linux-kernel - Re: [PATCH] backlight: check null deference of name when device is registered

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Date:	Mon, 7 Jan 2013 17:35:57 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Jingoo Han <jg1.han@...sung.com>
Cc:	"'LKML'" <linux-kernel@...r.kernel.org>,
	linux-fbdev@...r.kernel.org,
	"'Richard Purdie'" <rpurdie@...ys.net>,
	"'Devendra Naga'" <devendra.aaru@...il.com>
Subject: Re: [PATCH] backlight: check null deference of name when device is
 registered

On Tue, 08 Jan 2013 10:25:35 +0900 Jingoo Han <jg1.han@...sung.com> wrote:

> On Tuesday, January 08, 2013 9:02 AM, Andrew Morton wrote
> > On Fri, 04 Jan 2013 17:29:11 +0900
> > Jingoo Han <jg1.han@...sung.com> wrote:
> > 
> > > NULL deference of name is checked when device is registered.
> > > If the name is null, it will cause a kernel oops in dev_set_name().
> > >
> > > ...
> > >
> > > --- a/drivers/video/backlight/backlight.c
> > > +++ b/drivers/video/backlight/backlight.c
> > > @@ -292,6 +292,11 @@ struct backlight_device *backlight_device_register(const char *name,
> > >  	struct backlight_device *new_bd;
> > >  	int rc;
> > >
> > > +	if (name == NULL) {
> > > +		pr_err("backlight name is null\n");
> > > +		return ERR_PTR(-EINVAL);
> > > +	}
> > > +
> > >  	pr_debug("backlight_device_register: name=%s\n", name);
> > 
> > I don't understand this.
> > 
> > Is there some driver which is calling these functions with name=NULL?
> > If so, which one(s)?
> 
> No, there is no one.
> 
> > 
> > If "no" then why don't we declare that "passing name=NULL is a bug" and
> > leave the code as-is?
> 
> Do you mean following?
> 
> +	if (name == NULL)
> +		pr_err("passing name=NULL is a bug");
> +
>   	pr_debug("backlight_device_register: name=%s\n", name);

Nope; I'm suggesting we leave the code alone.  If someone passes in
NULL they will get a nice oops and their bug will then get fixed.

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