[PATCH nf-next] netfilter: nft_compat: restrict raw table targets/matches

[Florian Westphal <fw@strlen.de>]

xt targets and matches declaring .table = "raw" (CT, NOTRACK) rely on
only ever running in the legacy raw table's prerouting/output chains,
ahead of conntrack. nft_compat_chain_validate_dependency() already
enforces this kind of correspondence for "nat" by requiring the chain
type to actually be NAT, but did nothing for "raw": a rule wrapping
the CT target could be loaded into any hook and any priority via
nft_compat, including after the real conntrack hook has already run.

The CT target attaches a conntrack template to the skb when none is
set yet.

Require that a "raw" table dependency actually matches what xtables
enforces via the implict/builtin table dependency.

Fixes: 0ca743a55991 ("netfilter: nf_tables: add compatibility layer for x_tables")
Assisted-by: LLM
Signed-off-by: Florian Westphal <fw@strlen.de>
---
 net/netfilter/nft_compat.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/net/netfilter/nft_compat.c b/net/netfilter/nft_compat.c
index 63864b928259..88ddaf47f587 100644
--- a/net/netfilter/nft_compat.c
+++ b/net/netfilter/nft_compat.c
@@ -14,6 +14,7 @@
 #include <linux/netfilter/nf_tables.h>
 #include <linux/netfilter/nf_tables_compat.h>
 #include <linux/netfilter/x_tables.h>
+#include <linux/netfilter_ipv4.h>
 #include <linux/netfilter_ipv4/ip_tables.h>
 #include <linux/netfilter_ipv6/ip6_tables.h>
 #include <linux/netfilter_bridge/ebtables.h>
@@ -45,6 +46,20 @@ static int nft_compat_chain_validate_dependency(const struct nft_ctx *ctx,
 			type = NFT_CHAIN_T_NAT;
 		if (basechain->type->type != type)
 			return -EINVAL;
+	} else if (strcmp(tablename, "raw") == 0) {
+		/* iptables-nft emulates the legacy raw table, which only
+		 * ever has prerouting/output chains at this exact priority.
+		 */
+		if (ctx->family != NFPROTO_IPV4 &&
+		    ctx->family != NFPROTO_IPV6)
+			return -EINVAL;
+
+		if (basechain->ops.hooknum != NF_INET_PRE_ROUTING &&
+		    basechain->ops.hooknum != NF_INET_LOCAL_OUT)
+			return -EINVAL;
+
+		if (basechain->ops.priority != NF_IP_PRI_RAW)
+			return -EINVAL;
 	}
 
 	return 0;
-- 
2.55.0