Re: [PATCH v15 12/12] selftests/bpf: Add tests for dynamic pointers parameters in kfuncs

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

On Wed, 2022-08-31 at 18:54 +0200, Roberto Sassu wrote:
> 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.

Sorry, forgot to add this test to the deny list of s390.

I also rebased to the latest commit.

Let me know if I should resend.

Thanks

Roberto

> Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
> ---
>  .../bpf/prog_tests/kfunc_dynptr_param.c       | 102
> ++++++++++++++++++
>  .../bpf/progs/test_kfunc_dynptr_param.c       |  57 ++++++++++
>  2 files changed, 159 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/prog_tests/kfunc_dynptr_param.c
> b/tools/testing/selftests/bpf/prog_tests/kfunc_dynptr_param.c
> new file mode 100644
> index 000000000000..732897faf36b
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/kfunc_dynptr_param.c
> @@ -0,0 +1,102 @@
> +// 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);
> +}