Red Hat Bugzilla – Bug 59936
console.perms breaks
Last modified: 2007-04-18 12:40:26 EDT
Description of Problem: Version-Release number of selected component (if applicable): pam-0.75-19 How Reproducible: Often Steps to Reproduce: 1. Keep logging in as different users Actual Results: /dev entries that are supposed to get their permissions changed by console.perms do not get their permissions changed after a while Expected Results: Ownership of selected /dev entries should be given to the first console user who logs in, /every time/, not just the first couple. Additional Information: After logging in many different times as different users on various local ttys, the permissions on, say, /dev/dsp stop changing from user to user, for whoever happens to be the first user logged in at the console. The user name I use, 'nix', is the one most often used, since I'm the most frequent user of the computer in question. After logging in many times on various local ttys (X and otherwise), ownership of /dev files such as /dev/dsp remains mine even after I log out, the point at which it should revert to 600 root.root . I know this because, when I log in remotely as root (a remote login will not trigger a change in permissions, nor a change in ownership), and do ls -l /dev/dsp, I find that the owner is still 'nix', instead of 600 root.root. I tried removing /var/run/console.lock, followed by pam_console_apply. I also tried pam_console_apply -r. Running these worked (ownerships looked OK), but it didn't get the ownerships and permissions automagically changing again. Now, if someone wants to play, say, Tux Racer, I have to log in as root and explicitly give them permission to use /dev/dsp. Thanks for your help.
I think I may have found both the cause and the resolution of the bug. Cause: When I log in as any user via X, I get console ownership and various other goodies. When I kill X brutally (C-A-Backspace) instead of gracefully, Bad Things happen: - /etc/X11/xdm/TakeConsole doesn't get executed - /var/run/console.lock doesn't get removed - /var/run/console now contains a file called 'nix' that contains 1 byte:'1' Fix (as root): /etc/X11/xdm/TakeConsole rm /var/run/console.lock rm /var/run/console/nix1 pam_console_apply -r Consequently, I have been able to completely and consistently reproduce the behaviour: 1. Log in remotely as root. 2. useradd -g users nix1 3. passwd nix1 4. Log into X via gdm locally as nix1 5. C-A-Backspace (kills X) That's it, the ownership auto-assignment cycle is now broken, until (as mentioned): [root@...]# /etc/X11/xdm/TakeConsole [root@...]# rm /var/run/console.lock [root@...]# rm /var/console/nix1 [root@...]# pam_console_apply -r The crucial step seems to be rm /var/console/nix1 Would it be possible/wise to run these steps from someplace where the exit status of X is within the scope of the script (Checkable via $? or some such). By this I mean that you should include this kind of 'X-has-crashed-so-if-the-user-had-the-ownerships-then-fix-it-so-the-automagic-ownership-reassignment-works-again' check somewhere in the X/[xkg]dm-related scripts. Are these steps enough ? Am I missing something due to the fact that I'm not thoroughly familiar with the workings of these ownership assignments ? Thanks for your support.
(Using RH 7.2, pam-0.72-19, gdm-2.2.3.1-20) AFAICT this is caused by somewhat of a problem in pam_console: When you kill X with Ctrl-Alt-Backspace, the socket /tmp/.X11-unix/X0 (or X1, or ...) is removed. Then, when pam_console.c:pam_sm_close_session is called (in my case from gdm's gdm_slave_session_stop,gdm_verify_cleanup), it checks whether the 'tty' the user was logged in to (ie. :0, :1, etc...) actually exists. In the X display case, this translates to the existance of the mentioned /tmp/.X11-unix/X? file. This check now clearly fails, and so the console use-count isn't decremented and console.lock isn't removed, causing the problems mentioned in the original bugreport. To recap, the code path that causes this specific problem is: pam_session.c:pam_close_session(), calls (through dispatch and all that) pam_console.c:pam_sm_close_session(), calls config.y:check_console_name(), which checks the existance of /tmp/.X11-unix/X?
*** Bug 71468 has been marked as a duplicate of this bug. ***
It looks like this works ok in RHL 9 at least. I'm using gdm and I see /tmp/X11-unix/X0 after killing X with ctrl+alt+backspace.