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>

4 files changed, 141 insertions, 3 deletions

diff --git a/Documentation/networking/mpls-sysctl.txt b/Documentation/networking/mpls-sysctl.txt
index 639ddf0ece9b..9ed15f86c17c 100644
--- a/Documentation/networking/mpls-sysctl.txt
+++ b/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
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index bcbde799ec69..dae106a3a998 100644
--- a/include/linux/netdevice.h
+++ b/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())
diff --git a/net/mpls/af_mpls.c b/net/mpls/af_mpls.c
index db8a2ea6d4de..954810c76a86 100644
--- a/net/mpls/af_mpls.c
+++ b/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 @@ errout:
         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,
diff --git a/net/mpls/internal.h b/net/mpls/internal.h
index fb6de92052c4..693877d69606 100644
--- a/net/mpls/internal.h
+++ b/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)