Re: [PATCH bpf-next v7 3/3] bpf/selftests: Add selftests for new task kfuncs

[Alexei Starovoitov]

On Wed, Nov 16, 2022 at 09:24:02PM -0600, David Vernet wrote:
> A previous change added a series of kfuncs for storing struct
> task_struct objects as referenced kptrs. This patch adds a new
> task_kfunc test suite for validating their expected behavior.
> 
> Signed-off-by: David Vernet <void@xxxxxxxxxxxxx>
> ---
>  tools/testing/selftests/bpf/DENYLIST.s390x    |   1 +
>  .../selftests/bpf/prog_tests/task_kfunc.c     | 159 +++++++++++
>  .../selftests/bpf/progs/task_kfunc_common.h   |  71 +++++
>  .../selftests/bpf/progs/task_kfunc_failure.c  | 259 ++++++++++++++++++
>  .../selftests/bpf/progs/task_kfunc_success.c  | 149 ++++++++++
>  5 files changed, 639 insertions(+)
>  create mode 100644 tools/testing/selftests/bpf/prog_tests/task_kfunc.c
>  create mode 100644 tools/testing/selftests/bpf/progs/task_kfunc_common.h
>  create mode 100644 tools/testing/selftests/bpf/progs/task_kfunc_failure.c
>  create mode 100644 tools/testing/selftests/bpf/progs/task_kfunc_success.c
> 
> diff --git a/tools/testing/selftests/bpf/DENYLIST.s390x b/tools/testing/selftests/bpf/DENYLIST.s390x
> index be4e3d47ea3e..97e522828d6c 100644
> --- a/tools/testing/selftests/bpf/DENYLIST.s390x
> +++ b/tools/testing/selftests/bpf/DENYLIST.s390x
> @@ -53,6 +53,7 @@ skc_to_unix_sock                         # could not attach BPF object unexpecte
>  socket_cookie                            # prog_attach unexpected error: -524                                          (trampoline)
>  stacktrace_build_id                      # compare_map_keys stackid_hmap vs. stackmap err -2 errno 2                   (?)
>  tailcalls                                # tail_calls are not allowed in non-JITed programs with bpf-to-bpf calls      (?)
> +task_kfunc                               # JIT does not support calling kernel function
>  task_local_storage                       # failed to auto-attach program 'trace_exit_creds': -524                      (trampoline)
>  test_bpffs                               # bpffs test  failed 255                                                      (iterator)
>  test_bprm_opts                           # failed to auto-attach program 'secure_exec': -524                           (trampoline)
> diff --git a/tools/testing/selftests/bpf/prog_tests/task_kfunc.c b/tools/testing/selftests/bpf/prog_tests/task_kfunc.c
> new file mode 100644
> index 000000000000..a3aa36a4beb3
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/task_kfunc.c
> @@ -0,0 +1,159 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Copyright (c) 2022 Meta Platforms, Inc. and affiliates. */
> +
> +#define _GNU_SOURCE
> +#include <sys/wait.h>
> +#include <test_progs.h>
> +#include <unistd.h>
> +
> +#include "task_kfunc_failure.skel.h"
> +#include "task_kfunc_success.skel.h"
> +
> +static size_t log_buf_sz = 1 << 20; /* 1 MB */
> +static char obj_log_buf[1048576];
> +
> +static struct task_kfunc_success *open_load_task_kfunc_skel(void)
> +{
> +	struct task_kfunc_success *skel;
> +	int err;
> +
> +	skel = task_kfunc_success__open();
> +	if (!ASSERT_OK_PTR(skel, "skel_open"))
> +		return NULL;
> +
> +	skel->bss->pid = getpid();
> +
> +	err = task_kfunc_success__load(skel);
> +	if (!ASSERT_OK(err, "skel_load"))
> +		goto cleanup;
> +
> +	return skel;
> +
> +cleanup:
> +	task_kfunc_success__destroy(skel);
> +	return NULL;
> +}
> +
> +static void run_success_test(const char *prog_name)
> +{
> +	struct task_kfunc_success *skel;
> +	int status;
> +	pid_t child_pid;
> +	struct bpf_program *prog;
> +	struct bpf_link *link = NULL;
> +
> +	skel = open_load_task_kfunc_skel();
> +	if (!ASSERT_OK_PTR(skel, "open_load_skel"))
> +		return;
> +
> +	if (!ASSERT_OK(skel->bss->err, "pre_spawn_err"))
> +		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, "attached_link"))
> +		goto cleanup;
> +
> +	child_pid = fork();
> +	if (!ASSERT_GT(child_pid, -1, "child_pid"))
> +		goto cleanup;
> +	if (child_pid == 0)
> +		_exit(0);
> +	waitpid(child_pid, &status, 0);
> +
> +	ASSERT_OK(skel->bss->err, "post_wait_err");
> +
> +cleanup:
> +	bpf_link__destroy(link);
> +	task_kfunc_success__destroy(skel);
> +}
> +
> +static const char * const success_tests[] = {
> +	"test_task_acquire_release_argument",
> +	"test_task_acquire_release_current",
> +	"test_task_acquire_leave_in_map",
> +	"test_task_xchg_release",
> +	"test_task_get_release",
> +	"test_task_current_acquire_release",
> +};
> +
> +static struct {
> +	const char *prog_name;
> +	const char *expected_err_msg;
> +} failure_tests[] = {
> +	{"task_kfunc_acquire_untrusted", "R1 must be referenced or trusted"},
> +	{"task_kfunc_acquire_fp", "arg#0 pointer type STRUCT task_struct must point"},
> +	{"task_kfunc_acquire_unsafe_kretprobe", "reg type unsupported for arg#0 function"},
> +	{"task_kfunc_acquire_trusted_walked", "R1 must be referenced or trusted"},
> +	{"task_kfunc_acquire_null", "arg#0 pointer type STRUCT task_struct must point"},
> +	{"task_kfunc_acquire_unreleased", "Unreleased reference"},
> +	{"task_kfunc_get_non_kptr_param", "arg#0 expected pointer to map value"},
> +	{"task_kfunc_get_non_kptr_acquired", "arg#0 expected pointer to map value"},
> +	{"task_kfunc_get_null", "arg#0 expected pointer to map value"},
> +	{"task_kfunc_xchg_unreleased", "Unreleased reference"},
> +	{"task_kfunc_get_unreleased", "Unreleased reference"},
> +	{"task_kfunc_release_untrusted", "bpf_task_release arg#0 pointer had unexpected modifiers"},
> +	{"task_kfunc_release_fp", "arg#0 pointer type STRUCT task_struct must point"},
> +	{"task_kfunc_release_null", "bpf_task_release arg#0 pointer had unexpected modifiers"},
> +	{"task_kfunc_release_unacquired", "release kernel function bpf_task_release expects"},
> +};
> +
> +static void verify_fail(const char *prog_name, const char *expected_err_msg)
> +{
> +	LIBBPF_OPTS(bpf_object_open_opts, opts);
> +	struct task_kfunc_failure *skel;
> +	int err, i;
> +
> +	opts.kernel_log_buf = obj_log_buf;
> +	opts.kernel_log_size = log_buf_sz;
> +	opts.kernel_log_level = 1;
> +
> +	skel = task_kfunc_failure__open_opts(&opts);
> +	if (!ASSERT_OK_PTR(skel, "task_kfunc_failure__open_opts"))
> +		goto cleanup;
> +
> +	for (i = 0; i < ARRAY_SIZE(failure_tests); i++) {
> +		struct bpf_program *prog;
> +		const char *curr_name = failure_tests[i].prog_name;
> +
> +		prog = bpf_object__find_program_by_name(skel->obj, curr_name);
> +		if (!ASSERT_OK_PTR(prog, "bpf_object__find_program_by_name"))
> +			goto cleanup;
> +
> +		bpf_program__set_autoload(prog, !strcmp(curr_name, prog_name));
> +	}
> +
> +	err = task_kfunc_failure__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:
> +	task_kfunc_failure__destroy(skel);
> +}
> +
> +void test_task_kfunc(void)
> +{
> +	int i;
> +
> +	for (i = 0; i < ARRAY_SIZE(success_tests); i++) {
> +		if (!test__start_subtest(success_tests[i]))
> +			continue;
> +
> +		run_success_test(success_tests[i]);
> +	}
> +
> +	for (i = 0; i < ARRAY_SIZE(failure_tests); i++) {
> +		if (!test__start_subtest(failure_tests[i].prog_name))
> +			continue;
> +
> +		verify_fail(failure_tests[i].prog_name, failure_tests[i].expected_err_msg);
> +	}
> +}
> diff --git a/tools/testing/selftests/bpf/progs/task_kfunc_common.h b/tools/testing/selftests/bpf/progs/task_kfunc_common.h
> new file mode 100644
> index 000000000000..8489b952dc49
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/task_kfunc_common.h
> @@ -0,0 +1,71 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/* Copyright (c) 2022 Meta Platforms, Inc. and affiliates. */
> +
> +#ifndef _TASK_KFUNC_COMMON_H
> +#define _TASK_KFUNC_COMMON_H
> +
> +#include <errno.h>
> +#include <vmlinux.h>
> +#include <bpf/bpf_helpers.h>
> +#include <bpf/bpf_tracing.h>
> +
> +struct __tasks_kfunc_map_value {
> +	struct task_struct __kptr_ref * task;
> +};
> +
> +struct hash_map {
> +	__uint(type, BPF_MAP_TYPE_HASH);
> +	__type(key, int);
> +	__type(value, struct __tasks_kfunc_map_value);
> +	__uint(max_entries, 1);
> +} __tasks_kfunc_map SEC(".maps");
> +
> +struct task_struct *bpf_task_acquire(struct task_struct *p) __ksym;
> +struct task_struct *bpf_task_kptr_get(struct task_struct **pp) __ksym;
> +void bpf_task_release(struct task_struct *p) __ksym;
> +
> +static inline struct __tasks_kfunc_map_value *tasks_kfunc_map_value_lookup(struct task_struct *p)
> +{
> +	s32 pid;
> +	long status;
> +
> +	status = bpf_probe_read_kernel(&pid, sizeof(pid), &p->pid);
> +	if (status)
> +		return NULL;
> +
> +	return bpf_map_lookup_elem(&__tasks_kfunc_map, &pid);
> +}
> +
> +static inline int tasks_kfunc_map_insert(struct task_struct *p)
> +{
> +	struct __tasks_kfunc_map_value local, *v;
> +	long status;
> +	struct task_struct *acquired, *old;
> +	s32 pid;
> +
> +	status = bpf_probe_read_kernel(&pid, sizeof(pid), &p->pid);
> +	if (status)
> +		return status;
> +
> +	local.task = NULL;
> +	status = bpf_map_update_elem(&__tasks_kfunc_map, &pid, &local, BPF_NOEXIST);
> +	if (status)
> +		return status;
> +
> +	v = bpf_map_lookup_elem(&__tasks_kfunc_map, &pid);
> +	if (!v) {
> +		bpf_map_delete_elem(&__tasks_kfunc_map, &pid);
> +		return status;

here it will return 0, but probably should be returning error?

> +	}
> +
> +	acquired = bpf_task_acquire(p);
> +	old = bpf_kptr_xchg(&v->task, acquired);
> +	if (old) {
> +		bpf_task_release(old);
> +		return -EEXIST;
> +	}
> +
> +	return 0;
> +}
> +
> +#endif /* _TASK_KFUNC_COMMON_H */
> diff --git a/tools/testing/selftests/bpf/progs/task_kfunc_failure.c b/tools/testing/selftests/bpf/progs/task_kfunc_failure.c
> new file mode 100644
> index 000000000000..4c2e8a8f3544
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/task_kfunc_failure.c
> @@ -0,0 +1,259 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Copyright (c) 2022 Meta Platforms, Inc. and affiliates. */
> +
> +#include <vmlinux.h>
> +#include <bpf/bpf_tracing.h>
> +#include <bpf/bpf_helpers.h>
> +
> +#include "task_kfunc_common.h"
> +
> +char _license[] SEC("license") = "GPL";
> +
> +/* Prototype for all of the program trace events below:
> + *
> + * TRACE_EVENT(task_newtask,
> + *         TP_PROTO(struct task_struct *p, u64 clone_flags)
> + */
> +
> +static struct __tasks_kfunc_map_value *insert_lookup_task(struct task_struct *task)
> +{
> +	int status;
> +
> +	status = tasks_kfunc_map_insert(task);
> +	if (status)
> +		return NULL;
> +
> +	return tasks_kfunc_map_value_lookup(task);
> +}
> +
> +SEC("tp_btf/task_newtask")
> +int BPF_PROG(task_kfunc_acquire_untrusted, struct task_struct *task, u64 clone_flags)
> +{
> +	struct task_struct *acquired;
> +	struct __tasks_kfunc_map_value *v;
> +
> +	v = insert_lookup_task(task);
> +	if (!v)
> +		return 0;
> +
> +	/* Can't invoke bpf_task_acquire() on an untrusted pointer. */
> +	acquired = bpf_task_acquire(v->task);
> +	bpf_task_release(acquired);
> +
> +	return 0;
> +}
> +
> +SEC("tp_btf/task_newtask")
> +int BPF_PROG(task_kfunc_acquire_fp, struct task_struct *task, u64 clone_flags)
> +{
> +	struct task_struct *acquired, *stack_task = (struct task_struct *)&clone_flags;
> +
> +	/* Can't invoke bpf_task_acquire() on a random frame pointer. */
> +	acquired = bpf_task_acquire((struct task_struct *)&stack_task);
> +	bpf_task_release(acquired);
> +
> +	return 0;
> +}
> +
> +SEC("kretprobe/free_task")
> +int BPF_PROG(task_kfunc_acquire_unsafe_kretprobe, struct task_struct *task, u64 clone_flags)
> +{
> +	struct task_struct *acquired;
> +
> +	acquired = bpf_task_acquire(task);
> +	/* Can't release a bpf_task_acquire()'d task without a NULL check. */
> +	bpf_task_release(acquired);
> +
> +	return 0;
> +}
> +
> +SEC("tp_btf/task_newtask")
> +int BPF_PROG(task_kfunc_acquire_trusted_walked, struct task_struct *task, u64 clone_flags)
> +{
> +	struct task_struct *acquired;
> +
> +	/* Can't invoke bpf_task_acquire() on a trusted pointer obtained from walking a struct. */
> +	acquired = bpf_task_acquire(task->last_wakee);
> +	bpf_task_release(acquired);
> +
> +	return 0;
> +}
> +
> +
> +SEC("tp_btf/task_newtask")
> +int BPF_PROG(task_kfunc_acquire_null, struct task_struct *task, u64 clone_flags)
> +{
> +	struct task_struct *acquired;
> +
> +	/* Can't invoke bpf_task_acquire() on a NULL pointer. */
> +	acquired = bpf_task_acquire(NULL);
> +	if (!acquired)
> +		return 0;
> +	bpf_task_release(acquired);
> +
> +	return 0;
> +}
> +
> +SEC("tp_btf/task_newtask")
> +int BPF_PROG(task_kfunc_acquire_unreleased, struct task_struct *task, u64 clone_flags)
> +{
> +	struct task_struct *acquired;
> +
> +	acquired = bpf_task_acquire(task);
> +
> +	/* Acquired task is never released. */
> +
> +	return 0;
> +}
> +
> +SEC("tp_btf/task_newtask")
> +int BPF_PROG(task_kfunc_get_non_kptr_param, struct task_struct *task, u64 clone_flags)
> +{
> +	struct task_struct *kptr;
> +
> +	/* Cannot use bpf_task_kptr_get() on a non-kptr, even on a valid task. */
> +	kptr = bpf_task_kptr_get(&task);
> +	if (!kptr)
> +		return 0;
> +
> +	bpf_task_release(kptr);
> +
> +	return 0;
> +}
> +
> +SEC("tp_btf/task_newtask")
> +int BPF_PROG(task_kfunc_get_non_kptr_acquired, struct task_struct *task, u64 clone_flags)
> +{
> +	struct task_struct *kptr, *acquired;
> +
> +	acquired = bpf_task_acquire(task);
> +
> +	/* Cannot use bpf_task_kptr_get() on a non-kptr, even if it was acquired. */
> +	kptr = bpf_task_kptr_get(&acquired);
> +	bpf_task_release(acquired);
> +	if (!kptr)
> +		return 0;
> +
> +	bpf_task_release(kptr);
> +
> +	return 0;
> +}
> +
> +SEC("tp_btf/task_newtask")
> +int BPF_PROG(task_kfunc_get_null, struct task_struct *task, u64 clone_flags)
> +{
> +	struct task_struct *kptr;
> +
> +	/* Cannot use bpf_task_kptr_get() on a NULL pointer. */
> +	kptr = bpf_task_kptr_get(NULL);
> +	if (!kptr)
> +		return 0;
> +
> +	bpf_task_release(kptr);
> +
> +	return 0;
> +}
> +
> +SEC("tp_btf/task_newtask")
> +int BPF_PROG(task_kfunc_xchg_unreleased, struct task_struct *task, u64 clone_flags)
> +{
> +	struct task_struct *kptr;
> +	struct __tasks_kfunc_map_value *v;
> +
> +	v = insert_lookup_task(task);
> +	if (!v)
> +		return 0;
> +
> +	kptr = bpf_kptr_xchg(&v->task, NULL);
> +	if (!kptr)
> +		return 0;
> +
> +	/* Kptr retrieved from map is never released. */
> +
> +	return 0;
> +}
> +
> +SEC("tp_btf/task_newtask")
> +int BPF_PROG(task_kfunc_get_unreleased, struct task_struct *task, u64 clone_flags)
> +{
> +	struct task_struct *kptr;
> +	struct __tasks_kfunc_map_value *v;
> +
> +	v = insert_lookup_task(task);
> +	if (!v)
> +		return 0;
> +
> +	kptr = bpf_task_kptr_get(&v->task);
> +	if (!kptr)
> +		return 0;
> +
> +	/* Kptr acquired above is never released. */
> +
> +	return 0;
> +}
> +
> +SEC("tp_btf/task_newtask")
> +int BPF_PROG(task_kfunc_release_untrusted, struct task_struct *task, u64 clone_flags)
> +{
> +	struct __tasks_kfunc_map_value *v;
> +
> +	v = insert_lookup_task(task);
> +	if (!v)
> +		return 0;
> +
> +	/* Can't invoke bpf_task_release() on an untrusted pointer. */
> +	bpf_task_release(v->task);
> +
> +	return 0;
> +}
> +
> +SEC("tp_btf/task_newtask")
> +int BPF_PROG(task_kfunc_release_fp, struct task_struct *task, u64 clone_flags)
> +{
> +	struct task_struct *acquired = (struct task_struct *)&clone_flags;
> +
> +	/* Cannot release random frame pointer. */
> +	bpf_task_release(acquired);
> +
> +	return 0;
> +}
> +
> +SEC("tp_btf/task_newtask")
> +int BPF_PROG(task_kfunc_release_null, struct task_struct *task, u64 clone_flags)
> +{
> +	struct __tasks_kfunc_map_value local, *v;
> +	long status;
> +	struct task_struct *acquired, *old;
> +	s32 pid;
> +
> +	status = bpf_probe_read_kernel(&pid, sizeof(pid), &task->pid);
> +	if (status)
> +		return 0;
> +
> +	local.task = NULL;
> +	status = bpf_map_update_elem(&__tasks_kfunc_map, &pid, &local, BPF_NOEXIST);
> +	if (status)
> +		return status;
> +
> +	v = bpf_map_lookup_elem(&__tasks_kfunc_map, &pid);
> +	if (!v)
> +		return status;

should be return error instead?

> +
> +	acquired = bpf_task_acquire(task);
> +
> +	old = bpf_kptr_xchg(&v->task, acquired);
> +
> +	/* old cannot be passed to bpf_task_release() without a NULL check. */
> +	bpf_task_release(old);
> +
> +	return 0;
> +}
> +
> +SEC("tp_btf/task_newtask")
> +int BPF_PROG(task_kfunc_release_unacquired, struct task_struct *task, u64 clone_flags)
> +{
> +	/* Cannot release trusted task pointer which was not acquired. */
> +	bpf_task_release(task);
> +
> +	return 0;
> +}
> diff --git a/tools/testing/selftests/bpf/progs/task_kfunc_success.c b/tools/testing/selftests/bpf/progs/task_kfunc_success.c
> new file mode 100644
> index 000000000000..be4534b5ba2e
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/task_kfunc_success.c
> @@ -0,0 +1,149 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Copyright (c) 2022 Meta Platforms, Inc. and affiliates. */
> +
> +#include <vmlinux.h>
> +#include <bpf/bpf_tracing.h>
> +#include <bpf/bpf_helpers.h>
> +
> +#include "task_kfunc_common.h"
> +
> +char _license[] SEC("license") = "GPL";
> +
> +int err, pid;
> +
> +/* Prototype for all of the program trace events below:
> + *
> + * TRACE_EVENT(task_newtask,
> + *         TP_PROTO(struct task_struct *p, u64 clone_flags)
> + */
> +
> +static bool is_test_kfunc_task(void)
> +{
> +	int cur_pid = bpf_get_current_pid_tgid() >> 32;
> +
> +	return pid == cur_pid;
> +}
> +
> +static int test_acquire_release(struct task_struct *task)
> +{
> +	struct task_struct *acquired;
> +
> +	acquired = bpf_task_acquire(task);
> +	bpf_task_release(acquired);
> +
> +	return 0;
> +}
> +
> +SEC("tp_btf/task_newtask")
> +int BPF_PROG(test_task_acquire_release_argument, struct task_struct *task, u64 clone_flags)
> +{
> +	if (!is_test_kfunc_task())
> +		return 0;
> +
> +	return test_acquire_release(task);
> +}
> +
> +SEC("tp_btf/task_newtask")
> +int BPF_PROG(test_task_acquire_release_current, struct task_struct *task, u64 clone_flags)
> +{
> +	if (!is_test_kfunc_task())
> +		return 0;
> +
> +	return test_acquire_release(bpf_get_current_task_btf());
> +}
> +
> +SEC("tp_btf/task_newtask")
> +int BPF_PROG(test_task_acquire_leave_in_map, struct task_struct *task, u64 clone_flags)
> +{
> +	long status;
> +
> +	if (!is_test_kfunc_task())
> +		return 0;
> +
> +	status = tasks_kfunc_map_insert(task);
> +	if (status)
> +		err = 1;
> +
> +	return 0;
> +}
> +
> +SEC("tp_btf/task_newtask")
> +int BPF_PROG(test_task_xchg_release, struct task_struct *task, u64 clone_flags)
> +{
> +	struct task_struct *kptr;
> +	struct __tasks_kfunc_map_value *v;
> +	long status;
> +
> +	if (!is_test_kfunc_task())
> +		return 0;
> +
> +	status = tasks_kfunc_map_insert(task);
> +	if (status) {
> +		err = 1;
> +		return 0;
> +	}
> +
> +	v = tasks_kfunc_map_value_lookup(task);
> +	if (!v) {
> +		err = 2;
> +		return 0;
> +	}
> +
> +	kptr = bpf_kptr_xchg(&v->task, NULL);
> +	if (!kptr) {
> +		err = 3;
> +		return 0;
> +	}
> +
> +	bpf_task_release(kptr);
> +
> +	return 0;
> +}
> +
> +SEC("tp_btf/task_newtask")
> +int BPF_PROG(test_task_get_release, struct task_struct *task, u64 clone_flags)
> +{
> +	struct task_struct *kptr;
> +	struct __tasks_kfunc_map_value *v;
> +	long status;
> +
> +	if (!is_test_kfunc_task())
> +		return 0;
> +
> +	status = tasks_kfunc_map_insert(task);
> +	if (status) {
> +		err = 1;
> +		return 0;
> +	}
> +
> +	v = tasks_kfunc_map_value_lookup(task);
> +	if (!v) {
> +		err = 2;
> +		return 0;
> +	}
> +
> +	kptr = bpf_task_kptr_get(&v->task);
> +	if (!kptr) {
> +		err = 3;
> +		return 0;
> +	}
> +
> +	bpf_task_release(kptr);
> +
> +	return 0;
> +}
> +
> +SEC("tp_btf/task_newtask")
> +int BPF_PROG(test_task_current_acquire_release, struct task_struct *task, u64 clone_flags)
> +{
> +	struct task_struct *current, *acquired;
> +
> +	if (!is_test_kfunc_task())
> +		return 0;
> +
> +	current = bpf_get_current_task_btf();
> +	acquired = bpf_task_acquire(current);
> +	bpf_task_release(acquired);
> +
> +	return 0;
> +}
> -- 
> 2.38.1
>