Return-Path: Received: from mailhub.sw.ru ([195.214.232.25]:25763 "EHLO relay.sw.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751432AbdKMEZu (ORCPT ); Sun, 12 Nov 2017 23:25:50 -0500 From: Vasily Averin Subject: [PATCH] lockd: fix "list_add double add" caused by legacy signal interface To: "J. Bruce Fields" , Jeff Layton , linux-nfs@vger.kernel.org References: <20171109154444.GG8773@fieldses.org> Message-ID: <75f4472c-b9e2-6353-3af0-c4939ecfca41@virtuozzo.com> Date: Mon, 13 Nov 2017 07:25:40 +0300 MIME-Version: 1.0 In-Reply-To: <20171109154444.GG8773@fieldses.org> Content-Type: text/plain; charset=utf-8 Sender: linux-nfs-owner@vger.kernel.org List-ID: restart_grace() uses hardcoded init_net. It can cause to "list_add double add" in following scenario: 1) nfsd and lockd was started in several net namespaces 2) nfsd in init_net was stopped (lockd was not stopped because it have users from another net namespaces) 3) lockd got signal, called restart_grace() -> set_grace_period() and enabled lock_manager in hardcoded init_net. 4) nfsd in init_net is started again, its lockd_up() calls set_grace_period() and tries to add lock_manager into init_net 2nd time. Jeff Layton suggest: "Make it safe to call locks_start_grace multiple times on the same lock_manager. If it's already on the global grace_list, then don't try to add it again. With this change, we also need to ensure that the nfsd4 lock manager initializes the list before we call locks_start_grace. While we're at it, move the rest of the nfsd_net initialization into nfs4_state_create_net. I see no reason to have it spread over two functions like it is today." Suggested patch was updated to generate warning in described situation. Suggested-by: Jeff Layton Signed-off-by: Vasily Averin --- fs/nfs_common/grace.c | 6 +++++- fs/nfsd/nfs4state.c | 7 ++++--- 2 files changed, 9 insertions(+), 4 deletions(-) diff --git a/fs/nfs_common/grace.c b/fs/nfs_common/grace.c index bd3e2d3..5be08f0 100644 --- a/fs/nfs_common/grace.c +++ b/fs/nfs_common/grace.c @@ -30,7 +30,11 @@ locks_start_grace(struct net *net, struct lock_manager *lm) struct list_head *grace_list = net_generic(net, grace_net_id); spin_lock(&grace_lock); - list_add(&lm->list, grace_list); + if (list_empty(&lm->list)) + list_add(&lm->list, grace_list); + else + WARN(1, "double list_add attempt detected in net %x %s\n", + net->ns.inum, (net == &init_net) ? "(init_net)" : ""); spin_unlock(&grace_lock); } EXPORT_SYMBOL_GPL(locks_start_grace); diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c index 7345143..b29b5a1 100644 --- a/fs/nfsd/nfs4state.c +++ b/fs/nfsd/nfs4state.c @@ -7103,6 +7103,10 @@ static int nfs4_state_create_net(struct net *net) INIT_LIST_HEAD(&nn->sessionid_hashtbl[i]); nn->conf_name_tree = RB_ROOT; nn->unconf_name_tree = RB_ROOT; + nn->boot_time = get_seconds(); + nn->grace_ended = false; + nn->nfsd4_manager.block_opens = true; + INIT_LIST_HEAD(&nn->nfsd4_manager.list); INIT_LIST_HEAD(&nn->client_lru); INIT_LIST_HEAD(&nn->close_lru); INIT_LIST_HEAD(&nn->del_recall_lru); @@ -7160,9 +7164,6 @@ nfs4_state_start_net(struct net *net) ret = nfs4_state_create_net(net); if (ret) return ret; - nn->boot_time = get_seconds(); - nn->grace_ended = false; - nn->nfsd4_manager.block_opens = true; locks_start_grace(net, &nn->nfsd4_manager); nfsd4_client_tracking_init(net); printk(KERN_INFO "NFSD: starting %ld-second grace period (net %x)\n", -- 2.7.4