diff --git a/drivers/video/fbdev/sbuslib.c b/drivers/video/fbdev/sbuslib.c
index 90c51330969c2f027b4e2e83f98457db7f0265cf..01a7110e61a76a19167fae82d71e1f9efdb312e3 100644
--- a/drivers/video/fbdev/sbuslib.c
+++ b/drivers/video/fbdev/sbuslib.c
@@ -171,7 +171,7 @@ int sbusfb_ioctl_helper(unsigned long cmd, unsigned long arg,
 		    get_user(ublue, &c->blue))
 			return -EFAULT;
 
-		if (index + count > cmap->len)
+		if (index > cmap->len || count > cmap->len - index)
 			return -EINVAL;
 
 		for (i = 0; i < count; i++) {