ksmbd: smbd: fix dma_unmap_sg() nents

[ Upstream commit 98e3e2b ]

The dma_unmap_sg() functions should be called with the same nents as the
dma_map_sg(), not the value the map function returned.

Fixes: 0626e66 ("cifsd: add server handler for central processing and tranport layers")
Cc: <stable@vger.kernel.org>
Signed-off-by: Thomas Fourier <fourier.thomas@gmail.com>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
[ Context ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Thomas-fourier

fs/smb/server/transport_rdma.c

@@ -1108,14 +1108,12 @@ static int get_sg_list(void *buf, int size, struct scatterlist *sg_list, int nen
 
 static int get_mapped_sg_list(struct ib_device *device, void *buf, int size,
 			      struct scatterlist *sg_list, int nentries,
-			      enum dma_data_direction dir)
+			      enum dma_data_direction dir, int *npages)
 {
-	int npages;
-
-	npages = get_sg_list(buf, size, sg_list, nentries);
-	if (npages < 0)
+	*npages = get_sg_list(buf, size, sg_list, nentries);
+	if (*npages < 0)
 		return -EINVAL;
-	return ib_dma_map_sg(device, sg_list, npages, dir);
+	return ib_dma_map_sg(device, sg_list, *npages, dir);
 }
 
 static int post_sendmsg(struct smb_direct_transport *t,
@@ -1184,20 +1182,21 @@ static int smb_direct_post_send_data(struct smb_direct_transport *t,
 	for (i = 0; i < niov; i++) {
 		struct ib_sge *sge;
 		int sg_cnt;
+		int npages;
 
 		sg_init_table(sg, SMB_DIRECT_MAX_SEND_SGES - 1);
 		sg_cnt = get_mapped_sg_list(t->cm_id->device,
 					    iov[i].iov_base, iov[i].iov_len,
 					    sg, SMB_DIRECT_MAX_SEND_SGES - 1,
-					    DMA_TO_DEVICE);
+					    DMA_TO_DEVICE, &npages);
 		if (sg_cnt <= 0) {
 			pr_err("failed to map buffer\n");
 			ret = -ENOMEM;
 			goto err;
 		} else if (sg_cnt + msg->num_sge > SMB_DIRECT_MAX_SEND_SGES) {
 			pr_err("buffer not fitted into sges\n");
 			ret = -E2BIG;
-			ib_dma_unmap_sg(t->cm_id->device, sg, sg_cnt,
+			ib_dma_unmap_sg(t->cm_id->device, sg, npages,
 					DMA_TO_DEVICE);
 			goto err;
 		}