Re: [PATCH v2 3/4] fbmem: Prevent invalid virtual screen sizes in fb_set_var()
From: Geert Uytterhoeven <geert@linux-m68k.org>
Date: 2022-07-04 16:16:37
Also in:
dri-devel
Hi Helge, On Fri, Jul 1, 2022 at 10:23 PM Helge Deller [off-list ref] wrote:
Prevent that drivers configure a virtual screen resolution smaller than the physical screen resolution. This is important, because otherwise we may access memory outside of the graphics memory area. Give a kernel WARNing and show the driver name to help locating the buggy driver. Signed-off-by: Helge Deller <deller@gmx.de> Cc: stable@vger.kernel.org # v5.4+
Thanks for your patch!
quoted hunk ↗ jump to hunk
--- a/drivers/video/fbdev/core/fbmem.c +++ b/drivers/video/fbdev/core/fbmem.c@@ -1016,6 +1016,18 @@ fb_set_var(struct fb_info *info, struct fb_var_screeninfo *var) if (ret) return ret; + /* make sure virtual resolution >= physical resolution */ + if (WARN_ON(var->xres_virtual < var->xres)) {
WARN_ON_ONCE()? This does mean we would miss two or more buggy drivers in a single system.
+ pr_warn("fbcon: Fix up invalid xres %d for %s\n",xres_virtual?
+ var->xres_virtual, info->fix.id); + var->xres_virtual = var->xres;
I think it's better to not fix this up, but return -EINVAL instead. After all if we get here, we have a buggy driver that needs to be fixed.
+ }
+ if (WARN_ON(var->yres_virtual < var->yres)) {
+ pr_warn("fbcon: Fix up invalid yres %d for %s\n",
+ var->yres_virtual, info->fix.id);
+ var->yres_virtual = var->yres;
+ }Same for yres.
+
if ((var->activate & FB_ACTIVATE_MASK) != FB_ACTIVATE_NOW)
return 0;
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds