issue7213: Open the pipes used by subprocesses with the FD_CLOEXEC flag from

the C code, using pipe2() when available.  Adds unittests for close_fds and
cloexec behaviors.

6 files changed, 147 insertions, 15 deletions

diff --git a/Lib/subprocess.py b/Lib/subprocess.py
index 62dfd36..729a53b 100644
--- a/Lib/subprocess.py
+++ b/Lib/subprocess.py
@@ -390,6 +390,23 @@ else:
     # POSIX defines PIPE_BUF as >= 512.
     _PIPE_BUF = getattr(select, 'PIPE_BUF', 512)
 
+    if _posixsubprocess:
+        _create_pipe = _posixsubprocess.cloexec_pipe
+    else:
+        def _create_pipe():
+            try:
+                cloexec_flag = fcntl.FD_CLOEXEC
+            except AttributeError:
+                cloexec_flag = 1
+
+            fds = os.pipe()
+
+            old = fcntl.fcntl(fds[0], fcntl.F_GETFD)
+            fcntl.fcntl(fds[0], fcntl.F_SETFD, old | cloexec_flag)
+            old = fcntl.fcntl(fds[1], fcntl.F_GETFD)
+            fcntl.fcntl(fds[1], fcntl.F_SETFD, old | cloexec_flag)
+
+            return fds
 
 __all__ = ["Popen", "PIPE", "STDOUT", "call", "check_call", "getstatusoutput",
            "getoutput", "check_output", "CalledProcessError"]
@@ -1031,7 +1048,7 @@ class Popen(object):
             if stdin is None:
                 pass
             elif stdin == PIPE:
-                p2cread, p2cwrite = os.pipe()
+                p2cread, p2cwrite = _create_pipe()
             elif isinstance(stdin, int):
                 p2cread = stdin
             else:
@@ -1041,7 +1058,7 @@ class Popen(object):
             if stdout is None:
                 pass
             elif stdout == PIPE:
-                c2pread, c2pwrite = os.pipe()
+                c2pread, c2pwrite = _create_pipe()
             elif isinstance(stdout, int):
                 c2pwrite = stdout
             else:
@@ -1051,7 +1068,7 @@ class Popen(object):
             if stderr is None:
                 pass
             elif stderr == PIPE:
-                errread, errwrite = os.pipe()
+                errread, errwrite = _create_pipe()
             elif stderr == STDOUT:
                 errwrite = c2pwrite
             elif isinstance(stderr, int):
@@ -1065,16 +1082,6 @@ class Popen(object):
                     errread, errwrite)
 
 
-        def _set_cloexec_flag(self, fd):
-            try:
-                cloexec_flag = fcntl.FD_CLOEXEC
-            except AttributeError:
-                cloexec_flag = 1
-
-            old = fcntl.fcntl(fd, fcntl.F_GETFD)
-            fcntl.fcntl(fd, fcntl.F_SETFD, old | cloexec_flag)
-
-
         def _close_fds(self, but):
             os.closerange(3, but)
             os.closerange(but + 1, MAXFD)
@@ -1116,10 +1123,9 @@ class Popen(object):
             # For transferring possible exec failure from child to parent.
             # Data format: "exception name:hex errno:description"
             # Pickle is not used; it is complex and involves memory allocation.
-            errpipe_read, errpipe_write = os.pipe()
+            errpipe_read, errpipe_write = _create_pipe()
             try:
                 try:
-                    self._set_cloexec_flag(errpipe_write)
 
                     if _posixsubprocess:
                         # We must avoid complex work that could involve
diff --git a/Lib/test/subprocessdata/fd_status.py b/Lib/test/subprocessdata/fd_status.py
new file mode 100644
index 0000000..083b2f9
--- /dev/null
+++ b/Lib/test/subprocessdata/fd_status.py
@@ -0,0 +1,24 @@
+"""When called as a script, print a comma-separated list of the open
+file descriptors on stdout."""
+
+import errno
+import os
+import fcntl
+
+try:
+    _MAXFD = os.sysconf("SC_OPEN_MAX")
+except:
+    _MAXFD = 256
+
+def isopen(fd):
+    """Return True if the fd is open, and False otherwise"""
+    try:
+        fcntl.fcntl(fd, fcntl.F_GETFD, 0)
+    except IOError as e:
+        if e.errno == errno.EBADF:
+            return False
+        raise
+    return True
+
+if __name__ == "__main__":
+    print(','.join(str(fd) for fd in range(0, _MAXFD) if isopen(fd)))
diff --git a/Lib/test/subprocessdata/input_reader.py b/Lib/test/subprocessdata/input_reader.py
new file mode 100644
index 0000000..ccae5f3
--- /dev/null
+++ b/Lib/test/subprocessdata/input_reader.py
@@ -0,0 +1,7 @@
+"""When called as a script, consumes the input"""
+
+import sys
+
+if __name__ = "__main__":
+    for line in sys.stdin:
+        pass
diff --git a/Lib/test/subprocessdata/qcat.py b/Lib/test/subprocessdata/qcat.py
new file mode 100644
index 0000000..fe6f9db
--- /dev/null
+++ b/Lib/test/subprocessdata/qcat.py
@@ -0,0 +1,7 @@
+"""When ran as a script, simulates cat with no arguments."""
+
+import sys
+
+if __name__ == "__main__":
+    for line in sys.stdin:
+        sys.stdout.write(line)
diff --git a/Lib/test/subprocessdata/qgrep.py b/Lib/test/subprocessdata/qgrep.py
new file mode 100644
index 0000000..6990637
--- /dev/null
+++ b/Lib/test/subprocessdata/qgrep.py
@@ -0,0 +1,10 @@
+"""When called with a single argument, simulated fgrep with a single
+argument and no options."""
+
+import sys
+
+if __name__ == "__main__":
+    pattern = sys.argv[1]
+    for line in sys.stdin:
+        if pattern in line:
+            sys.stdout.write(line)
diff --git a/Lib/test/test_subprocess.py b/Lib/test/test_subprocess.py
index eaa26d2..74e7404 100644
--- a/Lib/test/test_subprocess.py
+++ b/Lib/test/test_subprocess.py
@@ -10,6 +10,7 @@ import time
 import re
 import sysconfig
 import warnings
+import select
 try:
     import gc
 except ImportError:
@@ -964,6 +965,83 @@ class POSIXProcessTestCase(BaseTestCase):
         exitcode = subprocess.call([program, "-c", "pass"], env=envb)
         self.assertEqual(exitcode, 0)
 
+    def test_pipe_cloexec(self):
+        sleeper = support.findfile("input_reader.py", subdir="subprocessdata")
+        fd_status = support.findfile("fd_status.py", subdir="subprocessdata")
+
+        p1 = subprocess.Popen([sys.executable, sleeper],
+                              stdin=subprocess.PIPE, stdout=subprocess.PIPE,
+                              stderr=subprocess.PIPE, close_fds=False)
+
+        self.addCleanup(p1.communicate, b'')
+
+        p2 = subprocess.Popen([sys.executable, fd_status],
+                              stdout=subprocess.PIPE, close_fds=False)
+
+        output, error = p2.communicate()
+        result_fds = set(map(int, output.split(b',')))
+        unwanted_fds = set([p1.stdin.fileno(), p1.stdout.fileno(),
+                            p1.stderr.fileno()])
+
+        self.assertFalse(result_fds & unwanted_fds,
+                         "Expected no fds from %r to be open in child, "
+                         "found %r" %
+                              (unwanted_fds, result_fds & unwanted_fds))
+
+    def test_pipe_cloexec_real_tools(self):
+        qcat = support.findfile("qcat.py", subdir="subprocessdata")
+        qgrep = support.findfile("qgrep.py", subdir="subprocessdata")
+
+        subdata = b'zxcvbn'
+        data = subdata * 4 + b'\n'
+
+        p1 = subprocess.Popen([sys.executable, qcat],
+                              stdin=subprocess.PIPE, stdout=subprocess.PIPE,
+                              close_fds=False)
+
+        p2 = subprocess.Popen([sys.executable, qgrep, subdata],
+                              stdin=p1.stdout, stdout=subprocess.PIPE,
+                              close_fds=False)
+
+        self.addCleanup(p1.wait)
+        self.addCleanup(p2.wait)
+        self.addCleanup(p1.terminate)
+        self.addCleanup(p2.terminate)
+
+        p1.stdin.write(data)
+        p1.stdin.close()
+
+        readfiles, ignored1, ignored2 = select.select([p2.stdout], [], [], 10)
+
+        self.assertTrue(readfiles, "The child hung")
+        self.assertEqual(p2.stdout.read(), data)
+
+    def test_close_fds(self):
+        fd_status = support.findfile("fd_status.py", subdir="subprocessdata")
+
+        fds = os.pipe()
+        self.addCleanup(os.close, fds[0])
+        self.addCleanup(os.close, fds[1])
+
+        open_fds = set(fds)
+
+        p = subprocess.Popen([sys.executable, fd_status],
+                             stdout=subprocess.PIPE, close_fds=False)
+        output, ignored = p.communicate()
+        remaining_fds = set(map(int, output.split(b',')))
+
+        self.assertEqual(remaining_fds & open_fds, open_fds,
+                         "Some fds were closed")
+
+        p = subprocess.Popen([sys.executable, fd_status],
+                             stdout=subprocess.PIPE, close_fds=True)
+        output, ignored = p.communicate()
+        remaining_fds = set(map(int, output.split(b',')))
+
+        self.assertFalse(remaining_fds & open_fds,
+                         "Some fds were left open")
+        self.assertIn(1, remaining_fds, "Subprocess failed")
+
 
 @unittest.skipUnless(mswindows, "Windows specific tests")
 class Win32ProcessTestCase(BaseTestCase):