Re: [syzbot] BUG: unable to handle kernel paging request in vga16fb_fillrect

[Geert Uytterhoeven]

Hi Tetsuo,

On Mon, Aug 30, 2021 at 4:53 PM Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> wrote:
> On Mon, Aug 30, 2021 at 4:38 PM Tetsuo Handa
> <penguin-kernel@xxxxxxxxxxxxxxxxxxx> wrote:
> > On 2021/08/30 23:30, Geert Uytterhoeven wrote:
> > > The highest possible value of maxmem inside vga16fb_check_var()
> > > is 65536.
> >
> > Yes.
> >
> > >
> > > So I believe
> > >
> > >     if (array_size(vxres, vyres) > maxmem)
> > >
> > > should work fine.
> >
> > My intent is to check at common path than individual module so that we don't
> > need to add same check to every module. Same approach is proposed at
> > https://lkml.kernel.org/r/1630294223-7225-1-git-send-email-tcs_kernel@xxxxxxxxxxx .
>
> Which I believe is wrong.
> Thanks for the pointer, I will reply to the actual patch...

Upon second look, that patch is not really wrong, as the check happens
after calling into info->fbops->fb_check_var().

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

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