Re: [PATCH] selftests/sched_ext: Fix bpf_link leak on early return in prog_run

[Andrea Righi <arighi@nvidia.com>]

Hi Liang,

On Thu, Jul 09, 2026 at 06:03:40PM +0800, luoliang@kylinos.cn wrote:
> From: Liang Luo <luoliang@kylinos.cn>
> 
> In prog_run's run(), the bpf_link is attached early but only destroyed
> on the success path. The three SCX_EQ assertions between attach and
> destroy expand to a direct 'return SCX_TEST_FAIL', so if any of them
> triggers, bpf_link__destroy() is never reached and the BPF scheduler
> stays loaded. All subsequent tests then fail to attach because SCX is
> not in the DISABLED state.
> 
> Convert those assertions to explicit checks that jump to a unified
> 'out' label which always runs the cleanup, matching the pattern used
> in cyclic_kick_wait.c.
> 
> Signed-off-by: Liang Luo <luoliang@kylinos.cn>

We could also add (optionally):

Fixes: a5db7817af78 ("sched_ext: Add selftests")

Other than that, looks good to me.

Reviewed-by: Andrea Righi <arighi@nvidia.com>

Thanks,
-Andrea

> ---
>  tools/testing/selftests/sched_ext/prog_run.c | 34 +++++++++++++++-----
>  1 file changed, 26 insertions(+), 8 deletions(-)
> 
> diff --git a/tools/testing/selftests/sched_ext/prog_run.c b/tools/testing/selftests/sched_ext/prog_run.c
> index 05974820ca69..1129ec2aaddc 100644
> --- a/tools/testing/selftests/sched_ext/prog_run.c
> +++ b/tools/testing/selftests/sched_ext/prog_run.c
> @@ -28,7 +28,8 @@ static enum scx_test_status setup(void **ctx)
>  static enum scx_test_status run(void *ctx)
>  {
>  	struct prog_run *skel = ctx;
> -	struct bpf_link *link;
> +	struct bpf_link *link = NULL;
> +	enum scx_test_status status = SCX_TEST_PASS;
>  	int prog_fd, err = 0;
>  
>  	prog_fd = bpf_program__fd(skel->progs.prog_run_syscall);
> @@ -42,23 +43,40 @@ static enum scx_test_status run(void *ctx)
>  	link = bpf_map__attach_struct_ops(skel->maps.prog_run_ops);
>  	if (!link) {
>  		SCX_ERR("Failed to attach scheduler");
> -		close(prog_fd);
> -		return SCX_TEST_FAIL;
> +		status = SCX_TEST_FAIL;
> +		goto out;
>  	}
>  
>  	err = bpf_prog_test_run_opts(prog_fd, &topts);
> -	SCX_EQ(err, 0);
> +	if (err) {
> +		SCX_ERR("BPF_PROG_RUN failed (%d)", err);
> +		status = SCX_TEST_FAIL;
> +		goto out;
> +	}
>  
>  	/* Assumes uei.kind is written last */
>  	while (skel->data->uei.kind == EXIT_KIND(SCX_EXIT_NONE))
>  		sched_yield();
>  
> -	SCX_EQ(skel->data->uei.kind, EXIT_KIND(SCX_EXIT_UNREG_BPF));
> -	SCX_EQ(skel->data->uei.exit_code, 0xdeadbeef);
> +	if (skel->data->uei.kind != EXIT_KIND(SCX_EXIT_UNREG_BPF)) {
> +		SCX_ERR("Unexpected exit kind: %llu",
> +			(unsigned long long)skel->data->uei.kind);
> +		status = SCX_TEST_FAIL;
> +		goto out;
> +	}
> +	if (skel->data->uei.exit_code != 0xdeadbeef) {
> +		SCX_ERR("Unexpected exit code: %lld",
> +			(long long)skel->data->uei.exit_code);
> +		status = SCX_TEST_FAIL;
> +		goto out;
> +	}
> +
> +out:
>  	close(prog_fd);
> -	bpf_link__destroy(link);
> +	if (link)
> +		bpf_link__destroy(link);
>  
> -	return SCX_TEST_PASS;
> +	return status;
>  }
>  
>  static void cleanup(void *ctx)
> -- 
> 2.43.0
>