1 files changed, 34 insertions, 29 deletions

diff --git a/kernel/signal.c b/kernel/signal.c
index 6b982f2cf524..d09692b40376 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -218,13 +218,13 @@ __sigqueue_alloc(int sig, struct task_struct *t, gfp_t flags, int override_rlimi
 	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) <=
@@ -423,7 +423,7 @@ 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;
 	}
@@ -607,6 +607,17 @@ 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
@@ -621,7 +632,7 @@ 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 */
@@ -949,9 +960,8 @@ 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);
@@ -1052,12 +1062,6 @@ 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.
  */
@@ -1175,19 +1179,19 @@ 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;
@@ -1196,14 +1200,16 @@ 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);
@@ -1837,11 +1843,6 @@ 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,
@@ -1853,6 +1854,10 @@ 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);