linux-kernel - Re: [PATCH] perf sched: Fix memory leaks in __cmd

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Date:   Wed, 24 Aug 2022 07:59:42 -0700
From:   Ian Rogers <irogers@...gle.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH] perf sched: Fix memory leaks in __cmd_record

On Wed, Aug 24, 2022 at 6:37 AM Arnaldo Carvalho de Melo
<acme@...nel.org> wrote:
>
> Em Tue, Aug 23, 2022 at 09:38:25PM -0700, Ian Rogers escreveu:
> > An array of strings is passed to cmd_record but not freed. As
> > cmd_record modifies the array, add another array as a copy that can be
> > mutated allowing the original array contents to all be freed.
> >
> > Detected with -fsanitize=address.
> >
> > Signed-off-by: Ian Rogers <irogers@...gle.com>
> > ---
> >  tools/perf/builtin-sched.c | 21 ++++++++++++++++-----
> >  1 file changed, 16 insertions(+), 5 deletions(-)
> >
> > diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c
> > index 2f6cd1b8b662..59ba14d2321c 100644
> > --- a/tools/perf/builtin-sched.c
> > +++ b/tools/perf/builtin-sched.c
> > @@ -3355,7 +3355,8 @@ static bool schedstat_events_exposed(void)
> >  static int __cmd_record(int argc, const char **argv)
> >  {
> >       unsigned int rec_argc, i, j;
> > -     const char **rec_argv;
> > +     char **rec_argv;
> > +     const char **rec_argv_copy;
> >       const char * const record_args[] = {
> >               "record",
> >               "-a",
> > @@ -3384,6 +3385,7 @@ static int __cmd_record(int argc, const char **argv)
> >               ARRAY_SIZE(schedstat_args) : 0;
> >
> >       struct tep_event *waking_event;
> > +     int ret;
> >
> >       /*
> >        * +2 for either "-e", "sched:sched_wakeup" or
> > @@ -3391,14 +3393,15 @@ static int __cmd_record(int argc, const char **argv)
> >        */
> >       rec_argc = ARRAY_SIZE(record_args) + 2 + schedstat_argc + argc - 1;
> >       rec_argv = calloc(rec_argc + 1, sizeof(char *));
> > +     rec_argv_copy = calloc(rec_argc + 1, sizeof(char *));
> >
> > -     if (rec_argv == NULL)
> > +     if (rec_argv == NULL || rec_argv_copy == NULL)
> >               return -ENOMEM;
>
> Here you´re leaking rec_argv if rec_argv_copy fails to be allocated, no?

Done in v2.

Thanks,
Ian

> - Arnaldo
>
> >
> >       for (i = 0; i < ARRAY_SIZE(record_args); i++)
> >               rec_argv[i] = strdup(record_args[i]);
> >
> > -     rec_argv[i++] = "-e";
> > +     rec_argv[i++] = strdup("-e");
> >       waking_event = trace_event__tp_format("sched", "sched_waking");
> >       if (!IS_ERR(waking_event))
> >               rec_argv[i++] = strdup("sched:sched_waking");
> > @@ -3409,11 +3412,19 @@ static int __cmd_record(int argc, const char **argv)
> >               rec_argv[i++] = strdup(schedstat_args[j]);
> >
> >       for (j = 1; j < (unsigned int)argc; j++, i++)
> > -             rec_argv[i] = argv[j];
> > +             rec_argv[i] = strdup(argv[j]);
> >
> >       BUG_ON(i != rec_argc);
> >
> > -     return cmd_record(i, rec_argv);
> > +     memcpy(rec_argv_copy, rec_argv, sizeof(char*) * rec_argc);
> > +     ret = cmd_record(rec_argc, rec_argv_copy);
> > +
> > +     for (i = 0; i < rec_argc; i++)
> > +             free(rec_argv[i]);
> > +     free(rec_argv);
> > +     free(rec_argv_copy);
> > +
> > +     return ret;
> >  }
> >
> >  int cmd_sched(int argc, const char **argv)
> > --
> > 2.37.2.609.g9ff673ca1a-goog
>
> --
>
> - Arnaldo