net/netrom: Fix socket locking

Patch "af_rose/x25: Sanity check the maximum user frame size"
(commit 83e0bbcb) from Alan Cox got
locking wrong. If we bail out due to user frame size being too large,
we must unlock the socket beforehand.
Signed-off-by: NJean Delvare <jdelvare@suse.de>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/netrom/af_netrom.c

@@ -1084,8 +1084,10 @@ static int nr_sendmsg(struct kiocb *iocb, struct socket *sock,
 
 	/* Build a packet - the conventional user limit is 236 bytes. We can
 	   do ludicrously large NetROM frames but must not overflow */
-	if (len > 65536)
-		return -EMSGSIZE;
+	if (len > 65536) {
+		err = -EMSGSIZE;
+		goto out;
+	}
 
 	SOCK_DEBUG(sk, "NET/ROM: sendto: building packet.\n");
 	size = len + NR_NETWORK_LEN + NR_TRANSPORT_LEN;