lightdm assert failure: lightdm: pam_mount.c:417: modify_pm_count: Assertion `user != ((void *)0)' failed.

[Patrik Lundquist]

Logged in with GNOME as session.

ProblemType: Crash
DistroRelease: Ubuntu 11.10
Package: lightdm 0.9.3-0ubuntu8
ProcVersionSignature: Ubuntu 3.0.0-9.14-generic 3.0.3
Uname: Linux 3.0.0-9-generic x86_64
NonfreeKernelModules: nvidia
Architecture: amd64
AssertionMessage: lightdm: pam_mount.c:417: modify_pm_count: Assertion `user != ((void *)0)' failed.
CrashCounter: 1
Date: Tue Aug 30 12:18:08 2011
ExecutablePath: /usr/sbin/lightdm
InstallationMedia: Ubuntu 10.04 LTS "Lucid Lynx" - Release amd64 (20100429)
ProcCmdline: lightdm
ProcEnviron: PATH=(custom, no user)
Signal: 6
SourcePackage: lightdm
StacktraceTop:
 __GI___assert_fail (assertion=0x7f0c2294a63c "user != ((void *)0)", file=<optimized out>, line=417, function=<optimized out>) at assert.c:81
 ?? () from /lib/security/pam_mount.so
 pam_sm_close_session () from /lib/security/pam_mount.so
 ?? () from /lib/x86_64-linux-gnu/libpam.so.0
 ?? ()
Title: lightdm assert failure: lightdm: pam_mount.c:417: modify_pm_count: Assertion `user != ((void *)0)' failed.
UpgradeStatus: Upgraded to oneiric on 2011-08-19 (10 days ago)
UserGroups:

[Apport retracing service (apport)]

StacktraceTop:
 __GI___assert_fail (assertion=0x7f0c2294a63c "user != ((void *)0)", file=<optimized out>, line=417, function=<optimized out>) at assert.c:81
 modify_pm_count (user=0x0, operation=0x7f0c2294a750 "-1", config=<optimized out>) at pam_mount.c:417
 pam_sm_close_session (pamh=<optimized out>, flags=<optimized out>, argc=<optimized out>, argv=<optimized out>) at pam_mount.c:718
 _pam_dispatch_aux (use_cached_chain=<optimized out>, resumed=<optimized out>, h=0x7f0c24017a10, flags=<optimized out>, pamh=0x7f0c24013a30) at pam_dispatch.c:110
 _pam_dispatch (pamh=0x7f0c24013a30, flags=<optimized out>, choice=5) at pam_dispatch.c:395

[PeterPall (peterpall)]

Actually it seems like the bug is in pam or similar, not in lightdm: I also get this message when attempting to use sudo, which is a completely different program using pam.

[PeterPall (peterpall)]

If you want to try to reconstruct the sudo error you have to run sudo twice, though:

sudo test
[here you will get no error message]
sudo test
[here you will get the error message]

Seems like the error is related to the mechanism that allows you to use sudo without having to enter the password again every time if the time span that has passed since the last use of sudo isn't too big.

[Robert Ancell (robert-ancell)]

Could you please test this in lightdm 1.1.6 (precise)? There has been a change to the way PAM is handled that should resolve this issue.

[Patrik Lundquist (patrik-lundquist)]

There's no GNOME session anymore in Precise but I tried the other sessions (Unity, Unity 2D, Recovery, User defined) and they all work for me.

[Robert Ancell (robert-ancell)]

Thanks, closing lightdm task. There may still be a PAM issue there, but lightdm now can handle PAM crashing so this shouldn't cause the daemon to stop.

[PeterPall (peterpall)]

Tried the first pre-alpha of Ubuntu 12.10. The bug seems not to be reproducible there with neither pam nor lightdm.