From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932547AbcCGXFr (ORCPT ); Mon, 7 Mar 2016 18:05:47 -0500 Received: from youngberry.canonical.com ([91.189.89.112]:39861 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932601AbcCGW4H (ORCPT ); Mon, 7 Mar 2016 17:56:07 -0500 From: Kamal Mostafa To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Andrew Lunn , Sven Eckelmann , Marek Lindner , Antonio Quartulli , Kamal Mostafa Subject: [PATCH 4.2.y-ckt 255/273] batman-adv: Avoid endless loop in bat-on-bat netdevice check Date: Mon, 7 Mar 2016 14:50:46 -0800 Message-Id: <1457391064-6660-256-git-send-email-kamal@canonical.com> X-Mailer: git-send-email 2.7.0 In-Reply-To: <1457391064-6660-1-git-send-email-kamal@canonical.com> References: <1457391064-6660-1-git-send-email-kamal@canonical.com> X-Extended-Stable: 4.2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.2.8-ckt5 -stable review patch. If anyone has any objections, please let me know. ---8<------------------------------------------------------------ From: Andrew Lunn commit 1bc4e2b000e7fa9773d6623bc8850561ce10a4fb upstream. batman-adv checks in different situation if a new device is already on top of a different batman-adv device. This is done by getting the iflink of a device and all its parent. It assumes that this iflink is always a parent device in an acyclic graph. But this assumption is broken by devices like veth which are actually a pair of two devices linked to each other. The recursive check would therefore get veth0 when calling dev_get_iflink on veth1. And it gets veth0 when calling dev_get_iflink with veth1. Creating a veth pair and loading batman-adv freezes parts of the system ip link add veth0 type veth peer name veth1 modprobe batman-adv An RCU stall will be detected on the system which cannot be fixed. INFO: rcu_sched self-detected stall on CPU 1: (5264 ticks this GP) idle=3e9/140000000000001/0 softirq=144683/144686 fqs=5249 (t=5250 jiffies g=46 c=45 q=43) Task dump for CPU 1: insmod R running task 0 247 245 0x00000008 ffffffff8151f140 ffffffff8107888e ffff88000fd141c0 ffffffff8151f140 0000000000000000 ffffffff81552df0 ffffffff8107b420 0000000000000001 ffff88000e3fa700 ffffffff81540b00 ffffffff8107d667 0000000000000001 Call Trace: [] ? rcu_dump_cpu_stacks+0x7e/0xd0 [] ? rcu_check_callbacks+0x3f0/0x6b0 [] ? hrtimer_run_queues+0x47/0x180 [] ? update_process_times+0x2d/0x50 [] ? tick_handle_periodic+0x1b/0x60 [] ? smp_trace_apic_timer_interrupt+0x5e/0x90 [] ? apic_timer_interrupt+0x82/0x90 [] ? __dev_get_by_index+0x37/0x40 [] ? batadv_hard_if_event+0xee/0x3a0 [batman_adv] [] ? register_netdevice_notifier+0x81/0x1a0 [...] This can be avoided by checking if two devices are each others parent and stopping the check in this situation. Fixes: b7eddd0b3950 ("batman-adv: prevent using any virtual device created on batman-adv as hard-interface") Signed-off-by: Andrew Lunn [sven@narfation.org: rewritten description, extracted fix] Signed-off-by: Sven Eckelmann Signed-off-by: Marek Lindner Signed-off-by: Antonio Quartulli Signed-off-by: Kamal Mostafa --- net/batman-adv/hard-interface.c | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+) diff --git a/net/batman-adv/hard-interface.c b/net/batman-adv/hard-interface.c index f4a15d2..3edf7b0 100644 --- a/net/batman-adv/hard-interface.c +++ b/net/batman-adv/hard-interface.c @@ -75,6 +75,28 @@ out: } /** + * batadv_mutual_parents - check if two devices are each others parent + * @dev1: 1st net_device + * @dev2: 2nd net_device + * + * veth devices come in pairs and each is the parent of the other! + * + * Return: true if the devices are each others parent, otherwise false + */ +static bool batadv_mutual_parents(const struct net_device *dev1, + const struct net_device *dev2) +{ + int dev1_parent_iflink = dev_get_iflink(dev1); + int dev2_parent_iflink = dev_get_iflink(dev2); + + if (!dev1_parent_iflink || !dev2_parent_iflink) + return false; + + return (dev1_parent_iflink == dev2->ifindex) && + (dev2_parent_iflink == dev1->ifindex); +} + +/** * batadv_is_on_batman_iface - check if a device is a batman iface descendant * @net_dev: the device to check * @@ -107,6 +129,9 @@ static bool batadv_is_on_batman_iface(const struct net_device *net_dev) if (WARN(!parent_dev, "Cannot find parent device")) return false; + if (batadv_mutual_parents(net_dev, parent_dev)) + return false; + ret = batadv_is_on_batman_iface(parent_dev); return ret; -- 2.7.0