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

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Message-ID: <20121122003835.GA24936@kroah.com>
Date:	Wed, 21 Nov 2012 16:38:35 -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 Thu, Nov 22, 2012 at 12:17:00AM +0100, Jiri Slaby wrote:
> On 11/22/2012 12:00 AM, Greg KH wrote:
> > 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?
> 
> I'm not disputing the assignment. Let it there. But I do not see any
> issues with the patch. What problem do you see exactly?

{sigh}  Nothing.  I don't know what I was thinking, my apologies
Sachin, there's nothing wrong with this patch.

I blame my fried brain, after reviewing all of those __dev* removal
patches :)

Sachin, can you resend these patches so I can apply them?

thanks,

greg k-h
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