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 [PATCH v2] fbdev: Detect integer underflow at "struct fbcon_ops"->clear_margins. from https://lkml.kernel.org/r/20200715015102.3814-1-penguin-kernel@xxxxxxxxxxxxxxxxxxx _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
