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From: Ken Raeburn <raeburn@redhat.com>
To: Coly Li <colyli@suse.de>
Cc: linux-bcache@vger.kernel.org, linux-block@vger.kernel.org,
	stable@vger.kernel.org
Subject: Re: [PATCH 1/2] bcache: avoid nr_stripes overflow in bcache_device_init()
Date: Sun, 12 Jul 2020 16:38:09 -0400	[thread overview]
Message-ID: <a504604d-ac8a-3276-e0b8-f42cb3782356@redhat.com> (raw)
In-Reply-To: <1011c22f-d186-6398-98e1-83f1c363dedd@suse.de>


On 7/12/20 1:49 PM, Coly Li wrote:
> On 2020/7/13 01:47, Coly Li wrote:
>> For some block devices which large capacity (e.g. 8TB) but small io_opt
>> size (e.g. 8 sectors), in bcache_device_init() the stripes number calcu-
>> lated by,
>> 	DIV_ROUND_UP_ULL(sectors, d->stripe_size);
>> might be overflow to the unsigned int bcache_device->nr_stripes.
>>
>> This patch uses an unsigned long variable to store DIV_ROUND_UP_ULL()
>> and after the value is checked to be available in unsigned int range,
>> sets it to bache_device->nr_stripes. Then the overflow is avoided.
> Hi Ken,
>
> Could you please to try whether these two patches may avoid the kernel
> panic ? I will post the overwhelm stripe_size patch later.
>
> Thanks.
>
> Coly Li
>
I will. But, from inspection: On a 32-bit system, "unsigned long" will 
still be 32 bits, but sector_t (u64) will still be 64 bits, so that 
assignment will still discard high bits before validation in that 
environment. I suggest "unsigned long long" or another specifically 
64-bit type.

Also, the VDO driver I work on doesn't support 32-bit platforms 
currently, so my own testing will be limited to 64-bit platforms.

Ken


  reply	other threads:[~2020-07-12 20:38 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-12 17:47 [PATCH 1/2] bcache: avoid nr_stripes overflow in bcache_device_init() Coly Li
2020-07-12 17:47 ` [PATCH 2/2] bcche: fix overflow in offset_to_stripe() Coly Li
2020-07-17 17:08   ` Sasha Levin
2020-07-12 17:49 ` [PATCH 1/2] bcache: avoid nr_stripes overflow in bcache_device_init() Coly Li
2020-07-12 20:38   ` Ken Raeburn [this message]
2020-07-13  3:35     ` Coly Li
2020-07-12 20:37 ` Jens Axboe
2020-07-13  3:34   ` Coly Li
2020-07-17 17:08 ` Sasha Levin

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