cxl: fix possible null-ptr-deref in cxl_pci_init_afu|adapter()

If device_register() fails in cxl_pci_afu|adapter(), the device
is not added, device_unregister() can not be called in the error
path, otherwise it will cause a null-ptr-deref because of removing
not added device.

As comment of device_register() says, it should use put_device() to give
up the reference in the error path. So split device_unregister() into
device_del() and put_device(), then goes to put dev when register fails.

Fixes: f204e0b8 ("cxl: Driver code for powernv PCIe based cards for userspace access")
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Acked-by: Andrew Donnellan <ajd@linux.ibm.com>
Acked-by: Frederic Barrat <fbarrat@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20221111145440.2426970-2-yangyingliang@huawei.com

drivers/misc/cxl/pci.c

@@ -1165,10 +1165,10 @@ static int pci_init_afu(struct cxl *adapter, int slice, struct pci_dev *dev)
 	 * if it returns an error!
 	 */
 	if ((rc = cxl_register_afu(afu)))
-		goto err_put1;
+		goto err_put_dev;
 
 	if ((rc = cxl_sysfs_afu_add(afu)))
-		goto err_put1;
+		goto err_del_dev;
 
 	adapter->afu[afu->slice] = afu;
 
@@ -1177,10 +1177,12 @@ static int pci_init_afu(struct cxl *adapter, int slice, struct pci_dev *dev)
 
 	return 0;
 
-err_put1:
+err_del_dev:
+	device_del(&afu->dev);
+err_put_dev:
 	pci_deconfigure_afu(afu);
 	cxl_debugfs_afu_remove(afu);
-	device_unregister(&afu->dev);
+	put_device(&afu->dev);
 	return rc;
 
 err_free_native:
@@ -1668,23 +1670,25 @@ static struct cxl *cxl_pci_init_adapter(struct pci_dev *dev)
 	 * even if it returns an error!
 	 */
 	if ((rc = cxl_register_adapter(adapter)))
-		goto err_put1;
+		goto err_put_dev;
 
 	if ((rc = cxl_sysfs_adapter_add(adapter)))
-		goto err_put1;
+		goto err_del_dev;
 
 	/* Release the context lock as adapter is configured */
 	cxl_adapter_context_unlock(adapter);
 
 	return adapter;
 
-err_put1:
+err_del_dev:
+	device_del(&adapter->dev);
+err_put_dev:
 	/* This should mirror cxl_remove_adapter, except without the
 	 * sysfs parts
 	 */
 	cxl_debugfs_adapter_remove(adapter);
 	cxl_deconfigure_adapter(adapter);
-	device_unregister(&adapter->dev);
+	put_device(&adapter->dev);
 	return ERR_PTR(rc);
 
 err_release: