[Python-checkins] gh-105375: Improve error handling in _ctypes (#105593)

[erlend-aasland]

https://github.com/python/cpython/commit/e8998e46a7ce8ad336e0941a6da6e50cb88d1e47
commit: e8998e46a7ce8ad336e0941a6da6e50cb88d1e47
branch: main
author: Erlend E. Aasland <erlend.aasland at protonmail.com>
committer: erlend-aasland <erlend.aasland at protonmail.com>
date: 2023-06-11T19:46:19Z
summary:

gh-105375: Improve error handling in _ctypes (#105593)

Prevent repeated PyLong_FromVoidPtr() from possibly overwriting the
current exception.

files:
A Misc/NEWS.d/next/Library/2023-06-09-21-40-45.gh-issue-105375._sZilh.rst
M Modules/_ctypes/callbacks.c

diff --git a/Misc/NEWS.d/next/Library/2023-06-09-21-40-45.gh-issue-105375._sZilh.rst b/Misc/NEWS.d/next/Library/2023-06-09-21-40-45.gh-issue-105375._sZilh.rst
new file mode 100644
index 0000000000000..87db4c2b4e22e
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2023-06-09-21-40-45.gh-issue-105375._sZilh.rst
@@ -0,0 +1 @@
+Fix bugs in :mod:`_ctypes` where exceptions could end up being overwritten.
diff --git a/Modules/_ctypes/callbacks.c b/Modules/_ctypes/callbacks.c
index 8e694ba852c1d..d71297f9c5c2f 100644
--- a/Modules/_ctypes/callbacks.c
+++ b/Modules/_ctypes/callbacks.c
@@ -479,12 +479,22 @@ long Call_GetClassObject(REFCLSID rclsid, REFIID riid, LPVOID *ppv)
 
     {
         PyObject *py_rclsid = PyLong_FromVoidPtr((void *)rclsid);
+        if (py_rclsid == NULL) {
+            Py_DECREF(func);
+            PyErr_WriteUnraisable(context ? context : Py_None);
+            return E_FAIL;
+        }
         PyObject *py_riid = PyLong_FromVoidPtr((void *)riid);
+        if (py_riid == NULL) {
+            Py_DECREF(func);
+            Py_DECREF(py_rclsid);
+            PyErr_WriteUnraisable(context ? context : Py_None);
+            return E_FAIL;
+        }
         PyObject *py_ppv = PyLong_FromVoidPtr(ppv);
-        if (!py_rclsid || !py_riid || !py_ppv) {
-            Py_XDECREF(py_rclsid);
-            Py_XDECREF(py_riid);
-            Py_XDECREF(py_ppv);
+        if (py_ppv == NULL) {
+            Py_DECREF(py_rclsid);
+            Py_DECREF(py_riid);
             Py_DECREF(func);
             PyErr_WriteUnraisable(context ? context : Py_None);
             return E_FAIL;