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/kaiser.h>
62 #include <linux/delayacct.h>
63 #include <linux/taskstats_kern.h>
64 #include <linux/random.h>
65 #include <linux/tty.h>
66 #include <linux/blkdev.h>
67 #include <linux/fs_struct.h>
68 #include <linux/magic.h>
69 #include <linux/perf_event.h>
70 #include <linux/posix-timers.h>
71 #include <linux/user-return-notifier.h>
72 #include <linux/oom.h>
73 #include <linux/khugepaged.h>
74 #include <linux/signalfd.h>
75 #include <linux/uprobes.h>
76 #include <linux/aio.h>
77 #include <linux/compiler.h>
78 #include <linux/sysctl.h>
79 #include <linux/kcov.h>
80
81 #include <asm/pgtable.h>
82 #include <asm/pgalloc.h>
83 #include <asm/uaccess.h>
84 #include <asm/mmu_context.h>
85 #include <asm/cacheflush.h>
86 #include <asm/tlbflush.h>
87
88 #include <trace/events/sched.h>
89
90 #define CREATE_TRACE_POINTS
91 #include <trace/events/task.h>
92
93 /*
94 * Minimum number of threads to boot the kernel
95 */
96 #define MIN_THREADS 20
97
98 /*
99 * Maximum number of threads
100 */
101 #define MAX_THREADS FUTEX_TID_MASK
102
103 /*
104 * Protected counters by write_lock_irq(&tasklist_lock)
105 */
106 unsigned long total_forks; /* Handle normal Linux uptimes. */
107 int nr_threads; /* The idle threads do not count.. */
108
109 int max_threads; /* tunable limit on nr_threads */
110
111 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
112
113 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */
114
115 #ifdef CONFIG_PROVE_RCU
lockdep_tasklist_lock_is_held(void)116 int lockdep_tasklist_lock_is_held(void)
117 {
118 return lockdep_is_held(&tasklist_lock);
119 }
120 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
121 #endif /* #ifdef CONFIG_PROVE_RCU */
122
nr_processes(void)123 int nr_processes(void)
124 {
125 int cpu;
126 int total = 0;
127
128 for_each_possible_cpu(cpu)
129 total += per_cpu(process_counts, cpu);
130
131 return total;
132 }
133
arch_release_task_struct(struct task_struct * tsk)134 void __weak arch_release_task_struct(struct task_struct *tsk)
135 {
136 }
137
138 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
139 static struct kmem_cache *task_struct_cachep;
140
alloc_task_struct_node(int node)141 static inline struct task_struct *alloc_task_struct_node(int node)
142 {
143 return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node);
144 }
145
free_task_struct(struct task_struct * tsk)146 static inline void free_task_struct(struct task_struct *tsk)
147 {
148 kmem_cache_free(task_struct_cachep, tsk);
149 }
150 #endif
151
arch_release_thread_stack(unsigned long * stack)152 void __weak arch_release_thread_stack(unsigned long *stack)
153 {
154 }
155
156 #ifndef CONFIG_ARCH_THREAD_STACK_ALLOCATOR
157
158 /*
159 * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
160 * kmemcache based allocator.
161 */
162 # if THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK)
163
164 #ifdef CONFIG_VMAP_STACK
165 /*
166 * vmalloc() is a bit slow, and calling vfree() enough times will force a TLB
167 * flush. Try to minimize the number of calls by caching stacks.
168 */
169 #define NR_CACHED_STACKS 2
170 static DEFINE_PER_CPU(struct vm_struct *, cached_stacks[NR_CACHED_STACKS]);
171 #endif
172
alloc_thread_stack_node(struct task_struct * tsk,int node)173 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node)
174 {
175 #ifdef CONFIG_VMAP_STACK
176 void *stack;
177 int i;
178
179 local_irq_disable();
180 for (i = 0; i < NR_CACHED_STACKS; i++) {
181 struct vm_struct *s = this_cpu_read(cached_stacks[i]);
182
183 if (!s)
184 continue;
185 this_cpu_write(cached_stacks[i], NULL);
186
187 tsk->stack_vm_area = s;
188 local_irq_enable();
189 return s->addr;
190 }
191 local_irq_enable();
192
193 stack = __vmalloc_node_range(THREAD_SIZE, THREAD_SIZE,
194 VMALLOC_START, VMALLOC_END,
195 THREADINFO_GFP | __GFP_HIGHMEM,
196 PAGE_KERNEL,
197 0, node, __builtin_return_address(0));
198
199 /*
200 * We can't call find_vm_area() in interrupt context, and
201 * free_thread_stack() can be called in interrupt context,
202 * so cache the vm_struct.
203 */
204 if (stack)
205 tsk->stack_vm_area = find_vm_area(stack);
206 return stack;
207 #else
208 struct page *page = alloc_pages_node(node, THREADINFO_GFP,
209 THREAD_SIZE_ORDER);
210
211 return page ? page_address(page) : NULL;
212 #endif
213 }
214
free_thread_stack(struct task_struct * tsk)215 static inline void free_thread_stack(struct task_struct *tsk)
216 {
217 kaiser_unmap_thread_stack(tsk->stack);
218 #ifdef CONFIG_VMAP_STACK
219 if (task_stack_vm_area(tsk)) {
220 unsigned long flags;
221 int i;
222
223 local_irq_save(flags);
224 for (i = 0; i < NR_CACHED_STACKS; i++) {
225 if (this_cpu_read(cached_stacks[i]))
226 continue;
227
228 this_cpu_write(cached_stacks[i], tsk->stack_vm_area);
229 local_irq_restore(flags);
230 return;
231 }
232 local_irq_restore(flags);
233
234 vfree(tsk->stack);
235 return;
236 }
237 #endif
238
239 __free_pages(virt_to_page(tsk->stack), THREAD_SIZE_ORDER);
240 }
241 # else
242 static struct kmem_cache *thread_stack_cache;
243
alloc_thread_stack_node(struct task_struct * tsk,int node)244 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk,
245 int node)
246 {
247 return kmem_cache_alloc_node(thread_stack_cache, THREADINFO_GFP, node);
248 }
249
free_thread_stack(struct task_struct * tsk)250 static void free_thread_stack(struct task_struct *tsk)
251 {
252 kmem_cache_free(thread_stack_cache, tsk->stack);
253 }
254
thread_stack_cache_init(void)255 void thread_stack_cache_init(void)
256 {
257 thread_stack_cache = kmem_cache_create("thread_stack", THREAD_SIZE,
258 THREAD_SIZE, 0, NULL);
259 BUG_ON(thread_stack_cache == NULL);
260 }
261 # endif
262 #endif
263
264 /* SLAB cache for signal_struct structures (tsk->signal) */
265 static struct kmem_cache *signal_cachep;
266
267 /* SLAB cache for sighand_struct structures (tsk->sighand) */
268 struct kmem_cache *sighand_cachep;
269
270 /* SLAB cache for files_struct structures (tsk->files) */
271 struct kmem_cache *files_cachep;
272
273 /* SLAB cache for fs_struct structures (tsk->fs) */
274 struct kmem_cache *fs_cachep;
275
276 /* SLAB cache for vm_area_struct structures */
277 struct kmem_cache *vm_area_cachep;
278
279 /* SLAB cache for mm_struct structures (tsk->mm) */
280 static struct kmem_cache *mm_cachep;
281
account_kernel_stack(struct task_struct * tsk,int account)282 static void account_kernel_stack(struct task_struct *tsk, int account)
283 {
284 void *stack = task_stack_page(tsk);
285 struct vm_struct *vm = task_stack_vm_area(tsk);
286
287 BUILD_BUG_ON(IS_ENABLED(CONFIG_VMAP_STACK) && PAGE_SIZE % 1024 != 0);
288
289 if (vm) {
290 int i;
291
292 BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE);
293
294 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
295 mod_zone_page_state(page_zone(vm->pages[i]),
296 NR_KERNEL_STACK_KB,
297 PAGE_SIZE / 1024 * account);
298 }
299
300 /* All stack pages belong to the same memcg. */
301 memcg_kmem_update_page_stat(vm->pages[0], MEMCG_KERNEL_STACK_KB,
302 account * (THREAD_SIZE / 1024));
303 } else {
304 /*
305 * All stack pages are in the same zone and belong to the
306 * same memcg.
307 */
308 struct page *first_page = virt_to_page(stack);
309
310 mod_zone_page_state(page_zone(first_page), NR_KERNEL_STACK_KB,
311 THREAD_SIZE / 1024 * account);
312
313 memcg_kmem_update_page_stat(first_page, MEMCG_KERNEL_STACK_KB,
314 account * (THREAD_SIZE / 1024));
315 }
316 }
317
release_task_stack(struct task_struct * tsk)318 static void release_task_stack(struct task_struct *tsk)
319 {
320 if (WARN_ON(tsk->state != TASK_DEAD))
321 return; /* Better to leak the stack than to free prematurely */
322
323 account_kernel_stack(tsk, -1);
324 arch_release_thread_stack(tsk->stack);
325 free_thread_stack(tsk);
326 tsk->stack = NULL;
327 #ifdef CONFIG_VMAP_STACK
328 tsk->stack_vm_area = NULL;
329 #endif
330 }
331
332 #ifdef CONFIG_THREAD_INFO_IN_TASK
put_task_stack(struct task_struct * tsk)333 void put_task_stack(struct task_struct *tsk)
334 {
335 if (atomic_dec_and_test(&tsk->stack_refcount))
336 release_task_stack(tsk);
337 }
338 #endif
339
free_task(struct task_struct * tsk)340 void free_task(struct task_struct *tsk)
341 {
342 #ifndef CONFIG_THREAD_INFO_IN_TASK
343 /*
344 * The task is finally done with both the stack and thread_info,
345 * so free both.
346 */
347 release_task_stack(tsk);
348 #else
349 /*
350 * If the task had a separate stack allocation, it should be gone
351 * by now.
352 */
353 WARN_ON_ONCE(atomic_read(&tsk->stack_refcount) != 0);
354 #endif
355 rt_mutex_debug_task_free(tsk);
356 ftrace_graph_exit_task(tsk);
357 put_seccomp_filter(tsk);
358 arch_release_task_struct(tsk);
359 free_task_struct(tsk);
360 }
361 EXPORT_SYMBOL(free_task);
362
free_signal_struct(struct signal_struct * sig)363 static inline void free_signal_struct(struct signal_struct *sig)
364 {
365 taskstats_tgid_free(sig);
366 sched_autogroup_exit(sig);
367 /*
368 * __mmdrop is not safe to call from softirq context on x86 due to
369 * pgd_dtor so postpone it to the async context
370 */
371 if (sig->oom_mm)
372 mmdrop_async(sig->oom_mm);
373 kmem_cache_free(signal_cachep, sig);
374 }
375
put_signal_struct(struct signal_struct * sig)376 static inline void put_signal_struct(struct signal_struct *sig)
377 {
378 if (atomic_dec_and_test(&sig->sigcnt))
379 free_signal_struct(sig);
380 }
381
__put_task_struct(struct task_struct * tsk)382 void __put_task_struct(struct task_struct *tsk)
383 {
384 WARN_ON(!tsk->exit_state);
385 WARN_ON(atomic_read(&tsk->usage));
386 WARN_ON(tsk == current);
387
388 cgroup_free(tsk);
389 task_numa_free(tsk);
390 security_task_free(tsk);
391 exit_creds(tsk);
392 delayacct_tsk_free(tsk);
393 put_signal_struct(tsk->signal);
394
395 if (!profile_handoff_task(tsk))
396 free_task(tsk);
397 }
398 EXPORT_SYMBOL_GPL(__put_task_struct);
399
arch_task_cache_init(void)400 void __init __weak arch_task_cache_init(void) { }
401
402 /*
403 * set_max_threads
404 */
set_max_threads(unsigned int max_threads_suggested)405 static void set_max_threads(unsigned int max_threads_suggested)
406 {
407 u64 threads;
408
409 /*
410 * The number of threads shall be limited such that the thread
411 * structures may only consume a small part of the available memory.
412 */
413 if (fls64(totalram_pages) + fls64(PAGE_SIZE) > 64)
414 threads = MAX_THREADS;
415 else
416 threads = div64_u64((u64) totalram_pages * (u64) PAGE_SIZE,
417 (u64) THREAD_SIZE * 8UL);
418
419 if (threads > max_threads_suggested)
420 threads = max_threads_suggested;
421
422 max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS);
423 }
424
425 #ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT
426 /* Initialized by the architecture: */
427 int arch_task_struct_size __read_mostly;
428 #endif
429
fork_init(void)430 void __init fork_init(void)
431 {
432 int i;
433 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
434 #ifndef ARCH_MIN_TASKALIGN
435 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES
436 #endif
437 /* create a slab on which task_structs can be allocated */
438 task_struct_cachep = kmem_cache_create("task_struct",
439 arch_task_struct_size, ARCH_MIN_TASKALIGN,
440 SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT, NULL);
441 #endif
442
443 /* do the arch specific task caches init */
444 arch_task_cache_init();
445
446 set_max_threads(MAX_THREADS);
447
448 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
449 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
450 init_task.signal->rlim[RLIMIT_SIGPENDING] =
451 init_task.signal->rlim[RLIMIT_NPROC];
452
453 for (i = 0; i < UCOUNT_COUNTS; i++) {
454 init_user_ns.ucount_max[i] = max_threads/2;
455 }
456 }
457
arch_dup_task_struct(struct task_struct * dst,struct task_struct * src)458 int __weak arch_dup_task_struct(struct task_struct *dst,
459 struct task_struct *src)
460 {
461 *dst = *src;
462 return 0;
463 }
464
set_task_stack_end_magic(struct task_struct * tsk)465 void set_task_stack_end_magic(struct task_struct *tsk)
466 {
467 unsigned long *stackend;
468
469 stackend = end_of_stack(tsk);
470 *stackend = STACK_END_MAGIC; /* for overflow detection */
471 }
472
dup_task_struct(struct task_struct * orig,int node)473 static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
474 {
475 struct task_struct *tsk;
476 unsigned long *stack;
477 struct vm_struct *stack_vm_area;
478 int err;
479
480 if (node == NUMA_NO_NODE)
481 node = tsk_fork_get_node(orig);
482 tsk = alloc_task_struct_node(node);
483 if (!tsk)
484 return NULL;
485
486 stack = alloc_thread_stack_node(tsk, node);
487 if (!stack)
488 goto free_tsk;
489
490 stack_vm_area = task_stack_vm_area(tsk);
491
492 err = arch_dup_task_struct(tsk, orig);
493
494 /*
495 * arch_dup_task_struct() clobbers the stack-related fields. Make
496 * sure they're properly initialized before using any stack-related
497 * functions again.
498 */
499 tsk->stack = stack;
500
501 err= kaiser_map_thread_stack(tsk->stack);
502 if (err)
503 goto free_stack;
504 #ifdef CONFIG_VMAP_STACK
505 tsk->stack_vm_area = stack_vm_area;
506 #endif
507 #ifdef CONFIG_THREAD_INFO_IN_TASK
508 atomic_set(&tsk->stack_refcount, 1);
509 #endif
510
511 if (err)
512 goto free_stack;
513
514 #ifdef CONFIG_SECCOMP
515 /*
516 * We must handle setting up seccomp filters once we're under
517 * the sighand lock in case orig has changed between now and
518 * then. Until then, filter must be NULL to avoid messing up
519 * the usage counts on the error path calling free_task.
520 */
521 tsk->seccomp.filter = NULL;
522 #endif
523
524 setup_thread_stack(tsk, orig);
525 clear_user_return_notifier(tsk);
526 clear_tsk_need_resched(tsk);
527 set_task_stack_end_magic(tsk);
528
529 #ifdef CONFIG_CC_STACKPROTECTOR
530 tsk->stack_canary = get_random_long();
531 #endif
532
533 /*
534 * One for us, one for whoever does the "release_task()" (usually
535 * parent)
536 */
537 atomic_set(&tsk->usage, 2);
538 #ifdef CONFIG_BLK_DEV_IO_TRACE
539 tsk->btrace_seq = 0;
540 #endif
541 tsk->splice_pipe = NULL;
542 tsk->task_frag.page = NULL;
543 tsk->wake_q.next = NULL;
544
545 account_kernel_stack(tsk, 1);
546
547 kcov_task_init(tsk);
548
549 return tsk;
550
551 free_stack:
552 free_thread_stack(tsk);
553 free_tsk:
554 free_task_struct(tsk);
555 return NULL;
556 }
557
558 #ifdef CONFIG_MMU
dup_mmap(struct mm_struct * mm,struct mm_struct * oldmm)559 static __latent_entropy int dup_mmap(struct mm_struct *mm,
560 struct mm_struct *oldmm)
561 {
562 struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
563 struct rb_node **rb_link, *rb_parent;
564 int retval;
565 unsigned long charge;
566
567 uprobe_start_dup_mmap();
568 if (down_write_killable(&oldmm->mmap_sem)) {
569 retval = -EINTR;
570 goto fail_uprobe_end;
571 }
572 flush_cache_dup_mm(oldmm);
573 uprobe_dup_mmap(oldmm, mm);
574 /*
575 * Not linked in yet - no deadlock potential:
576 */
577 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
578
579 /* No ordering required: file already has been exposed. */
580 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
581
582 mm->total_vm = oldmm->total_vm;
583 mm->data_vm = oldmm->data_vm;
584 mm->exec_vm = oldmm->exec_vm;
585 mm->stack_vm = oldmm->stack_vm;
586
587 rb_link = &mm->mm_rb.rb_node;
588 rb_parent = NULL;
589 pprev = &mm->mmap;
590 retval = ksm_fork(mm, oldmm);
591 if (retval)
592 goto out;
593 retval = khugepaged_fork(mm, oldmm);
594 if (retval)
595 goto out;
596
597 prev = NULL;
598 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
599 struct file *file;
600
601 if (mpnt->vm_flags & VM_DONTCOPY) {
602 vm_stat_account(mm, mpnt->vm_flags, -vma_pages(mpnt));
603 continue;
604 }
605 charge = 0;
606 if (mpnt->vm_flags & VM_ACCOUNT) {
607 unsigned long len = vma_pages(mpnt);
608
609 if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
610 goto fail_nomem;
611 charge = len;
612 }
613 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
614 if (!tmp)
615 goto fail_nomem;
616 *tmp = *mpnt;
617 INIT_LIST_HEAD(&tmp->anon_vma_chain);
618 retval = vma_dup_policy(mpnt, tmp);
619 if (retval)
620 goto fail_nomem_policy;
621 tmp->vm_mm = mm;
622 if (anon_vma_fork(tmp, mpnt))
623 goto fail_nomem_anon_vma_fork;
624 tmp->vm_flags &=
625 ~(VM_LOCKED|VM_LOCKONFAULT|VM_UFFD_MISSING|VM_UFFD_WP);
626 tmp->vm_next = tmp->vm_prev = NULL;
627 tmp->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
628 file = tmp->vm_file;
629 if (file) {
630 struct inode *inode = file_inode(file);
631 struct address_space *mapping = file->f_mapping;
632
633 get_file(file);
634 if (tmp->vm_flags & VM_DENYWRITE)
635 atomic_dec(&inode->i_writecount);
636 i_mmap_lock_write(mapping);
637 if (tmp->vm_flags & VM_SHARED)
638 atomic_inc(&mapping->i_mmap_writable);
639 flush_dcache_mmap_lock(mapping);
640 /* insert tmp into the share list, just after mpnt */
641 vma_interval_tree_insert_after(tmp, mpnt,
642 &mapping->i_mmap);
643 flush_dcache_mmap_unlock(mapping);
644 i_mmap_unlock_write(mapping);
645 }
646
647 /*
648 * Clear hugetlb-related page reserves for children. This only
649 * affects MAP_PRIVATE mappings. Faults generated by the child
650 * are not guaranteed to succeed, even if read-only
651 */
652 if (is_vm_hugetlb_page(tmp))
653 reset_vma_resv_huge_pages(tmp);
654
655 /*
656 * Link in the new vma and copy the page table entries.
657 */
658 *pprev = tmp;
659 pprev = &tmp->vm_next;
660 tmp->vm_prev = prev;
661 prev = tmp;
662
663 __vma_link_rb(mm, tmp, rb_link, rb_parent);
664 rb_link = &tmp->vm_rb.rb_right;
665 rb_parent = &tmp->vm_rb;
666
667 mm->map_count++;
668 retval = copy_page_range(mm, oldmm, mpnt);
669
670 if (tmp->vm_ops && tmp->vm_ops->open)
671 tmp->vm_ops->open(tmp);
672
673 if (retval)
674 goto out;
675 }
676 /* a new mm has just been created */
677 arch_dup_mmap(oldmm, mm);
678 retval = 0;
679 out:
680 up_write(&mm->mmap_sem);
681 flush_tlb_mm(oldmm);
682 up_write(&oldmm->mmap_sem);
683 fail_uprobe_end:
684 uprobe_end_dup_mmap();
685 return retval;
686 fail_nomem_anon_vma_fork:
687 mpol_put(vma_policy(tmp));
688 fail_nomem_policy:
689 kmem_cache_free(vm_area_cachep, tmp);
690 fail_nomem:
691 retval = -ENOMEM;
692 vm_unacct_memory(charge);
693 goto out;
694 }
695
mm_alloc_pgd(struct mm_struct * mm)696 static inline int mm_alloc_pgd(struct mm_struct *mm)
697 {
698 mm->pgd = pgd_alloc(mm);
699 if (unlikely(!mm->pgd))
700 return -ENOMEM;
701 return 0;
702 }
703
mm_free_pgd(struct mm_struct * mm)704 static inline void mm_free_pgd(struct mm_struct *mm)
705 {
706 pgd_free(mm, mm->pgd);
707 }
708 #else
dup_mmap(struct mm_struct * mm,struct mm_struct * oldmm)709 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
710 {
711 down_write(&oldmm->mmap_sem);
712 RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
713 up_write(&oldmm->mmap_sem);
714 return 0;
715 }
716 #define mm_alloc_pgd(mm) (0)
717 #define mm_free_pgd(mm)
718 #endif /* CONFIG_MMU */
719
720 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
721
722 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
723 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm)))
724
725 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
726
coredump_filter_setup(char * s)727 static int __init coredump_filter_setup(char *s)
728 {
729 default_dump_filter =
730 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
731 MMF_DUMP_FILTER_MASK;
732 return 1;
733 }
734
735 __setup("coredump_filter=", coredump_filter_setup);
736
737 #include <linux/init_task.h>
738
mm_init_aio(struct mm_struct * mm)739 static void mm_init_aio(struct mm_struct *mm)
740 {
741 #ifdef CONFIG_AIO
742 spin_lock_init(&mm->ioctx_lock);
743 mm->ioctx_table = NULL;
744 #endif
745 }
746
mm_init_owner(struct mm_struct * mm,struct task_struct * p)747 static void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
748 {
749 #ifdef CONFIG_MEMCG
750 mm->owner = p;
751 #endif
752 }
753
mm_init_uprobes_state(struct mm_struct * mm)754 static void mm_init_uprobes_state(struct mm_struct *mm)
755 {
756 #ifdef CONFIG_UPROBES
757 mm->uprobes_state.xol_area = NULL;
758 #endif
759 }
760
mm_init(struct mm_struct * mm,struct task_struct * p,struct user_namespace * user_ns)761 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
762 struct user_namespace *user_ns)
763 {
764 mm->mmap = NULL;
765 mm->mm_rb = RB_ROOT;
766 mm->vmacache_seqnum = 0;
767 atomic_set(&mm->mm_users, 1);
768 atomic_set(&mm->mm_count, 1);
769 init_rwsem(&mm->mmap_sem);
770 INIT_LIST_HEAD(&mm->mmlist);
771 mm->core_state = NULL;
772 atomic_long_set(&mm->nr_ptes, 0);
773 mm_nr_pmds_init(mm);
774 mm->map_count = 0;
775 mm->locked_vm = 0;
776 mm->pinned_vm = 0;
777 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
778 spin_lock_init(&mm->page_table_lock);
779 mm_init_cpumask(mm);
780 mm_init_aio(mm);
781 mm_init_owner(mm, p);
782 RCU_INIT_POINTER(mm->exe_file, NULL);
783 mmu_notifier_mm_init(mm);
784 clear_tlb_flush_pending(mm);
785 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
786 mm->pmd_huge_pte = NULL;
787 #endif
788 mm_init_uprobes_state(mm);
789
790 if (current->mm) {
791 mm->flags = current->mm->flags & MMF_INIT_MASK;
792 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK;
793 } else {
794 mm->flags = default_dump_filter;
795 mm->def_flags = 0;
796 }
797
798 if (mm_alloc_pgd(mm))
799 goto fail_nopgd;
800
801 if (init_new_context(p, mm))
802 goto fail_nocontext;
803
804 mm->user_ns = get_user_ns(user_ns);
805 return mm;
806
807 fail_nocontext:
808 mm_free_pgd(mm);
809 fail_nopgd:
810 free_mm(mm);
811 return NULL;
812 }
813
check_mm(struct mm_struct * mm)814 static void check_mm(struct mm_struct *mm)
815 {
816 int i;
817
818 for (i = 0; i < NR_MM_COUNTERS; i++) {
819 long x = atomic_long_read(&mm->rss_stat.count[i]);
820
821 if (unlikely(x))
822 printk(KERN_ALERT "BUG: Bad rss-counter state "
823 "mm:%p idx:%d val:%ld\n", mm, i, x);
824 }
825
826 if (atomic_long_read(&mm->nr_ptes))
827 pr_alert("BUG: non-zero nr_ptes on freeing mm: %ld\n",
828 atomic_long_read(&mm->nr_ptes));
829 if (mm_nr_pmds(mm))
830 pr_alert("BUG: non-zero nr_pmds on freeing mm: %ld\n",
831 mm_nr_pmds(mm));
832
833 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
834 VM_BUG_ON_MM(mm->pmd_huge_pte, mm);
835 #endif
836 }
837
838 /*
839 * Allocate and initialize an mm_struct.
840 */
mm_alloc(void)841 struct mm_struct *mm_alloc(void)
842 {
843 struct mm_struct *mm;
844
845 mm = allocate_mm();
846 if (!mm)
847 return NULL;
848
849 memset(mm, 0, sizeof(*mm));
850 return mm_init(mm, current, current_user_ns());
851 }
852
853 /*
854 * Called when the last reference to the mm
855 * is dropped: either by a lazy thread or by
856 * mmput. Free the page directory and the mm.
857 */
__mmdrop(struct mm_struct * mm)858 void __mmdrop(struct mm_struct *mm)
859 {
860 BUG_ON(mm == &init_mm);
861 mm_free_pgd(mm);
862 destroy_context(mm);
863 mmu_notifier_mm_destroy(mm);
864 check_mm(mm);
865 put_user_ns(mm->user_ns);
866 free_mm(mm);
867 }
868 EXPORT_SYMBOL_GPL(__mmdrop);
869
__mmput(struct mm_struct * mm)870 static inline void __mmput(struct mm_struct *mm)
871 {
872 VM_BUG_ON(atomic_read(&mm->mm_users));
873
874 uprobe_clear_state(mm);
875 exit_aio(mm);
876 ksm_exit(mm);
877 khugepaged_exit(mm); /* must run before exit_mmap */
878 exit_mmap(mm);
879 mm_put_huge_zero_page(mm);
880 set_mm_exe_file(mm, NULL);
881 if (!list_empty(&mm->mmlist)) {
882 spin_lock(&mmlist_lock);
883 list_del(&mm->mmlist);
884 spin_unlock(&mmlist_lock);
885 }
886 if (mm->binfmt)
887 module_put(mm->binfmt->module);
888 set_bit(MMF_OOM_SKIP, &mm->flags);
889 mmdrop(mm);
890 }
891
892 /*
893 * Decrement the use count and release all resources for an mm.
894 */
mmput(struct mm_struct * mm)895 void mmput(struct mm_struct *mm)
896 {
897 might_sleep();
898
899 if (atomic_dec_and_test(&mm->mm_users))
900 __mmput(mm);
901 }
902 EXPORT_SYMBOL_GPL(mmput);
903
904 #ifdef CONFIG_MMU
mmput_async_fn(struct work_struct * work)905 static void mmput_async_fn(struct work_struct *work)
906 {
907 struct mm_struct *mm = container_of(work, struct mm_struct, async_put_work);
908 __mmput(mm);
909 }
910
mmput_async(struct mm_struct * mm)911 void mmput_async(struct mm_struct *mm)
912 {
913 if (atomic_dec_and_test(&mm->mm_users)) {
914 INIT_WORK(&mm->async_put_work, mmput_async_fn);
915 schedule_work(&mm->async_put_work);
916 }
917 }
918 #endif
919
920 /**
921 * set_mm_exe_file - change a reference to the mm's executable file
922 *
923 * This changes mm's executable file (shown as symlink /proc/[pid]/exe).
924 *
925 * Main users are mmput() and sys_execve(). Callers prevent concurrent
926 * invocations: in mmput() nobody alive left, in execve task is single
927 * threaded. sys_prctl(PR_SET_MM_MAP/EXE_FILE) also needs to set the
928 * mm->exe_file, but does so without using set_mm_exe_file() in order
929 * to do avoid the need for any locks.
930 */
set_mm_exe_file(struct mm_struct * mm,struct file * new_exe_file)931 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
932 {
933 struct file *old_exe_file;
934
935 /*
936 * It is safe to dereference the exe_file without RCU as
937 * this function is only called if nobody else can access
938 * this mm -- see comment above for justification.
939 */
940 old_exe_file = rcu_dereference_raw(mm->exe_file);
941
942 if (new_exe_file)
943 get_file(new_exe_file);
944 rcu_assign_pointer(mm->exe_file, new_exe_file);
945 if (old_exe_file)
946 fput(old_exe_file);
947 }
948
949 /**
950 * get_mm_exe_file - acquire a reference to the mm's executable file
951 *
952 * Returns %NULL if mm has no associated executable file.
953 * User must release file via fput().
954 */
get_mm_exe_file(struct mm_struct * mm)955 struct file *get_mm_exe_file(struct mm_struct *mm)
956 {
957 struct file *exe_file;
958
959 rcu_read_lock();
960 exe_file = rcu_dereference(mm->exe_file);
961 if (exe_file && !get_file_rcu(exe_file))
962 exe_file = NULL;
963 rcu_read_unlock();
964 return exe_file;
965 }
966 EXPORT_SYMBOL(get_mm_exe_file);
967
968 /**
969 * get_task_exe_file - acquire a reference to the task's executable file
970 *
971 * Returns %NULL if task's mm (if any) has no associated executable file or
972 * this is a kernel thread with borrowed mm (see the comment above get_task_mm).
973 * User must release file via fput().
974 */
get_task_exe_file(struct task_struct * task)975 struct file *get_task_exe_file(struct task_struct *task)
976 {
977 struct file *exe_file = NULL;
978 struct mm_struct *mm;
979
980 task_lock(task);
981 mm = task->mm;
982 if (mm) {
983 if (!(task->flags & PF_KTHREAD))
984 exe_file = get_mm_exe_file(mm);
985 }
986 task_unlock(task);
987 return exe_file;
988 }
989 EXPORT_SYMBOL(get_task_exe_file);
990
991 /**
992 * get_task_mm - acquire a reference to the task's mm
993 *
994 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning
995 * this kernel workthread has transiently adopted a user mm with use_mm,
996 * to do its AIO) is not set and if so returns a reference to it, after
997 * bumping up the use count. User must release the mm via mmput()
998 * after use. Typically used by /proc and ptrace.
999 */
get_task_mm(struct task_struct * task)1000 struct mm_struct *get_task_mm(struct task_struct *task)
1001 {
1002 struct mm_struct *mm;
1003
1004 task_lock(task);
1005 mm = task->mm;
1006 if (mm) {
1007 if (task->flags & PF_KTHREAD)
1008 mm = NULL;
1009 else
1010 atomic_inc(&mm->mm_users);
1011 }
1012 task_unlock(task);
1013 return mm;
1014 }
1015 EXPORT_SYMBOL_GPL(get_task_mm);
1016
mm_access(struct task_struct * task,unsigned int mode)1017 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
1018 {
1019 struct mm_struct *mm;
1020 int err;
1021
1022 err = mutex_lock_killable(&task->signal->cred_guard_mutex);
1023 if (err)
1024 return ERR_PTR(err);
1025
1026 mm = get_task_mm(task);
1027 if (mm && mm != current->mm &&
1028 !ptrace_may_access(task, mode)) {
1029 mmput(mm);
1030 mm = ERR_PTR(-EACCES);
1031 }
1032 mutex_unlock(&task->signal->cred_guard_mutex);
1033
1034 return mm;
1035 }
1036
complete_vfork_done(struct task_struct * tsk)1037 static void complete_vfork_done(struct task_struct *tsk)
1038 {
1039 struct completion *vfork;
1040
1041 task_lock(tsk);
1042 vfork = tsk->vfork_done;
1043 if (likely(vfork)) {
1044 tsk->vfork_done = NULL;
1045 complete(vfork);
1046 }
1047 task_unlock(tsk);
1048 }
1049
wait_for_vfork_done(struct task_struct * child,struct completion * vfork)1050 static int wait_for_vfork_done(struct task_struct *child,
1051 struct completion *vfork)
1052 {
1053 int killed;
1054
1055 freezer_do_not_count();
1056 killed = wait_for_completion_killable(vfork);
1057 freezer_count();
1058
1059 if (killed) {
1060 task_lock(child);
1061 child->vfork_done = NULL;
1062 task_unlock(child);
1063 }
1064
1065 put_task_struct(child);
1066 return killed;
1067 }
1068
1069 /* Please note the differences between mmput and mm_release.
1070 * mmput is called whenever we stop holding onto a mm_struct,
1071 * error success whatever.
1072 *
1073 * mm_release is called after a mm_struct has been removed
1074 * from the current process.
1075 *
1076 * This difference is important for error handling, when we
1077 * only half set up a mm_struct for a new process and need to restore
1078 * the old one. Because we mmput the new mm_struct before
1079 * restoring the old one. . .
1080 * Eric Biederman 10 January 1998
1081 */
mm_release(struct task_struct * tsk,struct mm_struct * mm)1082 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
1083 {
1084 /* Get rid of any futexes when releasing the mm */
1085 #ifdef CONFIG_FUTEX
1086 if (unlikely(tsk->robust_list)) {
1087 exit_robust_list(tsk);
1088 tsk->robust_list = NULL;
1089 }
1090 #ifdef CONFIG_COMPAT
1091 if (unlikely(tsk->compat_robust_list)) {
1092 compat_exit_robust_list(tsk);
1093 tsk->compat_robust_list = NULL;
1094 }
1095 #endif
1096 if (unlikely(!list_empty(&tsk->pi_state_list)))
1097 exit_pi_state_list(tsk);
1098 #endif
1099
1100 uprobe_free_utask(tsk);
1101
1102 /* Get rid of any cached register state */
1103 deactivate_mm(tsk, mm);
1104
1105 /*
1106 * Signal userspace if we're not exiting with a core dump
1107 * because we want to leave the value intact for debugging
1108 * purposes.
1109 */
1110 if (tsk->clear_child_tid) {
1111 if (!(tsk->signal->flags & SIGNAL_GROUP_COREDUMP) &&
1112 atomic_read(&mm->mm_users) > 1) {
1113 /*
1114 * We don't check the error code - if userspace has
1115 * not set up a proper pointer then tough luck.
1116 */
1117 put_user(0, tsk->clear_child_tid);
1118 sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
1119 1, NULL, NULL, 0);
1120 }
1121 tsk->clear_child_tid = NULL;
1122 }
1123
1124 /*
1125 * All done, finally we can wake up parent and return this mm to him.
1126 * Also kthread_stop() uses this completion for synchronization.
1127 */
1128 if (tsk->vfork_done)
1129 complete_vfork_done(tsk);
1130 }
1131
1132 /*
1133 * Allocate a new mm structure and copy contents from the
1134 * mm structure of the passed in task structure.
1135 */
dup_mm(struct task_struct * tsk)1136 static struct mm_struct *dup_mm(struct task_struct *tsk)
1137 {
1138 struct mm_struct *mm, *oldmm = current->mm;
1139 int err;
1140
1141 mm = allocate_mm();
1142 if (!mm)
1143 goto fail_nomem;
1144
1145 memcpy(mm, oldmm, sizeof(*mm));
1146
1147 if (!mm_init(mm, tsk, mm->user_ns))
1148 goto fail_nomem;
1149
1150 err = dup_mmap(mm, oldmm);
1151 if (err)
1152 goto free_pt;
1153
1154 mm->hiwater_rss = get_mm_rss(mm);
1155 mm->hiwater_vm = mm->total_vm;
1156
1157 if (mm->binfmt && !try_module_get(mm->binfmt->module))
1158 goto free_pt;
1159
1160 return mm;
1161
1162 free_pt:
1163 /* don't put binfmt in mmput, we haven't got module yet */
1164 mm->binfmt = NULL;
1165 mmput(mm);
1166
1167 fail_nomem:
1168 return NULL;
1169 }
1170
copy_mm(unsigned long clone_flags,struct task_struct * tsk)1171 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
1172 {
1173 struct mm_struct *mm, *oldmm;
1174 int retval;
1175
1176 tsk->min_flt = tsk->maj_flt = 0;
1177 tsk->nvcsw = tsk->nivcsw = 0;
1178 #ifdef CONFIG_DETECT_HUNG_TASK
1179 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
1180 #endif
1181
1182 tsk->mm = NULL;
1183 tsk->active_mm = NULL;
1184
1185 /*
1186 * Are we cloning a kernel thread?
1187 *
1188 * We need to steal a active VM for that..
1189 */
1190 oldmm = current->mm;
1191 if (!oldmm)
1192 return 0;
1193
1194 /* initialize the new vmacache entries */
1195 vmacache_flush(tsk);
1196
1197 if (clone_flags & CLONE_VM) {
1198 atomic_inc(&oldmm->mm_users);
1199 mm = oldmm;
1200 goto good_mm;
1201 }
1202
1203 retval = -ENOMEM;
1204 mm = dup_mm(tsk);
1205 if (!mm)
1206 goto fail_nomem;
1207
1208 good_mm:
1209 tsk->mm = mm;
1210 tsk->active_mm = mm;
1211 return 0;
1212
1213 fail_nomem:
1214 return retval;
1215 }
1216
copy_fs(unsigned long clone_flags,struct task_struct * tsk)1217 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
1218 {
1219 struct fs_struct *fs = current->fs;
1220 if (clone_flags & CLONE_FS) {
1221 /* tsk->fs is already what we want */
1222 spin_lock(&fs->lock);
1223 if (fs->in_exec) {
1224 spin_unlock(&fs->lock);
1225 return -EAGAIN;
1226 }
1227 fs->users++;
1228 spin_unlock(&fs->lock);
1229 return 0;
1230 }
1231 tsk->fs = copy_fs_struct(fs);
1232 if (!tsk->fs)
1233 return -ENOMEM;
1234 return 0;
1235 }
1236
copy_files(unsigned long clone_flags,struct task_struct * tsk)1237 static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
1238 {
1239 struct files_struct *oldf, *newf;
1240 int error = 0;
1241
1242 /*
1243 * A background process may not have any files ...
1244 */
1245 oldf = current->files;
1246 if (!oldf)
1247 goto out;
1248
1249 if (clone_flags & CLONE_FILES) {
1250 atomic_inc(&oldf->count);
1251 goto out;
1252 }
1253
1254 newf = dup_fd(oldf, &error);
1255 if (!newf)
1256 goto out;
1257
1258 tsk->files = newf;
1259 error = 0;
1260 out:
1261 return error;
1262 }
1263
copy_io(unsigned long clone_flags,struct task_struct * tsk)1264 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
1265 {
1266 #ifdef CONFIG_BLOCK
1267 struct io_context *ioc = current->io_context;
1268 struct io_context *new_ioc;
1269
1270 if (!ioc)
1271 return 0;
1272 /*
1273 * Share io context with parent, if CLONE_IO is set
1274 */
1275 if (clone_flags & CLONE_IO) {
1276 ioc_task_link(ioc);
1277 tsk->io_context = ioc;
1278 } else if (ioprio_valid(ioc->ioprio)) {
1279 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE);
1280 if (unlikely(!new_ioc))
1281 return -ENOMEM;
1282
1283 new_ioc->ioprio = ioc->ioprio;
1284 put_io_context(new_ioc);
1285 }
1286 #endif
1287 return 0;
1288 }
1289
copy_sighand(unsigned long clone_flags,struct task_struct * tsk)1290 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
1291 {
1292 struct sighand_struct *sig;
1293
1294 if (clone_flags & CLONE_SIGHAND) {
1295 atomic_inc(¤t->sighand->count);
1296 return 0;
1297 }
1298 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1299 rcu_assign_pointer(tsk->sighand, sig);
1300 if (!sig)
1301 return -ENOMEM;
1302
1303 atomic_set(&sig->count, 1);
1304 memcpy(sig->action, current->sighand->action, sizeof(sig->action));
1305 return 0;
1306 }
1307
__cleanup_sighand(struct sighand_struct * sighand)1308 void __cleanup_sighand(struct sighand_struct *sighand)
1309 {
1310 if (atomic_dec_and_test(&sighand->count)) {
1311 signalfd_cleanup(sighand);
1312 /*
1313 * sighand_cachep is SLAB_DESTROY_BY_RCU so we can free it
1314 * without an RCU grace period, see __lock_task_sighand().
1315 */
1316 kmem_cache_free(sighand_cachep, sighand);
1317 }
1318 }
1319
1320 /*
1321 * Initialize POSIX timer handling for a thread group.
1322 */
posix_cpu_timers_init_group(struct signal_struct * sig)1323 static void posix_cpu_timers_init_group(struct signal_struct *sig)
1324 {
1325 unsigned long cpu_limit;
1326
1327 cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1328 if (cpu_limit != RLIM_INFINITY) {
1329 sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit);
1330 sig->cputimer.running = true;
1331 }
1332
1333 /* The timer lists. */
1334 INIT_LIST_HEAD(&sig->cpu_timers[0]);
1335 INIT_LIST_HEAD(&sig->cpu_timers[1]);
1336 INIT_LIST_HEAD(&sig->cpu_timers[2]);
1337 }
1338
copy_signal(unsigned long clone_flags,struct task_struct * tsk)1339 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
1340 {
1341 struct signal_struct *sig;
1342
1343 if (clone_flags & CLONE_THREAD)
1344 return 0;
1345
1346 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
1347 tsk->signal = sig;
1348 if (!sig)
1349 return -ENOMEM;
1350
1351 sig->nr_threads = 1;
1352 atomic_set(&sig->live, 1);
1353 atomic_set(&sig->sigcnt, 1);
1354
1355 /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */
1356 sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node);
1357 tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head);
1358
1359 init_waitqueue_head(&sig->wait_chldexit);
1360 sig->curr_target = tsk;
1361 init_sigpending(&sig->shared_pending);
1362 INIT_LIST_HEAD(&sig->posix_timers);
1363 seqlock_init(&sig->stats_lock);
1364 prev_cputime_init(&sig->prev_cputime);
1365
1366 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1367 sig->real_timer.function = it_real_fn;
1368
1369 task_lock(current->group_leader);
1370 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
1371 task_unlock(current->group_leader);
1372
1373 posix_cpu_timers_init_group(sig);
1374
1375 tty_audit_fork(sig);
1376 sched_autogroup_fork(sig);
1377
1378 sig->oom_score_adj = current->signal->oom_score_adj;
1379 sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1380
1381 sig->has_child_subreaper = current->signal->has_child_subreaper ||
1382 current->signal->is_child_subreaper;
1383
1384 mutex_init(&sig->cred_guard_mutex);
1385
1386 return 0;
1387 }
1388
copy_seccomp(struct task_struct * p)1389 static void copy_seccomp(struct task_struct *p)
1390 {
1391 #ifdef CONFIG_SECCOMP
1392 /*
1393 * Must be called with sighand->lock held, which is common to
1394 * all threads in the group. Holding cred_guard_mutex is not
1395 * needed because this new task is not yet running and cannot
1396 * be racing exec.
1397 */
1398 assert_spin_locked(¤t->sighand->siglock);
1399
1400 /* Ref-count the new filter user, and assign it. */
1401 get_seccomp_filter(current);
1402 p->seccomp = current->seccomp;
1403
1404 /*
1405 * Explicitly enable no_new_privs here in case it got set
1406 * between the task_struct being duplicated and holding the
1407 * sighand lock. The seccomp state and nnp must be in sync.
1408 */
1409 if (task_no_new_privs(current))
1410 task_set_no_new_privs(p);
1411
1412 /*
1413 * If the parent gained a seccomp mode after copying thread
1414 * flags and between before we held the sighand lock, we have
1415 * to manually enable the seccomp thread flag here.
1416 */
1417 if (p->seccomp.mode != SECCOMP_MODE_DISABLED)
1418 set_tsk_thread_flag(p, TIF_SECCOMP);
1419 #endif
1420 }
1421
SYSCALL_DEFINE1(set_tid_address,int __user *,tidptr)1422 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1423 {
1424 current->clear_child_tid = tidptr;
1425
1426 return task_pid_vnr(current);
1427 }
1428
rt_mutex_init_task(struct task_struct * p)1429 static void rt_mutex_init_task(struct task_struct *p)
1430 {
1431 raw_spin_lock_init(&p->pi_lock);
1432 #ifdef CONFIG_RT_MUTEXES
1433 p->pi_waiters = RB_ROOT;
1434 p->pi_waiters_leftmost = NULL;
1435 p->pi_blocked_on = NULL;
1436 #endif
1437 }
1438
1439 /*
1440 * Initialize POSIX timer handling for a single task.
1441 */
posix_cpu_timers_init(struct task_struct * tsk)1442 static void posix_cpu_timers_init(struct task_struct *tsk)
1443 {
1444 tsk->cputime_expires.prof_exp = 0;
1445 tsk->cputime_expires.virt_exp = 0;
1446 tsk->cputime_expires.sched_exp = 0;
1447 INIT_LIST_HEAD(&tsk->cpu_timers[0]);
1448 INIT_LIST_HEAD(&tsk->cpu_timers[1]);
1449 INIT_LIST_HEAD(&tsk->cpu_timers[2]);
1450 }
1451
1452 static inline void
init_task_pid(struct task_struct * task,enum pid_type type,struct pid * pid)1453 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid)
1454 {
1455 task->pids[type].pid = pid;
1456 }
1457
1458 /*
1459 * This creates a new process as a copy of the old one,
1460 * but does not actually start it yet.
1461 *
1462 * It copies the registers, and all the appropriate
1463 * parts of the process environment (as per the clone
1464 * flags). The actual kick-off is left to the caller.
1465 */
copy_process(unsigned long clone_flags,unsigned long stack_start,unsigned long stack_size,int __user * child_tidptr,struct pid * pid,int trace,unsigned long tls,int node)1466 static __latent_entropy struct task_struct *copy_process(
1467 unsigned long clone_flags,
1468 unsigned long stack_start,
1469 unsigned long stack_size,
1470 int __user *child_tidptr,
1471 struct pid *pid,
1472 int trace,
1473 unsigned long tls,
1474 int node)
1475 {
1476 int retval;
1477 struct task_struct *p;
1478
1479 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1480 return ERR_PTR(-EINVAL);
1481
1482 if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS))
1483 return ERR_PTR(-EINVAL);
1484
1485 /*
1486 * Thread groups must share signals as well, and detached threads
1487 * can only be started up within the thread group.
1488 */
1489 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1490 return ERR_PTR(-EINVAL);
1491
1492 /*
1493 * Shared signal handlers imply shared VM. By way of the above,
1494 * thread groups also imply shared VM. Blocking this case allows
1495 * for various simplifications in other code.
1496 */
1497 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1498 return ERR_PTR(-EINVAL);
1499
1500 /*
1501 * Siblings of global init remain as zombies on exit since they are
1502 * not reaped by their parent (swapper). To solve this and to avoid
1503 * multi-rooted process trees, prevent global and container-inits
1504 * from creating siblings.
1505 */
1506 if ((clone_flags & CLONE_PARENT) &&
1507 current->signal->flags & SIGNAL_UNKILLABLE)
1508 return ERR_PTR(-EINVAL);
1509
1510 /*
1511 * If the new process will be in a different pid or user namespace
1512 * do not allow it to share a thread group with the forking task.
1513 */
1514 if (clone_flags & CLONE_THREAD) {
1515 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) ||
1516 (task_active_pid_ns(current) !=
1517 current->nsproxy->pid_ns_for_children))
1518 return ERR_PTR(-EINVAL);
1519 }
1520
1521 retval = security_task_create(clone_flags);
1522 if (retval)
1523 goto fork_out;
1524
1525 retval = -ENOMEM;
1526 p = dup_task_struct(current, node);
1527 if (!p)
1528 goto fork_out;
1529
1530 ftrace_graph_init_task(p);
1531
1532 rt_mutex_init_task(p);
1533
1534 #ifdef CONFIG_PROVE_LOCKING
1535 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1536 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1537 #endif
1538 retval = -EAGAIN;
1539 if (atomic_read(&p->real_cred->user->processes) >=
1540 task_rlimit(p, RLIMIT_NPROC)) {
1541 if (p->real_cred->user != INIT_USER &&
1542 !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
1543 goto bad_fork_free;
1544 }
1545 current->flags &= ~PF_NPROC_EXCEEDED;
1546
1547 retval = copy_creds(p, clone_flags);
1548 if (retval < 0)
1549 goto bad_fork_free;
1550
1551 /*
1552 * If multiple threads are within copy_process(), then this check
1553 * triggers too late. This doesn't hurt, the check is only there
1554 * to stop root fork bombs.
1555 */
1556 retval = -EAGAIN;
1557 if (nr_threads >= max_threads)
1558 goto bad_fork_cleanup_count;
1559
1560 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */
1561 p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER);
1562 p->flags |= PF_FORKNOEXEC;
1563 INIT_LIST_HEAD(&p->children);
1564 INIT_LIST_HEAD(&p->sibling);
1565 rcu_copy_process(p);
1566 p->vfork_done = NULL;
1567 spin_lock_init(&p->alloc_lock);
1568
1569 init_sigpending(&p->pending);
1570
1571 p->utime = p->stime = p->gtime = 0;
1572 p->utimescaled = p->stimescaled = 0;
1573 prev_cputime_init(&p->prev_cputime);
1574
1575 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
1576 seqcount_init(&p->vtime_seqcount);
1577 p->vtime_snap = 0;
1578 p->vtime_snap_whence = VTIME_INACTIVE;
1579 #endif
1580
1581 #if defined(SPLIT_RSS_COUNTING)
1582 memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1583 #endif
1584
1585 p->default_timer_slack_ns = current->timer_slack_ns;
1586
1587 task_io_accounting_init(&p->ioac);
1588 acct_clear_integrals(p);
1589
1590 posix_cpu_timers_init(p);
1591
1592 p->start_time = ktime_get_ns();
1593 p->real_start_time = ktime_get_boot_ns();
1594 p->io_context = NULL;
1595 p->audit_context = NULL;
1596 cgroup_fork(p);
1597 #ifdef CONFIG_NUMA
1598 p->mempolicy = mpol_dup(p->mempolicy);
1599 if (IS_ERR(p->mempolicy)) {
1600 retval = PTR_ERR(p->mempolicy);
1601 p->mempolicy = NULL;
1602 goto bad_fork_cleanup_threadgroup_lock;
1603 }
1604 #endif
1605 #ifdef CONFIG_CPUSETS
1606 p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
1607 p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
1608 seqcount_init(&p->mems_allowed_seq);
1609 #endif
1610 #ifdef CONFIG_TRACE_IRQFLAGS
1611 p->irq_events = 0;
1612 p->hardirqs_enabled = 0;
1613 p->hardirq_enable_ip = 0;
1614 p->hardirq_enable_event = 0;
1615 p->hardirq_disable_ip = _THIS_IP_;
1616 p->hardirq_disable_event = 0;
1617 p->softirqs_enabled = 1;
1618 p->softirq_enable_ip = _THIS_IP_;
1619 p->softirq_enable_event = 0;
1620 p->softirq_disable_ip = 0;
1621 p->softirq_disable_event = 0;
1622 p->hardirq_context = 0;
1623 p->softirq_context = 0;
1624 #endif
1625
1626 p->pagefault_disabled = 0;
1627
1628 #ifdef CONFIG_LOCKDEP
1629 p->lockdep_depth = 0; /* no locks held yet */
1630 p->curr_chain_key = 0;
1631 p->lockdep_recursion = 0;
1632 #endif
1633
1634 #ifdef CONFIG_DEBUG_MUTEXES
1635 p->blocked_on = NULL; /* not blocked yet */
1636 #endif
1637 #ifdef CONFIG_BCACHE
1638 p->sequential_io = 0;
1639 p->sequential_io_avg = 0;
1640 #endif
1641
1642 /* Perform scheduler related setup. Assign this task to a CPU. */
1643 retval = sched_fork(clone_flags, p);
1644 if (retval)
1645 goto bad_fork_cleanup_policy;
1646
1647 retval = perf_event_init_task(p);
1648 if (retval)
1649 goto bad_fork_cleanup_policy;
1650 retval = audit_alloc(p);
1651 if (retval)
1652 goto bad_fork_cleanup_perf;
1653 /* copy all the process information */
1654 shm_init_task(p);
1655 retval = copy_semundo(clone_flags, p);
1656 if (retval)
1657 goto bad_fork_cleanup_audit;
1658 retval = copy_files(clone_flags, p);
1659 if (retval)
1660 goto bad_fork_cleanup_semundo;
1661 retval = copy_fs(clone_flags, p);
1662 if (retval)
1663 goto bad_fork_cleanup_files;
1664 retval = copy_sighand(clone_flags, p);
1665 if (retval)
1666 goto bad_fork_cleanup_fs;
1667 retval = copy_signal(clone_flags, p);
1668 if (retval)
1669 goto bad_fork_cleanup_sighand;
1670 retval = copy_mm(clone_flags, p);
1671 if (retval)
1672 goto bad_fork_cleanup_signal;
1673 retval = copy_namespaces(clone_flags, p);
1674 if (retval)
1675 goto bad_fork_cleanup_mm;
1676 retval = copy_io(clone_flags, p);
1677 if (retval)
1678 goto bad_fork_cleanup_namespaces;
1679 retval = copy_thread_tls(clone_flags, stack_start, stack_size, p, tls);
1680 if (retval)
1681 goto bad_fork_cleanup_io;
1682
1683 if (pid != &init_struct_pid) {
1684 pid = alloc_pid(p->nsproxy->pid_ns_for_children);
1685 if (IS_ERR(pid)) {
1686 retval = PTR_ERR(pid);
1687 goto bad_fork_cleanup_thread;
1688 }
1689 }
1690
1691 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1692 /*
1693 * Clear TID on mm_release()?
1694 */
1695 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL;
1696 #ifdef CONFIG_BLOCK
1697 p->plug = NULL;
1698 #endif
1699 #ifdef CONFIG_FUTEX
1700 p->robust_list = NULL;
1701 #ifdef CONFIG_COMPAT
1702 p->compat_robust_list = NULL;
1703 #endif
1704 INIT_LIST_HEAD(&p->pi_state_list);
1705 p->pi_state_cache = NULL;
1706 #endif
1707 /*
1708 * sigaltstack should be cleared when sharing the same VM
1709 */
1710 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1711 sas_ss_reset(p);
1712
1713 /*
1714 * Syscall tracing and stepping should be turned off in the
1715 * child regardless of CLONE_PTRACE.
1716 */
1717 user_disable_single_step(p);
1718 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1719 #ifdef TIF_SYSCALL_EMU
1720 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1721 #endif
1722 clear_all_latency_tracing(p);
1723
1724 /* ok, now we should be set up.. */
1725 p->pid = pid_nr(pid);
1726 if (clone_flags & CLONE_THREAD) {
1727 p->exit_signal = -1;
1728 p->group_leader = current->group_leader;
1729 p->tgid = current->tgid;
1730 } else {
1731 if (clone_flags & CLONE_PARENT)
1732 p->exit_signal = current->group_leader->exit_signal;
1733 else
1734 p->exit_signal = (clone_flags & CSIGNAL);
1735 p->group_leader = p;
1736 p->tgid = p->pid;
1737 }
1738
1739 p->nr_dirtied = 0;
1740 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
1741 p->dirty_paused_when = 0;
1742
1743 p->pdeath_signal = 0;
1744 INIT_LIST_HEAD(&p->thread_group);
1745 p->task_works = NULL;
1746
1747 threadgroup_change_begin(current);
1748 /*
1749 * Ensure that the cgroup subsystem policies allow the new process to be
1750 * forked. It should be noted the the new process's css_set can be changed
1751 * between here and cgroup_post_fork() if an organisation operation is in
1752 * progress.
1753 */
1754 retval = cgroup_can_fork(p);
1755 if (retval)
1756 goto bad_fork_free_pid;
1757
1758 /*
1759 * Make it visible to the rest of the system, but dont wake it up yet.
1760 * Need tasklist lock for parent etc handling!
1761 */
1762 write_lock_irq(&tasklist_lock);
1763
1764 /* CLONE_PARENT re-uses the old parent */
1765 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1766 p->real_parent = current->real_parent;
1767 p->parent_exec_id = current->parent_exec_id;
1768 } else {
1769 p->real_parent = current;
1770 p->parent_exec_id = current->self_exec_id;
1771 }
1772
1773 spin_lock(¤t->sighand->siglock);
1774
1775 /*
1776 * Copy seccomp details explicitly here, in case they were changed
1777 * before holding sighand lock.
1778 */
1779 copy_seccomp(p);
1780
1781 /*
1782 * Process group and session signals need to be delivered to just the
1783 * parent before the fork or both the parent and the child after the
1784 * fork. Restart if a signal comes in before we add the new process to
1785 * it's process group.
1786 * A fatal signal pending means that current will exit, so the new
1787 * thread can't slip out of an OOM kill (or normal SIGKILL).
1788 */
1789 recalc_sigpending();
1790 if (signal_pending(current)) {
1791 retval = -ERESTARTNOINTR;
1792 goto bad_fork_cancel_cgroup;
1793 }
1794 if (unlikely(!(ns_of_pid(pid)->nr_hashed & PIDNS_HASH_ADDING))) {
1795 retval = -ENOMEM;
1796 goto bad_fork_cancel_cgroup;
1797 }
1798
1799 if (likely(p->pid)) {
1800 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
1801
1802 init_task_pid(p, PIDTYPE_PID, pid);
1803 if (thread_group_leader(p)) {
1804 init_task_pid(p, PIDTYPE_PGID, task_pgrp(current));
1805 init_task_pid(p, PIDTYPE_SID, task_session(current));
1806
1807 if (is_child_reaper(pid)) {
1808 ns_of_pid(pid)->child_reaper = p;
1809 p->signal->flags |= SIGNAL_UNKILLABLE;
1810 }
1811
1812 p->signal->leader_pid = pid;
1813 p->signal->tty = tty_kref_get(current->signal->tty);
1814 list_add_tail(&p->sibling, &p->real_parent->children);
1815 list_add_tail_rcu(&p->tasks, &init_task.tasks);
1816 attach_pid(p, PIDTYPE_PGID);
1817 attach_pid(p, PIDTYPE_SID);
1818 __this_cpu_inc(process_counts);
1819 } else {
1820 current->signal->nr_threads++;
1821 atomic_inc(¤t->signal->live);
1822 atomic_inc(¤t->signal->sigcnt);
1823 list_add_tail_rcu(&p->thread_group,
1824 &p->group_leader->thread_group);
1825 list_add_tail_rcu(&p->thread_node,
1826 &p->signal->thread_head);
1827 }
1828 attach_pid(p, PIDTYPE_PID);
1829 nr_threads++;
1830 }
1831
1832 total_forks++;
1833 spin_unlock(¤t->sighand->siglock);
1834 syscall_tracepoint_update(p);
1835 write_unlock_irq(&tasklist_lock);
1836
1837 proc_fork_connector(p);
1838 cgroup_post_fork(p);
1839 threadgroup_change_end(current);
1840 perf_event_fork(p);
1841
1842 trace_task_newtask(p, clone_flags);
1843 uprobe_copy_process(p, clone_flags);
1844
1845 return p;
1846
1847 bad_fork_cancel_cgroup:
1848 spin_unlock(¤t->sighand->siglock);
1849 write_unlock_irq(&tasklist_lock);
1850 cgroup_cancel_fork(p);
1851 bad_fork_free_pid:
1852 threadgroup_change_end(current);
1853 if (pid != &init_struct_pid)
1854 free_pid(pid);
1855 bad_fork_cleanup_thread:
1856 exit_thread(p);
1857 bad_fork_cleanup_io:
1858 if (p->io_context)
1859 exit_io_context(p);
1860 bad_fork_cleanup_namespaces:
1861 exit_task_namespaces(p);
1862 bad_fork_cleanup_mm:
1863 if (p->mm)
1864 mmput(p->mm);
1865 bad_fork_cleanup_signal:
1866 if (!(clone_flags & CLONE_THREAD))
1867 free_signal_struct(p->signal);
1868 bad_fork_cleanup_sighand:
1869 __cleanup_sighand(p->sighand);
1870 bad_fork_cleanup_fs:
1871 exit_fs(p); /* blocking */
1872 bad_fork_cleanup_files:
1873 exit_files(p); /* blocking */
1874 bad_fork_cleanup_semundo:
1875 exit_sem(p);
1876 bad_fork_cleanup_audit:
1877 audit_free(p);
1878 bad_fork_cleanup_perf:
1879 perf_event_free_task(p);
1880 bad_fork_cleanup_policy:
1881 #ifdef CONFIG_NUMA
1882 mpol_put(p->mempolicy);
1883 bad_fork_cleanup_threadgroup_lock:
1884 #endif
1885 delayacct_tsk_free(p);
1886 bad_fork_cleanup_count:
1887 atomic_dec(&p->cred->user->processes);
1888 exit_creds(p);
1889 bad_fork_free:
1890 p->state = TASK_DEAD;
1891 put_task_stack(p);
1892 free_task(p);
1893 fork_out:
1894 return ERR_PTR(retval);
1895 }
1896
init_idle_pids(struct pid_link * links)1897 static inline void init_idle_pids(struct pid_link *links)
1898 {
1899 enum pid_type type;
1900
1901 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
1902 INIT_HLIST_NODE(&links[type].node); /* not really needed */
1903 links[type].pid = &init_struct_pid;
1904 }
1905 }
1906
fork_idle(int cpu)1907 struct task_struct *fork_idle(int cpu)
1908 {
1909 struct task_struct *task;
1910 task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0, 0,
1911 cpu_to_node(cpu));
1912 if (!IS_ERR(task)) {
1913 init_idle_pids(task->pids);
1914 init_idle(task, cpu);
1915 }
1916
1917 return task;
1918 }
1919
1920 /*
1921 * Ok, this is the main fork-routine.
1922 *
1923 * It copies the process, and if successful kick-starts
1924 * it and waits for it to finish using the VM if required.
1925 */
_do_fork(unsigned long clone_flags,unsigned long stack_start,unsigned long stack_size,int __user * parent_tidptr,int __user * child_tidptr,unsigned long tls)1926 long _do_fork(unsigned long clone_flags,
1927 unsigned long stack_start,
1928 unsigned long stack_size,
1929 int __user *parent_tidptr,
1930 int __user *child_tidptr,
1931 unsigned long tls)
1932 {
1933 struct task_struct *p;
1934 int trace = 0;
1935 long nr;
1936
1937 /*
1938 * Determine whether and which event to report to ptracer. When
1939 * called from kernel_thread or CLONE_UNTRACED is explicitly
1940 * requested, no event is reported; otherwise, report if the event
1941 * for the type of forking is enabled.
1942 */
1943 if (!(clone_flags & CLONE_UNTRACED)) {
1944 if (clone_flags & CLONE_VFORK)
1945 trace = PTRACE_EVENT_VFORK;
1946 else if ((clone_flags & CSIGNAL) != SIGCHLD)
1947 trace = PTRACE_EVENT_CLONE;
1948 else
1949 trace = PTRACE_EVENT_FORK;
1950
1951 if (likely(!ptrace_event_enabled(current, trace)))
1952 trace = 0;
1953 }
1954
1955 p = copy_process(clone_flags, stack_start, stack_size,
1956 child_tidptr, NULL, trace, tls, NUMA_NO_NODE);
1957 add_latent_entropy();
1958 /*
1959 * Do this prior waking up the new thread - the thread pointer
1960 * might get invalid after that point, if the thread exits quickly.
1961 */
1962 if (!IS_ERR(p)) {
1963 struct completion vfork;
1964 struct pid *pid;
1965
1966 trace_sched_process_fork(current, p);
1967
1968 pid = get_task_pid(p, PIDTYPE_PID);
1969 nr = pid_vnr(pid);
1970
1971 if (clone_flags & CLONE_PARENT_SETTID)
1972 put_user(nr, parent_tidptr);
1973
1974 if (clone_flags & CLONE_VFORK) {
1975 p->vfork_done = &vfork;
1976 init_completion(&vfork);
1977 get_task_struct(p);
1978 }
1979
1980 wake_up_new_task(p);
1981
1982 /* forking complete and child started to run, tell ptracer */
1983 if (unlikely(trace))
1984 ptrace_event_pid(trace, pid);
1985
1986 if (clone_flags & CLONE_VFORK) {
1987 if (!wait_for_vfork_done(p, &vfork))
1988 ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid);
1989 }
1990
1991 put_pid(pid);
1992 } else {
1993 nr = PTR_ERR(p);
1994 }
1995 return nr;
1996 }
1997
1998 #ifndef CONFIG_HAVE_COPY_THREAD_TLS
1999 /* For compatibility with architectures that call do_fork directly rather than
2000 * using the syscall entry points below. */
do_fork(unsigned long clone_flags,unsigned long stack_start,unsigned long stack_size,int __user * parent_tidptr,int __user * child_tidptr)2001 long do_fork(unsigned long clone_flags,
2002 unsigned long stack_start,
2003 unsigned long stack_size,
2004 int __user *parent_tidptr,
2005 int __user *child_tidptr)
2006 {
2007 return _do_fork(clone_flags, stack_start, stack_size,
2008 parent_tidptr, child_tidptr, 0);
2009 }
2010 #endif
2011
2012 /*
2013 * Create a kernel thread.
2014 */
kernel_thread(int (* fn)(void *),void * arg,unsigned long flags)2015 pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
2016 {
2017 return _do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn,
2018 (unsigned long)arg, NULL, NULL, 0);
2019 }
2020
2021 #ifdef __ARCH_WANT_SYS_FORK
SYSCALL_DEFINE0(fork)2022 SYSCALL_DEFINE0(fork)
2023 {
2024 #ifdef CONFIG_MMU
2025 return _do_fork(SIGCHLD, 0, 0, NULL, NULL, 0);
2026 #else
2027 /* can not support in nommu mode */
2028 return -EINVAL;
2029 #endif
2030 }
2031 #endif
2032
2033 #ifdef __ARCH_WANT_SYS_VFORK
SYSCALL_DEFINE0(vfork)2034 SYSCALL_DEFINE0(vfork)
2035 {
2036 return _do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0,
2037 0, NULL, NULL, 0);
2038 }
2039 #endif
2040
2041 #ifdef __ARCH_WANT_SYS_CLONE
2042 #ifdef CONFIG_CLONE_BACKWARDS
SYSCALL_DEFINE5(clone,unsigned long,clone_flags,unsigned long,newsp,int __user *,parent_tidptr,unsigned long,tls,int __user *,child_tidptr)2043 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2044 int __user *, parent_tidptr,
2045 unsigned long, tls,
2046 int __user *, child_tidptr)
2047 #elif defined(CONFIG_CLONE_BACKWARDS2)
2048 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags,
2049 int __user *, parent_tidptr,
2050 int __user *, child_tidptr,
2051 unsigned long, tls)
2052 #elif defined(CONFIG_CLONE_BACKWARDS3)
2053 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp,
2054 int, stack_size,
2055 int __user *, parent_tidptr,
2056 int __user *, child_tidptr,
2057 unsigned long, tls)
2058 #else
2059 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2060 int __user *, parent_tidptr,
2061 int __user *, child_tidptr,
2062 unsigned long, tls)
2063 #endif
2064 {
2065 return _do_fork(clone_flags, newsp, 0, parent_tidptr, child_tidptr, tls);
2066 }
2067 #endif
2068
2069 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
2070 #define ARCH_MIN_MMSTRUCT_ALIGN 0
2071 #endif
2072
sighand_ctor(void * data)2073 static void sighand_ctor(void *data)
2074 {
2075 struct sighand_struct *sighand = data;
2076
2077 spin_lock_init(&sighand->siglock);
2078 init_waitqueue_head(&sighand->signalfd_wqh);
2079 }
2080
proc_caches_init(void)2081 void __init proc_caches_init(void)
2082 {
2083 sighand_cachep = kmem_cache_create("sighand_cache",
2084 sizeof(struct sighand_struct), 0,
2085 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU|
2086 SLAB_NOTRACK|SLAB_ACCOUNT, sighand_ctor);
2087 signal_cachep = kmem_cache_create("signal_cache",
2088 sizeof(struct signal_struct), 0,
2089 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT,
2090 NULL);
2091 files_cachep = kmem_cache_create("files_cache",
2092 sizeof(struct files_struct), 0,
2093 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT,
2094 NULL);
2095 fs_cachep = kmem_cache_create("fs_cache",
2096 sizeof(struct fs_struct), 0,
2097 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT,
2098 NULL);
2099 /*
2100 * FIXME! The "sizeof(struct mm_struct)" currently includes the
2101 * whole struct cpumask for the OFFSTACK case. We could change
2102 * this to *only* allocate as much of it as required by the
2103 * maximum number of CPU's we can ever have. The cpumask_allocation
2104 * is at the end of the structure, exactly for that reason.
2105 */
2106 mm_cachep = kmem_cache_create("mm_struct",
2107 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
2108 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK|SLAB_ACCOUNT,
2109 NULL);
2110 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT);
2111 mmap_init();
2112 nsproxy_cache_init();
2113 }
2114
2115 /*
2116 * Check constraints on flags passed to the unshare system call.
2117 */
check_unshare_flags(unsigned long unshare_flags)2118 static int check_unshare_flags(unsigned long unshare_flags)
2119 {
2120 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
2121 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
2122 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET|
2123 CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP))
2124 return -EINVAL;
2125 /*
2126 * Not implemented, but pretend it works if there is nothing
2127 * to unshare. Note that unsharing the address space or the
2128 * signal handlers also need to unshare the signal queues (aka
2129 * CLONE_THREAD).
2130 */
2131 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
2132 if (!thread_group_empty(current))
2133 return -EINVAL;
2134 }
2135 if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) {
2136 if (atomic_read(¤t->sighand->count) > 1)
2137 return -EINVAL;
2138 }
2139 if (unshare_flags & CLONE_VM) {
2140 if (!current_is_single_threaded())
2141 return -EINVAL;
2142 }
2143
2144 return 0;
2145 }
2146
2147 /*
2148 * Unshare the filesystem structure if it is being shared
2149 */
unshare_fs(unsigned long unshare_flags,struct fs_struct ** new_fsp)2150 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
2151 {
2152 struct fs_struct *fs = current->fs;
2153
2154 if (!(unshare_flags & CLONE_FS) || !fs)
2155 return 0;
2156
2157 /* don't need lock here; in the worst case we'll do useless copy */
2158 if (fs->users == 1)
2159 return 0;
2160
2161 *new_fsp = copy_fs_struct(fs);
2162 if (!*new_fsp)
2163 return -ENOMEM;
2164
2165 return 0;
2166 }
2167
2168 /*
2169 * Unshare file descriptor table if it is being shared
2170 */
unshare_fd(unsigned long unshare_flags,struct files_struct ** new_fdp)2171 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
2172 {
2173 struct files_struct *fd = current->files;
2174 int error = 0;
2175
2176 if ((unshare_flags & CLONE_FILES) &&
2177 (fd && atomic_read(&fd->count) > 1)) {
2178 *new_fdp = dup_fd(fd, &error);
2179 if (!*new_fdp)
2180 return error;
2181 }
2182
2183 return 0;
2184 }
2185
2186 /*
2187 * unshare allows a process to 'unshare' part of the process
2188 * context which was originally shared using clone. copy_*
2189 * functions used by do_fork() cannot be used here directly
2190 * because they modify an inactive task_struct that is being
2191 * constructed. Here we are modifying the current, active,
2192 * task_struct.
2193 */
SYSCALL_DEFINE1(unshare,unsigned long,unshare_flags)2194 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
2195 {
2196 struct fs_struct *fs, *new_fs = NULL;
2197 struct files_struct *fd, *new_fd = NULL;
2198 struct cred *new_cred = NULL;
2199 struct nsproxy *new_nsproxy = NULL;
2200 int do_sysvsem = 0;
2201 int err;
2202
2203 /*
2204 * If unsharing a user namespace must also unshare the thread group
2205 * and unshare the filesystem root and working directories.
2206 */
2207 if (unshare_flags & CLONE_NEWUSER)
2208 unshare_flags |= CLONE_THREAD | CLONE_FS;
2209 /*
2210 * If unsharing vm, must also unshare signal handlers.
2211 */
2212 if (unshare_flags & CLONE_VM)
2213 unshare_flags |= CLONE_SIGHAND;
2214 /*
2215 * If unsharing a signal handlers, must also unshare the signal queues.
2216 */
2217 if (unshare_flags & CLONE_SIGHAND)
2218 unshare_flags |= CLONE_THREAD;
2219 /*
2220 * If unsharing namespace, must also unshare filesystem information.
2221 */
2222 if (unshare_flags & CLONE_NEWNS)
2223 unshare_flags |= CLONE_FS;
2224
2225 err = check_unshare_flags(unshare_flags);
2226 if (err)
2227 goto bad_unshare_out;
2228 /*
2229 * CLONE_NEWIPC must also detach from the undolist: after switching
2230 * to a new ipc namespace, the semaphore arrays from the old
2231 * namespace are unreachable.
2232 */
2233 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
2234 do_sysvsem = 1;
2235 err = unshare_fs(unshare_flags, &new_fs);
2236 if (err)
2237 goto bad_unshare_out;
2238 err = unshare_fd(unshare_flags, &new_fd);
2239 if (err)
2240 goto bad_unshare_cleanup_fs;
2241 err = unshare_userns(unshare_flags, &new_cred);
2242 if (err)
2243 goto bad_unshare_cleanup_fd;
2244 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
2245 new_cred, new_fs);
2246 if (err)
2247 goto bad_unshare_cleanup_cred;
2248
2249 if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
2250 if (do_sysvsem) {
2251 /*
2252 * CLONE_SYSVSEM is equivalent to sys_exit().
2253 */
2254 exit_sem(current);
2255 }
2256 if (unshare_flags & CLONE_NEWIPC) {
2257 /* Orphan segments in old ns (see sem above). */
2258 exit_shm(current);
2259 shm_init_task(current);
2260 }
2261
2262 if (new_nsproxy)
2263 switch_task_namespaces(current, new_nsproxy);
2264
2265 task_lock(current);
2266
2267 if (new_fs) {
2268 fs = current->fs;
2269 spin_lock(&fs->lock);
2270 current->fs = new_fs;
2271 if (--fs->users)
2272 new_fs = NULL;
2273 else
2274 new_fs = fs;
2275 spin_unlock(&fs->lock);
2276 }
2277
2278 if (new_fd) {
2279 fd = current->files;
2280 current->files = new_fd;
2281 new_fd = fd;
2282 }
2283
2284 task_unlock(current);
2285
2286 if (new_cred) {
2287 /* Install the new user namespace */
2288 commit_creds(new_cred);
2289 new_cred = NULL;
2290 }
2291 }
2292
2293 bad_unshare_cleanup_cred:
2294 if (new_cred)
2295 put_cred(new_cred);
2296 bad_unshare_cleanup_fd:
2297 if (new_fd)
2298 put_files_struct(new_fd);
2299
2300 bad_unshare_cleanup_fs:
2301 if (new_fs)
2302 free_fs_struct(new_fs);
2303
2304 bad_unshare_out:
2305 return err;
2306 }
2307
2308 /*
2309 * Helper to unshare the files of the current task.
2310 * We don't want to expose copy_files internals to
2311 * the exec layer of the kernel.
2312 */
2313
unshare_files(struct files_struct ** displaced)2314 int unshare_files(struct files_struct **displaced)
2315 {
2316 struct task_struct *task = current;
2317 struct files_struct *copy = NULL;
2318 int error;
2319
2320 error = unshare_fd(CLONE_FILES, ©);
2321 if (error || !copy) {
2322 *displaced = NULL;
2323 return error;
2324 }
2325 *displaced = task->files;
2326 task_lock(task);
2327 task->files = copy;
2328 task_unlock(task);
2329 return 0;
2330 }
2331
sysctl_max_threads(struct ctl_table * table,int write,void __user * buffer,size_t * lenp,loff_t * ppos)2332 int sysctl_max_threads(struct ctl_table *table, int write,
2333 void __user *buffer, size_t *lenp, loff_t *ppos)
2334 {
2335 struct ctl_table t;
2336 int ret;
2337 int threads = max_threads;
2338 int min = MIN_THREADS;
2339 int max = MAX_THREADS;
2340
2341 t = *table;
2342 t.data = &threads;
2343 t.extra1 = &min;
2344 t.extra2 = &max;
2345
2346 ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
2347 if (ret || !write)
2348 return ret;
2349
2350 set_max_threads(threads);
2351
2352 return 0;
2353 }
2354