Sharing folders between (virtual) systems

On the Proxmox I have installed three virtual systems:
* Linux Ubuntu server (Ubuntu Linux server has a public IP address)
* 2 x Win7


I need to make on Proxmox system a (read/write) directory accessable by Linux serwer and 2 Win7. At the same time I do not want the directory to be accessible to the public.

Can you suggest me something? Which way to best go (samba?) And how to configure the network?


Regards,
Bartek