Re: [Qemu-devel] [PATCH 0/1] display/bochs: fix pcie support (qemu security issue)

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 8/12/19 2:45 PM, Paolo Bonzini wrote:
> On 12/08/19 08:52, Gerd Hoffmann wrote:
>> Just found while investigating
>>   https://bugzilla.redhat.com/show_bug.cgi?id=1707118
>>
>> Found PCIe extended config space filled with random crap due to
>> allocation being too small (conventional pci config space only).
>>

Can you amend this information to the commit description?

<...

>> PCI(e) config space is guest writable.  Writes are limited by
>> write mask (which probably is also filled with random stuff),
> 
> Yes, it is also allocated with 256 bytes only.
> 
>> so the guest can only flip enabled bits.  But I suspect it
>> still might be exploitable, so rather serious because it might
>> be a host escape for the guest.  On the other hand the device
>> is probably not yet in widespread use.

...>

>> Migitation: use "-device bochs-display" as conventional pci
>> device only.
>>
>> Note: qemu 4.1 release is planned for tomorrow.
>>
>> Gerd Hoffmann (1):
>>   display/bochs: fix pcie support
>>
>>  hw/display/bochs-display.c | 7 ++++++-
>>  1 file changed, 6 insertions(+), 1 deletion(-)
>>
> 
> Looks good to me, and no other device seems to have the same issue.  We
> could add an assertion that pci_config_size has not increased after
> calling pc->realize.
> 
> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
> 
> Paolo
>