Linux Ethernet Bridging - Feb 2023 - [Bridge] [PATCH net-next 3/4] bridge: mcast: Move validation to a policy

Future patches are going to move parts of the bridge MDB code to the
common rtnetlink code in preparation for VXLAN MDB support. To
facilitate code sharing between both drivers, move the validation of the
top level attributes in RTM_{NEW,DEL}MDB messages to a policy that will
eventually be moved to the rtnetlink code.

Use 'NLA_NESTED' for 'MDBA_SET_ENTRY_ATTRS' instead of
NLA_POLICY_NESTED() as this attribute is going to be validated using
different policies in the underlying drivers.

Signed-off-by: Ido Schimmel <idosch at nvidia.com>
---
 net/bridge/br_mdb.c | 45 +++++++++++++++++++++++++++------------------
 1 file changed, 27 insertions(+), 18 deletions(-)

diff --git a/net/bridge/br_mdb.c b/net/bridge/br_mdb.c
index 96f36febfb30..25c48d81a597 100644
--- a/net/bridge/br_mdb.c
+++ b/net/bridge/br_mdb.c
@@ -683,51 +683,58 @@ static const struct nla_policy
br_mdbe_attrs_pol[MDBE_ATTR_MAX + 1] = {
 	[MDBE_ATTR_RTPROT] = NLA_POLICY_MIN(NLA_U8, RTPROT_STATIC),
 };
 
-static bool is_valid_mdb_entry(struct br_mdb_entry *entry,
-			       struct netlink_ext_ack *extack)
+static int validate_mdb_entry(const struct nlattr *attr,
+			      struct netlink_ext_ack *extack)
 {
+	struct br_mdb_entry *entry = nla_data(attr);
+
+	if (nla_len(attr) != sizeof(struct br_mdb_entry)) {
+		NL_SET_ERR_MSG_MOD(extack, "Invalid MDBA_SET_ENTRY attribute
length");
+		return -EINVAL;
+	}
+
 	if (entry->ifindex == 0) {
 		NL_SET_ERR_MSG_MOD(extack, "Zero entry ifindex is not allowed");
-		return false;
+		return -EINVAL;
 	}
 
 	if (entry->addr.proto == htons(ETH_P_IP)) {
 		if (!ipv4_is_multicast(entry->addr.u.ip4)) {
 			NL_SET_ERR_MSG_MOD(extack, "IPv4 entry group address is not
multicast");
-			return false;
+			return -EINVAL;
 		}
 		if (ipv4_is_local_multicast(entry->addr.u.ip4)) {
 			NL_SET_ERR_MSG_MOD(extack, "IPv4 entry group address is local
multicast");
-			return false;
+			return -EINVAL;
 		}
 #if IS_ENABLED(CONFIG_IPV6)
 	} else if (entry->addr.proto == htons(ETH_P_IPV6)) {
 		if (ipv6_addr_is_ll_all_nodes(&entry->addr.u.ip6)) {
 			NL_SET_ERR_MSG_MOD(extack, "IPv6 entry group address is link-local all
nodes");
-			return false;
+			return -EINVAL;
 		}
 #endif
 	} else if (entry->addr.proto == 0) {
 		/* L2 mdb */
 		if (!is_multicast_ether_addr(entry->addr.u.mac_addr)) {
 			NL_SET_ERR_MSG_MOD(extack, "L2 entry group is not multicast");
-			return false;
+			return -EINVAL;
 		}
 	} else {
 		NL_SET_ERR_MSG_MOD(extack, "Unknown entry protocol");
-		return false;
+		return -EINVAL;
 	}
 
 	if (entry->state != MDB_PERMANENT && entry->state !=
MDB_TEMPORARY) {
 		NL_SET_ERR_MSG_MOD(extack, "Unknown entry state");
-		return false;
+		return -EINVAL;
 	}
 	if (entry->vid >= VLAN_VID_MASK) {
 		NL_SET_ERR_MSG_MOD(extack, "Invalid entry VLAN id");
-		return false;
+		return -EINVAL;
 	}
 
-	return true;
+	return 0;
 }
 
 static bool is_valid_mdb_source(struct nlattr *attr, __be16 proto,
@@ -1292,6 +1299,14 @@ static int br_mdb_config_attrs_init(struct nlattr
*set_attrs,
 	return 0;
 }
 
+static const struct nla_policy mdba_policy[MDBA_SET_ENTRY_MAX + 1] = {
+	[MDBA_SET_ENTRY_UNSPEC] = { .strict_start_type = MDBA_SET_ENTRY_ATTRS + 1 },
+	[MDBA_SET_ENTRY] = NLA_POLICY_VALIDATE_FN(NLA_BINARY,
+						  validate_mdb_entry,
+						  sizeof(struct br_mdb_entry)),
+	[MDBA_SET_ENTRY_ATTRS] = { .type = NLA_NESTED },
+};
+
 static int br_mdb_config_init(struct net *net, const struct nlmsghdr *nlh,
 			      struct br_mdb_config *cfg,
 			      struct netlink_ext_ack *extack)
@@ -1302,7 +1317,7 @@ static int br_mdb_config_init(struct net *net, const
struct nlmsghdr *nlh,
 	int err;
 
 	err = nlmsg_parse_deprecated(nlh, sizeof(*bpm), tb,
-				     MDBA_SET_ENTRY_MAX, NULL, extack);
+				     MDBA_SET_ENTRY_MAX, mdba_policy, extack);
 	if (err)
 		return err;
 
@@ -1344,14 +1359,8 @@ static int br_mdb_config_init(struct net *net, const
struct nlmsghdr *nlh,
 		NL_SET_ERR_MSG_MOD(extack, "Missing MDBA_SET_ENTRY attribute");
 		return -EINVAL;
 	}
-	if (nla_len(tb[MDBA_SET_ENTRY]) != sizeof(struct br_mdb_entry)) {
-		NL_SET_ERR_MSG_MOD(extack, "Invalid MDBA_SET_ENTRY attribute
length");
-		return -EINVAL;
-	}
 
 	cfg->entry = nla_data(tb[MDBA_SET_ENTRY]);
-	if (!is_valid_mdb_entry(cfg->entry, extack))
-		return -EINVAL;
 
 	if (cfg->entry->ifindex != cfg->br->dev->ifindex) {
 		struct net_device *pdev;
-- 
2.37.3

On 2/9/23 09:18, Ido Schimmel wrote:
> Future patches are going to move parts of the bridge MDB code to the
> common rtnetlink code in preparation for VXLAN MDB support. To
> facilitate code sharing between both drivers, move the validation of the
> top level attributes in RTM_{NEW,DEL}MDB messages to a policy that will
> eventually be moved to the rtnetlink code.
> 
> Use 'NLA_NESTED' for 'MDBA_SET_ENTRY_ATTRS' instead of
> NLA_POLICY_NESTED() as this attribute is going to be validated using
> different policies in the underlying drivers.
> 
> Signed-off-by: Ido Schimmel <idosch at nvidia.com>
> ---
>   net/bridge/br_mdb.c | 45 +++++++++++++++++++++++++++------------------
>   1 file changed, 27 insertions(+), 18 deletions(-)
> 

Acked-by: Nikolay Aleksandrov <razor at blackwall.org>

On Thu,  9 Feb 2023 09:18:51 +0200 Ido Schimmel wrote:
> +	if (nla_len(attr) != sizeof(struct br_mdb_entry)) {
> +		NL_SET_ERR_MSG_MOD(extack, "Invalid MDBA_SET_ENTRY attribute
length");
> +		return -EINVAL;
Well, you're just moving it, but NL_SET_ERR_MSG_ATTR() would be better.
We shouldn't be adding _MOD() in the core implementation of the family.