[PATCH 1/2] wext: fix message delay/ordering
From: Johannes Berg <hidden>
Date: 2016-01-27 12:41:34
Also in:
linux-wireless
Subsystem:
802.11 (including cfg80211/nl80211), the rest · Maintainers:
Johannes Berg, Linus Torvalds
From: Johannes Berg <redacted>
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-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Reported-by: Beniamino Galvani <redacted>
Signed-off-by: Johannes Berg <redacted>
---
net/wireless/wext-core.c | 49 ++++++++++++++++++++++++++++++++++++++----------
1 file changed, 39 insertions(+), 10 deletions(-)
diff --git a/net/wireless/wext-core.c b/net/wireless/wext-core.c
index c8717c1d082e..5f429637efff 100644
--- a/net/wireless/wext-core.c
+++ b/net/wireless/wext-core.c@@ -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);
@@ -360,6 +393,11 @@ static struct pernet_operations wext_pernet_ops = { static int __init wireless_nlevent_init(void) { + int err = register_netdevice_notifier(&wext_netdev_notifier); + + if (err) + return err; + return register_pernet_subsys(&wext_pernet_ops); }
@@ -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); - }