[3.9] gh-97514: Don't use Linux abstract sockets for multiprocessing (GH-98501) ...

Linux abstract sockets are insecure as they lack any form of filesystem
permissions so their use allows anyone on the system to inject code into
the process.

This removes the default preference for abstract sockets in
multiprocessing introduced in Python 3.9+ via
https://github.com/python/cpython/pull/18866 while fixing
https://github.com/python/cpython/issues/84031.

Explicit use of an abstract socket by a user now generates a
RuntimeWarning.  If we choose to keep this warning, it should be
backported to the 3.7 and 3.8 branches.
(cherry picked from commit 49f61068f49747164988ffc5a442d2a63874fc17)

Co-authored-by: Gregory P. Smith <greg@krypto.org>
Gbp-Pq: Name 0010-3.9-gh-97514-Don-t-use-Linux-abstract-sockets-for-mu.patch

diff --git a/Lib/multiprocessing/connection.py b/Lib/multiprocessing/connection.py
index 510e4b5aba44a6755c4a63fec0d8b297b2066563..8e2facf92a94aa363a653a0032da4ea063f0162c 100644 (file)
--- a/Lib/multiprocessing/connection.py
+++ b/Lib/multiprocessing/connection.py
@@ -73,11 +73,6 @@ def arbitrary_address(family):
     if family == 'AF_INET':
         return ('localhost', 0)
     elif family == 'AF_UNIX':
-        # Prefer abstract sockets if possible to avoid problems with the address
-        # size.  When coding portable applications, some implementations have
-        # sun_path as short as 92 bytes in the sockaddr_un struct.
-        if util.abstract_sockets_supported:
-            return f"\0listener-{os.getpid()}-{next(_mmap_counter)}"
         return tempfile.mktemp(prefix='listener-', dir=util.get_temp_dir())
     elif family == 'AF_PIPE':
         return tempfile.mktemp(prefix=r'\\.\pipe\pyc-%d-%d-' %