[PATCH nf] netfilter: nf_tables: hit ENOENT on unexisting chain/flowtable update with missing attributes

[Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>]

If user does not specify hook number and priority, then assume this is
a chain/flowtable update. Therefore, report ENOENT which provides a
better hint than EINVAL. Set on extended netlink error report to refer
to the chain name.

Fixes: 5b6743fb2c2a ("netfilter: nf_tables: skip flowtable hooknum and priority on device updates")
Fixes: 5efe72698a97 ("netfilter: nf_tables: support for adding new devices to an existing netdev chain")
Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
---
>From userspace, this results in:

# nft list ruleset
table netdev x {
}
# nft add chain netdev x y { devices = { lo } \; }
Error: No such file or directory
add chain netdev x y { devices = { lo } ; }
                   ^

instead of EINVAL if the chain `y' does not exist.

 net/netfilter/nf_tables_api.c | 29 +++++++++++++++++------------
 1 file changed, 17 insertions(+), 12 deletions(-)

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index ef8d9f6a7e9c..69886041b994 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -2070,8 +2070,10 @@ static int nft_chain_parse_hook(struct net *net,
 
 	if (!basechain) {
 		if (!ha[NFTA_HOOK_HOOKNUM] ||
-		    !ha[NFTA_HOOK_PRIORITY])
-			return -EINVAL;
+		    !ha[NFTA_HOOK_PRIORITY]) {
+			NL_SET_BAD_ATTR(extack, nla[NFTA_CHAIN_NAME]);
+			return -ENOENT;
+		}
 
 		hook->num = ntohl(nla_get_be32(ha[NFTA_HOOK_HOOKNUM]));
 		hook->priority = ntohl(nla_get_be32(ha[NFTA_HOOK_PRIORITY]));
@@ -7695,7 +7697,7 @@ static const struct nla_policy nft_flowtable_hook_policy[NFTA_FLOWTABLE_HOOK_MAX
 };
 
 static int nft_flowtable_parse_hook(const struct nft_ctx *ctx,
-				    const struct nlattr *attr,
+				    const struct nlattr * const nla[],
 				    struct nft_flowtable_hook *flowtable_hook,
 				    struct nft_flowtable *flowtable,
 				    struct netlink_ext_ack *extack, bool add)
@@ -7707,15 +7709,18 @@ static int nft_flowtable_parse_hook(const struct nft_ctx *ctx,
 
 	INIT_LIST_HEAD(&flowtable_hook->list);
 
-	err = nla_parse_nested_deprecated(tb, NFTA_FLOWTABLE_HOOK_MAX, attr,
+	err = nla_parse_nested_deprecated(tb, NFTA_FLOWTABLE_HOOK_MAX,
+					  nla[NFTA_FLOWTABLE_HOOK],
 					  nft_flowtable_hook_policy, NULL);
 	if (err < 0)
 		return err;
 
 	if (add) {
 		if (!tb[NFTA_FLOWTABLE_HOOK_NUM] ||
-		    !tb[NFTA_FLOWTABLE_HOOK_PRIORITY])
-			return -EINVAL;
+		    !tb[NFTA_FLOWTABLE_HOOK_PRIORITY]) {
+			NL_SET_BAD_ATTR(extack, nla[NFTA_FLOWTABLE_NAME]);
+			return -ENOENT;
+		}
 
 		hooknum = ntohl(nla_get_be32(tb[NFTA_FLOWTABLE_HOOK_NUM]));
 		if (hooknum != NF_NETDEV_INGRESS)
@@ -7900,8 +7905,8 @@ static int nft_flowtable_update(struct nft_ctx *ctx, const struct nlmsghdr *nlh,
 	u32 flags;
 	int err;
 
-	err = nft_flowtable_parse_hook(ctx, nla[NFTA_FLOWTABLE_HOOK],
-				       &flowtable_hook, flowtable, extack, false);
+	err = nft_flowtable_parse_hook(ctx, nla, &flowtable_hook, flowtable,
+				       extack, false);
 	if (err < 0)
 		return err;
 
@@ -8046,8 +8051,8 @@ static int nf_tables_newflowtable(struct sk_buff *skb,
 	if (err < 0)
 		goto err3;
 
-	err = nft_flowtable_parse_hook(&ctx, nla[NFTA_FLOWTABLE_HOOK],
-				       &flowtable_hook, flowtable, extack, true);
+	err = nft_flowtable_parse_hook(&ctx, nla, &flowtable_hook, flowtable,
+				       extack, true);
 	if (err < 0)
 		goto err4;
 
@@ -8109,8 +8114,8 @@ static int nft_delflowtable_hook(struct nft_ctx *ctx,
 	struct nft_trans *trans;
 	int err;
 
-	err = nft_flowtable_parse_hook(ctx, nla[NFTA_FLOWTABLE_HOOK],
-				       &flowtable_hook, flowtable, extack, false);
+	err = nft_flowtable_parse_hook(ctx, nla, &flowtable_hook, flowtable,
+				       extack, false);
 	if (err < 0)
 		return err;
 
-- 
2.30.2