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1/*
2 * linux/kernel/exit.c
3 *
4 * Copyright (C) 1991, 1992 Linus Torvalds
5 */
6
7#include <linux/mm.h>
8#include <linux/slab.h>
9#include <linux/interrupt.h>
10#include <linux/module.h>
11#include <linux/capability.h>
12#include <linux/completion.h>
13#include <linux/personality.h>
14#include <linux/tty.h>
15#include <linux/iocontext.h>
16#include <linux/key.h>
17#include <linux/security.h>
18#include <linux/cpu.h>
19#include <linux/acct.h>
20#include <linux/tsacct_kern.h>
21#include <linux/file.h>
22#include <linux/fdtable.h>
23#include <linux/freezer.h>
24#include <linux/binfmts.h>
25#include <linux/nsproxy.h>
26#include <linux/pid_namespace.h>
27#include <linux/ptrace.h>
28#include <linux/profile.h>
29#include <linux/mount.h>
30#include <linux/proc_fs.h>
31#include <linux/kthread.h>
32#include <linux/mempolicy.h>
33#include <linux/taskstats_kern.h>
34#include <linux/delayacct.h>
35#include <linux/cgroup.h>
36#include <linux/syscalls.h>
37#include <linux/signal.h>
38#include <linux/posix-timers.h>
39#include <linux/cn_proc.h>
40#include <linux/mutex.h>
41#include <linux/futex.h>
42#include <linux/pipe_fs_i.h>
43#include <linux/audit.h> /* for audit_free() */
44#include <linux/resource.h>
45#include <linux/blkdev.h>
46#include <linux/task_io_accounting_ops.h>
47#include <linux/tracehook.h>
48#include <linux/fs_struct.h>
49#include <linux/init_task.h>
50#include <linux/perf_event.h>
51#include <trace/events/sched.h>
52#include <linux/hw_breakpoint.h>
53#include <linux/oom.h>
54#include <linux/writeback.h>
55#include <linux/shm.h>
56#include <linux/kcov.h>
57#include <linux/random.h>
58
59#include <linux/uaccess.h>
60#include <asm/unistd.h>
61#include <asm/pgtable.h>
62#include <asm/mmu_context.h>
63
64static void __unhash_process(struct task_struct *p, bool group_dead)
65{
66 nr_threads--;
67 detach_pid(p, PIDTYPE_PID);
68 if (group_dead) {
69 detach_pid(p, PIDTYPE_PGID);
70 detach_pid(p, PIDTYPE_SID);
71
72 list_del_rcu(&p->tasks);
73 list_del_init(&p->sibling);
74 __this_cpu_dec(process_counts);
75 }
76 list_del_rcu(&p->thread_group);
77 list_del_rcu(&p->thread_node);
78}
79
80/*
81 * This function expects the tasklist_lock write-locked.
82 */
83static void __exit_signal(struct task_struct *tsk)
84{
85 struct signal_struct *sig = tsk->signal;
86 bool group_dead = thread_group_leader(tsk);
87 struct sighand_struct *sighand;
88 struct tty_struct *uninitialized_var(tty);
89 cputime_t utime, stime;
90
91 sighand = rcu_dereference_check(tsk->sighand,
92 lockdep_tasklist_lock_is_held());
93 spin_lock(&sighand->siglock);
94
95#ifdef CONFIG_POSIX_TIMERS
96 posix_cpu_timers_exit(tsk);
97 if (group_dead) {
98 posix_cpu_timers_exit_group(tsk);
99 } else {
100 /*
101 * This can only happen if the caller is de_thread().
102 * FIXME: this is the temporary hack, we should teach
103 * posix-cpu-timers to handle this case correctly.
104 */
105 if (unlikely(has_group_leader_pid(tsk)))
106 posix_cpu_timers_exit_group(tsk);
107 }
108#endif
109
110 if (group_dead) {
111 tty = sig->tty;
112 sig->tty = NULL;
113 } else {
114 /*
115 * If there is any task waiting for the group exit
116 * then notify it:
117 */
118 if (sig->notify_count > 0 && !--sig->notify_count)
119 wake_up_process(sig->group_exit_task);
120
121 if (tsk == sig->curr_target)
122 sig->curr_target = next_thread(tsk);
123 }
124
125 add_device_randomness((const void*) &tsk->se.sum_exec_runtime,
126 sizeof(unsigned long long));
127
128 /*
129 * Accumulate here the counters for all threads as they die. We could
130 * skip the group leader because it is the last user of signal_struct,
131 * but we want to avoid the race with thread_group_cputime() which can
132 * see the empty ->thread_head list.
133 */
134 task_cputime(tsk, &utime, &stime);
135 write_seqlock(&sig->stats_lock);
136 sig->utime += utime;
137 sig->stime += stime;
138 sig->gtime += task_gtime(tsk);
139 sig->min_flt += tsk->min_flt;
140 sig->maj_flt += tsk->maj_flt;
141 sig->nvcsw += tsk->nvcsw;
142 sig->nivcsw += tsk->nivcsw;
143 sig->inblock += task_io_get_inblock(tsk);
144 sig->oublock += task_io_get_oublock(tsk);
145 task_io_accounting_add(&sig->ioac, &tsk->ioac);
146 sig->sum_sched_runtime += tsk->se.sum_exec_runtime;
147 sig->nr_threads--;
148 __unhash_process(tsk, group_dead);
149 write_sequnlock(&sig->stats_lock);
150
151 /*
152 * Do this under ->siglock, we can race with another thread
153 * doing sigqueue_free() if we have SIGQUEUE_PREALLOC signals.
154 */
155 flush_sigqueue(&tsk->pending);
156 tsk->sighand = NULL;
157 spin_unlock(&sighand->siglock);
158
159 __cleanup_sighand(sighand);
160 clear_tsk_thread_flag(tsk, TIF_SIGPENDING);
161 if (group_dead) {
162 flush_sigqueue(&sig->shared_pending);
163 tty_kref_put(tty);
164 }
165}
166
167static void delayed_put_task_struct(struct rcu_head *rhp)
168{
169 struct task_struct *tsk = container_of(rhp, struct task_struct, rcu);
170
171 perf_event_delayed_put(tsk);
172 trace_sched_process_free(tsk);
173 put_task_struct(tsk);
174}
175
176
177void release_task(struct task_struct *p)
178{
179 struct task_struct *leader;
180 int zap_leader;
181repeat:
182 /* don't need to get the RCU readlock here - the process is dead and
183 * can't be modifying its own credentials. But shut RCU-lockdep up */
184 rcu_read_lock();
185 atomic_dec(&__task_cred(p)->user->processes);
186 rcu_read_unlock();
187
188 proc_flush_task(p);
189
190 write_lock_irq(&tasklist_lock);
191 ptrace_release_task(p);
192 __exit_signal(p);
193
194 /*
195 * If we are the last non-leader member of the thread
196 * group, and the leader is zombie, then notify the
197 * group leader's parent process. (if it wants notification.)
198 */
199 zap_leader = 0;
200 leader = p->group_leader;
201 if (leader != p && thread_group_empty(leader)
202 && leader->exit_state == EXIT_ZOMBIE) {
203 /*
204 * If we were the last child thread and the leader has
205 * exited already, and the leader's parent ignores SIGCHLD,
206 * then we are the one who should release the leader.
207 */
208 zap_leader = do_notify_parent(leader, leader->exit_signal);
209 if (zap_leader)
210 leader->exit_state = EXIT_DEAD;
211 }
212
213 write_unlock_irq(&tasklist_lock);
214 release_thread(p);
215 call_rcu(&p->rcu, delayed_put_task_struct);
216
217 p = leader;
218 if (unlikely(zap_leader))
219 goto repeat;
220}
221
222/*
223 * Note that if this function returns a valid task_struct pointer (!NULL)
224 * task->usage must remain >0 for the duration of the RCU critical section.
225 */
226struct task_struct *task_rcu_dereference(struct task_struct **ptask)
227{
228 struct sighand_struct *sighand;
229 struct task_struct *task;
230
231 /*
232 * We need to verify that release_task() was not called and thus
233 * delayed_put_task_struct() can't run and drop the last reference
234 * before rcu_read_unlock(). We check task->sighand != NULL,
235 * but we can read the already freed and reused memory.
236 */
237retry:
238 task = rcu_dereference(*ptask);
239 if (!task)
240 return NULL;
241
242 probe_kernel_address(&task->sighand, sighand);
243
244 /*
245 * Pairs with atomic_dec_and_test() in put_task_struct(). If this task
246 * was already freed we can not miss the preceding update of this
247 * pointer.
248 */
249 smp_rmb();
250 if (unlikely(task != READ_ONCE(*ptask)))
251 goto retry;
252
253 /*
254 * We've re-checked that "task == *ptask", now we have two different
255 * cases:
256 *
257 * 1. This is actually the same task/task_struct. In this case
258 * sighand != NULL tells us it is still alive.
259 *
260 * 2. This is another task which got the same memory for task_struct.
261 * We can't know this of course, and we can not trust
262 * sighand != NULL.
263 *
264 * In this case we actually return a random value, but this is
265 * correct.
266 *
267 * If we return NULL - we can pretend that we actually noticed that
268 * *ptask was updated when the previous task has exited. Or pretend
269 * that probe_slab_address(&sighand) reads NULL.
270 *
271 * If we return the new task (because sighand is not NULL for any
272 * reason) - this is fine too. This (new) task can't go away before
273 * another gp pass.
274 *
275 * And note: We could even eliminate the false positive if re-read
276 * task->sighand once again to avoid the falsely NULL. But this case
277 * is very unlikely so we don't care.
278 */
279 if (!sighand)
280 return NULL;
281
282 return task;
283}
284
285struct task_struct *try_get_task_struct(struct task_struct **ptask)
286{
287 struct task_struct *task;
288
289 rcu_read_lock();
290 task = task_rcu_dereference(ptask);
291 if (task)
292 get_task_struct(task);
293 rcu_read_unlock();
294
295 return task;
296}
297
298/*
299 * Determine if a process group is "orphaned", according to the POSIX
300 * definition in 2.2.2.52. Orphaned process groups are not to be affected
301 * by terminal-generated stop signals. Newly orphaned process groups are
302 * to receive a SIGHUP and a SIGCONT.
303 *
304 * "I ask you, have you ever known what it is to be an orphan?"
305 */
306static int will_become_orphaned_pgrp(struct pid *pgrp,
307 struct task_struct *ignored_task)
308{
309 struct task_struct *p;
310
311 do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
312 if ((p == ignored_task) ||
313 (p->exit_state && thread_group_empty(p)) ||
314 is_global_init(p->real_parent))
315 continue;
316
317 if (task_pgrp(p->real_parent) != pgrp &&
318 task_session(p->real_parent) == task_session(p))
319 return 0;
320 } while_each_pid_task(pgrp, PIDTYPE_PGID, p);
321
322 return 1;
323}
324
325int is_current_pgrp_orphaned(void)
326{
327 int retval;
328
329 read_lock(&tasklist_lock);
330 retval = will_become_orphaned_pgrp(task_pgrp(current), NULL);
331 read_unlock(&tasklist_lock);
332
333 return retval;
334}
335
336static bool has_stopped_jobs(struct pid *pgrp)
337{
338 struct task_struct *p;
339
340 do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
341 if (p->signal->flags & SIGNAL_STOP_STOPPED)
342 return true;
343 } while_each_pid_task(pgrp, PIDTYPE_PGID, p);
344
345 return false;
346}
347
348/*
349 * Check to see if any process groups have become orphaned as
350 * a result of our exiting, and if they have any stopped jobs,
351 * send them a SIGHUP and then a SIGCONT. (POSIX 3.2.2.2)
352 */
353static void
354kill_orphaned_pgrp(struct task_struct *tsk, struct task_struct *parent)
355{
356 struct pid *pgrp = task_pgrp(tsk);
357 struct task_struct *ignored_task = tsk;
358
359 if (!parent)
360 /* exit: our father is in a different pgrp than
361 * we are and we were the only connection outside.
362 */
363 parent = tsk->real_parent;
364 else
365 /* reparent: our child is in a different pgrp than
366 * we are, and it was the only connection outside.
367 */
368 ignored_task = NULL;
369
370 if (task_pgrp(parent) != pgrp &&
371 task_session(parent) == task_session(tsk) &&
372 will_become_orphaned_pgrp(pgrp, ignored_task) &&
373 has_stopped_jobs(pgrp)) {
374 __kill_pgrp_info(SIGHUP, SEND_SIG_PRIV, pgrp);
375 __kill_pgrp_info(SIGCONT, SEND_SIG_PRIV, pgrp);
376 }
377}
378
379#ifdef CONFIG_MEMCG
380/*
381 * A task is exiting. If it owned this mm, find a new owner for the mm.
382 */
383void mm_update_next_owner(struct mm_struct *mm)
384{
385 struct task_struct *c, *g, *p = current;
386
387retry:
388 /*
389 * If the exiting or execing task is not the owner, it's
390 * someone else's problem.
391 */
392 if (mm->owner != p)
393 return;
394 /*
395 * The current owner is exiting/execing and there are no other
396 * candidates. Do not leave the mm pointing to a possibly
397 * freed task structure.
398 */
399 if (atomic_read(&mm->mm_users) <= 1) {
400 mm->owner = NULL;
401 return;
402 }
403
404 read_lock(&tasklist_lock);
405 /*
406 * Search in the children
407 */
408 list_for_each_entry(c, &p->children, sibling) {
409 if (c->mm == mm)
410 goto assign_new_owner;
411 }
412
413 /*
414 * Search in the siblings
415 */
416 list_for_each_entry(c, &p->real_parent->children, sibling) {
417 if (c->mm == mm)
418 goto assign_new_owner;
419 }
420
421 /*
422 * Search through everything else, we should not get here often.
423 */
424 for_each_process(g) {
425 if (g->flags & PF_KTHREAD)
426 continue;
427 for_each_thread(g, c) {
428 if (c->mm == mm)
429 goto assign_new_owner;
430 if (c->mm)
431 break;
432 }
433 }
434 read_unlock(&tasklist_lock);
435 /*
436 * We found no owner yet mm_users > 1: this implies that we are
437 * most likely racing with swapoff (try_to_unuse()) or /proc or
438 * ptrace or page migration (get_task_mm()). Mark owner as NULL.
439 */
440 mm->owner = NULL;
441 return;
442
443assign_new_owner:
444 BUG_ON(c == p);
445 get_task_struct(c);
446 /*
447 * The task_lock protects c->mm from changing.
448 * We always want mm->owner->mm == mm
449 */
450 task_lock(c);
451 /*
452 * Delay read_unlock() till we have the task_lock()
453 * to ensure that c does not slip away underneath us
454 */
455 read_unlock(&tasklist_lock);
456 if (c->mm != mm) {
457 task_unlock(c);
458 put_task_struct(c);
459 goto retry;
460 }
461 mm->owner = c;
462 task_unlock(c);
463 put_task_struct(c);
464}
465#endif /* CONFIG_MEMCG */
466
467/*
468 * Turn us into a lazy TLB process if we
469 * aren't already..
470 */
471static void exit_mm(struct task_struct *tsk)
472{
473 struct mm_struct *mm = tsk->mm;
474 struct core_state *core_state;
475
476 mm_release(tsk, mm);
477 if (!mm)
478 return;
479 sync_mm_rss(mm);
480 /*
481 * Serialize with any possible pending coredump.
482 * We must hold mmap_sem around checking core_state
483 * and clearing tsk->mm. The core-inducing thread
484 * will increment ->nr_threads for each thread in the
485 * group with ->mm != NULL.
486 */
487 down_read(&mm->mmap_sem);
488 core_state = mm->core_state;
489 if (core_state) {
490 struct core_thread self;
491
492 up_read(&mm->mmap_sem);
493
494 self.task = tsk;
495 self.next = xchg(&core_state->dumper.next, &self);
496 /*
497 * Implies mb(), the result of xchg() must be visible
498 * to core_state->dumper.
499 */
500 if (atomic_dec_and_test(&core_state->nr_threads))
501 complete(&core_state->startup);
502
503 for (;;) {
504 set_task_state(tsk, TASK_UNINTERRUPTIBLE);
505 if (!self.task) /* see coredump_finish() */
506 break;
507 freezable_schedule();
508 }
509 __set_task_state(tsk, TASK_RUNNING);
510 down_read(&mm->mmap_sem);
511 }
512 atomic_inc(&mm->mm_count);
513 BUG_ON(mm != tsk->active_mm);
514 /* more a memory barrier than a real lock */
515 task_lock(tsk);
516 tsk->mm = NULL;
517 up_read(&mm->mmap_sem);
518 enter_lazy_tlb(mm, current);
519 task_unlock(tsk);
520 mm_update_next_owner(mm);
521 mmput(mm);
522 if (test_thread_flag(TIF_MEMDIE))
523 exit_oom_victim();
524}
525
526static struct task_struct *find_alive_thread(struct task_struct *p)
527{
528 struct task_struct *t;
529
530 for_each_thread(p, t) {
531 if (!(t->flags & PF_EXITING))
532 return t;
533 }
534 return NULL;
535}
536
537static struct task_struct *find_child_reaper(struct task_struct *father)
538 __releases(&tasklist_lock)
539 __acquires(&tasklist_lock)
540{
541 struct pid_namespace *pid_ns = task_active_pid_ns(father);
542 struct task_struct *reaper = pid_ns->child_reaper;
543
544 if (likely(reaper != father))
545 return reaper;
546
547 reaper = find_alive_thread(father);
548 if (reaper) {
549 pid_ns->child_reaper = reaper;
550 return reaper;
551 }
552
553 write_unlock_irq(&tasklist_lock);
554 if (unlikely(pid_ns == &init_pid_ns)) {
555 panic("Attempted to kill init! exitcode=0x%08x\n",
556 father->signal->group_exit_code ?: father->exit_code);
557 }
558 zap_pid_ns_processes(pid_ns);
559 write_lock_irq(&tasklist_lock);
560
561 return father;
562}
563
564/*
565 * When we die, we re-parent all our children, and try to:
566 * 1. give them to another thread in our thread group, if such a member exists
567 * 2. give it to the first ancestor process which prctl'd itself as a
568 * child_subreaper for its children (like a service manager)
569 * 3. give it to the init process (PID 1) in our pid namespace
570 */
571static struct task_struct *find_new_reaper(struct task_struct *father,
572 struct task_struct *child_reaper)
573{
574 struct task_struct *thread, *reaper;
575
576 thread = find_alive_thread(father);
577 if (thread)
578 return thread;
579
580 if (father->signal->has_child_subreaper) {
581 /*
582 * Find the first ->is_child_subreaper ancestor in our pid_ns.
583 * We start from father to ensure we can not look into another
584 * namespace, this is safe because all its threads are dead.
585 */
586 for (reaper = father;
587 !same_thread_group(reaper, child_reaper);
588 reaper = reaper->real_parent) {
589 /* call_usermodehelper() descendants need this check */
590 if (reaper == &init_task)
591 break;
592 if (!reaper->signal->is_child_subreaper)
593 continue;
594 thread = find_alive_thread(reaper);
595 if (thread)
596 return thread;
597 }
598 }
599
600 return child_reaper;
601}
602
603/*
604* Any that need to be release_task'd are put on the @dead list.
605 */
606static void reparent_leader(struct task_struct *father, struct task_struct *p,
607 struct list_head *dead)
608{
609 if (unlikely(p->exit_state == EXIT_DEAD))
610 return;
611
612 /* We don't want people slaying init. */
613 p->exit_signal = SIGCHLD;
614
615 /* If it has exited notify the new parent about this child's death. */
616 if (!p->ptrace &&
617 p->exit_state == EXIT_ZOMBIE && thread_group_empty(p)) {
618 if (do_notify_parent(p, p->exit_signal)) {
619 p->exit_state = EXIT_DEAD;
620 list_add(&p->ptrace_entry, dead);
621 }
622 }
623
624 kill_orphaned_pgrp(p, father);
625}
626
627/*
628 * This does two things:
629 *
630 * A. Make init inherit all the child processes
631 * B. Check to see if any process groups have become orphaned
632 * as a result of our exiting, and if they have any stopped
633 * jobs, send them a SIGHUP and then a SIGCONT. (POSIX 3.2.2.2)
634 */
635static void forget_original_parent(struct task_struct *father,
636 struct list_head *dead)
637{
638 struct task_struct *p, *t, *reaper;
639
640 if (unlikely(!list_empty(&father->ptraced)))
641 exit_ptrace(father, dead);
642
643 /* Can drop and reacquire tasklist_lock */
644 reaper = find_child_reaper(father);
645 if (list_empty(&father->children))
646 return;
647
648 reaper = find_new_reaper(father, reaper);
649 list_for_each_entry(p, &father->children, sibling) {
650 for_each_thread(p, t) {
651 t->real_parent = reaper;
652 BUG_ON((!t->ptrace) != (t->parent == father));
653 if (likely(!t->ptrace))
654 t->parent = t->real_parent;
655 if (t->pdeath_signal)
656 group_send_sig_info(t->pdeath_signal,
657 SEND_SIG_NOINFO, t);
658 }
659 /*
660 * If this is a threaded reparent there is no need to
661 * notify anyone anything has happened.
662 */
663 if (!same_thread_group(reaper, father))
664 reparent_leader(father, p, dead);
665 }
666 list_splice_tail_init(&father->children, &reaper->children);
667}
668
669/*
670 * Send signals to all our closest relatives so that they know
671 * to properly mourn us..
672 */
673static void exit_notify(struct task_struct *tsk, int group_dead)
674{
675 bool autoreap;
676 struct task_struct *p, *n;
677 LIST_HEAD(dead);
678
679 write_lock_irq(&tasklist_lock);
680 forget_original_parent(tsk, &dead);
681
682 if (group_dead)
683 kill_orphaned_pgrp(tsk->group_leader, NULL);
684
685 if (unlikely(tsk->ptrace)) {
686 int sig = thread_group_leader(tsk) &&
687 thread_group_empty(tsk) &&
688 !ptrace_reparented(tsk) ?
689 tsk->exit_signal : SIGCHLD;
690 autoreap = do_notify_parent(tsk, sig);
691 } else if (thread_group_leader(tsk)) {
692 autoreap = thread_group_empty(tsk) &&
693 do_notify_parent(tsk, tsk->exit_signal);
694 } else {
695 autoreap = true;
696 }
697
698 tsk->exit_state = autoreap ? EXIT_DEAD : EXIT_ZOMBIE;
699 if (tsk->exit_state == EXIT_DEAD)
700 list_add(&tsk->ptrace_entry, &dead);
701
702 /* mt-exec, de_thread() is waiting for group leader */
703 if (unlikely(tsk->signal->notify_count < 0))
704 wake_up_process(tsk->signal->group_exit_task);
705 write_unlock_irq(&tasklist_lock);
706
707 list_for_each_entry_safe(p, n, &dead, ptrace_entry) {
708 list_del_init(&p->ptrace_entry);
709 release_task(p);
710 }
711}
712
713#ifdef CONFIG_DEBUG_STACK_USAGE
714static void check_stack_usage(void)
715{
716 static DEFINE_SPINLOCK(low_water_lock);
717 static int lowest_to_date = THREAD_SIZE;
718 unsigned long free;
719
720 free = stack_not_used(current);
721
722 if (free >= lowest_to_date)
723 return;
724
725 spin_lock(&low_water_lock);
726 if (free < lowest_to_date) {
727 pr_info("%s (%d) used greatest stack depth: %lu bytes left\n",
728 current->comm, task_pid_nr(current), free);
729 lowest_to_date = free;
730 }
731 spin_unlock(&low_water_lock);
732}
733#else
734static inline void check_stack_usage(void) {}
735#endif
736
737void __noreturn do_exit(long code)
738{
739 struct task_struct *tsk = current;
740 int group_dead;
741 TASKS_RCU(int tasks_rcu_i);
742
743 profile_task_exit(tsk);
744 kcov_task_exit(tsk);
745
746 WARN_ON(blk_needs_flush_plug(tsk));
747
748 if (unlikely(in_interrupt()))
749 panic("Aiee, killing interrupt handler!");
750 if (unlikely(!tsk->pid))
751 panic("Attempted to kill the idle task!");
752
753 /*
754 * If do_exit is called because this processes oopsed, it's possible
755 * that get_fs() was left as KERNEL_DS, so reset it to USER_DS before
756 * continuing. Amongst other possible reasons, this is to prevent
757 * mm_release()->clear_child_tid() from writing to a user-controlled
758 * kernel address.
759 */
760 set_fs(USER_DS);
761
762 ptrace_event(PTRACE_EVENT_EXIT, code);
763
764 validate_creds_for_do_exit(tsk);
765
766 /*
767 * We're taking recursive faults here in do_exit. Safest is to just
768 * leave this task alone and wait for reboot.
769 */
770 if (unlikely(tsk->flags & PF_EXITING)) {
771 pr_alert("Fixing recursive fault but reboot is needed!\n");
772 /*
773 * We can do this unlocked here. The futex code uses
774 * this flag just to verify whether the pi state
775 * cleanup has been done or not. In the worst case it
776 * loops once more. We pretend that the cleanup was
777 * done as there is no way to return. Either the
778 * OWNER_DIED bit is set by now or we push the blocked
779 * task into the wait for ever nirwana as well.
780 */
781 tsk->flags |= PF_EXITPIDONE;
782 set_current_state(TASK_UNINTERRUPTIBLE);
783 schedule();
784 }
785
786 exit_signals(tsk); /* sets PF_EXITING */
787 /*
788 * Ensure that all new tsk->pi_lock acquisitions must observe
789 * PF_EXITING. Serializes against futex.c:attach_to_pi_owner().
790 */
791 smp_mb();
792 /*
793 * Ensure that we must observe the pi_state in exit_mm() ->
794 * mm_release() -> exit_pi_state_list().
795 */
796 raw_spin_unlock_wait(&tsk->pi_lock);
797
798 if (unlikely(in_atomic())) {
799 pr_info("note: %s[%d] exited with preempt_count %d\n",
800 current->comm, task_pid_nr(current),
801 preempt_count());
802 preempt_count_set(PREEMPT_ENABLED);
803 }
804
805 /* sync mm's RSS info before statistics gathering */
806 if (tsk->mm)
807 sync_mm_rss(tsk->mm);
808 acct_update_integrals(tsk);
809 group_dead = atomic_dec_and_test(&tsk->signal->live);
810 if (group_dead) {
811#ifdef CONFIG_POSIX_TIMERS
812 hrtimer_cancel(&tsk->signal->real_timer);
813 exit_itimers(tsk->signal);
814#endif
815 if (tsk->mm)
816 setmax_mm_hiwater_rss(&tsk->signal->maxrss, tsk->mm);
817 }
818 acct_collect(code, group_dead);
819 if (group_dead)
820 tty_audit_exit();
821 audit_free(tsk);
822
823 tsk->exit_code = code;
824 taskstats_exit(tsk, group_dead);
825
826 exit_mm(tsk);
827
828 if (group_dead)
829 acct_process();
830 trace_sched_process_exit(tsk);
831
832 exit_sem(tsk);
833 exit_shm(tsk);
834 exit_files(tsk);
835 exit_fs(tsk);
836 if (group_dead)
837 disassociate_ctty(1);
838 exit_task_namespaces(tsk);
839 exit_task_work(tsk);
840 exit_thread(tsk);
841
842 /*
843 * Flush inherited counters to the parent - before the parent
844 * gets woken up by child-exit notifications.
845 *
846 * because of cgroup mode, must be called before cgroup_exit()
847 */
848 perf_event_exit_task(tsk);
849
850 sched_autogroup_exit_task(tsk);
851 cgroup_exit(tsk);
852
853 /*
854 * FIXME: do that only when needed, using sched_exit tracepoint
855 */
856 flush_ptrace_hw_breakpoint(tsk);
857
858 TASKS_RCU(preempt_disable());
859 TASKS_RCU(tasks_rcu_i = __srcu_read_lock(&tasks_rcu_exit_srcu));
860 TASKS_RCU(preempt_enable());
861 exit_notify(tsk, group_dead);
862 proc_exit_connector(tsk);
863 mpol_put_task_policy(tsk);
864#ifdef CONFIG_FUTEX
865 if (unlikely(current->pi_state_cache))
866 kfree(current->pi_state_cache);
867#endif
868 /*
869 * Make sure we are holding no locks:
870 */
871 debug_check_no_locks_held();
872 /*
873 * We can do this unlocked here. The futex code uses this flag
874 * just to verify whether the pi state cleanup has been done
875 * or not. In the worst case it loops once more.
876 */
877 tsk->flags |= PF_EXITPIDONE;
878
879 if (tsk->io_context)
880 exit_io_context(tsk);
881
882 if (tsk->splice_pipe)
883 free_pipe_info(tsk->splice_pipe);
884
885 if (tsk->task_frag.page)
886 put_page(tsk->task_frag.page);
887
888 validate_creds_for_do_exit(tsk);
889
890 check_stack_usage();
891 preempt_disable();
892 if (tsk->nr_dirtied)
893 __this_cpu_add(dirty_throttle_leaks, tsk->nr_dirtied);
894 exit_rcu();
895 TASKS_RCU(__srcu_read_unlock(&tasks_rcu_exit_srcu, tasks_rcu_i));
896
897 do_task_dead();
898}
899EXPORT_SYMBOL_GPL(do_exit);
900
901void complete_and_exit(struct completion *comp, long code)
902{
903 if (comp)
904 complete(comp);
905
906 do_exit(code);
907}
908EXPORT_SYMBOL(complete_and_exit);
909
910SYSCALL_DEFINE1(exit, int, error_code)
911{
912 do_exit((error_code&0xff)<<8);
913}
914
915/*
916 * Take down every thread in the group. This is called by fatal signals
917 * as well as by sys_exit_group (below).
918 */
919void
920do_group_exit(int exit_code)
921{
922 struct signal_struct *sig = current->signal;
923
924 BUG_ON(exit_code & 0x80); /* core dumps don't get here */
925
926 if (signal_group_exit(sig))
927 exit_code = sig->group_exit_code;
928 else if (!thread_group_empty(current)) {
929 struct sighand_struct *const sighand = current->sighand;
930
931 spin_lock_irq(&sighand->siglock);
932 if (signal_group_exit(sig))
933 /* Another thread got here before we took the lock. */
934 exit_code = sig->group_exit_code;
935 else {
936 sig->group_exit_code = exit_code;
937 sig->flags = SIGNAL_GROUP_EXIT;
938 zap_other_threads(current);
939 }
940 spin_unlock_irq(&sighand->siglock);
941 }
942
943 do_exit(exit_code);
944 /* NOTREACHED */
945}
946
947/*
948 * this kills every thread in the thread group. Note that any externally
949 * wait4()-ing process will get the correct exit code - even if this
950 * thread is not the thread group leader.
951 */
952SYSCALL_DEFINE1(exit_group, int, error_code)
953{
954 do_group_exit((error_code & 0xff) << 8);
955 /* NOTREACHED */
956 return 0;
957}
958
959struct wait_opts {
960 enum pid_type wo_type;
961 int wo_flags;
962 struct pid *wo_pid;
963
964 struct siginfo __user *wo_info;
965 int __user *wo_stat;
966 struct rusage __user *wo_rusage;
967
968 wait_queue_t child_wait;
969 int notask_error;
970};
971
972static inline
973struct pid *task_pid_type(struct task_struct *task, enum pid_type type)
974{
975 if (type != PIDTYPE_PID)
976 task = task->group_leader;
977 return task->pids[type].pid;
978}
979
980static int eligible_pid(struct wait_opts *wo, struct task_struct *p)
981{
982 return wo->wo_type == PIDTYPE_MAX ||
983 task_pid_type(p, wo->wo_type) == wo->wo_pid;
984}
985
986static int
987eligible_child(struct wait_opts *wo, bool ptrace, struct task_struct *p)
988{
989 if (!eligible_pid(wo, p))
990 return 0;
991
992 /*
993 * Wait for all children (clone and not) if __WALL is set or
994 * if it is traced by us.
995 */
996 if (ptrace || (wo->wo_flags & __WALL))
997 return 1;
998
999 /*
1000 * Otherwise, wait for clone children *only* if __WCLONE is set;
1001 * otherwise, wait for non-clone children *only*.
1002 *
1003 * Note: a "clone" child here is one that reports to its parent
1004 * using a signal other than SIGCHLD, or a non-leader thread which
1005 * we can only see if it is traced by us.
1006 */
1007 if ((p->exit_signal != SIGCHLD) ^ !!(wo->wo_flags & __WCLONE))
1008 return 0;
1009
1010 return 1;
1011}
1012
1013static int wait_noreap_copyout(struct wait_opts *wo, struct task_struct *p,
1014 pid_t pid, uid_t uid, int why, int status)
1015{
1016 struct siginfo __user *infop;
1017 int retval = wo->wo_rusage
1018 ? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
1019
1020 put_task_struct(p);
1021 infop = wo->wo_info;
1022 if (infop) {
1023 if (!retval)
1024 retval = put_user(SIGCHLD, &infop->si_signo);
1025 if (!retval)
1026 retval = put_user(0, &infop->si_errno);
1027 if (!retval)
1028 retval = put_user((short)why, &infop->si_code);
1029 if (!retval)
1030 retval = put_user(pid, &infop->si_pid);
1031 if (!retval)
1032 retval = put_user(uid, &infop->si_uid);
1033 if (!retval)
1034 retval = put_user(status, &infop->si_status);
1035 }
1036 if (!retval)
1037 retval = pid;
1038 return retval;
1039}
1040
1041/*
1042 * Handle sys_wait4 work for one task in state EXIT_ZOMBIE. We hold
1043 * read_lock(&tasklist_lock) on entry. If we return zero, we still hold
1044 * the lock and this task is uninteresting. If we return nonzero, we have
1045 * released the lock and the system call should return.
1046 */
1047static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p)
1048{
1049 int state, retval, status;
1050 pid_t pid = task_pid_vnr(p);
1051 uid_t uid = from_kuid_munged(current_user_ns(), task_uid(p));
1052 struct siginfo __user *infop;
1053
1054 if (!likely(wo->wo_flags & WEXITED))
1055 return 0;
1056
1057 if (unlikely(wo->wo_flags & WNOWAIT)) {
1058 int exit_code = p->exit_code;
1059 int why;
1060
1061 get_task_struct(p);
1062 read_unlock(&tasklist_lock);
1063 sched_annotate_sleep();
1064
1065 if ((exit_code & 0x7f) == 0) {
1066 why = CLD_EXITED;
1067 status = exit_code >> 8;
1068 } else {
1069 why = (exit_code & 0x80) ? CLD_DUMPED : CLD_KILLED;
1070 status = exit_code & 0x7f;
1071 }
1072 return wait_noreap_copyout(wo, p, pid, uid, why, status);
1073 }
1074 /*
1075 * Move the task's state to DEAD/TRACE, only one thread can do this.
1076 */
1077 state = (ptrace_reparented(p) && thread_group_leader(p)) ?
1078 EXIT_TRACE : EXIT_DEAD;
1079 if (cmpxchg(&p->exit_state, EXIT_ZOMBIE, state) != EXIT_ZOMBIE)
1080 return 0;
1081 /*
1082 * We own this thread, nobody else can reap it.
1083 */
1084 read_unlock(&tasklist_lock);
1085 sched_annotate_sleep();
1086
1087 /*
1088 * Check thread_group_leader() to exclude the traced sub-threads.
1089 */
1090 if (state == EXIT_DEAD && thread_group_leader(p)) {
1091 struct signal_struct *sig = p->signal;
1092 struct signal_struct *psig = current->signal;
1093 unsigned long maxrss;
1094 cputime_t tgutime, tgstime;
1095
1096 /*
1097 * The resource counters for the group leader are in its
1098 * own task_struct. Those for dead threads in the group
1099 * are in its signal_struct, as are those for the child
1100 * processes it has previously reaped. All these
1101 * accumulate in the parent's signal_struct c* fields.
1102 *
1103 * We don't bother to take a lock here to protect these
1104 * p->signal fields because the whole thread group is dead
1105 * and nobody can change them.
1106 *
1107 * psig->stats_lock also protects us from our sub-theads
1108 * which can reap other children at the same time. Until
1109 * we change k_getrusage()-like users to rely on this lock
1110 * we have to take ->siglock as well.
1111 *
1112 * We use thread_group_cputime_adjusted() to get times for
1113 * the thread group, which consolidates times for all threads
1114 * in the group including the group leader.
1115 */
1116 thread_group_cputime_adjusted(p, &tgutime, &tgstime);
1117 spin_lock_irq(¤t->sighand->siglock);
1118 write_seqlock(&psig->stats_lock);
1119 psig->cutime += tgutime + sig->cutime;
1120 psig->cstime += tgstime + sig->cstime;
1121 psig->cgtime += task_gtime(p) + sig->gtime + sig->cgtime;
1122 psig->cmin_flt +=
1123 p->min_flt + sig->min_flt + sig->cmin_flt;
1124 psig->cmaj_flt +=
1125 p->maj_flt + sig->maj_flt + sig->cmaj_flt;
1126 psig->cnvcsw +=
1127 p->nvcsw + sig->nvcsw + sig->cnvcsw;
1128 psig->cnivcsw +=
1129 p->nivcsw + sig->nivcsw + sig->cnivcsw;
1130 psig->cinblock +=
1131 task_io_get_inblock(p) +
1132 sig->inblock + sig->cinblock;
1133 psig->coublock +=
1134 task_io_get_oublock(p) +
1135 sig->oublock + sig->coublock;
1136 maxrss = max(sig->maxrss, sig->cmaxrss);
1137 if (psig->cmaxrss < maxrss)
1138 psig->cmaxrss = maxrss;
1139 task_io_accounting_add(&psig->ioac, &p->ioac);
1140 task_io_accounting_add(&psig->ioac, &sig->ioac);
1141 write_sequnlock(&psig->stats_lock);
1142 spin_unlock_irq(¤t->sighand->siglock);
1143 }
1144
1145 retval = wo->wo_rusage
1146 ? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
1147 status = (p->signal->flags & SIGNAL_GROUP_EXIT)
1148 ? p->signal->group_exit_code : p->exit_code;
1149 if (!retval && wo->wo_stat)
1150 retval = put_user(status, wo->wo_stat);
1151
1152 infop = wo->wo_info;
1153 if (!retval && infop)
1154 retval = put_user(SIGCHLD, &infop->si_signo);
1155 if (!retval && infop)
1156 retval = put_user(0, &infop->si_errno);
1157 if (!retval && infop) {
1158 int why;
1159
1160 if ((status & 0x7f) == 0) {
1161 why = CLD_EXITED;
1162 status >>= 8;
1163 } else {
1164 why = (status & 0x80) ? CLD_DUMPED : CLD_KILLED;
1165 status &= 0x7f;
1166 }
1167 retval = put_user((short)why, &infop->si_code);
1168 if (!retval)
1169 retval = put_user(status, &infop->si_status);
1170 }
1171 if (!retval && infop)
1172 retval = put_user(pid, &infop->si_pid);
1173 if (!retval && infop)
1174 retval = put_user(uid, &infop->si_uid);
1175 if (!retval)
1176 retval = pid;
1177
1178 if (state == EXIT_TRACE) {
1179 write_lock_irq(&tasklist_lock);
1180 /* We dropped tasklist, ptracer could die and untrace */
1181 ptrace_unlink(p);
1182
1183 /* If parent wants a zombie, don't release it now */
1184 state = EXIT_ZOMBIE;
1185 if (do_notify_parent(p, p->exit_signal))
1186 state = EXIT_DEAD;
1187 p->exit_state = state;
1188 write_unlock_irq(&tasklist_lock);
1189 }
1190 if (state == EXIT_DEAD)
1191 release_task(p);
1192
1193 return retval;
1194}
1195
1196static int *task_stopped_code(struct task_struct *p, bool ptrace)
1197{
1198 if (ptrace) {
1199 if (task_is_traced(p) && !(p->jobctl & JOBCTL_LISTENING))
1200 return &p->exit_code;
1201 } else {
1202 if (p->signal->flags & SIGNAL_STOP_STOPPED)
1203 return &p->signal->group_exit_code;
1204 }
1205 return NULL;
1206}
1207
1208/**
1209 * wait_task_stopped - Wait for %TASK_STOPPED or %TASK_TRACED
1210 * @wo: wait options
1211 * @ptrace: is the wait for ptrace
1212 * @p: task to wait for
1213 *
1214 * Handle sys_wait4() work for %p in state %TASK_STOPPED or %TASK_TRACED.
1215 *
1216 * CONTEXT:
1217 * read_lock(&tasklist_lock), which is released if return value is
1218 * non-zero. Also, grabs and releases @p->sighand->siglock.
1219 *
1220 * RETURNS:
1221 * 0 if wait condition didn't exist and search for other wait conditions
1222 * should continue. Non-zero return, -errno on failure and @p's pid on
1223 * success, implies that tasklist_lock is released and wait condition
1224 * search should terminate.
1225 */
1226static int wait_task_stopped(struct wait_opts *wo,
1227 int ptrace, struct task_struct *p)
1228{
1229 struct siginfo __user *infop;
1230 int retval, exit_code, *p_code, why;
1231 uid_t uid = 0; /* unneeded, required by compiler */
1232 pid_t pid;
1233
1234 /*
1235 * Traditionally we see ptrace'd stopped tasks regardless of options.
1236 */
1237 if (!ptrace && !(wo->wo_flags & WUNTRACED))
1238 return 0;
1239
1240 if (!task_stopped_code(p, ptrace))
1241 return 0;
1242
1243 exit_code = 0;
1244 spin_lock_irq(&p->sighand->siglock);
1245
1246 p_code = task_stopped_code(p, ptrace);
1247 if (unlikely(!p_code))
1248 goto unlock_sig;
1249
1250 exit_code = *p_code;
1251 if (!exit_code)
1252 goto unlock_sig;
1253
1254 if (!unlikely(wo->wo_flags & WNOWAIT))
1255 *p_code = 0;
1256
1257 uid = from_kuid_munged(current_user_ns(), task_uid(p));
1258unlock_sig:
1259 spin_unlock_irq(&p->sighand->siglock);
1260 if (!exit_code)
1261 return 0;
1262
1263 /*
1264 * Now we are pretty sure this task is interesting.
1265 * Make sure it doesn't get reaped out from under us while we
1266 * give up the lock and then examine it below. We don't want to
1267 * keep holding onto the tasklist_lock while we call getrusage and
1268 * possibly take page faults for user memory.
1269 */
1270 get_task_struct(p);
1271 pid = task_pid_vnr(p);
1272 why = ptrace ? CLD_TRAPPED : CLD_STOPPED;
1273 read_unlock(&tasklist_lock);
1274 sched_annotate_sleep();
1275
1276 if (unlikely(wo->wo_flags & WNOWAIT))
1277 return wait_noreap_copyout(wo, p, pid, uid, why, exit_code);
1278
1279 retval = wo->wo_rusage
1280 ? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
1281 if (!retval && wo->wo_stat)
1282 retval = put_user((exit_code << 8) | 0x7f, wo->wo_stat);
1283
1284 infop = wo->wo_info;
1285 if (!retval && infop)
1286 retval = put_user(SIGCHLD, &infop->si_signo);
1287 if (!retval && infop)
1288 retval = put_user(0, &infop->si_errno);
1289 if (!retval && infop)
1290 retval = put_user((short)why, &infop->si_code);
1291 if (!retval && infop)
1292 retval = put_user(exit_code, &infop->si_status);
1293 if (!retval && infop)
1294 retval = put_user(pid, &infop->si_pid);
1295 if (!retval && infop)
1296 retval = put_user(uid, &infop->si_uid);
1297 if (!retval)
1298 retval = pid;
1299 put_task_struct(p);
1300
1301 BUG_ON(!retval);
1302 return retval;
1303}
1304
1305/*
1306 * Handle do_wait work for one task in a live, non-stopped state.
1307 * read_lock(&tasklist_lock) on entry. If we return zero, we still hold
1308 * the lock and this task is uninteresting. If we return nonzero, we have
1309 * released the lock and the system call should return.
1310 */
1311static int wait_task_continued(struct wait_opts *wo, struct task_struct *p)
1312{
1313 int retval;
1314 pid_t pid;
1315 uid_t uid;
1316
1317 if (!unlikely(wo->wo_flags & WCONTINUED))
1318 return 0;
1319
1320 if (!(p->signal->flags & SIGNAL_STOP_CONTINUED))
1321 return 0;
1322
1323 spin_lock_irq(&p->sighand->siglock);
1324 /* Re-check with the lock held. */
1325 if (!(p->signal->flags & SIGNAL_STOP_CONTINUED)) {
1326 spin_unlock_irq(&p->sighand->siglock);
1327 return 0;
1328 }
1329 if (!unlikely(wo->wo_flags & WNOWAIT))
1330 p->signal->flags &= ~SIGNAL_STOP_CONTINUED;
1331 uid = from_kuid_munged(current_user_ns(), task_uid(p));
1332 spin_unlock_irq(&p->sighand->siglock);
1333
1334 pid = task_pid_vnr(p);
1335 get_task_struct(p);
1336 read_unlock(&tasklist_lock);
1337 sched_annotate_sleep();
1338
1339 if (!wo->wo_info) {
1340 retval = wo->wo_rusage
1341 ? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
1342 put_task_struct(p);
1343 if (!retval && wo->wo_stat)
1344 retval = put_user(0xffff, wo->wo_stat);
1345 if (!retval)
1346 retval = pid;
1347 } else {
1348 retval = wait_noreap_copyout(wo, p, pid, uid,
1349 CLD_CONTINUED, SIGCONT);
1350 BUG_ON(retval == 0);
1351 }
1352
1353 return retval;
1354}
1355
1356/*
1357 * Consider @p for a wait by @parent.
1358 *
1359 * -ECHILD should be in ->notask_error before the first call.
1360 * Returns nonzero for a final return, when we have unlocked tasklist_lock.
1361 * Returns zero if the search for a child should continue;
1362 * then ->notask_error is 0 if @p is an eligible child,
1363 * or another error from security_task_wait(), or still -ECHILD.
1364 */
1365static int wait_consider_task(struct wait_opts *wo, int ptrace,
1366 struct task_struct *p)
1367{
1368 /*
1369 * We can race with wait_task_zombie() from another thread.
1370 * Ensure that EXIT_ZOMBIE -> EXIT_DEAD/EXIT_TRACE transition
1371 * can't confuse the checks below.
1372 */
1373 int exit_state = ACCESS_ONCE(p->exit_state);
1374 int ret;
1375
1376 if (unlikely(exit_state == EXIT_DEAD))
1377 return 0;
1378
1379 ret = eligible_child(wo, ptrace, p);
1380 if (!ret)
1381 return ret;
1382
1383 ret = security_task_wait(p);
1384 if (unlikely(ret < 0)) {
1385 /*
1386 * If we have not yet seen any eligible child,
1387 * then let this error code replace -ECHILD.
1388 * A permission error will give the user a clue
1389 * to look for security policy problems, rather
1390 * than for mysterious wait bugs.
1391 */
1392 if (wo->notask_error)
1393 wo->notask_error = ret;
1394 return 0;
1395 }
1396
1397 if (unlikely(exit_state == EXIT_TRACE)) {
1398 /*
1399 * ptrace == 0 means we are the natural parent. In this case
1400 * we should clear notask_error, debugger will notify us.
1401 */
1402 if (likely(!ptrace))
1403 wo->notask_error = 0;
1404 return 0;
1405 }
1406
1407 if (likely(!ptrace) && unlikely(p->ptrace)) {
1408 /*
1409 * If it is traced by its real parent's group, just pretend
1410 * the caller is ptrace_do_wait() and reap this child if it
1411 * is zombie.
1412 *
1413 * This also hides group stop state from real parent; otherwise
1414 * a single stop can be reported twice as group and ptrace stop.
1415 * If a ptracer wants to distinguish these two events for its
1416 * own children it should create a separate process which takes
1417 * the role of real parent.
1418 */
1419 if (!ptrace_reparented(p))
1420 ptrace = 1;
1421 }
1422
1423 /* slay zombie? */
1424 if (exit_state == EXIT_ZOMBIE) {
1425 /* we don't reap group leaders with subthreads */
1426 if (!delay_group_leader(p)) {
1427 /*
1428 * A zombie ptracee is only visible to its ptracer.
1429 * Notification and reaping will be cascaded to the
1430 * real parent when the ptracer detaches.
1431 */
1432 if (unlikely(ptrace) || likely(!p->ptrace))
1433 return wait_task_zombie(wo, p);
1434 }
1435
1436 /*
1437 * Allow access to stopped/continued state via zombie by
1438 * falling through. Clearing of notask_error is complex.
1439 *
1440 * When !@ptrace:
1441 *
1442 * If WEXITED is set, notask_error should naturally be
1443 * cleared. If not, subset of WSTOPPED|WCONTINUED is set,
1444 * so, if there are live subthreads, there are events to
1445 * wait for. If all subthreads are dead, it's still safe
1446 * to clear - this function will be called again in finite
1447 * amount time once all the subthreads are released and
1448 * will then return without clearing.
1449 *
1450 * When @ptrace:
1451 *
1452 * Stopped state is per-task and thus can't change once the
1453 * target task dies. Only continued and exited can happen.
1454 * Clear notask_error if WCONTINUED | WEXITED.
1455 */
1456 if (likely(!ptrace) || (wo->wo_flags & (WCONTINUED | WEXITED)))
1457 wo->notask_error = 0;
1458 } else {
1459 /*
1460 * @p is alive and it's gonna stop, continue or exit, so
1461 * there always is something to wait for.
1462 */
1463 wo->notask_error = 0;
1464 }
1465
1466 /*
1467 * Wait for stopped. Depending on @ptrace, different stopped state
1468 * is used and the two don't interact with each other.
1469 */
1470 ret = wait_task_stopped(wo, ptrace, p);
1471 if (ret)
1472 return ret;
1473
1474 /*
1475 * Wait for continued. There's only one continued state and the
1476 * ptracer can consume it which can confuse the real parent. Don't
1477 * use WCONTINUED from ptracer. You don't need or want it.
1478 */
1479 return wait_task_continued(wo, p);
1480}
1481
1482/*
1483 * Do the work of do_wait() for one thread in the group, @tsk.
1484 *
1485 * -ECHILD should be in ->notask_error before the first call.
1486 * Returns nonzero for a final return, when we have unlocked tasklist_lock.
1487 * Returns zero if the search for a child should continue; then
1488 * ->notask_error is 0 if there were any eligible children,
1489 * or another error from security_task_wait(), or still -ECHILD.
1490 */
1491static int do_wait_thread(struct wait_opts *wo, struct task_struct *tsk)
1492{
1493 struct task_struct *p;
1494
1495 list_for_each_entry(p, &tsk->children, sibling) {
1496 int ret = wait_consider_task(wo, 0, p);
1497
1498 if (ret)
1499 return ret;
1500 }
1501
1502 return 0;
1503}
1504
1505static int ptrace_do_wait(struct wait_opts *wo, struct task_struct *tsk)
1506{
1507 struct task_struct *p;
1508
1509 list_for_each_entry(p, &tsk->ptraced, ptrace_entry) {
1510 int ret = wait_consider_task(wo, 1, p);
1511
1512 if (ret)
1513 return ret;
1514 }
1515
1516 return 0;
1517}
1518
1519static int child_wait_callback(wait_queue_t *wait, unsigned mode,
1520 int sync, void *key)
1521{
1522 struct wait_opts *wo = container_of(wait, struct wait_opts,
1523 child_wait);
1524 struct task_struct *p = key;
1525
1526 if (!eligible_pid(wo, p))
1527 return 0;
1528
1529 if ((wo->wo_flags & __WNOTHREAD) && wait->private != p->parent)
1530 return 0;
1531
1532 return default_wake_function(wait, mode, sync, key);
1533}
1534
1535void __wake_up_parent(struct task_struct *p, struct task_struct *parent)
1536{
1537 __wake_up_sync_key(&parent->signal->wait_chldexit,
1538 TASK_INTERRUPTIBLE, 1, p);
1539}
1540
1541static long do_wait(struct wait_opts *wo)
1542{
1543 struct task_struct *tsk;
1544 int retval;
1545
1546 trace_sched_process_wait(wo->wo_pid);
1547
1548 init_waitqueue_func_entry(&wo->child_wait, child_wait_callback);
1549 wo->child_wait.private = current;
1550 add_wait_queue(¤t->signal->wait_chldexit, &wo->child_wait);
1551repeat:
1552 /*
1553 * If there is nothing that can match our criteria, just get out.
1554 * We will clear ->notask_error to zero if we see any child that
1555 * might later match our criteria, even if we are not able to reap
1556 * it yet.
1557 */
1558 wo->notask_error = -ECHILD;
1559 if ((wo->wo_type < PIDTYPE_MAX) &&
1560 (!wo->wo_pid || hlist_empty(&wo->wo_pid->tasks[wo->wo_type])))
1561 goto notask;
1562
1563 set_current_state(TASK_INTERRUPTIBLE);
1564 read_lock(&tasklist_lock);
1565 tsk = current;
1566 do {
1567 retval = do_wait_thread(wo, tsk);
1568 if (retval)
1569 goto end;
1570
1571 retval = ptrace_do_wait(wo, tsk);
1572 if (retval)
1573 goto end;
1574
1575 if (wo->wo_flags & __WNOTHREAD)
1576 break;
1577 } while_each_thread(current, tsk);
1578 read_unlock(&tasklist_lock);
1579
1580notask:
1581 retval = wo->notask_error;
1582 if (!retval && !(wo->wo_flags & WNOHANG)) {
1583 retval = -ERESTARTSYS;
1584 if (!signal_pending(current)) {
1585 schedule();
1586 goto repeat;
1587 }
1588 }
1589end:
1590 __set_current_state(TASK_RUNNING);
1591 remove_wait_queue(¤t->signal->wait_chldexit, &wo->child_wait);
1592 return retval;
1593}
1594
1595SYSCALL_DEFINE5(waitid, int, which, pid_t, upid, struct siginfo __user *,
1596 infop, int, options, struct rusage __user *, ru)
1597{
1598 struct wait_opts wo;
1599 struct pid *pid = NULL;
1600 enum pid_type type;
1601 long ret;
1602
1603 if (options & ~(WNOHANG|WNOWAIT|WEXITED|WSTOPPED|WCONTINUED|
1604 __WNOTHREAD|__WCLONE|__WALL))
1605 return -EINVAL;
1606 if (!(options & (WEXITED|WSTOPPED|WCONTINUED)))
1607 return -EINVAL;
1608
1609 switch (which) {
1610 case P_ALL:
1611 type = PIDTYPE_MAX;
1612 break;
1613 case P_PID:
1614 type = PIDTYPE_PID;
1615 if (upid <= 0)
1616 return -EINVAL;
1617 break;
1618 case P_PGID:
1619 type = PIDTYPE_PGID;
1620 if (upid <= 0)
1621 return -EINVAL;
1622 break;
1623 default:
1624 return -EINVAL;
1625 }
1626
1627 if (type < PIDTYPE_MAX)
1628 pid = find_get_pid(upid);
1629
1630 wo.wo_type = type;
1631 wo.wo_pid = pid;
1632 wo.wo_flags = options;
1633 wo.wo_info = infop;
1634 wo.wo_stat = NULL;
1635 wo.wo_rusage = ru;
1636 ret = do_wait(&wo);
1637
1638 if (ret > 0) {
1639 ret = 0;
1640 } else if (infop) {
1641 /*
1642 * For a WNOHANG return, clear out all the fields
1643 * we would set so the user can easily tell the
1644 * difference.
1645 */
1646 if (!ret)
1647 ret = put_user(0, &infop->si_signo);
1648 if (!ret)
1649 ret = put_user(0, &infop->si_errno);
1650 if (!ret)
1651 ret = put_user(0, &infop->si_code);
1652 if (!ret)
1653 ret = put_user(0, &infop->si_pid);
1654 if (!ret)
1655 ret = put_user(0, &infop->si_uid);
1656 if (!ret)
1657 ret = put_user(0, &infop->si_status);
1658 }
1659
1660 put_pid(pid);
1661 return ret;
1662}
1663
1664SYSCALL_DEFINE4(wait4, pid_t, upid, int __user *, stat_addr,
1665 int, options, struct rusage __user *, ru)
1666{
1667 struct wait_opts wo;
1668 struct pid *pid = NULL;
1669 enum pid_type type;
1670 long ret;
1671
1672 if (options & ~(WNOHANG|WUNTRACED|WCONTINUED|
1673 __WNOTHREAD|__WCLONE|__WALL))
1674 return -EINVAL;
1675
1676 if (upid == -1)
1677 type = PIDTYPE_MAX;
1678 else if (upid < 0) {
1679 type = PIDTYPE_PGID;
1680 pid = find_get_pid(-upid);
1681 } else if (upid == 0) {
1682 type = PIDTYPE_PGID;
1683 pid = get_task_pid(current, PIDTYPE_PGID);
1684 } else /* upid > 0 */ {
1685 type = PIDTYPE_PID;
1686 pid = find_get_pid(upid);
1687 }
1688
1689 wo.wo_type = type;
1690 wo.wo_pid = pid;
1691 wo.wo_flags = options | WEXITED;
1692 wo.wo_info = NULL;
1693 wo.wo_stat = stat_addr;
1694 wo.wo_rusage = ru;
1695 ret = do_wait(&wo);
1696 put_pid(pid);
1697
1698 return ret;
1699}
1700
1701#ifdef __ARCH_WANT_SYS_WAITPID
1702
1703/*
1704 * sys_waitpid() remains for compatibility. waitpid() should be
1705 * implemented by calling sys_wait4() from libc.a.
1706 */
1707SYSCALL_DEFINE3(waitpid, pid_t, pid, int __user *, stat_addr, int, options)
1708{
1709 return sys_wait4(pid, stat_addr, options, NULL);
1710}
1711
1712#endif
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * linux/kernel/exit.c
4 *
5 * Copyright (C) 1991, 1992 Linus Torvalds
6 */
7
8#include <linux/mm.h>
9#include <linux/slab.h>
10#include <linux/sched/autogroup.h>
11#include <linux/sched/mm.h>
12#include <linux/sched/stat.h>
13#include <linux/sched/task.h>
14#include <linux/sched/task_stack.h>
15#include <linux/sched/cputime.h>
16#include <linux/interrupt.h>
17#include <linux/module.h>
18#include <linux/capability.h>
19#include <linux/completion.h>
20#include <linux/personality.h>
21#include <linux/tty.h>
22#include <linux/iocontext.h>
23#include <linux/key.h>
24#include <linux/cpu.h>
25#include <linux/acct.h>
26#include <linux/tsacct_kern.h>
27#include <linux/file.h>
28#include <linux/fdtable.h>
29#include <linux/freezer.h>
30#include <linux/binfmts.h>
31#include <linux/nsproxy.h>
32#include <linux/pid_namespace.h>
33#include <linux/ptrace.h>
34#include <linux/profile.h>
35#include <linux/mount.h>
36#include <linux/proc_fs.h>
37#include <linux/kthread.h>
38#include <linux/mempolicy.h>
39#include <linux/taskstats_kern.h>
40#include <linux/delayacct.h>
41#include <linux/cgroup.h>
42#include <linux/syscalls.h>
43#include <linux/signal.h>
44#include <linux/posix-timers.h>
45#include <linux/cn_proc.h>
46#include <linux/mutex.h>
47#include <linux/futex.h>
48#include <linux/pipe_fs_i.h>
49#include <linux/audit.h> /* for audit_free() */
50#include <linux/resource.h>
51#include <linux/blkdev.h>
52#include <linux/task_io_accounting_ops.h>
53#include <linux/tracehook.h>
54#include <linux/fs_struct.h>
55#include <linux/init_task.h>
56#include <linux/perf_event.h>
57#include <trace/events/sched.h>
58#include <linux/hw_breakpoint.h>
59#include <linux/oom.h>
60#include <linux/writeback.h>
61#include <linux/shm.h>
62#include <linux/kcov.h>
63#include <linux/random.h>
64#include <linux/rcuwait.h>
65#include <linux/compat.h>
66#include <linux/io_uring.h>
67
68#include <linux/uaccess.h>
69#include <asm/unistd.h>
70#include <asm/mmu_context.h>
71
72static void __unhash_process(struct task_struct *p, bool group_dead)
73{
74 nr_threads--;
75 detach_pid(p, PIDTYPE_PID);
76 if (group_dead) {
77 detach_pid(p, PIDTYPE_TGID);
78 detach_pid(p, PIDTYPE_PGID);
79 detach_pid(p, PIDTYPE_SID);
80
81 list_del_rcu(&p->tasks);
82 list_del_init(&p->sibling);
83 __this_cpu_dec(process_counts);
84 }
85 list_del_rcu(&p->thread_group);
86 list_del_rcu(&p->thread_node);
87}
88
89/*
90 * This function expects the tasklist_lock write-locked.
91 */
92static void __exit_signal(struct task_struct *tsk)
93{
94 struct signal_struct *sig = tsk->signal;
95 bool group_dead = thread_group_leader(tsk);
96 struct sighand_struct *sighand;
97 struct tty_struct *tty;
98 u64 utime, stime;
99
100 sighand = rcu_dereference_check(tsk->sighand,
101 lockdep_tasklist_lock_is_held());
102 spin_lock(&sighand->siglock);
103
104#ifdef CONFIG_POSIX_TIMERS
105 posix_cpu_timers_exit(tsk);
106 if (group_dead)
107 posix_cpu_timers_exit_group(tsk);
108#endif
109
110 if (group_dead) {
111 tty = sig->tty;
112 sig->tty = NULL;
113 } else {
114 /*
115 * If there is any task waiting for the group exit
116 * then notify it:
117 */
118 if (sig->notify_count > 0 && !--sig->notify_count)
119 wake_up_process(sig->group_exit_task);
120
121 if (tsk == sig->curr_target)
122 sig->curr_target = next_thread(tsk);
123 }
124
125 add_device_randomness((const void*) &tsk->se.sum_exec_runtime,
126 sizeof(unsigned long long));
127
128 /*
129 * Accumulate here the counters for all threads as they die. We could
130 * skip the group leader because it is the last user of signal_struct,
131 * but we want to avoid the race with thread_group_cputime() which can
132 * see the empty ->thread_head list.
133 */
134 task_cputime(tsk, &utime, &stime);
135 write_seqlock(&sig->stats_lock);
136 sig->utime += utime;
137 sig->stime += stime;
138 sig->gtime += task_gtime(tsk);
139 sig->min_flt += tsk->min_flt;
140 sig->maj_flt += tsk->maj_flt;
141 sig->nvcsw += tsk->nvcsw;
142 sig->nivcsw += tsk->nivcsw;
143 sig->inblock += task_io_get_inblock(tsk);
144 sig->oublock += task_io_get_oublock(tsk);
145 task_io_accounting_add(&sig->ioac, &tsk->ioac);
146 sig->sum_sched_runtime += tsk->se.sum_exec_runtime;
147 sig->nr_threads--;
148 __unhash_process(tsk, group_dead);
149 write_sequnlock(&sig->stats_lock);
150
151 /*
152 * Do this under ->siglock, we can race with another thread
153 * doing sigqueue_free() if we have SIGQUEUE_PREALLOC signals.
154 */
155 flush_sigqueue(&tsk->pending);
156 tsk->sighand = NULL;
157 spin_unlock(&sighand->siglock);
158
159 __cleanup_sighand(sighand);
160 clear_tsk_thread_flag(tsk, TIF_SIGPENDING);
161 if (group_dead) {
162 flush_sigqueue(&sig->shared_pending);
163 tty_kref_put(tty);
164 }
165}
166
167static void delayed_put_task_struct(struct rcu_head *rhp)
168{
169 struct task_struct *tsk = container_of(rhp, struct task_struct, rcu);
170
171 perf_event_delayed_put(tsk);
172 trace_sched_process_free(tsk);
173 put_task_struct(tsk);
174}
175
176void put_task_struct_rcu_user(struct task_struct *task)
177{
178 if (refcount_dec_and_test(&task->rcu_users))
179 call_rcu(&task->rcu, delayed_put_task_struct);
180}
181
182void release_task(struct task_struct *p)
183{
184 struct task_struct *leader;
185 struct pid *thread_pid;
186 int zap_leader;
187repeat:
188 /* don't need to get the RCU readlock here - the process is dead and
189 * can't be modifying its own credentials. But shut RCU-lockdep up */
190 rcu_read_lock();
191 dec_rlimit_ucounts(task_ucounts(p), UCOUNT_RLIMIT_NPROC, 1);
192 rcu_read_unlock();
193
194 cgroup_release(p);
195
196 write_lock_irq(&tasklist_lock);
197 ptrace_release_task(p);
198 thread_pid = get_pid(p->thread_pid);
199 __exit_signal(p);
200
201 /*
202 * If we are the last non-leader member of the thread
203 * group, and the leader is zombie, then notify the
204 * group leader's parent process. (if it wants notification.)
205 */
206 zap_leader = 0;
207 leader = p->group_leader;
208 if (leader != p && thread_group_empty(leader)
209 && leader->exit_state == EXIT_ZOMBIE) {
210 /*
211 * If we were the last child thread and the leader has
212 * exited already, and the leader's parent ignores SIGCHLD,
213 * then we are the one who should release the leader.
214 */
215 zap_leader = do_notify_parent(leader, leader->exit_signal);
216 if (zap_leader)
217 leader->exit_state = EXIT_DEAD;
218 }
219
220 write_unlock_irq(&tasklist_lock);
221 seccomp_filter_release(p);
222 proc_flush_pid(thread_pid);
223 put_pid(thread_pid);
224 release_thread(p);
225 put_task_struct_rcu_user(p);
226
227 p = leader;
228 if (unlikely(zap_leader))
229 goto repeat;
230}
231
232int rcuwait_wake_up(struct rcuwait *w)
233{
234 int ret = 0;
235 struct task_struct *task;
236
237 rcu_read_lock();
238
239 /*
240 * Order condition vs @task, such that everything prior to the load
241 * of @task is visible. This is the condition as to why the user called
242 * rcuwait_wake() in the first place. Pairs with set_current_state()
243 * barrier (A) in rcuwait_wait_event().
244 *
245 * WAIT WAKE
246 * [S] tsk = current [S] cond = true
247 * MB (A) MB (B)
248 * [L] cond [L] tsk
249 */
250 smp_mb(); /* (B) */
251
252 task = rcu_dereference(w->task);
253 if (task)
254 ret = wake_up_process(task);
255 rcu_read_unlock();
256
257 return ret;
258}
259EXPORT_SYMBOL_GPL(rcuwait_wake_up);
260
261/*
262 * Determine if a process group is "orphaned", according to the POSIX
263 * definition in 2.2.2.52. Orphaned process groups are not to be affected
264 * by terminal-generated stop signals. Newly orphaned process groups are
265 * to receive a SIGHUP and a SIGCONT.
266 *
267 * "I ask you, have you ever known what it is to be an orphan?"
268 */
269static int will_become_orphaned_pgrp(struct pid *pgrp,
270 struct task_struct *ignored_task)
271{
272 struct task_struct *p;
273
274 do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
275 if ((p == ignored_task) ||
276 (p->exit_state && thread_group_empty(p)) ||
277 is_global_init(p->real_parent))
278 continue;
279
280 if (task_pgrp(p->real_parent) != pgrp &&
281 task_session(p->real_parent) == task_session(p))
282 return 0;
283 } while_each_pid_task(pgrp, PIDTYPE_PGID, p);
284
285 return 1;
286}
287
288int is_current_pgrp_orphaned(void)
289{
290 int retval;
291
292 read_lock(&tasklist_lock);
293 retval = will_become_orphaned_pgrp(task_pgrp(current), NULL);
294 read_unlock(&tasklist_lock);
295
296 return retval;
297}
298
299static bool has_stopped_jobs(struct pid *pgrp)
300{
301 struct task_struct *p;
302
303 do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
304 if (p->signal->flags & SIGNAL_STOP_STOPPED)
305 return true;
306 } while_each_pid_task(pgrp, PIDTYPE_PGID, p);
307
308 return false;
309}
310
311/*
312 * Check to see if any process groups have become orphaned as
313 * a result of our exiting, and if they have any stopped jobs,
314 * send them a SIGHUP and then a SIGCONT. (POSIX 3.2.2.2)
315 */
316static void
317kill_orphaned_pgrp(struct task_struct *tsk, struct task_struct *parent)
318{
319 struct pid *pgrp = task_pgrp(tsk);
320 struct task_struct *ignored_task = tsk;
321
322 if (!parent)
323 /* exit: our father is in a different pgrp than
324 * we are and we were the only connection outside.
325 */
326 parent = tsk->real_parent;
327 else
328 /* reparent: our child is in a different pgrp than
329 * we are, and it was the only connection outside.
330 */
331 ignored_task = NULL;
332
333 if (task_pgrp(parent) != pgrp &&
334 task_session(parent) == task_session(tsk) &&
335 will_become_orphaned_pgrp(pgrp, ignored_task) &&
336 has_stopped_jobs(pgrp)) {
337 __kill_pgrp_info(SIGHUP, SEND_SIG_PRIV, pgrp);
338 __kill_pgrp_info(SIGCONT, SEND_SIG_PRIV, pgrp);
339 }
340}
341
342#ifdef CONFIG_MEMCG
343/*
344 * A task is exiting. If it owned this mm, find a new owner for the mm.
345 */
346void mm_update_next_owner(struct mm_struct *mm)
347{
348 struct task_struct *c, *g, *p = current;
349
350retry:
351 /*
352 * If the exiting or execing task is not the owner, it's
353 * someone else's problem.
354 */
355 if (mm->owner != p)
356 return;
357 /*
358 * The current owner is exiting/execing and there are no other
359 * candidates. Do not leave the mm pointing to a possibly
360 * freed task structure.
361 */
362 if (atomic_read(&mm->mm_users) <= 1) {
363 WRITE_ONCE(mm->owner, NULL);
364 return;
365 }
366
367 read_lock(&tasklist_lock);
368 /*
369 * Search in the children
370 */
371 list_for_each_entry(c, &p->children, sibling) {
372 if (c->mm == mm)
373 goto assign_new_owner;
374 }
375
376 /*
377 * Search in the siblings
378 */
379 list_for_each_entry(c, &p->real_parent->children, sibling) {
380 if (c->mm == mm)
381 goto assign_new_owner;
382 }
383
384 /*
385 * Search through everything else, we should not get here often.
386 */
387 for_each_process(g) {
388 if (g->flags & PF_KTHREAD)
389 continue;
390 for_each_thread(g, c) {
391 if (c->mm == mm)
392 goto assign_new_owner;
393 if (c->mm)
394 break;
395 }
396 }
397 read_unlock(&tasklist_lock);
398 /*
399 * We found no owner yet mm_users > 1: this implies that we are
400 * most likely racing with swapoff (try_to_unuse()) or /proc or
401 * ptrace or page migration (get_task_mm()). Mark owner as NULL.
402 */
403 WRITE_ONCE(mm->owner, NULL);
404 return;
405
406assign_new_owner:
407 BUG_ON(c == p);
408 get_task_struct(c);
409 /*
410 * The task_lock protects c->mm from changing.
411 * We always want mm->owner->mm == mm
412 */
413 task_lock(c);
414 /*
415 * Delay read_unlock() till we have the task_lock()
416 * to ensure that c does not slip away underneath us
417 */
418 read_unlock(&tasklist_lock);
419 if (c->mm != mm) {
420 task_unlock(c);
421 put_task_struct(c);
422 goto retry;
423 }
424 WRITE_ONCE(mm->owner, c);
425 task_unlock(c);
426 put_task_struct(c);
427}
428#endif /* CONFIG_MEMCG */
429
430/*
431 * Turn us into a lazy TLB process if we
432 * aren't already..
433 */
434static void exit_mm(void)
435{
436 struct mm_struct *mm = current->mm;
437 struct core_state *core_state;
438
439 exit_mm_release(current, mm);
440 if (!mm)
441 return;
442 sync_mm_rss(mm);
443 /*
444 * Serialize with any possible pending coredump.
445 * We must hold mmap_lock around checking core_state
446 * and clearing tsk->mm. The core-inducing thread
447 * will increment ->nr_threads for each thread in the
448 * group with ->mm != NULL.
449 */
450 mmap_read_lock(mm);
451 core_state = mm->core_state;
452 if (core_state) {
453 struct core_thread self;
454
455 mmap_read_unlock(mm);
456
457 self.task = current;
458 if (self.task->flags & PF_SIGNALED)
459 self.next = xchg(&core_state->dumper.next, &self);
460 else
461 self.task = NULL;
462 /*
463 * Implies mb(), the result of xchg() must be visible
464 * to core_state->dumper.
465 */
466 if (atomic_dec_and_test(&core_state->nr_threads))
467 complete(&core_state->startup);
468
469 for (;;) {
470 set_current_state(TASK_UNINTERRUPTIBLE);
471 if (!self.task) /* see coredump_finish() */
472 break;
473 freezable_schedule();
474 }
475 __set_current_state(TASK_RUNNING);
476 mmap_read_lock(mm);
477 }
478 mmgrab(mm);
479 BUG_ON(mm != current->active_mm);
480 /* more a memory barrier than a real lock */
481 task_lock(current);
482 /*
483 * When a thread stops operating on an address space, the loop
484 * in membarrier_private_expedited() may not observe that
485 * tsk->mm, and the loop in membarrier_global_expedited() may
486 * not observe a MEMBARRIER_STATE_GLOBAL_EXPEDITED
487 * rq->membarrier_state, so those would not issue an IPI.
488 * Membarrier requires a memory barrier after accessing
489 * user-space memory, before clearing tsk->mm or the
490 * rq->membarrier_state.
491 */
492 smp_mb__after_spinlock();
493 local_irq_disable();
494 current->mm = NULL;
495 membarrier_update_current_mm(NULL);
496 enter_lazy_tlb(mm, current);
497 local_irq_enable();
498 task_unlock(current);
499 mmap_read_unlock(mm);
500 mm_update_next_owner(mm);
501 mmput(mm);
502 if (test_thread_flag(TIF_MEMDIE))
503 exit_oom_victim();
504}
505
506static struct task_struct *find_alive_thread(struct task_struct *p)
507{
508 struct task_struct *t;
509
510 for_each_thread(p, t) {
511 if (!(t->flags & PF_EXITING))
512 return t;
513 }
514 return NULL;
515}
516
517static struct task_struct *find_child_reaper(struct task_struct *father,
518 struct list_head *dead)
519 __releases(&tasklist_lock)
520 __acquires(&tasklist_lock)
521{
522 struct pid_namespace *pid_ns = task_active_pid_ns(father);
523 struct task_struct *reaper = pid_ns->child_reaper;
524 struct task_struct *p, *n;
525
526 if (likely(reaper != father))
527 return reaper;
528
529 reaper = find_alive_thread(father);
530 if (reaper) {
531 pid_ns->child_reaper = reaper;
532 return reaper;
533 }
534
535 write_unlock_irq(&tasklist_lock);
536
537 list_for_each_entry_safe(p, n, dead, ptrace_entry) {
538 list_del_init(&p->ptrace_entry);
539 release_task(p);
540 }
541
542 zap_pid_ns_processes(pid_ns);
543 write_lock_irq(&tasklist_lock);
544
545 return father;
546}
547
548/*
549 * When we die, we re-parent all our children, and try to:
550 * 1. give them to another thread in our thread group, if such a member exists
551 * 2. give it to the first ancestor process which prctl'd itself as a
552 * child_subreaper for its children (like a service manager)
553 * 3. give it to the init process (PID 1) in our pid namespace
554 */
555static struct task_struct *find_new_reaper(struct task_struct *father,
556 struct task_struct *child_reaper)
557{
558 struct task_struct *thread, *reaper;
559
560 thread = find_alive_thread(father);
561 if (thread)
562 return thread;
563
564 if (father->signal->has_child_subreaper) {
565 unsigned int ns_level = task_pid(father)->level;
566 /*
567 * Find the first ->is_child_subreaper ancestor in our pid_ns.
568 * We can't check reaper != child_reaper to ensure we do not
569 * cross the namespaces, the exiting parent could be injected
570 * by setns() + fork().
571 * We check pid->level, this is slightly more efficient than
572 * task_active_pid_ns(reaper) != task_active_pid_ns(father).
573 */
574 for (reaper = father->real_parent;
575 task_pid(reaper)->level == ns_level;
576 reaper = reaper->real_parent) {
577 if (reaper == &init_task)
578 break;
579 if (!reaper->signal->is_child_subreaper)
580 continue;
581 thread = find_alive_thread(reaper);
582 if (thread)
583 return thread;
584 }
585 }
586
587 return child_reaper;
588}
589
590/*
591* Any that need to be release_task'd are put on the @dead list.
592 */
593static void reparent_leader(struct task_struct *father, struct task_struct *p,
594 struct list_head *dead)
595{
596 if (unlikely(p->exit_state == EXIT_DEAD))
597 return;
598
599 /* We don't want people slaying init. */
600 p->exit_signal = SIGCHLD;
601
602 /* If it has exited notify the new parent about this child's death. */
603 if (!p->ptrace &&
604 p->exit_state == EXIT_ZOMBIE && thread_group_empty(p)) {
605 if (do_notify_parent(p, p->exit_signal)) {
606 p->exit_state = EXIT_DEAD;
607 list_add(&p->ptrace_entry, dead);
608 }
609 }
610
611 kill_orphaned_pgrp(p, father);
612}
613
614/*
615 * This does two things:
616 *
617 * A. Make init inherit all the child processes
618 * B. Check to see if any process groups have become orphaned
619 * as a result of our exiting, and if they have any stopped
620 * jobs, send them a SIGHUP and then a SIGCONT. (POSIX 3.2.2.2)
621 */
622static void forget_original_parent(struct task_struct *father,
623 struct list_head *dead)
624{
625 struct task_struct *p, *t, *reaper;
626
627 if (unlikely(!list_empty(&father->ptraced)))
628 exit_ptrace(father, dead);
629
630 /* Can drop and reacquire tasklist_lock */
631 reaper = find_child_reaper(father, dead);
632 if (list_empty(&father->children))
633 return;
634
635 reaper = find_new_reaper(father, reaper);
636 list_for_each_entry(p, &father->children, sibling) {
637 for_each_thread(p, t) {
638 RCU_INIT_POINTER(t->real_parent, reaper);
639 BUG_ON((!t->ptrace) != (rcu_access_pointer(t->parent) == father));
640 if (likely(!t->ptrace))
641 t->parent = t->real_parent;
642 if (t->pdeath_signal)
643 group_send_sig_info(t->pdeath_signal,
644 SEND_SIG_NOINFO, t,
645 PIDTYPE_TGID);
646 }
647 /*
648 * If this is a threaded reparent there is no need to
649 * notify anyone anything has happened.
650 */
651 if (!same_thread_group(reaper, father))
652 reparent_leader(father, p, dead);
653 }
654 list_splice_tail_init(&father->children, &reaper->children);
655}
656
657/*
658 * Send signals to all our closest relatives so that they know
659 * to properly mourn us..
660 */
661static void exit_notify(struct task_struct *tsk, int group_dead)
662{
663 bool autoreap;
664 struct task_struct *p, *n;
665 LIST_HEAD(dead);
666
667 write_lock_irq(&tasklist_lock);
668 forget_original_parent(tsk, &dead);
669
670 if (group_dead)
671 kill_orphaned_pgrp(tsk->group_leader, NULL);
672
673 tsk->exit_state = EXIT_ZOMBIE;
674 if (unlikely(tsk->ptrace)) {
675 int sig = thread_group_leader(tsk) &&
676 thread_group_empty(tsk) &&
677 !ptrace_reparented(tsk) ?
678 tsk->exit_signal : SIGCHLD;
679 autoreap = do_notify_parent(tsk, sig);
680 } else if (thread_group_leader(tsk)) {
681 autoreap = thread_group_empty(tsk) &&
682 do_notify_parent(tsk, tsk->exit_signal);
683 } else {
684 autoreap = true;
685 }
686
687 if (autoreap) {
688 tsk->exit_state = EXIT_DEAD;
689 list_add(&tsk->ptrace_entry, &dead);
690 }
691
692 /* mt-exec, de_thread() is waiting for group leader */
693 if (unlikely(tsk->signal->notify_count < 0))
694 wake_up_process(tsk->signal->group_exit_task);
695 write_unlock_irq(&tasklist_lock);
696
697 list_for_each_entry_safe(p, n, &dead, ptrace_entry) {
698 list_del_init(&p->ptrace_entry);
699 release_task(p);
700 }
701}
702
703#ifdef CONFIG_DEBUG_STACK_USAGE
704static void check_stack_usage(void)
705{
706 static DEFINE_SPINLOCK(low_water_lock);
707 static int lowest_to_date = THREAD_SIZE;
708 unsigned long free;
709
710 free = stack_not_used(current);
711
712 if (free >= lowest_to_date)
713 return;
714
715 spin_lock(&low_water_lock);
716 if (free < lowest_to_date) {
717 pr_info("%s (%d) used greatest stack depth: %lu bytes left\n",
718 current->comm, task_pid_nr(current), free);
719 lowest_to_date = free;
720 }
721 spin_unlock(&low_water_lock);
722}
723#else
724static inline void check_stack_usage(void) {}
725#endif
726
727void __noreturn do_exit(long code)
728{
729 struct task_struct *tsk = current;
730 int group_dead;
731
732 /*
733 * We can get here from a kernel oops, sometimes with preemption off.
734 * Start by checking for critical errors.
735 * Then fix up important state like USER_DS and preemption.
736 * Then do everything else.
737 */
738
739 WARN_ON(blk_needs_flush_plug(tsk));
740
741 if (unlikely(in_interrupt()))
742 panic("Aiee, killing interrupt handler!");
743 if (unlikely(!tsk->pid))
744 panic("Attempted to kill the idle task!");
745
746 /*
747 * If do_exit is called because this processes oopsed, it's possible
748 * that get_fs() was left as KERNEL_DS, so reset it to USER_DS before
749 * continuing. Amongst other possible reasons, this is to prevent
750 * mm_release()->clear_child_tid() from writing to a user-controlled
751 * kernel address.
752 */
753 force_uaccess_begin();
754
755 if (unlikely(in_atomic())) {
756 pr_info("note: %s[%d] exited with preempt_count %d\n",
757 current->comm, task_pid_nr(current),
758 preempt_count());
759 preempt_count_set(PREEMPT_ENABLED);
760 }
761
762 profile_task_exit(tsk);
763 kcov_task_exit(tsk);
764
765 ptrace_event(PTRACE_EVENT_EXIT, code);
766
767 validate_creds_for_do_exit(tsk);
768
769 /*
770 * We're taking recursive faults here in do_exit. Safest is to just
771 * leave this task alone and wait for reboot.
772 */
773 if (unlikely(tsk->flags & PF_EXITING)) {
774 pr_alert("Fixing recursive fault but reboot is needed!\n");
775 futex_exit_recursive(tsk);
776 set_current_state(TASK_UNINTERRUPTIBLE);
777 schedule();
778 }
779
780 io_uring_files_cancel(tsk->files);
781 exit_signals(tsk); /* sets PF_EXITING */
782
783 /* sync mm's RSS info before statistics gathering */
784 if (tsk->mm)
785 sync_mm_rss(tsk->mm);
786 acct_update_integrals(tsk);
787 group_dead = atomic_dec_and_test(&tsk->signal->live);
788 if (group_dead) {
789 /*
790 * If the last thread of global init has exited, panic
791 * immediately to get a useable coredump.
792 */
793 if (unlikely(is_global_init(tsk)))
794 panic("Attempted to kill init! exitcode=0x%08x\n",
795 tsk->signal->group_exit_code ?: (int)code);
796
797#ifdef CONFIG_POSIX_TIMERS
798 hrtimer_cancel(&tsk->signal->real_timer);
799 exit_itimers(tsk->signal);
800#endif
801 if (tsk->mm)
802 setmax_mm_hiwater_rss(&tsk->signal->maxrss, tsk->mm);
803 }
804 acct_collect(code, group_dead);
805 if (group_dead)
806 tty_audit_exit();
807 audit_free(tsk);
808
809 tsk->exit_code = code;
810 taskstats_exit(tsk, group_dead);
811
812 exit_mm();
813
814 if (group_dead)
815 acct_process();
816 trace_sched_process_exit(tsk);
817
818 exit_sem(tsk);
819 exit_shm(tsk);
820 exit_files(tsk);
821 exit_fs(tsk);
822 if (group_dead)
823 disassociate_ctty(1);
824 exit_task_namespaces(tsk);
825 exit_task_work(tsk);
826 exit_thread(tsk);
827
828 /*
829 * Flush inherited counters to the parent - before the parent
830 * gets woken up by child-exit notifications.
831 *
832 * because of cgroup mode, must be called before cgroup_exit()
833 */
834 perf_event_exit_task(tsk);
835
836 sched_autogroup_exit_task(tsk);
837 cgroup_exit(tsk);
838
839 /*
840 * FIXME: do that only when needed, using sched_exit tracepoint
841 */
842 flush_ptrace_hw_breakpoint(tsk);
843
844 exit_tasks_rcu_start();
845 exit_notify(tsk, group_dead);
846 proc_exit_connector(tsk);
847 mpol_put_task_policy(tsk);
848#ifdef CONFIG_FUTEX
849 if (unlikely(current->pi_state_cache))
850 kfree(current->pi_state_cache);
851#endif
852 /*
853 * Make sure we are holding no locks:
854 */
855 debug_check_no_locks_held();
856
857 if (tsk->io_context)
858 exit_io_context(tsk);
859
860 if (tsk->splice_pipe)
861 free_pipe_info(tsk->splice_pipe);
862
863 if (tsk->task_frag.page)
864 put_page(tsk->task_frag.page);
865
866 validate_creds_for_do_exit(tsk);
867
868 check_stack_usage();
869 preempt_disable();
870 if (tsk->nr_dirtied)
871 __this_cpu_add(dirty_throttle_leaks, tsk->nr_dirtied);
872 exit_rcu();
873 exit_tasks_rcu_finish();
874
875 lockdep_free_task(tsk);
876 do_task_dead();
877}
878EXPORT_SYMBOL_GPL(do_exit);
879
880void complete_and_exit(struct completion *comp, long code)
881{
882 if (comp)
883 complete(comp);
884
885 do_exit(code);
886}
887EXPORT_SYMBOL(complete_and_exit);
888
889SYSCALL_DEFINE1(exit, int, error_code)
890{
891 do_exit((error_code&0xff)<<8);
892}
893
894/*
895 * Take down every thread in the group. This is called by fatal signals
896 * as well as by sys_exit_group (below).
897 */
898void
899do_group_exit(int exit_code)
900{
901 struct signal_struct *sig = current->signal;
902
903 BUG_ON(exit_code & 0x80); /* core dumps don't get here */
904
905 if (signal_group_exit(sig))
906 exit_code = sig->group_exit_code;
907 else if (!thread_group_empty(current)) {
908 struct sighand_struct *const sighand = current->sighand;
909
910 spin_lock_irq(&sighand->siglock);
911 if (signal_group_exit(sig))
912 /* Another thread got here before we took the lock. */
913 exit_code = sig->group_exit_code;
914 else {
915 sig->group_exit_code = exit_code;
916 sig->flags = SIGNAL_GROUP_EXIT;
917 zap_other_threads(current);
918 }
919 spin_unlock_irq(&sighand->siglock);
920 }
921
922 do_exit(exit_code);
923 /* NOTREACHED */
924}
925
926/*
927 * this kills every thread in the thread group. Note that any externally
928 * wait4()-ing process will get the correct exit code - even if this
929 * thread is not the thread group leader.
930 */
931SYSCALL_DEFINE1(exit_group, int, error_code)
932{
933 do_group_exit((error_code & 0xff) << 8);
934 /* NOTREACHED */
935 return 0;
936}
937
938struct waitid_info {
939 pid_t pid;
940 uid_t uid;
941 int status;
942 int cause;
943};
944
945struct wait_opts {
946 enum pid_type wo_type;
947 int wo_flags;
948 struct pid *wo_pid;
949
950 struct waitid_info *wo_info;
951 int wo_stat;
952 struct rusage *wo_rusage;
953
954 wait_queue_entry_t child_wait;
955 int notask_error;
956};
957
958static int eligible_pid(struct wait_opts *wo, struct task_struct *p)
959{
960 return wo->wo_type == PIDTYPE_MAX ||
961 task_pid_type(p, wo->wo_type) == wo->wo_pid;
962}
963
964static int
965eligible_child(struct wait_opts *wo, bool ptrace, struct task_struct *p)
966{
967 if (!eligible_pid(wo, p))
968 return 0;
969
970 /*
971 * Wait for all children (clone and not) if __WALL is set or
972 * if it is traced by us.
973 */
974 if (ptrace || (wo->wo_flags & __WALL))
975 return 1;
976
977 /*
978 * Otherwise, wait for clone children *only* if __WCLONE is set;
979 * otherwise, wait for non-clone children *only*.
980 *
981 * Note: a "clone" child here is one that reports to its parent
982 * using a signal other than SIGCHLD, or a non-leader thread which
983 * we can only see if it is traced by us.
984 */
985 if ((p->exit_signal != SIGCHLD) ^ !!(wo->wo_flags & __WCLONE))
986 return 0;
987
988 return 1;
989}
990
991/*
992 * Handle sys_wait4 work for one task in state EXIT_ZOMBIE. We hold
993 * read_lock(&tasklist_lock) on entry. If we return zero, we still hold
994 * the lock and this task is uninteresting. If we return nonzero, we have
995 * released the lock and the system call should return.
996 */
997static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p)
998{
999 int state, status;
1000 pid_t pid = task_pid_vnr(p);
1001 uid_t uid = from_kuid_munged(current_user_ns(), task_uid(p));
1002 struct waitid_info *infop;
1003
1004 if (!likely(wo->wo_flags & WEXITED))
1005 return 0;
1006
1007 if (unlikely(wo->wo_flags & WNOWAIT)) {
1008 status = p->exit_code;
1009 get_task_struct(p);
1010 read_unlock(&tasklist_lock);
1011 sched_annotate_sleep();
1012 if (wo->wo_rusage)
1013 getrusage(p, RUSAGE_BOTH, wo->wo_rusage);
1014 put_task_struct(p);
1015 goto out_info;
1016 }
1017 /*
1018 * Move the task's state to DEAD/TRACE, only one thread can do this.
1019 */
1020 state = (ptrace_reparented(p) && thread_group_leader(p)) ?
1021 EXIT_TRACE : EXIT_DEAD;
1022 if (cmpxchg(&p->exit_state, EXIT_ZOMBIE, state) != EXIT_ZOMBIE)
1023 return 0;
1024 /*
1025 * We own this thread, nobody else can reap it.
1026 */
1027 read_unlock(&tasklist_lock);
1028 sched_annotate_sleep();
1029
1030 /*
1031 * Check thread_group_leader() to exclude the traced sub-threads.
1032 */
1033 if (state == EXIT_DEAD && thread_group_leader(p)) {
1034 struct signal_struct *sig = p->signal;
1035 struct signal_struct *psig = current->signal;
1036 unsigned long maxrss;
1037 u64 tgutime, tgstime;
1038
1039 /*
1040 * The resource counters for the group leader are in its
1041 * own task_struct. Those for dead threads in the group
1042 * are in its signal_struct, as are those for the child
1043 * processes it has previously reaped. All these
1044 * accumulate in the parent's signal_struct c* fields.
1045 *
1046 * We don't bother to take a lock here to protect these
1047 * p->signal fields because the whole thread group is dead
1048 * and nobody can change them.
1049 *
1050 * psig->stats_lock also protects us from our sub-theads
1051 * which can reap other children at the same time. Until
1052 * we change k_getrusage()-like users to rely on this lock
1053 * we have to take ->siglock as well.
1054 *
1055 * We use thread_group_cputime_adjusted() to get times for
1056 * the thread group, which consolidates times for all threads
1057 * in the group including the group leader.
1058 */
1059 thread_group_cputime_adjusted(p, &tgutime, &tgstime);
1060 spin_lock_irq(¤t->sighand->siglock);
1061 write_seqlock(&psig->stats_lock);
1062 psig->cutime += tgutime + sig->cutime;
1063 psig->cstime += tgstime + sig->cstime;
1064 psig->cgtime += task_gtime(p) + sig->gtime + sig->cgtime;
1065 psig->cmin_flt +=
1066 p->min_flt + sig->min_flt + sig->cmin_flt;
1067 psig->cmaj_flt +=
1068 p->maj_flt + sig->maj_flt + sig->cmaj_flt;
1069 psig->cnvcsw +=
1070 p->nvcsw + sig->nvcsw + sig->cnvcsw;
1071 psig->cnivcsw +=
1072 p->nivcsw + sig->nivcsw + sig->cnivcsw;
1073 psig->cinblock +=
1074 task_io_get_inblock(p) +
1075 sig->inblock + sig->cinblock;
1076 psig->coublock +=
1077 task_io_get_oublock(p) +
1078 sig->oublock + sig->coublock;
1079 maxrss = max(sig->maxrss, sig->cmaxrss);
1080 if (psig->cmaxrss < maxrss)
1081 psig->cmaxrss = maxrss;
1082 task_io_accounting_add(&psig->ioac, &p->ioac);
1083 task_io_accounting_add(&psig->ioac, &sig->ioac);
1084 write_sequnlock(&psig->stats_lock);
1085 spin_unlock_irq(¤t->sighand->siglock);
1086 }
1087
1088 if (wo->wo_rusage)
1089 getrusage(p, RUSAGE_BOTH, wo->wo_rusage);
1090 status = (p->signal->flags & SIGNAL_GROUP_EXIT)
1091 ? p->signal->group_exit_code : p->exit_code;
1092 wo->wo_stat = status;
1093
1094 if (state == EXIT_TRACE) {
1095 write_lock_irq(&tasklist_lock);
1096 /* We dropped tasklist, ptracer could die and untrace */
1097 ptrace_unlink(p);
1098
1099 /* If parent wants a zombie, don't release it now */
1100 state = EXIT_ZOMBIE;
1101 if (do_notify_parent(p, p->exit_signal))
1102 state = EXIT_DEAD;
1103 p->exit_state = state;
1104 write_unlock_irq(&tasklist_lock);
1105 }
1106 if (state == EXIT_DEAD)
1107 release_task(p);
1108
1109out_info:
1110 infop = wo->wo_info;
1111 if (infop) {
1112 if ((status & 0x7f) == 0) {
1113 infop->cause = CLD_EXITED;
1114 infop->status = status >> 8;
1115 } else {
1116 infop->cause = (status & 0x80) ? CLD_DUMPED : CLD_KILLED;
1117 infop->status = status & 0x7f;
1118 }
1119 infop->pid = pid;
1120 infop->uid = uid;
1121 }
1122
1123 return pid;
1124}
1125
1126static int *task_stopped_code(struct task_struct *p, bool ptrace)
1127{
1128 if (ptrace) {
1129 if (task_is_traced(p) && !(p->jobctl & JOBCTL_LISTENING))
1130 return &p->exit_code;
1131 } else {
1132 if (p->signal->flags & SIGNAL_STOP_STOPPED)
1133 return &p->signal->group_exit_code;
1134 }
1135 return NULL;
1136}
1137
1138/**
1139 * wait_task_stopped - Wait for %TASK_STOPPED or %TASK_TRACED
1140 * @wo: wait options
1141 * @ptrace: is the wait for ptrace
1142 * @p: task to wait for
1143 *
1144 * Handle sys_wait4() work for %p in state %TASK_STOPPED or %TASK_TRACED.
1145 *
1146 * CONTEXT:
1147 * read_lock(&tasklist_lock), which is released if return value is
1148 * non-zero. Also, grabs and releases @p->sighand->siglock.
1149 *
1150 * RETURNS:
1151 * 0 if wait condition didn't exist and search for other wait conditions
1152 * should continue. Non-zero return, -errno on failure and @p's pid on
1153 * success, implies that tasklist_lock is released and wait condition
1154 * search should terminate.
1155 */
1156static int wait_task_stopped(struct wait_opts *wo,
1157 int ptrace, struct task_struct *p)
1158{
1159 struct waitid_info *infop;
1160 int exit_code, *p_code, why;
1161 uid_t uid = 0; /* unneeded, required by compiler */
1162 pid_t pid;
1163
1164 /*
1165 * Traditionally we see ptrace'd stopped tasks regardless of options.
1166 */
1167 if (!ptrace && !(wo->wo_flags & WUNTRACED))
1168 return 0;
1169
1170 if (!task_stopped_code(p, ptrace))
1171 return 0;
1172
1173 exit_code = 0;
1174 spin_lock_irq(&p->sighand->siglock);
1175
1176 p_code = task_stopped_code(p, ptrace);
1177 if (unlikely(!p_code))
1178 goto unlock_sig;
1179
1180 exit_code = *p_code;
1181 if (!exit_code)
1182 goto unlock_sig;
1183
1184 if (!unlikely(wo->wo_flags & WNOWAIT))
1185 *p_code = 0;
1186
1187 uid = from_kuid_munged(current_user_ns(), task_uid(p));
1188unlock_sig:
1189 spin_unlock_irq(&p->sighand->siglock);
1190 if (!exit_code)
1191 return 0;
1192
1193 /*
1194 * Now we are pretty sure this task is interesting.
1195 * Make sure it doesn't get reaped out from under us while we
1196 * give up the lock and then examine it below. We don't want to
1197 * keep holding onto the tasklist_lock while we call getrusage and
1198 * possibly take page faults for user memory.
1199 */
1200 get_task_struct(p);
1201 pid = task_pid_vnr(p);
1202 why = ptrace ? CLD_TRAPPED : CLD_STOPPED;
1203 read_unlock(&tasklist_lock);
1204 sched_annotate_sleep();
1205 if (wo->wo_rusage)
1206 getrusage(p, RUSAGE_BOTH, wo->wo_rusage);
1207 put_task_struct(p);
1208
1209 if (likely(!(wo->wo_flags & WNOWAIT)))
1210 wo->wo_stat = (exit_code << 8) | 0x7f;
1211
1212 infop = wo->wo_info;
1213 if (infop) {
1214 infop->cause = why;
1215 infop->status = exit_code;
1216 infop->pid = pid;
1217 infop->uid = uid;
1218 }
1219 return pid;
1220}
1221
1222/*
1223 * Handle do_wait work for one task in a live, non-stopped state.
1224 * read_lock(&tasklist_lock) on entry. If we return zero, we still hold
1225 * the lock and this task is uninteresting. If we return nonzero, we have
1226 * released the lock and the system call should return.
1227 */
1228static int wait_task_continued(struct wait_opts *wo, struct task_struct *p)
1229{
1230 struct waitid_info *infop;
1231 pid_t pid;
1232 uid_t uid;
1233
1234 if (!unlikely(wo->wo_flags & WCONTINUED))
1235 return 0;
1236
1237 if (!(p->signal->flags & SIGNAL_STOP_CONTINUED))
1238 return 0;
1239
1240 spin_lock_irq(&p->sighand->siglock);
1241 /* Re-check with the lock held. */
1242 if (!(p->signal->flags & SIGNAL_STOP_CONTINUED)) {
1243 spin_unlock_irq(&p->sighand->siglock);
1244 return 0;
1245 }
1246 if (!unlikely(wo->wo_flags & WNOWAIT))
1247 p->signal->flags &= ~SIGNAL_STOP_CONTINUED;
1248 uid = from_kuid_munged(current_user_ns(), task_uid(p));
1249 spin_unlock_irq(&p->sighand->siglock);
1250
1251 pid = task_pid_vnr(p);
1252 get_task_struct(p);
1253 read_unlock(&tasklist_lock);
1254 sched_annotate_sleep();
1255 if (wo->wo_rusage)
1256 getrusage(p, RUSAGE_BOTH, wo->wo_rusage);
1257 put_task_struct(p);
1258
1259 infop = wo->wo_info;
1260 if (!infop) {
1261 wo->wo_stat = 0xffff;
1262 } else {
1263 infop->cause = CLD_CONTINUED;
1264 infop->pid = pid;
1265 infop->uid = uid;
1266 infop->status = SIGCONT;
1267 }
1268 return pid;
1269}
1270
1271/*
1272 * Consider @p for a wait by @parent.
1273 *
1274 * -ECHILD should be in ->notask_error before the first call.
1275 * Returns nonzero for a final return, when we have unlocked tasklist_lock.
1276 * Returns zero if the search for a child should continue;
1277 * then ->notask_error is 0 if @p is an eligible child,
1278 * or still -ECHILD.
1279 */
1280static int wait_consider_task(struct wait_opts *wo, int ptrace,
1281 struct task_struct *p)
1282{
1283 /*
1284 * We can race with wait_task_zombie() from another thread.
1285 * Ensure that EXIT_ZOMBIE -> EXIT_DEAD/EXIT_TRACE transition
1286 * can't confuse the checks below.
1287 */
1288 int exit_state = READ_ONCE(p->exit_state);
1289 int ret;
1290
1291 if (unlikely(exit_state == EXIT_DEAD))
1292 return 0;
1293
1294 ret = eligible_child(wo, ptrace, p);
1295 if (!ret)
1296 return ret;
1297
1298 if (unlikely(exit_state == EXIT_TRACE)) {
1299 /*
1300 * ptrace == 0 means we are the natural parent. In this case
1301 * we should clear notask_error, debugger will notify us.
1302 */
1303 if (likely(!ptrace))
1304 wo->notask_error = 0;
1305 return 0;
1306 }
1307
1308 if (likely(!ptrace) && unlikely(p->ptrace)) {
1309 /*
1310 * If it is traced by its real parent's group, just pretend
1311 * the caller is ptrace_do_wait() and reap this child if it
1312 * is zombie.
1313 *
1314 * This also hides group stop state from real parent; otherwise
1315 * a single stop can be reported twice as group and ptrace stop.
1316 * If a ptracer wants to distinguish these two events for its
1317 * own children it should create a separate process which takes
1318 * the role of real parent.
1319 */
1320 if (!ptrace_reparented(p))
1321 ptrace = 1;
1322 }
1323
1324 /* slay zombie? */
1325 if (exit_state == EXIT_ZOMBIE) {
1326 /* we don't reap group leaders with subthreads */
1327 if (!delay_group_leader(p)) {
1328 /*
1329 * A zombie ptracee is only visible to its ptracer.
1330 * Notification and reaping will be cascaded to the
1331 * real parent when the ptracer detaches.
1332 */
1333 if (unlikely(ptrace) || likely(!p->ptrace))
1334 return wait_task_zombie(wo, p);
1335 }
1336
1337 /*
1338 * Allow access to stopped/continued state via zombie by
1339 * falling through. Clearing of notask_error is complex.
1340 *
1341 * When !@ptrace:
1342 *
1343 * If WEXITED is set, notask_error should naturally be
1344 * cleared. If not, subset of WSTOPPED|WCONTINUED is set,
1345 * so, if there are live subthreads, there are events to
1346 * wait for. If all subthreads are dead, it's still safe
1347 * to clear - this function will be called again in finite
1348 * amount time once all the subthreads are released and
1349 * will then return without clearing.
1350 *
1351 * When @ptrace:
1352 *
1353 * Stopped state is per-task and thus can't change once the
1354 * target task dies. Only continued and exited can happen.
1355 * Clear notask_error if WCONTINUED | WEXITED.
1356 */
1357 if (likely(!ptrace) || (wo->wo_flags & (WCONTINUED | WEXITED)))
1358 wo->notask_error = 0;
1359 } else {
1360 /*
1361 * @p is alive and it's gonna stop, continue or exit, so
1362 * there always is something to wait for.
1363 */
1364 wo->notask_error = 0;
1365 }
1366
1367 /*
1368 * Wait for stopped. Depending on @ptrace, different stopped state
1369 * is used and the two don't interact with each other.
1370 */
1371 ret = wait_task_stopped(wo, ptrace, p);
1372 if (ret)
1373 return ret;
1374
1375 /*
1376 * Wait for continued. There's only one continued state and the
1377 * ptracer can consume it which can confuse the real parent. Don't
1378 * use WCONTINUED from ptracer. You don't need or want it.
1379 */
1380 return wait_task_continued(wo, p);
1381}
1382
1383/*
1384 * Do the work of do_wait() for one thread in the group, @tsk.
1385 *
1386 * -ECHILD should be in ->notask_error before the first call.
1387 * Returns nonzero for a final return, when we have unlocked tasklist_lock.
1388 * Returns zero if the search for a child should continue; then
1389 * ->notask_error is 0 if there were any eligible children,
1390 * or still -ECHILD.
1391 */
1392static int do_wait_thread(struct wait_opts *wo, struct task_struct *tsk)
1393{
1394 struct task_struct *p;
1395
1396 list_for_each_entry(p, &tsk->children, sibling) {
1397 int ret = wait_consider_task(wo, 0, p);
1398
1399 if (ret)
1400 return ret;
1401 }
1402
1403 return 0;
1404}
1405
1406static int ptrace_do_wait(struct wait_opts *wo, struct task_struct *tsk)
1407{
1408 struct task_struct *p;
1409
1410 list_for_each_entry(p, &tsk->ptraced, ptrace_entry) {
1411 int ret = wait_consider_task(wo, 1, p);
1412
1413 if (ret)
1414 return ret;
1415 }
1416
1417 return 0;
1418}
1419
1420static int child_wait_callback(wait_queue_entry_t *wait, unsigned mode,
1421 int sync, void *key)
1422{
1423 struct wait_opts *wo = container_of(wait, struct wait_opts,
1424 child_wait);
1425 struct task_struct *p = key;
1426
1427 if (!eligible_pid(wo, p))
1428 return 0;
1429
1430 if ((wo->wo_flags & __WNOTHREAD) && wait->private != p->parent)
1431 return 0;
1432
1433 return default_wake_function(wait, mode, sync, key);
1434}
1435
1436void __wake_up_parent(struct task_struct *p, struct task_struct *parent)
1437{
1438 __wake_up_sync_key(&parent->signal->wait_chldexit,
1439 TASK_INTERRUPTIBLE, p);
1440}
1441
1442static bool is_effectively_child(struct wait_opts *wo, bool ptrace,
1443 struct task_struct *target)
1444{
1445 struct task_struct *parent =
1446 !ptrace ? target->real_parent : target->parent;
1447
1448 return current == parent || (!(wo->wo_flags & __WNOTHREAD) &&
1449 same_thread_group(current, parent));
1450}
1451
1452/*
1453 * Optimization for waiting on PIDTYPE_PID. No need to iterate through child
1454 * and tracee lists to find the target task.
1455 */
1456static int do_wait_pid(struct wait_opts *wo)
1457{
1458 bool ptrace;
1459 struct task_struct *target;
1460 int retval;
1461
1462 ptrace = false;
1463 target = pid_task(wo->wo_pid, PIDTYPE_TGID);
1464 if (target && is_effectively_child(wo, ptrace, target)) {
1465 retval = wait_consider_task(wo, ptrace, target);
1466 if (retval)
1467 return retval;
1468 }
1469
1470 ptrace = true;
1471 target = pid_task(wo->wo_pid, PIDTYPE_PID);
1472 if (target && target->ptrace &&
1473 is_effectively_child(wo, ptrace, target)) {
1474 retval = wait_consider_task(wo, ptrace, target);
1475 if (retval)
1476 return retval;
1477 }
1478
1479 return 0;
1480}
1481
1482static long do_wait(struct wait_opts *wo)
1483{
1484 int retval;
1485
1486 trace_sched_process_wait(wo->wo_pid);
1487
1488 init_waitqueue_func_entry(&wo->child_wait, child_wait_callback);
1489 wo->child_wait.private = current;
1490 add_wait_queue(¤t->signal->wait_chldexit, &wo->child_wait);
1491repeat:
1492 /*
1493 * If there is nothing that can match our criteria, just get out.
1494 * We will clear ->notask_error to zero if we see any child that
1495 * might later match our criteria, even if we are not able to reap
1496 * it yet.
1497 */
1498 wo->notask_error = -ECHILD;
1499 if ((wo->wo_type < PIDTYPE_MAX) &&
1500 (!wo->wo_pid || !pid_has_task(wo->wo_pid, wo->wo_type)))
1501 goto notask;
1502
1503 set_current_state(TASK_INTERRUPTIBLE);
1504 read_lock(&tasklist_lock);
1505
1506 if (wo->wo_type == PIDTYPE_PID) {
1507 retval = do_wait_pid(wo);
1508 if (retval)
1509 goto end;
1510 } else {
1511 struct task_struct *tsk = current;
1512
1513 do {
1514 retval = do_wait_thread(wo, tsk);
1515 if (retval)
1516 goto end;
1517
1518 retval = ptrace_do_wait(wo, tsk);
1519 if (retval)
1520 goto end;
1521
1522 if (wo->wo_flags & __WNOTHREAD)
1523 break;
1524 } while_each_thread(current, tsk);
1525 }
1526 read_unlock(&tasklist_lock);
1527
1528notask:
1529 retval = wo->notask_error;
1530 if (!retval && !(wo->wo_flags & WNOHANG)) {
1531 retval = -ERESTARTSYS;
1532 if (!signal_pending(current)) {
1533 schedule();
1534 goto repeat;
1535 }
1536 }
1537end:
1538 __set_current_state(TASK_RUNNING);
1539 remove_wait_queue(¤t->signal->wait_chldexit, &wo->child_wait);
1540 return retval;
1541}
1542
1543static long kernel_waitid(int which, pid_t upid, struct waitid_info *infop,
1544 int options, struct rusage *ru)
1545{
1546 struct wait_opts wo;
1547 struct pid *pid = NULL;
1548 enum pid_type type;
1549 long ret;
1550 unsigned int f_flags = 0;
1551
1552 if (options & ~(WNOHANG|WNOWAIT|WEXITED|WSTOPPED|WCONTINUED|
1553 __WNOTHREAD|__WCLONE|__WALL))
1554 return -EINVAL;
1555 if (!(options & (WEXITED|WSTOPPED|WCONTINUED)))
1556 return -EINVAL;
1557
1558 switch (which) {
1559 case P_ALL:
1560 type = PIDTYPE_MAX;
1561 break;
1562 case P_PID:
1563 type = PIDTYPE_PID;
1564 if (upid <= 0)
1565 return -EINVAL;
1566
1567 pid = find_get_pid(upid);
1568 break;
1569 case P_PGID:
1570 type = PIDTYPE_PGID;
1571 if (upid < 0)
1572 return -EINVAL;
1573
1574 if (upid)
1575 pid = find_get_pid(upid);
1576 else
1577 pid = get_task_pid(current, PIDTYPE_PGID);
1578 break;
1579 case P_PIDFD:
1580 type = PIDTYPE_PID;
1581 if (upid < 0)
1582 return -EINVAL;
1583
1584 pid = pidfd_get_pid(upid, &f_flags);
1585 if (IS_ERR(pid))
1586 return PTR_ERR(pid);
1587
1588 break;
1589 default:
1590 return -EINVAL;
1591 }
1592
1593 wo.wo_type = type;
1594 wo.wo_pid = pid;
1595 wo.wo_flags = options;
1596 wo.wo_info = infop;
1597 wo.wo_rusage = ru;
1598 if (f_flags & O_NONBLOCK)
1599 wo.wo_flags |= WNOHANG;
1600
1601 ret = do_wait(&wo);
1602 if (!ret && !(options & WNOHANG) && (f_flags & O_NONBLOCK))
1603 ret = -EAGAIN;
1604
1605 put_pid(pid);
1606 return ret;
1607}
1608
1609SYSCALL_DEFINE5(waitid, int, which, pid_t, upid, struct siginfo __user *,
1610 infop, int, options, struct rusage __user *, ru)
1611{
1612 struct rusage r;
1613 struct waitid_info info = {.status = 0};
1614 long err = kernel_waitid(which, upid, &info, options, ru ? &r : NULL);
1615 int signo = 0;
1616
1617 if (err > 0) {
1618 signo = SIGCHLD;
1619 err = 0;
1620 if (ru && copy_to_user(ru, &r, sizeof(struct rusage)))
1621 return -EFAULT;
1622 }
1623 if (!infop)
1624 return err;
1625
1626 if (!user_write_access_begin(infop, sizeof(*infop)))
1627 return -EFAULT;
1628
1629 unsafe_put_user(signo, &infop->si_signo, Efault);
1630 unsafe_put_user(0, &infop->si_errno, Efault);
1631 unsafe_put_user(info.cause, &infop->si_code, Efault);
1632 unsafe_put_user(info.pid, &infop->si_pid, Efault);
1633 unsafe_put_user(info.uid, &infop->si_uid, Efault);
1634 unsafe_put_user(info.status, &infop->si_status, Efault);
1635 user_write_access_end();
1636 return err;
1637Efault:
1638 user_write_access_end();
1639 return -EFAULT;
1640}
1641
1642long kernel_wait4(pid_t upid, int __user *stat_addr, int options,
1643 struct rusage *ru)
1644{
1645 struct wait_opts wo;
1646 struct pid *pid = NULL;
1647 enum pid_type type;
1648 long ret;
1649
1650 if (options & ~(WNOHANG|WUNTRACED|WCONTINUED|
1651 __WNOTHREAD|__WCLONE|__WALL))
1652 return -EINVAL;
1653
1654 /* -INT_MIN is not defined */
1655 if (upid == INT_MIN)
1656 return -ESRCH;
1657
1658 if (upid == -1)
1659 type = PIDTYPE_MAX;
1660 else if (upid < 0) {
1661 type = PIDTYPE_PGID;
1662 pid = find_get_pid(-upid);
1663 } else if (upid == 0) {
1664 type = PIDTYPE_PGID;
1665 pid = get_task_pid(current, PIDTYPE_PGID);
1666 } else /* upid > 0 */ {
1667 type = PIDTYPE_PID;
1668 pid = find_get_pid(upid);
1669 }
1670
1671 wo.wo_type = type;
1672 wo.wo_pid = pid;
1673 wo.wo_flags = options | WEXITED;
1674 wo.wo_info = NULL;
1675 wo.wo_stat = 0;
1676 wo.wo_rusage = ru;
1677 ret = do_wait(&wo);
1678 put_pid(pid);
1679 if (ret > 0 && stat_addr && put_user(wo.wo_stat, stat_addr))
1680 ret = -EFAULT;
1681
1682 return ret;
1683}
1684
1685int kernel_wait(pid_t pid, int *stat)
1686{
1687 struct wait_opts wo = {
1688 .wo_type = PIDTYPE_PID,
1689 .wo_pid = find_get_pid(pid),
1690 .wo_flags = WEXITED,
1691 };
1692 int ret;
1693
1694 ret = do_wait(&wo);
1695 if (ret > 0 && wo.wo_stat)
1696 *stat = wo.wo_stat;
1697 put_pid(wo.wo_pid);
1698 return ret;
1699}
1700
1701SYSCALL_DEFINE4(wait4, pid_t, upid, int __user *, stat_addr,
1702 int, options, struct rusage __user *, ru)
1703{
1704 struct rusage r;
1705 long err = kernel_wait4(upid, stat_addr, options, ru ? &r : NULL);
1706
1707 if (err > 0) {
1708 if (ru && copy_to_user(ru, &r, sizeof(struct rusage)))
1709 return -EFAULT;
1710 }
1711 return err;
1712}
1713
1714#ifdef __ARCH_WANT_SYS_WAITPID
1715
1716/*
1717 * sys_waitpid() remains for compatibility. waitpid() should be
1718 * implemented by calling sys_wait4() from libc.a.
1719 */
1720SYSCALL_DEFINE3(waitpid, pid_t, pid, int __user *, stat_addr, int, options)
1721{
1722 return kernel_wait4(pid, stat_addr, options, NULL);
1723}
1724
1725#endif
1726
1727#ifdef CONFIG_COMPAT
1728COMPAT_SYSCALL_DEFINE4(wait4,
1729 compat_pid_t, pid,
1730 compat_uint_t __user *, stat_addr,
1731 int, options,
1732 struct compat_rusage __user *, ru)
1733{
1734 struct rusage r;
1735 long err = kernel_wait4(pid, stat_addr, options, ru ? &r : NULL);
1736 if (err > 0) {
1737 if (ru && put_compat_rusage(&r, ru))
1738 return -EFAULT;
1739 }
1740 return err;
1741}
1742
1743COMPAT_SYSCALL_DEFINE5(waitid,
1744 int, which, compat_pid_t, pid,
1745 struct compat_siginfo __user *, infop, int, options,
1746 struct compat_rusage __user *, uru)
1747{
1748 struct rusage ru;
1749 struct waitid_info info = {.status = 0};
1750 long err = kernel_waitid(which, pid, &info, options, uru ? &ru : NULL);
1751 int signo = 0;
1752 if (err > 0) {
1753 signo = SIGCHLD;
1754 err = 0;
1755 if (uru) {
1756 /* kernel_waitid() overwrites everything in ru */
1757 if (COMPAT_USE_64BIT_TIME)
1758 err = copy_to_user(uru, &ru, sizeof(ru));
1759 else
1760 err = put_compat_rusage(&ru, uru);
1761 if (err)
1762 return -EFAULT;
1763 }
1764 }
1765
1766 if (!infop)
1767 return err;
1768
1769 if (!user_write_access_begin(infop, sizeof(*infop)))
1770 return -EFAULT;
1771
1772 unsafe_put_user(signo, &infop->si_signo, Efault);
1773 unsafe_put_user(0, &infop->si_errno, Efault);
1774 unsafe_put_user(info.cause, &infop->si_code, Efault);
1775 unsafe_put_user(info.pid, &infop->si_pid, Efault);
1776 unsafe_put_user(info.uid, &infop->si_uid, Efault);
1777 unsafe_put_user(info.status, &infop->si_status, Efault);
1778 user_write_access_end();
1779 return err;
1780Efault:
1781 user_write_access_end();
1782 return -EFAULT;
1783}
1784#endif
1785
1786/**
1787 * thread_group_exited - check that a thread group has exited
1788 * @pid: tgid of thread group to be checked.
1789 *
1790 * Test if the thread group represented by tgid has exited (all
1791 * threads are zombies, dead or completely gone).
1792 *
1793 * Return: true if the thread group has exited. false otherwise.
1794 */
1795bool thread_group_exited(struct pid *pid)
1796{
1797 struct task_struct *task;
1798 bool exited;
1799
1800 rcu_read_lock();
1801 task = pid_task(pid, PIDTYPE_PID);
1802 exited = !task ||
1803 (READ_ONCE(task->exit_state) && thread_group_empty(task));
1804 rcu_read_unlock();
1805
1806 return exited;
1807}
1808EXPORT_SYMBOL(thread_group_exited);
1809
1810__weak void abort(void)
1811{
1812 BUG();
1813
1814 /* if that doesn't kill us, halt */
1815 panic("Oops failed to kill thread");
1816}
1817EXPORT_SYMBOL(abort);