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=-10.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 5FF89C43441 for ; Mon, 19 Nov 2018 16:20:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 21C4B20851 for ; Mon, 19 Nov 2018 16:20:40 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="1dQRQTeA" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 21C4B20851 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-btrfs-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729891AbeKTCom (ORCPT ); Mon, 19 Nov 2018 21:44:42 -0500 Received: from mail.kernel.org ([198.145.29.99]:48704 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729825AbeKTCom (ORCPT ); Mon, 19 Nov 2018 21:44:42 -0500 Received: from localhost.localdomain (bl8-197-74.dsl.telepac.pt [85.241.197.74]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 7814620851 for ; Mon, 19 Nov 2018 16:20:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1542644438; bh=/ddrYELQ0zVB0BWoSGnmCdS6wrZ7Trw+0QnZOSh1k+U=; h=From:To:Subject:Date:From; b=1dQRQTeAZH6EW21HhQ7OfLIddoeYbzqslstgYDTE5nN5lJTCcJl+RACuM+3F1nNnL xVXhVhH+4F7R78UH2Mw8oIzAkS5gKEnByPdbyMeQj1M7defmNX45nEal3+Uvc9cDrN IVdRoXCn3xe230jzHIh3R1PAK+TldsMi81sVL6oI= From: fdmanana@kernel.org To: linux-btrfs@vger.kernel.org Subject: [PATCH] Btrfs: fix race between enabling quotas and subvolume creation Date: Mon, 19 Nov 2018 16:20:34 +0000 Message-Id: <20181119162034.13132-1-fdmanana@kernel.org> X-Mailer: git-send-email 2.11.0 Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org From: Filipe Manana We have a race between enabling quotas end subvolume creation that cause subvolume creation to fail with -EINVAL, and the following diagram shows how it happens: CPU 0 CPU 1 btrfs_ioctl() btrfs_ioctl_quota_ctl() btrfs_quota_enable() mutex_lock(fs_info->qgroup_ioctl_lock) btrfs_ioctl() create_subvol() btrfs_qgroup_inherit() -> save fs_info->quota_root into quota_root -> stores a NULL value -> tries to lock the mutex qgroup_ioctl_lock -> blocks waiting for the task at CPU0 -> sets BTRFS_FS_QUOTA_ENABLED in fs_info -> sets quota_root in fs_info->quota_root (non-NULL value) mutex_unlock(fs_info->qgroup_ioctl_lock) -> checks quota enabled flag is set -> returns -EINVAL because fs_info->quota_root was NULL before it acquired the mutex qgroup_ioctl_lock -> ioctl returns -EINVAL Returning -EINVAL to user space will be confusing if all the arguments passed to the subvolume creation ioctl were valid. Fix it by grabbing the value from fs_info->quota_root after acquiring the mutex. Signed-off-by: Filipe Manana --- fs/btrfs/qgroup.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c index ae1358253b7b..0bdf28499790 100644 --- a/fs/btrfs/qgroup.c +++ b/fs/btrfs/qgroup.c @@ -2250,7 +2250,7 @@ int btrfs_qgroup_inherit(struct btrfs_trans_handle *trans, u64 srcid, int i; u64 *i_qgroups; struct btrfs_fs_info *fs_info = trans->fs_info; - struct btrfs_root *quota_root = fs_info->quota_root; + struct btrfs_root *quota_root; struct btrfs_qgroup *srcgroup; struct btrfs_qgroup *dstgroup; u32 level_size = 0; @@ -2260,6 +2260,7 @@ int btrfs_qgroup_inherit(struct btrfs_trans_handle *trans, u64 srcid, if (!test_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags)) goto out; + quota_root = fs_info->quota_root; if (!quota_root) { ret = -EINVAL; goto out; -- 2.11.0