netdev - [PATCH AUTOSEL 4.4 36/38] mac80211: don't filter out beacons once we start CSA

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Date:   Tue, 22 Dec 2020 21:25:14 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Emmanuel Grumbach <emmanuel.grumbach@...el.com>,
        Luca Coelho <luciano.coelho@...el.com>,
        Johannes Berg <johannes.berg@...el.com>,
        Sasha Levin <sashal@...nel.org>,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org
Subject: [PATCH AUTOSEL 4.4 36/38] mac80211: don't filter out beacons once we start CSA

From: Emmanuel Grumbach <emmanuel.grumbach@...el.com>

[ Upstream commit 189a164d0fc6c59a22c4486d641d0a0a0d33387a ]

I hit a bug in which we started a CSA with an action frame,
but the AP changed its mind and didn't change the beacon.
The CSA wasn't cancelled and we lost the connection.

The beacons were ignored because they never changed: they
never contained any CSA IE. Because they never changed, the
CRC of the beacon didn't change either which made us ignore
the beacons instead of processing them.

Now what happens is:
1) beacon has CRC X and it is valid. No CSA IE in the beacon
2) as long as beacon's CRC X, don't process their IEs
3) rx action frame with CSA
4) invalidate the beacon's CRC
5) rx beacon, CRC is still X, but now it is invalid
6) process the beacon, detect there is no CSA IE
7) abort CSA

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@...el.com>
Signed-off-by: Luca Coelho <luciano.coelho@...el.com>
Link: https://lore.kernel.org/r/iwlwifi.20201206145305.83470b8407e6.I739b907598001362744692744be15335436b8351@changeid
Signed-off-by: Johannes Berg <johannes.berg@...el.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 net/mac80211/mlme.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
index 6a94b14817471..7b9766998c105 100644
--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -1296,6 +1296,7 @@ ieee80211_sta_process_chanswitch(struct ieee80211_sub_if_data *sdata,
 	sdata->csa_chandef = csa_ie.chandef;
 	sdata->csa_block_tx = csa_ie.mode;
 	ifmgd->csa_ignored_same_chan = false;
+	ifmgd->beacon_crc_valid = false;

 	if (sdata->csa_block_tx)
 		ieee80211_stop_vif_queues(local, sdata,
-- 
2.27.0