Ubuntu 14.04: lightdm crashes when user has NFS mounted home directory

[Thomas Ribbrock]

Situation:
- Freshly installed machine with Kubuntu 14.04 i386
- Create local user
- The home directory is mounted from a server using NFS4 (no Kerberos)

On login, lightdm claims that the password of the user is incorrect. The same user can log in without any problems on the console and can access his files. If I create a local home directory (w/o NFS), the user can log in via lightdm as well.

What I've seen so far with NFS home directory:

After a login attempt, /var/log/syslog shows:
[...]
Apr 15 14:42:30 pc1326 kernel: [73998.523174] lightdm[13641]: segfault at 0 ip b72a41c7 sp bfd2b2f0 error 4 in libc-2.19.so[b723f000+1a9000]

In /var/log/auth.log:
[...]Apr 15 14:42:30 pc1326 lightdm: pam_succeed_if(lightdm:auth): requirement "user ingroup nopasswdlogin" not met by user "testuser2"
Apr 15 14:42:30 pc1326 lightdm: pam_kwallet(lightdm:auth): pam_sm_authenticate

In /var/log/lightdm/lightdm.log:
[...]
[+74103.53s] DEBUG: Session pid=13162: Greeter start authentication for testuser2
[+74103.53s] DEBUG: Session pid=13689: Started with service 'lightdm', username 'testuser2'
[+74103.53s] DEBUG: Session pid=13689: Got 1 message(s) from PAM
[+74103.53s] DEBUG: Session pid=13162: Prompt greeter with 1 message(s)
[+74103.53s] DEBUG: Session pid=13162: Continue authentication
[+74103.67s] DEBUG: Session pid=13689: Terminated with signal 11
[+74103.67s] DEBUG: Session: Failed during authentication
[+74103.67s] DEBUG: Session pid=13162: Authenticate result for user testuser2: Authentication stopped before completion
[+74103.67s] DEBUG: Seat: Session stopped

lightdm:
  Installed: 1.10.0-0ubuntu3

Description: Ubuntu 14.04 LTS
Release: 14.04

[Luis Lucas (lfrlucas)]

Same problem here using Kubuntu 14.04.
Lightdm crashes (as reported in dmesg) when ldap users try to login.
In my case, Ldap users autenticate via kerberos (using sssd) and have home directories mounted via NFSv3.
My solution was to install and use KDM instead of lightdm!

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[[e-mail] (thomas-hottendorff)]

I have this problem too. Installed kdm to circumvent it for the time being.

[webrat (irc-webratz)]

I'm experiencing this issue also. To add some details i'll attach the apport file.
This is a fresh install of Ubuntu 14.04 using NFSv4 with Kerberos for the /home directories.

[Robert Ancell (robert-ancell)]

A backtrace is required to diagnose this but the logs above suggest it might be a bug in pam_kwallet.

[Philipp Wendler (philw85)]

Yes, you are right, the problem occurs only if pam-kwallet is installed. How can I generate a backtrace?

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Harald Sitter (apachelogger)]

For what it is worth, it would be really cool if you could upgrade pam-kwallet from proposed updates, as I absolutely expect your crash to be one of those that the version in proposed should fix:

bug #1314118
bug #1314119
bug #1314120

(instructions on how to enable the proposed updates are available in the last comment of those bug reports)

[Philipp Wendler (philw85)]

Indeed, after upgrading pam-kwallet to the version from trusty-proposed I can login without problems.

[Robert Ancell (robert-ancell)]

Marking the lightdm task as invalid as Philipp confirms this is a problem with pam-kwallet.

[Harald Sitter (apachelogger)]

The update has now been released. Thanks for the bug report.