selftests/bpf: Add tests for dynamic pointers parameters in kfuncs

Add tests to ensure that only supported dynamic pointer types are accepted,
that the passed argument is actually a dynamic pointer, that the passed
argument is a pointer to the stack, and that bpf_verify_pkcs7_signature()
correctly handles dynamic pointers with data set to NULL.

The tests are currently in the deny list for s390x (JIT does not support
calling kernel function).

Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20220920075951.929132-14-roberto.sassu@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 164 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/prog_tests/kfunc_dynptr_param.c b/tools/testing/selftests/bpf/prog_tests/kfunc_dynptr_param.c
new file mode 100644
index 000000000000..c210657d4d0a
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/kfunc_dynptr_param.c
@@ -0,0 +1,164 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Copyright (c) 2022 Facebook
+ * Copyright (C) 2022 Huawei Technologies Duesseldorf GmbH
+ *
+ * Author: Roberto Sassu <roberto.sassu@huawei.com>
+ */
+
+#include <test_progs.h>
+#include "test_kfunc_dynptr_param.skel.h"
+
+static size_t log_buf_sz = 1048576; /* 1 MB */
+static char obj_log_buf[1048576];
+
+static struct {
+	const char *prog_name;
+	const char *expected_verifier_err_msg;
+	int expected_runtime_err;
+} kfunc_dynptr_tests[] = {
+	{"dynptr_type_not_supp",
+	 "arg#0 pointer type STRUCT bpf_dynptr_kern points to unsupported dynamic pointer type", 0},
+	{"not_valid_dynptr",
+	 "arg#0 pointer type STRUCT bpf_dynptr_kern must be valid and initialized", 0},
+	{"not_ptr_to_stack", "arg#0 pointer type STRUCT bpf_dynptr_kern not to stack", 0},
+	{"dynptr_data_null", NULL, -EBADMSG},
+};
+
+static bool kfunc_not_supported;
+
+static int libbpf_print_cb(enum libbpf_print_level level, const char *fmt,
+			   va_list args)
+{
+	if (strcmp(fmt, "libbpf: extern (func ksym) '%s': not found in kernel or module BTFs\n"))
+		return 0;
+
+	if (strcmp(va_arg(args, char *), "bpf_verify_pkcs7_signature"))
+		return 0;
+
+	kfunc_not_supported = true;
+	return 0;
+}
+
+static void verify_fail(const char *prog_name, const char *expected_err_msg)
+{
+	struct test_kfunc_dynptr_param *skel;
+	LIBBPF_OPTS(bpf_object_open_opts, opts);
+	libbpf_print_fn_t old_print_cb;
+	struct bpf_program *prog;
+	int err;
+
+	opts.kernel_log_buf = obj_log_buf;
+	opts.kernel_log_size = log_buf_sz;
+	opts.kernel_log_level = 1;
+
+	skel = test_kfunc_dynptr_param__open_opts(&opts);
+	if (!ASSERT_OK_PTR(skel, "test_kfunc_dynptr_param__open_opts"))
+		goto cleanup;
+
+	prog = bpf_object__find_program_by_name(skel->obj, prog_name);
+	if (!ASSERT_OK_PTR(prog, "bpf_object__find_program_by_name"))
+		goto cleanup;
+
+	bpf_program__set_autoload(prog, true);
+
+	bpf_map__set_max_entries(skel->maps.ringbuf, getpagesize());
+
+	kfunc_not_supported = false;
+
+	old_print_cb = libbpf_set_print(libbpf_print_cb);
+	err = test_kfunc_dynptr_param__load(skel);
+	libbpf_set_print(old_print_cb);
+
+	if (err < 0 && kfunc_not_supported) {
+		fprintf(stderr,
+		  "%s:SKIP:bpf_verify_pkcs7_signature() kfunc not supported\n",
+		  __func__);
+		test__skip();
+		goto cleanup;
+	}
+
+	if (!ASSERT_ERR(err, "unexpected load success"))
+		goto cleanup;
+
+	if (!ASSERT_OK_PTR(strstr(obj_log_buf, expected_err_msg), "expected_err_msg")) {
+		fprintf(stderr, "Expected err_msg: %s\n", expected_err_msg);
+		fprintf(stderr, "Verifier output: %s\n", obj_log_buf);
+	}
+
+cleanup:
+	test_kfunc_dynptr_param__destroy(skel);
+}
+
+static void verify_success(const char *prog_name, int expected_runtime_err)
+{
+	struct test_kfunc_dynptr_param *skel;
+	libbpf_print_fn_t old_print_cb;
+	struct bpf_program *prog;
+	struct bpf_link *link;
+	__u32 next_id;
+	int err;
+
+	skel = test_kfunc_dynptr_param__open();
+	if (!ASSERT_OK_PTR(skel, "test_kfunc_dynptr_param__open"))
+		return;
+
+	skel->bss->pid = getpid();
+
+	bpf_map__set_max_entries(skel->maps.ringbuf, getpagesize());
+
+	kfunc_not_supported = false;
+
+	old_print_cb = libbpf_set_print(libbpf_print_cb);
+	err = test_kfunc_dynptr_param__load(skel);
+	libbpf_set_print(old_print_cb);
+
+	if (err < 0 && kfunc_not_supported) {
+		fprintf(stderr,
+		  "%s:SKIP:bpf_verify_pkcs7_signature() kfunc not supported\n",
+		  __func__);
+		test__skip();
+		goto cleanup;
+	}
+
+	if (!ASSERT_OK(err, "test_kfunc_dynptr_param__load"))
+		goto cleanup;
+
+	prog = bpf_object__find_program_by_name(skel->obj, prog_name);
+	if (!ASSERT_OK_PTR(prog, "bpf_object__find_program_by_name"))
+		goto cleanup;
+
+	link = bpf_program__attach(prog);
+	if (!ASSERT_OK_PTR(link, "bpf_program__attach"))
+		goto cleanup;
+
+	err = bpf_prog_get_next_id(0, &next_id);
+
+	bpf_link__destroy(link);
+
+	if (!ASSERT_OK(err, "bpf_prog_get_next_id"))
+		goto cleanup;
+
+	ASSERT_EQ(skel->bss->err, expected_runtime_err, "err");
+
+cleanup:
+	test_kfunc_dynptr_param__destroy(skel);
+}
+
+void test_kfunc_dynptr_param(void)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(kfunc_dynptr_tests); i++) {
+		if (!test__start_subtest(kfunc_dynptr_tests[i].prog_name))
+			continue;
+
+		if (kfunc_dynptr_tests[i].expected_verifier_err_msg)
+			verify_fail(kfunc_dynptr_tests[i].prog_name,
+			  kfunc_dynptr_tests[i].expected_verifier_err_msg);
+		else
+			verify_success(kfunc_dynptr_tests[i].prog_name,
+				kfunc_dynptr_tests[i].expected_runtime_err);
+	}
+}