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

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Message-ID: <20170412014808.GA3644@intel.com>
Date:   Wed, 12 Apr 2017 09:48:08 +0800
From:   "Du, Changbin" <changbin.du@...el.com>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     "Du, Changbin" <changbin.du@...el.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>, peterz@...radead.org,
        mingo@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] perf: fix double free at function
 perf_hpp__reset_output_field

On Tue, Apr 11, 2017 at 12:32:49PM +0200, Jiri Olsa wrote:
> On Tue, Apr 11, 2017 at 06:13:17PM +0800, Du, Changbin wrote:
> > > > >  
> > > > yes, this is an option. But for safety, I sugguest do not rely on list_del_init.
> > > > No rule rather than create one.
> > > > 
> > > > But anyway, both are ok for me. What's your options?
> > > 
> > > hum, also I dont think we need to touch that bit at all
> > > if we are going to remove it right away.. how about the
> > > change below?
> > > 
> > > jirka
> > > 
> > > 
> > > ---
> > > diff --git a/tools/perf/ui/hist.c b/tools/perf/ui/hist.c
> > > index 5d632dca672a..0ee7db43dd7d 100644
> > > --- a/tools/perf/ui/hist.c
> > > +++ b/tools/perf/ui/hist.c
> > > @@ -613,15 +613,15 @@ void perf_hpp__reset_output_field(struct perf_hpp_list *list)
> > >  
> > >  	/* reset output fields */
> > >  	perf_hpp_list__for_each_format_safe(list, fmt, tmp) {
> > > -		list_del_init(&fmt->list);
> > > -		list_del_init(&fmt->sort_list);
> > > +		list_del(&fmt->list);
> > > +		/* Remove the fmt from next loop processing. */
> > > +		list_del(&fmt->sort_list);
> > >  		fmt_free(fmt);
> > What if the fmt is not linked to sort_list? I see it is possible (please
> > checking perf_hpp__setup_output_field()). I am not sure if we really has
> > sunch case currently, just concern :)
> 
> if it's not linked to sort_list, then sort_list is initialized
> and list_del should do no harm
> 
ok, then it's fine if you insist.

> jirka

-- 
Thanks,
Changbin Du

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