2024-05-07 03:16:02

by Arnaldo Carvalho de Melo

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

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 <[email protected]>
Cc: Ian Rogers <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Kan Liang <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Yang Jihong <[email protected]>
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>
---
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

2024-05-08 23:41:08

by Ian Rogers

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

On Mon, May 6, 2024 at 8:15 PM <[email protected]> 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 <[email protected]>
> Cc: Ian Rogers <[email protected]>
> Cc: Jiri Olsa <[email protected]>
> Cc: Kan Liang <[email protected]>
> Cc: Namhyung Kim <[email protected]>
> Cc: Yang Jihong <[email protected]>
> Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

Reviewed-by: Ian Rogers <[email protected]>

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
>