> Date: Wed, 9 Oct 2024 16:23:11 +0200
> From: Alexander Bluhm <bl...@openbsd.org>
>
> On Tue, Oct 08, 2024 at 06:29:19PM +0000, Miod Vallat wrote:
> > > So it happens here:
> > >
> > > 1010 int
> > > 1011 wsdisplaywrite(dev_t dev, struct uio *uio, int flag)
> > > 1012 {
> > > 1013 struct wsdisplay_softc *sc;
> > > 1014 struct tty *tp;
> > > 1015 int unit;
> > > 1016 struct wsscreen *scr;
> > > 1017
> > > 1018 unit = WSDISPLAYUNIT(dev);
> > > * 1019 sc = wsdisplay_cd.cd_devs[unit];
> >
> > This would imply no wsdisplay device has attached, yet wscons has
> > claimed console (either efifb or a vga-compatible display).
>
> Would it make sense to copy the check from wsdisplayopen()
> instead of crashing in this case?
Not sure. We shouldn't be able to get here without passing the check
in wsdisplayopen() under normal corcumstances.
> Or should we prevent that situation on higher level?
Yes, but it is not clear what we should do. Presumably one of the
calls in wscn_video_init() succeeds, but then later on we don't
actually attach the corresponding device.
> Index: dev/wscons/wsdisplay.c
> ===================================================================
> RCS file: /data/mirror/openbsd/cvs/src/sys/dev/wscons/wsdisplay.c,v
> diff -u -p -r1.153 wsdisplay.c
> --- dev/wscons/wsdisplay.c 30 Sep 2024 01:41:49 -0000 1.153
> +++ dev/wscons/wsdisplay.c 9 Oct 2024 14:17:30 -0000
> @@ -1016,7 +1016,9 @@ wsdisplaywrite(dev_t dev, struct uio *ui
> struct wsscreen *scr;
>
> unit = WSDISPLAYUNIT(dev);
> - sc = wsdisplay_cd.cd_devs[unit];
> + if (unit >= wsdisplay_cd.cd_ndevs || /* make sure it was attached */
> + (sc = wsdisplay_cd.cd_devs[unit]) == NULL)
> + return (ENXIO);
>
> if (ISWSDISPLAYCTL(dev))
> return (0);
>
>
