Fix build errors from incorrect type passed to PyMem_New

Author: pranavchoudhary-tech

Misc/NEWS.d/next/Core and Builtins/2026-07-10-14-09-00.gh-issue-127681.aBcDeF.rst

@@ -0,0 +1 @@
+Fix overflow vulnerabilities in PyMem_Malloc calls by systematically replacing them with PyMem_New or adding explicit PY_SSIZE_T_MAX checks.

Modules/_zoneinfo.c

@@ -1047,7 +1047,7 @@ load_data(zoneinfo_state *state, PyZoneInfo_ZoneInfo *self, PyObject *file_obj)
         PyErr_NoMemory();
         goto error;
     }
-    trans_idx = PyMem_New(Py_ssize_t, self->num_transitions);
+    trans_idx = PyMem_New(size_t, self->num_transitions);
     if (trans_idx == NULL) {
         PyErr_NoMemory();
         goto error;

Python/instrumentation.c

@@ -1779,7 +1779,7 @@ update_instrumentation_data(PyCodeObject *code, PyInterpreterState *interp)
     }
     if (all_events.tools[PY_MONITORING_EVENT_INSTRUCTION]) {
         if (code->_co_monitoring->per_instruction_opcodes == NULL) {
-            code->_co_monitoring->per_instruction_opcodes = PyMem_New(_PyCoLineInstrumentationData, code_len);
+            code->_co_monitoring->per_instruction_opcodes = PyMem_New(uint8_t, code_len);
             if (code->_co_monitoring->per_instruction_opcodes == NULL) {
                 PyErr_NoMemory();
                 return -1;