linux-kernel - Re: [PATCH] perf map: Delete two variable initialisations before null pointer checks in sort__sym_from

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Message-ID: <CAP-5=fW08PRXst_LdcM442ASGYs48b4B+0PnkLWCUcODB9Ju2w@mail.gmail.com>
Date:   Thu, 13 Apr 2023 08:49:14 -0700
From:   Ian Rogers <irogers@...gle.com>
To:     Markus Elfring <Markus.Elfring@....de>
Cc:     kernel-janitors@...r.kernel.org, linux-perf-users@...r.kernel.org,
        Adrian Hunter <adrian.hunter@...el.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        German Gomez <german.gomez@....com>,
        Ingo Molnar <mingo@...hat.com>, Jiri Olsa <jolsa@...nel.org>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Mark Rutland <mark.rutland@....com>,
        Namhyung Kim <namhyung@...nel.org>, cocci@...ia.fr,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] perf map: Delete two variable initialisations before null
 pointer checks in sort__sym_from_cmp()

On Thu, Apr 13, 2023 at 6:03 AM Markus Elfring <Markus.Elfring@....de> wrote:
>
> Date: Thu, 13 Apr 2023 14:46:39 +0200
>
> Addresses of two data structure members were determined before
> corresponding null pointer checks in the implementation of
> the function “sort__sym_from_cmp”.
>
> Thus avoid the risk for undefined behaviour by removing extra
> initialisations for the local variables “from_l” and “from_r”
> (also because they were already reassigned with the same value
> behind this pointer check).
>
> This issue was detected by using the Coccinelle software.
>
> Fixes: 1b9e97a2a95e4941dcfa968c4b2e04022e9a343e ("perf tools: Fix report -F symbol_from for data without branch info")
> Signed-off-by: Markus Elfring <elfring@...rs.sourceforge.net>

Acked-by: Ian Rogers <irogers@...gle.com>

Thanks,
Ian

> ---
>  tools/perf/util/sort.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/tools/perf/util/sort.c b/tools/perf/util/sort.c
> index 80c9960c37e5..f2ffaf90648e 100644
> --- a/tools/perf/util/sort.c
> +++ b/tools/perf/util/sort.c
> @@ -1020,8 +1020,7 @@ static int hist_entry__dso_to_filter(struct hist_entry *he, int type,
>  static int64_t
>  sort__sym_from_cmp(struct hist_entry *left, struct hist_entry *right)
>  {
> -       struct addr_map_symbol *from_l = &left->branch_info->from;
> -       struct addr_map_symbol *from_r = &right->branch_info->from;
> +       struct addr_map_symbol *from_l, *from_r;
>
>         if (!left->branch_info || !right->branch_info)
>                 return cmp_null(left->branch_info, right->branch_info);
> --
> 2.40.0
>