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

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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>
This commit is contained in:
Patrick McHardy 2008-01-20 17:25:14 -08:00 committed by David S. Miller
parent d4782c323d
commit 68365458a4
2 changed files with 5 additions and 14 deletions
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14
drivers/net/veth.c
View file

@ -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);

5
net/core/rtnetlink.c
View file

@ -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);