1 files changed, 119 insertions, 63 deletions

diff --git a/kernel/signal.c b/kernel/signal.c
index 6705320784fd..dbd7fe073c55 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -22,12 +22,14 @@
 #include <linux/ptrace.h>
 #include <linux/signal.h>
 #include <linux/signalfd.h>
+#include <linux/ratelimit.h>
 #include <linux/tracehook.h>
 #include <linux/capability.h>
 #include <linux/freezer.h>
 #include <linux/pid_namespace.h>
 #include <linux/nsproxy.h>
-#include <trace/events/sched.h>
+#define CREATE_TRACE_POINTS
+#include <trace/events/signal.h>
 
 #include <asm/param.h>
 #include <asm/uaccess.h>
@@ -41,6 +43,8 @@
 
 static struct kmem_cache *sigqueue_cachep;
 
+int print_fatal_signals __read_mostly;
+
 static void __user *sig_handler(struct task_struct *t, int sig)
 {
         return t->sighand->action[sig - 1].sa.sa_handler;
@@ -155,62 +159,98 @@ void recalc_sigpending(void)
 
 /* Given the mask, find the first available signal that should be serviced. */
 
+#define SYNCHRONOUS_MASK \
+        (sigmask(SIGSEGV) | sigmask(SIGBUS) | sigmask(SIGILL) | \
+         sigmask(SIGTRAP) | sigmask(SIGFPE))
+
 int next_signal(struct sigpending *pending, sigset_t *mask)
 {
         unsigned long i, *s, *m, x;
         int sig = 0;
-        
+
         s = pending->signal.sig;
         m = mask->sig;
+
+        /*
+         * Handle the first word specially: it contains the
+         * synchronous signals that need to be dequeued first.
+         */
+        x = *s &~ *m;
+        if (x) {
+                if (x & SYNCHRONOUS_MASK)
+                        x &= SYNCHRONOUS_MASK;
+                sig = ffz(~x) + 1;
+                return sig;
+        }
+
         switch (_NSIG_WORDS) {
         default:
-                for (i = 0; i < _NSIG_WORDS; ++i, ++s, ++m)
-                        if ((x = *s &~ *m) != 0) {
-                                sig = ffz(~x) + i*_NSIG_BPW + 1;
-                                break;
-                        }
+                for (i = 1; i < _NSIG_WORDS; ++i) {
+                        x = *++s &~ *++m;
+                        if (!x)
+                                continue;
+                        sig = ffz(~x) + i*_NSIG_BPW + 1;
+                        break;
+                }
                 break;
 
-        case 2: if ((x = s[0] &~ m[0]) != 0)
-                        sig = 1;
-                else if ((x = s[1] &~ m[1]) != 0)
-                        sig = _NSIG_BPW + 1;
-                else
+        case 2:
+                x = s[1] &~ m[1];
+                if (!x)
                         break;
-                sig += ffz(~x);
+                sig = ffz(~x) + _NSIG_BPW + 1;
                 break;
 
-        case 1: if ((x = *s &~ *m) != 0)
-                        sig = ffz(~x) + 1;
+        case 1:
+                /* Nothing to do */
                 break;
         }
-        
+
         return sig;
 }
 
+static inline void print_dropped_signal(int sig)
+{
+        static DEFINE_RATELIMIT_STATE(ratelimit_state, 5 * HZ, 10);
+
+        if (!print_fatal_signals)
+                return;
+
+        if (!__ratelimit(&ratelimit_state))
+                return;
+
+        printk(KERN_INFO "%s/%d: reached RLIMIT_SIGPENDING, dropped signal %d\n",
+                                current->comm, current->pid, sig);
+}
+
 /*
  * allocate a new signal queue record
  * - this may be called without locks if and only if t == current, otherwise an
  *   appopriate lock must be held to stop the target task from exiting
  */
-static struct sigqueue *__sigqueue_alloc(struct task_struct *t, gfp_t flags,
-                                         int override_rlimit)
+static struct sigqueue *
+__sigqueue_alloc(int sig, struct task_struct *t, gfp_t flags, int override_rlimit)
 {
         struct sigqueue *q = NULL;
         struct user_struct *user;
 
         /*
-         * We won't get problems with the target's UID changing under us
-         * because changing it requires RCU be used, and if t != current, the
-         * caller must be holding the RCU readlock (by way of a spinlock) and
-         * we use RCU protection here
+         * Protect access to @t credentials. This can go away when all
+         * callers hold rcu read lock.
          */
+        rcu_read_lock();
         user = get_uid(__task_cred(t)->user);
         atomic_inc(&user->sigpending);
+        rcu_read_unlock();
+
         if (override_rlimit ||
             atomic_read(&user->sigpending) <=
-                        t->signal->rlim[RLIMIT_SIGPENDING].rlim_cur)
+                        task_rlimit(t, RLIMIT_SIGPENDING)) {
                 q = kmem_cache_alloc(sigqueue_cachep, flags);
+        } else {
+                print_dropped_signal(sig);
+        }
+
         if (unlikely(q == NULL)) {
                 atomic_dec(&user->sigpending);
                 free_uid(user);
@@ -400,7 +440,7 @@ still_pending:
                  */
                 info->si_signo = sig;
                 info->si_errno = 0;
-                info->si_code = 0;
+                info->si_code = SI_USER;
                 info->si_pid = 0;
                 info->si_uid = 0;
         }
@@ -584,6 +624,17 @@ static int rm_from_queue(unsigned long mask, struct sigpending *s)
         return 1;
 }
 
+static inline int is_si_special(const struct siginfo *info)
+{
+        return info <= SEND_SIG_FORCED;
+}
+
+static inline bool si_fromuser(const struct siginfo *info)
+{
+        return info == SEND_SIG_NOINFO ||
+                (!is_si_special(info) && SI_FROMUSER(info));
+}
+
 /*
  * Bad permissions for sending the signal
  * - the caller must hold at least the RCU read lock
@@ -598,7 +649,7 @@ static int check_kill_permission(int sig, struct siginfo *info,
         if (!valid_signal(sig))
                 return -EINVAL;
 
-        if (info != SEND_SIG_NOINFO && (is_si_special(info) || SI_FROMKERNEL(info)))
+        if (!si_fromuser(info))
                 return 0;
 
         error = audit_signal_info(sig, t); /* Let audit system see the signal */
@@ -834,7 +885,7 @@ static int __send_signal(int sig, struct siginfo *info, struct task_struct *t,
         struct sigqueue *q;
         int override_rlimit;
 
-        trace_sched_signal_send(sig, t);
+        trace_signal_generate(sig, info, t);
 
         assert_spin_locked(&t->sighand->siglock);
 
@@ -869,7 +920,7 @@ static int __send_signal(int sig, struct siginfo *info, struct task_struct *t,
         else
                 override_rlimit = 0;
 
-        q = __sigqueue_alloc(t, GFP_ATOMIC | __GFP_NOTRACK_FALSE_POSITIVE,
+        q = __sigqueue_alloc(sig, t, GFP_ATOMIC | __GFP_NOTRACK_FALSE_POSITIVE,
                 override_rlimit);
         if (q) {
                 list_add_tail(&q->list, &pending->list);
@@ -896,12 +947,21 @@ static int __send_signal(int sig, struct siginfo *info, struct task_struct *t,
                         break;
                 }
         } else if (!is_si_special(info)) {
-                if (sig >= SIGRTMIN && info->si_code != SI_USER)
-                /*
-                 * Queue overflow, abort.  We may abort if the signal was rt
-                 * and sent by user using something other than kill().
-                 */
+                if (sig >= SIGRTMIN && info->si_code != SI_USER) {
+                        /*
+                         * Queue overflow, abort.  We may abort if the
+                         * signal was rt and sent by user using something
+                         * other than kill().
+                         */
+                        trace_signal_overflow_fail(sig, group, info);
                         return -EAGAIN;
+                } else {
+                        /*
+                         * This is a silent loss of information.  We still
+                         * send the signal, but the *info bits are lost.
+                         */
+                        trace_signal_lose_info(sig, group, info);
+                }
         }
 
 out_set:
@@ -917,16 +977,13 @@ static int send_signal(int sig, struct siginfo *info, struct task_struct *t,
         int from_ancestor_ns = 0;
 
 #ifdef CONFIG_PID_NS
-        if (!is_si_special(info) && SI_FROMUSER(info) &&
-                        task_pid_nr_ns(current, task_active_pid_ns(t)) <= 0)
-                from_ancestor_ns = 1;
+        from_ancestor_ns = si_fromuser(info) &&
+                           !task_pid_nr_ns(current, task_active_pid_ns(t));
 #endif
 
         return __send_signal(sig, info, t, group, from_ancestor_ns);
 }
 
-int print_fatal_signals;
-
 static void print_fatal_signal(struct pt_regs *regs, int signr)
 {
         printk("%s/%d: potentially unexpected fatal signal %d.\n",
@@ -939,7 +996,8 @@ static void print_fatal_signal(struct pt_regs *regs, int signr)
                 for (i = 0; i < 16; i++) {
                         unsigned char insn;
 
-                        __get_user(insn, (unsigned char *)(regs->ip + i));
+                        if (get_user(insn, (unsigned char *)(regs->ip + i)))
+                                break;
                         printk("%02x ", insn);
                 }
         }
@@ -1022,12 +1080,6 @@ force_sig_info(int sig, struct siginfo *info, struct task_struct *t)
         return ret;
 }
 
-void
-force_sig_specific(int sig, struct task_struct *t)
-{
-        force_sig_info(sig, SEND_SIG_FORCED, t);
-}
-
 /*
  * Nuke all other threads in the group.
  */
@@ -1145,19 +1197,19 @@ int kill_pid_info_as_uid(int sig, struct siginfo *info, struct pid *pid,
         int ret = -EINVAL;
         struct task_struct *p;
         const struct cred *pcred;
+        unsigned long flags;
 
         if (!valid_signal(sig))
                 return ret;
 
-        read_lock(&tasklist_lock);
+        rcu_read_lock();
         p = pid_task(pid, PIDTYPE_PID);
         if (!p) {
                 ret = -ESRCH;
                 goto out_unlock;
         }
         pcred = __task_cred(p);
-        if ((info == SEND_SIG_NOINFO ||
-             (!is_si_special(info) && SI_FROMUSER(info))) &&
+        if (si_fromuser(info) &&
             euid != pcred->suid && euid != pcred->uid &&
             uid  != pcred->suid && uid  != pcred->uid) {
                 ret = -EPERM;
@@ -1166,14 +1218,16 @@ int kill_pid_info_as_uid(int sig, struct siginfo *info, struct pid *pid,
         ret = security_task_kill(p, info, sig, secid);
         if (ret)
                 goto out_unlock;
-        if (sig && p->sighand) {
-                unsigned long flags;
-                spin_lock_irqsave(&p->sighand->siglock, flags);
-                ret = __send_signal(sig, info, p, 1, 0);
-                spin_unlock_irqrestore(&p->sighand->siglock, flags);
+
+        if (sig) {
+                if (lock_task_sighand(p, &flags)) {
+                        ret = __send_signal(sig, info, p, 1, 0);
+                        unlock_task_sighand(p, &flags);
+                } else
+                        ret = -ESRCH;
         }
 out_unlock:
-        read_unlock(&tasklist_lock);
+        rcu_read_unlock();
         return ret;
 }
 EXPORT_SYMBOL_GPL(kill_pid_info_as_uid);
@@ -1293,19 +1347,19 @@ EXPORT_SYMBOL(kill_pid);
  * These functions support sending signals using preallocated sigqueue
  * structures.  This is needed "because realtime applications cannot
  * afford to lose notifications of asynchronous events, like timer
- * expirations or I/O completions".  In the case of Posix Timers 
+ * expirations or I/O completions".  In the case of Posix Timers
  * we allocate the sigqueue structure from the timer_create.  If this
  * allocation fails we are able to report the failure to the application
  * with an EAGAIN error.
  */
- 
 struct sigqueue *sigqueue_alloc(void)
 {
-        struct sigqueue *q;
+        struct sigqueue *q = __sigqueue_alloc(-1, current, GFP_KERNEL, 0);
 
-        if ((q = __sigqueue_alloc(current, GFP_KERNEL, 0)))
+        if (q)
                 q->flags |= SIGQUEUE_PREALLOC;
-        return(q);
+
+        return q;
 }
 
 void sigqueue_free(struct sigqueue *q)
@@ -1807,11 +1861,6 @@ relock:
 
         for (;;) {
                 struct k_sigaction *ka;
-
-                if (unlikely(signal->group_stop_count > 0) &&
-                    do_signal_stop(0))
-                        goto relock;
-
                 /*
                  * Tracing can induce an artifical signal and choose sigaction.
                  * The return value in @signr determines the default action,
@@ -1823,6 +1872,10 @@ relock:
                 if (unlikely(signr != 0))
                         ka = return_ka;
                 else {
+                        if (unlikely(signal->group_stop_count > 0) &&
+                            do_signal_stop(0))
+                                goto relock;
+
                         signr = dequeue_signal(current, &current->blocked,
                                                info);
 
@@ -1839,6 +1892,9 @@ relock:
                         ka = &sighand->action[signr-1];
                 }
 
+                /* Trace actually delivered signals. */
+                trace_signal_deliver(signr, info, ka);
+
                 if (ka->sa.sa_handler == SIG_IGN) /* Do nothing.  */
                         continue;
                 if (ka->sa.sa_handler != SIG_DFL) {