[<prev] [next>] [<thread-prev] [day] [month] [year] [list]
Message-ID: <5FADEC01265BADB6+20230803171126.134677-1-ye@kaige.org>
Date: Fri, 4 Aug 2023 01:11:26 +0800
From: Kaige Ye <ye@...ge.org>
To: irogers@...gle.com
Cc: acme@...nel.org, adrian.hunter@...el.com,
alexander.shishkin@...ux.intel.com, jolsa@...nel.org,
linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
mark.rutland@....com, mingo@...hat.com, namhyung@...nel.org,
peterz@...radead.org, ye@...ge.org
Subject: Re: [PATCH] perf stat-display: Check if snprintf()'s fmt argument is NULL
On Wed, 2 Aug 2023 10:45:47 -0700 Ian Rogers <irogers@...gle.com> 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>
> > ---
> > tools/perf/util/stat-display.c | 6 +++---
> > 1 file changed, 3 insertions(+), 3 deletions(-)
> >
> > diff --git a/tools/perf/util/stat-display.c b/tools/perf/util/stat-display.c
> > index 7329b3340..e8936cffd 100644
> > --- a/tools/perf/util/stat-display.c
> > +++ b/tools/perf/util/stat-display.c
> > @@ -438,7 +438,7 @@ static void print_metric_csv(struct perf_stat_config *config __maybe_unused,
> > fprintf(out, "%s%s", config->csv_sep, config->csv_sep);
> > return;
> > }
> > - snprintf(buf, sizeof(buf), fmt, val);
> > + snprintf(buf, sizeof(buf), fmt ?: "", val);
>
> Hi,
>
> I couldn't reproduce this error and the code immediately above here
> does null check fmt:
> https://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git/tree/tools/perf/util/stat-display.c?h=perf-tools-next#n437
Hi Ian,
I apologize for my carelessness. You're right, the code above doesn't need any change.
I'll send a new patch to fix it.
> Perhaps this is an older version of the perf tool? You can run "perf
> version" to determine this.
I found this bug with perf version 6.4.4, and I can reproduce the error with perf version 6.5.rc2.g76efcf004289.
The root cause is when I run `perf stat` like this:
$ perf stat --metric-only -x, -e instructions -- sleep 1
It'll hit this line:
https://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git/tree/tools/perf/util/stat-shadow.c#n318
The error can also be triggered by:
- Replace the `-x,` option with `-j`
- Replace the `-e instructions` option with `-e cycles`
Thanks,
Kaige
> [...]
Powered by blists - more mailing lists