savagefb: use display information in info not in var for panning

We must not use any information in the passed var besides xoffset,
yoffset and vmode as otherwise applications might abuse it. Also use the
aligned fix.line_length and not the (possible) unaligned xres_virtual.
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Tormod Volden <debian.tormod@gmail.com>

drivers/video/savage/savagefb_driver.c

@@ -1477,15 +1477,9 @@ static void savagefb_set_par_int(struct savagefb_par  *par, struct savage_reg *r
 	vgaHWProtect(par, 0);
 }
 
-static void savagefb_update_start(struct savagefb_par      *par,
-				  struct fb_var_screeninfo *var)
+static void savagefb_update_start(struct savagefb_par *par, int base)
 {
-	int base;
-
-	base = ((var->yoffset * var->xres_virtual + (var->xoffset & ~1))
-		* ((var->bits_per_pixel+7) / 8)) >> 2;
-
-	/* now program the start address registers */
+	/* program the start address registers */
 	vga_out16(0x3d4, (base & 0x00ff00) | 0x0c, par);
 	vga_out16(0x3d4, ((base & 0x00ff) << 8) | 0x0d, par);
 	vga_out8(0x3d4, 0x69, par);
@@ -1550,8 +1544,12 @@ static int savagefb_pan_display(struct fb_var_screeninfo *var,
 				struct fb_info           *info)
 {
 	struct savagefb_par *par = info->par;
+	int base;
+
+	base = (var->yoffset * info->fix.line_length
+	     + (var->xoffset & ~1) * ((info->var.bits_per_pixel+7) / 8)) >> 2;
 
-	savagefb_update_start(par, var);
+	savagefb_update_start(par, base);
 	return 0;
 }