[PATCH v16 12/12] selftests/bpf: Add tests for dynamic pointers parameters in kfuncs

[Roberto Sassu <roberto.sassu@huaweicloud.com>]

From: Roberto Sassu <roberto.sassu@huawei.com>

Add tests to ensure that only supported dynamic pointer types are accepted,
that the passed argument is actually a dynamic pointer, and that the passed
argument is a pointer to the stack.

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>
---
 tools/testing/selftests/bpf/DENYLIST.s390x    |   1 +
 .../bpf/prog_tests/kfunc_dynptr_param.c       | 103 ++++++++++++++++++
 .../bpf/progs/test_kfunc_dynptr_param.c       |  57 ++++++++++
 3 files changed, 161 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/kfunc_dynptr_param.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_kfunc_dynptr_param.c

diff --git a/tools/testing/selftests/bpf/DENYLIST.s390x b/tools/testing/selftests/bpf/DENYLIST.s390x
index 4e305baa5277..9a6dc3671c65 100644
--- a/tools/testing/selftests/bpf/DENYLIST.s390x
+++ b/tools/testing/selftests/bpf/DENYLIST.s390x
@@ -71,3 +71,4 @@ cgroup_hierarchical_stats                # JIT does not support calling kernel f
 htab_update                              # failed to attach: ERROR: strerror_r(-524)=22                                (trampoline)
 lookup_key                               # JIT does not support calling kernel function                                (kfunc)
 verify_pkcs7_sig                         # JIT does not support calling kernel function                                (kfunc)
+kfunc_dynptr_param                       # JIT does not support calling kernel function                                (kfunc)
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..ea655a5c9d8b
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/kfunc_dynptr_param.c
@@ -0,0 +1,103 @@
+// 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_err_msg;
+} kfunc_dynptr_tests[] = {
+	{"dynptr_type_not_supp",
+	 "arg#0 pointer type STRUCT bpf_dynptr_kern points to unsupported dynamic pointer type"},
+	{"not_valid_dynptr",
+	 "arg#0 pointer type STRUCT bpf_dynptr_kern must be valid and initialized"},
+	{"not_ptr_to_stack", "arg#0 pointer type STRUCT bpf_dynptr_kern not to stack"},
+};
+
+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);
+}
+
+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;
+
+		verify_fail(kfunc_dynptr_tests[i].prog_name,
+			    kfunc_dynptr_tests[i].expected_err_msg);
+	}
+}
diff --git a/tools/testing/selftests/bpf/progs/test_kfunc_dynptr_param.c b/tools/testing/selftests/bpf/progs/test_kfunc_dynptr_param.c
new file mode 100644
index 000000000000..2f09f91a1576
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_kfunc_dynptr_param.c
@@ -0,0 +1,57 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Copyright (C) 2022 Huawei Technologies Duesseldorf GmbH
+ *
+ * Author: Roberto Sassu <roberto.sassu@huawei.com>
+ */
+
+#include "vmlinux.h"
+#include <errno.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+struct bpf_dynptr {
+	__u64 :64;
+	__u64 :64;
+} __attribute__((aligned(8)));
+
+extern int bpf_verify_pkcs7_signature(struct bpf_dynptr *data_ptr,
+				      struct bpf_dynptr *sig_ptr,
+				      struct bpf_key *trusted_keyring) __ksym;
+
+struct {
+	__uint(type, BPF_MAP_TYPE_RINGBUF);
+} ringbuf SEC(".maps");
+
+char _license[] SEC("license") = "GPL";
+
+SEC("?lsm.s/bpf")
+int BPF_PROG(dynptr_type_not_supp, int cmd, union bpf_attr *attr,
+	     unsigned int size)
+{
+	char write_data[64] = "hello there, world!!";
+	struct bpf_dynptr ptr;
+
+	bpf_ringbuf_reserve_dynptr(&ringbuf, sizeof(write_data), 0, &ptr);
+
+	return bpf_verify_pkcs7_signature(&ptr, &ptr, NULL);
+}
+
+SEC("?lsm.s/bpf")
+int BPF_PROG(not_valid_dynptr, int cmd, union bpf_attr *attr, unsigned int size)
+{
+	unsigned long val;
+
+	return bpf_verify_pkcs7_signature((struct bpf_dynptr *)&val,
+					  (struct bpf_dynptr *)&val, NULL);
+}
+
+SEC("?lsm.s/bpf")
+int BPF_PROG(not_ptr_to_stack, int cmd, union bpf_attr *attr, unsigned int size)
+{
+	unsigned long val;
+
+	return bpf_verify_pkcs7_signature((struct bpf_dynptr *)val,
+					  (struct bpf_dynptr *)val, NULL);
+}
-- 
2.25.1