+/**
+ * parent_allows_removal - verify if it's ok to remove an exception
+ * @childcg: child cgroup from where the exception will be removed
+ * @ex: exception being removed
+ *
+ * When removing an exception in cgroups with default ALLOW policy, it must
+ * be checked if removing it will give the child cgroup more access than the
+ * parent.
+ *
+ * Return: true if it's ok to remove exception, false otherwise
+ */
+static bool parent_allows_removal(struct dev_cgroup *childcg,
+ struct dev_exception_item *ex)
+{
+ struct dev_cgroup *parent = css_to_devcgroup(css_parent(&childcg->css));
+
+ if (!parent)
+ return true;
+
+ /* It's always allowed to remove access to devices */
+ if (childcg->behavior == DEVCG_DEFAULT_DENY)
+ return true;
+
+ /*
+ * Make sure you're not removing part or a whole exception existing in
+ * the parent cgroup
+ */
+ return !match_exception_partial(&parent->exceptions, ex->type,
+ ex->major, ex->minor, ex->access);
+}
+