Commit d8853cfe authored Jun 13, 2024 by Ignat Korchagin Committed by Greg Kroah-Hartman Jun 16, 2024

netfilter: nf_tables: allow NFPROTO_INET in nft_(match/target)_validate()

[ Upstream commit 7e0f122c65912740327e4c54472acaa5f85868cb ]

Commit d0009effa886 ("netfilter: nf_tables: validate NFPROTO_* family") added
some validation of NFPROTO_* families in the nft_compat module, but it broke
the ability to use legacy iptables modules in dual-stack nftables.

While with legacy iptables one had to independently manage IPv4 and IPv6
tables, with nftables it is possible to have dual-stack tables sharing the
rules. Moreover, it was possible to use rules based on legacy iptables
match/target modules in dual-stack nftables.

As an example, the program from [2] creates an INET dual-stack family table
using an xt_bpf based rule, which looks like the following (the actual output
was generated with a patched nft tool as the current nft tool does not parse
dual stack tables with legacy match rules, so consider it for illustrative
purposes only):

table inet testfw {
  chain input {
    type filter hook prerouting priority filter; policy accept;
    bytecode counter packets 0 bytes 0 accept
  }
}

After d0009effa886 ("netfilter: nf_tables: validate NFPROTO_* family") we get
EOPNOTSUPP for the above program.

Fix this by allowing NFPROTO_INET for nft_(match/target)_validate(), but also
restrict the functions to classic iptables hooks.

Changes in v3:
  * clarify that upstream nft will not display such configuration properly and
    that the output was generated with a patched nft tool
  * remove example program from commit description and link to it instead
  * no code changes otherwise

Changes in v2:
  * restrict nft_(match/target)_validate() to classic iptables hooks
  * rewrite example program to use unmodified libnftnl

Fixes: d0009effa886 ("netfilter: nf_tables: validate NFPROTO_* family")
Link: https://lore.kernel.org/all/Zc1PfoWN38UuFJRI@calendula/T/#mc947262582c90fec044c7a3398cc92fac7afea72 [1]
Link: https://lore.kernel.org/all/20240220145509.53357-1-ignat@cloudflare.com/

 [2]
Reported-by: Jordan Griege <jgriege@cloudflare.com>
Signed-off-by: Ignat Korchagin <ignat@cloudflare.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent a6411f3c

net/netfilter/nft_compat.c

+20 −0

Original line number	Diff line number	Diff line
		@@ -321,10 +321,20 @@ static int nft_target_validate(const struct nft_ctx *ctx,

		if (ctx->family != NFPROTO_IPV4 &&
		ctx->family != NFPROTO_IPV6 &&
		ctx->family != NFPROTO_INET &&
		ctx->family != NFPROTO_BRIDGE &&
		ctx->family != NFPROTO_ARP)
		return -EOPNOTSUPP;

		ret = nft_chain_validate_hooks(ctx->chain,
		(1 << NF_INET_PRE_ROUTING) \|
		(1 << NF_INET_LOCAL_IN) \|
		(1 << NF_INET_FORWARD) \|
		(1 << NF_INET_LOCAL_OUT) \|
		(1 << NF_INET_POST_ROUTING));
		if (ret)
		return ret;

		if (nft_is_base_chain(ctx->chain)) {
		const struct nft_base_chain *basechain =
		nft_base_chain(ctx->chain);
		@@ -568,10 +578,20 @@ static int nft_match_validate(const struct nft_ctx *ctx,

		if (ctx->family != NFPROTO_IPV4 &&
		ctx->family != NFPROTO_IPV6 &&
		ctx->family != NFPROTO_INET &&
		ctx->family != NFPROTO_BRIDGE &&
		ctx->family != NFPROTO_ARP)
		return -EOPNOTSUPP;

		ret = nft_chain_validate_hooks(ctx->chain,
		(1 << NF_INET_PRE_ROUTING) \|
		(1 << NF_INET_LOCAL_IN) \|
		(1 << NF_INET_FORWARD) \|
		(1 << NF_INET_LOCAL_OUT) \|
		(1 << NF_INET_POST_ROUTING));
		if (ret)
		return ret;

		if (nft_is_base_chain(ctx->chain)) {
		const struct nft_base_chain *basechain =
		nft_base_chain(ctx->chain);