Re: [Qemu-devel] [RFC] sanitize memory on system reset

[Paolo Bonzini <pbonzini@redhat.com>]

Il 13/06/2013 07:56, Anthony Liguori ha scritto:
> Markus Armbruster <armbru@redhat.com> writes:
> 
>> Peter Lieven <pl@kamp.de> writes:
>>
>>> On 13.06.2013 10:40, Stefan Hajnoczi wrote:
>>>> On Thu, Jun 13, 2013 at 08:09:09AM +0200, Peter Lieven wrote:
>>>>> I was thinking if it would be a good idea to zeroize all memory
>>>>> resources on system reset and
>>>>> madvise dontneed them afterwards. This would avoid system reset
>>>>> attacks in case the attacker
>>>>> has only access to the console of a vServer but not on the physical
>>>>> host and it would shrink
>>>>> RSS size of the vServer siginificantly.
>>>> I wonder if you'll hit weird OS installers or PXE clients that rely on
>>>> stashing stuff in memory across reset.
>>> One point:
>>> Wouldn't a memory test which some systems do at startup break these as well?
>>
>> Systems that distinguish between warm and cold boot (such as PCs)
>> generally run POST only on cold boot.
>>
>> I'm not saying triggering warm reboot and expecting memory contents to
>> survive is a good idea, but it has been done.
> 
> Doesn't kexec do a warm reboot stashing the new kernel somewhere in
> memory?

No, it undoes most of the hardware setup and jumps to the new kernel.
It never goes through the BIOS.

Paolo