bpf/selftests: Add selftests for new task kfuncs
authorDavid Vernet <void@manifault.com>
Sun, 20 Nov 2022 05:10:04 +0000 (23:10 -0600)
committerAlexei Starovoitov <ast@kernel.org>
Sun, 20 Nov 2022 17:16:21 +0000 (09:16 -0800)
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@manifault.com>
Link: https://lore.kernel.org/r/20221120051004.3605026-5-void@manifault.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
tools/testing/selftests/bpf/DENYLIST.s390x
tools/testing/selftests/bpf/prog_tests/task_kfunc.c [new file with mode: 0644]
tools/testing/selftests/bpf/progs/task_kfunc_common.h [new file with mode: 0644]
tools/testing/selftests/bpf/progs/task_kfunc_failure.c [new file with mode: 0644]
tools/testing/selftests/bpf/progs/task_kfunc_success.c [new file with mode: 0644]

index 072243a..f70a677 100644 (file)
@@ -54,6 +54,7 @@ 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 (file)
index 0000000..4994fe6
--- /dev/null
@@ -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", "arg#0 is untrusted_ptr_or_null_ expected ptr_ or socket"},
+       {"task_kfunc_release_fp", "arg#0 pointer type STRUCT task_struct must point"},
+       {"task_kfunc_release_null", "arg#0 is ptr_or_null_ expected ptr_ or socket"},
+       {"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 (file)
index 0000000..160d6dd
--- /dev/null
@@ -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 -ENOENT;
+       }
+
+       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 (file)
index 0000000..93e934d
--- /dev/null
@@ -0,0 +1,260 @@
+// 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 -ENOENT;
+
+       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);
+       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 (file)
index 0000000..be4534b
--- /dev/null
@@ -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;
+}