[Devel] Re: pid namespace isolation broken with powertop

[Marc Aymerich]

On Thu, Jul 29, 2010 at 5:22 PM, Daniel Lezcano <daniel.lezcano at free.fr>wrote:

> 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...
>


Hi Daniel, I wouldn't worry too much about powertop

http://www.phoronix.com/scan.php?page=article&item=powertop_2010_test&num=1

br.

-- 
Marc
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