[PATCH v2] drm/gem: Fix mmap fake offset handling for drm_gem_object_funcs.mmap

[Gerd Hoffmann]

  Hi,

> > > I think for ttm just consistently using the one per-device mapping for
> > > everything, with all the fake offsets, is probably the quickest route.
> >
> > Hmm, not clear how to fit dmabufs into this.  dmabufs already have their
> > own file, inode and address space.  I'm not sure you can switch that
> > over to the per-device mapping in the first place, and even if you can I
> > have my doubts this is a good idea from a security point of view ...
> 
> You can (plenty drivers do that already),

Have pointer(s) to code?

> and not sure how that breaks
> security?

Go try mmap(fake-offset) on the dma-buf file handle to access other
buffers of the drm device?  Hmm, thinking again, I guess the
verify-access restrictions should prevent that.

cheers,
  Gerd