mac80211: allow transmitting deauth with tainted key

When we had a connection for WoWLAN and after resume it
needed to be disconnected, the previous commit enabled
sending a deauth frame to the AP. This frame would not
go through on MFP-enabled networks as the key for it is
marked tainted before the frame is transmitted.

Allow a tainted key to be used for deauth frames. Worst
case, we'll use a wrong key because the PTK was rekeyed
while suspended, but more likely the PTK is still fine
and the taint flag really only applies to the GTK(s).
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/tx.c

@@ -594,7 +594,8 @@ ieee80211_tx_h_select_key(struct ieee80211_tx_data *tx)
 			break;
 		}
 
-		if (unlikely(tx->key && tx->key->flags & KEY_FLAG_TAINTED))
+		if (unlikely(tx->key && tx->key->flags & KEY_FLAG_TAINTED &&
+			     !ieee80211_is_deauth(hdr->frame_control)))
 			return TX_DROP;
 
 		if (!skip_hw && tx->key &&