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[2620:137:e000::1:20]) by mx.google.com with ESMTP id gn25-20020a1709070d1900b007b874abc9b6si448853ejc.790.2022.11.24.05.49.48; Thu, 24 Nov 2022 05:50:12 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=QUARANTINE sp=QUARANTINE dis=NONE) header.from=huawei.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229898AbiKXNpf (ORCPT + 99 others); Thu, 24 Nov 2022 08:45:35 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36648 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230090AbiKXNp2 (ORCPT ); Thu, 24 Nov 2022 08:45:28 -0500 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8B336109581; Thu, 24 Nov 2022 05:45:23 -0800 (PST) Received: from dggpeml500025.china.huawei.com (unknown [172.30.72.54]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4NHzkm5pWJzmW6p; Thu, 24 Nov 2022 21:44:48 +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; Thu, 24 Nov 2022 21:45:21 +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; Thu, 24 Nov 2022 21:45:21 +0800 From: Li Nan To: , , CC: , , , , , Subject: [PATCH -next 1/2] blk-iocost: fix divide by 0 error in calc_lcoefs() Date: Thu, 24 Nov 2022 22:06:34 +0800 Message-ID: <20221124140635.695205-1-linan122@huawei.com> X-Mailer: git-send-email 2.31.1 MIME-Version: 1.0 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 X-Spam-Status: No, score=-4.2 required=5.0 tests=BAYES_00,RCVD_IN_DNSWL_MED, SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1750385623498599037?= X-GMAIL-MSGID: =?utf-8?q?1750385623498599037?= 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: 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 Reviewed-by: Andreas Herrmann --- block/blk-iocost.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/block/blk-iocost.c b/block/blk-iocost.c index f01359906c83..a38a5324bf10 100644 --- a/block/blk-iocost.c +++ b/block/blk-iocost.c @@ -306,6 +306,9 @@ enum { IOC_PAGE_SIZE = 1 << IOC_PAGE_SHIFT, IOC_SECT_TO_PAGE_SHIFT = IOC_PAGE_SHIFT - SECTOR_SHIFT, + /* avoid overflow */ + I_LCOEF_MAX = ULLONG_MAX - IOC_PAGE_SIZE, + /* if apart further than 16M, consider randio for linear model */ LCOEF_RANDIO_PAGES = 4096, }; @@ -3406,6 +3409,8 @@ static ssize_t ioc_cost_model_write(struct kernfs_open_file *of, char *input, goto einval; if (match_u64(&args[0], &v)) goto einval; + if (v > I_LCOEF_MAX) + goto einval; u[tok] = v; user = true; }