Issue #5292: Fixed mmap crash on its boundary access m[len(m)].

Lib/test/test_mmap.py

@@ -41,6 +41,10 @@ class MmapTests(unittest.TestCase):
             self.assertEqual(m[0], '\0')
             self.assertEqual(m[0:3], '\0\0\0')
 
+            # Shouldn't crash on boundary (Issue #5292)
+            self.assertRaises(IndexError, m.__getitem__, len(m))
+            self.assertRaises(IndexError, m.__setitem__, len(m), '\0')
+
             # Modify the file's content
             m[0] = '3'
             m[PAGESIZE +3: PAGESIZE +3+3] = 'bar'

Misc/NEWS

@@ -159,6 +159,8 @@ Core and Builtins
 Library
 -------
 
+- Issue #5292: Fixed mmap crash on its boundary access m[len(m)].
+
 - Issue #2279: distutils.sdist.add_defaults now add files 
   from the package_data and the data_files metadata.
 

Modules/mmapmodule.c

@@ -731,7 +731,7 @@ mmap_subscript(mmap_object *self, PyObject *item)
 			return NULL;
 		if (i < 0)
 			i += self->size;
-		if (i < 0 || (size_t)i > self->size) {
+		if (i < 0 || (size_t)i >= self->size) {
 			PyErr_SetString(PyExc_IndexError,
 				"mmap index out of range");
 			return NULL;
@@ -872,7 +872,7 @@ mmap_ass_subscript(mmap_object *self, PyObject *item, PyObject *value)
 			return -1;
 		if (i < 0)
 			i += self->size;
-		if (i < 0 || (size_t)i > self->size) {
+		if (i < 0 || (size_t)i >= self->size) {
 			PyErr_SetString(PyExc_IndexError,
 				"mmap index out of range");
 			return -1;