Bug 1313537

Summary: pam_lastlog may pass a NULL pointer to localtime_r
Product: Red Hat Enterprise Linux 7 Reporter: Paulo Andrade <pandrade>
Component: pamAssignee: Tomas Mraz <tmraz>
Status: CLOSED ERRATA QA Contact: Dalibor Pospíšil <dapospis>
Severity: medium Docs Contact:
Priority: medium    
Version: 7.2CC: dapospis, pkis, tmraz
Target Milestone: rc   
Target Release: ---   
Hardware: s390x   
OS: Linux   
Whiteboard:
Fixed In Version: pam-1.1.8-14.el7 Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of:
: 1341167 (view as bug list) Environment:
Last Closed: 2016-11-04 03:32:13 UTC Type: Bug
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:

Description Paulo Andrade 2016-03-01 20:23:08 UTC 
This problem is very difficult to reproduce. It did
happen all the time with the command:

$ su -

  The analysis of the code path shows:

    if (!(announce & LASTLOG_QUIET)) {

	if (last_login.ll_time) {

	    /* we want the date? */
	    if (announce & LASTLOG_DATE) {
	        struct tm *tm, tm_buf;
		time_t ll_time;

		ll_time = last_login.ll_time;
		tm = localtime_r (&ll_time, &tm_buf);
		strftime (the_time, sizeof (the_time),
	        /* TRANSLATORS: "strftime options for date of last login" */
			  _(" %a %b %e %H:%M:%S %Z %Y"), tm);

  The localtime_r call returns NULL, then it pass NULL
to strftime, and crashes.

  It should check the return value of localtime_r before
calling strftime.

  The user was told to execute:

# sed -e 's/\(pam_lastlog.so.*\)/\1 nodate/g' -i /etc/pam.d/postlogin

that fixed the problem, but more interestingly, after
reverting the sed script change, it continued to work,
so, the problem appears to have been a corrupted
last_login.ll_time, that may have been a corrupted
/var/log/lastlog
Comment 15 errata-xmlrpc 2016-11-04 03:32:13 UTC 
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://rhn.redhat.com/errata/RHBA-2016-2314.html