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