[PATCH v3 0/7] drm: Revert general use of struct drm_gem_object.dma_buf

[Thomas Zimmermann <tzimmermann@suse.de>]

Revert the use of drm_gem_object.dma_buf back to .import_attach->dmabuf
in the affected places. Separates references to imported and exported DMA
bufs within a GEM object; as before.

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 5307dce878d4 ("drm/gem: Acquire references on GEM
handles for framebuffers") and commit f6bfc9afc751 ("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.

v3:
- cc stable where necessary
v2:
- extended commit messages (Sima)
- drop the GEM-handle changes to be resolved separately

Thomas Zimmermann (7):
  Revert "drm/virtio: Use dma_buf from GEM object instance"
  Revert "drm/vmwgfx: Use dma_buf from GEM object instance"
  Revert "drm/etnaviv: Use dma_buf from GEM object instance"
  Revert "drm/prime: Use dma_buf from GEM object instance"
  Revert "drm/gem-framebuffer: Use dma_buf from GEM object instance"
  Revert "drm/gem-shmem: Use dma_buf from GEM object instance"
  Revert "drm/gem-dma: Use dma_buf from GEM object instance"

 drivers/gpu/drm/drm_gem_dma_helper.c         | 2 +-
 drivers/gpu/drm/drm_gem_framebuffer_helper.c | 8 ++++++--
 drivers/gpu/drm/drm_gem_shmem_helper.c       | 4 ++--
 drivers/gpu/drm/drm_prime.c                  | 8 +++++++-
 drivers/gpu/drm/etnaviv/etnaviv_gem_prime.c  | 4 ++--
 drivers/gpu/drm/virtio/virtgpu_prime.c       | 5 +++--
 drivers/gpu/drm/vmwgfx/vmwgfx_gem.c          | 6 +++---
 7 files changed, 24 insertions(+), 13 deletions(-)

-- 
2.50.0