Merge branch 'for-4.14-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

Pull cgroup fix from Tejun Heo:
 "The recent migration code updates assumed that migrations always
  execute from the top to the bottom once and didn't clean up internal
  states after each migration round; however, cgroup_transfer_tasks()
  repeats the inner steps multiple times and the garbage internal states
  from the previous iteration led to OOPS.

  Waiman fixed the bug by reinitializing the relevant states at the end
  of each migration round"

* 'for-4.14-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
  cgroup: Reinit cgroup_taskset structure before cgroup_migrate_execute() returns

Author: torvalds

kernel/cgroup/cgroup.c

@@ -2311,6 +2311,14 @@ static int cgroup_migrate_execute(struct cgroup_mgctx *mgctx)
 		list_del_init(&cset->mg_node);
 	}
 	spin_unlock_irq(&css_set_lock);
+
+	/*
+	 * Re-initialize the cgroup_taskset structure in case it is reused
+	 * again in another cgroup_migrate_add_task()/cgroup_migrate_execute()
+	 * iteration.
+	 */
+	tset->nr_tasks = 0;
+	tset->csets    = &tset->src_csets;
 	return ret;
 }