linux-kernel - [PATCH 3.16 370/410] batman-adv: fix header size check in batadv_dbg

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Message-ID: <lsq.1528380321.368545834@decadent.org.uk>
Date:   Thu, 07 Jun 2018 15:05:21 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Matthias Schiffer" <mschiffer@...verse-factory.net>,
        "Sven Eckelmann" <sven@...fation.org>,
        "Simon Wunderlich" <sw@...onwunderlich.de>
Subject: [PATCH 3.16 370/410] batman-adv: fix header size check in
 batadv_dbg_arp()

3.16.57-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Matthias Schiffer <mschiffer@...verse-factory.net>

commit 6f27d2c2a8c236d296201c19abb8533ec20d212b upstream.

Checking for 0 is insufficient: when an SKB without a batadv header, but
with a VLAN header is received, hdr_size will be 4, making the following
code interpret the Ethernet header as a batadv header.

Fixes: be1db4f6615b ("batman-adv: make the Distributed ARP Table vlan aware")
Signed-off-by: Matthias Schiffer <mschiffer@...verse-factory.net>
Signed-off-by: Sven Eckelmann <sven@...fation.org>
Signed-off-by: Simon Wunderlich <sw@...onwunderlich.de>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 net/batman-adv/distributed-arp-table.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/batman-adv/distributed-arp-table.c
+++ b/net/batman-adv/distributed-arp-table.c
@@ -343,7 +343,7 @@ static void batadv_dbg_arp(struct batadv
 		   batadv_arp_hw_src(skb, hdr_size), &ip_src,
 		   batadv_arp_hw_dst(skb, hdr_size), &ip_dst);
 
-	if (hdr_size == 0)
+	if (hdr_size < sizeof(struct batadv_unicast_packet))
 		return;
 
 	unicast_4addr_packet = (struct batadv_unicast_4addr_packet *)skb->data;