linux-kernel - Re: [PATCH v1 3/4] perf stat: Avoid metric-only segv

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Date: Tue, 13 Feb 2024 13:45:20 -0800
From: Namhyung Kim <namhyung@...nel.org>
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>, 
	Adrian Hunter <adrian.hunter@...el.com>, John Garry <john.g.garry@...cle.com>, 
	Kan Liang <kan.liang@...ux.intel.com>, James Clark <james.clark@....com>, 
	K Prateek Nayak <kprateek.nayak@....com>, Kaige Ye <ye@...ge.org>, linux-perf-users@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 3/4] perf stat: Avoid metric-only segv

On Fri, Feb 9, 2024 at 12:50 PM Ian Rogers <irogers@...gle.com> wrote:
>
> Cycles is recognized as part of a hard coded metric in stat-shadow.c,
> it may call print_metric_only with a NULL fmt string leading to a
> segfault. Handle the NULL fmt explicitly.
>
> Fixes: 088519f318be ("perf stat: Move the display functions to stat-display.c")
> Signed-off-by: Ian Rogers <irogers@...gle.com>
> ---
> Note, the fixes tag is to a refactor that moved the function. The bug
> existed before this.

Yeah I noticed that.

> ---
>  tools/perf/util/stat-display.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/perf/util/stat-display.c b/tools/perf/util/stat-display.c
> index 8c61f8627ebc..b7d00a538d70 100644
> --- a/tools/perf/util/stat-display.c
> +++ b/tools/perf/util/stat-display.c
> @@ -560,7 +560,7 @@ static void print_metric_only(struct perf_stat_config *config,
>         if (color)
>                 mlen += strlen(color) + sizeof(PERF_COLOR_RESET) - 1;
>
> -       color_snprintf(str, sizeof(str), color ?: "", fmt, val);
> +       color_snprintf(str, sizeof(str), color ?: "", fmt ?: "", val);

I was thinking about fixing the callers to pass valid format strings
but it seems they don't care about the output string anyway so
I think it's fine.

Thanks,
Namhyung


>         fprintf(out, "%*s ", mlen, str);
>         os->first = false;
>  }
> --
> 2.43.0.687.g38aa6559b0-goog
>