From: Kuniyuki Iwashima <kuniyu@amazon.com>
Date: Mon, 18 Jul 2022 17:26:49 +0000 (-0700)
Subject: tcp: Fix a data-race around sysctl_tcp_retrans_collapse.
X-Git-Tag: v5.10.134~31
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=daa8b5b8694c05a383fe43ffea679aa2153277cf;p=users%2Fdwmw2%2Flinux.git

tcp: Fix a data-race around sysctl_tcp_retrans_collapse.

[ Upstream commit 1a63cb91f0c2fcdeced6d6edee8d1d886583d139 ]

While reading sysctl_tcp_retrans_collapse, it can be changed
concurrently.  Thus, we need to add READ_ONCE() to its reader.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index ef64ee4c902a6..9b67c61576e4c 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -3100,7 +3100,7 @@ static void tcp_retrans_try_collapse(struct sock *sk, struct sk_buff *to,
 	struct sk_buff *skb = to, *tmp;
 	bool first = true;
 
-	if (!sock_net(sk)->ipv4.sysctl_tcp_retrans_collapse)
+	if (!READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_retrans_collapse))
 		return;
 	if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
 		return;