rtnetlink: bridge: Use a different policy for MDB bulk delete

For MDB bulk delete we will need to validate 'MDBA_SET_ENTRY'
differently compared to regular delete. Specifically, allow the ifindex
to be zero (in case not filtering on bridge port) and force the address
to be zero as bulk delete based on address is not supported.

Do that by introducing a new policy and choosing the correct policy
based on the presence of the 'NLM_F_BULK' flag in the netlink message
header. Use nlmsg_parse() for strict validation.
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Petr Machata <petrm@nvidia.com>
Acked-by: Nikolay Aleksandrov <razor@blackwall.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/rtnetlink.c

@@ -6410,17 +6410,64 @@ static int rtnl_mdb_add(struct sk_buff *skb, struct nlmsghdr *nlh,
 	return dev->netdev_ops->ndo_mdb_add(dev, tb, nlh->nlmsg_flags, extack);
 }
 
+static int rtnl_validate_mdb_entry_del_bulk(const struct nlattr *attr,
+					    struct netlink_ext_ack *extack)
+{
+	struct br_mdb_entry *entry = nla_data(attr);
+	struct br_mdb_entry zero_entry = {};
+
+	if (nla_len(attr) != sizeof(struct br_mdb_entry)) {
+		NL_SET_ERR_MSG_ATTR(extack, attr, "Invalid attribute length");
+		return -EINVAL;
+	}
+
+	if (entry->state != MDB_PERMANENT && entry->state != MDB_TEMPORARY) {
+		NL_SET_ERR_MSG(extack, "Unknown entry state");
+		return -EINVAL;
+	}
+
+	if (entry->flags) {
+		NL_SET_ERR_MSG(extack, "Entry flags cannot be set");
+		return -EINVAL;
+	}
+
+	if (entry->vid >= VLAN_N_VID - 1) {
+		NL_SET_ERR_MSG(extack, "Invalid entry VLAN id");
+		return -EINVAL;
+	}
+
+	if (memcmp(&entry->addr, &zero_entry.addr, sizeof(entry->addr))) {
+		NL_SET_ERR_MSG(extack, "Entry address cannot be set");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static const struct nla_policy mdba_del_bulk_policy[MDBA_SET_ENTRY_MAX + 1] = {
+	[MDBA_SET_ENTRY] = NLA_POLICY_VALIDATE_FN(NLA_BINARY,
+						  rtnl_validate_mdb_entry_del_bulk,
+						  sizeof(struct br_mdb_entry)),
+	[MDBA_SET_ENTRY_ATTRS] = { .type = NLA_NESTED },
+};
+
 static int rtnl_mdb_del(struct sk_buff *skb, struct nlmsghdr *nlh,
 			struct netlink_ext_ack *extack)
 {
+	bool del_bulk = !!(nlh->nlmsg_flags & NLM_F_BULK);
 	struct nlattr *tb[MDBA_SET_ENTRY_MAX + 1];
 	struct net *net = sock_net(skb->sk);
 	struct br_port_msg *bpm;
 	struct net_device *dev;
 	int err;
 
-	err = nlmsg_parse_deprecated(nlh, sizeof(*bpm), tb,
-				     MDBA_SET_ENTRY_MAX, mdba_policy, extack);
+	if (!del_bulk)
+		err = nlmsg_parse_deprecated(nlh, sizeof(*bpm), tb,
+					     MDBA_SET_ENTRY_MAX, mdba_policy,
+					     extack);
+	else
+		err = nlmsg_parse(nlh, sizeof(*bpm), tb, MDBA_SET_ENTRY_MAX,
+				  mdba_del_bulk_policy, extack);
 	if (err)
 		return err;