Commit d01d6d2b authored Dec 16, 2022 by Rob Clark Committed by Greg Kroah-Hartman Jan 18, 2023

drm/virtio: Fix GEM handle creation UAF



[ Upstream commit 52531258318ed59a2dc5a43df2eaf0eb1d65438e ]

Userspace can guess the handle value and try to race GEM object creation
with handle close, resulting in a use-after-free if we dereference the
object after dropping the handle's reference.  For that reason, dropping
the handle's reference must be done *after* we are done dereferencing
the object.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Reviewed-by: Chia-I Wu <olvaffe@gmail.com>
Fixes: 62fb7a5e ("virtio-gpu: add 3d/virgl support")
Cc: stable@vger.kernel.org
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221216233355.542197-2-robdclark@gmail.com


Signed-off-by: Sasha Levin <sashal@kernel.org>

parent 3030f11f

drivers/gpu/drm/virtio/virtgpu_ioctl.c

+9 −1

Original line number	Diff line number	Diff line
		@@ -327,10 +327,18 @@ static int virtio_gpu_resource_create_ioctl(struct drm_device dev, void data,
		drm_gem_object_release(obj);
		return ret;
		}
		drm_gem_object_put_unlocked(obj);

		rc->res_handle = qobj->hw_res_handle; /* similiar to a VM address */
		rc->bo_handle = handle;

		/*
		* The handle owns the reference now. But we must drop our
		* remaining reference after we no longer need to dereference
		* the obj. Otherwise userspace could guess the handle and
		* race closing it from another thread.
		*/
		drm_gem_object_put_unlocked(obj);

		return 0;
		}