vfio/pci: Re-order vfio_pci_probe()

vfio_add_group_dev() must be called only after all of the private data in
vdev is fully setup and ready, otherwise there could be races with user
space instantiating a device file descriptor and starting to call ops.

For instance vfio_pci_reflck_attach() sets vdev->reflck and
vfio_pci_open(), called by fops open, unconditionally derefs it, which
will crash if things get out of order.

Fixes: cc20d799 ("vfio/pci: Introduce VF token")
Fixes: e309df5b ("vfio/pci: Parallelize device open and release")
Fixes: 6eb70187 ("vfio-pci: Move idle devices to D3hot power state")
Fixes: ecaa1f6a ("vfio-pci: Add VGA arbiter client")
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Max Gurtovoy <mgurtovoy@nvidia.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Message-Id: <8-v3-225de1400dfc+4e074-vfio1_jgg@nvidia.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

drivers/vfio/pci/vfio_pci.c

@@ -2030,13 +2030,9 @@ static int vfio_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 	INIT_LIST_HEAD(&vdev->vma_list);
 	init_rwsem(&vdev->memory_lock);
 
-	ret = vfio_add_group_dev(&pdev->dev, &vfio_pci_ops, vdev);
-	if (ret)
-		goto out_free;
-
 	ret = vfio_pci_reflck_attach(vdev);
 	if (ret)
-		goto out_del_group_dev;
+		goto out_free;
 	ret = vfio_pci_vf_init(vdev);
 	if (ret)
 		goto out_reflck;
@@ -2060,15 +2056,20 @@ static int vfio_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 		vfio_pci_set_power_state(vdev, PCI_D3hot);
 	}
 
-	return ret;
+	ret = vfio_add_group_dev(&pdev->dev, &vfio_pci_ops, vdev);
+	if (ret)
+		goto out_power;
+	return 0;
 
+out_power:
+	if (!disable_idle_d3)
+		vfio_pci_set_power_state(vdev, PCI_D0);
 out_vf:
 	vfio_pci_vf_uninit(vdev);
 out_reflck:
 	vfio_pci_reflck_put(vdev->reflck);
-out_del_group_dev:
-	vfio_del_group_dev(&pdev->dev);
 out_free:
+	kfree(vdev->pm_save);
 	kfree(vdev);
 out_group_put:
 	vfio_iommu_group_put(group, &pdev->dev);