selftests/bpf: Test case for lacking CFI stub functions.

Ensure struct_ops rejects the registration of struct_ops types without
proper CFI stub functions.

bpf_test_no_cfi.ko is a module that attempts to register a struct_ops type
called "bpf_test_no_cfi_ops" with cfi_stubs of NULL and non-NULL value.
The NULL one should fail, and the non-NULL one should succeed. The module
can only be loaded successfully if these registrations yield the expected
results.

Signed-off-by: Kui-Feng Lee <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Martin KaFai Lau <[email protected]>

1 files changed, 35 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/prog_tests/test_struct_ops_no_cfi.c b/tools/testing/selftests/bpf/prog_tests/test_struct_ops_no_cfi.c
new file mode 100644
index 000000000000..106ea447965a
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/test_struct_ops_no_cfi.c
@@ -0,0 +1,35 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2024 Meta Platforms, Inc. and affiliates. */
+#include <test_progs.h>
+#include <testing_helpers.h>
+
+static void load_bpf_test_no_cfi(void)
+{
+	int fd;
+	int err;
+
+	fd = open("bpf_test_no_cfi.ko", O_RDONLY);
+	if (!ASSERT_GE(fd, 0, "open"))
+		return;
+
+	/* The module will try to register a struct_ops type without
+	 * cfi_stubs and with cfi_stubs.
+	 *
+	 * The one without cfi_stub should fail. The module will be loaded
+	 * successfully only if the result of the registration is as
+	 * expected, or it fails.
+	 */
+	err = finit_module(fd, "", 0);
+	close(fd);
+	if (!ASSERT_OK(err, "finit_module"))
+		return;
+
+	err = delete_module("bpf_test_no_cfi", 0);
+	ASSERT_OK(err, "delete_module");
+}
+
+void test_struct_ops_no_cfi(void)
+{
+	if (test__start_subtest("load_bpf_test_no_cfi"))
+		load_bpf_test_no_cfi();
+}