1 files changed, 22 insertions, 8 deletions

diff --git a/kernel/signal.c b/kernel/signal.c
index 31751868de8..324eff5468a 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -636,13 +636,33 @@ static inline bool si_fromuser(const struct siginfo *info)
 }
 
 /*
+ * called with RCU read lock from check_kill_permission()
+ */
+static int kill_ok_by_cred(struct task_struct *t)
+{
+	const struct cred *cred = current_cred();
+	const struct cred *tcred = __task_cred(t);
+
+	if (cred->user->user_ns == tcred->user->user_ns &&
+	    (cred->euid == tcred->suid ||
+	     cred->euid == tcred->uid ||
+	     cred->uid  == tcred->suid ||
+	     cred->uid  == tcred->uid))
+		return 1;
+
+	if (ns_capable(tcred->user->user_ns, CAP_KILL))
+		return 1;
+
+	return 0;
+}
+
+/*
  * Bad permissions for sending the signal
  * - the caller must hold the RCU read lock
  */
 static int check_kill_permission(int sig, struct siginfo *info,
 				 struct task_struct *t)
 {
-	const struct cred *cred, *tcred;
 	struct pid *sid;
 	int error;
 
@@ -656,14 +676,8 @@ static int check_kill_permission(int sig, struct siginfo *info,
 	if (error)
 		return error;
 
-	cred = current_cred();
-	tcred = __task_cred(t);
 	if (!same_thread_group(current, t) &&
-	    (cred->euid ^ tcred->suid) &&
-	    (cred->euid ^ tcred->uid) &&
-	    (cred->uid  ^ tcred->suid) &&
-	    (cred->uid  ^ tcred->uid) &&
-	    !capable(CAP_KILL)) {
+	    !kill_ok_by_cred(t)) {
 		switch (sig) {
 		case SIGCONT:
 			sid = task_session(t);