Merge branch 'nexthop-more-fine-grained-policies-for-netlink-message-validation'

Petr Machata says:

====================
nexthop: More fine-grained policies for netlink message validation

There is currently one policy that covers all attributes for next hop
object management. Actual validation is then done in code, which makes it
unobvious which attributes are acceptable when, and indeed that everything
is rejected as necessary.

In this series, split rtm_nh_policy to several policies that cover various
aspects of the next hop object configuration, and instead of open-coding
the validation, defer to nlmsg_parse(). This should make extending the next
hop code simpler as well, which will be relevant in near future for
resilient hashing implementation.

This was tested by running tools/testing/selftests/net/fib_nexthops.sh.
Additionally iproute2 was tweaked to issue "nexthop list id" as an
RTM_GETNEXTHOP dump request, instead of a straight get to test that
unexpected attributes are indeed rejected.
====================

Link: https://lore.kernel.org/r/cover.1611156111.git.petrm@nvidia.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

net/ipv4/nexthop.c

@@ -22,7 +22,7 @@ static void remove_nexthop(struct net *net, struct nexthop *nh,
 #define NH_DEV_HASHBITS  8
 #define NH_DEV_HASHSIZE (1U << NH_DEV_HASHBITS)
 
-static const struct nla_policy rtm_nh_policy[NHA_MAX + 1] = {
+static const struct nla_policy rtm_nh_policy_new[] = {
 	[NHA_ID]		= { .type = NLA_U32 },
 	[NHA_GROUP]		= { .type = NLA_BINARY },
 	[NHA_GROUP_TYPE]	= { .type = NLA_U16 },
@@ -31,6 +31,15 @@ static const struct nla_policy rtm_nh_policy[NHA_MAX + 1] = {
 	[NHA_GATEWAY]		= { .type = NLA_BINARY },
 	[NHA_ENCAP_TYPE]	= { .type = NLA_U16 },
 	[NHA_ENCAP]		= { .type = NLA_NESTED },
+	[NHA_FDB]		= { .type = NLA_FLAG },
+};
+
+static const struct nla_policy rtm_nh_policy_get[] = {
+	[NHA_ID]		= { .type = NLA_U32 },
+};
+
+static const struct nla_policy rtm_nh_policy_dump[] = {
+	[NHA_OIF]		= { .type = NLA_U32 },
 	[NHA_GROUPS]		= { .type = NLA_FLAG },
 	[NHA_MASTER]		= { .type = NLA_U32 },
 	[NHA_FDB]		= { .type = NLA_FLAG },
@@ -565,7 +574,8 @@ static int nh_check_attr_fdb_group(struct nexthop *nh, u8 *nh_family,
 	return 0;
 }
 
-static int nh_check_attr_group(struct net *net, struct nlattr *tb[],
+static int nh_check_attr_group(struct net *net,
+			       struct nlattr *tb[], size_t tb_size,
 			       struct netlink_ext_ack *extack)
 {
 	unsigned int len = nla_len(tb[NHA_GROUP]);
@@ -624,7 +634,7 @@ static int nh_check_attr_group(struct net *net, struct nlattr *tb[],
 			return -EINVAL;
 		}
 	}
-	for (i = NHA_GROUP_TYPE + 1; i < __NHA_MAX; ++i) {
+	for (i = NHA_GROUP_TYPE + 1; i < tb_size; ++i) {
 		if (!tb[i])
 			continue;
 		if (i == NHA_FDB)
@@ -1643,11 +1653,12 @@ static int rtm_to_nh_config(struct net *net, struct sk_buff *skb,
 			    struct netlink_ext_ack *extack)
 {
 	struct nhmsg *nhm = nlmsg_data(nlh);
-	struct nlattr *tb[NHA_MAX + 1];
+	struct nlattr *tb[ARRAY_SIZE(rtm_nh_policy_new)];
 	int err;
 
-	err = nlmsg_parse(nlh, sizeof(*nhm), tb, NHA_MAX, rtm_nh_policy,
-			  extack);
+	err = nlmsg_parse(nlh, sizeof(*nhm), tb,
+			  ARRAY_SIZE(rtm_nh_policy_new) - 1,
+			  rtm_nh_policy_new, extack);
 	if (err < 0)
 		return err;
 
@@ -1674,11 +1685,6 @@ static int rtm_to_nh_config(struct net *net, struct sk_buff *skb,
 		goto out;
 	}
 
-	if (tb[NHA_GROUPS] || tb[NHA_MASTER]) {
-		NL_SET_ERR_MSG(extack, "Invalid attributes in request");
-		goto out;
-	}
-
 	memset(cfg, 0, sizeof(*cfg));
 	cfg->nlflags = nlh->nlmsg_flags;
 	cfg->nlinfo.portid = NETLINK_CB(skb).portid;
@@ -1720,7 +1726,7 @@ static int rtm_to_nh_config(struct net *net, struct sk_buff *skb,
 			NL_SET_ERR_MSG(extack, "Invalid group type");
 			goto out;
 		}
-		err = nh_check_attr_group(net, tb, extack);
+		err = nh_check_attr_group(net, tb, ARRAY_SIZE(tb), extack);
 
 		/* no other attributes should be set */
 		goto out;
@@ -1842,28 +1848,16 @@ static int nh_valid_get_del_req(struct nlmsghdr *nlh, u32 *id,
 				struct netlink_ext_ack *extack)
 {
 	struct nhmsg *nhm = nlmsg_data(nlh);
-	struct nlattr *tb[NHA_MAX + 1];
-	int err, i;
+	struct nlattr *tb[ARRAY_SIZE(rtm_nh_policy_get)];
+	int err;
 
-	err = nlmsg_parse(nlh, sizeof(*nhm), tb, NHA_MAX, rtm_nh_policy,
-			  extack);
+	err = nlmsg_parse(nlh, sizeof(*nhm), tb,
+			  ARRAY_SIZE(rtm_nh_policy_get) - 1,
+			  rtm_nh_policy_get, extack);
 	if (err < 0)
 		return err;
 
 	err = -EINVAL;
-	for (i = 0; i < __NHA_MAX; ++i) {
-		if (!tb[i])
-			continue;
-
-		switch (i) {
-		case NHA_ID:
-			break;
-		default:
-			NL_SET_ERR_MSG_ATTR(extack, tb[i],
-					    "Unexpected attribute in request");
-			goto out;
-		}
-	}
 	if (nhm->nh_protocol || nhm->resvd || nhm->nh_scope || nhm->nh_flags) {
 		NL_SET_ERR_MSG(extack, "Invalid values in header");
 		goto out;
@@ -1991,48 +1985,35 @@ static int nh_valid_dump_req(const struct nlmsghdr *nlh, int *dev_idx,
 			     bool *fdb_filter, struct netlink_callback *cb)
 {
 	struct netlink_ext_ack *extack = cb->extack;
-	struct nlattr *tb[NHA_MAX + 1];
+	struct nlattr *tb[ARRAY_SIZE(rtm_nh_policy_dump)];
 	struct nhmsg *nhm;
-	int err, i;
+	int err;
 	u32 idx;
 
-	err = nlmsg_parse(nlh, sizeof(*nhm), tb, NHA_MAX, rtm_nh_policy,
-			  NULL);
+	err = nlmsg_parse(nlh, sizeof(*nhm), tb,
+			  ARRAY_SIZE(rtm_nh_policy_dump) - 1,
+			  rtm_nh_policy_dump, NULL);
 	if (err < 0)
 		return err;
 
-	for (i = 0; i <= NHA_MAX; ++i) {
-		if (!tb[i])
-			continue;
-
-		switch (i) {
-		case NHA_OIF:
-			idx = nla_get_u32(tb[i]);
+	if (tb[NHA_OIF]) {
+		idx = nla_get_u32(tb[NHA_OIF]);
 		if (idx > INT_MAX) {
 			NL_SET_ERR_MSG(extack, "Invalid device index");
 			return -EINVAL;
 		}
 		*dev_idx = idx;
-			break;
-		case NHA_MASTER:
-			idx = nla_get_u32(tb[i]);
+	}
+	if (tb[NHA_MASTER]) {
+		idx = nla_get_u32(tb[NHA_MASTER]);
 		if (idx > INT_MAX) {
 			NL_SET_ERR_MSG(extack, "Invalid master device index");
 			return -EINVAL;
 		}
 		*master_idx = idx;
-			break;
-		case NHA_GROUPS:
-			*group_filter = true;
-			break;
-		case NHA_FDB:
-			*fdb_filter = true;
-			break;
-		default:
-			NL_SET_ERR_MSG(extack, "Unsupported attribute in dump request");
-			return -EINVAL;
-		}
 	}
+	*group_filter = nla_get_flag(tb[NHA_GROUPS]);
+	*fdb_filter = nla_get_flag(tb[NHA_FDB]);
 
 	nhm = nlmsg_data(nlh);
 	if (nhm->nh_protocol || nhm->resvd || nhm->nh_scope || nhm->nh_flags) {