From: Tejun Heo <tj@kernel.org>
To: Yu Kuai <yukuai1@huaweicloud.com>
Cc: josef@toxicpanda.com, axboe@kernel.dk, cgroups@vger.kernel.org,
linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
yukuai3@huawei.com, yi.zhang@huawei.com, yangerkun@huawei.com
Subject: Re: [PATCH v4 4/5] blk-iocost: fix divide by 0 error in calc_lcoefs()
Date: Wed, 18 Jan 2023 07:18:29 -1000 [thread overview]
Message-ID: <Y8gp5ZeHbs/U1Qfe@slm.duckdns.org> (raw)
In-Reply-To: <20230117070806.3857142-5-yukuai1@huaweicloud.com>
On Tue, Jan 17, 2023 at 03:08:05PM +0800, Yu Kuai wrote:
> From: Li Nan <linan122@huawei.com>
>
> echo max of u64 to cost.model can cause divide by 0 error.
>
> # echo 8:0 rbps=18446744073709551615 > /sys/fs/cgroup/io.cost.model
>
> divide error: 0000 [#1] PREEMPT SMP
> RIP: 0010:calc_lcoefs+0x4c/0xc0
> Call Trace:
> <TASK>
> ioc_refresh_params+0x2b3/0x4f0
> ioc_cost_model_write+0x3cb/0x4c0
> ? _copy_from_iter+0x6d/0x6c0
> ? kernfs_fop_write_iter+0xfc/0x270
> cgroup_file_write+0xa0/0x200
> kernfs_fop_write_iter+0x17d/0x270
> vfs_write+0x414/0x620
> ksys_write+0x73/0x160
> __x64_sys_write+0x1e/0x30
> do_syscall_64+0x35/0x80
> entry_SYSCALL_64_after_hwframe+0x63/0xcd
>
> calc_lcoefs() uses the input value of cost.model in DIV_ROUND_UP_ULL,
> overflow would happen if bps plus IOC_PAGE_SIZE is greater than
> ULLONG_MAX, it can cause divide by 0 error.
>
> Fix the problem by setting basecost
>
> Signed-off-by: Li Nan <linan122@huawei.com>
> Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Acked-by: Tejun Heo <tj@kernel.org>
Thanks.
--
tejun
next prev parent reply other threads:[~2023-01-18 17:19 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-17 7:08 [PATCH v4 0/5] blk-iocost: random bugfix Yu Kuai
2023-01-17 7:08 ` [PATCH v4 1/5] blk-iocost: check return value of match_u64() Yu Kuai
2023-01-17 7:08 ` [PATCH v4 2/5] blk-iocost: don't allow to configure bio based device Yu Kuai
2023-01-17 7:08 ` [PATCH v4 3/5] blk-iocost: read params inside lock in sysfs apis Yu Kuai
2023-01-17 7:08 ` [PATCH v4 4/5] blk-iocost: fix divide by 0 error in calc_lcoefs() Yu Kuai
2023-01-18 17:18 ` Tejun Heo [this message]
2023-01-17 7:08 ` [PATCH v4 5/5] blk-iocost: change div64_u64 to DIV64_U64_ROUND_UP in ioc_refresh_params() Yu Kuai
2023-01-20 15:40 ` [PATCH v4 0/5] blk-iocost: random bugfix Jens Axboe
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