netfilter: nft_synproxy: avoid possible data-race on update operation

[ Upstream commit 36a3200 ]

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: ee394f9 ("netfilter: nft_synproxy: add synproxy stateful object support")
Signed-off-by: Fernando Fernandez Mancera <fmancera@suse.de>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>

Author: ffmancera

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;