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Message-ID: <4A3F84FD.3090700@gmail.com>
Date: Mon, 22 Jun 2009 09:19:57 -0400
From: Gregory Haskins <gregory.haskins@gmail.com>
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To: "Michael S. Tsirkin" <mst@redhat.com>
CC: Gregory Haskins <ghaskins@novell.com>, kvm@vger.kernel.org,
       linux-kernel@vger.kernel.org, avi@redhat.com, mtosatti@redhat.com,
       paulmck@linux.vnet.ibm.com, markmc@redhat.com
Subject: Re: [KVM PATCH v8 3/3] KVM: add iosignalfd support
References: <20090619002224.15859.97977.stgit@dev.haskins.net> <20090619003045.15859.73197.stgit@dev.haskins.net> <20090622104435.GA11594@redhat.com> <4A3F757C.6030508@novell.com> <20090622123022.GC12867@redhat.com> <4A3F8170.7000508@gmail.com> <20090622131351.GE12867@redhat.com>
In-Reply-To: <20090622131351.GE12867@redhat.com>
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Michael S. Tsirkin wrote:
> On Mon, Jun 22, 2009 at 09:04:48AM -0400, Gregory Haskins wrote:
>  =20
>> Sorry, Michael.  I missed that you had other comments after the
>> grammatical one.  Will answer inline
>>
>> Michael S. Tsirkin wrote:
>>    =20
>>> On Mon, Jun 22, 2009 at 08:13:48AM -0400, Gregory Haskins wrote:
>>>  =20
>>>      =20
>>>
>>>> If thats true, we are in trouble ;)
>>>>    =20
>>>>        =20
>>> I think it works at least on x86:
>>> http://en.wikipedia.org/wiki/Packed#x86_and_x86-64
>>>  =20
>>>      =20
>> Right, understood.  What I meant specifically is that if the (void*)va=
l
>> 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 w=
ord.
>>
>> Kind Regards,
>> -Greg
>>
>>    =20
>
> Yes, from what I saw of the code I think it can be BUG_ON.
> Avi?
>
>  =20

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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