From: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
To: Tejun Heo <tj@kernel.org>
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
Date: Tue, 25 Jun 2013 10:40:14 +0530 [thread overview]
Message-ID: <51C92636.2060006@linux.vnet.ibm.com> (raw)
In-Reply-To: <20130624225126.GO1918@mtj.dyndns.org>
On 06/25/2013 04:21 AM, Tejun Heo wrote:
> 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?
>
Hi Tejun,
Thanks for the reply and explanation. You are right. underflow results
in invalid condition.
Considering maxsector and sectors are unsigned long, and nr_sector is
unsigned int, probably safer bet is
(max_sector < sector + nr_sector), but still it would leave scope for
overflow.
Thanks again,
Raghu.
prev parent reply other threads:[~2013-06-25 5:06 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-06-23 17:17 [PATCH] block:Remove extra condition in end of disk check Raghavendra K T
2013-06-24 13:50 ` Raghavendra K T
2013-06-24 22:51 ` Tejun Heo
2013-06-25 5:10 ` Raghavendra K T [this message]
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