linux-kernel - Re: [PATCH] vmscan: Remove if statement that will never trigger

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <4E3252E2.1030101@jp.fujitsu.com>
Date:	Fri, 29 Jul 2011 15:27:46 +0900
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	jj@...osbits.net
CC:	linux-kernel@...r.kernel.org, linux-mm@...ck.org, riel@...hat.com,
	minchan.kim@...il.com, mgorman@...e.de, akpm@...ux-foundation.org,
	kanoj@....com, sct@...hat.com
Subject: Re: [PATCH] vmscan: Remove if statement that will never trigger

(2011/07/29 6:05), Jesper Juhl wrote:
> We have this code in mm/vmscan.c:shrink_slab() :
> ...
> 		if (total_scan < 0) {
> 			printk(KERN_ERR "shrink_slab: %pF negative objects to "
> 			       "delete nr=%ld\n",
> 			       shrinker->shrink, total_scan);
> 			total_scan = max_pass;
> 		}
> ...
> but since 'total_scan' is of type 'unsigned long' it will never be
> less than zero, so there is no way we'll ever enter the true branch of
> this if statement - so let's just remove it.
> 
> Signed-off-by: Jesper Juhl <jj@...osbits.net>
> ---
>  mm/vmscan.c |    6 ------
>  1 files changed, 0 insertions(+), 6 deletions(-)
> 
> 	Compile tested only.
> 
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 7ef6912..c07d9b1 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -271,12 +271,6 @@ unsigned long shrink_slab(struct shrink_control *shrink,
>  		delta *= max_pass;
>  		do_div(delta, lru_pages + 1);
>  		total_scan += delta;
> -		if (total_scan < 0) {
> -			printk(KERN_ERR "shrink_slab: %pF negative objects to "
> -			       "delete nr=%ld\n",
> -			       shrinker->shrink, total_scan);
> -			total_scan = max_pass;
> -		}
>  
>  		/*
>  		 * We need to avoid excessive windup on filesystem shrinkers

Good catch.

However this seems intended to catch a overflow. So, I'd suggest to make proper
overflow check instead.


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/