Issue #21058: Fix a leak of file descriptor in tempfile.NamedTemporaryFile(),

close the file descriptor if os.fdopen() fails

Lib/tempfile.py

@@ -460,8 +460,12 @@ def NamedTemporaryFile(mode='w+b', bufsize=-1, suffix="",
         flags |= _os.O_TEMPORARY
 
     (fd, name) = _mkstemp_inner(dir, prefix, suffix, flags)
-    file = _os.fdopen(fd, mode, bufsize)
-    return _TemporaryFileWrapper(file, name, delete)
+    try:
+        file = _os.fdopen(fd, mode, bufsize)
+        return _TemporaryFileWrapper(file, name, delete)
+    except Exception:
+        _os.close(fd)
+        raise
 
 if _os.name != 'posix' or _os.sys.platform == 'cygwin':
     # On non-POSIX and Cygwin systems, assume that we cannot unlink a file

Lib/test/test_tempfile.py

@@ -771,6 +771,24 @@ class test_NamedTemporaryFile(TC):
                 pass
         self.assertRaises(ValueError, use_closed)
 
+    def test_no_leak_fd(self):
+        # Issue #21058: don't leak file descriptor when fdopen() fails
+        old_close = os.close
+        old_fdopen = os.fdopen
+        closed = []
+        def close(fd):
+            closed.append(fd)
+        def fdopen(*args):
+            raise ValueError()
+        os.close = close
+        os.fdopen = fdopen
+        try:
+            self.assertRaises(ValueError, tempfile.NamedTemporaryFile)
+            self.assertEqual(len(closed), 1)
+        finally:
+            os.close = old_close
+            os.fdopen = old_fdopen
+
     # How to test the mode and bufsize parameters?
 
 test_classes.append(test_NamedTemporaryFile)

Misc/NEWS

@@ -40,6 +40,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #21058: Fix a leak of file descriptor in tempfile.NamedTemporaryFile(),
+  close the file descriptor if os.fdopen() fails
+
 - Issue #20283: RE pattern methods now accept the string keyword parameters
   as documented.  The pattern and source keyword parameters are left as
   deprecated aliases.