HowTo access Samba Share over VPN Tunnel?
Probably you need to allow access to your samba server from the ip class of your vpn. You need to find (or insert) the following line in your /etc/samba/smb.conf file
interfaces = 127.0.0.0/8 10.8.0.0/24
Don't forget to add every ip class that should have access to the shares.
Then reload your samba server
sudo service smbd reload
sudo service nmbd reload