Re: [PATCH v3 2/3] hw/virtio: Acquire RCU read lock in virtqueue_packed_drop_all()

[Stefano Garzarella]

On Mon, Oct 04, 2021 at 11:27:12AM +0200, Philippe Mathieu-Daudé wrote:
> On 10/4/21 11:23, Stefan Hajnoczi wrote:
> > On Mon, Sep 06, 2021 at 12:43:17PM +0200, Philippe Mathieu-Daudé wrote:
> > > vring_get_region_caches() must be called with the RCU read lock
> > > acquired. virtqueue_packed_drop_all() does not, and uses the
> > > 'caches' pointer. Fix that by using the RCU_READ_LOCK_GUARD()
> > > macro.
> >
> > Is this a bug that has been encountered, is it a latent bug, a code
> > cleanup, etc? The impact of this isn't clear but it sounds a little
> > scary so I wanted to check.
>
> I'll defer to Stefano, but IIUC it is a latent bug discovered
> during code audit.

Yep, I confirm this. We discovered it by discussing the documentation in 
a previous series.

Thanks,
Stefano