netdev - [Patch net] mlx5: check for malformed packets

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Message-Id: <20181201203837.3306-1-xiyou.wangcong@gmail.com>
Date:   Sat,  1 Dec 2018 12:38:36 -0800
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     netdev@...r.kernel.org
Cc:     Cong Wang <xiyou.wangcong@...il.com>,
        Tariq Toukan <tariqt@...lanox.com>,
        Saeed Mahameed <saeedm@...lanox.com>
Subject: [Patch net] mlx5: check for malformed packets

is_last_ethertype_ip() is used to check IP/IPv6 protocol before
parsing IP/IPv6 headers.

But __vlan_get_protocol() is only bound to skb->len, a malicious
packet could exhaust all skb->len by inserting sufficient ETH_P_8021AD
headers, and it may not even contain an IP/IPv6 header at all, so we
have to check if we are still safe to continue to parse IP/IPv6 header.
If not, treat it as non-IP packet.

This should not cause any crash as we stil have tail room in skb,
but we can't just rely on it either.

Cc: Tariq Toukan <tariqt@...lanox.com>
Cc: Saeed Mahameed <saeedm@...lanox.com>
Signed-off-by: Cong Wang <xiyou.wangcong@...il.com>
---
 drivers/net/ethernet/mellanox/mlx5/core/en_rx.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c b/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c
index 624eed345b5d..1e505013ebfd 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c
@@ -693,7 +693,18 @@ 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)) {
+		if (unlikely(*network_depth > skb->len - sizeof(struct iphdr)))
+			return false;
+		return true;
+	} else if (*proto == htons(ETH_P_IPV6)) {
+		if (unlikely(*network_depth > skb->len - sizeof(struct ipv6hdr)))
+			return false;
+		return true;
+	}
+
+	return false;
 }
 
 static inline void mlx5e_enable_ecn(struct mlx5e_rq *rq, struct sk_buff *skb)
-- 
2.19.1