Red Hat Bugzilla – Bug 109014
pam_console locks with mount point in fstab which device file does not exist
Last modified: 2007-11-30 17:10:33 EST
From Bugzilla Helper: User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.4.1) Gecko/20031027 Epiphany/1.0.4 Description of problem: pam_console hangs if you've got a line in /etc/fstab which the first field is a file that does not exist, and the second field is listed somewhere in /etc/security/console.perms (so it looks up for the device). Having such a line is quite common: I set up devlabel for my digital camera, so when the camera is not connected, devlabel removes /dev/camera, and I have a line in fstab which mounts /dev/camera /mnt/camera. So I once get locked in boot on when pam_console_apply is called in rc.sysinit, and another time when gdm tries to login and uses pam_console. killing gdm makes it work in next try, I don't know why. Discovered the bug first time when added a line like that in fstab, and found whats wrong simply from the many many open fds of gdm in /proc/asdf/fd/ Version-Release number of selected component (if applicable): pam-0.77-15 How reproducible: Always Steps to Reproduce: 1. Add /123 /mnt/floppy123 auto defaults 0 0 to /etc/fstab 2. Make sure /mnt/floppy* is listed in /etc/security/console.perms 3. Run pam_console_apply Actual Results: It never returns Expected Results: Should return Additional info:
Created attachment 96150 [details] Patch to fix. Patch to fix the problem. Here is the problem: In pam/modules/pam_console/chmod.c, in function change_file, which is supposed to chmod the file, in two cases it calls change_via_fstab, once if it's a directory, and once if the file does not exist! Which the second case is not needed, as a file that does not exist can't be a mount point either. But then it calls change_via_fstab, and if the non-existant file happens to be a mount point (which of course cannot be mounted), then the corresponding device file is passed to change_file, which again calls change_via_fstab, ... The patch simply removes the dead case.
The patch is obvious and just needs to be applied.
This shouldn't hang even without the patch because if the /123 file doesn't exist it will try only /mnt/floppy123 and this doesn't exist too so it recurses once more to change_via_fstab but this won't find anything and it fails. No infinite recursion.
Humm, tested on FC2 now and works. Maybe something changed in the mean time... Feel free to close. They say time heals everything!
I'll add a recursion test to be sure as part of solving the bug 88370.