linux-kernel - Re: [PATCH] selftests/bpf: improve file descriptor closure handling

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Date: Wed, 26 Jun 2024 16:41:56 -0700
From: Andrii Nakryiko <andrii.nakryiko@...il.com>
To: Ma Ke <make24@...as.ac.cn>
Cc: 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, jolsa@...nel.org, mykolal@...com, 
	shuah@...nel.org, iii@...ux.ibm.com, bpf@...r.kernel.org, 
	linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] selftests/bpf: improve file descriptor closure handling

On Wed, Jun 26, 2024 at 5:19 AM Ma Ke <make24@...as.ac.cn> wrote:
>
> serial_test_fexit_stress() has a non-robust handling of file descriptor
> closure. If an error occurs, the function may exit without closing open
> file descriptors, potentially causing resource leaks.
>
> Fix the issue by closing file descriptors in reverse order and starting
> from the last opened. Ensure proper closure even if an error occurs early.
>
> Fixes: 8fb9fb2f1728 ("selftests/bpf: Query BPF_MAX_TRAMP_LINKS using BTF")
> Signed-off-by: Ma Ke <make24@...as.ac.cn>
> ---
>  tools/testing/selftests/bpf/prog_tests/fexit_stress.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>

there is no need for this change, I've applied your previous patch but
adjusted > 0 checks, see my comment there. That should be enough.

> diff --git a/tools/testing/selftests/bpf/prog_tests/fexit_stress.c b/tools/testing/selftests/bpf/prog_tests/fexit_stress.c
> index 596536def43d..b1980bd61583 100644
> --- a/tools/testing/selftests/bpf/prog_tests/fexit_stress.c
> +++ b/tools/testing/selftests/bpf/prog_tests/fexit_stress.c
> @@ -49,11 +49,14 @@ void serial_test_fexit_stress(void)
>         ASSERT_OK(err, "bpf_prog_test_run_opts");
>
>  out:
> -       for (i = 0; i < bpf_max_tramp_links; i++) {
> +       if (i >= bpf_max_tramp_links)
> +               i = bpf_max_tramp_links - 1;
> +       while (i >= 0) {
>                 if (link_fd[i])
>                         close(link_fd[i]);
>                 if (fexit_fd[i])
>                         close(fexit_fd[i]);
> +               i--;
>         }
>         free(fd);
>  }
> --
> 2.25.1
>