Is it possible to stop Windows from changing permissions on a Linux SMB share?

"This is due to your Samba configuration. What you want is to set the file masks, so that when Samba creates or modifies a file, the permissions are kept at a known quantity.

This is what I use in my /etc/samba/smb.conf. These options are set explicitly for each share:

[sharename]
...
directory mask = 0755
create mask = 0644
...

See the Samba smb.conf documentation for the create mask and directory mask options. Use security mask if you want to mask ACLs as well.

It seems that under Ubuntu, the user public folders in Ubuntu may be controlled by the [public] share definition."