batman-adv: Make bat_priv->primary_if an rcu protected pointer

The rcu protected macros rcu_dereference() and rcu_assign_pointer()
for the bat_priv->primary_if need to be used, as well as spin/rcu locking.

Otherwise we might end up using a primary_if pointer pointing to already
freed memory.

Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>
Signed-off-by: Sven Eckelmann <sven@narfation.org>

1 files changed, 19 insertions, 14 deletions

diff --git a/net/batman-adv/gateway_client.c b/net/batman-adv/gateway_client.c
index af128eff2edf..65f39530799d 100644
--- a/net/batman-adv/gateway_client.c
+++ b/net/batman-adv/gateway_client.c
@@ -439,30 +439,32 @@ int gw_client_seq_print_text(struct seq_file *seq, void *offset)
 {
         struct net_device *net_dev = (struct net_device *)seq->private;
         struct bat_priv *bat_priv = netdev_priv(net_dev);
+        struct hard_iface *primary_if;
         struct gw_node *gw_node;
         struct hlist_node *node;
-        int gw_count = 0;
+        int gw_count = 0, ret = 0;
 
-        if (!bat_priv->primary_if) {
-
-                return seq_printf(seq, "BATMAN mesh %s disabled - please "
-                                  "specify interfaces to enable it\n",
-                                  net_dev->name);
+        primary_if = primary_if_get_selected(bat_priv);
+        if (!primary_if) {
+                ret = seq_printf(seq, "BATMAN mesh %s disabled - please "
+                                 "specify interfaces to enable it\n",
+                                 net_dev->name);
+                goto out;
         }
 
-        if (bat_priv->primary_if->if_status != IF_ACTIVE) {
-
-                return seq_printf(seq, "BATMAN mesh %s disabled - "
-                                       "primary interface not active\n",
-                                       net_dev->name);
+        if (primary_if->if_status != IF_ACTIVE) {
+                ret = seq_printf(seq, "BATMAN mesh %s disabled - "
+                                 "primary interface not active\n",
+                                 net_dev->name);
+                goto out;
         }
 
         seq_printf(seq, "      %-12s (%s/%i) %17s [%10s]: gw_class ... "
                    "[B.A.T.M.A.N. adv %s%s, MainIF/MAC: %s/%pM (%s)]\n",
                    "Gateway", "#", TQ_MAX_VALUE, "Nexthop",
                    "outgoingIF", SOURCE_VERSION, REVISION_VERSION_STR,
-                   bat_priv->primary_if->net_dev->name,
-                   bat_priv->primary_if->net_dev->dev_addr, net_dev->name);
+                   primary_if->net_dev->name,
+                   primary_if->net_dev->dev_addr, net_dev->name);
 
         rcu_read_lock();
         hlist_for_each_entry_rcu(gw_node, node, &bat_priv->gw_list, list) {
@@ -480,7 +482,10 @@ int gw_client_seq_print_text(struct seq_file *seq, void *offset)
         if (gw_count == 0)
                 seq_printf(seq, "No gateways in range ...\n");
 
-        return 0;
+out:
+        if (primary_if)
+                hardif_free_ref(primary_if);
+        return ret;
 }
 
 int gw_is_target(struct bat_priv *bat_priv, struct sk_buff *skb)