linux-kernel - Re: [PATCH] mm: incorrect overflow check in shrink

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Message-Id: <20111201183202.2e5bd872.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Thu, 1 Dec 2011 18:32:02 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Xi Wang <xi.wang@...il.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>,
	Minchan Kim <minchan.kim@...il.com>,
	Johannes Weiner <jweiner@...hat.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: incorrect overflow check in shrink_slab()

On Thu, 1 Dec 2011 04:20:34 -0500
Xi Wang <xi.wang@...il.com> wrote:

> total_scan is unsigned long, so the overflow check (total_scan < 0)
> didn't work.
> 
> Signed-off-by: Xi Wang <xi.wang@...il.com>

Nice catch but.... the 'total_scan" shouldn't be long ?
Rather than type casting ?

Thanks,
-Kame
> ---
>  mm/vmscan.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index a1893c0..46a04e7 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -270,7 +270,7 @@ unsigned long shrink_slab(struct shrink_control *shrink,
>  		delta *= max_pass;
>  		do_div(delta, lru_pages + 1);
>  		total_scan += delta;
> -		if (total_scan < 0) {
> +		if ((long)total_scan < 0) {
>  			printk(KERN_ERR "shrink_slab: %pF negative objects to "
>  			       "delete nr=%ld\n",
>  			       shrinker->shrink, total_scan);
> -- 
> 1.7.5.4
> 
> 
> 

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