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

On Tue, 6 Sept 2022 at 10:31, Roberto Sassu roberto.sassu@huaweicloud.com wrote:

On Tue, 2022-09-06 at 05:15 +0200, Kumar Kartikeya Dwivedi wrote:

...

On Mon, 5 Sept 2022 at 16:36, Roberto Sassu roberto.sassu@huaweicloud.com 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.

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);

Please also include a test where you cause the dynptr to be set to NULL, e.g. by passing invalid stuff to ringbuf_reserve_dynptr, and then try to pass it to bpf_verify_pkc7_signature.

Uhm, bpf_ringbuf_reserve_dynptr() is expecting a valid map. How else I can achieve it?

So? Just define a ringbuf map and pass to it? I'm missing why that is undesirable. It also needs to be a runtime test, not verifier test, I probably replied to the wrong patch.