From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752301AbdKVKMs (ORCPT ); Wed, 22 Nov 2017 05:12:48 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:32998 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752272AbdKVKMp (ORCPT ); Wed, 22 Nov 2017 05:12:45 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Fengguang Wu , Alexander Duyck , Linus Torvalds , Girish Moodalbail , Cong Wang , "David S. Miller" Subject: [PATCH 3.18 08/12] vlan: fix a use-after-free in vlan_device_event() Date: Wed, 22 Nov 2017 11:11:51 +0100 Message-Id: <20171122101057.442837605@linuxfoundation.org> X-Mailer: git-send-email 2.15.0 In-Reply-To: <20171122101056.996363808@linuxfoundation.org> References: <20171122101056.996363808@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 3.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Cong Wang [ Upstream commit 052d41c01b3a2e3371d66de569717353af489d63 ] After refcnt reaches zero, vlan_vid_del() could free dev->vlan_info via RCU: RCU_INIT_POINTER(dev->vlan_info, NULL); call_rcu(&vlan_info->rcu, vlan_info_rcu_free); However, the pointer 'grp' still points to that memory since it is set before vlan_vid_del(): vlan_info = rtnl_dereference(dev->vlan_info); if (!vlan_info) goto out; grp = &vlan_info->grp; Depends on when that RCU callback is scheduled, we could trigger a use-after-free in vlan_group_for_each_dev() right following this vlan_vid_del(). Fix it by moving vlan_vid_del() before setting grp. This is also symmetric to the vlan_vid_add() we call in vlan_device_event(). Reported-by: Fengguang Wu Fixes: efc73f4bbc23 ("net: Fix memory leak - vlan_info struct") Cc: Alexander Duyck Cc: Linus Torvalds Cc: Girish Moodalbail Signed-off-by: Cong Wang Reviewed-by: Girish Moodalbail Tested-by: Fengguang Wu Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/8021q/vlan.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) --- a/net/8021q/vlan.c +++ b/net/8021q/vlan.c @@ -376,6 +376,9 @@ static int vlan_device_event(struct noti dev->name); vlan_vid_add(dev, htons(ETH_P_8021Q), 0); } + if (event == NETDEV_DOWN && + (dev->features & NETIF_F_HW_VLAN_CTAG_FILTER)) + vlan_vid_del(dev, htons(ETH_P_8021Q), 0); vlan_info = rtnl_dereference(dev->vlan_info); if (!vlan_info) @@ -420,9 +423,6 @@ static int vlan_device_event(struct noti break; case NETDEV_DOWN: - if (dev->features & NETIF_F_HW_VLAN_CTAG_FILTER) - vlan_vid_del(dev, htons(ETH_P_8021Q), 0); - /* Put all VLANs for this dev in the down state too. */ vlan_group_for_each_dev(grp, i, vlandev) { flgs = vlandev->flags;