linux-kernel - [PATCH 4.9 26/34] vxlan: check tun_info options

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Message-Id: <20191108174647.848379113@linuxfoundation.org>
Date:   Fri,  8 Nov 2019 19:50:33 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Xin Long <lucien.xin@...il.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 4.9 26/34] vxlan: check tun_info options_len properly

From: Xin Long <lucien.xin@...il.com>

[ 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@...il.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 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;
 	}