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=-17.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A,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 5E377C47E48 for ; Thu, 15 Jul 2021 11:55:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 41CFD6117A for ; Thu, 15 Jul 2021 11:55:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230237AbhGOL6d (ORCPT ); Thu, 15 Jul 2021 07:58:33 -0400 Received: from smtp-out1.suse.de ([195.135.220.28]:59208 "EHLO smtp-out1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229927AbhGOL6c (ORCPT ); Thu, 15 Jul 2021 07:58:32 -0400 Received: from imap1.suse-dmz.suse.de (imap1.suse-dmz.suse.de [192.168.254.73]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id 301CA22A08; Thu, 15 Jul 2021 11:55:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1626350138; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=S0P5XBtGFEFlf02xC8Z0PQcajQCMzXtZPbZNkfbQBcI=; b=On8ITqXY3szBMaOX4uyA4mLGdeqWiLBEJK/Dfbpk0iOHe67oFS8jJkY7RhH9+GAiKVIiZX kwZu43aCGJV7C5ru5FBwFpqyW3aiJcF0wWH8pURBySyyElQwtxig2znzBtFS3g600x033z pTB44ZWTcSGA6jkIXBdp0ZGwc4E5OlQ= Received: from imap1.suse-dmz.suse.de (imap1.suse-dmz.suse.de [192.168.254.73]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap1.suse-dmz.suse.de (Postfix) with ESMTPS id 9D62F13D7E; Thu, 15 Jul 2021 11:55:37 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap1.suse-dmz.suse.de with ESMTPSA id WyiAIzki8GDdNAAAGKfGzw (envelope-from ); Thu, 15 Jul 2021 11:55:37 +0000 Subject: Re: [PATCH] btrfs: fix rw device counting in __btrfs_free_extra_devids To: Desmond Cheong Zhi Xi , clm@fb.com, josef@toxicpanda.com, dsterba@suse.com Cc: anand.jain@oracle.com, linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org, skhan@linuxfoundation.org, gregkh@linuxfoundation.org, linux-kernel-mentees@lists.linuxfoundation.org, syzbot+a70e2ad0879f160b9217@syzkaller.appspotmail.com References: <20210715103403.176695-1-desmondcheongzx@gmail.com> From: Nikolay Borisov Message-ID: <7ae7a858-9893-c41c-ed96-10651c295087@suse.com> Date: Thu, 15 Jul 2021 14:55:37 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <20210715103403.176695-1-desmondcheongzx@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 15.07.21 г. 13:34, Desmond Cheong Zhi Xi wrote: > Syzbot reports a warning in close_fs_devices that happens because > fs_devices->rw_devices is not 0 after calling btrfs_close_one_device > on each device. > > This happens when a writeable device is removed in > __btrfs_free_extra_devids, but the rw device count is not decremented > accordingly. So when close_fs_devices is called, the removed device is > still counted and we get an off by 1 error. > > Here is one call trace that was observed: > btrfs_mount_root(): > btrfs_scan_one_device(): > device_list_add(); <---------------- device added > btrfs_open_devices(): > open_fs_devices(): > btrfs_open_one_device(); <-------- rw device count ++ > btrfs_fill_super(): > open_ctree(): > btrfs_free_extra_devids(): > __btrfs_free_extra_devids(); <--- device removed > fail_tree_roots: > btrfs_close_devices(): > close_fs_devices(); <------- rw device count off by 1 > > Fixes: cf89af146b7e ("btrfs: dev-replace: fail mount if we don't have replace item with target device") > Reported-by: syzbot+a70e2ad0879f160b9217@syzkaller.appspotmail.com > Tested-by: syzbot+a70e2ad0879f160b9217@syzkaller.appspotmail.com > Signed-off-by: Desmond Cheong Zhi Xi Is there a reliable reproducer from syzbot? Can this be turned into an xfstest? > --- > fs/btrfs/volumes.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c > index 807502cd6510..916c25371658 100644 > --- a/fs/btrfs/volumes.c > +++ b/fs/btrfs/volumes.c > @@ -1078,6 +1078,7 @@ static void __btrfs_free_extra_devids(struct btrfs_fs_devices *fs_devices, > if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state)) { > list_del_init(&device->dev_alloc_list); > clear_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state); > + fs_devices->rw_devices--; > } > list_del_init(&device->dev_list); > fs_devices->num_devices--; >