batman-adv: release vlan object after checking the CRC

There is a refcounter unbalance in the CRC checking routine
invoked on OGM reception. A vlan object is retrieved (thus
its refcounter is increased by one) but it is never properly
released. This leads to a memleak because the vlan object
will never be free'd.

Fix this by releasing the vlan object after having read the
CRC.

Reported-by: Russell Senior <russell@personaltelco.net>
Reported-by: Daniel <daniel@makrotopia.org>
Reported-by: cmsv <cmsv@wirelesspt.net>
Signed-off-by: Antonio Quartulli <antonio@meshcoding.com>
Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>

net/batman-adv/translation-table.c

@@ -2262,6 +2262,7 @@ static bool batadv_tt_global_check_crc(struct batadv_orig_node *orig_node,
 {
 	struct batadv_tvlv_tt_vlan_data *tt_vlan_tmp;
 	struct batadv_orig_node_vlan *vlan;
+	uint32_t crc;
 	int i;
 
 	/* check if each received CRC matches the locally stored one */
@@ -2281,7 +2282,10 @@ static bool batadv_tt_global_check_crc(struct batadv_orig_node *orig_node,
 		if (!vlan)
 			return false;
 
-		if (vlan->tt.crc != ntohl(tt_vlan_tmp->crc))
+		crc = vlan->tt.crc;
+		batadv_orig_node_vlan_free_ref(vlan);
+
+		if (crc != ntohl(tt_vlan_tmp->crc))
 			return false;
 	}