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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,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 999B6C33CAF for ; Thu, 16 Jan 2020 18:15:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7828B2073A for ; Thu, 16 Jan 2020 18:15:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1579198514; bh=+Iu1QIvoLrD1qnpF7RJVVZI3OxOt0LCWPPdAv2W/3no=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=2szJ8tcX4WsFDlP6xFSBljWBMISj/BDA9rZwjxyMFwmzFczF2LnqckDkFn9Eax62r Fuv9rTl8X+Py0mtzLqFsrZmKvR0GGpHw5lb7lLI4sNmdt4vVnPbbPs9OkxKCdmfH20 upsy38o1Vk8mZMsxZUrIInknXNK7koLZDvgBDX+Y= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2436459AbgAPSPN (ORCPT ); Thu, 16 Jan 2020 13:15:13 -0500 Received: from mail.kernel.org ([198.145.29.99]:41844 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2392861AbgAPR3t (ORCPT ); Thu, 16 Jan 2020 12:29:49 -0500 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 3A76E24711; Thu, 16 Jan 2020 17:29:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1579195788; bh=+Iu1QIvoLrD1qnpF7RJVVZI3OxOt0LCWPPdAv2W/3no=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=yIUJjKMXUSByzgzpqReNJnn1djpK9cuW8yb2nLI70e3lBkpRw8VpmQJgcAXmCobNX WlbgjdHW0QNFk9PzrpsDqPOAa6U0HvVZDZyr6SYmgdqsUH4aAG+8TgDHHKmHX7FmFo 6DzaKkxCAxUvux+Vr28PfrmvuBuhGUzia5z3WroM= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: David Ahern , Rajendra Dendukuri , Eric Dumazet , "David S . Miller" , Sasha Levin , netdev@vger.kernel.org Subject: [PATCH AUTOSEL 4.14 310/371] ipv6: Handle race in addrconf_dad_work Date: Thu, 16 Jan 2020 12:23:02 -0500 Message-Id: <20200116172403.18149-253-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200116172403.18149-1-sashal@kernel.org> References: <20200116172403.18149-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore 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 a3ce2a21bb8969ae27917281244fa91bf5f286d7 ] 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. This scenario does not occur when the ipv6 address is not kept (net.ipv6.conf.all.keep_addr_on_down = 0) as addrconf_ifdown sets the state of the ifp to DEAD. Handle when the addresses are kept by checking IF_READY which is reset by addrconf_ifdown. The 'dead' flag for an inet6_addr is set only under rtnl, in addrconf_ifdown and it means the device is getting removed (or IPv6 is disabled). The interesting cases for changing the idev flag are addrconf_notify (NETDEV_UP and NETDEV_CHANGE) and addrconf_ifdown (reset the flag). The former does not have the idev lock - only rtnl; the latter has both. Based on that the existing dead + IF_READY check can be moved to right after the rtnl_lock in addrconf_dad_work. 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: Sasha Levin --- net/ipv6/addrconf.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c index a81201dd3a1a..57bc05ff88d3 100644 --- a/net/ipv6/addrconf.c +++ b/net/ipv6/addrconf.c @@ -3908,6 +3908,12 @@ static void addrconf_dad_work(struct work_struct *w) rtnl_lock(); + /* check if device was taken down before this delayed work + * function could be canceled + */ + if (idev->dead || !(idev->if_flags & IF_READY)) + goto out; + spin_lock_bh(&ifp->lock); if (ifp->state == INET6_IFADDR_STATE_PREDAD) { action = DAD_BEGIN; @@ -3953,11 +3959,6 @@ static void addrconf_dad_work(struct work_struct *w) goto out; write_lock_bh(&idev->lock); - if (idev->dead || !(idev->if_flags & IF_READY)) { - write_unlock_bh(&idev->lock); - goto out; - } - spin_lock(&ifp->lock); if (ifp->state == INET6_IFADDR_STATE_DEAD) { spin_unlock(&ifp->lock); -- 2.20.1