diff -r c0e63937efa7 Objects/bytearrayobject.c
--- a/Objects/bytearrayobject.c	Wed Nov 20 00:14:49 2013 +0100
+++ b/Objects/bytearrayobject.c	Wed Nov 20 00:47:39 2013 +0100
@@ -453,6 +453,7 @@ bytearray_setslice_linear(PyByteArrayObj
     Py_ssize_t avail = hi - lo;
     char *buf = PyByteArray_AS_STRING(self);
     Py_ssize_t growth = bytes_len - avail;
+    int res = 0;
     assert(avail >= 0);
 
     if (growth != 0) {
@@ -482,8 +483,28 @@ bytearray_setslice_linear(PyByteArrayObj
         }
         /* XXX(nnorwitz): need to verify this can't overflow! */
         if (PyByteArray_Resize(
-                (PyObject *)self, Py_SIZE(self) + growth) < 0)
-            return -1;
+                (PyObject *)self, Py_SIZE(self) + growth) < 0) {
+            /* Issue #19578: Handling the memory allocation failure here is
+               tricky here because the bytearray object has already been
+               modified. Depending on growth and lo, the behaviour is
+               different.
+
+               If growth < 0 and lo != 0, the operation is completed, but a
+               MemoryError is still raised and the memory block is not
+               shrinked. Otherwise, the bytearray is restored in its previous
+               state and a MemoryError is raised. */
+            if (growth < 0 && lo != 0) {
+                /* memmove() removed bytes, the bytearray object cannot be
+                   restored in its previous state. */
+                Py_SIZE(self) += growth;
+                res = -1;
+            }
+            else {
+                if (growth < 0)
+                    self->ob_start += growth;
+                return -1;
+            }
+        }
         buf = PyByteArray_AS_STRING(self);
         if (growth > 0) {
             /* Make the place for the additional bytes */
@@ -500,7 +521,7 @@ bytearray_setslice_linear(PyByteArrayObj
 
     if (bytes_len > 0)
         memcpy(buf + lo, bytes, bytes_len);
-    return 0;
+    return res;
 }
 
 static int