wifi: mac80211: fix crash in beacon protection for P2P-device

If beacon protection is active but the beacon cannot be
decrypted or is otherwise malformed, we call the cfg80211
API to report this to userspace, but that uses a netdev
pointer, which isn't present for P2P-Device. Fix this to
call it only conditionally to ensure cfg80211 won't crash
in the case of P2P-Device.

This fixes CVE-2022-42722.
Reported-by: Sönke Huster <shuster@seemoo.tu-darmstadt.de>
Fixes: 9eaf183a ("mac80211: Report beacon protection failures to user space")
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/rx.c

@@ -1978,10 +1978,11 @@ ieee80211_rx_h_decrypt(struct ieee80211_rx_data *rx)
 
 		if (mmie_keyidx < NUM_DEFAULT_KEYS + NUM_DEFAULT_MGMT_KEYS ||
 		    mmie_keyidx >= NUM_DEFAULT_KEYS + NUM_DEFAULT_MGMT_KEYS +
-		    NUM_DEFAULT_BEACON_KEYS) {
-			cfg80211_rx_unprot_mlme_mgmt(rx->sdata->dev,
-						     skb->data,
-						     skb->len);
+				   NUM_DEFAULT_BEACON_KEYS) {
+			if (rx->sdata->dev)
+				cfg80211_rx_unprot_mlme_mgmt(rx->sdata->dev,
+							     skb->data,
+							     skb->len);
 			return RX_DROP_MONITOR; /* unexpected BIP keyidx */
 		}
 
@@ -2131,7 +2132,8 @@ ieee80211_rx_h_decrypt(struct ieee80211_rx_data *rx)
 	/* either the frame has been decrypted or will be dropped */
 	status->flag |= RX_FLAG_DECRYPTED;
 
-	if (unlikely(ieee80211_is_beacon(fc) && result == RX_DROP_UNUSABLE))
+	if (unlikely(ieee80211_is_beacon(fc) && result == RX_DROP_UNUSABLE &&
+		     rx->sdata->dev))
 		cfg80211_rx_unprot_mlme_mgmt(rx->sdata->dev,
 					     skb->data, skb->len);