From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 83B65C33CAF for ; Mon, 13 Jan 2020 12:55:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 628422080D for ; Mon, 13 Jan 2020 12:55:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727289AbgAMMzc (ORCPT ); Mon, 13 Jan 2020 07:55:32 -0500 Received: from szxga05-in.huawei.com ([45.249.212.191]:8710 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726375AbgAMMzc (ORCPT ); Mon, 13 Jan 2020 07:55:32 -0500 Received: from DGGEMS414-HUB.china.huawei.com (unknown [172.30.72.58]) by Forcepoint Email with ESMTP id DF64D5A19E236C3B78D8; Mon, 13 Jan 2020 20:55:29 +0800 (CST) Received: from [127.0.0.1] (10.173.220.183) by DGGEMS414-HUB.china.huawei.com (10.3.19.214) with Microsoft SMTP Server id 14.3.439.0; Mon, 13 Jan 2020 20:55:19 +0800 Subject: Re: [PATCH] brd: check parameter validation before register_blkdev func To: Ming Lei CC: Jens Axboe , , "linux-kernel@vger.kernel.org" , , Mingfangsen , Guiyao , zhangsaisai , "wubo (T)" References: <342ee238-0e7c-c213-eecc-7062f24985cc@huawei.com> <20200113110003.GA13011@ming.t460p> From: Zhiqiang Liu Message-ID: Date: Mon, 13 Jan 2020 20:55:18 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.2.2 MIME-Version: 1.0 In-Reply-To: <20200113110003.GA13011@ming.t460p> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.173.220.183] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020/1/13 19:04, Ming Lei wrote: > On Fri, Jan 10, 2020 at 01:10:20PM +0800, Zhiqiang Liu wrote: >> >> In brd_init func, rd_nr num of brd_device are firstly allocated >> and add in brd_devices, then brd_devices are traversed to add each >> brd_device by calling add_disk func. When allocating brd_device, >> the disk->first_minor is set to i * max_part, if rd_nr * max_part >> is larger than MINORMASK, two different brd_device may have the same >> devt, then only one of them can be successfully added. >> when rmmod brd.ko, it will cause oops when calling brd_exit. >> >> Follow those steps: >> # modprobe brd rd_nr=3 rd_size=102400 max_part=1048576 >> # rmmod brd >> then, the oops will appear. >> >> Oops log: >> [ 726.613722] Call trace: >> [ 726.614175] kernfs_find_ns+0x24/0x130 >> [ 726.614852] kernfs_find_and_get_ns+0x44/0x68 >> [ 726.615749] sysfs_remove_group+0x38/0xb0 >> [ 726.616520] blk_trace_remove_sysfs+0x1c/0x28 >> [ 726.617320] blk_unregister_queue+0x98/0x100 >> [ 726.618105] del_gendisk+0x144/0x2b8 >> [ 726.618759] brd_exit+0x68/0x560 [brd] >> [ 726.619501] __arm64_sys_delete_module+0x19c/0x2a0 >> [ 726.620384] el0_svc_common+0x78/0x130 >> [ 726.621057] el0_svc_handler+0x38/0x78 >> [ 726.621738] el0_svc+0x8/0xc >> [ 726.622259] Code: aa0203f6 aa0103f7 aa1e03e0 d503201f (7940e260) >> >> Here, we add brd_check_par_valid func to check parameter >> validation before register_blkdev func. >> >> Signed-off-by: Zhiqiang Liu >> --- >> drivers/block/brd.c | 33 ++++++++++++++++++++++++++------- >> +static inline int brd_check_par_valid(void) >> +{ >> + if (unlikely(!rd_nr)) >> + rd_nr = 1; >> + >> + if (unlikely(!max_part)) >> + max_part = 1; >> + >> + if (rd_nr * max_part > MINORMASK) >> + return -EINVAL; >> + >> + return 0; >> + >> +} >> + >> static int __init brd_init(void) >> { >> struct brd_device *brd, *next; >> - int i; >> + int i, ret; >> >> /* >> * brd module now has a feature to instantiate underlying device >> @@ -488,11 +503,15 @@ static int __init brd_init(void) >> * dynamically. >> */ >> >> + ret = brd_check_par_valid(); >> + if (ret) { >> + pr_info("brd: invalid parameter setting!!!\n"); >> + return ret; >> + } >> + > > The max supported partition number is 256, see __alloc_disk_node(). > So even though one bigger number is passed to alloc_disk(), at most > 256 partitions are allowed on that disk. Maybe you can apply the > following way to avoid the issue: > > disk->first_minor = i * disk->minors; > > However, looks 'rd_nr' still needs to be validated(rd_nr < 2 ^ 23). > Thanks for your reply. As you said, minors is limited to DISK_MAX_PARTS in __alloc_disk_node when calling alloc_disk in brd_alloc func. We can set: disk->first_minor = i * disk->minors as your suggestion. As for 'rd_nr', I think we should make sure that 'disk->first_minor' should be not larger than MINORMASK. ->add_disk ->device_add_disk ->__device_add_disk ->blk_alloc_devt ->MKDEV If rd_nr > MINORMASK / min(max_part, DISK_MAX_PARTS), two different brd_device may have the same devt by calling MKDEV in blk_alloc_devt func. For example, MKDEV(1, 0) is equal to MKDEV(1, MINORMASK + 1). So we should check both rd_nr and max_part as follows, static inline int brd_check_par_valid(void) { if (unlikely(!rd_nr)) rd_nr = 1; if (unlikely(!max_part)) max_part = 1; if (max_part > DISK_MAX_PARTS) max_part = DISK_MAX_PARTS; if (rd_nr > MINORMASK / max_part) return -EINVAL; return 0; } I will send the v2 patch.