[PATCH 5.4 47/87] tcp: Fix a data-race around sysctl_tcp_early_retrans.

Greg Kroah-Hartman
2022-07-27T16:44:43Z

From: Kuniyuki Iwashima <kuniyu@amazon.com>

[ Upstream commit 52e65865deb6a36718a463030500f16530eaab74 ]

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

Fixes: eed530b6c676 ("tcp: early retransmit")
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_output.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 5cc345c4006e..72ee1fca0501 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2509,7 +2509,7 @@ bool tcp_schedule_loss_probe(struct sock *sk, bool advancing_rto)
if (rcu_access_pointer(tp->fastopen_rsk))
return false;

- early_retrans = sock_net(sk)->ipv4.sysctl_tcp_early_retrans;
+ early_retrans = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_early_retrans);
/* Schedule a loss probe in 2*RTT for SACK capable connections
* not in loss recovery, that are either limited by cwnd or application.
*/
--
2.35.1