From nobody Fri Sep 19 02:21:14 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6FA21C4332F for ; Wed, 30 Nov 2022 13:01:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235747AbiK3NBX (ORCPT ); Wed, 30 Nov 2022 08:01:23 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41436 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229929AbiK3NA5 (ORCPT ); Wed, 30 Nov 2022 08:00:57 -0500 Received: from szxga08-in.huawei.com (szxga08-in.huawei.com [45.249.212.255]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 665EF4AF34; Wed, 30 Nov 2022 05:00:56 -0800 (PST) Received: from dggpeml500025.china.huawei.com (unknown [172.30.72.54]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4NMfSY2Z9Gz15N01; Wed, 30 Nov 2022 21:00:13 +0800 (CST) Received: from dggpeml500003.china.huawei.com (7.185.36.200) by dggpeml500025.china.huawei.com (7.185.36.35) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.31; Wed, 30 Nov 2022 21:00:53 +0800 Received: from huawei.com (10.175.127.227) by dggpeml500003.china.huawei.com (7.185.36.200) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.31; Wed, 30 Nov 2022 21:00:52 +0800 From: Li Nan To: , , CC: , , , , , Subject: [PATCH -next v2 5/9] blk-iocost: fix divide by 0 error in calc_lcoefs() Date: Wed, 30 Nov 2022 21:21:52 +0800 Message-ID: <20221130132156.2836184-6-linan122@huawei.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20221130132156.2836184-1-linan122@huawei.com> References: <20221130132156.2836184-1-linan122@huawei.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Originating-IP: [10.175.127.227] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To dggpeml500003.china.huawei.com (7.185.36.200) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" echo max of u64 to cost.model can cause divide by 0 error. # echo 8:0 rbps=3D18446744073709551615 > /sys/fs/cgroup/io.cost.model divide error: 0000 [#1] PREEMPT SMP RIP: 0010:calc_lcoefs+0x4c/0xc0 Call Trace: 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.I_LCOEF_MAX is introduced to prevent it. Signed-off-by: Li Nan --- block/blk-iocost.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/block/blk-iocost.c b/block/blk-iocost.c index 3a96cd557c47..f4a754b9d10f 100644 --- a/block/blk-iocost.c +++ b/block/blk-iocost.c @@ -306,6 +306,9 @@ enum { IOC_PAGE_SIZE =3D 1 << IOC_PAGE_SHIFT, IOC_SECT_TO_PAGE_SHIFT =3D IOC_PAGE_SHIFT - SECTOR_SHIFT, =20 + /* avoid overflow */ + I_LCOEF_MAX =3D ULLONG_MAX - IOC_PAGE_SIZE, + /* if apart further than 16M, consider randio for linear model */ LCOEF_RANDIO_PAGES =3D 4096, }; @@ -3431,6 +3434,8 @@ static ssize_t ioc_cost_model_write(struct kernfs_ope= n_file *of, char *input, goto out_unlock; } =20 + if (v > I_LCOEF_MAX) + goto out_unlock; u[tok] =3D v; user =3D true; } --=20 2.31.1