ksmbd: smbd: change the return value of get_sg_list

Make get_sg_list return EINVAL if there aren't
mapped scatterlists.
Signed-off-by: Hyunchul Lee <hyc.lee@gmail.com>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/ksmbd/transport_rdma.c

@@ -1079,7 +1079,7 @@ static int get_sg_list(void *buf, int size, struct scatterlist *sg_list, int nen
 	int offset, len;
 	int i = 0;
 
-	if (nentries < get_buf_page_count(buf, size))
+	if (size <= 0 || nentries < get_buf_page_count(buf, size))
 		return -EINVAL;
 
 	offset = offset_in_page(buf);
@@ -1111,7 +1111,7 @@ static int get_mapped_sg_list(struct ib_device *device, void *buf, int size,
 	int npages;
 
 	npages = get_sg_list(buf, size, sg_list, nentries);
-	if (npages <= 0)
+	if (npages < 0)
 		return -EINVAL;
 	return ib_dma_map_sg(device, sg_list, npages, dir);
 }