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Date: Wed, 07 Oct 2009 08:48:32 -0500
From: Anthony Liguori <anthony@codemonkey.ws>
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Subject: [Qemu-devel] Re: [PATCH] fix virtio_blk serial pci config breakage,
	v2
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To: john cooper <john.cooper@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>, Rusty Russell <rusty@rustcorp.com.au>, qemu-devel@nongnu.org, Vadim Rozenfeld <vrozenfe@redhat.com>, jens.axboe@oracle.com, Avi Kivity <avi@redhat.com>

john cooper wrote:
> Michael S. Tsirkin wrote:
>   
>>> +    put_le16(p + 0, 0x0);                            /* ATA device */
>>> +    padstr((char *)(p + 23), QEMU_VERSION, 8);       /* firmware revision */
>>>       
>> QEMU version is currently a string like "0.11.50" which is exactly 8
>> bytes. What if someone makes it longer?  padstr will not 0
>> terminate string, and only partial data will be there.
>>     
>
> This code treats the field similar to the logic from which
> it derives (hw/ide.c) in that the field need not be nul
> terminated.  Quiet truncation to 8 bytes can occur here
> and in the existing usage but in a practical sense I don't
> see much of a recourse.  We can flag a warning but the
> data is realistically a best-effort attempt to provide
> relevant information in this field.  IOW overflowing
> this field probably isn't justification alone to modify
> a too long qemu version string.
>   

Hrm, we really shouldn't be exposing a version string to the guest in 
the first place.

That's a compatibility issue.

Really, I strongly dislike passing this identity page via virtio.  Why 
are we still going this route instead of just passing the S/N?

Regards,

Anthony Liguori