[LLC]: use rcu_dereference on receive handler

The receive hander pointer might be modified during network changes
of protocol. So use rcu_dereference (only matters on alpha).
Signed-off-by: NStephen Hemminger <shemminger@osdl.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/llc/llc_input.c

@@ -142,6 +142,8 @@ int llc_rcv(struct sk_buff *skb, struct net_device *dev,
 	struct llc_sap *sap;
 	struct llc_pdu_sn *pdu;
 	int dest;
+	int (*rcv)(struct sk_buff *, struct net_device *,
+		   struct packet_type *, struct net_device *);
 
 	/*
 	 * When the interface is in promisc. mode, drop all the crap that it
@@ -169,8 +171,9 @@ int llc_rcv(struct sk_buff *skb, struct net_device *dev,
 	 * First the upper layer protocols that don't need the full
 	 * LLC functionality
 	 */
-	if (sap->rcv_func) {
-		sap->rcv_func(skb, dev, pt, orig_dev);
+	rcv = rcu_dereference(sap->rcv_func);
+	if (rcv) {
+		rcv(skb, dev, pt, orig_dev);
 		goto out_put;
 	}
 	dest = llc_pdu_type(skb);