Bug 1304426

Summary: [rfe] /bin/su should be improved to reduce stack use
Product: Red Hat Enterprise Linux 7 Reporter: Striker Leggette <striker>
Component: util-linuxAssignee: Karel Zak <kzak>
Status: CLOSED ERRATA QA Contact: qe-baseos-daemons
Severity: unspecified Docs Contact:
Priority: unspecified    
Version: 7.2CC: sbeal, todoleza
Target Milestone: rc   
Target Release: ---   
Hardware: Unspecified   
OS: Unspecified   
Whiteboard:
Fixed In Version: util-linux-2.23.2-31.el7 Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2016-11-03 21:26:51 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 Striker Leggette 2016-02-03 14:59:35 UTC 
[+] Description of problem:
 /bin/su should print a warning if stack size is a low number

[+] Version-Release number of selected component (if applicable):


[+] How reproducible:
Always

[+] Steps to Reproduce:
1. $ ulimit -s 275
2. $ su
3.

[+] Actual results:
$ /bin/su
Segmentation fault

[+] Expected results:
$ /bin/su
Warning - stack size is $(ulimit -s)
This may cause unwanted results
Segmentation fault

[+] Additional info:
As of util-linux 2.23.2-26.el7, the tested minimal required stack size is 276.  Anything lower will cause /bin/su to segfault.  The /bin/su application should have an if, then (example) rule that if it matches 300 (example number) or lower, it prints a warning.
Comment 1 Striker Leggette 2016-02-03 15:13:20 UTC 
Since su is written in C, example:

if ( $(ulimit -s) < 300 )
    printf( "Warning - stack size is less than 300" );

Or, a more long-term solution would be to implement a separate function that allows itself to calculate it's own stack requirement and then match that against what is available and cleanly exit if the requirement is less than available.
Comment 2 Striker Leggette 2016-02-03 15:15:40 UTC 
By "cleanly exit if the requirement is less than available" I meant "cleanly exit if the requirement is greater than available".
Comment 10 Mike McCune 2016-03-28 22:54:17 UTC 
This bug was accidentally moved from POST to MODIFIED via an error in automation, please see mmccune with any questions
Comment 15 errata-xmlrpc 2016-11-03 21:26:51 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/RHSA-2016-2605.html