https://github.com/python/cpython/commit/3fe57207d692004858d1c7010ec1d747fe5a0076 commit: 3fe57207d692004858d1c7010ec1d747fe5a0076 branch: 3.15 author: Miss Islington (bot) <[email protected]> committer: picnixz <[email protected]> date: 2026-10-22T13:11:01-07:00 summary:
[3.15] gh-149527: fix creation of temporary socket files post GH-148578 (GH-149597) (#160269) gh-149527: fix creation of temporary socket files post GH-148578 (GH-149597) (cherry picked from commit d0212f6946dc6bbf82363bff0c93f6708abe76a7) Co-authored-by: Bénédikt Tran <[email protected]> files: A Misc/NEWS.d/next/Library/2026-05-09-12-58-04.gh-issue-149527.hX36Yh.rst M Lib/multiprocessing/connection.py M Lib/multiprocessing/util.py M Lib/test/test_multiprocessing_forkserver/test_misc.py diff --git a/Lib/multiprocessing/connection.py b/Lib/multiprocessing/connection.py index e37ec07d722ca86..15f6590288c9ab7 100644 --- a/Lib/multiprocessing/connection.py +++ b/Lib/multiprocessing/connection.py @@ -76,11 +76,12 @@ def arbitrary_address(family): if family == 'AF_INET': return ('localhost', 0) elif family == 'AF_UNIX': - # NOTE: util.get_temp_dir() is a 0o700 per-process directory. A - # mktemp-style ToC vs ToU concern is not important; bind() surfaces - # the extremely unlikely collision as EADDRINUSE. + # NOTE: util.get_temp_dir() is a 0o700 per-process directory. + # A mktemp-style ToC vs ToU concern is not important as bind() + # surfaces the extremely unlikely collision as EADDRINUSE. + suffix = os.urandom(util._TMPSOCK_SUFFIXLEN // 2).hex() return os.path.join(util.get_temp_dir(), - f'sock-{os.urandom(6).hex()}') + f"{util._TMPSOCK_PREFIX}{suffix}") elif family == 'AF_PIPE': return (r'\\.\pipe\pyc-%d-%d-%s' % (os.getpid(), next(_mmap_counter), os.urandom(8).hex())) diff --git a/Lib/multiprocessing/util.py b/Lib/multiprocessing/util.py index a84546bbb8fe1e3..28d5d30f7ac89fa 100644 --- a/Lib/multiprocessing/util.py +++ b/Lib/multiprocessing/util.py @@ -143,6 +143,41 @@ def is_abstract_socket_namespace(address): # On Windows platforms, we do not create AF_UNIX sockets. _SUN_PATH_MAX = None if os.name == 'nt' else 92 +# The temporary socket file path (without NULL terminator) is +# +# TEMPDIR/{_TMPPYMP_PREFIX}{S1}/{_TMPSOCK_PREFIX}{S2} +# +# where +# +# - S1 is a random suffix of length 8 generated by get_temp_dir(). +# This is used to generate the temporary sub-directory that will +# contains the socket file. Update _TMPPYMP_SUFFIXLEN accordingly +# if the random suffix length chosen by tempfile.mkdtemp() changes. +# +# - S2 is a random suffix of length 2N generated by os.urandom(N).hex() +# in multiprocessing.connection.arbitrary_address(). The value of N +# is not fixed and may vary across Python versions as to minimize +# collisions and path lengths. +# +_TMPPYMP_PREFIX = "pymp-" +_TMPPYMP_PREFIXLEN = len(_TMPPYMP_PREFIX) +_TMPPYMP_SUFFIXLEN = 8 +_TMPSOCK_PREFIX = "sock-" +_TMPSOCK_PREFIXLEN = len(_TMPSOCK_PREFIX) +_TMPSOCK_SUFFIXLEN = 12 + +# Length of the socket filepath from the chosen temporary directory, +# including a leading path separator and the path separator between +# the temporary subdirectory and the socket filename. +_SUN_PATH_LEN_RESERVED = ( + len(os.path.sep) + _TMPPYMP_PREFIXLEN + _TMPPYMP_SUFFIXLEN + + len(os.path.sep) + _TMPSOCK_PREFIXLEN + _TMPSOCK_SUFFIXLEN +) +assert ( + _SUN_PATH_MAX is None + or _SUN_PATH_LEN_RESERVED < _SUN_PATH_MAX +) + def _remove_temp_dir(rmtree, tempdir): rmtree(tempdir) @@ -161,9 +196,8 @@ def _get_base_temp_dir(tempfile): """ if os.name == 'nt': return None - # Most of the time, the default temporary directory is /tmp. Thus, - # listener sockets files "$TMPDIR/pymp-XXXXXXXX/sock-XXXXXXXX" do - # not have a path length exceeding SUN_PATH_MAX. + # Most of the time, the default temporary directory is /tmp. As such, + # the path length of listener sockets files does not exceed SUN_PATH_MAX. # # If users specify their own temporary directory, we may be unable # to create those files. Therefore, we fall back to the system-wide @@ -171,14 +205,7 @@ def _get_base_temp_dir(tempfile): # # See https://github.com/python/cpython/issues/132124. base_tempdir = tempfile.gettempdir() - # Files created in a temporary directory are suffixed by a string - # generated by tempfile._RandomNameSequence, which, by design, - # is 8 characters long. - # - # Thus, the socket file path length (without NULL terminator) will be: - # - # len(base_tempdir + '/pymp-XXXXXXXX' + '/sock-XXXXXXXX') - sun_path_len = len(base_tempdir) + 14 + 14 + sun_path_len = len(base_tempdir) + _SUN_PATH_LEN_RESERVED # Strict inequality to account for the NULL terminator. # See https://github.com/python/cpython/issues/140734. if sun_path_len < _SUN_PATH_MAX: @@ -206,8 +233,8 @@ def _get_base_temp_dir(tempfile): # not be able to write socket files out there. return base_tempdir warn("Ignoring user-defined temporary directory: %s", base_tempdir) - # at most max(map(len, dirlist)) + 14 + 14 = 36 characters - assert len(base_system_tempdir) + 14 + 14 < _SUN_PATH_MAX + # The following assertion must be satisfied with the chosen constants. + assert len(base_system_tempdir) + _SUN_PATH_LEN_RESERVED < _SUN_PATH_MAX return base_system_tempdir @@ -218,7 +245,7 @@ def get_temp_dir(): # Deferred until first use to keep importing this module cheap. import shutil, tempfile base_tempdir = _get_base_temp_dir(tempfile) - tempdir = tempfile.mkdtemp(prefix='pymp-', dir=base_tempdir) + tempdir = tempfile.mkdtemp(prefix=_TMPPYMP_PREFIX, dir=base_tempdir) info('created temp directory %s', tempdir) # keep a strong reference to shutil.rmtree(), since the finalizer # can be called late during Python shutdown diff --git a/Lib/test/test_multiprocessing_forkserver/test_misc.py b/Lib/test/test_multiprocessing_forkserver/test_misc.py index 9cae1b50f71e00b..a3ee2e2b73c3e19 100644 --- a/Lib/test/test_multiprocessing_forkserver/test_misc.py +++ b/Lib/test/test_multiprocessing_forkserver/test_misc.py @@ -1,7 +1,47 @@ +import os +import re import unittest +from multiprocessing.util import _SUN_PATH_MAX from test._test_multiprocessing import install_tests_in_module_dict +from test.support import os_helper, script_helper install_tests_in_module_dict(globals(), 'forkserver', exclude_types=True) + +class TestForkServerConfiguration(unittest.TestCase): + def test_respect_sun_path_max(self): + # Ensure that the calculation for temporary filepath lengths is correct. + # See https://github.com/python/cpython/issues/149527. + + cmd = '''if 1: + from multiprocessing.connection import arbitrary_address + from multiprocessing.util import get_temp_dir + if __name__ == "__main__": + print(get_temp_dir()) + print(arbitrary_address("AF_UNIX")) + ''' + with os_helper.temp_dir() as root: + self.assertLess(len(root), _SUN_PATH_MAX) + _, out, _ = script_helper.assert_python_ok('-c', cmd, TMPDIR=root) + res = out.decode().strip().splitlines() + self.assertEqual(len(res), 2) + + # get_temp_dir() with a TMPDIR that has a too large length ends up + # NOT being used as it is not possible to use it. In particular, + # the corresponding path will fallback to one of the "built-in" + # ones such as '/tmp', '/var/tmp', or '/usr/tmp'. + root_regex = "|".join(map(re.escape, [root, "/tmp", "/var/tmp", "/usr/tmp"])) + + temp_pymp = res[0] + self.assertLess(len(temp_pymp), _SUN_PATH_MAX) + temp_pymp_regex = os.path.join(root_regex, r"pymp-\w{8}") + self.assertRegex(temp_pymp, temp_pymp_regex) + + temp_sock = res[1] + self.assertLess(len(temp_sock), _SUN_PATH_MAX) + temp_sock_regex = os.path.join(temp_pymp_regex, r"sock-[0-9a-fA-F]{12}") + self.assertRegex(temp_sock, temp_sock_regex) + + if __name__ == '__main__': unittest.main() diff --git a/Misc/NEWS.d/next/Library/2026-05-09-12-58-04.gh-issue-149527.hX36Yh.rst b/Misc/NEWS.d/next/Library/2026-05-09-12-58-04.gh-issue-149527.hX36Yh.rst new file mode 100644 index 000000000000000..d75b285554c0fa8 --- /dev/null +++ b/Misc/NEWS.d/next/Library/2026-05-09-12-58-04.gh-issue-149527.hX36Yh.rst @@ -0,0 +1,3 @@ +:mod:`multiprocessing`: fix creation of temporary socket files following +:gh:`137335` (`PR#148578 <https://github.com/python/cpython/pull/148578>`__ +and corresponding backports). Patch by Bénédikt Tran. _______________________________________________ Python-checkins mailing list -- [email protected] To unsubscribe send an email to [email protected] https://mail.python.org/mailman3//lists/python-checkins.python.org Member address: [email protected]
