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

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Date:	Mon, 26 Aug 2013 13:43:15 -0600
From:	David Ahern <dsahern@...il.com>
To:	Dave Jones <davej@...hat.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	paulmck@...ux.vnet.ibm.com,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: suspicious RCU usage (perf)

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?

David

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