From: Kuniyuki Iwashima <kuniyu@amazon.com>
Date: Wed, 20 Jul 2022 16:50:24 +0000 (-0700)
Subject: tcp: Fix a data-race around sysctl_tcp_min_rtt_wlen.
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=bd07f2e70a4ba1b343e8e1efea4136411b1b114d;p=linux.git

tcp: Fix a data-race around sysctl_tcp_min_rtt_wlen.

[ Upstream commit 1330ffacd05fc9ac4159d19286ce119e22450ed2 ]

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

Fixes: f672258391b4 ("tcp: track min RTT using windowed min-filter")
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_input.c b/net/ipv4/tcp_input.c
index a5357ebfbcc0f..b925c766f1d24 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3050,7 +3050,7 @@ static void tcp_fastretrans_alert(struct sock *sk, const u32 prior_snd_una,
 
 static void tcp_update_rtt_min(struct sock *sk, u32 rtt_us, const int flag)
 {
-	u32 wlen = sock_net(sk)->ipv4.sysctl_tcp_min_rtt_wlen * HZ;
+	u32 wlen = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_min_rtt_wlen) * HZ;
 	struct tcp_sock *tp = tcp_sk(sk);
 
 	if ((flag & FLAG_ACK_MAYBE_DELAYED) && rtt_us > tcp_min_rtt(tp)) {