linux-kernel - Re: [RFC PATCH bpf-next v4 11/12] selftests/bpf: Add test for memcg_bpf

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Message-Id: <522167db42c30a5a277f7f3cf0042aae0835cf95606d04b9a251ddd2b3a66f93@mail.kernel.org>
Date: Mon, 26 Jan 2026 09:30:23 +0000 (UTC)
From: bot+bpf-ci@...nel.org
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Subject: Re: [RFC PATCH bpf-next v4 11/12] selftests/bpf: Add test for memcg_bpf_ops hierarchies

> diff --git a/tools/testing/selftests/bpf/prog_tests/memcg_ops.c b/tools/testing/selftests/bpf/prog_tests/memcg_ops.c
> index a019ba2387bc..08ac97752ac9 100644
> --- a/tools/testing/selftests/bpf/prog_tests/memcg_ops.c
> +++ b/tools/testing/selftests/bpf/prog_tests/memcg_ops.c
> @@ -539,3 +539,73 @@ void test_memcg_ops_below_min_over_high(void)

[ ... ]

> +void test_memcg_ops_hierarchies(void)
> +{
> +	int ret, first = -1, second = -1, third = -1;
> +	struct memcg_ops *skel;
                          ^^^^

Should skel be initialized to NULL here? The other tests in this file
(test_memcg_ops_over_high, test_memcg_ops_below_low_over_high, and
test_memcg_ops_below_min_over_high) all initialize their skeleton pointers
to NULL.

If any of the early checks fail (e.g. setup_cgroup_environment() or
create_and_get_cgroup()), the code jumps to cleanup where memcg_ops__detach()
is called. The skeleton __detach() function dereferences its argument without
checking for NULL, which would cause a crash with an uninitialized pointer.

> +	struct bpf_map *map;
> +	struct bpf_link *link1 = NULL, *link2 = NULL, *link3 = NULL;
> +	DECLARE_LIBBPF_OPTS(bpf_struct_ops_opts, opts);
> +
> +	ret = setup_cgroup_environment();
> +	if (!ASSERT_OK(ret, "setup_cgroup_environment"))
> +		goto cleanup;

[ ... ]

> +cleanup:
> +	bpf_link__destroy(link1);
> +	bpf_link__destroy(link2);
> +	bpf_link__destroy(link3);
> +	memcg_ops__detach(skel);
                         ^^^^

This dereferences skel without checking if it was ever assigned.

> +	close(first);
> +	close(second);
> +	close(third);
> +	cleanup_cgroup_environment();
> +}


---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md

CI run summary: https://github.com/kernel-patches/bpf/actions/runs/21352241149