Bug 161188 - Sometimes data/bss can be executable
Sometimes data/bss can be executable
Status: CLOSED ERRATA
Product: Red Hat Enterprise Linux 3
Classification: Red Hat
Component: kernel (Show other bugs)
3.0
All Linux
medium Severity high
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Assigned To: Ingo Molnar
Brian Brock
embargo=self,source=redhat,impact=imp...
: Security
Depends On:
Blocks: 168424
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Reported: 2005-06-21 03:53 EDT by Mark J. Cox (Product Security)
Modified: 2007-11-30 17:07 EST (History)
5 users (show)

See Also:
Fixed In Version: RHSA-2006-0144
Doc Type: Bug Fix
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Last Closed: 2006-03-15 11:08:06 EST
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Description Mark J. Cox (Product Security) 2005-06-21 03:53:03 EDT
The execshield code in RHEL3 is pretty similar so this probably applies to RHEL3
as well; if so this is a serious issue (see #161136) 

+++ This bug was initially created as a clone of Bug #161136 +++

Whilst playing with an X application I found that around 20% of the time
libraries would get loaded between bss and brk, therefore making the
applications bss and data executable.  Ingo discovered it was due to an
execshield bug:

"this patch fixes the fallback randomizer to randomize between 
16MB...start_brk, instead of 16MB...brk. ->brk is problematic because 
due to brk randomization it creates a hole between BSS and brk, where 
DSOs might be loaded randomly." "i have tested the patch against the exec-shield
patch(es) in Fedora, so it would be safe to apply. PIEs work fine and the 
randomization now works correctly."
Comment 5 Ernie Petrides 2005-09-30 02:44:51 EDT
A fix for this problem has just been committed to the RHEL3 U7
patch pool this evening (in kernel version 2.4.21-37.4.EL).
Comment 8 Red Hat Bugzilla 2006-03-15 11:08:06 EST
An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on the solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.

http://rhn.redhat.com/errata/RHSA-2006-0144.html

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