From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754486AbdJSNyA (ORCPT ); Thu, 19 Oct 2017 09:54:00 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:48612 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754453AbdJSNx5 (ORCPT ); Thu, 19 Oct 2017 09:53:57 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jeff Layton , "Yan, Zheng" , Ilya Dryomov , Sasha Levin Subject: [PATCH 4.4 40/46] ceph: clean up unsafe d_parent accesses in build_dentry_path Date: Thu, 19 Oct 2017 15:49:16 +0200 Message-Id: <20171019134847.712696064@linuxfoundation.org> X-Mailer: git-send-email 2.14.2 In-Reply-To: <20171019134845.293630834@linuxfoundation.org> References: <20171019134845.293630834@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jeff Layton [ Upstream commit c6b0b656ca24ede6657abb4a2cd910fa9c1879ba ] While we hold a reference to the dentry when build_dentry_path is called, we could end up racing with a rename that changes d_parent. Handle that situation correctly, by using the rcu_read_lock to ensure that the parent dentry and inode stick around long enough to safely check ceph_snap and ceph_ino. Link: http://tracker.ceph.com/issues/18148 Signed-off-by: Jeff Layton Reviewed-by: Yan, Zheng Signed-off-by: Ilya Dryomov Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- fs/ceph/mds_client.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) --- a/fs/ceph/mds_client.c +++ b/fs/ceph/mds_client.c @@ -1845,13 +1845,18 @@ static int build_dentry_path(struct dent int *pfreepath) { char *path; + struct inode *dir; - if (ceph_snap(d_inode(dentry->d_parent)) == CEPH_NOSNAP) { - *pino = ceph_ino(d_inode(dentry->d_parent)); + rcu_read_lock(); + dir = d_inode_rcu(dentry->d_parent); + if (dir && ceph_snap(dir) == CEPH_NOSNAP) { + *pino = ceph_ino(dir); + rcu_read_unlock(); *ppath = dentry->d_name.name; *ppathlen = dentry->d_name.len; return 0; } + rcu_read_unlock(); path = ceph_mdsc_build_path(dentry, ppathlen, pino, 1); if (IS_ERR(path)) return PTR_ERR(path);