net: Make accesses to ->br_port safe for sparse RCU

The new versions of the rcu_dereference() APIs requires that any pointers
passed to one of these APIs be fully defined.  The ->br_port field
in struct net_device points to a struct net_bridge_port, which is an
incomplete type.  This commit therefore changes ->br_port to be a void*,
and introduces a br_port() helper function to convert the type to struct
net_bridge_port, and applies this new helper function where required.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: David Miller <davem@davemloft.net>
Cc: Stephen Hemminger <shemminger@linux-foundation.org>
Cc: Eric Dumazet <eric.dumazet@gmail.com>

include/linux/if_bridge.h

@@ -101,6 +101,9 @@ struct __fdb_entry {
 
 #include <linux/netdevice.h>
 
+/* br_handle_frame_hook() needs the following forward declaration. */
+struct net_bridge_port;
+
 extern void brioctl_set(int (*ioctl_hook)(struct net *, unsigned int, void __user *));
 extern struct sk_buff *(*br_handle_frame_hook)(struct net_bridge_port *p,
 					       struct sk_buff *skb);

net/bridge/br_fdb.c

@@ -246,7 +246,7 @@ int br_fdb_test_addr(struct net_device *dev, unsigned char *addr)
 		return 0;
 
 	rcu_read_lock();
-	fdb = __br_fdb_get(dev->br_port->br, addr);
+	fdb = __br_fdb_get(br_port(dev)->br, addr);
 	ret = fdb && fdb->dst->dev != dev &&
 		fdb->dst->state == BR_STATE_FORWARDING;
 	rcu_read_unlock();

net/bridge/br_private.h

@@ -268,6 +268,11 @@ static inline int br_is_root_bridge(const struct net_bridge *br)
 	return !memcmp(&br->bridge_id, &br->designated_root, 8);
 }
 
+static inline struct net_bridge_port *br_port(const struct net_device *dev)
+{
+	return rcu_dereference(dev->br_port);
+}
+
 /* br_device.c */
 extern void br_dev_setup(struct net_device *dev);
 extern netdev_tx_t br_dev_xmit(struct sk_buff *skb,

net/bridge/netfilter/ebt_redirect.c

@@ -25,7 +25,7 @@ ebt_redirect_tg(struct sk_buff *skb, const struct xt_action_param *par)
 
 	if (par->hooknum != NF_BR_BROUTING)
 		memcpy(eth_hdr(skb)->h_dest,
-		       par->in->br_port->br->dev->dev_addr, ETH_ALEN);
+		       br_port(par->in)->br->dev->dev_addr, ETH_ALEN);
 	else
 		memcpy(eth_hdr(skb)->h_dest, par->in->dev_addr, ETH_ALEN);
 	skb->pkt_type = PACKET_HOST;

net/bridge/netfilter/ebt_ulog.c

@@ -178,7 +178,7 @@ static void ebt_ulog_packet(unsigned int hooknr, const struct sk_buff *skb,
 		strcpy(pm->physindev, in->name);
 		/* If in isn't a bridge, then physindev==indev */
 		if (in->br_port)
-			strcpy(pm->indev, in->br_port->br->dev->name);
+			strcpy(pm->indev, br_port(in)->br->dev->name);
 		else
 			strcpy(pm->indev, in->name);
 	} else
@@ -187,7 +187,7 @@ static void ebt_ulog_packet(unsigned int hooknr, const struct sk_buff *skb,
 	if (out) {
 		/* If out exists, then out is a bridge port */
 		strcpy(pm->physoutdev, out->name);
-		strcpy(pm->outdev, out->br_port->br->dev->name);
+		strcpy(pm->outdev, br_port(out)->br->dev->name);
 	} else
 		pm->outdev[0] = pm->physoutdev[0] = '\0';
 

net/bridge/netfilter/ebtables.c

@@ -141,10 +141,10 @@ ebt_basic_match(const struct ebt_entry *e, const struct ethhdr *h,
 	if (FWINV2(ebt_dev_check(e->out, out), EBT_IOUT))
 		return 1;
 	if ((!in || !in->br_port) ? 0 : FWINV2(ebt_dev_check(
-	   e->logical_in, in->br_port->br->dev), EBT_ILOGICALIN))
+	   e->logical_in, br_port(in)->br->dev), EBT_ILOGICALIN))
 		return 1;
 	if ((!out || !out->br_port) ? 0 : FWINV2(ebt_dev_check(
-	   e->logical_out, out->br_port->br->dev), EBT_ILOGICALOUT))
+	   e->logical_out, br_port(out)->br->dev), EBT_ILOGICALOUT))
 		return 1;
 
 	if (e->bitmask & EBT_SOURCEMAC) {

net/netfilter/nfnetlink_log.c

@@ -404,7 +404,7 @@ __build_packet_message(struct nfulnl_instance *inst,
 				     htonl(indev->ifindex));
 			/* this is the bridge group "brX" */
 			NLA_PUT_BE32(inst->skb, NFULA_IFINDEX_INDEV,
-				     htonl(indev->br_port->br->dev->ifindex));
+				     htonl(br_port(indev)->br->dev->ifindex));
 		} else {
 			/* Case 2: indev is bridge group, we need to look for
 			 * physical device (when called from ipv4) */
@@ -431,7 +431,7 @@ __build_packet_message(struct nfulnl_instance *inst,
 				     htonl(outdev->ifindex));
 			/* this is the bridge group "brX" */
 			NLA_PUT_BE32(inst->skb, NFULA_IFINDEX_OUTDEV,
-				     htonl(outdev->br_port->br->dev->ifindex));
+				     htonl(br_port(outdev)->br->dev->ifindex));
 		} else {
 			/* Case 2: indev is a bridge group, we need to look
 			 * for physical device (when called from ipv4) */

net/netfilter/nfnetlink_queue.c

@@ -297,7 +297,7 @@ nfqnl_build_packet_message(struct nfqnl_instance *queue,
 				     htonl(indev->ifindex));
 			/* this is the bridge group "brX" */
 			NLA_PUT_BE32(skb, NFQA_IFINDEX_INDEV,
-				     htonl(indev->br_port->br->dev->ifindex));
+				     htonl(br_port(indev)->br->dev->ifindex));
 		} else {
 			/* Case 2: indev is bridge group, we need to look for
 			 * physical device (when called from ipv4) */
@@ -322,7 +322,7 @@ nfqnl_build_packet_message(struct nfqnl_instance *queue,
 				     htonl(outdev->ifindex));
 			/* this is the bridge group "brX" */
 			NLA_PUT_BE32(skb, NFQA_IFINDEX_OUTDEV,
-				     htonl(outdev->br_port->br->dev->ifindex));
+				     htonl(br_port(outdev)->br->dev->ifindex));
 		} else {
 			/* Case 2: outdev is bridge group, we need to look for
 			 * physical output device (when called from ipv4) */