linux-kernel - [PATCH 4.14 260/496] batman-adv: fix header size check in batadv_dbg

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Date:   Mon, 28 May 2018 12:00:45 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Matthias Schiffer <mschiffer@...verse-factory.net>,
        Sven Eckelmann <sven@...fation.org>,
        Simon Wunderlich <sw@...onwunderlich.de>,
        Sasha Levin <alexander.levin@...rosoft.com>
Subject: [PATCH 4.14 260/496] batman-adv: fix header size check in batadv_dbg_arp()

4.14-stable review patch.  If anyone has any objections, please let me know.

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

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

[ Upstream commit 6f27d2c2a8c236d296201c19abb8533ec20d212b ]

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: Sasha Levin <alexander.levin@...rosoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 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
@@ -391,7 +391,7 @@ 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;