netdev - [PATCHv2 net-next 4/6] vxlan: check tun_info options

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Message-Id: <b870b739bf2819134a3de9f2a19132d978109e7a.1570547676.git.lucien.xin@gmail.com>
Date:   Tue,  8 Oct 2019 23:16:14 +0800
From:   Xin Long <lucien.xin@...il.com>
To:     network dev <netdev@...r.kernel.org>
Cc:     davem@...emloft.net, Jiri Benc <jbenc@...hat.com>,
        Thomas Graf <tgraf@...g.ch>, u9012063@...il.com
Subject: [PATCHv2 net-next 4/6] vxlan: check tun_info options_len properly

This patch is to improve the tun_info options_len by dropping
the skb when TUNNEL_VXLAN_OPT is set but options_len is less
than vxlan_metadata. This can void a potential out-of-bounds
access on ip_tun_info.

Signed-off-by: Xin Long <lucien.xin@...il.com>
---
 drivers/net/vxlan.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/net/vxlan.c b/drivers/net/vxlan.c
index 3d9bcc9..e0787286 100644
--- a/drivers/net/vxlan.c
+++ b/drivers/net/vxlan.c
@@ -2487,9 +2487,11 @@ static void vxlan_xmit_one(struct sk_buff *skb, struct net_device *dev,
 		vni = tunnel_id_to_key32(info->key.tun_id);
 		ifindex = 0;
 		dst_cache = &info->dst_cache;
-		if (info->options_len &&
-		    info->key.tun_flags & TUNNEL_VXLAN_OPT)
+		if (info->key.tun_flags & TUNNEL_VXLAN_OPT) {
+			if (info->options_len < sizeof(*md))
+				goto drop;
 			md = ip_tunnel_info_opts(info);
+		}
 		ttl = info->key.ttl;
 		tos = info->key.tos;
 		label = info->key.label;
-- 
2.1.0