Users may accidentally use the kselftest_test_result_*() functions in
their harness tests. If ksft_finished() is not used, the results
reported in this way are silently ignored.

Detect such false-positive cases and fail the test.

A more correct test would be to reject *any* usage of the ksft APIs but
that would force code churn on users.

Correct usages, which do use ksft_finished() will not trigger this
validation as the test will exit before it.

Reported-by: Yuwen Chen <ywen.chen@foxmail.com>
Link: https://lore.kernel.org/lkml/tencent_56D79AF3D23CEFAF882E83A2196EC1F12107@qq.com/
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>

---
This is intentionally a Link tag over a Closes tag, as the real fix will
be to the selftests.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
---
 tools/testing/selftests/kselftest_harness.h | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/tools/testing/selftests/kselftest_harness.h b/tools/testing/selftests/kselftest_harness.h
index baae6b7ded41..93dcba095338 100644
--- a/tools/testing/selftests/kselftest_harness.h
+++ b/tools/testing/selftests/kselftest_harness.h
@@ -1216,7 +1216,16 @@ static void __run_test(struct __fixture_metadata *f,
 		t->exit_code = KSFT_FAIL;
 	} else if (child == 0) {
 		setpgrp();
+
+		/* Reset state inherited from the harness */
+		ksft_reset_state();
+
 		t->fn(t, variant);
+
+		if (__test_passed(t) && (ksft_get_fail_cnt() || ksft_get_error_cnt())) {
+			ksft_print_msg("Illegal usage of low-level ksft APIs in harness test\n");
+			t->exit_code = KSFT_FAIL;
+		}
 		_exit(t->exit_code);
 	} else {
 		t->pid = child;

-- 
2.52.0