Commit bf32fecd authored Apr 02, 2012 by Jesse Gross

openvswitch: Add length check when retrieving TCP flags.



When collecting TCP flags we check that the IP header indicates that
a TCP header is present but not that the packet is actually long
enough to contain the header.  This adds a check to prevent reading
off the end of the packet.

In practice, this is only likely to result in reading of bad data and
not a crash due to the presence of struct skb_shared_info at the end
of the packet.

Signed-off-by: Jesse Gross <jesse@nicira.com>

parent dd775ae2

net/openvswitch/flow.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -183,7 +183,8 @@ void ovs_flow_used(struct sw_flow flow, struct sk_buff skb)
		u8 tcp_flags = 0;

		if (flow->key.eth.type == htons(ETH_P_IP) &&
		flow->key.ip.proto == IPPROTO_TCP) {
		flow->key.ip.proto == IPPROTO_TCP &&
		likely(skb->len >= skb_transport_offset(skb) + sizeof(struct tcphdr))) {
		u8 tcp = (u8 )tcp_hdr(skb);
		tcp_flags = *(tcp + TCP_FLAGS_OFFSET) & TCP_FLAG_MASK;
		}