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.
This commit is contained in:
Victor Stinner 2018-06-27 11:40:24 +02:00 committed by GitHub
parent f15f66d275
commit 2cc9d21fff
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GPG key ID: 4AEE18F83AFDEB23
4 changed files with 34 additions and 6 deletions

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@ -96,7 +96,15 @@ def spawn_main(pipe_handle, parent_pid=None, tracker_fd=None):
assert is_forking(sys.argv), "Not forking"
if sys.platform == 'win32':
import msvcrt
new_handle = reduction.steal_handle(parent_pid, pipe_handle)
import _winapi
if parent_pid is not None:
source_process = _winapi.OpenProcess(
_winapi.PROCESS_DUP_HANDLE, False, parent_pid)
else:
source_process = None
new_handle = reduction.duplicate(pipe_handle,
source_process=source_process)
fd = msvcrt.open_osfhandle(new_handle, os.O_RDONLY)
else:
from . import semaphore_tracker