[PATCH 4.9 26/34] vxlan: check tun_info options_len properly

From: Greg Kroah-Hartman
Date: Fri Nov 08 2019 - 13:56:56 EST


From: Xin Long <lucien.xin@xxxxxxxxx>

[ Upstream commit eadf52cf1852196a1363044dcda22fa5d7f296f7 ]

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: ee122c79d422 ("vxlan: Flow based tunneling")
Signed-off-by: Xin Long <lucien.xin@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/net/vxlan.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

--- a/drivers/net/vxlan.c
+++ b/drivers/net/vxlan.c
@@ -2049,8 +2049,11 @@ static void vxlan_xmit_one(struct sk_buf
label = info->key.label;
udp_sum = !!(info->key.tun_flags & TUNNEL_CSUM);

- if (info->options_len)
+ if (info->options_len) {
+ if (info->options_len < sizeof(*md))
+ goto drop;
md = ip_tunnel_info_opts(info);
+ }
} else {
md->gbp = skb->mark;
}