Subject: Re: [PATCH-next v2] loop: loop_set_status_from_info() check before
 assignment
To:     Zhong Jinghua <zhongjinghua@huawei.com>, axboe@kernel.dk,
        code@siddh.me, Matthew Wilcox <willy@infradead.org>,
        Christoph Hellwig <hch@lst.de>
Cc:     linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
        yi.zhang@huawei.com, houtao1@huawei.com, yangerkun@huawei.com,
        "yukuai (C)" <yukuai3@huawei.com>
References: <20230206020716.2036-1-zhongjinghua@huawei.com>
From:   Yu Kuai <yukuai1@huaweicloud.com>
Message-ID: <32179e8a-a3ca-9412-1977-fdaa7f065691@huaweicloud.com>
Date:   Mon, 6 Feb 2023 11:19:22 +0800
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Precedence: bulk

Hi,

?? 2023/02/06 10:07, Zhong Jinghua д??:
> 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.
> 

Please add a fix tag and cc stable:

Fixes: c490a0b5a4f3 ("loop: Check for overflow while configuring loop")

This commit doesn't fix the problem it described in commit message.

Thanks,
Kuai

> Signed-off-by: Zhong Jinghua <zhongjinghua@huawei.com>
> ---
>   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;
>