This is a note to let you know that I've just added the patch titled tcp: Fix data-races around sysctl_tcp_dsack. 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-data-races-around-sysctl_tcp_dsack.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 58ebb1c8b35a8ef38cd6927431e0fa7b173a632d Mon Sep 17 00:00:00 2001 From: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx> Date: Wed, 20 Jul 2022 09:50:12 -0700 Subject: tcp: Fix data-races around sysctl_tcp_dsack. From: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx> commit 58ebb1c8b35a8ef38cd6927431e0fa7b173a632d upstream. While reading sysctl_tcp_dsack, it can be changed concurrently. Thus, we need to add READ_ONCE() to its readers. 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 | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -4197,7 +4197,7 @@ static void tcp_dsack_set(struct sock *s { struct tcp_sock *tp = tcp_sk(sk); - if (tcp_is_sack(tp) && sock_net(sk)->ipv4.sysctl_tcp_dsack) { + if (tcp_is_sack(tp) && READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_dsack)) { int mib_idx; if (before(seq, tp->rcv_nxt)) @@ -4232,7 +4232,7 @@ static void tcp_send_dupack(struct sock NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKLOST); tcp_enter_quickack_mode(sk, TCP_MAX_QUICKACKS); - if (tcp_is_sack(tp) && sock_net(sk)->ipv4.sysctl_tcp_dsack) { + if (tcp_is_sack(tp) && READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_dsack)) { u32 end_seq = TCP_SKB_CB(skb)->end_seq; if (after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) 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