Re: [KVM PATCH v8 3/3] KVM: add iosignalfd support

Gregory Haskins
2009-06-22T13:20:17Z

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Michael S. Tsirkin wrote:
> On Mon, Jun 22, 2009 at 09:04:48AM -0400, Gregory Haskins wrote:
>
>> Sorry, Michael. I missed that you had other comments after the
>> grammatical one. Will answer inline
>>
>> Michael S. Tsirkin wrote:
>>
>>> On Mon, Jun 22, 2009 at 08:13:48AM -0400, Gregory Haskins wrote:
>>>
>>>
>>>
>>>> If thats true, we are in trouble ;)
>>>>
>>>>
>>> I think it works at least on x86:
>>> http://en.wikipedia.org/wiki/Packed#x86_and_x86-64
>>>
>>>
>> Right, understood. What I meant specifically is that if the (void*)val
>> pointer is allowed to be misaligned we are in trouble ;). I haven't
>> studied the implementation in front of the MMIO callback recently, but I
>> generally doubt thats the case. More than likely this is some buffer
>> that was kmalloced and that should already be aligned to the machine word.
>>
>> Kind Regards,
>> -Greg
>>
>>
>
> Yes, from what I saw of the code I think it can be BUG_ON.
> Avi?
>
>

The question to ask is whether a guest can influence that condition. If
they can, its an attack vector to crash the host. I suspect they can't,
however. Therefore, your recommendation is perhaps a good approach so
this condition cannot ever go unnoticed. Avi?

-Greg

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