From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4C3351D0787; Wed, 2 Oct 2024 13:40:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727876439; cv=none; b=mM3s0rsUydpcLUdq4EJBZcn8GdTIiyYsYY4sBSDI1g386BB1s6K0E+NcB7tmscpMk0e/I+fcH46KI3F9DWltCTDDXioEfXxdDg+zat3Brj18OFAFsXQXkyleK1V3Ry7LHscdtxZpCQXEDQLPyLVQigl5XWzSoEJ1aRi8c2pGMoA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727876439; c=relaxed/simple; bh=M0yYnU05VA/Fvpk66NUnNu2XmJef2kWM9uQUn/hrO08=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=umAVGJLtToAPn20B9fO5rmQfoVJ3iBGWxn/SjIswuU7sYyyq9ZfNailx1/ukDWRVumh5PHKiI/fArOHEiIY9sal6bHSHlw0Mt9P6KN/wZm/ZhuUtMELj6AYqeRTQg6VFRRSZ+ZCWCqiCIjjhqEdhs35Y9cWiqofgMd+YqI9od8w= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=IdfYeuCC; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="IdfYeuCC" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B9A43C4CEC5; Wed, 2 Oct 2024 13:40:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1727876439; bh=M0yYnU05VA/Fvpk66NUnNu2XmJef2kWM9uQUn/hrO08=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=IdfYeuCC8b8INibuoQzSWjwBuW2EwqZmitb7Ql8nRP4WeSZAoYSL7itK9J4ZBXXi0 YM+gs1j5ZZAEAj1ffsZ/b+k8jRriR7uimHI6ozUfkfLeyPtX5kQUJ5jMFkg5PdAxUR //ObGW4sI6Ha0LvY5q6NfCLoWNNVwwuWdR0wONUQ= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+20d7e439f76bbbd863a7@syzkaller.appspotmail.com, Jan Kara , Christian Brauner , Chao Yu , Jaegeuk Kim , Sasha Levin Subject: [PATCH 6.11 444/695] f2fs: fix to dont set SB_RDONLY in f2fs_handle_critical_error() Date: Wed, 2 Oct 2024 14:57:22 +0200 Message-ID: <20241002125840.179296473@linuxfoundation.org> X-Mailer: git-send-email 2.46.2 In-Reply-To: <20241002125822.467776898@linuxfoundation.org> References: <20241002125822.467776898@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.11-stable review patch. If anyone has any objections, please let me know. ------------------ From: Chao Yu [ Upstream commit 930c6ab93492c4b15436524e704950b364b2930c ] syzbot reports a f2fs bug as below: ------------[ cut here ]------------ WARNING: CPU: 1 PID: 58 at kernel/rcu/sync.c:177 rcu_sync_dtor+0xcd/0x180 kernel/rcu/sync.c:177 CPU: 1 UID: 0 PID: 58 Comm: kworker/1:2 Not tainted 6.10.0-syzkaller-12562-g1722389b0d86 #0 Workqueue: events destroy_super_work RIP: 0010:rcu_sync_dtor+0xcd/0x180 kernel/rcu/sync.c:177 Call Trace: percpu_free_rwsem+0x41/0x80 kernel/locking/percpu-rwsem.c:42 destroy_super_work+0xec/0x130 fs/super.c:282 process_one_work kernel/workqueue.c:3231 [inline] process_scheduled_works+0xa2c/0x1830 kernel/workqueue.c:3312 worker_thread+0x86d/0xd40 kernel/workqueue.c:3390 kthread+0x2f0/0x390 kernel/kthread.c:389 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244 As Christian Brauner pointed out [1]: the root cause is f2fs sets SB_RDONLY flag in internal function, rather than setting the flag covered w/ sb->s_umount semaphore via remount procedure, then below race condition causes this bug: - freeze_super() - sb_wait_write(sb, SB_FREEZE_WRITE) - sb_wait_write(sb, SB_FREEZE_PAGEFAULT) - sb_wait_write(sb, SB_FREEZE_FS) - f2fs_handle_critical_error - sb->s_flags |= SB_RDONLY - thaw_super - thaw_super_locked - sb_rdonly() is true, so it skips sb_freeze_unlock(sb, SB_FREEZE_FS) - deactivate_locked_super Since f2fs has almost the same logic as ext4 [2] when handling critical error in filesystem if it mounts w/ errors=remount-ro option: - set CP_ERROR_FLAG flag which indicates filesystem is stopped - record errors to superblock - set SB_RDONLY falg Once we set CP_ERROR_FLAG flag, all writable interfaces can detect the flag and stop any further updates on filesystem. So, it is safe to not set SB_RDONLY flag, let's remove the logic and keep in line w/ ext4 [3]. [1] https://lore.kernel.org/all/20240729-himbeeren-funknetz-96e62f9c7aee@brauner [2] https://lore.kernel.org/all/20240729132721.hxih6ehigadqf7wx@quack3 [3] https://lore.kernel.org/linux-ext4/20240805201241.27286-1-jack@suse.cz Fixes: b62e71be2110 ("f2fs: support errors=remount-ro|continue|panic mountoption") Reported-by: syzbot+20d7e439f76bbbd863a7@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/000000000000b90a8e061e21d12f@google.com/ Cc: Jan Kara Cc: Christian Brauner Signed-off-by: Chao Yu Reviewed-by: Christian Brauner Signed-off-by: Jaegeuk Kim Signed-off-by: Sasha Levin --- fs/f2fs/super.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c index 4e46cbd1fc2ba..80ce869d542c6 100644 --- a/fs/f2fs/super.c +++ b/fs/f2fs/super.c @@ -4173,12 +4173,14 @@ void f2fs_handle_critical_error(struct f2fs_sb_info *sbi, unsigned char reason, } f2fs_warn(sbi, "Remounting filesystem read-only"); + /* - * Make sure updated value of ->s_mount_flags will be visible before - * ->s_flags update + * We have already set CP_ERROR_FLAG flag to stop all updates + * to filesystem, so it doesn't need to set SB_RDONLY flag here + * because the flag should be set covered w/ sb->s_umount semaphore + * via remount procedure, otherwise, it will confuse code like + * freeze_super() which will lead to deadlocks and other problems. */ - smp_wmb(); - sb->s_flags |= SB_RDONLY; } static void f2fs_record_error_work(struct work_struct *work) -- 2.43.0