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Date:   Mon, 18 Jul 2022 10:26:47 -0700
From:   Kuniyuki Iwashima <kuniyu@...zon.com>
To:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        David Ahern <dsahern@...nel.org>
CC:     Kuniyuki Iwashima <kuniyu@...zon.com>,
        Kuniyuki Iwashima <kuni1840@...il.com>,
        <netdev@...r.kernel.org>, Andreas Petlund <apetlund@...ula.no>
Subject: [PATCH v1 net 09/15] tcp: Fix a data-race around sysctl_tcp_thin_linear_timeouts.

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@...zon.com>
---
CC: Andreas Petlund <apetlund@...ula.no>
---
 net/ipv4/tcp_timer.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index ec5277becc6a..50bba370486e 100644
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -578,7 +578,7 @@ void tcp_retransmit_timer(struct sock *sk)
 	 * 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;
-- 
2.30.2

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