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> 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> 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.
Upstream commit: http://git.kernel.org/linus/4253119acf412fd686ef4bd8749b5a4d70ea3a51 http://git.kernel.org/linus/827d42c9ac91ddd728e4f4a31fefb906ef2ceff7 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.
Both fixes are now in upstream kernel 2.6.31.7
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
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