On Wed, Jul 22, 2020 at 10:07:06AM +0200, Daniel Vetter wrote: > On Tue, Jul 21, 2020 at 6:08 PM Greg Kroah-Hartman > <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > > > > On Thu, Jul 16, 2020 at 08:27:21PM +0900, Tetsuo Handa wrote: > > > On 2020/07/16 19:00, Daniel Vetter wrote: > > > > On Thu, Jul 16, 2020 at 12:29:00AM +0900, Tetsuo Handa wrote: > > > >> On 2020/07/16 0:12, Dan Carpenter wrote: > > > >>> I've complained about integer overflows in fbdev for a long time... > > > >>> > > > >>> What I'd like to see is something like the following maybe. I don't > > > >>> know how to get the vc_data in fbmem.c so it doesn't include your checks > > > >>> for negative. > > > >> > > > >> Yes. Like I said "Thus, I consider that we need more sanity/constraints checks." at > > > >> https://lore.kernel.org/lkml/b1e7dd6a-fc22-bba8-0abb-d3e779329bce@xxxxxxxxxxxxxxxxxxx/ , > > > >> we want basic checks. That's a task for fbdev people who should be familiar with > > > >> necessary constraints. > > > > > > > > I think the worldwide supply of people who understand fbdev and willing to > > > > work on it is roughly 0. So if someone wants to fix this mess properly > > > > (which likely means adding tons of over/underflow checks at entry points, > > > > since you're never going to catch the driver bugs, there's too many and > > > > not enough people who care) they need to fix this themselves. > > > > > > But I think we can enforce reasonable constraint which is much stricter than Dan's basic_checks() > > > (which used INT_MAX). For example, do we need to accept var->{xres,yres} >= 1048576, for > > > "32768 rows or cols" * "32 pixels per character" = 1045876 and vc_do_resize() accepts only > > > rows and cols < 32768 ? > > > > > > > > > > > Just to avoid confusion here. > > > > > > > >> Anyway, my two patches are small and low cost; can we apply these patches regardless > > > >> of basic checks? > > > > > > > > Which two patches where? > > > > > > [PATCH v3] vt: Reject zero-sized screen buffer size. > > > from https://lkml.kernel.org/r/20200712111013.11881-1-penguin-kernel@xxxxxxxxxxxxxxxxxxx > > > > This is now in my tree. > > > > > [PATCH v2] fbdev: Detect integer underflow at "struct fbcon_ops"->clear_margins. > > > from https://lkml.kernel.org/r/20200715015102.3814-1-penguin-kernel@xxxxxxxxxxxxxxxxxxx > > > > That should be taken by the fbdev maintainer, but I can take it too if > > people want. > > Just missed this weeks pull request train and feeling like not worth > making this an exception (it's been broken forever after all), so > maybe best if you just add this to vt. > > Acked-by: Daniel Vetter <daniel.vetter@xxxxxxxx> > > Also this avoids the impression I know what's going on in fbdev code, > maybe with sufficient abandon from my side someone will pop up who > cares an fixes the bazillion of syzkaller issues we seem to have > around console/vt and everything related. Great, will go queue it up now, thanks! greg k-h _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
