linux-kernel - Re: [PATCH v1] perf pmu: Avoid uninitialized use of alias->str

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Message-ID: <CAM9d7ciUho=P8AnSq6inUudw15d8e=epke-XQFkpx5wuDgtikw@mail.gmail.com>
Date:   Tue, 29 Aug 2023 19:23:58 -0700
From:   Namhyung Kim <namhyung@...nel.org>
To:     Ian Rogers <irogers@...gle.com>
Cc:     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>,
        Kan Liang <kan.liang@...ux.intel.com>,
        James Clark <james.clark@....com>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        Sumanth Korikkar <sumanthk@...ux.ibm.com>,
        Thomas Richter <tmricht@...ux.ibm.com>,
        Jing Zhang <renyu.zj@...ux.alibaba.com>
Subject: Re: [PATCH v1] perf pmu: Avoid uninitialized use of alias->str

Hi Ian,

On Tue, Aug 29, 2023 at 5:05 PM Ian Rogers <irogers@...gle.com> wrote:
>
> alias is allocated with malloc allowing uninitialized memory to be
> accessed. The initialization of str was moved late after it could have
> been updated by a JSON event, however, this create a potential for an
> uninitialized use. Fix this by assigning str to NULL early. Testing on
> ARM (Raspberry Pi) showed a memory leak in the same code so add a
> zfree.
>
> Fixes: f63a536f03a2 ("perf pmu: Merge JSON events with sysfs at load time")
> Signed-off-by: Ian Rogers <irogers@...gle.com>

Acked-by: Namhyung Kim <namhyung@...nel.org>

Thanks,
Namhyung


> ---
>  tools/perf/util/pmu.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
> index cde33e01959a..b3f8f3f1e900 100644
> --- a/tools/perf/util/pmu.c
> +++ b/tools/perf/util/pmu.c
> @@ -532,6 +532,7 @@ static int perf_pmu__new_alias(struct perf_pmu *pmu, const char *name,
>         if (!alias)
>                 return -ENOMEM;
>
> +       alias->str = NULL;
>         INIT_LIST_HEAD(&alias->terms);
>         alias->scale = 1.0;
>         alias->unit[0] = '\0';
> @@ -593,6 +594,7 @@ static int perf_pmu__new_alias(struct perf_pmu *pmu, const char *name,
>                         ret += scnprintf(newval + ret, sizeof(newval) - ret,
>                                          "%s=%s", term->config, term->val.str);
>         }
> +       zfree(&alias->str);
>         alias->str = strdup(newval);
>         if (!pe)
>                 pmu->sysfs_aliases++;
> --
> 2.42.0.rc2.253.gd59a3bf2b4-goog
>