Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1751634AbaFDQz4 (ORCPT <rfc822;w@1wt.eu>);
	Wed, 4 Jun 2014 12:55:56 -0400
Received: from mail-pb0-f52.google.com ([209.85.160.52]:35196 "EHLO
	mail-pb0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1750773AbaFDQzz (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Wed, 4 Jun 2014 12:55:55 -0400
Message-ID: <538F4F99.2020502@kernel.dk>
Date: Wed, 04 Jun 2014 10:55:53 -0600
From: Jens Axboe <axboe@kernel.dk>
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.5.0
MIME-Version: 1.0
To: scameron@beardog.cce.hp.com, Julia Lawall <Julia.Lawall@lip6.fr>
CC: linux-kernel@vger.kernel.org
Subject: Re: [PATCH 7/10] cciss: use safer test on the result of find_first_zero_bit
References: <20140604145135.GC6970@beardog.cce.hp.com>
In-Reply-To: <20140604145135.GC6970@beardog.cce.hp.com>
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On 06/04/2014 08:51 AM, scameron@beardog.cce.hp.com wrote:
>> Find_first_zero_bit considers BITS_PER_LONG bits at a time, and thus may
>> return a larger number than the maximum position argument if that position
>> is not a multiple of BITS_PER_LONG.
>>
>> The semantic match that finds this problem is as follows:
>> (http://coccinelle.lip6.fr/)
>>
>> // <smpl>
>> @@
>> expression e1,e2,e3;
>> statement S1,S2;
>> @@
>>
>> e1 = find_first_zero_bit(e2,e3)
>> ...
>> if (e1 
>> - ==
>> + >=
>>   e3)
>> S1 else S2
>> // </smpl>
>>
>> Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
>>
>> ---
>>  drivers/block/cciss.c |    2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff -u -p a/drivers/block/cciss.c b/drivers/block/cciss.c
>> --- a/drivers/block/cciss.c
>> +++ b/drivers/block/cciss.c
>> @@ -980,7 +980,7 @@ static CommandList_struct *cmd_alloc(ctl
>>  
>>  	do {
>>  		i = find_first_zero_bit(h->cmd_pool_bits, h->nr_cmds);
>> -		if (i == h->nr_cmds)
>> +		if (i >= h->nr_cmds)
>>  			return NULL;
>>  	} while (test_and_set_bit(i, h->cmd_pool_bits) != 0);
>>  	c = h->cmd_pool + i;
> 
> 
> Thanks. Ack.
> 
> You can add
> 
> Reviewed-by: Stephen M. Cameron <scameron@beardog.cce.hp.com>
> 
> to this patch if you want.
> 
> You might consider adding "Cc: stable@vger.kernel.org" into the
> sign-off area as well.

There are two such instances in cciss.c, btw.

-- 
Jens Axboe

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