Commit 68365458 authored Jan 20, 2008 by Patrick McHardy Committed by David S. Miller Jan 20, 2008

[NET]: rtnl_link: fix use-after-free



When unregistering the rtnl_link_ops, all existing devices using
the ops are destroyed. With nested devices this may lead to a
use-after-free despite the use of for_each_netdev_safe() in case
the upper device is next in the device list and is destroyed
by the NETDEV_UNREGISTER notifier.

The easy fix is to restart scanning the device list after removing
a device. Alternatively we could add new devices to the front of
the list to avoid having dependant devices follow the device they
depend on. A third option would be to only restart scanning if
dev->iflink of the next device matches dev->ifindex of the current
one. For now this seems like the safest solution.

With this patch, the veth rtnl_link_ops unregistration can use
rtnl_link_unregister() directly since it now also handles destruction
of multiple devices at once.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent d4782c32

drivers/net/veth.c

+1 −13

Original line number	Diff line number	Diff line
		@@ -459,19 +459,7 @@ static __init int veth_init(void)

		static __exit void veth_exit(void)
		{
		struct veth_priv priv, next;

		rtnl_lock();
		/*
		* cannot trust __rtnl_link_unregister() to unregister all
		* devices, as each ->dellink call will remove two devices
		* from the list at once.
		*/
		list_for_each_entry_safe(priv, next, &veth_list, list)
		veth_dellink(priv->dev);

		__rtnl_link_unregister(&veth_link_ops);
		rtnl_unlock();
		rtnl_link_unregister(&veth_link_ops);
		}

		module_init(veth_init);

net/core/rtnetlink.c

+4 −1

Original line number	Diff line number	Diff line
		@@ -308,9 +308,12 @@ void __rtnl_link_unregister(struct rtnl_link_ops *ops)
		struct net *net;

		for_each_net(net) {
		restart:
		for_each_netdev_safe(net, dev, n) {
		if (dev->rtnl_link_ops == ops)
		if (dev->rtnl_link_ops == ops) {
		ops->dellink(dev);
		goto restart;
		}
		}
		}
		list_del(&ops->list);