netdev - Re: [RFC PATCH v1] vsock: check error queue to set EPOLLERR

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Date:   Thu, 2 Mar 2023 11:06:21 +0100
From:   Stefano Garzarella <sgarzare@...hat.com>
To:     Arseniy Krasnov <avkrasnov@...rdevices.ru>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, oxffffaa@...il.com,
        kernel@...rdevices.ru, virtualization@...ts.linux-foundation.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Bobby Eshleman <bobby.eshleman@...edance.com>
Subject: Re: [RFC PATCH v1] vsock: check error queue to set EPOLLERR

On Wed, Mar 01, 2023 at 08:19:45AM +0300, Arseniy Krasnov wrote:
>EPOLLERR must be set not only when there is error on the socket, but also
>when error queue of it is not empty (may be it contains some control
>messages). Without this patch 'poll()' won't detect data in error queue.

Do you have a reproducer?

>This patch is based on 'tcp_poll()'.

LGTM but we should add a Fixes tag.
It's not clear to me whether the problem depends on when we switched to 
using sk_buff or was pre-existing.

Do you have any idea when we introduced this issue?

Thanks,
Stefano

>
>Signed-off-by: Arseniy Krasnov <AVKrasnov@...rdevices.ru>
>---
> net/vmw_vsock/af_vsock.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
>diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
>index 19aea7cba26e..b5e51ef4a74c 100644
>--- a/net/vmw_vsock/af_vsock.c
>+++ b/net/vmw_vsock/af_vsock.c
>@@ -1026,7 +1026,7 @@ static __poll_t vsock_poll(struct file *file, struct socket *sock,
> 	poll_wait(file, sk_sleep(sk), wait);
> 	mask = 0;
>
>-	if (sk->sk_err)
>+	if (sk->sk_err || !skb_queue_empty_lockless(&sk->sk_error_queue))
> 		/* Signify that there has been an error on this socket. */
> 		mask |= EPOLLERR;
>
>-- 
>2.25.1
>