nmbd won't start after Samba minor ver upgrade

Hello there.

I've upgraded Samba yesterday and something went wrong, but I'm unable to figure out what - it's hard being a newbie!

root@Server:~# aptitude upgrade
The following partially installed packages will be configured:
  samba 
No packages will be installed, upgraded, or removed.
0 packages upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
Need to get 0 B of archives. After unpacking 0 B will be used.
Setting up samba (2:4.2.10+dfsg-0+deb8u2) ...
Starting SMB/CIFS daemon: smbd.
Starting NetBIOS name server: nmbd failed!
invoke-rc.d: initscript nmbd, action "start" failed.
dpkg: error processing package samba (--configure):
 subprocess installed post-installation script returned error exit status 1
Errors were encountered while processing:
 samba
E: Sub-process /usr/bin/dpkg returned an error code (1)
Failed to perform requested operation on package.  Trying to recover:
Setting up samba (2:4.2.10+dfsg-0+deb8u2) ...
Starting SMB/CIFS daemon: smbd.
Starting NetBIOS name server: nmbd failed!
invoke-rc.d: initscript nmbd, action "start" failed.
dpkg: error processing package samba (--configure):
 subprocess installed post-installation script returned error exit status 1
Errors were encountered while processing:
 samba

Here's what was upgraded:

[UPGRADE] samba:amd64 2:4.1.17+dfsg-2+deb8u2 -> 2:4.2.10+dfsg-0+deb8u2
[UPGRADE] samba-common:amd64 2:4.1.17+dfsg-2+deb8u2 -> 2:4.2.10+dfsg-0+deb8u2
[UPGRADE] samba-common-bin:amd64 2:4.1.17+dfsg-2+deb8u2 -> 2:4.2.10+dfsg-0+deb8u2
[UPGRADE] samba-dsdb-modules:amd64 2:4.1.17+dfsg-2+deb8u2 -> 2:4.2.10+dfsg-0+deb8u2
[UPGRADE] samba-libs:amd64 2:4.1.17+dfsg-2+deb8u2 -> 2:4.2.10+dfsg-0+deb8u2

I can't find anything useful in the logs. /var/log/apt/term.log :

Log started: 2016-05-02  18:49:54
Setting up samba (2:4.2.10+dfsg-0+deb8u2) ...
Starting SMB/CIFS daemon: smbd.
Starting NetBIOS name server: nmbd failed!
invoke-rc.d: initscript nmbd, action "start" failed.
dpkg: error processing package samba (--configure):
 subprocess installed post-installation script returned error exit status 1
Errors were encountered while processing:
 samba
Log ended: 2016-05-02  18:49:55

/var/log/apt/history.log :

Start-Date: 2016-05-02  18:49:54
Error: Sub-process /usr/bin/dpkg returned an error code (1)
End-Date: 2016-05-02  18:49:55

/var/log/samba/log.nmbd :

[2016/05/02 18:49:56,  0] ../source3/nmbd/nmbd.c:908(main)
  nmbd version 4.2.10-Debian started.
  Copyright Andrew Tridgell and the Samba Team 1992-2014

/var/log/dpkg.log :

2016-05-02 18:49:56 startup packages configure
2016-05-02 18:49:56 configure samba:amd64 2:4.2.10+dfsg-0+deb8u2 <none>
2016-05-02 18:49:56 status half-configured samba:amd64 2:4.2.10+dfsg-0+deb8u2

I tried :

root@Server:~# dpkg-reconfigure samba
/usr/sbin/dpkg-reconfigure: samba is broken or not fully installed

smbd, on the other hand, works fine.

After some Googling, I discovered that mounting /tmp with the noexec option could cause some packages to fail installation. Well, I've set noexec on /tmp some time ago, could that be the cause?

I tried changing APT::ExtractTemplates::TempDir to /var/tmp, which is not mounted with noexec, but there was no change. I've remounted /tmp with the exec option, but still got the same error. So either that's not the issue or I'm missing something here.

Any ideas?

root@Server:~# uname -a 
Linux Server 3.16.0-4-amd64 #1 SMP Debian 3.16.7-ckt25-1 (2016-03-06) x86_64 GNU/Linux
root@Server:~# cat /etc/issue
Debian GNU/Linux 8 \n \l

OK, it's an AppArmor issue. Not sure what exactly, as aa-logprof finds nothing wrong with the profiles, but I've switched nmdb state from enfore to complain and now it works properly.