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

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

Posted by Kaige Ye 2 years, 1 month ago

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@kaige.org>
---
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

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

Posted by Ian Rogers 2 years ago

On Thu, Aug 3, 2023 at 7:10 PM Kaige Ye <ye@kaige.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@kaige.org>

Thanks Kaige!

Reviewed-by: Ian Rogers <irogers@google.com>

> ---
> 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
>

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

Posted by Arnaldo Carvalho de Melo 2 years ago

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@kaige.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@kaige.org>
> 
> Thanks Kaige!
> 
> Reviewed-by: Ian Rogers <irogers@google.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