linux-kernel - Re: [PATCH v2] perf stat-display: Check if snprintf()'s fmt argument is NULL

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Date:   Mon, 21 Aug 2023 10:54:50 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Ian Rogers <irogers@...gle.com>
Cc:     Kaige Ye <ye@...ge.org>, peterz@...radead.org, mingo@...hat.com,
        mark.rutland@....com, alexander.shishkin@...ux.intel.com,
        jolsa@...nel.org, namhyung@...nel.org, adrian.hunter@...el.com,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] perf stat-display: Check if snprintf()'s fmt argument
 is NULL

Em Mon, Aug 14, 2023 at 01:24:06PM -0700, Ian Rogers escreveu:
> On Thu, Aug 3, 2023 at 7:10 PM Kaige Ye <ye@...ge.org> wrote:
> >
> > It is undefined behavior to pass NULL as snprintf()'s fmt argument.
> > Here is an example to trigger the problem:
> >
> >   $ perf stat --metric-only -x, -e instructions -- sleep 1
> >   insn per cycle,
> >   Segmentation fault (core dumped)
> >
> > With this patch:
> >
> >   $ perf stat --metric-only -x, -e instructions -- sleep 1
> >   insn per cycle,
> >   ,
> >
> > Signed-off-by: Kaige Ye <ye@...ge.org>
> 
> Thanks Kaige!
> 
> Reviewed-by: Ian Rogers <irogers@...gle.com>

Thanks, applied.

- Arnaldo

 
> > ---
> > V1 -> V2: Addressed Ian's comments (Ian Rogers)
> > ---
> >  tools/perf/util/stat-display.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/tools/perf/util/stat-display.c b/tools/perf/util/stat-display.c
> > index 7329b3340..031888545 100644
> > --- a/tools/perf/util/stat-display.c
> > +++ b/tools/perf/util/stat-display.c
> > @@ -578,7 +578,7 @@ static void print_metric_only_csv(struct perf_stat_config *config __maybe_unused
> >         if (!valid_only_metric(unit))
> >                 return;
> >         unit = fixunit(tbuf, os->evsel, unit);
> > -       snprintf(buf, sizeof buf, fmt, val);
> > +       snprintf(buf, sizeof(buf), fmt ?: "", val);
> >         ends = vals = skip_spaces(buf);
> >         while (isdigit(*ends) || *ends == '.')
> >                 ends++;
> > @@ -600,7 +600,7 @@ static void print_metric_only_json(struct perf_stat_config *config __maybe_unuse
> >         if (!valid_only_metric(unit))
> >                 return;
> >         unit = fixunit(tbuf, os->evsel, unit);
> > -       snprintf(buf, sizeof(buf), fmt, val);
> > +       snprintf(buf, sizeof(buf), fmt ?: "", val);
> >         ends = vals = skip_spaces(buf);
> >         while (isdigit(*ends) || *ends == '.')
> >                 ends++;
> >
> > base-commit: f6b8436bede3e80226e8b2100279c4450c73806a
> > --
> > 2.41.0
> >

-- 

- Arnaldo