linux-kernel - Re: [RFC PATCH v5 06/17] vsock: fix EPOLLERR set on non-empty error queue

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Message-ID: <bwcgwfiwf5siky3nqvcedenvooszd4vk2gfi6tkvge2ayfyim6@wihfy74lqoct>
Date:   Thu, 6 Jul 2023 18:54:16 +0200
From:   Stefano Garzarella <sgarzare@...hat.com>
To:     Arseniy Krasnov <AVKrasnov@...rdevices.ru>
Cc:     Stefan Hajnoczi <stefanha@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Bobby Eshleman <bobby.eshleman@...edance.com>,
        kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel@...rdevices.ru, oxffffaa@...il.com
Subject: Re: [RFC PATCH v5 06/17] vsock: fix EPOLLERR set on non-empty error
 queue

On Sat, Jul 01, 2023 at 09:39:36AM +0300, Arseniy Krasnov wrote:
>If socket's error queue is not empty, EPOLLERR must be set. Otherwise,
>reader of error queue won't detect data in it using EPOLLERR bit.
>Currently for AF_VSOCK this is reproducible only with MSG_ZEROCOPY, as
>this feature is the only user of an error queue of the socket.
>
>Fixes: d021c344051a ("VSOCK: Introduce VM Sockets")

Sorry if I confused you, but if without MSG_ZEROCOPY this is not an
issue, then we can remove the Fixes tag.

>Signed-off-by: Arseniy Krasnov <AVKrasnov@...rdevices.ru>
>---
> Changelog:
> v4 -> v5:
>  * Change commit message as Fix patch. Also add details that this
>    problem could be reproduced only with MSG_ZEROCOPY transmission
>    mode.
>
> 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 efb8a0937a13..45fd20c4ed50 100644
>--- a/net/vmw_vsock/af_vsock.c
>+++ b/net/vmw_vsock/af_vsock.c
>@@ -1030,7 +1030,7 @@ 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
>