Patch-mainline: v6.2-rc4
Git-commit: 52531258318ed59a2dc5a43df2eaf0eb1d65438e
References: git-fixes
From: Rob Clark <robdclark@chromium.org>
Date: Fri, 16 Dec 2022 15:33:55 -0800
Subject: [PATCH] drm/virtio: Fix GEM handle creation UAF
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: 62fb7a5e1096 ("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: Juergen Gross <jgross@suse.com>
---
drivers/gpu/drm/virtio/virtgpu_ioctl.c | 19 +++++++++++++++++--
1 file changed, 17 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/virtio/virtgpu_ioctl.c b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
index 5d05093014ac..9f4a90493aea 100644
--- a/drivers/gpu/drm/virtio/virtgpu_ioctl.c
+++ b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
@@ -358,10 +358,17 @@ 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;
+
+ /*
+ * 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);
if (vgdev->has_virgl_3d) {
virtio_gpu_unref_list(&validate_list);
--
2.35.3