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

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Date:   Tue, 11 Apr 2017 18:13:17 +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

> > >  
> > 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 :)

>  	}
>  
>  	/* reset sort keys */
>  	perf_hpp_list__for_each_sort_list_safe(list, fmt, tmp) {
> -		list_del_init(&fmt->list);
> -		list_del_init(&fmt->sort_list);
> +		list_del(&fmt->sort_list);
>  		fmt_free(fmt);
>  	}
>  }

-- 
Thanks,
Changbin Du

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