1 /* 2 * linux/kernel/signal.c 3 * 4 * Copyright (C) 1991, 1992 Linus Torvalds 5 * 6 * 1997-11-02 Modified for POSIX.1b signals by Richard Henderson 7 * 8 * 2003-06-02 Jim Houston - Concurrent Computer Corp. 9 * Changes to use preallocated sigqueue structures 10 * to allow signals to be sent reliably. 11 */ 12 13 #include <linux/slab.h> 14 #include <linux/export.h> 15 #include <linux/init.h> 16 #include <linux/sched.h> 17 #include <linux/fs.h> 18 #include <linux/tty.h> 19 #include <linux/binfmts.h> 20 #include <linux/coredump.h> 21 #include <linux/security.h> 22 #include <linux/syscalls.h> 23 #include <linux/ptrace.h> 24 #include <linux/signal.h> 25 #include <linux/signalfd.h> 26 #include <linux/ratelimit.h> 27 #include <linux/tracehook.h> 28 #include <linux/capability.h> 29 #include <linux/freezer.h> 30 #include <linux/pid_namespace.h> 31 #include <linux/nsproxy.h> 32 #include <linux/user_namespace.h> 33 #include <linux/uprobes.h> 34 #include <linux/compat.h> 35 #define CREATE_TRACE_POINTS 36 #include <trace/events/signal.h> 37 38 #include <asm/param.h> 39 #include <asm/uaccess.h> 40 #include <asm/unistd.h> 41 #include <asm/siginfo.h> 42 #include <asm/cacheflush.h> 43 #include "audit.h" /* audit_signal_info() */ 44 45 /* 46 * SLAB caches for signal bits. 47 */ 48 49 static struct kmem_cache *sigqueue_cachep; 50 51 int print_fatal_signals __read_mostly; 52 53 static void __user *sig_handler(struct task_struct *t, int sig) 54 { 55 return t->sighand->action[sig - 1].sa.sa_handler; 56 } 57 58 static int sig_handler_ignored(void __user *handler, int sig) 59 { 60 /* Is it explicitly or implicitly ignored? */ 61 return handler == SIG_IGN || 62 (handler == SIG_DFL && sig_kernel_ignore(sig)); 63 } 64 65 static int sig_task_ignored(struct task_struct *t, int sig, bool force) 66 { 67 void __user *handler; 68 69 handler = sig_handler(t, sig); 70 71 if (unlikely(t->signal->flags & SIGNAL_UNKILLABLE) && 72 handler == SIG_DFL && !force) 73 return 1; 74 75 return sig_handler_ignored(handler, sig); 76 } 77 78 static int sig_ignored(struct task_struct *t, int sig, bool force) 79 { 80 /* 81 * Blocked signals are never ignored, since the 82 * signal handler may change by the time it is 83 * unblocked. 84 */ 85 if (sigismember(&t->blocked, sig) || sigismember(&t->real_blocked, sig)) 86 return 0; 87 88 if (!sig_task_ignored(t, sig, force)) 89 return 0; 90 91 /* 92 * Tracers may want to know about even ignored signals. 93 */ 94 return !t->ptrace; 95 } 96 97 /* 98 * Re-calculate pending state from the set of locally pending 99 * signals, globally pending signals, and blocked signals. 100 */ 101 static inline int has_pending_signals(sigset_t *signal, sigset_t *blocked) 102 { 103 unsigned long ready; 104 long i; 105 106 switch (_NSIG_WORDS) { 107 default: 108 for (i = _NSIG_WORDS, ready = 0; --i >= 0 ;) 109 ready |= signal->sig[i] &~ blocked->sig[i]; 110 break; 111 112 case 4: ready = signal->sig[3] &~ blocked->sig[3]; 113 ready |= signal->sig[2] &~ blocked->sig[2]; 114 ready |= signal->sig[1] &~ blocked->sig[1]; 115 ready |= signal->sig[0] &~ blocked->sig[0]; 116 break; 117 118 case 2: ready = signal->sig[1] &~ blocked->sig[1]; 119 ready |= signal->sig[0] &~ blocked->sig[0]; 120 break; 121 122 case 1: ready = signal->sig[0] &~ blocked->sig[0]; 123 } 124 return ready != 0; 125 } 126 127 #define PENDING(p,b) has_pending_signals(&(p)->signal, (b)) 128 129 static int recalc_sigpending_tsk(struct task_struct *t) 130 { 131 if ((t->jobctl & JOBCTL_PENDING_MASK) || 132 PENDING(&t->pending, &t->blocked) || 133 PENDING(&t->signal->shared_pending, &t->blocked)) { 134 set_tsk_thread_flag(t, TIF_SIGPENDING); 135 return 1; 136 } 137 /* 138 * We must never clear the flag in another thread, or in current 139 * when it's possible the current syscall is returning -ERESTART*. 140 * So we don't clear it here, and only callers who know they should do. 141 */ 142 return 0; 143 } 144 145 /* 146 * After recalculating TIF_SIGPENDING, we need to make sure the task wakes up. 147 * This is superfluous when called on current, the wakeup is a harmless no-op. 148 */ 149 void recalc_sigpending_and_wake(struct task_struct *t) 150 { 151 if (recalc_sigpending_tsk(t)) 152 signal_wake_up(t, 0); 153 } 154 155 void recalc_sigpending(void) 156 { 157 if (!recalc_sigpending_tsk(current) && !freezing(current)) 158 clear_thread_flag(TIF_SIGPENDING); 159 160 } 161 162 /* Given the mask, find the first available signal that should be serviced. */ 163 164 #define SYNCHRONOUS_MASK \ 165 (sigmask(SIGSEGV) | sigmask(SIGBUS) | sigmask(SIGILL) | \ 166 sigmask(SIGTRAP) | sigmask(SIGFPE) | sigmask(SIGSYS)) 167 168 int next_signal(struct sigpending *pending, sigset_t *mask) 169 { 170 unsigned long i, *s, *m, x; 171 int sig = 0; 172 173 s = pending->signal.sig; 174 m = mask->sig; 175 176 /* 177 * Handle the first word specially: it contains the 178 * synchronous signals that need to be dequeued first. 179 */ 180 x = *s &~ *m; 181 if (x) { 182 if (x & SYNCHRONOUS_MASK) 183 x &= SYNCHRONOUS_MASK; 184 sig = ffz(~x) + 1; 185 return sig; 186 } 187 188 switch (_NSIG_WORDS) { 189 default: 190 for (i = 1; i < _NSIG_WORDS; ++i) { 191 x = *++s &~ *++m; 192 if (!x) 193 continue; 194 sig = ffz(~x) + i*_NSIG_BPW + 1; 195 break; 196 } 197 break; 198 199 case 2: 200 x = s[1] &~ m[1]; 201 if (!x) 202 break; 203 sig = ffz(~x) + _NSIG_BPW + 1; 204 break; 205 206 case 1: 207 /* Nothing to do */ 208 break; 209 } 210 211 return sig; 212 } 213 214 static inline void print_dropped_signal(int sig) 215 { 216 static DEFINE_RATELIMIT_STATE(ratelimit_state, 5 * HZ, 10); 217 218 if (!print_fatal_signals) 219 return; 220 221 if (!__ratelimit(&ratelimit_state)) 222 return; 223 224 printk(KERN_INFO "%s/%d: reached RLIMIT_SIGPENDING, dropped signal %d\n", 225 current->comm, current->pid, sig); 226 } 227 228 /** 229 * task_set_jobctl_pending - set jobctl pending bits 230 * @task: target task 231 * @mask: pending bits to set 232 * 233 * Clear @mask from @task->jobctl. @mask must be subset of 234 * %JOBCTL_PENDING_MASK | %JOBCTL_STOP_CONSUME | %JOBCTL_STOP_SIGMASK | 235 * %JOBCTL_TRAPPING. If stop signo is being set, the existing signo is 236 * cleared. If @task is already being killed or exiting, this function 237 * becomes noop. 238 * 239 * CONTEXT: 240 * Must be called with @task->sighand->siglock held. 241 * 242 * RETURNS: 243 * %true if @mask is set, %false if made noop because @task was dying. 244 */ 245 bool task_set_jobctl_pending(struct task_struct *task, unsigned int mask) 246 { 247 BUG_ON(mask & ~(JOBCTL_PENDING_MASK | JOBCTL_STOP_CONSUME | 248 JOBCTL_STOP_SIGMASK | JOBCTL_TRAPPING)); 249 BUG_ON((mask & JOBCTL_TRAPPING) && !(mask & JOBCTL_PENDING_MASK)); 250 251 if (unlikely(fatal_signal_pending(task) || (task->flags & PF_EXITING))) 252 return false; 253 254 if (mask & JOBCTL_STOP_SIGMASK) 255 task->jobctl &= ~JOBCTL_STOP_SIGMASK; 256 257 task->jobctl |= mask; 258 return true; 259 } 260 261 /** 262 * task_clear_jobctl_trapping - clear jobctl trapping bit 263 * @task: target task 264 * 265 * If JOBCTL_TRAPPING is set, a ptracer is waiting for us to enter TRACED. 266 * Clear it and wake up the ptracer. Note that we don't need any further 267 * locking. @task->siglock guarantees that @task->parent points to the 268 * ptracer. 269 * 270 * CONTEXT: 271 * Must be called with @task->sighand->siglock held. 272 */ 273 void task_clear_jobctl_trapping(struct task_struct *task) 274 { 275 if (unlikely(task->jobctl & JOBCTL_TRAPPING)) { 276 task->jobctl &= ~JOBCTL_TRAPPING; 277 wake_up_bit(&task->jobctl, JOBCTL_TRAPPING_BIT); 278 } 279 } 280 281 /** 282 * task_clear_jobctl_pending - clear jobctl pending bits 283 * @task: target task 284 * @mask: pending bits to clear 285 * 286 * Clear @mask from @task->jobctl. @mask must be subset of 287 * %JOBCTL_PENDING_MASK. If %JOBCTL_STOP_PENDING is being cleared, other 288 * STOP bits are cleared together. 289 * 290 * If clearing of @mask leaves no stop or trap pending, this function calls 291 * task_clear_jobctl_trapping(). 292 * 293 * CONTEXT: 294 * Must be called with @task->sighand->siglock held. 295 */ 296 void task_clear_jobctl_pending(struct task_struct *task, unsigned int mask) 297 { 298 BUG_ON(mask & ~JOBCTL_PENDING_MASK); 299 300 if (mask & JOBCTL_STOP_PENDING) 301 mask |= JOBCTL_STOP_CONSUME | JOBCTL_STOP_DEQUEUED; 302 303 task->jobctl &= ~mask; 304 305 if (!(task->jobctl & JOBCTL_PENDING_MASK)) 306 task_clear_jobctl_trapping(task); 307 } 308 309 /** 310 * task_participate_group_stop - participate in a group stop 311 * @task: task participating in a group stop 312 * 313 * @task has %JOBCTL_STOP_PENDING set and is participating in a group stop. 314 * Group stop states are cleared and the group stop count is consumed if 315 * %JOBCTL_STOP_CONSUME was set. If the consumption completes the group 316 * stop, the appropriate %SIGNAL_* flags are set. 317 * 318 * CONTEXT: 319 * Must be called with @task->sighand->siglock held. 320 * 321 * RETURNS: 322 * %true if group stop completion should be notified to the parent, %false 323 * otherwise. 324 */ 325 static bool task_participate_group_stop(struct task_struct *task) 326 { 327 struct signal_struct *sig = task->signal; 328 bool consume = task->jobctl & JOBCTL_STOP_CONSUME; 329 330 WARN_ON_ONCE(!(task->jobctl & JOBCTL_STOP_PENDING)); 331 332 task_clear_jobctl_pending(task, JOBCTL_STOP_PENDING); 333 334 if (!consume) 335 return false; 336 337 if (!WARN_ON_ONCE(sig->group_stop_count == 0)) 338 sig->group_stop_count--; 339 340 /* 341 * Tell the caller to notify completion iff we are entering into a 342 * fresh group stop. Read comment in do_signal_stop() for details. 343 */ 344 if (!sig->group_stop_count && !(sig->flags & SIGNAL_STOP_STOPPED)) { 345 sig->flags = SIGNAL_STOP_STOPPED; 346 return true; 347 } 348 return false; 349 } 350 351 /* 352 * allocate a new signal queue record 353 * - this may be called without locks if and only if t == current, otherwise an 354 * appropriate lock must be held to stop the target task from exiting 355 */ 356 static struct sigqueue * 357 __sigqueue_alloc(int sig, struct task_struct *t, gfp_t flags, int override_rlimit) 358 { 359 struct sigqueue *q = NULL; 360 struct user_struct *user; 361 362 /* 363 * Protect access to @t credentials. This can go away when all 364 * callers hold rcu read lock. 365 */ 366 rcu_read_lock(); 367 user = get_uid(__task_cred(t)->user); 368 atomic_inc(&user->sigpending); 369 rcu_read_unlock(); 370 371 if (override_rlimit || 372 atomic_read(&user->sigpending) <= 373 task_rlimit(t, RLIMIT_SIGPENDING)) { 374 q = kmem_cache_alloc(sigqueue_cachep, flags); 375 } else { 376 print_dropped_signal(sig); 377 } 378 379 if (unlikely(q == NULL)) { 380 atomic_dec(&user->sigpending); 381 free_uid(user); 382 } else { 383 INIT_LIST_HEAD(&q->list); 384 q->flags = 0; 385 q->user = user; 386 } 387 388 return q; 389 } 390 391 static void __sigqueue_free(struct sigqueue *q) 392 { 393 if (q->flags & SIGQUEUE_PREALLOC) 394 return; 395 atomic_dec(&q->user->sigpending); 396 free_uid(q->user); 397 kmem_cache_free(sigqueue_cachep, q); 398 } 399 400 void flush_sigqueue(struct sigpending *queue) 401 { 402 struct sigqueue *q; 403 404 sigemptyset(&queue->signal); 405 while (!list_empty(&queue->list)) { 406 q = list_entry(queue->list.next, struct sigqueue , list); 407 list_del_init(&q->list); 408 __sigqueue_free(q); 409 } 410 } 411 412 /* 413 * Flush all pending signals for a task. 414 */ 415 void __flush_signals(struct task_struct *t) 416 { 417 clear_tsk_thread_flag(t, TIF_SIGPENDING); 418 flush_sigqueue(&t->pending); 419 flush_sigqueue(&t->signal->shared_pending); 420 } 421 422 void flush_signals(struct task_struct *t) 423 { 424 unsigned long flags; 425 426 spin_lock_irqsave(&t->sighand->siglock, flags); 427 __flush_signals(t); 428 spin_unlock_irqrestore(&t->sighand->siglock, flags); 429 } 430 431 static void __flush_itimer_signals(struct sigpending *pending) 432 { 433 sigset_t signal, retain; 434 struct sigqueue *q, *n; 435 436 signal = pending->signal; 437 sigemptyset(&retain); 438 439 list_for_each_entry_safe(q, n, &pending->list, list) { 440 int sig = q->info.si_signo; 441 442 if (likely(q->info.si_code != SI_TIMER)) { 443 sigaddset(&retain, sig); 444 } else { 445 sigdelset(&signal, sig); 446 list_del_init(&q->list); 447 __sigqueue_free(q); 448 } 449 } 450 451 sigorsets(&pending->signal, &signal, &retain); 452 } 453 454 void flush_itimer_signals(void) 455 { 456 struct task_struct *tsk = current; 457 unsigned long flags; 458 459 spin_lock_irqsave(&tsk->sighand->siglock, flags); 460 __flush_itimer_signals(&tsk->pending); 461 __flush_itimer_signals(&tsk->signal->shared_pending); 462 spin_unlock_irqrestore(&tsk->sighand->siglock, flags); 463 } 464 465 void ignore_signals(struct task_struct *t) 466 { 467 int i; 468 469 for (i = 0; i < _NSIG; ++i) 470 t->sighand->action[i].sa.sa_handler = SIG_IGN; 471 472 flush_signals(t); 473 } 474 475 /* 476 * Flush all handlers for a task. 477 */ 478 479 void 480 flush_signal_handlers(struct task_struct *t, int force_default) 481 { 482 int i; 483 struct k_sigaction *ka = &t->sighand->action[0]; 484 for (i = _NSIG ; i != 0 ; i--) { 485 if (force_default || ka->sa.sa_handler != SIG_IGN) 486 ka->sa.sa_handler = SIG_DFL; 487 ka->sa.sa_flags = 0; 488 sigemptyset(&ka->sa.sa_mask); 489 ka++; 490 } 491 } 492 493 int unhandled_signal(struct task_struct *tsk, int sig) 494 { 495 void __user *handler = tsk->sighand->action[sig-1].sa.sa_handler; 496 if (is_global_init(tsk)) 497 return 1; 498 if (handler != SIG_IGN && handler != SIG_DFL) 499 return 0; 500 /* if ptraced, let the tracer determine */ 501 return !tsk->ptrace; 502 } 503 504 /* 505 * Notify the system that a driver wants to block all signals for this 506 * process, and wants to be notified if any signals at all were to be 507 * sent/acted upon. If the notifier routine returns non-zero, then the 508 * signal will be acted upon after all. If the notifier routine returns 0, 509 * then then signal will be blocked. Only one block per process is 510 * allowed. priv is a pointer to private data that the notifier routine 511 * can use to determine if the signal should be blocked or not. 512 */ 513 void 514 block_all_signals(int (*notifier)(void *priv), void *priv, sigset_t *mask) 515 { 516 unsigned long flags; 517 518 spin_lock_irqsave(¤t->sighand->siglock, flags); 519 current->notifier_mask = mask; 520 current->notifier_data = priv; 521 current->notifier = notifier; 522 spin_unlock_irqrestore(¤t->sighand->siglock, flags); 523 } 524 525 /* Notify the system that blocking has ended. */ 526 527 void 528 unblock_all_signals(void) 529 { 530 unsigned long flags; 531 532 spin_lock_irqsave(¤t->sighand->siglock, flags); 533 current->notifier = NULL; 534 current->notifier_data = NULL; 535 recalc_sigpending(); 536 spin_unlock_irqrestore(¤t->sighand->siglock, flags); 537 } 538 539 static void collect_signal(int sig, struct sigpending *list, siginfo_t *info) 540 { 541 struct sigqueue *q, *first = NULL; 542 543 /* 544 * Collect the siginfo appropriate to this signal. Check if 545 * there is another siginfo for the same signal. 546 */ 547 list_for_each_entry(q, &list->list, list) { 548 if (q->info.si_signo == sig) { 549 if (first) 550 goto still_pending; 551 first = q; 552 } 553 } 554 555 sigdelset(&list->signal, sig); 556 557 if (first) { 558 still_pending: 559 list_del_init(&first->list); 560 copy_siginfo(info, &first->info); 561 __sigqueue_free(first); 562 } else { 563 /* 564 * Ok, it wasn't in the queue. This must be 565 * a fast-pathed signal or we must have been 566 * out of queue space. So zero out the info. 567 */ 568 info->si_signo = sig; 569 info->si_errno = 0; 570 info->si_code = SI_USER; 571 info->si_pid = 0; 572 info->si_uid = 0; 573 } 574 } 575 576 static int __dequeue_signal(struct sigpending *pending, sigset_t *mask, 577 siginfo_t *info) 578 { 579 int sig = next_signal(pending, mask); 580 581 if (sig) { 582 if (current->notifier) { 583 if (sigismember(current->notifier_mask, sig)) { 584 if (!(current->notifier)(current->notifier_data)) { 585 clear_thread_flag(TIF_SIGPENDING); 586 return 0; 587 } 588 } 589 } 590 591 collect_signal(sig, pending, info); 592 } 593 594 return sig; 595 } 596 597 /* 598 * Dequeue a signal and return the element to the caller, which is 599 * expected to free it. 600 * 601 * All callers have to hold the siglock. 602 */ 603 int dequeue_signal(struct task_struct *tsk, sigset_t *mask, siginfo_t *info) 604 { 605 int signr; 606 607 /* We only dequeue private signals from ourselves, we don't let 608 * signalfd steal them 609 */ 610 signr = __dequeue_signal(&tsk->pending, mask, info); 611 if (!signr) { 612 signr = __dequeue_signal(&tsk->signal->shared_pending, 613 mask, info); 614 /* 615 * itimer signal ? 616 * 617 * itimers are process shared and we restart periodic 618 * itimers in the signal delivery path to prevent DoS 619 * attacks in the high resolution timer case. This is 620 * compliant with the old way of self-restarting 621 * itimers, as the SIGALRM is a legacy signal and only 622 * queued once. Changing the restart behaviour to 623 * restart the timer in the signal dequeue path is 624 * reducing the timer noise on heavy loaded !highres 625 * systems too. 626 */ 627 if (unlikely(signr == SIGALRM)) { 628 struct hrtimer *tmr = &tsk->signal->real_timer; 629 630 if (!hrtimer_is_queued(tmr) && 631 tsk->signal->it_real_incr.tv64 != 0) { 632 hrtimer_forward(tmr, tmr->base->get_time(), 633 tsk->signal->it_real_incr); 634 hrtimer_restart(tmr); 635 } 636 } 637 } 638 639 recalc_sigpending(); 640 if (!signr) 641 return 0; 642 643 if (unlikely(sig_kernel_stop(signr))) { 644 /* 645 * Set a marker that we have dequeued a stop signal. Our 646 * caller might release the siglock and then the pending 647 * stop signal it is about to process is no longer in the 648 * pending bitmasks, but must still be cleared by a SIGCONT 649 * (and overruled by a SIGKILL). So those cases clear this 650 * shared flag after we've set it. Note that this flag may 651 * remain set after the signal we return is ignored or 652 * handled. That doesn't matter because its only purpose 653 * is to alert stop-signal processing code when another 654 * processor has come along and cleared the flag. 655 */ 656 current->jobctl |= JOBCTL_STOP_DEQUEUED; 657 } 658 if ((info->si_code & __SI_MASK) == __SI_TIMER && info->si_sys_private) { 659 /* 660 * Release the siglock to ensure proper locking order 661 * of timer locks outside of siglocks. Note, we leave 662 * irqs disabled here, since the posix-timers code is 663 * about to disable them again anyway. 664 */ 665 spin_unlock(&tsk->sighand->siglock); 666 do_schedule_next_timer(info); 667 spin_lock(&tsk->sighand->siglock); 668 } 669 return signr; 670 } 671 672 /* 673 * Tell a process that it has a new active signal.. 674 * 675 * NOTE! we rely on the previous spin_lock to 676 * lock interrupts for us! We can only be called with 677 * "siglock" held, and the local interrupt must 678 * have been disabled when that got acquired! 679 * 680 * No need to set need_resched since signal event passing 681 * goes through ->blocked 682 */ 683 void signal_wake_up_state(struct task_struct *t, unsigned int state) 684 { 685 set_tsk_thread_flag(t, TIF_SIGPENDING); 686 /* 687 * TASK_WAKEKILL also means wake it up in the stopped/traced/killable 688 * case. We don't check t->state here because there is a race with it 689 * executing another processor and just now entering stopped state. 690 * By using wake_up_state, we ensure the process will wake up and 691 * handle its death signal. 692 */ 693 if (!wake_up_state(t, state | TASK_INTERRUPTIBLE)) 694 kick_process(t); 695 } 696 697 /* 698 * Remove signals in mask from the pending set and queue. 699 * Returns 1 if any signals were found. 700 * 701 * All callers must be holding the siglock. 702 * 703 * This version takes a sigset mask and looks at all signals, 704 * not just those in the first mask word. 705 */ 706 static int rm_from_queue_full(sigset_t *mask, struct sigpending *s) 707 { 708 struct sigqueue *q, *n; 709 sigset_t m; 710 711 sigandsets(&m, mask, &s->signal); 712 if (sigisemptyset(&m)) 713 return 0; 714 715 sigandnsets(&s->signal, &s->signal, mask); 716 list_for_each_entry_safe(q, n, &s->list, list) { 717 if (sigismember(mask, q->info.si_signo)) { 718 list_del_init(&q->list); 719 __sigqueue_free(q); 720 } 721 } 722 return 1; 723 } 724 /* 725 * Remove signals in mask from the pending set and queue. 726 * Returns 1 if any signals were found. 727 * 728 * All callers must be holding the siglock. 729 */ 730 static int rm_from_queue(unsigned long mask, struct sigpending *s) 731 { 732 struct sigqueue *q, *n; 733 734 if (!sigtestsetmask(&s->signal, mask)) 735 return 0; 736 737 sigdelsetmask(&s->signal, mask); 738 list_for_each_entry_safe(q, n, &s->list, list) { 739 if (q->info.si_signo < SIGRTMIN && 740 (mask & sigmask(q->info.si_signo))) { 741 list_del_init(&q->list); 742 __sigqueue_free(q); 743 } 744 } 745 return 1; 746 } 747 748 static inline int is_si_special(const struct siginfo *info) 749 { 750 return info <= SEND_SIG_FORCED; 751 } 752 753 static inline bool si_fromuser(const struct siginfo *info) 754 { 755 return info == SEND_SIG_NOINFO || 756 (!is_si_special(info) && SI_FROMUSER(info)); 757 } 758 759 /* 760 * called with RCU read lock from check_kill_permission() 761 */ 762 static int kill_ok_by_cred(struct task_struct *t) 763 { 764 const struct cred *cred = current_cred(); 765 const struct cred *tcred = __task_cred(t); 766 767 if (uid_eq(cred->euid, tcred->suid) || 768 uid_eq(cred->euid, tcred->uid) || 769 uid_eq(cred->uid, tcred->suid) || 770 uid_eq(cred->uid, tcred->uid)) 771 return 1; 772 773 if (ns_capable(tcred->user_ns, CAP_KILL)) 774 return 1; 775 776 return 0; 777 } 778 779 /* 780 * Bad permissions for sending the signal 781 * - the caller must hold the RCU read lock 782 */ 783 static int check_kill_permission(int sig, struct siginfo *info, 784 struct task_struct *t) 785 { 786 struct pid *sid; 787 int error; 788 789 if (!valid_signal(sig)) 790 return -EINVAL; 791 792 if (!si_fromuser(info)) 793 return 0; 794 795 error = audit_signal_info(sig, t); /* Let audit system see the signal */ 796 if (error) 797 return error; 798 799 if (!same_thread_group(current, t) && 800 !kill_ok_by_cred(t)) { 801 switch (sig) { 802 case SIGCONT: 803 sid = task_session(t); 804 /* 805 * We don't return the error if sid == NULL. The 806 * task was unhashed, the caller must notice this. 807 */ 808 if (!sid || sid == task_session(current)) 809 break; 810 default: 811 return -EPERM; 812 } 813 } 814 815 return security_task_kill(t, info, sig, 0); 816 } 817 818 /** 819 * ptrace_trap_notify - schedule trap to notify ptracer 820 * @t: tracee wanting to notify tracer 821 * 822 * This function schedules sticky ptrace trap which is cleared on the next 823 * TRAP_STOP to notify ptracer of an event. @t must have been seized by 824 * ptracer. 825 * 826 * If @t is running, STOP trap will be taken. If trapped for STOP and 827 * ptracer is listening for events, tracee is woken up so that it can 828 * re-trap for the new event. If trapped otherwise, STOP trap will be 829 * eventually taken without returning to userland after the existing traps 830 * are finished by PTRACE_CONT. 831 * 832 * CONTEXT: 833 * Must be called with @task->sighand->siglock held. 834 */ 835 static void ptrace_trap_notify(struct task_struct *t) 836 { 837 WARN_ON_ONCE(!(t->ptrace & PT_SEIZED)); 838 assert_spin_locked(&t->sighand->siglock); 839 840 task_set_jobctl_pending(t, JOBCTL_TRAP_NOTIFY); 841 ptrace_signal_wake_up(t, t->jobctl & JOBCTL_LISTENING); 842 } 843 844 /* 845 * Handle magic process-wide effects of stop/continue signals. Unlike 846 * the signal actions, these happen immediately at signal-generation 847 * time regardless of blocking, ignoring, or handling. This does the 848 * actual continuing for SIGCONT, but not the actual stopping for stop 849 * signals. The process stop is done as a signal action for SIG_DFL. 850 * 851 * Returns true if the signal should be actually delivered, otherwise 852 * it should be dropped. 853 */ 854 static int prepare_signal(int sig, struct task_struct *p, bool force) 855 { 856 struct signal_struct *signal = p->signal; 857 struct task_struct *t; 858 859 if (unlikely(signal->flags & SIGNAL_GROUP_EXIT)) { 860 /* 861 * The process is in the middle of dying, nothing to do. 862 */ 863 } else if (sig_kernel_stop(sig)) { 864 /* 865 * This is a stop signal. Remove SIGCONT from all queues. 866 */ 867 rm_from_queue(sigmask(SIGCONT), &signal->shared_pending); 868 t = p; 869 do { 870 rm_from_queue(sigmask(SIGCONT), &t->pending); 871 } while_each_thread(p, t); 872 } else if (sig == SIGCONT) { 873 unsigned int why; 874 /* 875 * Remove all stop signals from all queues, wake all threads. 876 */ 877 rm_from_queue(SIG_KERNEL_STOP_MASK, &signal->shared_pending); 878 t = p; 879 do { 880 task_clear_jobctl_pending(t, JOBCTL_STOP_PENDING); 881 rm_from_queue(SIG_KERNEL_STOP_MASK, &t->pending); 882 if (likely(!(t->ptrace & PT_SEIZED))) 883 wake_up_state(t, __TASK_STOPPED); 884 else 885 ptrace_trap_notify(t); 886 } while_each_thread(p, t); 887 888 /* 889 * Notify the parent with CLD_CONTINUED if we were stopped. 890 * 891 * If we were in the middle of a group stop, we pretend it 892 * was already finished, and then continued. Since SIGCHLD 893 * doesn't queue we report only CLD_STOPPED, as if the next 894 * CLD_CONTINUED was dropped. 895 */ 896 why = 0; 897 if (signal->flags & SIGNAL_STOP_STOPPED) 898 why |= SIGNAL_CLD_CONTINUED; 899 else if (signal->group_stop_count) 900 why |= SIGNAL_CLD_STOPPED; 901 902 if (why) { 903 /* 904 * The first thread which returns from do_signal_stop() 905 * will take ->siglock, notice SIGNAL_CLD_MASK, and 906 * notify its parent. See get_signal_to_deliver(). 907 */ 908 signal->flags = why | SIGNAL_STOP_CONTINUED; 909 signal->group_stop_count = 0; 910 signal->group_exit_code = 0; 911 } 912 } 913 914 return !sig_ignored(p, sig, force); 915 } 916 917 /* 918 * Test if P wants to take SIG. After we've checked all threads with this, 919 * it's equivalent to finding no threads not blocking SIG. Any threads not 920 * blocking SIG were ruled out because they are not running and already 921 * have pending signals. Such threads will dequeue from the shared queue 922 * as soon as they're available, so putting the signal on the shared queue 923 * will be equivalent to sending it to one such thread. 924 */ 925 static inline int wants_signal(int sig, struct task_struct *p) 926 { 927 if (sigismember(&p->blocked, sig)) 928 return 0; 929 if (p->flags & PF_EXITING) 930 return 0; 931 if (sig == SIGKILL) 932 return 1; 933 if (task_is_stopped_or_traced(p)) 934 return 0; 935 return task_curr(p) || !signal_pending(p); 936 } 937 938 static void complete_signal(int sig, struct task_struct *p, int group) 939 { 940 struct signal_struct *signal = p->signal; 941 struct task_struct *t; 942 943 /* 944 * Now find a thread we can wake up to take the signal off the queue. 945 * 946 * If the main thread wants the signal, it gets first crack. 947 * Probably the least surprising to the average bear. 948 */ 949 if (wants_signal(sig, p)) 950 t = p; 951 else if (!group || thread_group_empty(p)) 952 /* 953 * There is just one thread and it does not need to be woken. 954 * It will dequeue unblocked signals before it runs again. 955 */ 956 return; 957 else { 958 /* 959 * Otherwise try to find a suitable thread. 960 */ 961 t = signal->curr_target; 962 while (!wants_signal(sig, t)) { 963 t = next_thread(t); 964 if (t == signal->curr_target) 965 /* 966 * No thread needs to be woken. 967 * Any eligible threads will see 968 * the signal in the queue soon. 969 */ 970 return; 971 } 972 signal->curr_target = t; 973 } 974 975 /* 976 * Found a killable thread. If the signal will be fatal, 977 * then start taking the whole group down immediately. 978 */ 979 if (sig_fatal(p, sig) && 980 !(signal->flags & (SIGNAL_UNKILLABLE | SIGNAL_GROUP_EXIT)) && 981 !sigismember(&t->real_blocked, sig) && 982 (sig == SIGKILL || !t->ptrace)) { 983 /* 984 * This signal will be fatal to the whole group. 985 */ 986 if (!sig_kernel_coredump(sig)) { 987 /* 988 * Start a group exit and wake everybody up. 989 * This way we don't have other threads 990 * running and doing things after a slower 991 * thread has the fatal signal pending. 992 */ 993 signal->flags = SIGNAL_GROUP_EXIT; 994 signal->group_exit_code = sig; 995 signal->group_stop_count = 0; 996 t = p; 997 do { 998 task_clear_jobctl_pending(t, JOBCTL_PENDING_MASK); 999 sigaddset(&t->pending.signal, SIGKILL); 1000 signal_wake_up(t, 1); 1001 } while_each_thread(p, t); 1002 return; 1003 } 1004 } 1005 1006 /* 1007 * The signal is already in the shared-pending queue. 1008 * Tell the chosen thread to wake up and dequeue it. 1009 */ 1010 signal_wake_up(t, sig == SIGKILL); 1011 return; 1012 } 1013 1014 static inline int legacy_queue(struct sigpending *signals, int sig) 1015 { 1016 return (sig < SIGRTMIN) && sigismember(&signals->signal, sig); 1017 } 1018 1019 #ifdef CONFIG_USER_NS 1020 static inline void userns_fixup_signal_uid(struct siginfo *info, struct task_struct *t) 1021 { 1022 if (current_user_ns() == task_cred_xxx(t, user_ns)) 1023 return; 1024 1025 if (SI_FROMKERNEL(info)) 1026 return; 1027 1028 rcu_read_lock(); 1029 info->si_uid = from_kuid_munged(task_cred_xxx(t, user_ns), 1030 make_kuid(current_user_ns(), info->si_uid)); 1031 rcu_read_unlock(); 1032 } 1033 #else 1034 static inline void userns_fixup_signal_uid(struct siginfo *info, struct task_struct *t) 1035 { 1036 return; 1037 } 1038 #endif 1039 1040 static int __send_signal(int sig, struct siginfo *info, struct task_struct *t, 1041 int group, int from_ancestor_ns) 1042 { 1043 struct sigpending *pending; 1044 struct sigqueue *q; 1045 int override_rlimit; 1046 int ret = 0, result; 1047 1048 assert_spin_locked(&t->sighand->siglock); 1049 1050 result = TRACE_SIGNAL_IGNORED; 1051 if (!prepare_signal(sig, t, 1052 from_ancestor_ns || (info == SEND_SIG_FORCED))) 1053 goto ret; 1054 1055 pending = group ? &t->signal->shared_pending : &t->pending; 1056 /* 1057 * Short-circuit ignored signals and support queuing 1058 * exactly one non-rt signal, so that we can get more 1059 * detailed information about the cause of the signal. 1060 */ 1061 result = TRACE_SIGNAL_ALREADY_PENDING; 1062 if (legacy_queue(pending, sig)) 1063 goto ret; 1064 1065 result = TRACE_SIGNAL_DELIVERED; 1066 /* 1067 * fast-pathed signals for kernel-internal things like SIGSTOP 1068 * or SIGKILL. 1069 */ 1070 if (info == SEND_SIG_FORCED) 1071 goto out_set; 1072 1073 /* 1074 * Real-time signals must be queued if sent by sigqueue, or 1075 * some other real-time mechanism. It is implementation 1076 * defined whether kill() does so. We attempt to do so, on 1077 * the principle of least surprise, but since kill is not 1078 * allowed to fail with EAGAIN when low on memory we just 1079 * make sure at least one signal gets delivered and don't 1080 * pass on the info struct. 1081 */ 1082 if (sig < SIGRTMIN) 1083 override_rlimit = (is_si_special(info) || info->si_code >= 0); 1084 else 1085 override_rlimit = 0; 1086 1087 q = __sigqueue_alloc(sig, t, GFP_ATOMIC | __GFP_NOTRACK_FALSE_POSITIVE, 1088 override_rlimit); 1089 if (q) { 1090 list_add_tail(&q->list, &pending->list); 1091 switch ((unsigned long) info) { 1092 case (unsigned long) SEND_SIG_NOINFO: 1093 q->info.si_signo = sig; 1094 q->info.si_errno = 0; 1095 q->info.si_code = SI_USER; 1096 q->info.si_pid = task_tgid_nr_ns(current, 1097 task_active_pid_ns(t)); 1098 q->info.si_uid = from_kuid_munged(current_user_ns(), current_uid()); 1099 break; 1100 case (unsigned long) SEND_SIG_PRIV: 1101 q->info.si_signo = sig; 1102 q->info.si_errno = 0; 1103 q->info.si_code = SI_KERNEL; 1104 q->info.si_pid = 0; 1105 q->info.si_uid = 0; 1106 break; 1107 default: 1108 copy_siginfo(&q->info, info); 1109 if (from_ancestor_ns) 1110 q->info.si_pid = 0; 1111 break; 1112 } 1113 1114 userns_fixup_signal_uid(&q->info, t); 1115 1116 } else if (!is_si_special(info)) { 1117 if (sig >= SIGRTMIN && info->si_code != SI_USER) { 1118 /* 1119 * Queue overflow, abort. We may abort if the 1120 * signal was rt and sent by user using something 1121 * other than kill(). 1122 */ 1123 result = TRACE_SIGNAL_OVERFLOW_FAIL; 1124 ret = -EAGAIN; 1125 goto ret; 1126 } else { 1127 /* 1128 * This is a silent loss of information. We still 1129 * send the signal, but the *info bits are lost. 1130 */ 1131 result = TRACE_SIGNAL_LOSE_INFO; 1132 } 1133 } 1134 1135 out_set: 1136 signalfd_notify(t, sig); 1137 sigaddset(&pending->signal, sig); 1138 complete_signal(sig, t, group); 1139 ret: 1140 trace_signal_generate(sig, info, t, group, result); 1141 return ret; 1142 } 1143 1144 static int send_signal(int sig, struct siginfo *info, struct task_struct *t, 1145 int group) 1146 { 1147 int from_ancestor_ns = 0; 1148 1149 #ifdef CONFIG_PID_NS 1150 from_ancestor_ns = si_fromuser(info) && 1151 !task_pid_nr_ns(current, task_active_pid_ns(t)); 1152 #endif 1153 1154 return __send_signal(sig, info, t, group, from_ancestor_ns); 1155 } 1156 1157 static void print_fatal_signal(int signr) 1158 { 1159 struct pt_regs *regs = signal_pt_regs(); 1160 printk("%s/%d: potentially unexpected fatal signal %d.\n", 1161 current->comm, task_pid_nr(current), signr); 1162 1163 #if defined(__i386__) && !defined(__arch_um__) 1164 printk("code at %08lx: ", regs->ip); 1165 { 1166 int i; 1167 for (i = 0; i < 16; i++) { 1168 unsigned char insn; 1169 1170 if (get_user(insn, (unsigned char *)(regs->ip + i))) 1171 break; 1172 printk("%02x ", insn); 1173 } 1174 } 1175 #endif 1176 printk("\n"); 1177 preempt_disable(); 1178 show_regs(regs); 1179 preempt_enable(); 1180 } 1181 1182 static int __init setup_print_fatal_signals(char *str) 1183 { 1184 get_option (&str, &print_fatal_signals); 1185 1186 return 1; 1187 } 1188 1189 __setup("print-fatal-signals=", setup_print_fatal_signals); 1190 1191 int 1192 __group_send_sig_info(int sig, struct siginfo *info, struct task_struct *p) 1193 { 1194 return send_signal(sig, info, p, 1); 1195 } 1196 1197 static int 1198 specific_send_sig_info(int sig, struct siginfo *info, struct task_struct *t) 1199 { 1200 return send_signal(sig, info, t, 0); 1201 } 1202 1203 int do_send_sig_info(int sig, struct siginfo *info, struct task_struct *p, 1204 bool group) 1205 { 1206 unsigned long flags; 1207 int ret = -ESRCH; 1208 1209 if (lock_task_sighand(p, &flags)) { 1210 ret = send_signal(sig, info, p, group); 1211 unlock_task_sighand(p, &flags); 1212 } 1213 1214 return ret; 1215 } 1216 1217 /* 1218 * Force a signal that the process can't ignore: if necessary 1219 * we unblock the signal and change any SIG_IGN to SIG_DFL. 1220 * 1221 * Note: If we unblock the signal, we always reset it to SIG_DFL, 1222 * since we do not want to have a signal handler that was blocked 1223 * be invoked when user space had explicitly blocked it. 1224 * 1225 * We don't want to have recursive SIGSEGV's etc, for example, 1226 * that is why we also clear SIGNAL_UNKILLABLE. 1227 */ 1228 int 1229 force_sig_info(int sig, struct siginfo *info, struct task_struct *t) 1230 { 1231 unsigned long int flags; 1232 int ret, blocked, ignored; 1233 struct k_sigaction *action; 1234 1235 spin_lock_irqsave(&t->sighand->siglock, flags); 1236 action = &t->sighand->action[sig-1]; 1237 ignored = action->sa.sa_handler == SIG_IGN; 1238 blocked = sigismember(&t->blocked, sig); 1239 if (blocked || ignored) { 1240 action->sa.sa_handler = SIG_DFL; 1241 if (blocked) { 1242 sigdelset(&t->blocked, sig); 1243 recalc_sigpending_and_wake(t); 1244 } 1245 } 1246 if (action->sa.sa_handler == SIG_DFL) 1247 t->signal->flags &= ~SIGNAL_UNKILLABLE; 1248 ret = specific_send_sig_info(sig, info, t); 1249 spin_unlock_irqrestore(&t->sighand->siglock, flags); 1250 1251 return ret; 1252 } 1253 1254 /* 1255 * Nuke all other threads in the group. 1256 */ 1257 int zap_other_threads(struct task_struct *p) 1258 { 1259 struct task_struct *t = p; 1260 int count = 0; 1261 1262 p->signal->group_stop_count = 0; 1263 1264 while_each_thread(p, t) { 1265 task_clear_jobctl_pending(t, JOBCTL_PENDING_MASK); 1266 count++; 1267 1268 /* Don't bother with already dead threads */ 1269 if (t->exit_state) 1270 continue; 1271 sigaddset(&t->pending.signal, SIGKILL); 1272 signal_wake_up(t, 1); 1273 } 1274 1275 return count; 1276 } 1277 1278 struct sighand_struct *__lock_task_sighand(struct task_struct *tsk, 1279 unsigned long *flags) 1280 { 1281 struct sighand_struct *sighand; 1282 1283 for (;;) { 1284 local_irq_save(*flags); 1285 rcu_read_lock(); 1286 sighand = rcu_dereference(tsk->sighand); 1287 if (unlikely(sighand == NULL)) { 1288 rcu_read_unlock(); 1289 local_irq_restore(*flags); 1290 break; 1291 } 1292 1293 spin_lock(&sighand->siglock); 1294 if (likely(sighand == tsk->sighand)) { 1295 rcu_read_unlock(); 1296 break; 1297 } 1298 spin_unlock(&sighand->siglock); 1299 rcu_read_unlock(); 1300 local_irq_restore(*flags); 1301 } 1302 1303 return sighand; 1304 } 1305 1306 /* 1307 * send signal info to all the members of a group 1308 */ 1309 int group_send_sig_info(int sig, struct siginfo *info, struct task_struct *p) 1310 { 1311 int ret; 1312 1313 rcu_read_lock(); 1314 ret = check_kill_permission(sig, info, p); 1315 rcu_read_unlock(); 1316 1317 if (!ret && sig) 1318 ret = do_send_sig_info(sig, info, p, true); 1319 1320 return ret; 1321 } 1322 1323 /* 1324 * __kill_pgrp_info() sends a signal to a process group: this is what the tty 1325 * control characters do (^C, ^Z etc) 1326 * - the caller must hold at least a readlock on tasklist_lock 1327 */ 1328 int __kill_pgrp_info(int sig, struct siginfo *info, struct pid *pgrp) 1329 { 1330 struct task_struct *p = NULL; 1331 int retval, success; 1332 1333 success = 0; 1334 retval = -ESRCH; 1335 do_each_pid_task(pgrp, PIDTYPE_PGID, p) { 1336 int err = group_send_sig_info(sig, info, p); 1337 success |= !err; 1338 retval = err; 1339 } while_each_pid_task(pgrp, PIDTYPE_PGID, p); 1340 return success ? 0 : retval; 1341 } 1342 1343 int kill_pid_info(int sig, struct siginfo *info, struct pid *pid) 1344 { 1345 int error = -ESRCH; 1346 struct task_struct *p; 1347 1348 rcu_read_lock(); 1349 retry: 1350 p = pid_task(pid, PIDTYPE_PID); 1351 if (p) { 1352 error = group_send_sig_info(sig, info, p); 1353 if (unlikely(error == -ESRCH)) 1354 /* 1355 * The task was unhashed in between, try again. 1356 * If it is dead, pid_task() will return NULL, 1357 * if we race with de_thread() it will find the 1358 * new leader. 1359 */ 1360 goto retry; 1361 } 1362 rcu_read_unlock(); 1363 1364 return error; 1365 } 1366 1367 int kill_proc_info(int sig, struct siginfo *info, pid_t pid) 1368 { 1369 int error; 1370 rcu_read_lock(); 1371 error = kill_pid_info(sig, info, find_vpid(pid)); 1372 rcu_read_unlock(); 1373 return error; 1374 } 1375 1376 static int kill_as_cred_perm(const struct cred *cred, 1377 struct task_struct *target) 1378 { 1379 const struct cred *pcred = __task_cred(target); 1380 if (!uid_eq(cred->euid, pcred->suid) && !uid_eq(cred->euid, pcred->uid) && 1381 !uid_eq(cred->uid, pcred->suid) && !uid_eq(cred->uid, pcred->uid)) 1382 return 0; 1383 return 1; 1384 } 1385 1386 /* like kill_pid_info(), but doesn't use uid/euid of "current" */ 1387 int kill_pid_info_as_cred(int sig, struct siginfo *info, struct pid *pid, 1388 const struct cred *cred, u32 secid) 1389 { 1390 int ret = -EINVAL; 1391 struct task_struct *p; 1392 unsigned long flags; 1393 1394 if (!valid_signal(sig)) 1395 return ret; 1396 1397 rcu_read_lock(); 1398 p = pid_task(pid, PIDTYPE_PID); 1399 if (!p) { 1400 ret = -ESRCH; 1401 goto out_unlock; 1402 } 1403 if (si_fromuser(info) && !kill_as_cred_perm(cred, p)) { 1404 ret = -EPERM; 1405 goto out_unlock; 1406 } 1407 ret = security_task_kill(p, info, sig, secid); 1408 if (ret) 1409 goto out_unlock; 1410 1411 if (sig) { 1412 if (lock_task_sighand(p, &flags)) { 1413 ret = __send_signal(sig, info, p, 1, 0); 1414 unlock_task_sighand(p, &flags); 1415 } else 1416 ret = -ESRCH; 1417 } 1418 out_unlock: 1419 rcu_read_unlock(); 1420 return ret; 1421 } 1422 EXPORT_SYMBOL_GPL(kill_pid_info_as_cred); 1423 1424 /* 1425 * kill_something_info() interprets pid in interesting ways just like kill(2). 1426 * 1427 * POSIX specifies that kill(-1,sig) is unspecified, but what we have 1428 * is probably wrong. Should make it like BSD or SYSV. 1429 */ 1430 1431 static int kill_something_info(int sig, struct siginfo *info, pid_t pid) 1432 { 1433 int ret; 1434 1435 if (pid > 0) { 1436 rcu_read_lock(); 1437 ret = kill_pid_info(sig, info, find_vpid(pid)); 1438 rcu_read_unlock(); 1439 return ret; 1440 } 1441 1442 read_lock(&tasklist_lock); 1443 if (pid != -1) { 1444 ret = __kill_pgrp_info(sig, info, 1445 pid ? find_vpid(-pid) : task_pgrp(current)); 1446 } else { 1447 int retval = 0, count = 0; 1448 struct task_struct * p; 1449 1450 for_each_process(p) { 1451 if (task_pid_vnr(p) > 1 && 1452 !same_thread_group(p, current)) { 1453 int err = group_send_sig_info(sig, info, p); 1454 ++count; 1455 if (err != -EPERM) 1456 retval = err; 1457 } 1458 } 1459 ret = count ? retval : -ESRCH; 1460 } 1461 read_unlock(&tasklist_lock); 1462 1463 return ret; 1464 } 1465 1466 /* 1467 * These are for backward compatibility with the rest of the kernel source. 1468 */ 1469 1470 int send_sig_info(int sig, struct siginfo *info, struct task_struct *p) 1471 { 1472 /* 1473 * Make sure legacy kernel users don't send in bad values 1474 * (normal paths check this in check_kill_permission). 1475 */ 1476 if (!valid_signal(sig)) 1477 return -EINVAL; 1478 1479 return do_send_sig_info(sig, info, p, false); 1480 } 1481 1482 #define __si_special(priv) \ 1483 ((priv) ? SEND_SIG_PRIV : SEND_SIG_NOINFO) 1484 1485 int 1486 send_sig(int sig, struct task_struct *p, int priv) 1487 { 1488 return send_sig_info(sig, __si_special(priv), p); 1489 } 1490 1491 void 1492 force_sig(int sig, struct task_struct *p) 1493 { 1494 force_sig_info(sig, SEND_SIG_PRIV, p); 1495 } 1496 1497 /* 1498 * When things go south during signal handling, we 1499 * will force a SIGSEGV. And if the signal that caused 1500 * the problem was already a SIGSEGV, we'll want to 1501 * make sure we don't even try to deliver the signal.. 1502 */ 1503 int 1504 force_sigsegv(int sig, struct task_struct *p) 1505 { 1506 if (sig == SIGSEGV) { 1507 unsigned long flags; 1508 spin_lock_irqsave(&p->sighand->siglock, flags); 1509 p->sighand->action[sig - 1].sa.sa_handler = SIG_DFL; 1510 spin_unlock_irqrestore(&p->sighand->siglock, flags); 1511 } 1512 force_sig(SIGSEGV, p); 1513 return 0; 1514 } 1515 1516 int kill_pgrp(struct pid *pid, int sig, int priv) 1517 { 1518 int ret; 1519 1520 read_lock(&tasklist_lock); 1521 ret = __kill_pgrp_info(sig, __si_special(priv), pid); 1522 read_unlock(&tasklist_lock); 1523 1524 return ret; 1525 } 1526 EXPORT_SYMBOL(kill_pgrp); 1527 1528 int kill_pid(struct pid *pid, int sig, int priv) 1529 { 1530 return kill_pid_info(sig, __si_special(priv), pid); 1531 } 1532 EXPORT_SYMBOL(kill_pid); 1533 1534 /* 1535 * These functions support sending signals using preallocated sigqueue 1536 * structures. This is needed "because realtime applications cannot 1537 * afford to lose notifications of asynchronous events, like timer 1538 * expirations or I/O completions". In the case of POSIX Timers 1539 * we allocate the sigqueue structure from the timer_create. If this 1540 * allocation fails we are able to report the failure to the application 1541 * with an EAGAIN error. 1542 */ 1543 struct sigqueue *sigqueue_alloc(void) 1544 { 1545 struct sigqueue *q = __sigqueue_alloc(-1, current, GFP_KERNEL, 0); 1546 1547 if (q) 1548 q->flags |= SIGQUEUE_PREALLOC; 1549 1550 return q; 1551 } 1552 1553 void sigqueue_free(struct sigqueue *q) 1554 { 1555 unsigned long flags; 1556 spinlock_t *lock = ¤t->sighand->siglock; 1557 1558 BUG_ON(!(q->flags & SIGQUEUE_PREALLOC)); 1559 /* 1560 * We must hold ->siglock while testing q->list 1561 * to serialize with collect_signal() or with 1562 * __exit_signal()->flush_sigqueue(). 1563 */ 1564 spin_lock_irqsave(lock, flags); 1565 q->flags &= ~SIGQUEUE_PREALLOC; 1566 /* 1567 * If it is queued it will be freed when dequeued, 1568 * like the "regular" sigqueue. 1569 */ 1570 if (!list_empty(&q->list)) 1571 q = NULL; 1572 spin_unlock_irqrestore(lock, flags); 1573 1574 if (q) 1575 __sigqueue_free(q); 1576 } 1577 1578 int send_sigqueue(struct sigqueue *q, struct task_struct *t, int group) 1579 { 1580 int sig = q->info.si_signo; 1581 struct sigpending *pending; 1582 unsigned long flags; 1583 int ret, result; 1584 1585 BUG_ON(!(q->flags & SIGQUEUE_PREALLOC)); 1586 1587 ret = -1; 1588 if (!likely(lock_task_sighand(t, &flags))) 1589 goto ret; 1590 1591 ret = 1; /* the signal is ignored */ 1592 result = TRACE_SIGNAL_IGNORED; 1593 if (!prepare_signal(sig, t, false)) 1594 goto out; 1595 1596 ret = 0; 1597 if (unlikely(!list_empty(&q->list))) { 1598 /* 1599 * If an SI_TIMER entry is already queue just increment 1600 * the overrun count. 1601 */ 1602 BUG_ON(q->info.si_code != SI_TIMER); 1603 q->info.si_overrun++; 1604 result = TRACE_SIGNAL_ALREADY_PENDING; 1605 goto out; 1606 } 1607 q->info.si_overrun = 0; 1608 1609 signalfd_notify(t, sig); 1610 pending = group ? &t->signal->shared_pending : &t->pending; 1611 list_add_tail(&q->list, &pending->list); 1612 sigaddset(&pending->signal, sig); 1613 complete_signal(sig, t, group); 1614 result = TRACE_SIGNAL_DELIVERED; 1615 out: 1616 trace_signal_generate(sig, &q->info, t, group, result); 1617 unlock_task_sighand(t, &flags); 1618 ret: 1619 return ret; 1620 } 1621 1622 /* 1623 * Let a parent know about the death of a child. 1624 * For a stopped/continued status change, use do_notify_parent_cldstop instead. 1625 * 1626 * Returns true if our parent ignored us and so we've switched to 1627 * self-reaping. 1628 */ 1629 bool do_notify_parent(struct task_struct *tsk, int sig) 1630 { 1631 struct siginfo info; 1632 unsigned long flags; 1633 struct sighand_struct *psig; 1634 bool autoreap = false; 1635 1636 BUG_ON(sig == -1); 1637 1638 /* do_notify_parent_cldstop should have been called instead. */ 1639 BUG_ON(task_is_stopped_or_traced(tsk)); 1640 1641 BUG_ON(!tsk->ptrace && 1642 (tsk->group_leader != tsk || !thread_group_empty(tsk))); 1643 1644 if (sig != SIGCHLD) { 1645 /* 1646 * This is only possible if parent == real_parent. 1647 * Check if it has changed security domain. 1648 */ 1649 if (tsk->parent_exec_id != tsk->parent->self_exec_id) 1650 sig = SIGCHLD; 1651 } 1652 1653 info.si_signo = sig; 1654 info.si_errno = 0; 1655 /* 1656 * We are under tasklist_lock here so our parent is tied to 1657 * us and cannot change. 1658 * 1659 * task_active_pid_ns will always return the same pid namespace 1660 * until a task passes through release_task. 1661 * 1662 * write_lock() currently calls preempt_disable() which is the 1663 * same as rcu_read_lock(), but according to Oleg, this is not 1664 * correct to rely on this 1665 */ 1666 rcu_read_lock(); 1667 info.si_pid = task_pid_nr_ns(tsk, task_active_pid_ns(tsk->parent)); 1668 info.si_uid = from_kuid_munged(task_cred_xxx(tsk->parent, user_ns), 1669 task_uid(tsk)); 1670 rcu_read_unlock(); 1671 1672 info.si_utime = cputime_to_clock_t(tsk->utime + tsk->signal->utime); 1673 info.si_stime = cputime_to_clock_t(tsk->stime + tsk->signal->stime); 1674 1675 info.si_status = tsk->exit_code & 0x7f; 1676 if (tsk->exit_code & 0x80) 1677 info.si_code = CLD_DUMPED; 1678 else if (tsk->exit_code & 0x7f) 1679 info.si_code = CLD_KILLED; 1680 else { 1681 info.si_code = CLD_EXITED; 1682 info.si_status = tsk->exit_code >> 8; 1683 } 1684 1685 psig = tsk->parent->sighand; 1686 spin_lock_irqsave(&psig->siglock, flags); 1687 if (!tsk->ptrace && sig == SIGCHLD && 1688 (psig->action[SIGCHLD-1].sa.sa_handler == SIG_IGN || 1689 (psig->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDWAIT))) { 1690 /* 1691 * We are exiting and our parent doesn't care. POSIX.1 1692 * defines special semantics for setting SIGCHLD to SIG_IGN 1693 * or setting the SA_NOCLDWAIT flag: we should be reaped 1694 * automatically and not left for our parent's wait4 call. 1695 * Rather than having the parent do it as a magic kind of 1696 * signal handler, we just set this to tell do_exit that we 1697 * can be cleaned up without becoming a zombie. Note that 1698 * we still call __wake_up_parent in this case, because a 1699 * blocked sys_wait4 might now return -ECHILD. 1700 * 1701 * Whether we send SIGCHLD or not for SA_NOCLDWAIT 1702 * is implementation-defined: we do (if you don't want 1703 * it, just use SIG_IGN instead). 1704 */ 1705 autoreap = true; 1706 if (psig->action[SIGCHLD-1].sa.sa_handler == SIG_IGN) 1707 sig = 0; 1708 } 1709 if (valid_signal(sig) && sig) 1710 __group_send_sig_info(sig, &info, tsk->parent); 1711 __wake_up_parent(tsk, tsk->parent); 1712 spin_unlock_irqrestore(&psig->siglock, flags); 1713 1714 return autoreap; 1715 } 1716 1717 /** 1718 * do_notify_parent_cldstop - notify parent of stopped/continued state change 1719 * @tsk: task reporting the state change 1720 * @for_ptracer: the notification is for ptracer 1721 * @why: CLD_{CONTINUED|STOPPED|TRAPPED} to report 1722 * 1723 * Notify @tsk's parent that the stopped/continued state has changed. If 1724 * @for_ptracer is %false, @tsk's group leader notifies to its real parent. 1725 * If %true, @tsk reports to @tsk->parent which should be the ptracer. 1726 * 1727 * CONTEXT: 1728 * Must be called with tasklist_lock at least read locked. 1729 */ 1730 static void do_notify_parent_cldstop(struct task_struct *tsk, 1731 bool for_ptracer, int why) 1732 { 1733 struct siginfo info; 1734 unsigned long flags; 1735 struct task_struct *parent; 1736 struct sighand_struct *sighand; 1737 1738 if (for_ptracer) { 1739 parent = tsk->parent; 1740 } else { 1741 tsk = tsk->group_leader; 1742 parent = tsk->real_parent; 1743 } 1744 1745 info.si_signo = SIGCHLD; 1746 info.si_errno = 0; 1747 /* 1748 * see comment in do_notify_parent() about the following 4 lines 1749 */ 1750 rcu_read_lock(); 1751 info.si_pid = task_pid_nr_ns(tsk, task_active_pid_ns(parent)); 1752 info.si_uid = from_kuid_munged(task_cred_xxx(parent, user_ns), task_uid(tsk)); 1753 rcu_read_unlock(); 1754 1755 info.si_utime = cputime_to_clock_t(tsk->utime); 1756 info.si_stime = cputime_to_clock_t(tsk->stime); 1757 1758 info.si_code = why; 1759 switch (why) { 1760 case CLD_CONTINUED: 1761 info.si_status = SIGCONT; 1762 break; 1763 case CLD_STOPPED: 1764 info.si_status = tsk->signal->group_exit_code & 0x7f; 1765 break; 1766 case CLD_TRAPPED: 1767 info.si_status = tsk->exit_code & 0x7f; 1768 break; 1769 default: 1770 BUG(); 1771 } 1772 1773 sighand = parent->sighand; 1774 spin_lock_irqsave(&sighand->siglock, flags); 1775 if (sighand->action[SIGCHLD-1].sa.sa_handler != SIG_IGN && 1776 !(sighand->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDSTOP)) 1777 __group_send_sig_info(SIGCHLD, &info, parent); 1778 /* 1779 * Even if SIGCHLD is not generated, we must wake up wait4 calls. 1780 */ 1781 __wake_up_parent(tsk, parent); 1782 spin_unlock_irqrestore(&sighand->siglock, flags); 1783 } 1784 1785 static inline int may_ptrace_stop(void) 1786 { 1787 if (!likely(current->ptrace)) 1788 return 0; 1789 /* 1790 * Are we in the middle of do_coredump? 1791 * If so and our tracer is also part of the coredump stopping 1792 * is a deadlock situation, and pointless because our tracer 1793 * is dead so don't allow us to stop. 1794 * If SIGKILL was already sent before the caller unlocked 1795 * ->siglock we must see ->core_state != NULL. Otherwise it 1796 * is safe to enter schedule(). 1797 * 1798 * This is almost outdated, a task with the pending SIGKILL can't 1799 * block in TASK_TRACED. But PTRACE_EVENT_EXIT can be reported 1800 * after SIGKILL was already dequeued. 1801 */ 1802 if (unlikely(current->mm->core_state) && 1803 unlikely(current->mm == current->parent->mm)) 1804 return 0; 1805 1806 return 1; 1807 } 1808 1809 /* 1810 * Return non-zero if there is a SIGKILL that should be waking us up. 1811 * Called with the siglock held. 1812 */ 1813 static int sigkill_pending(struct task_struct *tsk) 1814 { 1815 return sigismember(&tsk->pending.signal, SIGKILL) || 1816 sigismember(&tsk->signal->shared_pending.signal, SIGKILL); 1817 } 1818 1819 /* 1820 * This must be called with current->sighand->siglock held. 1821 * 1822 * This should be the path for all ptrace stops. 1823 * We always set current->last_siginfo while stopped here. 1824 * That makes it a way to test a stopped process for 1825 * being ptrace-stopped vs being job-control-stopped. 1826 * 1827 * If we actually decide not to stop at all because the tracer 1828 * is gone, we keep current->exit_code unless clear_code. 1829 */ 1830 static void ptrace_stop(int exit_code, int why, int clear_code, siginfo_t *info) 1831 __releases(¤t->sighand->siglock) 1832 __acquires(¤t->sighand->siglock) 1833 { 1834 bool gstop_done = false; 1835 1836 if (arch_ptrace_stop_needed(exit_code, info)) { 1837 /* 1838 * The arch code has something special to do before a 1839 * ptrace stop. This is allowed to block, e.g. for faults 1840 * on user stack pages. We can't keep the siglock while 1841 * calling arch_ptrace_stop, so we must release it now. 1842 * To preserve proper semantics, we must do this before 1843 * any signal bookkeeping like checking group_stop_count. 1844 * Meanwhile, a SIGKILL could come in before we retake the 1845 * siglock. That must prevent us from sleeping in TASK_TRACED. 1846 * So after regaining the lock, we must check for SIGKILL. 1847 */ 1848 spin_unlock_irq(¤t->sighand->siglock); 1849 arch_ptrace_stop(exit_code, info); 1850 spin_lock_irq(¤t->sighand->siglock); 1851 if (sigkill_pending(current)) 1852 return; 1853 } 1854 1855 /* 1856 * We're committing to trapping. TRACED should be visible before 1857 * TRAPPING is cleared; otherwise, the tracer might fail do_wait(). 1858 * Also, transition to TRACED and updates to ->jobctl should be 1859 * atomic with respect to siglock and should be done after the arch 1860 * hook as siglock is released and regrabbed across it. 1861 */ 1862 set_current_state(TASK_TRACED); 1863 1864 current->last_siginfo = info; 1865 current->exit_code = exit_code; 1866 1867 /* 1868 * If @why is CLD_STOPPED, we're trapping to participate in a group 1869 * stop. Do the bookkeeping. Note that if SIGCONT was delievered 1870 * across siglock relocks since INTERRUPT was scheduled, PENDING 1871 * could be clear now. We act as if SIGCONT is received after 1872 * TASK_TRACED is entered - ignore it. 1873 */ 1874 if (why == CLD_STOPPED && (current->jobctl & JOBCTL_STOP_PENDING)) 1875 gstop_done = task_participate_group_stop(current); 1876 1877 /* any trap clears pending STOP trap, STOP trap clears NOTIFY */ 1878 task_clear_jobctl_pending(current, JOBCTL_TRAP_STOP); 1879 if (info && info->si_code >> 8 == PTRACE_EVENT_STOP) 1880 task_clear_jobctl_pending(current, JOBCTL_TRAP_NOTIFY); 1881 1882 /* entering a trap, clear TRAPPING */ 1883 task_clear_jobctl_trapping(current); 1884 1885 spin_unlock_irq(¤t->sighand->siglock); 1886 read_lock(&tasklist_lock); 1887 if (may_ptrace_stop()) { 1888 /* 1889 * Notify parents of the stop. 1890 * 1891 * While ptraced, there are two parents - the ptracer and 1892 * the real_parent of the group_leader. The ptracer should 1893 * know about every stop while the real parent is only 1894 * interested in the completion of group stop. The states 1895 * for the two don't interact with each other. Notify 1896 * separately unless they're gonna be duplicates. 1897 */ 1898 do_notify_parent_cldstop(current, true, why); 1899 if (gstop_done && ptrace_reparented(current)) 1900 do_notify_parent_cldstop(current, false, why); 1901 1902 /* 1903 * Don't want to allow preemption here, because 1904 * sys_ptrace() needs this task to be inactive. 1905 * 1906 * XXX: implement read_unlock_no_resched(). 1907 */ 1908 preempt_disable(); 1909 read_unlock(&tasklist_lock); 1910 preempt_enable_no_resched(); 1911 freezable_schedule(); 1912 } else { 1913 /* 1914 * By the time we got the lock, our tracer went away. 1915 * Don't drop the lock yet, another tracer may come. 1916 * 1917 * If @gstop_done, the ptracer went away between group stop 1918 * completion and here. During detach, it would have set 1919 * JOBCTL_STOP_PENDING on us and we'll re-enter 1920 * TASK_STOPPED in do_signal_stop() on return, so notifying 1921 * the real parent of the group stop completion is enough. 1922 */ 1923 if (gstop_done) 1924 do_notify_parent_cldstop(current, false, why); 1925 1926 /* tasklist protects us from ptrace_freeze_traced() */ 1927 __set_current_state(TASK_RUNNING); 1928 if (clear_code) 1929 current->exit_code = 0; 1930 read_unlock(&tasklist_lock); 1931 } 1932 1933 /* 1934 * We are back. Now reacquire the siglock before touching 1935 * last_siginfo, so that we are sure to have synchronized with 1936 * any signal-sending on another CPU that wants to examine it. 1937 */ 1938 spin_lock_irq(¤t->sighand->siglock); 1939 current->last_siginfo = NULL; 1940 1941 /* LISTENING can be set only during STOP traps, clear it */ 1942 current->jobctl &= ~JOBCTL_LISTENING; 1943 1944 /* 1945 * Queued signals ignored us while we were stopped for tracing. 1946 * So check for any that we should take before resuming user mode. 1947 * This sets TIF_SIGPENDING, but never clears it. 1948 */ 1949 recalc_sigpending_tsk(current); 1950 } 1951 1952 static void ptrace_do_notify(int signr, int exit_code, int why) 1953 { 1954 siginfo_t info; 1955 1956 memset(&info, 0, sizeof info); 1957 info.si_signo = signr; 1958 info.si_code = exit_code; 1959 info.si_pid = task_pid_vnr(current); 1960 info.si_uid = from_kuid_munged(current_user_ns(), current_uid()); 1961 1962 /* Let the debugger run. */ 1963 ptrace_stop(exit_code, why, 1, &info); 1964 } 1965 1966 void ptrace_notify(int exit_code) 1967 { 1968 BUG_ON((exit_code & (0x7f | ~0xffff)) != SIGTRAP); 1969 if (unlikely(current->task_works)) 1970 task_work_run(); 1971 1972 spin_lock_irq(¤t->sighand->siglock); 1973 ptrace_do_notify(SIGTRAP, exit_code, CLD_TRAPPED); 1974 spin_unlock_irq(¤t->sighand->siglock); 1975 } 1976 1977 /** 1978 * do_signal_stop - handle group stop for SIGSTOP and other stop signals 1979 * @signr: signr causing group stop if initiating 1980 * 1981 * If %JOBCTL_STOP_PENDING is not set yet, initiate group stop with @signr 1982 * and participate in it. If already set, participate in the existing 1983 * group stop. If participated in a group stop (and thus slept), %true is 1984 * returned with siglock released. 1985 * 1986 * If ptraced, this function doesn't handle stop itself. Instead, 1987 * %JOBCTL_TRAP_STOP is scheduled and %false is returned with siglock 1988 * untouched. The caller must ensure that INTERRUPT trap handling takes 1989 * places afterwards. 1990 * 1991 * CONTEXT: 1992 * Must be called with @current->sighand->siglock held, which is released 1993 * on %true return. 1994 * 1995 * RETURNS: 1996 * %false if group stop is already cancelled or ptrace trap is scheduled. 1997 * %true if participated in group stop. 1998 */ 1999 static bool do_signal_stop(int signr) 2000 __releases(¤t->sighand->siglock) 2001 { 2002 struct signal_struct *sig = current->signal; 2003 2004 if (!(current->jobctl & JOBCTL_STOP_PENDING)) { 2005 unsigned int gstop = JOBCTL_STOP_PENDING | JOBCTL_STOP_CONSUME; 2006 struct task_struct *t; 2007 2008 /* signr will be recorded in task->jobctl for retries */ 2009 WARN_ON_ONCE(signr & ~JOBCTL_STOP_SIGMASK); 2010 2011 if (!likely(current->jobctl & JOBCTL_STOP_DEQUEUED) || 2012 unlikely(signal_group_exit(sig))) 2013 return false; 2014 /* 2015 * There is no group stop already in progress. We must 2016 * initiate one now. 2017 * 2018 * While ptraced, a task may be resumed while group stop is 2019 * still in effect and then receive a stop signal and 2020 * initiate another group stop. This deviates from the 2021 * usual behavior as two consecutive stop signals can't 2022 * cause two group stops when !ptraced. That is why we 2023 * also check !task_is_stopped(t) below. 2024 * 2025 * The condition can be distinguished by testing whether 2026 * SIGNAL_STOP_STOPPED is already set. Don't generate 2027 * group_exit_code in such case. 2028 * 2029 * This is not necessary for SIGNAL_STOP_CONTINUED because 2030 * an intervening stop signal is required to cause two 2031 * continued events regardless of ptrace. 2032 */ 2033 if (!(sig->flags & SIGNAL_STOP_STOPPED)) 2034 sig->group_exit_code = signr; 2035 2036 sig->group_stop_count = 0; 2037 2038 if (task_set_jobctl_pending(current, signr | gstop)) 2039 sig->group_stop_count++; 2040 2041 for (t = next_thread(current); t != current; 2042 t = next_thread(t)) { 2043 /* 2044 * Setting state to TASK_STOPPED for a group 2045 * stop is always done with the siglock held, 2046 * so this check has no races. 2047 */ 2048 if (!task_is_stopped(t) && 2049 task_set_jobctl_pending(t, signr | gstop)) { 2050 sig->group_stop_count++; 2051 if (likely(!(t->ptrace & PT_SEIZED))) 2052 signal_wake_up(t, 0); 2053 else 2054 ptrace_trap_notify(t); 2055 } 2056 } 2057 } 2058 2059 if (likely(!current->ptrace)) { 2060 int notify = 0; 2061 2062 /* 2063 * If there are no other threads in the group, or if there 2064 * is a group stop in progress and we are the last to stop, 2065 * report to the parent. 2066 */ 2067 if (task_participate_group_stop(current)) 2068 notify = CLD_STOPPED; 2069 2070 __set_current_state(TASK_STOPPED); 2071 spin_unlock_irq(¤t->sighand->siglock); 2072 2073 /* 2074 * Notify the parent of the group stop completion. Because 2075 * we're not holding either the siglock or tasklist_lock 2076 * here, ptracer may attach inbetween; however, this is for 2077 * group stop and should always be delivered to the real 2078 * parent of the group leader. The new ptracer will get 2079 * its notification when this task transitions into 2080 * TASK_TRACED. 2081 */ 2082 if (notify) { 2083 read_lock(&tasklist_lock); 2084 do_notify_parent_cldstop(current, false, notify); 2085 read_unlock(&tasklist_lock); 2086 } 2087 2088 /* Now we don't run again until woken by SIGCONT or SIGKILL */ 2089 freezable_schedule(); 2090 return true; 2091 } else { 2092 /* 2093 * While ptraced, group stop is handled by STOP trap. 2094 * Schedule it and let the caller deal with it. 2095 */ 2096 task_set_jobctl_pending(current, JOBCTL_TRAP_STOP); 2097 return false; 2098 } 2099 } 2100 2101 /** 2102 * do_jobctl_trap - take care of ptrace jobctl traps 2103 * 2104 * When PT_SEIZED, it's used for both group stop and explicit 2105 * SEIZE/INTERRUPT traps. Both generate PTRACE_EVENT_STOP trap with 2106 * accompanying siginfo. If stopped, lower eight bits of exit_code contain 2107 * the stop signal; otherwise, %SIGTRAP. 2108 * 2109 * When !PT_SEIZED, it's used only for group stop trap with stop signal 2110 * number as exit_code and no siginfo. 2111 * 2112 * CONTEXT: 2113 * Must be called with @current->sighand->siglock held, which may be 2114 * released and re-acquired before returning with intervening sleep. 2115 */ 2116 static void do_jobctl_trap(void) 2117 { 2118 struct signal_struct *signal = current->signal; 2119 int signr = current->jobctl & JOBCTL_STOP_SIGMASK; 2120 2121 if (current->ptrace & PT_SEIZED) { 2122 if (!signal->group_stop_count && 2123 !(signal->flags & SIGNAL_STOP_STOPPED)) 2124 signr = SIGTRAP; 2125 WARN_ON_ONCE(!signr); 2126 ptrace_do_notify(signr, signr | (PTRACE_EVENT_STOP << 8), 2127 CLD_STOPPED); 2128 } else { 2129 WARN_ON_ONCE(!signr); 2130 ptrace_stop(signr, CLD_STOPPED, 0, NULL); 2131 current->exit_code = 0; 2132 } 2133 } 2134 2135 static int ptrace_signal(int signr, siginfo_t *info) 2136 { 2137 ptrace_signal_deliver(); 2138 /* 2139 * We do not check sig_kernel_stop(signr) but set this marker 2140 * unconditionally because we do not know whether debugger will 2141 * change signr. This flag has no meaning unless we are going 2142 * to stop after return from ptrace_stop(). In this case it will 2143 * be checked in do_signal_stop(), we should only stop if it was 2144 * not cleared by SIGCONT while we were sleeping. See also the 2145 * comment in dequeue_signal(). 2146 */ 2147 current->jobctl |= JOBCTL_STOP_DEQUEUED; 2148 ptrace_stop(signr, CLD_TRAPPED, 0, info); 2149 2150 /* We're back. Did the debugger cancel the sig? */ 2151 signr = current->exit_code; 2152 if (signr == 0) 2153 return signr; 2154 2155 current->exit_code = 0; 2156 2157 /* 2158 * Update the siginfo structure if the signal has 2159 * changed. If the debugger wanted something 2160 * specific in the siginfo structure then it should 2161 * have updated *info via PTRACE_SETSIGINFO. 2162 */ 2163 if (signr != info->si_signo) { 2164 info->si_signo = signr; 2165 info->si_errno = 0; 2166 info->si_code = SI_USER; 2167 rcu_read_lock(); 2168 info->si_pid = task_pid_vnr(current->parent); 2169 info->si_uid = from_kuid_munged(current_user_ns(), 2170 task_uid(current->parent)); 2171 rcu_read_unlock(); 2172 } 2173 2174 /* If the (new) signal is now blocked, requeue it. */ 2175 if (sigismember(¤t->blocked, signr)) { 2176 specific_send_sig_info(signr, info, current); 2177 signr = 0; 2178 } 2179 2180 return signr; 2181 } 2182 2183 int get_signal_to_deliver(siginfo_t *info, struct k_sigaction *return_ka, 2184 struct pt_regs *regs, void *cookie) 2185 { 2186 struct sighand_struct *sighand = current->sighand; 2187 struct signal_struct *signal = current->signal; 2188 int signr; 2189 2190 if (unlikely(current->task_works)) 2191 task_work_run(); 2192 2193 if (unlikely(uprobe_deny_signal())) 2194 return 0; 2195 2196 /* 2197 * Do this once, we can't return to user-mode if freezing() == T. 2198 * do_signal_stop() and ptrace_stop() do freezable_schedule() and 2199 * thus do not need another check after return. 2200 */ 2201 try_to_freeze(); 2202 2203 relock: 2204 spin_lock_irq(&sighand->siglock); 2205 /* 2206 * Every stopped thread goes here after wakeup. Check to see if 2207 * we should notify the parent, prepare_signal(SIGCONT) encodes 2208 * the CLD_ si_code into SIGNAL_CLD_MASK bits. 2209 */ 2210 if (unlikely(signal->flags & SIGNAL_CLD_MASK)) { 2211 int why; 2212 2213 if (signal->flags & SIGNAL_CLD_CONTINUED) 2214 why = CLD_CONTINUED; 2215 else 2216 why = CLD_STOPPED; 2217 2218 signal->flags &= ~SIGNAL_CLD_MASK; 2219 2220 spin_unlock_irq(&sighand->siglock); 2221 2222 /* 2223 * Notify the parent that we're continuing. This event is 2224 * always per-process and doesn't make whole lot of sense 2225 * for ptracers, who shouldn't consume the state via 2226 * wait(2) either, but, for backward compatibility, notify 2227 * the ptracer of the group leader too unless it's gonna be 2228 * a duplicate. 2229 */ 2230 read_lock(&tasklist_lock); 2231 do_notify_parent_cldstop(current, false, why); 2232 2233 if (ptrace_reparented(current->group_leader)) 2234 do_notify_parent_cldstop(current->group_leader, 2235 true, why); 2236 read_unlock(&tasklist_lock); 2237 2238 goto relock; 2239 } 2240 2241 for (;;) { 2242 struct k_sigaction *ka; 2243 2244 if (unlikely(current->jobctl & JOBCTL_STOP_PENDING) && 2245 do_signal_stop(0)) 2246 goto relock; 2247 2248 if (unlikely(current->jobctl & JOBCTL_TRAP_MASK)) { 2249 do_jobctl_trap(); 2250 spin_unlock_irq(&sighand->siglock); 2251 goto relock; 2252 } 2253 2254 signr = dequeue_signal(current, ¤t->blocked, info); 2255 2256 if (!signr) 2257 break; /* will return 0 */ 2258 2259 if (unlikely(current->ptrace) && signr != SIGKILL) { 2260 signr = ptrace_signal(signr, info); 2261 if (!signr) 2262 continue; 2263 } 2264 2265 ka = &sighand->action[signr-1]; 2266 2267 /* Trace actually delivered signals. */ 2268 trace_signal_deliver(signr, info, ka); 2269 2270 if (ka->sa.sa_handler == SIG_IGN) /* Do nothing. */ 2271 continue; 2272 if (ka->sa.sa_handler != SIG_DFL) { 2273 /* Run the handler. */ 2274 *return_ka = *ka; 2275 2276 if (ka->sa.sa_flags & SA_ONESHOT) 2277 ka->sa.sa_handler = SIG_DFL; 2278 2279 break; /* will return non-zero "signr" value */ 2280 } 2281 2282 /* 2283 * Now we are doing the default action for this signal. 2284 */ 2285 if (sig_kernel_ignore(signr)) /* Default is nothing. */ 2286 continue; 2287 2288 /* 2289 * Global init gets no signals it doesn't want. 2290 * Container-init gets no signals it doesn't want from same 2291 * container. 2292 * 2293 * Note that if global/container-init sees a sig_kernel_only() 2294 * signal here, the signal must have been generated internally 2295 * or must have come from an ancestor namespace. In either 2296 * case, the signal cannot be dropped. 2297 */ 2298 if (unlikely(signal->flags & SIGNAL_UNKILLABLE) && 2299 !sig_kernel_only(signr)) 2300 continue; 2301 2302 if (sig_kernel_stop(signr)) { 2303 /* 2304 * The default action is to stop all threads in 2305 * the thread group. The job control signals 2306 * do nothing in an orphaned pgrp, but SIGSTOP 2307 * always works. Note that siglock needs to be 2308 * dropped during the call to is_orphaned_pgrp() 2309 * because of lock ordering with tasklist_lock. 2310 * This allows an intervening SIGCONT to be posted. 2311 * We need to check for that and bail out if necessary. 2312 */ 2313 if (signr != SIGSTOP) { 2314 spin_unlock_irq(&sighand->siglock); 2315 2316 /* signals can be posted during this window */ 2317 2318 if (is_current_pgrp_orphaned()) 2319 goto relock; 2320 2321 spin_lock_irq(&sighand->siglock); 2322 } 2323 2324 if (likely(do_signal_stop(info->si_signo))) { 2325 /* It released the siglock. */ 2326 goto relock; 2327 } 2328 2329 /* 2330 * We didn't actually stop, due to a race 2331 * with SIGCONT or something like that. 2332 */ 2333 continue; 2334 } 2335 2336 spin_unlock_irq(&sighand->siglock); 2337 2338 /* 2339 * Anything else is fatal, maybe with a core dump. 2340 */ 2341 current->flags |= PF_SIGNALED; 2342 2343 if (sig_kernel_coredump(signr)) { 2344 if (print_fatal_signals) 2345 print_fatal_signal(info->si_signo); 2346 /* 2347 * If it was able to dump core, this kills all 2348 * other threads in the group and synchronizes with 2349 * their demise. If we lost the race with another 2350 * thread getting here, it set group_exit_code 2351 * first and our do_group_exit call below will use 2352 * that value and ignore the one we pass it. 2353 */ 2354 do_coredump(info); 2355 } 2356 2357 /* 2358 * Death signals, no core dump. 2359 */ 2360 do_group_exit(info->si_signo); 2361 /* NOTREACHED */ 2362 } 2363 spin_unlock_irq(&sighand->siglock); 2364 return signr; 2365 } 2366 2367 /** 2368 * signal_delivered - 2369 * @sig: number of signal being delivered 2370 * @info: siginfo_t of signal being delivered 2371 * @ka: sigaction setting that chose the handler 2372 * @regs: user register state 2373 * @stepping: nonzero if debugger single-step or block-step in use 2374 * 2375 * This function should be called when a signal has succesfully been 2376 * delivered. It updates the blocked signals accordingly (@ka->sa.sa_mask 2377 * is always blocked, and the signal itself is blocked unless %SA_NODEFER 2378 * is set in @ka->sa.sa_flags. Tracing is notified. 2379 */ 2380 void signal_delivered(int sig, siginfo_t *info, struct k_sigaction *ka, 2381 struct pt_regs *regs, int stepping) 2382 { 2383 sigset_t blocked; 2384 2385 /* A signal was successfully delivered, and the 2386 saved sigmask was stored on the signal frame, 2387 and will be restored by sigreturn. So we can 2388 simply clear the restore sigmask flag. */ 2389 clear_restore_sigmask(); 2390 2391 sigorsets(&blocked, ¤t->blocked, &ka->sa.sa_mask); 2392 if (!(ka->sa.sa_flags & SA_NODEFER)) 2393 sigaddset(&blocked, sig); 2394 set_current_blocked(&blocked); 2395 tracehook_signal_handler(sig, info, ka, regs, stepping); 2396 } 2397 2398 /* 2399 * It could be that complete_signal() picked us to notify about the 2400 * group-wide signal. Other threads should be notified now to take 2401 * the shared signals in @which since we will not. 2402 */ 2403 static void retarget_shared_pending(struct task_struct *tsk, sigset_t *which) 2404 { 2405 sigset_t retarget; 2406 struct task_struct *t; 2407 2408 sigandsets(&retarget, &tsk->signal->shared_pending.signal, which); 2409 if (sigisemptyset(&retarget)) 2410 return; 2411 2412 t = tsk; 2413 while_each_thread(tsk, t) { 2414 if (t->flags & PF_EXITING) 2415 continue; 2416 2417 if (!has_pending_signals(&retarget, &t->blocked)) 2418 continue; 2419 /* Remove the signals this thread can handle. */ 2420 sigandsets(&retarget, &retarget, &t->blocked); 2421 2422 if (!signal_pending(t)) 2423 signal_wake_up(t, 0); 2424 2425 if (sigisemptyset(&retarget)) 2426 break; 2427 } 2428 } 2429 2430 void exit_signals(struct task_struct *tsk) 2431 { 2432 int group_stop = 0; 2433 sigset_t unblocked; 2434 2435 /* 2436 * @tsk is about to have PF_EXITING set - lock out users which 2437 * expect stable threadgroup. 2438 */ 2439 threadgroup_change_begin(tsk); 2440 2441 if (thread_group_empty(tsk) || signal_group_exit(tsk->signal)) { 2442 tsk->flags |= PF_EXITING; 2443 threadgroup_change_end(tsk); 2444 return; 2445 } 2446 2447 spin_lock_irq(&tsk->sighand->siglock); 2448 /* 2449 * From now this task is not visible for group-wide signals, 2450 * see wants_signal(), do_signal_stop(). 2451 */ 2452 tsk->flags |= PF_EXITING; 2453 2454 threadgroup_change_end(tsk); 2455 2456 if (!signal_pending(tsk)) 2457 goto out; 2458 2459 unblocked = tsk->blocked; 2460 signotset(&unblocked); 2461 retarget_shared_pending(tsk, &unblocked); 2462 2463 if (unlikely(tsk->jobctl & JOBCTL_STOP_PENDING) && 2464 task_participate_group_stop(tsk)) 2465 group_stop = CLD_STOPPED; 2466 out: 2467 spin_unlock_irq(&tsk->sighand->siglock); 2468 2469 /* 2470 * If group stop has completed, deliver the notification. This 2471 * should always go to the real parent of the group leader. 2472 */ 2473 if (unlikely(group_stop)) { 2474 read_lock(&tasklist_lock); 2475 do_notify_parent_cldstop(tsk, false, group_stop); 2476 read_unlock(&tasklist_lock); 2477 } 2478 } 2479 2480 EXPORT_SYMBOL(recalc_sigpending); 2481 EXPORT_SYMBOL_GPL(dequeue_signal); 2482 EXPORT_SYMBOL(flush_signals); 2483 EXPORT_SYMBOL(force_sig); 2484 EXPORT_SYMBOL(send_sig); 2485 EXPORT_SYMBOL(send_sig_info); 2486 EXPORT_SYMBOL(sigprocmask); 2487 EXPORT_SYMBOL(block_all_signals); 2488 EXPORT_SYMBOL(unblock_all_signals); 2489 2490 2491 /* 2492 * System call entry points. 2493 */ 2494 2495 /** 2496 * sys_restart_syscall - restart a system call 2497 */ 2498 SYSCALL_DEFINE0(restart_syscall) 2499 { 2500 struct restart_block *restart = ¤t_thread_info()->restart_block; 2501 return restart->fn(restart); 2502 } 2503 2504 long do_no_restart_syscall(struct restart_block *param) 2505 { 2506 return -EINTR; 2507 } 2508 2509 static void __set_task_blocked(struct task_struct *tsk, const sigset_t *newset) 2510 { 2511 if (signal_pending(tsk) && !thread_group_empty(tsk)) { 2512 sigset_t newblocked; 2513 /* A set of now blocked but previously unblocked signals. */ 2514 sigandnsets(&newblocked, newset, ¤t->blocked); 2515 retarget_shared_pending(tsk, &newblocked); 2516 } 2517 tsk->blocked = *newset; 2518 recalc_sigpending(); 2519 } 2520 2521 /** 2522 * set_current_blocked - change current->blocked mask 2523 * @newset: new mask 2524 * 2525 * It is wrong to change ->blocked directly, this helper should be used 2526 * to ensure the process can't miss a shared signal we are going to block. 2527 */ 2528 void set_current_blocked(sigset_t *newset) 2529 { 2530 sigdelsetmask(newset, sigmask(SIGKILL) | sigmask(SIGSTOP)); 2531 __set_current_blocked(newset); 2532 } 2533 2534 void __set_current_blocked(const sigset_t *newset) 2535 { 2536 struct task_struct *tsk = current; 2537 2538 spin_lock_irq(&tsk->sighand->siglock); 2539 __set_task_blocked(tsk, newset); 2540 spin_unlock_irq(&tsk->sighand->siglock); 2541 } 2542 2543 /* 2544 * This is also useful for kernel threads that want to temporarily 2545 * (or permanently) block certain signals. 2546 * 2547 * NOTE! Unlike the user-mode sys_sigprocmask(), the kernel 2548 * interface happily blocks "unblockable" signals like SIGKILL 2549 * and friends. 2550 */ 2551 int sigprocmask(int how, sigset_t *set, sigset_t *oldset) 2552 { 2553 struct task_struct *tsk = current; 2554 sigset_t newset; 2555 2556 /* Lockless, only current can change ->blocked, never from irq */ 2557 if (oldset) 2558 *oldset = tsk->blocked; 2559 2560 switch (how) { 2561 case SIG_BLOCK: 2562 sigorsets(&newset, &tsk->blocked, set); 2563 break; 2564 case SIG_UNBLOCK: 2565 sigandnsets(&newset, &tsk->blocked, set); 2566 break; 2567 case SIG_SETMASK: 2568 newset = *set; 2569 break; 2570 default: 2571 return -EINVAL; 2572 } 2573 2574 __set_current_blocked(&newset); 2575 return 0; 2576 } 2577 2578 /** 2579 * sys_rt_sigprocmask - change the list of currently blocked signals 2580 * @how: whether to add, remove, or set signals 2581 * @nset: stores pending signals 2582 * @oset: previous value of signal mask if non-null 2583 * @sigsetsize: size of sigset_t type 2584 */ 2585 SYSCALL_DEFINE4(rt_sigprocmask, int, how, sigset_t __user *, nset, 2586 sigset_t __user *, oset, size_t, sigsetsize) 2587 { 2588 sigset_t old_set, new_set; 2589 int error; 2590 2591 /* XXX: Don't preclude handling different sized sigset_t's. */ 2592 if (sigsetsize != sizeof(sigset_t)) 2593 return -EINVAL; 2594 2595 old_set = current->blocked; 2596 2597 if (nset) { 2598 if (copy_from_user(&new_set, nset, sizeof(sigset_t))) 2599 return -EFAULT; 2600 sigdelsetmask(&new_set, sigmask(SIGKILL)|sigmask(SIGSTOP)); 2601 2602 error = sigprocmask(how, &new_set, NULL); 2603 if (error) 2604 return error; 2605 } 2606 2607 if (oset) { 2608 if (copy_to_user(oset, &old_set, sizeof(sigset_t))) 2609 return -EFAULT; 2610 } 2611 2612 return 0; 2613 } 2614 2615 long do_sigpending(void __user *set, unsigned long sigsetsize) 2616 { 2617 long error = -EINVAL; 2618 sigset_t pending; 2619 2620 if (sigsetsize > sizeof(sigset_t)) 2621 goto out; 2622 2623 spin_lock_irq(¤t->sighand->siglock); 2624 sigorsets(&pending, ¤t->pending.signal, 2625 ¤t->signal->shared_pending.signal); 2626 spin_unlock_irq(¤t->sighand->siglock); 2627 2628 /* Outside the lock because only this thread touches it. */ 2629 sigandsets(&pending, ¤t->blocked, &pending); 2630 2631 error = -EFAULT; 2632 if (!copy_to_user(set, &pending, sigsetsize)) 2633 error = 0; 2634 2635 out: 2636 return error; 2637 } 2638 2639 /** 2640 * sys_rt_sigpending - examine a pending signal that has been raised 2641 * while blocked 2642 * @set: stores pending signals 2643 * @sigsetsize: size of sigset_t type or larger 2644 */ 2645 SYSCALL_DEFINE2(rt_sigpending, sigset_t __user *, set, size_t, sigsetsize) 2646 { 2647 return do_sigpending(set, sigsetsize); 2648 } 2649 2650 #ifndef HAVE_ARCH_COPY_SIGINFO_TO_USER 2651 2652 int copy_siginfo_to_user(siginfo_t __user *to, siginfo_t *from) 2653 { 2654 int err; 2655 2656 if (!access_ok (VERIFY_WRITE, to, sizeof(siginfo_t))) 2657 return -EFAULT; 2658 if (from->si_code < 0) 2659 return __copy_to_user(to, from, sizeof(siginfo_t)) 2660 ? -EFAULT : 0; 2661 /* 2662 * If you change siginfo_t structure, please be sure 2663 * this code is fixed accordingly. 2664 * Please remember to update the signalfd_copyinfo() function 2665 * inside fs/signalfd.c too, in case siginfo_t changes. 2666 * It should never copy any pad contained in the structure 2667 * to avoid security leaks, but must copy the generic 2668 * 3 ints plus the relevant union member. 2669 */ 2670 err = __put_user(from->si_signo, &to->si_signo); 2671 err |= __put_user(from->si_errno, &to->si_errno); 2672 err |= __put_user((short)from->si_code, &to->si_code); 2673 switch (from->si_code & __SI_MASK) { 2674 case __SI_KILL: 2675 err |= __put_user(from->si_pid, &to->si_pid); 2676 err |= __put_user(from->si_uid, &to->si_uid); 2677 break; 2678 case __SI_TIMER: 2679 err |= __put_user(from->si_tid, &to->si_tid); 2680 err |= __put_user(from->si_overrun, &to->si_overrun); 2681 err |= __put_user(from->si_ptr, &to->si_ptr); 2682 break; 2683 case __SI_POLL: 2684 err |= __put_user(from->si_band, &to->si_band); 2685 err |= __put_user(from->si_fd, &to->si_fd); 2686 break; 2687 case __SI_FAULT: 2688 err |= __put_user(from->si_addr, &to->si_addr); 2689 #ifdef __ARCH_SI_TRAPNO 2690 err |= __put_user(from->si_trapno, &to->si_trapno); 2691 #endif 2692 #ifdef BUS_MCEERR_AO 2693 /* 2694 * Other callers might not initialize the si_lsb field, 2695 * so check explicitly for the right codes here. 2696 */ 2697 if (from->si_code == BUS_MCEERR_AR || from->si_code == BUS_MCEERR_AO) 2698 err |= __put_user(from->si_addr_lsb, &to->si_addr_lsb); 2699 #endif 2700 break; 2701 case __SI_CHLD: 2702 err |= __put_user(from->si_pid, &to->si_pid); 2703 err |= __put_user(from->si_uid, &to->si_uid); 2704 err |= __put_user(from->si_status, &to->si_status); 2705 err |= __put_user(from->si_utime, &to->si_utime); 2706 err |= __put_user(from->si_stime, &to->si_stime); 2707 break; 2708 case __SI_RT: /* This is not generated by the kernel as of now. */ 2709 case __SI_MESGQ: /* But this is */ 2710 err |= __put_user(from->si_pid, &to->si_pid); 2711 err |= __put_user(from->si_uid, &to->si_uid); 2712 err |= __put_user(from->si_ptr, &to->si_ptr); 2713 break; 2714 #ifdef __ARCH_SIGSYS 2715 case __SI_SYS: 2716 err |= __put_user(from->si_call_addr, &to->si_call_addr); 2717 err |= __put_user(from->si_syscall, &to->si_syscall); 2718 err |= __put_user(from->si_arch, &to->si_arch); 2719 break; 2720 #endif 2721 default: /* this is just in case for now ... */ 2722 err |= __put_user(from->si_pid, &to->si_pid); 2723 err |= __put_user(from->si_uid, &to->si_uid); 2724 break; 2725 } 2726 return err; 2727 } 2728 2729 #endif 2730 2731 /** 2732 * do_sigtimedwait - wait for queued signals specified in @which 2733 * @which: queued signals to wait for 2734 * @info: if non-null, the signal's siginfo is returned here 2735 * @ts: upper bound on process time suspension 2736 */ 2737 int do_sigtimedwait(const sigset_t *which, siginfo_t *info, 2738 const struct timespec *ts) 2739 { 2740 struct task_struct *tsk = current; 2741 long timeout = MAX_SCHEDULE_TIMEOUT; 2742 sigset_t mask = *which; 2743 int sig; 2744 2745 if (ts) { 2746 if (!timespec_valid(ts)) 2747 return -EINVAL; 2748 timeout = timespec_to_jiffies(ts); 2749 /* 2750 * We can be close to the next tick, add another one 2751 * to ensure we will wait at least the time asked for. 2752 */ 2753 if (ts->tv_sec || ts->tv_nsec) 2754 timeout++; 2755 } 2756 2757 /* 2758 * Invert the set of allowed signals to get those we want to block. 2759 */ 2760 sigdelsetmask(&mask, sigmask(SIGKILL) | sigmask(SIGSTOP)); 2761 signotset(&mask); 2762 2763 spin_lock_irq(&tsk->sighand->siglock); 2764 sig = dequeue_signal(tsk, &mask, info); 2765 if (!sig && timeout) { 2766 /* 2767 * None ready, temporarily unblock those we're interested 2768 * while we are sleeping in so that we'll be awakened when 2769 * they arrive. Unblocking is always fine, we can avoid 2770 * set_current_blocked(). 2771 */ 2772 tsk->real_blocked = tsk->blocked; 2773 sigandsets(&tsk->blocked, &tsk->blocked, &mask); 2774 recalc_sigpending(); 2775 spin_unlock_irq(&tsk->sighand->siglock); 2776 2777 timeout = schedule_timeout_interruptible(timeout); 2778 2779 spin_lock_irq(&tsk->sighand->siglock); 2780 __set_task_blocked(tsk, &tsk->real_blocked); 2781 siginitset(&tsk->real_blocked, 0); 2782 sig = dequeue_signal(tsk, &mask, info); 2783 } 2784 spin_unlock_irq(&tsk->sighand->siglock); 2785 2786 if (sig) 2787 return sig; 2788 return timeout ? -EINTR : -EAGAIN; 2789 } 2790 2791 /** 2792 * sys_rt_sigtimedwait - synchronously wait for queued signals specified 2793 * in @uthese 2794 * @uthese: queued signals to wait for 2795 * @uinfo: if non-null, the signal's siginfo is returned here 2796 * @uts: upper bound on process time suspension 2797 * @sigsetsize: size of sigset_t type 2798 */ 2799 SYSCALL_DEFINE4(rt_sigtimedwait, const sigset_t __user *, uthese, 2800 siginfo_t __user *, uinfo, const struct timespec __user *, uts, 2801 size_t, sigsetsize) 2802 { 2803 sigset_t these; 2804 struct timespec ts; 2805 siginfo_t info; 2806 int ret; 2807 2808 /* XXX: Don't preclude handling different sized sigset_t's. */ 2809 if (sigsetsize != sizeof(sigset_t)) 2810 return -EINVAL; 2811 2812 if (copy_from_user(&these, uthese, sizeof(these))) 2813 return -EFAULT; 2814 2815 if (uts) { 2816 if (copy_from_user(&ts, uts, sizeof(ts))) 2817 return -EFAULT; 2818 } 2819 2820 ret = do_sigtimedwait(&these, &info, uts ? &ts : NULL); 2821 2822 if (ret > 0 && uinfo) { 2823 if (copy_siginfo_to_user(uinfo, &info)) 2824 ret = -EFAULT; 2825 } 2826 2827 return ret; 2828 } 2829 2830 /** 2831 * sys_kill - send a signal to a process 2832 * @pid: the PID of the process 2833 * @sig: signal to be sent 2834 */ 2835 SYSCALL_DEFINE2(kill, pid_t, pid, int, sig) 2836 { 2837 struct siginfo info; 2838 2839 info.si_signo = sig; 2840 info.si_errno = 0; 2841 info.si_code = SI_USER; 2842 info.si_pid = task_tgid_vnr(current); 2843 info.si_uid = from_kuid_munged(current_user_ns(), current_uid()); 2844 2845 return kill_something_info(sig, &info, pid); 2846 } 2847 2848 static int 2849 do_send_specific(pid_t tgid, pid_t pid, int sig, struct siginfo *info) 2850 { 2851 struct task_struct *p; 2852 int error = -ESRCH; 2853 2854 rcu_read_lock(); 2855 p = find_task_by_vpid(pid); 2856 if (p && (tgid <= 0 || task_tgid_vnr(p) == tgid)) { 2857 error = check_kill_permission(sig, info, p); 2858 /* 2859 * The null signal is a permissions and process existence 2860 * probe. No signal is actually delivered. 2861 */ 2862 if (!error && sig) { 2863 error = do_send_sig_info(sig, info, p, false); 2864 /* 2865 * If lock_task_sighand() failed we pretend the task 2866 * dies after receiving the signal. The window is tiny, 2867 * and the signal is private anyway. 2868 */ 2869 if (unlikely(error == -ESRCH)) 2870 error = 0; 2871 } 2872 } 2873 rcu_read_unlock(); 2874 2875 return error; 2876 } 2877 2878 static int do_tkill(pid_t tgid, pid_t pid, int sig) 2879 { 2880 struct siginfo info; 2881 2882 info.si_signo = sig; 2883 info.si_errno = 0; 2884 info.si_code = SI_TKILL; 2885 info.si_pid = task_tgid_vnr(current); 2886 info.si_uid = from_kuid_munged(current_user_ns(), current_uid()); 2887 2888 return do_send_specific(tgid, pid, sig, &info); 2889 } 2890 2891 /** 2892 * sys_tgkill - send signal to one specific thread 2893 * @tgid: the thread group ID of the thread 2894 * @pid: the PID of the thread 2895 * @sig: signal to be sent 2896 * 2897 * This syscall also checks the @tgid and returns -ESRCH even if the PID 2898 * exists but it's not belonging to the target process anymore. This 2899 * method solves the problem of threads exiting and PIDs getting reused. 2900 */ 2901 SYSCALL_DEFINE3(tgkill, pid_t, tgid, pid_t, pid, int, sig) 2902 { 2903 /* This is only valid for single tasks */ 2904 if (pid <= 0 || tgid <= 0) 2905 return -EINVAL; 2906 2907 return do_tkill(tgid, pid, sig); 2908 } 2909 2910 /** 2911 * sys_tkill - send signal to one specific task 2912 * @pid: the PID of the task 2913 * @sig: signal to be sent 2914 * 2915 * Send a signal to only one task, even if it's a CLONE_THREAD task. 2916 */ 2917 SYSCALL_DEFINE2(tkill, pid_t, pid, int, sig) 2918 { 2919 /* This is only valid for single tasks */ 2920 if (pid <= 0) 2921 return -EINVAL; 2922 2923 return do_tkill(0, pid, sig); 2924 } 2925 2926 /** 2927 * sys_rt_sigqueueinfo - send signal information to a signal 2928 * @pid: the PID of the thread 2929 * @sig: signal to be sent 2930 * @uinfo: signal info to be sent 2931 */ 2932 SYSCALL_DEFINE3(rt_sigqueueinfo, pid_t, pid, int, sig, 2933 siginfo_t __user *, uinfo) 2934 { 2935 siginfo_t info; 2936 2937 if (copy_from_user(&info, uinfo, sizeof(siginfo_t))) 2938 return -EFAULT; 2939 2940 /* Not even root can pretend to send signals from the kernel. 2941 * Nor can they impersonate a kill()/tgkill(), which adds source info. 2942 */ 2943 if (info.si_code >= 0 || info.si_code == SI_TKILL) { 2944 /* We used to allow any < 0 si_code */ 2945 WARN_ON_ONCE(info.si_code < 0); 2946 return -EPERM; 2947 } 2948 info.si_signo = sig; 2949 2950 /* POSIX.1b doesn't mention process groups. */ 2951 return kill_proc_info(sig, &info, pid); 2952 } 2953 2954 long do_rt_tgsigqueueinfo(pid_t tgid, pid_t pid, int sig, siginfo_t *info) 2955 { 2956 /* This is only valid for single tasks */ 2957 if (pid <= 0 || tgid <= 0) 2958 return -EINVAL; 2959 2960 /* Not even root can pretend to send signals from the kernel. 2961 * Nor can they impersonate a kill()/tgkill(), which adds source info. 2962 */ 2963 if (info->si_code >= 0 || info->si_code == SI_TKILL) { 2964 /* We used to allow any < 0 si_code */ 2965 WARN_ON_ONCE(info->si_code < 0); 2966 return -EPERM; 2967 } 2968 info->si_signo = sig; 2969 2970 return do_send_specific(tgid, pid, sig, info); 2971 } 2972 2973 SYSCALL_DEFINE4(rt_tgsigqueueinfo, pid_t, tgid, pid_t, pid, int, sig, 2974 siginfo_t __user *, uinfo) 2975 { 2976 siginfo_t info; 2977 2978 if (copy_from_user(&info, uinfo, sizeof(siginfo_t))) 2979 return -EFAULT; 2980 2981 return do_rt_tgsigqueueinfo(tgid, pid, sig, &info); 2982 } 2983 2984 int do_sigaction(int sig, struct k_sigaction *act, struct k_sigaction *oact) 2985 { 2986 struct task_struct *t = current; 2987 struct k_sigaction *k; 2988 sigset_t mask; 2989 2990 if (!valid_signal(sig) || sig < 1 || (act && sig_kernel_only(sig))) 2991 return -EINVAL; 2992 2993 k = &t->sighand->action[sig-1]; 2994 2995 spin_lock_irq(¤t->sighand->siglock); 2996 if (oact) 2997 *oact = *k; 2998 2999 if (act) { 3000 sigdelsetmask(&act->sa.sa_mask, 3001 sigmask(SIGKILL) | sigmask(SIGSTOP)); 3002 *k = *act; 3003 /* 3004 * POSIX 3.3.1.3: 3005 * "Setting a signal action to SIG_IGN for a signal that is 3006 * pending shall cause the pending signal to be discarded, 3007 * whether or not it is blocked." 3008 * 3009 * "Setting a signal action to SIG_DFL for a signal that is 3010 * pending and whose default action is to ignore the signal 3011 * (for example, SIGCHLD), shall cause the pending signal to 3012 * be discarded, whether or not it is blocked" 3013 */ 3014 if (sig_handler_ignored(sig_handler(t, sig), sig)) { 3015 sigemptyset(&mask); 3016 sigaddset(&mask, sig); 3017 rm_from_queue_full(&mask, &t->signal->shared_pending); 3018 do { 3019 rm_from_queue_full(&mask, &t->pending); 3020 t = next_thread(t); 3021 } while (t != current); 3022 } 3023 } 3024 3025 spin_unlock_irq(¤t->sighand->siglock); 3026 return 0; 3027 } 3028 3029 int 3030 do_sigaltstack (const stack_t __user *uss, stack_t __user *uoss, unsigned long sp) 3031 { 3032 stack_t oss; 3033 int error; 3034 3035 oss.ss_sp = (void __user *) current->sas_ss_sp; 3036 oss.ss_size = current->sas_ss_size; 3037 oss.ss_flags = sas_ss_flags(sp); 3038 3039 if (uss) { 3040 void __user *ss_sp; 3041 size_t ss_size; 3042 int ss_flags; 3043 3044 error = -EFAULT; 3045 if (!access_ok(VERIFY_READ, uss, sizeof(*uss))) 3046 goto out; 3047 error = __get_user(ss_sp, &uss->ss_sp) | 3048 __get_user(ss_flags, &uss->ss_flags) | 3049 __get_user(ss_size, &uss->ss_size); 3050 if (error) 3051 goto out; 3052 3053 error = -EPERM; 3054 if (on_sig_stack(sp)) 3055 goto out; 3056 3057 error = -EINVAL; 3058 /* 3059 * Note - this code used to test ss_flags incorrectly: 3060 * old code may have been written using ss_flags==0 3061 * to mean ss_flags==SS_ONSTACK (as this was the only 3062 * way that worked) - this fix preserves that older 3063 * mechanism. 3064 */ 3065 if (ss_flags != SS_DISABLE && ss_flags != SS_ONSTACK && ss_flags != 0) 3066 goto out; 3067 3068 if (ss_flags == SS_DISABLE) { 3069 ss_size = 0; 3070 ss_sp = NULL; 3071 } else { 3072 error = -ENOMEM; 3073 if (ss_size < MINSIGSTKSZ) 3074 goto out; 3075 } 3076 3077 current->sas_ss_sp = (unsigned long) ss_sp; 3078 current->sas_ss_size = ss_size; 3079 } 3080 3081 error = 0; 3082 if (uoss) { 3083 error = -EFAULT; 3084 if (!access_ok(VERIFY_WRITE, uoss, sizeof(*uoss))) 3085 goto out; 3086 error = __put_user(oss.ss_sp, &uoss->ss_sp) | 3087 __put_user(oss.ss_size, &uoss->ss_size) | 3088 __put_user(oss.ss_flags, &uoss->ss_flags); 3089 } 3090 3091 out: 3092 return error; 3093 } 3094 #ifdef CONFIG_GENERIC_SIGALTSTACK 3095 SYSCALL_DEFINE2(sigaltstack,const stack_t __user *,uss, stack_t __user *,uoss) 3096 { 3097 return do_sigaltstack(uss, uoss, current_user_stack_pointer()); 3098 } 3099 #endif 3100 3101 int restore_altstack(const stack_t __user *uss) 3102 { 3103 int err = do_sigaltstack(uss, NULL, current_user_stack_pointer()); 3104 /* squash all but EFAULT for now */ 3105 return err == -EFAULT ? err : 0; 3106 } 3107 3108 int __save_altstack(stack_t __user *uss, unsigned long sp) 3109 { 3110 struct task_struct *t = current; 3111 return __put_user((void __user *)t->sas_ss_sp, &uss->ss_sp) | 3112 __put_user(sas_ss_flags(sp), &uss->ss_flags) | 3113 __put_user(t->sas_ss_size, &uss->ss_size); 3114 } 3115 3116 #ifdef CONFIG_COMPAT 3117 #ifdef CONFIG_GENERIC_SIGALTSTACK 3118 COMPAT_SYSCALL_DEFINE2(sigaltstack, 3119 const compat_stack_t __user *, uss_ptr, 3120 compat_stack_t __user *, uoss_ptr) 3121 { 3122 stack_t uss, uoss; 3123 int ret; 3124 mm_segment_t seg; 3125 3126 if (uss_ptr) { 3127 compat_stack_t uss32; 3128 3129 memset(&uss, 0, sizeof(stack_t)); 3130 if (copy_from_user(&uss32, uss_ptr, sizeof(compat_stack_t))) 3131 return -EFAULT; 3132 uss.ss_sp = compat_ptr(uss32.ss_sp); 3133 uss.ss_flags = uss32.ss_flags; 3134 uss.ss_size = uss32.ss_size; 3135 } 3136 seg = get_fs(); 3137 set_fs(KERNEL_DS); 3138 ret = do_sigaltstack((stack_t __force __user *) (uss_ptr ? &uss : NULL), 3139 (stack_t __force __user *) &uoss, 3140 compat_user_stack_pointer()); 3141 set_fs(seg); 3142 if (ret >= 0 && uoss_ptr) { 3143 if (!access_ok(VERIFY_WRITE, uoss_ptr, sizeof(compat_stack_t)) || 3144 __put_user(ptr_to_compat(uoss.ss_sp), &uoss_ptr->ss_sp) || 3145 __put_user(uoss.ss_flags, &uoss_ptr->ss_flags) || 3146 __put_user(uoss.ss_size, &uoss_ptr->ss_size)) 3147 ret = -EFAULT; 3148 } 3149 return ret; 3150 } 3151 3152 int compat_restore_altstack(const compat_stack_t __user *uss) 3153 { 3154 int err = compat_sys_sigaltstack(uss, NULL); 3155 /* squash all but -EFAULT for now */ 3156 return err == -EFAULT ? err : 0; 3157 } 3158 3159 int __compat_save_altstack(compat_stack_t __user *uss, unsigned long sp) 3160 { 3161 struct task_struct *t = current; 3162 return __put_user(ptr_to_compat((void __user *)t->sas_ss_sp), &uss->ss_sp) | 3163 __put_user(sas_ss_flags(sp), &uss->ss_flags) | 3164 __put_user(t->sas_ss_size, &uss->ss_size); 3165 } 3166 #endif 3167 #endif 3168 3169 #ifdef __ARCH_WANT_SYS_SIGPENDING 3170 3171 /** 3172 * sys_sigpending - examine pending signals 3173 * @set: where mask of pending signal is returned 3174 */ 3175 SYSCALL_DEFINE1(sigpending, old_sigset_t __user *, set) 3176 { 3177 return do_sigpending(set, sizeof(*set)); 3178 } 3179 3180 #endif 3181 3182 #ifdef __ARCH_WANT_SYS_SIGPROCMASK 3183 /** 3184 * sys_sigprocmask - examine and change blocked signals 3185 * @how: whether to add, remove, or set signals 3186 * @nset: signals to add or remove (if non-null) 3187 * @oset: previous value of signal mask if non-null 3188 * 3189 * Some platforms have their own version with special arguments; 3190 * others support only sys_rt_sigprocmask. 3191 */ 3192 3193 SYSCALL_DEFINE3(sigprocmask, int, how, old_sigset_t __user *, nset, 3194 old_sigset_t __user *, oset) 3195 { 3196 old_sigset_t old_set, new_set; 3197 sigset_t new_blocked; 3198 3199 old_set = current->blocked.sig[0]; 3200 3201 if (nset) { 3202 if (copy_from_user(&new_set, nset, sizeof(*nset))) 3203 return -EFAULT; 3204 3205 new_blocked = current->blocked; 3206 3207 switch (how) { 3208 case SIG_BLOCK: 3209 sigaddsetmask(&new_blocked, new_set); 3210 break; 3211 case SIG_UNBLOCK: 3212 sigdelsetmask(&new_blocked, new_set); 3213 break; 3214 case SIG_SETMASK: 3215 new_blocked.sig[0] = new_set; 3216 break; 3217 default: 3218 return -EINVAL; 3219 } 3220 3221 set_current_blocked(&new_blocked); 3222 } 3223 3224 if (oset) { 3225 if (copy_to_user(oset, &old_set, sizeof(*oset))) 3226 return -EFAULT; 3227 } 3228 3229 return 0; 3230 } 3231 #endif /* __ARCH_WANT_SYS_SIGPROCMASK */ 3232 3233 #ifdef __ARCH_WANT_SYS_RT_SIGACTION 3234 /** 3235 * sys_rt_sigaction - alter an action taken by a process 3236 * @sig: signal to be sent 3237 * @act: new sigaction 3238 * @oact: used to save the previous sigaction 3239 * @sigsetsize: size of sigset_t type 3240 */ 3241 SYSCALL_DEFINE4(rt_sigaction, int, sig, 3242 const struct sigaction __user *, act, 3243 struct sigaction __user *, oact, 3244 size_t, sigsetsize) 3245 { 3246 struct k_sigaction new_sa, old_sa; 3247 int ret = -EINVAL; 3248 3249 /* XXX: Don't preclude handling different sized sigset_t's. */ 3250 if (sigsetsize != sizeof(sigset_t)) 3251 goto out; 3252 3253 if (act) { 3254 if (copy_from_user(&new_sa.sa, act, sizeof(new_sa.sa))) 3255 return -EFAULT; 3256 } 3257 3258 ret = do_sigaction(sig, act ? &new_sa : NULL, oact ? &old_sa : NULL); 3259 3260 if (!ret && oact) { 3261 if (copy_to_user(oact, &old_sa.sa, sizeof(old_sa.sa))) 3262 return -EFAULT; 3263 } 3264 out: 3265 return ret; 3266 } 3267 #endif /* __ARCH_WANT_SYS_RT_SIGACTION */ 3268 3269 #ifdef __ARCH_WANT_SYS_SGETMASK 3270 3271 /* 3272 * For backwards compatibility. Functionality superseded by sigprocmask. 3273 */ 3274 SYSCALL_DEFINE0(sgetmask) 3275 { 3276 /* SMP safe */ 3277 return current->blocked.sig[0]; 3278 } 3279 3280 SYSCALL_DEFINE1(ssetmask, int, newmask) 3281 { 3282 int old = current->blocked.sig[0]; 3283 sigset_t newset; 3284 3285 siginitset(&newset, newmask); 3286 set_current_blocked(&newset); 3287 3288 return old; 3289 } 3290 #endif /* __ARCH_WANT_SGETMASK */ 3291 3292 #ifdef __ARCH_WANT_SYS_SIGNAL 3293 /* 3294 * For backwards compatibility. Functionality superseded by sigaction. 3295 */ 3296 SYSCALL_DEFINE2(signal, int, sig, __sighandler_t, handler) 3297 { 3298 struct k_sigaction new_sa, old_sa; 3299 int ret; 3300 3301 new_sa.sa.sa_handler = handler; 3302 new_sa.sa.sa_flags = SA_ONESHOT | SA_NOMASK; 3303 sigemptyset(&new_sa.sa.sa_mask); 3304 3305 ret = do_sigaction(sig, &new_sa, &old_sa); 3306 3307 return ret ? ret : (unsigned long)old_sa.sa.sa_handler; 3308 } 3309 #endif /* __ARCH_WANT_SYS_SIGNAL */ 3310 3311 #ifdef __ARCH_WANT_SYS_PAUSE 3312 3313 SYSCALL_DEFINE0(pause) 3314 { 3315 while (!signal_pending(current)) { 3316 current->state = TASK_INTERRUPTIBLE; 3317 schedule(); 3318 } 3319 return -ERESTARTNOHAND; 3320 } 3321 3322 #endif 3323 3324 int sigsuspend(sigset_t *set) 3325 { 3326 current->saved_sigmask = current->blocked; 3327 set_current_blocked(set); 3328 3329 current->state = TASK_INTERRUPTIBLE; 3330 schedule(); 3331 set_restore_sigmask(); 3332 return -ERESTARTNOHAND; 3333 } 3334 3335 #ifdef __ARCH_WANT_SYS_RT_SIGSUSPEND 3336 /** 3337 * sys_rt_sigsuspend - replace the signal mask for a value with the 3338 * @unewset value until a signal is received 3339 * @unewset: new signal mask value 3340 * @sigsetsize: size of sigset_t type 3341 */ 3342 SYSCALL_DEFINE2(rt_sigsuspend, sigset_t __user *, unewset, size_t, sigsetsize) 3343 { 3344 sigset_t newset; 3345 3346 /* XXX: Don't preclude handling different sized sigset_t's. */ 3347 if (sigsetsize != sizeof(sigset_t)) 3348 return -EINVAL; 3349 3350 if (copy_from_user(&newset, unewset, sizeof(newset))) 3351 return -EFAULT; 3352 return sigsuspend(&newset); 3353 } 3354 #endif /* __ARCH_WANT_SYS_RT_SIGSUSPEND */ 3355 3356 __attribute__((weak)) const char *arch_vma_name(struct vm_area_struct *vma) 3357 { 3358 return NULL; 3359 } 3360 3361 void __init signals_init(void) 3362 { 3363 sigqueue_cachep = KMEM_CACHE(sigqueue, SLAB_PANIC); 3364 } 3365 3366 #ifdef CONFIG_KGDB_KDB 3367 #include <linux/kdb.h> 3368 /* 3369 * kdb_send_sig_info - Allows kdb to send signals without exposing 3370 * signal internals. This function checks if the required locks are 3371 * available before calling the main signal code, to avoid kdb 3372 * deadlocks. 3373 */ 3374 void 3375 kdb_send_sig_info(struct task_struct *t, struct siginfo *info) 3376 { 3377 static struct task_struct *kdb_prev_t; 3378 int sig, new_t; 3379 if (!spin_trylock(&t->sighand->siglock)) { 3380 kdb_printf("Can't do kill command now.\n" 3381 "The sigmask lock is held somewhere else in " 3382 "kernel, try again later\n"); 3383 return; 3384 } 3385 spin_unlock(&t->sighand->siglock); 3386 new_t = kdb_prev_t != t; 3387 kdb_prev_t = t; 3388 if (t->state != TASK_RUNNING && new_t) { 3389 kdb_printf("Process is not RUNNING, sending a signal from " 3390 "kdb risks deadlock\n" 3391 "on the run queue locks. " 3392 "The signal has _not_ been sent.\n" 3393 "Reissue the kill command if you want to risk " 3394 "the deadlock.\n"); 3395 return; 3396 } 3397 sig = info->si_signo; 3398 if (send_sig_info(sig, info, t)) 3399 kdb_printf("Fail to deliver Signal %d to process %d.\n", 3400 sig, t->pid); 3401 else 3402 kdb_printf("Signal %d is sent to process %d.\n", sig, t->pid); 3403 } 3404 #endif /* CONFIG_KGDB_KDB */ 3405