linux-kernel - Re: [PATCH] perf jevents: Fix resource leak in process

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Message-ID: <87e66585-1564-3523-59f6-cab15b7e1717@huawei.com>
Date:   Wed, 16 Oct 2019 11:40:57 +0100
From:   John Garry <john.garry@...wei.com>
To:     Yunfeng Ye <yeyunfeng@...wei.com>, <peterz@...radead.org>,
        <mingo@...hat.com>, <acme@...nel.org>, <mark.rutland@....com>,
        <alexander.shishkin@...ux.intel.com>, <jolsa@...hat.com>,
        <namhyung@...nel.org>, <ak@...ux.intel.com>,
        <lukemujica@...gle.com>, <kan.liang@...ux.intel.com>,
        <yuzenghui@...wei.com>
CC:     <linux-kernel@...r.kernel.org>, <hushiyuan@...wei.com>,
        <linfeilong@...wei.com>
Subject: Re: [PATCH] perf jevents: Fix resource leak in process_mapfile()

On 16/10/2019 08:47, Yunfeng Ye wrote:
> There are memory leaks and file descriptor resource leaks in
> process_mapfile().
>
> Fix this by adding free() and fclose() on the error paths.
>
> Fixes: 80eeb67fe577 ("perf jevents: Program to convert JSON file")
> Signed-off-by: Yunfeng Ye <yeyunfeng@...wei.com>
> ---
>  tools/perf/pmu-events/jevents.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/tools/perf/pmu-events/jevents.c b/tools/perf/pmu-events/jevents.c
> index e2837260ca4d..6e60d4cff592 100644
> --- a/tools/perf/pmu-events/jevents.c
> +++ b/tools/perf/pmu-events/jevents.c
> @@ -758,6 +758,7 @@ static int process_mapfile(FILE *outfp, char *fpath)
>  	char *line, *p;
>  	int line_num;
>  	char *tblname;
> +	int ret = 0;
>
>  	pr_info("%s: Processing mapfile %s\n", prog, fpath);
>
> @@ -769,6 +770,7 @@ static int process_mapfile(FILE *outfp, char *fpath)
>  	if (!mapfp) {
>  		pr_info("%s: Error %s opening %s\n", prog, strerror(errno),
>  				fpath);
> +		free(line);
>  		return -1;
>  	}
>
> @@ -795,7 +797,8 @@ static int process_mapfile(FILE *outfp, char *fpath)
>  			/* TODO Deal with lines longer than 16K */
>  			pr_info("%s: Mapfile %s: line %d too long, aborting\n",
>  					prog, fpath, line_num);
> -			return -1;
> +			ret = -1;
> +			goto out;

There's a subtle change of behaviour here, i.e. now calling 
print_mapping_table_suffix(), but I don't think that it makes any 
difference.

However, does outfp remain open also in this case:

main(int argc, char *argv[])
{
...

if (process_mapfile(eventsfp, mapfile)) {
	pr_info("%s: Error processing mapfile %s\n", prog, mapfile);
	/* Make build fail */
	return 1;
}

return 0;

empty_map:
	fclose(eventsfp);
	...
}

I think that this code works on the basis that the program exits on any 
sort of error and releases resources automatically. Having said that, it 
is a good practice to tidy up.

John

>  		}
>  		line[strlen(line)-1] = '\0';
>
> @@ -825,7 +828,9 @@ static int process_mapfile(FILE *outfp, char *fpath)
>
>  out:
>  	print_mapping_table_suffix(outfp);
> -	return 0;
> +	fclose(mapfp);
> +	free(line);
> +	return ret;
>  }
>
>  /*
>