bpo-33929: multiprocessing: fix handle leak on race condition (GH-7921)
Fix a race condition in Popen of
multiprocessing.popen_spawn_win32. The child process now duplicates
the read end of pipe instead of "stealing" it.
Previously, the read end of pipe was "stolen" by the child process,
but it leaked a handle if the child process had been terminated
before it could steal the handle from the parent process.
diff --git a/Lib/multiprocessing/reduction.py b/Lib/multiprocessing/reduction.py
index deca19c..473fd59 100644
--- a/Lib/multiprocessing/reduction.py
+++ b/Lib/multiprocessing/reduction.py
@@ -68,12 +68,16 @@
__all__ += ['DupHandle', 'duplicate', 'steal_handle']
import _winapi
- def duplicate(handle, target_process=None, inheritable=False):
+ def duplicate(handle, target_process=None, inheritable=False,
+ *, source_process=None):
'''Duplicate a handle. (target_process is a handle not a pid!)'''
+ current_process = _winapi.GetCurrentProcess()
+ if source_process is None:
+ source_process = current_process
if target_process is None:
- target_process = _winapi.GetCurrentProcess()
+ target_process = current_process
return _winapi.DuplicateHandle(
- _winapi.GetCurrentProcess(), handle, target_process,
+ source_process, handle, target_process,
0, inheritable, _winapi.DUPLICATE_SAME_ACCESS)
def steal_handle(source_pid, handle):