linux-kernel - Re: [PATCH] drivers/base/core: refcount kobject and bus on device attribute read / store

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Message-ID: <YNJXfNfn4+CaKOyz@kroah.com>
Date:   Tue, 22 Jun 2021 23:34:52 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Luis Chamberlain <mcgrof@...nel.org>
Cc:     rafael@...nel.org, jeyu@...nel.org, ngupta@...are.org,
        sergey.senozhatsky.work@...il.com, minchan@...nel.org,
        axboe@...nel.dk, mbenes@...e.com, jpoimboe@...hat.com,
        tglx@...utronix.de, keescook@...omium.org, jikos@...nel.org,
        rostedt@...dmis.org, peterz@...radead.org,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drivers/base/core: refcount kobject and bus on device
 attribute read / store

On Tue, Jun 22, 2021 at 02:06:59PM -0700, Luis Chamberlain wrote:
>  static ssize_t dev_attr_show(struct kobject *kobj, struct attribute *attr,
>  			     char *buf)
>  {
> -	struct device_attribute *dev_attr = to_dev_attr(attr);
> -	struct device *dev = kobj_to_dev(kobj);
> +	struct device_attribute *dev_attr;
> +	struct device *dev;
> +	struct bus_type *bus = NULL;
>  	ssize_t ret = -EIO;
>  
> +	dev = get_device(kobj_to_dev(kobj));
> +	if (!dev)
> +		return ret;

That check is impossible to ever hit, please recognize what things like
kobj_to_dev() really are doing when calling it.

thanks,

greg k-h