Re: [PATCH 08/15] drm: omapdrm: gem: Mask out private flags passed from userspace

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Emil,

On Monday 07 December 2015 14:13:43 Emil Velikov wrote:
> On 4 December 2015 at 22:27, Laurent Pinchart wrote:
> > The 8 high order bits of the buffer flags are reserved for internal use.
> > Mask them out from the flags passed by userspace.
> 
> Ouch... I know that the Intel guys are pretty rigorous about input
> validation, although I wonder how many drivers are (partially or not)
> missing these.
> 
> > Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> > ---
> > 
> >  drivers/gpu/drm/omapdrm/omap_drv.c | 9 ++++++---
> >  include/uapi/drm/omap_drm.h        | 1 +
> >  2 files changed, 7 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/omapdrm/omap_drv.c
> > b/drivers/gpu/drm/omapdrm/omap_drv.c index 83d63d71062c..e405ab23d7a6
> > 100644
> > --- a/drivers/gpu/drm/omapdrm/omap_drv.c
> > +++ b/drivers/gpu/drm/omapdrm/omap_drv.c
> > @@ -551,10 +551,13 @@ static int ioctl_gem_new(struct drm_device *dev,
> > void *data,
> >                 struct drm_file *file_priv)
> >  {
> >         struct drm_omap_gem_new *args = data;
> > +       u32 flags = args->flags & OMAP_BO_USER_MASK;
> > +
> >         VERB("%p:%p: size=0x%08x, flags=%08x", dev, file_priv,
> > -                       args->size.bytes, args->flags);
> > -       return omap_gem_new_handle(dev, file_priv, args->size,
> > -                       args->flags, &args->handle);
> > +            args->size.bytes, flags);
> > +
> > +       return omap_gem_new_handle(dev, file_priv, args->size, flags,
> > +                                  &args->handle);
> >  }
> >  
> >  static int ioctl_gem_cpu_prep(struct drm_device *dev, void *data,
> > diff --git a/include/uapi/drm/omap_drm.h b/include/uapi/drm/omap_drm.h
> > index 1d0b1172664e..6852c26e8f78 100644
> > --- a/include/uapi/drm/omap_drm.h
> > +++ b/include/uapi/drm/omap_drm.h
> > @@ -36,6 +36,7 @@ struct drm_omap_param {
> > 
> >  #define OMAP_BO_SCANOUT        0x00000001      /* scanout capable (phys
> >  contiguous) */
> >  #define OMAP_BO_CACHE_MASK     0x00000006      /* cache type mask, see
> >  cache modes */
> >  #define OMAP_BO_TILED_MASK     0x00000f00      /* tiled mapping mask, see
> >  tiled modes */
> > +#define OMAP_BO_USER_MASK      0x00ffffff      /* flags settable by
> > userspace */
>
> Fwiw I'm not too sure that adding the mask here  (UAPI) is a good
> idea.

Good point, I'll make it private.

> If you like to keep it, I'd suggest that it encapsulates only what's
> currently available. Might even want to move the individual masks in the
> respective sections/hunks. Speaking of which - OMAP_BO_TILED_MASK should be
> 0x00000300, shouldn't it ?

I suppose 0x00000f00 was chosen to reserve a couple of bits for additional 
tiled modes.

-- 
Regards,

Laurent Pinchart

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