linux-kernel - Re: suspicious RCU usage (perf)

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Date:	Mon, 26 Aug 2013 15:49:24 -0400
From:	Dave Jones <davej@...hat.com>
To:	David Ahern <dsahern@...il.com>
Cc:	Steven Rostedt <rostedt@...dmis.org>, paulmck@...ux.vnet.ibm.com,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: suspicious RCU usage (perf)

On Mon, Aug 26, 2013 at 01:43:15PM -0600, David Ahern wrote:
 > 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@...hat.com> 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?

Ah, yeah, that'll be it. Good catch.

Sorry for the false alarm Steve ;)

	Dave

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