Re: [RFC PATCH 2/3] selftests/bpf: add memcg eBPF struct ops test

diff --git a/tools/testing/selftests/bpf/prog_tests/memcg_ops.c b/tools/testing/selftests/bpf/prog_tests/memcg_ops.c new file mode 100644 index 000000000..3f989bcfb --- /dev/null +++ b/tools/testing/selftests/bpf/prog_tests/memcg_ops.c

[ ... ]

+void test_memcg_ops_double_attach(void) +{

• struct bpf_object *obj, *obj2;
• struct bpf_map *map, *map2;
• struct bpf_link *link = NULL, *link2 = NULL;
• int err;
• obj = bpf_object__open_file("memcg_ops.bpf.o", NULL);
• err = libbpf_get_error(obj);
• if (CHECK_FAIL(err)) {

• obj = NULL;
  

• goto out;
  

• }
• err = bpf_object__load(obj);
• if (CHECK_FAIL(err))

• goto out;
  

• map = bpf_object__find_map_by_name(obj, "mcg_ops");
• if (!ASSERT_OK_PTR(map, "bpf_object__find_map_by_name"))

• goto out;
  

• link = bpf_map__attach_struct_ops(map);
• if (!ASSERT_OK_PTR(link, "bpf_map__attach_struct_ops"))

• goto out;
  

• obj2 = bpf_object__open_file("memcg_ops.bpf.o", NULL);
• err = libbpf_get_error(obj2);
• if (CHECK_FAIL(err)) {

• obj2 = NULL;
  

• goto out;
  

• }
• err = bpf_object__load(obj2);
• if (CHECK_FAIL(err))

• goto out;
  

• map2 = bpf_object__find_map_by_name(obj2, "mcg_ops");
• if (!ASSERT_OK_PTR(map, "bpf_object__find_map_by_name"))

^^^

In test_memcg_ops_double_attach(), the NULL check is validating the wrong variable. The code retrieves map2 from obj2, but then checks map (from the first object) instead of map2. This means if bpf_object__find_map_by_name() returns NULL for map2, the test won't catch it and will proceed to use the potentially NULL map2 pointer in the subsequent attach call.

Should this be checking map2 instead?

• goto out;
  

• link2 = bpf_map__attach_struct_ops(map2);
• if (!ASSERT_ERR_PTR(link2, "bpf_map__attach_struct_ops")) {

• bpf_link__destroy(link2);
  

• goto out;
  

• }

+out:

• if (link)

• bpf_link__destroy(link);
  

• if (obj)

• bpf_object__close(obj);
  

• if (obj2)

• bpf_object__close(obj2);
  

+}

--- 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/19486904708