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.

Fixes: e6df12b2bb07 ("vxlan: Flow based tunneling")
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/vxlan.c b/drivers/net/vxlan.c
index fcf028220bcac27276c1e88843c5e5031fb90c9f..ac5c597aa703357f8288285f82ad88b27b6fa3ff 100644 (file)
--- 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;