do_mq_notify(): saner skb freeing on failures

cleanup is convoluted enough as it is; it's easier to have early
failure outs do explicit kfree_skb(nc), rather than going to
contortions needed to reuse the cleanup from late failures.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Author: Al Viro

ipc/mqueue.c

@@ -1347,8 +1347,8 @@ static int do_mq_notify(mqd_t mqdes, const struct sigevent *notification)
 			if (copy_from_user(nc->data,
 					notification->sigev_value.sival_ptr,
 					NOTIFY_COOKIE_LEN)) {
-				ret = -EFAULT;
-				goto free_skb;
+				kfree_skb(nc);
+				return -EFAULT;
 			}
 
 			/* TODO: add a header? */
@@ -1357,16 +1357,14 @@ static int do_mq_notify(mqd_t mqdes, const struct sigevent *notification)
 retry:
 			sock = netlink_getsockbyfd(notification->sigev_signo);
 			if (IS_ERR(sock)) {
-				ret = PTR_ERR(sock);
-				goto free_skb;
+				kfree_skb(nc);
+				return PTR_ERR(sock);
 			}
 
 			timeo = MAX_SCHEDULE_TIMEOUT;
 			ret = netlink_attachskb(sock, nc, &timeo, NULL);
-			if (ret == 1) {
-				sock = NULL;
+			if (ret == 1)
 				goto retry;
-			}
 			if (ret)
 				return ret;
 		}
@@ -1425,10 +1423,6 @@ static int do_mq_notify(mqd_t mqdes, const struct sigevent *notification)
 out:
 	if (sock)
 		netlink_detachskb(sock, nc);
-	else
-free_skb:
-		dev_kfree_skb(nc);
-
 	return ret;
 }