linux-kernel - Re: [PATCH] perf test: Fix msan uninitialized use.

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Date:   Thu, 24 Sep 2020 16:12:31 -0700
From:   Ian Rogers <irogers@...gle.com>
To:     Nick Desaulniers <ndesaulniers@...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@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH] perf test: Fix msan uninitialized use.

On Wed, Sep 23, 2020 at 4:37 PM Nick Desaulniers
<ndesaulniers@...gle.com> wrote:
>
> On Wed, Sep 23, 2020 at 2:07 PM 'Ian Rogers' via Clang Built Linux
> <clang-built-linux@...glegroups.com> wrote:
> >
> > Ensure 'st' is initialized before an error branch is taken.
> > Fixes test "67: Parse and process metrics" with LLVM msan:
> > ==6757==WARNING: MemorySanitizer: use-of-uninitialized-value
> >     #0 0x5570edae947d in rblist__exit tools/perf/util/rblist.c:114:2
> >     #1 0x5570edb1c6e8 in runtime_stat__exit tools/perf/util/stat-shadow.c:141:2
> >     #2 0x5570ed92cfae in __compute_metric tools/perf/tests/parse-metric.c:187:2
> >     #3 0x5570ed92cb74 in compute_metric tools/perf/tests/parse-metric.c:196:9
> >     #4 0x5570ed92c6d8 in test_recursion_fail tools/perf/tests/parse-metric.c:318:2
> >     #5 0x5570ed92b8c8 in test__parse_metric tools/perf/tests/parse-metric.c:356:2
> >     #6 0x5570ed8de8c1 in run_test tools/perf/tests/builtin-test.c:410:9
> >     #7 0x5570ed8ddadf in test_and_print tools/perf/tests/builtin-test.c:440:9
> >     #8 0x5570ed8dca04 in __cmd_test tools/perf/tests/builtin-test.c:661:4
> >     #9 0x5570ed8dbc07 in cmd_test tools/perf/tests/builtin-test.c:807:9
> >     #10 0x5570ed7326cc in run_builtin tools/perf/perf.c:313:11
> >     #11 0x5570ed731639 in handle_internal_command tools/perf/perf.c:365:8
> >     #12 0x5570ed7323cd in run_argv tools/perf/perf.c:409:2
> >     #13 0x5570ed731076 in main tools/perf/perf.c:539:3
> >
> > Fixes: commit f5a56570a3f2 ("perf test: Fix memory leaks in parse-metric test")
> > Signed-off-by: Ian Rogers <irogers@...gle.com>
>
> Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>
>
> Orthogonal:
> The case where metricgroup__parse_groups_test() can fail in
> __compute_metric() also looks curious. Should &metric_events be passed
> to metricgroup__rblist_exit() in that case?

Thanks Nick! Checking metricgroup.c, metricgroup__rblist_init does
occur even if an error is returned. So there isn't an error, but that
doesn't mean the code couldn't be cleaner :-)

Ian

> > ---
> >  tools/perf/tests/parse-metric.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/tools/perf/tests/parse-metric.c b/tools/perf/tests/parse-metric.c
> > index aea4f970fccc..7c1bde01cb50 100644
> > --- a/tools/perf/tests/parse-metric.c
> > +++ b/tools/perf/tests/parse-metric.c
> > @@ -157,6 +157,7 @@ static int __compute_metric(const char *name, struct value *vals,
> >         }
> >
> >         perf_evlist__set_maps(&evlist->core, cpus, NULL);
> > +       runtime_stat__init(&st);
> >
> >         /* Parse the metric into metric_events list. */
> >         err = metricgroup__parse_groups_test(evlist, &map, name,
> > @@ -170,7 +171,6 @@ static int __compute_metric(const char *name, struct value *vals,
> >                 goto out;
> >
> >         /* Load the runtime stats with given numbers for events. */
> > -       runtime_stat__init(&st);
> >         load_runtime_stat(&st, evlist, vals);
> >
> >         /* And execute the metric */
> > --
> > 2.28.0.681.g6f77f65b4e-goog
> >
> > --
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>
>
>
> --
> Thanks,
> ~Nick Desaulniers