mac80211: add missing sanity checks for action frames

Various missing sanity checks caused rejected action frames to be
interpreted as channel switch announcements, which can cause a client
mode interface to switch away from its operating channel, thereby losing
connectivity. This patch ensures that only spectrum management action
frames are processed by the CSA handling function and prevents rejected
action frames from getting processed by the MLME code.

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Cc: stable@kernel.org
Signed-off-by: John W. Linville <linville@tuxdriver.com>

net/mac80211/mlme.c

@@ -1963,7 +1963,9 @@ static void ieee80211_sta_rx_queued_mgmt(struct ieee80211_sub_if_data *sdata,
 			rma = ieee80211_rx_mgmt_disassoc(sdata, mgmt, skb->len);
 			break;
 		case IEEE80211_STYPE_ACTION:
-			/* XXX: differentiate, can only happen for CSA now! */
+			if (mgmt->u.action.category != WLAN_CATEGORY_SPECTRUM_MGMT)
+				break;
+
 			ieee80211_sta_process_chanswitch(sdata,
 					&mgmt->u.action.u.chan_switch.sw_elem,
 					ifmgd->associated);

net/mac80211/rx.c

@@ -2015,6 +2015,10 @@ ieee80211_rx_h_action(struct ieee80211_rx_data *rx)
 		}
 		break;
 	default:
+		/* do not process rejected action frames */
+		if (mgmt->u.action.category & 0x80)
+			return RX_DROP_MONITOR;
+
 		return RX_CONTINUE;
 	}