Re: [PATCH V2] device-assignment pci: correct pci config size default for cap version 2 endpoints

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, Jul 21, 2011 at 11:02:53AM -0600, Alex Williamson wrote:
> This is crazy, why would we only test this for PCI_CAP_ID_EXP?  If the
> test is going to go in device-assignment, we need to wrap
> pci_add_capability and do it for all callers.  However, maybe we can get
> MST to take it in pci_add_capability() if we make the test more
> complete...  something like:
> 
> if ((pos < 256 && size > 256 - pos) ||
>     (pci_config_size() > 256 && pos > 256 &&
>      size > pci_config_size() - pos)) {
>    ... badness
> 
> Thanks,
> 
> Alex

We expect device assignment to be able to corrupt
guest memory but not qemu memory. So we must validate
whatever we get from the device, and I think this
validation belongs in device-assignment.c:

IOW I think input should be validated where it's
input, while we still know it's untrusted,
instead of relying on core to validate parameters.

Makes sense?

-- 
MST