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=-8.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 7956AC433ED for ; Fri, 9 Apr 2021 16:44:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 478DC610E5 for ; Fri, 9 Apr 2021 16:44:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233978AbhDIQog (ORCPT ); Fri, 9 Apr 2021 12:44:36 -0400 Received: from outgoing-auth-1.mit.edu ([18.9.28.11]:54432 "EHLO outgoing.mit.edu" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S229665AbhDIQof (ORCPT ); Fri, 9 Apr 2021 12:44:35 -0400 Received: from cwcc.thunk.org (pool-72-74-133-215.bstnma.fios.verizon.net [72.74.133.215]) (authenticated bits=0) (User authenticated as tytso@ATHENA.MIT.EDU) by outgoing.mit.edu (8.14.7/8.12.4) with ESMTP id 139Gi0DU016716 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Fri, 9 Apr 2021 12:44:00 -0400 Received: by cwcc.thunk.org (Postfix, from userid 15806) id F0DF715C3B12; Fri, 9 Apr 2021 12:43:59 -0400 (EDT) Date: Fri, 9 Apr 2021 12:43:59 -0400 From: "Theodore Ts'o" To: Jan Kara Cc: Zhang Yi , linux-ext4@vger.kernel.org, adilger.kernel@dilger.ca Subject: Re: [PATCH] ext4: do not set SB_ACTIVE in ext4_orphan_cleanup() Message-ID: References: <20210331033138.918975-1-yi.zhang@huawei.com> <20210331095920.GF30749@quack2.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210331095920.GF30749@quack2.suse.cz> Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org On Wed, Mar 31, 2021 at 11:59:20AM +0200, Jan Kara wrote: > On Wed 31-03-21 11:31:38, Zhang Yi wrote: > > When CONFIG_QUOTA is enabled, if we failed to mount the filesystem due > > to some error happens behind ext4_orphan_cleanup(), it will end up > > triggering a after free issue of super_block. The problem is that > > ext4_orphan_cleanup() will set SB_ACTIVE flag if CONFIG_QUOTA is > > enabled, after we cleanup the truncated inodes, the last iput() will put > > them into the lru list, and these inodes' pages may probably dirty and > > will be write back by the writeback thread, so it could be raced by > > freeing super_block in the error path of mount_bdev(). > > > > After check the setting of SB_ACTIVE flag in ext4_orphan_cleanup(), it > > was used to ensure updating the quota file properly, but evict inode and > > trash data immediately in the last iput does not affect the quotafile, > > so setting the SB_ACTIVE flag seems not required[1]. Fix this issue by > > just remove the SB_ACTIVE setting. > > Thanks for the patch. Let me rephrase the changelog a little: > > When CONFIG_QUOTA is enabled and if we later fail to finish mounting the > filesystem due to some error after ext4_orphan_cleanup(), we may hit use > after free issues. The problem is that ext4_orphan_cleanup() sets SB_ACTIVE > flag and so inodes processed during the orphan cleanup are put to the > superblock's LRU list instead of being immediately destroyed. However the > path handling error recovery after failed ->fill_super() call does not > destroy inodes attached to the superblock and so they are left active in > memory while the superblock is freed. > > Originally, SB_ACTIVE setting was added so that updated quota information > is not destroyed when we drop quota inode references after orphan cleanup. > However VFS does not purge dirty inode pages without SB_ACTIVE flag for many > years already. So just remove the hack with setting SB_ACTIVE flag from > ext4_orphan_cleanup(). > > Also feel free to add: > > Reviewed-by: Jan Kara > > Honza Applied, thanks. - Ted