gh-92888: Fix memoryview bad __index__ use after free (GH-92946) (GH-93950)

(cherry picked from commit 11190c4ad0)

Co-authored-by: chilaxan <35645806+chilaxan@users.noreply.github.com>
Co-authored-by: Serhiy Storchaka <3659035+serhiy-storchaka@users.noreply.github.com>

Lib/test/test_memoryview.py

@@ -545,6 +545,107 @@ class OtherTest(unittest.TestCase):
             with self.assertRaises(TypeError):
                 pickle.dumps(m, proto)
 
+    def test_use_released_memory(self):
+        # gh-92888: Previously it was possible to use a memoryview even after
+        # backing buffer is freed in certain cases. This tests that those
+        # cases raise an exception.
+        size = 128
+        def release():
+            m.release()
+            nonlocal ba
+            ba = bytearray(size)
+        class MyIndex:
+            def __index__(self):
+                release()
+                return 4
+        class MyFloat:
+            def __float__(self):
+                release()
+                return 4.25
+        class MyBool:
+            def __bool__(self):
+                release()
+                return True
+
+        ba = None
+        m = memoryview(bytearray(b'\xff'*size))
+        with self.assertRaises(ValueError):
+            m[MyIndex()]
+
+        ba = None
+        m = memoryview(bytearray(b'\xff'*size))
+        self.assertEqual(list(m[:MyIndex()]), [255] * 4)
+
+        ba = None
+        m = memoryview(bytearray(b'\xff'*size))
+        self.assertEqual(list(m[MyIndex():8]), [255] * 4)
+
+        ba = None
+        m = memoryview(bytearray(b'\xff'*size)).cast('B', (64, 2))
+        with self.assertRaisesRegex(ValueError, "operation forbidden"):
+            m[MyIndex(), 0]
+
+        ba = None
+        m = memoryview(bytearray(b'\xff'*size)).cast('B', (2, 64))
+        with self.assertRaisesRegex(ValueError, "operation forbidden"):
+            m[0, MyIndex()]
+
+        ba = None
+        m = memoryview(bytearray(b'\xff'*size))
+        with self.assertRaisesRegex(ValueError, "operation forbidden"):
+            m[MyIndex()] = 42
+        self.assertEqual(ba[:8], b'\0'*8)
+
+        ba = None
+        m = memoryview(bytearray(b'\xff'*size))
+        with self.assertRaisesRegex(ValueError, "operation forbidden"):
+            m[:MyIndex()] = b'spam'
+        self.assertEqual(ba[:8], b'\0'*8)
+
+        ba = None
+        m = memoryview(bytearray(b'\xff'*size))
+        with self.assertRaisesRegex(ValueError, "operation forbidden"):
+            m[MyIndex():8] = b'spam'
+        self.assertEqual(ba[:8], b'\0'*8)
+
+        ba = None
+        m = memoryview(bytearray(b'\xff'*size)).cast('B', (64, 2))
+        with self.assertRaisesRegex(ValueError, "operation forbidden"):
+            m[MyIndex(), 0] = 42
+        self.assertEqual(ba[8:16], b'\0'*8)
+        ba = None
+        m = memoryview(bytearray(b'\xff'*size)).cast('B', (2, 64))
+        with self.assertRaisesRegex(ValueError, "operation forbidden"):
+            m[0, MyIndex()] = 42
+        self.assertEqual(ba[:8], b'\0'*8)
+
+        ba = None
+        m = memoryview(bytearray(b'\xff'*size))
+        with self.assertRaisesRegex(ValueError, "operation forbidden"):
+            m[0] = MyIndex()
+        self.assertEqual(ba[:8], b'\0'*8)
+
+        for fmt in 'bhilqnBHILQN':
+            with self.subTest(fmt=fmt):
+                ba = None
+                m = memoryview(bytearray(b'\xff'*size)).cast(fmt)
+                with self.assertRaisesRegex(ValueError, "operation forbidden"):
+                    m[0] = MyIndex()
+                self.assertEqual(ba[:8], b'\0'*8)
+
+        for fmt in 'fd':
+            with self.subTest(fmt=fmt):
+                ba = None
+                m = memoryview(bytearray(b'\xff'*size)).cast(fmt)
+                with self.assertRaisesRegex(ValueError, "operation forbidden"):
+                    m[0] = MyFloat()
+                self.assertEqual(ba[:8], b'\0'*8)
+
+        ba = None
+        m = memoryview(bytearray(b'\xff'*size)).cast('?')
+        with self.assertRaisesRegex(ValueError, "operation forbidden"):
+            m[0] = MyBool()
+        self.assertEqual(ba[:8], b'\0'*8)
 
 if __name__ == "__main__":
     unittest.main()