Commit 0ecfb8dd authored by Thomas Zimmermann's avatar Thomas Zimmermann
Browse files

Revert "drm/virtio: Use dma_buf from GEM object instance" 



This reverts commit 415cb458.

The dma_buf field in struct drm_gem_object is not stable over the
object instance's lifetime. The field becomes NULL when user space
releases the final GEM handle on the buffer object. This resulted
in a NULL-pointer deref.

Workarounds in commit 5307dce8 ("drm/gem: Acquire references on
GEM handles for framebuffers") and commit f6bfc9af ("drm/framebuffer:
Acquire internal references on GEM handles") only solved the problem
partially. They especially don't work for buffer objects without a DRM
framebuffer associated.

Hence, this revert to going back to using .import_attach->dmabuf.

Signed-off-by: default avatarThomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: default avatarSimona Vetter <simona.vetter@ffwll.ch>
Acked-by: default avatarChristian König <christian.koenig@amd.com>
Acked-by: default avatarZack Rusin <zack.rusin@broadcom.com>
Link: https://lore.kernel.org/r/20250715155934.150656-3-tzimmermann@suse.de
parent 15f77764

drivers/gpu/drm/virtio/virtgpu_prime.c

+3 −2
Original line number Diff line number Diff line
@@ -204,15 +204,16 @@ static void virtgpu_dma_buf_free_obj(struct drm_gem_object *obj) 
{

	struct virtio_gpu_object *bo = gem_to_virtio_gpu_obj(obj);

	struct virtio_gpu_device *vgdev = obj->dev->dev_private;

	struct dma_buf_attachment *attach = obj->import_attach;



	if (drm_gem_is_imported(obj)) {

		struct dma_buf *dmabuf = obj->dma_buf;

		struct dma_buf *dmabuf = attach->dmabuf;



		dma_resv_lock(dmabuf->resv, NULL);

		virtgpu_dma_buf_unmap(bo);

		dma_resv_unlock(dmabuf->resv);



		dma_buf_detach(dmabuf, obj->import_attach);

		dma_buf_detach(dmabuf, attach);

		dma_buf_put(dmabuf);

	}