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 {

net/bridge/br_vlan.c

@@ -54,9 +54,9 @@ static void __vlan_add_flags(struct net_bridge_vlan *v, u16 flags)
 	struct net_bridge_vlan_group *vg;
 
 	if (br_vlan_is_master(v))
-		vg = v->br->vlgrp;
+		vg = br_vlan_group(v->br);
 	else
-		vg = v->port->vlgrp;
+		vg = nbp_vlan_group(v->port);
 
 	if (flags & BRIDGE_VLAN_INFO_PVID)
 		__vlan_add_pvid(vg, v->vid);
@@ -91,11 +91,16 @@ static int __vlan_vid_add(struct net_device *dev, struct net_bridge *br,
 
 static void __vlan_add_list(struct net_bridge_vlan *v)
 {
+	struct net_bridge_vlan_group *vg;
 	struct list_head *headp, *hpos;
 	struct net_bridge_vlan *vent;
 
-	headp = br_vlan_is_master(v) ? &v->br->vlgrp->vlan_list :
-				       &v->port->vlgrp->vlan_list;
+	if (br_vlan_is_master(v))
+		vg = br_vlan_group(v->br);
+	else
+		vg = nbp_vlan_group(v->port);
+
+	headp = &vg->vlan_list;
 	list_for_each_prev(hpos, headp) {
 		vent = list_entry(hpos, struct net_bridge_vlan, vlist);
 		if (v->vid < vent->vid)
@@ -137,14 +142,16 @@ static int __vlan_vid_del(struct net_device *dev, struct net_bridge *br,
  */
 static struct net_bridge_vlan *br_vlan_get_master(struct net_bridge *br, u16 vid)
 {
+	struct net_bridge_vlan_group *vg;
 	struct net_bridge_vlan *masterv;
 
-	masterv = br_vlan_find(br->vlgrp, vid);
+	vg = br_vlan_group(br);
+	masterv = br_vlan_find(vg, vid);
 	if (!masterv) {
 		/* missing global ctx, create it now */
 		if (br_vlan_add(br, vid, 0))
 			return NULL;
-		masterv = br_vlan_find(br->vlgrp, vid);
+		masterv = br_vlan_find(vg, vid);
 		if (WARN_ON(!masterv))
 			return NULL;
 	}
@@ -155,11 +162,14 @@ static struct net_bridge_vlan *br_vlan_get_master(struct net_bridge *br, u16 vid
 
 static void br_vlan_put_master(struct net_bridge_vlan *masterv)
 {
+	struct net_bridge_vlan_group *vg;
+
 	if (!br_vlan_is_master(masterv))
 		return;
 
+	vg = br_vlan_group(masterv->br);
 	if (atomic_dec_and_test(&masterv->refcnt)) {
-		rhashtable_remove_fast(&masterv->br->vlgrp->vlan_hash,
+		rhashtable_remove_fast(&vg->vlan_hash,
 				       &masterv->vnode, br_vlan_rht_params);
 		__vlan_del_list(masterv);
 		kfree_rcu(masterv, rcu);
@@ -189,12 +199,12 @@ static int __vlan_add(struct net_bridge_vlan *v, u16 flags)
 	if (br_vlan_is_master(v)) {
 		br = v->br;
 		dev = br->dev;
-		vg = br->vlgrp;
+		vg = br_vlan_group(br);
 	} else {
 		p = v->port;
 		br = p->br;
 		dev = p->dev;
-		vg = p->vlgrp;
+		vg = nbp_vlan_group(p);
 	}
 
 	if (p) {
@@ -266,10 +276,10 @@ static int __vlan_del(struct net_bridge_vlan *v)
 	int err = 0;
 
 	if (br_vlan_is_master(v)) {
-		vg = v->br->vlgrp;
+		vg = br_vlan_group(v->br);
 	} else {
 		p = v->port;
-		vg = v->port->vlgrp;
+		vg = nbp_vlan_group(v->port);
 		masterv = v->brvlan;
 	}
 
@@ -305,7 +315,7 @@ static void __vlan_flush(struct net_bridge_vlan_group *vlgrp)
 	list_for_each_entry_safe(vlan, tmp, &vlgrp->vlan_list, vlist)
 		__vlan_del(vlan);
 	rhashtable_destroy(&vlgrp->vlan_hash);
-	kfree(vlgrp);
+	kfree_rcu(vlgrp, rcu);
 }
 
 struct sk_buff *br_handle_vlan(struct net_bridge *br,
@@ -467,7 +477,7 @@ bool br_should_learn(struct net_bridge_port *p, struct sk_buff *skb, u16 *vid)
 	if (!br->vlan_enabled)
 		return true;
 
-	vg = p->vlgrp;
+	vg = nbp_vlan_group(p);
 	if (!vg || !vg->num_vlans)
 		return false;
 
@@ -493,12 +503,14 @@ bool br_should_learn(struct net_bridge_port *p, struct sk_buff *skb, u16 *vid)
  */
 int br_vlan_add(struct net_bridge *br, u16 vid, u16 flags)
 {
+	struct net_bridge_vlan_group *vg;
 	struct net_bridge_vlan *vlan;
 	int ret;
 
 	ASSERT_RTNL();
 
-	vlan = br_vlan_find(br->vlgrp, vid);
+	vg = br_vlan_group(br);
+	vlan = br_vlan_find(vg, vid);
 	if (vlan) {
 		if (!br_vlan_is_brentry(vlan)) {
 			/* Trying to change flags of non-existent bridge vlan */
@@ -513,7 +525,7 @@ int br_vlan_add(struct net_bridge *br, u16 vid, u16 flags)
 			}
 			atomic_inc(&vlan->refcnt);
 			vlan->flags |= BRIDGE_VLAN_INFO_BRENTRY;
-			br->vlgrp->num_vlans++;
+			vg->num_vlans++;
 		}
 		__vlan_add_flags(vlan, flags);
 		return 0;
@@ -541,11 +553,13 @@ int br_vlan_add(struct net_bridge *br, u16 vid, u16 flags)
  */
 int br_vlan_delete(struct net_bridge *br, u16 vid)
 {
+	struct net_bridge_vlan_group *vg;
 	struct net_bridge_vlan *v;
 
 	ASSERT_RTNL();
 
-	v = br_vlan_find(br->vlgrp, vid);
+	vg = br_vlan_group(br);
+	v = br_vlan_find(vg, vid);
 	if (!v || !br_vlan_is_brentry(v))
 		return -ENOENT;
 
@@ -626,6 +640,7 @@ int __br_vlan_set_proto(struct net_bridge *br, __be16 proto)
 	int err = 0;
 	struct net_bridge_port *p;
 	struct net_bridge_vlan *vlan;
+	struct net_bridge_vlan_group *vg;
 	__be16 oldproto;
 
 	if (br->vlan_proto == proto)
@@ -633,7 +648,8 @@ int __br_vlan_set_proto(struct net_bridge *br, __be16 proto)
 
 	/* Add VLANs for the new proto to the device filter. */
 	list_for_each_entry(p, &br->port_list, list) {
-		list_for_each_entry(vlan, &p->vlgrp->vlan_list, vlist) {
+		vg = nbp_vlan_group(p);
+		list_for_each_entry(vlan, &vg->vlan_list, vlist) {
 			err = vlan_vid_add(p->dev, proto, vlan->vid);
 			if (err)
 				goto err_filt;
@@ -647,19 +663,23 @@ int __br_vlan_set_proto(struct net_bridge *br, __be16 proto)
 	br_recalculate_fwd_mask(br);
 
 	/* Delete VLANs for the old proto from the device filter. */
-	list_for_each_entry(p, &br->port_list, list)
-		list_for_each_entry(vlan, &p->vlgrp->vlan_list, vlist)
+	list_for_each_entry(p, &br->port_list, list) {
+		vg = nbp_vlan_group(p);
+		list_for_each_entry(vlan, &vg->vlan_list, vlist)
 			vlan_vid_del(p->dev, oldproto, vlan->vid);
+	}
 
 	return 0;
 
 err_filt:
-	list_for_each_entry_continue_reverse(vlan, &p->vlgrp->vlan_list, vlist)
+	list_for_each_entry_continue_reverse(vlan, &vg->vlan_list, vlist)
 		vlan_vid_del(p->dev, proto, vlan->vid);
 
-	list_for_each_entry_continue_reverse(p, &br->port_list, list)
-		list_for_each_entry(vlan, &p->vlgrp->vlan_list, vlist)
+	list_for_each_entry_continue_reverse(p, &br->port_list, list) {
+		vg = nbp_vlan_group(p);
+		list_for_each_entry(vlan, &vg->vlan_list, vlist)
 			vlan_vid_del(p->dev, proto, vlan->vid);
+	}
 
 	return err;
 }
@@ -703,11 +723,11 @@ static void br_vlan_disable_default_pvid(struct net_bridge *br)
 	/* Disable default_pvid on all ports where it is still
 	 * configured.
 	 */
-	if (vlan_default_pvid(br->vlgrp, pvid))
+	if (vlan_default_pvid(br_vlan_group(br), pvid))
 		br_vlan_delete(br, pvid);
 
 	list_for_each_entry(p, &br->port_list, list) {
-		if (vlan_default_pvid(p->vlgrp, pvid))
+		if (vlan_default_pvid(nbp_vlan_group(p), pvid))
 			nbp_vlan_delete(p, pvid);
 	}
 
@@ -717,6 +737,7 @@ static void br_vlan_disable_default_pvid(struct net_bridge *br)
 int __br_vlan_set_default_pvid(struct net_bridge *br, u16 pvid)
 {
 	const struct net_bridge_vlan *pvent;
+	struct net_bridge_vlan_group *vg;
 	struct net_bridge_port *p;
 	u16 old_pvid;
 	int err = 0;
@@ -737,8 +758,9 @@ int __br_vlan_set_default_pvid(struct net_bridge *br, u16 pvid)
 	/* Update default_pvid config only if we do not conflict with
 	 * user configuration.
 	 */
-	pvent = br_vlan_find(br->vlgrp, pvid);
-	if ((!old_pvid || vlan_default_pvid(br->vlgrp, old_pvid)) &&
+	vg = br_vlan_group(br);
+	pvent = br_vlan_find(vg, pvid);
+	if ((!old_pvid || vlan_default_pvid(vg, old_pvid)) &&
 	    (!pvent || !br_vlan_should_use(pvent))) {
 		err = br_vlan_add(br, pvid,
 				  BRIDGE_VLAN_INFO_PVID |
@@ -754,9 +776,10 @@ int __br_vlan_set_default_pvid(struct net_bridge *br, u16 pvid)
 		/* Update default_pvid config only if we do not conflict with
 		 * user configuration.
 		 */
+		vg = nbp_vlan_group(p);
 		if ((old_pvid &&
-		     !vlan_default_pvid(p->vlgrp, old_pvid)) ||
-		    br_vlan_find(p->vlgrp, pvid))
+		     !vlan_default_pvid(vg, old_pvid)) ||
+		    br_vlan_find(vg, pvid))
 			continue;
 
 		err = nbp_vlan_add(p, pvid,
@@ -825,17 +848,19 @@ int br_vlan_set_default_pvid(struct net_bridge *br, unsigned long val)
 
 int br_vlan_init(struct net_bridge *br)
 {
+	struct net_bridge_vlan_group *vg;
 	int ret = -ENOMEM;
 
-	br->vlgrp = kzalloc(sizeof(struct net_bridge_vlan_group), GFP_KERNEL);
-	if (!br->vlgrp)
+	vg = kzalloc(sizeof(*vg), GFP_KERNEL);
+	if (!vg)
 		goto out;
-	ret = rhashtable_init(&br->vlgrp->vlan_hash, &br_vlan_rht_params);
+	ret = rhashtable_init(&vg->vlan_hash, &br_vlan_rht_params);
 	if (ret)
 		goto err_rhtbl;
-	INIT_LIST_HEAD(&br->vlgrp->vlan_list);
+	INIT_LIST_HEAD(&vg->vlan_list);
 	br->vlan_proto = htons(ETH_P_8021Q);
 	br->default_pvid = 1;
+	rcu_assign_pointer(br->vlgrp, vg);
 	ret = br_vlan_add(br, 1,
 			  BRIDGE_VLAN_INFO_PVID | BRIDGE_VLAN_INFO_UNTAGGED |
 			  BRIDGE_VLAN_INFO_BRENTRY);
@@ -846,9 +871,9 @@ int br_vlan_init(struct net_bridge *br)
 	return ret;
 
 err_vlan_add:
-	rhashtable_destroy(&br->vlgrp->vlan_hash);
+	rhashtable_destroy(&vg->vlan_hash);
 err_rhtbl:
-	kfree(br->vlgrp);
+	kfree(vg);
 
 	goto out;
 }
@@ -866,9 +891,7 @@ int nbp_vlan_init(struct net_bridge_port *p)
 	if (ret)
 		goto err_rhtbl;
 	INIT_LIST_HEAD(&vg->vlan_list);
-	/* Make sure everything's committed before publishing vg */
-	smp_wmb();
-	p->vlgrp = vg;
+	rcu_assign_pointer(p->vlgrp, vg);
 	if (p->br->default_pvid) {
 		ret = nbp_vlan_add(p, p->br->default_pvid,
 				   BRIDGE_VLAN_INFO_PVID |
@@ -897,7 +920,7 @@ int nbp_vlan_add(struct net_bridge_port *port, u16 vid, u16 flags)
 
 	ASSERT_RTNL();
 
-	vlan = br_vlan_find(port->vlgrp, vid);
+	vlan = br_vlan_find(nbp_vlan_group(port), vid);
 	if (vlan) {
 		__vlan_add_flags(vlan, flags);
 		return 0;
@@ -925,7 +948,7 @@ int nbp_vlan_delete(struct net_bridge_port *port, u16 vid)
 
 	ASSERT_RTNL();
 
-	v = br_vlan_find(port->vlgrp, vid);
+	v = br_vlan_find(nbp_vlan_group(port), vid);
 	if (!v)
 		return -ENOENT;
 	br_fdb_find_delete_local(port->br, port, port->dev->dev_addr, vid);
@@ -936,12 +959,14 @@ int nbp_vlan_delete(struct net_bridge_port *port, u16 vid)
 
 void nbp_vlan_flush(struct net_bridge_port *port)
 {
+	struct net_bridge_vlan_group *vg;
 	struct net_bridge_vlan *vlan;
 
 	ASSERT_RTNL();
 
-	list_for_each_entry(vlan, &port->vlgrp->vlan_list, vlist)
+	vg = nbp_vlan_group(port);
+	list_for_each_entry(vlan, &vg->vlan_list, vlist)
 		vlan_vid_del(port->dev, port->br->vlan_proto, vlan->vid);
 
-	__vlan_flush(nbp_vlan_group(port));
+	__vlan_flush(vg);
 }