atafb: test virtual screen range before subtraction on unsigned

dx and dy are u32's, so the test should occur before the subtraction

Signed-off-by: Roel Kluin <12o3l@tiscali.nl>
Cc: Tim Schmielau <tim@physik3.uni-rostock.de>
Cc: Krzysztof Helt <krzysztof.h1@wp.pl>
Cc: Antonino Daplas <adaplas@pol.net>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/drivers/video/atafb.c b/drivers/video/atafb.c
index fa55d35..77eb8b3 100644 (file)
--- a/drivers/video/atafb.c
+++ b/drivers/video/atafb.c
@@ -2593,13 +2593,16 @@ static void atafb_copyarea(struct fb_info *info, const struct fb_copyarea *area)
        width = x2 - dx;
        height = y2 - dy;
 
+       if (area->sx + dx < area->dx || area->sy + dy < area->dy)
+               return;
+
        /* update sx,sy */
        sx = area->sx + (dx - area->dx);
        sy = area->sy + (dy - area->dy);
 
        /* the source must be completely inside the virtual screen */
-       if (sx < 0 || sy < 0 || (sx + width) > info->var.xres_virtual ||
-           (sy + height) > info->var.yres_virtual)
+       if (sx + width > info->var.xres_virtual ||
+                       sy + height > info->var.yres_virtual)
                return;
 
        if (dy > sy || (dy == sy && dx > sx)) {