2023-07-24 20:48:20

by Ian Rogers

Subject: [PATCH v1 1/4] perf stat: Avoid uninitialized use of perf_stat_config

perf_event__read_stat_config will assign values based on number of
tags and tag values. Initialize the structs to zero before they are
assigned so that no uninitialized values can be seen.

This potential error was reported by GCC with LTO enabled.

Signed-off-by: Ian Rogers <[email protected]>
---
tools/perf/tests/stat.c | 2 +-
tools/perf/util/stat.c | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/perf/tests/stat.c b/tools/perf/tests/stat.c
index 500974040fe3..706780fb5695 100644
--- a/tools/perf/tests/stat.c
+++ b/tools/perf/tests/stat.c
@@ -27,7 +27,7 @@ static int process_stat_config_event(struct perf_tool *tool __maybe_unused,
struct machine *machine __maybe_unused)
{
struct perf_record_stat_config *config = &event->stat_config;
- struct perf_stat_config stat_config;
+ struct perf_stat_config stat_config = {};

#define HAS(term, val) \
has_term(config, PERF_STAT_CONFIG_TERM__##term, val)
diff --git a/tools/perf/util/stat.c b/tools/perf/util/stat.c
index 967e583392c7..ec3506042217 100644
--- a/tools/perf/util/stat.c
+++ b/tools/perf/util/stat.c
@@ -729,7 +729,7 @@ size_t perf_event__fprintf_stat_round(union perf_event *event, FILE *fp)

size_t perf_event__fprintf_stat_config(union perf_event *event, FILE *fp)
{
- struct perf_stat_config sc;
+ struct perf_stat_config sc = {};
size_t ret;

perf_event__read_stat_config(&sc, &event->stat_config);
--
2.41.0.487.g6d72f3e995-goog

2023-07-24 21:44:32

by Nick Desaulniers

Subject: Re: [PATCH v1 1/4] perf stat: Avoid uninitialized use of perf_stat_config

On Mon, Jul 24, 2023 at 1:12 PM Ian Rogers <[email protected]> wrote:
>
> perf_event__read_stat_config will assign values based on number of
> tags and tag values. Initialize the structs to zero before they are
> assigned so that no uninitialized values can be seen.
>
> This potential error was reported by GCC with LTO enabled.
>
> Signed-off-by: Ian Rogers <[email protected]>
> ---
> tools/perf/tests/stat.c | 2 +-
> tools/perf/util/stat.c | 2 +-
> 2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/tools/perf/tests/stat.c b/tools/perf/tests/stat.c
> index 500974040fe3..706780fb5695 100644
> --- a/tools/perf/tests/stat.c
> +++ b/tools/perf/tests/stat.c
> @@ -27,7 +27,7 @@ static int process_stat_config_event(struct perf_tool *tool __maybe_unused,
> struct machine *machine __maybe_unused)
> {
> struct perf_record_stat_config *config = &event->stat_config;
> - struct perf_stat_config stat_config;
> + struct perf_stat_config stat_config = {};

^ how did this code ever work?

1. stat_config is not initialized
2. perf_event__read_stat_config maybe assigns to &stat_config->__val
3. process_stat_config_event() tests other members of stat_config

I hope I've missed something obvious.


Reviewed-by: Nick Desaulniers <[email protected]>

>
> #define HAS(term, val) \
> has_term(config, PERF_STAT_CONFIG_TERM__##term, val)
> diff --git a/tools/perf/util/stat.c b/tools/perf/util/stat.c
> index 967e583392c7..ec3506042217 100644
> --- a/tools/perf/util/stat.c
> +++ b/tools/perf/util/stat.c
> @@ -729,7 +729,7 @@ size_t perf_event__fprintf_stat_round(union perf_event *event, FILE *fp)
>
> size_t perf_event__fprintf_stat_config(union perf_event *event, FILE *fp)
> {
> - struct perf_stat_config sc;
> + struct perf_stat_config sc = {};
> size_t ret;
>
> perf_event__read_stat_config(&sc, &event->stat_config);
> --
> 2.41.0.487.g6d72f3e995-goog
>


--
Thanks,
~Nick Desaulniers