linux-kernel - Re: [PATCH 06/20] staging/lustre: fix comparison between signed and unsigned

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Date:	Mon, 2 Feb 2015 07:44:00 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	Dan Carpenter <dan.carpenter@...cle.com>
Cc:	green@...uxhacker.ru, devel@...verdev.osuosl.org,
	Dmitry Eremin <dmitry.eremin@...el.com>,
	Andreas Dilger <andreas.dilger@...el.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Oleg Drokin <oleg.drokin@...el.com>
Subject: Re: [PATCH 06/20] staging/lustre: fix comparison between signed and
 unsigned

On Mon, Feb 02, 2015 at 04:02:31PM +0300, Dan Carpenter wrote:
> On Sun, Feb 01, 2015 at 09:52:05PM -0500, green@...uxhacker.ru wrote:
> > From: Dmitry Eremin <dmitry.eremin@...el.com>
> > 
> > Expression if (size != (ssize_t)size) is always false.
> > Therefore no bounds check errors detected.
> 
> The original code actually worked as designed.  The integer overflow
> could only happen on 32 bit systems and the test only was true for 32
> bit systems.
> 
> > -	if (size != (ssize_t)size)
> > +	if (size > ~((size_t)0)>>1)
> >  		return -1;
> 
> The problem is that the code was unclear.  I think the new code is even
> more complicated to look at.

I agree, I don't even understand what the new code is doing.

What is this code supposed to be protecting from?  And -1?  That should
never be a return value...

thanks,

greg k-h
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