Gnome Xorg sessions fail to start with LDAP users (but Wayland or local users work). Xorg crashes with SIGSEGV in ?? from _init() from xf86RandR12Init() from xf86CrtcScreenInit()

[Timo Denissen]

When trying to login to Gnome with an remote user from an LDAP (LDAP is available and connectable when in GDM) using X11, GDM loops around three to five times before actually granting access to the desktop.

This does not happen when
a) Wayland is used instead of X11 or,
b) the LDAP server is not reachable during login, using X11, or
c) a local user is logged in instead, using X11

The LDAP connection is established using the Univention Domain Join Client: https://launchpad.net/~univention-dev/+archive/ubuntu/ppa?field.series_filter=bionic

Do you require additional information?

Release:
Description: Ubuntu 18.04.3 LTS
Release: 18.04

GDM3:
gdm3:
  Installed: 3.28.3-0ubuntu18.04.4
  Candidate: 3.28.3-0ubuntu18.04.4
  Version table:
 *** 3.28.3-0ubuntu18.04.4 500
        500 http://de.archive.ubuntu.com/ubuntu bionic-updates/main amd64 Packages
        500 http://security.ubuntu.com/ubuntu bionic-security/main amd64 Packages
        100 /var/lib/dpkg/status
     3.28.0-0ubuntu1 500
        500 http://de.archive.ubuntu.com/ubuntu bionic/main amd64 Packages

[Sebastien Bacher (seb128)]

Thank you for your bug report, that looks like an upstream issue could you maybe report it on https://gitlab.gnome.org/GNOME/gdm/issues/ ?

It could also help to enable Debug in /etc/gdm3/custom.conf , restart and attach a 'journalctl -b 0' log to the bug

[Sebastien Bacher (seb128)]

Could you also give details on what you mean 'GDM loops around three to five times'? Do you get bounced back to the login and need to enter your password several time? Does it display a spinenr that 'loops'? Does it reload in some way by itself before loading fine by itself?

[Timo Denissen (timodenissen)]

I'll add the log asap.

> Could you also give details on what you mean 'GDM loops around three to five times'?
Sure. GDM starts, I select my user to log in with, I enter my password, the screen goes blank for two seconds, and I'm back at the user selection.

The password is not entered incorrectly, because if I mistype the password I get the corresponding error message saying "Your password is wrong".

[Daniel van Vugt (vanvugt)]

Since you say the problem only happens with X11 and not Wayland, I assume that refers to the choice of login session. Worth noting that the login screen itself uses Wayland and not X11 :)

So if the only problem here is starting X sessions, please:

1. Reboot to clear the system log.
2. Try to log in with X11 once, it should fail.
3. Reboot the system again, immediately.
4. Try to log in with Wayland, it should succeed.
5. Run this command to gather the log of the failed attempt:

   journalctl -b-1 > prevboot.txt

6. Run these commands to give us extra information about the system:

   dmesg > dmesg.txt
   lspci -k > lspcik.txt

7. Attach all three text files here.

[Daniel van Vugt (vanvugt)]

Also, be warned that if the problem only occurs with the PPA https://launchpad.net/~univention-dev/+archive/ubuntu/ppa?field.series_filter=bionic then we may have to close this bug as that is not part of Ubuntu. You may need to report the bug to Univention instead:

  https://forge.univention.org/bugzilla/index.cgi

[Timo Denissen (timodenissen)]

Attached are the three requested files.

[Daniel van Vugt (vanvugt)]

Thanks. It appears this is a simple Xorg crash:

Jan 02 08:09:39 ektorp /usr/lib/gdm3/gdm-x-session[4553]: (EE)
Jan 02 08:09:39 ektorp /usr/lib/gdm3/gdm-x-session[4553]: (EE) Backtrace:
Jan 02 08:09:39 ektorp /usr/lib/gdm3/gdm-x-session[4553]: (EE) 0: /usr/lib/xorg/Xorg (OsLookupColor+0x139) [0x55e75e46d7d9]
Jan 02 08:09:39 ektorp /usr/lib/gdm3/gdm-x-session[4553]: (EE) 1: /lib/x86_64-linux-gnu/libpthread.so.0 (funlockfile+0x50) [0x7f98acf708df]
Jan 02 08:09:39 ektorp /usr/lib/gdm3/gdm-x-session[4553]: (EE) 2: /usr/lib/xorg/modules/drivers/modesetting_drv.so (_init+0x6501) [0x7f98aa25b251]
Jan 02 08:09:39 ektorp /usr/lib/gdm3/gdm-x-session[4553]: (EE) 3: /usr/lib/xorg/Xorg (xf86RandR12Init+0x394) [0x55e75e38cae4]
Jan 02 08:09:39 ektorp /usr/lib/gdm3/gdm-x-session[4553]: (EE) 4: /usr/lib/xorg/Xorg (xf86CrtcScreenInit+0x2b) [0x55e75e37f58b]
Jan 02 08:09:39 ektorp /usr/lib/gdm3/gdm-x-session[4553]: (EE) 5: /usr/lib/xorg/modules/drivers/modesetting_drv.so (_init+0x3d0e) [0x7f98aa255eee]
Jan 02 08:09:39 ektorp /usr/lib/gdm3/gdm-x-session[4553]: (EE) 6: /usr/lib/xorg/Xorg (AddScreen+0xd7) [0x55e75e3107e7]
Jan 02 08:09:39 ektorp /usr/lib/gdm3/gdm-x-session[4553]: (EE) 7: /usr/lib/xorg/Xorg (InitOutput+0x3ce) [0x55e75e350c0e]
Jan 02 08:09:39 ektorp /usr/lib/gdm3/gdm-x-session[4553]: (EE) 8: /usr/lib/xorg/Xorg (InitFonts+0x1dd) [0x55e75e31438d]
Jan 02 08:09:39 ektorp /usr/lib/gdm3/gdm-x-session[4553]: (EE) 9: /lib/x86_64-linux-gnu/libc.so.6 (__libc_start_main+0xe7) [0x7f98acb8eb97]
Jan 02 08:09:39 ektorp /usr/lib/gdm3/gdm-x-session[4553]: (EE) 10: /usr/lib/xorg/Xorg (_start+0x2a) [0x55e75e2fe1ea]
Jan 02 08:09:39 ektorp /usr/lib/gdm3/gdm-x-session[4553]: (EE)
Jan 02 08:09:39 ektorp /usr/lib/gdm3/gdm-x-session[4553]: (EE) Segmentation fault at address 0x30
Jan 02 08:09:39 ektorp /usr/lib/gdm3/gdm-x-session[4553]: (EE)
Jan 02 08:09:39 ektorp /usr/lib/gdm3/gdm-x-session[4553]: Fatal server error:
Jan 02 08:09:39 ektorp /usr/lib/gdm3/gdm-x-session[4553]: (EE) Caught signal 11 (Segmentation fault). Server aborting

[Daniel van Vugt (vanvugt)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. It sounds like some part of the system has crashed. To help us find the cause of the crash please follow these steps:

1. Look in /var/crash for crash files and if found run:
    ubuntu-bug YOURFILE.crash
Then tell us the ID of the newly-created bug.

2. If step 1 failed then look at https://errors.ubuntu.com/user/ID where ID is the content of file /var/lib/whoopsie/whoopsie-id on the machine. Do you find any links to recent problems on that page? If so then please send the links to us.

3. If step 2 also failed then apply the workaround from bug 994921, reboot, reproduce the crash, and retry step 1.

Please take care to avoid attaching .crash files to bugs as we are unable to process them as file attachments. It would also be a security risk for yourself.

[Timo Denissen (timodenissen)]

I executed "ubuntu-bug /var/crash/crashfile.crash" but can't see a bug ID.

On my whoopsie page, no new entry is created.

How do I find out which bug ID was assigned to my ubuntu-bug call?

[Daniel van Vugt (vanvugt)]

Try step 2 in comment #11, or try replacing 'ubuntu-bug' with 'apport-cli'.

[Timo Denissen (timodenissen)]

apport-cli failed as well.

This is the crash report from yestermorning: https://errors.ubuntu.com/oops/24bfc517-306a-11ea-a772-fa163ee63de6.

[Daniel van Vugt (vanvugt)]

Thanks but the error tracker seems to have had trouble with that :(

> This problem failed to retrace because there was no crash signature after retracing.

I can't see why...

I think the next step should be to get another Xorg log with the crash details to confirm it remains the same. To do that please follow steps 1-5,7 again in comment #4.

[Timo Denissen (timodenissen)]

dmesg.txt (new)

[Timo Denissen (timodenissen)]

Attached are the three log files, and a new crash report (upload now worked with apport-cli): https://errors.ubuntu.com/oops/327a1f18-32cd-11ea-b1f2-fa163e983629

[Daniel van Vugt (vanvugt)]

Thanks. The crash report is not usable according to the robots, not sure why...

However your new prevboot.txt is useful and shows:

Jan 09 11:40:31 ektorp /usr/lib/gdm3/gdm-x-session[3134]: (EE)
Jan 09 11:40:31 ektorp /usr/lib/gdm3/gdm-x-session[3134]: (EE) Backtrace:
Jan 09 11:40:31 ektorp /usr/lib/gdm3/gdm-x-session[3134]: (EE) 0: /usr/lib/xorg/Xorg (OsLookupColor+0x139) [0x555af506d7d9]
Jan 09 11:40:31 ektorp /usr/lib/gdm3/gdm-x-session[3134]: (EE) 1: /lib/x86_64-linux-gnu/libpthread.so.0 (funlockfile+0x50) [0x7f69368f68df]
Jan 09 11:40:31 ektorp /usr/lib/gdm3/gdm-x-session[3134]: (EE) 2: /usr/lib/xorg/modules/drivers/modesetting_drv.so (_init+0x6501) [0x7f6933be1251]
Jan 09 11:40:31 ektorp /usr/lib/gdm3/gdm-x-session[3134]: (EE) 3: /usr/lib/xorg/Xorg (xf86RandR12Init+0x394) [0x555af4f8cae4]
Jan 09 11:40:31 ektorp /usr/lib/gdm3/gdm-x-session[3134]: (EE) 4: /usr/lib/xorg/Xorg (xf86CrtcScreenInit+0x2b) [0x555af4f7f58b]
Jan 09 11:40:31 ektorp /usr/lib/gdm3/gdm-x-session[3134]: (EE) 5: /usr/lib/xorg/modules/drivers/modesetting_drv.so (_init+0x3d0e) [0x7f6933bdbeee]
Jan 09 11:40:31 ektorp /usr/lib/gdm3/gdm-x-session[3134]: (EE) 6: /usr/lib/xorg/Xorg (AddScreen+0xd7) [0x555af4f107e7]
Jan 09 11:40:31 ektorp /usr/lib/gdm3/gdm-x-session[3134]: (EE) 7: /usr/lib/xorg/Xorg (InitOutput+0x3ce) [0x555af4f50c0e]
Jan 09 11:40:31 ektorp /usr/lib/gdm3/gdm-x-session[3134]: (EE) 8: /usr/lib/xorg/Xorg (InitFonts+0x1dd) [0x555af4f1438d]
Jan 09 11:40:31 ektorp /usr/lib/gdm3/gdm-x-session[3134]: (EE) 9: /lib/x86_64-linux-gnu/libc.so.6 (__libc_start_main+0xe7) [0x7f6936514b97]
Jan 09 11:40:31 ektorp /usr/lib/gdm3/gdm-x-session[3134]: (EE) 10: /usr/lib/xorg/Xorg (_start+0x2a) [0x555af4efe1ea]
Jan 09 11:40:31 ektorp /usr/lib/gdm3/gdm-x-session[3134]: (EE)
Jan 09 11:40:31 ektorp /usr/lib/gdm3/gdm-x-session[3134]: (EE) Segmentation fault at address 0x30
Jan 09 11:40:31 ektorp /usr/lib/gdm3/gdm-x-session[3134]: (EE)
Jan 09 11:40:31 ektorp /usr/lib/gdm3/gdm-x-session[3134]: Fatal server error:
Jan 09 11:40:31 ektorp /usr/lib/gdm3/gdm-x-session[3134]: (EE) Caught signal 11 (Segmentation fault). Server aborting
Jan 09 11:40:31 ektorp /usr/lib/gdm3/gdm-x-session[3134]: (EE)

which seems to agree with comments #8-#10.

[Daniel van Vugt (vanvugt)]

I did just find and create bug 1859112. This might be the same as that one but we can't be sure without line number info.

[Timo Denissen (timodenissen)]

So far, this issue did not occur using Ubuntu 20.04. I'll keep you up to date.