Quoting Aristeu Rozanski (aris@xxxxxxxxxx):
> +/**
> + * propagate_exception - propagates a new exception to the children
> + * @devcg_root: device cgroup that added a new exception
> + *
> + * returns: 0 in case of success, != 0 in case of error
> + */
> +static int propagate_exception(struct dev_cgroup *devcg_root)
> +{
> + struct cgroup *root = devcg_root->css.cgroup;
> + struct dev_cgroup *devcg, *parent, *tmp;
> + int rc = 0;
> + LIST_HEAD(pending);
> +
> + get_online_devcg(root, &pending);
> +
> + list_for_each_entry_safe(devcg, tmp, &pending, propagate_pending) {
> + parent = cgroup_to_devcgroup(devcg->css.cgroup->parent);
> +
> + dev_exception_clean(&devcg->exceptions);
> + if (devcg->behavior == parent->behavior) {
> + rc = dev_exceptions_copy(&devcg->exceptions, &parent->exceptions);
Let's say parent A and child B both have DEFAULT_DENY, with a set of let's
say 5 whitelist exceptions. Now the parent adds two more whitelist
exceptions. As you say, we don't propagate those.
Now the parent removes one of it's whitelist exceptions.
devcgroup_update_access() calls dev_exception_rm() followed by
propagate_exception(), which comes here and copies the parent's
whitelist - including the two new whitelist rules - to the
child.
-serge
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