Bug 541149 (CVE-2009-4026, CVE-2009-4027)

Summary: CVE-2009-4026 CVE-2009-4027 kernel: mac80211: fix spurious delBA handling
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: high Docs Contact:
Priority: high    
Version: unspecifiedCC: dfeng, dhoward, jolsa, jpirko, jskrabal, lgoncalv, linville, lwang, rcvalle, security-response-team
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard: impact=important,source=vendor-sec,reported=20091125,public=20091130,cvss2=7.8/AV:N/AC:L/Au:N/C:N/I:N/A:C,cwe=CWE-617
Fixed In Version: Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2010-12-21 17:05:44 EST Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: ---
Bug Depends On: 541151, 541152    
Bug Blocks:    

Description Eugene Teo (Security Response) 2009-11-24 22:28:36 EST
Lennert Buytenhek noticed that delBA handling in mac80211 was broken and has remotely triggerable problems, some of which are due to some code shuffling I did that ended up changing the order in which things were done -- this was

  commit d75636ef9c1af224f1097941879d5a8db7cd04e5
  Author: Johannes Berg <johannes@sipsolutions.net>
  Date:   Tue Feb 10 21:25:53 2009 +0100

    mac80211: RX aggregation: clean up stop session

and other parts were already present in the original

  commit d92684e66091c0f0101819619b315b4bb8b5bcc5
  Author: Ron Rindjunsky <ron.rindjunsky@intel.com>
  Date:   Mon Jan 28 14:07:22 2008 +0200

      mac80211: A-MPDU Tx add delBA from recipient support

The first problem is that I moved a BUG_ON before various checks -- thereby making it possible to hit. As the comment indicates, the BUG_ON can be removed since the ampdu_action callback must already exist when the state is != IDLE.

The second problem isn't easily exploitable but there's a race condition due to unconditionally setting the state to OPERATIONAL when a delBA frame is received, even when no aggregation session was ever initiated. All the drivers
accept stopping the session even then, but that opens a race window where crashes could happen before the driver accepts it. Right now, a WARN_ON may happen with non-HT drivers, while the race opens only for HT drivers.

For this case, there are two things necessary to fix it:
 1) don't process spurious delBA frames, and be more careful about the session state; don't drop the lock

 2) HT drivers need to be prepared to handle a session stop even before the session was really started -- this is true for all drivers (that support aggregation) but iwlwifi which can be fixed easily. The other HT drivers (ath9k and ar9170) are behaving properly already.
Comment 4 Eugene Teo (Security Response) 2009-11-30 23:08:08 EST
Upstream commit:

Commits 4253119a and 827d42c9 (first problem) = CVE-2009-4026
Commit 827d42c9 (second problem) = CVE-2009-4027

Note that CVE-2009-4026 did not affect the versions of the Linux kernel as shipped with Red Hat Enterprise Linux 3, 4, 5 and Red Hat Enterprise MRG. 

CVE-2009-4027 did not affect the versions of the Linux kernel as shipped with Red Hat Enterprise Linux 3, 4 and Red Hat Enterprise MRG. We will be addressing this in Red Hat Enterprise Linux 5 soon.
Comment 7 Chuck Ebbert 2009-12-08 17:57:13 EST
Both fixes are now in upstream kernel
Comment 8 errata-xmlrpc 2010-03-30 02:49:05 EDT
This issue has been addressed in following products:

  Red Hat Enterprise Linux 5

Via RHSA-2010:0178 https://rhn.redhat.com/errata/RHSA-2010-0178.html
Comment 11 errata-xmlrpc 2010-04-27 08:46:04 EDT
This issue has been addressed in following products:

  Red Hat Enterprise Linux 5.4.Z - Server Only

Via RHSA-2010:0380 https://rhn.redhat.com/errata/RHSA-2010-0380.html