Date: Fri, 12 Jun 2015 21:29:42 -0400
From: Steven Rostedt <rostedt@goodmis.org>
To: Vince Weaver <vincent.weaver@maine.edu>
Cc: linux-kernel@vger.kernel.org, Peter Zijlstra <a.p.zijlstra@chello.nl>,
        Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>
Subject: Re: perf,ftrace: fuzzer triggers warning in trace_events_filter
 code
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On Fri, 12 Jun 2015 21:15:10 -0400 (EDT)
Vince Weaver <vincent.weaver@maine.edu> wrote:

> On Fri, 12 Jun 2015, Steven Rostedt wrote:
> 
> > On Fri, 12 Jun 2015 17:18:22 -0400 (EDT)
> > Vince Weaver <vincent.weaver@maine.edu> wrote:
> > 
> > > 
> > > So I've modified my fuzzer to try to exercise the 
> > > PERF_EVENT_IOC_SET_FILTER ioctl() and it is starting to turn up some 
> > > warnings.
> > 
> > Is there any way to know what the filter string you used that generated
> > this?
> 
> Various seem to trigger it.  One example is
> 
> 	ext4:ext4_truncate_exit
> 	(((dev<=913)blocks==916)common_type&756)
> 

Thanks, OK, I know what the issue is. I'm also thinking the solution
may simply be removing that WARN_ON(). But I'll look at it a little
deeper before deciding that.

The WARN_ON() simply detected an anomaly, but nothing breaks when that
anomaly occurs. Well, I don't see anything breaking, it just expected
that we couldn't get to this path, but now we know we can. Thus the
solution is to remove the WARN_ON() or detect the bad filter before
getting there.

-- Steve
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