Re: [Xen-devel] [PATCH 0/2] Xen/mem_event: Do not rely on the toolstack being bug-free

[Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>]

On 07/17/2014 10:01 PM, Aravindh Puthiyaparambil (aravindp) wrote:
>> Xen performs insufficient validation of the contents of mem_event responses
>>from the toolstack.  As a result, a buggy toolstack could cause Xen to walk 
>>off
>> the end of a domain's vcpu list, and get out of sync with vcpu pause 
>> reference
>> counts.
>>
>> These two fixes are compile tested only, as I have no way to plausibly test 
>> the
>> mem-event functionality itself.
> 
> One easy way of testing is to use the tools/tests/xen-access test program 
> which exercises mem_access and thereby mem_event. It is fairly easy to run. 
> Bring up a domain and execute " xen-access <domain_id> write|exec". But I 
> understand if you are under time constraints and cannot do it. If you Cc me 
> on these patches, I will gladly test them for you.

Indeed, our application is very xen-access-like (except quite a bit more
involved), and I've tested the original patches with 5 different domains
3 times over - but it's a well-behaved citizen of the Xen ecosystem and
there were no gimmicks involved. No mem_events piled up, and there was
always just one mem_event handler per domain.

Everything went without a hitch, but I did not try to pause the domain
while it was running or try to trick the hypervisor in any way.


Thanks,
Razvan Cojocaru

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