[Devel] Re: pid namespace isolation broken with powertop

[Daniel Lezcano]

On 07/29/2010 04:35 PM, Nathan Lynch wrote:
> On Thu, 2010-07-29 at 14:30 +0200, Daniel Lezcano wrote:
>    
>> Hi all,
>>
>> I noticed all the tasks of the host are listed in /proc/timer_stats
>> These information is not virtualized neither isolated within a container.
>>
>> I was expecting to see only the tasks in the container with the
>> corresponding pids.
>>
>> I am not sure this is something critical, but the usage of powertop in
>> the container shows all the tasks of the system.
>>
>> While looking at the code in kernel/time/timer.c, it is not obvious to
>> fix this isolation because it is the pid number which is stored in a
>> list, so there is not enough informations to discriminate the pid
>> namespace against the current one.
>>
>> I am wondering if:
>>
>>    1) is it worth to isolate these informations ? (IMHO, yes).
>>    2) should the stats be stored per pid namespace or adding an hash
>> value + pid namespace as a key in the timer stats list ?
>>      
> Well, powertop is used for monitoring and modifying global system
> characteristics (e.g. processor C states, USB autosuspend) that don't
> make sense to virtualize.  Many events in /proc/timer_stats are
> accocunted to pid 0 (swapper/idle).  I think the question is whether a
> pidns-relative slice of timer events will be useful or just confusing.
>    

IMHO I find confusing to see all the applications name/pid running on 
the whole system (host + containers) from a container. Even if these 
applications are not accessible, that gives informations to the 
container on what is running on the system and I think we should 
consider that as a security breach.

We can just "hide" the content of this file for a pid namespace 
different of the init pid namespace, but that may suppress the 
possibility to investigate with powertop the consumption of a specific 
appliance, as accurate as it could be...

Thanks
   -- Daniel

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