net: bridge: Set strict_start_type for br_policy

Set any new attributes added to br_policy to be parsed strictly, to
prevent userspace from passing garbage.
Signed-off-by: Johannes Nixdorf <jnixdorf-oss@avm.de>
Acked-by: Nikolay Aleksandrov <razor@blackwall.org>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Link: https://lore.kernel.org/r/20231016-fdb_limit-v5-4-32cddff87758@avm.deSigned-off-by: Jakub Kicinski <kuba@kernel.org>

net/bridge/br_netlink.c

@@ -1229,6 +1229,8 @@ static size_t br_port_get_slave_size(const struct net_device *brdev,
 }
 
 static const struct nla_policy br_policy[IFLA_BR_MAX + 1] = {
+	[IFLA_BR_UNSPEC]	= { .strict_start_type =
+				    IFLA_BR_FDB_N_LEARNED },
 	[IFLA_BR_FORWARD_DELAY]	= { .type = NLA_U32 },
 	[IFLA_BR_HELLO_TIME]	= { .type = NLA_U32 },
 	[IFLA_BR_MAX_AGE]	= { .type = NLA_U32 },