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