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 <20190807113244.GA9605@krava>
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From:   Ian Rogers <irogers@google.com>
Date:   Fri, 25 Oct 2019 15:11:02 -0700
Message-ID: <CAP-5=fW8k6YWBYno2RWV5_mojn-0crvmPcLynKGBO_3WMCXfEA@mail.gmail.com>
Subject: Re: [PATCH v2] Fix annotate.c use of uninitialized value error
To:     Jiri Olsa <jolsa@redhat.com>
Cc:     Numfor Mbiziwo-Tiapo <nums@google.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Namhyung Kim <namhyung@kernel.org>,
        Song Liu <songliubraving@fb.com>, mbd@fb.com,
        LKML <linux-kernel@vger.kernel.org>,
        Stephane Eranian <eranian@google.com>
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It looks like this wasn't merged to tip. Does anything need addressing
to get it merged?

Thanks,
Ian

On Wed, Aug 7, 2019 at 4:32 AM Jiri Olsa <jolsa@redhat.com> wrote:
>
> On Mon, Jul 29, 2019 at 01:57:50PM -0700, Numfor Mbiziwo-Tiapo wrote:
> > Our local MSAN (Memory Sanitizer) build of perf throws a warning
> > that comes from the "dso__disassemble_filename" function in
> > "tools/perf/util/annotate.c" when running perf record.
> >
> > The warning stems from the call to readlink, in which "build_id_path"
> > was being read into "linkname". Since readlink does not null terminate,
> > an uninitialized memory access would later occur when "linkname" is
> > passed into the strstr function. This is simply fixed by null-terminating
> > "linkname" after the call to readlink.
> >
> > To reproduce this warning, build perf by running:
> > make -C tools/perf CLANG=1 CC=clang EXTRA_CFLAGS="-fsanitize=memory\
> >  -fsanitize-memory-track-origins"
> >
> > (Additionally, llvm might have to be installed and clang might have to
> > be specified as the compiler - export CC=/usr/bin/clang)
> >
> > then running:
> > tools/perf/perf record -o - ls / | tools/perf/perf --no-pager annotate\
> >  -i - --stdio
> >
> > Please see the cover letter for why false positive warnings may be
> > generated.
> >
> > Signed-off-by: Numfor Mbiziwo-Tiapo <nums@google.com>
>
> Acked-by: Jiri Olsa <jolsa@kernel.org>
>
> thanks,
> jirka
>
> > ---
> >  tools/perf/util/annotate.c | 15 +++++++++++----
> >  1 file changed, 11 insertions(+), 4 deletions(-)
> >
> > diff --git a/tools/perf/util/annotate.c b/tools/perf/util/annotate.c
> > index 70de8f6b3aee..e1b075b52dce 100644
> > --- a/tools/perf/util/annotate.c
> > +++ b/tools/perf/util/annotate.c
> > @@ -1627,6 +1627,7 @@ static int dso__disassemble_filename(struct dso *dso, char *filename, size_t fil
> >       char *build_id_filename;
> >       char *build_id_path = NULL;
> >       char *pos;
> > +     int len;
> >
> >       if (dso->symtab_type == DSO_BINARY_TYPE__KALLSYMS &&
> >           !dso__is_kcore(dso))
> > @@ -1655,10 +1656,16 @@ static int dso__disassemble_filename(struct dso *dso, char *filename, size_t fil
> >       if (pos && strlen(pos) < SBUILD_ID_SIZE - 2)
> >               dirname(build_id_path);
> >
> > -     if (dso__is_kcore(dso) ||
> > -         readlink(build_id_path, linkname, sizeof(linkname)) < 0 ||
> > -         strstr(linkname, DSO__NAME_KALLSYMS) ||
> > -         access(filename, R_OK)) {
> > +     if (dso__is_kcore(dso))
> > +             goto fallback;
> > +
> > +     len = readlink(build_id_path, linkname, sizeof(linkname) - 1);
> > +     if (len < 0)
> > +             goto fallback;
> > +
> > +     linkname[len] = '\0';
> > +     if (strstr(linkname, DSO__NAME_KALLSYMS) ||
> > +             access(filename, R_OK)) {
> >  fallback:
> >               /*
> >                * If we don't have build-ids or the build-id file isn't in the
> > --
> > 2.22.0.709.g102302147b-goog
> >