linux-kernel - Re: [PATCH v2 06/18] perf buildid-cache: Fix use of uninitialized value

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Date:   Sun, 8 Oct 2023 23:06:44 -0700
From:   Namhyung Kim <namhyung@...nel.org>
To:     Ian Rogers <irogers@...gle.com>
Cc:     Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>,
        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@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Yicong Yang <yangyicong@...ilicon.com>,
        Jonathan Cameron <jonathan.cameron@...wei.com>,
        Yang Jihong <yangjihong1@...wei.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Ming Wang <wangming01@...ngson.cn>,
        Huacai Chen <chenhuacai@...nel.org>,
        Sean Christopherson <seanjc@...gle.com>,
        K Prateek Nayak <kprateek.nayak@....com>,
        Yanteng Si <siyanteng@...ngson.cn>,
        Yuan Can <yuancan@...wei.com>,
        Ravi Bangoria <ravi.bangoria@....com>,
        James Clark <james.clark@....com>, llvm@...ts.linux.dev,
        linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        bpf@...r.kernel.org
Subject: Re: [PATCH v2 06/18] perf buildid-cache: Fix use of uninitialized value

On Thu, Oct 5, 2023 at 4:09 PM Ian Rogers <irogers@...gle.com> wrote:
>
> The buildid filename is first determined and then from this the
> buildid read. If getting the filename fails then the buildid will be
> used for a later memcmp uninitialized. Detected by clang-tidy.
>
> Signed-off-by: Ian Rogers <irogers@...gle.com>
> ---
>  tools/perf/builtin-buildid-cache.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/tools/perf/builtin-buildid-cache.c b/tools/perf/builtin-buildid-cache.c
> index cd381693658b..e2a40f1d9225 100644
> --- a/tools/perf/builtin-buildid-cache.c
> +++ b/tools/perf/builtin-buildid-cache.c
> @@ -277,8 +277,10 @@ static bool dso__missing_buildid_cache(struct dso *dso, int parm __maybe_unused)
>         char filename[PATH_MAX];
>         struct build_id bid;
>
> -       if (dso__build_id_filename(dso, filename, sizeof(filename), false) &&
> -           filename__read_build_id(filename, &bid) == -1) {
> +       if (!dso__build_id_filename(dso, filename, sizeof(filename), false))
> +               return true;

This won't print anything and ignore the file which changes
the existing behavior.  But if it fails to read the build-id, I
don't think there is not much we can do with it.  IIUC the
original intention of -M/--missing option is to list files that
have a build-id but it's not in the build-id cache.  So maybe
it's ok to silently ignore it.

Thanks,
Namhyung


> +
> +       if (filename__read_build_id(filename, &bid) == -1) {
>                 if (errno == ENOENT)
>                         return false;
>
> --
> 2.42.0.609.gbb76f46606-goog
>