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: <IRQ> [<ffffffff8107888e>] ? rcu_dump_cpu_stacks+0x7e/0xd0 [<ffffffff8107b420>] ? rcu_check_callbacks+0x3f0/0x6b0 [<ffffffff8107d667>] ? hrtimer_run_queues+0x47/0x180 [<ffffffff8107cf9d>] ? update_process_times+0x2d/0x50 [<ffffffff810873fb>] ? tick_handle_periodic+0x1b/0x60 [<ffffffff810290ae>] ? smp_trace_apic_timer_interrupt+0x5e/0x90 [<ffffffff813bbae2>] ? apic_timer_interrupt+0x82/0x90 <EOI> [<ffffffff812c3fd7>] ? __dev_get_by_index+0x37/0x40 [<ffffffffa0031f3e>] ? batadv_hard_if_event+0xee/0x3a0 [batman_adv] [<ffffffff812c5801>] ? register_netdevice_notifier+0x81/0x1a0 [...]
Signed-off-by: Sven Eckelmann sven@narfation.org Cc: Jetmir Gigollai jetmir_gigollaj@web.de --- compat-include/linux/netdevice.h | 6 ------ net/batman-adv/hard-interface.c | 42 ---------------------------------------- 2 files changed, 48 deletions(-)
diff --git a/compat-include/linux/netdevice.h b/compat-include/linux/netdevice.h index f19f624..0e4fcc8 100644 --- a/compat-include/linux/netdevice.h +++ b/compat-include/linux/netdevice.h @@ -111,10 +111,4 @@ static inline int batadv_netdev_set_master(struct net_device *slave,
#endif /* < KERNEL_VERSION(3, 17, 0) */
-#if LINUX_VERSION_CODE < KERNEL_VERSION(4, 1, 0) - -#define dev_get_iflink(_net_dev) ((_net_dev)->iflink) - -#endif /* < KERNEL_VERSION(3, 19, 0) */ - #endif /* _NET_BATMAN_ADV_COMPAT_LINUX_NETDEVICE_H_ */ diff --git a/net/batman-adv/hard-interface.c b/net/batman-adv/hard-interface.c index bef9147..0c2643d 100644 --- a/net/batman-adv/hard-interface.c +++ b/net/batman-adv/hard-interface.c @@ -75,44 +75,6 @@ out: return hard_iface; }
-/** - * batadv_is_on_batman_iface - check if a device is a batman iface descendant - * @net_dev: the device to check - * - * If the user creates any virtual device on top of a batman-adv interface, it - * is important to prevent this new interface to be used to create a new mesh - * network (this behaviour would lead to a batman-over-batman configuration). - * This function recursively checks all the fathers of the device passed as - * argument looking for a batman-adv soft interface. - * - * Return: true if the device is descendant of a batman-adv mesh interface (or - * if it is a batman-adv interface itself), false otherwise - */ -static bool batadv_is_on_batman_iface(const struct net_device *net_dev) -{ - struct net_device *parent_dev; - bool ret; - - /* check if this is a batman-adv mesh interface */ - if (batadv_softif_is_valid(net_dev)) - return true; - - /* no more parents..stop recursion */ - if (dev_get_iflink(net_dev) == 0 || - dev_get_iflink(net_dev) == net_dev->ifindex) - return false; - - /* recurse over the parent device */ - parent_dev = __dev_get_by_index(&init_net, dev_get_iflink(net_dev)); - /* if we got a NULL parent_dev there is something broken.. */ - if (WARN(!parent_dev, "Cannot find parent device")) - return false; - - ret = batadv_is_on_batman_iface(parent_dev); - - return ret; -} - static int batadv_is_valid_iface(const struct net_device *net_dev) { if (net_dev->flags & IFF_LOOPBACK) @@ -124,10 +86,6 @@ static int batadv_is_valid_iface(const struct net_device *net_dev) if (net_dev->addr_len != ETH_ALEN) return 0;
- /* no batman over batman */ - if (batadv_is_on_batman_iface(net_dev)) - return 0; - return 1; }