xref: /linux/kernel/exit.c (revision ed7171ff9fabc49ae6ed42fbd082a576473836fc)
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 #include <linux/uaccess.h>
73 
74 #include <uapi/linux/wait.h>
75 
76 #include <asm/unistd.h>
77 #include <asm/mmu_context.h>
78 
79 #include "exit.h"
80 
81 /*
82  * The default value should be high enough to not crash a system that randomly
83  * crashes its kernel from time to time, but low enough to at least not permit
84  * overflowing 32-bit refcounts or the ldsem writer count.
85  */
86 static unsigned int oops_limit = 10000;
87 
88 #ifdef CONFIG_SYSCTL
89 static struct ctl_table kern_exit_table[] = {
90 	{
91 		.procname       = "oops_limit",
92 		.data           = &oops_limit,
93 		.maxlen         = sizeof(oops_limit),
94 		.mode           = 0644,
95 		.proc_handler   = proc_douintvec,
96 	},
97 };
98 
99 static __init int kernel_exit_sysctls_init(void)
100 {
101 	register_sysctl_init("kernel", kern_exit_table);
102 	return 0;
103 }
104 late_initcall(kernel_exit_sysctls_init);
105 #endif
106 
107 static atomic_t oops_count = ATOMIC_INIT(0);
108 
109 #ifdef CONFIG_SYSFS
110 static ssize_t oops_count_show(struct kobject *kobj, struct kobj_attribute *attr,
111 			       char *page)
112 {
113 	return sysfs_emit(page, "%d\n", atomic_read(&oops_count));
114 }
115 
116 static struct kobj_attribute oops_count_attr = __ATTR_RO(oops_count);
117 
118 static __init int kernel_exit_sysfs_init(void)
119 {
120 	sysfs_add_file_to_group(kernel_kobj, &oops_count_attr.attr, NULL);
121 	return 0;
122 }
123 late_initcall(kernel_exit_sysfs_init);
124 #endif
125 
126 static void __unhash_process(struct task_struct *p, bool group_dead)
127 {
128 	nr_threads--;
129 	detach_pid(p, PIDTYPE_PID);
130 	if (group_dead) {
131 		detach_pid(p, PIDTYPE_TGID);
132 		detach_pid(p, PIDTYPE_PGID);
133 		detach_pid(p, PIDTYPE_SID);
134 
135 		list_del_rcu(&p->tasks);
136 		list_del_init(&p->sibling);
137 		__this_cpu_dec(process_counts);
138 	}
139 	list_del_rcu(&p->thread_node);
140 }
141 
142 /*
143  * This function expects the tasklist_lock write-locked.
144  */
145 static void __exit_signal(struct task_struct *tsk)
146 {
147 	struct signal_struct *sig = tsk->signal;
148 	bool group_dead = thread_group_leader(tsk);
149 	struct sighand_struct *sighand;
150 	struct tty_struct *tty;
151 	u64 utime, stime;
152 
153 	sighand = rcu_dereference_check(tsk->sighand,
154 					lockdep_tasklist_lock_is_held());
155 	spin_lock(&sighand->siglock);
156 
157 #ifdef CONFIG_POSIX_TIMERS
158 	posix_cpu_timers_exit(tsk);
159 	if (group_dead)
160 		posix_cpu_timers_exit_group(tsk);
161 #endif
162 
163 	if (group_dead) {
164 		tty = sig->tty;
165 		sig->tty = NULL;
166 	} else {
167 		/*
168 		 * If there is any task waiting for the group exit
169 		 * then notify it:
170 		 */
171 		if (sig->notify_count > 0 && !--sig->notify_count)
172 			wake_up_process(sig->group_exec_task);
173 
174 		if (tsk == sig->curr_target)
175 			sig->curr_target = next_thread(tsk);
176 	}
177 
178 	add_device_randomness((const void*) &tsk->se.sum_exec_runtime,
179 			      sizeof(unsigned long long));
180 
181 	/*
182 	 * Accumulate here the counters for all threads as they die. We could
183 	 * skip the group leader because it is the last user of signal_struct,
184 	 * but we want to avoid the race with thread_group_cputime() which can
185 	 * see the empty ->thread_head list.
186 	 */
187 	task_cputime(tsk, &utime, &stime);
188 	write_seqlock(&sig->stats_lock);
189 	sig->utime += utime;
190 	sig->stime += stime;
191 	sig->gtime += task_gtime(tsk);
192 	sig->min_flt += tsk->min_flt;
193 	sig->maj_flt += tsk->maj_flt;
194 	sig->nvcsw += tsk->nvcsw;
195 	sig->nivcsw += tsk->nivcsw;
196 	sig->inblock += task_io_get_inblock(tsk);
197 	sig->oublock += task_io_get_oublock(tsk);
198 	task_io_accounting_add(&sig->ioac, &tsk->ioac);
199 	sig->sum_sched_runtime += tsk->se.sum_exec_runtime;
200 	sig->nr_threads--;
201 	__unhash_process(tsk, group_dead);
202 	write_sequnlock(&sig->stats_lock);
203 
204 	/*
205 	 * Do this under ->siglock, we can race with another thread
206 	 * doing sigqueue_free() if we have SIGQUEUE_PREALLOC signals.
207 	 */
208 	flush_sigqueue(&tsk->pending);
209 	tsk->sighand = NULL;
210 	spin_unlock(&sighand->siglock);
211 
212 	__cleanup_sighand(sighand);
213 	clear_tsk_thread_flag(tsk, TIF_SIGPENDING);
214 	if (group_dead) {
215 		flush_sigqueue(&sig->shared_pending);
216 		tty_kref_put(tty);
217 	}
218 }
219 
220 static void delayed_put_task_struct(struct rcu_head *rhp)
221 {
222 	struct task_struct *tsk = container_of(rhp, struct task_struct, rcu);
223 
224 	kprobe_flush_task(tsk);
225 	rethook_flush_task(tsk);
226 	perf_event_delayed_put(tsk);
227 	trace_sched_process_free(tsk);
228 	put_task_struct(tsk);
229 }
230 
231 void put_task_struct_rcu_user(struct task_struct *task)
232 {
233 	if (refcount_dec_and_test(&task->rcu_users))
234 		call_rcu(&task->rcu, delayed_put_task_struct);
235 }
236 
237 void __weak release_thread(struct task_struct *dead_task)
238 {
239 }
240 
241 void release_task(struct task_struct *p)
242 {
243 	struct task_struct *leader;
244 	struct pid *thread_pid;
245 	int zap_leader;
246 repeat:
247 	/* don't need to get the RCU readlock here - the process is dead and
248 	 * can't be modifying its own credentials. But shut RCU-lockdep up */
249 	rcu_read_lock();
250 	dec_rlimit_ucounts(task_ucounts(p), UCOUNT_RLIMIT_NPROC, 1);
251 	rcu_read_unlock();
252 
253 	cgroup_release(p);
254 
255 	write_lock_irq(&tasklist_lock);
256 	ptrace_release_task(p);
257 	thread_pid = get_pid(p->thread_pid);
258 	__exit_signal(p);
259 
260 	/*
261 	 * If we are the last non-leader member of the thread
262 	 * group, and the leader is zombie, then notify the
263 	 * group leader's parent process. (if it wants notification.)
264 	 */
265 	zap_leader = 0;
266 	leader = p->group_leader;
267 	if (leader != p && thread_group_empty(leader)
268 			&& leader->exit_state == EXIT_ZOMBIE) {
269 		/*
270 		 * If we were the last child thread and the leader has
271 		 * exited already, and the leader's parent ignores SIGCHLD,
272 		 * then we are the one who should release the leader.
273 		 */
274 		zap_leader = do_notify_parent(leader, leader->exit_signal);
275 		if (zap_leader)
276 			leader->exit_state = EXIT_DEAD;
277 	}
278 
279 	write_unlock_irq(&tasklist_lock);
280 	proc_flush_pid(thread_pid);
281 	put_pid(thread_pid);
282 	release_thread(p);
283 	put_task_struct_rcu_user(p);
284 
285 	p = leader;
286 	if (unlikely(zap_leader))
287 		goto repeat;
288 }
289 
290 int rcuwait_wake_up(struct rcuwait *w)
291 {
292 	int ret = 0;
293 	struct task_struct *task;
294 
295 	rcu_read_lock();
296 
297 	/*
298 	 * Order condition vs @task, such that everything prior to the load
299 	 * of @task is visible. This is the condition as to why the user called
300 	 * rcuwait_wake() in the first place. Pairs with set_current_state()
301 	 * barrier (A) in rcuwait_wait_event().
302 	 *
303 	 *    WAIT                WAKE
304 	 *    [S] tsk = current	  [S] cond = true
305 	 *        MB (A)	      MB (B)
306 	 *    [L] cond		  [L] tsk
307 	 */
308 	smp_mb(); /* (B) */
309 
310 	task = rcu_dereference(w->task);
311 	if (task)
312 		ret = wake_up_process(task);
313 	rcu_read_unlock();
314 
315 	return ret;
316 }
317 EXPORT_SYMBOL_GPL(rcuwait_wake_up);
318 
319 /*
320  * Determine if a process group is "orphaned", according to the POSIX
321  * definition in 2.2.2.52.  Orphaned process groups are not to be affected
322  * by terminal-generated stop signals.  Newly orphaned process groups are
323  * to receive a SIGHUP and a SIGCONT.
324  *
325  * "I ask you, have you ever known what it is to be an orphan?"
326  */
327 static int will_become_orphaned_pgrp(struct pid *pgrp,
328 					struct task_struct *ignored_task)
329 {
330 	struct task_struct *p;
331 
332 	do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
333 		if ((p == ignored_task) ||
334 		    (p->exit_state && thread_group_empty(p)) ||
335 		    is_global_init(p->real_parent))
336 			continue;
337 
338 		if (task_pgrp(p->real_parent) != pgrp &&
339 		    task_session(p->real_parent) == task_session(p))
340 			return 0;
341 	} while_each_pid_task(pgrp, PIDTYPE_PGID, p);
342 
343 	return 1;
344 }
345 
346 int is_current_pgrp_orphaned(void)
347 {
348 	int retval;
349 
350 	read_lock(&tasklist_lock);
351 	retval = will_become_orphaned_pgrp(task_pgrp(current), NULL);
352 	read_unlock(&tasklist_lock);
353 
354 	return retval;
355 }
356 
357 static bool has_stopped_jobs(struct pid *pgrp)
358 {
359 	struct task_struct *p;
360 
361 	do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
362 		if (p->signal->flags & SIGNAL_STOP_STOPPED)
363 			return true;
364 	} while_each_pid_task(pgrp, PIDTYPE_PGID, p);
365 
366 	return false;
367 }
368 
369 /*
370  * Check to see if any process groups have become orphaned as
371  * a result of our exiting, and if they have any stopped jobs,
372  * send them a SIGHUP and then a SIGCONT. (POSIX 3.2.2.2)
373  */
374 static void
375 kill_orphaned_pgrp(struct task_struct *tsk, struct task_struct *parent)
376 {
377 	struct pid *pgrp = task_pgrp(tsk);
378 	struct task_struct *ignored_task = tsk;
379 
380 	if (!parent)
381 		/* exit: our father is in a different pgrp than
382 		 * we are and we were the only connection outside.
383 		 */
384 		parent = tsk->real_parent;
385 	else
386 		/* reparent: our child is in a different pgrp than
387 		 * we are, and it was the only connection outside.
388 		 */
389 		ignored_task = NULL;
390 
391 	if (task_pgrp(parent) != pgrp &&
392 	    task_session(parent) == task_session(tsk) &&
393 	    will_become_orphaned_pgrp(pgrp, ignored_task) &&
394 	    has_stopped_jobs(pgrp)) {
395 		__kill_pgrp_info(SIGHUP, SEND_SIG_PRIV, pgrp);
396 		__kill_pgrp_info(SIGCONT, SEND_SIG_PRIV, pgrp);
397 	}
398 }
399 
400 static void coredump_task_exit(struct task_struct *tsk)
401 {
402 	struct core_state *core_state;
403 
404 	/*
405 	 * Serialize with any possible pending coredump.
406 	 * We must hold siglock around checking core_state
407 	 * and setting PF_POSTCOREDUMP.  The core-inducing thread
408 	 * will increment ->nr_threads for each thread in the
409 	 * group without PF_POSTCOREDUMP set.
410 	 */
411 	spin_lock_irq(&tsk->sighand->siglock);
412 	tsk->flags |= PF_POSTCOREDUMP;
413 	core_state = tsk->signal->core_state;
414 	spin_unlock_irq(&tsk->sighand->siglock);
415 	if (core_state) {
416 		struct core_thread self;
417 
418 		self.task = current;
419 		if (self.task->flags & PF_SIGNALED)
420 			self.next = xchg(&core_state->dumper.next, &self);
421 		else
422 			self.task = NULL;
423 		/*
424 		 * Implies mb(), the result of xchg() must be visible
425 		 * to core_state->dumper.
426 		 */
427 		if (atomic_dec_and_test(&core_state->nr_threads))
428 			complete(&core_state->startup);
429 
430 		for (;;) {
431 			set_current_state(TASK_UNINTERRUPTIBLE|TASK_FREEZABLE);
432 			if (!self.task) /* see coredump_finish() */
433 				break;
434 			schedule();
435 		}
436 		__set_current_state(TASK_RUNNING);
437 	}
438 }
439 
440 #ifdef CONFIG_MEMCG
441 /* drops tasklist_lock if succeeds */
442 static bool __try_to_set_owner(struct task_struct *tsk, struct mm_struct *mm)
443 {
444 	bool ret = false;
445 
446 	task_lock(tsk);
447 	if (likely(tsk->mm == mm)) {
448 		/* tsk can't pass exit_mm/exec_mmap and exit */
449 		read_unlock(&tasklist_lock);
450 		WRITE_ONCE(mm->owner, tsk);
451 		lru_gen_migrate_mm(mm);
452 		ret = true;
453 	}
454 	task_unlock(tsk);
455 	return ret;
456 }
457 
458 static bool try_to_set_owner(struct task_struct *g, struct mm_struct *mm)
459 {
460 	struct task_struct *t;
461 
462 	for_each_thread(g, t) {
463 		struct mm_struct *t_mm = READ_ONCE(t->mm);
464 		if (t_mm == mm) {
465 			if (__try_to_set_owner(t, mm))
466 				return true;
467 		} else if (t_mm)
468 			break;
469 	}
470 
471 	return false;
472 }
473 
474 /*
475  * A task is exiting.   If it owned this mm, find a new owner for the mm.
476  */
477 void mm_update_next_owner(struct mm_struct *mm)
478 {
479 	struct task_struct *g, *p = current;
480 
481 	/*
482 	 * If the exiting or execing task is not the owner, it's
483 	 * someone else's problem.
484 	 */
485 	if (mm->owner != p)
486 		return;
487 	/*
488 	 * The current owner is exiting/execing and there are no other
489 	 * candidates.  Do not leave the mm pointing to a possibly
490 	 * freed task structure.
491 	 */
492 	if (atomic_read(&mm->mm_users) <= 1) {
493 		WRITE_ONCE(mm->owner, NULL);
494 		return;
495 	}
496 
497 	read_lock(&tasklist_lock);
498 	/*
499 	 * Search in the children
500 	 */
501 	list_for_each_entry(g, &p->children, sibling) {
502 		if (try_to_set_owner(g, mm))
503 			goto ret;
504 	}
505 	/*
506 	 * Search in the siblings
507 	 */
508 	list_for_each_entry(g, &p->real_parent->children, sibling) {
509 		if (try_to_set_owner(g, mm))
510 			goto ret;
511 	}
512 	/*
513 	 * Search through everything else, we should not get here often.
514 	 */
515 	for_each_process(g) {
516 		if (atomic_read(&mm->mm_users) <= 1)
517 			break;
518 		if (g->flags & PF_KTHREAD)
519 			continue;
520 		if (try_to_set_owner(g, mm))
521 			goto ret;
522 	}
523 	read_unlock(&tasklist_lock);
524 	/*
525 	 * We found no owner yet mm_users > 1: this implies that we are
526 	 * most likely racing with swapoff (try_to_unuse()) or /proc or
527 	 * ptrace or page migration (get_task_mm()).  Mark owner as NULL.
528 	 */
529 	WRITE_ONCE(mm->owner, NULL);
530  ret:
531 	return;
532 
533 }
534 #endif /* CONFIG_MEMCG */
535 
536 /*
537  * Turn us into a lazy TLB process if we
538  * aren't already..
539  */
540 static void exit_mm(void)
541 {
542 	struct mm_struct *mm = current->mm;
543 
544 	exit_mm_release(current, mm);
545 	if (!mm)
546 		return;
547 	mmap_read_lock(mm);
548 	mmgrab_lazy_tlb(mm);
549 	BUG_ON(mm != current->active_mm);
550 	/* more a memory barrier than a real lock */
551 	task_lock(current);
552 	/*
553 	 * When a thread stops operating on an address space, the loop
554 	 * in membarrier_private_expedited() may not observe that
555 	 * tsk->mm, and the loop in membarrier_global_expedited() may
556 	 * not observe a MEMBARRIER_STATE_GLOBAL_EXPEDITED
557 	 * rq->membarrier_state, so those would not issue an IPI.
558 	 * Membarrier requires a memory barrier after accessing
559 	 * user-space memory, before clearing tsk->mm or the
560 	 * rq->membarrier_state.
561 	 */
562 	smp_mb__after_spinlock();
563 	local_irq_disable();
564 	current->mm = NULL;
565 	membarrier_update_current_mm(NULL);
566 	enter_lazy_tlb(mm, current);
567 	local_irq_enable();
568 	task_unlock(current);
569 	mmap_read_unlock(mm);
570 	mm_update_next_owner(mm);
571 	mmput(mm);
572 	if (test_thread_flag(TIF_MEMDIE))
573 		exit_oom_victim();
574 }
575 
576 static struct task_struct *find_alive_thread(struct task_struct *p)
577 {
578 	struct task_struct *t;
579 
580 	for_each_thread(p, t) {
581 		if (!(t->flags & PF_EXITING))
582 			return t;
583 	}
584 	return NULL;
585 }
586 
587 static struct task_struct *find_child_reaper(struct task_struct *father,
588 						struct list_head *dead)
589 	__releases(&tasklist_lock)
590 	__acquires(&tasklist_lock)
591 {
592 	struct pid_namespace *pid_ns = task_active_pid_ns(father);
593 	struct task_struct *reaper = pid_ns->child_reaper;
594 	struct task_struct *p, *n;
595 
596 	if (likely(reaper != father))
597 		return reaper;
598 
599 	reaper = find_alive_thread(father);
600 	if (reaper) {
601 		pid_ns->child_reaper = reaper;
602 		return reaper;
603 	}
604 
605 	write_unlock_irq(&tasklist_lock);
606 
607 	list_for_each_entry_safe(p, n, dead, ptrace_entry) {
608 		list_del_init(&p->ptrace_entry);
609 		release_task(p);
610 	}
611 
612 	zap_pid_ns_processes(pid_ns);
613 	write_lock_irq(&tasklist_lock);
614 
615 	return father;
616 }
617 
618 /*
619  * When we die, we re-parent all our children, and try to:
620  * 1. give them to another thread in our thread group, if such a member exists
621  * 2. give it to the first ancestor process which prctl'd itself as a
622  *    child_subreaper for its children (like a service manager)
623  * 3. give it to the init process (PID 1) in our pid namespace
624  */
625 static struct task_struct *find_new_reaper(struct task_struct *father,
626 					   struct task_struct *child_reaper)
627 {
628 	struct task_struct *thread, *reaper;
629 
630 	thread = find_alive_thread(father);
631 	if (thread)
632 		return thread;
633 
634 	if (father->signal->has_child_subreaper) {
635 		unsigned int ns_level = task_pid(father)->level;
636 		/*
637 		 * Find the first ->is_child_subreaper ancestor in our pid_ns.
638 		 * We can't check reaper != child_reaper to ensure we do not
639 		 * cross the namespaces, the exiting parent could be injected
640 		 * by setns() + fork().
641 		 * We check pid->level, this is slightly more efficient than
642 		 * task_active_pid_ns(reaper) != task_active_pid_ns(father).
643 		 */
644 		for (reaper = father->real_parent;
645 		     task_pid(reaper)->level == ns_level;
646 		     reaper = reaper->real_parent) {
647 			if (reaper == &init_task)
648 				break;
649 			if (!reaper->signal->is_child_subreaper)
650 				continue;
651 			thread = find_alive_thread(reaper);
652 			if (thread)
653 				return thread;
654 		}
655 	}
656 
657 	return child_reaper;
658 }
659 
660 /*
661 * Any that need to be release_task'd are put on the @dead list.
662  */
663 static void reparent_leader(struct task_struct *father, struct task_struct *p,
664 				struct list_head *dead)
665 {
666 	if (unlikely(p->exit_state == EXIT_DEAD))
667 		return;
668 
669 	/* We don't want people slaying init. */
670 	p->exit_signal = SIGCHLD;
671 
672 	/* If it has exited notify the new parent about this child's death. */
673 	if (!p->ptrace &&
674 	    p->exit_state == EXIT_ZOMBIE && thread_group_empty(p)) {
675 		if (do_notify_parent(p, p->exit_signal)) {
676 			p->exit_state = EXIT_DEAD;
677 			list_add(&p->ptrace_entry, dead);
678 		}
679 	}
680 
681 	kill_orphaned_pgrp(p, father);
682 }
683 
684 /*
685  * This does two things:
686  *
687  * A.  Make init inherit all the child processes
688  * B.  Check to see if any process groups have become orphaned
689  *	as a result of our exiting, and if they have any stopped
690  *	jobs, send them a SIGHUP and then a SIGCONT.  (POSIX 3.2.2.2)
691  */
692 static void forget_original_parent(struct task_struct *father,
693 					struct list_head *dead)
694 {
695 	struct task_struct *p, *t, *reaper;
696 
697 	if (unlikely(!list_empty(&father->ptraced)))
698 		exit_ptrace(father, dead);
699 
700 	/* Can drop and reacquire tasklist_lock */
701 	reaper = find_child_reaper(father, dead);
702 	if (list_empty(&father->children))
703 		return;
704 
705 	reaper = find_new_reaper(father, reaper);
706 	list_for_each_entry(p, &father->children, sibling) {
707 		for_each_thread(p, t) {
708 			RCU_INIT_POINTER(t->real_parent, reaper);
709 			BUG_ON((!t->ptrace) != (rcu_access_pointer(t->parent) == father));
710 			if (likely(!t->ptrace))
711 				t->parent = t->real_parent;
712 			if (t->pdeath_signal)
713 				group_send_sig_info(t->pdeath_signal,
714 						    SEND_SIG_NOINFO, t,
715 						    PIDTYPE_TGID);
716 		}
717 		/*
718 		 * If this is a threaded reparent there is no need to
719 		 * notify anyone anything has happened.
720 		 */
721 		if (!same_thread_group(reaper, father))
722 			reparent_leader(father, p, dead);
723 	}
724 	list_splice_tail_init(&father->children, &reaper->children);
725 }
726 
727 /*
728  * Send signals to all our closest relatives so that they know
729  * to properly mourn us..
730  */
731 static void exit_notify(struct task_struct *tsk, int group_dead)
732 {
733 	bool autoreap;
734 	struct task_struct *p, *n;
735 	LIST_HEAD(dead);
736 
737 	write_lock_irq(&tasklist_lock);
738 	forget_original_parent(tsk, &dead);
739 
740 	if (group_dead)
741 		kill_orphaned_pgrp(tsk->group_leader, NULL);
742 
743 	tsk->exit_state = EXIT_ZOMBIE;
744 	/*
745 	 * sub-thread or delay_group_leader(), wake up the
746 	 * PIDFD_THREAD waiters.
747 	 */
748 	if (!thread_group_empty(tsk))
749 		do_notify_pidfd(tsk);
750 
751 	if (unlikely(tsk->ptrace)) {
752 		int sig = thread_group_leader(tsk) &&
753 				thread_group_empty(tsk) &&
754 				!ptrace_reparented(tsk) ?
755 			tsk->exit_signal : SIGCHLD;
756 		autoreap = do_notify_parent(tsk, sig);
757 	} else if (thread_group_leader(tsk)) {
758 		autoreap = thread_group_empty(tsk) &&
759 			do_notify_parent(tsk, tsk->exit_signal);
760 	} else {
761 		autoreap = true;
762 	}
763 
764 	if (autoreap) {
765 		tsk->exit_state = EXIT_DEAD;
766 		list_add(&tsk->ptrace_entry, &dead);
767 	}
768 
769 	/* mt-exec, de_thread() is waiting for group leader */
770 	if (unlikely(tsk->signal->notify_count < 0))
771 		wake_up_process(tsk->signal->group_exec_task);
772 	write_unlock_irq(&tasklist_lock);
773 
774 	list_for_each_entry_safe(p, n, &dead, ptrace_entry) {
775 		list_del_init(&p->ptrace_entry);
776 		release_task(p);
777 	}
778 }
779 
780 #ifdef CONFIG_DEBUG_STACK_USAGE
781 static void check_stack_usage(void)
782 {
783 	static DEFINE_SPINLOCK(low_water_lock);
784 	static int lowest_to_date = THREAD_SIZE;
785 	unsigned long free;
786 
787 	free = stack_not_used(current);
788 
789 	if (free >= lowest_to_date)
790 		return;
791 
792 	spin_lock(&low_water_lock);
793 	if (free < lowest_to_date) {
794 		pr_info("%s (%d) used greatest stack depth: %lu bytes left\n",
795 			current->comm, task_pid_nr(current), free);
796 		lowest_to_date = free;
797 	}
798 	spin_unlock(&low_water_lock);
799 }
800 #else
801 static inline void check_stack_usage(void) {}
802 #endif
803 
804 static void synchronize_group_exit(struct task_struct *tsk, long code)
805 {
806 	struct sighand_struct *sighand = tsk->sighand;
807 	struct signal_struct *signal = tsk->signal;
808 
809 	spin_lock_irq(&sighand->siglock);
810 	signal->quick_threads--;
811 	if ((signal->quick_threads == 0) &&
812 	    !(signal->flags & SIGNAL_GROUP_EXIT)) {
813 		signal->flags = SIGNAL_GROUP_EXIT;
814 		signal->group_exit_code = code;
815 		signal->group_stop_count = 0;
816 	}
817 	spin_unlock_irq(&sighand->siglock);
818 }
819 
820 void __noreturn do_exit(long code)
821 {
822 	struct task_struct *tsk = current;
823 	int group_dead;
824 
825 	WARN_ON(irqs_disabled());
826 
827 	synchronize_group_exit(tsk, code);
828 
829 	WARN_ON(tsk->plug);
830 
831 	kcov_task_exit(tsk);
832 	kmsan_task_exit(tsk);
833 
834 	coredump_task_exit(tsk);
835 	ptrace_event(PTRACE_EVENT_EXIT, code);
836 	user_events_exit(tsk);
837 
838 	io_uring_files_cancel();
839 	exit_signals(tsk);  /* sets PF_EXITING */
840 
841 	seccomp_filter_release(tsk);
842 
843 	acct_update_integrals(tsk);
844 	group_dead = atomic_dec_and_test(&tsk->signal->live);
845 	if (group_dead) {
846 		/*
847 		 * If the last thread of global init has exited, panic
848 		 * immediately to get a useable coredump.
849 		 */
850 		if (unlikely(is_global_init(tsk)))
851 			panic("Attempted to kill init! exitcode=0x%08x\n",
852 				tsk->signal->group_exit_code ?: (int)code);
853 
854 #ifdef CONFIG_POSIX_TIMERS
855 		hrtimer_cancel(&tsk->signal->real_timer);
856 		exit_itimers(tsk);
857 #endif
858 		if (tsk->mm)
859 			setmax_mm_hiwater_rss(&tsk->signal->maxrss, tsk->mm);
860 	}
861 	acct_collect(code, group_dead);
862 	if (group_dead)
863 		tty_audit_exit();
864 	audit_free(tsk);
865 
866 	tsk->exit_code = code;
867 	taskstats_exit(tsk, group_dead);
868 
869 	exit_mm();
870 
871 	if (group_dead)
872 		acct_process();
873 	trace_sched_process_exit(tsk);
874 
875 	exit_sem(tsk);
876 	exit_shm(tsk);
877 	exit_files(tsk);
878 	exit_fs(tsk);
879 	if (group_dead)
880 		disassociate_ctty(1);
881 	exit_task_namespaces(tsk);
882 	exit_task_work(tsk);
883 	exit_thread(tsk);
884 
885 	/*
886 	 * Flush inherited counters to the parent - before the parent
887 	 * gets woken up by child-exit notifications.
888 	 *
889 	 * because of cgroup mode, must be called before cgroup_exit()
890 	 */
891 	perf_event_exit_task(tsk);
892 
893 	sched_autogroup_exit_task(tsk);
894 	cgroup_exit(tsk);
895 
896 	/*
897 	 * FIXME: do that only when needed, using sched_exit tracepoint
898 	 */
899 	flush_ptrace_hw_breakpoint(tsk);
900 
901 	exit_tasks_rcu_start();
902 	exit_notify(tsk, group_dead);
903 	proc_exit_connector(tsk);
904 	mpol_put_task_policy(tsk);
905 #ifdef CONFIG_FUTEX
906 	if (unlikely(current->pi_state_cache))
907 		kfree(current->pi_state_cache);
908 #endif
909 	/*
910 	 * Make sure we are holding no locks:
911 	 */
912 	debug_check_no_locks_held();
913 
914 	if (tsk->io_context)
915 		exit_io_context(tsk);
916 
917 	if (tsk->splice_pipe)
918 		free_pipe_info(tsk->splice_pipe);
919 
920 	if (tsk->task_frag.page)
921 		put_page(tsk->task_frag.page);
922 
923 	exit_task_stack_account(tsk);
924 
925 	check_stack_usage();
926 	preempt_disable();
927 	if (tsk->nr_dirtied)
928 		__this_cpu_add(dirty_throttle_leaks, tsk->nr_dirtied);
929 	exit_rcu();
930 	exit_tasks_rcu_finish();
931 
932 	lockdep_free_task(tsk);
933 	do_task_dead();
934 }
935 
936 void __noreturn make_task_dead(int signr)
937 {
938 	/*
939 	 * Take the task off the cpu after something catastrophic has
940 	 * happened.
941 	 *
942 	 * We can get here from a kernel oops, sometimes with preemption off.
943 	 * Start by checking for critical errors.
944 	 * Then fix up important state like USER_DS and preemption.
945 	 * Then do everything else.
946 	 */
947 	struct task_struct *tsk = current;
948 	unsigned int limit;
949 
950 	if (unlikely(in_interrupt()))
951 		panic("Aiee, killing interrupt handler!");
952 	if (unlikely(!tsk->pid))
953 		panic("Attempted to kill the idle task!");
954 
955 	if (unlikely(irqs_disabled())) {
956 		pr_info("note: %s[%d] exited with irqs disabled\n",
957 			current->comm, task_pid_nr(current));
958 		local_irq_enable();
959 	}
960 	if (unlikely(in_atomic())) {
961 		pr_info("note: %s[%d] exited with preempt_count %d\n",
962 			current->comm, task_pid_nr(current),
963 			preempt_count());
964 		preempt_count_set(PREEMPT_ENABLED);
965 	}
966 
967 	/*
968 	 * Every time the system oopses, if the oops happens while a reference
969 	 * to an object was held, the reference leaks.
970 	 * If the oops doesn't also leak memory, repeated oopsing can cause
971 	 * reference counters to wrap around (if they're not using refcount_t).
972 	 * This means that repeated oopsing can make unexploitable-looking bugs
973 	 * exploitable through repeated oopsing.
974 	 * To make sure this can't happen, place an upper bound on how often the
975 	 * kernel may oops without panic().
976 	 */
977 	limit = READ_ONCE(oops_limit);
978 	if (atomic_inc_return(&oops_count) >= limit && limit)
979 		panic("Oopsed too often (kernel.oops_limit is %d)", limit);
980 
981 	/*
982 	 * We're taking recursive faults here in make_task_dead. Safest is to just
983 	 * leave this task alone and wait for reboot.
984 	 */
985 	if (unlikely(tsk->flags & PF_EXITING)) {
986 		pr_alert("Fixing recursive fault but reboot is needed!\n");
987 		futex_exit_recursive(tsk);
988 		tsk->exit_state = EXIT_DEAD;
989 		refcount_inc(&tsk->rcu_users);
990 		do_task_dead();
991 	}
992 
993 	do_exit(signr);
994 }
995 
996 SYSCALL_DEFINE1(exit, int, error_code)
997 {
998 	do_exit((error_code&0xff)<<8);
999 }
1000 
1001 /*
1002  * Take down every thread in the group.  This is called by fatal signals
1003  * as well as by sys_exit_group (below).
1004  */
1005 void __noreturn
1006 do_group_exit(int exit_code)
1007 {
1008 	struct signal_struct *sig = current->signal;
1009 
1010 	if (sig->flags & SIGNAL_GROUP_EXIT)
1011 		exit_code = sig->group_exit_code;
1012 	else if (sig->group_exec_task)
1013 		exit_code = 0;
1014 	else {
1015 		struct sighand_struct *const sighand = current->sighand;
1016 
1017 		spin_lock_irq(&sighand->siglock);
1018 		if (sig->flags & SIGNAL_GROUP_EXIT)
1019 			/* Another thread got here before we took the lock.  */
1020 			exit_code = sig->group_exit_code;
1021 		else if (sig->group_exec_task)
1022 			exit_code = 0;
1023 		else {
1024 			sig->group_exit_code = exit_code;
1025 			sig->flags = SIGNAL_GROUP_EXIT;
1026 			zap_other_threads(current);
1027 		}
1028 		spin_unlock_irq(&sighand->siglock);
1029 	}
1030 
1031 	do_exit(exit_code);
1032 	/* NOTREACHED */
1033 }
1034 
1035 /*
1036  * this kills every thread in the thread group. Note that any externally
1037  * wait4()-ing process will get the correct exit code - even if this
1038  * thread is not the thread group leader.
1039  */
1040 SYSCALL_DEFINE1(exit_group, int, error_code)
1041 {
1042 	do_group_exit((error_code & 0xff) << 8);
1043 	/* NOTREACHED */
1044 	return 0;
1045 }
1046 
1047 static int eligible_pid(struct wait_opts *wo, struct task_struct *p)
1048 {
1049 	return	wo->wo_type == PIDTYPE_MAX ||
1050 		task_pid_type(p, wo->wo_type) == wo->wo_pid;
1051 }
1052 
1053 static int
1054 eligible_child(struct wait_opts *wo, bool ptrace, struct task_struct *p)
1055 {
1056 	if (!eligible_pid(wo, p))
1057 		return 0;
1058 
1059 	/*
1060 	 * Wait for all children (clone and not) if __WALL is set or
1061 	 * if it is traced by us.
1062 	 */
1063 	if (ptrace || (wo->wo_flags & __WALL))
1064 		return 1;
1065 
1066 	/*
1067 	 * Otherwise, wait for clone children *only* if __WCLONE is set;
1068 	 * otherwise, wait for non-clone children *only*.
1069 	 *
1070 	 * Note: a "clone" child here is one that reports to its parent
1071 	 * using a signal other than SIGCHLD, or a non-leader thread which
1072 	 * we can only see if it is traced by us.
1073 	 */
1074 	if ((p->exit_signal != SIGCHLD) ^ !!(wo->wo_flags & __WCLONE))
1075 		return 0;
1076 
1077 	return 1;
1078 }
1079 
1080 /*
1081  * Handle sys_wait4 work for one task in state EXIT_ZOMBIE.  We hold
1082  * read_lock(&tasklist_lock) on entry.  If we return zero, we still hold
1083  * the lock and this task is uninteresting.  If we return nonzero, we have
1084  * released the lock and the system call should return.
1085  */
1086 static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p)
1087 {
1088 	int state, status;
1089 	pid_t pid = task_pid_vnr(p);
1090 	uid_t uid = from_kuid_munged(current_user_ns(), task_uid(p));
1091 	struct waitid_info *infop;
1092 
1093 	if (!likely(wo->wo_flags & WEXITED))
1094 		return 0;
1095 
1096 	if (unlikely(wo->wo_flags & WNOWAIT)) {
1097 		status = (p->signal->flags & SIGNAL_GROUP_EXIT)
1098 			? p->signal->group_exit_code : p->exit_code;
1099 		get_task_struct(p);
1100 		read_unlock(&tasklist_lock);
1101 		sched_annotate_sleep();
1102 		if (wo->wo_rusage)
1103 			getrusage(p, RUSAGE_BOTH, wo->wo_rusage);
1104 		put_task_struct(p);
1105 		goto out_info;
1106 	}
1107 	/*
1108 	 * Move the task's state to DEAD/TRACE, only one thread can do this.
1109 	 */
1110 	state = (ptrace_reparented(p) && thread_group_leader(p)) ?
1111 		EXIT_TRACE : EXIT_DEAD;
1112 	if (cmpxchg(&p->exit_state, EXIT_ZOMBIE, state) != EXIT_ZOMBIE)
1113 		return 0;
1114 	/*
1115 	 * We own this thread, nobody else can reap it.
1116 	 */
1117 	read_unlock(&tasklist_lock);
1118 	sched_annotate_sleep();
1119 
1120 	/*
1121 	 * Check thread_group_leader() to exclude the traced sub-threads.
1122 	 */
1123 	if (state == EXIT_DEAD && thread_group_leader(p)) {
1124 		struct signal_struct *sig = p->signal;
1125 		struct signal_struct *psig = current->signal;
1126 		unsigned long maxrss;
1127 		u64 tgutime, tgstime;
1128 
1129 		/*
1130 		 * The resource counters for the group leader are in its
1131 		 * own task_struct.  Those for dead threads in the group
1132 		 * are in its signal_struct, as are those for the child
1133 		 * processes it has previously reaped.  All these
1134 		 * accumulate in the parent's signal_struct c* fields.
1135 		 *
1136 		 * We don't bother to take a lock here to protect these
1137 		 * p->signal fields because the whole thread group is dead
1138 		 * and nobody can change them.
1139 		 *
1140 		 * psig->stats_lock also protects us from our sub-threads
1141 		 * which can reap other children at the same time.
1142 		 *
1143 		 * We use thread_group_cputime_adjusted() to get times for
1144 		 * the thread group, which consolidates times for all threads
1145 		 * in the group including the group leader.
1146 		 */
1147 		thread_group_cputime_adjusted(p, &tgutime, &tgstime);
1148 		write_seqlock_irq(&psig->stats_lock);
1149 		psig->cutime += tgutime + sig->cutime;
1150 		psig->cstime += tgstime + sig->cstime;
1151 		psig->cgtime += task_gtime(p) + sig->gtime + sig->cgtime;
1152 		psig->cmin_flt +=
1153 			p->min_flt + sig->min_flt + sig->cmin_flt;
1154 		psig->cmaj_flt +=
1155 			p->maj_flt + sig->maj_flt + sig->cmaj_flt;
1156 		psig->cnvcsw +=
1157 			p->nvcsw + sig->nvcsw + sig->cnvcsw;
1158 		psig->cnivcsw +=
1159 			p->nivcsw + sig->nivcsw + sig->cnivcsw;
1160 		psig->cinblock +=
1161 			task_io_get_inblock(p) +
1162 			sig->inblock + sig->cinblock;
1163 		psig->coublock +=
1164 			task_io_get_oublock(p) +
1165 			sig->oublock + sig->coublock;
1166 		maxrss = max(sig->maxrss, sig->cmaxrss);
1167 		if (psig->cmaxrss < maxrss)
1168 			psig->cmaxrss = maxrss;
1169 		task_io_accounting_add(&psig->ioac, &p->ioac);
1170 		task_io_accounting_add(&psig->ioac, &sig->ioac);
1171 		write_sequnlock_irq(&psig->stats_lock);
1172 	}
1173 
1174 	if (wo->wo_rusage)
1175 		getrusage(p, RUSAGE_BOTH, wo->wo_rusage);
1176 	status = (p->signal->flags & SIGNAL_GROUP_EXIT)
1177 		? p->signal->group_exit_code : p->exit_code;
1178 	wo->wo_stat = status;
1179 
1180 	if (state == EXIT_TRACE) {
1181 		write_lock_irq(&tasklist_lock);
1182 		/* We dropped tasklist, ptracer could die and untrace */
1183 		ptrace_unlink(p);
1184 
1185 		/* If parent wants a zombie, don't release it now */
1186 		state = EXIT_ZOMBIE;
1187 		if (do_notify_parent(p, p->exit_signal))
1188 			state = EXIT_DEAD;
1189 		p->exit_state = state;
1190 		write_unlock_irq(&tasklist_lock);
1191 	}
1192 	if (state == EXIT_DEAD)
1193 		release_task(p);
1194 
1195 out_info:
1196 	infop = wo->wo_info;
1197 	if (infop) {
1198 		if ((status & 0x7f) == 0) {
1199 			infop->cause = CLD_EXITED;
1200 			infop->status = status >> 8;
1201 		} else {
1202 			infop->cause = (status & 0x80) ? CLD_DUMPED : CLD_KILLED;
1203 			infop->status = status & 0x7f;
1204 		}
1205 		infop->pid = pid;
1206 		infop->uid = uid;
1207 	}
1208 
1209 	return pid;
1210 }
1211 
1212 static int *task_stopped_code(struct task_struct *p, bool ptrace)
1213 {
1214 	if (ptrace) {
1215 		if (task_is_traced(p) && !(p->jobctl & JOBCTL_LISTENING))
1216 			return &p->exit_code;
1217 	} else {
1218 		if (p->signal->flags & SIGNAL_STOP_STOPPED)
1219 			return &p->signal->group_exit_code;
1220 	}
1221 	return NULL;
1222 }
1223 
1224 /**
1225  * wait_task_stopped - Wait for %TASK_STOPPED or %TASK_TRACED
1226  * @wo: wait options
1227  * @ptrace: is the wait for ptrace
1228  * @p: task to wait for
1229  *
1230  * Handle sys_wait4() work for %p in state %TASK_STOPPED or %TASK_TRACED.
1231  *
1232  * CONTEXT:
1233  * read_lock(&tasklist_lock), which is released if return value is
1234  * non-zero.  Also, grabs and releases @p->sighand->siglock.
1235  *
1236  * RETURNS:
1237  * 0 if wait condition didn't exist and search for other wait conditions
1238  * should continue.  Non-zero return, -errno on failure and @p's pid on
1239  * success, implies that tasklist_lock is released and wait condition
1240  * search should terminate.
1241  */
1242 static int wait_task_stopped(struct wait_opts *wo,
1243 				int ptrace, struct task_struct *p)
1244 {
1245 	struct waitid_info *infop;
1246 	int exit_code, *p_code, why;
1247 	uid_t uid = 0; /* unneeded, required by compiler */
1248 	pid_t pid;
1249 
1250 	/*
1251 	 * Traditionally we see ptrace'd stopped tasks regardless of options.
1252 	 */
1253 	if (!ptrace && !(wo->wo_flags & WUNTRACED))
1254 		return 0;
1255 
1256 	if (!task_stopped_code(p, ptrace))
1257 		return 0;
1258 
1259 	exit_code = 0;
1260 	spin_lock_irq(&p->sighand->siglock);
1261 
1262 	p_code = task_stopped_code(p, ptrace);
1263 	if (unlikely(!p_code))
1264 		goto unlock_sig;
1265 
1266 	exit_code = *p_code;
1267 	if (!exit_code)
1268 		goto unlock_sig;
1269 
1270 	if (!unlikely(wo->wo_flags & WNOWAIT))
1271 		*p_code = 0;
1272 
1273 	uid = from_kuid_munged(current_user_ns(), task_uid(p));
1274 unlock_sig:
1275 	spin_unlock_irq(&p->sighand->siglock);
1276 	if (!exit_code)
1277 		return 0;
1278 
1279 	/*
1280 	 * Now we are pretty sure this task is interesting.
1281 	 * Make sure it doesn't get reaped out from under us while we
1282 	 * give up the lock and then examine it below.  We don't want to
1283 	 * keep holding onto the tasklist_lock while we call getrusage and
1284 	 * possibly take page faults for user memory.
1285 	 */
1286 	get_task_struct(p);
1287 	pid = task_pid_vnr(p);
1288 	why = ptrace ? CLD_TRAPPED : CLD_STOPPED;
1289 	read_unlock(&tasklist_lock);
1290 	sched_annotate_sleep();
1291 	if (wo->wo_rusage)
1292 		getrusage(p, RUSAGE_BOTH, wo->wo_rusage);
1293 	put_task_struct(p);
1294 
1295 	if (likely(!(wo->wo_flags & WNOWAIT)))
1296 		wo->wo_stat = (exit_code << 8) | 0x7f;
1297 
1298 	infop = wo->wo_info;
1299 	if (infop) {
1300 		infop->cause = why;
1301 		infop->status = exit_code;
1302 		infop->pid = pid;
1303 		infop->uid = uid;
1304 	}
1305 	return pid;
1306 }
1307 
1308 /*
1309  * Handle do_wait work for one task in a live, non-stopped state.
1310  * read_lock(&tasklist_lock) on entry.  If we return zero, we still hold
1311  * the lock and this task is uninteresting.  If we return nonzero, we have
1312  * released the lock and the system call should return.
1313  */
1314 static int wait_task_continued(struct wait_opts *wo, struct task_struct *p)
1315 {
1316 	struct waitid_info *infop;
1317 	pid_t pid;
1318 	uid_t uid;
1319 
1320 	if (!unlikely(wo->wo_flags & WCONTINUED))
1321 		return 0;
1322 
1323 	if (!(p->signal->flags & SIGNAL_STOP_CONTINUED))
1324 		return 0;
1325 
1326 	spin_lock_irq(&p->sighand->siglock);
1327 	/* Re-check with the lock held.  */
1328 	if (!(p->signal->flags & SIGNAL_STOP_CONTINUED)) {
1329 		spin_unlock_irq(&p->sighand->siglock);
1330 		return 0;
1331 	}
1332 	if (!unlikely(wo->wo_flags & WNOWAIT))
1333 		p->signal->flags &= ~SIGNAL_STOP_CONTINUED;
1334 	uid = from_kuid_munged(current_user_ns(), task_uid(p));
1335 	spin_unlock_irq(&p->sighand->siglock);
1336 
1337 	pid = task_pid_vnr(p);
1338 	get_task_struct(p);
1339 	read_unlock(&tasklist_lock);
1340 	sched_annotate_sleep();
1341 	if (wo->wo_rusage)
1342 		getrusage(p, RUSAGE_BOTH, wo->wo_rusage);
1343 	put_task_struct(p);
1344 
1345 	infop = wo->wo_info;
1346 	if (!infop) {
1347 		wo->wo_stat = 0xffff;
1348 	} else {
1349 		infop->cause = CLD_CONTINUED;
1350 		infop->pid = pid;
1351 		infop->uid = uid;
1352 		infop->status = SIGCONT;
1353 	}
1354 	return pid;
1355 }
1356 
1357 /*
1358  * Consider @p for a wait by @parent.
1359  *
1360  * -ECHILD should be in ->notask_error before the first call.
1361  * Returns nonzero for a final return, when we have unlocked tasklist_lock.
1362  * Returns zero if the search for a child should continue;
1363  * then ->notask_error is 0 if @p is an eligible child,
1364  * or still -ECHILD.
1365  */
1366 static int wait_consider_task(struct wait_opts *wo, int ptrace,
1367 				struct task_struct *p)
1368 {
1369 	/*
1370 	 * We can race with wait_task_zombie() from another thread.
1371 	 * Ensure that EXIT_ZOMBIE -> EXIT_DEAD/EXIT_TRACE transition
1372 	 * can't confuse the checks below.
1373 	 */
1374 	int exit_state = READ_ONCE(p->exit_state);
1375 	int ret;
1376 
1377 	if (unlikely(exit_state == EXIT_DEAD))
1378 		return 0;
1379 
1380 	ret = eligible_child(wo, ptrace, p);
1381 	if (!ret)
1382 		return ret;
1383 
1384 	if (unlikely(exit_state == EXIT_TRACE)) {
1385 		/*
1386 		 * ptrace == 0 means we are the natural parent. In this case
1387 		 * we should clear notask_error, debugger will notify us.
1388 		 */
1389 		if (likely(!ptrace))
1390 			wo->notask_error = 0;
1391 		return 0;
1392 	}
1393 
1394 	if (likely(!ptrace) && unlikely(p->ptrace)) {
1395 		/*
1396 		 * If it is traced by its real parent's group, just pretend
1397 		 * the caller is ptrace_do_wait() and reap this child if it
1398 		 * is zombie.
1399 		 *
1400 		 * This also hides group stop state from real parent; otherwise
1401 		 * a single stop can be reported twice as group and ptrace stop.
1402 		 * If a ptracer wants to distinguish these two events for its
1403 		 * own children it should create a separate process which takes
1404 		 * the role of real parent.
1405 		 */
1406 		if (!ptrace_reparented(p))
1407 			ptrace = 1;
1408 	}
1409 
1410 	/* slay zombie? */
1411 	if (exit_state == EXIT_ZOMBIE) {
1412 		/* we don't reap group leaders with subthreads */
1413 		if (!delay_group_leader(p)) {
1414 			/*
1415 			 * A zombie ptracee is only visible to its ptracer.
1416 			 * Notification and reaping will be cascaded to the
1417 			 * real parent when the ptracer detaches.
1418 			 */
1419 			if (unlikely(ptrace) || likely(!p->ptrace))
1420 				return wait_task_zombie(wo, p);
1421 		}
1422 
1423 		/*
1424 		 * Allow access to stopped/continued state via zombie by
1425 		 * falling through.  Clearing of notask_error is complex.
1426 		 *
1427 		 * When !@ptrace:
1428 		 *
1429 		 * If WEXITED is set, notask_error should naturally be
1430 		 * cleared.  If not, subset of WSTOPPED|WCONTINUED is set,
1431 		 * so, if there are live subthreads, there are events to
1432 		 * wait for.  If all subthreads are dead, it's still safe
1433 		 * to clear - this function will be called again in finite
1434 		 * amount time once all the subthreads are released and
1435 		 * will then return without clearing.
1436 		 *
1437 		 * When @ptrace:
1438 		 *
1439 		 * Stopped state is per-task and thus can't change once the
1440 		 * target task dies.  Only continued and exited can happen.
1441 		 * Clear notask_error if WCONTINUED | WEXITED.
1442 		 */
1443 		if (likely(!ptrace) || (wo->wo_flags & (WCONTINUED | WEXITED)))
1444 			wo->notask_error = 0;
1445 	} else {
1446 		/*
1447 		 * @p is alive and it's gonna stop, continue or exit, so
1448 		 * there always is something to wait for.
1449 		 */
1450 		wo->notask_error = 0;
1451 	}
1452 
1453 	/*
1454 	 * Wait for stopped.  Depending on @ptrace, different stopped state
1455 	 * is used and the two don't interact with each other.
1456 	 */
1457 	ret = wait_task_stopped(wo, ptrace, p);
1458 	if (ret)
1459 		return ret;
1460 
1461 	/*
1462 	 * Wait for continued.  There's only one continued state and the
1463 	 * ptracer can consume it which can confuse the real parent.  Don't
1464 	 * use WCONTINUED from ptracer.  You don't need or want it.
1465 	 */
1466 	return wait_task_continued(wo, p);
1467 }
1468 
1469 /*
1470  * Do the work of do_wait() for one thread in the group, @tsk.
1471  *
1472  * -ECHILD should be in ->notask_error before the first call.
1473  * Returns nonzero for a final return, when we have unlocked tasklist_lock.
1474  * Returns zero if the search for a child should continue; then
1475  * ->notask_error is 0 if there were any eligible children,
1476  * or still -ECHILD.
1477  */
1478 static int do_wait_thread(struct wait_opts *wo, struct task_struct *tsk)
1479 {
1480 	struct task_struct *p;
1481 
1482 	list_for_each_entry(p, &tsk->children, sibling) {
1483 		int ret = wait_consider_task(wo, 0, p);
1484 
1485 		if (ret)
1486 			return ret;
1487 	}
1488 
1489 	return 0;
1490 }
1491 
1492 static int ptrace_do_wait(struct wait_opts *wo, struct task_struct *tsk)
1493 {
1494 	struct task_struct *p;
1495 
1496 	list_for_each_entry(p, &tsk->ptraced, ptrace_entry) {
1497 		int ret = wait_consider_task(wo, 1, p);
1498 
1499 		if (ret)
1500 			return ret;
1501 	}
1502 
1503 	return 0;
1504 }
1505 
1506 bool pid_child_should_wake(struct wait_opts *wo, struct task_struct *p)
1507 {
1508 	if (!eligible_pid(wo, p))
1509 		return false;
1510 
1511 	if ((wo->wo_flags & __WNOTHREAD) && wo->child_wait.private != p->parent)
1512 		return false;
1513 
1514 	return true;
1515 }
1516 
1517 static int child_wait_callback(wait_queue_entry_t *wait, unsigned mode,
1518 				int sync, void *key)
1519 {
1520 	struct wait_opts *wo = container_of(wait, struct wait_opts,
1521 						child_wait);
1522 	struct task_struct *p = key;
1523 
1524 	if (pid_child_should_wake(wo, p))
1525 		return default_wake_function(wait, mode, sync, key);
1526 
1527 	return 0;
1528 }
1529 
1530 void __wake_up_parent(struct task_struct *p, struct task_struct *parent)
1531 {
1532 	__wake_up_sync_key(&parent->signal->wait_chldexit,
1533 			   TASK_INTERRUPTIBLE, p);
1534 }
1535 
1536 static bool is_effectively_child(struct wait_opts *wo, bool ptrace,
1537 				 struct task_struct *target)
1538 {
1539 	struct task_struct *parent =
1540 		!ptrace ? target->real_parent : target->parent;
1541 
1542 	return current == parent || (!(wo->wo_flags & __WNOTHREAD) &&
1543 				     same_thread_group(current, parent));
1544 }
1545 
1546 /*
1547  * Optimization for waiting on PIDTYPE_PID. No need to iterate through child
1548  * and tracee lists to find the target task.
1549  */
1550 static int do_wait_pid(struct wait_opts *wo)
1551 {
1552 	bool ptrace;
1553 	struct task_struct *target;
1554 	int retval;
1555 
1556 	ptrace = false;
1557 	target = pid_task(wo->wo_pid, PIDTYPE_TGID);
1558 	if (target && is_effectively_child(wo, ptrace, target)) {
1559 		retval = wait_consider_task(wo, ptrace, target);
1560 		if (retval)
1561 			return retval;
1562 	}
1563 
1564 	ptrace = true;
1565 	target = pid_task(wo->wo_pid, PIDTYPE_PID);
1566 	if (target && target->ptrace &&
1567 	    is_effectively_child(wo, ptrace, target)) {
1568 		retval = wait_consider_task(wo, ptrace, target);
1569 		if (retval)
1570 			return retval;
1571 	}
1572 
1573 	return 0;
1574 }
1575 
1576 long __do_wait(struct wait_opts *wo)
1577 {
1578 	long retval;
1579 
1580 	/*
1581 	 * If there is nothing that can match our criteria, just get out.
1582 	 * We will clear ->notask_error to zero if we see any child that
1583 	 * might later match our criteria, even if we are not able to reap
1584 	 * it yet.
1585 	 */
1586 	wo->notask_error = -ECHILD;
1587 	if ((wo->wo_type < PIDTYPE_MAX) &&
1588 	   (!wo->wo_pid || !pid_has_task(wo->wo_pid, wo->wo_type)))
1589 		goto notask;
1590 
1591 	read_lock(&tasklist_lock);
1592 
1593 	if (wo->wo_type == PIDTYPE_PID) {
1594 		retval = do_wait_pid(wo);
1595 		if (retval)
1596 			return retval;
1597 	} else {
1598 		struct task_struct *tsk = current;
1599 
1600 		do {
1601 			retval = do_wait_thread(wo, tsk);
1602 			if (retval)
1603 				return retval;
1604 
1605 			retval = ptrace_do_wait(wo, tsk);
1606 			if (retval)
1607 				return retval;
1608 
1609 			if (wo->wo_flags & __WNOTHREAD)
1610 				break;
1611 		} while_each_thread(current, tsk);
1612 	}
1613 	read_unlock(&tasklist_lock);
1614 
1615 notask:
1616 	retval = wo->notask_error;
1617 	if (!retval && !(wo->wo_flags & WNOHANG))
1618 		return -ERESTARTSYS;
1619 
1620 	return retval;
1621 }
1622 
1623 static long do_wait(struct wait_opts *wo)
1624 {
1625 	int retval;
1626 
1627 	trace_sched_process_wait(wo->wo_pid);
1628 
1629 	init_waitqueue_func_entry(&wo->child_wait, child_wait_callback);
1630 	wo->child_wait.private = current;
1631 	add_wait_queue(&current->signal->wait_chldexit, &wo->child_wait);
1632 
1633 	do {
1634 		set_current_state(TASK_INTERRUPTIBLE);
1635 		retval = __do_wait(wo);
1636 		if (retval != -ERESTARTSYS)
1637 			break;
1638 		if (signal_pending(current))
1639 			break;
1640 		schedule();
1641 	} while (1);
1642 
1643 	__set_current_state(TASK_RUNNING);
1644 	remove_wait_queue(&current->signal->wait_chldexit, &wo->child_wait);
1645 	return retval;
1646 }
1647 
1648 int kernel_waitid_prepare(struct wait_opts *wo, int which, pid_t upid,
1649 			  struct waitid_info *infop, int options,
1650 			  struct rusage *ru)
1651 {
1652 	unsigned int f_flags = 0;
1653 	struct pid *pid = NULL;
1654 	enum pid_type type;
1655 
1656 	if (options & ~(WNOHANG|WNOWAIT|WEXITED|WSTOPPED|WCONTINUED|
1657 			__WNOTHREAD|__WCLONE|__WALL))
1658 		return -EINVAL;
1659 	if (!(options & (WEXITED|WSTOPPED|WCONTINUED)))
1660 		return -EINVAL;
1661 
1662 	switch (which) {
1663 	case P_ALL:
1664 		type = PIDTYPE_MAX;
1665 		break;
1666 	case P_PID:
1667 		type = PIDTYPE_PID;
1668 		if (upid <= 0)
1669 			return -EINVAL;
1670 
1671 		pid = find_get_pid(upid);
1672 		break;
1673 	case P_PGID:
1674 		type = PIDTYPE_PGID;
1675 		if (upid < 0)
1676 			return -EINVAL;
1677 
1678 		if (upid)
1679 			pid = find_get_pid(upid);
1680 		else
1681 			pid = get_task_pid(current, PIDTYPE_PGID);
1682 		break;
1683 	case P_PIDFD:
1684 		type = PIDTYPE_PID;
1685 		if (upid < 0)
1686 			return -EINVAL;
1687 
1688 		pid = pidfd_get_pid(upid, &f_flags);
1689 		if (IS_ERR(pid))
1690 			return PTR_ERR(pid);
1691 
1692 		break;
1693 	default:
1694 		return -EINVAL;
1695 	}
1696 
1697 	wo->wo_type	= type;
1698 	wo->wo_pid	= pid;
1699 	wo->wo_flags	= options;
1700 	wo->wo_info	= infop;
1701 	wo->wo_rusage	= ru;
1702 	if (f_flags & O_NONBLOCK)
1703 		wo->wo_flags |= WNOHANG;
1704 
1705 	return 0;
1706 }
1707 
1708 static long kernel_waitid(int which, pid_t upid, struct waitid_info *infop,
1709 			  int options, struct rusage *ru)
1710 {
1711 	struct wait_opts wo;
1712 	long ret;
1713 
1714 	ret = kernel_waitid_prepare(&wo, which, upid, infop, options, ru);
1715 	if (ret)
1716 		return ret;
1717 
1718 	ret = do_wait(&wo);
1719 	if (!ret && !(options & WNOHANG) && (wo.wo_flags & WNOHANG))
1720 		ret = -EAGAIN;
1721 
1722 	put_pid(wo.wo_pid);
1723 	return ret;
1724 }
1725 
1726 SYSCALL_DEFINE5(waitid, int, which, pid_t, upid, struct siginfo __user *,
1727 		infop, int, options, struct rusage __user *, ru)
1728 {
1729 	struct rusage r;
1730 	struct waitid_info info = {.status = 0};
1731 	long err = kernel_waitid(which, upid, &info, options, ru ? &r : NULL);
1732 	int signo = 0;
1733 
1734 	if (err > 0) {
1735 		signo = SIGCHLD;
1736 		err = 0;
1737 		if (ru && copy_to_user(ru, &r, sizeof(struct rusage)))
1738 			return -EFAULT;
1739 	}
1740 	if (!infop)
1741 		return err;
1742 
1743 	if (!user_write_access_begin(infop, sizeof(*infop)))
1744 		return -EFAULT;
1745 
1746 	unsafe_put_user(signo, &infop->si_signo, Efault);
1747 	unsafe_put_user(0, &infop->si_errno, Efault);
1748 	unsafe_put_user(info.cause, &infop->si_code, Efault);
1749 	unsafe_put_user(info.pid, &infop->si_pid, Efault);
1750 	unsafe_put_user(info.uid, &infop->si_uid, Efault);
1751 	unsafe_put_user(info.status, &infop->si_status, Efault);
1752 	user_write_access_end();
1753 	return err;
1754 Efault:
1755 	user_write_access_end();
1756 	return -EFAULT;
1757 }
1758 
1759 long kernel_wait4(pid_t upid, int __user *stat_addr, int options,
1760 		  struct rusage *ru)
1761 {
1762 	struct wait_opts wo;
1763 	struct pid *pid = NULL;
1764 	enum pid_type type;
1765 	long ret;
1766 
1767 	if (options & ~(WNOHANG|WUNTRACED|WCONTINUED|
1768 			__WNOTHREAD|__WCLONE|__WALL))
1769 		return -EINVAL;
1770 
1771 	/* -INT_MIN is not defined */
1772 	if (upid == INT_MIN)
1773 		return -ESRCH;
1774 
1775 	if (upid == -1)
1776 		type = PIDTYPE_MAX;
1777 	else if (upid < 0) {
1778 		type = PIDTYPE_PGID;
1779 		pid = find_get_pid(-upid);
1780 	} else if (upid == 0) {
1781 		type = PIDTYPE_PGID;
1782 		pid = get_task_pid(current, PIDTYPE_PGID);
1783 	} else /* upid > 0 */ {
1784 		type = PIDTYPE_PID;
1785 		pid = find_get_pid(upid);
1786 	}
1787 
1788 	wo.wo_type	= type;
1789 	wo.wo_pid	= pid;
1790 	wo.wo_flags	= options | WEXITED;
1791 	wo.wo_info	= NULL;
1792 	wo.wo_stat	= 0;
1793 	wo.wo_rusage	= ru;
1794 	ret = do_wait(&wo);
1795 	put_pid(pid);
1796 	if (ret > 0 && stat_addr && put_user(wo.wo_stat, stat_addr))
1797 		ret = -EFAULT;
1798 
1799 	return ret;
1800 }
1801 
1802 int kernel_wait(pid_t pid, int *stat)
1803 {
1804 	struct wait_opts wo = {
1805 		.wo_type	= PIDTYPE_PID,
1806 		.wo_pid		= find_get_pid(pid),
1807 		.wo_flags	= WEXITED,
1808 	};
1809 	int ret;
1810 
1811 	ret = do_wait(&wo);
1812 	if (ret > 0 && wo.wo_stat)
1813 		*stat = wo.wo_stat;
1814 	put_pid(wo.wo_pid);
1815 	return ret;
1816 }
1817 
1818 SYSCALL_DEFINE4(wait4, pid_t, upid, int __user *, stat_addr,
1819 		int, options, struct rusage __user *, ru)
1820 {
1821 	struct rusage r;
1822 	long err = kernel_wait4(upid, stat_addr, options, ru ? &r : NULL);
1823 
1824 	if (err > 0) {
1825 		if (ru && copy_to_user(ru, &r, sizeof(struct rusage)))
1826 			return -EFAULT;
1827 	}
1828 	return err;
1829 }
1830 
1831 #ifdef __ARCH_WANT_SYS_WAITPID
1832 
1833 /*
1834  * sys_waitpid() remains for compatibility. waitpid() should be
1835  * implemented by calling sys_wait4() from libc.a.
1836  */
1837 SYSCALL_DEFINE3(waitpid, pid_t, pid, int __user *, stat_addr, int, options)
1838 {
1839 	return kernel_wait4(pid, stat_addr, options, NULL);
1840 }
1841 
1842 #endif
1843 
1844 #ifdef CONFIG_COMPAT
1845 COMPAT_SYSCALL_DEFINE4(wait4,
1846 	compat_pid_t, pid,
1847 	compat_uint_t __user *, stat_addr,
1848 	int, options,
1849 	struct compat_rusage __user *, ru)
1850 {
1851 	struct rusage r;
1852 	long err = kernel_wait4(pid, stat_addr, options, ru ? &r : NULL);
1853 	if (err > 0) {
1854 		if (ru && put_compat_rusage(&r, ru))
1855 			return -EFAULT;
1856 	}
1857 	return err;
1858 }
1859 
1860 COMPAT_SYSCALL_DEFINE5(waitid,
1861 		int, which, compat_pid_t, pid,
1862 		struct compat_siginfo __user *, infop, int, options,
1863 		struct compat_rusage __user *, uru)
1864 {
1865 	struct rusage ru;
1866 	struct waitid_info info = {.status = 0};
1867 	long err = kernel_waitid(which, pid, &info, options, uru ? &ru : NULL);
1868 	int signo = 0;
1869 	if (err > 0) {
1870 		signo = SIGCHLD;
1871 		err = 0;
1872 		if (uru) {
1873 			/* kernel_waitid() overwrites everything in ru */
1874 			if (COMPAT_USE_64BIT_TIME)
1875 				err = copy_to_user(uru, &ru, sizeof(ru));
1876 			else
1877 				err = put_compat_rusage(&ru, uru);
1878 			if (err)
1879 				return -EFAULT;
1880 		}
1881 	}
1882 
1883 	if (!infop)
1884 		return err;
1885 
1886 	if (!user_write_access_begin(infop, sizeof(*infop)))
1887 		return -EFAULT;
1888 
1889 	unsafe_put_user(signo, &infop->si_signo, Efault);
1890 	unsafe_put_user(0, &infop->si_errno, Efault);
1891 	unsafe_put_user(info.cause, &infop->si_code, Efault);
1892 	unsafe_put_user(info.pid, &infop->si_pid, Efault);
1893 	unsafe_put_user(info.uid, &infop->si_uid, Efault);
1894 	unsafe_put_user(info.status, &infop->si_status, Efault);
1895 	user_write_access_end();
1896 	return err;
1897 Efault:
1898 	user_write_access_end();
1899 	return -EFAULT;
1900 }
1901 #endif
1902 
1903 /*
1904  * This needs to be __function_aligned as GCC implicitly makes any
1905  * implementation of abort() cold and drops alignment specified by
1906  * -falign-functions=N.
1907  *
1908  * See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88345#c11
1909  */
1910 __weak __function_aligned void abort(void)
1911 {
1912 	BUG();
1913 
1914 	/* if that doesn't kill us, halt */
1915 	panic("Oops failed to kill thread");
1916 }
1917 EXPORT_SYMBOL(abort);
1918