为什么在user_controller中的参数允许操作上出现Rails语法错误？

我创建了一个user_controller，使用以下语法从根本上扩展了devise用户设置：

class UsersController < ApplicationController
    def index
        @users = User.order('created_at DESC').all
    end
    def create
      @user = User.create(user_params)
    end

    private

    def user_params
      params.permit :user (:avatar, :email, :password, :password_confirmation )
    end
end

在我的模型user.rb中，我有：

class User < ActiveRecord::Base
  # Include default devise modules. Others available are:
  # :confirmable, :lockable, :timeoutable and :omniauthable
  devise :database_authenticatable, :registerable,
         :recoverable, :rememberable, :trackable, :validatable


  has_attached_file :avatar, styles: {
        large: "600x450#",
        medium: "250x250#",
        small: "100x100#"
    }, :default_url => "/images/:style/filler.png"
  #validates_attachment_content_type :avatar, :content_type => ["image/jpg", "image/jpeg", "image/png", "image/gif"]
  validates_attachment_content_type :avatar, :content_type => /\Aimage\/.*\Z/
  validates :avatar, :email, :password, presence: true


end

这些都可以正常工作，但是当我重新加载页面时，我得到一个奇怪的错误，它说有语法错误，并且很奇怪，因为它在此之前就已经在工作了。我假设它与Rails版本有关的某种语法错误。

错误是：

Error details saved to: /tmp/passenger-error-9mVpXM.html
  Message from application: /home/deployer/staging/releases/20140806094001/app/controllers/users_controller.rb:11: syntax error, unexpected ',', expecting ')'
...require(:user).permit (:avatar, :email, :password, :password...
...                               ^
/home/deployer/staging/releases/20140806094001/app/controllers/users_controller.rb:11: syntax error, unexpected ',', expecting :: or '[' or '.'
...it (:avatar, :email, :password, :password_confirmation )
...                               ^ (SyntaxError)

这有什么明显的错误吗？