linux-kernel - Re: [PATCH v1 1/4] perf stat: Avoid uninitialized use of perf_stat

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Date:   Mon, 24 Jul 2023 14:09:19 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Ian Rogers <irogers@...gle.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Tom Rix <trix@...hat.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Yang Jihong <yangjihong1@...wei.com>,
        Ravi Bangoria <ravi.bangoria@....com>,
        Carsten Haitzler <carsten.haitzler@....com>,
        Zhengjun Xing <zhengjun.xing@...ux.intel.com>,
        James Clark <james.clark@....com>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        bpf@...r.kernel.org, llvm@...ts.linux.dev, maskray@...gle.com
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 <irogers@...gle.com> 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 <irogers@...gle.com>
> ---
>  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 <ndesaulniers@...gle.com>

>
>  #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