https://github.com/python/cpython/commit/932221bc01aebc971ac0bc33bc589503f9c1097c
commit: 932221bc01aebc971ac0bc33bc589503f9c1097c
branch: 3.13
author: Miss Islington (bot) <31488909+miss-isling...@users.noreply.github.com>
committer: gpshead <68491+gpsh...@users.noreply.github.com>
date: 2025-08-04T07:38:49-07:00
summary:
[3.13] gh-132124: improve safety nets for creating AF_UNIX socket files
(GH-134085) (#134448)
* gh-132124: improve safety nets for creating AF_UNIX socket files (GH-134085)
* ensure that we can create AF_UNIX socket files
* emit a warning if system-wide temporary directory is used
(cherry picked from commit 1a07a01014bde23acd2684916ef38dc0cd73c2de)
Co-authored-by: Bénédikt Tran <10796600+picn...@users.noreply.github.com>
* rename warn -> _warn for the 3.13.x backport
* Update Misc/NEWS.d/next/Library/2025-05-16-12-40-37.gh-issue-132124.T_5Odx.rst
---------
Co-authored-by: Bénédikt Tran <10796600+picn...@users.noreply.github.com>
Co-authored-by: Gregory P. Smith <g...@krypto.org>
files:
A Misc/NEWS.d/next/Library/2025-05-16-12-40-37.gh-issue-132124.T_5Odx.rst
M Lib/multiprocessing/connection.py
M Lib/multiprocessing/util.py
M Lib/tempfile.py
diff --git a/Lib/multiprocessing/connection.py
b/Lib/multiprocessing/connection.py
index 8caddd204d7c98..abd88adf76e700 100644
--- a/Lib/multiprocessing/connection.py
+++ b/Lib/multiprocessing/connection.py
@@ -74,7 +74,7 @@ def arbitrary_address(family):
if family == 'AF_INET':
return ('localhost', 0)
elif family == 'AF_UNIX':
- return tempfile.mktemp(prefix='listener-', dir=util.get_temp_dir())
+ return tempfile.mktemp(prefix='sock-', dir=util.get_temp_dir())
elif family == 'AF_PIPE':
return tempfile.mktemp(prefix=r'\\.\pipe\pyc-%d-%d-' %
(os.getpid(), next(_mmap_counter)), dir="")
diff --git a/Lib/multiprocessing/util.py b/Lib/multiprocessing/util.py
index 75dde02d88c533..e7e48c65f7a4be 100644
--- a/Lib/multiprocessing/util.py
+++ b/Lib/multiprocessing/util.py
@@ -34,6 +34,7 @@
DEBUG = 10
INFO = 20
SUBWARNING = 25
+WARNING = 30
LOGGER_NAME = 'multiprocessing'
DEFAULT_LOGGING_FORMAT = '[%(levelname)s/%(processName)s] %(message)s'
@@ -53,6 +54,10 @@ def info(msg, *args):
if _logger:
_logger.log(INFO, msg, *args, stacklevel=2)
+def _warn(msg, *args):
+ if _logger:
+ _logger.log(WARNING, msg, *args, stacklevel=2)
+
def sub_warning(msg, *args):
if _logger:
_logger.log(SUBWARNING, msg, *args, stacklevel=2)
@@ -121,6 +126,21 @@ def is_abstract_socket_namespace(address):
# Function returning a temp directory which will be removed on exit
#
+# Maximum length of a socket file path is usually between 92 and 108 [1],
+# but Linux is known to use a size of 108 [2]. BSD-based systems usually
+# use a size of 104 or 108 and Windows does not create AF_UNIX sockets.
+#
+# [1]: https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/sys_un.h.html
+# [2]: https://man7.org/linux/man-pages/man7/unix.7.html.
+
+if sys.platform == 'linux':
+ _SUN_PATH_MAX = 108
+elif sys.platform.startswith(('openbsd', 'freebsd')):
+ _SUN_PATH_MAX = 104
+else:
+ # On Windows platforms, we do not create AF_UNIX sockets.
+ _SUN_PATH_MAX = None if os.name == 'nt' else 92
+
def _remove_temp_dir(rmtree, tempdir):
rmtree(tempdir)
@@ -130,12 +150,67 @@ def _remove_temp_dir(rmtree, tempdir):
if current_process is not None:
current_process._config['tempdir'] = None
+def _get_base_temp_dir(tempfile):
+ """Get a temporary directory where socket files will be created.
+
+ To prevent additional imports, pass a pre-imported 'tempfile' module.
+ """
+ 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.
+ #
+ # If users specify their own temporary directory, we may be unable
+ # to create those files. Therefore, we fall back to the system-wide
+ # temporary directory /tmp, assumed to exist on POSIX systems.
+ #
+ # 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 length of socket filename will be:
+ #
+ # len(base_tempdir + '/pymp-XXXXXXXX' + '/sock-XXXXXXXX')
+ sun_path_len = len(base_tempdir) + 14 + 14
+ if sun_path_len <= _SUN_PATH_MAX:
+ return base_tempdir
+ # Fallback to the default system-wide temporary directory.
+ # This ignores user-defined environment variables.
+ #
+ # On POSIX systems, /tmp MUST be writable by any application [1].
+ # We however emit a warning if this is not the case to prevent
+ # obscure errors later in the execution.
+ #
+ # On some legacy systems, /var/tmp and /usr/tmp can be present
+ # and will be used instead.
+ #
+ # [1]: https://refspecs.linuxfoundation.org/FHS_3.0/fhs/ch03s18.html
+ dirlist = ['/tmp', '/var/tmp', '/usr/tmp']
+ try:
+ base_system_tempdir = tempfile._get_default_tempdir(dirlist)
+ except FileNotFoundError:
+ _warn("Process-wide temporary directory %s will not be usable for "
+ "creating socket files and no usable system-wide temporary "
+ "directory was found in %s", base_tempdir, dirlist)
+ # At this point, the system-wide temporary directory is not usable
+ # but we may assume that the user-defined one is, even if we will
+ # 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
+ return base_system_tempdir
+
def get_temp_dir():
# get name of a temp directory which will be automatically cleaned up
tempdir = process.current_process()._config.get('tempdir')
if tempdir is None:
import shutil, tempfile
- tempdir = tempfile.mkdtemp(prefix='pymp-')
+ base_tempdir = _get_base_temp_dir(tempfile)
+ tempdir = tempfile.mkdtemp(prefix='pymp-', 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/tempfile.py b/Lib/tempfile.py
index 67aa13f494d27d..8036e93cd6d775 100644
--- a/Lib/tempfile.py
+++ b/Lib/tempfile.py
@@ -180,7 +180,7 @@ def _candidate_tempdir_list():
return dirlist
-def _get_default_tempdir():
+def _get_default_tempdir(dirlist=None):
"""Calculate the default directory to use for temporary files.
This routine should be called exactly once.
@@ -190,7 +190,8 @@ def _get_default_tempdir():
service, the name of the test file must be randomized."""
namer = _RandomNameSequence()
- dirlist = _candidate_tempdir_list()
+ if dirlist is None:
+ dirlist = _candidate_tempdir_list()
for dir in dirlist:
if dir != _os.curdir:
diff --git
a/Misc/NEWS.d/next/Library/2025-05-16-12-40-37.gh-issue-132124.T_5Odx.rst
b/Misc/NEWS.d/next/Library/2025-05-16-12-40-37.gh-issue-132124.T_5Odx.rst
new file mode 100644
index 00000000000000..2a72d306d6fc4b
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2025-05-16-12-40-37.gh-issue-132124.T_5Odx.rst
@@ -0,0 +1,4 @@
+On POSIX-compliant systems, :func:`!multiprocessing.util.get_temp_dir` now
+ignores :envvar:`TMPDIR` (and similar environment variables) if the path
+length of ``AF_UNIX`` socket files exceeds the platform-specific maximum
+length when using the *forkserver* start method. Patch by Bénédikt Tran.
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