gdm-simple-slave crashed with SIGSEGV in _nss_compat_getpwnam_r()

StacktraceTop:
 _nss_compat_getpwnam_r (name=0x0, pwd=0xb742ec40, buffer=0x8bde400 "P\347B\267P\347B\267\370\343\275\b\370\343\275\bct_get_username: assertion `session != NULL' failed", buflen=1024, errnop=0xb70966e8) at nss_compat/compat-pwd.c:860
 __getpwnam_r (name=0x0, resbuf=0xb742ec40, buffer=0x8bde400 "P\347B\267P\347B\267\370\343\275\b\370\343\275\bct_get_username: assertion `session != NULL' failed", buflen=1024, result=0xbfd38708) at ../nss/getXXbyYY_r.c:256
 getpwnam (name=0x0) at ../nss/getXXbyYY.c:117
 home_dir_using_ecryptfs (username=<value optimized out>) at gdm-simple-slave.c:640
 idle_connect_to_display (slave=0x8bcb800) at gdm-simple-slave.c:1435

seems a bug in the recent gdm update:

home_dir_using_ecryptfs (const gchar *username)
...
        info = getpwnam (username);

that call is done with a NULL username

gdm is not default in oneiric but that's a segfault and should still be fixed there

for me it happens also at boot..don't know why but it tries to start gdm instead of lightdm..it gives error and stops booting..then if i execute sudo lightdm it starts without problems and almost everything works (it's still alpha 2)..i found the error executing dmesg..
I upgrade ubuntu from 11.04 to 11.10 about a month ago..
for now I solved it executing in boot Ctrl + Alt + F6 and then sudo lightdm..hope this may help someone with the same problems..

Happened after upgrading from 11.04 to 11.10, amd64

Update kdm

Happened after upgrading from 11.04 to 11.10, ia32
Couple of days worked fine, but today fails

My duplicate of this bug here: #877170

Hello

 The only thing I could do in similar circumstances 2 months ago was apt-get install kdm and use kdm instead of gdm, (all this Gnome 3 software is to wise for me).

Have a Nice Day

Btw bug can be easily workarounded

$ sudo apt-get install lightdm
$ sudo nano /etc/X11/default-display-manager

and write to it: /usr/sbin/lightdm (instead of /usr/sbin/gdm for gdm)

I can work with out distractions now :)
Thanks

MeToo.

After upgrading from 10.04 to 10.10, 11.04, then 11.10, I started getting this bug.

The fix for me was to disable autologin (and other options?) by doing this
"mv /etc/gdm/custom /etc/gdm/custom.conf.bak" and rebooting.

Got this crash after executing "guest-session" from the GNOME terminal.

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

Bug is still present in 12.04. Installed clean and removed unity components. Replaced lightdm with gdm. Crash comes up every time a user is logged in.

Possibly not the same problem, but I had set up auto-login for a new user without thinking about it. Going back into user manager and switching off auto-login appears to have fixed my gdm issue.

It happened to me in Ubuntu 12.04. I uninstalled unity and unity-2d and installed gdm and gnome-shell. When I rebooted, everything was working fine. But when I selected the option "Don't ask for password while logging in" from "System-settings -> user accounts", the next time rebooting hung with the error message "cannot write bytes: Broken pipe".

This bug was fixed in the package gdm - 3.0.4-0ubuntu16

---------------
gdm (3.0.4-0ubuntu16) quantal; urgency=low

  * debian/patches/42_no_ecryptfs_autologin.patch:
    - don't try to get infos on null usernames (lp: #805154)
 -- Sebastien Bacher <email address hidden> Fri, 06 Jul 2012 12:10:10 +0200

Thank you for fixing this problem.
Will the updated package appear in precise as well?
The current version as per 2012-08-05 is still 3.0.4-0ubuntu15.

I can confirm this bug still exists on Precise.
IMHO it should have higher importance, as it is a show-stopper.

Appearently still happening in Precise (on two of my systems). Please fix it for the LTS, thanks!

The change from 3.0.4-0ubuntu16 is trivial: two lines plus a bit of quilt noise. For me at least the crash is easily reproduced by activating automatic login, and the patch fixes it. Would be lovely to have this uploaded if possible. Thanks for considering.

Thanks for the debdiff, I just uploaded it into the queue for precise-proposed.

Hello Blümchen, or anyone else affected,

Accepted gdm into precise-proposed. The package will build now and be available at http://launchpad.net/ubuntu/+source/gdm/3.0.4-0ubuntu15.3 in a few hours, and then in the -proposed repository.

Please help us by testing this new package. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Your feedback will aid us getting this update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug, mentioning the version of the package you tested, and change the tag from verification-needed to verification-done. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed. In either case, details of your testing will help us make a better decision.

Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in advance!

Following the test case in the description...

~$ cat /etc/gdm/custom.conf
[daemon]
AutomaticLoginEnable=true
AutomaticLogin=rtandy

... with gdm from precise-updates:

~$ dpkg-query -W gdm
gdm 3.0.4-0ubuntu15.2

gdm crashes to a text console and the segfault is recorded in dmesg:

[ 15.338261] gdm-simple-slav[1075]: segfault at 0 ip b651e69e sp bfc90860 error 4 in libnss_compat-2.15.so[b651b000+7000]

After installing gdm from precise-proposed and rebooting:

~$ dpkg-query -W gdm
gdm 3.0.4-0ubuntu15.3

gdm starts properly and automatically logs me in to my desktop session.

Marking verified.

This bug was fixed in the package gdm - 3.0.4-0ubuntu15.3

---------------
gdm (3.0.4-0ubuntu15.3) precise; urgency=low

  * debian/patches/42_no_ecryptfs_autologin.patch:
    - don't try to get infos on null usernames (lp: #805154)
 -- Ryan Tandy <email address hidden> Mon, 25 Nov 2013 13:33:30 -0800

The verification of the Stable Release Update for gdm has completed successfully and the package has now been released to -updates. Subsequently, the Ubuntu Stable Release Updates Team is being unsubscribed and will not receive messages about this bug report. In the event that you encounter a regression using the package from -updates please report a new bug using ubuntu-bug and tag the bug report regression-update so we can easily find any regresssions.