference to it, after
707 : * bumping up the use count. User must release the mm via mmput()
708 : * after use. Typically used by /proc and ptrace.
709 : */
710 2175 : struct mm_struct *get_task_mm(struct task_struct *task)
711 : {
712 : struct mm_struct *mm;
713 :
714 : task_lock(task);
715 2175 : mm = task->mm;
716 2175 : if (mm) {
717 1085 : if (task->flags & PF_KTHREAD)
718 : mm = NULL;
719 : else
720 1085 : atomic_inc(&mm->mm_users);
721 : }
722 : task_unlock(task);
723 2175 : return mm;
724 : }
725 : EXPORT_SYMBOL_GPL(get_task_mm);
726 :
727 0 : struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
728 : {
729 : struct mm_struct *mm;
730 : int err;
731 :
732 0 : err = mutex_lock_killable(&task->signal->cred_guard_mutex);
733 0 : if (err)
734 0 : return ERR_PTR(err);
735 :
736 0 : mm = get_task_mm(task);
737 0 : if (mm && mm != current->mm &&
738 0 : !ptrace_may_access(task, mode)) {
739 0 : mmput(mm);
740 : mm = ERR_PTR(-EACCES);
741 : }
742 0 : mutex_unlock(&task->signal->cred_guard_mutex);
743 :
744 0 : return mm;
745 : }
746 :
747 11 : static void complete_vfork_done(struct task_struct *tsk)
748 : {
749 : struct completion *vfork;
750 :
751 : task_lock(tsk);
752 11 : vfork = tsk->vfork_done;
753 11 : if (likely(vfork)) {
754 11 : tsk->vfork_done = NULL;
755 11 : complete(vfork);
756 : }
757 : task_unlock(tsk);
758 11 : }
759 :
760 0 : static int wait_for_vfork_done(struct task_struct *child,
761 : struct completion *vfork)
762 : {
763 : int killed;
764 :
765 : freezer_do_not_count();
766 0 : killed = wait_for_completion_killable(vfork);
767 : freezer_count();
768 :
769 0 : if (killed) {
770 : task_lock(child);
771 0 : child->vfork_done = NULL;
772 : task_unlock(child);
773 : }
774 :
775 : put_task_struct(child);
776 0 : return killed;
777 : }
778 :
779 : /* Please note the differences between mmput and mm_release.
780 : * mmput is called whenever we stop holding onto a mm_struct,
781 : * error success whatever.
782 : *
783 : * mm_release is called after a mm_struct has been removed
784 : * from the current process.
785 : *
786 : * This difference is important for error handling, when we
787 : * only half set up a mm_struct for a new process and need to restore
788 : * the old one. Because we mmput the new mm_struct before
789 : * restoring the old one. . .
790 : * Eric Biederman 10 January 1998
791 : */
792 5063 : void mm_release(struct task_struct *tsk, struct mm_struct *mm)
793 : {
794 : /* Get rid of any futexes when releasing the mm */
795 : #ifdef CONFIG_FUTEX
796 5063 : if (unlikely(tsk->robust_list)) {
797 236 : exit_robust_list(tsk);
798 236 : tsk->robust_list = NULL;
799 : }
800 : #ifdef CONFIG_COMPAT
801 : if (unlikely(tsk->compat_robust_list)) {
802 : compat_exit_robust_list(tsk);
803 : tsk->compat_robust_list = NULL;
804 : }
805 : #endif
806 10126 : if (unlikely(!list_empty(&tsk->pi_state_list)))
807 0 : exit_pi_state_list(tsk);
808 : #endif
809 :
810 : uprobe_free_utask(tsk);
811 :
812 : /* Get rid of any cached register state */
813 : deactivate_mm(tsk, mm);
814 :
815 : /*
816 : * If we're exiting normally, clear a user-space tid field if
817 : * requested. We leave this alone when dying by signal, to leave
818 : * the value intact in a core dump, and to save the unnecessary
819 : * trouble, say, a killed vfork parent shouldn't touch this mm.
820 : * Userland only wants this done for a sys_exit.
821 : */
822 5063 : if (tsk->clear_child_tid) {
823 6220 : if (!(tsk->flags & PF_SIGNALED) &&
824 3107 : atomic_read(&mm->mm_users) > 1) {
825 : /*
826 : * We don't check the error code - if userspace has
827 : * not set up a proper pointer then tough luck.
828 : */
829 0 : put_user(0, tsk->clear_child_tid);
830 0 : sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
831 : 1, NULL, NULL, 0);
832 : }
833 3113 : tsk->clear_child_tid = NULL;
834 : }
835 :
836 : /*
837 : * All done, finally we can wake up parent and return this mm to him.
838 : * Also kthread_stop() uses this completion for synchronization.
839 : */
840 5063 : if (tsk->vfork_done)
841 11 : complete_vfork_done(tsk);
842 5063 : }
843 :
844 : /*
845 : * Allocate a new mm structure and copy contents from the
846 : * mm structure of the passed in task structure.
847 : */
848 2895 : static struct mm_struct *dup_mm(struct task_struct *tsk)
849 : {
850 2895 : struct mm_struct *mm, *oldmm = current->mm;
851 : int err;
852 :
853 2895 : mm = allocate_mm();
854 2895 : if (!mm)
855 : goto fail_nomem;
856 :
857 2895 : memcpy(mm, oldmm, sizeof(*mm));
858 :
859 2895 : if (!mm_init(mm, tsk))
860 : goto fail_nomem;
861 :
862 : dup_mm_exe_file(oldmm, mm);
863 :
864 2895 : err = dup_mmap(mm, oldmm);
865 2895 : if (err)
866 : goto free_pt;
867 :
868 2895 : mm->hiwater_rss = get_mm_rss(mm);
869 2895 : mm->hiwater_vm = mm->total_vm;
870 :
871 2895 : if (mm->binfmt && !try_module_get(mm->binfmt->module))
872 : goto free_pt;
873 :
874 2895 : return mm;
875 :
876 : free_pt:
877 : /* don't put binfmt in mmput, we haven't got module yet */
878 0 : mm->binfmt = NULL;
879 0 : mmput(mm);
880 :
881 : fail_nomem:
882 : return NULL;
883 : }
884 :
885 2993 : static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
886 : {
887 : struct mm_struct *mm, *oldmm;
888 : int retval;
889 :
890 2993 : tsk->min_flt = tsk->maj_flt = 0;
891 2993 : tsk->nvcsw = tsk->nivcsw = 0;
892 : #ifdef CONFIG_DETECT_HUNG_TASK
893 2993 : tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
894 : #endif
895 :
896 2993 : tsk->mm = NULL;
897 2993 : tsk->active_mm = NULL;
898 :
899 : /*
900 : * Are we cloning a kernel thread?
901 : *
902 : * We need to steal a active VM for that..
903 : */
904 2993 : oldmm = current->mm;
905 2993 : if (!oldmm)
906 : return 0;
907 :
908 : /* initialize the new vmacache entries */
909 : vmacache_flush(tsk);
910 :
911 2901 : if (clone_flags & CLONE_VM) {
912 6 : atomic_inc(&oldmm->mm_users);
913 : mm = oldmm;
914 6 : goto good_mm;
915 : }
916 :
917 : retval = -ENOMEM;
918 2895 : mm = dup_mm(tsk);
919 2895 : if (!mm)
920 : goto fail_nomem;
921 :
922 : good_mm:
923 2901 : tsk->mm = mm;
924 2901 : tsk->active_mm = mm;
925 2901 : return 0;
926 :
927 : fail_nomem:
928 : return retval;
929 : }
930 :
931 2993 : static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
932 : {
933 2993 : struct fs_struct *fs = current->fs;
934 2993 : if (clone_flags & CLONE_FS) {
935 : /* tsk->fs is already what we want */
936 : spin_lock(&fs->lock);
937 76 : if (fs->in_exec) {
938 : spin_unlock(&fs->lock);
939 : return -EAGAIN;
940 : }
941 76 : fs->users++;
942 : spin_unlock(&fs->lock);
943 : return 0;
944 : }
945 2917 : tsk->fs = copy_fs_struct(fs);
946 2917 : if (!tsk->fs)
947 : return -ENOMEM;
948 2917 : return 0;
949 : }
950 :
951 2993 : static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
952 : {
953 : struct files_struct *oldf, *newf;
954 2993 : int error = 0;
955 :
956 : /*
957 : * A background process may not have any files ...
958 : */
959 2993 : oldf = current->files;
960 2993 : if (!oldf)
961 : goto out;
962 :
963 2993 : if (clone_flags & CLONE_FILES) {
964 75 : atomic_inc(&oldf->count);
965 : goto out;
966 : }
967 :
968 2918 : newf = dup_fd(oldf, &error);
969 2918 : if (!newf)
970 : goto out;
971 :
972 2918 : tsk->files = newf;
973 2918 : error = 0;
974 : out:
975 2993 : return error;
976 : }
977 :
978 2993 : static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
979 : {
980 : #ifdef CONFIG_BLOCK
981 2993 : struct io_context *ioc = current->io_context;
982 : struct io_context *new_ioc;
983 :
984 2993 : if (!ioc)
985 : return 0;
986 : /*
987 : * Share io context with parent, if CLONE_IO is set
988 : */
989 1017 : if (clone_flags & CLONE_IO) {
990 : ioc_task_link(ioc);
991 0 : tsk->io_context = ioc;
992 1017 : } else if (ioprio_valid(ioc->ioprio)) {
993 0 : new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE);
994 0 : if (unlikely(!new_ioc))
995 : return -ENOMEM;
996 :
997 0 : new_ioc->ioprio = ioc->ioprio;
998 0 : put_io_context(new_ioc);
999 : }
1000 : #endif
1001 : return 0;
1002 : }
1003 :
1004 2993 : static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
1005 : {
1006 : struct sighand_struct *sig;
1007 :
1008 2993 : if (clone_flags & CLONE_SIGHAND) {
1009 6 : atomic_inc(¤t->sighand->count);
1010 6 : return 0;
1011 : }
1012 2987 : sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1013 2987 : rcu_assign_pointer(tsk->sighand, sig);
1014 2987 : if (!sig)
1015 : return -ENOMEM;
1016 2987 : atomic_set(&sig->count, 1);
1017 5974 : memcpy(sig->action, current->sighand->action, sizeof(sig->action));
1018 2987 : return 0;
1019 : }
1020 :
1021 2915 : void __cleanup_sighand(struct sighand_struct *sighand)
1022 : {
1023 5830 : if (atomic_dec_and_test(&sighand->count)) {
1024 2915 : signalfd_cleanup(sighand);
1025 : /*
1026 : * sighand_cachep is SLAB_DESTROY_BY_RCU so we can free it
1027 : * without an RCU grace period, see __lock_task_sighand().
1028 : */
1029 2915 : kmem_cache_free(sighand_cachep, sighand);
1030 : }
1031 2915 : }
1032 :
1033 : /*
1034 : * Initialize POSIX timer handling for a thread group.
1035 : */
1036 : static void posix_cpu_timers_init_group(struct signal_struct *sig)
1037 : {
1038 : unsigned long cpu_limit;
1039 :
1040 : /* Thread group counters. */
1041 : thread_group_cputime_init(sig);
1042 :
1043 2987 : cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1044 2987 : if (cpu_limit != RLIM_INFINITY) {
1045 0 : sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit);
1046 0 : sig->cputimer.running = 1;
1047 : }
1048 :
1049 : /* The timer lists. */
1050 2987 : INIT_LIST_HEAD(&sig->cpu_timers[0]);
1051 2987 : INIT_LIST_HEAD(&sig->cpu_timers[1]);
1052 2987 : INIT_LIST_HEAD(&sig->cpu_timers[2]);
1053 : }
1054 :
1055 2993 : static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
1056 : {
1057 : struct signal_struct *sig;
1058 :
1059 2993 : if (clone_flags & CLONE_THREAD)
1060 : return 0;
1061 :
1062 2987 : sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
1063 2987 : tsk->signal = sig;
1064 2987 : if (!sig)
1065 : return -ENOMEM;
1066 :
1067 2987 : sig->nr_threads = 1;
1068 2987 : atomic_set(&sig->live, 1);
1069 2987 : atomic_set(&sig->sigcnt, 1);
1070 :
1071 : /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */
1072 2987 : sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node);
1073 2987 : tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head);
1074 :
1075 2987 : init_waitqueue_head(&sig->wait_chldexit);
1076 2987 : sig->curr_target = tsk;
1077 : init_sigpending(&sig->shared_pending);
1078 2987 : INIT_LIST_HEAD(&sig->posix_timers);
1079 : seqlock_init(&sig->stats_lock);
1080 :
1081 2987 : hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1082 2987 : sig->real_timer.function = it_real_fn;
1083 :
1084 : task_lock(current->group_leader);
1085 5974 : memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
1086 : task_unlock(current->group_leader);
1087 :
1088 : posix_cpu_timers_init_group(sig);
1089 :
1090 2987 : tty_audit_fork(sig);
1091 2987 : sched_autogroup_fork(sig);
1092 :
1093 : #ifdef CONFIG_CGROUPS
1094 2987 : init_rwsem(&sig->group_rwsem);
1095 : #endif
1096 :
1097 2987 : sig->oom_score_adj = current->signal->oom_score_adj;
1098 2987 : sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1099 :
1100 2987 : sig->has_child_subreaper = current->signal->has_child_subreaper ||
1101 : current->signal->is_child_subreaper;
1102 :
1103 2987 : mutex_init(&sig->cred_guard_mutex);
1104 :
1105 2987 : return 0;
1106 : }
1107 :
1108 2993 : static void copy_seccomp(struct task_struct *p)
1109 : {
1110 : #ifdef CONFIG_SECCOMP
1111 : /*
1112 : * Must be called with sighand->lock held, which is common to
1113 : * all threads in the group. Holding cred_guard_mutex is not
1114 : * needed because this new task is not yet running and cannot
1115 : * be racing exec.
1116 : */
1117 : assert_spin_locked(¤t->sighand->siglock);
1118 :
1119 : /* Ref-count the new filter user, and assign it. */
1120 2993 : get_seccomp_filter(current);
1121 2993 : p->seccomp = current->seccomp;
1122 :
1123 : /*
1124 : * Explicitly enable no_new_privs here in case it got set
1125 : * between the task_struct being duplicated and holding the
1126 : * sighand lock. The seccomp state and nnp must be in sync.
1127 : */
1128 5986 : if (task_no_new_privs(current))
1129 : task_set_no_new_privs(p);
1130 :
1131 : /*
1132 : * If the parent gained a seccomp mode after copying thread
1133 : * flags and between before we held the sighand lock, we have
1134 : * to manually enable the seccomp thread flag here.
1135 : */
1136 2993 : if (p->seccomp.mode != SECCOMP_MODE_DISABLED)
1137 : set_tsk_thread_flag(p, TIF_SECCOMP);
1138 : #endif
1139 2993 : }
1140 :
1141 478 : SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1142 : {
1143 239 : current->clear_child_tid = tidptr;
1144 :
1145 239 : return task_pid_vnr(current);
1146 : }
1147 :
1148 : static void rt_mutex_init_task(struct task_struct *p)
1149 : {
1150 : raw_spin_lock_init(&p->pi_lock);
1151 : #ifdef CONFIG_RT_MUTEXES
1152 2993 : p->pi_waiters = RB_ROOT;
1153 2993 : p->pi_waiters_leftmost = NULL;
1154 2993 : p->pi_blocked_on = NULL;
1155 : #endif
1156 : }
1157 :
1158 : /*
1159 : * Initialize POSIX timer handling for a single task.
1160 : */
1161 : static void posix_cpu_timers_init(struct task_struct *tsk)
1162 : {
1163 2993 : tsk->cputime_expires.prof_exp = 0;
1164 2993 : tsk->cputime_expires.virt_exp = 0;
1165 2993 : tsk->cputime_expires.sched_exp = 0;
1166 2993 : INIT_LIST_HEAD(&tsk->cpu_timers[0]);
1167 2993 : INIT_LIST_HEAD(&tsk->cpu_timers[1]);
1168 2993 : INIT_LIST_HEAD(&tsk->cpu_timers[2]);
1169 : }
1170 :
1171 : static inline void
1172 : init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid)
1173 : {
1174 8964 : task->pids[type].pid = pid;
1175 : }
1176 :
1177 : /*
1178 : * This creates a new process as a copy of the old one,
1179 : * but does not actually start it yet.
1180 : *
1181 : * It copies the registers, and all the appropriate
1182 : * parts of the process environment (as per the clone
1183 : * flags). The actual kick-off is left to the caller.
1184 : */
1185 2993 : static struct task_struct *copy_process(unsigned long clone_flags,
1186 : unsigned long stack_start,
1187 : unsigned long stack_size,
1188 : int __user *child_tidptr,
1189 : struct pid *pid,
1190 : int trace)
1191 : {
1192 : int retval;
1193 : struct task_struct *p;
1194 :
1195 2993 : if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1196 : return ERR_PTR(-EINVAL);
1197 :
1198 2993 : if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS))
1199 : return ERR_PTR(-EINVAL);
1200 :
1201 : /*
1202 : * Thread groups must share signals as well, and detached threads
1203 : * can only be started up within the thread group.
1204 : */
1205 2993 : if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1206 : return ERR_PTR(-EINVAL);
1207 :
1208 : /*
1209 : * Shared signal handlers imply shared VM. By way of the above,
1210 : * thread groups also imply shared VM. Blocking this case allows
1211 : * for various simplifications in other code.
1212 : */
1213 2993 : if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1214 : return ERR_PTR(-EINVAL);
1215 :
1216 : /*
1217 : * Siblings of global init remain as zombies on exit since they are
1218 : * not reaped by their parent (swapper). To solve this and to avoid
1219 : * multi-rooted process trees, prevent global and container-inits
1220 : * from creating siblings.
1221 : */
1222 2993 : if ((clone_flags & CLONE_PARENT) &&
1223 0 : current->signal->flags & SIGNAL_UNKILLABLE)
1224 : return ERR_PTR(-EINVAL);
1225 :
1226 : /*
1227 : * If the new process will be in a different pid or user namespace
1228 : * do not allow it to share a thread group or signal handlers or
1229 : * parent with the forking task.
1230 : */
1231 2993 : if (clone_flags & CLONE_SIGHAND) {
1232 12 : if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) ||
1233 6 : (task_active_pid_ns(current) !=
1234 6 : current->nsproxy->pid_ns_for_children))
1235 : return ERR_PTR(-EINVAL);
1236 : }
1237 :
1238 : retval = security_task_create(clone_flags);
1239 : if (retval)
1240 : goto fork_out;
1241 :
1242 : retval = -ENOMEM;
1243 2993 : p = dup_task_struct(current);
1244 2993 : if (!p)
1245 : goto fork_out;
1246 :
1247 : ftrace_graph_init_task(p);
1248 :
1249 : rt_mutex_init_task(p);
1250 :
1251 : #ifdef CONFIG_PROVE_LOCKING
1252 : DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1253 : DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1254 : #endif
1255 : retval = -EAGAIN;
1256 5986 : if (atomic_read(&p->real_cred->user->processes) >=
1257 : task_rlimit(p, RLIMIT_NPROC)) {
1258 0 : if (p->real_cred->user != INIT_USER &&
1259 0 : !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
1260 : goto bad_fork_free;
1261 : }
1262 2993 : current->flags &= ~PF_NPROC_EXCEEDED;
1263 :
1264 2993 : retval = copy_creds(p, clone_flags);
1265 2993 : if (retval < 0)
1266 : goto bad_fork_free;
1267 :
1268 : /*
1269 : * If multiple threads are within copy_process(), then this check
1270 : * triggers too late. This doesn't hurt, the check is only there
1271 : * to stop root fork bombs.
1272 : */
1273 : retval = -EAGAIN;
1274 2993 : if (nr_threads >= max_threads)
1275 : goto bad_fork_cleanup_count;
1276 :
1277 2993 : if (!try_module_get(task_thread_info(p)->exec_domain->module))
1278 : goto bad_fork_cleanup_count;
1279 :
1280 : delayacct_tsk_init(p); /* Must remain after dup_task_struct() */
1281 2993 : p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER);
1282 2993 : p->flags |= PF_FORKNOEXEC;
1283 2993 : INIT_LIST_HEAD(&p->children);
1284 2993 : INIT_LIST_HEAD(&p->sibling);
1285 : rcu_copy_process(p);
1286 2993 : p->vfork_done = NULL;
1287 : spin_lock_init(&p->alloc_lock);
1288 :
1289 : init_sigpending(&p->pending);
1290 :
1291 2993 : p->utime = p->stime = p->gtime = 0;
1292 2993 : p->utimescaled = p->stimescaled = 0;
1293 : #ifndef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
1294 2993 : p->prev_cputime.utime = p->prev_cputime.stime = 0;
1295 : #endif
1296 : #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
1297 : seqlock_init(&p->vtime_seqlock);
1298 : p->vtime_snap = 0;
1299 : p->vtime_snap_whence = VTIME_SLEEPING;
1300 : #endif
1301 :
1302 : #if defined(SPLIT_RSS_COUNTING)
1303 : memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1304 : #endif
1305 :
1306 2993 : p->default_timer_slack_ns = current->timer_slack_ns;
1307 :
1308 2993 : task_io_accounting_init(&p->ioac);
1309 2993 : acct_clear_integrals(p);
1310 :
1311 : posix_cpu_timers_init(p);
1312 :
1313 2993 : p->start_time = ktime_get_ns();
1314 2993 : p->real_start_time = ktime_get_boot_ns();
1315 2993 : p->io_context = NULL;
1316 2993 : p->audit_context = NULL;
1317 2993 : if (clone_flags & CLONE_THREAD)
1318 6 : threadgroup_change_begin(current);
1319 2993 : cgroup_fork(p);
1320 : #ifdef CONFIG_NUMA
1321 : p->mempolicy = mpol_dup(p->mempolicy);
1322 : if (IS_ERR(p->mempolicy)) {
1323 : retval = PTR_ERR(p->mempolicy);
1324 : p->mempolicy = NULL;
1325 : goto bad_fork_cleanup_threadgroup_lock;
1326 : }
1327 : #endif
1328 : #ifdef CONFIG_CPUSETS
1329 : p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
1330 : p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
1331 : seqcount_init(&p->mems_allowed_seq);
1332 : #endif
1333 : #ifdef CONFIG_TRACE_IRQFLAGS
1334 : p->irq_events = 0;
1335 : p->hardirqs_enabled = 0;
1336 : p->hardirq_enable_ip = 0;
1337 : p->hardirq_enable_event = 0;
1338 : p->hardirq_disable_ip = _THIS_IP_;
1339 : p->hardirq_disable_event = 0;
1340 : p->softirqs_enabled = 1;
1341 : p->softirq_enable_ip = _THIS_IP_;
1342 : p->softirq_enable_event = 0;
1343 : p->softirq_disable_ip = 0;
1344 : p->softirq_disable_event = 0;
1345 : p->hardirq_context = 0;
1346 : p->softirq_context = 0;
1347 : #endif
1348 : #ifdef CONFIG_LOCKDEP
1349 : p->lockdep_depth = 0; /* no locks held yet */
1350 : p->curr_chain_key = 0;
1351 : p->lockdep_recursion = 0;
1352 : #endif
1353 :
1354 : #ifdef CONFIG_DEBUG_MUTEXES
1355 : p->blocked_on = NULL; /* not blocked yet */
1356 : #endif
1357 : #ifdef CONFIG_BCACHE
1358 : p->sequential_io = 0;
1359 : p->sequential_io_avg = 0;
1360 : #endif
1361 :
1362 : /* Perform scheduler related setup. Assign this task to a CPU. */
1363 2993 : retval = sched_fork(clone_flags, p);
1364 2993 : if (retval)
1365 : goto bad_fork_cleanup_policy;
1366 :
1367 2993 : retval = perf_event_init_task(p);
1368 2993 : if (retval)
1369 : goto bad_fork_cleanup_policy;
1370 : retval = audit_alloc(p);
1371 : if (retval)
1372 : goto bad_fork_cleanup_perf;
1373 : /* copy all the process information */
1374 2993 : shm_init_task(p);
1375 2993 : retval = copy_semundo(clone_flags, p);
1376 2993 : if (retval)
1377 : goto bad_fork_cleanup_audit;
1378 2993 : retval = copy_files(clone_flags, p);
1379 2993 : if (retval)
1380 : goto bad_fork_cleanup_semundo;
1381 2993 : retval = copy_fs(clone_flags, p);
1382 2993 : if (retval)
1383 : goto bad_fork_cleanup_files;
1384 2993 : retval = copy_sighand(clone_flags, p);
1385 2993 : if (retval)
1386 : goto bad_fork_cleanup_fs;
1387 2993 : retval = copy_signal(clone_flags, p);
1388 2993 : if (retval)
1389 : goto bad_fork_cleanup_sighand;
1390 2993 : retval = copy_mm(clone_flags, p);
1391 2992 : if (retval)
1392 : goto bad_fork_cleanup_signal;
1393 2993 : retval = copy_namespaces(clone_flags, p);
1394 2993 : if (retval)
1395 : goto bad_fork_cleanup_mm;
1396 2993 : retval = copy_io(clone_flags, p);
1397 2993 : if (retval)
1398 : goto bad_fork_cleanup_namespaces;
1399 2993 : retval = copy_thread(clone_flags, stack_start, stack_size, p);
1400 2993 : if (retval)
1401 : goto bad_fork_cleanup_io;
1402 :
1403 2993 : if (pid != &init_struct_pid) {
1404 : retval = -ENOMEM;
1405 2993 : pid = alloc_pid(p->nsproxy->pid_ns_for_children);
1406 2993 : if (!pid)
1407 : goto bad_fork_cleanup_io;
1408 : }
1409 :
1410 2993 : p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1411 : /*
1412 : * Clear TID on mm_release()?
1413 : */
1414 2993 : p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL;
1415 : #ifdef CONFIG_BLOCK
1416 2993 : p->plug = NULL;
1417 : #endif
1418 : #ifdef CONFIG_FUTEX
1419 2993 : p->robust_list = NULL;
1420 : #ifdef CONFIG_COMPAT
1421 : p->compat_robust_list = NULL;
1422 : #endif
1423 2993 : INIT_LIST_HEAD(&p->pi_state_list);
1424 2993 : p->pi_state_cache = NULL;
1425 : #endif
1426 : /*
1427 : * sigaltstack should be cleared when sharing the same VM
1428 : */
1429 2993 : if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1430 98 : p->sas_ss_sp = p->sas_ss_size = 0;
1431 :
1432 : /*
1433 : * Syscall tracing and stepping should be turned off in the
1434 : * child regardless of CLONE_PTRACE.
1435 : */
1436 : user_disable_single_step(p);
1437 : clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1438 : #ifdef TIF_SYSCALL_EMU
1439 : clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1440 : #endif
1441 : clear_all_latency_tracing(p);
1442 :
1443 : /* ok, now we should be set up.. */
1444 2993 : p->pid = pid_nr(pid);
1445 2993 : if (clone_flags & CLONE_THREAD) {
1446 6 : p->exit_signal = -1;
1447 6 : p->group_leader = current->group_leader;
1448 6 : p->tgid = current->tgid;
1449 : } else {
1450 2987 : if (clone_flags & CLONE_PARENT)
1451 0 : p->exit_signal = current->group_leader->exit_signal;
1452 : else
1453 2987 : p->exit_signal = (clone_flags & CSIGNAL);
1454 2987 : p->group_leader = p;
1455 2987 : p->tgid = p->pid;
1456 : }
1457 :
1458 2993 : p->nr_dirtied = 0;
1459 2993 : p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
1460 2993 : p->dirty_paused_when = 0;
1461 :
1462 2993 : p->pdeath_signal = 0;
1463 2993 : INIT_LIST_HEAD(&p->thread_group);
1464 2993 : p->task_works = NULL;
1465 :
1466 : /*
1467 : * Make it visible to the rest of the system, but dont wake it up yet.
1468 : * Need tasklist lock for parent etc handling!
1469 : */
1470 2993 : write_lock_irq(&tasklist_lock);
1471 :
1472 : /* CLONE_PARENT re-uses the old parent */
1473 2993 : if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1474 6 : p->real_parent = current->real_parent;
1475 6 : p->parent_exec_id = current->parent_exec_id;
1476 : } else {
1477 2987 : p->real_parent = current;
1478 2987 : p->parent_exec_id = current->self_exec_id;
1479 : }
1480 :
1481 : spin_lock(¤t->sighand->siglock);
1482 :
1483 : /*
1484 : * Copy seccomp details explicitly here, in case they were changed
1485 : * before holding sighand lock.
1486 : */
1487 2993 : copy_seccomp(p);
1488 :
1489 : /*
1490 : * Process group and session signals need to be delivered to just the
1491 : * parent before the fork or both the parent and the child after the
1492 : * fork. Restart if a signal comes in before we add the new process to
1493 : * it's process group.
1494 : * A fatal signal pending means that current will exit, so the new
1495 : * thread can't slip out of an OOM kill (or normal SIGKILL).
1496 : */
1497 2993 : recalc_sigpending();
1498 5986 : if (signal_pending(current)) {
1499 : spin_unlock(¤t->sighand->siglock);
1500 2 : write_unlock_irq(&tasklist_lock);
1501 : retval = -ERESTARTNOINTR;
1502 : goto bad_fork_free_pid;
1503 : }
1504 :
1505 2992 : if (likely(p->pid)) {
1506 2992 : ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
1507 :
1508 : init_task_pid(p, PIDTYPE_PID, pid);
1509 2992 : if (thread_group_leader(p)) {
1510 2986 : init_task_pid(p, PIDTYPE_PGID, task_pgrp(current));
1511 2986 : init_task_pid(p, PIDTYPE_SID, task_session(current));
1512 :
1513 2986 : if (is_child_reaper(pid)) {
1514 1 : ns_of_pid(pid)->child_reaper = p;
1515 1 : p->signal->flags |= SIGNAL_UNKILLABLE;
1516 : }
1517 :
1518 2986 : p->signal->leader_pid = pid;
1519 5972 : p->signal->tty = tty_kref_get(current->signal->tty);
1520 2986 : list_add_tail(&p->sibling, &p->real_parent->children);
1521 2986 : list_add_tail_rcu(&p->tasks, &init_task.tasks);
1522 2986 : attach_pid(p, PIDTYPE_PGID);
1523 2986 : attach_pid(p, PIDTYPE_SID);
1524 2986 : __this_cpu_inc(process_counts);
1525 : } else {
1526 6 : current->signal->nr_threads++;
1527 6 : atomic_inc(¤t->signal->live);
1528 6 : atomic_inc(¤t->signal->sigcnt);
1529 6 : list_add_tail_rcu(&p->thread_group,
1530 6 : &p->group_leader->thread_group);
1531 12 : list_add_tail_rcu(&p->thread_node,
1532 6 : &p->signal->thread_head);
1533 : }
1534 2992 : attach_pid(p, PIDTYPE_PID);
1535 2992 : nr_threads++;
1536 : }
1537 :
1538 2992 : total_forks++;
1539 : spin_unlock(¤t->sighand->siglock);
1540 : syscall_tracepoint_update(p);
1541 5984 : write_unlock_irq(&tasklist_lock);
1542 :
1543 : proc_fork_connector(p);
1544 2992 : cgroup_post_fork(p);
1545 2992 : if (clone_flags & CLONE_THREAD)
1546 6 : threadgroup_change_end(current);
1547 2992 : perf_event_fork(p);
1548 :
1549 : trace_task_newtask(p, clone_flags);
1550 : uprobe_copy_process(p, clone_flags);
1551 :
1552 2992 : return p;
1553 :
1554 : bad_fork_free_pid:
1555 1 : if (pid != &init_struct_pid)
1556 1 : free_pid(pid);
1557 : bad_fork_cleanup_io:
1558 1 : if (p->io_context)
1559 0 : exit_io_context(p);
1560 : bad_fork_cleanup_namespaces:
1561 1 : exit_task_namespaces(p);
1562 : bad_fork_cleanup_mm:
1563 2 : if (p->mm)
1564 1 : mmput(p->mm);
1565 : bad_fork_cleanup_signal:
1566 1 : if (!(clone_flags & CLONE_THREAD))
1567 1 : free_signal_struct(p->signal);
1568 : bad_fork_cleanup_sighand:
1569 1 : __cleanup_sighand(p->sighand);
1570 : bad_fork_cleanup_fs:
1571 1 : exit_fs(p); /* blocking */
1572 : bad_fork_cleanup_files:
1573 1 : exit_files(p); /* blocking */
1574 : bad_fork_cleanup_semundo:
1575 1 : exit_sem(p);
1576 : bad_fork_cleanup_audit:
1577 : audit_free(p);
1578 : bad_fork_cleanup_perf:
1579 1 : perf_event_free_task(p);
1580 : bad_fork_cleanup_policy:
1581 : #ifdef CONFIG_NUMA
1582 : mpol_put(p->mempolicy);
1583 : bad_fork_cleanup_threadgroup_lock:
1584 : #endif
1585 1 : if (clone_flags & CLONE_THREAD)
1586 0 : threadgroup_change_end(current);
1587 : delayacct_tsk_free(p);
1588 1 : module_put(task_thread_info(p)->exec_domain->module);
1589 : bad_fork_cleanup_count:
1590 1 : atomic_dec(&p->cred->user->processes);
1591 1 : exit_creds(p);
1592 : bad_fork_free:
1593 1 : free_task(p);
1594 : fork_out:
1595 1 : return ERR_PTR(retval);
1596 : }
1597 :
1598 : static inline void init_idle_pids(struct pid_link *links)
1599 : {
1600 : enum pid_type type;
1601 :
1602 0 : for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
1603 0 : INIT_HLIST_NODE(&links[type].node); /* not really needed */
1604 0 : links[type].pid = &init_struct_pid;
1605 : }
1606 : }
1607 :
1608 0 : struct task_struct *fork_idle(int cpu)
1609 : {
1610 : struct task_struct *task;
1611 0 : task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0);
1612 0 : if (!IS_ERR(task)) {
1613 0 : init_idle_pids(task->pids);
1614 0 : init_idle(task, cpu);
1615 : }
1616 :
1617 0 : return task;
1618 : }
1619 :
1620 : /*
1621 : * Ok, this is the main fork-routine.
1622 : *
1623 : * It copies the process, and if successful kick-starts
1624 : * it and waits for it to finish using the VM if required.
1625 : */
1626 2993 : long do_fork(unsigned long clone_flags,
1627 : unsigned long stack_start,
1628 : unsigned long stack_size,
1629 : int __user *parent_tidptr,
1630 : int __user *child_tidptr)
1631 : {
1632 : struct task_struct *p;
1633 : int trace = 0;
1634 : long nr;
1635 :
1636 : /*
1637 : * Determine whether and which event to report to ptracer. When
1638 : * called from kernel_thread or CLONE_UNTRACED is explicitly
1639 : * requested, no event is reported; otherwise, report if the event
1640 : * for the type of forking is enabled.
1641 : */
1642 2993 : if (!(clone_flags & CLONE_UNTRACED)) {
1643 2901 : if (clone_flags & CLONE_VFORK)
1644 : trace = PTRACE_EVENT_VFORK;
1645 2901 : else if ((clone_flags & CSIGNAL) != SIGCHLD)
1646 : trace = PTRACE_EVENT_CLONE;
1647 : else
1648 : trace = PTRACE_EVENT_FORK;
1649 :
1650 5802 : if (likely(!ptrace_event_enabled(current, trace)))
1651 : trace = 0;
1652 : }
1653 :
1654 2993 : p = copy_process(clone_flags, stack_start, stack_size,
1655 : child_tidptr, NULL, trace);
1656 : /*
1657 : * Do this prior waking up the new thread - the thread pointer
1658 : * might get invalid after that point, if the thread exits quickly.
1659 : */
1660 2993 : if (!IS_ERR(p)) {
1661 : struct completion vfork;
1662 : struct pid *pid;
1663 :
1664 : trace_sched_process_fork(current, p);
1665 :
1666 2992 : pid = get_task_pid(p, PIDTYPE_PID);
1667 2992 : nr = pid_vnr(pid);
1668 :
1669 2992 : if (clone_flags & CLONE_PARENT_SETTID)
1670 6 : put_user(nr, parent_tidptr);
1671 :
1672 2992 : if (clone_flags & CLONE_VFORK) {
1673 0 : p->vfork_done = &vfork;
1674 : init_completion(&vfork);
1675 0 : get_task_struct(p);
1676 : }
1677 :
1678 2992 : wake_up_new_task(p);
1679 :
1680 : /* forking complete and child started to run, tell ptracer */
1681 2992 : if (unlikely(trace))
1682 : ptrace_event_pid(trace, pid);
1683 :
1684 2992 : if (clone_flags & CLONE_VFORK) {
1685 0 : if (!wait_for_vfork_done(p, &vfork))
1686 : ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid);
1687 : }
1688 :
1689 2992 : put_pid(pid);
1690 : } else {
1691 : nr = PTR_ERR(p);
1692 : }
1693 2993 : return nr;
1694 : }
1695 :
1696 : /*
1697 : * Create a kernel thread.
1698 : */
1699 92 : pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
1700 : {
1701 92 : return do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn,
1702 : (unsigned long)arg, NULL, NULL);
1703 : }
1704 :
1705 : #ifdef __ARCH_WANT_SYS_FORK
1706 0 : SYSCALL_DEFINE0(fork)
1707 : {
1708 : #ifdef CONFIG_MMU
1709 0 : return do_fork(SIGCHLD, 0, 0, NULL, NULL);
1710 : #else
1711 : /* can not support in nommu mode */
1712 : return -EINVAL;
1713 : #endif
1714 : }
1715 : #endif
1716 :
1717 : #ifdef __ARCH_WANT_SYS_VFORK
1718 0 : SYSCALL_DEFINE0(vfork)
1719 : {
1720 0 : return do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0,
1721 : 0, NULL, NULL);
1722 : }
1723 : #endif
1724 :
1725 : #ifdef __ARCH_WANT_SYS_CLONE
1726 : #ifdef CONFIG_CLONE_BACKWARDS
1727 5802 : SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
1728 : int __user *, parent_tidptr,
1729 : int, tls_val,
1730 : int __user *, child_tidptr)
1731 : #elif defined(CONFIG_CLONE_BACKWARDS2)
1732 : SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags,
1733 : int __user *, parent_tidptr,
1734 : int __user *, child_tidptr,
1735 : int, tls_val)
1736 : #elif defined(CONFIG_CLONE_BACKWARDS3)
1737 : SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp,
1738 : int, stack_size,
1739 : int __user *, parent_tidptr,
1740 : int __user *, child_tidptr,
1741 : int, tls_val)
1742 : #else
1743 : SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
1744 : int __user *, parent_tidptr,
1745 : int __user *, child_tidptr,
1746 : int, tls_val)
1747 : #endif
1748 : {
1749 2901 : return do_fork(clone_flags, newsp, 0, parent_tidptr, child_tidptr);
1750 : }
1751 : #endif
1752 :
1753 : #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1754 : #define ARCH_MIN_MMSTRUCT_ALIGN 0
1755 : #endif
1756 :
1757 108 : static void sighand_ctor(void *data)
1758 : {
1759 : struct sighand_struct *sighand = data;
1760 :
1761 : spin_lock_init(&sighand->siglock);
1762 108 : init_waitqueue_head(&sighand->signalfd_wqh);
1763 108 : }
1764 :
1765 1 : void __init proc_caches_init(void)
1766 : {
1767 1 : sighand_cachep = kmem_cache_create("sighand_cache",
1768 : sizeof(struct sighand_struct), 0,
1769 : SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU|
1770 : SLAB_NOTRACK, sighand_ctor);
1771 1 : signal_cachep = kmem_cache_create("signal_cache",
1772 : sizeof(struct signal_struct), 0,
1773 : SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1774 1 : files_cachep = kmem_cache_create("files_cache",
1775 : sizeof(struct files_struct), 0,
1776 : SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1777 1 : fs_cachep = kmem_cache_create("fs_cache",
1778 : sizeof(struct fs_struct), 0,
1779 : SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1780 : /*
1781 : * FIXME! The "sizeof(struct mm_struct)" currently includes the
1782 : * whole struct cpumask for the OFFSTACK case. We could change
1783 : * this to *only* allocate as much of it as required by the
1784 : * maximum number of CPU's we can ever have. The cpumask_allocation
1785 : * is at the end of the structure, exactly for that reason.
1786 : */
1787 1 : mm_cachep = kmem_cache_create("mm_struct",
1788 : sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1789 : SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1790 1 : vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC);
1791 1 : mmap_init();
1792 1 : nsproxy_cache_init();
1793 1 : }
1794 :
1795 : /*
1796 : * Check constraints on flags passed to the unshare system call.
1797 : */
1798 1 : static int check_unshare_flags(unsigned long unshare_flags)
1799 : {
1800 1 : if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1801 : CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1802 : CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET|
1803 : CLONE_NEWUSER|CLONE_NEWPID))
1804 : return -EINVAL;
1805 : /*
1806 : * Not implemented, but pretend it works if there is nothing to
1807 : * unshare. Note that unsharing CLONE_THREAD or CLONE_SIGHAND
1808 : * needs to unshare vm.
1809 : */
1810 1 : if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
1811 : /* FIXME: get_task_mm() increments ->mm_users */
1812 0 : if (atomic_read(¤t->mm->mm_users) > 1)
1813 : return -EINVAL;
1814 : }
1815 :
1816 1 : return 0;
1817 : }
1818 :
1819 : /*
1820 : * Unshare the filesystem structure if it is being shared
1821 : */
1822 1 : static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1823 : {
1824 1 : struct fs_struct *fs = current->fs;
1825 :
1826 1 : if (!(unshare_flags & CLONE_FS) || !fs)
1827 : return 0;
1828 :
1829 : /* don't need lock here; in the worst case we'll do useless copy */
1830 1 : if (fs->users == 1)
1831 : return 0;
1832 :
1833 1 : *new_fsp = copy_fs_struct(fs);
1834 1 : if (!*new_fsp)
1835 : return -ENOMEM;
1836 :
1837 1 : return 0;
1838 : }
1839 :
1840 : /*
1841 : * Unshare file descriptor table if it is being shared
1842 : */
1843 2248 : static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1844 : {
1845 2248 : struct files_struct *fd = current->files;
1846 2248 : int error = 0;
1847 :
1848 2248 : if ((unshare_flags & CLONE_FILES) &&
1849 2247 : (fd && atomic_read(&fd->count) > 1)) {
1850 0 : *new_fdp = dup_fd(fd, &error);
1851 0 : if (!*new_fdp)
1852 0 : return error;
1853 : }
1854 :
1855 : return 0;
1856 : }
1857 :
1858 : /*
1859 : * unshare allows a process to 'unshare' part of the process
1860 : * context which was originally shared using clone. copy_*
1861 : * functions used by do_fork() cannot be used here directly
1862 : * because they modify an inactive task_struct that is being
1863 : * constructed. Here we are modifying the current, active,
1864 : * task_struct.
1865 : */
1866 2 : SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
1867 : {
1868 1 : struct fs_struct *fs, *new_fs = NULL;
1869 1 : struct files_struct *fd, *new_fd = NULL;
1870 : struct cred *new_cred = NULL;
1871 1 : struct nsproxy *new_nsproxy = NULL;
1872 : int do_sysvsem = 0;
1873 : int err;
1874 :
1875 : /*
1876 : * If unsharing a user namespace must also unshare the thread.
1877 : */
1878 1 : if (unshare_flags & CLONE_NEWUSER)
1879 0 : unshare_flags |= CLONE_THREAD | CLONE_FS;
1880 : /*
1881 : * If unsharing a thread from a thread group, must also unshare vm.
1882 : */
1883 1 : if (unshare_flags & CLONE_THREAD)
1884 0 : unshare_flags |= CLONE_VM;
1885 : /*
1886 : * If unsharing vm, must also unshare signal handlers.
1887 : */
1888 1 : if (unshare_flags & CLONE_VM)
1889 0 : unshare_flags |= CLONE_SIGHAND;
1890 : /*
1891 : * If unsharing namespace, must also unshare filesystem information.
1892 : */
1893 1 : if (unshare_flags & CLONE_NEWNS)
1894 1 : unshare_flags |= CLONE_FS;
1895 :
1896 1 : err = check_unshare_flags(unshare_flags);
1897 1 : if (err)
1898 : goto bad_unshare_out;
1899 : /*
1900 : * CLONE_NEWIPC must also detach from the undolist: after switching
1901 : * to a new ipc namespace, the semaphore arrays from the old
1902 : * namespace are unreachable.
1903 : */
1904 1 : if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1905 : do_sysvsem = 1;
1906 1 : err = unshare_fs(unshare_flags, &new_fs);
1907 1 : if (err)
1908 : goto bad_unshare_out;
1909 1 : err = unshare_fd(unshare_flags, &new_fd);
1910 1 : if (err)
1911 : goto bad_unshare_cleanup_fs;
1912 : err = unshare_userns(unshare_flags, &new_cred);
1913 1 : if (err)
1914 : goto bad_unshare_cleanup_fd;
1915 1 : err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
1916 : new_cred, new_fs);
1917 1 : if (err)
1918 : goto bad_unshare_cleanup_cred;
1919 :
1920 1 : if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
1921 1 : if (do_sysvsem) {
1922 : /*
1923 : * CLONE_SYSVSEM is equivalent to sys_exit().
1924 : */
1925 0 : exit_sem(current);
1926 : }
1927 1 : if (unshare_flags & CLONE_NEWIPC) {
1928 : /* Orphan segments in old ns (see sem above). */
1929 0 : exit_shm(current);
1930 0 : shm_init_task(current);
1931 : }
1932 :
1933 1 : if (new_nsproxy)
1934 1 : switch_task_namespaces(current, new_nsproxy);
1935 :
1936 : task_lock(current);
1937 :
1938 1 : if (new_fs) {
1939 1 : fs = current->fs;
1940 : spin_lock(&fs->lock);
1941 1 : current->fs = new_fs;
1942 1 : if (--fs->users)
1943 1 : new_fs = NULL;
1944 : else
1945 0 : new_fs = fs;
1946 : spin_unlock(&fs->lock);
1947 : }
1948 :
1949 1 : if (new_fd) {
1950 0 : fd = current->files;
1951 0 : current->files = new_fd;
1952 0 : new_fd = fd;
1953 : }
1954 :
1955 : task_unlock(current);
1956 :
1957 : if (new_cred) {
1958 : /* Install the new user namespace */
1959 : commit_creds(new_cred);
1960 : new_cred = NULL;
1961 : }
1962 : }
1963 :
1964 : bad_unshare_cleanup_cred:
1965 : if (new_cred)
1966 : put_cred(new_cred);
1967 : bad_unshare_cleanup_fd:
1968 1 : if (new_fd)
1969 0 : put_files_struct(new_fd);
1970 :
1971 : bad_unshare_cleanup_fs:
1972 1 : if (new_fs)
1973 0 : free_fs_struct(new_fs);
1974 :
1975 : bad_unshare_out:
1976 : return err;
1977 : }
1978 :
1979 : /*
1980 : * Helper to unshare the files of the current task.
1981 : * We don't want to expose copy_files internals to
1982 : * the exec layer of the kernel.
1983 : */
1984 :
1985 2247 : int unshare_files(struct files_struct **displaced)
1986 : {
1987 2247 : struct task_struct *task = current;
1988 2247 : struct files_struct *copy = NULL;
1989 : int error;
1990 :
1991 2247 : error = unshare_fd(CLONE_FILES, ©);
1992 2247 : if (error || !copy) {
1993 2247 : *displaced = NULL;
1994 2247 : return error;
1995 : }
1996 0 : *displaced = task->files;
1997 : task_lock(task);
1998 0 : task->files = copy;
1999 : task_unlock(task);
2000 : return 0;
2001 : }
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