bridge: Fix skb leak when multicast parsing fails on TX

On the bridge TX path we're leaking an skb when br_multicast_rcv
returns an error.
Reported-by: NDavid Lamparter <equinox@diac24.net>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/bridge/br_device.c

@@ -48,8 +48,10 @@ netdev_tx_t br_dev_xmit(struct sk_buff *skb, struct net_device *dev)
 
 	rcu_read_lock();
 	if (is_multicast_ether_addr(dest)) {
-		if (br_multicast_rcv(br, NULL, skb))
+		if (br_multicast_rcv(br, NULL, skb)) {
+			kfree_skb(skb);
 			goto out;
+		}
 
 		mdst = br_mdb_get(br, skb);
 		if (mdst || BR_INPUT_SKB_CB_MROUTERS_ONLY(skb))