In multi account environment, gdm starts looping , making failed login noises; pam_unix(gdm:auth)

[jan]

Logging in as user1, then as user2, then using Ubuntu for a while.
After logging OUT as user 1, I start to repeatedly hear failed login noises.
Apparently, gdm starts looping.

At a rate of 40 pairs per minute, /var/log/auth.log gets filled with
gdm[6553]: pam_unix(gdm:auth): check pass; user unknown
gdm[6553]: pam_unix(gdm:auth): authentication failure; logname= uid=0 euid=0 tty=:0 ruser= rhost=

Logging out as user2 stops this.

Either some input device is trying to send something to gdm, or the console is not correctly connected, or gdm is buggy.

As the root cause is unknown, and the login process is involved, this behavior, of side-effects from it, might have security implications.

It does NOT happen all the time.

$ lsb_release -rd
Description: Ubuntu 8.04.1
Release: 8.04

I disabled Software Sound Mixing (ESD) as otherwise hang-up like situations seem to occur with other software that tries to use sound output.

[Sebastien Bacher (seb128)]

Thank you for your bug report, that's not a security issue and there is no other similar bug

[Eder Bastos (riskbreaker927)]

I want to report that I've also had this problem with Hardy, Intrepid, and Jaunty. I don't know if it is a hardware issue so let me know what information I need to post. The same text loops in my auth.log:

May 31 15:21:33 mulletsystemX gdm[3195]: pam_unix(gdm:auth): check pass; user unknown
May 31 15:21:33 mulletsystemX gdm[3195]: pam_unix(gdm:auth): authentication failure; logname= uid=0 euid=0 tty=:0 ruser= rhost=

[Eder Bastos (riskbreaker927)]

I'm not sure what specifically causes it, but the situation in the original post is true. In addition, when this does happen, generally I no longer have sound in the X session I'm trying to use, which makes this bug a little more important I think. I've been able to work around the issue by either restarting the X server, logging out one of the users, or pressing ctrl+alt+F10 which brings me to the login screen and for some reason stops it from looping (it displays the message saying that an invalid login occured once.) These aren't really acceptable workarounds though.

[Sebastien Bacher (seb128)]

Could you try if that's still an issue on karmic?

[Jakob Unterwurzacher (jakobunt)]

I see it right now on karmic.

To trigger it:
1) Login as jakob
2) Switch user, login as gast
3) Switch user, login back to jakob

/var/log/gdm/:2-slave.log fills with:
--------
gdm-session-worker[3963]: pam_unix(gdm:auth): authentication failure; logname= uid=0 euid=0 tty=:2 ruser= rhost= user=jakob
gdm-session-worker[3967]: pam_unix(gdm:auth): authentication failure; logname= uid=0 euid=0 tty=:2 ruser= rhost= user=jakob
gdm-session-worker[3971]: pam_unix(gdm:auth): authentication failure; logname= uid=0 euid=0 tty=:2 ruser= rhost= user=jakob
--------

/var/log/gdm/:2-greeter.log fills with (original is in german, i translated it to english)
--------
Window manager warning: Buggy client sent a _NET_ACTIVE_WINDOW message with a timestamp of 0 for 0x1600028 (Login window)
Window manager warning: meta_window_activate called by a pager with a 0 timestamp; the pager needs to be fixed.
Window manager warning: Buggy client sent a _NET_ACTIVE_WINDOW message with a timestamp of 0 for 0x1600028 (Login window)
Window manager warning: meta_window_activate called by a pager with a 0 timestamp; the pager needs to be fixed.
--------

Additionally, gdm-simple-slave and gdm-simple-greeter start leaking memory. I rebooted as both processes reached 100MB of private writeable memory each.

[vito (ovitorio)]

I confirm this bug on a system with the following configuration:

lsb_release -rd
Description: Ubuntu 8.04.4 LTS
Release: 8.04

Asus P4PE motherboard, ATI RV350 AS [Radeon 9550] graphic card. The video driver in use: xserver-xorg-video-ati.

I experience this bug as described by the original reporter, except that neither user's logout, no gdm restart does not help. The only thing to stop this annoyance is to reboot.

There are additional problems that accompany this bug on my system. I am not sure whether they realy are related, or just overlap, or one causes the others. But to me they all look as a part of a larger picture and might be symptoms of a deeper problem.

It may be important to note that the bug in question here and the ones I'm going to describe below, showed up approximately at the same time - 1-2 months ago. They happen once in a wile, with abut the same frequency and not always all together.

It also may be important to note, that before mentioned period of time I had a perfectly stable LTS machine. Thus it looks like these problems slipped in with the last 1-2 months updates.

1. About 4-5 times in the mentioned period my monitor all at a sudden get black with a message "no signal" on it. Twice a keyboard was blocked completely and I had no choice but push the power button off. One time Ctrl-Backspace helped. Another 1-2 times I used "Magic Key" sequence (RSEIUB) to reboot.

While troubleshooting "no signal" problem I found all at a sudden that my "direct rendering" was Off with an glxgears reported very low frame rate - about 220 FS comparing with usual 1700-1800 FS. Reinstalling xserver-xorg-video-ati and other related packages seemingly fixed things.

But on the next day, after the second user get logout and I get login, I checked my video driver state, and found the problem was back: no "direct rendering" and low frame rate.

At this moment I found system log showed gdm running at the background in an loop attempting to login as the described by original bug reporter endlessly. And after I turned my speakers on I was certainly greeted with damn drumbeats.

This was the first time I had some indication 2 problems might be related (X get slow because gdm was taking a lot of resources?).

2. About within the same period of time my system stopped reacting on mouse clicks properly. Occasionally there are periods with quite a notable delay between a mouse click and the system response. Sometimes to close a window I have to click on the Close button 2-3 times for system to react.

Sorry for a messy and lengthy description. It's quite difficult to provide with what I started seeing as a one picture. Unfortunately neither of above I can really reproduce. They come and they go. The larger scale troubles, like gdm looping and monitor loosing signal, do not happen very often. But the mouse gets retarded and video frame rate gets low on a daily basis now.

The last thing to mention. I share my desktop with another user. We run it all day long and use Switch User applet intensively. It is quite a rare case that one of use logout.

Hope this helps.

[Vladimir Fonov (vladimir-fonov)]

Hello,

I confirm this bug on a Ubuntu 8.04.4 LTS , we have 3 identical machines running pretty much the same installation of Ubuntu, but only one of them seem to develop this problem. Once user logs in to the system these messages are being generated at a rate of approximately 1/sec