Index: python3/Lib/test/test_subprocess.py
===================================================================
--- python3.orig/Lib/test/test_subprocess.py
+++ python3/Lib/test/test_subprocess.py
@@ -621,6 +621,16 @@ class ProcessTestCase(BaseTestCase):
         self.assertFalse(os.path.exists(ofname))
         self.assertFalse(os.path.exists(efname))
 
+    def test_inouterr_fileobj(self):
+        # stdin, stdout and stderr are all set to a /dev/null file object
+        devnull = os.open(os.devnull, os.O_RDWR)
+        p = subprocess.Popen([sys.executable, "-c", 'import sys; sys.exit(0)'],
+                             stdin = devnull,
+                             stdout = devnull,
+                             stderr = devnull)
+        p.wait()
+        self.assertEqual(p.returncode, 0)
+
 
 # context manager
 class _SuppressCoreFiles(object):
Index: python3/Modules/_posixsubprocess.c
===================================================================
--- python3.orig/Modules/_posixsubprocess.c
+++ python3/Modules/_posixsubprocess.c
@@ -99,10 +99,10 @@ static void child_exec(char *const exec_
     if (p2cread > 2) {
         POSIX_CALL(close(p2cread));
     }
-    if (c2pwrite > 2) {
+    if (c2pwrite != p2cread && c2pwrite > 2) {
         POSIX_CALL(close(c2pwrite));
     }
-    if (errwrite != c2pwrite && errwrite > 2) {
+    if (errwrite != p2cread && errwrite != c2pwrite && errwrite > 2) {
         POSIX_CALL(close(errwrite));
     }