s390/crypto: fix aes_s390 crypto module unload problem

If a machine has no hardware support for the xts-aes or ctr-aes algorithms
they are not registered in aes_s390_init. But aes_s390_fini unconditionally
unregisters the algorithms which causes crypto_remove_alg to crash.
Add two flag variables to remember if xts-aes and ctr-aes have been added.

Signed-off-by: Ingo Tuchscherer <ingo.tuchscherer@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/crypto/aes_s390.c

@@ -725,6 +725,8 @@ static struct crypto_alg xts_aes_alg = {
 	}
 };
 
+static int xts_aes_alg_reg;
+
 static int ctr_aes_set_key(struct crypto_tfm *tfm, const u8 *in_key,
 			   unsigned int key_len)
 {
@@ -846,6 +848,8 @@ static struct crypto_alg ctr_aes_alg = {
 	}
 };
 
+static int ctr_aes_alg_reg;
+
 static int __init aes_s390_init(void)
 {
 	int ret;
@@ -884,6 +888,7 @@ static int __init aes_s390_init(void)
 		ret = crypto_register_alg(&xts_aes_alg);
 		if (ret)
 			goto xts_aes_err;
+		xts_aes_alg_reg = 1;
 	}
 
 	if (crypt_s390_func_available(KMCTR_AES_128_ENCRYPT,
@@ -902,6 +907,7 @@ static int __init aes_s390_init(void)
 			free_page((unsigned long) ctrblk);
 			goto ctr_aes_err;
 		}
+		ctr_aes_alg_reg = 1;
 	}
 
 out:
@@ -921,9 +927,12 @@ static int __init aes_s390_init(void)
 
 static void __exit aes_s390_fini(void)
 {
-	crypto_unregister_alg(&ctr_aes_alg);
-	free_page((unsigned long) ctrblk);
-	crypto_unregister_alg(&xts_aes_alg);
+	if (ctr_aes_alg_reg) {
+		crypto_unregister_alg(&ctr_aes_alg);
+		free_page((unsigned long) ctrblk);
+	}
+	if (xts_aes_alg_reg)
+		crypto_unregister_alg(&xts_aes_alg);
 	crypto_unregister_alg(&cbc_aes_alg);
 	crypto_unregister_alg(&ecb_aes_alg);
 	crypto_unregister_alg(&aes_alg);