bridge: tunnel: fix attribute checks in br_parse_vlan_tunnel_info

These checks should go after the attributes have been parsed otherwise
we're using tb uninitialized.

Fixes: efa5356b ("bridge: per vlan dst_metadata netlink support")
Reported-by: NColin Ian King <colin.king@canonical.com>
Signed-off-by: NNikolay Aleksandrov <nikolay@cumulusnetworks.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/bridge/br_netlink_tunnel.c

@@ -229,15 +229,15 @@ int br_parse_vlan_tunnel_info(struct nlattr *attr,
 
 	memset(tinfo, 0, sizeof(*tinfo));
 
-	if (!tb[IFLA_BRIDGE_VLAN_TUNNEL_ID] ||
-	    !tb[IFLA_BRIDGE_VLAN_TUNNEL_VID])
-		return -EINVAL;
-
 	err = nla_parse_nested(tb, IFLA_BRIDGE_VLAN_TUNNEL_MAX,
 			       attr, vlan_tunnel_policy);
 	if (err < 0)
 		return err;
 
+	if (!tb[IFLA_BRIDGE_VLAN_TUNNEL_ID] ||
+	    !tb[IFLA_BRIDGE_VLAN_TUNNEL_VID])
+		return -EINVAL;
+
 	tun_id = nla_get_u32(tb[IFLA_BRIDGE_VLAN_TUNNEL_ID]);
 	vid = nla_get_u16(tb[IFLA_BRIDGE_VLAN_TUNNEL_VID]);
 	if (vid >= VLAN_VID_MASK)