linux-kernel - Re: [PATCH] block: fix the bio_vec array index out-of-bounds test

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Message-ID: <20090512112729.GI4140@kernel.dk>
Date:	Tue, 12 May 2009 13:27:29 +0200
From:	Jens Axboe <jens.axboe@...cle.com>
To:	Kazuhisa Ichikawa <ki@...ilou.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] block: fix the bio_vec array index out-of-bounds test

On Fri, May 08 2009, Kazuhisa Ichikawa wrote:
> From: Kazuhisa Ichikawa <ki@...ilou.com>
> 
> Current bio_vec array index out-of-bounds test within 
> __end_that_request_first() does not seem correct. 
> It checks bio->bi_idx against bio->bi_vcnt, but the subsequent code 
> uses idx (which is, bio->bi_idx + next_idx) as the array index into 
> bio_vec array. This means that the test really make sense only at 
> the first iteration of !(nr_bytes >=bio->bi_size) case (when next_idx 
> == zero). Fix this by replacing bio->bi_idx with idx.
> (This patch applies to 2.6.30-rc4.)
> 
> Signed-off-by: Kazuhisa Ichikawa <ki@...ilou.com>
> ---
> 
> --- linux-2.6.30-rc4/block/blk-core.c.ORIG	2009-05-08 00:00:10.000000000 +0900
> +++ linux-2.6.30-rc4/block/blk-core.c	2009-05-08 00:00:10.000000000 +0900
> @@ -1768,10 +1768,10 @@ static int __end_that_request_first(stru
>  		} else {
>  			int idx = bio->bi_idx + next_idx;
>  
> -			if (unlikely(bio->bi_idx >= bio->bi_vcnt)) {
> +			if (unlikely(idx >= bio->bi_vcnt)) {
>  				blk_dump_rq_flags(req, "__end_that");
>  				printk(KERN_ERR "%s: bio idx %d >= vcnt %d\n",
> -				       __func__, bio->bi_idx, bio->bi_vcnt);
> +				       __func__, idx, bio->bi_vcnt);
>  				break;
>  			}

Thanks!

-- 
Jens Axboe

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