[Intel-gfx] [PATCH 2/3] drm/i915/sdvo: Robustify the dtd<->drm_mode conversions

[Ville Syrjälä]

On Tue, Sep 10, 2013 at 12:50:25PM +0200, Daniel Vetter wrote:
> On Tue, Sep 10, 2013 at 12:26 PM, Ville Syrjälä
> <ville.syrjala at linux.intel.com> wrote:
> >>  static void intel_sdvo_get_mode_from_dtd(struct drm_display_mode * mode,
> >>                                        const struct intel_sdvo_dtd *dtd)
> >>  {
> >> +     memset(mode, 0, sizeof(*mode));
> >
> > I have a theoretical worry that someone might end up calling this on a
> > mode that sits on some list or was actually allocated and has a proper
> > object id which we'd leak here.
> >
> > To make it totally safe you could populate a pristine mode struct and
> > use drm_mode_copy() to overwrite adjusted_mode. Assuming we're not so
> > short on stack space that our oversized mode struct would cause issues.
> > Other options would be to add some WARNs to catch wrongdoers, or embed
> > a temp mode for this purpose inside the intel_sdvo struct.
> 
> We can't really check for this since list_empty on stack garbage won't
> work too well, either. And e.g. ->get_config has the pipe config on
> the stack. So I think we just need to do review here. I also think the
> risk is pretty low, this is all used in internal structures around
> pipe_config, where the mode is never linked.

Well, another idea would be to add drm_mode_clear() what would do the
memset() but preserve the id and list head.

-- 
Ville Syrjälä
Intel OTC