can: j1939: fix resource leak of skb on error return paths

Currently the error return paths do not free skb and this results in a
memory leak. Fix this by freeing them before the return.

Addresses-Coverity: ("Resource leak")
Fixes: 9d71dd0c ("can: add support of SAE J1939 protocol")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Acked-by: Oleksij Rempel <o.rempel@pengutronix.de>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

net/can/j1939/socket.c

@@ -909,8 +909,10 @@ void j1939_sk_errqueue(struct j1939_session *session,
 	memset(serr, 0, sizeof(*serr));
 	switch (type) {
 	case J1939_ERRQUEUE_ACK:
-		if (!(sk->sk_tsflags & SOF_TIMESTAMPING_TX_ACK))
+		if (!(sk->sk_tsflags & SOF_TIMESTAMPING_TX_ACK)) {
+			kfree_skb(skb);
 			return;
+		}
 
 		serr->ee.ee_errno = ENOMSG;
 		serr->ee.ee_origin = SO_EE_ORIGIN_TIMESTAMPING;
@@ -918,8 +920,10 @@ void j1939_sk_errqueue(struct j1939_session *session,
 		state = "ACK";
 		break;
 	case J1939_ERRQUEUE_SCHED:
-		if (!(sk->sk_tsflags & SOF_TIMESTAMPING_TX_SCHED))
+		if (!(sk->sk_tsflags & SOF_TIMESTAMPING_TX_SCHED)) {
+			kfree_skb(skb);
 			return;
+		}
 
 		serr->ee.ee_errno = ENOMSG;
 		serr->ee.ee_origin = SO_EE_ORIGIN_TIMESTAMPING;