linux-kernel - Re: [PATCH net-next v3 1/9] sysfs: add sysfs_file_change_owner{_by

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Message-ID: <20200220112049.GF3374196@kroah.com>
Date:   Thu, 20 Feb 2020 12:20:49 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Christian Brauner <christian.brauner@...ntu.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Pavel Machek <pavel@....cz>, Jakub Kicinski <kuba@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Stephen Hemminger <stephen@...workplumber.org>,
        linux-pm@...r.kernel.org
Subject: Re: [PATCH net-next v3 1/9] sysfs: add
 sysfs_file_change_owner{_by_name}()

On Tue, Feb 18, 2020 at 05:29:35PM +0100, Christian Brauner wrote:
> +/**
> + *	sysfs_file_change_owner - change owner of a file.
> + *	@kobj:	object.
> + *	@kuid: new owner's kuid
> + *	@kgid: new owner's kgid
> + */
> +int sysfs_file_change_owner(struct kobject *kobj, kuid_t kuid, kgid_t kgid)
> +{
> +	struct kernfs_node *kn;
> +	int error;
> +
> +	if (!kobj->state_in_sysfs)
> +		return -EINVAL;
> +
> +	kernfs_get(kobj->sd);
> +
> +	kn = kobj->sd;
> +	error = internal_change_owner(kn, kobj, kuid, kgid);
> +
> +	kernfs_put(kn);
> +
> +	return error;
> +}
> +EXPORT_SYMBOL_GPL(sysfs_file_change_owner);

Oops, wait, what "file" are you changing here?  You aren't changing the
kobject's attributes, but rather a file in the kobject's directory,
right?  But kobj->sd is the directory of the kobject itself, so why
isn't this function just the same thing as sysfs_change_owner()?

Why would you call this function at all?

confused,

greg k-h