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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,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 C0F9DC10F14 for ; Sun, 6 Oct 2019 17:58:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9C82E20700 for ; Sun, 6 Oct 2019 17:58:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1570384697; bh=anC2h8HLrJ225GNI/6kpNgNtxjSNr0e6gzPUyAcYfdU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=CHHvkmHkNDYIWmxAKzDHACpRmf3Ykg9ZXu5V74uBR8d5DE6f2bDizJCid7YvfuevW Hg5kuZYFfl2PkI6+1AUo4qmOloaTsKrQxHpTICwOuIrIg9yaxq3Z5/Y7SNwVRH/hix o7B4kdkmunl40iqoM4LEzzU4owW2YftLqFA4SYK0= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729562AbfJFRcY (ORCPT ); Sun, 6 Oct 2019 13:32:24 -0400 Received: from mail.kernel.org ([198.145.29.99]:58818 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729549AbfJFRcV (ORCPT ); Sun, 6 Oct 2019 13:32:21 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 4B9562080F; Sun, 6 Oct 2019 17:32:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1570383140; bh=anC2h8HLrJ225GNI/6kpNgNtxjSNr0e6gzPUyAcYfdU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=QZRvN+wvJDQC9P15RWvM0OWSymTmkryqsFoI7jygdz7LB6+l776YUaxR8dXvYL/MB cmvmTo9/aPqFYRrnW30LSGqROj1QWJdzKSQuOZbzYDcjSCdki6o5005P3S3Sie+jrF ipq6lyrARj/H+wKlTdffwkCXrdC8z+YqiZUl8YW8= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Rajendra Dendukuri , David Ahern , Eric Dumazet , "David S. Miller" Subject: [PATCH 4.19 084/106] ipv6: Handle missing host route in __ipv6_ifa_notify Date: Sun, 6 Oct 2019 19:21:30 +0200 Message-Id: <20191006171158.119464512@linuxfoundation.org> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20191006171124.641144086@linuxfoundation.org> References: <20191006171124.641144086@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: David Ahern [ Upstream commit 2d819d250a1393a3e725715425ab70a0e0772a71 ] Rajendra reported a kernel panic when a link was taken down: [ 6870.263084] BUG: unable to handle kernel NULL pointer dereference at 00000000000000a8 [ 6870.271856] IP: [] __ipv6_ifa_notify+0x154/0x290 [ 6870.570501] Call Trace: [ 6870.573238] [] ? ipv6_ifa_notify+0x26/0x40 [ 6870.579665] [] ? addrconf_dad_completed+0x4c/0x2c0 [ 6870.586869] [] ? ipv6_dev_mc_inc+0x196/0x260 [ 6870.593491] [] ? addrconf_dad_work+0x10a/0x430 [ 6870.600305] [] ? __switch_to_asm+0x34/0x70 [ 6870.606732] [] ? process_one_work+0x18a/0x430 [ 6870.613449] [] ? worker_thread+0x4d/0x490 [ 6870.619778] [] ? process_one_work+0x430/0x430 [ 6870.626495] [] ? kthread+0xd9/0xf0 [ 6870.632145] [] ? __switch_to_asm+0x34/0x70 [ 6870.638573] [] ? kthread_park+0x60/0x60 [ 6870.644707] [] ? ret_from_fork+0x57/0x70 [ 6870.650936] Code: 31 c0 31 d2 41 b9 20 00 08 02 b9 09 00 00 0 addrconf_dad_work is kicked to be scheduled when a device is brought up. There is a race between addrcond_dad_work getting scheduled and taking the rtnl lock and a process taking the link down (under rtnl). The latter removes the host route from the inet6_addr as part of addrconf_ifdown which is run for NETDEV_DOWN. The former attempts to use the host route in __ipv6_ifa_notify. If the down event removes the host route due to the race to the rtnl, then the BUG listed above occurs. Since the DAD sequence can not be aborted, add a check for the missing host route in __ipv6_ifa_notify. The only way this should happen is due to the previously mentioned race. The host route is created when the address is added to an interface; it is only removed on a down event where the address is kept. Add a warning if the host route is missing AND the device is up; this is a situation that should never happen. Fixes: f1705ec197e7 ("net: ipv6: Make address flushing on ifdown optional") Reported-by: Rajendra Dendukuri Signed-off-by: David Ahern Reviewed-by: Eric Dumazet Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/ipv6/addrconf.c | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-) --- a/net/ipv6/addrconf.c +++ b/net/ipv6/addrconf.c @@ -5678,13 +5678,20 @@ static void __ipv6_ifa_notify(int event, switch (event) { case RTM_NEWADDR: /* - * If the address was optimistic - * we inserted the route at the start of - * our DAD process, so we don't need - * to do it again + * If the address was optimistic we inserted the route at the + * start of our DAD process, so we don't need to do it again. + * If the device was taken down in the middle of the DAD + * cycle there is a race where we could get here without a + * host route, so nothing to insert. That will be fixed when + * the device is brought up. */ - if (!rcu_access_pointer(ifp->rt->fib6_node)) + if (ifp->rt && !rcu_access_pointer(ifp->rt->fib6_node)) { ip6_ins_rt(net, ifp->rt); + } else if (!ifp->rt && (ifp->idev->dev->flags & IFF_UP)) { + pr_warn("BUG: Address %pI6c on device %s is missing its host route.\n", + &ifp->addr, ifp->idev->dev->name); + } + if (ifp->idev->cnf.forwarding) addrconf_join_anycast(ifp); if (!ipv6_addr_any(&ifp->peer_addr))