bridge: Pull ip header into skb->data before looking into ip header.

If lower layer driver leaves the ip header in the skb fragment, it needs to
be first pulled into skb->data before inspecting ip header length or ip version
number.
Signed-off-by: Sarveshwar Bandi <sarveshwar.bandi@emulex.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/bridge/br_netfilter.c

@@ -265,6 +265,9 @@ static int br_parse_ip_options(struct sk_buff *skb)
 	struct net_device *dev = skb->dev;
 	u32 len;
 
+	if (!pskb_may_pull(skb, sizeof(struct iphdr)))
+		goto inhdr_error;
+
 	iph = ip_hdr(skb);
 	opt = &(IPCB(skb)->opt);