개념 설명 전체 · v6.18.37 / 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 */ 87 static unsigned int oops_limit = 10000; 88 89 #ifdef CONFIG_SYSCTL 90 static 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 }; 99 100 static __init int kernel_exit_sysctls_init(void) 101 { 102 register_sysctl_init("kernel", kern_exit_table); 103 return 0; 104 } 105 late_initcall(kernel_exit_sysctls_init); 106 #endif 107 108 static atomic_t oops_count = ATOMIC_INIT(0); 109 110 #ifdef CONFIG_SYSFS 111 static 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 } 116 117 static struct kobj_attribute oops_count_attr = __ATTR_RO(oops_count); 118 119 static __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 } 124 late_initcall(kernel_exit_sysfs_init); 125 #endif 126 127 /* 128 * For things release_task() would like to do *after* tasklist_lock is released. 129 */ 130 struct release_task_post { 131 struct pid *pids[PIDTYPE_MAX]; 132 }; 133 134 static 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 */ 159 static 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 } 222 223 static 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 } 233 234 void 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 } 239 240 void __weak release_thread(struct task_struct *dead_task) 241 { 242 } 243 244 void 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; 250 repeat: 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. But shut RCU-lockdep up */ 255 rcu_read_lock(); 256 dec_rlimit_ucounts(task_ucounts(p), UCOUNT_RLIMIT_NPROC, 1); 257 rcu_read_unlock(); 258 259 pidfs_exit(p); 260 cgroup_release(p); 261 262 /* Retrieve @thread_pid before __unhash_process() may set it to NULL. */ 263 thread_pid = task_pid(p); 264 265 write_lock_irq(&tasklist_lock); 266 ptrace_release_task(p); 267 __exit_signal(&post, p); 268 269 /* 270 * If we are the last non-leader member of the thread 271 * group, and the leader is zombie, then notify the 272 * group leader's parent process. (if it wants notification.) 273 */ 274 zap_leader = 0; 275 leader = p->group_leader; 276 if (leader != p && thread_group_empty(leader) 277 && leader->exit_state == EXIT_ZOMBIE) { 278 /* for pidfs_exit() and do_notify_parent() */ 279 if (leader->signal->flags & SIGNAL_GROUP_EXIT) 280 leader->exit_code = leader->signal->group_exit_code; 281 /* 282 * If we were the last child thread and the leader has 283 * exited already, and the leader's parent ignores SIGCHLD, 284 * then we are the one who should release the leader. 285 */ 286 zap_leader = do_notify_parent(leader, leader->exit_signal); 287 if (zap_leader) 288 leader->exit_state = EXIT_DEAD; 289 } 290 291 write_unlock_irq(&tasklist_lock); 292 /* @thread_pid can't go away until free_pids() below */ 293 proc_flush_pid(thread_pid); 294 add_device_randomness(&p->se.sum_exec_runtime, 295 sizeof(p->se.sum_exec_runtime)); 296 free_pids(post.pids); 297 release_thread(p); 298 /* 299 * This task was already removed from the process/thread/pid lists 300 * and lock_task_sighand(p) can't succeed. Nobody else can touch 301 * ->pending or, if group dead, signal->shared_pending. We can call 302 * flush_sigqueue() lockless. 303 */ 304 flush_sigqueue(&p->pending); 305 if (thread_group_leader(p)) 306 flush_sigqueue(&p->signal->shared_pending); 307 308 put_task_struct_rcu_user(p); 309 310 p = leader; 311 if (unlikely(zap_leader)) 312 goto repeat; 313 } 314 315 int rcuwait_wake_up(struct rcuwait *w) 316 { 317 int ret = 0; 318 struct task_struct *task; 319 320 rcu_read_lock(); 321 322 /* 323 * Order condition vs @task, such that everything prior to the load 324 * of @task is visible. This is the condition as to why the user called 325 * rcuwait_wake() in the first place. Pairs with set_current_state() 326 * barrier (A) in rcuwait_wait_event(). 327 * 328 * WAIT WAKE 329 * [S] tsk = current [S] cond = true 330 * MB (A) MB (B) 331 * [L] cond [L] tsk 332 */ 333 smp_mb(); /* (B) */ 334 335 task = rcu_dereference(w->task); 336 if (task) 337 ret = wake_up_process(task); 338 rcu_read_unlock(); 339 340 return ret; 341 } 342 EXPORT_SYMBOL_GPL(rcuwait_wake_up); 343 344 /* 345 * Determine if a process group is "orphaned", according to the POSIX 346 * definition in 2.2.2.52. Orphaned process groups are not to be affected 347 * by terminal-generated stop signals. Newly orphaned process groups are 348 * to receive a SIGHUP and a SIGCONT. 349 * 350 * "I ask you, have you ever known what it is to be an orphan?" 351 */ 352 static int will_become_orphaned_pgrp(struct pid *pgrp, 353 struct task_struct *ignored_task) 354 { 355 struct task_struct *p; 356 357 do_each_pid_task(pgrp, PIDTYPE_PGID, p) { 358 if ((p == ignored_task) || 359 (p->exit_state && thread_group_empty(p)) || 360 is_global_init(p->real_parent)) 361 continue; 362 363 if (task_pgrp(p->real_parent) != pgrp && 364 task_session(p->real_parent) == task_session(p)) 365 return 0; 366 } while_each_pid_task(pgrp, PIDTYPE_PGID, p); 367 368 return 1; 369 } 370 371 int is_current_pgrp_orphaned(void) 372 { 373 int retval; 374 375 read_lock(&tasklist_lock); 376 retval = will_become_orphaned_pgrp(task_pgrp(current), NULL); 377 read_unlock(&tasklist_lock); 378 379 return retval; 380 } 381 382 static bool has_stopped_jobs(struct pid *pgrp) 383 { 384 struct task_struct *p; 385 386 do_each_pid_task(pgrp, PIDTYPE_PGID, p) { 387 if (p->signal->flags & SIGNAL_STOP_STOPPED) 388 return true; 389 } while_each_pid_task(pgrp, PIDTYPE_PGID, p); 390 391 return false; 392 } 393 394 /* 395 * Check to see if any process groups have become orphaned as 396 * a result of our exiting, and if they have any stopped jobs, 397 * send them a SIGHUP and then a SIGCONT. (POSIX 3.2.2.2) 398 */ 399 static void 400 kill_orphaned_pgrp(struct task_struct *tsk, struct task_struct *parent) 401 { 402 struct pid *pgrp = task_pgrp(tsk); 403 struct task_struct *ignored_task = tsk; 404 405 if (!parent) 406 /* exit: our father is in a different pgrp than 407 * we are and we were the only connection outside. 408 */ 409 parent = tsk->real_parent; 410 else 411 /* reparent: our child is in a different pgrp than 412 * we are, and it was the only connection outside. 413 */ 414 ignored_task = NULL; 415 416 if (task_pgrp(parent) != pgrp && 417 task_session(parent) == task_session(tsk) && 418 will_become_orphaned_pgrp(pgrp, ignored_task) && 419 has_stopped_jobs(pgrp)) { 420 __kill_pgrp_info(SIGHUP, SEND_SIG_PRIV, pgrp); 421 __kill_pgrp_info(SIGCONT, SEND_SIG_PRIV, pgrp); 422 } 423 } 424 425 static void coredump_task_exit(struct task_struct *tsk, 426 struct core_state *core_state) 427 { 428 struct core_thread self; 429 430 self.task = tsk; 431 if (self.task->flags & PF_SIGNALED) 432 self.next = xchg(&core_state->dumper.next, &self); 433 else 434 self.task = NULL; 435 /* 436 * Implies mb(), the result of xchg() must be visible 437 * to core_state->dumper. 438 */ 439 if (atomic_dec_and_test(&core_state->nr_threads)) 440 complete(&core_state->startup); 441 442 for (;;) { 443 set_current_state(TASK_IDLE|TASK_FREEZABLE); 444 if (!self.task) /* see coredump_finish() */ 445 break; 446 schedule(); 447 } 448 __set_current_state(TASK_RUNNING); 449 } 450 451 #ifdef CONFIG_MEMCG 452 /* drops tasklist_lock if succeeds */ 453 static bool __try_to_set_owner(struct task_struct *tsk, struct mm_struct *mm) 454 { 455 bool ret = false; 456 457 task_lock(tsk); 458 if (likely(tsk->mm == mm)) { 459 /* tsk can't pass exit_mm/exec_mmap and exit */ 460 read_unlock(&tasklist_lock); 461 WRITE_ONCE(mm->owner, tsk); 462 lru_gen_migrate_mm(mm); 463 ret = true; 464 } 465 task_unlock(tsk); 466 return ret; 467 } 468 469 static bool try_to_set_owner(struct task_struct *g, struct mm_struct *mm) 470 { 471 struct task_struct *t; 472 473 for_each_thread(g, t) { 474 struct mm_struct *t_mm = READ_ONCE(t->mm); 475 if (t_mm == mm) { 476 if (__try_to_set_owner(t, mm)) 477 return true; 478 } else if (t_mm) 479 break; 480 } 481 482 return false; 483 } 484 485 /* 486 * A task is exiting. If it owned this mm, find a new owner for the mm. 487 */ 488 void mm_update_next_owner(struct mm_struct *mm) 489 { 490 struct task_struct *g, *p = current; 491 492 /* 493 * If the exiting or execing task is not the owner, it's 494 * someone else's problem. 495 */ 496 if (mm->owner != p) 497 return; 498 /* 499 * The current owner is exiting/execing and there are no other 500 * candidates. Do not leave the mm pointing to a possibly 501 * freed task structure. 502 */ 503 if (atomic_read(&mm->mm_users) <= 1) { 504 WRITE_ONCE(mm->owner, NULL); 505 return; 506 } 507 508 read_lock(&tasklist_lock); 509 /* 510 * Search in the children 511 */ 512 list_for_each_entry(g, &p->children, sibling) { 513 if (try_to_set_owner(g, mm)) 514 goto ret; 515 } 516 /* 517 * Search in the siblings 518 */ 519 list_for_each_entry(g, &p->real_parent->children, sibling) { 520 if (try_to_set_owner(g, mm)) 521 goto ret; 522 } 523 /* 524 * Search through everything else, we should not get here often. 525 */ 526 for_each_process(g) { 527 if (atomic_read(&mm->mm_users) <= 1) 528 break; 529 if (g->flags & PF_KTHREAD) 530 continue; 531 if (try_to_set_owner(g, mm)) 532 goto ret; 533 } 534 read_unlock(&tasklist_lock); 535 /* 536 * We found no owner yet mm_users > 1: this implies that we are 537 * most likely racing with swapoff (try_to_unuse()) or /proc or 538 * ptrace or page migration (get_task_mm()). Mark owner as NULL. 539 */ 540 WRITE_ONCE(mm->owner, NULL); 541 ret: 542 return; 543 544 } 545 #endif /* CONFIG_MEMCG */ 546 547 /* 548 * Turn us into a lazy TLB process if we 549 * aren't already.. 550 */ 551 static void exit_mm(void) 552 { 553 struct mm_struct *mm = current->mm; 554 555 exit_mm_release(current, mm); 556 if (!mm) 557 return; 558 mmap_read_lock(mm); 559 mmgrab_lazy_tlb(mm); 560 BUG_ON(mm != current->active_mm); 561 /* more a memory barrier than a real lock */ 562 task_lock(current); 563 /* 564 * When a thread stops operating on an address space, the loop 565 * in membarrier_private_expedited() may not observe that 566 * tsk->mm, and the loop in membarrier_global_expedited() may 567 * not observe a MEMBARRIER_STATE_GLOBAL_EXPEDITED 568 * rq->membarrier_state, so those would not issue an IPI. 569 * Membarrier requires a memory barrier after accessing 570 * user-space memory, before clearing tsk->mm or the 571 * rq->membarrier_state. 572 */ 573 smp_mb__after_spinlock(); 574 local_irq_disable(); 575 current->user_dumpable = (get_dumpable(mm) == SUID_DUMP_USER); 576 current->mm = NULL; 577 membarrier_update_current_mm(NULL); 578 enter_lazy_tlb(mm, current); 579 local_irq_enable(); 580 task_unlock(current); 581 mmap_read_unlock(mm); 582 mm_update_next_owner(mm); 583 mmput(mm); 584 if (test_thread_flag(TIF_MEMDIE)) 585 exit_oom_victim(); 586 } 587 588 static struct task_struct *find_alive_thread(struct task_struct *p) 589 { 590 struct task_struct *t; 591 592 for_each_thread(p, t) { 593 if (!(t->flags & PF_EXITING)) 594 return t; 595 } 596 return NULL; 597 } 598 599 static struct task_struct *find_child_reaper(struct task_struct *father, 600 struct list_head *dead) 601 __releases(&tasklist_lock) 602 __acquires(&tasklist_lock) 603 { 604 struct pid_namespace *pid_ns = task_active_pid_ns(father); 605 struct task_struct *reaper = pid_ns->child_reaper; 606 struct task_struct *p, *n; 607 608 if (likely(reaper != father)) 609 return reaper; 610 611 reaper = find_alive_thread(father); 612 if (reaper) { 613 pid_ns->child_reaper = reaper; 614 return reaper; 615 } 616 617 write_unlock_irq(&tasklist_lock); 618 619 list_for_each_entry_safe(p, n, dead, ptrace_entry) { 620 list_del_init(&p->ptrace_entry); 621 release_task(p); 622 } 623 624 zap_pid_ns_processes(pid_ns); 625 write_lock_irq(&tasklist_lock); 626 627 return father; 628 } 629 630 /* 631 * When we die, we re-parent all our children, and try to: 632 * 1. give them to another thread in our thread group, if such a member exists 633 * 2. give it to the first ancestor process which prctl'd itself as a 634 * child_subreaper for its children (like a service manager) 635 * 3. give it to the init process (PID 1) in our pid namespace 636 */ 637 static struct task_struct *find_new_reaper(struct task_struct *father, 638 struct task_struct *child_reaper) 639 { 640 struct task_struct *thread, *reaper; 641 642 thread = find_alive_thread(father); 643 if (thread) 644 return thread; 645 646 if (father->signal->has_child_subreaper) { 647 unsigned int ns_level = task_pid(father)->level; 648 /* 649 * Find the first ->is_child_subreaper ancestor in our pid_ns. 650 * We can't check reaper != child_reaper to ensure we do not 651 * cross the namespaces, the exiting parent could be injected 652 * by setns() + fork(). 653 * We check pid->level, this is slightly more efficient than 654 * task_active_pid_ns(reaper) != task_active_pid_ns(father). 655 */ 656 for (reaper = father->real_parent; 657 task_pid(reaper)->level == ns_level; 658 reaper = reaper->real_parent) { 659 if (reaper == &init_task) 660 break; 661 if (!reaper->signal->is_child_subreaper) 662 continue; 663 thread = find_alive_thread(reaper); 664 if (thread) 665 return thread; 666 } 667 } 668 669 return child_reaper; 670 } 671 672 /* 673 * Any that need to be release_task'd are put on the @dead list. 674 */ 675 static void reparent_leader(struct task_struct *father, struct task_struct *p, 676 struct list_head *dead) 677 { 678 if (unlikely(p->exit_state == EXIT_DEAD)) 679 return; 680 681 /* We don't want people slaying init. */ 682 p->exit_signal = SIGCHLD; 683 684 /* If it has exited notify the new parent about this child's death. */ 685 if (!p->ptrace && 686 p->exit_state == EXIT_ZOMBIE && thread_group_empty(p)) { 687 if (do_notify_parent(p, p->exit_signal)) { 688 p->exit_state = EXIT_DEAD; 689 list_add(&p->ptrace_entry, dead); 690 } 691 } 692 693 kill_orphaned_pgrp(p, father); 694 } 695 696 /* 697 * Make init inherit all the child processes 698 */ 699 static void forget_original_parent(struct task_struct *father, 700 struct list_head *dead) 701 { 702 struct task_struct *p, *t, *reaper; 703 704 if (unlikely(!list_empty(&father->ptraced))) 705 exit_ptrace(father, dead); 706 707 /* Can drop and reacquire tasklist_lock */ 708 reaper = find_child_reaper(father, dead); 709 if (list_empty(&father->children)) 710 return; 711 712 reaper = find_new_reaper(father, reaper); 713 list_for_each_entry(p, &father->children, sibling) { 714 for_each_thread(p, t) { 715 RCU_INIT_POINTER(t->real_parent, reaper); 716 BUG_ON((!t->ptrace) != (rcu_access_pointer(t->parent) == father)); 717 if (likely(!t->ptrace)) 718 t->parent = t->real_parent; 719 if (t->pdeath_signal) 720 group_send_sig_info(t->pdeath_signal, 721 SEND_SIG_NOINFO, t, 722 PIDTYPE_TGID); 723 } 724 /* 725 * If this is a threaded reparent there is no need to 726 * notify anyone anything has happened. 727 */ 728 if (!same_thread_group(reaper, father)) 729 reparent_leader(father, p, dead); 730 } 731 list_splice_tail_init(&father->children, &reaper->children); 732 } 733 734 /* 735 * Send signals to all our closest relatives so that they know 736 * to properly mourn us.. 737 */ 738 static void exit_notify(struct task_struct *tsk, int group_dead) 739 { 740 bool autoreap; 741 struct task_struct *p, *n; 742 LIST_HEAD(dead); 743 744 write_lock_irq(&tasklist_lock); 745 forget_original_parent(tsk, &dead); 746 747 if (group_dead) 748 kill_orphaned_pgrp(tsk->group_leader, NULL); 749 750 tsk->exit_state = EXIT_ZOMBIE; 751 752 if (unlikely(tsk->ptrace)) { 753 int sig = thread_group_leader(tsk) && 754 thread_group_empty(tsk) && 755 !ptrace_reparented(tsk) ? 756 tsk->exit_signal : SIGCHLD; 757 autoreap = do_notify_parent(tsk, sig); 758 } else if (thread_group_leader(tsk)) { 759 autoreap = thread_group_empty(tsk) && 760 do_notify_parent(tsk, tsk->exit_signal); 761 } else { 762 autoreap = true; 763 /* untraced sub-thread */ 764 do_notify_pidfd(tsk); 765 } 766 767 if (autoreap) { 768 tsk->exit_state = EXIT_DEAD; 769 list_add(&tsk->ptrace_entry, &dead); 770 } 771 772 /* mt-exec, de_thread() is waiting for group leader */ 773 if (unlikely(tsk->signal->notify_count < 0)) 774 wake_up_process(tsk->signal->group_exec_task); 775 write_unlock_irq(&tasklist_lock); 776 777 list_for_each_entry_safe(p, n, &dead, ptrace_entry) { 778 list_del_init(&p->ptrace_entry); 779 release_task(p); 780 } 781 } 782 783 #ifdef CONFIG_DEBUG_STACK_USAGE 784 #ifdef CONFIG_STACK_GROWSUP 785 unsigned long stack_not_used(struct task_struct *p) 786 { 787 unsigned long *n = end_of_stack(p); 788 789 do { /* Skip over canary */ 790 n--; 791 } while (!*n); 792 793 return (unsigned long)end_of_stack(p) - (unsigned long)n; 794 } 795 #else /* !CONFIG_STACK_GROWSUP */ 796 unsigned long stack_not_used(struct task_struct *p) 797 { 798 unsigned long *n = end_of_stack(p); 799 800 do { /* Skip over canary */ 801 n++; 802 } while (!*n); 803 804 return (unsigned long)n - (unsigned long)end_of_stack(p); 805 } 806 #endif /* CONFIG_STACK_GROWSUP */ 807 808 /* Count the maximum pages reached in kernel stacks */ 809 static inline void kstack_histogram(unsigned long used_stack) 810 { 811 #ifdef CONFIG_VM_EVENT_COUNTERS 812 if (used_stack <= 1024) 813 count_vm_event(KSTACK_1K); 814 #if THREAD_SIZE > 1024 815 else if (used_stack <= 2048) 816 count_vm_event(KSTACK_2K); 817 #endif 818 #if THREAD_SIZE > 2048 819 else if (used_stack <= 4096) 820 count_vm_event(KSTACK_4K); 821 #endif 822 #if THREAD_SIZE > 4096 823 else if (used_stack <= 8192) 824 count_vm_event(KSTACK_8K); 825 #endif 826 #if THREAD_SIZE > 8192 827 else if (used_stack <= 16384) 828 count_vm_event(KSTACK_16K); 829 #endif 830 #if THREAD_SIZE > 16384 831 else if (used_stack <= 32768) 832 count_vm_event(KSTACK_32K); 833 #endif 834 #if THREAD_SIZE > 32768 835 else if (used_stack <= 65536) 836 count_vm_event(KSTACK_64K); 837 #endif 838 #if THREAD_SIZE > 65536 839 else 840 count_vm_event(KSTACK_REST); 841 #endif 842 #endif /* CONFIG_VM_EVENT_COUNTERS */ 843 } 844 845 static void check_stack_usage(void) 846 { 847 static DEFINE_SPINLOCK(low_water_lock); 848 static int lowest_to_date = THREAD_SIZE; 849 unsigned long free; 850 851 free = stack_not_used(current); 852 kstack_histogram(THREAD_SIZE - free); 853 854 if (free >= lowest_to_date) 855 return; 856 857 spin_lock(&low_water_lock); 858 if (free < lowest_to_date) { 859 pr_info("%s (%d) used greatest stack depth: %lu bytes left\n", 860 current->comm, task_pid_nr(current), free); 861 lowest_to_date = free; 862 } 863 spin_unlock(&low_water_lock); 864 } 865 #else /* !CONFIG_DEBUG_STACK_USAGE */ 866 static inline void check_stack_usage(void) {} 867 #endif /* CONFIG_DEBUG_STACK_USAGE */ 868 869 static void synchronize_group_exit(struct task_struct *tsk, long code) 870 { 871 struct sighand_struct *sighand = tsk->sighand; 872 struct signal_struct *signal = tsk->signal; 873 struct core_state *core_state; 874 875 spin_lock_irq(&sighand->siglock); 876 signal->quick_threads--; 877 if ((signal->quick_threads == 0) && 878 !(signal->flags & SIGNAL_GROUP_EXIT)) { 879 signal->flags = SIGNAL_GROUP_EXIT; 880 signal->group_exit_code = code; 881 signal->group_stop_count = 0; 882 } 883 /* 884 * Serialize with any possible pending coredump. 885 * We must hold siglock around checking core_state 886 * and setting PF_POSTCOREDUMP. The core-inducing thread 887 * will increment ->nr_threads for each thread in the 888 * group without PF_POSTCOREDUMP set. 889 */ 890 tsk->flags |= PF_POSTCOREDUMP; 891 core_state = signal->core_state; 892 spin_unlock_irq(&sighand->siglock); 893 894 if (unlikely(core_state)) 895 coredump_task_exit(tsk, core_state); 896 } 897 898 void __noreturn do_exit(long code) 899 { 900 struct task_struct *tsk = current; 901 struct kthread *kthread; 902 int group_dead; 903 904 WARN_ON(irqs_disabled()); 905 WARN_ON(tsk->plug); 906 907 kthread = tsk_is_kthread(tsk); 908 if (unlikely(kthread)) 909 kthread_do_exit(kthread, code); 910 911 kcov_task_exit(tsk); 912 kmsan_task_exit(tsk); 913 914 synchronize_group_exit(tsk, code); 915 ptrace_event(PTRACE_EVENT_EXIT, code); 916 user_events_exit(tsk); 917 918 io_uring_files_cancel(); 919 exit_signals(tsk); /* sets PF_EXITING */ 920 921 seccomp_filter_release(tsk); 922 923 acct_update_integrals(tsk); 924 group_dead = atomic_dec_and_test(&tsk->signal->live); 925 if (group_dead) { 926 /* 927 * If the last thread of global init has exited, panic 928 * immediately to get a useable coredump. 929 */ 930 if (unlikely(is_global_init(tsk))) 931 panic("Attempted to kill init! exitcode=0x%08x\n", 932 tsk->signal->group_exit_code ?: (int)code); 933 934 #ifdef CONFIG_POSIX_TIMERS 935 hrtimer_cancel(&tsk->signal->real_timer); 936 exit_itimers(tsk); 937 #endif 938 if (tsk->mm) 939 setmax_mm_hiwater_rss(&tsk->signal->maxrss, tsk->mm); 940 } 941 acct_collect(code, group_dead); 942 if (group_dead) 943 tty_audit_exit(); 944 audit_free(tsk); 945 946 tsk->exit_code = code; 947 taskstats_exit(tsk, group_dead); 948 unwind_deferred_task_exit(tsk); 949 trace_sched_process_exit(tsk, group_dead); 950 951 /* 952 * Since sampling can touch ->mm, make sure to stop everything before we 953 * tear it down. 954 * 955 * Also flushes inherited counters to the parent - before the parent 956 * gets woken up by child-exit notifications. 957 */ 958 perf_event_exit_task(tsk); 959 960 exit_mm(); 961 962 if (group_dead) 963 acct_process(); 964 965 exit_sem(tsk); 966 exit_shm(tsk); 967 exit_files(tsk); 968 exit_fs(tsk); 969 if (group_dead) 970 disassociate_ctty(1); 971 exit_task_namespaces(tsk); 972 exit_task_work(tsk); 973 exit_thread(tsk); 974 975 sched_autogroup_exit_task(tsk); 976 cgroup_exit(tsk); 977 978 /* 979 * FIXME: do that only when needed, using sched_exit tracepoint 980 */ 981 flush_ptrace_hw_breakpoint(tsk); 982 983 exit_tasks_rcu_start(); 984 exit_notify(tsk, group_dead); 985 proc_exit_connector(tsk); 986 mpol_put_task_policy(tsk); 987 #ifdef CONFIG_FUTEX 988 if (unlikely(current->pi_state_cache)) 989 kfree(current->pi_state_cache); 990 #endif 991 /* 992 * Make sure we are holding no locks: 993 */ 994 debug_check_no_locks_held(); 995 996 if (tsk->io_context) 997 exit_io_context(tsk); 998 999 if (tsk->splice_pipe) 1000 free_pipe_info(tsk->splice_pipe); 1001 1002 if (tsk->task_frag.page) 1003 put_page(tsk->task_frag.page); 1004 1005 exit_task_stack_account(tsk); 1006 1007 check_stack_usage(); 1008 preempt_disable(); 1009 if (tsk->nr_dirtied) 1010 __this_cpu_add(dirty_throttle_leaks, tsk->nr_dirtied); 1011 exit_rcu(); 1012 exit_tasks_rcu_finish(); 1013 1014 lockdep_free_task(tsk); 1015 do_task_dead(); 1016 } 1017 EXPORT_SYMBOL(do_exit); 1018 1019 void __noreturn make_task_dead(int signr) 1020 { 1021 /* 1022 * Take the task off the cpu after something catastrophic has 1023 * happened. 1024 * 1025 * We can get here from a kernel oops, sometimes with preemption off. 1026 * Start by checking for critical errors. 1027 * Then fix up important state like USER_DS and preemption. 1028 * Then do everything else. 1029 */ 1030 struct task_struct *tsk = current; 1031 unsigned int limit; 1032 1033 if (unlikely(in_interrupt())) 1034 panic("Aiee, killing interrupt handler!"); 1035 if (unlikely(!tsk->pid)) 1036 panic("Attempted to kill the idle task!"); 1037 1038 if (unlikely(irqs_disabled())) { 1039 pr_info("note: %s[%d] exited with irqs disabled\n", 1040 current->comm, task_pid_nr(current)); 1041 local_irq_enable(); 1042 } 1043 if (unlikely(in_atomic())) { 1044 pr_info("note: %s[%d] exited with preempt_count %d\n", 1045 current->comm, task_pid_nr(current), 1046 preempt_count()); 1047 preempt_count_set(PREEMPT_ENABLED); 1048 } 1049 1050 /* 1051 * Every time the system oopses, if the oops happens while a reference 1052 * to an object was held, the reference leaks. 1053 * If the oops doesn't also leak memory, repeated oopsing can cause 1054 * reference counters to wrap around (if they're not using refcount_t). 1055 * This means that repeated oopsing can make unexploitable-looking bugs 1056 * exploitable through repeated oopsing. 1057 * To make sure this can't happen, place an upper bound on how often the 1058 * kernel may oops without panic(). 1059 */ 1060 limit = READ_ONCE(oops_limit); 1061 if (atomic_inc_return(&oops_count) >= limit && limit) 1062 panic("Oopsed too often (kernel.oops_limit is %d)", limit); 1063 1064 /* 1065 * We're taking recursive faults here in make_task_dead. Safest is to just 1066 * leave this task alone and wait for reboot. 1067 */ 1068 if (unlikely(tsk->flags & PF_EXITING)) { 1069 pr_alert("Fixing recursive fault but reboot is needed!\n"); 1070 futex_exit_recursive(tsk); 1071 tsk->exit_state = EXIT_DEAD; 1072 refcount_inc(&tsk->rcu_users); 1073 preempt_disable(); 1074 do_task_dead(); 1075 } 1076 1077 do_exit(signr); 1078 } 1079 1080 SYSCALL_DEFINE1(exit, int, error_code) 1081 { 1082 do_exit((error_code&0xff)<<8); 1083 } 1084 1085 /* 1086 * Take down every thread in the group. This is called by fatal signals 1087 * as well as by sys_exit_group (below). 1088 */ 1089 void __noreturn 1090 do_group_exit(int exit_code) 1091 { 1092 struct signal_struct *sig = current->signal; 1093 1094 if (sig->flags & SIGNAL_GROUP_EXIT) 1095 exit_code = sig->group_exit_code; 1096 else if (sig->group_exec_task) 1097 exit_code = 0; 1098 else { 1099 struct sighand_struct *const sighand = current->sighand; 1100 1101 spin_lock_irq(&sighand->siglock); 1102 if (sig->flags & SIGNAL_GROUP_EXIT) 1103 /* Another thread got here before we took the lock. */ 1104 exit_code = sig->group_exit_code; 1105 else if (sig->group_exec_task) 1106 exit_code = 0; 1107 else { 1108 sig->group_exit_code = exit_code; 1109 sig->flags = SIGNAL_GROUP_EXIT; 1110 zap_other_threads(current); 1111 } 1112 spin_unlock_irq(&sighand->siglock); 1113 } 1114 1115 do_exit(exit_code); 1116 /* NOTREACHED */ 1117 } 1118 1119 /* 1120 * this kills every thread in the thread group. Note that any externally 1121 * wait4()-ing process will get the correct exit code - even if this 1122 * thread is not the thread group leader. 1123 */ 1124 SYSCALL_DEFINE1(exit_group, int, error_code) 1125 { 1126 do_group_exit((error_code & 0xff) << 8); 1127 /* NOTREACHED */ 1128 return 0; 1129 } 1130 1131 static int eligible_pid(struct wait_opts *wo, struct task_struct *p) 1132 { 1133 return wo->wo_type == PIDTYPE_MAX || 1134 task_pid_type(p, wo->wo_type) == wo->wo_pid; 1135 } 1136 1137 static int 1138 eligible_child(struct wait_opts *wo, bool ptrace, struct task_struct *p) 1139 { 1140 if (!eligible_pid(wo, p)) 1141 return 0; 1142 1143 /* 1144 * Wait for all children (clone and not) if __WALL is set or 1145 * if it is traced by us. 1146 */ 1147 if (ptrace || (wo->wo_flags & __WALL)) 1148 return 1; 1149 1150 /* 1151 * Otherwise, wait for clone children *only* if __WCLONE is set; 1152 * otherwise, wait for non-clone children *only*. 1153 * 1154 * Note: a "clone" child here is one that reports to its parent 1155 * using a signal other than SIGCHLD, or a non-leader thread which 1156 * we can only see if it is traced by us. 1157 */ 1158 if ((p->exit_signal != SIGCHLD) ^ !!(wo->wo_flags & __WCLONE)) 1159 return 0; 1160 1161 return 1; 1162 } 1163 1164 /* 1165 * Handle sys_wait4 work for one task in state EXIT_ZOMBIE. We hold 1166 * read_lock(&tasklist_lock) on entry. If we return zero, we still hold 1167 * the lock and this task is uninteresting. If we return nonzero, we have 1168 * released the lock and the system call should return. 1169 */ 1170 static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p) 1171 { 1172 int state, status; 1173 pid_t pid = task_pid_vnr(p); 1174 uid_t uid = from_kuid_munged(current_user_ns(), task_uid(p)); 1175 struct waitid_info *infop; 1176 1177 if (!likely(wo->wo_flags & WEXITED)) 1178 return 0; 1179 1180 if (unlikely(wo->wo_flags & WNOWAIT)) { 1181 status = (p->signal->flags & SIGNAL_GROUP_EXIT) 1182 ? p->signal->group_exit_code : p->exit_code; 1183 get_task_struct(p); 1184 read_unlock(&tasklist_lock); 1185 sched_annotate_sleep(); 1186 if (wo->wo_rusage) 1187 getrusage(p, RUSAGE_BOTH, wo->wo_rusage); 1188 put_task_struct(p); 1189 goto out_info; 1190 } 1191 /* 1192 * Move the task's state to DEAD/TRACE, only one thread can do this. 1193 */ 1194 state = (ptrace_reparented(p) && thread_group_leader(p)) ? 1195 EXIT_TRACE : EXIT_DEAD; 1196 if (cmpxchg(&p->exit_state, EXIT_ZOMBIE, state) != EXIT_ZOMBIE) 1197 return 0; 1198 /* 1199 * We own this thread, nobody else can reap it. 1200 */ 1201 read_unlock(&tasklist_lock); 1202 sched_annotate_sleep(); 1203 1204 /* 1205 * Check thread_group_leader() to exclude the traced sub-threads. 1206 */ 1207 if (state == EXIT_DEAD && thread_group_leader(p)) { 1208 struct signal_struct *sig = p->signal; 1209 struct signal_struct *psig = current->signal; 1210 unsigned long maxrss; 1211 u64 tgutime, tgstime; 1212 1213 /* 1214 * The resource counters for the group leader are in its 1215 * own task_struct. Those for dead threads in the group 1216 * are in its signal_struct, as are those for the child 1217 * processes it has previously reaped. All these 1218 * accumulate in the parent's signal_struct c* fields. 1219 * 1220 * We don't bother to take a lock here to protect these 1221 * p->signal fields because the whole thread group is dead 1222 * and nobody can change them. 1223 * 1224 * psig->stats_lock also protects us from our sub-threads 1225 * which can reap other children at the same time. 1226 * 1227 * We use thread_group_cputime_adjusted() to get times for 1228 * the thread group, which consolidates times for all threads 1229 * in the group including the group leader. 1230 */ 1231 thread_group_cputime_adjusted(p, &tgutime, &tgstime); 1232 write_seqlock_irq(&psig->stats_lock); 1233 psig->cutime += tgutime + sig->cutime; 1234 psig->cstime += tgstime + sig->cstime; 1235 psig->cgtime += task_gtime(p) + sig->gtime + sig->cgtime; 1236 psig->cmin_flt += 1237 p->min_flt + sig->min_flt + sig->cmin_flt; 1238 psig->cmaj_flt += 1239 p->maj_flt + sig->maj_flt + sig->cmaj_flt; 1240 psig->cnvcsw += 1241 p->nvcsw + sig->nvcsw + sig->cnvcsw; 1242 psig->cnivcsw += 1243 p->nivcsw + sig->nivcsw + sig->cnivcsw; 1244 psig->cinblock += 1245 task_io_get_inblock(p) + 1246 sig->inblock + sig->cinblock; 1247 psig->coublock += 1248 task_io_get_oublock(p) + 1249 sig->oublock + sig->coublock; 1250 maxrss = max(sig->maxrss, sig->cmaxrss); 1251 if (psig->cmaxrss < maxrss) 1252 psig->cmaxrss = maxrss; 1253 task_io_accounting_add(&psig->ioac, &p->ioac); 1254 task_io_accounting_add(&psig->ioac, &sig->ioac); 1255 write_sequnlock_irq(&psig->stats_lock); 1256 } 1257 1258 if (wo->wo_rusage) 1259 getrusage(p, RUSAGE_BOTH, wo->wo_rusage); 1260 status = (p->signal->flags & SIGNAL_GROUP_EXIT) 1261 ? p->signal->group_exit_code : p->exit_code; 1262 wo->wo_stat = status; 1263 1264 if (state == EXIT_TRACE) { 1265 write_lock_irq(&tasklist_lock); 1266 /* We dropped tasklist, ptracer could die and untrace */ 1267 ptrace_unlink(p); 1268 1269 /* If parent wants a zombie, don't release it now */ 1270 state = EXIT_ZOMBIE; 1271 if (do_notify_parent(p, p->exit_signal)) 1272 state = EXIT_DEAD; 1273 p->exit_state = state; 1274 write_unlock_irq(&tasklist_lock); 1275 } 1276 if (state == EXIT_DEAD) 1277 release_task(p); 1278 1279 out_info: 1280 infop = wo->wo_info; 1281 if (infop) { 1282 if ((status & 0x7f) == 0) { 1283 infop->cause = CLD_EXITED; 1284 infop->status = status >> 8; 1285 } else { 1286 infop->cause = (status & 0x80) ? CLD_DUMPED : CLD_KILLED; 1287 infop->status = status & 0x7f; 1288 } 1289 infop->pid = pid; 1290 infop->uid = uid; 1291 } 1292 1293 return pid; 1294 } 1295 1296 static int *task_stopped_code(struct task_struct *p, bool ptrace) 1297 { 1298 if (ptrace) { 1299 if (task_is_traced(p) && !(p->jobctl & JOBCTL_LISTENING)) 1300 return &p->exit_code; 1301 } else { 1302 if (p->signal->flags & SIGNAL_STOP_STOPPED) 1303 return &p->signal->group_exit_code; 1304 } 1305 return NULL; 1306 } 1307 1308 /** 1309 * wait_task_stopped - Wait for %TASK_STOPPED or %TASK_TRACED 1310 * @wo: wait options 1311 * @ptrace: is the wait for ptrace 1312 * @p: task to wait for 1313 * 1314 * Handle sys_wait4() work for %p in state %TASK_STOPPED or %TASK_TRACED. 1315 * 1316 * CONTEXT: 1317 * read_lock(&tasklist_lock), which is released if return value is 1318 * non-zero. Also, grabs and releases @p->sighand->siglock. 1319 * 1320 * RETURNS: 1321 * 0 if wait condition didn't exist and search for other wait conditions 1322 * should continue. Non-zero return, -errno on failure and @p's pid on 1323 * success, implies that tasklist_lock is released and wait condition 1324 * search should terminate. 1325 */ 1326 static int wait_task_stopped(struct wait_opts *wo, 1327 int ptrace, struct task_struct *p) 1328 { 1329 struct waitid_info *infop; 1330 int exit_code, *p_code, why; 1331 uid_t uid = 0; /* unneeded, required by compiler */ 1332 pid_t pid; 1333 1334 /* 1335 * Traditionally we see ptrace'd stopped tasks regardless of options. 1336 */ 1337 if (!ptrace && !(wo->wo_flags & WUNTRACED)) 1338 return 0; 1339 1340 if (!task_stopped_code(p, ptrace)) 1341 return 0; 1342 1343 exit_code = 0; 1344 spin_lock_irq(&p->sighand->siglock); 1345 1346 p_code = task_stopped_code(p, ptrace); 1347 if (unlikely(!p_code)) 1348 goto unlock_sig; 1349 1350 exit_code = *p_code; 1351 if (!exit_code) 1352 goto unlock_sig; 1353 1354 if (!unlikely(wo->wo_flags & WNOWAIT)) 1355 *p_code = 0; 1356 1357 uid = from_kuid_munged(current_user_ns(), task_uid(p)); 1358 unlock_sig: 1359 spin_unlock_irq(&p->sighand->siglock); 1360 if (!exit_code) 1361 return 0; 1362 1363 /* 1364 * Now we are pretty sure this task is interesting. 1365 * Make sure it doesn't get reaped out from under us while we 1366 * give up the lock and then examine it below. We don't want to 1367 * keep holding onto the tasklist_lock while we call getrusage and 1368 * possibly take page faults for user memory. 1369 */ 1370 get_task_struct(p); 1371 pid = task_pid_vnr(p); 1372 why = ptrace ? CLD_TRAPPED : CLD_STOPPED; 1373 read_unlock(&tasklist_lock); 1374 sched_annotate_sleep(); 1375 if (wo->wo_rusage) 1376 getrusage(p, RUSAGE_BOTH, wo->wo_rusage); 1377 put_task_struct(p); 1378 1379 if (likely(!(wo->wo_flags & WNOWAIT))) 1380 wo->wo_stat = (exit_code << 8) | 0x7f; 1381 1382 infop = wo->wo_info; 1383 if (infop) { 1384 infop->cause = why; 1385 infop->status = exit_code; 1386 infop->pid = pid; 1387 infop->uid = uid; 1388 } 1389 return pid; 1390 } 1391 1392 /* 1393 * Handle do_wait work for one task in a live, non-stopped state. 1394 * read_lock(&tasklist_lock) on entry. If we return zero, we still hold 1395 * the lock and this task is uninteresting. If we return nonzero, we have 1396 * released the lock and the system call should return. 1397 */ 1398 static int wait_task_continued(struct wait_opts *wo, struct task_struct *p) 1399 { 1400 struct waitid_info *infop; 1401 pid_t pid; 1402 uid_t uid; 1403 1404 if (!unlikely(wo->wo_flags & WCONTINUED)) 1405 return 0; 1406 1407 if (!(p->signal->flags & SIGNAL_STOP_CONTINUED)) 1408 return 0; 1409 1410 spin_lock_irq(&p->sighand->siglock); 1411 /* Re-check with the lock held. */ 1412 if (!(p->signal->flags & SIGNAL_STOP_CONTINUED)) { 1413 spin_unlock_irq(&p->sighand->siglock); 1414 return 0; 1415 } 1416 if (!unlikely(wo->wo_flags & WNOWAIT)) 1417 p->signal->flags &= ~SIGNAL_STOP_CONTINUED; 1418 uid = from_kuid_munged(current_user_ns(), task_uid(p)); 1419 spin_unlock_irq(&p->sighand->siglock); 1420 1421 pid = task_pid_vnr(p); 1422 get_task_struct(p); 1423 read_unlock(&tasklist_lock); 1424 sched_annotate_sleep(); 1425 if (wo->wo_rusage) 1426 getrusage(p, RUSAGE_BOTH, wo->wo_rusage); 1427 put_task_struct(p); 1428 1429 infop = wo->wo_info; 1430 if (!infop) { 1431 wo->wo_stat = 0xffff; 1432 } else { 1433 infop->cause = CLD_CONTINUED; 1434 infop->pid = pid; 1435 infop->uid = uid; 1436 infop->status = SIGCONT; 1437 } 1438 return pid; 1439 } 1440 1441 /* 1442 * Consider @p for a wait by @parent. 1443 * 1444 * -ECHILD should be in ->notask_error before the first call. 1445 * Returns nonzero for a final return, when we have unlocked tasklist_lock. 1446 * Returns zero if the search for a child should continue; 1447 * then ->notask_error is 0 if @p is an eligible child, 1448 * or still -ECHILD. 1449 */ 1450 static int wait_consider_task(struct wait_opts *wo, int ptrace, 1451 struct task_struct *p) 1452 { 1453 /* 1454 * We can race with wait_task_zombie() from another thread. 1455 * Ensure that EXIT_ZOMBIE -> EXIT_DEAD/EXIT_TRACE transition 1456 * can't confuse the checks below. 1457 */ 1458 int exit_state = READ_ONCE(p->exit_state); 1459 int ret; 1460 1461 if (unlikely(exit_state == EXIT_DEAD)) 1462 return 0; 1463 1464 ret = eligible_child(wo, ptrace, p); 1465 if (!ret) 1466 return ret; 1467 1468 if (unlikely(exit_state == EXIT_TRACE)) { 1469 /* 1470 * ptrace == 0 means we are the natural parent. In this case 1471 * we should clear notask_error, debugger will notify us. 1472 */ 1473 if (likely(!ptrace)) 1474 wo->notask_error = 0; 1475 return 0; 1476 } 1477 1478 if (likely(!ptrace) && unlikely(p->ptrace)) { 1479 /* 1480 * If it is traced by its real parent's group, just pretend 1481 * the caller is ptrace_do_wait() and reap this child if it 1482 * is zombie. 1483 * 1484 * This also hides group stop state from real parent; otherwise 1485 * a single stop can be reported twice as group and ptrace stop. 1486 * If a ptracer wants to distinguish these two events for its 1487 * own children it should create a separate process which takes 1488 * the role of real parent. 1489 */ 1490 if (!ptrace_reparented(p)) 1491 ptrace = 1; 1492 } 1493 1494 /* slay zombie? */ 1495 if (exit_state == EXIT_ZOMBIE) { 1496 /* we don't reap group leaders with subthreads */ 1497 if (!delay_group_leader(p)) { 1498 /* 1499 * A zombie ptracee is only visible to its ptracer. 1500 * Notification and reaping will be cascaded to the 1501 * real parent when the ptracer detaches. 1502 */ 1503 if (unlikely(ptrace) || likely(!p->ptrace)) 1504 return wait_task_zombie(wo, p); 1505 } 1506 1507 /* 1508 * Allow access to stopped/continued state via zombie by 1509 * falling through. Clearing of notask_error is complex. 1510 * 1511 * When !@ptrace: 1512 * 1513 * If WEXITED is set, notask_error should naturally be 1514 * cleared. If not, subset of WSTOPPED|WCONTINUED is set, 1515 * so, if there are live subthreads, there are events to 1516 * wait for. If all subthreads are dead, it's still safe 1517 * to clear - this function will be called again in finite 1518 * amount time once all the subthreads are released and 1519 * will then return without clearing. 1520 * 1521 * When @ptrace: 1522 * 1523 * Stopped state is per-task and thus can't change once the 1524 * target task dies. Only continued and exited can happen. 1525 * Clear notask_error if WCONTINUED | WEXITED. 1526 */ 1527 if (likely(!ptrace) || (wo->wo_flags & (WCONTINUED | WEXITED))) 1528 wo->notask_error = 0; 1529 } else { 1530 /* 1531 * @p is alive and it's gonna stop, continue or exit, so 1532 * there always is something to wait for. 1533 */ 1534 wo->notask_error = 0; 1535 } 1536 1537 /* 1538 * Wait for stopped. Depending on @ptrace, different stopped state 1539 * is used and the two don't interact with each other. 1540 */ 1541 ret = wait_task_stopped(wo, ptrace, p); 1542 if (ret) 1543 return ret; 1544 1545 /* 1546 * Wait for continued. There's only one continued state and the 1547 * ptracer can consume it which can confuse the real parent. Don't 1548 * use WCONTINUED from ptracer. You don't need or want it. 1549 */ 1550 return wait_task_continued(wo, p); 1551 } 1552 1553 /* 1554 * Do the work of do_wait() for one thread in the group, @tsk. 1555 * 1556 * -ECHILD should be in ->notask_error before the first call. 1557 * Returns nonzero for a final return, when we have unlocked tasklist_lock. 1558 * Returns zero if the search for a child should continue; then 1559 * ->notask_error is 0 if there were any eligible children, 1560 * or still -ECHILD. 1561 */ 1562 static int do_wait_thread(struct wait_opts *wo, struct task_struct *tsk) 1563 { 1564 struct task_struct *p; 1565 1566 list_for_each_entry(p, &tsk->children, sibling) { 1567 int ret = wait_consider_task(wo, 0, p); 1568 1569 if (ret) 1570 return ret; 1571 } 1572 1573 return 0; 1574 } 1575 1576 static int ptrace_do_wait(struct wait_opts *wo, struct task_struct *tsk) 1577 { 1578 struct task_struct *p; 1579 1580 list_for_each_entry(p, &tsk->ptraced, ptrace_entry) { 1581 int ret = wait_consider_task(wo, 1, p); 1582 1583 if (ret) 1584 return ret; 1585 } 1586 1587 return 0; 1588 } 1589 1590 bool pid_child_should_wake(struct wait_opts *wo, struct task_struct *p) 1591 { 1592 if (!eligible_pid(wo, p)) 1593 return false; 1594 1595 if ((wo->wo_flags & __WNOTHREAD) && wo->child_wait.private != p->parent) 1596 return false; 1597 1598 return true; 1599 } 1600 1601 static int child_wait_callback(wait_queue_entry_t *wait, unsigned mode, 1602 int sync, void *key) 1603 { 1604 struct wait_opts *wo = container_of(wait, struct wait_opts, 1605 child_wait); 1606 struct task_struct *p = key; 1607 1608 if (pid_child_should_wake(wo, p)) 1609 return default_wake_function(wait, mode, sync, key); 1610 1611 return 0; 1612 } 1613 1614 void __wake_up_parent(struct task_struct *p, struct task_struct *parent) 1615 { 1616 __wake_up_sync_key(&parent->signal->wait_chldexit, 1617 TASK_INTERRUPTIBLE, p); 1618 } 1619 1620 static bool is_effectively_child(struct wait_opts *wo, bool ptrace, 1621 struct task_struct *target) 1622 { 1623 struct task_struct *parent = 1624 !ptrace ? target->real_parent : target->parent; 1625 1626 return current == parent || (!(wo->wo_flags & __WNOTHREAD) && 1627 same_thread_group(current, parent)); 1628 } 1629 1630 /* 1631 * Optimization for waiting on PIDTYPE_PID. No need to iterate through child 1632 * and tracee lists to find the target task. 1633 */ 1634 static int do_wait_pid(struct wait_opts *wo) 1635 { 1636 bool ptrace; 1637 struct task_struct *target; 1638 int retval; 1639 1640 ptrace = false; 1641 target = pid_task(wo->wo_pid, PIDTYPE_TGID); 1642 if (target && is_effectively_child(wo, ptrace, target)) { 1643 retval = wait_consider_task(wo, ptrace, target); 1644 if (retval) 1645 return retval; 1646 } 1647 1648 ptrace = true; 1649 target = pid_task(wo->wo_pid, PIDTYPE_PID); 1650 if (target && target->ptrace && 1651 is_effectively_child(wo, ptrace, target)) { 1652 retval = wait_consider_task(wo, ptrace, target); 1653 if (retval) 1654 return retval; 1655 } 1656 1657 return 0; 1658 } 1659 1660 long __do_wait(struct wait_opts *wo) 1661 { 1662 long retval; 1663 1664 /* 1665 * If there is nothing that can match our criteria, just get out. 1666 * We will clear ->notask_error to zero if we see any child that 1667 * might later match our criteria, even if we are not able to reap 1668 * it yet. 1669 */ 1670 wo->notask_error = -ECHILD; 1671 if ((wo->wo_type < PIDTYPE_MAX) && 1672 (!wo->wo_pid || !pid_has_task(wo->wo_pid, wo->wo_type))) 1673 goto notask; 1674 1675 read_lock(&tasklist_lock); 1676 1677 if (wo->wo_type == PIDTYPE_PID) { 1678 retval = do_wait_pid(wo); 1679 if (retval) 1680 return retval; 1681 } else { 1682 struct task_struct *tsk = current; 1683 1684 do { 1685 retval = do_wait_thread(wo, tsk); 1686 if (retval) 1687 return retval; 1688 1689 retval = ptrace_do_wait(wo, tsk); 1690 if (retval) 1691 return retval; 1692 1693 if (wo->wo_flags & __WNOTHREAD) 1694 break; 1695 } while_each_thread(current, tsk); 1696 } 1697 read_unlock(&tasklist_lock); 1698 1699 notask: 1700 retval = wo->notask_error; 1701 if (!retval && !(wo->wo_flags & WNOHANG)) 1702 return -ERESTARTSYS; 1703 1704 return retval; 1705 } 1706 1707 static long do_wait(struct wait_opts *wo) 1708 { 1709 int retval; 1710 1711 trace_sched_process_wait(wo->wo_pid); 1712 1713 init_waitqueue_func_entry(&wo->child_wait, child_wait_callback); 1714 wo->child_wait.private = current; 1715 add_wait_queue(¤t->signal->wait_chldexit, &wo->child_wait); 1716 1717 do { 1718 set_current_state(TASK_INTERRUPTIBLE); 1719 retval = __do_wait(wo); 1720 if (retval != -ERESTARTSYS) 1721 break; 1722 if (signal_pending(current)) 1723 break; 1724 schedule(); 1725 } while (1); 1726 1727 __set_current_state(TASK_RUNNING); 1728 remove_wait_queue(¤t->signal->wait_chldexit, &wo->child_wait); 1729 return retval; 1730 } 1731 1732 int kernel_waitid_prepare(struct wait_opts *wo, int which, pid_t upid, 1733 struct waitid_info *infop, int options, 1734 struct rusage *ru) 1735 { 1736 unsigned int f_flags = 0; 1737 struct pid *pid = NULL; 1738 enum pid_type type; 1739 1740 if (options & ~(WNOHANG|WNOWAIT|WEXITED|WSTOPPED|WCONTINUED| 1741 __WNOTHREAD|__WCLONE|__WALL)) 1742 return -EINVAL; 1743 if (!(options & (WEXITED|WSTOPPED|WCONTINUED))) 1744 return -EINVAL; 1745 1746 switch (which) { 1747 case P_ALL: 1748 type = PIDTYPE_MAX; 1749 break; 1750 case P_PID: 1751 type = PIDTYPE_PID; 1752 if (upid <= 0) 1753 return -EINVAL; 1754 1755 pid = find_get_pid(upid); 1756 break; 1757 case P_PGID: 1758 type = PIDTYPE_PGID; 1759 if (upid < 0) 1760 return -EINVAL; 1761 1762 if (upid) 1763 pid = find_get_pid(upid); 1764 else 1765 pid = get_task_pid(current, PIDTYPE_PGID); 1766 break; 1767 case P_PIDFD: 1768 type = PIDTYPE_PID; 1769 if (upid < 0) 1770 return -EINVAL; 1771 1772 pid = pidfd_get_pid(upid, &f_flags); 1773 if (IS_ERR(pid)) 1774 return PTR_ERR(pid); 1775 1776 break; 1777 default: 1778 return -EINVAL; 1779 } 1780 1781 wo->wo_type = type; 1782 wo->wo_pid = pid; 1783 wo->wo_flags = options; 1784 wo->wo_info = infop; 1785 wo->wo_rusage = ru; 1786 if (f_flags & O_NONBLOCK) 1787 wo->wo_flags |= WNOHANG; 1788 1789 return 0; 1790 } 1791 1792 static long kernel_waitid(int which, pid_t upid, struct waitid_info *infop, 1793 int options, struct rusage *ru) 1794 { 1795 struct wait_opts wo; 1796 long ret; 1797 1798 ret = kernel_waitid_prepare(&wo, which, upid, infop, options, ru); 1799 if (ret) 1800 return ret; 1801 1802 ret = do_wait(&wo); 1803 if (!ret && !(options & WNOHANG) && (wo.wo_flags & WNOHANG)) 1804 ret = -EAGAIN; 1805 1806 put_pid(wo.wo_pid); 1807 return ret; 1808 } 1809 1810 SYSCALL_DEFINE5(waitid, int, which, pid_t, upid, struct siginfo __user *, 1811 infop, int, options, struct rusage __user *, ru) 1812 { 1813 struct rusage r; 1814 struct waitid_info info = {.status = 0}; 1815 long err = kernel_waitid(which, upid, &info, options, ru ? &r : NULL); 1816 int signo = 0; 1817 1818 if (err > 0) { 1819 signo = SIGCHLD; 1820 err = 0; 1821 if (ru && copy_to_user(ru, &r, sizeof(struct rusage))) 1822 return -EFAULT; 1823 } 1824 if (!infop) 1825 return err; 1826 1827 if (!user_write_access_begin(infop, sizeof(*infop))) 1828 return -EFAULT; 1829 1830 unsafe_put_user(signo, &infop->si_signo, Efault); 1831 unsafe_put_user(0, &infop->si_errno, Efault); 1832 unsafe_put_user(info.cause, &infop->si_code, Efault); 1833 unsafe_put_user(info.pid, &infop->si_pid, Efault); 1834 unsafe_put_user(info.uid, &infop->si_uid, Efault); 1835 unsafe_put_user(info.status, &infop->si_status, Efault); 1836 user_write_access_end(); 1837 return err; 1838 Efault: 1839 user_write_access_end(); 1840 return -EFAULT; 1841 } 1842 1843 long kernel_wait4(pid_t upid, int __user *stat_addr, int options, 1844 struct rusage *ru) 1845 { 1846 struct wait_opts wo; 1847 struct pid *pid = NULL; 1848 enum pid_type type; 1849 long ret; 1850 1851 if (options & ~(WNOHANG|WUNTRACED|WCONTINUED| 1852 __WNOTHREAD|__WCLONE|__WALL)) 1853 return -EINVAL; 1854 1855 /* -INT_MIN is not defined */ 1856 if (upid == INT_MIN) 1857 return -ESRCH; 1858 1859 if (upid == -1) 1860 type = PIDTYPE_MAX; 1861 else if (upid < 0) { 1862 type = PIDTYPE_PGID; 1863 pid = find_get_pid(-upid); 1864 } else if (upid == 0) { 1865 type = PIDTYPE_PGID; 1866 pid = get_task_pid(current, PIDTYPE_PGID); 1867 } else /* upid > 0 */ { 1868 type = PIDTYPE_PID; 1869 pid = find_get_pid(upid); 1870 } 1871 1872 wo.wo_type = type; 1873 wo.wo_pid = pid; 1874 wo.wo_flags = options | WEXITED; 1875 wo.wo_info = NULL; 1876 wo.wo_stat = 0; 1877 wo.wo_rusage = ru; 1878 ret = do_wait(&wo); 1879 put_pid(pid); 1880 if (ret > 0 && stat_addr && put_user(wo.wo_stat, stat_addr)) 1881 ret = -EFAULT; 1882 1883 return ret; 1884 } 1885 1886 int kernel_wait(pid_t pid, int *stat) 1887 { 1888 struct wait_opts wo = { 1889 .wo_type = PIDTYPE_PID, 1890 .wo_pid = find_get_pid(pid), 1891 .wo_flags = WEXITED, 1892 }; 1893 int ret; 1894 1895 ret = do_wait(&wo); 1896 if (ret > 0 && wo.wo_stat) 1897 *stat = wo.wo_stat; 1898 put_pid(wo.wo_pid); 1899 return ret; 1900 } 1901 1902 SYSCALL_DEFINE4(wait4, pid_t, upid, int __user *, stat_addr, 1903 int, options, struct rusage __user *, ru) 1904 { 1905 struct rusage r; 1906 long err = kernel_wait4(upid, stat_addr, options, ru ? &r : NULL); 1907 1908 if (err > 0) { 1909 if (ru && copy_to_user(ru, &r, sizeof(struct rusage))) 1910 return -EFAULT; 1911 } 1912 return err; 1913 } 1914 1915 #ifdef __ARCH_WANT_SYS_WAITPID 1916 1917 /* 1918 * sys_waitpid() remains for compatibility. waitpid() should be 1919 * implemented by calling sys_wait4() from libc.a. 1920 */ 1921 SYSCALL_DEFINE3(waitpid, pid_t, pid, int __user *, stat_addr, int, options) 1922 { 1923 return kernel_wait4(pid, stat_addr, options, NULL); 1924 } 1925 1926 #endif 1927 1928 #ifdef CONFIG_COMPAT 1929 COMPAT_SYSCALL_DEFINE4(wait4, 1930 compat_pid_t, pid, 1931 compat_uint_t __user *, stat_addr, 1932 int, options, 1933 struct compat_rusage __user *, ru) 1934 { 1935 struct rusage r; 1936 long err = kernel_wait4(pid, stat_addr, options, ru ? &r : NULL); 1937 if (err > 0) { 1938 if (ru && put_compat_rusage(&r, ru)) 1939 return -EFAULT; 1940 } 1941 return err; 1942 } 1943 1944 COMPAT_SYSCALL_DEFINE5(waitid, 1945 int, which, compat_pid_t, pid, 1946 struct compat_siginfo __user *, infop, int, options, 1947 struct compat_rusage __user *, uru) 1948 { 1949 struct rusage ru; 1950 struct waitid_info info = {.status = 0}; 1951 long err = kernel_waitid(which, pid, &info, options, uru ? &ru : NULL); 1952 int signo = 0; 1953 if (err > 0) { 1954 signo = SIGCHLD; 1955 err = 0; 1956 if (uru) { 1957 /* kernel_waitid() overwrites everything in ru */ 1958 if (COMPAT_USE_64BIT_TIME) 1959 err = copy_to_user(uru, &ru, sizeof(ru)); 1960 else 1961 err = put_compat_rusage(&ru, uru); 1962 if (err) 1963 return -EFAULT; 1964 } 1965 } 1966 1967 if (!infop) 1968 return err; 1969 1970 if (!user_write_access_begin(infop, sizeof(*infop))) 1971 return -EFAULT; 1972 1973 unsafe_put_user(signo, &infop->si_signo, Efault); 1974 unsafe_put_user(0, &infop->si_errno, Efault); 1975 unsafe_put_user(info.cause, &infop->si_code, Efault); 1976 unsafe_put_user(info.pid, &infop->si_pid, Efault); 1977 unsafe_put_user(info.uid, &infop->si_uid, Efault); 1978 unsafe_put_user(info.status, &infop->si_status, Efault); 1979 user_write_access_end(); 1980 return err; 1981 Efault: 1982 user_write_access_end(); 1983 return -EFAULT; 1984 } 1985 #endif 1986 1987 /* 1988 * This needs to be __function_aligned as GCC implicitly makes any 1989 * implementation of abort() cold and drops alignment specified by 1990 * -falign-functions=N. 1991 * 1992 * See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88345#c11 1993 */ 1994 __weak __function_aligned void abort(void) 1995 { 1996 BUG(); 1997 1998 /* if that doesn't kill us, halt */ 1999 panic("Oops failed to kill thread"); 2000 } 2001 EXPORT_SYMBOL(abort);