From fb4ef4a52b79a22ad382bfe77332642d02aef773 Mon Sep 17 00:00:00 2001 From: Thomas Zimmermann Date: Tue, 15 Jul 2025 17:58:14 +0200 Subject: [PATCH] Revert "drm/prime: Use dma_buf from GEM object instance" MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit This reverts commit f83a9b8c7fd0557b0c50784bfdc1bbe9140c9bf8. 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/20250715155934.150656-5-tzimmermann@suse.de --- drivers/gpu/drm/drm_prime.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c index d828502268b8e..a0a5d725eab06 100644 --- a/drivers/gpu/drm/drm_prime.c +++ b/drivers/gpu/drm/drm_prime.c @@ -453,7 +453,13 @@ struct dma_buf *drm_gem_prime_handle_to_dmabuf(struct drm_device *dev, } mutex_lock(&dev->object_name_lock); - /* re-export the original imported/exported object */ + /* re-export the original imported object */ + if (obj->import_attach) { + dmabuf = obj->import_attach->dmabuf; + get_dma_buf(dmabuf); + goto out_have_obj; + } + if (obj->dma_buf) { get_dma_buf(obj->dma_buf); dmabuf = obj->dma_buf; -- 2.47.2