crypto: afalg: fix a NULL pointer dereference

Test-crypto-hash calls qcrypto_hash_bytesv/digest/base64 with
errp=NULL, this will cause a NULL pointer dereference if afalg_driver
doesn't support requested algos:

    ret = qcrypto_hash_afalg_driver.hash_bytesv(alg, iov, niov,
                                                result, resultlen,
                                                errp);
    if (ret == 0) {
        return ret;
    }

    error_free(*errp);  // <--- here

Because the error message is thrown away immediately, we should
just pass NULL to hash_bytesv(). There is also the same problem in
afalg-backend cipher & hmac, let's fix them together.

Reviewed-by: Eric Blake <eblake@redhat.com>
Reported-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Longpeng <longpeng2@huawei.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>

crypto/cipher.c

@@ -164,11 +164,10 @@ QCryptoCipher *qcrypto_cipher_new(QCryptoCipherAlgorithm alg,
 {
     QCryptoCipher *cipher;
     void *ctx = NULL;
-    Error *err2 = NULL;
     QCryptoCipherDriver *drv = NULL;
 
 #ifdef CONFIG_AF_ALG
-    ctx = qcrypto_afalg_cipher_ctx_new(alg, mode, key, nkey, &err2);
+    ctx = qcrypto_afalg_cipher_ctx_new(alg, mode, key, nkey, NULL);
     if (ctx) {
         drv = &qcrypto_cipher_afalg_driver;
     }
@@ -177,12 +176,10 @@ QCryptoCipher *qcrypto_cipher_new(QCryptoCipherAlgorithm alg,
     if (!ctx) {
         ctx = qcrypto_cipher_ctx_new(alg, mode, key, nkey, errp);
         if (!ctx) {
-            error_free(err2);
             return NULL;
         }
 
         drv = &qcrypto_cipher_lib_driver;
-        error_free(err2);
     }
 
     cipher = g_new0(QCryptoCipher, 1);

crypto/hash.c

@@ -48,19 +48,16 @@ int qcrypto_hash_bytesv(QCryptoHashAlgorithm alg,
 {
 #ifdef CONFIG_AF_ALG
     int ret;
-
+    /*
+     * TODO:
+     * Maybe we should treat some afalg errors as fatal
+     */
     ret = qcrypto_hash_afalg_driver.hash_bytesv(alg, iov, niov,
                                                 result, resultlen,
-                                                errp);
+                                                NULL);
     if (ret == 0) {
         return ret;
     }
-
-    /*
-     * TODO:
-     * Maybe we should treat some afalg errors as fatal
-     */
-    error_free(*errp);
 #endif
 
     return qcrypto_hash_lib_driver.hash_bytesv(alg, iov, niov,

crypto/hmac.c

@@ -90,11 +90,10 @@ QCryptoHmac *qcrypto_hmac_new(QCryptoHashAlgorithm alg,
 {
     QCryptoHmac *hmac;
     void *ctx = NULL;
-    Error *err2 = NULL;
     QCryptoHmacDriver *drv = NULL;
 
 #ifdef CONFIG_AF_ALG
-    ctx = qcrypto_afalg_hmac_ctx_new(alg, key, nkey, &err2);
+    ctx = qcrypto_afalg_hmac_ctx_new(alg, key, nkey, NULL);
     if (ctx) {
         drv = &qcrypto_hmac_afalg_driver;
     }
@@ -107,7 +106,6 @@ QCryptoHmac *qcrypto_hmac_new(QCryptoHashAlgorithm alg,
         }
 
         drv = &qcrypto_hmac_lib_driver;
-        error_free(err2);
     }
 
     hmac = g_new0(QCryptoHmac, 1);