Re: [PATCH-next v2] loop: loop_set_status_from_info() check before assignment

[Yu Kuai]

Hi,

在 2023/02/06 10:07, Zhong Jinghua 写道:
> 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@xxxxxxxxxx>
> ---
>   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;