kconfig: Fix BrokenPipeError warnings in selftests

The kconfig test harness ("make testconfig") was generating BrokenPipeError
warnings when running interactive tests like oldaskconfig and oldconfig:

  /usr/lib/python3/dist-packages/_pytest/unraisableexception.py:85: PytestUnraisableExceptionWarning: Exception ignored in: <_io.BufferedWriter name=12>

  Traceback (most recent call last):
    File "/srv/code/scripts/kconfig/tests/conftest.py", line 127, in oldaskconfig
      return self._run_conf('--oldaskconfig', dot_config=dot_config,
             ~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
                            interactive=True, in_keys=in_keys)
                            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  BrokenPipeError: [Errno 32] Broken pipe

The issue occurred when the test framework attempted to write to stdin
after the conf subprocess had already exited.

Wrap stdin write operations in try/except to catch BrokenPipeError and
stop sending more input. Add explicit flush() after writes so we can see
delivery errors immediately. Ignore BrokenPipeError when closing stdin.
Explicitly call wait() to validate subprocess termination.

Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lore.kernel.org/r/20250923213422.1105654-1-kees@kernel.org
Signed-off-by: Kees Cook <kees@kernel.org>

diff --git a/scripts/kconfig/tests/conftest.py b/scripts/kconfig/tests/conftest.py
index 2a2a7e2da06087524badbe3c5a12ad2c8c9ae8b8..d94b79e012c04beee2b5674157f8ec38f5537210 100644 (file)
--- a/scripts/kconfig/tests/conftest.py
+++ b/scripts/kconfig/tests/conftest.py
@@ -81,7 +81,22 @@ class Conf:
                 # For interactive modes such as oldaskconfig, oldconfig,
                 # send 'Enter' key until the program finishes.
                 if interactive:
-                    ps.stdin.write(b'\n')
+                    try:
+                        ps.stdin.write(b'\n')
+                        ps.stdin.flush()
+                    except (BrokenPipeError, OSError):
+                        # Process has exited, stop sending input
+                        break
+
+            # Close stdin gracefully
+            try:
+                ps.stdin.close()
+            except (BrokenPipeError, OSError):
+                # Ignore broken pipe on close
+                pass
+
+            # Wait for process to complete
+            ps.wait()
 
             self.retcode = ps.returncode
             self.stdout = ps.stdout.read().decode()