Issue #25659: Merge ctypes fix from 3.6

3 files changed, 20 insertions, 3 deletions

diff --git a/Lib/ctypes/test/test_frombuffer.py b/Lib/ctypes/test/test_frombuffer.py
index 29c5a19328..7ab38f1b03 100644
--- a/Lib/ctypes/test/test_frombuffer.py
+++ b/Lib/ctypes/test/test_frombuffer.py
@@ -120,5 +120,13 @@ class Test(unittest.TestCase):
         with self.assertRaises(ValueError):
             (c_int * 1).from_buffer_copy(a, 16 * sizeof(c_int))
 
+    def test_abstract(self):
+        self.assertRaises(TypeError, Array.from_buffer, bytearray(10))
+        self.assertRaises(TypeError, Structure.from_buffer, bytearray(10))
+        self.assertRaises(TypeError, Union.from_buffer, bytearray(10))
+        self.assertRaises(TypeError, Array.from_buffer_copy, b"123")
+        self.assertRaises(TypeError, Structure.from_buffer_copy, b"123")
+        self.assertRaises(TypeError, Union.from_buffer_copy, b"123")
+
 if __name__ == '__main__':
     unittest.main()
diff --git a/Misc/NEWS b/Misc/NEWS
index b965a75b0d..bbd0b4179f 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -131,6 +131,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #25659: In ctypes, prevent a crash calling the from_buffer() and
+  from_buffer_copy() methods on abstract classes like Array.
+
 - Issue #28548: In the "http.server" module, parse the protocol version if
   possible, to avoid using HTTP 0.9 in some error responses.
 
diff --git a/Modules/_ctypes/_ctypes.c b/Modules/_ctypes/_ctypes.c
index de1ae3d0cb..0a9201e3f4 100644
--- a/Modules/_ctypes/_ctypes.c
+++ b/Modules/_ctypes/_ctypes.c
@@ -463,7 +463,10 @@ CDataType_from_buffer(PyObject *type, PyObject *args)
     Py_ssize_t offset = 0;
 
     StgDictObject *dict = PyType_stgdict(type);
-    assert (dict);
+    if (!dict) {
+        PyErr_SetString(PyExc_TypeError, "abstract class");
+        return NULL;
+    }
 
     if (!PyArg_ParseTuple(args, "O|n:from_buffer", &obj, &offset))
         return NULL;
@@ -531,9 +534,12 @@ CDataType_from_buffer_copy(PyObject *type, PyObject *args)
     Py_ssize_t offset = 0;
     PyObject *result;
     StgDictObject *dict = PyType_stgdict(type);
-    assert (dict);
+    if (!dict) {
+        PyErr_SetString(PyExc_TypeError, "abstract class");
+        return NULL;
+    }
 
-    if (!PyArg_ParseTuple(args, "y*|n:from_buffer", &buffer, &offset))
+    if (!PyArg_ParseTuple(args, "y*|n:from_buffer_copy", &buffer, &offset))
         return NULL;
 
     if (offset < 0) {