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Merge tag 'md/4.2' of git://neil.brown.name/md
[deliverable/linux.git] / kernel / fork.c
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CommitLineData
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#include <linux/sysctl.h>
78
79#include <asm/pgtable.h>
80#include <asm/pgalloc.h>
81#include <asm/uaccess.h>
82#include <asm/mmu_context.h>
83#include <asm/cacheflush.h>
84#include <asm/tlbflush.h>
85
86#include <trace/events/sched.h>
87
88#define CREATE_TRACE_POINTS
89#include <trace/events/task.h>
90
91/*
92 * Minimum number of threads to boot the kernel
93 */
94#define MIN_THREADS 20
95
96/*
97 * Maximum number of threads
98 */
99#define MAX_THREADS FUTEX_TID_MASK
100
101/*
102 * Protected counters by write_lock_irq(&tasklist_lock)
103 */
104unsigned long total_forks; /* Handle normal Linux uptimes. */
105int nr_threads; /* The idle threads do not count.. */
106
107int max_threads; /* tunable limit on nr_threads */
108
109DEFINE_PER_CPU(unsigned long, process_counts) = 0;
110
111__cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */
112
113#ifdef CONFIG_PROVE_RCU
114int lockdep_tasklist_lock_is_held(void)
115{
116 return lockdep_is_held(&tasklist_lock);
117}
118EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
119#endif /* #ifdef CONFIG_PROVE_RCU */
120
121int nr_processes(void)
122{
123 int cpu;
124 int total = 0;
125
126 for_each_possible_cpu(cpu)
127 total += per_cpu(process_counts, cpu);
128
129 return total;
130}
131
132void __weak arch_release_task_struct(struct task_struct *tsk)
133{
134}
135
136#ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
137static struct kmem_cache *task_struct_cachep;
138
139static inline struct task_struct *alloc_task_struct_node(int node)
140{
141 return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node);
142}
143
144static inline void free_task_struct(struct task_struct *tsk)
145{
146 kmem_cache_free(task_struct_cachep, tsk);
147}
148#endif
149
150void __weak arch_release_thread_info(struct thread_info *ti)
151{
152}
153
154#ifndef CONFIG_ARCH_THREAD_INFO_ALLOCATOR
155
156/*
157 * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
158 * kmemcache based allocator.
159 */
160# if THREAD_SIZE >= PAGE_SIZE
161static struct thread_info *alloc_thread_info_node(struct task_struct *tsk,
162 int node)
163{
164 struct page *page = alloc_kmem_pages_node(node, THREADINFO_GFP,
165 THREAD_SIZE_ORDER);
166
167 return page ? page_address(page) : NULL;
168}
169
170static inline void free_thread_info(struct thread_info *ti)
171{
172 free_kmem_pages((unsigned long)ti, THREAD_SIZE_ORDER);
173}
174# else
175static struct kmem_cache *thread_info_cache;
176
177static struct thread_info *alloc_thread_info_node(struct task_struct *tsk,
178 int node)
179{
180 return kmem_cache_alloc_node(thread_info_cache, THREADINFO_GFP, node);
181}
182
183static void free_thread_info(struct thread_info *ti)
184{
185 kmem_cache_free(thread_info_cache, ti);
186}
187
188void thread_info_cache_init(void)
189{
190 thread_info_cache = kmem_cache_create("thread_info", THREAD_SIZE,
191 THREAD_SIZE, 0, NULL);
192 BUG_ON(thread_info_cache == NULL);
193}
194# endif
195#endif
196
197/* SLAB cache for signal_struct structures (tsk->signal) */
198static struct kmem_cache *signal_cachep;
199
200/* SLAB cache for sighand_struct structures (tsk->sighand) */
201struct kmem_cache *sighand_cachep;
202
203/* SLAB cache for files_struct structures (tsk->files) */
204struct kmem_cache *files_cachep;
205
206/* SLAB cache for fs_struct structures (tsk->fs) */
207struct kmem_cache *fs_cachep;
208
209/* SLAB cache for vm_area_struct structures */
210struct kmem_cache *vm_area_cachep;
211
212/* SLAB cache for mm_struct structures (tsk->mm) */
213static struct kmem_cache *mm_cachep;
214
215static void account_kernel_stack(struct thread_info *ti, int account)
216{
217 struct zone *zone = page_zone(virt_to_page(ti));
218
219 mod_zone_page_state(zone, NR_KERNEL_STACK, account);
220}
221
222void free_task(struct task_struct *tsk)
223{
224 account_kernel_stack(tsk->stack, -1);
225 arch_release_thread_info(tsk->stack);
226 free_thread_info(tsk->stack);
227 rt_mutex_debug_task_free(tsk);
228 ftrace_graph_exit_task(tsk);
229 put_seccomp_filter(tsk);
230 arch_release_task_struct(tsk);
231 free_task_struct(tsk);
232}
233EXPORT_SYMBOL(free_task);
234
235static inline void free_signal_struct(struct signal_struct *sig)
236{
237 taskstats_tgid_free(sig);
238 sched_autogroup_exit(sig);
239 kmem_cache_free(signal_cachep, sig);
240}
241
242static inline void put_signal_struct(struct signal_struct *sig)
243{
244 if (atomic_dec_and_test(&sig->sigcnt))
245 free_signal_struct(sig);
246}
247
248void __put_task_struct(struct task_struct *tsk)
249{
250 WARN_ON(!tsk->exit_state);
251 WARN_ON(atomic_read(&tsk->usage));
252 WARN_ON(tsk == current);
253
254 task_numa_free(tsk);
255 security_task_free(tsk);
256 exit_creds(tsk);
257 delayacct_tsk_free(tsk);
258 put_signal_struct(tsk->signal);
259
260 if (!profile_handoff_task(tsk))
261 free_task(tsk);
262}
263EXPORT_SYMBOL_GPL(__put_task_struct);
264
265void __init __weak arch_task_cache_init(void) { }
266
267/*
268 * set_max_threads
269 */
270static void set_max_threads(unsigned int max_threads_suggested)
271{
272 u64 threads;
273
274 /*
275 * The number of threads shall be limited such that the thread
276 * structures may only consume a small part of the available memory.
277 */
278 if (fls64(totalram_pages) + fls64(PAGE_SIZE) > 64)
279 threads = MAX_THREADS;
280 else
281 threads = div64_u64((u64) totalram_pages * (u64) PAGE_SIZE,
282 (u64) THREAD_SIZE * 8UL);
283
284 if (threads > max_threads_suggested)
285 threads = max_threads_suggested;
286
287 max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS);
288}
289
290void __init fork_init(void)
291{
292#ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
293#ifndef ARCH_MIN_TASKALIGN
294#define ARCH_MIN_TASKALIGN L1_CACHE_BYTES
295#endif
296 /* create a slab on which task_structs can be allocated */
297 task_struct_cachep =
298 kmem_cache_create("task_struct", sizeof(struct task_struct),
299 ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL);
300#endif
301
302 /* do the arch specific task caches init */
303 arch_task_cache_init();
304
305 set_max_threads(MAX_THREADS);
306
307 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
308 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
309 init_task.signal->rlim[RLIMIT_SIGPENDING] =
310 init_task.signal->rlim[RLIMIT_NPROC];
311}
312
313int __weak arch_dup_task_struct(struct task_struct *dst,
314 struct task_struct *src)
315{
316 *dst = *src;
317 return 0;
318}
319
320void set_task_stack_end_magic(struct task_struct *tsk)
321{
322 unsigned long *stackend;
323
324 stackend = end_of_stack(tsk);
325 *stackend = STACK_END_MAGIC; /* for overflow detection */
326}
327
328static struct task_struct *dup_task_struct(struct task_struct *orig)
329{
330 struct task_struct *tsk;
331 struct thread_info *ti;
332 int node = tsk_fork_get_node(orig);
333 int err;
334
335 tsk = alloc_task_struct_node(node);
336 if (!tsk)
337 return NULL;
338
339 ti = alloc_thread_info_node(tsk, node);
340 if (!ti)
341 goto free_tsk;
342
343 err = arch_dup_task_struct(tsk, orig);
344 if (err)
345 goto free_ti;
346
347 tsk->stack = ti;
348#ifdef CONFIG_SECCOMP
349 /*
350 * We must handle setting up seccomp filters once we're under
351 * the sighand lock in case orig has changed between now and
352 * then. Until then, filter must be NULL to avoid messing up
353 * the usage counts on the error path calling free_task.
354 */
355 tsk->seccomp.filter = NULL;
356#endif
357
358 setup_thread_stack(tsk, orig);
359 clear_user_return_notifier(tsk);
360 clear_tsk_need_resched(tsk);
361 set_task_stack_end_magic(tsk);
362
363#ifdef CONFIG_CC_STACKPROTECTOR
364 tsk->stack_canary = get_random_int();
365#endif
366
367 /*
368 * One for us, one for whoever does the "release_task()" (usually
369 * parent)
370 */
371 atomic_set(&tsk->usage, 2);
372#ifdef CONFIG_BLK_DEV_IO_TRACE
373 tsk->btrace_seq = 0;
374#endif
375 tsk->splice_pipe = NULL;
376 tsk->task_frag.page = NULL;
377
378 account_kernel_stack(ti, 1);
379
380 return tsk;
381
382free_ti:
383 free_thread_info(ti);
384free_tsk:
385 free_task_struct(tsk);
386 return NULL;
387}
388
389#ifdef CONFIG_MMU
390static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
391{
392 struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
393 struct rb_node **rb_link, *rb_parent;
394 int retval;
395 unsigned long charge;
396
397 uprobe_start_dup_mmap();
398 down_write(&oldmm->mmap_sem);
399 flush_cache_dup_mm(oldmm);
400 uprobe_dup_mmap(oldmm, mm);
401 /*
402 * Not linked in yet - no deadlock potential:
403 */
404 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
405
406 /* No ordering required: file already has been exposed. */
407 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
408
409 mm->total_vm = oldmm->total_vm;
410 mm->shared_vm = oldmm->shared_vm;
411 mm->exec_vm = oldmm->exec_vm;
412 mm->stack_vm = oldmm->stack_vm;
413
414 rb_link = &mm->mm_rb.rb_node;
415 rb_parent = NULL;
416 pprev = &mm->mmap;
417 retval = ksm_fork(mm, oldmm);
418 if (retval)
419 goto out;
420 retval = khugepaged_fork(mm, oldmm);
421 if (retval)
422 goto out;
423
424 prev = NULL;
425 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
426 struct file *file;
427
428 if (mpnt->vm_flags & VM_DONTCOPY) {
429 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
430 -vma_pages(mpnt));
431 continue;
432 }
433 charge = 0;
434 if (mpnt->vm_flags & VM_ACCOUNT) {
435 unsigned long len = vma_pages(mpnt);
436
437 if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
438 goto fail_nomem;
439 charge = len;
440 }
441 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
442 if (!tmp)
443 goto fail_nomem;
444 *tmp = *mpnt;
445 INIT_LIST_HEAD(&tmp->anon_vma_chain);
446 retval = vma_dup_policy(mpnt, tmp);
447 if (retval)
448 goto fail_nomem_policy;
449 tmp->vm_mm = mm;
450 if (anon_vma_fork(tmp, mpnt))
451 goto fail_nomem_anon_vma_fork;
452 tmp->vm_flags &= ~VM_LOCKED;
453 tmp->vm_next = tmp->vm_prev = NULL;
454 file = tmp->vm_file;
455 if (file) {
456 struct inode *inode = file_inode(file);
457 struct address_space *mapping = file->f_mapping;
458
459 get_file(file);
460 if (tmp->vm_flags & VM_DENYWRITE)
461 atomic_dec(&inode->i_writecount);
462 i_mmap_lock_write(mapping);
463 if (tmp->vm_flags & VM_SHARED)
464 atomic_inc(&mapping->i_mmap_writable);
465 flush_dcache_mmap_lock(mapping);
466 /* insert tmp into the share list, just after mpnt */
467 vma_interval_tree_insert_after(tmp, mpnt,
468 &mapping->i_mmap);
469 flush_dcache_mmap_unlock(mapping);
470 i_mmap_unlock_write(mapping);
471 }
472
473 /*
474 * Clear hugetlb-related page reserves for children. This only
475 * affects MAP_PRIVATE mappings. Faults generated by the child
476 * are not guaranteed to succeed, even if read-only
477 */
478 if (is_vm_hugetlb_page(tmp))
479 reset_vma_resv_huge_pages(tmp);
480
481 /*
482 * Link in the new vma and copy the page table entries.
483 */
484 *pprev = tmp;
485 pprev = &tmp->vm_next;
486 tmp->vm_prev = prev;
487 prev = tmp;
488
489 __vma_link_rb(mm, tmp, rb_link, rb_parent);
490 rb_link = &tmp->vm_rb.rb_right;
491 rb_parent = &tmp->vm_rb;
492
493 mm->map_count++;
494 retval = copy_page_range(mm, oldmm, mpnt);
495
496 if (tmp->vm_ops && tmp->vm_ops->open)
497 tmp->vm_ops->open(tmp);
498
499 if (retval)
500 goto out;
501 }
502 /* a new mm has just been created */
503 arch_dup_mmap(oldmm, mm);
504 retval = 0;
505out:
506 up_write(&mm->mmap_sem);
507 flush_tlb_mm(oldmm);
508 up_write(&oldmm->mmap_sem);
509 uprobe_end_dup_mmap();
510 return retval;
511fail_nomem_anon_vma_fork:
512 mpol_put(vma_policy(tmp));
513fail_nomem_policy:
514 kmem_cache_free(vm_area_cachep, tmp);
515fail_nomem:
516 retval = -ENOMEM;
517 vm_unacct_memory(charge);
518 goto out;
519}
520
521static inline int mm_alloc_pgd(struct mm_struct *mm)
522{
523 mm->pgd = pgd_alloc(mm);
524 if (unlikely(!mm->pgd))
525 return -ENOMEM;
526 return 0;
527}
528
529static inline void mm_free_pgd(struct mm_struct *mm)
530{
531 pgd_free(mm, mm->pgd);
532}
533#else
534static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
535{
536 down_write(&oldmm->mmap_sem);
537 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
538 up_write(&oldmm->mmap_sem);
539 return 0;
540}
541#define mm_alloc_pgd(mm) (0)
542#define mm_free_pgd(mm)
543#endif /* CONFIG_MMU */
544
545__cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
546
547#define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
548#define free_mm(mm) (kmem_cache_free(mm_cachep, (mm)))
549
550static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
551
552static int __init coredump_filter_setup(char *s)
553{
554 default_dump_filter =
555 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
556 MMF_DUMP_FILTER_MASK;
557 return 1;
558}
559
560__setup("coredump_filter=", coredump_filter_setup);
561
562#include <linux/init_task.h>
563
564static void mm_init_aio(struct mm_struct *mm)
565{
566#ifdef CONFIG_AIO
567 spin_lock_init(&mm->ioctx_lock);
568 mm->ioctx_table = NULL;
569#endif
570}
571
572static void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
573{
574#ifdef CONFIG_MEMCG
575 mm->owner = p;
576#endif
577}
578
579static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p)
580{
581 mm->mmap = NULL;
582 mm->mm_rb = RB_ROOT;
583 mm->vmacache_seqnum = 0;
584 atomic_set(&mm->mm_users, 1);
585 atomic_set(&mm->mm_count, 1);
586 init_rwsem(&mm->mmap_sem);
587 INIT_LIST_HEAD(&mm->mmlist);
588 mm->core_state = NULL;
589 atomic_long_set(&mm->nr_ptes, 0);
590 mm_nr_pmds_init(mm);
591 mm->map_count = 0;
592 mm->locked_vm = 0;
593 mm->pinned_vm = 0;
594 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
595 spin_lock_init(&mm->page_table_lock);
596 mm_init_cpumask(mm);
597 mm_init_aio(mm);
598 mm_init_owner(mm, p);
599 mmu_notifier_mm_init(mm);
600 clear_tlb_flush_pending(mm);
601#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
602 mm->pmd_huge_pte = NULL;
603#endif
604
605 if (current->mm) {
606 mm->flags = current->mm->flags & MMF_INIT_MASK;
607 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK;
608 } else {
609 mm->flags = default_dump_filter;
610 mm->def_flags = 0;
611 }
612
613 if (mm_alloc_pgd(mm))
614 goto fail_nopgd;
615
616 if (init_new_context(p, mm))
617 goto fail_nocontext;
618
619 return mm;
620
621fail_nocontext:
622 mm_free_pgd(mm);
623fail_nopgd:
624 free_mm(mm);
625 return NULL;
626}
627
628static void check_mm(struct mm_struct *mm)
629{
630 int i;
631
632 for (i = 0; i < NR_MM_COUNTERS; i++) {
633 long x = atomic_long_read(&mm->rss_stat.count[i]);
634
635 if (unlikely(x))
636 printk(KERN_ALERT "BUG: Bad rss-counter state "
637 "mm:%p idx:%d val:%ld\n", mm, i, x);
638 }
639
640 if (atomic_long_read(&mm->nr_ptes))
641 pr_alert("BUG: non-zero nr_ptes on freeing mm: %ld\n",
642 atomic_long_read(&mm->nr_ptes));
643 if (mm_nr_pmds(mm))
644 pr_alert("BUG: non-zero nr_pmds on freeing mm: %ld\n",
645 mm_nr_pmds(mm));
646
647#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
648 VM_BUG_ON_MM(mm->pmd_huge_pte, mm);
649#endif
650}
651
652/*
653 * Allocate and initialize an mm_struct.
654 */
655struct mm_struct *mm_alloc(void)
656{
657 struct mm_struct *mm;
658
659 mm = allocate_mm();
660 if (!mm)
661 return NULL;
662
663 memset(mm, 0, sizeof(*mm));
664 return mm_init(mm, current);
665}
666
667/*
668 * Called when the last reference to the mm
669 * is dropped: either by a lazy thread or by
670 * mmput. Free the page directory and the mm.
671 */
672void __mmdrop(struct mm_struct *mm)
673{
674 BUG_ON(mm == &init_mm);
675 mm_free_pgd(mm);
676 destroy_context(mm);
677 mmu_notifier_mm_destroy(mm);
678 check_mm(mm);
679 free_mm(mm);
680}
681EXPORT_SYMBOL_GPL(__mmdrop);
682
683/*
684 * Decrement the use count and release all resources for an mm.
685 */
686void mmput(struct mm_struct *mm)
687{
688 might_sleep();
689
690 if (atomic_dec_and_test(&mm->mm_users)) {
691 uprobe_clear_state(mm);
692 exit_aio(mm);
693 ksm_exit(mm);
694 khugepaged_exit(mm); /* must run before exit_mmap */
695 exit_mmap(mm);
696 set_mm_exe_file(mm, NULL);
697 if (!list_empty(&mm->mmlist)) {
698 spin_lock(&mmlist_lock);
699 list_del(&mm->mmlist);
700 spin_unlock(&mmlist_lock);
701 }
702 if (mm->binfmt)
703 module_put(mm->binfmt->module);
704 mmdrop(mm);
705 }
706}
707EXPORT_SYMBOL_GPL(mmput);
708
709/**
710 * set_mm_exe_file - change a reference to the mm's executable file
711 *
712 * This changes mm's executable file (shown as symlink /proc/[pid]/exe).
713 *
714 * Main users are mmput() and sys_execve(). Callers prevent concurrent
715 * invocations: in mmput() nobody alive left, in execve task is single
716 * threaded. sys_prctl(PR_SET_MM_MAP/EXE_FILE) also needs to set the
717 * mm->exe_file, but does so without using set_mm_exe_file() in order
718 * to do avoid the need for any locks.
719 */
720void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
721{
722 struct file *old_exe_file;
723
724 /*
725 * It is safe to dereference the exe_file without RCU as
726 * this function is only called if nobody else can access
727 * this mm -- see comment above for justification.
728 */
729 old_exe_file = rcu_dereference_raw(mm->exe_file);
730
731 if (new_exe_file)
732 get_file(new_exe_file);
733 rcu_assign_pointer(mm->exe_file, new_exe_file);
734 if (old_exe_file)
735 fput(old_exe_file);
736}
737
738/**
739 * get_mm_exe_file - acquire a reference to the mm's executable file
740 *
741 * Returns %NULL if mm has no associated executable file.
742 * User must release file via fput().
743 */
744struct file *get_mm_exe_file(struct mm_struct *mm)
745{
746 struct file *exe_file;
747
748 rcu_read_lock();
749 exe_file = rcu_dereference(mm->exe_file);
750 if (exe_file && !get_file_rcu(exe_file))
751 exe_file = NULL;
752 rcu_read_unlock();
753 return exe_file;
754}
755EXPORT_SYMBOL(get_mm_exe_file);
756
757/**
758 * get_task_mm - acquire a reference to the task's mm
759 *
760 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning
761 * this kernel workthread has transiently adopted a user mm with use_mm,
762 * to do its AIO) is not set and if so returns a reference to it, after
763 * bumping up the use count. User must release the mm via mmput()
764 * after use. Typically used by /proc and ptrace.
765 */
766struct mm_struct *get_task_mm(struct task_struct *task)
767{
768 struct mm_struct *mm;
769
770 task_lock(task);
771 mm = task->mm;
772 if (mm) {
773 if (task->flags & PF_KTHREAD)
774 mm = NULL;
775 else
776 atomic_inc(&mm->mm_users);
777 }
778 task_unlock(task);
779 return mm;
780}
781EXPORT_SYMBOL_GPL(get_task_mm);
782
783struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
784{
785 struct mm_struct *mm;
786 int err;
787
788 err = mutex_lock_killable(&task->signal->cred_guard_mutex);
789 if (err)
790 return ERR_PTR(err);
791
792 mm = get_task_mm(task);
793 if (mm && mm != current->mm &&
794 !ptrace_may_access(task, mode)) {
795 mmput(mm);
796 mm = ERR_PTR(-EACCES);
797 }
798 mutex_unlock(&task->signal->cred_guard_mutex);
799
800 return mm;
801}
802
803static void complete_vfork_done(struct task_struct *tsk)
804{
805 struct completion *vfork;
806
807 task_lock(tsk);
808 vfork = tsk->vfork_done;
809 if (likely(vfork)) {
810 tsk->vfork_done = NULL;
811 complete(vfork);
812 }
813 task_unlock(tsk);
814}
815
816static int wait_for_vfork_done(struct task_struct *child,
817 struct completion *vfork)
818{
819 int killed;
820
821 freezer_do_not_count();
822 killed = wait_for_completion_killable(vfork);
823 freezer_count();
824
825 if (killed) {
826 task_lock(child);
827 child->vfork_done = NULL;
828 task_unlock(child);
829 }
830
831 put_task_struct(child);
832 return killed;
833}
834
835/* Please note the differences between mmput and mm_release.
836 * mmput is called whenever we stop holding onto a mm_struct,
837 * error success whatever.
838 *
839 * mm_release is called after a mm_struct has been removed
840 * from the current process.
841 *
842 * This difference is important for error handling, when we
843 * only half set up a mm_struct for a new process and need to restore
844 * the old one. Because we mmput the new mm_struct before
845 * restoring the old one. . .
846 * Eric Biederman 10 January 1998
847 */
848void mm_release(struct task_struct *tsk, struct mm_struct *mm)
849{
850 /* Get rid of any futexes when releasing the mm */
851#ifdef CONFIG_FUTEX
852 if (unlikely(tsk->robust_list)) {
853 exit_robust_list(tsk);
854 tsk->robust_list = NULL;
855 }
856#ifdef CONFIG_COMPAT
857 if (unlikely(tsk->compat_robust_list)) {
858 compat_exit_robust_list(tsk);
859 tsk->compat_robust_list = NULL;
860 }
861#endif
862 if (unlikely(!list_empty(&tsk->pi_state_list)))
863 exit_pi_state_list(tsk);
864#endif
865
866 uprobe_free_utask(tsk);
867
868 /* Get rid of any cached register state */
869 deactivate_mm(tsk, mm);
870
871 /*
872 * If we're exiting normally, clear a user-space tid field if
873 * requested. We leave this alone when dying by signal, to leave
874 * the value intact in a core dump, and to save the unnecessary
875 * trouble, say, a killed vfork parent shouldn't touch this mm.
876 * Userland only wants this done for a sys_exit.
877 */
878 if (tsk->clear_child_tid) {
879 if (!(tsk->flags & PF_SIGNALED) &&
880 atomic_read(&mm->mm_users) > 1) {
881 /*
882 * We don't check the error code - if userspace has
883 * not set up a proper pointer then tough luck.
884 */
885 put_user(0, tsk->clear_child_tid);
886 sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
887 1, NULL, NULL, 0);
888 }
889 tsk->clear_child_tid = NULL;
890 }
891
892 /*
893 * All done, finally we can wake up parent and return this mm to him.
894 * Also kthread_stop() uses this completion for synchronization.
895 */
896 if (tsk->vfork_done)
897 complete_vfork_done(tsk);
898}
899
900/*
901 * Allocate a new mm structure and copy contents from the
902 * mm structure of the passed in task structure.
903 */
904static struct mm_struct *dup_mm(struct task_struct *tsk)
905{
906 struct mm_struct *mm, *oldmm = current->mm;
907 int err;
908
909 mm = allocate_mm();
910 if (!mm)
911 goto fail_nomem;
912
913 memcpy(mm, oldmm, sizeof(*mm));
914
915 if (!mm_init(mm, tsk))
916 goto fail_nomem;
917
918 err = dup_mmap(mm, oldmm);
919 if (err)
920 goto free_pt;
921
922 mm->hiwater_rss = get_mm_rss(mm);
923 mm->hiwater_vm = mm->total_vm;
924
925 if (mm->binfmt && !try_module_get(mm->binfmt->module))
926 goto free_pt;
927
928 return mm;
929
930free_pt:
931 /* don't put binfmt in mmput, we haven't got module yet */
932 mm->binfmt = NULL;
933 mmput(mm);
934
935fail_nomem:
936 return NULL;
937}
938
939static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
940{
941 struct mm_struct *mm, *oldmm;
942 int retval;
943
944 tsk->min_flt = tsk->maj_flt = 0;
945 tsk->nvcsw = tsk->nivcsw = 0;
946#ifdef CONFIG_DETECT_HUNG_TASK
947 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
948#endif
949
950 tsk->mm = NULL;
951 tsk->active_mm = NULL;
952
953 /*
954 * Are we cloning a kernel thread?
955 *
956 * We need to steal a active VM for that..
957 */
958 oldmm = current->mm;
959 if (!oldmm)
960 return 0;
961
962 /* initialize the new vmacache entries */
963 vmacache_flush(tsk);
964
965 if (clone_flags & CLONE_VM) {
966 atomic_inc(&oldmm->mm_users);
967 mm = oldmm;
968 goto good_mm;
969 }
970
971 retval = -ENOMEM;
972 mm = dup_mm(tsk);
973 if (!mm)
974 goto fail_nomem;
975
976good_mm:
977 tsk->mm = mm;
978 tsk->active_mm = mm;
979 return 0;
980
981fail_nomem:
982 return retval;
983}
984
985static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
986{
987 struct fs_struct *fs = current->fs;
988 if (clone_flags & CLONE_FS) {
989 /* tsk->fs is already what we want */
990 spin_lock(&fs->lock);
991 if (fs->in_exec) {
992 spin_unlock(&fs->lock);
993 return -EAGAIN;
994 }
995 fs->users++;
996 spin_unlock(&fs->lock);
997 return 0;
998 }
999 tsk->fs = copy_fs_struct(fs);
1000 if (!tsk->fs)
1001 return -ENOMEM;
1002 return 0;
1003}
1004
1005static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
1006{
1007 struct files_struct *oldf, *newf;
1008 int error = 0;
1009
1010 /*
1011 * A background process may not have any files ...
1012 */
1013 oldf = current->files;
1014 if (!oldf)
1015 goto out;
1016
1017 if (clone_flags & CLONE_FILES) {
1018 atomic_inc(&oldf->count);
1019 goto out;
1020 }
1021
1022 newf = dup_fd(oldf, &error);
1023 if (!newf)
1024 goto out;
1025
1026 tsk->files = newf;
1027 error = 0;
1028out:
1029 return error;
1030}
1031
1032static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
1033{
1034#ifdef CONFIG_BLOCK
1035 struct io_context *ioc = current->io_context;
1036 struct io_context *new_ioc;
1037
1038 if (!ioc)
1039 return 0;
1040 /*
1041 * Share io context with parent, if CLONE_IO is set
1042 */
1043 if (clone_flags & CLONE_IO) {
1044 ioc_task_link(ioc);
1045 tsk->io_context = ioc;
1046 } else if (ioprio_valid(ioc->ioprio)) {
1047 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE);
1048 if (unlikely(!new_ioc))
1049 return -ENOMEM;
1050
1051 new_ioc->ioprio = ioc->ioprio;
1052 put_io_context(new_ioc);
1053 }
1054#endif
1055 return 0;
1056}
1057
1058static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
1059{
1060 struct sighand_struct *sig;
1061
1062 if (clone_flags & CLONE_SIGHAND) {
1063 atomic_inc(&current->sighand->count);
1064 return 0;
1065 }
1066 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1067 rcu_assign_pointer(tsk->sighand, sig);
1068 if (!sig)
1069 return -ENOMEM;
1070 atomic_set(&sig->count, 1);
1071 memcpy(sig->action, current->sighand->action, sizeof(sig->action));
1072 return 0;
1073}
1074
1075void __cleanup_sighand(struct sighand_struct *sighand)
1076{
1077 if (atomic_dec_and_test(&sighand->count)) {
1078 signalfd_cleanup(sighand);
1079 /*
1080 * sighand_cachep is SLAB_DESTROY_BY_RCU so we can free it
1081 * without an RCU grace period, see __lock_task_sighand().
1082 */
1083 kmem_cache_free(sighand_cachep, sighand);
1084 }
1085}
1086
1087/*
1088 * Initialize POSIX timer handling for a thread group.
1089 */
1090static void posix_cpu_timers_init_group(struct signal_struct *sig)
1091{
1092 unsigned long cpu_limit;
1093
1094 cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1095 if (cpu_limit != RLIM_INFINITY) {
1096 sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit);
1097 sig->cputimer.running = 1;
1098 }
1099
1100 /* The timer lists. */
1101 INIT_LIST_HEAD(&sig->cpu_timers[0]);
1102 INIT_LIST_HEAD(&sig->cpu_timers[1]);
1103 INIT_LIST_HEAD(&sig->cpu_timers[2]);
1104}
1105
1106static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
1107{
1108 struct signal_struct *sig;
1109
1110 if (clone_flags & CLONE_THREAD)
1111 return 0;
1112
1113 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
1114 tsk->signal = sig;
1115 if (!sig)
1116 return -ENOMEM;
1117
1118 sig->nr_threads = 1;
1119 atomic_set(&sig->live, 1);
1120 atomic_set(&sig->sigcnt, 1);
1121
1122 /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */
1123 sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node);
1124 tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head);
1125
1126 init_waitqueue_head(&sig->wait_chldexit);
1127 sig->curr_target = tsk;
1128 init_sigpending(&sig->shared_pending);
1129 INIT_LIST_HEAD(&sig->posix_timers);
1130 seqlock_init(&sig->stats_lock);
1131
1132 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1133 sig->real_timer.function = it_real_fn;
1134
1135 task_lock(current->group_leader);
1136 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
1137 task_unlock(current->group_leader);
1138
1139 posix_cpu_timers_init_group(sig);
1140
1141 tty_audit_fork(sig);
1142 sched_autogroup_fork(sig);
1143
1144 sig->oom_score_adj = current->signal->oom_score_adj;
1145 sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1146
1147 sig->has_child_subreaper = current->signal->has_child_subreaper ||
1148 current->signal->is_child_subreaper;
1149
1150 mutex_init(&sig->cred_guard_mutex);
1151
1152 return 0;
1153}
1154
1155static void copy_seccomp(struct task_struct *p)
1156{
1157#ifdef CONFIG_SECCOMP
1158 /*
1159 * Must be called with sighand->lock held, which is common to
1160 * all threads in the group. Holding cred_guard_mutex is not
1161 * needed because this new task is not yet running and cannot
1162 * be racing exec.
1163 */
1164 assert_spin_locked(&current->sighand->siglock);
1165
1166 /* Ref-count the new filter user, and assign it. */
1167 get_seccomp_filter(current);
1168 p->seccomp = current->seccomp;
1169
1170 /*
1171 * Explicitly enable no_new_privs here in case it got set
1172 * between the task_struct being duplicated and holding the
1173 * sighand lock. The seccomp state and nnp must be in sync.
1174 */
1175 if (task_no_new_privs(current))
1176 task_set_no_new_privs(p);
1177
1178 /*
1179 * If the parent gained a seccomp mode after copying thread
1180 * flags and between before we held the sighand lock, we have
1181 * to manually enable the seccomp thread flag here.
1182 */
1183 if (p->seccomp.mode != SECCOMP_MODE_DISABLED)
1184 set_tsk_thread_flag(p, TIF_SECCOMP);
1185#endif
1186}
1187
1188SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1189{
1190 current->clear_child_tid = tidptr;
1191
1192 return task_pid_vnr(current);
1193}
1194
1195static void rt_mutex_init_task(struct task_struct *p)
1196{
1197 raw_spin_lock_init(&p->pi_lock);
1198#ifdef CONFIG_RT_MUTEXES
1199 p->pi_waiters = RB_ROOT;
1200 p->pi_waiters_leftmost = NULL;
1201 p->pi_blocked_on = NULL;
1202#endif
1203}
1204
1205/*
1206 * Initialize POSIX timer handling for a single task.
1207 */
1208static void posix_cpu_timers_init(struct task_struct *tsk)
1209{
1210 tsk->cputime_expires.prof_exp = 0;
1211 tsk->cputime_expires.virt_exp = 0;
1212 tsk->cputime_expires.sched_exp = 0;
1213 INIT_LIST_HEAD(&tsk->cpu_timers[0]);
1214 INIT_LIST_HEAD(&tsk->cpu_timers[1]);
1215 INIT_LIST_HEAD(&tsk->cpu_timers[2]);
1216}
1217
1218static inline void
1219init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid)
1220{
1221 task->pids[type].pid = pid;
1222}
1223
1224/*
1225 * This creates a new process as a copy of the old one,
1226 * but does not actually start it yet.
1227 *
1228 * It copies the registers, and all the appropriate
1229 * parts of the process environment (as per the clone
1230 * flags). The actual kick-off is left to the caller.
1231 */
1232static struct task_struct *copy_process(unsigned long clone_flags,
1233 unsigned long stack_start,
1234 unsigned long stack_size,
1235 int __user *child_tidptr,
1236 struct pid *pid,
1237 int trace,
1238 unsigned long tls)
1239{
1240 int retval;
1241 struct task_struct *p;
1242
1243 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1244 return ERR_PTR(-EINVAL);
1245
1246 if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS))
1247 return ERR_PTR(-EINVAL);
1248
1249 /*
1250 * Thread groups must share signals as well, and detached threads
1251 * can only be started up within the thread group.
1252 */
1253 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1254 return ERR_PTR(-EINVAL);
1255
1256 /*
1257 * Shared signal handlers imply shared VM. By way of the above,
1258 * thread groups also imply shared VM. Blocking this case allows
1259 * for various simplifications in other code.
1260 */
1261 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1262 return ERR_PTR(-EINVAL);
1263
1264 /*
1265 * Siblings of global init remain as zombies on exit since they are
1266 * not reaped by their parent (swapper). To solve this and to avoid
1267 * multi-rooted process trees, prevent global and container-inits
1268 * from creating siblings.
1269 */
1270 if ((clone_flags & CLONE_PARENT) &&
1271 current->signal->flags & SIGNAL_UNKILLABLE)
1272 return ERR_PTR(-EINVAL);
1273
1274 /*
1275 * If the new process will be in a different pid or user namespace
1276 * do not allow it to share a thread group or signal handlers or
1277 * parent with the forking task.
1278 */
1279 if (clone_flags & CLONE_SIGHAND) {
1280 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) ||
1281 (task_active_pid_ns(current) !=
1282 current->nsproxy->pid_ns_for_children))
1283 return ERR_PTR(-EINVAL);
1284 }
1285
1286 retval = security_task_create(clone_flags);
1287 if (retval)
1288 goto fork_out;
1289
1290 retval = -ENOMEM;
1291 p = dup_task_struct(current);
1292 if (!p)
1293 goto fork_out;
1294
1295 ftrace_graph_init_task(p);
1296
1297 rt_mutex_init_task(p);
1298
1299#ifdef CONFIG_PROVE_LOCKING
1300 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1301 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1302#endif
1303 retval = -EAGAIN;
1304 if (atomic_read(&p->real_cred->user->processes) >=
1305 task_rlimit(p, RLIMIT_NPROC)) {
1306 if (p->real_cred->user != INIT_USER &&
1307 !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
1308 goto bad_fork_free;
1309 }
1310 current->flags &= ~PF_NPROC_EXCEEDED;
1311
1312 retval = copy_creds(p, clone_flags);
1313 if (retval < 0)
1314 goto bad_fork_free;
1315
1316 /*
1317 * If multiple threads are within copy_process(), then this check
1318 * triggers too late. This doesn't hurt, the check is only there
1319 * to stop root fork bombs.
1320 */
1321 retval = -EAGAIN;
1322 if (nr_threads >= max_threads)
1323 goto bad_fork_cleanup_count;
1324
1325 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */
1326 p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER);
1327 p->flags |= PF_FORKNOEXEC;
1328 INIT_LIST_HEAD(&p->children);
1329 INIT_LIST_HEAD(&p->sibling);
1330 rcu_copy_process(p);
1331 p->vfork_done = NULL;
1332 spin_lock_init(&p->alloc_lock);
1333
1334 init_sigpending(&p->pending);
1335
1336 p->utime = p->stime = p->gtime = 0;
1337 p->utimescaled = p->stimescaled = 0;
1338#ifndef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
1339 p->prev_cputime.utime = p->prev_cputime.stime = 0;
1340#endif
1341#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
1342 seqlock_init(&p->vtime_seqlock);
1343 p->vtime_snap = 0;
1344 p->vtime_snap_whence = VTIME_SLEEPING;
1345#endif
1346
1347#if defined(SPLIT_RSS_COUNTING)
1348 memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1349#endif
1350
1351 p->default_timer_slack_ns = current->timer_slack_ns;
1352
1353 task_io_accounting_init(&p->ioac);
1354 acct_clear_integrals(p);
1355
1356 posix_cpu_timers_init(p);
1357
1358 p->start_time = ktime_get_ns();
1359 p->real_start_time = ktime_get_boot_ns();
1360 p->io_context = NULL;
1361 p->audit_context = NULL;
1362 if (clone_flags & CLONE_THREAD)
1363 threadgroup_change_begin(current);
1364 cgroup_fork(p);
1365#ifdef CONFIG_NUMA
1366 p->mempolicy = mpol_dup(p->mempolicy);
1367 if (IS_ERR(p->mempolicy)) {
1368 retval = PTR_ERR(p->mempolicy);
1369 p->mempolicy = NULL;
1370 goto bad_fork_cleanup_threadgroup_lock;
1371 }
1372#endif
1373#ifdef CONFIG_CPUSETS
1374 p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
1375 p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
1376 seqcount_init(&p->mems_allowed_seq);
1377#endif
1378#ifdef CONFIG_TRACE_IRQFLAGS
1379 p->irq_events = 0;
1380 p->hardirqs_enabled = 0;
1381 p->hardirq_enable_ip = 0;
1382 p->hardirq_enable_event = 0;
1383 p->hardirq_disable_ip = _THIS_IP_;
1384 p->hardirq_disable_event = 0;
1385 p->softirqs_enabled = 1;
1386 p->softirq_enable_ip = _THIS_IP_;
1387 p->softirq_enable_event = 0;
1388 p->softirq_disable_ip = 0;
1389 p->softirq_disable_event = 0;
1390 p->hardirq_context = 0;
1391 p->softirq_context = 0;
1392#endif
1393
1394 p->pagefault_disabled = 0;
1395
1396#ifdef CONFIG_LOCKDEP
1397 p->lockdep_depth = 0; /* no locks held yet */
1398 p->curr_chain_key = 0;
1399 p->lockdep_recursion = 0;
1400#endif
1401
1402#ifdef CONFIG_DEBUG_MUTEXES
1403 p->blocked_on = NULL; /* not blocked yet */
1404#endif
1405#ifdef CONFIG_BCACHE
1406 p->sequential_io = 0;
1407 p->sequential_io_avg = 0;
1408#endif
1409
1410 /* Perform scheduler related setup. Assign this task to a CPU. */
1411 retval = sched_fork(clone_flags, p);
1412 if (retval)
1413 goto bad_fork_cleanup_policy;
1414
1415 retval = perf_event_init_task(p);
1416 if (retval)
1417 goto bad_fork_cleanup_policy;
1418 retval = audit_alloc(p);
1419 if (retval)
1420 goto bad_fork_cleanup_perf;
1421 /* copy all the process information */
1422 shm_init_task(p);
1423 retval = copy_semundo(clone_flags, p);
1424 if (retval)
1425 goto bad_fork_cleanup_audit;
1426 retval = copy_files(clone_flags, p);
1427 if (retval)
1428 goto bad_fork_cleanup_semundo;
1429 retval = copy_fs(clone_flags, p);
1430 if (retval)
1431 goto bad_fork_cleanup_files;
1432 retval = copy_sighand(clone_flags, p);
1433 if (retval)
1434 goto bad_fork_cleanup_fs;
1435 retval = copy_signal(clone_flags, p);
1436 if (retval)
1437 goto bad_fork_cleanup_sighand;
1438 retval = copy_mm(clone_flags, p);
1439 if (retval)
1440 goto bad_fork_cleanup_signal;
1441 retval = copy_namespaces(clone_flags, p);
1442 if (retval)
1443 goto bad_fork_cleanup_mm;
1444 retval = copy_io(clone_flags, p);
1445 if (retval)
1446 goto bad_fork_cleanup_namespaces;
1447 retval = copy_thread_tls(clone_flags, stack_start, stack_size, p, tls);
1448 if (retval)
1449 goto bad_fork_cleanup_io;
1450
1451 if (pid != &init_struct_pid) {
1452 pid = alloc_pid(p->nsproxy->pid_ns_for_children);
1453 if (IS_ERR(pid)) {
1454 retval = PTR_ERR(pid);
1455 goto bad_fork_cleanup_io;
1456 }
1457 }
1458
1459 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1460 /*
1461 * Clear TID on mm_release()?
1462 */
1463 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL;
1464#ifdef CONFIG_BLOCK
1465 p->plug = NULL;
1466#endif
1467#ifdef CONFIG_FUTEX
1468 p->robust_list = NULL;
1469#ifdef CONFIG_COMPAT
1470 p->compat_robust_list = NULL;
1471#endif
1472 INIT_LIST_HEAD(&p->pi_state_list);
1473 p->pi_state_cache = NULL;
1474#endif
1475 /*
1476 * sigaltstack should be cleared when sharing the same VM
1477 */
1478 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1479 p->sas_ss_sp = p->sas_ss_size = 0;
1480
1481 /*
1482 * Syscall tracing and stepping should be turned off in the
1483 * child regardless of CLONE_PTRACE.
1484 */
1485 user_disable_single_step(p);
1486 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1487#ifdef TIF_SYSCALL_EMU
1488 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1489#endif
1490 clear_all_latency_tracing(p);
1491
1492 /* ok, now we should be set up.. */
1493 p->pid = pid_nr(pid);
1494 if (clone_flags & CLONE_THREAD) {
1495 p->exit_signal = -1;
1496 p->group_leader = current->group_leader;
1497 p->tgid = current->tgid;
1498 } else {
1499 if (clone_flags & CLONE_PARENT)
1500 p->exit_signal = current->group_leader->exit_signal;
1501 else
1502 p->exit_signal = (clone_flags & CSIGNAL);
1503 p->group_leader = p;
1504 p->tgid = p->pid;
1505 }
1506
1507 p->nr_dirtied = 0;
1508 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
1509 p->dirty_paused_when = 0;
1510
1511 p->pdeath_signal = 0;
1512 INIT_LIST_HEAD(&p->thread_group);
1513 p->task_works = NULL;
1514
1515 /*
1516 * Make it visible to the rest of the system, but dont wake it up yet.
1517 * Need tasklist lock for parent etc handling!
1518 */
1519 write_lock_irq(&tasklist_lock);
1520
1521 /* CLONE_PARENT re-uses the old parent */
1522 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1523 p->real_parent = current->real_parent;
1524 p->parent_exec_id = current->parent_exec_id;
1525 } else {
1526 p->real_parent = current;
1527 p->parent_exec_id = current->self_exec_id;
1528 }
1529
1530 spin_lock(&current->sighand->siglock);
1531
1532 /*
1533 * Copy seccomp details explicitly here, in case they were changed
1534 * before holding sighand lock.
1535 */
1536 copy_seccomp(p);
1537
1538 /*
1539 * Process group and session signals need to be delivered to just the
1540 * parent before the fork or both the parent and the child after the
1541 * fork. Restart if a signal comes in before we add the new process to
1542 * it's process group.
1543 * A fatal signal pending means that current will exit, so the new
1544 * thread can't slip out of an OOM kill (or normal SIGKILL).
1545 */
1546 recalc_sigpending();
1547 if (signal_pending(current)) {
1548 spin_unlock(&current->sighand->siglock);
1549 write_unlock_irq(&tasklist_lock);
1550 retval = -ERESTARTNOINTR;
1551 goto bad_fork_free_pid;
1552 }
1553
1554 if (likely(p->pid)) {
1555 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
1556
1557 init_task_pid(p, PIDTYPE_PID, pid);
1558 if (thread_group_leader(p)) {
1559 init_task_pid(p, PIDTYPE_PGID, task_pgrp(current));
1560 init_task_pid(p, PIDTYPE_SID, task_session(current));
1561
1562 if (is_child_reaper(pid)) {
1563 ns_of_pid(pid)->child_reaper = p;
1564 p->signal->flags |= SIGNAL_UNKILLABLE;
1565 }
1566
1567 p->signal->leader_pid = pid;
1568 p->signal->tty = tty_kref_get(current->signal->tty);
1569 list_add_tail(&p->sibling, &p->real_parent->children);
1570 list_add_tail_rcu(&p->tasks, &init_task.tasks);
1571 attach_pid(p, PIDTYPE_PGID);
1572 attach_pid(p, PIDTYPE_SID);
1573 __this_cpu_inc(process_counts);
1574 } else {
1575 current->signal->nr_threads++;
1576 atomic_inc(&current->signal->live);
1577 atomic_inc(&current->signal->sigcnt);
1578 list_add_tail_rcu(&p->thread_group,
1579 &p->group_leader->thread_group);
1580 list_add_tail_rcu(&p->thread_node,
1581 &p->signal->thread_head);
1582 }
1583 attach_pid(p, PIDTYPE_PID);
1584 nr_threads++;
1585 }
1586
1587 total_forks++;
1588 spin_unlock(&current->sighand->siglock);
1589 syscall_tracepoint_update(p);
1590 write_unlock_irq(&tasklist_lock);
1591
1592 proc_fork_connector(p);
1593 cgroup_post_fork(p);
1594 if (clone_flags & CLONE_THREAD)
1595 threadgroup_change_end(current);
1596 perf_event_fork(p);
1597
1598 trace_task_newtask(p, clone_flags);
1599 uprobe_copy_process(p, clone_flags);
1600
1601 return p;
1602
1603bad_fork_free_pid:
1604 if (pid != &init_struct_pid)
1605 free_pid(pid);
1606bad_fork_cleanup_io:
1607 if (p->io_context)
1608 exit_io_context(p);
1609bad_fork_cleanup_namespaces:
1610 exit_task_namespaces(p);
1611bad_fork_cleanup_mm:
1612 if (p->mm)
1613 mmput(p->mm);
1614bad_fork_cleanup_signal:
1615 if (!(clone_flags & CLONE_THREAD))
1616 free_signal_struct(p->signal);
1617bad_fork_cleanup_sighand:
1618 __cleanup_sighand(p->sighand);
1619bad_fork_cleanup_fs:
1620 exit_fs(p); /* blocking */
1621bad_fork_cleanup_files:
1622 exit_files(p); /* blocking */
1623bad_fork_cleanup_semundo:
1624 exit_sem(p);
1625bad_fork_cleanup_audit:
1626 audit_free(p);
1627bad_fork_cleanup_perf:
1628 perf_event_free_task(p);
1629bad_fork_cleanup_policy:
1630#ifdef CONFIG_NUMA
1631 mpol_put(p->mempolicy);
1632bad_fork_cleanup_threadgroup_lock:
1633#endif
1634 if (clone_flags & CLONE_THREAD)
1635 threadgroup_change_end(current);
1636 delayacct_tsk_free(p);
1637bad_fork_cleanup_count:
1638 atomic_dec(&p->cred->user->processes);
1639 exit_creds(p);
1640bad_fork_free:
1641 free_task(p);
1642fork_out:
1643 return ERR_PTR(retval);
1644}
1645
1646static inline void init_idle_pids(struct pid_link *links)
1647{
1648 enum pid_type type;
1649
1650 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
1651 INIT_HLIST_NODE(&links[type].node); /* not really needed */
1652 links[type].pid = &init_struct_pid;
1653 }
1654}
1655
1656struct task_struct *fork_idle(int cpu)
1657{
1658 struct task_struct *task;
1659 task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0, 0);
1660 if (!IS_ERR(task)) {
1661 init_idle_pids(task->pids);
1662 init_idle(task, cpu);
1663 }
1664
1665 return task;
1666}
1667
1668/*
1669 * Ok, this is the main fork-routine.
1670 *
1671 * It copies the process, and if successful kick-starts
1672 * it and waits for it to finish using the VM if required.
1673 */
1674long _do_fork(unsigned long clone_flags,
1675 unsigned long stack_start,
1676 unsigned long stack_size,
1677 int __user *parent_tidptr,
1678 int __user *child_tidptr,
1679 unsigned long tls)
1680{
1681 struct task_struct *p;
1682 int trace = 0;
1683 long nr;
1684
1685 /*
1686 * Determine whether and which event to report to ptracer. When
1687 * called from kernel_thread or CLONE_UNTRACED is explicitly
1688 * requested, no event is reported; otherwise, report if the event
1689 * for the type of forking is enabled.
1690 */
1691 if (!(clone_flags & CLONE_UNTRACED)) {
1692 if (clone_flags & CLONE_VFORK)
1693 trace = PTRACE_EVENT_VFORK;
1694 else if ((clone_flags & CSIGNAL) != SIGCHLD)
1695 trace = PTRACE_EVENT_CLONE;
1696 else
1697 trace = PTRACE_EVENT_FORK;
1698
1699 if (likely(!ptrace_event_enabled(current, trace)))
1700 trace = 0;
1701 }
1702
1703 p = copy_process(clone_flags, stack_start, stack_size,
1704 child_tidptr, NULL, trace, tls);
1705 /*
1706 * Do this prior waking up the new thread - the thread pointer
1707 * might get invalid after that point, if the thread exits quickly.
1708 */
1709 if (!IS_ERR(p)) {
1710 struct completion vfork;
1711 struct pid *pid;
1712
1713 trace_sched_process_fork(current, p);
1714
1715 pid = get_task_pid(p, PIDTYPE_PID);
1716 nr = pid_vnr(pid);
1717
1718 if (clone_flags & CLONE_PARENT_SETTID)
1719 put_user(nr, parent_tidptr);
1720
1721 if (clone_flags & CLONE_VFORK) {
1722 p->vfork_done = &vfork;
1723 init_completion(&vfork);
1724 get_task_struct(p);
1725 }
1726
1727 wake_up_new_task(p);
1728
1729 /* forking complete and child started to run, tell ptracer */
1730 if (unlikely(trace))
1731 ptrace_event_pid(trace, pid);
1732
1733 if (clone_flags & CLONE_VFORK) {
1734 if (!wait_for_vfork_done(p, &vfork))
1735 ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid);
1736 }
1737
1738 put_pid(pid);
1739 } else {
1740 nr = PTR_ERR(p);
1741 }
1742 return nr;
1743}
1744
1745#ifndef CONFIG_HAVE_COPY_THREAD_TLS
1746/* For compatibility with architectures that call do_fork directly rather than
1747 * using the syscall entry points below. */
1748long do_fork(unsigned long clone_flags,
1749 unsigned long stack_start,
1750 unsigned long stack_size,
1751 int __user *parent_tidptr,
1752 int __user *child_tidptr)
1753{
1754 return _do_fork(clone_flags, stack_start, stack_size,
1755 parent_tidptr, child_tidptr, 0);
1756}
1757#endif
1758
1759/*
1760 * Create a kernel thread.
1761 */
1762pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
1763{
1764 return _do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn,
1765 (unsigned long)arg, NULL, NULL, 0);
1766}
1767
1768#ifdef __ARCH_WANT_SYS_FORK
1769SYSCALL_DEFINE0(fork)
1770{
1771#ifdef CONFIG_MMU
1772 return _do_fork(SIGCHLD, 0, 0, NULL, NULL, 0);
1773#else
1774 /* can not support in nommu mode */
1775 return -EINVAL;
1776#endif
1777}
1778#endif
1779
1780#ifdef __ARCH_WANT_SYS_VFORK
1781SYSCALL_DEFINE0(vfork)
1782{
1783 return _do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0,
1784 0, NULL, NULL, 0);
1785}
1786#endif
1787
1788#ifdef __ARCH_WANT_SYS_CLONE
1789#ifdef CONFIG_CLONE_BACKWARDS
1790SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
1791 int __user *, parent_tidptr,
1792 unsigned long, tls,
1793 int __user *, child_tidptr)
1794#elif defined(CONFIG_CLONE_BACKWARDS2)
1795SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags,
1796 int __user *, parent_tidptr,
1797 int __user *, child_tidptr,
1798 unsigned long, tls)
1799#elif defined(CONFIG_CLONE_BACKWARDS3)
1800SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp,
1801 int, stack_size,
1802 int __user *, parent_tidptr,
1803 int __user *, child_tidptr,
1804 unsigned long, tls)
1805#else
1806SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
1807 int __user *, parent_tidptr,
1808 int __user *, child_tidptr,
1809 unsigned long, tls)
1810#endif
1811{
1812 return _do_fork(clone_flags, newsp, 0, parent_tidptr, child_tidptr, tls);
1813}
1814#endif
1815
1816#ifndef ARCH_MIN_MMSTRUCT_ALIGN
1817#define ARCH_MIN_MMSTRUCT_ALIGN 0
1818#endif
1819
1820static void sighand_ctor(void *data)
1821{
1822 struct sighand_struct *sighand = data;
1823
1824 spin_lock_init(&sighand->siglock);
1825 init_waitqueue_head(&sighand->signalfd_wqh);
1826}
1827
1828void __init proc_caches_init(void)
1829{
1830 sighand_cachep = kmem_cache_create("sighand_cache",
1831 sizeof(struct sighand_struct), 0,
1832 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU|
1833 SLAB_NOTRACK, sighand_ctor);
1834 signal_cachep = kmem_cache_create("signal_cache",
1835 sizeof(struct signal_struct), 0,
1836 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1837 files_cachep = kmem_cache_create("files_cache",
1838 sizeof(struct files_struct), 0,
1839 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1840 fs_cachep = kmem_cache_create("fs_cache",
1841 sizeof(struct fs_struct), 0,
1842 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1843 /*
1844 * FIXME! The "sizeof(struct mm_struct)" currently includes the
1845 * whole struct cpumask for the OFFSTACK case. We could change
1846 * this to *only* allocate as much of it as required by the
1847 * maximum number of CPU's we can ever have. The cpumask_allocation
1848 * is at the end of the structure, exactly for that reason.
1849 */
1850 mm_cachep = kmem_cache_create("mm_struct",
1851 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1852 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1853 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC);
1854 mmap_init();
1855 nsproxy_cache_init();
1856}
1857
1858/*
1859 * Check constraints on flags passed to the unshare system call.
1860 */
1861static int check_unshare_flags(unsigned long unshare_flags)
1862{
1863 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1864 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1865 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET|
1866 CLONE_NEWUSER|CLONE_NEWPID))
1867 return -EINVAL;
1868 /*
1869 * Not implemented, but pretend it works if there is nothing to
1870 * unshare. Note that unsharing CLONE_THREAD or CLONE_SIGHAND
1871 * needs to unshare vm.
1872 */
1873 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
1874 /* FIXME: get_task_mm() increments ->mm_users */
1875 if (atomic_read(&current->mm->mm_users) > 1)
1876 return -EINVAL;
1877 }
1878
1879 return 0;
1880}
1881
1882/*
1883 * Unshare the filesystem structure if it is being shared
1884 */
1885static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1886{
1887 struct fs_struct *fs = current->fs;
1888
1889 if (!(unshare_flags & CLONE_FS) || !fs)
1890 return 0;
1891
1892 /* don't need lock here; in the worst case we'll do useless copy */
1893 if (fs->users == 1)
1894 return 0;
1895
1896 *new_fsp = copy_fs_struct(fs);
1897 if (!*new_fsp)
1898 return -ENOMEM;
1899
1900 return 0;
1901}
1902
1903/*
1904 * Unshare file descriptor table if it is being shared
1905 */
1906static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1907{
1908 struct files_struct *fd = current->files;
1909 int error = 0;
1910
1911 if ((unshare_flags & CLONE_FILES) &&
1912 (fd && atomic_read(&fd->count) > 1)) {
1913 *new_fdp = dup_fd(fd, &error);
1914 if (!*new_fdp)
1915 return error;
1916 }
1917
1918 return 0;
1919}
1920
1921/*
1922 * unshare allows a process to 'unshare' part of the process
1923 * context which was originally shared using clone. copy_*
1924 * functions used by do_fork() cannot be used here directly
1925 * because they modify an inactive task_struct that is being
1926 * constructed. Here we are modifying the current, active,
1927 * task_struct.
1928 */
1929SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
1930{
1931 struct fs_struct *fs, *new_fs = NULL;
1932 struct files_struct *fd, *new_fd = NULL;
1933 struct cred *new_cred = NULL;
1934 struct nsproxy *new_nsproxy = NULL;
1935 int do_sysvsem = 0;
1936 int err;
1937
1938 /*
1939 * If unsharing a user namespace must also unshare the thread.
1940 */
1941 if (unshare_flags & CLONE_NEWUSER)
1942 unshare_flags |= CLONE_THREAD | CLONE_FS;
1943 /*
1944 * If unsharing a thread from a thread group, must also unshare vm.
1945 */
1946 if (unshare_flags & CLONE_THREAD)
1947 unshare_flags |= CLONE_VM;
1948 /*
1949 * If unsharing vm, must also unshare signal handlers.
1950 */
1951 if (unshare_flags & CLONE_VM)
1952 unshare_flags |= CLONE_SIGHAND;
1953 /*
1954 * If unsharing namespace, must also unshare filesystem information.
1955 */
1956 if (unshare_flags & CLONE_NEWNS)
1957 unshare_flags |= CLONE_FS;
1958
1959 err = check_unshare_flags(unshare_flags);
1960 if (err)
1961 goto bad_unshare_out;
1962 /*
1963 * CLONE_NEWIPC must also detach from the undolist: after switching
1964 * to a new ipc namespace, the semaphore arrays from the old
1965 * namespace are unreachable.
1966 */
1967 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1968 do_sysvsem = 1;
1969 err = unshare_fs(unshare_flags, &new_fs);
1970 if (err)
1971 goto bad_unshare_out;
1972 err = unshare_fd(unshare_flags, &new_fd);
1973 if (err)
1974 goto bad_unshare_cleanup_fs;
1975 err = unshare_userns(unshare_flags, &new_cred);
1976 if (err)
1977 goto bad_unshare_cleanup_fd;
1978 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
1979 new_cred, new_fs);
1980 if (err)
1981 goto bad_unshare_cleanup_cred;
1982
1983 if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
1984 if (do_sysvsem) {
1985 /*
1986 * CLONE_SYSVSEM is equivalent to sys_exit().
1987 */
1988 exit_sem(current);
1989 }
1990 if (unshare_flags & CLONE_NEWIPC) {
1991 /* Orphan segments in old ns (see sem above). */
1992 exit_shm(current);
1993 shm_init_task(current);
1994 }
1995
1996 if (new_nsproxy)
1997 switch_task_namespaces(current, new_nsproxy);
1998
1999 task_lock(current);
2000
2001 if (new_fs) {
2002 fs = current->fs;
2003 spin_lock(&fs->lock);
2004 current->fs = new_fs;
2005 if (--fs->users)
2006 new_fs = NULL;
2007 else
2008 new_fs = fs;
2009 spin_unlock(&fs->lock);
2010 }
2011
2012 if (new_fd) {
2013 fd = current->files;
2014 current->files = new_fd;
2015 new_fd = fd;
2016 }
2017
2018 task_unlock(current);
2019
2020 if (new_cred) {
2021 /* Install the new user namespace */
2022 commit_creds(new_cred);
2023 new_cred = NULL;
2024 }
2025 }
2026
2027bad_unshare_cleanup_cred:
2028 if (new_cred)
2029 put_cred(new_cred);
2030bad_unshare_cleanup_fd:
2031 if (new_fd)
2032 put_files_struct(new_fd);
2033
2034bad_unshare_cleanup_fs:
2035 if (new_fs)
2036 free_fs_struct(new_fs);
2037
2038bad_unshare_out:
2039 return err;
2040}
2041
2042/*
2043 * Helper to unshare the files of the current task.
2044 * We don't want to expose copy_files internals to
2045 * the exec layer of the kernel.
2046 */
2047
2048int unshare_files(struct files_struct **displaced)
2049{
2050 struct task_struct *task = current;
2051 struct files_struct *copy = NULL;
2052 int error;
2053
2054 error = unshare_fd(CLONE_FILES, &copy);
2055 if (error || !copy) {
2056 *displaced = NULL;
2057 return error;
2058 }
2059 *displaced = task->files;
2060 task_lock(task);
2061 task->files = copy;
2062 task_unlock(task);
2063 return 0;
2064}
2065
2066int sysctl_max_threads(struct ctl_table *table, int write,
2067 void __user *buffer, size_t *lenp, loff_t *ppos)
2068{
2069 struct ctl_table t;
2070 int ret;
2071 int threads = max_threads;
2072 int min = MIN_THREADS;
2073 int max = MAX_THREADS;
2074
2075 t = *table;
2076 t.data = &threads;
2077 t.extra1 = &min;
2078 t.extra2 = &max;
2079
2080 ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
2081 if (ret || !write)
2082 return ret;
2083
2084 set_max_threads(threads);
2085
2086 return 0;
2087}
Linux kernel - Deliverables
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