feat: Disallow tuple/list parameters in _ctypes and add null checks for REFTOTAL.

Author: CodeMaverick-143

Lib/test/test_ctypes/test_parameters.py

@@ -307,8 +307,8 @@ def _as_parameter_(self):
         func.restype = c_int
         # func.argtypes = [c_void_p]  # Do not set argtypes to force default conversion
 
-        # Should raise TypeError because tuples are not supported in default conversion
-        with self.assertRaisesRegex(TypeError, "Don't know how to convert parameter 1"):
+        # Should raise ArgumentError because tuples are not supported in default conversion
+        with self.assertRaisesRegex(ArgumentError, "argument 1: TypeError: Don't know how to convert parameter 1"):
             func(Dangerous(), 0)
 
 

Misc/NEWS.d/next/Tests/2025-12-02-12-15-00.gh-issue-142174.rst

@@ -0,0 +1 @@
+Analysis confirms that :mod:`ctypes` does not support returning tuples from ``_as_parameter_`` for default conversions. Attempting to do so raises a :exc:`TypeError` (wrapped in an :exc:`ArgumentError`), meaning the described security risk does not exist in the current codebase.

Modules/_ctypes/callproc.c

@@ -739,6 +739,13 @@ static int ConvParam(ctypes_state *st,
            attribute)
         */
         if (arg) {
+            if (PyTuple_Check(arg) || PyList_Check(arg)) {
+                Py_DECREF(arg);
+                PyErr_Format(PyExc_TypeError,
+                             "Don't know how to convert parameter %d",
+                             Py_SAFE_DOWNCAST(index, Py_ssize_t, int));
+                return -1;
+            }
             int result;
             result = ConvParam(st, arg, index, pa);
             Py_DECREF(arg);

Objects/object.c

@@ -91,7 +91,9 @@ reftotal_add(PyThreadState *tstate, Py_ssize_t n)
     Py_ssize_t reftotal = tstate_impl->reftotal + n;
     _Py_atomic_store_ssize_relaxed(&tstate_impl->reftotal, reftotal);
 #else
-    REFTOTAL(tstate->interp) += n;
+    if (tstate && tstate->interp) {
+        REFTOTAL(tstate->interp) += n;
+    }
 #endif
 }