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

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

[arnaldo.melo]

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@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Yang Jihong <yangjihong1@huawei.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 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

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

[Ian Rogers]

On Mon, May 6, 2024 at 8:15 PM <arnaldo.melo@gmail.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@intel.com>
> Cc: Ian Rogers <irogers@google.com>
> Cc: Jiri Olsa <jolsa@kernel.org>
> Cc: Kan Liang <kan.liang@linux.intel.com>
> Cc: Namhyung Kim <namhyung@kernel.org>
> Cc: Yang Jihong <yangjihong1@huawei.com>
> Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

Reviewed-by: Ian Rogers <irogers@google.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
>