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