Permission denied when create or write files in multi-user mode

Hi, I deploy JupyterHub on docker use the multi-user Hub image from here. I create 2 users(test_user1, test_user2) in jupyterhub admin panel and I can see 2 folder which named by username in /home.
When I login jupyterhub as test_user1, I just have write permission in my user folder like /home/test_user1. When I write something in /home or /home/test_user2, I get the following error:

[E 2022-01-04 05:07:01.191 SingleUserLabApp filemanager:464] Error while saving file: test_user1/Untitled.ipynb [Errno 13] Permission denied: '/home/test_user2/.ipynb_checkpoints/Untitled-checkpoint.ipynb'

    PermissionError: [Errno 13] Permission denied: '/home/test_user2/.ipynb_checkpoints/Untitled-checkpoint.ipynb'

[W 2022-01-04 05:43:34.136 SingleUserLabApp web:1787] 403 POST /user/test_user1/api/contents?1641275014131 (::ffff: Permission denied: Untitled Folder

[W 2022-01-04 05:43:34.136 SingleUserLabApp handlers:622] Permission denied: Untitled Folder

The same error happen will happen when I use some extension like tabnine which need to modify the package file in the installation folder of it.

I have try to run chmod 777 as root to make it can be written or read. But the error still happen. I’m not sure the permission issue is happen in JupyterHub level or OS system level and how to solve it.
This is my configuration:

c.Spawner.default_url = '/lab/home'
c.Spawner.notebook_dir = '/home'
c.Authenticator.admin_users = {'test_user1'}
c.LocalAuthenticator.create_system_users = True
c.JupyterHub.authenticator_class = 'jupyterhub.auth.DummyAuthenticator'
c.DummyAuthenticator.password = "*******************************************"

Any help is appreciated~