Hi Helge,

On Thu, Jun 30, 2022 at 9:17 PM Helge Deller [off-list ref] wrote:

On 6/30/22 21:11, Geert Uytterhoeven wrote:

quoted

On Wed, Jun 29, 2022 at 10:00 PM Helge Deller [off-list ref] wrote:

quoted

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.

Signed-off-by: Helge Deller <deller@gmx.de>
Cc: stable@vger.kernel.org # v5.4+

Thanks for your patch!

quoted

--- a/drivers/video/fbdev/core/fbmem.c
+++ b/drivers/video/fbdev/core/fbmem.c

@@ -1006,6 +1006,12 @@ fb_set_var(struct fb_info *info, struct fb_var_screeninfo *var)
        if (var->xres < 8 || var->yres < 8)
                return -EINVAL;

+       /* make sure virtual resolution >= physical resolution */
+       if (WARN_ON(var->xres_virtual < var->xres))
+               var->xres_virtual = var->xres;
+       if (WARN_ON(var->yres_virtual < var->yres))
+               var->yres_virtual = var->yres;

This should be moved below the call to info->fbops->fb_check_var(),
so the WARN_ON() catches buggy fbdev drivers, not userspace fuzzers.

Yes, makes sense.

And print the name of the frame buffer device driver, so people know
who to blame.

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