Legal analysis: It is definitely illegal to open a canteen in a dormitory and engage in food business and sales without a business license and food sales license.

Legal basis: Measures for the Administration of Food Business License

Article 2 Anyone who engages in food sales and catering services within the territory of People's Republic of China (PRC) shall obtain a food business license according to law. These Measures shall apply to the application, acceptance, examination, decision, supervision and inspection of food business license.

Article 45 Anyone who engages in food business activities without a food business license shall be punished by the local food and drug supervision and administration department at or above the county level in accordance with the provisions of Article 122 of the Food Safety Law of People's Republic of China (PRC).