[BUGFIX] Assure NDArray.reshape does not change the array size

python/mxnet/ndarray/ndarray.py

@@ -1546,7 +1546,12 @@ def reshape(self, *shape, **kwargs):
                                            c_array(ctypes.c_int64, shape),
                                            reverse,
                                            ctypes.byref(handle)))
-        return self.__class__(handle=handle, writable=self.writable)
+        res = self.__class__(handle=handle, writable=self.writable)
+
+        # Array size should not change
+        if np.prod(res.shape) != np.prod(self.shape):
+            raise ValueError('Cannot reshape array of size {} into shape {}'.format(np.prod(self.shape), shape))
+        return res
 
     def reshape_like(self, *args, **kwargs):
         """Convenience fluent method for :py:func:`reshape_like`.

tests/python/unittest/test_ndarray.py

@@ -237,7 +237,8 @@ def test_ndarray_reshape():
     assert same(tensor.reshape(-1, 15).reshape(0, -4, 3, -1).asnumpy(), true_res.reshape(2, 3, 5).asnumpy())
     assert same(tensor.reshape(-1, 0).asnumpy(), true_res.reshape(10, 3).asnumpy())
     assert same(tensor.reshape(-1, 0, reverse=True).asnumpy(), true_res.reshape(6, 5).asnumpy())
-
+    # https://github.com/apache/incubator-mxnet/issues/18886
+    assertRaises(ValueError, tensor.reshape, (2, 3))
 
 @with_seed()
 def test_ndarray_flatten():