How to avoid multiple DB access for Sails.js policy and controller?

I put role checking in policy:

module.exports = function(req, res, next) {
    var postId = req.param('postId');
    var userId = req.session.user.id;

    Post.findOne({id: postId})
        .exec( function (err, post) {
            if (err) { return next(err); }

            if (!post) {
                return res.notFound('Post not found');
            }

            if (post.author !== userId) {
                return res.forbidden('Not the author');
            }

            next();
        });
};

And in PostController, I need to fetch the post again

update: function (req, res) {
    var postId = req.param('postId');
    Post.findOne({id: postId})
        .exec( function (err, post) {
        // Update the post here

I would like to know if there is a decent way to fetch the post record from DB with only one time?