1// SPDX-License-Identifier: GPL-2.0-only
   2/*
   3 *  linux/kernel/exit.c
   4 *
   5 *  Copyright (C) 1991, 1992  Linus Torvalds
   6 */
   7
   8#include <linux/mm.h>
   9#include <linux/slab.h>
  10#include <linux/sched/autogroup.h>
  11#include <linux/sched/mm.h>
  12#include <linux/sched/stat.h>
  13#include <linux/sched/task.h>
  14#include <linux/sched/task_stack.h>
  15#include <linux/sched/cputime.h>
  16#include <linux/interrupt.h>
  17#include <linux/module.h>
  18#include <linux/capability.h>
  19#include <linux/completion.h>
  20#include <linux/personality.h>
  21#include <linux/tty.h>
  22#include <linux/iocontext.h>
  23#include <linux/key.h>
  24#include <linux/cpu.h>
  25#include <linux/acct.h>
  26#include <linux/tsacct_kern.h>
  27#include <linux/file.h>
  28#include <linux/fdtable.h>
  29#include <linux/freezer.h>
  30#include <linux/binfmts.h>
  31#include <linux/nsproxy.h>
  32#include <linux/pid_namespace.h>
  33#include <linux/ptrace.h>
  34#include <linux/profile.h>
  35#include <linux/mount.h>
  36#include <linux/proc_fs.h>
  37#include <linux/kthread.h>
  38#include <linux/mempolicy.h>
  39#include <linux/taskstats_kern.h>
  40#include <linux/delayacct.h>
  41#include <linux/cgroup.h>
  42#include <linux/syscalls.h>
  43#include <linux/signal.h>
  44#include <linux/posix-timers.h>
  45#include <linux/cn_proc.h>
  46#include <linux/mutex.h>
  47#include <linux/futex.h>
  48#include <linux/pipe_fs_i.h>
  49#include <linux/audit.h> /* for audit_free() */
  50#include <linux/resource.h>
  51#include <linux/task_io_accounting_ops.h>
  52#include <linux/blkdev.h>
  53#include <linux/task_work.h>
 
  54#include <linux/fs_struct.h>
  55#include <linux/init_task.h>
  56#include <linux/perf_event.h>
  57#include <trace/events/sched.h>
  58#include <linux/hw_breakpoint.h>
  59#include <linux/oom.h>
  60#include <linux/writeback.h>
  61#include <linux/shm.h>
  62#include <linux/kcov.h>
  63#include <linux/kmsan.h>
  64#include <linux/random.h>
  65#include <linux/rcuwait.h>
  66#include <linux/compat.h>
  67#include <linux/io_uring.h>
  68#include <linux/kprobes.h>
  69#include <linux/rethook.h>
  70#include <linux/sysfs.h>
  71#include <linux/user_events.h>
  72#include <linux/uaccess.h>
  73
  74#include <uapi/linux/wait.h>
  75
 
  76#include <asm/unistd.h>
  77#include <asm/mmu_context.h>
  78
  79#include "exit.h"
  80
  81/*
  82 * The default value should be high enough to not crash a system that randomly
  83 * crashes its kernel from time to time, but low enough to at least not permit
  84 * overflowing 32-bit refcounts or the ldsem writer count.
  85 */
  86static unsigned int oops_limit = 10000;
  87
  88#ifdef CONFIG_SYSCTL
  89static struct ctl_table kern_exit_table[] = {
  90	{
  91		.procname       = "oops_limit",
  92		.data           = &oops_limit,
  93		.maxlen         = sizeof(oops_limit),
  94		.mode           = 0644,
  95		.proc_handler   = proc_douintvec,
  96	},
  97	{ }
  98};
  99
 100static __init int kernel_exit_sysctls_init(void)
 101{
 102	register_sysctl_init("kernel", kern_exit_table);
 103	return 0;
 104}
 105late_initcall(kernel_exit_sysctls_init);
 106#endif
 107
 108static atomic_t oops_count = ATOMIC_INIT(0);
 109
 110#ifdef CONFIG_SYSFS
 111static ssize_t oops_count_show(struct kobject *kobj, struct kobj_attribute *attr,
 112			       char *page)
 113{
 114	return sysfs_emit(page, "%d\n", atomic_read(&oops_count));
 115}
 116
 117static struct kobj_attribute oops_count_attr = __ATTR_RO(oops_count);
 118
 119static __init int kernel_exit_sysfs_init(void)
 120{
 121	sysfs_add_file_to_group(kernel_kobj, &oops_count_attr.attr, NULL);
 122	return 0;
 123}
 124late_initcall(kernel_exit_sysfs_init);
 125#endif
 126
 127static void __unhash_process(struct task_struct *p, bool group_dead)
 128{
 129	nr_threads--;
 130	detach_pid(p, PIDTYPE_PID);
 131	if (group_dead) {
 132		detach_pid(p, PIDTYPE_TGID);
 133		detach_pid(p, PIDTYPE_PGID);
 134		detach_pid(p, PIDTYPE_SID);
 135
 136		list_del_rcu(&p->tasks);
 137		list_del_init(&p->sibling);
 138		__this_cpu_dec(process_counts);
 139	}
 
 140	list_del_rcu(&p->thread_node);
 141}
 142
 143/*
 144 * This function expects the tasklist_lock write-locked.
 145 */
 146static void __exit_signal(struct task_struct *tsk)
 147{
 148	struct signal_struct *sig = tsk->signal;
 149	bool group_dead = thread_group_leader(tsk);
 150	struct sighand_struct *sighand;
 151	struct tty_struct *tty;
 152	u64 utime, stime;
 153
 154	sighand = rcu_dereference_check(tsk->sighand,
 155					lockdep_tasklist_lock_is_held());
 156	spin_lock(&sighand->siglock);
 157
 158#ifdef CONFIG_POSIX_TIMERS
 159	posix_cpu_timers_exit(tsk);
 160	if (group_dead)
 161		posix_cpu_timers_exit_group(tsk);
 162#endif
 163
 164	if (group_dead) {
 165		tty = sig->tty;
 166		sig->tty = NULL;
 167	} else {
 168		/*
 169		 * If there is any task waiting for the group exit
 170		 * then notify it:
 171		 */
 172		if (sig->notify_count > 0 && !--sig->notify_count)
 173			wake_up_process(sig->group_exec_task);
 174
 175		if (tsk == sig->curr_target)
 176			sig->curr_target = next_thread(tsk);
 177	}
 178
 179	add_device_randomness((const void*) &tsk->se.sum_exec_runtime,
 180			      sizeof(unsigned long long));
 181
 182	/*
 183	 * Accumulate here the counters for all threads as they die. We could
 184	 * skip the group leader because it is the last user of signal_struct,
 185	 * but we want to avoid the race with thread_group_cputime() which can
 186	 * see the empty ->thread_head list.
 187	 */
 188	task_cputime(tsk, &utime, &stime);
 189	write_seqlock(&sig->stats_lock);
 190	sig->utime += utime;
 191	sig->stime += stime;
 192	sig->gtime += task_gtime(tsk);
 193	sig->min_flt += tsk->min_flt;
 194	sig->maj_flt += tsk->maj_flt;
 195	sig->nvcsw += tsk->nvcsw;
 196	sig->nivcsw += tsk->nivcsw;
 197	sig->inblock += task_io_get_inblock(tsk);
 198	sig->oublock += task_io_get_oublock(tsk);
 199	task_io_accounting_add(&sig->ioac, &tsk->ioac);
 200	sig->sum_sched_runtime += tsk->se.sum_exec_runtime;
 201	sig->nr_threads--;
 202	__unhash_process(tsk, group_dead);
 203	write_sequnlock(&sig->stats_lock);
 204
 205	/*
 206	 * Do this under ->siglock, we can race with another thread
 207	 * doing sigqueue_free() if we have SIGQUEUE_PREALLOC signals.
 208	 */
 209	flush_sigqueue(&tsk->pending);
 210	tsk->sighand = NULL;
 211	spin_unlock(&sighand->siglock);
 212
 213	__cleanup_sighand(sighand);
 214	clear_tsk_thread_flag(tsk, TIF_SIGPENDING);
 215	if (group_dead) {
 216		flush_sigqueue(&sig->shared_pending);
 217		tty_kref_put(tty);
 218	}
 219}
 220
 221static void delayed_put_task_struct(struct rcu_head *rhp)
 222{
 223	struct task_struct *tsk = container_of(rhp, struct task_struct, rcu);
 224
 225	kprobe_flush_task(tsk);
 226	rethook_flush_task(tsk);
 227	perf_event_delayed_put(tsk);
 228	trace_sched_process_free(tsk);
 229	put_task_struct(tsk);
 230}
 231
 232void put_task_struct_rcu_user(struct task_struct *task)
 233{
 234	if (refcount_dec_and_test(&task->rcu_users))
 235		call_rcu(&task->rcu, delayed_put_task_struct);
 236}
 237
 238void __weak release_thread(struct task_struct *dead_task)
 239{
 240}
 241
 242void release_task(struct task_struct *p)
 243{
 244	struct task_struct *leader;
 245	struct pid *thread_pid;
 246	int zap_leader;
 247repeat:
 248	/* don't need to get the RCU readlock here - the process is dead and
 249	 * can't be modifying its own credentials. But shut RCU-lockdep up */
 250	rcu_read_lock();
 251	dec_rlimit_ucounts(task_ucounts(p), UCOUNT_RLIMIT_NPROC, 1);
 252	rcu_read_unlock();
 253
 254	cgroup_release(p);
 255
 256	write_lock_irq(&tasklist_lock);
 257	ptrace_release_task(p);
 258	thread_pid = get_pid(p->thread_pid);
 259	__exit_signal(p);
 260
 261	/*
 262	 * If we are the last non-leader member of the thread
 263	 * group, and the leader is zombie, then notify the
 264	 * group leader's parent process. (if it wants notification.)
 265	 */
 266	zap_leader = 0;
 267	leader = p->group_leader;
 268	if (leader != p && thread_group_empty(leader)
 269			&& leader->exit_state == EXIT_ZOMBIE) {
 270		/*
 271		 * If we were the last child thread and the leader has
 272		 * exited already, and the leader's parent ignores SIGCHLD,
 273		 * then we are the one who should release the leader.
 274		 */
 275		zap_leader = do_notify_parent(leader, leader->exit_signal);
 276		if (zap_leader)
 277			leader->exit_state = EXIT_DEAD;
 278	}
 279
 280	write_unlock_irq(&tasklist_lock);
 281	seccomp_filter_release(p);
 282	proc_flush_pid(thread_pid);
 283	put_pid(thread_pid);
 284	release_thread(p);
 285	put_task_struct_rcu_user(p);
 286
 287	p = leader;
 288	if (unlikely(zap_leader))
 289		goto repeat;
 290}
 291
 292int rcuwait_wake_up(struct rcuwait *w)
 293{
 294	int ret = 0;
 295	struct task_struct *task;
 296
 297	rcu_read_lock();
 298
 299	/*
 300	 * Order condition vs @task, such that everything prior to the load
 301	 * of @task is visible. This is the condition as to why the user called
 302	 * rcuwait_wake() in the first place. Pairs with set_current_state()
 303	 * barrier (A) in rcuwait_wait_event().
 304	 *
 305	 *    WAIT                WAKE
 306	 *    [S] tsk = current	  [S] cond = true
 307	 *        MB (A)	      MB (B)
 308	 *    [L] cond		  [L] tsk
 309	 */
 310	smp_mb(); /* (B) */
 311
 312	task = rcu_dereference(w->task);
 313	if (task)
 314		ret = wake_up_process(task);
 315	rcu_read_unlock();
 316
 317	return ret;
 318}
 319EXPORT_SYMBOL_GPL(rcuwait_wake_up);
 320
 321/*
 322 * Determine if a process group is "orphaned", according to the POSIX
 323 * definition in 2.2.2.52.  Orphaned process groups are not to be affected
 324 * by terminal-generated stop signals.  Newly orphaned process groups are
 325 * to receive a SIGHUP and a SIGCONT.
 326 *
 327 * "I ask you, have you ever known what it is to be an orphan?"
 328 */
 329static int will_become_orphaned_pgrp(struct pid *pgrp,
 330					struct task_struct *ignored_task)
 331{
 332	struct task_struct *p;
 333
 334	do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
 335		if ((p == ignored_task) ||
 336		    (p->exit_state && thread_group_empty(p)) ||
 337		    is_global_init(p->real_parent))
 338			continue;
 339
 340		if (task_pgrp(p->real_parent) != pgrp &&
 341		    task_session(p->real_parent) == task_session(p))
 342			return 0;
 343	} while_each_pid_task(pgrp, PIDTYPE_PGID, p);
 344
 345	return 1;
 346}
 347
 348int is_current_pgrp_orphaned(void)
 349{
 350	int retval;
 351
 352	read_lock(&tasklist_lock);
 353	retval = will_become_orphaned_pgrp(task_pgrp(current), NULL);
 354	read_unlock(&tasklist_lock);
 355
 356	return retval;
 357}
 358
 359static bool has_stopped_jobs(struct pid *pgrp)
 360{
 361	struct task_struct *p;
 362
 363	do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
 364		if (p->signal->flags & SIGNAL_STOP_STOPPED)
 365			return true;
 366	} while_each_pid_task(pgrp, PIDTYPE_PGID, p);
 367
 368	return false;
 369}
 370
 371/*
 372 * Check to see if any process groups have become orphaned as
 373 * a result of our exiting, and if they have any stopped jobs,
 374 * send them a SIGHUP and then a SIGCONT. (POSIX 3.2.2.2)
 375 */
 376static void
 377kill_orphaned_pgrp(struct task_struct *tsk, struct task_struct *parent)
 378{
 379	struct pid *pgrp = task_pgrp(tsk);
 380	struct task_struct *ignored_task = tsk;
 381
 382	if (!parent)
 383		/* exit: our father is in a different pgrp than
 384		 * we are and we were the only connection outside.
 385		 */
 386		parent = tsk->real_parent;
 387	else
 388		/* reparent: our child is in a different pgrp than
 389		 * we are, and it was the only connection outside.
 390		 */
 391		ignored_task = NULL;
 392
 393	if (task_pgrp(parent) != pgrp &&
 394	    task_session(parent) == task_session(tsk) &&
 395	    will_become_orphaned_pgrp(pgrp, ignored_task) &&
 396	    has_stopped_jobs(pgrp)) {
 397		__kill_pgrp_info(SIGHUP, SEND_SIG_PRIV, pgrp);
 398		__kill_pgrp_info(SIGCONT, SEND_SIG_PRIV, pgrp);
 399	}
 400}
 401
 402static void coredump_task_exit(struct task_struct *tsk)
 403{
 404	struct core_state *core_state;
 405
 406	/*
 407	 * Serialize with any possible pending coredump.
 408	 * We must hold siglock around checking core_state
 409	 * and setting PF_POSTCOREDUMP.  The core-inducing thread
 410	 * will increment ->nr_threads for each thread in the
 411	 * group without PF_POSTCOREDUMP set.
 412	 */
 413	spin_lock_irq(&tsk->sighand->siglock);
 414	tsk->flags |= PF_POSTCOREDUMP;
 415	core_state = tsk->signal->core_state;
 416	spin_unlock_irq(&tsk->sighand->siglock);
 417
 418	/* The vhost_worker does not particpate in coredumps */
 419	if (core_state &&
 420	    ((tsk->flags & (PF_IO_WORKER | PF_USER_WORKER)) != PF_USER_WORKER)) {
 421		struct core_thread self;
 422
 423		self.task = current;
 424		if (self.task->flags & PF_SIGNALED)
 425			self.next = xchg(&core_state->dumper.next, &self);
 426		else
 427			self.task = NULL;
 428		/*
 429		 * Implies mb(), the result of xchg() must be visible
 430		 * to core_state->dumper.
 431		 */
 432		if (atomic_dec_and_test(&core_state->nr_threads))
 433			complete(&core_state->startup);
 434
 435		for (;;) {
 436			set_current_state(TASK_UNINTERRUPTIBLE|TASK_FREEZABLE);
 437			if (!self.task) /* see coredump_finish() */
 438				break;
 439			schedule();
 440		}
 441		__set_current_state(TASK_RUNNING);
 442	}
 443}
 444
 445#ifdef CONFIG_MEMCG
 446/*
 447 * A task is exiting.   If it owned this mm, find a new owner for the mm.
 448 */
 449void mm_update_next_owner(struct mm_struct *mm)
 450{
 451	struct task_struct *c, *g, *p = current;
 452
 453retry:
 454	/*
 455	 * If the exiting or execing task is not the owner, it's
 456	 * someone else's problem.
 457	 */
 458	if (mm->owner != p)
 459		return;
 460	/*
 461	 * The current owner is exiting/execing and there are no other
 462	 * candidates.  Do not leave the mm pointing to a possibly
 463	 * freed task structure.
 464	 */
 465	if (atomic_read(&mm->mm_users) <= 1) {
 466		WRITE_ONCE(mm->owner, NULL);
 467		return;
 468	}
 469
 470	read_lock(&tasklist_lock);
 471	/*
 472	 * Search in the children
 473	 */
 474	list_for_each_entry(c, &p->children, sibling) {
 475		if (c->mm == mm)
 476			goto assign_new_owner;
 477	}
 478
 479	/*
 480	 * Search in the siblings
 481	 */
 482	list_for_each_entry(c, &p->real_parent->children, sibling) {
 483		if (c->mm == mm)
 484			goto assign_new_owner;
 485	}
 486
 487	/*
 488	 * Search through everything else, we should not get here often.
 489	 */
 490	for_each_process(g) {
 491		if (g->flags & PF_KTHREAD)
 492			continue;
 493		for_each_thread(g, c) {
 494			if (c->mm == mm)
 495				goto assign_new_owner;
 496			if (c->mm)
 497				break;
 498		}
 499	}
 500	read_unlock(&tasklist_lock);
 501	/*
 502	 * We found no owner yet mm_users > 1: this implies that we are
 503	 * most likely racing with swapoff (try_to_unuse()) or /proc or
 504	 * ptrace or page migration (get_task_mm()).  Mark owner as NULL.
 505	 */
 506	WRITE_ONCE(mm->owner, NULL);
 507	return;
 508
 509assign_new_owner:
 510	BUG_ON(c == p);
 511	get_task_struct(c);
 512	/*
 513	 * The task_lock protects c->mm from changing.
 514	 * We always want mm->owner->mm == mm
 515	 */
 516	task_lock(c);
 517	/*
 518	 * Delay read_unlock() till we have the task_lock()
 519	 * to ensure that c does not slip away underneath us
 520	 */
 521	read_unlock(&tasklist_lock);
 522	if (c->mm != mm) {
 523		task_unlock(c);
 524		put_task_struct(c);
 525		goto retry;
 526	}
 527	WRITE_ONCE(mm->owner, c);
 528	lru_gen_migrate_mm(mm);
 529	task_unlock(c);
 530	put_task_struct(c);
 531}
 532#endif /* CONFIG_MEMCG */
 533
 534/*
 535 * Turn us into a lazy TLB process if we
 536 * aren't already..
 537 */
 538static void exit_mm(void)
 539{
 540	struct mm_struct *mm = current->mm;
 
 541
 542	exit_mm_release(current, mm);
 543	if (!mm)
 544		return;
 
 
 
 
 
 
 
 
 545	mmap_read_lock(mm);
 546	mmgrab_lazy_tlb(mm);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 547	BUG_ON(mm != current->active_mm);
 548	/* more a memory barrier than a real lock */
 549	task_lock(current);
 550	/*
 551	 * When a thread stops operating on an address space, the loop
 552	 * in membarrier_private_expedited() may not observe that
 553	 * tsk->mm, and the loop in membarrier_global_expedited() may
 554	 * not observe a MEMBARRIER_STATE_GLOBAL_EXPEDITED
 555	 * rq->membarrier_state, so those would not issue an IPI.
 556	 * Membarrier requires a memory barrier after accessing
 557	 * user-space memory, before clearing tsk->mm or the
 558	 * rq->membarrier_state.
 559	 */
 560	smp_mb__after_spinlock();
 561	local_irq_disable();
 562	current->mm = NULL;
 563	membarrier_update_current_mm(NULL);
 564	enter_lazy_tlb(mm, current);
 565	local_irq_enable();
 566	task_unlock(current);
 567	mmap_read_unlock(mm);
 568	mm_update_next_owner(mm);
 569	mmput(mm);
 570	if (test_thread_flag(TIF_MEMDIE))
 571		exit_oom_victim();
 572}
 573
 574static struct task_struct *find_alive_thread(struct task_struct *p)
 575{
 576	struct task_struct *t;
 577
 578	for_each_thread(p, t) {
 579		if (!(t->flags & PF_EXITING))
 580			return t;
 581	}
 582	return NULL;
 583}
 584
 585static struct task_struct *find_child_reaper(struct task_struct *father,
 586						struct list_head *dead)
 587	__releases(&tasklist_lock)
 588	__acquires(&tasklist_lock)
 589{
 590	struct pid_namespace *pid_ns = task_active_pid_ns(father);
 591	struct task_struct *reaper = pid_ns->child_reaper;
 592	struct task_struct *p, *n;
 593
 594	if (likely(reaper != father))
 595		return reaper;
 596
 597	reaper = find_alive_thread(father);
 598	if (reaper) {
 599		pid_ns->child_reaper = reaper;
 600		return reaper;
 601	}
 602
 603	write_unlock_irq(&tasklist_lock);
 604
 605	list_for_each_entry_safe(p, n, dead, ptrace_entry) {
 606		list_del_init(&p->ptrace_entry);
 607		release_task(p);
 608	}
 609
 610	zap_pid_ns_processes(pid_ns);
 611	write_lock_irq(&tasklist_lock);
 612
 613	return father;
 614}
 615
 616/*
 617 * When we die, we re-parent all our children, and try to:
 618 * 1. give them to another thread in our thread group, if such a member exists
 619 * 2. give it to the first ancestor process which prctl'd itself as a
 620 *    child_subreaper for its children (like a service manager)
 621 * 3. give it to the init process (PID 1) in our pid namespace
 622 */
 623static struct task_struct *find_new_reaper(struct task_struct *father,
 624					   struct task_struct *child_reaper)
 625{
 626	struct task_struct *thread, *reaper;
 627
 628	thread = find_alive_thread(father);
 629	if (thread)
 630		return thread;
 631
 632	if (father->signal->has_child_subreaper) {
 633		unsigned int ns_level = task_pid(father)->level;
 634		/*
 635		 * Find the first ->is_child_subreaper ancestor in our pid_ns.
 636		 * We can't check reaper != child_reaper to ensure we do not
 637		 * cross the namespaces, the exiting parent could be injected
 638		 * by setns() + fork().
 639		 * We check pid->level, this is slightly more efficient than
 640		 * task_active_pid_ns(reaper) != task_active_pid_ns(father).
 641		 */
 642		for (reaper = father->real_parent;
 643		     task_pid(reaper)->level == ns_level;
 644		     reaper = reaper->real_parent) {
 645			if (reaper == &init_task)
 646				break;
 647			if (!reaper->signal->is_child_subreaper)
 648				continue;
 649			thread = find_alive_thread(reaper);
 650			if (thread)
 651				return thread;
 652		}
 653	}
 654
 655	return child_reaper;
 656}
 657
 658/*
 659* Any that need to be release_task'd are put on the @dead list.
 660 */
 661static void reparent_leader(struct task_struct *father, struct task_struct *p,
 662				struct list_head *dead)
 663{
 664	if (unlikely(p->exit_state == EXIT_DEAD))
 665		return;
 666
 667	/* We don't want people slaying init. */
 668	p->exit_signal = SIGCHLD;
 669
 670	/* If it has exited notify the new parent about this child's death. */
 671	if (!p->ptrace &&
 672	    p->exit_state == EXIT_ZOMBIE && thread_group_empty(p)) {
 673		if (do_notify_parent(p, p->exit_signal)) {
 674			p->exit_state = EXIT_DEAD;
 675			list_add(&p->ptrace_entry, dead);
 676		}
 677	}
 678
 679	kill_orphaned_pgrp(p, father);
 680}
 681
 682/*
 683 * This does two things:
 684 *
 685 * A.  Make init inherit all the child processes
 686 * B.  Check to see if any process groups have become orphaned
 687 *	as a result of our exiting, and if they have any stopped
 688 *	jobs, send them a SIGHUP and then a SIGCONT.  (POSIX 3.2.2.2)
 689 */
 690static void forget_original_parent(struct task_struct *father,
 691					struct list_head *dead)
 692{
 693	struct task_struct *p, *t, *reaper;
 694
 695	if (unlikely(!list_empty(&father->ptraced)))
 696		exit_ptrace(father, dead);
 697
 698	/* Can drop and reacquire tasklist_lock */
 699	reaper = find_child_reaper(father, dead);
 700	if (list_empty(&father->children))
 701		return;
 702
 703	reaper = find_new_reaper(father, reaper);
 704	list_for_each_entry(p, &father->children, sibling) {
 705		for_each_thread(p, t) {
 706			RCU_INIT_POINTER(t->real_parent, reaper);
 707			BUG_ON((!t->ptrace) != (rcu_access_pointer(t->parent) == father));
 708			if (likely(!t->ptrace))
 709				t->parent = t->real_parent;
 710			if (t->pdeath_signal)
 711				group_send_sig_info(t->pdeath_signal,
 712						    SEND_SIG_NOINFO, t,
 713						    PIDTYPE_TGID);
 714		}
 715		/*
 716		 * If this is a threaded reparent there is no need to
 717		 * notify anyone anything has happened.
 718		 */
 719		if (!same_thread_group(reaper, father))
 720			reparent_leader(father, p, dead);
 721	}
 722	list_splice_tail_init(&father->children, &reaper->children);
 723}
 724
 725/*
 726 * Send signals to all our closest relatives so that they know
 727 * to properly mourn us..
 728 */
 729static void exit_notify(struct task_struct *tsk, int group_dead)
 730{
 731	bool autoreap;
 732	struct task_struct *p, *n;
 733	LIST_HEAD(dead);
 734
 735	write_lock_irq(&tasklist_lock);
 736	forget_original_parent(tsk, &dead);
 737
 738	if (group_dead)
 739		kill_orphaned_pgrp(tsk->group_leader, NULL);
 740
 741	tsk->exit_state = EXIT_ZOMBIE;
 742	if (unlikely(tsk->ptrace)) {
 743		int sig = thread_group_leader(tsk) &&
 744				thread_group_empty(tsk) &&
 745				!ptrace_reparented(tsk) ?
 746			tsk->exit_signal : SIGCHLD;
 747		autoreap = do_notify_parent(tsk, sig);
 748	} else if (thread_group_leader(tsk)) {
 749		autoreap = thread_group_empty(tsk) &&
 750			do_notify_parent(tsk, tsk->exit_signal);
 751	} else {
 752		autoreap = true;
 753	}
 754
 755	if (autoreap) {
 756		tsk->exit_state = EXIT_DEAD;
 757		list_add(&tsk->ptrace_entry, &dead);
 758	}
 759
 760	/* mt-exec, de_thread() is waiting for group leader */
 761	if (unlikely(tsk->signal->notify_count < 0))
 762		wake_up_process(tsk->signal->group_exec_task);
 763	write_unlock_irq(&tasklist_lock);
 764
 765	list_for_each_entry_safe(p, n, &dead, ptrace_entry) {
 766		list_del_init(&p->ptrace_entry);
 767		release_task(p);
 768	}
 769}
 770
 771#ifdef CONFIG_DEBUG_STACK_USAGE
 772static void check_stack_usage(void)
 773{
 774	static DEFINE_SPINLOCK(low_water_lock);
 775	static int lowest_to_date = THREAD_SIZE;
 776	unsigned long free;
 777
 778	free = stack_not_used(current);
 779
 780	if (free >= lowest_to_date)
 781		return;
 782
 783	spin_lock(&low_water_lock);
 784	if (free < lowest_to_date) {
 785		pr_info("%s (%d) used greatest stack depth: %lu bytes left\n",
 786			current->comm, task_pid_nr(current), free);
 787		lowest_to_date = free;
 788	}
 789	spin_unlock(&low_water_lock);
 790}
 791#else
 792static inline void check_stack_usage(void) {}
 793#endif
 794
 795static void synchronize_group_exit(struct task_struct *tsk, long code)
 796{
 797	struct sighand_struct *sighand = tsk->sighand;
 798	struct signal_struct *signal = tsk->signal;
 799
 800	spin_lock_irq(&sighand->siglock);
 801	signal->quick_threads--;
 802	if ((signal->quick_threads == 0) &&
 803	    !(signal->flags & SIGNAL_GROUP_EXIT)) {
 804		signal->flags = SIGNAL_GROUP_EXIT;
 805		signal->group_exit_code = code;
 806		signal->group_stop_count = 0;
 807	}
 808	spin_unlock_irq(&sighand->siglock);
 809}
 810
 811void __noreturn do_exit(long code)
 812{
 813	struct task_struct *tsk = current;
 814	int group_dead;
 815
 816	WARN_ON(irqs_disabled());
 
 
 
 
 
 
 
 
 
 
 
 
 817
 818	synchronize_group_exit(tsk, code);
 
 
 
 
 
 
 
 819
 820	WARN_ON(tsk->plug);
 
 
 
 
 
 821
 
 822	kcov_task_exit(tsk);
 823	kmsan_task_exit(tsk);
 824
 825	coredump_task_exit(tsk);
 826	ptrace_event(PTRACE_EVENT_EXIT, code);
 827	user_events_exit(tsk);
 828
 829	io_uring_files_cancel();
 
 
 
 
 
 
 
 
 
 
 
 
 
 830	exit_signals(tsk);  /* sets PF_EXITING */
 831
 
 
 
 832	acct_update_integrals(tsk);
 833	group_dead = atomic_dec_and_test(&tsk->signal->live);
 834	if (group_dead) {
 835		/*
 836		 * If the last thread of global init has exited, panic
 837		 * immediately to get a useable coredump.
 838		 */
 839		if (unlikely(is_global_init(tsk)))
 840			panic("Attempted to kill init! exitcode=0x%08x\n",
 841				tsk->signal->group_exit_code ?: (int)code);
 842
 843#ifdef CONFIG_POSIX_TIMERS
 844		hrtimer_cancel(&tsk->signal->real_timer);
 845		exit_itimers(tsk);
 846#endif
 847		if (tsk->mm)
 848			setmax_mm_hiwater_rss(&tsk->signal->maxrss, tsk->mm);
 849	}
 850	acct_collect(code, group_dead);
 851	if (group_dead)
 852		tty_audit_exit();
 853	audit_free(tsk);
 854
 855	tsk->exit_code = code;
 856	taskstats_exit(tsk, group_dead);
 857
 858	exit_mm();
 859
 860	if (group_dead)
 861		acct_process();
 862	trace_sched_process_exit(tsk);
 863
 864	exit_sem(tsk);
 865	exit_shm(tsk);
 866	exit_files(tsk);
 867	exit_fs(tsk);
 868	if (group_dead)
 869		disassociate_ctty(1);
 870	exit_task_namespaces(tsk);
 871	exit_task_work(tsk);
 872	exit_thread(tsk);
 873
 874	/*
 875	 * Flush inherited counters to the parent - before the parent
 876	 * gets woken up by child-exit notifications.
 877	 *
 878	 * because of cgroup mode, must be called before cgroup_exit()
 879	 */
 880	perf_event_exit_task(tsk);
 881
 882	sched_autogroup_exit_task(tsk);
 883	cgroup_exit(tsk);
 884
 885	/*
 886	 * FIXME: do that only when needed, using sched_exit tracepoint
 887	 */
 888	flush_ptrace_hw_breakpoint(tsk);
 889
 890	exit_tasks_rcu_start();
 891	exit_notify(tsk, group_dead);
 892	proc_exit_connector(tsk);
 893	mpol_put_task_policy(tsk);
 894#ifdef CONFIG_FUTEX
 895	if (unlikely(current->pi_state_cache))
 896		kfree(current->pi_state_cache);
 897#endif
 898	/*
 899	 * Make sure we are holding no locks:
 900	 */
 901	debug_check_no_locks_held();
 902
 903	if (tsk->io_context)
 904		exit_io_context(tsk);
 905
 906	if (tsk->splice_pipe)
 907		free_pipe_info(tsk->splice_pipe);
 908
 909	if (tsk->task_frag.page)
 910		put_page(tsk->task_frag.page);
 911
 912	exit_task_stack_account(tsk);
 913
 914	check_stack_usage();
 915	preempt_disable();
 916	if (tsk->nr_dirtied)
 917		__this_cpu_add(dirty_throttle_leaks, tsk->nr_dirtied);
 918	exit_rcu();
 919	exit_tasks_rcu_finish();
 920
 921	lockdep_free_task(tsk);
 922	do_task_dead();
 923}
 
 924
 925void __noreturn make_task_dead(int signr)
 926{
 927	/*
 928	 * Take the task off the cpu after something catastrophic has
 929	 * happened.
 930	 *
 931	 * We can get here from a kernel oops, sometimes with preemption off.
 932	 * Start by checking for critical errors.
 933	 * Then fix up important state like USER_DS and preemption.
 934	 * Then do everything else.
 935	 */
 936	struct task_struct *tsk = current;
 937	unsigned int limit;
 938
 939	if (unlikely(in_interrupt()))
 940		panic("Aiee, killing interrupt handler!");
 941	if (unlikely(!tsk->pid))
 942		panic("Attempted to kill the idle task!");
 943
 944	if (unlikely(irqs_disabled())) {
 945		pr_info("note: %s[%d] exited with irqs disabled\n",
 946			current->comm, task_pid_nr(current));
 947		local_irq_enable();
 948	}
 949	if (unlikely(in_atomic())) {
 950		pr_info("note: %s[%d] exited with preempt_count %d\n",
 951			current->comm, task_pid_nr(current),
 952			preempt_count());
 953		preempt_count_set(PREEMPT_ENABLED);
 954	}
 955
 956	/*
 957	 * Every time the system oopses, if the oops happens while a reference
 958	 * to an object was held, the reference leaks.
 959	 * If the oops doesn't also leak memory, repeated oopsing can cause
 960	 * reference counters to wrap around (if they're not using refcount_t).
 961	 * This means that repeated oopsing can make unexploitable-looking bugs
 962	 * exploitable through repeated oopsing.
 963	 * To make sure this can't happen, place an upper bound on how often the
 964	 * kernel may oops without panic().
 965	 */
 966	limit = READ_ONCE(oops_limit);
 967	if (atomic_inc_return(&oops_count) >= limit && limit)
 968		panic("Oopsed too often (kernel.oops_limit is %d)", limit);
 969
 970	/*
 971	 * We're taking recursive faults here in make_task_dead. Safest is to just
 972	 * leave this task alone and wait for reboot.
 973	 */
 974	if (unlikely(tsk->flags & PF_EXITING)) {
 975		pr_alert("Fixing recursive fault but reboot is needed!\n");
 976		futex_exit_recursive(tsk);
 977		tsk->exit_state = EXIT_DEAD;
 978		refcount_inc(&tsk->rcu_users);
 979		do_task_dead();
 980	}
 981
 982	do_exit(signr);
 983}
 
 984
 985SYSCALL_DEFINE1(exit, int, error_code)
 986{
 987	do_exit((error_code&0xff)<<8);
 988}
 989
 990/*
 991 * Take down every thread in the group.  This is called by fatal signals
 992 * as well as by sys_exit_group (below).
 993 */
 994void __noreturn
 995do_group_exit(int exit_code)
 996{
 997	struct signal_struct *sig = current->signal;
 998
 999	if (sig->flags & SIGNAL_GROUP_EXIT)
 
 
1000		exit_code = sig->group_exit_code;
1001	else if (sig->group_exec_task)
1002		exit_code = 0;
1003	else {
1004		struct sighand_struct *const sighand = current->sighand;
1005
1006		spin_lock_irq(&sighand->siglock);
1007		if (sig->flags & SIGNAL_GROUP_EXIT)
1008			/* Another thread got here before we took the lock.  */
1009			exit_code = sig->group_exit_code;
1010		else if (sig->group_exec_task)
1011			exit_code = 0;
1012		else {
1013			sig->group_exit_code = exit_code;
1014			sig->flags = SIGNAL_GROUP_EXIT;
1015			zap_other_threads(current);
1016		}
1017		spin_unlock_irq(&sighand->siglock);
1018	}
1019
1020	do_exit(exit_code);
1021	/* NOTREACHED */
1022}
1023
1024/*
1025 * this kills every thread in the thread group. Note that any externally
1026 * wait4()-ing process will get the correct exit code - even if this
1027 * thread is not the thread group leader.
1028 */
1029SYSCALL_DEFINE1(exit_group, int, error_code)
1030{
1031	do_group_exit((error_code & 0xff) << 8);
1032	/* NOTREACHED */
1033	return 0;
1034}
1035
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1036static int eligible_pid(struct wait_opts *wo, struct task_struct *p)
1037{
1038	return	wo->wo_type == PIDTYPE_MAX ||
1039		task_pid_type(p, wo->wo_type) == wo->wo_pid;
1040}
1041
1042static int
1043eligible_child(struct wait_opts *wo, bool ptrace, struct task_struct *p)
1044{
1045	if (!eligible_pid(wo, p))
1046		return 0;
1047
1048	/*
1049	 * Wait for all children (clone and not) if __WALL is set or
1050	 * if it is traced by us.
1051	 */
1052	if (ptrace || (wo->wo_flags & __WALL))
1053		return 1;
1054
1055	/*
1056	 * Otherwise, wait for clone children *only* if __WCLONE is set;
1057	 * otherwise, wait for non-clone children *only*.
1058	 *
1059	 * Note: a "clone" child here is one that reports to its parent
1060	 * using a signal other than SIGCHLD, or a non-leader thread which
1061	 * we can only see if it is traced by us.
1062	 */
1063	if ((p->exit_signal != SIGCHLD) ^ !!(wo->wo_flags & __WCLONE))
1064		return 0;
1065
1066	return 1;
1067}
1068
1069/*
1070 * Handle sys_wait4 work for one task in state EXIT_ZOMBIE.  We hold
1071 * read_lock(&tasklist_lock) on entry.  If we return zero, we still hold
1072 * the lock and this task is uninteresting.  If we return nonzero, we have
1073 * released the lock and the system call should return.
1074 */
1075static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p)
1076{
1077	int state, status;
1078	pid_t pid = task_pid_vnr(p);
1079	uid_t uid = from_kuid_munged(current_user_ns(), task_uid(p));
1080	struct waitid_info *infop;
1081
1082	if (!likely(wo->wo_flags & WEXITED))
1083		return 0;
1084
1085	if (unlikely(wo->wo_flags & WNOWAIT)) {
1086		status = (p->signal->flags & SIGNAL_GROUP_EXIT)
1087			? p->signal->group_exit_code : p->exit_code;
1088		get_task_struct(p);
1089		read_unlock(&tasklist_lock);
1090		sched_annotate_sleep();
1091		if (wo->wo_rusage)
1092			getrusage(p, RUSAGE_BOTH, wo->wo_rusage);
1093		put_task_struct(p);
1094		goto out_info;
1095	}
1096	/*
1097	 * Move the task's state to DEAD/TRACE, only one thread can do this.
1098	 */
1099	state = (ptrace_reparented(p) && thread_group_leader(p)) ?
1100		EXIT_TRACE : EXIT_DEAD;
1101	if (cmpxchg(&p->exit_state, EXIT_ZOMBIE, state) != EXIT_ZOMBIE)
1102		return 0;
1103	/*
1104	 * We own this thread, nobody else can reap it.
1105	 */
1106	read_unlock(&tasklist_lock);
1107	sched_annotate_sleep();
1108
1109	/*
1110	 * Check thread_group_leader() to exclude the traced sub-threads.
1111	 */
1112	if (state == EXIT_DEAD && thread_group_leader(p)) {
1113		struct signal_struct *sig = p->signal;
1114		struct signal_struct *psig = current->signal;
1115		unsigned long maxrss;
1116		u64 tgutime, tgstime;
1117
1118		/*
1119		 * The resource counters for the group leader are in its
1120		 * own task_struct.  Those for dead threads in the group
1121		 * are in its signal_struct, as are those for the child
1122		 * processes it has previously reaped.  All these
1123		 * accumulate in the parent's signal_struct c* fields.
1124		 *
1125		 * We don't bother to take a lock here to protect these
1126		 * p->signal fields because the whole thread group is dead
1127		 * and nobody can change them.
1128		 *
1129		 * psig->stats_lock also protects us from our sub-threads
1130		 * which can reap other children at the same time.
 
 
1131		 *
1132		 * We use thread_group_cputime_adjusted() to get times for
1133		 * the thread group, which consolidates times for all threads
1134		 * in the group including the group leader.
1135		 */
1136		thread_group_cputime_adjusted(p, &tgutime, &tgstime);
1137		write_seqlock_irq(&psig->stats_lock);
 
1138		psig->cutime += tgutime + sig->cutime;
1139		psig->cstime += tgstime + sig->cstime;
1140		psig->cgtime += task_gtime(p) + sig->gtime + sig->cgtime;
1141		psig->cmin_flt +=
1142			p->min_flt + sig->min_flt + sig->cmin_flt;
1143		psig->cmaj_flt +=
1144			p->maj_flt + sig->maj_flt + sig->cmaj_flt;
1145		psig->cnvcsw +=
1146			p->nvcsw + sig->nvcsw + sig->cnvcsw;
1147		psig->cnivcsw +=
1148			p->nivcsw + sig->nivcsw + sig->cnivcsw;
1149		psig->cinblock +=
1150			task_io_get_inblock(p) +
1151			sig->inblock + sig->cinblock;
1152		psig->coublock +=
1153			task_io_get_oublock(p) +
1154			sig->oublock + sig->coublock;
1155		maxrss = max(sig->maxrss, sig->cmaxrss);
1156		if (psig->cmaxrss < maxrss)
1157			psig->cmaxrss = maxrss;
1158		task_io_accounting_add(&psig->ioac, &p->ioac);
1159		task_io_accounting_add(&psig->ioac, &sig->ioac);
1160		write_sequnlock_irq(&psig->stats_lock);
 
1161	}
1162
1163	if (wo->wo_rusage)
1164		getrusage(p, RUSAGE_BOTH, wo->wo_rusage);
1165	status = (p->signal->flags & SIGNAL_GROUP_EXIT)
1166		? p->signal->group_exit_code : p->exit_code;
1167	wo->wo_stat = status;
1168
1169	if (state == EXIT_TRACE) {
1170		write_lock_irq(&tasklist_lock);
1171		/* We dropped tasklist, ptracer could die and untrace */
1172		ptrace_unlink(p);
1173
1174		/* If parent wants a zombie, don't release it now */
1175		state = EXIT_ZOMBIE;
1176		if (do_notify_parent(p, p->exit_signal))
1177			state = EXIT_DEAD;
1178		p->exit_state = state;
1179		write_unlock_irq(&tasklist_lock);
1180	}
1181	if (state == EXIT_DEAD)
1182		release_task(p);
1183
1184out_info:
1185	infop = wo->wo_info;
1186	if (infop) {
1187		if ((status & 0x7f) == 0) {
1188			infop->cause = CLD_EXITED;
1189			infop->status = status >> 8;
1190		} else {
1191			infop->cause = (status & 0x80) ? CLD_DUMPED : CLD_KILLED;
1192			infop->status = status & 0x7f;
1193		}
1194		infop->pid = pid;
1195		infop->uid = uid;
1196	}
1197
1198	return pid;
1199}
1200
1201static int *task_stopped_code(struct task_struct *p, bool ptrace)
1202{
1203	if (ptrace) {
1204		if (task_is_traced(p) && !(p->jobctl & JOBCTL_LISTENING))
1205			return &p->exit_code;
1206	} else {
1207		if (p->signal->flags & SIGNAL_STOP_STOPPED)
1208			return &p->signal->group_exit_code;
1209	}
1210	return NULL;
1211}
1212
1213/**
1214 * wait_task_stopped - Wait for %TASK_STOPPED or %TASK_TRACED
1215 * @wo: wait options
1216 * @ptrace: is the wait for ptrace
1217 * @p: task to wait for
1218 *
1219 * Handle sys_wait4() work for %p in state %TASK_STOPPED or %TASK_TRACED.
1220 *
1221 * CONTEXT:
1222 * read_lock(&tasklist_lock), which is released if return value is
1223 * non-zero.  Also, grabs and releases @p->sighand->siglock.
1224 *
1225 * RETURNS:
1226 * 0 if wait condition didn't exist and search for other wait conditions
1227 * should continue.  Non-zero return, -errno on failure and @p's pid on
1228 * success, implies that tasklist_lock is released and wait condition
1229 * search should terminate.
1230 */
1231static int wait_task_stopped(struct wait_opts *wo,
1232				int ptrace, struct task_struct *p)
1233{
1234	struct waitid_info *infop;
1235	int exit_code, *p_code, why;
1236	uid_t uid = 0; /* unneeded, required by compiler */
1237	pid_t pid;
1238
1239	/*
1240	 * Traditionally we see ptrace'd stopped tasks regardless of options.
1241	 */
1242	if (!ptrace && !(wo->wo_flags & WUNTRACED))
1243		return 0;
1244
1245	if (!task_stopped_code(p, ptrace))
1246		return 0;
1247
1248	exit_code = 0;
1249	spin_lock_irq(&p->sighand->siglock);
1250
1251	p_code = task_stopped_code(p, ptrace);
1252	if (unlikely(!p_code))
1253		goto unlock_sig;
1254
1255	exit_code = *p_code;
1256	if (!exit_code)
1257		goto unlock_sig;
1258
1259	if (!unlikely(wo->wo_flags & WNOWAIT))
1260		*p_code = 0;
1261
1262	uid = from_kuid_munged(current_user_ns(), task_uid(p));
1263unlock_sig:
1264	spin_unlock_irq(&p->sighand->siglock);
1265	if (!exit_code)
1266		return 0;
1267
1268	/*
1269	 * Now we are pretty sure this task is interesting.
1270	 * Make sure it doesn't get reaped out from under us while we
1271	 * give up the lock and then examine it below.  We don't want to
1272	 * keep holding onto the tasklist_lock while we call getrusage and
1273	 * possibly take page faults for user memory.
1274	 */
1275	get_task_struct(p);
1276	pid = task_pid_vnr(p);
1277	why = ptrace ? CLD_TRAPPED : CLD_STOPPED;
1278	read_unlock(&tasklist_lock);
1279	sched_annotate_sleep();
1280	if (wo->wo_rusage)
1281		getrusage(p, RUSAGE_BOTH, wo->wo_rusage);
1282	put_task_struct(p);
1283
1284	if (likely(!(wo->wo_flags & WNOWAIT)))
1285		wo->wo_stat = (exit_code << 8) | 0x7f;
1286
1287	infop = wo->wo_info;
1288	if (infop) {
1289		infop->cause = why;
1290		infop->status = exit_code;
1291		infop->pid = pid;
1292		infop->uid = uid;
1293	}
1294	return pid;
1295}
1296
1297/*
1298 * Handle do_wait work for one task in a live, non-stopped state.
1299 * read_lock(&tasklist_lock) on entry.  If we return zero, we still hold
1300 * the lock and this task is uninteresting.  If we return nonzero, we have
1301 * released the lock and the system call should return.
1302 */
1303static int wait_task_continued(struct wait_opts *wo, struct task_struct *p)
1304{
1305	struct waitid_info *infop;
1306	pid_t pid;
1307	uid_t uid;
1308
1309	if (!unlikely(wo->wo_flags & WCONTINUED))
1310		return 0;
1311
1312	if (!(p->signal->flags & SIGNAL_STOP_CONTINUED))
1313		return 0;
1314
1315	spin_lock_irq(&p->sighand->siglock);
1316	/* Re-check with the lock held.  */
1317	if (!(p->signal->flags & SIGNAL_STOP_CONTINUED)) {
1318		spin_unlock_irq(&p->sighand->siglock);
1319		return 0;
1320	}
1321	if (!unlikely(wo->wo_flags & WNOWAIT))
1322		p->signal->flags &= ~SIGNAL_STOP_CONTINUED;
1323	uid = from_kuid_munged(current_user_ns(), task_uid(p));
1324	spin_unlock_irq(&p->sighand->siglock);
1325
1326	pid = task_pid_vnr(p);
1327	get_task_struct(p);
1328	read_unlock(&tasklist_lock);
1329	sched_annotate_sleep();
1330	if (wo->wo_rusage)
1331		getrusage(p, RUSAGE_BOTH, wo->wo_rusage);
1332	put_task_struct(p);
1333
1334	infop = wo->wo_info;
1335	if (!infop) {
1336		wo->wo_stat = 0xffff;
1337	} else {
1338		infop->cause = CLD_CONTINUED;
1339		infop->pid = pid;
1340		infop->uid = uid;
1341		infop->status = SIGCONT;
1342	}
1343	return pid;
1344}
1345
1346/*
1347 * Consider @p for a wait by @parent.
1348 *
1349 * -ECHILD should be in ->notask_error before the first call.
1350 * Returns nonzero for a final return, when we have unlocked tasklist_lock.
1351 * Returns zero if the search for a child should continue;
1352 * then ->notask_error is 0 if @p is an eligible child,
1353 * or still -ECHILD.
1354 */
1355static int wait_consider_task(struct wait_opts *wo, int ptrace,
1356				struct task_struct *p)
1357{
1358	/*
1359	 * We can race with wait_task_zombie() from another thread.
1360	 * Ensure that EXIT_ZOMBIE -> EXIT_DEAD/EXIT_TRACE transition
1361	 * can't confuse the checks below.
1362	 */
1363	int exit_state = READ_ONCE(p->exit_state);
1364	int ret;
1365
1366	if (unlikely(exit_state == EXIT_DEAD))
1367		return 0;
1368
1369	ret = eligible_child(wo, ptrace, p);
1370	if (!ret)
1371		return ret;
1372
1373	if (unlikely(exit_state == EXIT_TRACE)) {
1374		/*
1375		 * ptrace == 0 means we are the natural parent. In this case
1376		 * we should clear notask_error, debugger will notify us.
1377		 */
1378		if (likely(!ptrace))
1379			wo->notask_error = 0;
1380		return 0;
1381	}
1382
1383	if (likely(!ptrace) && unlikely(p->ptrace)) {
1384		/*
1385		 * If it is traced by its real parent's group, just pretend
1386		 * the caller is ptrace_do_wait() and reap this child if it
1387		 * is zombie.
1388		 *
1389		 * This also hides group stop state from real parent; otherwise
1390		 * a single stop can be reported twice as group and ptrace stop.
1391		 * If a ptracer wants to distinguish these two events for its
1392		 * own children it should create a separate process which takes
1393		 * the role of real parent.
1394		 */
1395		if (!ptrace_reparented(p))
1396			ptrace = 1;
1397	}
1398
1399	/* slay zombie? */
1400	if (exit_state == EXIT_ZOMBIE) {
1401		/* we don't reap group leaders with subthreads */
1402		if (!delay_group_leader(p)) {
1403			/*
1404			 * A zombie ptracee is only visible to its ptracer.
1405			 * Notification and reaping will be cascaded to the
1406			 * real parent when the ptracer detaches.
1407			 */
1408			if (unlikely(ptrace) || likely(!p->ptrace))
1409				return wait_task_zombie(wo, p);
1410		}
1411
1412		/*
1413		 * Allow access to stopped/continued state via zombie by
1414		 * falling through.  Clearing of notask_error is complex.
1415		 *
1416		 * When !@ptrace:
1417		 *
1418		 * If WEXITED is set, notask_error should naturally be
1419		 * cleared.  If not, subset of WSTOPPED|WCONTINUED is set,
1420		 * so, if there are live subthreads, there are events to
1421		 * wait for.  If all subthreads are dead, it's still safe
1422		 * to clear - this function will be called again in finite
1423		 * amount time once all the subthreads are released and
1424		 * will then return without clearing.
1425		 *
1426		 * When @ptrace:
1427		 *
1428		 * Stopped state is per-task and thus can't change once the
1429		 * target task dies.  Only continued and exited can happen.
1430		 * Clear notask_error if WCONTINUED | WEXITED.
1431		 */
1432		if (likely(!ptrace) || (wo->wo_flags & (WCONTINUED | WEXITED)))
1433			wo->notask_error = 0;
1434	} else {
1435		/*
1436		 * @p is alive and it's gonna stop, continue or exit, so
1437		 * there always is something to wait for.
1438		 */
1439		wo->notask_error = 0;
1440	}
1441
1442	/*
1443	 * Wait for stopped.  Depending on @ptrace, different stopped state
1444	 * is used and the two don't interact with each other.
1445	 */
1446	ret = wait_task_stopped(wo, ptrace, p);
1447	if (ret)
1448		return ret;
1449
1450	/*
1451	 * Wait for continued.  There's only one continued state and the
1452	 * ptracer can consume it which can confuse the real parent.  Don't
1453	 * use WCONTINUED from ptracer.  You don't need or want it.
1454	 */
1455	return wait_task_continued(wo, p);
1456}
1457
1458/*
1459 * Do the work of do_wait() for one thread in the group, @tsk.
1460 *
1461 * -ECHILD should be in ->notask_error before the first call.
1462 * Returns nonzero for a final return, when we have unlocked tasklist_lock.
1463 * Returns zero if the search for a child should continue; then
1464 * ->notask_error is 0 if there were any eligible children,
1465 * or still -ECHILD.
1466 */
1467static int do_wait_thread(struct wait_opts *wo, struct task_struct *tsk)
1468{
1469	struct task_struct *p;
1470
1471	list_for_each_entry(p, &tsk->children, sibling) {
1472		int ret = wait_consider_task(wo, 0, p);
1473
1474		if (ret)
1475			return ret;
1476	}
1477
1478	return 0;
1479}
1480
1481static int ptrace_do_wait(struct wait_opts *wo, struct task_struct *tsk)
1482{
1483	struct task_struct *p;
1484
1485	list_for_each_entry(p, &tsk->ptraced, ptrace_entry) {
1486		int ret = wait_consider_task(wo, 1, p);
1487
1488		if (ret)
1489			return ret;
1490	}
1491
1492	return 0;
1493}
1494
1495bool pid_child_should_wake(struct wait_opts *wo, struct task_struct *p)
1496{
1497	if (!eligible_pid(wo, p))
1498		return false;
1499
1500	if ((wo->wo_flags & __WNOTHREAD) && wo->child_wait.private != p->parent)
1501		return false;
1502
1503	return true;
1504}
1505
1506static int child_wait_callback(wait_queue_entry_t *wait, unsigned mode,
1507				int sync, void *key)
1508{
1509	struct wait_opts *wo = container_of(wait, struct wait_opts,
1510						child_wait);
1511	struct task_struct *p = key;
1512
1513	if (pid_child_should_wake(wo, p))
1514		return default_wake_function(wait, mode, sync, key);
1515
1516	return 0;
 
 
 
1517}
1518
1519void __wake_up_parent(struct task_struct *p, struct task_struct *parent)
1520{
1521	__wake_up_sync_key(&parent->signal->wait_chldexit,
1522			   TASK_INTERRUPTIBLE, p);
1523}
1524
1525static bool is_effectively_child(struct wait_opts *wo, bool ptrace,
1526				 struct task_struct *target)
1527{
1528	struct task_struct *parent =
1529		!ptrace ? target->real_parent : target->parent;
1530
1531	return current == parent || (!(wo->wo_flags & __WNOTHREAD) &&
1532				     same_thread_group(current, parent));
1533}
1534
1535/*
1536 * Optimization for waiting on PIDTYPE_PID. No need to iterate through child
1537 * and tracee lists to find the target task.
1538 */
1539static int do_wait_pid(struct wait_opts *wo)
1540{
1541	bool ptrace;
1542	struct task_struct *target;
1543	int retval;
1544
1545	ptrace = false;
1546	target = pid_task(wo->wo_pid, PIDTYPE_TGID);
1547	if (target && is_effectively_child(wo, ptrace, target)) {
1548		retval = wait_consider_task(wo, ptrace, target);
1549		if (retval)
1550			return retval;
1551	}
1552
1553	ptrace = true;
1554	target = pid_task(wo->wo_pid, PIDTYPE_PID);
1555	if (target && target->ptrace &&
1556	    is_effectively_child(wo, ptrace, target)) {
1557		retval = wait_consider_task(wo, ptrace, target);
1558		if (retval)
1559			return retval;
1560	}
1561
1562	return 0;
1563}
1564
1565long __do_wait(struct wait_opts *wo)
1566{
1567	long retval;
1568
 
 
 
 
 
 
1569	/*
1570	 * If there is nothing that can match our criteria, just get out.
1571	 * We will clear ->notask_error to zero if we see any child that
1572	 * might later match our criteria, even if we are not able to reap
1573	 * it yet.
1574	 */
1575	wo->notask_error = -ECHILD;
1576	if ((wo->wo_type < PIDTYPE_MAX) &&
1577	   (!wo->wo_pid || !pid_has_task(wo->wo_pid, wo->wo_type)))
1578		goto notask;
1579
 
1580	read_lock(&tasklist_lock);
1581
1582	if (wo->wo_type == PIDTYPE_PID) {
1583		retval = do_wait_pid(wo);
1584		if (retval)
1585			return retval;
1586	} else {
1587		struct task_struct *tsk = current;
1588
1589		do {
1590			retval = do_wait_thread(wo, tsk);
1591			if (retval)
1592				return retval;
1593
1594			retval = ptrace_do_wait(wo, tsk);
1595			if (retval)
1596				return retval;
1597
1598			if (wo->wo_flags & __WNOTHREAD)
1599				break;
1600		} while_each_thread(current, tsk);
1601	}
1602	read_unlock(&tasklist_lock);
1603
1604notask:
1605	retval = wo->notask_error;
1606	if (!retval && !(wo->wo_flags & WNOHANG))
1607		return -ERESTARTSYS;
1608
1609	return retval;
1610}
1611
1612static long do_wait(struct wait_opts *wo)
1613{
1614	int retval;
1615
1616	trace_sched_process_wait(wo->wo_pid);
1617
1618	init_waitqueue_func_entry(&wo->child_wait, child_wait_callback);
1619	wo->child_wait.private = current;
1620	add_wait_queue(&current->signal->wait_chldexit, &wo->child_wait);
1621
1622	do {
1623		set_current_state(TASK_INTERRUPTIBLE);
1624		retval = __do_wait(wo);
1625		if (retval != -ERESTARTSYS)
1626			break;
1627		if (signal_pending(current))
1628			break;
1629		schedule();
1630	} while (1);
1631
1632	__set_current_state(TASK_RUNNING);
1633	remove_wait_queue(&current->signal->wait_chldexit, &wo->child_wait);
1634	return retval;
1635}
1636
1637int kernel_waitid_prepare(struct wait_opts *wo, int which, pid_t upid,
1638			  struct waitid_info *infop, int options,
1639			  struct rusage *ru)
1640{
1641	unsigned int f_flags = 0;
1642	struct pid *pid = NULL;
1643	enum pid_type type;
 
 
1644
1645	if (options & ~(WNOHANG|WNOWAIT|WEXITED|WSTOPPED|WCONTINUED|
1646			__WNOTHREAD|__WCLONE|__WALL))
1647		return -EINVAL;
1648	if (!(options & (WEXITED|WSTOPPED|WCONTINUED)))
1649		return -EINVAL;
1650
1651	switch (which) {
1652	case P_ALL:
1653		type = PIDTYPE_MAX;
1654		break;
1655	case P_PID:
1656		type = PIDTYPE_PID;
1657		if (upid <= 0)
1658			return -EINVAL;
1659
1660		pid = find_get_pid(upid);
1661		break;
1662	case P_PGID:
1663		type = PIDTYPE_PGID;
1664		if (upid < 0)
1665			return -EINVAL;
1666
1667		if (upid)
1668			pid = find_get_pid(upid);
1669		else
1670			pid = get_task_pid(current, PIDTYPE_PGID);
1671		break;
1672	case P_PIDFD:
1673		type = PIDTYPE_PID;
1674		if (upid < 0)
1675			return -EINVAL;
1676
1677		pid = pidfd_get_pid(upid, &f_flags);
1678		if (IS_ERR(pid))
1679			return PTR_ERR(pid);
1680
1681		break;
1682	default:
1683		return -EINVAL;
1684	}
1685
1686	wo->wo_type	= type;
1687	wo->wo_pid	= pid;
1688	wo->wo_flags	= options;
1689	wo->wo_info	= infop;
1690	wo->wo_rusage	= ru;
1691	if (f_flags & O_NONBLOCK)
1692		wo->wo_flags |= WNOHANG;
1693
1694	return 0;
1695}
1696
1697static long kernel_waitid(int which, pid_t upid, struct waitid_info *infop,
1698			  int options, struct rusage *ru)
1699{
1700	struct wait_opts wo;
1701	long ret;
1702
1703	ret = kernel_waitid_prepare(&wo, which, upid, infop, options, ru);
1704	if (ret)
1705		return ret;
1706
1707	ret = do_wait(&wo);
1708	if (!ret && !(options & WNOHANG) && (wo.wo_flags & WNOHANG))
1709		ret = -EAGAIN;
1710
1711	put_pid(wo.wo_pid);
1712	return ret;
1713}
1714
1715SYSCALL_DEFINE5(waitid, int, which, pid_t, upid, struct siginfo __user *,
1716		infop, int, options, struct rusage __user *, ru)
1717{
1718	struct rusage r;
1719	struct waitid_info info = {.status = 0};
1720	long err = kernel_waitid(which, upid, &info, options, ru ? &r : NULL);
1721	int signo = 0;
1722
1723	if (err > 0) {
1724		signo = SIGCHLD;
1725		err = 0;
1726		if (ru && copy_to_user(ru, &r, sizeof(struct rusage)))
1727			return -EFAULT;
1728	}
1729	if (!infop)
1730		return err;
1731
1732	if (!user_write_access_begin(infop, sizeof(*infop)))
1733		return -EFAULT;
1734
1735	unsafe_put_user(signo, &infop->si_signo, Efault);
1736	unsafe_put_user(0, &infop->si_errno, Efault);
1737	unsafe_put_user(info.cause, &infop->si_code, Efault);
1738	unsafe_put_user(info.pid, &infop->si_pid, Efault);
1739	unsafe_put_user(info.uid, &infop->si_uid, Efault);
1740	unsafe_put_user(info.status, &infop->si_status, Efault);
1741	user_write_access_end();
1742	return err;
1743Efault:
1744	user_write_access_end();
1745	return -EFAULT;
1746}
1747
1748long kernel_wait4(pid_t upid, int __user *stat_addr, int options,
1749		  struct rusage *ru)
1750{
1751	struct wait_opts wo;
1752	struct pid *pid = NULL;
1753	enum pid_type type;
1754	long ret;
1755
1756	if (options & ~(WNOHANG|WUNTRACED|WCONTINUED|
1757			__WNOTHREAD|__WCLONE|__WALL))
1758		return -EINVAL;
1759
1760	/* -INT_MIN is not defined */
1761	if (upid == INT_MIN)
1762		return -ESRCH;
1763
1764	if (upid == -1)
1765		type = PIDTYPE_MAX;
1766	else if (upid < 0) {
1767		type = PIDTYPE_PGID;
1768		pid = find_get_pid(-upid);
1769	} else if (upid == 0) {
1770		type = PIDTYPE_PGID;
1771		pid = get_task_pid(current, PIDTYPE_PGID);
1772	} else /* upid > 0 */ {
1773		type = PIDTYPE_PID;
1774		pid = find_get_pid(upid);
1775	}
1776
1777	wo.wo_type	= type;
1778	wo.wo_pid	= pid;
1779	wo.wo_flags	= options | WEXITED;
1780	wo.wo_info	= NULL;
1781	wo.wo_stat	= 0;
1782	wo.wo_rusage	= ru;
1783	ret = do_wait(&wo);
1784	put_pid(pid);
1785	if (ret > 0 && stat_addr && put_user(wo.wo_stat, stat_addr))
1786		ret = -EFAULT;
1787
1788	return ret;
1789}
1790
1791int kernel_wait(pid_t pid, int *stat)
1792{
1793	struct wait_opts wo = {
1794		.wo_type	= PIDTYPE_PID,
1795		.wo_pid		= find_get_pid(pid),
1796		.wo_flags	= WEXITED,
1797	};
1798	int ret;
1799
1800	ret = do_wait(&wo);
1801	if (ret > 0 && wo.wo_stat)
1802		*stat = wo.wo_stat;
1803	put_pid(wo.wo_pid);
1804	return ret;
1805}
1806
1807SYSCALL_DEFINE4(wait4, pid_t, upid, int __user *, stat_addr,
1808		int, options, struct rusage __user *, ru)
1809{
1810	struct rusage r;
1811	long err = kernel_wait4(upid, stat_addr, options, ru ? &r : NULL);
1812
1813	if (err > 0) {
1814		if (ru && copy_to_user(ru, &r, sizeof(struct rusage)))
1815			return -EFAULT;
1816	}
1817	return err;
1818}
1819
1820#ifdef __ARCH_WANT_SYS_WAITPID
1821
1822/*
1823 * sys_waitpid() remains for compatibility. waitpid() should be
1824 * implemented by calling sys_wait4() from libc.a.
1825 */
1826SYSCALL_DEFINE3(waitpid, pid_t, pid, int __user *, stat_addr, int, options)
1827{
1828	return kernel_wait4(pid, stat_addr, options, NULL);
1829}
1830
1831#endif
1832
1833#ifdef CONFIG_COMPAT
1834COMPAT_SYSCALL_DEFINE4(wait4,
1835	compat_pid_t, pid,
1836	compat_uint_t __user *, stat_addr,
1837	int, options,
1838	struct compat_rusage __user *, ru)
1839{
1840	struct rusage r;
1841	long err = kernel_wait4(pid, stat_addr, options, ru ? &r : NULL);
1842	if (err > 0) {
1843		if (ru && put_compat_rusage(&r, ru))
1844			return -EFAULT;
1845	}
1846	return err;
1847}
1848
1849COMPAT_SYSCALL_DEFINE5(waitid,
1850		int, which, compat_pid_t, pid,
1851		struct compat_siginfo __user *, infop, int, options,
1852		struct compat_rusage __user *, uru)
1853{
1854	struct rusage ru;
1855	struct waitid_info info = {.status = 0};
1856	long err = kernel_waitid(which, pid, &info, options, uru ? &ru : NULL);
1857	int signo = 0;
1858	if (err > 0) {
1859		signo = SIGCHLD;
1860		err = 0;
1861		if (uru) {
1862			/* kernel_waitid() overwrites everything in ru */
1863			if (COMPAT_USE_64BIT_TIME)
1864				err = copy_to_user(uru, &ru, sizeof(ru));
1865			else
1866				err = put_compat_rusage(&ru, uru);
1867			if (err)
1868				return -EFAULT;
1869		}
1870	}
1871
1872	if (!infop)
1873		return err;
1874
1875	if (!user_write_access_begin(infop, sizeof(*infop)))
1876		return -EFAULT;
1877
1878	unsafe_put_user(signo, &infop->si_signo, Efault);
1879	unsafe_put_user(0, &infop->si_errno, Efault);
1880	unsafe_put_user(info.cause, &infop->si_code, Efault);
1881	unsafe_put_user(info.pid, &infop->si_pid, Efault);
1882	unsafe_put_user(info.uid, &infop->si_uid, Efault);
1883	unsafe_put_user(info.status, &infop->si_status, Efault);
1884	user_write_access_end();
1885	return err;
1886Efault:
1887	user_write_access_end();
1888	return -EFAULT;
1889}
1890#endif
1891
1892/**
1893 * thread_group_exited - check that a thread group has exited
1894 * @pid: tgid of thread group to be checked.
1895 *
1896 * Test if the thread group represented by tgid has exited (all
1897 * threads are zombies, dead or completely gone).
1898 *
1899 * Return: true if the thread group has exited. false otherwise.
1900 */
1901bool thread_group_exited(struct pid *pid)
1902{
1903	struct task_struct *task;
1904	bool exited;
1905
1906	rcu_read_lock();
1907	task = pid_task(pid, PIDTYPE_PID);
1908	exited = !task ||
1909		(READ_ONCE(task->exit_state) && thread_group_empty(task));
1910	rcu_read_unlock();
1911
1912	return exited;
1913}
1914EXPORT_SYMBOL(thread_group_exited);
1915
1916/*
1917 * This needs to be __function_aligned as GCC implicitly makes any
1918 * implementation of abort() cold and drops alignment specified by
1919 * -falign-functions=N.
1920 *
1921 * See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88345#c11
1922 */
1923__weak __function_aligned void abort(void)
1924{
1925	BUG();
1926
1927	/* if that doesn't kill us, halt */
1928	panic("Oops failed to kill thread");
1929}
1930EXPORT_SYMBOL(abort);