linux-kernel - Re: [PATCH 1/1] perf kwork: Use zfree() to avoid possibly accessing dangling pointers

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Date: Wed, 8 May 2024 16:40:40 -0700
From: Ian Rogers <irogers@...gle.com>
To: arnaldo.melo@...il.com
Cc: Yang Jihong <yangjihong1@...wei.com>, Adrian Hunter <adrian.hunter@...el.com>, 
	Jiri Olsa <jolsa@...nel.org>, Kan Liang <kan.liang@...ux.intel.com>, 
	Namhyung Kim <namhyung@...nel.org>, 
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, linux-perf-users@...r.kernel.org
Subject: Re: [PATCH 1/1] perf kwork: Use zfree() to avoid possibly accessing
 dangling pointers

On Mon, May 6, 2024 at 8:15 PM <arnaldo.melo@...il.com> wrote:
>
> When freeing a->b it is good practice to set a->b to NULL using
> zfree(&a->b) so that when we have a bug where a reference to a freed 'a'
> pointer is kept somewhere, we can more quickly cause a segfault if some
> code tries to use a->b.
>
> Convert one such case in the 'perf kwork' codebase.
>
> Cc: Adrian Hunter <adrian.hunter@...el.com>
> Cc: Ian Rogers <irogers@...gle.com>
> Cc: Jiri Olsa <jolsa@...nel.org>
> Cc: Kan Liang <kan.liang@...ux.intel.com>
> Cc: Namhyung Kim <namhyung@...nel.org>
> Cc: Yang Jihong <yangjihong1@...wei.com>
> Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>

Reviewed-by: Ian Rogers <irogers@...gle.com>

Thanks,
Ian

> ---
>  tools/perf/builtin-kwork.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/perf/builtin-kwork.c b/tools/perf/builtin-kwork.c
> index 0092b9b39611d7e9..56e3f3a5e03a2d66 100644
> --- a/tools/perf/builtin-kwork.c
> +++ b/tools/perf/builtin-kwork.c
> @@ -2230,7 +2230,7 @@ static int perf_kwork__top(struct perf_kwork *kwork)
>         perf_kwork__top_report(kwork);
>
>  out:
> -       free(kwork->top_stat.cpus_runtime);
> +       zfree(&kwork->top_stat.cpus_runtime);
>         return ret;
>  }
>
> --
> 2.44.0
>