tcp: correct memory barrier usage in tcp_check_space()

BugLink: http://bugs.launchpad.net/bugs/1745046
[ 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@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Jason Baron <jbaron@akamai.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Reported-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 6de7cc6bc448efb0efb55dfdb89b5f37b4576b9f..bce48faa50cefb9e6978999ea0cfa726544700ed 100644 (file)
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -4939,7 +4939,7 @@ static void tcp_check_space(struct sock *sk)
        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);