ctypes callback functions only support 'fundamental' result types.

Check this and raise an error when something else is used - before
this change ctypes would hang or crash when such a callback was
called.  This is a partial fix for #1574584.

Will backport to release25-maint.

1 files changed, 5 insertions, 2 deletions

diff --git a/Modules/_ctypes/callbacks.c b/Modules/_ctypes/callbacks.c
index 41ec0f5..0e5d6c0 100644
--- a/Modules/_ctypes/callbacks.c
+++ b/Modules/_ctypes/callbacks.c
@@ -293,8 +293,11 @@ ffi_info *AllocFunctionCallback(PyObject *callable,
 		p->restype = &ffi_type_void;
 	} else {
 		StgDictObject *dict = PyType_stgdict(restype);
-		if (dict == NULL)
-			goto error;
+		if (dict == NULL || dict->setfunc == NULL) {
+		  PyErr_SetString(PyExc_TypeError,
+				  "invalid result type for callback function");
+		  goto error;
+		}
 		p->setfunc = dict->setfunc;
 		p->restype = &dict->ffi_type_pointer;
 	}