From: Florian Westphal <fw@strlen.de>
Date: Sat, 20 Aug 2022 15:54:06 +0000 (+0200)
Subject: netfilter: nft_tproxy: restrict to prerouting hook
X-Git-Tag: v4.19.273~21
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0b21edf4cc13516716848e0a4fdf726aa2a62cd9;p=thirdparty%2Fkernel%2Fstable.git

netfilter: nft_tproxy: restrict to prerouting hook

commit 18bbc3213383a82b05383827f4b1b882e3f0a5a5 upstream.

TPROXY is only allowed from prerouting, but nft_tproxy doesn't check this.
This fixes a crash (null dereference) when using tproxy from e.g. output.

Fixes: 4ed8eb6570a4 ("netfilter: nf_tables: Add native tproxy support")
Reported-by: Shell Chen <xierch@gmail.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Qingfang DENG <dqfext@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/net/netfilter/nft_tproxy.c b/net/netfilter/nft_tproxy.c
index b97ab1198b03f..a0e30bf4a845c 100644
--- a/net/netfilter/nft_tproxy.c
+++ b/net/netfilter/nft_tproxy.c
@@ -289,6 +289,13 @@ static int nft_tproxy_dump(struct sk_buff *skb,
 	return 0;
 }
 
+static int nft_tproxy_validate(const struct nft_ctx *ctx,
+			       const struct nft_expr *expr,
+			       const struct nft_data **data)
+{
+	return nft_chain_validate_hooks(ctx->chain, 1 << NF_INET_PRE_ROUTING);
+}
+
 static struct nft_expr_type nft_tproxy_type;
 static const struct nft_expr_ops nft_tproxy_ops = {
 	.type		= &nft_tproxy_type,
@@ -296,6 +303,7 @@ static const struct nft_expr_ops nft_tproxy_ops = {
 	.eval		= nft_tproxy_eval,
 	.init		= nft_tproxy_init,
 	.dump		= nft_tproxy_dump,
+	.validate	= nft_tproxy_validate,
 };
 
 static struct nft_expr_type nft_tproxy_type __read_mostly = {