linux-kernel - Re: [PATCH v2] perf: fix double free at function perf_hpp__reset_output

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Date:   Sun, 9 Apr 2017 19:05:52 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     "Du, Changbin" <changbin.du@...el.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] perf: fix double free at function
 perf_hpp__reset_output_field

On Wed, Apr 05, 2017 at 10:44:22AM +0800, Du, Changbin wrote:
> On Tue, Apr 04, 2017 at 12:51:03PM -0300, Arnaldo Carvalho de Melo wrote:
> > Em Wed, Apr 05, 2017 at 12:34:59AM +0900, Namhyung Kim escreveu:
> > > Hi Arnaldo,
> > > 
> > > On Wed, Apr 5, 2017 at 12:19 AM, Arnaldo Carvalho de Melo
> > > <acme@...nel.org> wrote:
> > > > Em Mon, Mar 27, 2017 at 02:22:55PM +0800, changbin.du@...el.com escreveu:
> > > >> From: Changbin Du <changbin.du@...el.com>
> > > >>
> > > >> Some perf_hpp_fmt both registered at field and sort list. For such
> > > >> instance, we only can free it when removed from the both lists. This
> > > >> function currently only used by self-test code, but still should fix
> > > >> it.
> > > >
> > > > Looks sane, applying,
> > > >
> > > > Jiri, Namhyung, please holler (or ack) if needed,
> > > 
> > > Did you actually see the double free problem?  AFAICS the old code
> > 
> > I assumed that he had seen it, in some self-test code, Changbin, can you
> > please show command output or further describe when this patch would be
> > necessary?
> > 
> Arnaldo, I did observe this issue but not in self-test code. The self-test code
> uses that function but does not have a case that a fmt linked to two both list. 
> I found this issue when I try to add 'dynamic sort' feature to perf, which
> I use this function to reset out fields.

could you post it with the rest of your patches? might be easier to review

thanks,
jirka