lightdm crashed with SIGSEGV in g_list_last()

[James Hunt]

Latest update to lightdm broke boot for me as ligthdm crashes on startup.

dmesg shows:

[ 38.108529] lightdm[1621]: segfault at 3f7 ip b74ada42 sp bff82ccc error 4 in libglib-2.0.so.0.3703.0[b746b000+102000]
[ 39.364988] init: lightdm main process (1621) killed by SEGV signal

ProblemType: Crash
DistroRelease: Ubuntu 13.10
Package: lightdm 1.7.6-0ubuntu1
ProcVersionSignature: Ubuntu 3.10.0-3.12-generic 3.10.1
Uname: Linux 3.10.0-3-generic i686
NonfreeKernelModules: nvidia
ApportVersion: 2.11-0ubuntu1
Architecture: i386
Date: Mon Jul 22 08:52:53 2013
ExecutablePath: /usr/sbin/lightdm
InstallationDate: Installed on 2010-10-21 (1005 days ago)
InstallationMedia: Ubuntu 10.10 "Maverick Meerkat" - Release i386 (20101007)
LightdmConfig:
 [SeatDefaults]
 greeter-session=unity-greeter
 user-session=ubuntu
MarkForUpload: True
ProcCmdline: lightdm
ProcEnviron:
 TERM=linux
 PATH=(custom, no user)
SegvAnalysis:
 Segfault happened at: 0xb7467a42 <g_list_last+18>: mov 0x4(%eax),%edx
 PC (0xb7467a42) ok
 source "0x4(%eax)" (0x000003f7) not located in a known VMA region (needed readable region)!
 destination "%edx" ok
SegvReason: reading NULL VMA
Signal: 11
SourcePackage: lightdm
StacktraceTop:
 g_list_last () from /lib/i386-linux-gnu/libglib-2.0.so.0
 g_list_append () from /lib/i386-linux-gnu/libglib-2.0.so.0
 ?? ()
 __libc_start_main (main=0x804c570, argc=1, ubp_av=0xbfd75f44, init=0x8065a10, fini=0x8065a80, rtld_fini=0xb7731600 <_dl_fini>, stack_end=0xbfd75f3c) at libc-start.c:260
 ?? ()
Title: lightdm crashed with SIGSEGV in g_list_last()
UpgradeStatus: Upgraded to saucy on 2013-06-23 (28 days ago)
UserGroups:

[Apport retracing service (apport)]

StacktraceTop:
 g_list_last (list=list@entry=0x3f3) at /build/buildd/glib2.0-2.37.3/./glib/glist.c:868
 g_list_append (list=list@entry=0x3f3, data=0x8db9680) at /build/buildd/glib2.0-2.37.3/./glib/glist.c:238
 main (argc=1, argv=0xbfd75f44) at lightdm.c:1038

[Launchpad Janitor (janitor)]

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

[James Hunt (jamesodhunt)]

Manually downloading the old revision and rebooting does resolve the problem for me:

$ wget http://gb.archive.ubuntu.com/ubuntu/pool/main/l/lightdm/lightdm_1.7.4-0ubuntu1_i386.deb
$ wget http://gb.archive.ubuntu.com/ubuntu/pool/main/l/lightdm/liblightdm-gobject-1-0_1.7.4-0ubuntu1_i386.deb
$ sudo dpkg -i lightdm_1.7.4-0ubuntu1_i386.deb liblightdm-gobject-1-0_1.7.4-0ubuntu1_i386.deb

[James Hunt (jamesodhunt)]

The default behaviour of the boot with this bug is that the greeter never appears; you just see the Ubuntu pulsing plymouth theme.

However, the system has booted so you can switch to a text console (control+alt+f1 for example), login and take remedial action as shown in #6.