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

To repeat:

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

Bug description:

As part of the hsr master device destruction, hsr_del_port() is called for each of
the hsr ports. At each such call, the master device is updated regarding features
and mtu. When the master device is freed before the slave interfaces, master will
be NULL in hsr_del_port(), which led to a NULL pointer dereference.

Additionally, dev_put() was called on the master device itself in hsr_del_port(),
causing a refcnt error.

A third bug in the same code path was that the rtnl lock was not taken before
hsr_del_port() was called as part of hsr_dev_destroy().

The reporter (Nicolas Dichtel) also said: "hsr_netdev_notify() supposes that the
port will always be available when the notification is for an hsr interface. It's
wrong. For example, netdev_wait_allrefs() may resend NETDEV_UNREGISTER.". As a
precaution against this, a check for port == NULL was added in hsr_dev_notify().

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>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/hsr/hsr_device.c b/net/hsr/hsr_device.c
index a138d75751df2fb46219168c01fd1bf5cce24d43..44d27469ae55982d1895021b79ba76a85c1324a8 100644 (file)
--- 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 779d28b65417a6e62b687d8f5ea36d6be285f417..cd37d0011b424824fd113ffd4da59f36c116996a 100644 (file)
--- 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 a348dcbcd683e6858248bf17ee73e7e24d08b4ea..7d37366cc695554ae243f940869b46d26f598b65 100644 (file)
--- 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);
 }