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[PATCH 4.4 24/50] wext: fix message delay/ordering

From Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Newsgroups linux.kernel
Subject [PATCH 4.4 24/50] wext: fix message delay/ordering
Date 2016-03-14 19:20 +0100
Message-ID <rcFg0-7qA-63@gated-at.bofh.it> (permalink)
References <rcEWC-73F-7@gated-at.bofh.it>
Organization linux.* mail to news gateway

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4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Johannes Berg <johannes.berg@intel.com>

commit 8bf862739a7786ae72409220914df960a0aa80d8 upstream.

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.

Reported-by: Beniamino Galvani <bgalvani@redhat.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 net/wireless/wext-core.c |   51 ++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 40 insertions(+), 11 deletions(-)

--- 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);
@@ -360,7 +393,12 @@ static struct pernet_operations wext_per
 
 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();
 }

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[PATCH 4.4 00/50] 4.4.6-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-14 19:10 +0100
  [PATCH 4.4 11/50] KVM: MMU: fix reserved bit check for ept=0/CR0.WP=0/CR4.SMEP=1/EFER.NX=0 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-14 19:10 +0100
  [PATCH 4.4 47/50] MIPS: smp.c: Fix uninitialised temp_foreign_map Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-14 19:10 +0100
  [PATCH 4.4 10/50] KVM: MMU: fix ept=0/pte.u=1/pte.w=0/CR0.WP=0/CR4.SMEP=1/EFER.NX=0 combo Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-14 19:10 +0100
  [PATCH 4.4 14/50] tracing: Fix check for cpu online when event is disabled Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-14 19:10 +0100
  [PATCH 4.4 39/50] Revert "drm/radeon/pm: adjust display configuration after powerstate" Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-14 19:20 +0100
  [PATCH 4.4 30/50] mac80211: minstrel_ht: set default tx aggregation timeout to 0 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-14 19:20 +0100
  [PATCH 4.4 21/50] ASoC: wm8958: Fix enum ctl accesses in a wrong type Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-14 19:20 +0100
  [PATCH 4.4 27/50] iwlwifi: mvm: inc pending frames counter also when txing non-sta Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-14 19:20 +0100
  [PATCH 4.4 43/50] userfaultfd: dont block on the last VM updates at exit time Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-14 19:20 +0100
  [PATCH 4.4 32/50] mac80211: check PN correctly for GCMP-encrypted fragmented MPDUs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-14 19:20 +0100
  [PATCH 4.4 26/50] can: gs_usb: fixed disconnect bug by removing erroneous use of kfree() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-14 19:20 +0100
  [PATCH 4.4 40/50] powerpc: Fix dedotify for binutils >= 2.26 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-14 19:20 +0100
  [PATCH 4.4 28/50] mac80211: minstrel: Change expected throughput unit back to Kbps Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-14 19:20 +0100
  [PATCH 4.4 33/50] mac80211: Fix Public Action frame RX in AP mode Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-14 19:20 +0100
  [PATCH 4.4 41/50] powerpc/powernv: Add a kmsg_dumper that flushes console output on panic Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-14 19:20 +0100
  [PATCH 4.4 29/50] mac80211: fix use of uninitialised values in RX aggregation Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-14 19:20 +0100
  [PATCH 4.4 22/50] ovl: ignore lower entries when checking purity of non-directory entries Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-14 19:20 +0100
  [PATCH 4.4 04/50] ARM: OMAP2+: hwmod: Introduce ti,no-idle dt property Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-14 19:20 +0100
  [PATCH 4.4 45/50] ovl: fix getcwd() failure after unsuccessful rmdir Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-14 19:20 +0100
  [PATCH 4.4 23/50] ovl: fix working on distributed fs as lower layer Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-14 19:20 +0100
  [PATCH 4.4 03/50] ARM: dts: dra7: do not gate cpsw clock due to errata i877 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-14 19:20 +0100
  [PATCH 4.4 02/50] ARM: mvebu: fix overlap of Crypto SRAM with PCIe memory window Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-14 19:20 +0100
  [PATCH 4.4 24/50] wext: fix message delay/ordering Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-14 19:20 +0100
  [PATCH 4.4 06/50] kvm: cap halt polling at exactly halt_poll_ns Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-14 19:20 +0100
  [PATCH 4.4 44/50] ovl: copy new uid/gid into overlayfs runtime inode Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-14 19:20 +0100
  [PATCH 4.4 35/50] x86/mm: Fix slow_virt_to_phys() for X86_PAE again Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-14 19:20 +0100
  [PATCH 4.4 42/50] powerpc/powernv: Fix OPAL_CONSOLE_FLUSH prototype and usages Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-14 19:20 +0100
  [PATCH 4.4 34/50] gpu: ipu-v3: Do not bail out on missing optional port nodes Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-14 19:20 +0100
  [PATCH 4.4 15/50] dmaengine: at_xdmac: fix residue computation Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-14 19:30 +0100
  [PATCH 4.4 25/50] cfg80211/wext: fix message ordering Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-14 19:30 +0100
  [PATCH 4.4 20/50] ASoC: wm8994: Fix enum ctl accesses in a wrong type Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-14 19:30 +0100
  [PATCH 4.4 19/50] ASoC: samsung: Use IRQ safe spin lock calls Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-14 19:30 +0100
  Re: [PATCH 4.4 00/50] 4.4.6-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2016-03-15 00:20 +0100
    Re: [PATCH 4.4 00/50] 4.4.6-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-16 16:50 +0100
  Re: [PATCH 4.4 00/50] 4.4.6-stable review Guenter Roeck <linux@roeck-us.net> - 2016-03-15 03:40 +0100
    Re: [PATCH 4.4 00/50] 4.4.6-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-16 16:50 +0100

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