Issue #12786: Set communication pipes used by subprocess.Popen CLOEXEC to avoid
them being inherited by other subprocesses.
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@ -1035,7 +1035,7 @@ class Popen(object):
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if stdin is None:
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pass
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elif stdin == PIPE:
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p2cread, p2cwrite = os.pipe()
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p2cread, p2cwrite = self.pipe_cloexec()
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elif isinstance(stdin, int):
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p2cread = stdin
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else:
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@ -1045,7 +1045,7 @@ class Popen(object):
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if stdout is None:
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pass
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elif stdout == PIPE:
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c2pread, c2pwrite = os.pipe()
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c2pread, c2pwrite = self.pipe_cloexec()
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elif isinstance(stdout, int):
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c2pwrite = stdout
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else:
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@ -1055,7 +1055,7 @@ class Popen(object):
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if stderr is None:
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pass
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elif stderr == PIPE:
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errread, errwrite = os.pipe()
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errread, errwrite = self.pipe_cloexec()
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elif stderr == STDOUT:
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errwrite = c2pwrite
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elif isinstance(stderr, int):
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@ -1082,6 +1082,18 @@ class Popen(object):
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fcntl.fcntl(fd, fcntl.F_SETFD, old & ~cloexec_flag)
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def pipe_cloexec(self):
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"""Create a pipe with FDs set CLOEXEC."""
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# Pipes' FDs are set CLOEXEC by default because we don't want them
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# to be inherited by other subprocesses: the CLOEXEC flag is removed
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# from the child's FDs by _dup2(), between fork() and exec().
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# This is not atomic: we would need the pipe2() syscall for that.
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r, w = os.pipe()
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self._set_cloexec_flag(r)
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self._set_cloexec_flag(w)
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return r, w
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def _close_fds(self, but):
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if hasattr(os, 'closerange'):
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os.closerange(3, but)
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@ -1120,11 +1132,9 @@ class Popen(object):
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# For transferring possible exec failure from child to parent
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# The first char specifies the exception type: 0 means
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# OSError, 1 means some other error.
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errpipe_read, errpipe_write = os.pipe()
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errpipe_read, errpipe_write = self.pipe_cloexec()
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try:
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try:
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self._set_cloexec_flag(errpipe_write)
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gc_was_enabled = gc.isenabled()
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# Disable gc to avoid bug where gc -> file_dealloc ->
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# write to stderr -> hang. http://bugs.python.org/issue1336
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@ -995,6 +995,37 @@ class POSIXProcessTestCase(BaseTestCase):
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self.assertRaises(OSError, os.waitpid, pid, 0)
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self.assertNotIn(ident, [id(o) for o in subprocess._active])
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def test_pipe_cloexec(self):
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# Issue 12786: check that the communication pipes' FDs are set CLOEXEC,
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# and are not inherited by another child process.
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p1 = subprocess.Popen([sys.executable, "-c",
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'import os;'
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'os.read(0, 1)'
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],
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stdin=subprocess.PIPE, stdout=subprocess.PIPE,
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stderr=subprocess.PIPE)
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p2 = subprocess.Popen([sys.executable, "-c", """if True:
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import os, errno, sys
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for fd in %r:
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try:
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os.close(fd)
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except OSError as e:
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if e.errno != errno.EBADF:
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raise
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else:
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sys.exit(1)
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sys.exit(0)
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""" % [f.fileno() for f in (p1.stdin, p1.stdout,
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p1.stderr)]
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],
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stdin=subprocess.PIPE, stdout=subprocess.PIPE,
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stderr=subprocess.PIPE, close_fds=False)
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p1.communicate('foo')
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_, stderr = p2.communicate()
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self.assertEqual(p2.returncode, 0, "Unexpected error: " + repr(stderr))
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@unittest.skipUnless(mswindows, "Windows specific tests")
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class Win32ProcessTestCase(BaseTestCase):
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