2024-05-07 03:12:37

by Arnaldo Carvalho de Melo

Subject: [PATCH 1/1] perf callchain: 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 callchain code.

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]>
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>
---
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

2024-05-08 23:40:37

by Ian Rogers

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 <[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 callchain code.
>
> 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]>
> Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

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

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
>