Subject: Re: [PATCH-next v2] loop: loop_set_status_from_info() check before
 assignment
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>
From:   Hou Tao <houtao1@huawei.com>
Message-ID: <d9486c88-33b1-3dc1-d58c-89de73679e50@huawei.com>
Date:   Mon, 6 Feb 2023 10:55:47 +0800
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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;