[PATCH bpf-next 2/2] selftests/bpf: Add selftests for bpf_task_from_pid()

David Vernet
2022-11-22T14:54:53Z

Add some selftest testcases that validate the expected behavior of the
bpf_task_from_pid() kfunc that was added in the prior patch.

Signed-off-by: David Vernet <void@manifault.com>
---
.../selftests/bpf/prog_tests/task_kfunc.c | 4 +
.../selftests/bpf/progs/task_kfunc_common.h | 1 +
.../selftests/bpf/progs/task_kfunc_failure.c | 13 ++++
.../selftests/bpf/progs/task_kfunc_success.c | 73 +++++++++++++++++++
4 files changed, 91 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/task_kfunc.c b/tools/testing/selftests/bpf/prog_tests/task_kfunc.c
index 4994fe6092cc..ffd8ef4303c8 100644
--- a/tools/testing/selftests/bpf/prog_tests/task_kfunc.c
+++ b/tools/testing/selftests/bpf/prog_tests/task_kfunc.c
@@ -78,6 +78,9 @@ static const char * const success_tests[] = {
"test_task_xchg_release",
"test_task_get_release",
"test_task_current_acquire_release",
+ "test_task_from_pid_arg",
+ "test_task_from_pid_current",
+ "test_task_from_pid_invalid",
};

static struct {
@@ -99,6 +102,7 @@ static struct {
{"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"},
+ {"task_kfunc_from_pid_no_null_check", "arg#0 is ptr_or_null_ expected ptr_ or socket"},
};

static void verify_fail(const char *prog_name, const char *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
index 160d6dde00be..c0ffd171743e 100644
--- a/tools/testing/selftests/bpf/progs/task_kfunc_common.h
+++ b/tools/testing/selftests/bpf/progs/task_kfunc_common.h
@@ -23,6 +23,7 @@ struct hash_map {
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;
+struct task_struct *bpf_task_from_pid(s32 pid) __ksym;

static inline struct __tasks_kfunc_map_value *tasks_kfunc_map_value_lookup(struct task_struct *p)
{
diff --git a/tools/testing/selftests/bpf/progs/task_kfunc_failure.c b/tools/testing/selftests/bpf/progs/task_kfunc_failure.c
index 93e934ddfcb6..e310473190d5 100644
--- a/tools/testing/selftests/bpf/progs/task_kfunc_failure.c
+++ b/tools/testing/selftests/bpf/progs/task_kfunc_failure.c
@@ -258,3 +258,16 @@ int BPF_PROG(task_kfunc_release_unacquired, struct task_struct *task, u64 clone_

return 0;
}
+
+SEC("tp_btf/task_newtask")
+int BPF_PROG(task_kfunc_from_pid_no_null_check, struct task_struct *task, u64 clone_flags)
+{
+ struct task_struct *acquired;
+
+ acquired = bpf_task_from_pid(task->pid);
+
+ /* Releasing bpf_task_from_pid() lookup without a NULL check. */
+ bpf_task_release(acquired);
+
+ return 0;
+}
diff --git a/tools/testing/selftests/bpf/progs/task_kfunc_success.c b/tools/testing/selftests/bpf/progs/task_kfunc_success.c
index be4534b5ba2e..60c7ead41cfc 100644
--- a/tools/testing/selftests/bpf/progs/task_kfunc_success.c
+++ b/tools/testing/selftests/bpf/progs/task_kfunc_success.c
@@ -147,3 +147,76 @@ int BPF_PROG(test_task_current_acquire_release, struct task_struct *task, u64 cl

return 0;
}
+
+static void lookup_compare_pid(const struct task_struct *p)
+{
+ struct task_struct *acquired;
+
+ acquired = bpf_task_from_pid(p->pid);
+ if (!acquired) {
+ err = 1;
+ return;
+ }
+
+ if (acquired->pid != p->pid)
+ err = 2;
+ bpf_task_release(acquired);
+}
+
+SEC("tp_btf/task_newtask")
+int BPF_PROG(test_task_from_pid_arg, struct task_struct *task, u64 clone_flags)
+{
+ struct task_struct *acquired;
+
+ if (!is_test_kfunc_task())
+ return 0;
+
+ lookup_compare_pid(task);
+ return 0;
+}
+
+SEC("tp_btf/task_newtask")
+int BPF_PROG(test_task_from_pid_current, struct task_struct *task, u64 clone_flags)
+{
+ struct task_struct *current, *acquired;
+
+ if (!is_test_kfunc_task())
+ return 0;
+
+ lookup_compare_pid(bpf_get_current_task_btf());
+ return 0;
+}
+
+static int is_pid_lookup_valid(s32 pid)
+{
+ struct task_struct *acquired;
+
+ acquired = bpf_task_from_pid(pid);
+ if (acquired) {
+ bpf_task_release(acquired);
+ return 1;
+ }
+
+ return 0;
+}
+
+SEC("tp_btf/task_newtask")
+int BPF_PROG(test_task_from_pid_invalid, struct task_struct *task, u64 clone_flags)
+{
+ struct task_struct *acquired;
+
+ if (!is_test_kfunc_task())
+ return 0;
+
+ if (is_pid_lookup_valid(-1)) {
+ err = 1;
+ return 0;
+ }
+
+ if (is_pid_lookup_valid(0xcafef00d)) {
+ err = 2;
+ return 0;
+ }
+
+ return 0;
+}
--
2.38.1