This is a note to let you know that I've just added the patch titled tcp: Fix a data-race around sysctl_tcp_comp_sack_slack_ns. to the 5.15-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: tcp-fix-a-data-race-around-sysctl_tcp_comp_sack_slac.patch and it can be found in the queue-5.15 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit d01503cad72cd3674173d67418ac2e164136ede7 Author: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx> Date: Fri Jul 22 11:22:02 2022 -0700 tcp: Fix a data-race around sysctl_tcp_comp_sack_slack_ns. [ Upstream commit 22396941a7f343d704738360f9ef0e6576489d43 ] While reading sysctl_tcp_comp_sack_slack_ns, it can be changed concurrently. Thus, we need to add READ_ONCE() to its reader. Fixes: a70437cc09a1 ("tcp: add hrtimer slack to sack compression") Signed-off-by: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 486ca1d5b436..7b593865b4ae 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -5517,7 +5517,7 @@ static void __tcp_ack_snd_check(struct sock *sk, int ofo_possible) rtt * (NSEC_PER_USEC >> 3)/20); sock_hold(sk); hrtimer_start_range_ns(&tp->compressed_ack_timer, ns_to_ktime(delay), - sock_net(sk)->ipv4.sysctl_tcp_comp_sack_slack_ns, + READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_comp_sack_slack_ns), HRTIMER_MODE_REL_PINNED_SOFT); }