bridge: vlan: use proper rcu for the vlgrp member

The bridge and port's vlgrp member is already used in RCU way, currently
we rely on the fact that it cannot disappear while the port exists but
that is error-prone and we might miss places with improper locking
(either RCU or RTNL must be held to walk the vlan_list). So make it
official and use RCU for vlgrp to catch offenders. Introduce proper vlgrp
accessors and use them consistently throughout the code.

Signed-off-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
Reviewed-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/bridge/br_device.c

@@ -56,7 +56,7 @@ netdev_tx_t br_dev_xmit(struct sk_buff *skb, struct net_device *dev)
 	skb_reset_mac_header(skb);
 	skb_pull(skb, ETH_HLEN);
 
-	if (!br_allowed_ingress(br, br_vlan_group(br), skb, &vid))
+	if (!br_allowed_ingress(br, br_vlan_group_rcu(br), skb, &vid))
 		goto out;
 
 	if (is_broadcast_ether_addr(dest))

net/bridge/br_forward.c

@@ -32,7 +32,7 @@ static inline int should_deliver(const struct net_bridge_port *p,
 {
 	struct net_bridge_vlan_group *vg;
 
-	vg = nbp_vlan_group(p);
+	vg = nbp_vlan_group_rcu(p);
 	return ((p->flags & BR_HAIRPIN_MODE) || skb->dev != p->dev) &&
 		br_allowed_egress(vg, skb) && p->state == BR_STATE_FORWARDING;
 }
@@ -80,7 +80,7 @@ static void __br_deliver(const struct net_bridge_port *to, struct sk_buff *skb)
 {
 	struct net_bridge_vlan_group *vg;
 
-	vg = nbp_vlan_group(to);
+	vg = nbp_vlan_group_rcu(to);
 	skb = br_handle_vlan(to->br, vg, skb);
 	if (!skb)
 		return;
@@ -112,7 +112,7 @@ static void __br_forward(const struct net_bridge_port *to, struct sk_buff *skb)
 		return;
 	}
 
-	vg = nbp_vlan_group(to);
+	vg = nbp_vlan_group_rcu(to);
 	skb = br_handle_vlan(to->br, vg, skb);
 	if (!skb)
 		return;

net/bridge/br_input.c

@@ -44,7 +44,7 @@ static int br_pass_frame_up(struct sk_buff *skb)
 	brstats->rx_bytes += skb->len;
 	u64_stats_update_end(&brstats->syncp);
 
-	vg = br_vlan_group(br);
+	vg = br_vlan_group_rcu(br);
 	/* Bridge is just like any other port.  Make sure the
 	 * packet is allowed except in promisc modue when someone
 	 * may be running packet capture.
@@ -140,7 +140,7 @@ int br_handle_frame_finish(struct net *net, struct sock *sk, struct sk_buff *skb
 	if (!p || p->state == BR_STATE_DISABLED)
 		goto drop;
 
-	if (!br_allowed_ingress(p->br, nbp_vlan_group(p), skb, &vid))
+	if (!br_allowed_ingress(p->br, nbp_vlan_group_rcu(p), skb, &vid))
 		goto out;
 
 	/* insert into forwarding database after filtering to avoid spoofing */

net/bridge/br_netlink.c

@@ -102,10 +102,10 @@ static size_t br_get_link_af_size_filtered(const struct net_device *dev,
 	rcu_read_lock();
 	if (br_port_exists(dev)) {
 		p = br_port_get_rcu(dev);
-		vg = nbp_vlan_group(p);
+		vg = nbp_vlan_group_rcu(p);
 	} else if (dev->priv_flags & IFF_EBRIDGE) {
 		br = netdev_priv(dev);
-		vg = br_vlan_group(br);
+		vg = br_vlan_group_rcu(br);
 	}
 	num_vlan_infos = br_get_num_vlan_infos(vg, filter_mask);
 	rcu_read_unlock();

net/bridge/br_private.h

@@ -132,6 +132,7 @@ struct net_bridge_vlan_group {
 	struct list_head		vlan_list;
 	u16				num_vlans;
 	u16				pvid;
+	struct rcu_head			rcu;
 };
 
 struct net_bridge_fdb_entry
@@ -229,7 +230,7 @@ struct net_bridge_port
 	struct netpoll			*np;
 #endif
 #ifdef CONFIG_BRIDGE_VLAN_FILTERING
-	struct net_bridge_vlan_group	*vlgrp;
+	struct net_bridge_vlan_group	__rcu *vlgrp;
 #endif
 };
 
@@ -337,7 +338,7 @@ struct net_bridge
 	struct kobject			*ifobj;
 	u32				auto_cnt;
 #ifdef CONFIG_BRIDGE_VLAN_FILTERING
-	struct net_bridge_vlan_group	*vlgrp;
+	struct net_bridge_vlan_group	__rcu *vlgrp;
 	u8				vlan_enabled;
 	__be16				vlan_proto;
 	u16				default_pvid;
@@ -700,13 +701,25 @@ int nbp_get_num_vlan_infos(struct net_bridge_port *p, u32 filter_mask);
 static inline struct net_bridge_vlan_group *br_vlan_group(
 					const struct net_bridge *br)
 {
-	return br->vlgrp;
+	return rtnl_dereference(br->vlgrp);
 }
 
 static inline struct net_bridge_vlan_group *nbp_vlan_group(
 					const struct net_bridge_port *p)
 {
-	return p->vlgrp;
+	return rtnl_dereference(p->vlgrp);
+}
+
+static inline struct net_bridge_vlan_group *br_vlan_group_rcu(
+					const struct net_bridge *br)
+{
+	return rcu_dereference(br->vlgrp);
+}
+
+static inline struct net_bridge_vlan_group *nbp_vlan_group_rcu(
+					const struct net_bridge_port *p)
+{
+	return rcu_dereference(p->vlgrp);
 }
 
 /* Since bridge now depends on 8021Q module, but the time bridge sees the
@@ -853,6 +866,19 @@ static inline struct net_bridge_vlan_group *nbp_vlan_group(
 {
 	return NULL;
 }
+
+static inline struct net_bridge_vlan_group *br_vlan_group_rcu(
+					const struct net_bridge *br)
+{
+	return NULL;
+}
+
+static inline struct net_bridge_vlan_group *nbp_vlan_group_rcu(
+					const struct net_bridge_port *p)
+{
+	return NULL;
+}
+
 #endif
 
 struct nf_br_ops {