Re: [Qemu-devel] [PATCH RFC 2/2] block: Warn on insecure format probing

[Stefan Hajnoczi]

On Thu, Oct 30, 2014 at 01:49:22PM +0100, Markus Armbruster wrote:
> Kevin Wolf <address@hidden> writes:
> 
> > Am 29.10.2014 um 14:54 hat Markus Armbruster geschrieben:
> >> Anthony tried something similar (commit 79368c8), but couldn't get it
> >> right (commit 8b33d9e).
> >
> > The discussion back then: http://patchwork.ozlabs.org/patch/58980/
> >
> > The problem with Anthony's code was that he didn't handle a qiov
> > correctly that had unaligned members. With today's block layer, this is
> > not a big deal to implement correctly. We're running coroutines instead
> > of AIO callbacks and we don't have to do all the manual qiov fixing
> > magic that Anthony had in his patch, util/iov.c provides all you need.
> >
> > I'll send out an RFC series that implements this.
> 
> I'm strongly opposed to this idea.

Me too.  Meddling with the guest is wrong and just adds a new problem!

It is perfectly okay for backup appliances, nested virtualization, or
disk management appliances to write image format headers to raw disks.

I'm am 100% against trying to detect the guest writing image format
headers to raw disks.

Probing is not a guest problem.  It is a QEMU problem.  Fix QEMU, don't
cripple the guest.

Stefan

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