Re: [nf PATCH] netfilter: nf_tables: Fix for deleting base chains with payload

[Pablo Neira Ayuso <pablo@netfilter.org>]

[-- Attachment #1: Type: text/plain, Size: 843 bytes --]

On Sun, Jun 18, 2023 at 04:59:38PM +0200, Pablo Neira Ayuso wrote:
> Hi Phil,
> 
> On Fri, Jun 16, 2023 at 05:56:11PM +0200, Phil Sutter wrote:
> > When deleting a base chain, iptables-nft simply submits the whole chain
> > to the kernel, including the NFTA_CHAIN_HOOK attribute. The new code
> > added by fixed commit then turned this into a chain update, destroying
> > the hook but not the chain itself.
> > 
> > Detect the situation by checking if the chain's hook list becomes empty
> > after removing all submitted hooks from it. A base chain without hooks
> > is pointless, so revert back to deleting the chain.
> > 
> > Note the 'goto err_chain_del_hook', error path takes care of undoing the
> > hook_list modification and releasing the unused chain_hook.
> 
> Could you give a try to this alternative patch?

This is the full patch.

[-- Attachment #2: 0001-netfilter-nf_tables-Fix-for-deleting-base-chains-wit.patch --]
[-- Type: text/x-diff, Size: 2717 bytes --]

From 6d09ac39a91bffb91d6cdc08b97c03fc4f23594e Mon Sep 17 00:00:00 2001
From: Phil Sutter <phil@nwl.cc>
Date: Fri, 16 Jun 2023 17:56:11 +0200
Subject: [PATCH nf] netfilter: nf_tables: Fix for deleting base chains with
 payload

When deleting a base chain, iptables-nft simply submits the whole chain
to the kernel, including the NFTA_CHAIN_HOOK attribute. The new code
added by fixed commit then turned this into a chain update, destroying
the hook but not the chain itself.

Detect the situation by checking if the chain's hook list becomes empty
after removing all submitted hooks from it. A base chain without hooks
is pointless, so revert back to deleting the chain.

Note the 'goto err_chain_del_hook', error path takes care of undoing the
hook_list modification and releasing the unused chain_hook.

Fixes: 7d937b107108f ("netfilter: nf_tables: support for deleting devices in an existing netdev chain")
Signed-off-by: Phil Sutter <phil@nwl.cc>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 net/netfilter/nf_tables_api.c | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index c1db2f4b2aa4..4c7937fd803f 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -2811,21 +2811,18 @@ static int nf_tables_newchain(struct sk_buff *skb, const struct nfnl_info *info,
 	return nf_tables_addchain(&ctx, family, genmask, policy, flags, extack);
 }
 
-static int nft_delchain_hook(struct nft_ctx *ctx, struct nft_chain *chain,
+static int nft_delchain_hook(struct nft_ctx *ctx,
+			     struct nft_base_chain *basechain,
 			     struct netlink_ext_ack *extack)
 {
+	const struct nft_chain *chain = &basechain->chain;
 	const struct nlattr * const *nla = ctx->nla;
 	struct nft_chain_hook chain_hook = {};
-	struct nft_base_chain *basechain;
 	struct nft_hook *this, *hook;
 	LIST_HEAD(chain_del_list);
 	struct nft_trans *trans;
 	int err;
 
-	if (!nft_is_base_chain(chain))
-		return -EOPNOTSUPP;
-
-	basechain = nft_base_chain(chain);
 	err = nft_chain_parse_hook(ctx->net, basechain, nla, &chain_hook,
 				   ctx->family, chain->flags, extack);
 	if (err < 0)
@@ -2910,7 +2907,12 @@ static int nf_tables_delchain(struct sk_buff *skb, const struct nfnl_info *info,
 		if (chain->flags & NFT_CHAIN_HW_OFFLOAD)
 			return -EOPNOTSUPP;
 
-		return nft_delchain_hook(&ctx, chain, extack);
+		if (nft_is_base_chain(chain)) {
+			struct nft_base_chain *basechain = nft_base_chain(chain);
+
+			if (nft_base_chain_netdev(table->family, basechain->ops.hooknum))
+				return nft_delchain_hook(&ctx, basechain, extack);
+		}
 	}
 
 	if (info->nlh->nlmsg_flags & NLM_F_NONREC &&
-- 
2.30.2