bridge: mcast: Add a centralized error path

Subsequent patches will add memory allocations in br_mdb_config_init()
as the MDB configuration structure will include a linked list of source
entries. This memory will need to be freed regardless if br_mdb_add()
succeeded or failed.

As a preparation for this change, add a centralized error path where the
memory will be freed.

Note that br_mdb_del() already has one error path and therefore does not
require any changes.

Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Acked-by: Nikolay Aleksandrov <razor@blackwall.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/bridge/br_mdb.c

@@ -1053,28 +1053,29 @@ static int br_mdb_add(struct sk_buff *skb, struct nlmsghdr *nlh,
 	if (err)
 		return err;
 
+	err = -EINVAL;
 	/* host join errors which can happen before creating the group */
 	if (!cfg.p && !br_group_is_l2(&cfg.group)) {
 		/* don't allow any flags for host-joined IP groups */
 		if (cfg.entry->state) {
 			NL_SET_ERR_MSG_MOD(extack, "Flags are not allowed for host groups");
-			return -EINVAL;
+			goto out;
 		}
 		if (!br_multicast_is_star_g(&cfg.group)) {
 			NL_SET_ERR_MSG_MOD(extack, "Groups with sources cannot be manually host joined");
-			return -EINVAL;
+			goto out;
 		}
 	}
 
 	if (br_group_is_l2(&cfg.group) && cfg.entry->state != MDB_PERMANENT) {
 		NL_SET_ERR_MSG_MOD(extack, "Only permanent L2 entries allowed");
-		return -EINVAL;
+		goto out;
 	}
 
 	if (cfg.p) {
 		if (cfg.p->state == BR_STATE_DISABLED && cfg.entry->state != MDB_PERMANENT) {
 			NL_SET_ERR_MSG_MOD(extack, "Port is in disabled state and entry is not permanent");
-			return -EINVAL;
+			goto out;
 		}
 		vg = nbp_vlan_group(cfg.p);
 	} else {
@@ -1096,6 +1097,7 @@ static int br_mdb_add(struct sk_buff *skb, struct nlmsghdr *nlh,
 		err = __br_mdb_add(&cfg, extack);
 	}
 
+out:
 	return err;
 }