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/task_io_accounting_ops.h>
52 #include <linux/blkdev.h>
53 #include <linux/task_work.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/kmsan.h>
64 #include <linux/random.h>
65 #include <linux/rcuwait.h>
66 #include <linux/compat.h>
67 #include <linux/io_uring.h>
68 #include <linux/kprobes.h>
69 #include <linux/rethook.h>
70 #include <linux/sysfs.h>
71 #include <linux/user_events.h>
72
73 #include <linux/uaccess.h>
74 #include <asm/unistd.h>
75 #include <asm/mmu_context.h>
76
77 /*
78 * The default value should be high enough to not crash a system that randomly
79 * crashes its kernel from time to time, but low enough to at least not permit
80 * overflowing 32-bit refcounts or the ldsem writer count.
81 */
82 static unsigned int oops_limit = 10000;
83
84 #ifdef CONFIG_SYSCTL
85 static struct ctl_table kern_exit_table[] = {
86 {
87 .procname = "oops_limit",
88 .data = &oops_limit,
89 .maxlen = sizeof(oops_limit),
90 .mode = 0644,
91 .proc_handler = proc_douintvec,
92 },
93 { }
94 };
95
kernel_exit_sysctls_init(void)96 static __init int kernel_exit_sysctls_init(void)
97 {
98 register_sysctl_init("kernel", kern_exit_table);
99 return 0;
100 }
101 late_initcall(kernel_exit_sysctls_init);
102 #endif
103
104 static atomic_t oops_count = ATOMIC_INIT(0);
105
106 #ifdef CONFIG_SYSFS
oops_count_show(struct kobject * kobj,struct kobj_attribute * attr,char * page)107 static ssize_t oops_count_show(struct kobject *kobj, struct kobj_attribute *attr,
108 char *page)
109 {
110 return sysfs_emit(page, "%d\n", atomic_read(&oops_count));
111 }
112
113 static struct kobj_attribute oops_count_attr = __ATTR_RO(oops_count);
114
kernel_exit_sysfs_init(void)115 static __init int kernel_exit_sysfs_init(void)
116 {
117 sysfs_add_file_to_group(kernel_kobj, &oops_count_attr.attr, NULL);
118 return 0;
119 }
120 late_initcall(kernel_exit_sysfs_init);
121 #endif
122
__unhash_process(struct task_struct * p,bool group_dead)123 static void __unhash_process(struct task_struct *p, bool group_dead)
124 {
125 nr_threads--;
126 detach_pid(p, PIDTYPE_PID);
127 if (group_dead) {
128 detach_pid(p, PIDTYPE_TGID);
129 detach_pid(p, PIDTYPE_PGID);
130 detach_pid(p, PIDTYPE_SID);
131
132 list_del_rcu(&p->tasks);
133 list_del_init(&p->sibling);
134 __this_cpu_dec(process_counts);
135 }
136 list_del_rcu(&p->thread_group);
137 list_del_rcu(&p->thread_node);
138 }
139
140 /*
141 * This function expects the tasklist_lock write-locked.
142 */
__exit_signal(struct task_struct * tsk)143 static void __exit_signal(struct task_struct *tsk)
144 {
145 struct signal_struct *sig = tsk->signal;
146 bool group_dead = thread_group_leader(tsk);
147 struct sighand_struct *sighand;
148 struct tty_struct *tty;
149 u64 utime, stime;
150
151 sighand = rcu_dereference_check(tsk->sighand,
152 lockdep_tasklist_lock_is_held());
153 spin_lock(&sighand->siglock);
154
155 #ifdef CONFIG_POSIX_TIMERS
156 posix_cpu_timers_exit(tsk);
157 if (group_dead)
158 posix_cpu_timers_exit_group(tsk);
159 #endif
160
161 if (group_dead) {
162 tty = sig->tty;
163 sig->tty = NULL;
164 } else {
165 /*
166 * If there is any task waiting for the group exit
167 * then notify it:
168 */
169 if (sig->notify_count > 0 && !--sig->notify_count)
170 wake_up_process(sig->group_exec_task);
171
172 if (tsk == sig->curr_target)
173 sig->curr_target = next_thread(tsk);
174 }
175
176 add_device_randomness((const void*) &tsk->se.sum_exec_runtime,
177 sizeof(unsigned long long));
178
179 /*
180 * Accumulate here the counters for all threads as they die. We could
181 * skip the group leader because it is the last user of signal_struct,
182 * but we want to avoid the race with thread_group_cputime() which can
183 * see the empty ->thread_head list.
184 */
185 task_cputime(tsk, &utime, &stime);
186 write_seqlock(&sig->stats_lock);
187 sig->utime += utime;
188 sig->stime += stime;
189 sig->gtime += task_gtime(tsk);
190 sig->min_flt += tsk->min_flt;
191 sig->maj_flt += tsk->maj_flt;
192 sig->nvcsw += tsk->nvcsw;
193 sig->nivcsw += tsk->nivcsw;
194 sig->inblock += task_io_get_inblock(tsk);
195 sig->oublock += task_io_get_oublock(tsk);
196 task_io_accounting_add(&sig->ioac, &tsk->ioac);
197 sig->sum_sched_runtime += tsk->se.sum_exec_runtime;
198 sig->nr_threads--;
199 __unhash_process(tsk, group_dead);
200 write_sequnlock(&sig->stats_lock);
201
202 /*
203 * Do this under ->siglock, we can race with another thread
204 * doing sigqueue_free() if we have SIGQUEUE_PREALLOC signals.
205 */
206 flush_sigqueue(&tsk->pending);
207 tsk->sighand = NULL;
208 spin_unlock(&sighand->siglock);
209
210 __cleanup_sighand(sighand);
211 clear_tsk_thread_flag(tsk, TIF_SIGPENDING);
212 if (group_dead) {
213 flush_sigqueue(&sig->shared_pending);
214 tty_kref_put(tty);
215 }
216 }
217
delayed_put_task_struct(struct rcu_head * rhp)218 static void delayed_put_task_struct(struct rcu_head *rhp)
219 {
220 struct task_struct *tsk = container_of(rhp, struct task_struct, rcu);
221
222 kprobe_flush_task(tsk);
223 rethook_flush_task(tsk);
224 perf_event_delayed_put(tsk);
225 trace_sched_process_free(tsk);
226 put_task_struct(tsk);
227 }
228
put_task_struct_rcu_user(struct task_struct * task)229 void put_task_struct_rcu_user(struct task_struct *task)
230 {
231 if (refcount_dec_and_test(&task->rcu_users))
232 call_rcu(&task->rcu, delayed_put_task_struct);
233 }
234
release_thread(struct task_struct * dead_task)235 void __weak release_thread(struct task_struct *dead_task)
236 {
237 }
238
release_task(struct task_struct * p)239 void release_task(struct task_struct *p)
240 {
241 struct task_struct *leader;
242 struct pid *thread_pid;
243 int zap_leader;
244 repeat:
245 /* don't need to get the RCU readlock here - the process is dead and
246 * can't be modifying its own credentials. But shut RCU-lockdep up */
247 rcu_read_lock();
248 dec_rlimit_ucounts(task_ucounts(p), UCOUNT_RLIMIT_NPROC, 1);
249 rcu_read_unlock();
250
251 cgroup_release(p);
252
253 write_lock_irq(&tasklist_lock);
254 ptrace_release_task(p);
255 thread_pid = get_pid(p->thread_pid);
256 __exit_signal(p);
257
258 /*
259 * If we are the last non-leader member of the thread
260 * group, and the leader is zombie, then notify the
261 * group leader's parent process. (if it wants notification.)
262 */
263 zap_leader = 0;
264 leader = p->group_leader;
265 if (leader != p && thread_group_empty(leader)
266 && leader->exit_state == EXIT_ZOMBIE) {
267 /*
268 * If we were the last child thread and the leader has
269 * exited already, and the leader's parent ignores SIGCHLD,
270 * then we are the one who should release the leader.
271 */
272 zap_leader = do_notify_parent(leader, leader->exit_signal);
273 if (zap_leader)
274 leader->exit_state = EXIT_DEAD;
275 }
276
277 write_unlock_irq(&tasklist_lock);
278 seccomp_filter_release(p);
279 proc_flush_pid(thread_pid);
280 put_pid(thread_pid);
281 release_thread(p);
282 put_task_struct_rcu_user(p);
283
284 p = leader;
285 if (unlikely(zap_leader))
286 goto repeat;
287 }
288
rcuwait_wake_up(struct rcuwait * w)289 int rcuwait_wake_up(struct rcuwait *w)
290 {
291 int ret = 0;
292 struct task_struct *task;
293
294 rcu_read_lock();
295
296 /*
297 * Order condition vs @task, such that everything prior to the load
298 * of @task is visible. This is the condition as to why the user called
299 * rcuwait_wake() in the first place. Pairs with set_current_state()
300 * barrier (A) in rcuwait_wait_event().
301 *
302 * WAIT WAKE
303 * [S] tsk = current [S] cond = true
304 * MB (A) MB (B)
305 * [L] cond [L] tsk
306 */
307 smp_mb(); /* (B) */
308
309 task = rcu_dereference(w->task);
310 if (task)
311 ret = wake_up_process(task);
312 rcu_read_unlock();
313
314 return ret;
315 }
316 EXPORT_SYMBOL_GPL(rcuwait_wake_up);
317
318 /*
319 * Determine if a process group is "orphaned", according to the POSIX
320 * definition in 2.2.2.52. Orphaned process groups are not to be affected
321 * by terminal-generated stop signals. Newly orphaned process groups are
322 * to receive a SIGHUP and a SIGCONT.
323 *
324 * "I ask you, have you ever known what it is to be an orphan?"
325 */
will_become_orphaned_pgrp(struct pid * pgrp,struct task_struct * ignored_task)326 static int will_become_orphaned_pgrp(struct pid *pgrp,
327 struct task_struct *ignored_task)
328 {
329 struct task_struct *p;
330
331 do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
332 if ((p == ignored_task) ||
333 (p->exit_state && thread_group_empty(p)) ||
334 is_global_init(p->real_parent))
335 continue;
336
337 if (task_pgrp(p->real_parent) != pgrp &&
338 task_session(p->real_parent) == task_session(p))
339 return 0;
340 } while_each_pid_task(pgrp, PIDTYPE_PGID, p);
341
342 return 1;
343 }
344
is_current_pgrp_orphaned(void)345 int is_current_pgrp_orphaned(void)
346 {
347 int retval;
348
349 read_lock(&tasklist_lock);
350 retval = will_become_orphaned_pgrp(task_pgrp(current), NULL);
351 read_unlock(&tasklist_lock);
352
353 return retval;
354 }
355
has_stopped_jobs(struct pid * pgrp)356 static bool has_stopped_jobs(struct pid *pgrp)
357 {
358 struct task_struct *p;
359
360 do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
361 if (p->signal->flags & SIGNAL_STOP_STOPPED)
362 return true;
363 } while_each_pid_task(pgrp, PIDTYPE_PGID, p);
364
365 return false;
366 }
367
368 /*
369 * Check to see if any process groups have become orphaned as
370 * a result of our exiting, and if they have any stopped jobs,
371 * send them a SIGHUP and then a SIGCONT. (POSIX 3.2.2.2)
372 */
373 static void
kill_orphaned_pgrp(struct task_struct * tsk,struct task_struct * parent)374 kill_orphaned_pgrp(struct task_struct *tsk, struct task_struct *parent)
375 {
376 struct pid *pgrp = task_pgrp(tsk);
377 struct task_struct *ignored_task = tsk;
378
379 if (!parent)
380 /* exit: our father is in a different pgrp than
381 * we are and we were the only connection outside.
382 */
383 parent = tsk->real_parent;
384 else
385 /* reparent: our child is in a different pgrp than
386 * we are, and it was the only connection outside.
387 */
388 ignored_task = NULL;
389
390 if (task_pgrp(parent) != pgrp &&
391 task_session(parent) == task_session(tsk) &&
392 will_become_orphaned_pgrp(pgrp, ignored_task) &&
393 has_stopped_jobs(pgrp)) {
394 __kill_pgrp_info(SIGHUP, SEND_SIG_PRIV, pgrp);
395 __kill_pgrp_info(SIGCONT, SEND_SIG_PRIV, pgrp);
396 }
397 }
398
coredump_task_exit(struct task_struct * tsk)399 static void coredump_task_exit(struct task_struct *tsk)
400 {
401 struct core_state *core_state;
402
403 /*
404 * Serialize with any possible pending coredump.
405 * We must hold siglock around checking core_state
406 * and setting PF_POSTCOREDUMP. The core-inducing thread
407 * will increment ->nr_threads for each thread in the
408 * group without PF_POSTCOREDUMP set.
409 */
410 spin_lock_irq(&tsk->sighand->siglock);
411 tsk->flags |= PF_POSTCOREDUMP;
412 core_state = tsk->signal->core_state;
413 spin_unlock_irq(&tsk->sighand->siglock);
414
415 /* The vhost_worker does not particpate in coredumps */
416 if (core_state &&
417 ((tsk->flags & (PF_IO_WORKER | PF_USER_WORKER)) != PF_USER_WORKER)) {
418 struct core_thread self;
419
420 self.task = current;
421 if (self.task->flags & PF_SIGNALED)
422 self.next = xchg(&core_state->dumper.next, &self);
423 else
424 self.task = NULL;
425 /*
426 * Implies mb(), the result of xchg() must be visible
427 * to core_state->dumper.
428 */
429 if (atomic_dec_and_test(&core_state->nr_threads))
430 complete(&core_state->startup);
431
432 for (;;) {
433 set_current_state(TASK_UNINTERRUPTIBLE|TASK_FREEZABLE);
434 if (!self.task) /* see coredump_finish() */
435 break;
436 schedule();
437 }
438 __set_current_state(TASK_RUNNING);
439 }
440 }
441
442 #ifdef CONFIG_MEMCG
443 /*
444 * A task is exiting. If it owned this mm, find a new owner for the mm.
445 */
mm_update_next_owner(struct mm_struct * mm)446 void mm_update_next_owner(struct mm_struct *mm)
447 {
448 struct task_struct *c, *g, *p = current;
449
450 retry:
451 /*
452 * If the exiting or execing task is not the owner, it's
453 * someone else's problem.
454 */
455 if (mm->owner != p)
456 return;
457 /*
458 * The current owner is exiting/execing and there are no other
459 * candidates. Do not leave the mm pointing to a possibly
460 * freed task structure.
461 */
462 if (atomic_read(&mm->mm_users) <= 1) {
463 WRITE_ONCE(mm->owner, NULL);
464 return;
465 }
466
467 read_lock(&tasklist_lock);
468 /*
469 * Search in the children
470 */
471 list_for_each_entry(c, &p->children, sibling) {
472 if (c->mm == mm)
473 goto assign_new_owner;
474 }
475
476 /*
477 * Search in the siblings
478 */
479 list_for_each_entry(c, &p->real_parent->children, sibling) {
480 if (c->mm == mm)
481 goto assign_new_owner;
482 }
483
484 /*
485 * Search through everything else, we should not get here often.
486 */
487 for_each_process(g) {
488 if (g->flags & PF_KTHREAD)
489 continue;
490 for_each_thread(g, c) {
491 if (c->mm == mm)
492 goto assign_new_owner;
493 if (c->mm)
494 break;
495 }
496 }
497 read_unlock(&tasklist_lock);
498 /*
499 * We found no owner yet mm_users > 1: this implies that we are
500 * most likely racing with swapoff (try_to_unuse()) or /proc or
501 * ptrace or page migration (get_task_mm()). Mark owner as NULL.
502 */
503 WRITE_ONCE(mm->owner, NULL);
504 return;
505
506 assign_new_owner:
507 BUG_ON(c == p);
508 get_task_struct(c);
509 /*
510 * The task_lock protects c->mm from changing.
511 * We always want mm->owner->mm == mm
512 */
513 task_lock(c);
514 /*
515 * Delay read_unlock() till we have the task_lock()
516 * to ensure that c does not slip away underneath us
517 */
518 read_unlock(&tasklist_lock);
519 if (c->mm != mm) {
520 task_unlock(c);
521 put_task_struct(c);
522 goto retry;
523 }
524 WRITE_ONCE(mm->owner, c);
525 lru_gen_migrate_mm(mm);
526 task_unlock(c);
527 put_task_struct(c);
528 }
529 #endif /* CONFIG_MEMCG */
530
531 /*
532 * Turn us into a lazy TLB process if we
533 * aren't already..
534 */
exit_mm(void)535 static void exit_mm(void)
536 {
537 struct mm_struct *mm = current->mm;
538
539 exit_mm_release(current, mm);
540 if (!mm)
541 return;
542 sync_mm_rss(mm);
543 mmap_read_lock(mm);
544 mmgrab_lazy_tlb(mm);
545 BUG_ON(mm != current->active_mm);
546 /* more a memory barrier than a real lock */
547 task_lock(current);
548 /*
549 * When a thread stops operating on an address space, the loop
550 * in membarrier_private_expedited() may not observe that
551 * tsk->mm, and the loop in membarrier_global_expedited() may
552 * not observe a MEMBARRIER_STATE_GLOBAL_EXPEDITED
553 * rq->membarrier_state, so those would not issue an IPI.
554 * Membarrier requires a memory barrier after accessing
555 * user-space memory, before clearing tsk->mm or the
556 * rq->membarrier_state.
557 */
558 smp_mb__after_spinlock();
559 local_irq_disable();
560 current->mm = NULL;
561 membarrier_update_current_mm(NULL);
562 enter_lazy_tlb(mm, current);
563 local_irq_enable();
564 task_unlock(current);
565 mmap_read_unlock(mm);
566 mm_update_next_owner(mm);
567 mmput(mm);
568 if (test_thread_flag(TIF_MEMDIE))
569 exit_oom_victim();
570 }
571
find_alive_thread(struct task_struct * p)572 static struct task_struct *find_alive_thread(struct task_struct *p)
573 {
574 struct task_struct *t;
575
576 for_each_thread(p, t) {
577 if (!(t->flags & PF_EXITING))
578 return t;
579 }
580 return NULL;
581 }
582
find_child_reaper(struct task_struct * father,struct list_head * dead)583 static struct task_struct *find_child_reaper(struct task_struct *father,
584 struct list_head *dead)
585 __releases(&tasklist_lock)
586 __acquires(&tasklist_lock)
587 {
588 struct pid_namespace *pid_ns = task_active_pid_ns(father);
589 struct task_struct *reaper = pid_ns->child_reaper;
590 struct task_struct *p, *n;
591
592 if (likely(reaper != father))
593 return reaper;
594
595 reaper = find_alive_thread(father);
596 if (reaper) {
597 pid_ns->child_reaper = reaper;
598 return reaper;
599 }
600
601 write_unlock_irq(&tasklist_lock);
602
603 list_for_each_entry_safe(p, n, dead, ptrace_entry) {
604 list_del_init(&p->ptrace_entry);
605 release_task(p);
606 }
607
608 zap_pid_ns_processes(pid_ns);
609 write_lock_irq(&tasklist_lock);
610
611 return father;
612 }
613
614 /*
615 * When we die, we re-parent all our children, and try to:
616 * 1. give them to another thread in our thread group, if such a member exists
617 * 2. give it to the first ancestor process which prctl'd itself as a
618 * child_subreaper for its children (like a service manager)
619 * 3. give it to the init process (PID 1) in our pid namespace
620 */
find_new_reaper(struct task_struct * father,struct task_struct * child_reaper)621 static struct task_struct *find_new_reaper(struct task_struct *father,
622 struct task_struct *child_reaper)
623 {
624 struct task_struct *thread, *reaper;
625
626 thread = find_alive_thread(father);
627 if (thread)
628 return thread;
629
630 if (father->signal->has_child_subreaper) {
631 unsigned int ns_level = task_pid(father)->level;
632 /*
633 * Find the first ->is_child_subreaper ancestor in our pid_ns.
634 * We can't check reaper != child_reaper to ensure we do not
635 * cross the namespaces, the exiting parent could be injected
636 * by setns() + fork().
637 * We check pid->level, this is slightly more efficient than
638 * task_active_pid_ns(reaper) != task_active_pid_ns(father).
639 */
640 for (reaper = father->real_parent;
641 task_pid(reaper)->level == ns_level;
642 reaper = reaper->real_parent) {
643 if (reaper == &init_task)
644 break;
645 if (!reaper->signal->is_child_subreaper)
646 continue;
647 thread = find_alive_thread(reaper);
648 if (thread)
649 return thread;
650 }
651 }
652
653 return child_reaper;
654 }
655
656 /*
657 * Any that need to be release_task'd are put on the @dead list.
658 */
reparent_leader(struct task_struct * father,struct task_struct * p,struct list_head * dead)659 static void reparent_leader(struct task_struct *father, struct task_struct *p,
660 struct list_head *dead)
661 {
662 if (unlikely(p->exit_state == EXIT_DEAD))
663 return;
664
665 /* We don't want people slaying init. */
666 p->exit_signal = SIGCHLD;
667
668 /* If it has exited notify the new parent about this child's death. */
669 if (!p->ptrace &&
670 p->exit_state == EXIT_ZOMBIE && thread_group_empty(p)) {
671 if (do_notify_parent(p, p->exit_signal)) {
672 p->exit_state = EXIT_DEAD;
673 list_add(&p->ptrace_entry, dead);
674 }
675 }
676
677 kill_orphaned_pgrp(p, father);
678 }
679
680 /*
681 * This does two things:
682 *
683 * A. Make init inherit all the child processes
684 * B. Check to see if any process groups have become orphaned
685 * as a result of our exiting, and if they have any stopped
686 * jobs, send them a SIGHUP and then a SIGCONT. (POSIX 3.2.2.2)
687 */
forget_original_parent(struct task_struct * father,struct list_head * dead)688 static void forget_original_parent(struct task_struct *father,
689 struct list_head *dead)
690 {
691 struct task_struct *p, *t, *reaper;
692
693 if (unlikely(!list_empty(&father->ptraced)))
694 exit_ptrace(father, dead);
695
696 /* Can drop and reacquire tasklist_lock */
697 reaper = find_child_reaper(father, dead);
698 if (list_empty(&father->children))
699 return;
700
701 reaper = find_new_reaper(father, reaper);
702 list_for_each_entry(p, &father->children, sibling) {
703 for_each_thread(p, t) {
704 RCU_INIT_POINTER(t->real_parent, reaper);
705 BUG_ON((!t->ptrace) != (rcu_access_pointer(t->parent) == father));
706 if (likely(!t->ptrace))
707 t->parent = t->real_parent;
708 if (t->pdeath_signal)
709 group_send_sig_info(t->pdeath_signal,
710 SEND_SIG_NOINFO, t,
711 PIDTYPE_TGID);
712 }
713 /*
714 * If this is a threaded reparent there is no need to
715 * notify anyone anything has happened.
716 */
717 if (!same_thread_group(reaper, father))
718 reparent_leader(father, p, dead);
719 }
720 list_splice_tail_init(&father->children, &reaper->children);
721 }
722
723 /*
724 * Send signals to all our closest relatives so that they know
725 * to properly mourn us..
726 */
exit_notify(struct task_struct * tsk,int group_dead)727 static void exit_notify(struct task_struct *tsk, int group_dead)
728 {
729 bool autoreap;
730 struct task_struct *p, *n;
731 LIST_HEAD(dead);
732
733 write_lock_irq(&tasklist_lock);
734 forget_original_parent(tsk, &dead);
735
736 if (group_dead)
737 kill_orphaned_pgrp(tsk->group_leader, NULL);
738
739 tsk->exit_state = EXIT_ZOMBIE;
740 if (unlikely(tsk->ptrace)) {
741 int sig = thread_group_leader(tsk) &&
742 thread_group_empty(tsk) &&
743 !ptrace_reparented(tsk) ?
744 tsk->exit_signal : SIGCHLD;
745 autoreap = do_notify_parent(tsk, sig);
746 } else if (thread_group_leader(tsk)) {
747 autoreap = thread_group_empty(tsk) &&
748 do_notify_parent(tsk, tsk->exit_signal);
749 } else {
750 autoreap = true;
751 }
752
753 if (autoreap) {
754 tsk->exit_state = EXIT_DEAD;
755 list_add(&tsk->ptrace_entry, &dead);
756 }
757
758 /* mt-exec, de_thread() is waiting for group leader */
759 if (unlikely(tsk->signal->notify_count < 0))
760 wake_up_process(tsk->signal->group_exec_task);
761 write_unlock_irq(&tasklist_lock);
762
763 list_for_each_entry_safe(p, n, &dead, ptrace_entry) {
764 list_del_init(&p->ptrace_entry);
765 release_task(p);
766 }
767 }
768
769 #ifdef CONFIG_DEBUG_STACK_USAGE
check_stack_usage(void)770 static void check_stack_usage(void)
771 {
772 static DEFINE_SPINLOCK(low_water_lock);
773 static int lowest_to_date = THREAD_SIZE;
774 unsigned long free;
775
776 free = stack_not_used(current);
777
778 if (free >= lowest_to_date)
779 return;
780
781 spin_lock(&low_water_lock);
782 if (free < lowest_to_date) {
783 pr_info("%s (%d) used greatest stack depth: %lu bytes left\n",
784 current->comm, task_pid_nr(current), free);
785 lowest_to_date = free;
786 }
787 spin_unlock(&low_water_lock);
788 }
789 #else
check_stack_usage(void)790 static inline void check_stack_usage(void) {}
791 #endif
792
synchronize_group_exit(struct task_struct * tsk,long code)793 static void synchronize_group_exit(struct task_struct *tsk, long code)
794 {
795 struct sighand_struct *sighand = tsk->sighand;
796 struct signal_struct *signal = tsk->signal;
797
798 spin_lock_irq(&sighand->siglock);
799 signal->quick_threads--;
800 if ((signal->quick_threads == 0) &&
801 !(signal->flags & SIGNAL_GROUP_EXIT)) {
802 signal->flags = SIGNAL_GROUP_EXIT;
803 signal->group_exit_code = code;
804 signal->group_stop_count = 0;
805 }
806 spin_unlock_irq(&sighand->siglock);
807 }
808
do_exit(long code)809 void __noreturn do_exit(long code)
810 {
811 struct task_struct *tsk = current;
812 int group_dead;
813
814 WARN_ON(irqs_disabled());
815
816 synchronize_group_exit(tsk, code);
817
818 WARN_ON(tsk->plug);
819
820 kcov_task_exit(tsk);
821 kmsan_task_exit(tsk);
822
823 coredump_task_exit(tsk);
824 ptrace_event(PTRACE_EVENT_EXIT, code);
825 user_events_exit(tsk);
826
827 io_uring_files_cancel();
828 exit_signals(tsk); /* sets PF_EXITING */
829
830 /* sync mm's RSS info before statistics gathering */
831 if (tsk->mm)
832 sync_mm_rss(tsk->mm);
833 acct_update_integrals(tsk);
834 group_dead = atomic_dec_and_test(&tsk->signal->live);
835 if (group_dead) {
836 /*
837 * If the last thread of global init has exited, panic
838 * immediately to get a useable coredump.
839 */
840 if (unlikely(is_global_init(tsk)))
841 panic("Attempted to kill init! exitcode=0x%08x\n",
842 tsk->signal->group_exit_code ?: (int)code);
843
844 #ifdef CONFIG_POSIX_TIMERS
845 hrtimer_cancel(&tsk->signal->real_timer);
846 exit_itimers(tsk);
847 #endif
848 if (tsk->mm)
849 setmax_mm_hiwater_rss(&tsk->signal->maxrss, tsk->mm);
850 }
851 acct_collect(code, group_dead);
852 if (group_dead)
853 tty_audit_exit();
854 audit_free(tsk);
855
856 tsk->exit_code = code;
857 taskstats_exit(tsk, group_dead);
858
859 exit_mm();
860
861 if (group_dead)
862 acct_process();
863 trace_sched_process_exit(tsk);
864
865 exit_sem(tsk);
866 exit_shm(tsk);
867 exit_files(tsk);
868 exit_fs(tsk);
869 if (group_dead)
870 disassociate_ctty(1);
871 exit_task_namespaces(tsk);
872 exit_task_work(tsk);
873 exit_thread(tsk);
874
875 /*
876 * Flush inherited counters to the parent - before the parent
877 * gets woken up by child-exit notifications.
878 *
879 * because of cgroup mode, must be called before cgroup_exit()
880 */
881 perf_event_exit_task(tsk);
882
883 sched_autogroup_exit_task(tsk);
884 cgroup_exit(tsk);
885
886 /*
887 * FIXME: do that only when needed, using sched_exit tracepoint
888 */
889 flush_ptrace_hw_breakpoint(tsk);
890
891 exit_tasks_rcu_start();
892 exit_notify(tsk, group_dead);
893 proc_exit_connector(tsk);
894 mpol_put_task_policy(tsk);
895 #ifdef CONFIG_FUTEX
896 if (unlikely(current->pi_state_cache))
897 kfree(current->pi_state_cache);
898 #endif
899 /*
900 * Make sure we are holding no locks:
901 */
902 debug_check_no_locks_held();
903
904 if (tsk->io_context)
905 exit_io_context(tsk);
906
907 if (tsk->splice_pipe)
908 free_pipe_info(tsk->splice_pipe);
909
910 if (tsk->task_frag.page)
911 put_page(tsk->task_frag.page);
912
913 exit_task_stack_account(tsk);
914
915 check_stack_usage();
916 preempt_disable();
917 if (tsk->nr_dirtied)
918 __this_cpu_add(dirty_throttle_leaks, tsk->nr_dirtied);
919 exit_rcu();
920 exit_tasks_rcu_finish();
921
922 lockdep_free_task(tsk);
923 do_task_dead();
924 }
925
make_task_dead(int signr)926 void __noreturn make_task_dead(int signr)
927 {
928 /*
929 * Take the task off the cpu after something catastrophic has
930 * happened.
931 *
932 * We can get here from a kernel oops, sometimes with preemption off.
933 * Start by checking for critical errors.
934 * Then fix up important state like USER_DS and preemption.
935 * Then do everything else.
936 */
937 struct task_struct *tsk = current;
938 unsigned int limit;
939
940 if (unlikely(in_interrupt()))
941 panic("Aiee, killing interrupt handler!");
942 if (unlikely(!tsk->pid))
943 panic("Attempted to kill the idle task!");
944
945 if (unlikely(irqs_disabled())) {
946 pr_info("note: %s[%d] exited with irqs disabled\n",
947 current->comm, task_pid_nr(current));
948 local_irq_enable();
949 }
950 if (unlikely(in_atomic())) {
951 pr_info("note: %s[%d] exited with preempt_count %d\n",
952 current->comm, task_pid_nr(current),
953 preempt_count());
954 preempt_count_set(PREEMPT_ENABLED);
955 }
956
957 /*
958 * Every time the system oopses, if the oops happens while a reference
959 * to an object was held, the reference leaks.
960 * If the oops doesn't also leak memory, repeated oopsing can cause
961 * reference counters to wrap around (if they're not using refcount_t).
962 * This means that repeated oopsing can make unexploitable-looking bugs
963 * exploitable through repeated oopsing.
964 * To make sure this can't happen, place an upper bound on how often the
965 * kernel may oops without panic().
966 */
967 limit = READ_ONCE(oops_limit);
968 if (atomic_inc_return(&oops_count) >= limit && limit)
969 panic("Oopsed too often (kernel.oops_limit is %d)", limit);
970
971 /*
972 * We're taking recursive faults here in make_task_dead. Safest is to just
973 * leave this task alone and wait for reboot.
974 */
975 if (unlikely(tsk->flags & PF_EXITING)) {
976 pr_alert("Fixing recursive fault but reboot is needed!\n");
977 futex_exit_recursive(tsk);
978 tsk->exit_state = EXIT_DEAD;
979 refcount_inc(&tsk->rcu_users);
980 do_task_dead();
981 }
982
983 do_exit(signr);
984 }
985
SYSCALL_DEFINE1(exit,int,error_code)986 SYSCALL_DEFINE1(exit, int, error_code)
987 {
988 do_exit((error_code&0xff)<<8);
989 }
990
991 /*
992 * Take down every thread in the group. This is called by fatal signals
993 * as well as by sys_exit_group (below).
994 */
995 void __noreturn
do_group_exit(int exit_code)996 do_group_exit(int exit_code)
997 {
998 struct signal_struct *sig = current->signal;
999
1000 if (sig->flags & SIGNAL_GROUP_EXIT)
1001 exit_code = sig->group_exit_code;
1002 else if (sig->group_exec_task)
1003 exit_code = 0;
1004 else {
1005 struct sighand_struct *const sighand = current->sighand;
1006
1007 spin_lock_irq(&sighand->siglock);
1008 if (sig->flags & SIGNAL_GROUP_EXIT)
1009 /* Another thread got here before we took the lock. */
1010 exit_code = sig->group_exit_code;
1011 else if (sig->group_exec_task)
1012 exit_code = 0;
1013 else {
1014 sig->group_exit_code = exit_code;
1015 sig->flags = SIGNAL_GROUP_EXIT;
1016 zap_other_threads(current);
1017 }
1018 spin_unlock_irq(&sighand->siglock);
1019 }
1020
1021 do_exit(exit_code);
1022 /* NOTREACHED */
1023 }
1024
1025 /*
1026 * this kills every thread in the thread group. Note that any externally
1027 * wait4()-ing process will get the correct exit code - even if this
1028 * thread is not the thread group leader.
1029 */
SYSCALL_DEFINE1(exit_group,int,error_code)1030 SYSCALL_DEFINE1(exit_group, int, error_code)
1031 {
1032 do_group_exit((error_code & 0xff) << 8);
1033 /* NOTREACHED */
1034 return 0;
1035 }
1036
1037 struct waitid_info {
1038 pid_t pid;
1039 uid_t uid;
1040 int status;
1041 int cause;
1042 };
1043
1044 struct wait_opts {
1045 enum pid_type wo_type;
1046 int wo_flags;
1047 struct pid *wo_pid;
1048
1049 struct waitid_info *wo_info;
1050 int wo_stat;
1051 struct rusage *wo_rusage;
1052
1053 wait_queue_entry_t child_wait;
1054 int notask_error;
1055 };
1056
eligible_pid(struct wait_opts * wo,struct task_struct * p)1057 static int eligible_pid(struct wait_opts *wo, struct task_struct *p)
1058 {
1059 return wo->wo_type == PIDTYPE_MAX ||
1060 task_pid_type(p, wo->wo_type) == wo->wo_pid;
1061 }
1062
1063 static int
eligible_child(struct wait_opts * wo,bool ptrace,struct task_struct * p)1064 eligible_child(struct wait_opts *wo, bool ptrace, struct task_struct *p)
1065 {
1066 if (!eligible_pid(wo, p))
1067 return 0;
1068
1069 /*
1070 * Wait for all children (clone and not) if __WALL is set or
1071 * if it is traced by us.
1072 */
1073 if (ptrace || (wo->wo_flags & __WALL))
1074 return 1;
1075
1076 /*
1077 * Otherwise, wait for clone children *only* if __WCLONE is set;
1078 * otherwise, wait for non-clone children *only*.
1079 *
1080 * Note: a "clone" child here is one that reports to its parent
1081 * using a signal other than SIGCHLD, or a non-leader thread which
1082 * we can only see if it is traced by us.
1083 */
1084 if ((p->exit_signal != SIGCHLD) ^ !!(wo->wo_flags & __WCLONE))
1085 return 0;
1086
1087 return 1;
1088 }
1089
1090 /*
1091 * Handle sys_wait4 work for one task in state EXIT_ZOMBIE. We hold
1092 * read_lock(&tasklist_lock) on entry. If we return zero, we still hold
1093 * the lock and this task is uninteresting. If we return nonzero, we have
1094 * released the lock and the system call should return.
1095 */
wait_task_zombie(struct wait_opts * wo,struct task_struct * p)1096 static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p)
1097 {
1098 int state, status;
1099 pid_t pid = task_pid_vnr(p);
1100 uid_t uid = from_kuid_munged(current_user_ns(), task_uid(p));
1101 struct waitid_info *infop;
1102
1103 if (!likely(wo->wo_flags & WEXITED))
1104 return 0;
1105
1106 if (unlikely(wo->wo_flags & WNOWAIT)) {
1107 status = (p->signal->flags & SIGNAL_GROUP_EXIT)
1108 ? p->signal->group_exit_code : p->exit_code;
1109 get_task_struct(p);
1110 read_unlock(&tasklist_lock);
1111 sched_annotate_sleep();
1112 if (wo->wo_rusage)
1113 getrusage(p, RUSAGE_BOTH, wo->wo_rusage);
1114 put_task_struct(p);
1115 goto out_info;
1116 }
1117 /*
1118 * Move the task's state to DEAD/TRACE, only one thread can do this.
1119 */
1120 state = (ptrace_reparented(p) && thread_group_leader(p)) ?
1121 EXIT_TRACE : EXIT_DEAD;
1122 if (cmpxchg(&p->exit_state, EXIT_ZOMBIE, state) != EXIT_ZOMBIE)
1123 return 0;
1124 /*
1125 * We own this thread, nobody else can reap it.
1126 */
1127 read_unlock(&tasklist_lock);
1128 sched_annotate_sleep();
1129
1130 /*
1131 * Check thread_group_leader() to exclude the traced sub-threads.
1132 */
1133 if (state == EXIT_DEAD && thread_group_leader(p)) {
1134 struct signal_struct *sig = p->signal;
1135 struct signal_struct *psig = current->signal;
1136 unsigned long maxrss;
1137 u64 tgutime, tgstime;
1138
1139 /*
1140 * The resource counters for the group leader are in its
1141 * own task_struct. Those for dead threads in the group
1142 * are in its signal_struct, as are those for the child
1143 * processes it has previously reaped. All these
1144 * accumulate in the parent's signal_struct c* fields.
1145 *
1146 * We don't bother to take a lock here to protect these
1147 * p->signal fields because the whole thread group is dead
1148 * and nobody can change them.
1149 *
1150 * psig->stats_lock also protects us from our sub-threads
1151 * which can reap other children at the same time. Until
1152 * we change k_getrusage()-like users to rely on this lock
1153 * we have to take ->siglock as well.
1154 *
1155 * We use thread_group_cputime_adjusted() to get times for
1156 * the thread group, which consolidates times for all threads
1157 * in the group including the group leader.
1158 */
1159 thread_group_cputime_adjusted(p, &tgutime, &tgstime);
1160 spin_lock_irq(¤t->sighand->siglock);
1161 write_seqlock(&psig->stats_lock);
1162 psig->cutime += tgutime + sig->cutime;
1163 psig->cstime += tgstime + sig->cstime;
1164 psig->cgtime += task_gtime(p) + sig->gtime + sig->cgtime;
1165 psig->cmin_flt +=
1166 p->min_flt + sig->min_flt + sig->cmin_flt;
1167 psig->cmaj_flt +=
1168 p->maj_flt + sig->maj_flt + sig->cmaj_flt;
1169 psig->cnvcsw +=
1170 p->nvcsw + sig->nvcsw + sig->cnvcsw;
1171 psig->cnivcsw +=
1172 p->nivcsw + sig->nivcsw + sig->cnivcsw;
1173 psig->cinblock +=
1174 task_io_get_inblock(p) +
1175 sig->inblock + sig->cinblock;
1176 psig->coublock +=
1177 task_io_get_oublock(p) +
1178 sig->oublock + sig->coublock;
1179 maxrss = max(sig->maxrss, sig->cmaxrss);
1180 if (psig->cmaxrss < maxrss)
1181 psig->cmaxrss = maxrss;
1182 task_io_accounting_add(&psig->ioac, &p->ioac);
1183 task_io_accounting_add(&psig->ioac, &sig->ioac);
1184 write_sequnlock(&psig->stats_lock);
1185 spin_unlock_irq(¤t->sighand->siglock);
1186 }
1187
1188 if (wo->wo_rusage)
1189 getrusage(p, RUSAGE_BOTH, wo->wo_rusage);
1190 status = (p->signal->flags & SIGNAL_GROUP_EXIT)
1191 ? p->signal->group_exit_code : p->exit_code;
1192 wo->wo_stat = status;
1193
1194 if (state == EXIT_TRACE) {
1195 write_lock_irq(&tasklist_lock);
1196 /* We dropped tasklist, ptracer could die and untrace */
1197 ptrace_unlink(p);
1198
1199 /* If parent wants a zombie, don't release it now */
1200 state = EXIT_ZOMBIE;
1201 if (do_notify_parent(p, p->exit_signal))
1202 state = EXIT_DEAD;
1203 p->exit_state = state;
1204 write_unlock_irq(&tasklist_lock);
1205 }
1206 if (state == EXIT_DEAD)
1207 release_task(p);
1208
1209 out_info:
1210 infop = wo->wo_info;
1211 if (infop) {
1212 if ((status & 0x7f) == 0) {
1213 infop->cause = CLD_EXITED;
1214 infop->status = status >> 8;
1215 } else {
1216 infop->cause = (status & 0x80) ? CLD_DUMPED : CLD_KILLED;
1217 infop->status = status & 0x7f;
1218 }
1219 infop->pid = pid;
1220 infop->uid = uid;
1221 }
1222
1223 return pid;
1224 }
1225
task_stopped_code(struct task_struct * p,bool ptrace)1226 static int *task_stopped_code(struct task_struct *p, bool ptrace)
1227 {
1228 if (ptrace) {
1229 if (task_is_traced(p) && !(p->jobctl & JOBCTL_LISTENING))
1230 return &p->exit_code;
1231 } else {
1232 if (p->signal->flags & SIGNAL_STOP_STOPPED)
1233 return &p->signal->group_exit_code;
1234 }
1235 return NULL;
1236 }
1237
1238 /**
1239 * wait_task_stopped - Wait for %TASK_STOPPED or %TASK_TRACED
1240 * @wo: wait options
1241 * @ptrace: is the wait for ptrace
1242 * @p: task to wait for
1243 *
1244 * Handle sys_wait4() work for %p in state %TASK_STOPPED or %TASK_TRACED.
1245 *
1246 * CONTEXT:
1247 * read_lock(&tasklist_lock), which is released if return value is
1248 * non-zero. Also, grabs and releases @p->sighand->siglock.
1249 *
1250 * RETURNS:
1251 * 0 if wait condition didn't exist and search for other wait conditions
1252 * should continue. Non-zero return, -errno on failure and @p's pid on
1253 * success, implies that tasklist_lock is released and wait condition
1254 * search should terminate.
1255 */
wait_task_stopped(struct wait_opts * wo,int ptrace,struct task_struct * p)1256 static int wait_task_stopped(struct wait_opts *wo,
1257 int ptrace, struct task_struct *p)
1258 {
1259 struct waitid_info *infop;
1260 int exit_code, *p_code, why;
1261 uid_t uid = 0; /* unneeded, required by compiler */
1262 pid_t pid;
1263
1264 /*
1265 * Traditionally we see ptrace'd stopped tasks regardless of options.
1266 */
1267 if (!ptrace && !(wo->wo_flags & WUNTRACED))
1268 return 0;
1269
1270 if (!task_stopped_code(p, ptrace))
1271 return 0;
1272
1273 exit_code = 0;
1274 spin_lock_irq(&p->sighand->siglock);
1275
1276 p_code = task_stopped_code(p, ptrace);
1277 if (unlikely(!p_code))
1278 goto unlock_sig;
1279
1280 exit_code = *p_code;
1281 if (!exit_code)
1282 goto unlock_sig;
1283
1284 if (!unlikely(wo->wo_flags & WNOWAIT))
1285 *p_code = 0;
1286
1287 uid = from_kuid_munged(current_user_ns(), task_uid(p));
1288 unlock_sig:
1289 spin_unlock_irq(&p->sighand->siglock);
1290 if (!exit_code)
1291 return 0;
1292
1293 /*
1294 * Now we are pretty sure this task is interesting.
1295 * Make sure it doesn't get reaped out from under us while we
1296 * give up the lock and then examine it below. We don't want to
1297 * keep holding onto the tasklist_lock while we call getrusage and
1298 * possibly take page faults for user memory.
1299 */
1300 get_task_struct(p);
1301 pid = task_pid_vnr(p);
1302 why = ptrace ? CLD_TRAPPED : CLD_STOPPED;
1303 read_unlock(&tasklist_lock);
1304 sched_annotate_sleep();
1305 if (wo->wo_rusage)
1306 getrusage(p, RUSAGE_BOTH, wo->wo_rusage);
1307 put_task_struct(p);
1308
1309 if (likely(!(wo->wo_flags & WNOWAIT)))
1310 wo->wo_stat = (exit_code << 8) | 0x7f;
1311
1312 infop = wo->wo_info;
1313 if (infop) {
1314 infop->cause = why;
1315 infop->status = exit_code;
1316 infop->pid = pid;
1317 infop->uid = uid;
1318 }
1319 return pid;
1320 }
1321
1322 /*
1323 * Handle do_wait work for one task in a live, non-stopped state.
1324 * read_lock(&tasklist_lock) on entry. If we return zero, we still hold
1325 * the lock and this task is uninteresting. If we return nonzero, we have
1326 * released the lock and the system call should return.
1327 */
wait_task_continued(struct wait_opts * wo,struct task_struct * p)1328 static int wait_task_continued(struct wait_opts *wo, struct task_struct *p)
1329 {
1330 struct waitid_info *infop;
1331 pid_t pid;
1332 uid_t uid;
1333
1334 if (!unlikely(wo->wo_flags & WCONTINUED))
1335 return 0;
1336
1337 if (!(p->signal->flags & SIGNAL_STOP_CONTINUED))
1338 return 0;
1339
1340 spin_lock_irq(&p->sighand->siglock);
1341 /* Re-check with the lock held. */
1342 if (!(p->signal->flags & SIGNAL_STOP_CONTINUED)) {
1343 spin_unlock_irq(&p->sighand->siglock);
1344 return 0;
1345 }
1346 if (!unlikely(wo->wo_flags & WNOWAIT))
1347 p->signal->flags &= ~SIGNAL_STOP_CONTINUED;
1348 uid = from_kuid_munged(current_user_ns(), task_uid(p));
1349 spin_unlock_irq(&p->sighand->siglock);
1350
1351 pid = task_pid_vnr(p);
1352 get_task_struct(p);
1353 read_unlock(&tasklist_lock);
1354 sched_annotate_sleep();
1355 if (wo->wo_rusage)
1356 getrusage(p, RUSAGE_BOTH, wo->wo_rusage);
1357 put_task_struct(p);
1358
1359 infop = wo->wo_info;
1360 if (!infop) {
1361 wo->wo_stat = 0xffff;
1362 } else {
1363 infop->cause = CLD_CONTINUED;
1364 infop->pid = pid;
1365 infop->uid = uid;
1366 infop->status = SIGCONT;
1367 }
1368 return pid;
1369 }
1370
1371 /*
1372 * Consider @p for a wait by @parent.
1373 *
1374 * -ECHILD should be in ->notask_error before the first call.
1375 * Returns nonzero for a final return, when we have unlocked tasklist_lock.
1376 * Returns zero if the search for a child should continue;
1377 * then ->notask_error is 0 if @p is an eligible child,
1378 * or still -ECHILD.
1379 */
wait_consider_task(struct wait_opts * wo,int ptrace,struct task_struct * p)1380 static int wait_consider_task(struct wait_opts *wo, int ptrace,
1381 struct task_struct *p)
1382 {
1383 /*
1384 * We can race with wait_task_zombie() from another thread.
1385 * Ensure that EXIT_ZOMBIE -> EXIT_DEAD/EXIT_TRACE transition
1386 * can't confuse the checks below.
1387 */
1388 int exit_state = READ_ONCE(p->exit_state);
1389 int ret;
1390
1391 if (unlikely(exit_state == EXIT_DEAD))
1392 return 0;
1393
1394 ret = eligible_child(wo, ptrace, p);
1395 if (!ret)
1396 return ret;
1397
1398 if (unlikely(exit_state == EXIT_TRACE)) {
1399 /*
1400 * ptrace == 0 means we are the natural parent. In this case
1401 * we should clear notask_error, debugger will notify us.
1402 */
1403 if (likely(!ptrace))
1404 wo->notask_error = 0;
1405 return 0;
1406 }
1407
1408 if (likely(!ptrace) && unlikely(p->ptrace)) {
1409 /*
1410 * If it is traced by its real parent's group, just pretend
1411 * the caller is ptrace_do_wait() and reap this child if it
1412 * is zombie.
1413 *
1414 * This also hides group stop state from real parent; otherwise
1415 * a single stop can be reported twice as group and ptrace stop.
1416 * If a ptracer wants to distinguish these two events for its
1417 * own children it should create a separate process which takes
1418 * the role of real parent.
1419 */
1420 if (!ptrace_reparented(p))
1421 ptrace = 1;
1422 }
1423
1424 /* slay zombie? */
1425 if (exit_state == EXIT_ZOMBIE) {
1426 /* we don't reap group leaders with subthreads */
1427 if (!delay_group_leader(p)) {
1428 /*
1429 * A zombie ptracee is only visible to its ptracer.
1430 * Notification and reaping will be cascaded to the
1431 * real parent when the ptracer detaches.
1432 */
1433 if (unlikely(ptrace) || likely(!p->ptrace))
1434 return wait_task_zombie(wo, p);
1435 }
1436
1437 /*
1438 * Allow access to stopped/continued state via zombie by
1439 * falling through. Clearing of notask_error is complex.
1440 *
1441 * When !@ptrace:
1442 *
1443 * If WEXITED is set, notask_error should naturally be
1444 * cleared. If not, subset of WSTOPPED|WCONTINUED is set,
1445 * so, if there are live subthreads, there are events to
1446 * wait for. If all subthreads are dead, it's still safe
1447 * to clear - this function will be called again in finite
1448 * amount time once all the subthreads are released and
1449 * will then return without clearing.
1450 *
1451 * When @ptrace:
1452 *
1453 * Stopped state is per-task and thus can't change once the
1454 * target task dies. Only continued and exited can happen.
1455 * Clear notask_error if WCONTINUED | WEXITED.
1456 */
1457 if (likely(!ptrace) || (wo->wo_flags & (WCONTINUED | WEXITED)))
1458 wo->notask_error = 0;
1459 } else {
1460 /*
1461 * @p is alive and it's gonna stop, continue or exit, so
1462 * there always is something to wait for.
1463 */
1464 wo->notask_error = 0;
1465 }
1466
1467 /*
1468 * Wait for stopped. Depending on @ptrace, different stopped state
1469 * is used and the two don't interact with each other.
1470 */
1471 ret = wait_task_stopped(wo, ptrace, p);
1472 if (ret)
1473 return ret;
1474
1475 /*
1476 * Wait for continued. There's only one continued state and the
1477 * ptracer can consume it which can confuse the real parent. Don't
1478 * use WCONTINUED from ptracer. You don't need or want it.
1479 */
1480 return wait_task_continued(wo, p);
1481 }
1482
1483 /*
1484 * Do the work of do_wait() for one thread in the group, @tsk.
1485 *
1486 * -ECHILD should be in ->notask_error before the first call.
1487 * Returns nonzero for a final return, when we have unlocked tasklist_lock.
1488 * Returns zero if the search for a child should continue; then
1489 * ->notask_error is 0 if there were any eligible children,
1490 * or still -ECHILD.
1491 */
do_wait_thread(struct wait_opts * wo,struct task_struct * tsk)1492 static int do_wait_thread(struct wait_opts *wo, struct task_struct *tsk)
1493 {
1494 struct task_struct *p;
1495
1496 list_for_each_entry(p, &tsk->children, sibling) {
1497 int ret = wait_consider_task(wo, 0, p);
1498
1499 if (ret)
1500 return ret;
1501 }
1502
1503 return 0;
1504 }
1505
ptrace_do_wait(struct wait_opts * wo,struct task_struct * tsk)1506 static int ptrace_do_wait(struct wait_opts *wo, struct task_struct *tsk)
1507 {
1508 struct task_struct *p;
1509
1510 list_for_each_entry(p, &tsk->ptraced, ptrace_entry) {
1511 int ret = wait_consider_task(wo, 1, p);
1512
1513 if (ret)
1514 return ret;
1515 }
1516
1517 return 0;
1518 }
1519
child_wait_callback(wait_queue_entry_t * wait,unsigned mode,int sync,void * key)1520 static int child_wait_callback(wait_queue_entry_t *wait, unsigned mode,
1521 int sync, void *key)
1522 {
1523 struct wait_opts *wo = container_of(wait, struct wait_opts,
1524 child_wait);
1525 struct task_struct *p = key;
1526
1527 if (!eligible_pid(wo, p))
1528 return 0;
1529
1530 if ((wo->wo_flags & __WNOTHREAD) && wait->private != p->parent)
1531 return 0;
1532
1533 return default_wake_function(wait, mode, sync, key);
1534 }
1535
__wake_up_parent(struct task_struct * p,struct task_struct * parent)1536 void __wake_up_parent(struct task_struct *p, struct task_struct *parent)
1537 {
1538 __wake_up_sync_key(&parent->signal->wait_chldexit,
1539 TASK_INTERRUPTIBLE, p);
1540 }
1541
is_effectively_child(struct wait_opts * wo,bool ptrace,struct task_struct * target)1542 static bool is_effectively_child(struct wait_opts *wo, bool ptrace,
1543 struct task_struct *target)
1544 {
1545 struct task_struct *parent =
1546 !ptrace ? target->real_parent : target->parent;
1547
1548 return current == parent || (!(wo->wo_flags & __WNOTHREAD) &&
1549 same_thread_group(current, parent));
1550 }
1551
1552 /*
1553 * Optimization for waiting on PIDTYPE_PID. No need to iterate through child
1554 * and tracee lists to find the target task.
1555 */
do_wait_pid(struct wait_opts * wo)1556 static int do_wait_pid(struct wait_opts *wo)
1557 {
1558 bool ptrace;
1559 struct task_struct *target;
1560 int retval;
1561
1562 ptrace = false;
1563 target = pid_task(wo->wo_pid, PIDTYPE_TGID);
1564 if (target && is_effectively_child(wo, ptrace, target)) {
1565 retval = wait_consider_task(wo, ptrace, target);
1566 if (retval)
1567 return retval;
1568 }
1569
1570 ptrace = true;
1571 target = pid_task(wo->wo_pid, PIDTYPE_PID);
1572 if (target && target->ptrace &&
1573 is_effectively_child(wo, ptrace, target)) {
1574 retval = wait_consider_task(wo, ptrace, target);
1575 if (retval)
1576 return retval;
1577 }
1578
1579 return 0;
1580 }
1581
do_wait(struct wait_opts * wo)1582 static long do_wait(struct wait_opts *wo)
1583 {
1584 int retval;
1585
1586 trace_sched_process_wait(wo->wo_pid);
1587
1588 init_waitqueue_func_entry(&wo->child_wait, child_wait_callback);
1589 wo->child_wait.private = current;
1590 add_wait_queue(¤t->signal->wait_chldexit, &wo->child_wait);
1591 repeat:
1592 /*
1593 * If there is nothing that can match our criteria, just get out.
1594 * We will clear ->notask_error to zero if we see any child that
1595 * might later match our criteria, even if we are not able to reap
1596 * it yet.
1597 */
1598 wo->notask_error = -ECHILD;
1599 if ((wo->wo_type < PIDTYPE_MAX) &&
1600 (!wo->wo_pid || !pid_has_task(wo->wo_pid, wo->wo_type)))
1601 goto notask;
1602
1603 set_current_state(TASK_INTERRUPTIBLE);
1604 read_lock(&tasklist_lock);
1605
1606 if (wo->wo_type == PIDTYPE_PID) {
1607 retval = do_wait_pid(wo);
1608 if (retval)
1609 goto end;
1610 } else {
1611 struct task_struct *tsk = current;
1612
1613 do {
1614 retval = do_wait_thread(wo, tsk);
1615 if (retval)
1616 goto end;
1617
1618 retval = ptrace_do_wait(wo, tsk);
1619 if (retval)
1620 goto end;
1621
1622 if (wo->wo_flags & __WNOTHREAD)
1623 break;
1624 } while_each_thread(current, tsk);
1625 }
1626 read_unlock(&tasklist_lock);
1627
1628 notask:
1629 retval = wo->notask_error;
1630 if (!retval && !(wo->wo_flags & WNOHANG)) {
1631 retval = -ERESTARTSYS;
1632 if (!signal_pending(current)) {
1633 schedule();
1634 goto repeat;
1635 }
1636 }
1637 end:
1638 __set_current_state(TASK_RUNNING);
1639 remove_wait_queue(¤t->signal->wait_chldexit, &wo->child_wait);
1640 return retval;
1641 }
1642
kernel_waitid(int which,pid_t upid,struct waitid_info * infop,int options,struct rusage * ru)1643 static long kernel_waitid(int which, pid_t upid, struct waitid_info *infop,
1644 int options, struct rusage *ru)
1645 {
1646 struct wait_opts wo;
1647 struct pid *pid = NULL;
1648 enum pid_type type;
1649 long ret;
1650 unsigned int f_flags = 0;
1651
1652 if (options & ~(WNOHANG|WNOWAIT|WEXITED|WSTOPPED|WCONTINUED|
1653 __WNOTHREAD|__WCLONE|__WALL))
1654 return -EINVAL;
1655 if (!(options & (WEXITED|WSTOPPED|WCONTINUED)))
1656 return -EINVAL;
1657
1658 switch (which) {
1659 case P_ALL:
1660 type = PIDTYPE_MAX;
1661 break;
1662 case P_PID:
1663 type = PIDTYPE_PID;
1664 if (upid <= 0)
1665 return -EINVAL;
1666
1667 pid = find_get_pid(upid);
1668 break;
1669 case P_PGID:
1670 type = PIDTYPE_PGID;
1671 if (upid < 0)
1672 return -EINVAL;
1673
1674 if (upid)
1675 pid = find_get_pid(upid);
1676 else
1677 pid = get_task_pid(current, PIDTYPE_PGID);
1678 break;
1679 case P_PIDFD:
1680 type = PIDTYPE_PID;
1681 if (upid < 0)
1682 return -EINVAL;
1683
1684 pid = pidfd_get_pid(upid, &f_flags);
1685 if (IS_ERR(pid))
1686 return PTR_ERR(pid);
1687
1688 break;
1689 default:
1690 return -EINVAL;
1691 }
1692
1693 wo.wo_type = type;
1694 wo.wo_pid = pid;
1695 wo.wo_flags = options;
1696 wo.wo_info = infop;
1697 wo.wo_rusage = ru;
1698 if (f_flags & O_NONBLOCK)
1699 wo.wo_flags |= WNOHANG;
1700
1701 ret = do_wait(&wo);
1702 if (!ret && !(options & WNOHANG) && (f_flags & O_NONBLOCK))
1703 ret = -EAGAIN;
1704
1705 put_pid(pid);
1706 return ret;
1707 }
1708
SYSCALL_DEFINE5(waitid,int,which,pid_t,upid,struct siginfo __user *,infop,int,options,struct rusage __user *,ru)1709 SYSCALL_DEFINE5(waitid, int, which, pid_t, upid, struct siginfo __user *,
1710 infop, int, options, struct rusage __user *, ru)
1711 {
1712 struct rusage r;
1713 struct waitid_info info = {.status = 0};
1714 long err = kernel_waitid(which, upid, &info, options, ru ? &r : NULL);
1715 int signo = 0;
1716
1717 if (err > 0) {
1718 signo = SIGCHLD;
1719 err = 0;
1720 if (ru && copy_to_user(ru, &r, sizeof(struct rusage)))
1721 return -EFAULT;
1722 }
1723 if (!infop)
1724 return err;
1725
1726 if (!user_write_access_begin(infop, sizeof(*infop)))
1727 return -EFAULT;
1728
1729 unsafe_put_user(signo, &infop->si_signo, Efault);
1730 unsafe_put_user(0, &infop->si_errno, Efault);
1731 unsafe_put_user(info.cause, &infop->si_code, Efault);
1732 unsafe_put_user(info.pid, &infop->si_pid, Efault);
1733 unsafe_put_user(info.uid, &infop->si_uid, Efault);
1734 unsafe_put_user(info.status, &infop->si_status, Efault);
1735 user_write_access_end();
1736 return err;
1737 Efault:
1738 user_write_access_end();
1739 return -EFAULT;
1740 }
1741
kernel_wait4(pid_t upid,int __user * stat_addr,int options,struct rusage * ru)1742 long kernel_wait4(pid_t upid, int __user *stat_addr, int options,
1743 struct rusage *ru)
1744 {
1745 struct wait_opts wo;
1746 struct pid *pid = NULL;
1747 enum pid_type type;
1748 long ret;
1749
1750 if (options & ~(WNOHANG|WUNTRACED|WCONTINUED|
1751 __WNOTHREAD|__WCLONE|__WALL))
1752 return -EINVAL;
1753
1754 /* -INT_MIN is not defined */
1755 if (upid == INT_MIN)
1756 return -ESRCH;
1757
1758 if (upid == -1)
1759 type = PIDTYPE_MAX;
1760 else if (upid < 0) {
1761 type = PIDTYPE_PGID;
1762 pid = find_get_pid(-upid);
1763 } else if (upid == 0) {
1764 type = PIDTYPE_PGID;
1765 pid = get_task_pid(current, PIDTYPE_PGID);
1766 } else /* upid > 0 */ {
1767 type = PIDTYPE_PID;
1768 pid = find_get_pid(upid);
1769 }
1770
1771 wo.wo_type = type;
1772 wo.wo_pid = pid;
1773 wo.wo_flags = options | WEXITED;
1774 wo.wo_info = NULL;
1775 wo.wo_stat = 0;
1776 wo.wo_rusage = ru;
1777 ret = do_wait(&wo);
1778 put_pid(pid);
1779 if (ret > 0 && stat_addr && put_user(wo.wo_stat, stat_addr))
1780 ret = -EFAULT;
1781
1782 return ret;
1783 }
1784
kernel_wait(pid_t pid,int * stat)1785 int kernel_wait(pid_t pid, int *stat)
1786 {
1787 struct wait_opts wo = {
1788 .wo_type = PIDTYPE_PID,
1789 .wo_pid = find_get_pid(pid),
1790 .wo_flags = WEXITED,
1791 };
1792 int ret;
1793
1794 ret = do_wait(&wo);
1795 if (ret > 0 && wo.wo_stat)
1796 *stat = wo.wo_stat;
1797 put_pid(wo.wo_pid);
1798 return ret;
1799 }
1800
SYSCALL_DEFINE4(wait4,pid_t,upid,int __user *,stat_addr,int,options,struct rusage __user *,ru)1801 SYSCALL_DEFINE4(wait4, pid_t, upid, int __user *, stat_addr,
1802 int, options, struct rusage __user *, ru)
1803 {
1804 struct rusage r;
1805 long err = kernel_wait4(upid, stat_addr, options, ru ? &r : NULL);
1806
1807 if (err > 0) {
1808 if (ru && copy_to_user(ru, &r, sizeof(struct rusage)))
1809 return -EFAULT;
1810 }
1811 return err;
1812 }
1813
1814 #ifdef __ARCH_WANT_SYS_WAITPID
1815
1816 /*
1817 * sys_waitpid() remains for compatibility. waitpid() should be
1818 * implemented by calling sys_wait4() from libc.a.
1819 */
SYSCALL_DEFINE3(waitpid,pid_t,pid,int __user *,stat_addr,int,options)1820 SYSCALL_DEFINE3(waitpid, pid_t, pid, int __user *, stat_addr, int, options)
1821 {
1822 return kernel_wait4(pid, stat_addr, options, NULL);
1823 }
1824
1825 #endif
1826
1827 #ifdef CONFIG_COMPAT
COMPAT_SYSCALL_DEFINE4(wait4,compat_pid_t,pid,compat_uint_t __user *,stat_addr,int,options,struct compat_rusage __user *,ru)1828 COMPAT_SYSCALL_DEFINE4(wait4,
1829 compat_pid_t, pid,
1830 compat_uint_t __user *, stat_addr,
1831 int, options,
1832 struct compat_rusage __user *, ru)
1833 {
1834 struct rusage r;
1835 long err = kernel_wait4(pid, stat_addr, options, ru ? &r : NULL);
1836 if (err > 0) {
1837 if (ru && put_compat_rusage(&r, ru))
1838 return -EFAULT;
1839 }
1840 return err;
1841 }
1842
COMPAT_SYSCALL_DEFINE5(waitid,int,which,compat_pid_t,pid,struct compat_siginfo __user *,infop,int,options,struct compat_rusage __user *,uru)1843 COMPAT_SYSCALL_DEFINE5(waitid,
1844 int, which, compat_pid_t, pid,
1845 struct compat_siginfo __user *, infop, int, options,
1846 struct compat_rusage __user *, uru)
1847 {
1848 struct rusage ru;
1849 struct waitid_info info = {.status = 0};
1850 long err = kernel_waitid(which, pid, &info, options, uru ? &ru : NULL);
1851 int signo = 0;
1852 if (err > 0) {
1853 signo = SIGCHLD;
1854 err = 0;
1855 if (uru) {
1856 /* kernel_waitid() overwrites everything in ru */
1857 if (COMPAT_USE_64BIT_TIME)
1858 err = copy_to_user(uru, &ru, sizeof(ru));
1859 else
1860 err = put_compat_rusage(&ru, uru);
1861 if (err)
1862 return -EFAULT;
1863 }
1864 }
1865
1866 if (!infop)
1867 return err;
1868
1869 if (!user_write_access_begin(infop, sizeof(*infop)))
1870 return -EFAULT;
1871
1872 unsafe_put_user(signo, &infop->si_signo, Efault);
1873 unsafe_put_user(0, &infop->si_errno, Efault);
1874 unsafe_put_user(info.cause, &infop->si_code, Efault);
1875 unsafe_put_user(info.pid, &infop->si_pid, Efault);
1876 unsafe_put_user(info.uid, &infop->si_uid, Efault);
1877 unsafe_put_user(info.status, &infop->si_status, Efault);
1878 user_write_access_end();
1879 return err;
1880 Efault:
1881 user_write_access_end();
1882 return -EFAULT;
1883 }
1884 #endif
1885
1886 /**
1887 * thread_group_exited - check that a thread group has exited
1888 * @pid: tgid of thread group to be checked.
1889 *
1890 * Test if the thread group represented by tgid has exited (all
1891 * threads are zombies, dead or completely gone).
1892 *
1893 * Return: true if the thread group has exited. false otherwise.
1894 */
thread_group_exited(struct pid * pid)1895 bool thread_group_exited(struct pid *pid)
1896 {
1897 struct task_struct *task;
1898 bool exited;
1899
1900 rcu_read_lock();
1901 task = pid_task(pid, PIDTYPE_PID);
1902 exited = !task ||
1903 (READ_ONCE(task->exit_state) && thread_group_empty(task));
1904 rcu_read_unlock();
1905
1906 return exited;
1907 }
1908 EXPORT_SYMBOL(thread_group_exited);
1909
1910 /*
1911 * This needs to be __function_aligned as GCC implicitly makes any
1912 * implementation of abort() cold and drops alignment specified by
1913 * -falign-functions=N.
1914 *
1915 * See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88345#c11
1916 */
abort(void)1917 __weak __function_aligned void abort(void)
1918 {
1919 BUG();
1920
1921 /* if that doesn't kill us, halt */
1922 panic("Oops failed to kill thread");
1923 }
1924 EXPORT_SYMBOL(abort);
1925