From patchwork Thu Aug 3 06:06:48 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Qu Wenruo X-Patchwork-Id: 13339274 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A7F1DC001DF for ; Thu, 3 Aug 2023 06:07:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232659AbjHCGHW (ORCPT ); Thu, 3 Aug 2023 02:07:22 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36402 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232735AbjHCGHR (ORCPT ); Thu, 3 Aug 2023 02:07:17 -0400 Received: from smtp-out2.suse.de (smtp-out2.suse.de [IPv6:2001:67c:2178:6::1d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5D28730CF for ; Wed, 2 Aug 2023 23:07:13 -0700 (PDT) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (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-out2.suse.de (Postfix) with ESMTPS id E355B1F45A; Thu, 3 Aug 2023 06:07:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1691042830; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=mKmqw6Z1jkyHPHXSmij0N2tnpEXUa0guYn4Bxeex/R8=; b=aWRGjBNW0PZsTorgg0G6G+hzioGM/CP+HWl3HJ3mWFbQ6jIzb4BQD/Ae7PndeH74J0rzTW YxkHAJJ0GC9LeZF5kINYIBjfhF2MvRfSYAyELG138ZJZtfDRfYr8Uwb4i9EgJNAo1iV7lt CIdFmDLkh/0EKLMlIsdW/mEIEyOgWoI= Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (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 imap2.suse-dmz.suse.de (Postfix) with ESMTPS id BE92F134B0; Thu, 3 Aug 2023 06:07:09 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id wIEuIQ1Ey2TlDQAAMHmgww (envelope-from ); Thu, 03 Aug 2023 06:07:09 +0000 From: Qu Wenruo To: linux-btrfs@vger.kernel.org Cc: Filipe Manana , syzbot+ae97a827ae1c3336bbb4@syzkaller.appspotmail.com Subject: [PATCH v3 1/3] btrfs: avoid race with qgroup tree creation and relocation Date: Thu, 3 Aug 2023 14:06:48 +0800 Message-ID: X-Mailer: git-send-email 2.41.0 In-Reply-To: References: MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org [BUG] Syzbot reported a weird ASSERT() triggered inside prepare_to_merge(). assertion failed: root->reloc_root == reloc_root, in fs/btrfs/relocation.c:1919 ------------[ cut here ]------------ kernel BUG at fs/btrfs/relocation.c:1919! invalid opcode: 0000 [#1] PREEMPT SMP KASAN CPU: 0 PID: 9904 Comm: syz-executor.3 Not tainted 6.4.0-syzkaller-08881-g533925cb7604 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/27/2023 RIP: 0010:prepare_to_merge+0xbb2/0xc40 fs/btrfs/relocation.c:1919 Code: fe e9 f5 (...) RSP: 0018:ffffc9000325f760 EFLAGS: 00010246 RAX: 000000000000004f RBX: ffff888075644030 RCX: 1481ccc522da5800 RDX: ffffc90005c09000 RSI: 00000000000364ca RDI: 00000000000364cb RBP: ffffc9000325f870 R08: ffffffff816f33ac R09: 1ffff9200064bea0 R10: dffffc0000000000 R11: fffff5200064bea1 R12: ffff888075644000 R13: ffff88803b166000 R14: ffff88803b166560 R15: ffff88803b166558 FS: 00007f4e305fd700(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000056080679c000 CR3: 00000000193ad000 CR4: 00000000003506f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: relocate_block_group+0xa5d/0xcd0 fs/btrfs/relocation.c:3749 btrfs_relocate_block_group+0x7ab/0xd70 fs/btrfs/relocation.c:4087 btrfs_relocate_chunk+0x12c/0x3b0 fs/btrfs/volumes.c:3283 __btrfs_balance+0x1b06/0x2690 fs/btrfs/volumes.c:4018 btrfs_balance+0xbdb/0x1120 fs/btrfs/volumes.c:4402 btrfs_ioctl_balance+0x496/0x7c0 fs/btrfs/ioctl.c:3604 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:870 [inline] __se_sys_ioctl+0xf8/0x170 fs/ioctl.c:856 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd RIP: 0033:0x7f4e2f88c389 [CAUSE] With extra debugging, the offending reloc_root is for quota tree (rootid 8). Normally we should not use reloc tree for quota root at all, as reloc trees are only for subvolume trees. But there is a race between quota enabling and relocation, this happens after commit 85724171b302 ("btrfs: fix the btrfs_get_global_root return value"). Before that commit, for quota and free space tree, we exit immediately if we can not grab it from fs_info. But now we would try to read it from disk, just as if they are fs trees, this sets ROOT_SHAREABLE flags in such race: Thread A | Thread B ---------------------------------+------------------------------ btrfs_quota_enable() | | | btrfs_get_root_ref() | | |- btrfs_get_global_root() | | | Returned NULL | | |- btrfs_lookup_fs_root() | | | Returned NULL |- btrfs_create_tree() | | | Now quota root item is | | | inserted | |- btrfs_read_tree_root() | | | Got the newly inserted quota root | | |- btrfs_init_fs_root() | | | Set ROOT_SHAREABLE flag [FIX] Get back to the old behavior by returning PTR_ERR(-ENOENT) if the target objectid is not a subvolume tree or data reloc tree. Reviewed-by: Filipe Manana Fixes: 85724171b302 ("btrfs: fix the btrfs_get_global_root return value") Reported-and-tested-by: syzbot+ae97a827ae1c3336bbb4@syzkaller.appspotmail.com Signed-off-by: Qu Wenruo --- fs/btrfs/disk-io.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c index da51e5750443..5fd336c597e9 100644 --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -1300,6 +1300,16 @@ static struct btrfs_root *btrfs_get_root_ref(struct btrfs_fs_info *fs_info, root = btrfs_get_global_root(fs_info, objectid); if (root) return root; + + /* + * If we're called for non-subvolume trees, and above function didn't + * found one, do not try to read it from disk. + * + * This is mostly for fst and quota trees, which can change at runtime + * and should only be grabbed from fs_info. + */ + if (!is_fstree(objectid) && objectid != BTRFS_DATA_RELOC_TREE_OBJECTID) + return ERR_PTR(-ENOENT); again: root = btrfs_lookup_fs_root(fs_info, objectid); if (root) {