batman-adv: fix integer overflow on buff_pos

commit 0799e59 upstream.

Fixing an integer overflow present in batadv_iv_ogm_send_to_if. The size
check is done using the int type in batadv_iv_ogm_aggr_packet whereas the
buff_pos variable uses the s16 type. This could lead to an out-of-bound
read.

Cc: stable@vger.kernel.org
Fixes: c6c8fea ("net: Add batman-adv meshing protocol")
Signed-off-by: Lyes Bourennani <lbourennani@fuzzinglabs.com>
Signed-off-by: Alexis Pinson <apinson@fuzzinglabs.com>
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: m1nds

net/batman-adv/bat_iv_ogm.c

@@ -334,7 +334,7 @@ static void batadv_iv_ogm_send_to_if(struct batadv_forw_packet *forw_packet,
 	struct batadv_priv *bat_priv = netdev_priv(hard_iface->soft_iface);
 	const char *fwd_str;
 	u8 packet_num;
-	s16 buff_pos;
+	int buff_pos;
 	struct batadv_ogm_packet *batadv_ogm_packet;
 	struct sk_buff *skb;
 	u8 *packet_pos;