userns: Teach inode_capable to understand inodes whose uids map to other namespaces.

 * targeted at it's own user namespace and that the given inode is owned

 * by the current user namespace or a child namespace.

 *

 * Currently inodes can only be owned by the initial user namespace.

 * Currently we check to see if an inode is owned by the current

 * user namespace by seeing if the inode's owner maps into the

 * current user namespace.

 *

 */

bool inode_capable(const struct inode *inode, int cap)

{

	struct user_namespace *ns = current_user_ns();

	return ns_capable(ns, cap) && (ns == &init_user_ns);

	return ns_capable(ns, cap) && kuid_has_mapping(ns, inode->i_uid);

}