Commit 6d496e95 authored by Thomas Zimmermann's avatar Thomas Zimmermann
Browse files

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



This reverts commit 1a148af0.

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/20250715155934.150656-7-tzimmermann@suse.de
parent 2712ca87

drivers/gpu/drm/drm_gem_shmem_helper.c

+2 −2
Original line number Diff line number Diff line
@@ -349,7 +349,7 @@ int drm_gem_shmem_vmap_locked(struct drm_gem_shmem_object *shmem, 
	int ret = 0;



	if (drm_gem_is_imported(obj)) {

		ret = dma_buf_vmap(obj->dma_buf, map);

		ret = dma_buf_vmap(obj->import_attach->dmabuf, map);

	} else {

		pgprot_t prot = PAGE_KERNEL;
@@ -409,7 +409,7 @@ void drm_gem_shmem_vunmap_locked(struct drm_gem_shmem_object *shmem, 
	struct drm_gem_object *obj = &shmem->base;



	if (drm_gem_is_imported(obj)) {

		dma_buf_vunmap(obj->dma_buf, map);

		dma_buf_vunmap(obj->import_attach->dmabuf, map);

	} else {

		dma_resv_assert_held(shmem->base.resv);