This is a note to let you know that I've just added the patch titled tcp: correct memory barrier usage in tcp_check_space() to the 4.9-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-correct-memory-barrier-usage-in-tcp_check_space.patch and it can be found in the queue-4.9 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From foo@baz Wed Dec 6 17:39:55 CET 2017 From: Jason Baron <jbaron@xxxxxxxxxx> Date: Tue, 24 Jan 2017 21:49:41 -0500 Subject: tcp: correct memory barrier usage in tcp_check_space() From: Jason Baron <jbaron@xxxxxxxxxx> [ Upstream commit 56d806222ace4c3aeae516cd7a855340fb2839d8 ] sock_reset_flag() maps to __clear_bit() not the atomic version clear_bit(). Thus, we need smp_mb(), smp_mb__after_atomic() is not sufficient. Fixes: 3c7151275c0c ("tcp: add memory barriers to write space paths") Cc: Eric Dumazet <eric.dumazet@xxxxxxxxx> Cc: Oleg Nesterov <oleg@xxxxxxxxxx> Signed-off-by: Jason Baron <jbaron@xxxxxxxxxx> Acked-by: Eric Dumazet <edumazet@xxxxxxxxxx> Reported-by: Oleg Nesterov <oleg@xxxxxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxx> 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 @@ -5081,7 +5081,7 @@ static void tcp_check_space(struct sock if (sock_flag(sk, SOCK_QUEUE_SHRUNK)) { sock_reset_flag(sk, SOCK_QUEUE_SHRUNK); /* pairs with tcp_poll() */ - smp_mb__after_atomic(); + smp_mb(); if (sk->sk_socket && test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) tcp_new_space(sk); Patches currently in stable-queue which might be from jbaron@xxxxxxxxxx are queue-4.9/tcp-correct-memory-barrier-usage-in-tcp_check_space.patch