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wext: fix message delay/ordering

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Beniamino reported that he was getting an RTM_NEWLINK message for a
given interface, after the RTM_DELLINK for it. It turns out that the
message is a wireless extensions message, which was sent because the
interface had been connected and disconnection while it was deleted
caused a wext message.

For its netlink messages, wext uses RTM_NEWLINK, but the message is
without all the regular rtnetlink attributes, so "ip monitor link"
prints just rudimentary information:

5: wlan1: <BROADCAST,MULTICAST> mtu 1500 qdisc mq state DOWN group default
    link/ether 02:00:00:00:01:00 brd ff:ff:ff:ff:ff:ff
Deleted 5: wlan1: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default
    link/ether 02:00:00:00:01:00 brd ff:ff:ff:ff:ff:ff
5: wlan1: <BROADCAST,MULTICAST,UP>
    link/ether
(from my hwsim reproduction)

This can cause userspace to get confused since it doesn't expect an
RTM_NEWLINK message after RTM_DELLINK.

The reason for this is that wext schedules a worker to send out the
messages, and the scheduling delay can cause the messages to get out
to userspace in different order.

To fix this, have wext register a netdevice notifier and flush out
any pending messages when netdevice state changes. This fixes any
ordering whenever the original message wasn't sent by a notifier
itself.

Cc: stable@vger.kernel.org
Reported-by: Beniamino Galvani <bgalvani@redhat.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
This commit is contained in:
Johannes Berg 2016-01-27 12:37:52 +01:00
parent 6736fde967
commit 8bf862739a
1 changed files with 40 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

51
net/wireless/wext-core.c
View File

@ -342,6 +342,39 @@ static const int compat_event_type_size[] = {
/* IW event code */
static void wireless_nlevent_flush(void)
{
struct sk_buff *skb;
struct net *net;
ASSERT_RTNL();
for_each_net(net) {
while ((skb = skb_dequeue(&net->wext_nlevents)))
rtnl_notify(skb, net, 0, RTNLGRP_LINK, NULL,
GFP_KERNEL);
}
}
static int wext_netdev_notifier_call(struct notifier_block *nb,
unsigned long state, void *ptr)
{
/*
* When a netdev changes state in any way, flush all pending messages
* to avoid them going out in a strange order, e.g. RTM_NEWLINK after
* RTM_DELLINK, or with IFF_UP after without IFF_UP during dev_close()
* or similar - all of which could otherwise happen due to delays from
* schedule_work().
*/
wireless_nlevent_flush();
return NOTIFY_OK;
}
static struct notifier_block wext_netdev_notifier = {
.notifier_call = wext_netdev_notifier_call,
};
static int __net_init wext_pernet_init(struct net *net)
{
skb_queue_head_init(&net->wext_nlevents);
@ -360,7 +393,12 @@ static struct pernet_operations wext_pernet_ops = {
static int __init wireless_nlevent_init(void)
{
return register_pernet_subsys(&wext_pernet_ops);
int err = register_pernet_subsys(&wext_pernet_ops);
if (err)
return err;
return register_netdevice_notifier(&wext_netdev_notifier);
}
subsys_initcall(wireless_nlevent_init);
@ -368,17 +406,8 @@ subsys_initcall(wireless_nlevent_init);
/* Process events generated by the wireless layer or the driver. */
static void wireless_nlevent_process(struct work_struct *work)
{
struct sk_buff *skb;
struct net *net;
rtnl_lock();
for_each_net(net) {
while ((skb = skb_dequeue(&net->wext_nlevents)))
rtnl_notify(skb, net, 0, RTNLGRP_LINK, NULL,
GFP_KERNEL);
}
wireless_nlevent_flush();
rtnl_unlock();
}