crypto: virtio - deal with unsupported input sizes

Return -EINVAL for input sizes that are not a multiple of the AES
block size, since they are not supported by our CBC chaining mode.

While at it, remove the pr_err() that reports unsupported key sizes
being used: we shouldn't spam the kernel log with that.

Fixes: dbaf0624ffa5 ("crypto: add virtio-crypto driver")
Cc: "Michael S. Tsirkin" <[e-mail]>
Cc: Jason Wang <[e-mail]>
Cc: Gonglei <[e-mail]>
Cc: [e-mail]
Signed-off-by: Ard Biesheuvel <[e-mail]>
Signed-off-by: Herbert Xu <[e-mail]>

drivers/crypto/virtio/virtio_crypto_algs.c

···
 		*alg = VIRTIO_CRYPTO_CIPHER_AES_CBC;
 		break;
 	default:
-		pr_err("virtio_crypto: Unsupported key length: %d\n",
-			key_len);
 		return -EINVAL;
 	}
 	return 0;
···
 	/* Use the first data virtqueue as default */
 	struct data_queue *data_vq = &vcrypto->data_vq[0];
 
+	if (!req->nbytes)
+		return 0;
+	if (req->nbytes % AES_BLOCK_SIZE)
+		return -EINVAL;
+
 	vc_req->dataq = data_vq;
 	vc_req->alg_cb = virtio_crypto_dataq_sym_callback;
 	vc_sym_req->ablkcipher_ctx = ctx;
···
 	struct virtio_crypto *vcrypto = ctx->vcrypto;
 	/* Use the first data virtqueue as default */
 	struct data_queue *data_vq = &vcrypto->data_vq[0];
+
+	if (!req->nbytes)
+		return 0;
+	if (req->nbytes % AES_BLOCK_SIZE)
+		return -EINVAL;
 
 	vc_req->dataq = data_vq;
 	vc_req->alg_cb = virtio_crypto_dataq_sym_callback;