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Date: Thu, 09 Sep 2010 15:02:24 +0200
From: Kevin Wolf <kwolf@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH] raw: Fix image header protection
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To: Anthony Liguori <anthony@codemonkey.ws>
Cc: qemu-devel@nongnu.org

Am 09.09.2010 14:52, schrieb Anthony Liguori:
> On 09/09/2010 07:44 AM, Kevin Wolf wrote:
>>> Isn't this an unbounded, guest controlled, malloc?  IOW, a guest could
>>> do a request of 4GB and on a 32-bit system crash the qemu instance.
>>>      
>> If you're concerned about that, we need to ban qemu_iovec_to_buffer()
>> completely. Currently we do the same thing for every write request for
>> every format but raw.
> 
> And QED ;-)

qed doesn't exist. We have something some notices from a brainstorming
thread that should become a specification some day. And yes, there's
some prototype code. That's everything we have today.

Anyway, if you declare qemu_iovec_to_buffer() broken, it doesn't really
matter if n-1 formats or n-2 formats are broken...

>>   Or instead of completely removing it, we could add
>> a size limit, though I suspect that would mean violating some specs.
>>    
> 
> One thing I was thinking of trying was splitting off the first sector 
> into a linear buffer, then allocating a new iovec and adjusting the new 
> iovec to cover the new request minus the first sector.

That doesn't help any of the other use cases. Either we consider it a
problem or not. If we do, it must be fixed everywhere.

Kevin