From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754162AbdGYTgE (ORCPT ); Tue, 25 Jul 2017 15:36:04 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:36698 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754111AbdGYTZS (ORCPT ); Tue, 25 Jul 2017 15:25:18 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, "Yan, Zheng" , Ilya Dryomov Subject: [PATCH 4.12 165/196] ceph: fix race in concurrent readdir Date: Tue, 25 Jul 2017 12:22:44 -0700 Message-Id: <20170725192054.225459134@linuxfoundation.org> X-Mailer: git-send-email 2.13.3 In-Reply-To: <20170725192046.422343510@linuxfoundation.org> References: <20170725192046.422343510@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 4.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Yan, Zheng commit 84583cfb973c4313955c6231cc9cb3772d280b15 upstream. For a large directory, program needs to issue multiple readdir syscalls to get all dentries. When there are multiple programs read the directory concurrently. Following sequence of events can happen. - program calls readdir with pos = 2. ceph sends readdir request to mds. The reply contains N1 entries. ceph adds these N1 entries to readdir cache. - program calls readdir with pos = N1+2. The readdir is satisfied by the readdir cache, N2 entries are returned. (Other program calls readdir in the middle, which fills the cache) - program calls readdir with pos = N1+N2+2. ceph sends readdir request to mds. The reply contains N3 entries and it reaches directory end. ceph adds these N3 entries to the readdir cache and marks directory complete. The second readdir call does not update fi->readdir_cache_idx. ceph add the last N3 entries to wrong places. Signed-off-by: "Yan, Zheng" Signed-off-by: Ilya Dryomov Signed-off-by: Greg Kroah-Hartman --- fs/ceph/dir.c | 5 +++++ 1 file changed, 5 insertions(+) --- a/fs/ceph/dir.c +++ b/fs/ceph/dir.c @@ -271,6 +271,11 @@ out: if (ret < 0) err = ret; dput(last); + /* last_name no longer match cache index */ + if (fi->readdir_cache_idx >= 0) { + fi->readdir_cache_idx = -1; + fi->dir_release_count = 0; + } } return err; }