Re: [Qemu-devel] [Qemu-stable] [PATCH] fdc: force the fifo access to be in bounds of the allocated buffer

[John Snow]

On 05/13/2015 04:02 PM, Peter Lieven wrote:
> Am 13.05.2015 um 21:52 schrieb Markus Armbruster:
>> Peter Lieven <address@hidden> writes:
>>
>>> Am 13.05.2015 um 21:09 schrieb Stefan Priebe:
>>>> Am 13.05.2015 um 21:05 schrieb Stefan Weil:
>>>>> Am 13.05.2015 um 20:59 schrieb Stefan Priebe:
>>>>>> Am 13.05.2015 um 20:51 schrieb Stefan Weil:
>>>>>>> Hi,
>>>>>>>
>>>>>>> I just noticed this patch because my provider told me that my KVM based
>>>>>>> server
>>>>>>> needs a reboot because of a CVE (see this German news:
>>>>>>> http://www.heise.de/newsticker/meldung/Venom-Schwachstelle-Aus-Hypervisor-ausbrechen-und-VMs-ausspionieren-2649614.html)
>>>>>>>
>>>>>> Isn't a live migration to a fixed version enough instead of a reboot?
>>>>>>
>>>>>> Stefan
>>>>> Good point. A live migration would be sufficient - if there are no bugs
>>>>> in QEMU's live migration.
>>>> just migrating all our customer machines and wanted to be sure that
>>>> live migration is enough.
>>> Just to confirm: If Qemu is started with -nodefaults and there is no
>>> fdc configuration the system is not affected by this CVE?
>> Not true.  The FD controller is still there.  It has no drives attached
>> then, but is vulnerable all the same.
> 
> Are you sure? With -nodefaults the hmp command 'info block' returns nothing 
> and
> the guest sees no floppy drive.
> 
> Without -nodefaults I indeed see floppy0 and I have /dev/fd0 in the guest 
> respectively.
> 
> Peter
> 

It's not the *drive* that is the problem, it is the *controller*.