crypto: qat - do not offload zero length requests

If a zero length request is submitted through the skcipher api,
do not offload it and return success.

Reviewed-by: Conor Mcloughlin <conor.mcloughlin@intel.com>
Tested-by: Sergey Portnoy <sergey.portnoy@intel.com>
Signed-off-by: Giovanni Cabiddu <giovanni.cabiddu@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/qat/qat_common/qat_algs.c

@@ -1058,6 +1058,9 @@ static int qat_alg_ablkcipher_encrypt(struct ablkcipher_request *req)
 	struct device *dev = &GET_DEV(ctx->inst->accel_dev);
 	int ret, ctr = 0;
 
+	if (req->nbytes == 0)
+		return 0;
+
 	qat_req->iv = dma_alloc_coherent(dev, AES_BLOCK_SIZE,
 					 &qat_req->iv_paddr, GFP_ATOMIC);
 	if (!qat_req->iv)
@@ -1115,6 +1118,9 @@ static int qat_alg_ablkcipher_decrypt(struct ablkcipher_request *req)
 	struct device *dev = &GET_DEV(ctx->inst->accel_dev);
 	int ret, ctr = 0;
 
+	if (req->nbytes == 0)
+		return 0;
+
 	qat_req->iv = dma_alloc_coherent(dev, AES_BLOCK_SIZE,
 					 &qat_req->iv_paddr, GFP_ATOMIC);
 	if (!qat_req->iv)