crypto: algif_skcipher - Add key check exception for cipher_null

This patch adds an exception to the key check so that cipher_null
users may continue to use algif_skcipher without setting a key.

Cc: stable@vger.kernel.org
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
diff --git a/crypto/algif_skcipher.c b/crypto/algif_skcipher.c
index 110bab4..4a5bdb6 100644
--- a/crypto/algif_skcipher.c
+++ b/crypto/algif_skcipher.c
@@ -978,7 +978,7 @@
 {
 	struct skcipher_tfm *tfm = private;
 
-	if (!tfm->has_key)
+	if (!tfm->has_key && crypto_skcipher_has_setkey(tfm->skcipher))
 		return -ENOKEY;
 
 	return skcipher_accept_parent_common(private, sk);