bpo-38031: Fix a possible assertion failure in _io.FileIO() (GH-GH-5688)

(cherry picked from commit d386115039e75c332c8471c239cf7dc5dee791a7)

Co-authored-by: Zackery Spytz <zspytz@gmail.com>

3 files changed, 15 insertions, 1 deletions

diff --git a/Lib/test/test_io.py b/Lib/test/test_io.py
index fb83762..fcc7ebb 100644
--- a/Lib/test/test_io.py
+++ b/Lib/test/test_io.py
@@ -880,6 +880,14 @@ class IOTest(unittest.TestCase):
             open('non-existent', 'r', opener=badopener)
         self.assertEqual(str(cm.exception), 'opener returned -2')
 
+    def test_opener_invalid_fd(self):
+        # Check that OSError is raised with error code EBADF if the
+        # opener returns an invalid file descriptor (see gh-82212).
+        fd = os_helper.make_bad_fd()
+        with self.assertRaises(OSError) as cm:
+            self.open('foo', opener=lambda name, flags: fd)
+        self.assertEqual(cm.exception.errno, errno.EBADF)
+
     def test_fileio_closefd(self):
         # Issue #4841
         with self.open(__file__, 'rb') as f1, \
diff --git a/Misc/NEWS.d/next/Core and Builtins/2019-09-04-19-09-49.bpo-38031.Yq4L72.rst b/Misc/NEWS.d/next/Core and Builtins/2019-09-04-19-09-49.bpo-38031.Yq4L72.rst
new file mode 100644
index 0000000..b596437
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2019-09-04-19-09-49.bpo-38031.Yq4L72.rst
@@ -0,0 +1,2 @@
+Fix a possible assertion failure in :class:`io.FileIO` when the opener
+returns an invalid file descriptor.
diff --git a/Modules/_io/fileio.c b/Modules/_io/fileio.c
index b9856b3..bf34b7c 100644
--- a/Modules/_io/fileio.c
+++ b/Modules/_io/fileio.c
@@ -494,8 +494,12 @@ _Py_COMP_DIAG_POP
     ret = -1;
     if (!fd_is_own)
         self->fd = -1;
-    if (self->fd >= 0)
+    if (self->fd >= 0) {
+        PyObject *exc, *val, *tb;
+        PyErr_Fetch(&exc, &val, &tb);
         internal_close(self);
+        _PyErr_ChainExceptions(exc, val, tb);
+    }
 
  done:
 #ifdef MS_WINDOWS