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drm/virtio: Fix GEM handle creation UAF

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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: 62fb7a5e10 ("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
This commit is contained in:
Rob Clark 2022-12-16 15:33:55 -08:00 committed by Dmitry Osipenko
parent 0688773f07
commit 5253125831
1 changed files with 17 additions and 2 deletions
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19
drivers/gpu/drm/virtio/virtgpu_ioctl.c
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@ -358,10 +358,18 @@ static int virtio_gpu_resource_create_ioctl(struct drm_device *dev, void *data,
drm_gem_object_release(obj);
return ret;
}
drm_gem_object_put(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(obj);
return 0;
}
@ -723,11 +731,18 @@ static int virtio_gpu_resource_create_blob_ioctl(struct drm_device *dev,
drm_gem_object_release(obj);
return ret;
}
drm_gem_object_put(obj);
rc_blob->res_handle = bo->hw_res_handle;
rc_blob->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(obj);
return 0;
}