Re: [libvirt] [PATCH] qemu: forbid large value wraparound in balloon period collection
On 02/25/2015 08:10 AM, Martin Kletzander wrote:
On Tue, Feb 24, 2015 at 04:28:18PM +0100, Erik Skultety wrote:
> We do parse and represent period collection as unsigned int in our
> internal structures, however commit
> d5c67e7f4523450023b89b69c16472582c85eeaf converts this to int, thus
> wrapping
> around inputs greater than INT_MAX which results in an error from QEMU.
> This patch adds a check into QEMU driver, because period attribute is
> only supported by QEMU.
>
Well, there are couple more things broken.
1) Change to this patch:
It is written in the description that period can me 0 or more, so
it would make sense to guard all the drivers (ideally at one
place) together. If that changes, the check can be moved to
individual drivers, but for now anything outside <0,INT_MAX>
doesn't make sense.
Well stats collection period is only used by QEMU, but the issue here is
it's quite impossible to do it unified for all drivers, possibly at one
place, because you can't do it right after the domain gets parsed
(otherwise domain disappears after daemon's restart) and we already do
check this at client's side (both virsh cmd routine and our public API
virDomainSetMemoryStatsPeriod). However, this patch doesn't fix the
issue anyway, as the check is at a wrong place.
2) Curiosity:
<membaloon model='virtio'>
<stats period='5'/>
<address .../>
</membaloon>
This ^^ fails validation because <stats/> must come *after*
<address/> (WAT) even though all other device elements *require*
the address to be last (why would we even do that!).
Will include fix for this one in the next versions :).
3) Invalid number gets still parsed in the XML and it only wraps to
negative when sending to the monitor at the guest's start.
We can't do much about this, can we?
Thank you for your review :),
Erik