[Bug 1880193] [NEW] autofs: Assertion 'set_remove(iterator->links, link) == link' failed at src/shared/userdb.c:314, function userdb_on_query_reply(). Aborting.

[Michael Andreev]

Public bug reported:

autofs has a periodic error on mounting shares in Ubuntu 20.04 (it happens about 1 time out of 5):
"Assertion 'set_remove(iterator->links, link) == link' failed at src/shared/userdb.c:314, function userdb_on_query_reply(). Aborting.
Aborted (core dumped)"


`autofs.service` restart (or `automount` app restart) fixes this issue.
However if some of home dirs (like `Desktop` or `Documents`) are mounted
by `autofs`, user can't login into Ubuntu Desktop Environment (PC
freezes on login with black screen). Since this error can prevent user
log in, it might be considered as critical bug.


It happens both in `autofs` systemd service and by direct execution of
`automount` app (`automount -f -d` command).


May be it's an underlying error in `systemd` library (I found the line,
mentioned in error, in its source codes).


This issue has place in Ubuntu 20.04 (it works correctly in Ubuntu
18.04):

> lsb_release -rd
Description: Ubuntu 20.04 LTS
Release: 20.04


Packages versions:

> apt-cache policy autofs systemd
autofs:
  Installed: 5.1.6-2
  Candidate: 5.1.6-2
  Version table:
 *** 5.1.6-2 500
        500 http://ru.archive.ubuntu.com/ubuntu focal/main amd64 Packages
        100 /var/lib/dpkg/status
systemd:
  Installed: 245.4-4ubuntu3
  Candidate: 245.4-4ubuntu3
  Version table:
 *** 245.4-4ubuntu3 500
        500 http://ru.archive.ubuntu.com/ubuntu focal/main amd64 Packages
        100 /var/lib/dpkg/status


Steps to reproduce:
1. Ubuntu 20.04 clean install
2. `apt install realmd sssd sssd-tools libnss-sss libpam-sss adcli samba-common-bin`
3. `realm join DOMAIN.NAME`
4. Enable makehomedir by command: `pam-auth-update`
5. `apt install cifs-utils`
6. `apt install autofs`
7. Add next line inside [domain/DOMAIN.EXT] section into /etc/sssd/sssd.conf: `krb5_ccname_template = FILE:%d/krb5cc_%U`
8. Reboot
9. Login as domain user and try to open directory, mounted by `autofs` (in my configuration shares are provided by AD).
10. `autofs.service` stops with the error above about 1 time out of 5 (not always).

Found workaround:
Add `Restart=always` into `[Service]` section in `/lib/systemd/system/autofs.service` file (in other words configure auto-restart on failures for autofs service).


Attachments:
1. Full log of `automount -f -d` command.

** Affects: autofs (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: focal

** Attachment added: "automount logs"
   https://bugs.launchpad.net/bugs/1880193/+attachment/5375661/+files/automount-logs-2.txt

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https://bugs.launchpad.net/bugs/1880193

Title:
  autofs: Assertion 'set_remove(iterator->links, link) == link' failed
  at src/shared/userdb.c:314, function userdb_on_query_reply().
  Aborting.

Status in autofs package in Ubuntu:
  New

Bug description:
  autofs has a periodic error on mounting shares in Ubuntu 20.04 (it happens about 1 time out of 5):
  "Assertion 'set_remove(iterator->links, link) == link' failed at src/shared/userdb.c:314, function userdb_on_query_reply(). Aborting.
  Aborted (core dumped)"


  `autofs.service` restart (or `automount` app restart) fixes this
  issue. However if some of home dirs (like `Desktop` or `Documents`)
  are mounted by `autofs`, user can't login into Ubuntu Desktop
  Environment (PC freezes on login with black screen). Since this error
  can prevent user log in, it might be considered as critical bug.


  It happens both in `autofs` systemd service and by direct execution of
  `automount` app (`automount -f -d` command).


  May be it's an underlying error in `systemd` library (I found the
  line, mentioned in error, in its source codes).


  This issue has place in Ubuntu 20.04 (it works correctly in Ubuntu
  18.04):

  > lsb_release -rd
  Description: Ubuntu 20.04 LTS
  Release: 20.04


  Packages versions:

  > apt-cache policy autofs systemd
  autofs:
    Installed: 5.1.6-2
    Candidate: 5.1.6-2
    Version table:
   *** 5.1.6-2 500
          500 http://ru.archive.ubuntu.com/ubuntu focal/main amd64 Packages
          100 /var/lib/dpkg/status
  systemd:
    Installed: 245.4-4ubuntu3
    Candidate: 245.4-4ubuntu3
    Version table:
   *** 245.4-4ubuntu3 500
          500 http://ru.archive.ubuntu.com/ubuntu focal/main amd64 Packages
          100 /var/lib/dpkg/status


  Steps to reproduce:
  1. Ubuntu 20.04 clean install
  2. `apt install realmd sssd sssd-tools libnss-sss libpam-sss adcli samba-common-bin`
  3. `realm join DOMAIN.NAME`
  4. Enable makehomedir by command: `pam-auth-update`
  5. `apt install cifs-utils`
  6. `apt install autofs`
  7. Add next line inside [domain/DOMAIN.EXT] section into /etc/sssd/sssd.conf: `krb5_ccname_template = FILE:%d/krb5cc_%U`
  8. Reboot
  9. Login as domain user and try to open directory, mounted by `autofs` (in my configuration shares are provided by AD).
  10. `autofs.service` stops with the error above about 1 time out of 5 (not always).

  Found workaround:
  Add `Restart=always` into `[Service]` section in `/lib/systemd/system/autofs.service` file (in other words configure auto-restart on failures for autofs service).


  Attachments:
  1. Full log of `automount -f -d` command.

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