Re: [Qemu-devel] [PATCH] Make default invocation of block drivers safer

[Kevin Wolf]

Am 15.07.2010 14:57, schrieb Anthony Liguori:
> On 07/15/2010 04:10 AM, Stefan Hajnoczi wrote:
>> I think there are actually two issues here:
>>
>> 1. Confusing QEMU so it sees an image with a different format than expected.
>>
>> This is important because it's unexpected behavior for a user who puts
>> a QCOW2 image onto a raw disk to find the disk itself turn into a
>> QCOW2 disk on next reboot.
>>
>> I also worry about this bug because it means that in a scenario where
>> format= is not explicitly given, the VM can change its disk image
>> format.  This is a problem because the host administrator might have
>> used raw files and be unhappy to find that the user is able to exploit
>> a (hypothetical) security issue in the vmdk code despite having
>> created the VM with a raw image.
>>    
> 
> One of the nasty things in QEMU right now is that we have absolutely no 
> way to persist information about the guest and we have no persistent 
> definition of the guest.
> 
> All of our VMs are basically stateless across invocations and that 
> really makes things like this difficult.

On the one hand, yes, it can be nasty in some situations. But on the
other hand, when I first used qemu back in 0.6.0 times or so, what
really impressed me was how easy it was to use. No long config files to
create or anything, "qemu -hda my_image" (and maybe one or two other
options) and it just worked. We should try not to lose too much of this
ease of use.

Kevin