Ember.js: How to save model with many-to-many relationship?

I have two models (Role, Permission) with many-to-many relationship. There is a list of permissions and role can have some of them. I want to create edit page for Roles and add there Permissions as a checkboxes list.

edit template:

<form>
    {{input type="text" placeholder="role name" value=name}}
    <br />
    {{#each permissions_list}}
        <label>
            {{input type="checkbox" name="permissions[]"}}{{name}}
        </label><br />
    {{/each}}
    <button {{action 'save'}}>Edit</button>
</form>

models:

    var Role = DS.Model.extend({
        agents: DS.hasMany('agent', {async: false}),
        name: DS.attr('string'),
        permissions: DS.hasMany('permission', {async: true})
    });

    var Permission = DS.Model.extend({
        type: DS.attr('string'),
        name: DS.attr('string'),
        roles: DS.hasMany('permission', {async: false})
    });

edit role controller

    export default Ember.ObjectController.extend({
        permissions_list: [],
        actions: {
            save: function() {
                return this.get('model').save();
            }
        },
        load_permissions: function() {
            this.set('permissions_list', this.store.find('permission'));
        }.on('init')
    });

The problems:

1. I can't find out how to mark checkbox as checked if this permissions is already in model.permissions


2. I can't save permissions on on role saving. Controller does not see "permissions" data (this.get('permissions') in edit role controller)

permissions - list of permissions, that role contains

permissions_list - list of all permissions at database