I have a share with "inherit permissions = yes". I have a directory in the share with mode rwxrwsr-x. If I create a subdirectory, the modes are rwxrws---. The same happens with a parent directory with mode rwxrwxr-x (resulting in rwxrwx---).
The permissions of the newly created subdirectory are independent of the OS used to create them and apparently independent of the umask when using smbfs (mount.cifs).
The following is an excerpt from smb.conf and contains everything related to permissions, modes, etc. of the share.
force group = +mi inherit permissions = yes inherit owner = yes nt acl support = no
I added "nt acl support = no" for testing purposes and it does not seem to make a difference.
Does "inherit permissions" not work for non-user, non-group modes?