mac80211: use driver-indicated transmitter STA only for data frames

When I originally introduced using the driver-indicated station as an
optimisation to avoid the hashtable lookup/iteration, of course it
wasn't intended to really functionally change anything.

I neglected, however, to take into account VLAN interfaces, which have
the property that management and data frames are handled differently:
data frames go directly to the station and the VLAN while management
frames continue to be processed over the underlying/associated AP-type
interface. As a consequence, when a driver used this optimisation for
management frames and the user enabled VLANs, my change broke things
since any management frames, particularly disassoc/deauth, were missed
by hostapd.

Fix this by restoring the original code path for non-data frames, they
aren't critical for performance to begin with.

This fixes https://bugzilla.kernel.org/show_bug.cgi?id=194713.

Big thanks goes to Jarek who bisected the issue and provided a very
detailed bug report, including the crucial information that he was
using VLANs in his configuration.

Cc: stable@vger.kernel.org
Fixes: 771e846bea9e ("mac80211: allow passing transmitter station on RX")
Reported-and-tested-by: Jarek Kamiński <jarek@freeside.be>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/rx.c

@@ -4086,15 +4086,17 @@ static void __ieee80211_rx_handle_packet(struct ieee80211_hw *hw,
 		     ieee80211_is_beacon(hdr->frame_control)))
 		ieee80211_scan_rx(local, skb);
 
-	if (pubsta) {
-		rx.sta = container_of(pubsta, struct sta_info, sta);
-		rx.sdata = rx.sta->sdata;
-		if (ieee80211_prepare_and_rx_handle(&rx, skb, true))
-			return;
-		goto out;
-	} else if (ieee80211_is_data(fc)) {
+	if (ieee80211_is_data(fc)) {
 		struct sta_info *sta, *prev_sta;
 
+		if (pubsta) {
+			rx.sta = container_of(pubsta, struct sta_info, sta);
+			rx.sdata = rx.sta->sdata;
+			if (ieee80211_prepare_and_rx_handle(&rx, skb, true))
+				return;
+			goto out;
+		}
+
 		prev_sta = NULL;
 
 		for_each_sta_info(local, hdr->addr2, sta, tmp) {