Issue #6274. Fixed a potential FD leak in subprocess.py.

Lib/subprocess.py

@@ -999,6 +999,8 @@ class Popen(object):
             # The first char specifies the exception type: 0 means
             # OSError, 1 means some other error.
             errpipe_read, errpipe_write = os.pipe()
+            try:
+                try:
                     self._set_cloexec_flag(errpipe_write)
 
                     gc_was_enabled = gc.isenabled()
@@ -1072,7 +1074,10 @@ class Popen(object):
                     # Parent
                     if gc_was_enabled:
                         gc.enable()
+                finally:
+                    # be sure the FD is closed no matter what
                     os.close(errpipe_write)
+
                 if p2cread is not None and p2cwrite is not None:
                     os.close(p2cread)
                 if c2pwrite is not None and c2pread is not None:
@@ -1082,7 +1087,10 @@ class Popen(object):
 
                 # Wait for exec to fail or succeed; possibly raising exception
                 data = os.read(errpipe_read, 1048576) # Exceptions limited to 1 MB
+            finally:
+                # be sure the FD is closed no matter what
                 os.close(errpipe_read)
+
             if data != "":
                 os.waitpid(self.pid, 0)
                 child_exception = pickle.loads(data)

Misc/NEWS

@@ -56,6 +56,8 @@ Core and Builtins
 Library
 -------
 
+- Issue #6274: Fixed possible file descriptors leak in subprocess.py
+
 - Issue #6271: mmap tried to close invalid file handle (-1) when annonymous.
   (On Unix)