[PATCH 5.19 050/158] netfilter: nft_tproxy: restrict to prerouting hook

Greg Kroah-Hartman
2022-08-29T11:21:54Z

From: Florian Westphal <fw@strlen.de>

[ Upstream commit 18bbc3213383a82b05383827f4b1b882e3f0a5a5 ]

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: Sasha Levin <sashal@kernel.org>
---
net/netfilter/nft_tproxy.c | 8 ++++++++
1 file changed, 8 insertions(+)

diff --git a/net/netfilter/nft_tproxy.c b/net/netfilter/nft_tproxy.c
index 801f013971dfa..a701ad64f10af 100644
--- a/net/netfilter/nft_tproxy.c
+++ b/net/netfilter/nft_tproxy.c
@@ -312,6 +312,13 @@ 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,
@@ -321,6 +328,7 @@ static const struct nft_expr_ops nft_tproxy_ops = {
.destroy = nft_tproxy_destroy,
.dump = nft_tproxy_dump,
.reduce = NFT_REDUCE_READONLY,
+ .validate = nft_tproxy_validate,
};

static struct nft_expr_type nft_tproxy_type __read_mostly = {
--
2.35.1