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

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Date: Wed, 8 May 2024 16:40:15 -0700
From: Ian Rogers <irogers@...gle.com>
To: Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: 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 callchain: Use zfree() to avoid possibly
 accessing dangling pointers

On Mon, May 6, 2024 at 8:12 PM Arnaldo Carvalho de Melo <acme@...nel.org> 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 callchain code.
>
> 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>
> Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>

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

Thanks,
Ian

> ---
>  tools/perf/util/callchain.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/perf/util/callchain.c b/tools/perf/util/callchain.c
> index 68feed8718096f78..1730b852a947400f 100644
> --- a/tools/perf/util/callchain.c
> +++ b/tools/perf/util/callchain.c
> @@ -606,7 +606,7 @@ fill_node(struct callchain_node *node, struct callchain_cursor *cursor)
>                                         call->brtype_stat = zalloc(sizeof(*call->brtype_stat));
>                                         if (!call->brtype_stat) {
>                                                 perror("not enough memory for the code path branch statistics");
> -                                               free(call->brtype_stat);
> +                                               zfree(&call->brtype_stat);
>                                                 return -ENOMEM;
>                                         }
>                                 }
> --
> 2.44.0
>