linux-kernel - Re: [PATCH v4 4/4] drivers: base: handle module

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Message-ID: <2025041538-coming-busload-3813@gregkh>
Date: Tue, 15 Apr 2025 17:29:46 +0200
From: Greg KH <gregkh@...uxfoundation.org>
To: Shyam Saini <shyamsaini@...ux.microsoft.com>
Cc: linux-kernel@...r.kernel.org, linux-modules@...r.kernel.org,
	petr.pavlu@...e.com, code@...icks.com, linux@...musvillemoes.dk,
	christophe.leroy@...roup.eu, hch@...radead.org, mcgrof@...nel.org,
	frkaya@...ux.microsoft.com, vijayb@...ux.microsoft.com,
	linux@...ssschuh.net, samitolvanen@...gle.com, da.gomez@...sung.com,
	rafael@...nel.org, dakr@...nel.org, stable@...nel.org
Subject: Re: [PATCH v4 4/4] drivers: base: handle module_kobject creation

On Thu, Feb 27, 2025 at 10:49:30AM -0800, Shyam Saini wrote:
> module_add_driver() relies on module_kset list for
> /sys/module/<built-in-module>/drivers directory creation.
> 
> Since,
> commit 96a1a2412acba ("kernel/params.c: defer most of param_sysfs_init() to late_initcall time")
> drivers which are initialized from subsys_initcall() or any other
> higher precedence initcall couldn't find the related kobject entry
> in the module_kset list because module_kset is not fully populated
> by the time module_add_driver() refers it. As a consequence,
> module_add_driver() returns early without calling make_driver_name().
> Therefore, /sys/module/<built-in-module>/drivers is never created.
> 
> Fix this issue by letting module_add_driver() handle module_kobject
> creation itself.
> 
> Fixes: 96a1a2412acb ("kernel/params.c: defer most of param_sysfs_init() to late_initcall time")
> Cc: stable@...nel.org
> Suggested-by: Rasmus Villemoes <linux@...musvillemoes.dk>
> Signed-off-by: Shyam Saini <shyamsaini@...ux.microsoft.com>
> ---
>  drivers/base/module.c | 13 +++++--------
>  1 file changed, 5 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/base/module.c b/drivers/base/module.c
> index 5bc71bea883a..218aaa096455 100644
> --- a/drivers/base/module.c
> +++ b/drivers/base/module.c
> @@ -42,16 +42,13 @@ int module_add_driver(struct module *mod, const struct device_driver *drv)
>  	if (mod)
>  		mk = &mod->mkobj;
>  	else if (drv->mod_name) {
> -		struct kobject *mkobj;
> -
> -		/* Lookup built-in module entry in /sys/modules */
> -		mkobj = kset_find_obj(module_kset, drv->mod_name);
> -		if (mkobj) {
> -			mk = container_of(mkobj, struct module_kobject, kobj);
> +		/* Lookup or create built-in module entry in /sys/modules */
> +		mk = lookup_or_create_module_kobject(drv->mod_name);
> +		if (mk) {
>  			/* remember our module structure */
>  			drv->p->mkobj = mk;
> -			/* kset_find_obj took a reference */
> -			kobject_put(mkobj);
> +			/* lookup_or_create_module_kobject took a reference */
> +			kobject_put(&mk->kobj);
>  		}
>  	}
>  
> -- 
> 2.34.1

Acked-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>