batman-adv: tt: prevent TVLV OOB check overflow

commit 7a581d9 upstream.

A TT unicast TVLV contains the number of VLANs stored in it. This number is
an u16 and gets multiplied by the size of the struct
batadv_tvlv_tt_vlan_data (8 bytes). The size can therefore overflow the u16
used to store the tt_vlan_len. All additional safety checks to prevent
out-of-bounds access of the TVLV buffer are invalid due to this overflow.

Using size_t prevents this overflow and ensures that the safety checks
compare against the actual buffer requirements.

Cc: stable@vger.kernel.org
Fixes: 7ea7b4a ("batman-adv: make the TT CRC logic VLAN specific")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: ecsv

net/batman-adv/translation-table.c

@@ -4101,7 +4101,8 @@ static int batadv_tt_tvlv_unicast_handler_v1(struct batadv_priv *bat_priv,
 					     u16 tvlv_value_len)
 {
 	struct batadv_tvlv_tt_data *tt_data;
-	u16 tt_vlan_len, tt_num_entries;
+	u16 tt_num_entries;
+	size_t tt_vlan_len;
 	char tt_flag;
 	bool ret;