Re: [Xen-devel] [PATCH] QEMU "drive_init()" Disk Format Security Bypass

[Markus Armbruster <armbru@xxxxxxxxxx>]

Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx> writes:

> Markus Armbruster writes ("Re: [Xen-devel] [PATCH] QEMU "drive_init()" Disk 
> Format Security Bypass"):
>> Patch looks sane.  I backported it to F-8 and verified that:
>> 
>> 1. usbdevice = "disk:IMG" opens the image IMG raw regardless of file
>>    contents.  Same for monitor command usb_add disk:IMG.
>> 
>> 2. usbdevice = "disk-qcow:IMG" opens the qcow image IMG correctly.
>>    Same for monitor command usb_add disk-qcow:IMG.
>
> Good, thanks.
>
>> I believe monitor command change is still broken.  I tried "change fda
>> IMG", with a qcow image IMG, and it was opened qcow.  But changing to
>> a raw image failed; I think that feature was broken by by your
>> security fix.
>
> Yes, this is expected.  If this is a problem then we need a more
> sophisticated solution.  NB that hopefully xen-unstable will acquire a
> much more recent qemu shortly so there is no need to fix it right now
> for xen-unstable unless it's a big problem which I think it probably
> isn't given how long it's been like this now ...
>
> Ian.

We could plug the hole by forcing raw in do_change_block().
One-liner, minor loss of functionality.  What do you think?

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