Re: [GIT PULL] tracing: final fixes for events and some

From: Dave Jones
Date: Tue Aug 13 2013 - 07:45:26 EST

On Tue, Aug 13, 2013 at 01:06:18PM +0200, Ingo Molnar wrote:
> * Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:
> > On Mon, 12 Aug 2013 22:39:22 -0400
> > Dave Jones <davej@xxxxxxxxxx> wrote:
> >
> >
> > > I'm not sure why I got cc'd on this, but for my part, the perf/tracing
> > > related bugs I've found recently may have been there for ages, but
> > > they were triggerable as non-root users.
> >
> > Which bug was able to trigger with non-root? The hash one that you
> > reported? That is something with the function tracer. Are you able to
> > enable function tracing as non-root?
> >
> > Or is it because you gave more permissions for non-root to use extra
> > perf commands. Because no one but root should be able to enable function
> > tracing, as that can add a large overhead to the system.
> Hm, also, tracepoints should in general only be accessible to root - all
> sorts of random privileged info leaks through tracepoints, a thorough
> review and sanitizing is needed to expose that to users. (and that does
> not consider the complication caused by exposing timing info.)

With the benefit of sleep, I might take that back, though I'm working
from memory of a bug that I've not seen in over a month.

I may have been chasing a user-triggerable bug, and used tracing (as root)
to diagnose and then walked into one of these.

But the recent fix where you had a test-case that did module unloads
didn't really seem to fit the profile of what I was seeing.
It's feasible that my fuzzer can trigger module _loads_, but I
don't think there's any way we can trigger an rmmod.


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