From: Kuniyuki Iwashima <kuniyu@amazon.com>
Date: Mon, 18 Jul 2022 17:26:47 +0000 (-0700)
Subject: tcp: Fix a data-race around sysctl_tcp_thin_linear_timeouts.
X-Git-Tag: v5.15.73~1984
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=404c53ccdebd11f96954f4070cffac8e0b4d5cb6;p=platform%2Fkernel%2Flinux-rpi.git

tcp: Fix a data-race around sysctl_tcp_thin_linear_timeouts.

[ Upstream commit 7c6f2a86ca590d5187a073d987e9599985fb1c7c ]

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

Fixes: 36e31b0af587 ("net: TCP thin linear timeouts")
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_timer.c b/net/ipv4/tcp_timer.c
index ec5277b..50bba37 100644
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -578,7 +578,7 @@ out_reset_timer:
 	 * linear-timeout retransmissions into a black hole
 	 */
 	if (sk->sk_state == TCP_ESTABLISHED &&
-	    (tp->thin_lto || net->ipv4.sysctl_tcp_thin_linear_timeouts) &&
+	    (tp->thin_lto || READ_ONCE(net->ipv4.sysctl_tcp_thin_linear_timeouts)) &&
 	    tcp_stream_is_thin(tp) &&
 	    icsk->icsk_retransmits <= TCP_THIN_LINEAR_RETRIES) {
 		icsk->icsk_backoff = 0;