Commit 56b08fdc authored Feb 27, 2015 by Arvid Brodin Committed by David S. Miller Mar 01, 2015

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: 51f3c605 ("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>

parent 187d6785

net/hsr/hsr_device.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -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);

net/hsr/hsr_main.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -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;
		}

net/hsr/hsr_slave.c

+7 −3

Original line number	Diff line number	Diff line
		@@ -181,8 +181,10 @@ void hsr_del_port(struct hsr_port *port)
		list_del_rcu(&port->port_list);

		if (port != master) {
		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();

		if (port != master)
		dev_put(port->dev);
		}

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