diff --git a/Lib/test/test_os.py b/Lib/test/test_os.py index 5f73af81d45..36ad587760d 100644 --- a/Lib/test/test_os.py +++ b/Lib/test/test_os.py @@ -24,6 +24,7 @@ import subprocess import sys import sysconfig import tempfile +import textwrap import time import types import unittest @@ -2883,6 +2884,49 @@ class Win32NtTests(unittest.TestCase): self.assertEqual(0, handle_delta) + @support.requires_subprocess() + def test_stat_unlink_race(self): + # bpo-46785: the implementation of os.stat() falls back to reading + # the parent directory if CreateFileW() fails with a permission + # error. If reading the parent directory fails because the file or + # directory are subsequently unlinked, or because the volume or + # share are no longer available, then the original permission error + # should not be restored. + filename = os_helper.TESTFN + self.addCleanup(os_helper.unlink, filename) + deadline = time.time() + 5 + command = textwrap.dedent("""\ + import os + import sys + import time + + filename = sys.argv[1] + deadline = float(sys.argv[2]) + + while time.time() < deadline: + try: + with open(filename, "w") as f: + pass + except OSError: + pass + try: + os.remove(filename) + except OSError: + pass + """) + + with subprocess.Popen([sys.executable, '-c', command, filename, str(deadline)]) as proc: + while time.time() < deadline: + try: + os.stat(filename) + except FileNotFoundError as e: + assert e.winerror == 2 # ERROR_FILE_NOT_FOUND + try: + proc.wait(1) + except subprocess.TimeoutExpired: + proc.terminate() + + @os_helper.skip_unless_symlink class NonLocalSymlinkTests(unittest.TestCase): diff --git a/Misc/ACKS b/Misc/ACKS index 5e66a2e757a..30b698f90e8 100644 --- a/Misc/ACKS +++ b/Misc/ACKS @@ -1705,6 +1705,7 @@ Anthony Starks David Steele Oliver Steele Greg Stein +Itai Steinherz Marek Stepniowski Baruch Sterin Chris Stern diff --git a/Misc/NEWS.d/next/Windows/2022-03-13-20-35-41.bpo-46785.Pnknyl.rst b/Misc/NEWS.d/next/Windows/2022-03-13-20-35-41.bpo-46785.Pnknyl.rst new file mode 100644 index 00000000000..0a87abd77c8 --- /dev/null +++ b/Misc/NEWS.d/next/Windows/2022-03-13-20-35-41.bpo-46785.Pnknyl.rst @@ -0,0 +1 @@ +Fix race condition between :func:`os.stat` and unlinking a file on Windows, by using errors codes returned by ``FindFirstFileW()`` when appropriate in ``win32_xstat_impl``. diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c index a2ea5079969..a7f57804687 100644 --- a/Modules/posixmodule.c +++ b/Modules/posixmodule.c @@ -1890,7 +1890,17 @@ win32_xstat_impl(const wchar_t *path, struct _Py_stat_struct *result, /* Try reading the parent directory. */ if (!attributes_from_dir(path, &fileInfo, &tagInfo.ReparseTag)) { /* Cannot read the parent directory. */ - SetLastError(error); + switch (GetLastError()) { + case ERROR_FILE_NOT_FOUND: /* File cannot be found */ + case ERROR_PATH_NOT_FOUND: /* File parent directory cannot be found */ + case ERROR_NOT_READY: /* Drive exists but unavailable */ + case ERROR_BAD_NET_NAME: /* Remote drive unavailable */ + break; + /* Restore the error from CreateFileW(). */ + default: + SetLastError(error); + } + return -1; } if (fileInfo.dwFileAttributes & FILE_ATTRIBUTE_REPARSE_POINT) {