From 6d496e9569983a0d7a05be6661126d0702cf94f7 Mon Sep 17 00:00:00 2001 From: Thomas Zimmermann Date: Tue, 15 Jul 2025 17:58:16 +0200 Subject: [PATCH] Revert "drm/gem-shmem: Use dma_buf from GEM object instance" MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit This reverts commit 1a148af06000e545e714fe3210af3d77ff903c11. 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. Hence, this revert to going back to using .import_attach->dmabuf. v3: - cc stable Signed-off-by: Thomas Zimmermann Reviewed-by: Simona Vetter Acked-by: Christian König Acked-by: Zack Rusin Cc: # v6.15+ Link: https://lore.kernel.org/r/20250715155934.150656-7-tzimmermann@suse.de --- drivers/gpu/drm/drm_gem_shmem_helper.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c index aa43265f4f4f6..a5dbee6974ab6 100644 --- a/drivers/gpu/drm/drm_gem_shmem_helper.c +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c @@ -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); -- 2.47.2