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
>
