linux-kernel - Re: Re: [PATCH] driver-core: Fix null reference in subsys_interface

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Message-ID: <20120117005944.GA14863@suse.de>
Date:	Mon, 16 Jan 2012 16:59:44 -0800
From:	Greg KH <gregkh@...e.de>
To:	최종환 <jhbird.choi@...sung.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	김국진 <kgene.kim@...sung.com>
Subject: Re: Re: [PATCH] driver-core: Fix null reference in
 subsys_interface_unregister

On Tue, Jan 17, 2012 at 12:35:35AM +0000, 최종환 wrote:
> Greg KH wrote:
> 
> >On Sat, Jan 14, 2012 at 11:06:03AM +0900, jhbird.choi@...sung.com wrote:
> >> From: Jonghwan Choi 
> > >
> > >Check if the sif is not NULL before de-referencing it
> 
> >Why would it be?  Have you hit this somehow?  If so, in what code?
> 
> > thanks,
> 
> > greg k-h
> 
> 
> diff --git a/drivers/base/bus.c b/drivers/base/bus.c
> index 99dc592..4ddb38b 100644
> --- a/drivers/base/bus.c
> +++ b/drivers/base/bus.c
> @@ -1193,13 +1193,15 @@ EXPORT_SYMBOL_GPL(subsys_interface_register);
> 
>  void subsys_interface_unregister(struct subsys_interface *sif)
>  {
> -       struct bus_type *subsys = sif->subsys;   // -> Sif is already used, that means sif is not null
> +       struct bus_type *subsys;
>         struct subsys_dev_iter iter;
>         struct device *dev;
> 
> -       if (!sif)  // -> Check whether sif is null 
> +       if (!sif || !sif->subsys)
>                 return;
> 
> +       subsys = sif->subsys;
> +
>         mutex_lock(&subsys->p->mutex);
>         list_del_init(&sif->node);
>         if (sif->remove_dev) {
> -- 
> 
> sif is already used, but  null pointer check for sif later.
> so i think that sif should be checked before use it.

Yes, you are right, I missed the previous usage.  I'll queue this up for
3.4.

thanks,

greg k-h
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