This is a note to let you know that I've just added the patch titled tcp: Fix a data-race around sysctl_tcp_frto. to the 4.19-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_frto.patch and it can be found in the queue-4.19 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 706c6202a3589f290e1ef9be0584a8f4a3cc0507 Mon Sep 17 00:00:00 2001 From: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx> Date: Wed, 20 Jul 2022 09:50:15 -0700 Subject: tcp: Fix a data-race around sysctl_tcp_frto. From: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx> commit 706c6202a3589f290e1ef9be0584a8f4a3cc0507 upstream. While reading sysctl_tcp_frto, it can be changed concurrently. Thus, we need to add READ_ONCE() to its reader. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- net/ipv4/tcp_input.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -2018,7 +2018,7 @@ void tcp_enter_loss(struct sock *sk) * loss recovery is underway except recurring timeout(s) on * the same SND.UNA (sec 3.2). Disable F-RTO on path MTU probing */ - tp->frto = net->ipv4.sysctl_tcp_frto && + tp->frto = READ_ONCE(net->ipv4.sysctl_tcp_frto) && (new_recovery || icsk->icsk_retransmits) && !inet_csk(sk)->icsk_mtup.probe_size; } Patches currently in stable-queue which might be from kuniyu@xxxxxxxxxx are queue-4.19/tcp-fix-a-data-race-around-sysctl_tcp_app_win.patch queue-4.19/tcp-fix-a-data-race-around-sysctl_tcp_nometrics_save.patch queue-4.19/tcp-fix-a-data-race-around-sysctl_tcp_adv_win_scale.patch queue-4.19/tcp-fix-a-data-race-around-sysctl_tcp_frto.patch queue-4.19/tcp-fix-data-races-around-sysctl_tcp_dsack.patch