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/freezer.h>
  29#include <linux/binfmts.h>
  30#include <linux/nsproxy.h>
  31#include <linux/pid_namespace.h>
  32#include <linux/ptrace.h>
  33#include <linux/profile.h>
  34#include <linux/mount.h>
  35#include <linux/proc_fs.h>
  36#include <linux/kthread.h>
  37#include <linux/mempolicy.h>
  38#include <linux/taskstats_kern.h>
  39#include <linux/delayacct.h>
  40#include <linux/cgroup.h>
  41#include <linux/syscalls.h>
  42#include <linux/signal.h>
  43#include <linux/posix-timers.h>
  44#include <linux/cn_proc.h>
  45#include <linux/mutex.h>
  46#include <linux/futex.h>
  47#include <linux/pipe_fs_i.h>
  48#include <linux/audit.h> /* for audit_free() */
  49#include <linux/resource.h>
  50#include <linux/task_io_accounting_ops.h>
  51#include <linux/blkdev.h>
  52#include <linux/task_work.h>
  53#include <linux/fs_struct.h>
  54#include <linux/init_task.h>
  55#include <linux/perf_event.h>
  56#include <trace/events/sched.h>
  57#include <linux/hw_breakpoint.h>
  58#include <linux/oom.h>
  59#include <linux/writeback.h>
  60#include <linux/shm.h>
  61#include <linux/kcov.h>
  62#include <linux/kmsan.h>
  63#include <linux/random.h>
  64#include <linux/rcuwait.h>
  65#include <linux/compat.h>
  66#include <linux/io_uring.h>
  67#include <linux/kprobes.h>
  68#include <linux/rethook.h>
  69#include <linux/sysfs.h>
  70#include <linux/user_events.h>
  71#include <linux/uaccess.h>
  72
  73#include <uapi/linux/wait.h>
  74
  75#include <asm/unistd.h>
  76#include <asm/mmu_context.h>
  77
  78#include "exit.h"
  79
  80/*
  81 * The default value should be high enough to not crash a system that randomly
  82 * crashes its kernel from time to time, but low enough to at least not permit
  83 * overflowing 32-bit refcounts or the ldsem writer count.
  84 */
  85static unsigned int oops_limit = 10000;
  86
  87#ifdef CONFIG_SYSCTL
  88static struct ctl_table kern_exit_table[] = {
  89	{
  90		.procname       = "oops_limit",
  91		.data           = &oops_limit,
  92		.maxlen         = sizeof(oops_limit),
  93		.mode           = 0644,
  94		.proc_handler   = proc_douintvec,
  95	},
 
  96};
  97
  98static __init int kernel_exit_sysctls_init(void)
  99{
 100	register_sysctl_init("kernel", kern_exit_table);
 101	return 0;
 102}
 103late_initcall(kernel_exit_sysctls_init);
 104#endif
 105
 106static atomic_t oops_count = ATOMIC_INIT(0);
 107
 108#ifdef CONFIG_SYSFS
 109static ssize_t oops_count_show(struct kobject *kobj, struct kobj_attribute *attr,
 110			       char *page)
 111{
 112	return sysfs_emit(page, "%d\n", atomic_read(&oops_count));
 113}
 114
 115static struct kobj_attribute oops_count_attr = __ATTR_RO(oops_count);
 116
 117static __init int kernel_exit_sysfs_init(void)
 118{
 119	sysfs_add_file_to_group(kernel_kobj, &oops_count_attr.attr, NULL);
 120	return 0;
 121}
 122late_initcall(kernel_exit_sysfs_init);
 123#endif
 124
 125static void __unhash_process(struct task_struct *p, bool group_dead)
 126{
 127	nr_threads--;
 128	detach_pid(p, PIDTYPE_PID);
 129	if (group_dead) {
 130		detach_pid(p, PIDTYPE_TGID);
 131		detach_pid(p, PIDTYPE_PGID);
 132		detach_pid(p, PIDTYPE_SID);
 133
 134		list_del_rcu(&p->tasks);
 135		list_del_init(&p->sibling);
 136		__this_cpu_dec(process_counts);
 137	}
 138	list_del_rcu(&p->thread_node);
 139}
 140
 141/*
 142 * This function expects the tasklist_lock write-locked.
 143 */
 144static void __exit_signal(struct task_struct *tsk)
 145{
 146	struct signal_struct *sig = tsk->signal;
 147	bool group_dead = thread_group_leader(tsk);
 148	struct sighand_struct *sighand;
 149	struct tty_struct *tty;
 150	u64 utime, stime;
 151
 152	sighand = rcu_dereference_check(tsk->sighand,
 153					lockdep_tasklist_lock_is_held());
 154	spin_lock(&sighand->siglock);
 155
 156#ifdef CONFIG_POSIX_TIMERS
 157	posix_cpu_timers_exit(tsk);
 158	if (group_dead)
 159		posix_cpu_timers_exit_group(tsk);
 160#endif
 161
 162	if (group_dead) {
 163		tty = sig->tty;
 164		sig->tty = NULL;
 165	} else {
 166		/*
 167		 * If there is any task waiting for the group exit
 168		 * then notify it:
 169		 */
 170		if (sig->notify_count > 0 && !--sig->notify_count)
 171			wake_up_process(sig->group_exec_task);
 172
 173		if (tsk == sig->curr_target)
 174			sig->curr_target = next_thread(tsk);
 175	}
 176
 177	add_device_randomness((const void*) &tsk->se.sum_exec_runtime,
 178			      sizeof(unsigned long long));
 179
 180	/*
 181	 * Accumulate here the counters for all threads as they die. We could
 182	 * skip the group leader because it is the last user of signal_struct,
 183	 * but we want to avoid the race with thread_group_cputime() which can
 184	 * see the empty ->thread_head list.
 185	 */
 186	task_cputime(tsk, &utime, &stime);
 187	write_seqlock(&sig->stats_lock);
 188	sig->utime += utime;
 189	sig->stime += stime;
 190	sig->gtime += task_gtime(tsk);
 191	sig->min_flt += tsk->min_flt;
 192	sig->maj_flt += tsk->maj_flt;
 193	sig->nvcsw += tsk->nvcsw;
 194	sig->nivcsw += tsk->nivcsw;
 195	sig->inblock += task_io_get_inblock(tsk);
 196	sig->oublock += task_io_get_oublock(tsk);
 197	task_io_accounting_add(&sig->ioac, &tsk->ioac);
 198	sig->sum_sched_runtime += tsk->se.sum_exec_runtime;
 199	sig->nr_threads--;
 200	__unhash_process(tsk, group_dead);
 201	write_sequnlock(&sig->stats_lock);
 202
 203	/*
 204	 * Do this under ->siglock, we can race with another thread
 205	 * doing sigqueue_free() if we have SIGQUEUE_PREALLOC signals.
 206	 */
 207	flush_sigqueue(&tsk->pending);
 208	tsk->sighand = NULL;
 209	spin_unlock(&sighand->siglock);
 210
 211	__cleanup_sighand(sighand);
 212	clear_tsk_thread_flag(tsk, TIF_SIGPENDING);
 213	if (group_dead) {
 214		flush_sigqueue(&sig->shared_pending);
 215		tty_kref_put(tty);
 216	}
 217}
 218
 219static void delayed_put_task_struct(struct rcu_head *rhp)
 220{
 221	struct task_struct *tsk = container_of(rhp, struct task_struct, rcu);
 222
 223	kprobe_flush_task(tsk);
 224	rethook_flush_task(tsk);
 225	perf_event_delayed_put(tsk);
 226	trace_sched_process_free(tsk);
 227	put_task_struct(tsk);
 228}
 229
 230void put_task_struct_rcu_user(struct task_struct *task)
 231{
 232	if (refcount_dec_and_test(&task->rcu_users))
 233		call_rcu(&task->rcu, delayed_put_task_struct);
 234}
 235
 236void __weak release_thread(struct task_struct *dead_task)
 237{
 238}
 239
 240void release_task(struct task_struct *p)
 241{
 242	struct task_struct *leader;
 243	struct pid *thread_pid;
 244	int zap_leader;
 245repeat:
 246	/* don't need to get the RCU readlock here - the process is dead and
 247	 * can't be modifying its own credentials. But shut RCU-lockdep up */
 248	rcu_read_lock();
 249	dec_rlimit_ucounts(task_ucounts(p), UCOUNT_RLIMIT_NPROC, 1);
 250	rcu_read_unlock();
 251
 252	cgroup_release(p);
 253
 254	write_lock_irq(&tasklist_lock);
 255	ptrace_release_task(p);
 256	thread_pid = get_pid(p->thread_pid);
 257	__exit_signal(p);
 258
 259	/*
 260	 * If we are the last non-leader member of the thread
 261	 * group, and the leader is zombie, then notify the
 262	 * group leader's parent process. (if it wants notification.)
 263	 */
 264	zap_leader = 0;
 265	leader = p->group_leader;
 266	if (leader != p && thread_group_empty(leader)
 267			&& leader->exit_state == EXIT_ZOMBIE) {
 268		/*
 269		 * If we were the last child thread and the leader has
 270		 * exited already, and the leader's parent ignores SIGCHLD,
 271		 * then we are the one who should release the leader.
 272		 */
 273		zap_leader = do_notify_parent(leader, leader->exit_signal);
 274		if (zap_leader)
 275			leader->exit_state = EXIT_DEAD;
 276	}
 277
 278	write_unlock_irq(&tasklist_lock);
 
 279	proc_flush_pid(thread_pid);
 280	put_pid(thread_pid);
 281	release_thread(p);
 282	put_task_struct_rcu_user(p);
 283
 284	p = leader;
 285	if (unlikely(zap_leader))
 286		goto repeat;
 287}
 288
 289int rcuwait_wake_up(struct rcuwait *w)
 290{
 291	int ret = 0;
 292	struct task_struct *task;
 293
 294	rcu_read_lock();
 295
 296	/*
 297	 * Order condition vs @task, such that everything prior to the load
 298	 * of @task is visible. This is the condition as to why the user called
 299	 * rcuwait_wake() in the first place. Pairs with set_current_state()
 300	 * barrier (A) in rcuwait_wait_event().
 301	 *
 302	 *    WAIT                WAKE
 303	 *    [S] tsk = current	  [S] cond = true
 304	 *        MB (A)	      MB (B)
 305	 *    [L] cond		  [L] tsk
 306	 */
 307	smp_mb(); /* (B) */
 308
 309	task = rcu_dereference(w->task);
 310	if (task)
 311		ret = wake_up_process(task);
 312	rcu_read_unlock();
 313
 314	return ret;
 315}
 316EXPORT_SYMBOL_GPL(rcuwait_wake_up);
 317
 318/*
 319 * Determine if a process group is "orphaned", according to the POSIX
 320 * definition in 2.2.2.52.  Orphaned process groups are not to be affected
 321 * by terminal-generated stop signals.  Newly orphaned process groups are
 322 * to receive a SIGHUP and a SIGCONT.
 323 *
 324 * "I ask you, have you ever known what it is to be an orphan?"
 325 */
 326static int will_become_orphaned_pgrp(struct pid *pgrp,
 327					struct task_struct *ignored_task)
 328{
 329	struct task_struct *p;
 330
 331	do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
 332		if ((p == ignored_task) ||
 333		    (p->exit_state && thread_group_empty(p)) ||
 334		    is_global_init(p->real_parent))
 335			continue;
 336
 337		if (task_pgrp(p->real_parent) != pgrp &&
 338		    task_session(p->real_parent) == task_session(p))
 339			return 0;
 340	} while_each_pid_task(pgrp, PIDTYPE_PGID, p);
 341
 342	return 1;
 343}
 344
 345int is_current_pgrp_orphaned(void)
 346{
 347	int retval;
 348
 349	read_lock(&tasklist_lock);
 350	retval = will_become_orphaned_pgrp(task_pgrp(current), NULL);
 351	read_unlock(&tasklist_lock);
 352
 353	return retval;
 354}
 355
 356static bool has_stopped_jobs(struct pid *pgrp)
 357{
 358	struct task_struct *p;
 359
 360	do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
 361		if (p->signal->flags & SIGNAL_STOP_STOPPED)
 362			return true;
 363	} while_each_pid_task(pgrp, PIDTYPE_PGID, p);
 364
 365	return false;
 366}
 367
 368/*
 369 * Check to see if any process groups have become orphaned as
 370 * a result of our exiting, and if they have any stopped jobs,
 371 * send them a SIGHUP and then a SIGCONT. (POSIX 3.2.2.2)
 372 */
 373static void
 374kill_orphaned_pgrp(struct task_struct *tsk, struct task_struct *parent)
 375{
 376	struct pid *pgrp = task_pgrp(tsk);
 377	struct task_struct *ignored_task = tsk;
 378
 379	if (!parent)
 380		/* exit: our father is in a different pgrp than
 381		 * we are and we were the only connection outside.
 382		 */
 383		parent = tsk->real_parent;
 384	else
 385		/* reparent: our child is in a different pgrp than
 386		 * we are, and it was the only connection outside.
 387		 */
 388		ignored_task = NULL;
 389
 390	if (task_pgrp(parent) != pgrp &&
 391	    task_session(parent) == task_session(tsk) &&
 392	    will_become_orphaned_pgrp(pgrp, ignored_task) &&
 393	    has_stopped_jobs(pgrp)) {
 394		__kill_pgrp_info(SIGHUP, SEND_SIG_PRIV, pgrp);
 395		__kill_pgrp_info(SIGCONT, SEND_SIG_PRIV, pgrp);
 396	}
 397}
 398
 399static void coredump_task_exit(struct task_struct *tsk)
 400{
 401	struct core_state *core_state;
 402
 403	/*
 404	 * Serialize with any possible pending coredump.
 405	 * We must hold siglock around checking core_state
 406	 * and setting PF_POSTCOREDUMP.  The core-inducing thread
 407	 * will increment ->nr_threads for each thread in the
 408	 * group without PF_POSTCOREDUMP set.
 409	 */
 410	spin_lock_irq(&tsk->sighand->siglock);
 411	tsk->flags |= PF_POSTCOREDUMP;
 412	core_state = tsk->signal->core_state;
 413	spin_unlock_irq(&tsk->sighand->siglock);
 414	if (core_state) {
 
 
 
 415		struct core_thread self;
 416
 417		self.task = current;
 418		if (self.task->flags & PF_SIGNALED)
 419			self.next = xchg(&core_state->dumper.next, &self);
 420		else
 421			self.task = NULL;
 422		/*
 423		 * Implies mb(), the result of xchg() must be visible
 424		 * to core_state->dumper.
 425		 */
 426		if (atomic_dec_and_test(&core_state->nr_threads))
 427			complete(&core_state->startup);
 428
 429		for (;;) {
 430			set_current_state(TASK_IDLE|TASK_FREEZABLE);
 431			if (!self.task) /* see coredump_finish() */
 432				break;
 433			schedule();
 434		}
 435		__set_current_state(TASK_RUNNING);
 436	}
 437}
 438
 439#ifdef CONFIG_MEMCG
 440/* drops tasklist_lock if succeeds */
 441static bool __try_to_set_owner(struct task_struct *tsk, struct mm_struct *mm)
 442{
 443	bool ret = false;
 444
 445	task_lock(tsk);
 446	if (likely(tsk->mm == mm)) {
 447		/* tsk can't pass exit_mm/exec_mmap and exit */
 448		read_unlock(&tasklist_lock);
 449		WRITE_ONCE(mm->owner, tsk);
 450		lru_gen_migrate_mm(mm);
 451		ret = true;
 452	}
 453	task_unlock(tsk);
 454	return ret;
 455}
 456
 457static bool try_to_set_owner(struct task_struct *g, struct mm_struct *mm)
 458{
 459	struct task_struct *t;
 460
 461	for_each_thread(g, t) {
 462		struct mm_struct *t_mm = READ_ONCE(t->mm);
 463		if (t_mm == mm) {
 464			if (__try_to_set_owner(t, mm))
 465				return true;
 466		} else if (t_mm)
 467			break;
 468	}
 469
 470	return false;
 471}
 472
 473/*
 474 * A task is exiting.   If it owned this mm, find a new owner for the mm.
 475 */
 476void mm_update_next_owner(struct mm_struct *mm)
 477{
 478	struct task_struct *g, *p = current;
 479
 
 480	/*
 481	 * If the exiting or execing task is not the owner, it's
 482	 * someone else's problem.
 483	 */
 484	if (mm->owner != p)
 485		return;
 486	/*
 487	 * The current owner is exiting/execing and there are no other
 488	 * candidates.  Do not leave the mm pointing to a possibly
 489	 * freed task structure.
 490	 */
 491	if (atomic_read(&mm->mm_users) <= 1) {
 492		WRITE_ONCE(mm->owner, NULL);
 493		return;
 494	}
 495
 496	read_lock(&tasklist_lock);
 497	/*
 498	 * Search in the children
 499	 */
 500	list_for_each_entry(g, &p->children, sibling) {
 501		if (try_to_set_owner(g, mm))
 502			goto ret;
 503	}
 
 504	/*
 505	 * Search in the siblings
 506	 */
 507	list_for_each_entry(g, &p->real_parent->children, sibling) {
 508		if (try_to_set_owner(g, mm))
 509			goto ret;
 510	}
 
 511	/*
 512	 * Search through everything else, we should not get here often.
 513	 */
 514	for_each_process(g) {
 515		if (atomic_read(&mm->mm_users) <= 1)
 516			break;
 517		if (g->flags & PF_KTHREAD)
 518			continue;
 519		if (try_to_set_owner(g, mm))
 520			goto ret;
 
 
 
 
 521	}
 522	read_unlock(&tasklist_lock);
 523	/*
 524	 * We found no owner yet mm_users > 1: this implies that we are
 525	 * most likely racing with swapoff (try_to_unuse()) or /proc or
 526	 * ptrace or page migration (get_task_mm()).  Mark owner as NULL.
 527	 */
 528	WRITE_ONCE(mm->owner, NULL);
 529 ret:
 530	return;
 531
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 532}
 533#endif /* CONFIG_MEMCG */
 534
 535/*
 536 * Turn us into a lazy TLB process if we
 537 * aren't already..
 538 */
 539static void exit_mm(void)
 540{
 541	struct mm_struct *mm = current->mm;
 542
 543	exit_mm_release(current, mm);
 544	if (!mm)
 545		return;
 546	mmap_read_lock(mm);
 547	mmgrab_lazy_tlb(mm);
 548	BUG_ON(mm != current->active_mm);
 549	/* more a memory barrier than a real lock */
 550	task_lock(current);
 551	/*
 552	 * When a thread stops operating on an address space, the loop
 553	 * in membarrier_private_expedited() may not observe that
 554	 * tsk->mm, and the loop in membarrier_global_expedited() may
 555	 * not observe a MEMBARRIER_STATE_GLOBAL_EXPEDITED
 556	 * rq->membarrier_state, so those would not issue an IPI.
 557	 * Membarrier requires a memory barrier after accessing
 558	 * user-space memory, before clearing tsk->mm or the
 559	 * rq->membarrier_state.
 560	 */
 561	smp_mb__after_spinlock();
 562	local_irq_disable();
 563	current->mm = NULL;
 564	membarrier_update_current_mm(NULL);
 565	enter_lazy_tlb(mm, current);
 566	local_irq_enable();
 567	task_unlock(current);
 568	mmap_read_unlock(mm);
 569	mm_update_next_owner(mm);
 570	mmput(mm);
 571	if (test_thread_flag(TIF_MEMDIE))
 572		exit_oom_victim();
 573}
 574
 575static struct task_struct *find_alive_thread(struct task_struct *p)
 576{
 577	struct task_struct *t;
 578
 579	for_each_thread(p, t) {
 580		if (!(t->flags & PF_EXITING))
 581			return t;
 582	}
 583	return NULL;
 584}
 585
 586static struct task_struct *find_child_reaper(struct task_struct *father,
 587						struct list_head *dead)
 588	__releases(&tasklist_lock)
 589	__acquires(&tasklist_lock)
 590{
 591	struct pid_namespace *pid_ns = task_active_pid_ns(father);
 592	struct task_struct *reaper = pid_ns->child_reaper;
 593	struct task_struct *p, *n;
 594
 595	if (likely(reaper != father))
 596		return reaper;
 597
 598	reaper = find_alive_thread(father);
 599	if (reaper) {
 600		pid_ns->child_reaper = reaper;
 601		return reaper;
 602	}
 603
 604	write_unlock_irq(&tasklist_lock);
 605
 606	list_for_each_entry_safe(p, n, dead, ptrace_entry) {
 607		list_del_init(&p->ptrace_entry);
 608		release_task(p);
 609	}
 610
 611	zap_pid_ns_processes(pid_ns);
 612	write_lock_irq(&tasklist_lock);
 613
 614	return father;
 615}
 616
 617/*
 618 * When we die, we re-parent all our children, and try to:
 619 * 1. give them to another thread in our thread group, if such a member exists
 620 * 2. give it to the first ancestor process which prctl'd itself as a
 621 *    child_subreaper for its children (like a service manager)
 622 * 3. give it to the init process (PID 1) in our pid namespace
 623 */
 624static struct task_struct *find_new_reaper(struct task_struct *father,
 625					   struct task_struct *child_reaper)
 626{
 627	struct task_struct *thread, *reaper;
 628
 629	thread = find_alive_thread(father);
 630	if (thread)
 631		return thread;
 632
 633	if (father->signal->has_child_subreaper) {
 634		unsigned int ns_level = task_pid(father)->level;
 635		/*
 636		 * Find the first ->is_child_subreaper ancestor in our pid_ns.
 637		 * We can't check reaper != child_reaper to ensure we do not
 638		 * cross the namespaces, the exiting parent could be injected
 639		 * by setns() + fork().
 640		 * We check pid->level, this is slightly more efficient than
 641		 * task_active_pid_ns(reaper) != task_active_pid_ns(father).
 642		 */
 643		for (reaper = father->real_parent;
 644		     task_pid(reaper)->level == ns_level;
 645		     reaper = reaper->real_parent) {
 646			if (reaper == &init_task)
 647				break;
 648			if (!reaper->signal->is_child_subreaper)
 649				continue;
 650			thread = find_alive_thread(reaper);
 651			if (thread)
 652				return thread;
 653		}
 654	}
 655
 656	return child_reaper;
 657}
 658
 659/*
 660* Any that need to be release_task'd are put on the @dead list.
 661 */
 662static void reparent_leader(struct task_struct *father, struct task_struct *p,
 663				struct list_head *dead)
 664{
 665	if (unlikely(p->exit_state == EXIT_DEAD))
 666		return;
 667
 668	/* We don't want people slaying init. */
 669	p->exit_signal = SIGCHLD;
 670
 671	/* If it has exited notify the new parent about this child's death. */
 672	if (!p->ptrace &&
 673	    p->exit_state == EXIT_ZOMBIE && thread_group_empty(p)) {
 674		if (do_notify_parent(p, p->exit_signal)) {
 675			p->exit_state = EXIT_DEAD;
 676			list_add(&p->ptrace_entry, dead);
 677		}
 678	}
 679
 680	kill_orphaned_pgrp(p, father);
 681}
 682
 683/*
 684 * This does two things:
 685 *
 686 * A.  Make init inherit all the child processes
 687 * B.  Check to see if any process groups have become orphaned
 688 *	as a result of our exiting, and if they have any stopped
 689 *	jobs, send them a SIGHUP and then a SIGCONT.  (POSIX 3.2.2.2)
 690 */
 691static void forget_original_parent(struct task_struct *father,
 692					struct list_head *dead)
 693{
 694	struct task_struct *p, *t, *reaper;
 695
 696	if (unlikely(!list_empty(&father->ptraced)))
 697		exit_ptrace(father, dead);
 698
 699	/* Can drop and reacquire tasklist_lock */
 700	reaper = find_child_reaper(father, dead);
 701	if (list_empty(&father->children))
 702		return;
 703
 704	reaper = find_new_reaper(father, reaper);
 705	list_for_each_entry(p, &father->children, sibling) {
 706		for_each_thread(p, t) {
 707			RCU_INIT_POINTER(t->real_parent, reaper);
 708			BUG_ON((!t->ptrace) != (rcu_access_pointer(t->parent) == father));
 709			if (likely(!t->ptrace))
 710				t->parent = t->real_parent;
 711			if (t->pdeath_signal)
 712				group_send_sig_info(t->pdeath_signal,
 713						    SEND_SIG_NOINFO, t,
 714						    PIDTYPE_TGID);
 715		}
 716		/*
 717		 * If this is a threaded reparent there is no need to
 718		 * notify anyone anything has happened.
 719		 */
 720		if (!same_thread_group(reaper, father))
 721			reparent_leader(father, p, dead);
 722	}
 723	list_splice_tail_init(&father->children, &reaper->children);
 724}
 725
 726/*
 727 * Send signals to all our closest relatives so that they know
 728 * to properly mourn us..
 729 */
 730static void exit_notify(struct task_struct *tsk, int group_dead)
 731{
 732	bool autoreap;
 733	struct task_struct *p, *n;
 734	LIST_HEAD(dead);
 735
 736	write_lock_irq(&tasklist_lock);
 737	forget_original_parent(tsk, &dead);
 738
 739	if (group_dead)
 740		kill_orphaned_pgrp(tsk->group_leader, NULL);
 741
 742	tsk->exit_state = EXIT_ZOMBIE;
 743	/*
 744	 * sub-thread or delay_group_leader(), wake up the
 745	 * PIDFD_THREAD waiters.
 746	 */
 747	if (!thread_group_empty(tsk))
 748		do_notify_pidfd(tsk);
 749
 750	if (unlikely(tsk->ptrace)) {
 751		int sig = thread_group_leader(tsk) &&
 752				thread_group_empty(tsk) &&
 753				!ptrace_reparented(tsk) ?
 754			tsk->exit_signal : SIGCHLD;
 755		autoreap = do_notify_parent(tsk, sig);
 756	} else if (thread_group_leader(tsk)) {
 757		autoreap = thread_group_empty(tsk) &&
 758			do_notify_parent(tsk, tsk->exit_signal);
 759	} else {
 760		autoreap = true;
 761	}
 762
 763	if (autoreap) {
 764		tsk->exit_state = EXIT_DEAD;
 765		list_add(&tsk->ptrace_entry, &dead);
 766	}
 767
 768	/* mt-exec, de_thread() is waiting for group leader */
 769	if (unlikely(tsk->signal->notify_count < 0))
 770		wake_up_process(tsk->signal->group_exec_task);
 771	write_unlock_irq(&tasklist_lock);
 772
 773	list_for_each_entry_safe(p, n, &dead, ptrace_entry) {
 774		list_del_init(&p->ptrace_entry);
 775		release_task(p);
 776	}
 777}
 778
 779#ifdef CONFIG_DEBUG_STACK_USAGE
 780unsigned long stack_not_used(struct task_struct *p)
 781{
 782	unsigned long *n = end_of_stack(p);
 783
 784	do {	/* Skip over canary */
 785# ifdef CONFIG_STACK_GROWSUP
 786		n--;
 787# else
 788		n++;
 789# endif
 790	} while (!*n);
 791
 792# ifdef CONFIG_STACK_GROWSUP
 793	return (unsigned long)end_of_stack(p) - (unsigned long)n;
 794# else
 795	return (unsigned long)n - (unsigned long)end_of_stack(p);
 796# endif
 797}
 798
 799/* Count the maximum pages reached in kernel stacks */
 800static inline void kstack_histogram(unsigned long used_stack)
 801{
 802#ifdef CONFIG_VM_EVENT_COUNTERS
 803	if (used_stack <= 1024)
 804		count_vm_event(KSTACK_1K);
 805#if THREAD_SIZE > 1024
 806	else if (used_stack <= 2048)
 807		count_vm_event(KSTACK_2K);
 808#endif
 809#if THREAD_SIZE > 2048
 810	else if (used_stack <= 4096)
 811		count_vm_event(KSTACK_4K);
 812#endif
 813#if THREAD_SIZE > 4096
 814	else if (used_stack <= 8192)
 815		count_vm_event(KSTACK_8K);
 816#endif
 817#if THREAD_SIZE > 8192
 818	else if (used_stack <= 16384)
 819		count_vm_event(KSTACK_16K);
 820#endif
 821#if THREAD_SIZE > 16384
 822	else if (used_stack <= 32768)
 823		count_vm_event(KSTACK_32K);
 824#endif
 825#if THREAD_SIZE > 32768
 826	else if (used_stack <= 65536)
 827		count_vm_event(KSTACK_64K);
 828#endif
 829#if THREAD_SIZE > 65536
 830	else
 831		count_vm_event(KSTACK_REST);
 832#endif
 833#endif /* CONFIG_VM_EVENT_COUNTERS */
 834}
 835
 836static void check_stack_usage(void)
 837{
 838	static DEFINE_SPINLOCK(low_water_lock);
 839	static int lowest_to_date = THREAD_SIZE;
 840	unsigned long free;
 841
 842	free = stack_not_used(current);
 843	kstack_histogram(THREAD_SIZE - free);
 844
 845	if (free >= lowest_to_date)
 846		return;
 847
 848	spin_lock(&low_water_lock);
 849	if (free < lowest_to_date) {
 850		pr_info("%s (%d) used greatest stack depth: %lu bytes left\n",
 851			current->comm, task_pid_nr(current), free);
 852		lowest_to_date = free;
 853	}
 854	spin_unlock(&low_water_lock);
 855}
 856#else
 857static inline void check_stack_usage(void) {}
 858#endif
 859
 860static void synchronize_group_exit(struct task_struct *tsk, long code)
 861{
 862	struct sighand_struct *sighand = tsk->sighand;
 863	struct signal_struct *signal = tsk->signal;
 864
 865	spin_lock_irq(&sighand->siglock);
 866	signal->quick_threads--;
 867	if ((signal->quick_threads == 0) &&
 868	    !(signal->flags & SIGNAL_GROUP_EXIT)) {
 869		signal->flags = SIGNAL_GROUP_EXIT;
 870		signal->group_exit_code = code;
 871		signal->group_stop_count = 0;
 872	}
 873	spin_unlock_irq(&sighand->siglock);
 874}
 875
 876void __noreturn do_exit(long code)
 877{
 878	struct task_struct *tsk = current;
 879	int group_dead;
 880
 881	WARN_ON(irqs_disabled());
 882
 883	synchronize_group_exit(tsk, code);
 884
 885	WARN_ON(tsk->plug);
 886
 887	kcov_task_exit(tsk);
 888	kmsan_task_exit(tsk);
 889
 890	coredump_task_exit(tsk);
 891	ptrace_event(PTRACE_EVENT_EXIT, code);
 892	user_events_exit(tsk);
 893
 894	io_uring_files_cancel();
 895	exit_signals(tsk);  /* sets PF_EXITING */
 896
 897	seccomp_filter_release(tsk);
 898
 899	acct_update_integrals(tsk);
 900	group_dead = atomic_dec_and_test(&tsk->signal->live);
 901	if (group_dead) {
 902		/*
 903		 * If the last thread of global init has exited, panic
 904		 * immediately to get a useable coredump.
 905		 */
 906		if (unlikely(is_global_init(tsk)))
 907			panic("Attempted to kill init! exitcode=0x%08x\n",
 908				tsk->signal->group_exit_code ?: (int)code);
 909
 910#ifdef CONFIG_POSIX_TIMERS
 911		hrtimer_cancel(&tsk->signal->real_timer);
 912		exit_itimers(tsk);
 913#endif
 914		if (tsk->mm)
 915			setmax_mm_hiwater_rss(&tsk->signal->maxrss, tsk->mm);
 916	}
 917	acct_collect(code, group_dead);
 918	if (group_dead)
 919		tty_audit_exit();
 920	audit_free(tsk);
 921
 922	tsk->exit_code = code;
 923	taskstats_exit(tsk, group_dead);
 924
 925	exit_mm();
 926
 927	if (group_dead)
 928		acct_process();
 929	trace_sched_process_exit(tsk);
 930
 931	exit_sem(tsk);
 932	exit_shm(tsk);
 933	exit_files(tsk);
 934	exit_fs(tsk);
 935	if (group_dead)
 936		disassociate_ctty(1);
 937	exit_task_namespaces(tsk);
 938	exit_task_work(tsk);
 939	exit_thread(tsk);
 940
 941	/*
 942	 * Flush inherited counters to the parent - before the parent
 943	 * gets woken up by child-exit notifications.
 944	 *
 945	 * because of cgroup mode, must be called before cgroup_exit()
 946	 */
 947	perf_event_exit_task(tsk);
 948
 949	sched_autogroup_exit_task(tsk);
 950	cgroup_exit(tsk);
 951
 952	/*
 953	 * FIXME: do that only when needed, using sched_exit tracepoint
 954	 */
 955	flush_ptrace_hw_breakpoint(tsk);
 956
 957	exit_tasks_rcu_start();
 958	exit_notify(tsk, group_dead);
 959	proc_exit_connector(tsk);
 960	mpol_put_task_policy(tsk);
 961#ifdef CONFIG_FUTEX
 962	if (unlikely(current->pi_state_cache))
 963		kfree(current->pi_state_cache);
 964#endif
 965	/*
 966	 * Make sure we are holding no locks:
 967	 */
 968	debug_check_no_locks_held();
 969
 970	if (tsk->io_context)
 971		exit_io_context(tsk);
 972
 973	if (tsk->splice_pipe)
 974		free_pipe_info(tsk->splice_pipe);
 975
 976	if (tsk->task_frag.page)
 977		put_page(tsk->task_frag.page);
 978
 979	exit_task_stack_account(tsk);
 980
 981	check_stack_usage();
 982	preempt_disable();
 983	if (tsk->nr_dirtied)
 984		__this_cpu_add(dirty_throttle_leaks, tsk->nr_dirtied);
 985	exit_rcu();
 986	exit_tasks_rcu_finish();
 987
 988	lockdep_free_task(tsk);
 989	do_task_dead();
 990}
 991
 992void __noreturn make_task_dead(int signr)
 993{
 994	/*
 995	 * Take the task off the cpu after something catastrophic has
 996	 * happened.
 997	 *
 998	 * We can get here from a kernel oops, sometimes with preemption off.
 999	 * Start by checking for critical errors.
1000	 * Then fix up important state like USER_DS and preemption.
1001	 * Then do everything else.
1002	 */
1003	struct task_struct *tsk = current;
1004	unsigned int limit;
1005
1006	if (unlikely(in_interrupt()))
1007		panic("Aiee, killing interrupt handler!");
1008	if (unlikely(!tsk->pid))
1009		panic("Attempted to kill the idle task!");
1010
1011	if (unlikely(irqs_disabled())) {
1012		pr_info("note: %s[%d] exited with irqs disabled\n",
1013			current->comm, task_pid_nr(current));
1014		local_irq_enable();
1015	}
1016	if (unlikely(in_atomic())) {
1017		pr_info("note: %s[%d] exited with preempt_count %d\n",
1018			current->comm, task_pid_nr(current),
1019			preempt_count());
1020		preempt_count_set(PREEMPT_ENABLED);
1021	}
1022
1023	/*
1024	 * Every time the system oopses, if the oops happens while a reference
1025	 * to an object was held, the reference leaks.
1026	 * If the oops doesn't also leak memory, repeated oopsing can cause
1027	 * reference counters to wrap around (if they're not using refcount_t).
1028	 * This means that repeated oopsing can make unexploitable-looking bugs
1029	 * exploitable through repeated oopsing.
1030	 * To make sure this can't happen, place an upper bound on how often the
1031	 * kernel may oops without panic().
1032	 */
1033	limit = READ_ONCE(oops_limit);
1034	if (atomic_inc_return(&oops_count) >= limit && limit)
1035		panic("Oopsed too often (kernel.oops_limit is %d)", limit);
1036
1037	/*
1038	 * We're taking recursive faults here in make_task_dead. Safest is to just
1039	 * leave this task alone and wait for reboot.
1040	 */
1041	if (unlikely(tsk->flags & PF_EXITING)) {
1042		pr_alert("Fixing recursive fault but reboot is needed!\n");
1043		futex_exit_recursive(tsk);
1044		tsk->exit_state = EXIT_DEAD;
1045		refcount_inc(&tsk->rcu_users);
1046		do_task_dead();
1047	}
1048
1049	do_exit(signr);
1050}
1051
1052SYSCALL_DEFINE1(exit, int, error_code)
1053{
1054	do_exit((error_code&0xff)<<8);
1055}
1056
1057/*
1058 * Take down every thread in the group.  This is called by fatal signals
1059 * as well as by sys_exit_group (below).
1060 */
1061void __noreturn
1062do_group_exit(int exit_code)
1063{
1064	struct signal_struct *sig = current->signal;
1065
1066	if (sig->flags & SIGNAL_GROUP_EXIT)
1067		exit_code = sig->group_exit_code;
1068	else if (sig->group_exec_task)
1069		exit_code = 0;
1070	else {
1071		struct sighand_struct *const sighand = current->sighand;
1072
1073		spin_lock_irq(&sighand->siglock);
1074		if (sig->flags & SIGNAL_GROUP_EXIT)
1075			/* Another thread got here before we took the lock.  */
1076			exit_code = sig->group_exit_code;
1077		else if (sig->group_exec_task)
1078			exit_code = 0;
1079		else {
1080			sig->group_exit_code = exit_code;
1081			sig->flags = SIGNAL_GROUP_EXIT;
1082			zap_other_threads(current);
1083		}
1084		spin_unlock_irq(&sighand->siglock);
1085	}
1086
1087	do_exit(exit_code);
1088	/* NOTREACHED */
1089}
1090
1091/*
1092 * this kills every thread in the thread group. Note that any externally
1093 * wait4()-ing process will get the correct exit code - even if this
1094 * thread is not the thread group leader.
1095 */
1096SYSCALL_DEFINE1(exit_group, int, error_code)
1097{
1098	do_group_exit((error_code & 0xff) << 8);
1099	/* NOTREACHED */
1100	return 0;
1101}
1102
1103static int eligible_pid(struct wait_opts *wo, struct task_struct *p)
1104{
1105	return	wo->wo_type == PIDTYPE_MAX ||
1106		task_pid_type(p, wo->wo_type) == wo->wo_pid;
1107}
1108
1109static int
1110eligible_child(struct wait_opts *wo, bool ptrace, struct task_struct *p)
1111{
1112	if (!eligible_pid(wo, p))
1113		return 0;
1114
1115	/*
1116	 * Wait for all children (clone and not) if __WALL is set or
1117	 * if it is traced by us.
1118	 */
1119	if (ptrace || (wo->wo_flags & __WALL))
1120		return 1;
1121
1122	/*
1123	 * Otherwise, wait for clone children *only* if __WCLONE is set;
1124	 * otherwise, wait for non-clone children *only*.
1125	 *
1126	 * Note: a "clone" child here is one that reports to its parent
1127	 * using a signal other than SIGCHLD, or a non-leader thread which
1128	 * we can only see if it is traced by us.
1129	 */
1130	if ((p->exit_signal != SIGCHLD) ^ !!(wo->wo_flags & __WCLONE))
1131		return 0;
1132
1133	return 1;
1134}
1135
1136/*
1137 * Handle sys_wait4 work for one task in state EXIT_ZOMBIE.  We hold
1138 * read_lock(&tasklist_lock) on entry.  If we return zero, we still hold
1139 * the lock and this task is uninteresting.  If we return nonzero, we have
1140 * released the lock and the system call should return.
1141 */
1142static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p)
1143{
1144	int state, status;
1145	pid_t pid = task_pid_vnr(p);
1146	uid_t uid = from_kuid_munged(current_user_ns(), task_uid(p));
1147	struct waitid_info *infop;
1148
1149	if (!likely(wo->wo_flags & WEXITED))
1150		return 0;
1151
1152	if (unlikely(wo->wo_flags & WNOWAIT)) {
1153		status = (p->signal->flags & SIGNAL_GROUP_EXIT)
1154			? p->signal->group_exit_code : p->exit_code;
1155		get_task_struct(p);
1156		read_unlock(&tasklist_lock);
1157		sched_annotate_sleep();
1158		if (wo->wo_rusage)
1159			getrusage(p, RUSAGE_BOTH, wo->wo_rusage);
1160		put_task_struct(p);
1161		goto out_info;
1162	}
1163	/*
1164	 * Move the task's state to DEAD/TRACE, only one thread can do this.
1165	 */
1166	state = (ptrace_reparented(p) && thread_group_leader(p)) ?
1167		EXIT_TRACE : EXIT_DEAD;
1168	if (cmpxchg(&p->exit_state, EXIT_ZOMBIE, state) != EXIT_ZOMBIE)
1169		return 0;
1170	/*
1171	 * We own this thread, nobody else can reap it.
1172	 */
1173	read_unlock(&tasklist_lock);
1174	sched_annotate_sleep();
1175
1176	/*
1177	 * Check thread_group_leader() to exclude the traced sub-threads.
1178	 */
1179	if (state == EXIT_DEAD && thread_group_leader(p)) {
1180		struct signal_struct *sig = p->signal;
1181		struct signal_struct *psig = current->signal;
1182		unsigned long maxrss;
1183		u64 tgutime, tgstime;
1184
1185		/*
1186		 * The resource counters for the group leader are in its
1187		 * own task_struct.  Those for dead threads in the group
1188		 * are in its signal_struct, as are those for the child
1189		 * processes it has previously reaped.  All these
1190		 * accumulate in the parent's signal_struct c* fields.
1191		 *
1192		 * We don't bother to take a lock here to protect these
1193		 * p->signal fields because the whole thread group is dead
1194		 * and nobody can change them.
1195		 *
1196		 * psig->stats_lock also protects us from our sub-threads
1197		 * which can reap other children at the same time.
1198		 *
1199		 * We use thread_group_cputime_adjusted() to get times for
1200		 * the thread group, which consolidates times for all threads
1201		 * in the group including the group leader.
1202		 */
1203		thread_group_cputime_adjusted(p, &tgutime, &tgstime);
1204		write_seqlock_irq(&psig->stats_lock);
1205		psig->cutime += tgutime + sig->cutime;
1206		psig->cstime += tgstime + sig->cstime;
1207		psig->cgtime += task_gtime(p) + sig->gtime + sig->cgtime;
1208		psig->cmin_flt +=
1209			p->min_flt + sig->min_flt + sig->cmin_flt;
1210		psig->cmaj_flt +=
1211			p->maj_flt + sig->maj_flt + sig->cmaj_flt;
1212		psig->cnvcsw +=
1213			p->nvcsw + sig->nvcsw + sig->cnvcsw;
1214		psig->cnivcsw +=
1215			p->nivcsw + sig->nivcsw + sig->cnivcsw;
1216		psig->cinblock +=
1217			task_io_get_inblock(p) +
1218			sig->inblock + sig->cinblock;
1219		psig->coublock +=
1220			task_io_get_oublock(p) +
1221			sig->oublock + sig->coublock;
1222		maxrss = max(sig->maxrss, sig->cmaxrss);
1223		if (psig->cmaxrss < maxrss)
1224			psig->cmaxrss = maxrss;
1225		task_io_accounting_add(&psig->ioac, &p->ioac);
1226		task_io_accounting_add(&psig->ioac, &sig->ioac);
1227		write_sequnlock_irq(&psig->stats_lock);
1228	}
1229
1230	if (wo->wo_rusage)
1231		getrusage(p, RUSAGE_BOTH, wo->wo_rusage);
1232	status = (p->signal->flags & SIGNAL_GROUP_EXIT)
1233		? p->signal->group_exit_code : p->exit_code;
1234	wo->wo_stat = status;
1235
1236	if (state == EXIT_TRACE) {
1237		write_lock_irq(&tasklist_lock);
1238		/* We dropped tasklist, ptracer could die and untrace */
1239		ptrace_unlink(p);
1240
1241		/* If parent wants a zombie, don't release it now */
1242		state = EXIT_ZOMBIE;
1243		if (do_notify_parent(p, p->exit_signal))
1244			state = EXIT_DEAD;
1245		p->exit_state = state;
1246		write_unlock_irq(&tasklist_lock);
1247	}
1248	if (state == EXIT_DEAD)
1249		release_task(p);
1250
1251out_info:
1252	infop = wo->wo_info;
1253	if (infop) {
1254		if ((status & 0x7f) == 0) {
1255			infop->cause = CLD_EXITED;
1256			infop->status = status >> 8;
1257		} else {
1258			infop->cause = (status & 0x80) ? CLD_DUMPED : CLD_KILLED;
1259			infop->status = status & 0x7f;
1260		}
1261		infop->pid = pid;
1262		infop->uid = uid;
1263	}
1264
1265	return pid;
1266}
1267
1268static int *task_stopped_code(struct task_struct *p, bool ptrace)
1269{
1270	if (ptrace) {
1271		if (task_is_traced(p) && !(p->jobctl & JOBCTL_LISTENING))
1272			return &p->exit_code;
1273	} else {
1274		if (p->signal->flags & SIGNAL_STOP_STOPPED)
1275			return &p->signal->group_exit_code;
1276	}
1277	return NULL;
1278}
1279
1280/**
1281 * wait_task_stopped - Wait for %TASK_STOPPED or %TASK_TRACED
1282 * @wo: wait options
1283 * @ptrace: is the wait for ptrace
1284 * @p: task to wait for
1285 *
1286 * Handle sys_wait4() work for %p in state %TASK_STOPPED or %TASK_TRACED.
1287 *
1288 * CONTEXT:
1289 * read_lock(&tasklist_lock), which is released if return value is
1290 * non-zero.  Also, grabs and releases @p->sighand->siglock.
1291 *
1292 * RETURNS:
1293 * 0 if wait condition didn't exist and search for other wait conditions
1294 * should continue.  Non-zero return, -errno on failure and @p's pid on
1295 * success, implies that tasklist_lock is released and wait condition
1296 * search should terminate.
1297 */
1298static int wait_task_stopped(struct wait_opts *wo,
1299				int ptrace, struct task_struct *p)
1300{
1301	struct waitid_info *infop;
1302	int exit_code, *p_code, why;
1303	uid_t uid = 0; /* unneeded, required by compiler */
1304	pid_t pid;
1305
1306	/*
1307	 * Traditionally we see ptrace'd stopped tasks regardless of options.
1308	 */
1309	if (!ptrace && !(wo->wo_flags & WUNTRACED))
1310		return 0;
1311
1312	if (!task_stopped_code(p, ptrace))
1313		return 0;
1314
1315	exit_code = 0;
1316	spin_lock_irq(&p->sighand->siglock);
1317
1318	p_code = task_stopped_code(p, ptrace);
1319	if (unlikely(!p_code))
1320		goto unlock_sig;
1321
1322	exit_code = *p_code;
1323	if (!exit_code)
1324		goto unlock_sig;
1325
1326	if (!unlikely(wo->wo_flags & WNOWAIT))
1327		*p_code = 0;
1328
1329	uid = from_kuid_munged(current_user_ns(), task_uid(p));
1330unlock_sig:
1331	spin_unlock_irq(&p->sighand->siglock);
1332	if (!exit_code)
1333		return 0;
1334
1335	/*
1336	 * Now we are pretty sure this task is interesting.
1337	 * Make sure it doesn't get reaped out from under us while we
1338	 * give up the lock and then examine it below.  We don't want to
1339	 * keep holding onto the tasklist_lock while we call getrusage and
1340	 * possibly take page faults for user memory.
1341	 */
1342	get_task_struct(p);
1343	pid = task_pid_vnr(p);
1344	why = ptrace ? CLD_TRAPPED : CLD_STOPPED;
1345	read_unlock(&tasklist_lock);
1346	sched_annotate_sleep();
1347	if (wo->wo_rusage)
1348		getrusage(p, RUSAGE_BOTH, wo->wo_rusage);
1349	put_task_struct(p);
1350
1351	if (likely(!(wo->wo_flags & WNOWAIT)))
1352		wo->wo_stat = (exit_code << 8) | 0x7f;
1353
1354	infop = wo->wo_info;
1355	if (infop) {
1356		infop->cause = why;
1357		infop->status = exit_code;
1358		infop->pid = pid;
1359		infop->uid = uid;
1360	}
1361	return pid;
1362}
1363
1364/*
1365 * Handle do_wait work for one task in a live, non-stopped state.
1366 * read_lock(&tasklist_lock) on entry.  If we return zero, we still hold
1367 * the lock and this task is uninteresting.  If we return nonzero, we have
1368 * released the lock and the system call should return.
1369 */
1370static int wait_task_continued(struct wait_opts *wo, struct task_struct *p)
1371{
1372	struct waitid_info *infop;
1373	pid_t pid;
1374	uid_t uid;
1375
1376	if (!unlikely(wo->wo_flags & WCONTINUED))
1377		return 0;
1378
1379	if (!(p->signal->flags & SIGNAL_STOP_CONTINUED))
1380		return 0;
1381
1382	spin_lock_irq(&p->sighand->siglock);
1383	/* Re-check with the lock held.  */
1384	if (!(p->signal->flags & SIGNAL_STOP_CONTINUED)) {
1385		spin_unlock_irq(&p->sighand->siglock);
1386		return 0;
1387	}
1388	if (!unlikely(wo->wo_flags & WNOWAIT))
1389		p->signal->flags &= ~SIGNAL_STOP_CONTINUED;
1390	uid = from_kuid_munged(current_user_ns(), task_uid(p));
1391	spin_unlock_irq(&p->sighand->siglock);
1392
1393	pid = task_pid_vnr(p);
1394	get_task_struct(p);
1395	read_unlock(&tasklist_lock);
1396	sched_annotate_sleep();
1397	if (wo->wo_rusage)
1398		getrusage(p, RUSAGE_BOTH, wo->wo_rusage);
1399	put_task_struct(p);
1400
1401	infop = wo->wo_info;
1402	if (!infop) {
1403		wo->wo_stat = 0xffff;
1404	} else {
1405		infop->cause = CLD_CONTINUED;
1406		infop->pid = pid;
1407		infop->uid = uid;
1408		infop->status = SIGCONT;
1409	}
1410	return pid;
1411}
1412
1413/*
1414 * Consider @p for a wait by @parent.
1415 *
1416 * -ECHILD should be in ->notask_error before the first call.
1417 * Returns nonzero for a final return, when we have unlocked tasklist_lock.
1418 * Returns zero if the search for a child should continue;
1419 * then ->notask_error is 0 if @p is an eligible child,
1420 * or still -ECHILD.
1421 */
1422static int wait_consider_task(struct wait_opts *wo, int ptrace,
1423				struct task_struct *p)
1424{
1425	/*
1426	 * We can race with wait_task_zombie() from another thread.
1427	 * Ensure that EXIT_ZOMBIE -> EXIT_DEAD/EXIT_TRACE transition
1428	 * can't confuse the checks below.
1429	 */
1430	int exit_state = READ_ONCE(p->exit_state);
1431	int ret;
1432
1433	if (unlikely(exit_state == EXIT_DEAD))
1434		return 0;
1435
1436	ret = eligible_child(wo, ptrace, p);
1437	if (!ret)
1438		return ret;
1439
1440	if (unlikely(exit_state == EXIT_TRACE)) {
1441		/*
1442		 * ptrace == 0 means we are the natural parent. In this case
1443		 * we should clear notask_error, debugger will notify us.
1444		 */
1445		if (likely(!ptrace))
1446			wo->notask_error = 0;
1447		return 0;
1448	}
1449
1450	if (likely(!ptrace) && unlikely(p->ptrace)) {
1451		/*
1452		 * If it is traced by its real parent's group, just pretend
1453		 * the caller is ptrace_do_wait() and reap this child if it
1454		 * is zombie.
1455		 *
1456		 * This also hides group stop state from real parent; otherwise
1457		 * a single stop can be reported twice as group and ptrace stop.
1458		 * If a ptracer wants to distinguish these two events for its
1459		 * own children it should create a separate process which takes
1460		 * the role of real parent.
1461		 */
1462		if (!ptrace_reparented(p))
1463			ptrace = 1;
1464	}
1465
1466	/* slay zombie? */
1467	if (exit_state == EXIT_ZOMBIE) {
1468		/* we don't reap group leaders with subthreads */
1469		if (!delay_group_leader(p)) {
1470			/*
1471			 * A zombie ptracee is only visible to its ptracer.
1472			 * Notification and reaping will be cascaded to the
1473			 * real parent when the ptracer detaches.
1474			 */
1475			if (unlikely(ptrace) || likely(!p->ptrace))
1476				return wait_task_zombie(wo, p);
1477		}
1478
1479		/*
1480		 * Allow access to stopped/continued state via zombie by
1481		 * falling through.  Clearing of notask_error is complex.
1482		 *
1483		 * When !@ptrace:
1484		 *
1485		 * If WEXITED is set, notask_error should naturally be
1486		 * cleared.  If not, subset of WSTOPPED|WCONTINUED is set,
1487		 * so, if there are live subthreads, there are events to
1488		 * wait for.  If all subthreads are dead, it's still safe
1489		 * to clear - this function will be called again in finite
1490		 * amount time once all the subthreads are released and
1491		 * will then return without clearing.
1492		 *
1493		 * When @ptrace:
1494		 *
1495		 * Stopped state is per-task and thus can't change once the
1496		 * target task dies.  Only continued and exited can happen.
1497		 * Clear notask_error if WCONTINUED | WEXITED.
1498		 */
1499		if (likely(!ptrace) || (wo->wo_flags & (WCONTINUED | WEXITED)))
1500			wo->notask_error = 0;
1501	} else {
1502		/*
1503		 * @p is alive and it's gonna stop, continue or exit, so
1504		 * there always is something to wait for.
1505		 */
1506		wo->notask_error = 0;
1507	}
1508
1509	/*
1510	 * Wait for stopped.  Depending on @ptrace, different stopped state
1511	 * is used and the two don't interact with each other.
1512	 */
1513	ret = wait_task_stopped(wo, ptrace, p);
1514	if (ret)
1515		return ret;
1516
1517	/*
1518	 * Wait for continued.  There's only one continued state and the
1519	 * ptracer can consume it which can confuse the real parent.  Don't
1520	 * use WCONTINUED from ptracer.  You don't need or want it.
1521	 */
1522	return wait_task_continued(wo, p);
1523}
1524
1525/*
1526 * Do the work of do_wait() for one thread in the group, @tsk.
1527 *
1528 * -ECHILD should be in ->notask_error before the first call.
1529 * Returns nonzero for a final return, when we have unlocked tasklist_lock.
1530 * Returns zero if the search for a child should continue; then
1531 * ->notask_error is 0 if there were any eligible children,
1532 * or still -ECHILD.
1533 */
1534static int do_wait_thread(struct wait_opts *wo, struct task_struct *tsk)
1535{
1536	struct task_struct *p;
1537
1538	list_for_each_entry(p, &tsk->children, sibling) {
1539		int ret = wait_consider_task(wo, 0, p);
1540
1541		if (ret)
1542			return ret;
1543	}
1544
1545	return 0;
1546}
1547
1548static int ptrace_do_wait(struct wait_opts *wo, struct task_struct *tsk)
1549{
1550	struct task_struct *p;
1551
1552	list_for_each_entry(p, &tsk->ptraced, ptrace_entry) {
1553		int ret = wait_consider_task(wo, 1, p);
1554
1555		if (ret)
1556			return ret;
1557	}
1558
1559	return 0;
1560}
1561
1562bool pid_child_should_wake(struct wait_opts *wo, struct task_struct *p)
1563{
1564	if (!eligible_pid(wo, p))
1565		return false;
1566
1567	if ((wo->wo_flags & __WNOTHREAD) && wo->child_wait.private != p->parent)
1568		return false;
1569
1570	return true;
1571}
1572
1573static int child_wait_callback(wait_queue_entry_t *wait, unsigned mode,
1574				int sync, void *key)
1575{
1576	struct wait_opts *wo = container_of(wait, struct wait_opts,
1577						child_wait);
1578	struct task_struct *p = key;
1579
1580	if (pid_child_should_wake(wo, p))
1581		return default_wake_function(wait, mode, sync, key);
1582
1583	return 0;
1584}
1585
1586void __wake_up_parent(struct task_struct *p, struct task_struct *parent)
1587{
1588	__wake_up_sync_key(&parent->signal->wait_chldexit,
1589			   TASK_INTERRUPTIBLE, p);
1590}
1591
1592static bool is_effectively_child(struct wait_opts *wo, bool ptrace,
1593				 struct task_struct *target)
1594{
1595	struct task_struct *parent =
1596		!ptrace ? target->real_parent : target->parent;
1597
1598	return current == parent || (!(wo->wo_flags & __WNOTHREAD) &&
1599				     same_thread_group(current, parent));
1600}
1601
1602/*
1603 * Optimization for waiting on PIDTYPE_PID. No need to iterate through child
1604 * and tracee lists to find the target task.
1605 */
1606static int do_wait_pid(struct wait_opts *wo)
1607{
1608	bool ptrace;
1609	struct task_struct *target;
1610	int retval;
1611
1612	ptrace = false;
1613	target = pid_task(wo->wo_pid, PIDTYPE_TGID);
1614	if (target && is_effectively_child(wo, ptrace, target)) {
1615		retval = wait_consider_task(wo, ptrace, target);
1616		if (retval)
1617			return retval;
1618	}
1619
1620	ptrace = true;
1621	target = pid_task(wo->wo_pid, PIDTYPE_PID);
1622	if (target && target->ptrace &&
1623	    is_effectively_child(wo, ptrace, target)) {
1624		retval = wait_consider_task(wo, ptrace, target);
1625		if (retval)
1626			return retval;
1627	}
1628
1629	return 0;
1630}
1631
1632long __do_wait(struct wait_opts *wo)
1633{
1634	long retval;
1635
1636	/*
1637	 * If there is nothing that can match our criteria, just get out.
1638	 * We will clear ->notask_error to zero if we see any child that
1639	 * might later match our criteria, even if we are not able to reap
1640	 * it yet.
1641	 */
1642	wo->notask_error = -ECHILD;
1643	if ((wo->wo_type < PIDTYPE_MAX) &&
1644	   (!wo->wo_pid || !pid_has_task(wo->wo_pid, wo->wo_type)))
1645		goto notask;
1646
1647	read_lock(&tasklist_lock);
1648
1649	if (wo->wo_type == PIDTYPE_PID) {
1650		retval = do_wait_pid(wo);
1651		if (retval)
1652			return retval;
1653	} else {
1654		struct task_struct *tsk = current;
1655
1656		do {
1657			retval = do_wait_thread(wo, tsk);
1658			if (retval)
1659				return retval;
1660
1661			retval = ptrace_do_wait(wo, tsk);
1662			if (retval)
1663				return retval;
1664
1665			if (wo->wo_flags & __WNOTHREAD)
1666				break;
1667		} while_each_thread(current, tsk);
1668	}
1669	read_unlock(&tasklist_lock);
1670
1671notask:
1672	retval = wo->notask_error;
1673	if (!retval && !(wo->wo_flags & WNOHANG))
1674		return -ERESTARTSYS;
1675
1676	return retval;
1677}
1678
1679static long do_wait(struct wait_opts *wo)
1680{
1681	int retval;
1682
1683	trace_sched_process_wait(wo->wo_pid);
1684
1685	init_waitqueue_func_entry(&wo->child_wait, child_wait_callback);
1686	wo->child_wait.private = current;
1687	add_wait_queue(&current->signal->wait_chldexit, &wo->child_wait);
1688
1689	do {
1690		set_current_state(TASK_INTERRUPTIBLE);
1691		retval = __do_wait(wo);
1692		if (retval != -ERESTARTSYS)
1693			break;
1694		if (signal_pending(current))
1695			break;
1696		schedule();
1697	} while (1);
1698
1699	__set_current_state(TASK_RUNNING);
1700	remove_wait_queue(&current->signal->wait_chldexit, &wo->child_wait);
1701	return retval;
1702}
1703
1704int kernel_waitid_prepare(struct wait_opts *wo, int which, pid_t upid,
1705			  struct waitid_info *infop, int options,
1706			  struct rusage *ru)
1707{
1708	unsigned int f_flags = 0;
1709	struct pid *pid = NULL;
1710	enum pid_type type;
1711
1712	if (options & ~(WNOHANG|WNOWAIT|WEXITED|WSTOPPED|WCONTINUED|
1713			__WNOTHREAD|__WCLONE|__WALL))
1714		return -EINVAL;
1715	if (!(options & (WEXITED|WSTOPPED|WCONTINUED)))
1716		return -EINVAL;
1717
1718	switch (which) {
1719	case P_ALL:
1720		type = PIDTYPE_MAX;
1721		break;
1722	case P_PID:
1723		type = PIDTYPE_PID;
1724		if (upid <= 0)
1725			return -EINVAL;
1726
1727		pid = find_get_pid(upid);
1728		break;
1729	case P_PGID:
1730		type = PIDTYPE_PGID;
1731		if (upid < 0)
1732			return -EINVAL;
1733
1734		if (upid)
1735			pid = find_get_pid(upid);
1736		else
1737			pid = get_task_pid(current, PIDTYPE_PGID);
1738		break;
1739	case P_PIDFD:
1740		type = PIDTYPE_PID;
1741		if (upid < 0)
1742			return -EINVAL;
1743
1744		pid = pidfd_get_pid(upid, &f_flags);
1745		if (IS_ERR(pid))
1746			return PTR_ERR(pid);
1747
1748		break;
1749	default:
1750		return -EINVAL;
1751	}
1752
1753	wo->wo_type	= type;
1754	wo->wo_pid	= pid;
1755	wo->wo_flags	= options;
1756	wo->wo_info	= infop;
1757	wo->wo_rusage	= ru;
1758	if (f_flags & O_NONBLOCK)
1759		wo->wo_flags |= WNOHANG;
1760
1761	return 0;
1762}
1763
1764static long kernel_waitid(int which, pid_t upid, struct waitid_info *infop,
1765			  int options, struct rusage *ru)
1766{
1767	struct wait_opts wo;
1768	long ret;
1769
1770	ret = kernel_waitid_prepare(&wo, which, upid, infop, options, ru);
1771	if (ret)
1772		return ret;
1773
1774	ret = do_wait(&wo);
1775	if (!ret && !(options & WNOHANG) && (wo.wo_flags & WNOHANG))
1776		ret = -EAGAIN;
1777
1778	put_pid(wo.wo_pid);
1779	return ret;
1780}
1781
1782SYSCALL_DEFINE5(waitid, int, which, pid_t, upid, struct siginfo __user *,
1783		infop, int, options, struct rusage __user *, ru)
1784{
1785	struct rusage r;
1786	struct waitid_info info = {.status = 0};
1787	long err = kernel_waitid(which, upid, &info, options, ru ? &r : NULL);
1788	int signo = 0;
1789
1790	if (err > 0) {
1791		signo = SIGCHLD;
1792		err = 0;
1793		if (ru && copy_to_user(ru, &r, sizeof(struct rusage)))
1794			return -EFAULT;
1795	}
1796	if (!infop)
1797		return err;
1798
1799	if (!user_write_access_begin(infop, sizeof(*infop)))
1800		return -EFAULT;
1801
1802	unsafe_put_user(signo, &infop->si_signo, Efault);
1803	unsafe_put_user(0, &infop->si_errno, Efault);
1804	unsafe_put_user(info.cause, &infop->si_code, Efault);
1805	unsafe_put_user(info.pid, &infop->si_pid, Efault);
1806	unsafe_put_user(info.uid, &infop->si_uid, Efault);
1807	unsafe_put_user(info.status, &infop->si_status, Efault);
1808	user_write_access_end();
1809	return err;
1810Efault:
1811	user_write_access_end();
1812	return -EFAULT;
1813}
1814
1815long kernel_wait4(pid_t upid, int __user *stat_addr, int options,
1816		  struct rusage *ru)
1817{
1818	struct wait_opts wo;
1819	struct pid *pid = NULL;
1820	enum pid_type type;
1821	long ret;
1822
1823	if (options & ~(WNOHANG|WUNTRACED|WCONTINUED|
1824			__WNOTHREAD|__WCLONE|__WALL))
1825		return -EINVAL;
1826
1827	/* -INT_MIN is not defined */
1828	if (upid == INT_MIN)
1829		return -ESRCH;
1830
1831	if (upid == -1)
1832		type = PIDTYPE_MAX;
1833	else if (upid < 0) {
1834		type = PIDTYPE_PGID;
1835		pid = find_get_pid(-upid);
1836	} else if (upid == 0) {
1837		type = PIDTYPE_PGID;
1838		pid = get_task_pid(current, PIDTYPE_PGID);
1839	} else /* upid > 0 */ {
1840		type = PIDTYPE_PID;
1841		pid = find_get_pid(upid);
1842	}
1843
1844	wo.wo_type	= type;
1845	wo.wo_pid	= pid;
1846	wo.wo_flags	= options | WEXITED;
1847	wo.wo_info	= NULL;
1848	wo.wo_stat	= 0;
1849	wo.wo_rusage	= ru;
1850	ret = do_wait(&wo);
1851	put_pid(pid);
1852	if (ret > 0 && stat_addr && put_user(wo.wo_stat, stat_addr))
1853		ret = -EFAULT;
1854
1855	return ret;
1856}
1857
1858int kernel_wait(pid_t pid, int *stat)
1859{
1860	struct wait_opts wo = {
1861		.wo_type	= PIDTYPE_PID,
1862		.wo_pid		= find_get_pid(pid),
1863		.wo_flags	= WEXITED,
1864	};
1865	int ret;
1866
1867	ret = do_wait(&wo);
1868	if (ret > 0 && wo.wo_stat)
1869		*stat = wo.wo_stat;
1870	put_pid(wo.wo_pid);
1871	return ret;
1872}
1873
1874SYSCALL_DEFINE4(wait4, pid_t, upid, int __user *, stat_addr,
1875		int, options, struct rusage __user *, ru)
1876{
1877	struct rusage r;
1878	long err = kernel_wait4(upid, stat_addr, options, ru ? &r : NULL);
1879
1880	if (err > 0) {
1881		if (ru && copy_to_user(ru, &r, sizeof(struct rusage)))
1882			return -EFAULT;
1883	}
1884	return err;
1885}
1886
1887#ifdef __ARCH_WANT_SYS_WAITPID
1888
1889/*
1890 * sys_waitpid() remains for compatibility. waitpid() should be
1891 * implemented by calling sys_wait4() from libc.a.
1892 */
1893SYSCALL_DEFINE3(waitpid, pid_t, pid, int __user *, stat_addr, int, options)
1894{
1895	return kernel_wait4(pid, stat_addr, options, NULL);
1896}
1897
1898#endif
1899
1900#ifdef CONFIG_COMPAT
1901COMPAT_SYSCALL_DEFINE4(wait4,
1902	compat_pid_t, pid,
1903	compat_uint_t __user *, stat_addr,
1904	int, options,
1905	struct compat_rusage __user *, ru)
1906{
1907	struct rusage r;
1908	long err = kernel_wait4(pid, stat_addr, options, ru ? &r : NULL);
1909	if (err > 0) {
1910		if (ru && put_compat_rusage(&r, ru))
1911			return -EFAULT;
1912	}
1913	return err;
1914}
1915
1916COMPAT_SYSCALL_DEFINE5(waitid,
1917		int, which, compat_pid_t, pid,
1918		struct compat_siginfo __user *, infop, int, options,
1919		struct compat_rusage __user *, uru)
1920{
1921	struct rusage ru;
1922	struct waitid_info info = {.status = 0};
1923	long err = kernel_waitid(which, pid, &info, options, uru ? &ru : NULL);
1924	int signo = 0;
1925	if (err > 0) {
1926		signo = SIGCHLD;
1927		err = 0;
1928		if (uru) {
1929			/* kernel_waitid() overwrites everything in ru */
1930			if (COMPAT_USE_64BIT_TIME)
1931				err = copy_to_user(uru, &ru, sizeof(ru));
1932			else
1933				err = put_compat_rusage(&ru, uru);
1934			if (err)
1935				return -EFAULT;
1936		}
1937	}
1938
1939	if (!infop)
1940		return err;
1941
1942	if (!user_write_access_begin(infop, sizeof(*infop)))
1943		return -EFAULT;
1944
1945	unsafe_put_user(signo, &infop->si_signo, Efault);
1946	unsafe_put_user(0, &infop->si_errno, Efault);
1947	unsafe_put_user(info.cause, &infop->si_code, Efault);
1948	unsafe_put_user(info.pid, &infop->si_pid, Efault);
1949	unsafe_put_user(info.uid, &infop->si_uid, Efault);
1950	unsafe_put_user(info.status, &infop->si_status, Efault);
1951	user_write_access_end();
1952	return err;
1953Efault:
1954	user_write_access_end();
1955	return -EFAULT;
1956}
1957#endif
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1958
1959/*
1960 * This needs to be __function_aligned as GCC implicitly makes any
1961 * implementation of abort() cold and drops alignment specified by
1962 * -falign-functions=N.
1963 *
1964 * See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88345#c11
1965 */
1966__weak __function_aligned void abort(void)
1967{
1968	BUG();
1969
1970	/* if that doesn't kill us, halt */
1971	panic("Oops failed to kill thread");
1972}
1973EXPORT_SYMBOL(abort);