Crypto/chcr: Calculate src and dst sg lengths separately for dma map

This patch calculates src and dst sg lengths separately for
dma mapping in case of aead operation.

This fixes a panic which occurs due to the accessing of a zero
length sg.
Panic:
[  138.173225] kernel BUG at drivers/iommu/intel-iommu.c:1184!
Signed-off-by: Ayush Sawal <ayush.sawal@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/crypto/chelsio/chcr_algo.c

@@ -2590,11 +2590,22 @@ int chcr_aead_dma_map(struct device *dev,
 	struct chcr_aead_reqctx  *reqctx = aead_request_ctx(req);
 	struct crypto_aead *tfm = crypto_aead_reqtfm(req);
 	unsigned int authsize = crypto_aead_authsize(tfm);
-	int dst_size;
+	int src_len, dst_len;
 
-	dst_size = req->assoclen + req->cryptlen + (op_type ?
+	/* calculate and handle src and dst sg length separately
+	 * for inplace and out-of place operations
+	 */
+	if (req->src == req->dst) {
+		src_len = req->assoclen + req->cryptlen + (op_type ?
 							0 : authsize);
-	if (!req->cryptlen || !dst_size)
+		dst_len = src_len;
+	} else {
+		src_len = req->assoclen + req->cryptlen;
+		dst_len = req->assoclen + req->cryptlen + (op_type ?
+							-authsize : authsize);
+	}
+
+	if (!req->cryptlen || !src_len || !dst_len)
 		return 0;
 	reqctx->iv_dma = dma_map_single(dev, reqctx->iv, (IV + reqctx->b0_len),
 					DMA_BIDIRECTIONAL);
@@ -2606,19 +2617,22 @@ int chcr_aead_dma_map(struct device *dev,
 		reqctx->b0_dma = 0;
 	if (req->src == req->dst) {
 		error = dma_map_sg(dev, req->src,
-				sg_nents_for_len(req->src, dst_size),
+				sg_nents_for_len(req->src, src_len),
 					DMA_BIDIRECTIONAL);
 		if (!error)
 			goto err;
 	} else {
-		error = dma_map_sg(dev, req->src, sg_nents(req->src),
+		error = dma_map_sg(dev, req->src,
+				   sg_nents_for_len(req->src, src_len),
 				   DMA_TO_DEVICE);
 		if (!error)
 			goto err;
-		error = dma_map_sg(dev, req->dst, sg_nents(req->dst),
+		error = dma_map_sg(dev, req->dst,
+				   sg_nents_for_len(req->dst, dst_len),
 				   DMA_FROM_DEVICE);
 		if (!error) {
-			dma_unmap_sg(dev, req->src, sg_nents(req->src),
+			dma_unmap_sg(dev, req->src,
+				     sg_nents_for_len(req->src, src_len),
 				     DMA_TO_DEVICE);
 			goto err;
 		}
@@ -2637,23 +2651,36 @@ void chcr_aead_dma_unmap(struct device *dev,
 	struct chcr_aead_reqctx  *reqctx = aead_request_ctx(req);
 	struct crypto_aead *tfm = crypto_aead_reqtfm(req);
 	unsigned int authsize = crypto_aead_authsize(tfm);
-	int dst_size;
+	int src_len, dst_len;
 
-	dst_size = req->assoclen + req->cryptlen + (op_type ?
+	/* calculate and handle src and dst sg length separately
+	 * for inplace and out-of place operations
+	 */
+	if (req->src == req->dst) {
+		src_len = req->assoclen + req->cryptlen + (op_type ?
 							0 : authsize);
-	if (!req->cryptlen || !dst_size)
+		dst_len = src_len;
+	} else {
+		src_len = req->assoclen + req->cryptlen;
+		dst_len = req->assoclen + req->cryptlen + (op_type ?
+						-authsize : authsize);
+	}
+
+	if (!req->cryptlen || !src_len || !dst_len)
 		return;
 
 	dma_unmap_single(dev, reqctx->iv_dma, (IV + reqctx->b0_len),
 					DMA_BIDIRECTIONAL);
 	if (req->src == req->dst) {
 		dma_unmap_sg(dev, req->src,
-			     sg_nents_for_len(req->src, dst_size),
+			     sg_nents_for_len(req->src, src_len),
 			     DMA_BIDIRECTIONAL);
 	} else {
-		dma_unmap_sg(dev, req->src, sg_nents(req->src),
+		dma_unmap_sg(dev, req->src,
+			     sg_nents_for_len(req->src, src_len),
 			     DMA_TO_DEVICE);
-		dma_unmap_sg(dev, req->dst, sg_nents(req->dst),
+		dma_unmap_sg(dev, req->dst,
+			     sg_nents_for_len(req->dst, dst_len),
 			     DMA_FROM_DEVICE);
 	}
 }