linux-kernel - Re: [PATCH 4/5] perf stat: Avoid segv if core.user

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Date:   Mon, 28 Mar 2022 13:46:29 -0700
From:   Ian Rogers <irogers@...gle.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Mike Leach <mike.leach@...aro.org>,
        Leo Yan <leo.yan@...aro.org>,
        John Garry <john.garry@...wei.com>,
        Will Deacon <will@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Kajol Jain <kjain@...ux.ibm.com>,
        James Clark <james.clark@....com>,
        German Gomez <german.gomez@....com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Riccardo Mancini <rickyman7@...il.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Alexey Bayduraev <alexey.v.bayduraev@...ux.intel.com>,
        Alexander Antonov <alexander.antonov@...ux.intel.com>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org,
        netdev@...r.kernel.org, bpf@...r.kernel.org,
        Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH 4/5] perf stat: Avoid segv if core.user_cpus isn't set.

On Mon, Mar 28, 2022 at 1:32 PM Arnaldo Carvalho de Melo
<acme@...nel.org> wrote:
>
> Em Sun, Mar 27, 2022 at 11:24:13PM -0700, Ian Rogers escreveu:
> > Passing null to perf_cpu_map__max doesn't make sense as there is no
> > valid max. Avoid this problem by null checking in
> > perf_stat_init_aggr_mode.
>
> Applying this one after changing user_cpus back to cpus as this is a fix
> independent of this patchset.
>
> In the future, please try to have such patches at the beginning of the
> series, so that  they can get cherry-picked more easily.

Ack. The problem is best exhibited when the intersect happens, without
it getting a reproducer wasn't something I was able to do.

Thanks,
Ian

> - Arnaldo
>
> > Signed-off-by: Ian Rogers <irogers@...gle.com>
> > ---
> >  tools/perf/builtin-stat.c | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
> > index 5bee529f7656..ecd5cf4fd872 100644
> > --- a/tools/perf/builtin-stat.c
> > +++ b/tools/perf/builtin-stat.c
> > @@ -1472,7 +1472,10 @@ static int perf_stat_init_aggr_mode(void)
> >        * taking the highest cpu number to be the size of
> >        * the aggregation translate cpumap.
> >        */
> > -     nr = perf_cpu_map__max(evsel_list->core.user_cpus).cpu;
> > +     if (evsel_list->core.user_cpus)
> > +             nr = perf_cpu_map__max(evsel_list->core.user_cpus).cpu;
> > +     else
> > +             nr = 0;
> >       stat_config.cpus_aggr_map = cpu_aggr_map__empty_new(nr + 1);
> >       return stat_config.cpus_aggr_map ? 0 : -ENOMEM;
> >  }
> > --
> > 2.35.1.1021.g381101b075-goog
>
> --
>
> - Arnaldo