Subject: Re: [PATCH-next v2] loop: loop_set_status_from_info() check before
 assignment
From:   Hou Tao <houtao1@huawei.com>
To:     Zhong Jinghua <zhongjinghua@huawei.com>, <axboe@kernel.dk>
CC:     <linux-block@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <yi.zhang@huawei.com>, <yukuai3@huawei.com>, <yangerkun@huawei.com>
References: <20230206020716.2036-1-zhongjinghua@huawei.com>
 <d9486c88-33b1-3dc1-d58c-89de73679e50@huawei.com>
Message-ID: <34b13dab-d364-9ff6-a771-aed0b01c5897@huawei.com>
Date:   Mon, 6 Feb 2023 11:02:33 +0800
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Please disregard my reply. I did not notice it is not an internal email between
our team members.

On 2/6/2023 10:55 AM, Hou Tao wrote:
>
> On 2/6/2023 10:07 AM, Zhong Jinghua wrote:
>> In loop_set_status_from_info(), lo->lo_offset and lo->lo_sizelimit should
>> be checked before reassignment, because if an overflow error occurs, the
>> original correct value will be changed to the wrong value, and it will not
>> be changed back.
>>
>> Modifying to the wrong value logic is always not quiet right, we hope to
>> optimize this.
>>
>> Signed-off-by: Zhong Jinghua <zhongjinghua@huawei.com>
> LGTM
>> ---
>>  v1->v2: Modify note: overflowing -> overflow 
>>  drivers/block/loop.c | 8 ++++----
>>  1 file changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/block/loop.c b/drivers/block/loop.c
>> index 1518a6423279..1b35cbd029c7 100644
>> --- a/drivers/block/loop.c
>> +++ b/drivers/block/loop.c
>> @@ -977,13 +977,13 @@ loop_set_status_from_info(struct loop_device *lo,
>>  		return -EINVAL;
>>  	}
>>  
>> +	/* Avoid assigning overflow values */
>> +	if (info->lo_offset > LLONG_MAX || info->lo_sizelimit > LLONG_MAX)
>> +		return -EOVERFLOW;
>> +
>>  	lo->lo_offset = info->lo_offset;
>>  	lo->lo_sizelimit = info->lo_sizelimit;
>>  
>> -	/* loff_t vars have been assigned __u64 */
>> -	if (lo->lo_offset < 0 || lo->lo_sizelimit < 0)
>> -		return -EOVERFLOW;
>> -
>>  	memcpy(lo->lo_file_name, info->lo_file_name, LO_NAME_SIZE);
>>  	lo->lo_file_name[LO_NAME_SIZE-1] = 0;
>>  	lo->lo_flags = info->lo_flags;