This is a note to let you know that I've just added the patch titled
drm/virtio: Fix GEM handle creation UAF
to the 4.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
drm-virtio-fix-gem-handle-creation-uaf.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit bbca764a1324b52ab58dcee7935dc73fa0a6b951
Author: Rob Clark <robdclark@xxxxxxxxxxxx>
Date: Fri Dec 16 15:33:55 2022 -0800
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@xxxxxxxxxxxx>
Reviewed-by: Chia-I Wu <olvaffe@xxxxxxxxx>
Fixes: 62fb7a5e1096 ("virtio-gpu: add 3d/virgl support")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@xxxxxxxxxxxxx>
Link: https://patchwork.freedesktop.org/patch/msgid/20221216233355.542197-2-robdclark@xxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/gpu/drm/virtio/virtgpu_ioctl.c b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
index 8d2f5ded86d6..a539843a03ba 100644
--- a/drivers/gpu/drm/virtio/virtgpu_ioctl.c
+++ b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
@@ -309,7 +309,6 @@ static int virtio_gpu_resource_create_ioctl(struct drm_device *dev, void *data,
}
return ret;
}
- drm_gem_object_put_unlocked(obj);
rc->res_handle = res_id; /* similiar to a VM address */
rc->bo_handle = handle;
@@ -318,6 +317,15 @@ static int virtio_gpu_resource_create_ioctl(struct drm_device *dev, void *data,
virtio_gpu_unref_list(&validate_list);
dma_fence_put(&fence->f);
}
+
+ /*
+ * 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;
fail_unref:
if (vgdev->has_virgl_3d) {
