netdev - [PATCH net 3/6] netfilter: nft_synproxy: avoid possible data-race on update operation

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Message-ID: <20260102114128.7007-4-fw@strlen.de>
Date: Fri,  2 Jan 2026 12:41:25 +0100
From: Florian Westphal <fw@...len.de>
To: <netdev@...r.kernel.org>
Cc: Paolo Abeni <pabeni@...hat.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	<netfilter-devel@...r.kernel.org>,
	pablo@...filter.org
Subject: [PATCH net 3/6] netfilter: nft_synproxy: avoid possible data-race on update operation

From: Fernando Fernandez Mancera <fmancera@...e.de>

During nft_synproxy eval we are reading nf_synproxy_info struct which
can be modified on update operation concurrently. As nf_synproxy_info
struct fits in 32 bits, use READ_ONCE/WRITE_ONCE annotations.

Fixes: ee394f96ad75 ("netfilter: nft_synproxy: add synproxy stateful object support")
Signed-off-by: Fernando Fernandez Mancera <fmancera@...e.de>
Signed-off-by: Florian Westphal <fw@...len.de>
---
 net/netfilter/nft_synproxy.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/net/netfilter/nft_synproxy.c b/net/netfilter/nft_synproxy.c
index 5d3e51825985..4d3e5a31b412 100644
--- a/net/netfilter/nft_synproxy.c
+++ b/net/netfilter/nft_synproxy.c
@@ -48,7 +48,7 @@ static void nft_synproxy_eval_v4(const struct nft_synproxy *priv,
 				 struct tcphdr *_tcph,
 				 struct synproxy_options *opts)
 {
-	struct nf_synproxy_info info = priv->info;
+	struct nf_synproxy_info info = READ_ONCE(priv->info);
 	struct net *net = nft_net(pkt);
 	struct synproxy_net *snet = synproxy_pernet(net);
 	struct sk_buff *skb = pkt->skb;
@@ -79,7 +79,7 @@ static void nft_synproxy_eval_v6(const struct nft_synproxy *priv,
 				 struct tcphdr *_tcph,
 				 struct synproxy_options *opts)
 {
-	struct nf_synproxy_info info = priv->info;
+	struct nf_synproxy_info info = READ_ONCE(priv->info);
 	struct net *net = nft_net(pkt);
 	struct synproxy_net *snet = synproxy_pernet(net);
 	struct sk_buff *skb = pkt->skb;
@@ -340,7 +340,7 @@ static void nft_synproxy_obj_update(struct nft_object *obj,
 	struct nft_synproxy *newpriv = nft_obj_data(newobj);
 	struct nft_synproxy *priv = nft_obj_data(obj);
 
-	priv->info = newpriv->info;
+	WRITE_ONCE(priv->info, newpriv->info);
 }
 
 static struct nft_object_type nft_synproxy_obj_type;
-- 
2.51.2