This is a note to let you know that I've just added the patch titled tcp: Fix a data-race around sysctl_tcp_challenge_ack_limit. to the 5.4-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_challenge_ack_limit.patch and it can be found in the queue-5.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From db3815a2fa691da145cfbe834584f31ad75df9ff Mon Sep 17 00:00:00 2001 From: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx> Date: Wed, 20 Jul 2022 09:50:21 -0700 Subject: tcp: Fix a data-race around sysctl_tcp_challenge_ack_limit. From: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx> commit db3815a2fa691da145cfbe834584f31ad75df9ff upstream. While reading sysctl_tcp_challenge_ack_limit, it can be changed concurrently. Thus, we need to add READ_ONCE() to its reader. Fixes: 282f23c6ee34 ("tcp: implement RFC 5961 3.2") 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 @@ -3484,7 +3484,7 @@ static void tcp_send_challenge_ack(struc /* Then check host-wide RFC 5961 rate limit. */ now = jiffies / HZ; if (now != challenge_timestamp) { - u32 ack_limit = net->ipv4.sysctl_tcp_challenge_ack_limit; + u32 ack_limit = READ_ONCE(net->ipv4.sysctl_tcp_challenge_ack_limit); u32 half = (ack_limit + 1) >> 1; challenge_timestamp = now; Patches currently in stable-queue which might be from kuniyu@xxxxxxxxxx are queue-5.4/tcp-fix-a-data-race-around-sysctl_tcp_app_win.patch queue-5.4/tcp-fix-a-data-race-around-sysctl_tcp_limit_output_bytes.patch queue-5.4/tcp-fix-a-data-race-around-sysctl_tcp_nometrics_save.patch queue-5.4/tcp-fix-a-data-race-around-sysctl_tcp_adv_win_scale.patch queue-5.4/tcp-fix-a-data-race-around-sysctl_tcp_frto.patch queue-5.4/tcp-fix-data-races-around-sysctl_tcp_dsack.patch queue-5.4/tcp-fix-a-data-race-around-sysctl_tcp_challenge_ack_limit.patch queue-5.4/net-ping6-fix-memleak-in-ipv6_renew_options.patch