I got a Samba share to which every user is allowed to access and within that share there are directories for each group set on server so it looks like this:
ls -l drwsrws--- 11 root p_01 4096 2018-01-17 Share1 drwsrws--- 13 root p_02 4096 2018-01-17 Share2
SUID is set so when user creates new file/directory within that directory it will inherit it's permissions along with owning group. And that works just fine both on local computer and as Samba share (both on Linux and Windows).
The problem is that when user copy a file from Share1 to Share2 it would also copy permissions (with owning group).
When I copy the same file locally on server it would get the permissions from parent directory as desired.
2018-10-15 EDIT: Here's relevant parts of smb.conf:
[global] passdb backend = tdbsam printing = cups printcap name = cups printcap cache time = 750 cups options = raw map to guest = Bad User include = /etc/samba/dhcp.conf logon path = \\%L\profiles\.msprofile logon home = \\%L\%U\.9xprofile logon drive = P: usershare allow guests = No add machine script = /usr/sbin/useradd -c Machine -d /var/lib/nobody -s /bin/false %m$ domain logons = No domain master = No netbios name = SERVER security = user wins support = Yes workgroup = NORDPRIM [NORDPRIM] inherit acls = Yes path = /data/NORDPRIM read only = No inherit permissions = Yes force create mode = 774 create mask = 774 directory mask = 2775 force directory mode = 2775 vfs objects = recycle