linux-kernel - Re: [PATCH bpf-next v2] selftests/bpf:fix a resource leak

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Message-ID: <273183c9-101c-422b-9fcd-a9921c127cb1@linuxfoundation.org>
Date: Wed, 10 Jul 2024 09:30:04 -0600
From: Shuah Khan <skhan@...uxfoundation.org>
To: Zhu Jun <zhujun2@...s.chinamobile.com>, jolsa@...nel.org,
 shuah@...nel.org, ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
 martin.lau@...ux.dev, eddyz87@...il.com, song@...nel.org,
 yonghong.song@...ux.dev, john.fastabend@...il.com, kpsingh@...nel.org,
 sdf@...ichev.me, haoluo@...gle.com, mykolal@...com, bpf@...r.kernel.org,
 linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org,
 Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH bpf-next v2] selftests/bpf:fix a resource leak

On 7/9/24 19:59, Zhu Jun wrote:
> The requested resources should be closed before return
> in main(), otherwise resource leak will occur
> 
> Signed-off-by: Zhu Jun <zhujun2@...s.chinamobile.com>

How did you find this problem? Please give more details
on the tool used including the output from the tool.
> ---
> Changes in v2:
>   - check for cg_fd >= 0 and have just one out label
> 
>   tools/testing/selftests/bpf/test_sockmap.c | 11 +++++++----
>   1 file changed, 7 insertions(+), 4 deletions(-)
> 
> diff --git a/tools/testing/selftests/bpf/test_sockmap.c b/tools/testing/selftests/bpf/test_sockmap.c
> index a34e95040994..285a9a714666 100644
> --- a/tools/testing/selftests/bpf/test_sockmap.c
> +++ b/tools/testing/selftests/bpf/test_sockmap.c
> @@ -2075,8 +2075,10 @@ int main(int argc, char **argv)
>   
>   	if (!cg_fd) {
>   		cg_fd = cgroup_setup_and_join(CG_PATH);
> -		if (cg_fd < 0)
> -			return cg_fd;
> +		if (cg_fd < 0) {
> +			err = cg_fd;
> +			goto out;
> +		}

I don't this this improves the code - it makes it more complex.
If you want to improve this - add the same error message that
gets printed out for

case 'c':

in argument parsing.

fprintf(stderr, "ERROR: (%i) open cg path failed: %s\n",
                  cg_fd, optarg);
>   		cg_created = 1;
>   	}
>   
> @@ -2092,7 +2094,7 @@ int main(int argc, char **argv)
>   	if (err) {
>   		fprintf(stderr, "populate program: (%s) %s\n",
>   			bpf_file, strerror(errno));
> -		return 1;
> +		goto out;

This looks good to me.

>   	}
>   	running = 1;
>   
> @@ -2109,7 +2111,8 @@ int main(int argc, char **argv)
>   		free(options.whitelist);
>   	if (options.blacklist)
>   		free(options.blacklist);
> -	close(cg_fd);
> +	if (cg_fd >= 0)

Why is this check necessary?
> +		close(cg_fd);


>   	if (cg_created)
>   		cleanup_cgroup_environment();
>   	return err;

thanks,
-- Shuah