From 827d42c9ac91ddd728e4f4a31fefb906ef2ceff7 Mon Sep 17 00:00:00 2001 From: Johannes Berg Date: Sun, 22 Nov 2009 12:28:41 +0100 Subject: mac80211: fix spurious delBA handling 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 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 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. Reported-by: Lennert Buytenhek Cc: stable@kernel.org Signed-off-by: Johannes Berg Signed-off-by: John W. Linville --- include/net/mac80211.h | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'include') diff --git a/include/net/mac80211.h b/include/net/mac80211.h index c75b960c8ac..998c30fc898 100644 --- a/include/net/mac80211.h +++ b/include/net/mac80211.h @@ -1283,6 +1283,12 @@ enum ieee80211_filter_flags { * * These flags are used with the ampdu_action() callback in * &struct ieee80211_ops to indicate which action is needed. + * + * Note that drivers MUST be able to deal with a TX aggregation + * session being stopped even before they OK'ed starting it by + * calling ieee80211_start_tx_ba_cb(_irqsafe), because the peer + * might receive the addBA frame and send a delBA right away! + * * @IEEE80211_AMPDU_RX_START: start Rx aggregation * @IEEE80211_AMPDU_RX_STOP: stop Rx aggregation * @IEEE80211_AMPDU_TX_START: start Tx aggregation -- cgit v1.2.3-70-g09d2