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Date: Mon, 24 Jun 2013 15:51:26 -0700
From: Tejun Heo <tj@kernel.org>
To: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Cc: LKML <linux-kernel@vger.kernel.org>, Andrew Morton <akpm@osdl.org>,
        Jens Axboe <axboe@kernel.dk>, Kiyoshi Ueda <k-ueda@ct.jp.nec.com>,
        Lin Ming <ming.m.lin@intel.com>, Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH] block:Remove extra condition in end of disk check
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References: <20130623171711.7127.16248.sendpatchset@codeblue.in.ibm.com>
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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