linux-kernel - Re: [PATCH] block:Remove extra condition in end of disk check

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Message-ID: <20130624225126.GO1918@mtj.dyndns.org>
Date:	Mon, 24 Jun 2013 15:51:26 -0700
From:	Tejun Heo <tj@...nel.org>
To:	Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>
Cc:	LKML <linux-kernel@...r.kernel.org>, Andrew Morton <akpm@...l.org>,
	Jens Axboe <axboe@...nel.dk>,
	Kiyoshi Ueda <k-ueda@...jp.nec.com>,
	Lin Ming <ming.m.lin@...el.com>, Christoph Hellwig <hch@....de>
Subject: Re: [PATCH] block:Remove extra condition in end of disk check

On Mon, Jun 24, 2013 at 07:20:12PM +0530, Raghavendra K T wrote:
> >@@ -1656,7 +1656,7 @@ static inline int bio_check_eod(struct bio *bio, unsigned int nr_sectors)
> >  	if (maxsector) {
> >  		sector_t sector = bio->bi_sector;
> >
> >-		if (maxsector < nr_sectors || maxsector - nr_sectors < sector) {
> >+		if (maxsector - nr_sectors < sector) {

If maxsector < nr_sectors, the subtraction will underflow making it a
very large number and fail to detect the invalid condition, no?

Thanks.

-- 
tejun
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