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exit.c
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linux-6.19.14/kernel/exit.c
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/unwind_deferred.h> 72#include <linux/uaccess.h> 73#include <linux/pidfs.h> 74 75#include <uapi/linux/wait.h> 76 77#include <asm/unistd.h> 78#include <asm/mmu_context.h> 79 80#include "exit.h" 81 82/* 83 * The default value should be high enough to not crash a system that randomly 84 * crashes its kernel from time to time, but low enough to at least not permit 85 * overflowing 32-bit refcounts or the ldsem writer count. 86 */ 87static unsigned int oops_limit = 10000; 88 89#ifdef CONFIG_SYSCTL 90static const struct ctl_table kern_exit_table[] = { 91 { 92 .procname = "oops_limit", 93 .data = &oops_limit, 94 .maxlen = sizeof(oops_limit), 95 .mode = 0644, 96 .proc_handler = proc_douintvec, 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 126 127/* 128 * For things release_task() would like to do *after* tasklist_lock is released. 129 */ 130struct release_task_post { 131 struct pid *pids[PIDTYPE_MAX]; 132}; 133 134static void __unhash_process(struct release_task_post *post, struct task_struct *p, 135 bool group_dead) 136{ 137 struct pid *pid = task_pid(p); 138 139 nr_threads--; 140 141 detach_pid(post->pids, p, PIDTYPE_PID); 142 wake_up_all(&pid->wait_pidfd); 143 144 if (group_dead) { 145 detach_pid(post->pids, p, PIDTYPE_TGID); 146 detach_pid(post->pids, p, PIDTYPE_PGID); 147 detach_pid(post->pids, p, PIDTYPE_SID); 148 149 list_del_rcu(&p->tasks); 150 list_del_init(&p->sibling); 151 __this_cpu_dec(process_counts); 152 } 153 list_del_rcu(&p->thread_node); 154} 155 156/* 157 * This function expects the tasklist_lock write-locked. 158 */ 159static void __exit_signal(struct release_task_post *post, struct task_struct *tsk) 160{ 161 struct signal_struct *sig = tsk->signal; 162 bool group_dead = thread_group_leader(tsk); 163 struct sighand_struct *sighand; 164 struct tty_struct *tty; 165 u64 utime, stime; 166 167 sighand = rcu_dereference_check(tsk->sighand, 168 lockdep_tasklist_lock_is_held()); 169 spin_lock(&sighand->siglock); 170 171#ifdef CONFIG_POSIX_TIMERS 172 posix_cpu_timers_exit(tsk); 173 if (group_dead) 174 posix_cpu_timers_exit_group(tsk); 175#endif 176 177 if (group_dead) { 178 tty = sig->tty; 179 sig->tty = NULL; 180 } else { 181 /* 182 * If there is any task waiting for the group exit 183 * then notify it: 184 */ 185 if (sig->notify_count > 0 && !--sig->notify_count) 186 wake_up_process(sig->group_exec_task); 187 188 if (tsk == sig->curr_target) 189 sig->curr_target = next_thread(tsk); 190 } 191 192 /* 193 * Accumulate here the counters for all threads as they die. We could 194 * skip the group leader because it is the last user of signal_struct, 195 * but we want to avoid the race with thread_group_cputime() which can 196 * see the empty ->thread_head list. 197 */ 198 task_cputime(tsk, &utime, &stime); 199 write_seqlock(&sig->stats_lock); 200 sig->utime += utime; 201 sig->stime += stime; 202 sig->gtime += task_gtime(tsk); 203 sig->min_flt += tsk->min_flt; 204 sig->maj_flt += tsk->maj_flt; 205 sig->nvcsw += tsk->nvcsw; 206 sig->nivcsw += tsk->nivcsw; 207 sig->inblock += task_io_get_inblock(tsk); 208 sig->oublock += task_io_get_oublock(tsk); 209 task_io_accounting_add(&sig->ioac, &tsk->ioac); 210 sig->sum_sched_runtime += tsk->se.sum_exec_runtime; 211 sig->nr_threads--; 212 __unhash_process(post, tsk, group_dead); 213 write_sequnlock(&sig->stats_lock); 214 215 tsk->sighand = NULL; 216 spin_unlock(&sighand->siglock); 217 218 __cleanup_sighand(sighand); 219 if (group_dead) 220 tty_kref_put(tty); 221} 222 223static void delayed_put_task_struct(struct rcu_head *rhp) 224{ 225 struct task_struct *tsk = container_of(rhp, struct task_struct, rcu); 226 227 kprobe_flush_task(tsk); 228 rethook_flush_task(tsk); 229 perf_event_delayed_put(tsk); 230 trace_sched_process_free(tsk); 231 put_task_struct(tsk); 232} 233 234void put_task_struct_rcu_user(struct task_struct *task) 235{ 236 if (refcount_dec_and_test(&task->rcu_users)) 237 call_rcu(&task->rcu, delayed_put_task_struct); 238} 239 240void __weak release_thread(struct task_struct *dead_task) 241{ 242} 243 244void release_task(struct task_struct *p) 245{ 246 struct release_task_post post; 247 struct task_struct *leader; 248 struct pid *thread_pid; 249 int zap_leader; 250repeat: 251 memset(&post, 0, sizeof(post)); 252 253 /* don't need to get the RCU readlock here - the process is dead and 254 * can't be modifying its own credentials. */ 255 dec_rlimit_ucounts(task_ucounts(p), UCOUNT_RLIMIT_NPROC, 1); 256 257 pidfs_exit(p); 258 cgroup_task_release(p); 259 260 /* Retrieve @thread_pid before __unhash_process() may set it to NULL. */ 261 thread_pid = task_pid(p); 262 263 write_lock_irq(&tasklist_lock); 264 ptrace_release_task(p); 265 __exit_signal(&post, p); 266 267 /* 268 * If we are the last non-leader member of the thread 269 * group, and the leader is zombie, then notify the 270 * group leader's parent process. (if it wants notification.) 271 */ 272 zap_leader = 0; 273 leader = p->group_leader; 274 if (leader != p && thread_group_empty(leader) 275 && leader->exit_state == EXIT_ZOMBIE) { 276 /* for pidfs_exit() and do_notify_parent() */ 277 if (leader->signal->flags & SIGNAL_GROUP_EXIT) 278 leader->exit_code = leader->signal->group_exit_code; 279 /* 280 * If we were the last child thread and the leader has 281 * exited already, and the leader's parent ignores SIGCHLD, 282 * then we are the one who should release the leader. 283 */ 284 zap_leader = do_notify_parent(leader, leader->exit_signal); 285 if (zap_leader) 286 leader->exit_state = EXIT_DEAD; 287 } 288 289 write_unlock_irq(&tasklist_lock); 290 /* @thread_pid can't go away until free_pids() below */ 291 proc_flush_pid(thread_pid); 292 exit_cred_namespaces(p); 293 add_device_randomness(&p->se.sum_exec_runtime, 294 sizeof(p->se.sum_exec_runtime)); 295 free_pids(post.pids); 296 release_thread(p); 297 /* 298 * This task was already removed from the process/thread/pid lists 299 * and lock_task_sighand(p) can't succeed. Nobody else can touch 300 * ->pending or, if group dead, signal->shared_pending. We can call 301 * flush_sigqueue() lockless. 302 */ 303 flush_sigqueue(&p->pending); 304 if (thread_group_leader(p)) 305 flush_sigqueue(&p->signal->shared_pending); 306 307 put_task_struct_rcu_user(p); 308 309 p = leader; 310 if (unlikely(zap_leader)) 311 goto repeat; 312} 313 314int rcuwait_wake_up(struct rcuwait *w) 315{ 316 int ret = 0; 317 struct task_struct *task; 318 319 rcu_read_lock(); 320 321 /* 322 * Order condition vs @task, such that everything prior to the load 323 * of @task is visible. This is the condition as to why the user called 324 * rcuwait_wake() in the first place. Pairs with set_current_state() 325 * barrier (A) in rcuwait_wait_event(). 326 * 327 * WAIT WAKE 328 * [S] tsk = current [S] cond = true 329 * MB (A) MB (B) 330 * [L] cond [L] tsk 331 */ 332 smp_mb(); /* (B) */ 333 334 task = rcu_dereference(w->task); 335 if (task) 336 ret = wake_up_process(task); 337 rcu_read_unlock(); 338 339 return ret; 340} 341EXPORT_SYMBOL_GPL(rcuwait_wake_up); 342 343/* 344 * Determine if a process group is "orphaned", according to the POSIX 345 * definition in 2.2.2.52. Orphaned process groups are not to be affected 346 * by terminal-generated stop signals. Newly orphaned process groups are 347 * to receive a SIGHUP and a SIGCONT. 348 * 349 * "I ask you, have you ever known what it is to be an orphan?" 350 */ 351static int will_become_orphaned_pgrp(struct pid *pgrp, 352 struct task_struct *ignored_task) 353{ 354 struct task_struct *p; 355 356 do_each_pid_task(pgrp, PIDTYPE_PGID, p) { 357 if ((p == ignored_task) || 358 (p->exit_state && thread_group_empty(p)) || 359 is_global_init(p->real_parent)) 360 continue; 361 362 if (task_pgrp(p->real_parent) != pgrp && 363 task_session(p->real_parent) == task_session(p)) 364 return 0; 365 } while_each_pid_task(pgrp, PIDTYPE_PGID, p); 366 367 return 1; 368} 369 370int is_current_pgrp_orphaned(void) 371{ 372 int retval; 373 374 read_lock(&tasklist_lock); 375 retval = will_become_orphaned_pgrp(task_pgrp(current), NULL); 376 read_unlock(&tasklist_lock); 377 378 return retval; 379} 380 381static bool has_stopped_jobs(struct pid *pgrp) 382{ 383 struct task_struct *p; 384 385 do_each_pid_task(pgrp, PIDTYPE_PGID, p) { 386 if (p->signal->flags & SIGNAL_STOP_STOPPED) 387 return true; 388 } while_each_pid_task(pgrp, PIDTYPE_PGID, p); 389 390 return false; 391} 392 393/* 394 * Check to see if any process groups have become orphaned as 395 * a result of our exiting, and if they have any stopped jobs, 396 * send them a SIGHUP and then a SIGCONT. (POSIX 3.2.2.2) 397 */ 398static void 399kill_orphaned_pgrp(struct task_struct *tsk, struct task_struct *parent) 400{ 401 struct pid *pgrp = task_pgrp(tsk); 402 struct task_struct *ignored_task = tsk; 403 404 if (!parent) 405 /* exit: our father is in a different pgrp than 406 * we are and we were the only connection outside. 407 */ 408 parent = tsk->real_parent; 409 else 410 /* reparent: our child is in a different pgrp than 411 * we are, and it was the only connection outside. 412 */ 413 ignored_task = NULL; 414 415 if (task_pgrp(parent) != pgrp && 416 task_session(parent) == task_session(tsk) && 417 will_become_orphaned_pgrp(pgrp, ignored_task) && 418 has_stopped_jobs(pgrp)) { 419 __kill_pgrp_info(SIGHUP, SEND_SIG_PRIV, pgrp); 420 __kill_pgrp_info(SIGCONT, SEND_SIG_PRIV, pgrp); 421 } 422} 423 424static void coredump_task_exit(struct task_struct *tsk, 425 struct core_state *core_state) 426{ 427 struct core_thread self; 428 429 self.task = tsk; 430 if (self.task->flags & PF_SIGNALED) 431 self.next = xchg(&core_state->dumper.next, &self); 432 else 433 self.task = NULL; 434 /* 435 * Implies mb(), the result of xchg() must be visible 436 * to core_state->dumper. 437 */ 438 if (atomic_dec_and_test(&core_state->nr_threads)) 439 complete(&core_state->startup); 440 441 for (;;) { 442 set_current_state(TASK_IDLE|TASK_FREEZABLE); 443 if (!self.task) /* see coredump_finish() */ 444 break; 445 schedule(); 446 } 447 __set_current_state(TASK_RUNNING); 448} 449 450#ifdef CONFIG_MEMCG 451/* drops tasklist_lock if succeeds */ 452static bool __try_to_set_owner(struct task_struct *tsk, struct mm_struct *mm) 453{ 454 bool ret = false; 455 456 task_lock(tsk); 457 if (likely(tsk->mm == mm)) { 458 /* tsk can't pass exit_mm/exec_mmap and exit */ 459 read_unlock(&tasklist_lock); 460 WRITE_ONCE(mm->owner, tsk); 461 lru_gen_migrate_mm(mm); 462 ret = true; 463 } 464 task_unlock(tsk); 465 return ret; 466} 467 468static bool try_to_set_owner(struct task_struct *g, struct mm_struct *mm) 469{ 470 struct task_struct *t; 471 472 for_each_thread(g, t) { 473 struct mm_struct *t_mm = READ_ONCE(t->mm); 474 if (t_mm == mm) { 475 if (__try_to_set_owner(t, mm)) 476 return true; 477 } else if (t_mm) 478 break; 479 } 480 481 return false; 482} 483 484/* 485 * A task is exiting. If it owned this mm, find a new owner for the mm. 486 */ 487void mm_update_next_owner(struct mm_struct *mm) 488{ 489 struct task_struct *g, *p = current; 490 491 /* 492 * If the exiting or execing task is not the owner, it's 493 * someone else's problem. 494 */ 495 if (mm->owner != p) 496 return; 497 /* 498 * The current owner is exiting/execing and there are no other 499 * candidates. Do not leave the mm pointing to a possibly 500 * freed task structure. 501 */ 502 if (atomic_read(&mm->mm_users) <= 1) { 503 WRITE_ONCE(mm->owner, NULL); 504 return; 505 } 506 507 read_lock(&tasklist_lock); 508 /* 509 * Search in the children 510 */ 511 list_for_each_entry(g, &p->children, sibling) { 512 if (try_to_set_owner(g, mm)) 513 goto ret; 514 } 515 /* 516 * Search in the siblings 517 */ 518 list_for_each_entry(g, &p->real_parent->children, sibling) { 519 if (try_to_set_owner(g, mm)) 520 goto ret; 521 } 522 /* 523 * Search through everything else, we should not get here often. 524 */ 525 for_each_process(g) { 526 if (atomic_read(&mm->mm_users) <= 1) 527 break; 528 if (g->flags & PF_KTHREAD) 529 continue; 530 if (try_to_set_owner(g, mm)) 531 goto ret; 532 } 533 read_unlock(&tasklist_lock); 534 /* 535 * We found no owner yet mm_users > 1: this implies that we are 536 * most likely racing with swapoff (try_to_unuse()) or /proc or 537 * ptrace or page migration (get_task_mm()). Mark owner as NULL. 538 */ 539 WRITE_ONCE(mm->owner, NULL); 540 ret: 541 return; 542 543} 544#endif /* CONFIG_MEMCG */ 545 546/* 547 * Turn us into a lazy TLB process if we 548 * aren't already.. 549 */ 550static void exit_mm(void) 551{ 552 struct mm_struct *mm = current->mm; 553 554 exit_mm_release(current, mm); 555 if (!mm) 556 return; 557 mmap_read_lock(mm); 558 mmgrab_lazy_tlb(mm); 559 BUG_ON(mm != current->active_mm); 560 /* more a memory barrier than a real lock */ 561 task_lock(current); 562 /* 563 * When a thread stops operating on an address space, the loop 564 * in membarrier_private_expedited() may not observe that 565 * tsk->mm, and the loop in membarrier_global_expedited() may 566 * not observe a MEMBARRIER_STATE_GLOBAL_EXPEDITED 567 * rq->membarrier_state, so those would not issue an IPI. 568 * Membarrier requires a memory barrier after accessing 569 * user-space memory, before clearing tsk->mm or the 570 * rq->membarrier_state. 571 */ 572 smp_mb__after_spinlock(); 573 local_irq_disable(); 574 current->mm = NULL; 575 membarrier_update_current_mm(NULL); 576 enter_lazy_tlb(mm, current); 577 local_irq_enable(); 578 task_unlock(current); 579 mmap_read_unlock(mm); 580 mm_update_next_owner(mm); 581 mmput(mm); 582 if (test_thread_flag(TIF_MEMDIE)) 583 exit_oom_victim(); 584} 585 586static struct task_struct *find_alive_thread(struct task_struct *p) 587{ 588 struct task_struct *t; 589 590 for_each_thread(p, t) { 591 if (!(t->flags & PF_EXITING)) 592 return t; 593 } 594 return NULL; 595} 596 597static struct task_struct *find_child_reaper(struct task_struct *father, 598 struct list_head *dead) 599 __releases(&tasklist_lock) 600 __acquires(&tasklist_lock) 601{ 602 struct pid_namespace *pid_ns = task_active_pid_ns(father); 603 struct task_struct *reaper = pid_ns->child_reaper; 604 struct task_struct *p, *n; 605 606 if (likely(reaper != father)) 607 return reaper; 608 609 reaper = find_alive_thread(father); 610 if (reaper) { 611 pid_ns->child_reaper = reaper; 612 return reaper; 613 } 614 615 write_unlock_irq(&tasklist_lock); 616 617 list_for_each_entry_safe(p, n, dead, ptrace_entry) { 618 list_del_init(&p->ptrace_entry); 619 release_task(p); 620 } 621 622 zap_pid_ns_processes(pid_ns); 623 write_lock_irq(&tasklist_lock); 624 625 return father; 626} 627 628/* 629 * When we die, we re-parent all our children, and try to: 630 * 1. give them to another thread in our thread group, if such a member exists 631 * 2. give it to the first ancestor process which prctl'd itself as a 632 * child_subreaper for its children (like a service manager) 633 * 3. give it to the init process (PID 1) in our pid namespace 634 */ 635static struct task_struct *find_new_reaper(struct task_struct *father, 636 struct task_struct *child_reaper) 637{ 638 struct task_struct *thread, *reaper; 639 640 thread = find_alive_thread(father); 641 if (thread) 642 return thread; 643 644 if (father->signal->has_child_subreaper) { 645 unsigned int ns_level = task_pid(father)->level; 646 /* 647 * Find the first ->is_child_subreaper ancestor in our pid_ns. 648 * We can't check reaper != child_reaper to ensure we do not 649 * cross the namespaces, the exiting parent could be injected 650 * by setns() + fork(). 651 * We check pid->level, this is slightly more efficient than 652 * task_active_pid_ns(reaper) != task_active_pid_ns(father). 653 */ 654 for (reaper = father->real_parent; 655 task_pid(reaper)->level == ns_level; 656 reaper = reaper->real_parent) { 657 if (reaper == &init_task) 658 break; 659 if (!reaper->signal->is_child_subreaper) 660 continue; 661 thread = find_alive_thread(reaper); 662 if (thread) 663 return thread; 664 } 665 } 666 667 return child_reaper; 668} 669 670/* 671* Any that need to be release_task'd are put on the @dead list. 672 */ 673static void reparent_leader(struct task_struct *father, struct task_struct *p, 674 struct list_head *dead) 675{ 676 if (unlikely(p->exit_state == EXIT_DEAD)) 677 return; 678 679 /* We don't want people slaying init. */ 680 p->exit_signal = SIGCHLD; 681 682 /* If it has exited notify the new parent about this child's death. */ 683 if (!p->ptrace && 684 p->exit_state == EXIT_ZOMBIE && thread_group_empty(p)) { 685 if (do_notify_parent(p, p->exit_signal)) { 686 p->exit_state = EXIT_DEAD; 687 list_add(&p->ptrace_entry, dead); 688 } 689 } 690 691 kill_orphaned_pgrp(p, father); 692} 693 694/* 695 * Make init inherit all the child processes 696 */ 697static void forget_original_parent(struct task_struct *father, 698 struct list_head *dead) 699{ 700 struct task_struct *p, *t, *reaper; 701 702 if (unlikely(!list_empty(&father->ptraced))) 703 exit_ptrace(father, dead); 704 705 /* Can drop and reacquire tasklist_lock */ 706 reaper = find_child_reaper(father, dead); 707 if (list_empty(&father->children)) 708 return; 709 710 reaper = find_new_reaper(father, reaper); 711 list_for_each_entry(p, &father->children, sibling) { 712 for_each_thread(p, t) { 713 RCU_INIT_POINTER(t->real_parent, reaper); 714 BUG_ON((!t->ptrace) != (rcu_access_pointer(t->parent) == father)); 715 if (likely(!t->ptrace)) 716 t->parent = t->real_parent; 717 if (t->pdeath_signal) 718 group_send_sig_info(t->pdeath_signal, 719 SEND_SIG_NOINFO, t, 720 PIDTYPE_TGID); 721 } 722 /* 723 * If this is a threaded reparent there is no need to 724 * notify anyone anything has happened. 725 */ 726 if (!same_thread_group(reaper, father)) 727 reparent_leader(father, p, dead); 728 } 729 list_splice_tail_init(&father->children, &reaper->children); 730} 731 732/* 733 * Send signals to all our closest relatives so that they know 734 * to properly mourn us.. 735 */ 736static void exit_notify(struct task_struct *tsk, int group_dead) 737{ 738 bool autoreap; 739 struct task_struct *p, *n; 740 LIST_HEAD(dead); 741 742 write_lock_irq(&tasklist_lock); 743 forget_original_parent(tsk, &dead); 744 745 if (group_dead) 746 kill_orphaned_pgrp(tsk->group_leader, NULL); 747 748 tsk->exit_state = EXIT_ZOMBIE; 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 /* untraced sub-thread */ 762 do_notify_pidfd(tsk); 763 } 764 765 if (autoreap) { 766 tsk->exit_state = EXIT_DEAD; 767 list_add(&tsk->ptrace_entry, &dead); 768 } 769 770 /* mt-exec, de_thread() is waiting for group leader */ 771 if (unlikely(tsk->signal->notify_count < 0)) 772 wake_up_process(tsk->signal->group_exec_task); 773 write_unlock_irq(&tasklist_lock); 774 775 list_for_each_entry_safe(p, n, &dead, ptrace_entry) { 776 list_del_init(&p->ptrace_entry); 777 release_task(p); 778 } 779} 780 781#ifdef CONFIG_DEBUG_STACK_USAGE 782#ifdef CONFIG_STACK_GROWSUP 783unsigned long stack_not_used(struct task_struct *p) 784{ 785 unsigned long *n = end_of_stack(p); 786 787 do { /* Skip over canary */ 788 n--; 789 } while (!*n); 790 791 return (unsigned long)end_of_stack(p) - (unsigned long)n; 792} 793#else /* !CONFIG_STACK_GROWSUP */ 794unsigned long stack_not_used(struct task_struct *p) 795{ 796 unsigned long *n = end_of_stack(p); 797 798 do { /* Skip over canary */ 799 n++; 800 } while (!*n); 801 802 return (unsigned long)n - (unsigned long)end_of_stack(p); 803} 804#endif /* CONFIG_STACK_GROWSUP */ 805 806/* Count the maximum pages reached in kernel stacks */ 807static inline void kstack_histogram(unsigned long used_stack) 808{ 809#ifdef CONFIG_VM_EVENT_COUNTERS 810 if (used_stack <= 1024) 811 count_vm_event(KSTACK_1K); 812#if THREAD_SIZE > 1024 813 else if (used_stack <= 2048) 814 count_vm_event(KSTACK_2K); 815#endif 816#if THREAD_SIZE > 2048 817 else if (used_stack <= 4096) 818 count_vm_event(KSTACK_4K); 819#endif 820#if THREAD_SIZE > 4096 821 else if (used_stack <= 8192) 822 count_vm_event(KSTACK_8K); 823#endif 824#if THREAD_SIZE > 8192 825 else if (used_stack <= 16384) 826 count_vm_event(KSTACK_16K); 827#endif 828#if THREAD_SIZE > 16384 829 else if (used_stack <= 32768) 830 count_vm_event(KSTACK_32K); 831#endif 832#if THREAD_SIZE > 32768 833 else if (used_stack <= 65536) 834 count_vm_event(KSTACK_64K); 835#endif 836#if THREAD_SIZE > 65536 837 else 838 count_vm_event(KSTACK_REST); 839#endif 840#endif /* CONFIG_VM_EVENT_COUNTERS */ 841} 842 843static void check_stack_usage(void) 844{ 845 static DEFINE_SPINLOCK(low_water_lock); 846 static int lowest_to_date = THREAD_SIZE; 847 unsigned long free; 848 849 free = stack_not_used(current); 850 kstack_histogram(THREAD_SIZE - free); 851 852 if (free >= lowest_to_date) 853 return; 854 855 spin_lock(&low_water_lock); 856 if (free < lowest_to_date) { 857 pr_info("%s (%d) used greatest stack depth: %lu bytes left\n", 858 current->comm, task_pid_nr(current), free); 859 lowest_to_date = free; 860 } 861 spin_unlock(&low_water_lock); 862} 863#else /* !CONFIG_DEBUG_STACK_USAGE */ 864static inline void check_stack_usage(void) {} 865#endif /* CONFIG_DEBUG_STACK_USAGE */ 866 867static void synchronize_group_exit(struct task_struct *tsk, long code) 868{ 869 struct sighand_struct *sighand = tsk->sighand; 870 struct signal_struct *signal = tsk->signal; 871 struct core_state *core_state; 872 873 spin_lock_irq(&sighand->siglock); 874 signal->quick_threads--; 875 if ((signal->quick_threads == 0) && 876 !(signal->flags & SIGNAL_GROUP_EXIT)) { 877 signal->flags = SIGNAL_GROUP_EXIT; 878 signal->group_exit_code = code; 879 signal->group_stop_count = 0; 880 } 881 /* 882 * Serialize with any possible pending coredump. 883 * We must hold siglock around checking core_state 884 * and setting PF_POSTCOREDUMP. The core-inducing thread 885 * will increment ->nr_threads for each thread in the 886 * group without PF_POSTCOREDUMP set. 887 */ 888 tsk->flags |= PF_POSTCOREDUMP; 889 core_state = signal->core_state; 890 spin_unlock_irq(&sighand->siglock); 891 892 if (unlikely(core_state)) 893 coredump_task_exit(tsk, core_state); 894} 895 896void __noreturn do_exit(long code) 897{ 898 struct task_struct *tsk = current; 899 struct kthread *kthread; 900 int group_dead; 901 902 WARN_ON(irqs_disabled()); 903 WARN_ON(tsk->plug); 904 905 kthread = tsk_is_kthread(tsk); 906 if (unlikely(kthread)) 907 kthread_do_exit(kthread, code); 908 909 kcov_task_exit(tsk); 910 kmsan_task_exit(tsk); 911 912 synchronize_group_exit(tsk, code); 913 ptrace_event(PTRACE_EVENT_EXIT, code); 914 user_events_exit(tsk); 915 916 io_uring_files_cancel(); 917 sched_mm_cid_exit(tsk); 918 exit_signals(tsk); /* sets PF_EXITING */ 919 920 seccomp_filter_release(tsk); 921 922 acct_update_integrals(tsk); 923 group_dead = atomic_dec_and_test(&tsk->signal->live); 924 if (group_dead) { 925 /* 926 * If the last thread of global init has exited, panic 927 * immediately to get a useable coredump. 928 */ 929 if (unlikely(is_global_init(tsk))) 930 panic("Attempted to kill init! exitcode=0x%08x\n", 931 tsk->signal->group_exit_code ?: (int)code); 932 933#ifdef CONFIG_POSIX_TIMERS 934 hrtimer_cancel(&tsk->signal->real_timer); 935 exit_itimers(tsk); 936#endif 937 if (tsk->mm) 938 setmax_mm_hiwater_rss(&tsk->signal->maxrss, tsk->mm); 939 } 940 acct_collect(code, group_dead); 941 if (group_dead) 942 tty_audit_exit(); 943 audit_free(tsk); 944 945 tsk->exit_code = code; 946 taskstats_exit(tsk, group_dead); 947 trace_sched_process_exit(tsk, group_dead); 948 949 /* 950 * Since sampling can touch ->mm, make sure to stop everything before we 951 * tear it down. 952 * 953 * Also flushes inherited counters to the parent - before the parent 954 * gets woken up by child-exit notifications. 955 */ 956 perf_event_exit_task(tsk); 957 /* 958 * PF_EXITING (above) ensures unwind_deferred_request() will no 959 * longer add new unwinds. While exit_mm() (below) will destroy the 960 * abaility to do unwinds. So flush any pending unwinds here. 961 */ 962 unwind_deferred_task_exit(tsk); 963 964 exit_mm(); 965 966 if (group_dead) 967 acct_process(); 968 969 exit_sem(tsk); 970 exit_shm(tsk); 971 exit_files(tsk); 972 exit_fs(tsk); 973 if (group_dead) 974 disassociate_ctty(1); 975 exit_nsproxy_namespaces(tsk); 976 exit_task_work(tsk); 977 exit_thread(tsk); 978 979 sched_autogroup_exit_task(tsk); 980 cgroup_task_exit(tsk); 981 982 /* 983 * FIXME: do that only when needed, using sched_exit tracepoint 984 */ 985 flush_ptrace_hw_breakpoint(tsk); 986 987 exit_tasks_rcu_start(); 988 exit_notify(tsk, group_dead); 989 proc_exit_connector(tsk); 990 mpol_put_task_policy(tsk); 991#ifdef CONFIG_FUTEX 992 if (unlikely(current->pi_state_cache)) 993 kfree(current->pi_state_cache); 994#endif 995 /* 996 * Make sure we are holding no locks: 997 */ 998 debug_check_no_locks_held(); 999 1000 if (tsk->io_context) 1001 exit_io_context(tsk); 1002 1003 if (tsk->splice_pipe) 1004 free_pipe_info(tsk->splice_pipe); 1005 1006 if (tsk->task_frag.page) 1007 put_page(tsk->task_frag.page); 1008 1009 exit_task_stack_account(tsk); 1010 1011 check_stack_usage(); 1012 preempt_disable(); 1013 if (tsk->nr_dirtied) 1014 __this_cpu_add(dirty_throttle_leaks, tsk->nr_dirtied); 1015 exit_rcu(); 1016 exit_tasks_rcu_finish(); 1017 1018 lockdep_free_task(tsk); 1019 do_task_dead(); 1020} 1021EXPORT_SYMBOL(do_exit); 1022 1023void __noreturn make_task_dead(int signr) 1024{ 1025 /* 1026 * Take the task off the cpu after something catastrophic has 1027 * happened. 1028 * 1029 * We can get here from a kernel oops, sometimes with preemption off. 1030 * Start by checking for critical errors. 1031 * Then fix up important state like USER_DS and preemption. 1032 * Then do everything else. 1033 */ 1034 struct task_struct *tsk = current; 1035 unsigned int limit; 1036 1037 if (unlikely(in_interrupt())) 1038 panic("Aiee, killing interrupt handler!"); 1039 if (unlikely(!tsk->pid)) 1040 panic("Attempted to kill the idle task!"); 1041 1042 if (unlikely(irqs_disabled())) { 1043 pr_info("note: %s[%d] exited with irqs disabled\n", 1044 current->comm, task_pid_nr(current)); 1045 local_irq_enable(); 1046 } 1047 if (unlikely(in_atomic())) { 1048 pr_info("note: %s[%d] exited with preempt_count %d\n", 1049 current->comm, task_pid_nr(current), 1050 preempt_count()); 1051 preempt_count_set(PREEMPT_ENABLED); 1052 } 1053 1054 /* 1055 * Every time the system oopses, if the oops happens while a reference 1056 * to an object was held, the reference leaks. 1057 * If the oops doesn't also leak memory, repeated oopsing can cause 1058 * reference counters to wrap around (if they're not using refcount_t). 1059 * This means that repeated oopsing can make unexploitable-looking bugs 1060 * exploitable through repeated oopsing. 1061 * To make sure this can't happen, place an upper bound on how often the 1062 * kernel may oops without panic(). 1063 */ 1064 limit = READ_ONCE(oops_limit); 1065 if (atomic_inc_return(&oops_count) >= limit && limit) 1066 panic("Oopsed too often (kernel.oops_limit is %d)", limit); 1067 1068 /* 1069 * We're taking recursive faults here in make_task_dead. Safest is to just 1070 * leave this task alone and wait for reboot. 1071 */ 1072 if (unlikely(tsk->flags & PF_EXITING)) { 1073 pr_alert("Fixing recursive fault but reboot is needed!\n"); 1074 futex_exit_recursive(tsk); 1075 tsk->exit_state = EXIT_DEAD; 1076 refcount_inc(&tsk->rcu_users); 1077 do_task_dead(); 1078 } 1079 1080 do_exit(signr); 1081} 1082 1083SYSCALL_DEFINE1(exit, int, error_code) 1084{ 1085 do_exit((error_code&0xff)<<8); 1086} 1087 1088/* 1089 * Take down every thread in the group. This is called by fatal signals 1090 * as well as by sys_exit_group (below). 1091 */ 1092void __noreturn 1093do_group_exit(int exit_code) 1094{ 1095 struct signal_struct *sig = current->signal; 1096 1097 if (sig->flags & SIGNAL_GROUP_EXIT) 1098 exit_code = sig->group_exit_code; 1099 else if (sig->group_exec_task) 1100 exit_code = 0; 1101 else { 1102 struct sighand_struct *const sighand = current->sighand; 1103 1104 spin_lock_irq(&sighand->siglock); 1105 if (sig->flags & SIGNAL_GROUP_EXIT) 1106 /* Another thread got here before we took the lock. */ 1107 exit_code = sig->group_exit_code; 1108 else if (sig->group_exec_task) 1109 exit_code = 0; 1110 else { 1111 sig->group_exit_code = exit_code; 1112 sig->flags = SIGNAL_GROUP_EXIT; 1113 zap_other_threads(current); 1114 } 1115 spin_unlock_irq(&sighand->siglock); 1116 } 1117 1118 do_exit(exit_code); 1119 /* NOTREACHED */ 1120} 1121 1122/* 1123 * this kills every thread in the thread group. Note that any externally 1124 * wait4()-ing process will get the correct exit code - even if this 1125 * thread is not the thread group leader. 1126 */ 1127SYSCALL_DEFINE1(exit_group, int, error_code) 1128{ 1129 do_group_exit((error_code & 0xff) << 8); 1130 /* NOTREACHED */ 1131 return 0; 1132} 1133 1134static int eligible_pid(struct wait_opts *wo, struct task_struct *p) 1135{ 1136 return wo->wo_type == PIDTYPE_MAX || 1137 task_pid_type(p, wo->wo_type) == wo->wo_pid; 1138} 1139 1140static int 1141eligible_child(struct wait_opts *wo, bool ptrace, struct task_struct *p) 1142{ 1143 if (!eligible_pid(wo, p)) 1144 return 0; 1145 1146 /* 1147 * Wait for all children (clone and not) if __WALL is set or 1148 * if it is traced by us. 1149 */ 1150 if (ptrace || (wo->wo_flags & __WALL)) 1151 return 1; 1152 1153 /* 1154 * Otherwise, wait for clone children *only* if __WCLONE is set; 1155 * otherwise, wait for non-clone children *only*. 1156 * 1157 * Note: a "clone" child here is one that reports to its parent 1158 * using a signal other than SIGCHLD, or a non-leader thread which 1159 * we can only see if it is traced by us. 1160 */ 1161 if ((p->exit_signal != SIGCHLD) ^ !!(wo->wo_flags & __WCLONE)) 1162 return 0; 1163 1164 return 1; 1165} 1166 1167/* 1168 * Handle sys_wait4 work for one task in state EXIT_ZOMBIE. We hold 1169 * read_lock(&tasklist_lock) on entry. If we return zero, we still hold 1170 * the lock and this task is uninteresting. If we return nonzero, we have 1171 * released the lock and the system call should return. 1172 */ 1173static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p) 1174{ 1175 int state, status; 1176 pid_t pid = task_pid_vnr(p); 1177 uid_t uid = from_kuid_munged(current_user_ns(), task_uid(p)); 1178 struct waitid_info *infop; 1179 1180 if (!likely(wo->wo_flags & WEXITED)) 1181 return 0; 1182 1183 if (unlikely(wo->wo_flags & WNOWAIT)) { 1184 status = (p->signal->flags & SIGNAL_GROUP_EXIT) 1185 ? p->signal->group_exit_code : p->exit_code; 1186 get_task_struct(p); 1187 read_unlock(&tasklist_lock); 1188 sched_annotate_sleep(); 1189 if (wo->wo_rusage) 1190 getrusage(p, RUSAGE_BOTH, wo->wo_rusage); 1191 put_task_struct(p); 1192 goto out_info; 1193 } 1194 /* 1195 * Move the task's state to DEAD/TRACE, only one thread can do this. 1196 */ 1197 state = (ptrace_reparented(p) && thread_group_leader(p)) ? 1198 EXIT_TRACE : EXIT_DEAD; 1199 if (cmpxchg(&p->exit_state, EXIT_ZOMBIE, state) != EXIT_ZOMBIE) 1200 return 0; 1201 /* 1202 * We own this thread, nobody else can reap it. 1203 */ 1204 read_unlock(&tasklist_lock); 1205 sched_annotate_sleep(); 1206 1207 /* 1208 * Check thread_group_leader() to exclude the traced sub-threads. 1209 */ 1210 if (state == EXIT_DEAD && thread_group_leader(p)) { 1211 struct signal_struct *sig = p->signal; 1212 struct signal_struct *psig = current->signal; 1213 unsigned long maxrss; 1214 u64 tgutime, tgstime; 1215 1216 /* 1217 * The resource counters for the group leader are in its 1218 * own task_struct. Those for dead threads in the group 1219 * are in its signal_struct, as are those for the child 1220 * processes it has previously reaped. All these 1221 * accumulate in the parent's signal_struct c* fields. 1222 * 1223 * We don't bother to take a lock here to protect these 1224 * p->signal fields because the whole thread group is dead 1225 * and nobody can change them. 1226 * 1227 * psig->stats_lock also protects us from our sub-threads 1228 * which can reap other children at the same time. 1229 * 1230 * We use thread_group_cputime_adjusted() to get times for 1231 * the thread group, which consolidates times for all threads 1232 * in the group including the group leader. 1233 */ 1234 thread_group_cputime_adjusted(p, &tgutime, &tgstime); 1235 write_seqlock_irq(&psig->stats_lock); 1236 psig->cutime += tgutime + sig->cutime; 1237 psig->cstime += tgstime + sig->cstime; 1238 psig->cgtime += task_gtime(p) + sig->gtime + sig->cgtime; 1239 psig->cmin_flt += 1240 p->min_flt + sig->min_flt + sig->cmin_flt; 1241 psig->cmaj_flt += 1242 p->maj_flt + sig->maj_flt + sig->cmaj_flt; 1243 psig->cnvcsw += 1244 p->nvcsw + sig->nvcsw + sig->cnvcsw; 1245 psig->cnivcsw += 1246 p->nivcsw + sig->nivcsw + sig->cnivcsw; 1247 psig->cinblock += 1248 task_io_get_inblock(p) + 1249 sig->inblock + sig->cinblock; 1250 psig->coublock += 1251 task_io_get_oublock(p) + 1252 sig->oublock + sig->coublock; 1253 maxrss = max(sig->maxrss, sig->cmaxrss); 1254 if (psig->cmaxrss < maxrss) 1255 psig->cmaxrss = maxrss; 1256 task_io_accounting_add(&psig->ioac, &p->ioac); 1257 task_io_accounting_add(&psig->ioac, &sig->ioac); 1258 write_sequnlock_irq(&psig->stats_lock); 1259 } 1260 1261 if (wo->wo_rusage) 1262 getrusage(p, RUSAGE_BOTH, wo->wo_rusage); 1263 status = (p->signal->flags & SIGNAL_GROUP_EXIT) 1264 ? p->signal->group_exit_code : p->exit_code; 1265 wo->wo_stat = status; 1266 1267 if (state == EXIT_TRACE) { 1268 write_lock_irq(&tasklist_lock); 1269 /* We dropped tasklist, ptracer could die and untrace */ 1270 ptrace_unlink(p); 1271 1272 /* If parent wants a zombie, don't release it now */ 1273 state = EXIT_ZOMBIE; 1274 if (do_notify_parent(p, p->exit_signal)) 1275 state = EXIT_DEAD; 1276 p->exit_state = state; 1277 write_unlock_irq(&tasklist_lock); 1278 } 1279 if (state == EXIT_DEAD) 1280 release_task(p); 1281 1282out_info: 1283 infop = wo->wo_info; 1284 if (infop) { 1285 if ((status & 0x7f) == 0) { 1286 infop->cause = CLD_EXITED; 1287 infop->status = status >> 8; 1288 } else { 1289 infop->cause = (status & 0x80) ? CLD_DUMPED : CLD_KILLED; 1290 infop->status = status & 0x7f; 1291 } 1292 infop->pid = pid; 1293 infop->uid = uid; 1294 } 1295 1296 return pid; 1297} 1298 1299static int *task_stopped_code(struct task_struct *p, bool ptrace) 1300{ 1301 if (ptrace) { 1302 if (task_is_traced(p) && !(p->jobctl & JOBCTL_LISTENING)) 1303 return &p->exit_code; 1304 } else { 1305 if (p->signal->flags & SIGNAL_STOP_STOPPED) 1306 return &p->signal->group_exit_code; 1307 } 1308 return NULL; 1309} 1310 1311/** 1312 * wait_task_stopped - Wait for %TASK_STOPPED or %TASK_TRACED 1313 * @wo: wait options 1314 * @ptrace: is the wait for ptrace 1315 * @p: task to wait for 1316 * 1317 * Handle sys_wait4() work for %p in state %TASK_STOPPED or %TASK_TRACED. 1318 * 1319 * CONTEXT: 1320 * read_lock(&tasklist_lock), which is released if return value is 1321 * non-zero. Also, grabs and releases @p->sighand->siglock. 1322 * 1323 * RETURNS: 1324 * 0 if wait condition didn't exist and search for other wait conditions 1325 * should continue. Non-zero return, -errno on failure and @p's pid on 1326 * success, implies that tasklist_lock is released and wait condition 1327 * search should terminate. 1328 */ 1329static int wait_task_stopped(struct wait_opts *wo, 1330 int ptrace, struct task_struct *p) 1331{ 1332 struct waitid_info *infop; 1333 int exit_code, *p_code, why; 1334 uid_t uid = 0; /* unneeded, required by compiler */ 1335 pid_t pid; 1336 1337 /* 1338 * Traditionally we see ptrace'd stopped tasks regardless of options. 1339 */ 1340 if (!ptrace && !(wo->wo_flags & WUNTRACED)) 1341 return 0; 1342 1343 if (!task_stopped_code(p, ptrace)) 1344 return 0; 1345 1346 exit_code = 0; 1347 spin_lock_irq(&p->sighand->siglock); 1348 1349 p_code = task_stopped_code(p, ptrace); 1350 if (unlikely(!p_code)) 1351 goto unlock_sig; 1352 1353 exit_code = *p_code; 1354 if (!exit_code) 1355 goto unlock_sig; 1356 1357 if (!unlikely(wo->wo_flags & WNOWAIT)) 1358 *p_code = 0; 1359 1360 uid = from_kuid_munged(current_user_ns(), task_uid(p)); 1361unlock_sig: 1362 spin_unlock_irq(&p->sighand->siglock); 1363 if (!exit_code) 1364 return 0; 1365 1366 /* 1367 * Now we are pretty sure this task is interesting. 1368 * Make sure it doesn't get reaped out from under us while we 1369 * give up the lock and then examine it below. We don't want to 1370 * keep holding onto the tasklist_lock while we call getrusage and 1371 * possibly take page faults for user memory. 1372 */ 1373 get_task_struct(p); 1374 pid = task_pid_vnr(p); 1375 why = ptrace ? CLD_TRAPPED : CLD_STOPPED; 1376 read_unlock(&tasklist_lock); 1377 sched_annotate_sleep(); 1378 if (wo->wo_rusage) 1379 getrusage(p, RUSAGE_BOTH, wo->wo_rusage); 1380 put_task_struct(p); 1381 1382 if (likely(!(wo->wo_flags & WNOWAIT))) 1383 wo->wo_stat = (exit_code << 8) | 0x7f; 1384 1385 infop = wo->wo_info; 1386 if (infop) { 1387 infop->cause = why; 1388 infop->status = exit_code; 1389 infop->pid = pid; 1390 infop->uid = uid; 1391 } 1392 return pid; 1393} 1394 1395/* 1396 * Handle do_wait work for one task in a live, non-stopped state. 1397 * read_lock(&tasklist_lock) on entry. If we return zero, we still hold 1398 * the lock and this task is uninteresting. If we return nonzero, we have 1399 * released the lock and the system call should return. 1400 */ 1401static int wait_task_continued(struct wait_opts *wo, struct task_struct *p) 1402{ 1403 struct waitid_info *infop; 1404 pid_t pid; 1405 uid_t uid; 1406 1407 if (!unlikely(wo->wo_flags & WCONTINUED)) 1408 return 0; 1409 1410 if (!(p->signal->flags & SIGNAL_STOP_CONTINUED)) 1411 return 0; 1412 1413 spin_lock_irq(&p->sighand->siglock); 1414 /* Re-check with the lock held. */ 1415 if (!(p->signal->flags & SIGNAL_STOP_CONTINUED)) { 1416 spin_unlock_irq(&p->sighand->siglock); 1417 return 0; 1418 } 1419 if (!unlikely(wo->wo_flags & WNOWAIT)) 1420 p->signal->flags &= ~SIGNAL_STOP_CONTINUED; 1421 uid = from_kuid_munged(current_user_ns(), task_uid(p)); 1422 spin_unlock_irq(&p->sighand->siglock); 1423 1424 pid = task_pid_vnr(p); 1425 get_task_struct(p); 1426 read_unlock(&tasklist_lock); 1427 sched_annotate_sleep(); 1428 if (wo->wo_rusage) 1429 getrusage(p, RUSAGE_BOTH, wo->wo_rusage); 1430 put_task_struct(p); 1431 1432 infop = wo->wo_info; 1433 if (!infop) { 1434 wo->wo_stat = 0xffff; 1435 } else { 1436 infop->cause = CLD_CONTINUED; 1437 infop->pid = pid; 1438 infop->uid = uid; 1439 infop->status = SIGCONT; 1440 } 1441 return pid; 1442} 1443 1444/* 1445 * Consider @p for a wait by @parent. 1446 * 1447 * -ECHILD should be in ->notask_error before the first call. 1448 * Returns nonzero for a final return, when we have unlocked tasklist_lock. 1449 * Returns zero if the search for a child should continue; 1450 * then ->notask_error is 0 if @p is an eligible child, 1451 * or still -ECHILD. 1452 */ 1453static int wait_consider_task(struct wait_opts *wo, int ptrace, 1454 struct task_struct *p) 1455{ 1456 /* 1457 * We can race with wait_task_zombie() from another thread. 1458 * Ensure that EXIT_ZOMBIE -> EXIT_DEAD/EXIT_TRACE transition 1459 * can't confuse the checks below. 1460 */ 1461 int exit_state = READ_ONCE(p->exit_state); 1462 int ret; 1463 1464 if (unlikely(exit_state == EXIT_DEAD)) 1465 return 0; 1466 1467 ret = eligible_child(wo, ptrace, p); 1468 if (!ret) 1469 return ret; 1470 1471 if (unlikely(exit_state == EXIT_TRACE)) { 1472 /* 1473 * ptrace == 0 means we are the natural parent. In this case 1474 * we should clear notask_error, debugger will notify us. 1475 */ 1476 if (likely(!ptrace)) 1477 wo->notask_error = 0; 1478 return 0; 1479 } 1480 1481 if (likely(!ptrace) && unlikely(p->ptrace)) { 1482 /* 1483 * If it is traced by its real parent's group, just pretend 1484 * the caller is ptrace_do_wait() and reap this child if it 1485 * is zombie. 1486 * 1487 * This also hides group stop state from real parent; otherwise 1488 * a single stop can be reported twice as group and ptrace stop. 1489 * If a ptracer wants to distinguish these two events for its 1490 * own children it should create a separate process which takes 1491 * the role of real parent. 1492 */ 1493 if (!ptrace_reparented(p)) 1494 ptrace = 1; 1495 } 1496 1497 /* slay zombie? */ 1498 if (exit_state == EXIT_ZOMBIE) { 1499 /* we don't reap group leaders with subthreads */ 1500 if (!delay_group_leader(p)) { 1501 /* 1502 * A zombie ptracee is only visible to its ptracer. 1503 * Notification and reaping will be cascaded to the 1504 * real parent when the ptracer detaches. 1505 */ 1506 if (unlikely(ptrace) || likely(!p->ptrace)) 1507 return wait_task_zombie(wo, p); 1508 } 1509 1510 /* 1511 * Allow access to stopped/continued state via zombie by 1512 * falling through. Clearing of notask_error is complex. 1513 * 1514 * When !@ptrace: 1515 * 1516 * If WEXITED is set, notask_error should naturally be 1517 * cleared. If not, subset of WSTOPPED|WCONTINUED is set, 1518 * so, if there are live subthreads, there are events to 1519 * wait for. If all subthreads are dead, it's still safe 1520 * to clear - this function will be called again in finite 1521 * amount time once all the subthreads are released and 1522 * will then return without clearing. 1523 * 1524 * When @ptrace: 1525 * 1526 * Stopped state is per-task and thus can't change once the 1527 * target task dies. Only continued and exited can happen. 1528 * Clear notask_error if WCONTINUED | WEXITED. 1529 */ 1530 if (likely(!ptrace) || (wo->wo_flags & (WCONTINUED | WEXITED))) 1531 wo->notask_error = 0; 1532 } else { 1533 /* 1534 * @p is alive and it's gonna stop, continue or exit, so 1535 * there always is something to wait for. 1536 */ 1537 wo->notask_error = 0; 1538 } 1539 1540 /* 1541 * Wait for stopped. Depending on @ptrace, different stopped state 1542 * is used and the two don't interact with each other. 1543 */ 1544 ret = wait_task_stopped(wo, ptrace, p); 1545 if (ret) 1546 return ret; 1547 1548 /* 1549 * Wait for continued. There's only one continued state and the 1550 * ptracer can consume it which can confuse the real parent. Don't 1551 * use WCONTINUED from ptracer. You don't need or want it. 1552 */ 1553 return wait_task_continued(wo, p); 1554} 1555 1556/* 1557 * Do the work of do_wait() for one thread in the group, @tsk. 1558 * 1559 * -ECHILD should be in ->notask_error before the first call. 1560 * Returns nonzero for a final return, when we have unlocked tasklist_lock. 1561 * Returns zero if the search for a child should continue; then 1562 * ->notask_error is 0 if there were any eligible children, 1563 * or still -ECHILD. 1564 */ 1565static int do_wait_thread(struct wait_opts *wo, struct task_struct *tsk) 1566{ 1567 struct task_struct *p; 1568 1569 list_for_each_entry(p, &tsk->children, sibling) { 1570 int ret = wait_consider_task(wo, 0, p); 1571 1572 if (ret) 1573 return ret; 1574 } 1575 1576 return 0; 1577} 1578 1579static int ptrace_do_wait(struct wait_opts *wo, struct task_struct *tsk) 1580{ 1581 struct task_struct *p; 1582 1583 list_for_each_entry(p, &tsk->ptraced, ptrace_entry) { 1584 int ret = wait_consider_task(wo, 1, p); 1585 1586 if (ret) 1587 return ret; 1588 } 1589 1590 return 0; 1591} 1592 1593bool pid_child_should_wake(struct wait_opts *wo, struct task_struct *p) 1594{ 1595 if (!eligible_pid(wo, p)) 1596 return false; 1597 1598 if ((wo->wo_flags & __WNOTHREAD) && wo->child_wait.private != p->parent) 1599 return false; 1600 1601 return true; 1602} 1603 1604static int child_wait_callback(wait_queue_entry_t *wait, unsigned mode, 1605 int sync, void *key) 1606{ 1607 struct wait_opts *wo = container_of(wait, struct wait_opts, 1608 child_wait); 1609 struct task_struct *p = key; 1610 1611 if (pid_child_should_wake(wo, p)) 1612 return default_wake_function(wait, mode, sync, key); 1613 1614 return 0; 1615} 1616 1617void __wake_up_parent(struct task_struct *p, struct task_struct *parent) 1618{ 1619 __wake_up_sync_key(&parent->signal->wait_chldexit, 1620 TASK_INTERRUPTIBLE, p); 1621} 1622 1623static bool is_effectively_child(struct wait_opts *wo, bool ptrace, 1624 struct task_struct *target) 1625{ 1626 struct task_struct *parent = 1627 !ptrace ? target->real_parent : target->parent; 1628 1629 return current == parent || (!(wo->wo_flags & __WNOTHREAD) && 1630 same_thread_group(current, parent)); 1631} 1632 1633/* 1634 * Optimization for waiting on PIDTYPE_PID. No need to iterate through child 1635 * and tracee lists to find the target task. 1636 */ 1637static int do_wait_pid(struct wait_opts *wo) 1638{ 1639 bool ptrace; 1640 struct task_struct *target; 1641 int retval; 1642 1643 ptrace = false; 1644 target = pid_task(wo->wo_pid, PIDTYPE_TGID); 1645 if (target && is_effectively_child(wo, ptrace, target)) { 1646 retval = wait_consider_task(wo, ptrace, target); 1647 if (retval) 1648 return retval; 1649 } 1650 1651 ptrace = true; 1652 target = pid_task(wo->wo_pid, PIDTYPE_PID); 1653 if (target && target->ptrace && 1654 is_effectively_child(wo, ptrace, target)) { 1655 retval = wait_consider_task(wo, ptrace, target); 1656 if (retval) 1657 return retval; 1658 } 1659 1660 return 0; 1661} 1662 1663long __do_wait(struct wait_opts *wo) 1664{ 1665 long retval; 1666 1667 /* 1668 * If there is nothing that can match our criteria, just get out. 1669 * We will clear ->notask_error to zero if we see any child that 1670 * might later match our criteria, even if we are not able to reap 1671 * it yet. 1672 */ 1673 wo->notask_error = -ECHILD; 1674 if ((wo->wo_type < PIDTYPE_MAX) && 1675 (!wo->wo_pid || !pid_has_task(wo->wo_pid, wo->wo_type))) 1676 goto notask; 1677 1678 read_lock(&tasklist_lock); 1679 1680 if (wo->wo_type == PIDTYPE_PID) { 1681 retval = do_wait_pid(wo); 1682 if (retval) 1683 return retval; 1684 } else { 1685 struct task_struct *tsk = current; 1686 1687 do { 1688 retval = do_wait_thread(wo, tsk); 1689 if (retval) 1690 return retval; 1691 1692 retval = ptrace_do_wait(wo, tsk); 1693 if (retval) 1694 return retval; 1695 1696 if (wo->wo_flags & __WNOTHREAD) 1697 break; 1698 } while_each_thread(current, tsk); 1699 } 1700 read_unlock(&tasklist_lock); 1701 1702notask: 1703 retval = wo->notask_error; 1704 if (!retval && !(wo->wo_flags & WNOHANG)) 1705 return -ERESTARTSYS; 1706 1707 return retval; 1708} 1709 1710static long do_wait(struct wait_opts *wo) 1711{ 1712 int retval; 1713 1714 trace_sched_process_wait(wo->wo_pid); 1715 1716 init_waitqueue_func_entry(&wo->child_wait, child_wait_callback); 1717 wo->child_wait.private = current; 1718 add_wait_queue(¤t->signal->wait_chldexit, &wo->child_wait); 1719 1720 do { 1721 set_current_state(TASK_INTERRUPTIBLE); 1722 retval = __do_wait(wo); 1723 if (retval != -ERESTARTSYS) 1724 break; 1725 if (signal_pending(current)) 1726 break; 1727 schedule(); 1728 } while (1); 1729 1730 __set_current_state(TASK_RUNNING); 1731 remove_wait_queue(¤t->signal->wait_chldexit, &wo->child_wait); 1732 return retval; 1733} 1734 1735int kernel_waitid_prepare(struct wait_opts *wo, int which, pid_t upid, 1736 struct waitid_info *infop, int options, 1737 struct rusage *ru) 1738{ 1739 unsigned int f_flags = 0; 1740 struct pid *pid = NULL; 1741 enum pid_type type; 1742 1743 if (options & ~(WNOHANG|WNOWAIT|WEXITED|WSTOPPED|WCONTINUED| 1744 __WNOTHREAD|__WCLONE|__WALL)) 1745 return -EINVAL; 1746 if (!(options & (WEXITED|WSTOPPED|WCONTINUED))) 1747 return -EINVAL; 1748 1749 switch (which) { 1750 case P_ALL: 1751 type = PIDTYPE_MAX; 1752 break; 1753 case P_PID: 1754 type = PIDTYPE_PID; 1755 if (upid <= 0) 1756 return -EINVAL; 1757 1758 pid = find_get_pid(upid); 1759 break; 1760 case P_PGID: 1761 type = PIDTYPE_PGID; 1762 if (upid < 0) 1763 return -EINVAL; 1764 1765 if (upid) 1766 pid = find_get_pid(upid); 1767 else 1768 pid = get_task_pid(current, PIDTYPE_PGID); 1769 break; 1770 case P_PIDFD: 1771 type = PIDTYPE_PID; 1772 if (upid < 0) 1773 return -EINVAL; 1774 1775 pid = pidfd_get_pid(upid, &f_flags); 1776 if (IS_ERR(pid)) 1777 return PTR_ERR(pid); 1778 1779 break; 1780 default: 1781 return -EINVAL; 1782 } 1783 1784 wo->wo_type = type; 1785 wo->wo_pid = pid; 1786 wo->wo_flags = options; 1787 wo->wo_info = infop; 1788 wo->wo_rusage = ru; 1789 if (f_flags & O_NONBLOCK) 1790 wo->wo_flags |= WNOHANG; 1791 1792 return 0; 1793} 1794 1795static long kernel_waitid(int which, pid_t upid, struct waitid_info *infop, 1796 int options, struct rusage *ru) 1797{ 1798 struct wait_opts wo; 1799 long ret; 1800 1801 ret = kernel_waitid_prepare(&wo, which, upid, infop, options, ru); 1802 if (ret) 1803 return ret; 1804 1805 ret = do_wait(&wo); 1806 if (!ret && !(options & WNOHANG) && (wo.wo_flags & WNOHANG)) 1807 ret = -EAGAIN; 1808 1809 put_pid(wo.wo_pid); 1810 return ret; 1811} 1812 1813SYSCALL_DEFINE5(waitid, int, which, pid_t, upid, struct siginfo __user *, 1814 infop, int, options, struct rusage __user *, ru) 1815{ 1816 struct rusage r; 1817 struct waitid_info info = {.status = 0}; 1818 long err = kernel_waitid(which, upid, &info, options, ru ? &r : NULL); 1819 int signo = 0; 1820 1821 if (err > 0) { 1822 signo = SIGCHLD; 1823 err = 0; 1824 if (ru && copy_to_user(ru, &r, sizeof(struct rusage))) 1825 return -EFAULT; 1826 } 1827 if (!infop) 1828 return err; 1829 1830 if (!user_write_access_begin(infop, sizeof(*infop))) 1831 return -EFAULT; 1832 1833 unsafe_put_user(signo, &infop->si_signo, Efault); 1834 unsafe_put_user(0, &infop->si_errno, Efault); 1835 unsafe_put_user(info.cause, &infop->si_code, Efault); 1836 unsafe_put_user(info.pid, &infop->si_pid, Efault); 1837 unsafe_put_user(info.uid, &infop->si_uid, Efault); 1838 unsafe_put_user(info.status, &infop->si_status, Efault); 1839 user_write_access_end(); 1840 return err; 1841Efault: 1842 user_write_access_end(); 1843 return -EFAULT; 1844} 1845 1846long kernel_wait4(pid_t upid, int __user *stat_addr, int options, 1847 struct rusage *ru) 1848{ 1849 struct wait_opts wo; 1850 struct pid *pid = NULL; 1851 enum pid_type type; 1852 long ret; 1853 1854 if (options & ~(WNOHANG|WUNTRACED|WCONTINUED| 1855 __WNOTHREAD|__WCLONE|__WALL)) 1856 return -EINVAL; 1857 1858 /* -INT_MIN is not defined */ 1859 if (upid == INT_MIN) 1860 return -ESRCH; 1861 1862 if (upid == -1) 1863 type = PIDTYPE_MAX; 1864 else if (upid < 0) { 1865 type = PIDTYPE_PGID; 1866 pid = find_get_pid(-upid); 1867 } else if (upid == 0) { 1868 type = PIDTYPE_PGID; 1869 pid = get_task_pid(current, PIDTYPE_PGID); 1870 } else /* upid > 0 */ { 1871 type = PIDTYPE_PID; 1872 pid = find_get_pid(upid); 1873 } 1874 1875 wo.wo_type = type; 1876 wo.wo_pid = pid; 1877 wo.wo_flags = options | WEXITED; 1878 wo.wo_info = NULL; 1879 wo.wo_stat = 0; 1880 wo.wo_rusage = ru; 1881 ret = do_wait(&wo); 1882 put_pid(pid); 1883 if (ret > 0 && stat_addr && put_user(wo.wo_stat, stat_addr)) 1884 ret = -EFAULT; 1885 1886 return ret; 1887} 1888 1889int kernel_wait(pid_t pid, int *stat) 1890{ 1891 struct wait_opts wo = { 1892 .wo_type = PIDTYPE_PID, 1893 .wo_pid = find_get_pid(pid), 1894 .wo_flags = WEXITED, 1895 }; 1896 int ret; 1897 1898 ret = do_wait(&wo); 1899 if (ret > 0 && wo.wo_stat) 1900 *stat = wo.wo_stat; 1901 put_pid(wo.wo_pid); 1902 return ret; 1903} 1904 1905SYSCALL_DEFINE4(wait4, pid_t, upid, int __user *, stat_addr, 1906 int, options, struct rusage __user *, ru) 1907{ 1908 struct rusage r; 1909 long err = kernel_wait4(upid, stat_addr, options, ru ? &r : NULL); 1910 1911 if (err > 0) { 1912 if (ru && copy_to_user(ru, &r, sizeof(struct rusage))) 1913 return -EFAULT; 1914 } 1915 return err; 1916} 1917 1918#ifdef __ARCH_WANT_SYS_WAITPID 1919 1920/* 1921 * sys_waitpid() remains for compatibility. waitpid() should be 1922 * implemented by calling sys_wait4() from libc.a. 1923 */ 1924SYSCALL_DEFINE3(waitpid, pid_t, pid, int __user *, stat_addr, int, options) 1925{ 1926 return kernel_wait4(pid, stat_addr, options, NULL); 1927} 1928 1929#endif 1930 1931#ifdef CONFIG_COMPAT 1932COMPAT_SYSCALL_DEFINE4(wait4, 1933 compat_pid_t, pid, 1934 compat_uint_t __user *, stat_addr, 1935 int, options, 1936 struct compat_rusage __user *, ru) 1937{ 1938 struct rusage r; 1939 long err = kernel_wait4(pid, stat_addr, options, ru ? &r : NULL); 1940 if (err > 0) { 1941 if (ru && put_compat_rusage(&r, ru)) 1942 return -EFAULT; 1943 } 1944 return err; 1945} 1946 1947COMPAT_SYSCALL_DEFINE5(waitid, 1948 int, which, compat_pid_t, pid, 1949 struct compat_siginfo __user *, infop, int, options, 1950 struct compat_rusage __user *, uru) 1951{ 1952 struct rusage ru; 1953 struct waitid_info info = {.status = 0}; 1954 long err = kernel_waitid(which, pid, &info, options, uru ? &ru : NULL); 1955 int signo = 0; 1956 if (err > 0) { 1957 signo = SIGCHLD; 1958 err = 0; 1959 if (uru) { 1960 /* kernel_waitid() overwrites everything in ru */ 1961 if (COMPAT_USE_64BIT_TIME) 1962 err = copy_to_user(uru, &ru, sizeof(ru)); 1963 else 1964 err = put_compat_rusage(&ru, uru); 1965 if (err) 1966 return -EFAULT; 1967 } 1968 } 1969 1970 if (!infop) 1971 return err; 1972 1973 if (!user_write_access_begin(infop, sizeof(*infop))) 1974 return -EFAULT; 1975 1976 unsafe_put_user(signo, &infop->si_signo, Efault); 1977 unsafe_put_user(0, &infop->si_errno, Efault); 1978 unsafe_put_user(info.cause, &infop->si_code, Efault); 1979 unsafe_put_user(info.pid, &infop->si_pid, Efault); 1980 unsafe_put_user(info.uid, &infop->si_uid, Efault); 1981 unsafe_put_user(info.status, &infop->si_status, Efault); 1982 user_write_access_end(); 1983 return err; 1984Efault: 1985 user_write_access_end(); 1986 return -EFAULT; 1987} 1988#endif 1989 1990/* 1991 * This needs to be __function_aligned as GCC implicitly makes any 1992 * implementation of abort() cold and drops alignment specified by 1993 * -falign-functions=N. 1994 * 1995 * See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88345#c11 1996 */ 1997__weak __function_aligned void abort(void) 1998{ 1999 BUG(); 2000 2001 /* if that doesn't kill us, halt */ 2002 panic("Oops failed to kill thread"); 2003} 2004EXPORT_SYMBOL(abort);
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