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=-12.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 D332FC4338F for ; Wed, 18 Aug 2021 10:08:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BA64960524 for ; Wed, 18 Aug 2021 10:08:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233118AbhHRKJZ (ORCPT ); Wed, 18 Aug 2021 06:09:25 -0400 Received: from www262.sakura.ne.jp ([202.181.97.72]:55214 "EHLO www262.sakura.ne.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233399AbhHRKJY (ORCPT ); Wed, 18 Aug 2021 06:09:24 -0400 Received: from fsav312.sakura.ne.jp (fsav312.sakura.ne.jp [153.120.85.143]) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTP id 17IA8S0N053142; Wed, 18 Aug 2021 19:08:28 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Received: from www262.sakura.ne.jp (202.181.97.72) by fsav312.sakura.ne.jp (F-Secure/fsigk_smtp/550/fsav312.sakura.ne.jp); Wed, 18 Aug 2021 19:08:28 +0900 (JST) X-Virus-Status: clean(F-Secure/fsigk_smtp/550/fsav312.sakura.ne.jp) Received: from [192.168.1.9] (M106072142033.v4.enabler.ne.jp [106.72.142.33]) (authenticated bits=0) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTPSA id 17IA8SF8053137 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NO); Wed, 18 Aug 2021 19:08:28 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Subject: Re: sort out the lock order in the loop driver To: Jens Axboe , Christoph Hellwig Cc: Hillf Danton , Pavel Tatashin , "Reviewed-by : Tyler Hicks" , linux-block@vger.kernel.org, Greg Kroah-Hartman References: <20210818062455.211065-1-hch@lst.de> From: Tetsuo Handa Message-ID: <87997eac-a0bc-c643-0b88-87b09af4e61f@i-love.sakura.ne.jp> Date: Wed, 18 Aug 2021 19:08:27 +0900 User-Agent: Mozilla/5.0 (Windows NT 6.3; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: <20210818062455.211065-1-hch@lst.de> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 2021/08/18 15:24, Christoph Hellwig wrote: > Hi Jens, > > this series sorts out lock order reversals involving the block layer > open_mutex by drastically reducing the scope of loop_ctl_mutex. To do > so it first merges the cryptoloop module into the main loop driver > as the unregistrtion of transfers on live loop devices was causing > some nasty locking interactions. > > Diffstat: > b/drivers/block/Kconfig | 6 > b/drivers/block/Makefile | 1 > b/drivers/block/loop.c | 327 ++++++++++++++++++++++++--------------------- > b/drivers/block/loop.h | 30 ---- > drivers/block/cryptoloop.c | 204 ---------------------------- > 5 files changed, 188 insertions(+), 380 deletions(-) > Despite big change, this series introduces at least three bugs by ignoring what lock protects what resource and/or operation. Locking explanation is very very wrong. I never want this series merged for v5.14/v5.15 and stable kernels. (1) Will crash at uninitialized mutex_lock_killable(). (2) Will crash at unprotected idr_remove(). (3) Will crash syzbot due to hitting WARNING messages (at least two different causes).