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

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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>
This commit is contained in:
Roberto Sassu 2022-09-20 09:59:51 +02:00 committed by Alexei Starovoitov
parent fc97590668
commit b94fa9f9dc
3 changed files with 259 additions and 0 deletions
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1
tools/testing/selftests/bpf/DENYLIST.s390x
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@ -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)

164
tools/testing/selftests/bpf/prog_tests/kfunc_dynptr_param.c Normal file
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@ -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);
}
}

94
tools/testing/selftests/bpf/progs/test_kfunc_dynptr_param.c Normal file
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@ -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;
}