Commit 1918e79b authored by Thomas Zimmermann's avatar Thomas Zimmermann
Browse files

Revert "drm/gem-dma: Use dma_buf from GEM object instance" 



This reverts commit e8afa155.

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.

v3:
- cc stable

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>
Cc: <stable@vger.kernel.org> # v6.15+
Link: https://lore.kernel.org/r/20250715155934.150656-8-tzimmermann@suse.de
parent 6d496e95

drivers/gpu/drm/drm_gem_dma_helper.c

+1 −1
Original line number Diff line number Diff line
@@ -230,7 +230,7 @@ void drm_gem_dma_free(struct drm_gem_dma_object *dma_obj) 


	if (drm_gem_is_imported(gem_obj)) {

		if (dma_obj->vaddr)

			dma_buf_vunmap_unlocked(gem_obj->dma_buf, &map);

			dma_buf_vunmap_unlocked(gem_obj->import_attach->dmabuf, &map);

		drm_prime_gem_destroy(gem_obj, dma_obj->sgt);

	} else if (dma_obj->vaddr) {

		if (dma_obj->map_noncoherent)