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>

diff --git a/tools/testing/selftests/bpf/DENYLIST.s390x b/tools/testing/selftests/bpf/DENYLIST.s390x
index a992fd9..17e074e 100644 (file)
--- a/tools/testing/selftests/bpf/DENYLIST.s390x
+++ b/tools/testing/selftests/bpf/DENYLIST.s390x
@@ -74,3 +74,4 @@ tracing_struct                           # failed to auto-attach: -524
 user_ringbuf                             # failed to find kernel BTF type ID of '__s390x_sys_prctl': -3                (?)
 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 (file)
index 0000000..c210657
--- /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);
+       }
+}

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 (file)
index 0000000..ce39d09
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_kfunc_dynptr_param.c
@@ -0,0 +1,94 @@
+// 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>
+
+extern struct bpf_key *bpf_lookup_system_key(__u64 id) __ksym;
+extern void bpf_key_put(struct bpf_key *key) __ksym;
+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");
+
+struct {
+       __uint(type, BPF_MAP_TYPE_ARRAY);
+       __uint(max_entries, 1);
+       __type(key, __u32);
+       __type(value, __u32);
+} array_map SEC(".maps");
+
+int err, pid;
+
+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);
+}
+
+SEC("lsm.s/bpf")
+int BPF_PROG(dynptr_data_null, int cmd, union bpf_attr *attr, unsigned int size)
+{
+       struct bpf_key *trusted_keyring;
+       struct bpf_dynptr ptr;
+       __u32 *value;
+       int ret, zero = 0;
+
+       if (bpf_get_current_pid_tgid() >> 32 != pid)
+               return 0;
+
+       value = bpf_map_lookup_elem(&array_map, &zero);
+       if (!value)
+               return 0;
+
+       /* Pass invalid flags. */
+       ret = bpf_dynptr_from_mem(value, sizeof(*value), ((__u64)~0ULL), &ptr);
+       if (ret != -EINVAL)
+               return 0;
+
+       trusted_keyring = bpf_lookup_system_key(0);
+       if (!trusted_keyring)
+               return 0;
+
+       err = bpf_verify_pkcs7_signature(&ptr, &ptr, trusted_keyring);
+
+       bpf_key_put(trusted_keyring);
+
+       return 0;
+}