On Thu, 2017-03-30 at 09:35 +0900, Seiichi Ikarashi wrote:
> Similar to a4d258036ed9 ("tcp: Fix race in tcp_poll").
>
> Between receiving a packet and tcp_poll(), sk->sk_err is protected by memory
> barriers but
> sk->sk_shutdown and sk->sk_state are not.
...
> So possibly, POLLIN|POLLRDNORM|POLLRDHUP might
> not be set even when receiving a RST packet.
>
> Signed-off-by: Seiichi Ikarashi <s.ikara...@jp.fujitsu.com>
>
> ---
> net/ipv4/tcp.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
> index cf45555..c8bc86e 100644
> --- a/net/ipv4/tcp.c
> +++ b/net/ipv4/tcp.c
> @@ -456,6 +456,8 @@ unsigned int tcp_poll(struct file *file, struct socket
> *sock, poll_table *wait)
>
> sock_poll_wait(file, sk_sleep(sk), wait);
>
> + /* This barrier is coupled with smp_wmb() in tcp_reset() */
> + smp_rmb();
> state = sk_state_load(sk);
Are you telling us that sk_state_load() has no barrier ?
This would imply that smp_load_acquire() should be replaced ?
> if (state == TCP_LISTEN)
> return inet_csk_listen_poll(sk);
> @@ -540,8 +542,6 @@ unsigned int tcp_poll(struct file *file, struct socket
> *sock, poll_table *wait)
> */
> mask |= POLLOUT | POLLWRNORM;
> }
> - /* This barrier is coupled with smp_wmb() in tcp_reset() */
> - smp_rmb();
> if (sk->sk_err || !skb_queue_empty(&sk->sk_error_queue))
> mask |= POLLERR;
>
> @@ -3291,6 +3291,9 @@ void tcp_done(struct sock *sk)
>
> sk->sk_shutdown = SHUTDOWN_MASK;
>
> + /* This barrier is coupled with smp_rmb() in tcp_poll() */
> + smp_wmb();
> +
> if (!sock_flag(sk, SOCK_DEAD))
> sk->sk_state_change(sk);
> else
Might I ask on which arch you got a problem ?
Thanks !
