mac80211: fix tx->skb NULL pointer dereference

In function ieee80211_tx_h_encrypt the var info was
initialized from tx->skb, since the fucntion
is called after the function ieee80211_tx_h_fragment
tx->skb is not valid anymore.
Signed-off-by: NYoni Divinsky <yoni.divinsky@ti.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

net/mac80211/tx.c

@@ -1001,8 +1001,6 @@ ieee80211_tx_h_stats(struct ieee80211_tx_data *tx)
 static ieee80211_tx_result debug_noinline
 ieee80211_tx_h_encrypt(struct ieee80211_tx_data *tx)
 {
-	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(tx->skb);
-
 	if (!tx->key)
 		return TX_CONTINUE;
 
@@ -1017,13 +1015,7 @@ ieee80211_tx_h_encrypt(struct ieee80211_tx_data *tx)
 	case WLAN_CIPHER_SUITE_AES_CMAC:
 		return ieee80211_crypto_aes_cmac_encrypt(tx);
 	default:
-		/* handle hw-only algorithm */
-		if (info->control.hw_key) {
-			ieee80211_tx_set_protected(tx);
-			return TX_CONTINUE;
-		}
-		break;
-
+		return ieee80211_crypto_hw_encrypt(tx);
 	}
 
 	return TX_DROP;

net/mac80211/wpa.c

@@ -643,3 +643,22 @@ ieee80211_crypto_aes_cmac_decrypt(struct ieee80211_rx_data *rx)
 
 	return RX_CONTINUE;
 }
+
+ieee80211_tx_result
+ieee80211_crypto_hw_encrypt(struct ieee80211_tx_data *tx)
+{
+	struct sk_buff *skb;
+	struct ieee80211_tx_info *info = NULL;
+
+	skb_queue_walk(&tx->skbs, skb) {
+		info  = IEEE80211_SKB_CB(skb);
+
+		/* handle hw-only algorithm */
+		if (!info->control.hw_key)
+			return TX_DROP;
+	}
+
+	ieee80211_tx_set_protected(tx);
+
+	return TX_CONTINUE;
+}

net/mac80211/wpa.h

@@ -32,5 +32,7 @@ ieee80211_tx_result
 ieee80211_crypto_aes_cmac_encrypt(struct ieee80211_tx_data *tx);
 ieee80211_rx_result
 ieee80211_crypto_aes_cmac_decrypt(struct ieee80211_rx_data *rx);
+ieee80211_tx_result
+ieee80211_crypto_hw_encrypt(struct ieee80211_tx_data *tx);
 
 #endif /* WPA_H */