net/mlx5e: Rx, Check ip headers sanity

In the two places is_last_ethertype_ip is being called, the caller will
be looking inside the ip header, to be safe, add ip{4,6} header sanity
check. And return true only on valid ip headers, i.e: the whole header
is contained in the linear part of the skb.

Note: Such situation is very rare and hard to reproduce, since mlx5e
allocates a large enough headroom to contain the largest header one can
imagine.

Fixes: fe1dc069 ("net/mlx5e: don't set CHECKSUM_COMPLETE on SCTP packets")
Reported-by: Cong Wang <xiyou.wangcong@gmail.com>
Reviewed-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>

drivers/net/ethernet/mellanox/mlx5/core/en_rx.c

@@ -692,7 +692,14 @@ static inline bool is_last_ethertype_ip(struct sk_buff *skb, int *network_depth,
 {
 	*proto = ((struct ethhdr *)skb->data)->h_proto;
 	*proto = __vlan_get_protocol(skb, *proto, network_depth);
-	return (*proto == htons(ETH_P_IP) || *proto == htons(ETH_P_IPV6));
+
+	if (*proto == htons(ETH_P_IP))
+		return pskb_may_pull(skb, *network_depth + sizeof(struct iphdr));
+
+	if (*proto == htons(ETH_P_IPV6))
+		return pskb_may_pull(skb, *network_depth + sizeof(struct ipv6hdr));
+
+	return false;
 }
 
 static inline void mlx5e_enable_ecn(struct mlx5e_rq *rq, struct sk_buff *skb)