linux-kernel - Re: [PATCH 1/1] vhost: Protect the virtqueue from being cleared whilst still in use

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Message-ID: <Yh9B+wKDKXHZ6ly/@google.com>
Date:   Wed, 2 Mar 2022 10:07:55 +0000
From:   Lee Jones <lee.jones@...aro.org>
To:     Stefano Garzarella <sgarzare@...hat.com>
Cc:     mst@...hat.com, jasowang@...hat.com, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org,
        netdev@...r.kernel.org, stable@...r.kernel.org,
        syzbot+adc3cb32385586bec859@...kaller.appspotmail.com
Subject: Re: [PATCH 1/1] vhost: Protect the virtqueue from being cleared
 whilst still in use

On Wed, 02 Mar 2022, Stefano Garzarella wrote:

> On Wed, Mar 02, 2022 at 07:54:21AM +0000, Lee Jones wrote:
> > vhost_vsock_handle_tx_kick() already holds the mutex during its call
> > to vhost_get_vq_desc().  All we have to do is take the same lock
> > during virtqueue clean-up and we mitigate the reported issues.
> > 
> > Link: https://syzkaller.appspot.com/bug?extid=279432d30d825e63ba00
> 
> This issue is similar to [1] that should be already fixed upstream by [2].
> 
> However I think this patch would have prevented some issues, because
> vhost_vq_reset() sets vq->private to NULL, preventing the worker from
> running.
> 
> Anyway I think that when we enter in vhost_dev_cleanup() the worker should
> be already stopped, so it shouldn't be necessary to take the mutex. But in
> order to prevent future issues maybe it's better to take them, so:


> Reviewed-by: Stefano Garzarella <sgarzare@...hat.com>

Thanks for the analysis and the review Stefano.

-- 
Lee Jones [李琼斯]
Principal Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
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