mac80211: tx: do not drop non-robust mgmt to non-MFP stas.

When drop_unencrypted is enabled and MFP is disabled,
non-robust management frames for not-yet associated STA are dropped.
This isn't visible as many management frames sent from the kernel
have TX_INTFL_DONT_ENCRYPT set and management frames injected
from a monitor vif have TX_CTL_INJECTED so aren't dropped.
But management frames sent from userspace via NL80211_CMD_FRAME
do not have this flag set, so are dropped.

This patch make it always accept non-robust management frames.
Signed-off-by: Nicolas Cavallari <cavallar@lri.fr>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/tx.c

@@ -552,6 +552,9 @@ ieee80211_tx_h_select_key(struct ieee80211_tx_data *tx)
 		 !(ieee80211_is_action(hdr->frame_control) &&
 		   tx->sta && test_sta_flag(tx->sta, WLAN_STA_MFP)))
 		tx->key = NULL;
+	else if (ieee80211_is_mgmt(hdr->frame_control) &&
+		 !ieee80211_is_robust_mgmt_frame(hdr))
+		tx->key = NULL;
 	else {
 		I802_DEBUG_INC(tx->local->tx_handlers_drop_unencrypted);
 		return TX_DROP;