[PATCH 5.4 49/87] tcp: Fix a data-race around sysctl_tcp_thin_linear_timeouts.

Greg Kroah-Hartman
2022-07-27T16:44:57Z

From: Kuniyuki Iwashima <kuniyu@amazon.com>

[ 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>
---
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 26da44e196ed..a0107eb02ae4 100644
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -569,7 +569,7 @@ 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;
--
2.35.1