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, 93 insertions, 101 deletions

diff --git a/net/batman-adv/routing.c b/net/batman-adv/routing.c
index f212abe..b7d43ca 100644
--- a/net/batman-adv/routing.c
+++ b/net/batman-adv/routing.c
@@ -87,18 +87,20 @@ static void update_route(struct bat_priv *bat_priv,
 			 struct neigh_node *neigh_node,
 			 unsigned char *hna_buff, int hna_buff_len)
 {
-	struct neigh_node *neigh_node_tmp;
+	struct neigh_node *curr_router;
+
+	curr_router = orig_node_get_router(orig_node);
 
 	/* route deleted */
-	if ((orig_node->router) && (!neigh_node)) {
+	if ((curr_router) && (!neigh_node)) {
 
 		bat_dbg(DBG_ROUTES, bat_priv, "Deleting route towards: %pM\n",
 			orig_node->orig);
 		hna_global_del_orig(bat_priv, orig_node,
 				    "originator timed out");
 
-		/* route added */
-	} else if ((!orig_node->router) && (neigh_node)) {
+	/* route added */
+	} else if ((!curr_router) && (neigh_node)) {
 
 		bat_dbg(DBG_ROUTES, bat_priv,
 			"Adding route towards: %pM (via %pM)\n",
@@ -106,21 +108,29 @@ static void update_route(struct bat_priv *bat_priv,
 		hna_global_add_orig(bat_priv, orig_node,
 				    hna_buff, hna_buff_len);
 
-		/* route changed */
+	/* route changed */
 	} else {
 		bat_dbg(DBG_ROUTES, bat_priv,
 			"Changing route towards: %pM "
 			"(now via %pM - was via %pM)\n",
 			orig_node->orig, neigh_node->addr,
-			orig_node->router->addr);
+			curr_router->addr);
 	}
 
+	if (curr_router)
+		neigh_node_free_ref(curr_router);
+
+	/* increase refcount of new best neighbor */
 	if (neigh_node && !atomic_inc_not_zero(&neigh_node->refcount))
 		neigh_node = NULL;
-	neigh_node_tmp = orig_node->router;
-	orig_node->router = neigh_node;
-	if (neigh_node_tmp)
-		neigh_node_free_ref(neigh_node_tmp);
+
+	spin_lock_bh(&orig_node->neigh_list_lock);
+	rcu_assign_pointer(orig_node->router, neigh_node);
+	spin_unlock_bh(&orig_node->neigh_list_lock);
+
+	/* decrease refcount of previous best neighbor */
+	if (curr_router)
+		neigh_node_free_ref(curr_router);
 }
 
 
@@ -128,16 +138,23 @@ void update_routes(struct bat_priv *bat_priv, struct orig_node *orig_node,
 		   struct neigh_node *neigh_node, unsigned char *hna_buff,
 		   int hna_buff_len)
 {
+	struct neigh_node *router = NULL;
 
 	if (!orig_node)
-		return;
+		goto out;
+
+	router = orig_node_get_router(orig_node);
 
-	if (orig_node->router != neigh_node)
+	if (router != neigh_node)
 		update_route(bat_priv, orig_node, neigh_node,
 			     hna_buff, hna_buff_len);
 	/* may be just HNA changed */
 	else
 		update_HNA(bat_priv, orig_node, hna_buff, hna_buff_len);
+
+out:
+	if (router)
+		neigh_node_free_ref(router);
 }
 
 static int is_bidirectional_neigh(struct orig_node *orig_node,
@@ -288,8 +305,8 @@ static void bonding_candidate_add(struct orig_node *orig_node,
 				  struct neigh_node *neigh_node)
 {
 	struct hlist_node *node;
-	struct neigh_node *tmp_neigh_node;
-	uint8_t best_tq, interference_candidate = 0;
+	struct neigh_node *tmp_neigh_node, *router = NULL;
+	uint8_t interference_candidate = 0;
 
 	spin_lock_bh(&orig_node->neigh_list_lock);
 
@@ -298,13 +315,12 @@ static void bonding_candidate_add(struct orig_node *orig_node,
 			 neigh_node->orig_node->primary_addr))
 		goto candidate_del;
 
-	if (!orig_node->router)
+	router = orig_node_get_router(orig_node);
+	if (!router)
 		goto candidate_del;
 
-	best_tq = orig_node->router->tq_avg;
-
 	/* ... and is good enough to be considered */
-	if (neigh_node->tq_avg < best_tq - BONDING_TQ_THRESHOLD)
+	if (neigh_node->tq_avg < router->tq_avg - BONDING_TQ_THRESHOLD)
 		goto candidate_del;
 
 	/**
@@ -350,7 +366,9 @@ candidate_del:
 
 out:
 	spin_unlock_bh(&orig_node->neigh_list_lock);
-	return;
+
+	if (router)
+		neigh_node_free_ref(router);
 }
 
 /* copy primary address for bonding */
@@ -373,6 +391,7 @@ static void update_orig(struct bat_priv *bat_priv,
 			char is_duplicate)
 {
 	struct neigh_node *neigh_node = NULL, *tmp_neigh_node = NULL;
+	struct neigh_node *router = NULL;
 	struct orig_node *orig_node_tmp;
 	struct hlist_node *node;
 	int tmp_hna_buff_len;
@@ -441,19 +460,18 @@ static void update_orig(struct bat_priv *bat_priv,
 
 	/* if this neighbor already is our next hop there is nothing
 	 * to change */
-	if (orig_node->router == neigh_node)
+	router = orig_node_get_router(orig_node);
+	if (router == neigh_node)
 		goto update_hna;
 
 	/* if this neighbor does not offer a better TQ we won't consider it */
-	if ((orig_node->router) &&
-	    (orig_node->router->tq_avg > neigh_node->tq_avg))
+	if (router && (router->tq_avg > neigh_node->tq_avg))
 		goto update_hna;
 
 	/* if the TQ is the same and the link not more symetric we
 	 * won't consider it either */
-	if ((orig_node->router) &&
-	     (neigh_node->tq_avg == orig_node->router->tq_avg)) {
-		orig_node_tmp = orig_node->router->orig_node;
+	if (router && (neigh_node->tq_avg == router->tq_avg)) {
+		orig_node_tmp = router->orig_node;
 		spin_lock_bh(&orig_node_tmp->ogm_cnt_lock);
 		bcast_own_sum_orig =
 			orig_node_tmp->bcast_own_sum[if_incoming->if_num];
@@ -474,7 +492,7 @@ static void update_orig(struct bat_priv *bat_priv,
 	goto update_gw;
 
 update_hna:
-	update_routes(bat_priv, orig_node, orig_node->router,
+	update_routes(bat_priv, orig_node, router,
 		      hna_buff, tmp_hna_buff_len);
 
 update_gw:
@@ -496,6 +514,8 @@ unlock:
 out:
 	if (neigh_node)
 		neigh_node_free_ref(neigh_node);
+	if (router)
+		neigh_node_free_ref(router);
 }
 
 /* checks whether the host restarted and is in the protection time.
@@ -603,6 +623,8 @@ void receive_bat_packet(struct ethhdr *ethhdr,
 	struct bat_priv *bat_priv = netdev_priv(if_incoming->soft_iface);
 	struct hard_iface *hard_iface;
 	struct orig_node *orig_neigh_node, *orig_node;
+	struct neigh_node *router = NULL, *router_router = NULL;
+	struct neigh_node *orig_neigh_router = NULL;
 	char has_directlink_flag;
 	char is_my_addr = 0, is_my_orig = 0, is_my_oldorig = 0;
 	char is_broadcast = 0, is_bidirectional, is_single_hop_neigh;
@@ -747,14 +769,15 @@ void receive_bat_packet(struct ethhdr *ethhdr,
 		goto out;
 	}
 
+	router = orig_node_get_router(orig_node);
+	if (router)
+		router_router = orig_node_get_router(router->orig_node);
+
 	/* avoid temporary routing loops */
-	if ((orig_node->router) &&
-	    (orig_node->router->orig_node->router) &&
-	    (compare_eth(orig_node->router->addr,
-			 batman_packet->prev_sender)) &&
+	if (router && router_router &&
+	    (compare_eth(router->addr, batman_packet->prev_sender)) &&
 	    !(compare_eth(batman_packet->orig, batman_packet->prev_sender)) &&
-	    (compare_eth(orig_node->router->addr,
-			 orig_node->router->orig_node->router->addr))) {
+	    (compare_eth(router->addr, router_router->addr))) {
 		bat_dbg(DBG_BATMAN, bat_priv,
 			"Drop packet: ignoring all rebroadcast packets that "
 			"may make me loop (sender: %pM)\n", ethhdr->h_source);
@@ -769,9 +792,11 @@ void receive_bat_packet(struct ethhdr *ethhdr,
 	if (!orig_neigh_node)
 		goto out;
 
+	orig_neigh_router = orig_node_get_router(orig_neigh_node);
+
 	/* drop packet if sender is not a direct neighbor and if we
 	 * don't route towards it */
-	if (!is_single_hop_neigh && (!orig_neigh_node->router)) {
+	if (!is_single_hop_neigh && (!orig_neigh_router)) {
 		bat_dbg(DBG_BATMAN, bat_priv,
 			"Drop packet: OGM via unknown neighbor!\n");
 		goto out_neigh;
@@ -825,6 +850,13 @@ out_neigh:
 	if ((orig_neigh_node) && (!is_single_hop_neigh))
 		orig_node_free_ref(orig_neigh_node);
 out:
+	if (router)
+		neigh_node_free_ref(router);
+	if (router_router)
+		neigh_node_free_ref(router_router);
+	if (orig_neigh_router)
+		neigh_node_free_ref(orig_neigh_router);
+
 	orig_node_free_ref(orig_node);
 }
 
@@ -869,7 +901,7 @@ static int recv_my_icmp_packet(struct bat_priv *bat_priv,
 			       struct sk_buff *skb, size_t icmp_len)
 {
 	struct orig_node *orig_node = NULL;
-	struct neigh_node *neigh_node = NULL;
+	struct neigh_node *router = NULL;
 	struct icmp_packet_rr *icmp_packet;
 	int ret = NET_RX_DROP;
 
@@ -886,23 +918,13 @@ static int recv_my_icmp_packet(struct bat_priv *bat_priv,
 
 	/* answer echo request (ping) */
 	/* get routing information */
-	rcu_read_lock();
 	orig_node = orig_hash_find(bat_priv, icmp_packet->orig);
-
 	if (!orig_node)
-		goto unlock;
-
-	neigh_node = orig_node->router;
-
-	if (!neigh_node)
-		goto unlock;
-
-	if (!atomic_inc_not_zero(&neigh_node->refcount)) {
-		neigh_node = NULL;
-		goto unlock;
-	}
+		goto out;
 
-	rcu_read_unlock();
+	router = orig_node_get_router(orig_node);
+	if (!router)
+		goto out;
 
 	/* create a copy of the skb, if needed, to modify it. */
 	if (skb_cow(skb, sizeof(struct ethhdr)) < 0)
@@ -916,15 +938,12 @@ static int recv_my_icmp_packet(struct bat_priv *bat_priv,
 	icmp_packet->msg_type = ECHO_REPLY;
 	icmp_packet->ttl = TTL;
 
-	send_skb_packet(skb, neigh_node->if_incoming, neigh_node->addr);
+	send_skb_packet(skb, router->if_incoming, router->addr);
 	ret = NET_RX_SUCCESS;
-	goto out;
 
-unlock:
-	rcu_read_unlock();
 out:
-	if (neigh_node)
-		neigh_node_free_ref(neigh_node);
+	if (router)
+		neigh_node_free_ref(router);
 	if (orig_node)
 		orig_node_free_ref(orig_node);
 	return ret;
@@ -934,7 +953,7 @@ static int recv_icmp_ttl_exceeded(struct bat_priv *bat_priv,
 				  struct sk_buff *skb)
 {
 	struct orig_node *orig_node = NULL;
-	struct neigh_node *neigh_node = NULL;
+	struct neigh_node *router = NULL;
 	struct icmp_packet *icmp_packet;
 	int ret = NET_RX_DROP;
 
@@ -952,23 +971,13 @@ static int recv_icmp_ttl_exceeded(struct bat_priv *bat_priv,
 		goto out;
 
 	/* get routing information */
-	rcu_read_lock();
 	orig_node = orig_hash_find(bat_priv, icmp_packet->orig);
-
 	if (!orig_node)
-		goto unlock;
-
-	neigh_node = orig_node->router;
-
-	if (!neigh_node)
-		goto unlock;
-
-	if (!atomic_inc_not_zero(&neigh_node->refcount)) {
-		neigh_node = NULL;
-		goto unlock;
-	}
+		goto out;
 
-	rcu_read_unlock();
+	router = orig_node_get_router(orig_node);
+	if (!router)
+		goto out;
 
 	/* create a copy of the skb, if needed, to modify it. */
 	if (skb_cow(skb, sizeof(struct ethhdr)) < 0)
@@ -982,15 +991,12 @@ static int recv_icmp_ttl_exceeded(struct bat_priv *bat_priv,
 	icmp_packet->msg_type = TTL_EXCEEDED;
 	icmp_packet->ttl = TTL;
 
-	send_skb_packet(skb, neigh_node->if_incoming, neigh_node->addr);
+	send_skb_packet(skb, router->if_incoming, router->addr);
 	ret = NET_RX_SUCCESS;
-	goto out;
 
-unlock:
-	rcu_read_unlock();
 out:
-	if (neigh_node)
-		neigh_node_free_ref(neigh_node);
+	if (router)
+		neigh_node_free_ref(router);
 	if (orig_node)
 		orig_node_free_ref(orig_node);
 	return ret;
@@ -1003,7 +1009,7 @@ int recv_icmp_packet(struct sk_buff *skb, struct hard_iface *recv_if)
 	struct icmp_packet_rr *icmp_packet;
 	struct ethhdr *ethhdr;
 	struct orig_node *orig_node = NULL;
-	struct neigh_node *neigh_node = NULL;
+	struct neigh_node *router = NULL;
 	int hdr_size = sizeof(struct icmp_packet);
 	int ret = NET_RX_DROP;
 
@@ -1050,23 +1056,13 @@ int recv_icmp_packet(struct sk_buff *skb, struct hard_iface *recv_if)
 		return recv_icmp_ttl_exceeded(bat_priv, skb);
 
 	/* get routing information */
-	rcu_read_lock();
 	orig_node = orig_hash_find(bat_priv, icmp_packet->dst);
-
 	if (!orig_node)
-		goto unlock;
-
-	neigh_node = orig_node->router;
-
-	if (!neigh_node)
-		goto unlock;
-
-	if (!atomic_inc_not_zero(&neigh_node->refcount)) {
-		neigh_node = NULL;
-		goto unlock;
-	}
+		goto out;
 
-	rcu_read_unlock();
+	router = orig_node_get_router(orig_node);
+	if (!router)
+		goto out;
 
 	/* create a copy of the skb, if needed, to modify it. */
 	if (skb_cow(skb, sizeof(struct ethhdr)) < 0)
@@ -1078,15 +1074,12 @@ int recv_icmp_packet(struct sk_buff *skb, struct hard_iface *recv_if)
 	icmp_packet->ttl--;
 
 	/* route it */
-	send_skb_packet(skb, neigh_node->if_incoming, neigh_node->addr);
+	send_skb_packet(skb, router->if_incoming, router->addr);
 	ret = NET_RX_SUCCESS;
-	goto out;
 
-unlock:
-	rcu_read_unlock();
 out:
-	if (neigh_node)
-		neigh_node_free_ref(neigh_node);
+	if (router)
+		neigh_node_free_ref(router);
 	if (orig_node)
 		orig_node_free_ref(orig_node);
 	return ret;
@@ -1208,7 +1201,8 @@ struct neigh_node *find_router(struct bat_priv *bat_priv,
 	if (!orig_node)
 		return NULL;
 
-	if (!orig_node->router)
+	router = orig_node_get_router(orig_node);
+	if (!router)
 		return NULL;
 
 	/* without bonding, the first node should
@@ -1217,9 +1211,8 @@ struct neigh_node *find_router(struct bat_priv *bat_priv,
 
 	rcu_read_lock();
 	/* select default router to output */
-	router = orig_node->router;
-	router_orig = orig_node->router->orig_node;
-	if (!router_orig || !atomic_inc_not_zero(&router->refcount)) {
+	router_orig = router->orig_node;
+	if (!router_orig) {
 		rcu_read_unlock();
 		return NULL;
 	}
@@ -1251,7 +1244,6 @@ struct neigh_node *find_router(struct bat_priv *bat_priv,
 	if (atomic_read(&primary_orig_node->bond_candidates) < 2)
 		goto return_router;
 
-
 	/* all nodes between should choose a candidate which
 	 * is is not on the interface where the packet came
 	 * in. */