[libvirt] [PATCH] qemu: Put format=raw onto cmd line for SCSI passthrough

[Daniel P. Berrangé]

On Fri, Oct 12, 2018 at 02:27:26PM +0200, Michal Privoznik wrote:
> On 10/12/2018 02:17 PM, Daniel P. Berrangé wrote:
> > On Fri, Oct 12, 2018 at 01:14:51PM +0200, Michal Privoznik wrote:
> >> https://bugzilla.redhat.com/show_bug.cgi?id=1632833
> >>
> >> When doing a SCSI passthrough we don't put format= onto the
> >> command line. This causes qemu to probe the format automatically
> >> which ends up in a warning in the domain log and possible qemu
> >> disabling writes to the first block (according to the warning
> >> message).
> > 
> > If the warning message is correct, this should have been reported
> > as a security bug to libvirt and given a CVE.
> 
> Why is that? It the message is correct, qemu would prevent from writing
> to the first block. No harm there.

Only QEMU >= 2.3.0 has that protection, so this is not
something we can rely to avoid calling it a CVE. It just
means distros when QEMU >=2.3.0 would not be affected by
the CVE.

> > On the other hand if the warning from QEMU isn't correct, then
> > QEMU shouldn't have printed the warning about it being dangerous.
> 
> In my testing I was able to write to the first block. Therefore, IMO
> qemu is throwing incorrect warning message.
> 
> > 
> > So something is missing here either way.
> 
> Sure, but that doesn't invalidate my patch, does it?

Only the commit message - if this is a security flaw, we must be more
explicit about it in the commit.


Regards,
Daniel
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