From a9344cdffa30fdf60154d645f9e74ab3d67ae2e9 Mon Sep 17 00:00:00 2001 From: Cody Maloney Date: Tue, 30 Jul 2024 18:39:54 -0700 Subject: [PATCH] gh-121381 Remove subprocess._USE_VFORK escape hatch (#121383) This flag was added as an escape hatch in gh-91401 and backported to Python 3.10. The flag broke at some point between its addition and now. As there is currently no publicly known environments that require this, remove it rather than work on fixing it. This leaves the flag in the subprocess module to not break code which may have used / checked the flag itself. discussion: https://discuss.python.org/t/subprocess-use-vfork-escape-hatch-broken-fix-or-remove/56915/2 --- Doc/library/subprocess.rst | 25 ++++--------------- Lib/multiprocessing/util.py | 3 +-- Lib/subprocess.py | 3 +-- Lib/test/test_capi/test_misc.py | 6 ++--- Lib/test/test_subprocess.py | 22 +--------------- ...-06-28-23-17-22.gh-issue-121381.i2xL7P.rst | 2 ++ Modules/_posixsubprocess.c | 7 +++--- Modules/clinic/_posixsubprocess.c.h | 15 ++++------- 8 files changed, 21 insertions(+), 62 deletions(-) create mode 100644 Misc/NEWS.d/next/Core and Builtins/2024-06-28-23-17-22.gh-issue-121381.i2xL7P.rst diff --git a/Doc/library/subprocess.rst b/Doc/library/subprocess.rst index a0ba97f429b..f10a8085e64 100644 --- a/Doc/library/subprocess.rst +++ b/Doc/library/subprocess.rst @@ -1561,36 +1561,22 @@ runtime): Module which provides function to parse and escape command lines. -.. _disable_vfork: .. _disable_posix_spawn: -Disabling use of ``vfork()`` or ``posix_spawn()`` -^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ +Disable use of ``posix_spawn()`` +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ On Linux, :mod:`subprocess` defaults to using the ``vfork()`` system call internally when it is safe to do so rather than ``fork()``. This greatly improves performance. -If you ever encounter a presumed highly unusual situation where you need to -prevent ``vfork()`` from being used by Python, you can set the -:const:`subprocess._USE_VFORK` attribute to a false value. - -:: - - subprocess._USE_VFORK = False # See CPython issue gh-NNNNNN. - -Setting this has no impact on use of ``posix_spawn()`` which could use -``vfork()`` internally within its libc implementation. There is a similar -:const:`subprocess._USE_POSIX_SPAWN` attribute if you need to prevent use of -that. - :: subprocess._USE_POSIX_SPAWN = False # See CPython issue gh-NNNNNN. -It is safe to set these to false on any Python version. They will have no -effect on older versions when unsupported. Do not assume the attributes are -available to read. Despite their names, a true value does not indicate that the +It is safe to set this to false on any Python version. It will have no +effect on older or newer versions where unsupported. Do not assume the attribute +is available to read. Despite the name, a true value does not indicate the corresponding function will be used, only that it may be. Please file issues any time you have to use these private knobs with a way to @@ -1598,4 +1584,3 @@ reproduce the issue you were seeing. Link to that issue from a comment in your code. .. versionadded:: 3.8 ``_USE_POSIX_SPAWN`` -.. versionadded:: 3.11 ``_USE_VFORK`` diff --git a/Lib/multiprocessing/util.py b/Lib/multiprocessing/util.py index 4f471fbde71..d48ef8a86b3 100644 --- a/Lib/multiprocessing/util.py +++ b/Lib/multiprocessing/util.py @@ -445,8 +445,7 @@ def spawnv_passfds(path, args, passfds): return _posixsubprocess.fork_exec( args, [path], True, passfds, None, None, -1, -1, -1, -1, -1, -1, errpipe_read, errpipe_write, - False, False, -1, None, None, None, -1, None, - subprocess._USE_VFORK) + False, False, -1, None, None, None, -1, None) finally: os.close(errpipe_read) os.close(errpipe_write) diff --git a/Lib/subprocess.py b/Lib/subprocess.py index bc08878db31..88f0230b05f 100644 --- a/Lib/subprocess.py +++ b/Lib/subprocess.py @@ -749,7 +749,6 @@ def _use_posix_spawn(): # These are primarily fail-safe knobs for negatives. A True value does not # guarantee the given libc/syscall API will be used. _USE_POSIX_SPAWN = _use_posix_spawn() -_USE_VFORK = True _HAVE_POSIX_SPAWN_CLOSEFROM = hasattr(os, 'POSIX_SPAWN_CLOSEFROM') @@ -1902,7 +1901,7 @@ class Popen: errpipe_read, errpipe_write, restore_signals, start_new_session, process_group, gid, gids, uid, umask, - preexec_fn, _USE_VFORK) + preexec_fn) self._child_created = True finally: # be sure the FD is closed no matter what diff --git a/Lib/test/test_capi/test_misc.py b/Lib/test/test_capi/test_misc.py index 9de97c0c2c7..5c4547da1bd 100644 --- a/Lib/test/test_capi/test_misc.py +++ b/Lib/test/test_capi/test_misc.py @@ -120,7 +120,7 @@ class CAPITest(unittest.TestCase): return 1 with self.assertRaisesRegex(TypeError, 'indexing'): _posixsubprocess.fork_exec( - 1,Z(),True,(1, 2),5,6,7,8,9,10,11,12,13,14,True,True,17,False,19,20,21,22,False) + 1,Z(),True,(1, 2),5,6,7,8,9,10,11,12,13,14,True,True,17,False,19,20,21,22) # Issue #15736: overflow in _PySequence_BytesToCharpArray() class Z(object): def __len__(self): @@ -128,7 +128,7 @@ class CAPITest(unittest.TestCase): def __getitem__(self, i): return b'x' self.assertRaises(MemoryError, _posixsubprocess.fork_exec, - 1,Z(),True,(1, 2),5,6,7,8,9,10,11,12,13,14,True,True,17,False,19,20,21,22,False) + 1,Z(),True,(1, 2),5,6,7,8,9,10,11,12,13,14,True,True,17,False,19,20,21,22) @unittest.skipUnless(_posixsubprocess, '_posixsubprocess required for this test.') def test_subprocess_fork_exec(self): @@ -138,7 +138,7 @@ class CAPITest(unittest.TestCase): # Issue #15738: crash in subprocess_fork_exec() self.assertRaises(TypeError, _posixsubprocess.fork_exec, - Z(),[b'1'],True,(1, 2),5,6,7,8,9,10,11,12,13,14,True,True,17,False,19,20,21,22,False) + Z(),[b'1'],True,(1, 2),5,6,7,8,9,10,11,12,13,14,True,True,17,False,19,20,21,22) @unittest.skipIf(MISSING_C_DOCSTRINGS, "Signature information for builtins requires docstrings") diff --git a/Lib/test/test_subprocess.py b/Lib/test/test_subprocess.py index 9412a2d737b..f065b9c9bb1 100644 --- a/Lib/test/test_subprocess.py +++ b/Lib/test/test_subprocess.py @@ -3278,7 +3278,7 @@ class POSIXProcessTestCase(BaseTestCase): 1, 2, 3, 4, True, True, 0, None, None, None, -1, - None, True) + None) self.assertIn('fds_to_keep', str(c.exception)) finally: if not gc_enabled: @@ -3413,25 +3413,6 @@ class POSIXProcessTestCase(BaseTestCase): self.assertEqual(out.strip(), b"OK") self.assertIn(b"preexec_fn not supported at interpreter shutdown", err) - @unittest.skipIf(not sysconfig.get_config_var("HAVE_VFORK"), - "vfork() not enabled by configure.") - @mock.patch("subprocess._fork_exec") - @mock.patch("subprocess._USE_POSIX_SPAWN", new=False) - def test__use_vfork(self, mock_fork_exec): - self.assertTrue(subprocess._USE_VFORK) # The default value regardless. - mock_fork_exec.side_effect = RuntimeError("just testing args") - with self.assertRaises(RuntimeError): - subprocess.run([sys.executable, "-c", "pass"]) - mock_fork_exec.assert_called_once() - # NOTE: These assertions are *ugly* as they require the last arg - # to remain the have_vfork boolean. We really need to refactor away - # from the giant "wall of args" internal C extension API. - self.assertTrue(mock_fork_exec.call_args.args[-1]) - with mock.patch.object(subprocess, '_USE_VFORK', False): - with self.assertRaises(RuntimeError): - subprocess.run([sys.executable, "-c", "pass"]) - self.assertFalse(mock_fork_exec.call_args_list[-1].args[-1]) - @unittest.skipIf(not sysconfig.get_config_var("HAVE_VFORK"), "vfork() not enabled by configure.") @unittest.skipIf(sys.platform != "linux", "Linux only, requires strace.") @@ -3478,7 +3459,6 @@ class POSIXProcessTestCase(BaseTestCase): # Test that each individual thing that would disable the use of vfork # actually disables it. for sub_name, preamble, sp_kwarg, expect_permission_error in ( - ("!use_vfork", "subprocess._USE_VFORK = False", "", False), ("preexec", "", "preexec_fn=lambda: None", False), ("setgid", "", f"group={os.getgid()}", True), ("setuid", "", f"user={os.getuid()}", True), diff --git a/Misc/NEWS.d/next/Core and Builtins/2024-06-28-23-17-22.gh-issue-121381.i2xL7P.rst b/Misc/NEWS.d/next/Core and Builtins/2024-06-28-23-17-22.gh-issue-121381.i2xL7P.rst new file mode 100644 index 00000000000..3a02145378e --- /dev/null +++ b/Misc/NEWS.d/next/Core and Builtins/2024-06-28-23-17-22.gh-issue-121381.i2xL7P.rst @@ -0,0 +1,2 @@ +Remove ``subprocess._USE_VFORK`` escape hatch code and documentation. +It was added just in case, and doesn't have any known cases that require it. diff --git a/Modules/_posixsubprocess.c b/Modules/_posixsubprocess.c index daec4ad708d..ad6d7ceda84 100644 --- a/Modules/_posixsubprocess.c +++ b/Modules/_posixsubprocess.c @@ -977,7 +977,6 @@ _posixsubprocess.fork_exec as subprocess_fork_exec uid as uid_object: object child_umask: int preexec_fn: object - allow_vfork: bool / Spawn a fresh new child process. @@ -1014,8 +1013,8 @@ subprocess_fork_exec_impl(PyObject *module, PyObject *process_args, pid_t pgid_to_set, PyObject *gid_object, PyObject *extra_groups_packed, PyObject *uid_object, int child_umask, - PyObject *preexec_fn, int allow_vfork) -/*[clinic end generated code: output=7ee4f6ee5cf22b5b input=51757287ef266ffa]*/ + PyObject *preexec_fn) +/*[clinic end generated code: output=288464dc56e373c7 input=f311c3bcb5dd55c8]*/ { PyObject *converted_args = NULL, *fast_args = NULL; PyObject *preexec_fn_args_tuple = NULL; @@ -1218,7 +1217,7 @@ subprocess_fork_exec_impl(PyObject *module, PyObject *process_args, #ifdef VFORK_USABLE /* Use vfork() only if it's safe. See the comment above child_exec(). */ sigset_t old_sigs; - if (preexec_fn == Py_None && allow_vfork && + if (preexec_fn == Py_None && uid == (uid_t)-1 && gid == (gid_t)-1 && extra_group_size < 0) { /* Block all signals to ensure that no signal handlers are run in the * child process while it shares memory with us. Note that signals diff --git a/Modules/clinic/_posixsubprocess.c.h b/Modules/clinic/_posixsubprocess.c.h index dd7644de6b7..d52629cf6ea 100644 --- a/Modules/clinic/_posixsubprocess.c.h +++ b/Modules/clinic/_posixsubprocess.c.h @@ -9,7 +9,7 @@ PyDoc_STRVAR(subprocess_fork_exec__doc__, " env, p2cread, p2cwrite, c2pread, c2pwrite, errread, errwrite,\n" " errpipe_read, errpipe_write, restore_signals, call_setsid,\n" " pgid_to_set, gid, extra_groups, uid, child_umask, preexec_fn,\n" -" allow_vfork, /)\n" +" /)\n" "--\n" "\n" "Spawn a fresh new child process.\n" @@ -48,7 +48,7 @@ subprocess_fork_exec_impl(PyObject *module, PyObject *process_args, pid_t pgid_to_set, PyObject *gid_object, PyObject *extra_groups_packed, PyObject *uid_object, int child_umask, - PyObject *preexec_fn, int allow_vfork); + PyObject *preexec_fn); static PyObject * subprocess_fork_exec(PyObject *module, PyObject *const *args, Py_ssize_t nargs) @@ -76,9 +76,8 @@ subprocess_fork_exec(PyObject *module, PyObject *const *args, Py_ssize_t nargs) PyObject *uid_object; int child_umask; PyObject *preexec_fn; - int allow_vfork; - if (!_PyArg_CheckPositional("fork_exec", nargs, 23, 23)) { + if (!_PyArg_CheckPositional("fork_exec", nargs, 22, 22)) { goto exit; } process_args = args[0]; @@ -146,13 +145,9 @@ subprocess_fork_exec(PyObject *module, PyObject *const *args, Py_ssize_t nargs) goto exit; } preexec_fn = args[21]; - allow_vfork = PyObject_IsTrue(args[22]); - if (allow_vfork < 0) { - goto exit; - } - return_value = subprocess_fork_exec_impl(module, process_args, executable_list, close_fds, py_fds_to_keep, cwd_obj, env_list, p2cread, p2cwrite, c2pread, c2pwrite, errread, errwrite, errpipe_read, errpipe_write, restore_signals, call_setsid, pgid_to_set, gid_object, extra_groups_packed, uid_object, child_umask, preexec_fn, allow_vfork); + return_value = subprocess_fork_exec_impl(module, process_args, executable_list, close_fds, py_fds_to_keep, cwd_obj, env_list, p2cread, p2cwrite, c2pread, c2pwrite, errread, errwrite, errpipe_read, errpipe_write, restore_signals, call_setsid, pgid_to_set, gid_object, extra_groups_packed, uid_object, child_umask, preexec_fn); exit: return return_value; } -/*[clinic end generated code: output=48555f5965a871be input=a9049054013a1b77]*/ +/*[clinic end generated code: output=942bc2748a9c2785 input=a9049054013a1b77]*/