diff --git a/drivers/video/via/viafbdev.c b/drivers/video/via/viafbdev.c
index 10d8c4b4bae..d8df17a7d5f 100644
--- a/drivers/video/via/viafbdev.c
+++ b/drivers/video/via/viafbdev.c
@@ -680,7 +680,7 @@ static int viafb_ioctl(struct fb_info *info, u_int cmd, u_long arg)
 		if (!viafb_gamma_table)
 			return -ENOMEM;
 		if (copy_from_user(viafb_gamma_table, argp,
-				sizeof(viafb_gamma_table))) {
+				256 * sizeof(u32))) {
 			kfree(viafb_gamma_table);
 			return -EFAULT;
 		}
@@ -694,7 +694,7 @@ static int viafb_ioctl(struct fb_info *info, u_int cmd, u_long arg)
 			return -ENOMEM;
 		viafb_get_gamma_table(viafb_gamma_table);
 		if (copy_to_user(argp, viafb_gamma_table,
-			sizeof(viafb_gamma_table))) {
+			256 * sizeof(u32))) {
 			kfree(viafb_gamma_table);
 			return -EFAULT;
 		}