linux-kernel - Re: [PATCH] perf buildid: Avoid copy of uninitialized memory

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Message-ID: <CAP-5=fXg28wcW93tfiN6mdFHj0+eSRE3dL3LTv53bRYuezjZDg@mail.gmail.com>
Date:   Thu, 19 Jan 2023 08:08:13 -0800
From:   Ian Rogers <irogers@...gle.com>
To:     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>,
        Namhyung Kim <namhyung@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>, Ian Rogers <irogers@...gle.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Leo Yan <leo.yan@...aro.org>, linux-perf-users@...r.kernel.org,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev
Cc:     Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH] perf buildid: Avoid copy of uninitialized memory

On Fri, Jan 13, 2023 at 10:57 AM Ian Rogers <irogers@...gle.com> wrote:
>
> build_id__init only copies the buildid data up to size leaving the
> rest of the data array uninitialized. Copying the full array during
> synthesis means the written event contains uninitialized memory.  This
> was detected by the Clang/LLVM memory sanitizer.
>
> Signed-off-by: Ian Rogers <irogers@...gle.com>
> ---
>  tools/perf/util/synthetic-events.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/perf/util/synthetic-events.c b/tools/perf/util/synthetic-events.c
> index 3ab6a92b1a6d..348d05e4ec03 100644
> --- a/tools/perf/util/synthetic-events.c
> +++ b/tools/perf/util/synthetic-events.c
> @@ -2219,7 +2219,7 @@ int perf_event__synthesize_build_id(struct perf_tool *tool, struct dso *pos, u16
>
>         len = pos->long_name_len + 1;
>         len = PERF_ALIGN(len, NAME_ALIGN);
> -       memcpy(&ev.build_id.build_id, pos->bid.data, sizeof(pos->bid.data));
> +       memcpy(&ev.build_id.build_id, pos->bid.data, pos->bid.size);

Ping. Should be an uncontroversial change to fix a copy of
uninitialized memory into the perf.data file during synthesis.

Thanks,
Ian

>         ev.build_id.size = pos->bid.size;
>         ev.build_id.header.type = PERF_RECORD_HEADER_BUILD_ID;
>         ev.build_id.header.misc = misc | PERF_RECORD_MISC_BUILD_ID_SIZE;
> --
> 2.39.0.314.g84b9a713c41-goog
>