linux-kernel - Re: System crash with perf

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Date:   Sat, 2 Feb 2019 12:58:07 -0500 (EST)
From:   Vince Weaver <vincent.weaver@...ne.edu>
To:     Jiri Olsa <jolsa@...hat.com>
cc:     Vince Weaver <vincent.weaver@...ne.edu>,
        Ravi Bangoria <ravi.bangoria@...ux.ibm.com>,
        lkml <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        linux-perf-users@...r.kernel.org,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Andi Kleen <ak@...ux.intel.com>, eranian@...gle.com,
        "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
Subject: Re: System crash with perf_fuzzer (kernel: 5.0.0-rc3)

On Fri, 1 Feb 2019, Jiri Olsa wrote:

> > 
> > I've just started fuzzing with the patch applied.  Often it takes a few 
> > hours to trigger the bug.
> 
> cool, thanks

I let it run overnight and no crash.

> > Added question about this bug.  It appeared that the crash was triggered 
> > by the BTS driver over-writing kernel memory.  The data being written, was 
> > this user controllable?  Meaning, is this a security issue being fixed, or 
> > just a crashing issue?
> 
> yea, I have an example that can trigger it immediately

I mean: the crash is happening because data structures are getting 
over-written by the BTS driver.  Depending who and what is doing this, 
this could be a security issue (i.e. if it was raw BTS data that was 
partially userspace controlled values).  Though even if this were the case 
it would probably be hard to exploit.

Vince