[B.A.T.M.A.N.] [PATCH] batman-adv: fix memory access by setting mac_header in DAT

[Antonio Quartulli <antonio@meshcoding.com>]

In the TX path we now have functions that rely on the
skb->mac_header field. DAT does not set such field when
creating its own ARP packets thus leading to wrong memory
access.

Fix it by always setting the mac_header after having forged
the ARP packet.

Reported-by: Russel Senior <russell@personaltelco.net>
Signed-off-by: Antonio Quartulli <antonio@meshcoding.com>
Tested-by: Russel Senior <russell@personaltelco.net>
---
 distributed-arp-table.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/distributed-arp-table.c b/distributed-arp-table.c
index 6da587a..0b69b61 100644
--- a/distributed-arp-table.c
+++ b/distributed-arp-table.c
@@ -1028,6 +1028,11 @@ bool batadv_dat_snoop_incoming_arp_request(struct batadv_priv *bat_priv,
 	if (!skb_new)
 		goto out;
 
+	/* the rest of the TX path assumes that the mac_header offset pointing
+	 * to the inner Ethernet header has been set, therefore reset it now.
+	 */
+	skb_reset_mac_header(skb_new);
+
 	if (vid & BATADV_VLAN_HAS_TAG)
 		skb_new = vlan_insert_tag(skb_new, htons(ETH_P_8021Q),
 					  vid & VLAN_VID_MASK);
-- 
1.8.5.3