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Sender: Tejun Heo <htejun@gmail.com>
Date:   Mon, 28 Nov 2022 09:58:18 -1000
From:   Tejun Heo <tj@kernel.org>
To:     Li Jinlin <lijinlin3@huawei.com>
Cc:     josef@toxicpanda.com, axboe@kernel.dk, cgroups@vger.kernel.org,
        linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
        liuzhiqiang26@huawei.com
Subject: Re: [PATCH v2] blk-iocost: fix shift-out-of-bounds in
 iocg_hick_delay()
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References: <20221128030413.882998-1-lijinlin3@huawei.com>
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On Mon, Nov 28, 2022 at 11:04:13AM +0800, Li Jinlin wrote:
>  	/* calculate the current delay in effect - 1/2 every second */
>  	tdelta = now->now - iocg->delay_at;
>  	if (iocg->delay)
> -		delay = iocg->delay >> div64_u64(tdelta, USEC_PER_SEC);
> +		delay = iocg->delay >>
> +			min_t(u64, div64_u64(tdelta, USEC_PER_SEC), 63);

I replied earlier but the right thing to do here is setting delay to 0 if
the shift is >= 64.

Thanks.

-- 
tejun