Bug 809687 (CVE-2012-2100)

Summary: CVE-2012-2100 kernel: ext4: fix inconsistency in ext4_fill_flex_info()
Product: [Other] Security Response Reporter: Eugene Teo (Security Response) <eteo>
Component: vulnerabilityAssignee: Red Hat Product Security <security-response-team>
Status: CLOSED ERRATA QA Contact:
Severity: low Docs Contact:
Priority: low    
Version: unspecifiedCC: agordeev, aiyengar, anton, arozansk, bhu, dhoward, esandeen, fhrbata, jkacur, jlieskov, kernel-mgr, lgoncalv, lwang, plougher, pmatouse, rt-maint, rwheeler, sforsber, vgoyal, williams
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
Fixed In Version: Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2013-08-24 13:17:18 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Bug Depends On: 809688, 809689, 809690, 809691, 809692, 809693    
Bug Blocks: 809684    

Description Eugene Teo (Security Response) 2012-04-04 04:11:07 UTC
Commit 503358ae01b70ce6909d19dd01287093f6b6271c ("ext4: avoid divide by zero when trying to mount a corrupted file system") fixes CVE-2009-4307 by performing a sanity check on s_log_groups_per_flex, since it can be set to a bogus value by an attacker.

More info from Wang Xi:
The first commit (503358ae) fixes the division by zero.  The fix is not perfect because:
1) Theoretically, a standard-conforming C compiler could generate code that is still vulnerable to division by zero, but I was not aware of any compilers doing that.
2) Logically, we should have groups_per_flex = 2^s_log_groups_per_flex, and the fix doesn't really ensure that.  This is obviously not good, but not sure how bad the consequence would be.

Introduced by:

Upstream commit:

Comment 3 Eugene Teo (Security Response) 2012-04-04 04:19:24 UTC
Created kernel tracking bugs for this issue

Affects: fedora-all [bug 809693]

Comment 4 Eugene Teo (Security Response) 2012-04-04 04:24:58 UTC
Upstream commit d50f2ab6 suffers from a buffer overflow issue, see

Comment 6 Vincent Danen 2012-04-12 20:25:06 UTC
This was assigned the name CVE-2012-2100:


Comment 12 Vincent Danen 2012-11-01 18:21:31 UTC

This issue did not affect the versions of the Linux kernel as shipped with Red Hat Enterprise MRG 2.

Comment 15 errata-xmlrpc 2012-11-13 15:37:51 UTC
This issue has been addressed in following products:

  Red Hat Enterprise Linux 5

Via RHSA-2012:1445 https://rhn.redhat.com/errata/RHSA-2012-1445.html

Comment 16 errata-xmlrpc 2012-12-18 22:34:22 UTC
This issue has been addressed in following products:

  Red Hat Enterprise Linux 6

Via RHSA-2012:1580 https://rhn.redhat.com/errata/RHSA-2012-1580.html