Merge branch 'mpls'

Robert Shearman says:

====================
mpls: ABI changes for security and correctness

V2:
 - don't treat loopback interfaces specially by enabling mpls by
   default

These changes make mpls not be enabled by default on all
interfaces when in use for security, along with ensuring that a label
not valid as an outgoing label can be added in mpls routes.

This series contains three ABI/behaviour-affecting changes which have
been split out from "[PATCH net-next v4 0/6] mpls: Behaviour-changing
improvements" without any further modification. These changes need to
be considered for 4.1 otherwise we'll be stuck with the current
behaviour/ABI forever.
====================
Reviewed-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/networking/mpls-sysctl.txt

@@ -18,3 +18,12 @@ platform_labels - INTEGER
 
 	Possible values: 0 - 1048575
 	Default: 0
+
+conf/<interface>/input - BOOL
+	Control whether packets can be input on this interface.
+
+	If disabled, packets will be discarded without further
+	processing.
+
+	0 - disabled (default)
+	not 0 - enabled

include/linux/netdevice.h

@@ -60,6 +60,7 @@ struct phy_device;
 struct wireless_dev;
 /* 802.15.4 specific */
 struct wpan_dev;
+struct mpls_dev;
 
 void netdev_set_default_ethtool_ops(struct net_device *dev,
 				    const struct ethtool_ops *ops);
@@ -1627,6 +1628,9 @@ struct net_device {
 	void			*ax25_ptr;
 	struct wireless_dev	*ieee80211_ptr;
 	struct wpan_dev		*ieee802154_ptr;
+#if IS_ENABLED(CONFIG_MPLS_ROUTING)
+	struct mpls_dev __rcu	*mpls_ptr;
+#endif
 
 /*
  * Cache lines mostly used on receive path (including eth_type_trans())

net/mpls/af_mpls.c

@@ -53,6 +53,11 @@ static struct mpls_route *mpls_route_input_rcu(struct net *net, unsigned index)
 	return rt;
 }
 
+static inline struct mpls_dev *mpls_dev_get(const struct net_device *dev)
+{
+	return rcu_dereference_rtnl(dev->mpls_ptr);
+}
+
 static bool mpls_output_possible(const struct net_device *dev)
 {
 	return dev && (dev->flags & IFF_UP) && netif_carrier_ok(dev);
@@ -136,6 +141,7 @@ static int mpls_forward(struct sk_buff *skb, struct net_device *dev,
 	struct mpls_route *rt;
 	struct mpls_entry_decoded dec;
 	struct net_device *out_dev;
+	struct mpls_dev *mdev;
 	unsigned int hh_len;
 	unsigned int new_header_size;
 	unsigned int mtu;
@@ -143,6 +149,10 @@ static int mpls_forward(struct sk_buff *skb, struct net_device *dev,
 
 	/* Careful this entire function runs inside of an rcu critical section */
 
+	mdev = mpls_dev_get(dev);
+	if (!mdev || !mdev->input_enabled)
+		goto drop;
+
 	if (skb->pkt_type != PACKET_HOST)
 		goto drop;
 
@@ -352,9 +362,9 @@ static int mpls_route_add(struct mpls_route_config *cfg)
 	if (!dev)
 		goto errout;
 
-	/* For now just support ethernet devices */
+	/* Ensure this is a supported device */
 	err = -EINVAL;
-	if ((dev->type != ARPHRD_ETHER) && (dev->type != ARPHRD_LOOPBACK))
+	if (!mpls_dev_get(dev))
 		goto errout;
 
 	err = -EINVAL;
@@ -428,10 +438,89 @@ static int mpls_route_del(struct mpls_route_config *cfg)
 	return err;
 }
 
+#define MPLS_PERDEV_SYSCTL_OFFSET(field)	\
+	(&((struct mpls_dev *)0)->field)
+
+static const struct ctl_table mpls_dev_table[] = {
+	{
+		.procname	= "input",
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+		.data		= MPLS_PERDEV_SYSCTL_OFFSET(input_enabled),
+	},
+	{ }
+};
+
+static int mpls_dev_sysctl_register(struct net_device *dev,
+				    struct mpls_dev *mdev)
+{
+	char path[sizeof("net/mpls/conf/") + IFNAMSIZ];
+	struct ctl_table *table;
+	int i;
+
+	table = kmemdup(&mpls_dev_table, sizeof(mpls_dev_table), GFP_KERNEL);
+	if (!table)
+		goto out;
+
+	/* Table data contains only offsets relative to the base of
+	 * the mdev at this point, so make them absolute.
+	 */
+	for (i = 0; i < ARRAY_SIZE(mpls_dev_table); i++)
+		table[i].data = (char *)mdev + (uintptr_t)table[i].data;
+
+	snprintf(path, sizeof(path), "net/mpls/conf/%s", dev->name);
+
+	mdev->sysctl = register_net_sysctl(dev_net(dev), path, table);
+	if (!mdev->sysctl)
+		goto free;
+
+	return 0;
+
+free:
+	kfree(table);
+out:
+	return -ENOBUFS;
+}
+
+static void mpls_dev_sysctl_unregister(struct mpls_dev *mdev)
+{
+	struct ctl_table *table;
+
+	table = mdev->sysctl->ctl_table_arg;
+	unregister_net_sysctl_table(mdev->sysctl);
+	kfree(table);
+}
+
+static struct mpls_dev *mpls_add_dev(struct net_device *dev)
+{
+	struct mpls_dev *mdev;
+	int err = -ENOMEM;
+
+	ASSERT_RTNL();
+
+	mdev = kzalloc(sizeof(*mdev), GFP_KERNEL);
+	if (!mdev)
+		return ERR_PTR(err);
+
+	err = mpls_dev_sysctl_register(dev, mdev);
+	if (err)
+		goto free;
+
+	rcu_assign_pointer(dev->mpls_ptr, mdev);
+
+	return mdev;
+
+free:
+	kfree(mdev);
+	return ERR_PTR(err);
+}
+
 static void mpls_ifdown(struct net_device *dev)
 {
 	struct mpls_route __rcu **platform_label;
 	struct net *net = dev_net(dev);
+	struct mpls_dev *mdev;
 	unsigned index;
 
 	platform_label = rtnl_dereference(net->mpls.platform_label);
@@ -443,14 +532,35 @@ static void mpls_ifdown(struct net_device *dev)
 			continue;
 		rt->rt_dev = NULL;
 	}
+
+	mdev = mpls_dev_get(dev);
+	if (!mdev)
+		return;
+
+	mpls_dev_sysctl_unregister(mdev);
+
+	RCU_INIT_POINTER(dev->mpls_ptr, NULL);
+
+	kfree(mdev);
 }
 
 static int mpls_dev_notify(struct notifier_block *this, unsigned long event,
 			   void *ptr)
 {
 	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
+	struct mpls_dev *mdev;
 
 	switch(event) {
+	case NETDEV_REGISTER:
+		/* For now just support ethernet devices */
+		if ((dev->type == ARPHRD_ETHER) ||
+		    (dev->type == ARPHRD_LOOPBACK)) {
+			mdev = mpls_add_dev(dev);
+			if (IS_ERR(mdev))
+				return notifier_from_errno(PTR_ERR(mdev));
+		}
+		break;
+
 	case NETDEV_UNREGISTER:
 		mpls_ifdown(dev);
 		break;
@@ -536,6 +646,15 @@ int nla_get_labels(const struct nlattr *nla,
 		if ((dec.bos != bos) || dec.ttl || dec.tc)
 			return -EINVAL;
 
+		switch (dec.label) {
+		case LABEL_IMPLICIT_NULL:
+			/* RFC3032: This is a label that an LSR may
+			 * assign and distribute, but which never
+			 * actually appears in the encapsulation.
+			 */
+			return -EINVAL;
+		}
+
 		label[i] = dec.label;
 	}
 	*labels = nla_labels;
@@ -912,7 +1031,7 @@ static int mpls_platform_labels(struct ctl_table *table, int write,
 	return ret;
 }
 
-static struct ctl_table mpls_table[] = {
+static const struct ctl_table mpls_table[] = {
 	{
 		.procname	= "platform_labels",
 		.data		= NULL,

net/mpls/internal.h

@@ -22,6 +22,12 @@ struct mpls_entry_decoded {
 	u8 bos;
 };
 
+struct mpls_dev {
+	int			input_enabled;
+
+	struct ctl_table_header *sysctl;
+};
+
 struct sk_buff;
 
 static inline struct mpls_shim_hdr *mpls_hdr(const struct sk_buff *skb)