[PATCH net] net/hsr: Fix NULL pointer dereference and refcnt bugs when deleting a HSR interface.

[Arvid Brodin <arvid.brodin@alten.se>]

How to repeat:

$ sudo ip link add hsr0 type hsr slave1 <if1> slave2 <if2>
$ sudo ip link del hsr0
BUG: unable to handle kernel NULL pointer dereference at 0000000000000018
IP: [<ffffffff8187f495>] hsr_del_port+0x15/0xa0
etc...

Reported-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Fixes: 51f3c605318b056a ("net/hsr: Move slave init to hsr_slave.c.")
Signed-off-by: Arvid Brodin <arvid.brodin@alten.se>
---
 net/hsr/hsr_device.c |  3 +++
 net/hsr/hsr_main.c   |  4 ++++
 net/hsr/hsr_slave.c  | 10 +++++++---
 3 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/net/hsr/hsr_device.c b/net/hsr/hsr_device.c
index a138d75..44d2746 100644
--- a/net/hsr/hsr_device.c
+++ b/net/hsr/hsr_device.c
@@ -359,8 +359,11 @@ static void hsr_dev_destroy(struct net_device *hsr_dev)
 	struct hsr_port *port;
 
 	hsr = netdev_priv(hsr_dev);
+
+	rtnl_lock();
 	hsr_for_each_port(hsr, port)
 		hsr_del_port(port);
+	rtnl_unlock();
 
 	del_timer_sync(&hsr->prune_timer);
 	del_timer_sync(&hsr->announce_timer);
diff --git a/net/hsr/hsr_main.c b/net/hsr/hsr_main.c
index 779d28b..cd37d00 100644
--- a/net/hsr/hsr_main.c
+++ b/net/hsr/hsr_main.c
@@ -36,6 +36,10 @@ static int hsr_netdev_notify(struct notifier_block *nb, unsigned long event,
 			return NOTIFY_DONE;	/* Not an HSR device */
 		hsr = netdev_priv(dev);
 		port = hsr_port_get_hsr(hsr, HSR_PT_MASTER);
+		if (port == NULL) {
+			/* Resend of notification concerning removed device? */
+			return NOTIFY_DONE;
+		}
 	} else {
 		hsr = port->hsr;
 	}
diff --git a/net/hsr/hsr_slave.c b/net/hsr/hsr_slave.c
index a348dcb..7d37366 100644
--- a/net/hsr/hsr_slave.c
+++ b/net/hsr/hsr_slave.c
@@ -181,8 +181,10 @@ void hsr_del_port(struct hsr_port *port)
 	list_del_rcu(&port->port_list);
 
 	if (port != master) {
-		netdev_update_features(master->dev);
-		dev_set_mtu(master->dev, hsr_get_max_mtu(hsr));
+		if (master != NULL) {
+			netdev_update_features(master->dev);
+			dev_set_mtu(master->dev, hsr_get_max_mtu(hsr));
+		}
 		netdev_rx_handler_unregister(port->dev);
 		dev_set_promiscuity(port->dev, -1);
 	}
@@ -192,5 +194,7 @@ void hsr_del_port(struct hsr_port *port)
 	 */
 
 	synchronize_rcu();
-	dev_put(port->dev);
+
+	if (port != master)
+		dev_put(port->dev);
 }
-- 
2.0.4

-- 
Arvid Brodin | Consultant (Linux)
ALTEN | Knarrarnäsgatan 7 | SE-164 40 Kista | Sweden
arvid.brodin@alten.se | www.alten.se/en/