linux-kernel - Re: [PATCH 1/1] tty: vt: Remove redundant null check before kfree.

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Message-ID: <20121121230057.GA29095@kroah.com>
Date:	Wed, 21 Nov 2012 15:00:57 -0800
From:	Greg KH <gregkh@...uxfoundation.org>
To:	Jiri Slaby <jslaby@...e.cz>
Cc:	Sachin Kamat <sachin.kamat@...aro.org>,
	linux-kernel@...r.kernel.org, patches@...aro.org
Subject: Re: [PATCH 1/1] tty: vt: Remove redundant null check before kfree.

On Wed, Nov 21, 2012 at 11:43:34PM +0100, Jiri Slaby wrote:
> On 11/21/2012 03:46 PM, Greg KH wrote:
> > On Wed, Nov 21, 2012 at 10:49:07AM +0530, Sachin Kamat wrote:
> >> --- a/drivers/tty/vt/consolemap.c
> >> +++ b/drivers/tty/vt/consolemap.c
> >> @@ -410,10 +410,8 @@ static void con_release_unimap(struct uni_pagedir *p)
> >>  		kfree(p->inverse_translations[i]);
> >>  		p->inverse_translations[i] = NULL;
> >>  	}
> >> -	if (p->inverse_trans_unicode) {
> >> -		kfree(p->inverse_trans_unicode);
> >> -		p->inverse_trans_unicode = NULL;
> >> -	}
> >> +	kfree(p->inverse_trans_unicode);
> >> +	p->inverse_trans_unicode = NULL;
> > 
> > kfree with NULL is a no-op, but the line after that just caused a kernel
> > crash if it was NULL, so I can't accept this type of thing.
> 
> Greg, I'm not sure -- what do you mean here? The change actually looks
> fine to me... We do not dereference p->inverse_trans_unicode there.

If we never dereference it, why is it being set to NULL?

greg k-h
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