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

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Date:   Wed, 24 Aug 2022 10:37:14 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Ian Rogers <irogers@...gle.com>
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

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?

- 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