lightdm-example-gtk-greeter crashed with SIGSEGV in __strcmp_ssse3()

Bug #809890 reported by Loïc Minier
266
This bug affects 29 people
Affects Status Importance Assigned to Milestone
lightdm (Ubuntu)
Fix Released
Medium
Robert Ancell
Oneiric
Fix Released
Medium
Robert Ancell

Bug Description

When selecting my user name on the lightdm login screen, I get a blank screen and can't login; the greeter has just crashed.

ProblemType: Crash
DistroRelease: Ubuntu 11.10
Package: lightdm-greeter-example-gtk 0.4.3-0ubuntu1
ProcVersionSignature: Ubuntu 3.0.0-5.6-generic 3.0.0-rc7
Uname: Linux 3.0.0-5-generic x86_64
Architecture: amd64
Date: Wed Jul 13 15:44:50 2011
ExecutablePath: /usr/lib/lightdm/lightdm-example-gtk-greeter
ProcCmdline: /usr/lib/lightdm/lightdm-example-gtk-greeter
ProcEnviron:
 PATH=(custom, no user)
 SHELL=/bin/false
SegvAnalysis:
 Segfault happened at: 0x7fd81462517a <__strcmp_ssse3+26>: movlpd (%rsi),%xmm2
 PC (0x7fd81462517a) ok
 source "(%rsi)" (0x00000000) not located in a known VMA region (needed readable region)!
 destination "%xmm2" ok
SegvReason: reading NULL VMA
Signal: 11
SourcePackage: lightdm
Stacktrace:
 #0 __strcmp_ssse3 () at ../sysdeps/x86_64/multiarch/../strcmp.S:214
 No locals.
 #1 0x0000000000403dfd in _start ()
 No symbol table info available.
StacktraceTop:
 __strcmp_ssse3 () at ../sysdeps/x86_64/multiarch/../strcmp.S:214
 _start ()
Title: lightdm-example-gtk-greeter crashed with SIGSEGV in __strcmp_ssse3()
UpgradeStatus: Upgraded to oneiric on 2009-12-07 (582 days ago)
UserGroups:

Loïc Minier (lool)
visibility: private → public
Changed in lightdm (Ubuntu):
importance: Undecided → Critical
status: New → Confirmed
Revision history for this message
Barry Warsaw (barry) wrote :

A workaround that I noticed in the duped bug.

Choose "Other..." and provide your user name and password. No crash, and it will successfully log you in.

Revision history for this message
Etienne Tourigny (etiennesky) wrote :

Same here, workaround works also.

BUT: I use Ubuntu classic (no Unity), and have to select it every time. It seems there is no way to set it as default... Bug #806064

Revision history for this message
Doug McMahon (mc3man) wrote :

Just to note - as far as installs with current iso 07/15 this seems to affect the live cd and only the first login on an install
After that lightdm does provide a password box for the primary user

It doesn't however provide password box for any added user(s) Bug #811058

Revision history for this message
Doug McMahon (mc3man) wrote :

A bit more on new user accounts -
If trying to login in normally it will crash out to blank screen, but just like the main user if you use 'other' once for any new user than the next time all will be fine, a password box will appear
This only happens after using 'other' , multiple attempts at a normal login for the new account will keep crashing

Revision history for this message
Jason Conti (jconti) wrote :

Thanks to Doug's addition info, I think I managed to track down this problem after creating a new user to test. When clicking the username in lightdm-example-gtk-greeter, start_authentication() is executed in lightdm-example-gtk-greeter.c. If the user is anything but "Other" or "Guest", the greeter attempts to load the user's ~/.dmrc file to look up the default session. Since this user has never logged in, there is no ~/.dmrc file, so the session name is NULL. This NULL session is then passed to set_session() in lightdm-example-gtk-greeter.c, which attempts to compare the name with all the available session using strcmp, which crashes because session is NULL. Could probably use g_strcmp0, but I think the better option is just to add a g_return_if_fail (session != NULL) to the start of the file. I rebuilt with this patch, and haven't been able to crash it in the same way since.

Revision history for this message
Jason Conti (jconti) wrote :

Actually, it seems that logs a nasty message to /var/log/lightdm/:0-greeter.log, but it isn't really a critical problem, so maybe it should just be a simple: if(session == NULL) return;

tags: added: patch
Revision history for this message
Apport retracing service (apport) wrote : This bug is a duplicate

Thank you for taking the time to report this crash and helping to make Ubuntu better. This particular crash has already been reported and is a duplicate of bug #811222, so is being marked as such. Please look at the other bug report to see if there is any missing information that you can provide, or to see if there is a workaround for the bug. Additionally, any further discussion regarding the bug should occur in the other report. Please continue to report any other bugs you may find.

tags: removed: need-amd64-retrace
Revision history for this message
Martin Pitt (pitti) wrote :

Robert, can you please check the attached patch?

Changed in lightdm (Ubuntu Oneiric):
assignee: nobody → Robert Ancell (robert-ancell)
tags: added: bugpattern-needed
Revision history for this message
Shanekpiper (shanekpiper) wrote :

With LightDM installed on boot up I have a blank screen and it hangs after battery check [OK], if I uninstall lightdm and use gdm, it hangs on the Ubuntu 11.10 text bootup splash. To login I have to drop to tty and 'sudo gdm' if I sudo lightdm I get a blank screen again.

Changed in lightdm (Ubuntu Oneiric):
status: Confirmed → Invalid
Revision history for this message
Eliah Kagan (degeneracypressure) wrote :

Given the content of https://bugs.launchpad.net/ubuntu/+source/lightdm/+bug/809890/comments/10, it is virtually certain that marking this bug Invalid and converting to a question was an error. Changing back to Confirmed.

Changed in lightdm (Ubuntu Oneiric):
status: Invalid → Confirmed
Revision history for this message
Doug McMahon (mc3man) wrote :

At least here the issue seems to have been fixed a while ago. (- the lack of a .dmrc at 1st. login
This has been tested on a couple of fresh installs, creating & logging into a new user and a live session using the current daily build
In all cases am presented with a password box, both with the gtk and unity greeters

Revision history for this message
Loïc Minier (lool) wrote :

This is a bug, please don't convert it to a question; thanks

Revision history for this message
Martin Pitt (pitti) wrote :

We use the unity greeter now, so not very relevant any more.

Changed in lightdm (Ubuntu Oneiric):
importance: Critical → Medium
Brad Figg (brad-figg)
tags: added: rls-mgr-o-tracking
Revision history for this message
Robert Ancell (robert-ancell) wrote :

I'm going to mark this fix released, lightdm-example-gtk-greeter hasn't existed for some time and the duplicates are all old. If this exists in the replacement lightdm-gtk-greeter we'll track this in another bug.

Changed in lightdm (Ubuntu Oneiric):
status: Confirmed → Fix Released
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