[Bug 1792400] Re: smbd failed in host when both lxd container and host have smbd

 Christian Ehrhardt  1792400 at bugs.launchpad.net
Tue Oct 9 12:19:04 UTC 2018 

Without any containers it (re-)starts fine:

systemctl restart smbd; sleep 2s; systemctl status smbd
● smbd.service - LSB: start Samba SMB/CIFS daemon (smbd)
   Loaded: loaded (/etc/init.d/smbd; bad; vendor preset: enabled)
   Active: active (running) since Tue 2018-10-09 11:58:52 UTC; 2s ago
     Docs: man:systemd-sysv-generator(8)
  Process: 8925 ExecStop=/etc/init.d/smbd stop (code=exited, status=0/SUCCESS)
  Process: 8932 ExecStart=/etc/init.d/smbd start (code=exited, status=0/SUCCESS)
    Tasks: 3
   Memory: 21.7M
      CPU: 200ms
   CGroup: /system.slice/smbd.service
           ├─8943 /usr/sbin/smbd -D
           ├─8944 /usr/sbin/smbd -D
           └─8947 /usr/sbin/smbd -D

Oct 09 11:58:52 x systemd[1]: Starting LSB: start Samba SMB/CIFS daemon (smbd)...
Oct 09 11:58:52 x smbd[8932]:  * Starting SMB/CIFS daemon smbd
Oct 09 11:58:52 x smbd[8932]:    ...done.
Oct 09 11:58:52 x systemd[1]: Started LSB: start Samba SMB/CIFS daemon (smbd).

But if I add a container with a smb binary it will fail to restart:

● smbd.service - LSB: start Samba SMB/CIFS daemon (smbd)
   Loaded: loaded (/etc/init.d/smbd; bad; vendor preset: enabled)
   Active: active (exited) since Tue 2018-10-09 12:02:41 UTC; 2s ago
     Docs: man:systemd-sysv-generator(8)
  Process: 12732 ExecStop=/etc/init.d/smbd stop (code=exited, status=0/SUCCESS)
  Process: 12739 ExecStart=/etc/init.d/smbd start (code=exited, status=0/SUCCESS)

Oct 09 12:02:41 x systemd[1]: Starting LSB: start Samba SMB/CIFS daemon (smbd)...
Oct 09 12:02:41 x smbd[12739]:  * Starting SMB/CIFS daemon smbd
Oct 09 12:02:41 x smbd[12739]:    ...done.
Oct 09 12:02:41 x systemd[1]: Started LSB: start Samba SMB/CIFS daemon (smbd).



This will block (as initially reported) and be non-obvious until one realizes the process from the container is what blocks this.


Installing from proposed

root at x:~# apt install samba
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following additional packages will be installed:
  libwbclient0 python-samba samba-common samba-common-bin samba-libs
Suggested packages:
  bind9 bind9utils ctdb ldb-tools smbldap-tools winbind heimdal-clients
Recommended packages:
  samba-dsdb-modules samba-vfs-modules
The following packages will be upgraded:
  libwbclient0 python-samba samba samba-common samba-common-bin samba-libs
6 upgraded, 0 newly installed, 0 to remove and 23 not upgraded.
Need to get 7759 kB of archives.
After this operation, 0 B of additional disk space will be used.
Do you want to continue? [Y/n] Y
Get:1 http://archive.ubuntu.com/ubuntu xenial-proposed/main amd64 python-samba amd64 2:4.3.11+dfsg-0ubuntu0.16.04.17 [1059 kB]
Get:2 http://archive.ubuntu.com/ubuntu xenial-proposed/main amd64 samba-common-bin amd64 2:4.3.11+dfsg-0ubuntu0.16.04.17 [506 kB]
Get:3 http://archive.ubuntu.com/ubuntu xenial-proposed/main amd64 samba-libs amd64 2:4.3.11+dfsg-0ubuntu0.16.04.17 [5172 kB]
Get:4 http://archive.ubuntu.com/ubuntu xenial-proposed/main amd64 libwbclient0 amd64 2:4.3.11+dfsg-0ubuntu0.16.04.17 [30.3 kB]
Get:5 http://archive.ubuntu.com/ubuntu xenial-proposed/main amd64 samba amd64 2:4.3.11+dfsg-0ubuntu0.16.04.17 [908 kB]
Get:6 http://archive.ubuntu.com/ubuntu xenial-proposed/main amd64 samba-common all 2:4.3.11+dfsg-0ubuntu0.16.04.17 [83.7 kB]
Fetched 7759 kB in 1s (5118 kB/s)     
Preconfiguring packages ...
(Reading database ... 47300 files and directories currently installed.)
Preparing to unpack .../python-samba_2%3a4.3.11+dfsg-0ubuntu0.16.04.17_amd64.deb ...
Unpacking python-samba (2:4.3.11+dfsg-0ubuntu0.16.04.17) over (2:4.3.11+dfsg-0ubuntu0.16.04.16) ...
Preparing to unpack .../samba-common-bin_2%3a4.3.11+dfsg-0ubuntu0.16.04.17_amd64.deb ...
Unpacking samba-common-bin (2:4.3.11+dfsg-0ubuntu0.16.04.17) over (2:4.3.11+dfsg-0ubuntu0.16.04.16) ...
Preparing to unpack .../samba-libs_2%3a4.3.11+dfsg-0ubuntu0.16.04.17_amd64.deb ...
Unpacking samba-libs:amd64 (2:4.3.11+dfsg-0ubuntu0.16.04.17) over (2:4.3.11+dfsg-0ubuntu0.16.04.16) ...
Preparing to unpack .../libwbclient0_2%3a4.3.11+dfsg-0ubuntu0.16.04.17_amd64.deb ...
Unpacking libwbclient0:amd64 (2:4.3.11+dfsg-0ubuntu0.16.04.17) over (2:4.3.11+dfsg-0ubuntu0.16.04.16) ...
Preparing to unpack .../samba_2%3a4.3.11+dfsg-0ubuntu0.16.04.17_amd64.deb ...
Unpacking samba (2:4.3.11+dfsg-0ubuntu0.16.04.17) over (2:4.3.11+dfsg-0ubuntu0.16.04.16) ...
Preparing to unpack .../samba-common_2%3a4.3.11+dfsg-0ubuntu0.16.04.17_all.deb ...
Unpacking samba-common (2:4.3.11+dfsg-0ubuntu0.16.04.17) over (2:4.3.11+dfsg-0ubuntu0.16.04.16) ...
Processing triggers for man-db (2.7.5-1) ...
Processing triggers for libc-bin (2.23-0ubuntu10) ...
Processing triggers for systemd (229-4ubuntu21.4) ...
Processing triggers for ureadahead (0.100.0-19) ...
Processing triggers for ufw (0.35-0ubuntu2) ...
Setting up libwbclient0:amd64 (2:4.3.11+dfsg-0ubuntu0.16.04.17) ...
Setting up samba-libs:amd64 (2:4.3.11+dfsg-0ubuntu0.16.04.17) ...
Setting up python-samba (2:4.3.11+dfsg-0ubuntu0.16.04.17) ...
Setting up samba-common (2:4.3.11+dfsg-0ubuntu0.16.04.17) ...
Setting up samba-common-bin (2:4.3.11+dfsg-0ubuntu0.16.04.17) ...
Setting up samba (2:4.3.11+dfsg-0ubuntu0.16.04.17) ...
Installing new version of config file /etc/init.d/nmbd ...
Installing new version of config file /etc/init.d/samba-ad-dc ...
Installing new version of config file /etc/init.d/smbd ...
Processing triggers for libc-bin (2.23-0ubuntu10) ...
Processing triggers for systemd (229-4ubuntu21.4) ...
Processing triggers for ureadahead (0.100.0-19) ...


---

Trying to restart again:

# systemctl restart smbd; sleep 2s; systemctl status smbd
● smbd.service - LSB: start Samba SMB/CIFS daemon (smbd)
   Loaded: loaded (/etc/init.d/smbd; bad; vendor preset: enabled)
   Active: active (running) since Tue 2018-10-09 12:05:11 UTC; 2s ago
     Docs: man:systemd-sysv-generator(8)
  Process: 14092 ExecStop=/etc/init.d/smbd stop (code=exited, status=0/SUCCESS)
  Process: 14099 ExecStart=/etc/init.d/smbd start (code=exited, status=0/SUCCESS)
    Tasks: 3
   Memory: 14.0M
      CPU: 196ms
   CGroup: /system.slice/smbd.service
           ├─14110 /usr/sbin/smbd -D
           ├─14111 /usr/sbin/smbd -D
           └─14114 /usr/sbin/smbd -D

Oct 09 12:05:11 x systemd[1]: Starting LSB: start Samba SMB/CIFS daemon (smbd)...
Oct 09 12:05:11 x smbd[14099]:  * Starting SMB/CIFS daemon smbd
Oct 09 12:05:11 x smbd[14099]:    ...done.
Oct 09 12:05:11 x systemd[1]: Started LSB: start Samba SMB/CIFS daemon (smbd).


---

Starting a background process
md5sum /dev/urandom &
[1] 15863

# ps axlf | grep -e md5 -e smbd
0     0 15863  6310  20   0   7720   660 -      R    ?          1:43  \_ md5sum /dev/urandom
0     0 15919  6310  20   0  14620   984 pipe_w S+   ?          0:00  \_ grep --color=auto -e md5 -e smbd
5     0 15855     1  20   0 336632 16104 poll_s Ss   ?          0:00 /usr/sbin/smbd -D
1     0 15857 15855  20   0 328524  4460 poll_s S    ?          0:00  \_ /usr/sbin/smbd -D
1     0 15859 15855  20   0 336632  6312 poll_s S    ?          0:00  \_ /usr/sbin/smbd -D

put the pid 15863 in /var/run/samba/smbd.pid to "simulate" a stale
pidfile.

# systemctl restart smbd; sleep 2s; systemctl status smbd
[1]+  Terminated              md5sum /dev/urandom
● smbd.service - LSB: start Samba SMB/CIFS daemon (smbd)
   Loaded: loaded (/etc/init.d/smbd; bad; vendor preset: enabled)
   Active: active (running) since Tue 2018-10-09 12:10:00 UTC; 2s ago
     Docs: man:systemd-sysv-generator(8)
  Process: 15923 ExecStop=/etc/init.d/smbd stop (code=exited, status=0/SUCCESS)
  Process: 15955 ExecStart=/etc/init.d/smbd start (code=exited, status=0/SUCCESS)
    Tasks: 3
   Memory: 7.7M
      CPU: 138ms
   CGroup: /system.slice/smbd.service
           ├─15855 /usr/sbin/smbd -D
           ├─15857 /usr/sbin/smbd -D
           └─15859 /usr/sbin/smbd -D

Oct 09 12:10:00 x systemd[1]: Starting LSB: start Samba SMB/CIFS daemon (smbd)...
Oct 09 12:10:00 x smbd[15955]:  * Starting SMB/CIFS daemon smbd
Oct 09 12:10:00 x smbd[15955]:    ...done.
Oct 09 12:10:00 x systemd[1]: Started LSB: start Samba SMB/CIFS daemon (smbd).

The other process was killed AND the intended service not restarted.

After the fix this behaves like this:

ps axlf | grep -e md5 -e smbd
0     0 17341  6310  20   0   7720   764 -      R    ?          2:04  \_ md5sum /dev/urandom
0     0 17433  6310  20   0  14620  1092 pipe_w S+   ?          0:00  \_ grep --color=auto -e md5 -e smbd
5     0 17427     1  20   0 336632 15820 poll_s Ss   ?          0:00 /usr/sbin/smbd -D
1     0 17428 17427  20   0 328524  4376 poll_s S    ?          0:00  \_ /usr/sbin/smbd -D
1     0 17430 17427  20   0 336632  6536 poll_s S    ?          0:00  \_ /usr/sbin/smbd -D

again putting 17341 into the pidfile to simulate a stale pidfile.

It is no more killing the wrong process by accident now.

---

Both changes working as intended now.
Also none of our tests along found issues with the changes.

Marking verified.

Note: I'd be fine to give this a few extra days in proposed just to be
sure, unless there is a new security update or any such - then lets push
this out before that one.

** Tags removed: verification-needed verification-needed-xenial
** Tags added: verification-done verification-done-xenial

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https://bugs.launchpad.net/bugs/1792400

Title:
  smbd failed in host when both lxd container and host have smbd

Status in samba package in Ubuntu:
  Fix Released
Status in samba source package in Trusty:
  Triaged
Status in samba source package in Xenial:
  Fix Committed

Bug description:
  [Impact]

   * Issue: the current init script
     * won't start samba related services on the host if there is a process 
       of the same binary in a container
     * might on stop affect a process that it was not intended to stop

   * Solution: Fix init scripts to
     * start action to have a safer process detection with containers around
     * stop action to not affect unintended processes due to stale pidfiles

  [Test Case]

   * 1. Start a container
   * 2. Start samba in the Container (or winbind or nmbd)
   * 3. Start samba in the host (or winbind or nmbd)
    => it will not start as such a binary is already running
   * #2 and #3 can be switched, and then as 4. restart smbd in the host
    => it will shut down but not re-start

  Fixed: The container process should have no influence

   This also fixes issues where the pidfile would not be updated
   * install and start smbd
   * "Simulate" a corrupted pidfile by putting the PID of a different
     process in it
   * stop the sambd service
    => without the fixes this will drag down the other process you put in
       the pidfile

  Fixed: a stale pidfile entry should not let non-smbd (or winbind,
  nmbd) processes be affected

  [Regression Potential]

   * We tried to think of all edge cases of these start/stop actions but
     didn't come up with one that is broken. Aside from missing one of those
     cases there might be non-archive scripts that expect the old behavior.
     But even for thse no critical ones came to my mind so far.
     Worst case there'd be a combination that leads to the service
     no(re-)starting after the SRU - so thinking about potential cases is
     important.

  [Other Info]

   * n/a

  ---

  Setup: install smbd in host and lxd-container.

  Now restart smbd in host:

  service smbd restart
  All is OK.
  Problem: nmap shows "closed" on ports 139 and 445. And users cannot use smbd server in host.

    ● smbd.service - LSB: start Samba SMB/CIFS daemon (smbd)
     Loaded: loaded (/etc/init.d/smbd; bad; vendor preset: enabled)
     Active: active (exited) since Die 2016-10-18 17:35:23 CEST; 2s ago
       Docs: man:systemd-sysv-generator(8)
    Process: 24218 ExecStop=/etc/init.d/smbd stop (code=exited, status=0/SUCCESS)
    Process: 21980 ExecReload=/etc/init.d/smbd reload (code=exited, status=0/SUCCESS)
    Process: 25190 ExecStart=/etc/init.d/smbd start (code=exited, status=0/SUCCESS)

  Okt 18 17:35:22 speedy systemd[1]: Starting LSB: start Samba SMB/CIFS daemon (smbd)...
  Okt 18 17:35:23 speedy smbd[25190]:  * Starting SMB/CIFS daemon smbd
  Okt 18 17:35:23 speedy smbd[25190]:    ...done.
  Okt 18 17:35:23 speedy systemd[1]: Started LSB: start Samba SMB/CIFS daemon (smbd).

  ps axf | grep smbd:

  25356 pts/2    S+     0:00  |   \_ grep --color=auto smbd
  19915 ?        Ss     0:08      \_ /usr/sbin/smbd -D
  19919 ?        S      0:00          \_ /usr/sbin/smbd -D

  However, netstat -tpln | grep "smbd" returns nothing and also nmap
  shows "closed" on ports 139 and 445.

  Workaround [1]:
  change /etc/init.d/smbd:
   if ! start-stop-daemon --start --quiet --oknodo --exec /usr/sbin/smbd -- -D ; then

  to

   if ! start-stop-daemon --start --quiet --oknodo --pidfile
  /var/run/samba/smbd.pid --exec /usr/sbin/smbd -- -D ; then

  I reported this to:
  https://discuss.linuxcontainers.org/t/samba-in-host-and-container/2523

  apt-cache policy samba
  samba:
    Installed: 2:4.3.11+dfsg-0ubuntu0.16.04.15
    Candidate: 2:4.3.11+dfsg-0ubuntu0.16.04.16
    Version table:
       2:4.3.11+dfsg-0ubuntu0.16.04.16 500
          500 http://de.archive.ubuntu.com/ubuntu xenial-updates/main amd64 Packages
   *** 2:4.3.11+dfsg-0ubuntu0.16.04.15 500
          500 http://security.ubuntu.com/ubuntu xenial-security/main amd64 Packages
          100 /var/lib/dpkg/status
       2:4.3.8+dfsg-0ubuntu1 500
          500 http://de.archive.ubuntu.com/ubuntu xenial/main amd64 Packages

  1. https://serverfault.com/questions/810544/samba-daemon-does-not-
  work-as-systemd-service-but-works-in-foreground

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