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Bug 1134430 - pam_limits does not always count the user logins correctly for testing maxlogins
Summary: pam_limits does not always count the user logins correctly for testing maxlogins
Keywords:
Status: CLOSED DUPLICATE of bug 1080023
Alias: None
Product: Red Hat Enterprise Linux 7
Classification: Red Hat
Component: pam
Version: 7.1
Hardware: All
OS: Unspecified
unspecified
unspecified
Target Milestone: rc
: ---
Assignee: Tomas Mraz
QA Contact: BaseOS QE Security Team
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2014-08-27 13:46 UTC by Tomas Mraz
Modified: 2014-09-10 14:47 UTC (History)
2 users (show)

Fixed In Version:
Doc Type: Bug Fix
Doc Text:
Clone Of: 1054936
Environment:
Last Closed: 2014-09-10 14:47:46 UTC
Target Upstream Version:
Embargoed:

Attachments (Terms of Use)

Description Tomas Mraz 2014-08-27 13:46:21 UTC 
Description of problem:
pam_limits has the ability to limit the number of logins for a user.  There are times where there is a utmp entry for a user who is not actually logged on (usually the result of a program crashing).   pam_limits will count this entry as a login and if this puts the user over the limit (in our case 1) the user cannot log in.

Version-Release number of selected component (if applicable):
pam-1.1.1-4

How reproducible:
You can sometimes get this condition by doing a kill -9 on the user's login process, generally more often if it is a X11/xdm login.   You can also create a bugus entry in utmp using utmpdump to restore the utmp file.

Steps to Reproduce:
1. utmpdump into a file
2. log a user off
3. restore the utmp from the file
4. If maxlogins = 1 you can't log on.

Actual results:

User cannot log on

Expected results:

User can log on.

Additional info:

pam_limits reads the utmp file to find the logins for a user but does not verify that the login is still active.  By checking the process PID of the entry you can determine this.  This is the mechanism that "who" uses (you won't see the "ghost" entries in "who".)  I have included a patch to pam_limits that uses the same mechanism as "who" to ensure that utmp records are valid.
Comment 2 Tomas Mraz 2014-09-10 14:47:46 UTC 

*** This bug has been marked as a duplicate of bug 1080023 ***
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