Root/kernel/signal.c

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

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