Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932354AbdGCNlK (ORCPT ); Mon, 3 Jul 2017 09:41:10 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:35574 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932332AbdGCNlF (ORCPT ); Mon, 3 Jul 2017 09:41:05 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Wei Chen , Hannes Frederic Sowa , Xin Long , "David S. Miller" Subject: [PATCH 4.9 016/172] ipv6: fix calling in6_ifa_hold incorrectly for dad work Date: Mon, 3 Jul 2017 15:33:16 +0200 Message-Id: <20170703133415.006555475@linuxfoundation.org> X-Mailer: git-send-email 2.13.2 In-Reply-To: <20170703133414.260777365@linuxfoundation.org> References: <20170703133414.260777365@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 Content-Length: 2184 Lines: 64 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Xin Long [ Upstream commit f8a894b218138888542a5058d0e902378fd0d4ec ] Now when starting the dad work in addrconf_mod_dad_work, if the dad work is idle and queued, it needs to hold ifa. The problem is there's one gap in [1], during which if the pending dad work is removed elsewhere. It will miss to hold ifa, but the dad word is still idea and queue. if (!delayed_work_pending(&ifp->dad_work)) in6_ifa_hold(ifp); <--------------[1] mod_delayed_work(addrconf_wq, &ifp->dad_work, delay); An use-after-free issue can be caused by this. Chen Wei found this issue when WARN_ON(!hlist_unhashed(&ifp->addr_lst)) in net6_ifa_finish_destroy was hit because of it. As Hannes' suggestion, this patch is to fix it by holding ifa first in addrconf_mod_dad_work, then calling mod_delayed_work and putting ifa if the dad_work is already in queue. Note that this patch did not choose to fix it with: if (!mod_delayed_work(delay)) in6_ifa_hold(ifp); As with it, when delay == 0, dad_work would be scheduled immediately, all addrconf_mod_dad_work(0) callings had to be moved under ifp->lock. Reported-by: Wei Chen Suggested-by: Hannes Frederic Sowa Acked-by: Hannes Frederic Sowa Signed-off-by: Xin Long Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/ipv6/addrconf.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) --- a/net/ipv6/addrconf.c +++ b/net/ipv6/addrconf.c @@ -315,9 +315,9 @@ static void addrconf_mod_rs_timer(struct static void addrconf_mod_dad_work(struct inet6_ifaddr *ifp, unsigned long delay) { - if (!delayed_work_pending(&ifp->dad_work)) - in6_ifa_hold(ifp); - mod_delayed_work(addrconf_wq, &ifp->dad_work, delay); + in6_ifa_hold(ifp); + if (mod_delayed_work(addrconf_wq, &ifp->dad_work, delay)) + in6_ifa_put(ifp); } static int snmp6_alloc_dev(struct inet6_dev *idev)