mac80211: connect with HT20 if HT40 is not permitted

Some changes to fix issues with HT40 APs in Korea
and follow-up changes to allow using HT40 even if
the local regulatory database disallows it caused
issues with iwlwifi (and could cause issues with
other devices); iwlwifi firmware would assert if
you tried to connect to an AP that has an invalid
configuration (e.g. using HT40- on channel 140.)

Fix this, while avoiding the "Korean AP" issue by
disabling HT40 and advertising HT20 to the AP
when connecting.

Cc: stable@vger.kernel.org [3.6]
Reported-by: Florian Reitmeir <florian@reitmeir.org>
Tested-by: Florian Reitmeir <florian@reitmeir.org>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 20 insertions, 10 deletions

diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
index e510a33fec76..1b7eed252fe9 100644
--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -3099,22 +3099,32 @@ static int ieee80211_prep_channel(struct ieee80211_sub_if_data *sdata,
                                    ht_cfreq, ht_oper->primary_chan,
                                    cbss->channel->band);
                         ht_oper = NULL;
+                } else {
+                        channel_type = NL80211_CHAN_HT20;
                 }
         }
 
-        if (ht_oper) {
-                channel_type = NL80211_CHAN_HT20;
+        if (ht_oper && sband->ht_cap.cap & IEEE80211_HT_CAP_SUP_WIDTH_20_40) {
+                /*
+                 * cfg80211 already verified that the channel itself can
+                 * be used, but it didn't check that we can do the right
+                 * HT type, so do that here as well. If HT40 isn't allowed
+                 * on this channel, disable 40 MHz operation.
+                 */
 
-                if (sband->ht_cap.cap & IEEE80211_HT_CAP_SUP_WIDTH_20_40) {
-                        switch (ht_oper->ht_param &
-                                        IEEE80211_HT_PARAM_CHA_SEC_OFFSET) {
-                        case IEEE80211_HT_PARAM_CHA_SEC_ABOVE:
+                switch (ht_oper->ht_param & IEEE80211_HT_PARAM_CHA_SEC_OFFSET) {
+                case IEEE80211_HT_PARAM_CHA_SEC_ABOVE:
+                        if (cbss->channel->flags & IEEE80211_CHAN_NO_HT40PLUS)
+                                ifmgd->flags |= IEEE80211_STA_DISABLE_40MHZ;
+                        else
                                 channel_type = NL80211_CHAN_HT40PLUS;
-                                break;
-                        case IEEE80211_HT_PARAM_CHA_SEC_BELOW:
+                        break;
+                case IEEE80211_HT_PARAM_CHA_SEC_BELOW:
+                        if (cbss->channel->flags & IEEE80211_CHAN_NO_HT40MINUS)
+                                ifmgd->flags |= IEEE80211_STA_DISABLE_40MHZ;
+                        else
                                 channel_type = NL80211_CHAN_HT40MINUS;
-                                break;
-                        }
+                        break;
                 }
         }