linux-kernel - Re: [PATCH v4 2/2] bsearch: prevent overflow when computing middle comparison element

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Message-ID: <20100924055012.GC18432@haskell.muteddisk.com>
Date:	Thu, 23 Sep 2010 22:50:12 -0700
From:	matt mooney <mfm@...eddisk.com>
To:	Rusty Russell <rusty@...tcorp.com.au>
Cc:	André Goddard Rosa <andre.goddard@...il.com>,
	linux-kernel@...r.kernel.org,
	Alan Jenkins <alan-jenkins@...fmail.co.uk>,
	Tim Abbott <tabbott@...lice.com>
Subject: Re: [PATCH v4 2/2] bsearch: prevent overflow when computing middle
 comparison element

On 10:56 Thu 23 Sep     , Rusty Russell wrote:
> On Thu, 23 Sep 2010 12:12:13 am André Goddard Rosa wrote:
> > On Fri, Nov 13, 2009 at 8:42 PM, Rusty Russell <rusty@...tcorp.com.au> wrote:
> > > On Sat, 14 Nov 2009 01:33:04 am Thiago Farina wrote:
> > >> Hi Rusty,
> > >>
> > >> On Thu, Nov 12, 2009 at 11:06 AM, Rusty Russell <rusty@...tcorp.com.au> wrote:
> > >> > On Wed, 11 Nov 2009 01:30:25 am André Goddard Rosa wrote:
> > >> >> It's really difficult to occur in practice because the sum of the lower
> > >> >> and higher limits must overflow an int variable, but it can occur when
> > >> >> working with large arrays. We'd better safe than sorry by avoiding this
> > >> >> overflow situation when computing the middle element for comparison.
> > >> >
> > >> > I applied all these, after testing.  In future would have been nice for you
> > >> > to have posted a test patch so I didn't have make my own...
> > >>
> > >> Where did you apply this patch?
> > >
> > > To my kernel series, which means it is now in linux-next.
> > >
> > > Hope that helps,
> > > Rusty.
> > >
> > 
> > Hi, Rusty!
> > 
> >     Is there any chance that this patchset will land into mainline anytime soon?
> > 
> >     Here we have another use for the binary search function:
> >         http://marc.info/?l=linux-kernel&m=128515012817787&w=2
> 
> "Unused code is buggy code".  Can we have some users please?  Do people
> care that uninlining means an indirect fn call now for cmp?
> 
> Nonetheless, I've merged all the fixes together:
>

[snip]

> +#include <linux/module.h>
> +#include <linux/bsearch.h>
> +
> +/*
> + * bsearch - binary search an array of elements
> + * @key: pointer to item being searched for
> + * @base: pointer to data to sort

The comment for "@base" seems wrong. It appears that it should say "pointer to
sorted data" or "pointer to search data" instead.

-mfm
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