it is not possible to change value 'ldap filter' by setting it in smb.conf.
samba is always using its default setting:
ldap filter = (&(uid=%u)(objectClass=sambaAccount))
We're not fixing any non-security bugs in the 2.2 series of Samba - sorry. I've
tested it in 3.0 and the ldap filter setting is used properly.
There have been no other reports of this parameter being broken though. Are you
sure it isn't a configuration problem?