linux-kernel - Re: [RFC v1 01/16] perf kwork: Fix incorrect and missing free atom in work_push

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Date:   Sun, 3 Sep 2023 21:05:06 -0700
From:   Ian Rogers <irogers@...gle.com>
To:     Yang Jihong <yangjihong1@...wei.com>
Cc:     peterz@...radead.org, mingo@...hat.com, acme@...nel.org,
        mark.rutland@....com, alexander.shishkin@...ux.intel.com,
        jolsa@...nel.org, namhyung@...nel.org, adrian.hunter@...el.com,
        kan.liang@...ux.intel.com, sandipan.das@....com,
        ravi.bangoria@....com, linux-kernel@...r.kernel.org,
        linux-perf-users@...r.kernel.org
Subject: Re: [RFC v1 01/16] perf kwork: Fix incorrect and missing free atom in work_push_atom()

On Sat, Aug 12, 2023 at 1:52 AM Yang Jihong <yangjihong1@...wei.com> wrote:
>
> 1. Atoms are managed in page mode and should be released using atom_free()
>    instead of free().
> 2. When the event does not match, the atom needs to free.
>
> Fixes: f98919ec4fcc ("perf kwork: Implement 'report' subcommand")
> Signed-off-by: Yang Jihong <yangjihong1@...wei.com>

Reviewed-by: Ian Rogers <irogers@...gle.com>

> ---
>  tools/perf/builtin-kwork.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/tools/perf/builtin-kwork.c b/tools/perf/builtin-kwork.c
> index 14bf7a8429e7..73b5dc099a8a 100644
> --- a/tools/perf/builtin-kwork.c
> +++ b/tools/perf/builtin-kwork.c
> @@ -406,12 +406,14 @@ static int work_push_atom(struct perf_kwork *kwork,
>
>         work = work_findnew(&class->work_root, &key, &kwork->cmp_id);
>         if (work == NULL) {
> -               free(atom);
> +               atom_free(atom);

Presumably this is fixing a memory-leak. It would be nice if kwork had
perf tests, then our builds with -fsanitize=address would highlight
this kind of issue. Here is a build command I use for this:
make -C tools/perf O=/tmp/perf DEBUG=1 EXTRA_CFLAGS="-O0 -g
-fno-omit-frame-pointer -fsanitize=address" BUILD_BPF_SKEL=1
NO_LIBTRACEEVENT=1

Thanks,
Ian

>                 return -1;
>         }
>
> -       if (!profile_event_match(kwork, work, sample))
> +       if (!profile_event_match(kwork, work, sample)) {
> +               atom_free(atom);
>                 return 0;
> +       }
>
>         if (dst_type < KWORK_TRACE_MAX) {
>                 dst_atom = list_last_entry_or_null(&work->atom_list[dst_type],
> --
> 2.30.GIT
>