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

[Ian Rogers <irogers@google.com>]

On Fri, Jan 13, 2023 at 10:57 AM Ian Rogers <irogers@google.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@google.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
>