selftests/bpf: Dynptr tests

This patch adds tests for dynptrs, which include cases that the
verifier needs to reject (for example, a bpf_ringbuf_reserve_dynptr
without a corresponding bpf_ringbuf_submit/discard_dynptr) as well
as cases that should successfully pass.
Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20220523210712.3641569-7-joannelkoong@gmail.com

tools/testing/selftests/bpf/prog_tests/dynptr.c

+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2022 Facebook */
+
+#include <test_progs.h>
+#include "dynptr_fail.skel.h"
+#include "dynptr_success.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;
+} dynptr_tests[] = {
+	/* failure cases */
+	{"ringbuf_missing_release1", "Unreleased reference id=1"},
+	{"ringbuf_missing_release2", "Unreleased reference id=2"},
+	{"ringbuf_missing_release_callback", "Unreleased reference id"},
+	{"use_after_invalid", "Expected an initialized dynptr as arg #3"},
+	{"ringbuf_invalid_api", "type=mem expected=alloc_mem"},
+	{"add_dynptr_to_map1", "invalid indirect read from stack"},
+	{"add_dynptr_to_map2", "invalid indirect read from stack"},
+	{"data_slice_out_of_bounds_ringbuf", "value is outside of the allowed memory range"},
+	{"data_slice_out_of_bounds_map_value", "value is outside of the allowed memory range"},
+	{"data_slice_use_after_release", "invalid mem access 'scalar'"},
+	{"data_slice_missing_null_check1", "invalid mem access 'mem_or_null'"},
+	{"data_slice_missing_null_check2", "invalid mem access 'mem_or_null'"},
+	{"invalid_helper1", "invalid indirect read from stack"},
+	{"invalid_helper2", "Expected an initialized dynptr as arg #3"},
+	{"invalid_write1", "Expected an initialized dynptr as arg #1"},
+	{"invalid_write2", "Expected an initialized dynptr as arg #3"},
+	{"invalid_write3", "Expected an initialized ringbuf dynptr as arg #1"},
+	{"invalid_write4", "arg 1 is an unacquired reference"},
+	{"invalid_read1", "invalid read from stack"},
+	{"invalid_read2", "cannot pass in dynptr at an offset"},
+	{"invalid_read3", "invalid read from stack"},
+	{"invalid_read4", "invalid read from stack"},
+	{"invalid_offset", "invalid write to stack"},
+	{"global", "type=map_value expected=fp"},
+	{"release_twice", "arg 1 is an unacquired reference"},
+	{"release_twice_callback", "arg 1 is an unacquired reference"},
+	{"dynptr_from_mem_invalid_api",
+		"Unsupported reg type fp for bpf_dynptr_from_mem data"},
+
+	/* success cases */
+	{"test_read_write", NULL},
+	{"test_data_slice", NULL},
+	{"test_ringbuf", NULL},
+};
+
+static void verify_fail(const char *prog_name, const char *expected_err_msg)
+{
+	LIBBPF_OPTS(bpf_object_open_opts, opts);
+	struct bpf_program *prog;
+	struct dynptr_fail *skel;
+	int err;
+
+	opts.kernel_log_buf = obj_log_buf;
+	opts.kernel_log_size = log_buf_sz;
+	opts.kernel_log_level = 1;
+
+	skel = dynptr_fail__open_opts(&opts);
+	if (!ASSERT_OK_PTR(skel, "dynptr_fail__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());
+
+	err = dynptr_fail__load(skel);
+	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:
+	dynptr_fail__destroy(skel);
+}
+
+static void verify_success(const char *prog_name)
+{
+	struct dynptr_success *skel;
+	struct bpf_program *prog;
+	struct bpf_link *link;
+
+	skel = dynptr_success__open();
+	if (!ASSERT_OK_PTR(skel, "dynptr_success__open"))
+		return;
+
+	skel->bss->pid = getpid();
+
+	bpf_map__set_max_entries(skel->maps.ringbuf, getpagesize());
+
+	dynptr_success__load(skel);
+	if (!ASSERT_OK_PTR(skel, "dynptr_success__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;
+
+	usleep(1);
+
+	ASSERT_EQ(skel->bss->err, 0, "err");
+
+	bpf_link__destroy(link);
+
+cleanup:
+	dynptr_success__destroy(skel);
+}
+
+void test_dynptr(void)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(dynptr_tests); i++) {
+		if (!test__start_subtest(dynptr_tests[i].prog_name))
+			continue;
+
+		if (dynptr_tests[i].expected_err_msg)
+			verify_fail(dynptr_tests[i].prog_name,
+				    dynptr_tests[i].expected_err_msg);
+		else
+			verify_success(dynptr_tests[i].prog_name);
+	}
+}

tools/testing/selftests/bpf/progs/dynptr_success.c

+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2022 Facebook */
+
+#include <string.h>
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include "bpf_misc.h"
+#include "errno.h"
+
+char _license[] SEC("license") = "GPL";
+
+int pid, err, val;
+
+struct sample {
+	int pid;
+	int seq;
+	long value;
+	char comm[16];
+};
+
+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");
+
+SEC("tp/syscalls/sys_enter_nanosleep")
+int test_read_write(void *ctx)
+{
+	char write_data[64] = "hello there, world!!";
+	char read_data[64] = {}, buf[64] = {};
+	struct bpf_dynptr ptr;
+	int i;
+
+	if (bpf_get_current_pid_tgid() >> 32 != pid)
+		return 0;
+
+	bpf_ringbuf_reserve_dynptr(&ringbuf, sizeof(write_data), 0, &ptr);
+
+	/* Write data into the dynptr */
+	err = err ?: bpf_dynptr_write(&ptr, 0, write_data, sizeof(write_data));
+
+	/* Read the data that was written into the dynptr */
+	err = err ?: bpf_dynptr_read(read_data, sizeof(read_data), &ptr, 0);
+
+	/* Ensure the data we read matches the data we wrote */
+	for (i = 0; i < sizeof(read_data); i++) {
+		if (read_data[i] != write_data[i]) {
+			err = 1;
+			break;
+		}
+	}
+
+	bpf_ringbuf_discard_dynptr(&ptr, 0);
+	return 0;
+}
+
+SEC("tp/syscalls/sys_enter_nanosleep")
+int test_data_slice(void *ctx)
+{
+	__u32 key = 0, val = 235, *map_val;
+	struct bpf_dynptr ptr;
+	__u32 map_val_size;
+	void *data;
+
+	map_val_size = sizeof(*map_val);
+
+	if (bpf_get_current_pid_tgid() >> 32 != pid)
+		return 0;
+
+	bpf_map_update_elem(&array_map, &key, &val, 0);
+
+	map_val = bpf_map_lookup_elem(&array_map, &key);
+	if (!map_val) {
+		err = 1;
+		return 0;
+	}
+
+	bpf_dynptr_from_mem(map_val, map_val_size, 0, &ptr);
+
+	/* Try getting a data slice that is out of range */
+	data = bpf_dynptr_data(&ptr, map_val_size + 1, 1);
+	if (data) {
+		err = 2;
+		return 0;
+	}
+
+	/* Try getting more bytes than available */
+	data = bpf_dynptr_data(&ptr, 0, map_val_size + 1);
+	if (data) {
+		err = 3;
+		return 0;
+	}
+
+	data = bpf_dynptr_data(&ptr, 0, sizeof(__u32));
+	if (!data) {
+		err = 4;
+		return 0;
+	}
+
+	*(__u32 *)data = 999;
+
+	err = bpf_probe_read_kernel(&val, sizeof(val), data);
+	if (err)
+		return 0;
+
+	if (val != *(int *)data)
+		err = 5;
+
+	return 0;
+}
+
+static int ringbuf_callback(__u32 index, void *data)
+{
+	struct sample *sample;
+
+	struct bpf_dynptr *ptr = (struct bpf_dynptr *)data;
+
+	sample = bpf_dynptr_data(ptr, 0, sizeof(*sample));
+	if (!sample)
+		err = 2;
+	else
+		sample->pid += index;
+
+	return 0;
+}
+
+SEC("tp/syscalls/sys_enter_nanosleep")
+int test_ringbuf(void *ctx)
+{
+	struct bpf_dynptr ptr;
+	struct sample *sample;
+
+	if (bpf_get_current_pid_tgid() >> 32 != pid)
+		return 0;
+
+	val = 100;
+
+	/* check that you can reserve a dynamic size reservation */
+	err = bpf_ringbuf_reserve_dynptr(&ringbuf, val, 0, &ptr);
+
+	sample = err ? NULL : bpf_dynptr_data(&ptr, 0, sizeof(*sample));
+	if (!sample) {
+		err = 1;
+		goto done;
+	}
+
+	sample->pid = 10;
+
+	/* Can pass dynptr to callback functions */
+	bpf_loop(10, ringbuf_callback, &ptr, 0);
+
+	if (sample->pid != 55)
+		err = 2;
+
+done:
+	bpf_ringbuf_discard_dynptr(&ptr, 0);
+	return 0;
+}