Issue #15726: Fix incorrect bounds checking in PyState_FindModule.

Patch by Robin Schreiber.

Misc/NEWS

@@ -10,6 +10,9 @@ What's New in Python 3.3.0 Release Candidate 1?
 Core and Builtins
 -----------------
 
+- Issue #15726: Fix incorrect bounds checking in PyState_FindModule.
+  Patch by Robin Schreiber.
+
 - Issue #15604: Update uses of PyObject_IsTrue() to check for and handle
   errors correctly.  Patch by Serhiy Storchaka.
 

Python/pystate.c

@@ -248,7 +248,7 @@ PyState_FindModule(struct PyModuleDef* module)
         return NULL;
     if (state->modules_by_index == NULL)
         return NULL;
-    if (index > PyList_GET_SIZE(state->modules_by_index))
+    if (index >= PyList_GET_SIZE(state->modules_by_index))
         return NULL;
     res = PyList_GET_ITEM(state->modules_by_index, index);
     return res==Py_None ? NULL : res;