net: bridge: don't cache ether dest pointer on input

We would cache ether dst pointer on input in br_handle_frame_finish but
after the neigh suppress code that could lead to a stale pointer since
both ipv4 and ipv6 suppress code do pskb_may_pull. This means we have to
always reload it after the suppress code so there's no point in having
it cached just retrieve it directly.

Fixes: 057658cb ("bridge: suppress arp pkts on BR_NEIGH_SUPPRESS ports")
Fixes: ed842fae ("bridge: suppress nd pkts on BR_NEIGH_SUPPRESS ports")
Signed-off-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/bridge/br_input.c

@@ -74,7 +74,6 @@ int br_handle_frame_finish(struct net *net, struct sock *sk, struct sk_buff *skb
 	struct net_bridge_fdb_entry *dst = NULL;
 	struct net_bridge_mdb_entry *mdst;
 	bool local_rcv, mcast_hit = false;
-	const unsigned char *dest;
 	struct net_bridge *br;
 	u16 vid = 0;
 
@@ -92,10 +91,9 @@ int br_handle_frame_finish(struct net *net, struct sock *sk, struct sk_buff *skb
 		br_fdb_update(br, p, eth_hdr(skb)->h_source, vid, false);
 
 	local_rcv = !!(br->dev->flags & IFF_PROMISC);
-	dest = eth_hdr(skb)->h_dest;
-	if (is_multicast_ether_addr(dest)) {
+	if (is_multicast_ether_addr(eth_hdr(skb)->h_dest)) {
 		/* by definition the broadcast is also a multicast address */
-		if (is_broadcast_ether_addr(dest)) {
+		if (is_broadcast_ether_addr(eth_hdr(skb)->h_dest)) {
 			pkt_type = BR_PKT_BROADCAST;
 			local_rcv = true;
 		} else {
@@ -145,7 +143,7 @@ int br_handle_frame_finish(struct net *net, struct sock *sk, struct sk_buff *skb
 		}
 		break;
 	case BR_PKT_UNICAST:
-		dst = br_fdb_find_rcu(br, dest, vid);
+		dst = br_fdb_find_rcu(br, eth_hdr(skb)->h_dest, vid);
 	default:
 		break;
 	}