Re: [Qemu-devel] [PATCH 1/2] virtio-9p: print error message and exit instead of BUG_ON()

[Greg Kurz <groug@kaod.org>]

On Thu, 8 Sep 2016 10:59:26 +0200
Cornelia Huck <cornelia.huck@de.ibm.com> wrote:

> On Wed, 07 Sep 2016 19:19:24 +0200
> Greg Kurz <groug@kaod.org> wrote:
> 
> > Calling assert() really makes sense when hitting a genuine bug, which calls
> > for a fix in QEMU. However, when something goes wrong because the guest
> > sends a malformed message, it is better to write down a more meaningul
> > error message and exit.
> > 
> > Signed-off-by: Greg Kurz <groug@kaod.org>
> > ---
> >  hw/9pfs/virtio-9p-device.c |   20 ++++++++++++++++++--
> >  1 file changed, 18 insertions(+), 2 deletions(-)  
> 
> While this is an improvement over the current state, I don't think the
> guest should be able to kill qemu just by doing something stupid.
> 

Hi Connie,

I'm glad you're pointing this out... this was also my impression, but
since there are a bunch of sanity checks in the virtio code that cause
QEMU to exit (even recently added like 1e7aed70144b), I did not dare
stand up :)

> The right way to go is to mark the virtio device as broken and stop
> doing any processing until the guest resets it. I think Stefan had a
> patch series doing that for some base virtio errors, but I'd have to
> search for it.
> 

I'd be glad to have a look and try to address this issue.

Thanks !

--
Greg