batman-adv: Make orig_node->router an rcu protected pointer

The rcu protected macros rcu_dereference() and rcu_assign_pointer()
for the orig_node->router need to be used, as well as spin/rcu locking.
Otherwise we might end up using a router pointer pointing to already
freed memory.

Therefore this commit introduces the safe getter method
orig_node_get_router().

Signed-off-by: Linus Lüssing <linus.luessing@web.de>
Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>
Signed-off-by: Sven Eckelmann <sven@narfation.org>

1 files changed, 48 insertions, 32 deletions

diff --git a/net/batman-adv/gateway_client.c b/net/batman-adv/gateway_client.c
index 879ac1594869..42a8a7ba06e6 100644
--- a/net/batman-adv/gateway_client.c
+++ b/net/batman-adv/gateway_client.c
@@ -98,6 +98,7 @@ void gw_election(struct bat_priv *bat_priv)
 {
         struct hlist_node *node;
         struct gw_node *gw_node, *curr_gw, *curr_gw_tmp = NULL;
+        struct neigh_node *router;
         uint8_t max_tq = 0;
         uint32_t max_gw_factor = 0, tmp_gw_factor = 0;
         int down, up;
@@ -133,10 +134,11 @@ void gw_election(struct bat_priv *bat_priv)
         }
 
         hlist_for_each_entry_rcu(gw_node, node, &bat_priv->gw_list, list) {
-                if (!gw_node->orig_node->router)
+                if (gw_node->deleted)
                         continue;
 
-                if (gw_node->deleted)
+                router = orig_node_get_router(gw_node->orig_node);
+                if (!router)
                         continue;
 
                 switch (atomic_read(&bat_priv->gw_sel_class)) {
@@ -144,15 +146,14 @@ void gw_election(struct bat_priv *bat_priv)
                         gw_bandwidth_to_kbit(gw_node->orig_node->gw_flags,
                                              &down, &up);
 
-                        tmp_gw_factor = (gw_node->orig_node->router->tq_avg *
-                                         gw_node->orig_node->router->tq_avg *
+                        tmp_gw_factor = (router->tq_avg * router->tq_avg *
                                          down * 100 * 100) /
                                          (TQ_LOCAL_WINDOW_SIZE *
                                          TQ_LOCAL_WINDOW_SIZE * 64);
 
                         if ((tmp_gw_factor > max_gw_factor) ||
                             ((tmp_gw_factor == max_gw_factor) &&
-                             (gw_node->orig_node->router->tq_avg > max_tq)))
+                             (router->tq_avg > max_tq)))
                                 curr_gw_tmp = gw_node;
                         break;
 
@@ -164,19 +165,25 @@ void gw_election(struct bat_priv *bat_priv)
                           *     soon as a better gateway appears which has
                           *     $routing_class more tq points)
                           **/
-                        if (gw_node->orig_node->router->tq_avg > max_tq)
+                        if (router->tq_avg > max_tq)
                                 curr_gw_tmp = gw_node;
                         break;
                 }
 
-                if (gw_node->orig_node->router->tq_avg > max_tq)
-                        max_tq = gw_node->orig_node->router->tq_avg;
+                if (router->tq_avg > max_tq)
+                        max_tq = router->tq_avg;
 
                 if (tmp_gw_factor > max_gw_factor)
                         max_gw_factor = tmp_gw_factor;
+
+                neigh_node_free_ref(router);
         }
 
         if (curr_gw != curr_gw_tmp) {
+                router = orig_node_get_router(curr_gw_tmp->orig_node);
+                if (!router)
+                        goto out;
+
                 if ((curr_gw) && (!curr_gw_tmp))
                         bat_dbg(DBG_BATMAN, bat_priv,
                                 "Removing selected gateway - "
@@ -187,45 +194,47 @@ void gw_election(struct bat_priv *bat_priv)
                                 "(gw_flags: %i, tq: %i)\n",
                                 curr_gw_tmp->orig_node->orig,
                                 curr_gw_tmp->orig_node->gw_flags,
-                                curr_gw_tmp->orig_node->router->tq_avg);
+                                router->tq_avg);
                 else
                         bat_dbg(DBG_BATMAN, bat_priv,
                                 "Changing route to gateway %pM "
                                 "(gw_flags: %i, tq: %i)\n",
                                 curr_gw_tmp->orig_node->orig,
                                 curr_gw_tmp->orig_node->gw_flags,
-                                curr_gw_tmp->orig_node->router->tq_avg);
+                                router->tq_avg);
 
+                neigh_node_free_ref(router);
                 gw_select(bat_priv, curr_gw_tmp);
         }
 
+out:
         rcu_read_unlock();
 }
 
 void gw_check_election(struct bat_priv *bat_priv, struct orig_node *orig_node)
 {
         struct orig_node *curr_gw_orig;
+        struct neigh_node *router_gw = NULL, *router_orig = NULL;
         uint8_t gw_tq_avg, orig_tq_avg;
 
         curr_gw_orig = gw_get_selected(bat_priv);
         if (!curr_gw_orig)
                 goto deselect;
 
-        rcu_read_lock();
-        if (!curr_gw_orig->router)
-                goto deselect_rcu;
+        router_gw = orig_node_get_router(curr_gw_orig);
+        if (!router_gw)
+                goto deselect;
 
         /* this node already is the gateway */
         if (curr_gw_orig == orig_node)
-                goto out_rcu;
-
-        if (!orig_node->router)
-                goto out_rcu;
+                goto out;
 
-        gw_tq_avg = curr_gw_orig->router->tq_avg;
-        rcu_read_unlock();
+        router_orig = orig_node_get_router(orig_node);
+        if (!router_orig)
+                goto out;
 
-        orig_tq_avg = orig_node->router->tq_avg;
+        gw_tq_avg = router_gw->tq_avg;
+        orig_tq_avg = router_orig->tq_avg;
 
         /* the TQ value has to be better */
         if (orig_tq_avg < gw_tq_avg)
@@ -243,18 +252,16 @@ void gw_check_election(struct bat_priv *bat_priv, struct orig_node *orig_node)
                 "Restarting gateway selection: better gateway found (tq curr: "
                 "%i, tq new: %i)\n",
                 gw_tq_avg, orig_tq_avg);
-        goto deselect;
 
-out_rcu:
-        rcu_read_unlock();
-        goto out;
-deselect_rcu:
-        rcu_read_unlock();
 deselect:
         gw_deselect(bat_priv);
 out:
         if (curr_gw_orig)
                 orig_node_free_ref(curr_gw_orig);
+        if (router_gw)
+                neigh_node_free_ref(router_gw);
+        if (router_orig)
+                neigh_node_free_ref(router_orig);
 
         return;
 }
@@ -362,23 +369,30 @@ void gw_node_purge(struct bat_priv *bat_priv)
         spin_unlock_bh(&bat_priv->gw_list_lock);
 }
 
+/**
+ * fails if orig_node has no router
+ */
 static int _write_buffer_text(struct bat_priv *bat_priv,
                               struct seq_file *seq, struct gw_node *gw_node)
 {
         struct gw_node *curr_gw;
-        int down, up, ret;
+        struct neigh_node *router;
+        int down, up, ret = -1;
 
         gw_bandwidth_to_kbit(gw_node->orig_node->gw_flags, &down, &up);
 
+        router = orig_node_get_router(gw_node->orig_node);
+        if (!router)
+                goto out;
+
         rcu_read_lock();
         curr_gw = rcu_dereference(bat_priv->curr_gw);
 
         ret = seq_printf(seq, "%s %pM (%3i) %pM [%10s]: %3i - %i%s/%i%s\n",
                        (curr_gw == gw_node ? "=>" : "  "),
                        gw_node->orig_node->orig,
-                       gw_node->orig_node->router->tq_avg,
-                       gw_node->orig_node->router->addr,
-                       gw_node->orig_node->router->if_incoming->net_dev->name,
+                       router->tq_avg, router->addr,
+                       router->if_incoming->net_dev->name,
                        gw_node->orig_node->gw_flags,
                        (down > 2048 ? down / 1024 : down),
                        (down > 2048 ? "MBit" : "KBit"),
@@ -386,6 +400,8 @@ static int _write_buffer_text(struct bat_priv *bat_priv,
                        (up > 2048 ? "MBit" : "KBit"));
 
         rcu_read_unlock();
+        neigh_node_free_ref(router);
+out:
         return ret;
 }
 
@@ -423,10 +439,10 @@ int gw_client_seq_print_text(struct seq_file *seq, void *offset)
                 if (gw_node->deleted)
                         continue;
 
-                if (!gw_node->orig_node->router)
+                /* fails if orig_node has no router */
+                if (_write_buffer_text(bat_priv, seq, gw_node) < 0)
                         continue;
 
-                _write_buffer_text(bat_priv, seq, gw_node);
                 gw_count++;
         }
         rcu_read_unlock();