Re: suspicious RCU usage (perf)

From: David Ahern
Date: Mon Aug 26 2013 - 15:43:47 EST


On 8/26/13 12:29 PM, Dave Jones wrote:
On Mon, Aug 26, 2013 at 02:18:14PM -0400, Steven Rostedt wrote:
> On Mon, 26 Aug 2013 13:50:12 -0400
> Dave Jones <davej@xxxxxxxxxx> wrote:
> >
> > This was triggered as a regular user fwiw.
> > I had not been running perf, or any other tracing. It was just left
> > fuzzing over the weekend with no interaction at all.
>
> So you are telling me that ftrace was enabled by a regular user? If so,
> that's a huge issue.

quite.

> So my question to you. If you were not running perf or any other
> tracing, and this is all just non-root user. How the hell did perf
> function tracing get started on your box????

What mechanisms are available that would trigger it being enabled ?

Is there some path through sys_perf_open_event that might be
missing a capability check perhaps ?

Do you have /sys/kernel/debug with access permissions?

David

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