On Wed, Dec 17, 2014 at 12:09:47PM -0500, Alex Deucher wrote: > On Wed, Dec 17, 2014 at 6:56 AM, <ville.syrjala@xxxxxxxxxxxxxxx> wrote: > > From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> > > > > We had a bug in i915 land recently where X passed in a zeroed mode with > > mode_valid=1 to setcrtc. That didn't go down so well and caused a > > div-by-zero in i915. > > > > For a long time I've been thinking that we need some real checks to > > validate the modes we feed into the hardware. I started to sketch out > > something for that but it quickly turned into a bit of a nightmare > > with the whole panel fitter, stereo 3D, SDVO etc. special cases we > > have in i915. > > > > So I gave up on that for now, and instead cooked up this small series > > to add some basic sanity checks to the mode validation, and also apply > > the same sanity checks to user provided modes. This is enough to > > prevent the div-by-zero in i915 with buggy X. > > > > The risk is that we start to reject some modes that more or less worked > > by accident before. Given how lax we've been in handling the panel fitter > > on i915 for instance, this could be a real problem if people have been > > useing custom modes that have been filled out only partially. But I'm > > hoping the number of users doing that is so small that we can risk it. > > > > The other concern is drivers which might also provide funky modes from > > their .get_modes(). I tried to look at all the drivers a bit, and most > > produce modes via EDID, CVT, DMT, or drm_display_mode_from_videomode(). > > All of those look safe, except mode->clock might be an issue with > > drm_display_mode_from_videomode(), but hopefully there's some kind of > > clock provided in most cases. I didn't dig through all the nooks and > > crannies in all drivers though, so may have missed something. > > For the series: > > Reviewed-by: Alex Deucher <alexander.deucher@xxxxxxx> All pulled into my drm misc branch. Thanks, Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
