openvswitch: Read tcp flags only then the tranport header is present.

Only the first IP fragment can have a TCP header, check for this.
Signed-off-by: NJarno Rajahalme <jrajahalme@nicira.com>
Signed-off-by: NJesse Gross <jesse@nicira.com>

net/openvswitch/flow.c

@@ -73,6 +73,7 @@ void ovs_flow_stats_update(struct sw_flow *flow, struct sk_buff *skb)
 
 	if ((flow->key.eth.type == htons(ETH_P_IP) ||
 	     flow->key.eth.type == htons(ETH_P_IPV6)) &&
+	    flow->key.ip.frag != OVS_FRAG_TYPE_LATER &&
 	    flow->key.ip.proto == IPPROTO_TCP &&
 	    likely(skb->len >= skb_transport_offset(skb) + sizeof(struct tcphdr))) {
 		tcp_flags = TCP_FLAGS_BE16(tcp_hdr(skb));