gh-110260: Check for PyList_SetItem() errors in termios module (GH-110261)

Author: sobolevn

Modules/termios.c

@@ -120,37 +120,52 @@ termios_tcgetattr_impl(PyObject *module, int fd)
         v = PyBytes_FromStringAndSize(&ch, 1);
         if (v == NULL)
             goto err;
-        PyList_SetItem(cc, i, v);
+        PyList_SET_ITEM(cc, i, v);
     }
 
     /* Convert the MIN and TIME slots to integer.  On some systems, the
        MIN and TIME slots are the same as the EOF and EOL slots.  So we
        only do this in noncanonical input mode.  */
     if ((mode.c_lflag & ICANON) == 0) {
         v = PyLong_FromLong((long)mode.c_cc[VMIN]);
-        if (v == NULL)
+        if (v == NULL) {
+            goto err;
+        }
+        if (PyList_SetItem(cc, VMIN, v) < 0) {
             goto err;
-        PyList_SetItem(cc, VMIN, v);
+        }
         v = PyLong_FromLong((long)mode.c_cc[VTIME]);
-        if (v == NULL)
+        if (v == NULL) {
+            goto err;
+        }
+        if (PyList_SetItem(cc, VTIME, v) < 0) {
             goto err;
-        PyList_SetItem(cc, VTIME, v);
+        }
     }
 
-    if (!(v = PyList_New(7)))
-        goto err;
-
-    PyList_SetItem(v, 0, PyLong_FromLong((long)mode.c_iflag));
-    PyList_SetItem(v, 1, PyLong_FromLong((long)mode.c_oflag));
-    PyList_SetItem(v, 2, PyLong_FromLong((long)mode.c_cflag));
-    PyList_SetItem(v, 3, PyLong_FromLong((long)mode.c_lflag));
-    PyList_SetItem(v, 4, PyLong_FromLong((long)ispeed));
-    PyList_SetItem(v, 5, PyLong_FromLong((long)ospeed));
-    if (PyErr_Occurred()) {
-        Py_DECREF(v);
+    if (!(v = PyList_New(7))) {
         goto err;
     }
-    PyList_SetItem(v, 6, cc);
+
+#define ADD_LONG_ITEM(index, val) \
+    do { \
+        PyObject *l = PyLong_FromLong((long)val); \
+        if (l == NULL) { \
+            Py_DECREF(v); \
+            goto err; \
+        } \
+        PyList_SET_ITEM(v, index, l); \
+    } while (0)
+
+    ADD_LONG_ITEM(0, mode.c_iflag);
+    ADD_LONG_ITEM(1, mode.c_oflag);
+    ADD_LONG_ITEM(2, mode.c_cflag);
+    ADD_LONG_ITEM(3, mode.c_lflag);
+    ADD_LONG_ITEM(4, ispeed);
+    ADD_LONG_ITEM(5, ospeed);
+#undef ADD_LONG_ITEM
+
+    PyList_SET_ITEM(v, 6, cc);
     return v;
   err:
     Py_DECREF(cc);