Re: [PATCH] driver core: faux: fix root device registration

["Danilo Krummrich" <dakr@kernel.org>]

On Fri Apr 24, 2026 at 12:22 PM CEST, Johan Hovold wrote:
> diff --git a/drivers/base/faux.c b/drivers/base/faux.c
> index fb3e42f21362..402ed119dfdf 100644
> --- a/drivers/base/faux.c
> +++ b/drivers/base/faux.c
> @@ -133,6 +133,9 @@ struct faux_device *faux_device_create_with_groups(const char *name,
>  	struct device *dev;
>  	int ret;
>  
> +	if (IS_ERR_OR_NULL(faux_bus_root))
> +		return NULL;

As Greg mentioned, if this happens we already have a much bigger fundamental
problem earlier in the boot process.

Anyway, I think this check only catches when root_device_register() fails, but
everything that comes after root_device_register() in faux_bus_init() still
leaves us with a dangling pointer.

> +
>  	faux_obj = kzalloc_obj(*faux_obj);
>  	if (!faux_obj)
>  		return NULL;
> @@ -234,17 +237,9 @@ int __init faux_bus_init(void)
>  {
>  	int ret;
>  
> -	faux_bus_root = kzalloc_obj(*faux_bus_root);
> -	if (!faux_bus_root)
> -		return -ENOMEM;
> -
> -	dev_set_name(faux_bus_root, "faux");
> -
> -	ret = device_register(faux_bus_root);
> -	if (ret) {
> -		put_device(faux_bus_root);
> -		return ret;
> -	}
> +	faux_bus_root = root_device_register("faux");
> +	if (IS_ERR(faux_bus_root))
> +		return PTR_ERR(faux_bus_root);
>  
>  	ret = bus_register(&faux_bus_type);
>  	if (ret)
> @@ -260,6 +255,6 @@ int __init faux_bus_init(void)
>  	bus_unregister(&faux_bus_type);
>  
>  error_bus:
> -	device_unregister(faux_bus_root);
> +	root_device_unregister(faux_bus_root);
>  	return ret;
>  }
> -- 
> 2.53.0