net/netrom: Fix socket locking

Patch "af_rose/x25: Sanity check the maximum user frame size"
(commit 83e0bbcbe2145f160fbaa109b0439dae7f4a38a9) 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: Jean Delvare <jdelvare@suse.de>
Signed-off-by: David 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;