/etc/apparmor.d/abstractions/winbind is in apparmor 2.7.102-0ubuntu3.11.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18  | # ------------------------------------------------------------------
#
#    Copyright (C) 2002-2009 Novell/SUSE
#    Copyright (C) 2009 Canonical Ltd.
#
#    This program is free software; you can redistribute it and/or
#    modify it under the terms of version 2 of the GNU General Public
#    License published by the Free Software Foundation.
#
# ------------------------------------------------------------------
  # pam_winbindd
  /tmp/.winbindd/pipe  rw,
  /var/{lib,run}/samba/winbindd_privileged/pipe rw,
  /etc/samba/smb.conf         r,
  /usr/lib*/samba/valid.dat   r,
  /usr/lib*/samba/upcase.dat  r,
  /usr/lib*/samba/lowcase.dat r,
 |