mac80211: improve error checking if WEP fails to init

Do this by poisoning the values of wep_tx_tfm and wep_rx_tfm if either
crypto allocation fails.
Reported-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

net/mac80211/wep.c

@@ -32,13 +32,16 @@ int ieee80211_wep_init(struct ieee80211_local *local)
 
 	local->wep_tx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0,
 						CRYPTO_ALG_ASYNC);
-	if (IS_ERR(local->wep_tx_tfm))
+	if (IS_ERR(local->wep_tx_tfm)) {
+		local->wep_rx_tfm = ERR_PTR(-EINVAL);
 		return PTR_ERR(local->wep_tx_tfm);
+	}
 
 	local->wep_rx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0,
 						CRYPTO_ALG_ASYNC);
 	if (IS_ERR(local->wep_rx_tfm)) {
 		crypto_free_blkcipher(local->wep_tx_tfm);
+		local->wep_tx_tfm = ERR_PTR(-EINVAL);
 		return PTR_ERR(local->wep_rx_tfm);
 	}