crypto: qat - Prevent dma mapping zero length assoc data

Do not attempt to dma map associated data if it is zero length.

Cc: stable@vger.kernel.org
Signed-off-by: Tadeusz Struk <tadeusz.struk@intel.com>
Tested-by: Nikolay Aleksandrov <nikolay@redhat.com>
Reviewed-by: Prarit Bhargava <prarit@redhat.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/qat/qat_common/qat_algs.c

@@ -605,6 +605,8 @@ static int qat_alg_sgl_to_bufl(struct qat_crypto_instance *inst,
 		goto err;
 
 	for_each_sg(assoc, sg, assoc_n, i) {
+		if (!sg->length)
+			continue;
 		bufl->bufers[bufs].addr = dma_map_single(dev,
 							 sg_virt(sg),
 							 sg->length,