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v0.5.1
https://github.com/python/cpython
09 December 2020, 11:06:31 UTC
Revision b90c68586e1f2c45c736dd38880f182be267e2ef authored by Miss Islington (bot) on 06 February 2018, 06:51:10 UTC, committed by Gregory P. Smith on 06 February 2018, 06:51:10 UTC 
bpo-32777: Fix _Py_set_inheritable async-safety in subprocess (GH-5560) (GH-5563)
 
Fix a rare but potential pre-exec child process deadlock in subprocess on POSIX systems when marking file descriptors inheritable on exec in the child process.  This bug appears to have been introduced in 3.4 with the inheritable file descriptors support.

This also changes Python/fileutils.c `set_inheritable` to use the "slow" two `fcntl` syscall path instead of the "fast" single `ioctl` syscall path when asked to be async signal safe (by way of being asked not to raise exceptions).  `ioctl` is not a POSIX async-signal-safe approved function.

ref: http://pubs.opengroup.org/onlinepubs/9699919799/functions/V2_chap02.html
(cherry picked from commit c1e46e94de38a92f98736af9a42d89c3975a9919)

Co-authored-by: Alexey Izbyshev <izbyshev@users.noreply.github.com>
1 parent 7bd5a75
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Tip revision: b90c68586e1f2c45c736dd38880f182be267e2ef authored by Miss Islington (bot) on 06 February 2018, 06:51:10 UTC
bpo-32777: Fix _Py_set_inheritable async-safety in subprocess (GH-5560) (GH-5563)
Tip revision: b90c685
test_stringptr.py 
import unittest
from test import support
from ctypes import *

import _ctypes_test

lib = CDLL(_ctypes_test.__file__)

class StringPtrTestCase(unittest.TestCase):

    @support.refcount_test
    def test__POINTER_c_char(self):
        class X(Structure):
            _fields_ = [("str", POINTER(c_char))]
        x = X()

        # NULL pointer access
        self.assertRaises(ValueError, getattr, x.str, "contents")
        b = c_buffer(b"Hello, World")
        from sys import getrefcount as grc
        self.assertEqual(grc(b), 2)
        x.str = b
        self.assertEqual(grc(b), 3)

        # POINTER(c_char) and Python string is NOT compatible
        # POINTER(c_char) and c_buffer() is compatible
        for i in range(len(b)):
            self.assertEqual(b[i], x.str[i])

        self.assertRaises(TypeError, setattr, x, "str", "Hello, World")

    def test__c_char_p(self):
        class X(Structure):
            _fields_ = [("str", c_char_p)]
        x = X()

        # c_char_p and Python string is compatible
        # c_char_p and c_buffer is NOT compatible
        self.assertEqual(x.str, None)
        x.str = b"Hello, World"
        self.assertEqual(x.str, b"Hello, World")
        b = c_buffer(b"Hello, World")
        self.assertRaises(TypeError, setattr, x, b"str", b)


    def test_functions(self):
        strchr = lib.my_strchr
        strchr.restype = c_char_p

        # c_char_p and Python string is compatible
        # c_char_p and c_buffer are now compatible
        strchr.argtypes = c_char_p, c_char
        self.assertEqual(strchr(b"abcdef", b"c"), b"cdef")
        self.assertEqual(strchr(c_buffer(b"abcdef"), b"c"), b"cdef")

        # POINTER(c_char) and Python string is NOT compatible
        # POINTER(c_char) and c_buffer() is compatible
        strchr.argtypes = POINTER(c_char), c_char
        buf = c_buffer(b"abcdef")
        self.assertEqual(strchr(buf, b"c"), b"cdef")
        self.assertEqual(strchr(b"abcdef", b"c"), b"cdef")

        # XXX These calls are dangerous, because the first argument
        # to strchr is no longer valid after the function returns!
        # So we must keep a reference to buf separately

        strchr.restype = POINTER(c_char)
        buf = c_buffer(b"abcdef")
        r = strchr(buf, b"c")
        x = r[0], r[1], r[2], r[3], r[4]
        self.assertEqual(x, (b"c", b"d", b"e", b"f", b"\000"))
        del buf
        # x1 will NOT be the same as x, usually:
        x1 = r[0], r[1], r[2], r[3], r[4]

if __name__ == '__main__':
    unittest.main()
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