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

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Message-ID: <Yi85dls3CCc2i1iK@google.com>
Date:   Mon, 14 Mar 2022 12:47:50 +0000
From:   Lee Jones <lee.jones@...aro.org>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     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
Subject: Re: [PATCH 1/1] vhost: Protect the virtqueue from being cleared
 whilst still in use

On Mon, 14 Mar 2022, Michael S. Tsirkin wrote:

> On Mon, Mar 14, 2022 at 08:43:02AM +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 here is take the same lock
> > during virtqueue clean-up and we mitigate the reported issues.
> > 
> > Also WARN() as a precautionary measure.  The purpose of this is to
> > capture possible future race conditions which may pop up over time.
> > 
> > Cc: <stable@...r.kernel.org>
> > Signed-off-by: Lee Jones <lee.jones@...aro.org>
> 
> Pls refer to my previous responses to this patch.  I'd like to see an
> argument for why this will make future bugs less and not more likely.

If you think the previous 'check owner' patch fixes all of the
concurrency issues, then this patch can be dropped.

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