[PATCH] drm/panthor: Enforce DRM_PANTHOR_BO_NO_MMAP

[Liviu Dudau]

On Tue, Apr 15, 2025 at 01:18:42PM +0200, Boris Brezillon wrote:
> On Tue, 15 Apr 2025 12:57:10 +0200
> Boris Brezillon <boris.brezillon at collabora.com> wrote:
> 
> > Right now the DRM_PANTHOR_BO_NO_MMAP flag is ignored by
> > panthor_ioctl_bo_mmap_offset(), meaning BOs with this flag set can
> > still be mmap-ed.
> > 
> > Fortunately, this bug only impacts user BOs, because kernel BOs are not
> > exposed to userspace (they don't have a BO handle), so they can't
> > be mmap-ed anyway. Given all user BOs setting this flag are private
> > anyway (not shareable), there's no potential data leak.
> > 
> > Fixes: 4bdca1150792 ("drm/panthor: Add the driver frontend block")
> > Signed-off-by: Boris Brezillon <boris.brezillon at collabora.com>
> > ---
> >  drivers/gpu/drm/panthor/panthor_drv.c | 5 +++++
> >  1 file changed, 5 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/panthor/panthor_drv.c b/drivers/gpu/drm/panthor/panthor_drv.c
> > index 15d8e2bcf6ad..1499df07f512 100644
> > --- a/drivers/gpu/drm/panthor/panthor_drv.c
> > +++ b/drivers/gpu/drm/panthor/panthor_drv.c
> > @@ -940,6 +940,7 @@ static int panthor_ioctl_bo_mmap_offset(struct drm_device *ddev, void *data,
> >  					struct drm_file *file)
> >  {
> >  	struct drm_panthor_bo_mmap_offset *args = data;
> > +	struct panthor_gem_object *bo;
> >  	struct drm_gem_object *obj;
> >  	int ret;
> >  
> > @@ -950,6 +951,10 @@ static int panthor_ioctl_bo_mmap_offset(struct drm_device *ddev, void *data,
> >  	if (!obj)
> >  		return -ENOENT;
> >  
> > +	bo = to_panthor_bo(obj);
> > +	if (bo->flags & DRM_PANTHOR_BO_NO_MMAP)
> > +		return -EINVAL;
> 
> Maybe it should be EPERM instead of EINVAL here.

Yeah, I agree. With that change:

Reviewed-by: Liviu Dudau <liviu.dudau at arm.com>

Best regards,
Liviu

> 
> > +
> >  	ret = drm_gem_create_mmap_offset(obj);
> >  	if (ret)
> >  		goto out;
> 

-- 
====================
| I would like to |
| fix the world,  |
| but they're not |
| giving me the   |
 \ source code!  /
  ---------------
    ¯\_(ツ)_/¯