On Wed, Nov 20, 2019 at 2:08 PM Gerd Hoffmann <kraxel@xxxxxxxxxx> wrote: > > Ah, we're not going to replace the mapping on the dma-buf file. Only > > the file of the vma structure. Doing the former would indeed be pretty > > bad from a security pov. > > Now where do I get a filp from? Can I just call drm_open? Hm, now I wonder whether it's maybe ok to just exchange the filp->f_mapping. As long as we don't mix up the kinds of mapping and page-cache management that can happon on a given address_space structure (that's why I'm not keeon the shmem mapping reused, since shmem uses the same address_space structure internally to manage the page allocations - address_space both contains the page cache for a file, and also the reverse mapping information). So kinda what drm_open does, except we do that to the dma-buf file. So exactly what amdgpu is doing and that I just complained about :-) Aside: the amdgpu isn't great because it's racy, userspace could have guessed the fd and already started an mmap before we managed to update stuff. But aside from that maybe rolling out the amdgpu trick for everyone is the right way? -Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
