[PATCH 12/13] mac80211: disallow band-switch during CSA

[Luca Coelho <luca@coelho.fi>]

From: Johannes Berg <johannes.berg@intel.com>

If the AP advertises a band switch during CSA, we will not have
the right information to continue working with it, since it will
likely (have to) change its capabilities and we don't track any
capability changes at all. Additionally, we store e.g. supported
rates per band, and that information would become invalid.

Since this is a fringe scenario, just disconnect explicitly.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
---
 net/mac80211/mlme.c | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
index 6de63ba6b1c8..67829667d394 100644
--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -1417,6 +1417,17 @@ ieee80211_sta_process_chanswitch(struct ieee80211_sub_if_data *sdata,
 		return;
 	}
 
+	if (sdata->vif.bss_conf.chandef.chan->band !=
+	    csa_ie.chandef.chan->band) {
+		sdata_info(sdata,
+			   "AP %pM switches to different band (%d MHz, width:%d, CF1/2: %d/%d MHz), disconnecting\n",
+			   ifmgd->associated->bssid,
+			   csa_ie.chandef.chan->center_freq,
+			   csa_ie.chandef.width, csa_ie.chandef.center_freq1,
+			   csa_ie.chandef.center_freq2);
+		goto lock_and_drop_connection;
+	}
+
 	if (!cfg80211_chandef_usable(local->hw.wiphy, &csa_ie.chandef,
 				     IEEE80211_CHAN_DISABLED)) {
 		sdata_info(sdata,
@@ -1429,9 +1440,7 @@ ieee80211_sta_process_chanswitch(struct ieee80211_sub_if_data *sdata,
 			   csa_ie.chandef.width, csa_ie.chandef.center_freq1,
 			   csa_ie.chandef.freq1_offset,
 			   csa_ie.chandef.center_freq2);
-		ieee80211_queue_work(&local->hw,
-				     &ifmgd->csa_connection_drop_work);
-		return;
+		goto lock_and_drop_connection;
 	}
 
 	if (cfg80211_chandef_identical(&csa_ie.chandef,
@@ -1516,6 +1525,9 @@ ieee80211_sta_process_chanswitch(struct ieee80211_sub_if_data *sdata,
 			  TU_TO_EXP_TIME((csa_ie.count - 1) *
 					 cbss->beacon_interval));
 	return;
+ lock_and_drop_connection:
+	mutex_lock(&local->mtx);
+	mutex_lock(&local->chanctx_mtx);
  drop_connection:
 	/*
 	 * This is just so that the disconnect flow will know that
-- 
2.29.2