bridge: Fix netpoll support

There are multiple problems with the newly added netpoll support:

1) Use-after-free on each netpoll packet.
2) Invoking unsafe code on netpoll/IRQ path.
3) Breaks when netpoll is enabled on the underlying device.

This patch fixes all of these problems.  In particular, we now
allocate proper netpoll structures for each underlying device.

We only allow netpoll to be enabled on the bridge when all the
devices underneath it support netpoll.  Once it is enabled, we
do not allow non-netpoll devices to join the bridge (until netpoll
is disabled again).

This allows us to do away with the npinfo juggling that caused
problem number 1.

Incidentally this patch fixes number 2 by bypassing unsafe code
such as multicast snooping and netfilter.

Reported-by: Qianfeng Zhang <frzhang@redhat.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 61 insertions, 47 deletions

diff --git a/net/bridge/br_device.c b/net/bridge/br_device.c
index f8cb908db81f..6f3a9279be30 100644
--- a/net/bridge/br_device.c
+++ b/net/bridge/br_device.c
@@ -47,6 +47,10 @@ netdev_tx_t br_dev_xmit(struct sk_buff *skb, struct net_device *dev)
 	skb_pull(skb, ETH_HLEN);
 
 	if (is_multicast_ether_addr(dest)) {
+		if (unlikely(netpoll_tx_running(dev))) {
+			br_flood_deliver(br, skb);
+			goto out;
+		}
 		if (br_multicast_rcv(br, NULL, skb))
 			goto out;
 
@@ -199,72 +203,81 @@ static int br_set_tx_csum(struct net_device *dev, u32 data)
 }
 
 #ifdef CONFIG_NET_POLL_CONTROLLER
-static bool br_devices_support_netpoll(struct net_bridge *br)
+static void br_poll_controller(struct net_device *br_dev)
 {
-	struct net_bridge_port *p;
-	bool ret = true;
-	int count = 0;
-	unsigned long flags;
-
-	spin_lock_irqsave(&br->lock, flags);
-	list_for_each_entry(p, &br->port_list, list) {
-		count++;
-		if ((p->dev->priv_flags & IFF_DISABLE_NETPOLL) ||
-		    !p->dev->netdev_ops->ndo_poll_controller)
-			ret = false;
-	}
-	spin_unlock_irqrestore(&br->lock, flags);
-	return count != 0 && ret;
 }
 
-static void br_poll_controller(struct net_device *br_dev)
+static void br_netpoll_cleanup(struct net_device *dev)
 {
-	struct netpoll *np = br_dev->npinfo->netpoll;
+	struct net_bridge *br = netdev_priv(dev);
+	struct net_bridge_port *p, *n;
 
-	if (np->real_dev != br_dev)
-		netpoll_poll_dev(np->real_dev);
+	list_for_each_entry_safe(p, n, &br->port_list, list) {
+		br_netpoll_disable(p);
+	}
 }
 
-void br_netpoll_cleanup(struct net_device *dev)
+static int br_netpoll_setup(struct net_device *dev, struct netpoll_info *ni)
 {
 	struct net_bridge *br = netdev_priv(dev);
 	struct net_bridge_port *p, *n;
-	const struct net_device_ops *ops;
+	int err = 0;
 
 	list_for_each_entry_safe(p, n, &br->port_list, list) {
-		if (p->dev) {
-			ops = p->dev->netdev_ops;
-			if (ops->ndo_netpoll_cleanup)
-				ops->ndo_netpoll_cleanup(p->dev);
-			else
-				p->dev->npinfo = NULL;
-		}
+		if (!p->dev)
+			continue;
+
+		err = br_netpoll_enable(p);
+		if (err)
+			goto fail;
 	}
+
+out:
+	return err;
+
+fail:
+	br_netpoll_cleanup(dev);
+	goto out;
 }
 
-void br_netpoll_disable(struct net_bridge *br,
-			struct net_device *dev)
+int br_netpoll_enable(struct net_bridge_port *p)
 {
-	if (br_devices_support_netpoll(br))
-		br->dev->priv_flags &= ~IFF_DISABLE_NETPOLL;
-	if (dev->netdev_ops->ndo_netpoll_cleanup)
-		dev->netdev_ops->ndo_netpoll_cleanup(dev);
-	else
-		dev->npinfo = NULL;
+	struct netpoll *np;
+	int err = 0;
+
+	np = kzalloc(sizeof(*p->np), GFP_KERNEL);
+	err = -ENOMEM;
+	if (!np)
+		goto out;
+
+	np->dev = p->dev;
+
+	err = __netpoll_setup(np);
+	if (err) {
+		kfree(np);
+		goto out;
+	}
+
+	p->np = np;
+
+out:
+	return err;
 }
 
-void br_netpoll_enable(struct net_bridge *br,
-		       struct net_device *dev)
+void br_netpoll_disable(struct net_bridge_port *p)
 {
-	if (br_devices_support_netpoll(br)) {
-		br->dev->priv_flags &= ~IFF_DISABLE_NETPOLL;
-		if (br->dev->npinfo)
-			dev->npinfo = br->dev->npinfo;
-	} else if (!(br->dev->priv_flags & IFF_DISABLE_NETPOLL)) {
-		br->dev->priv_flags |= IFF_DISABLE_NETPOLL;
-		br_info(br,"new device %s does not support netpoll (disabling)",
-			dev->name);
-	}
+	struct netpoll *np = p->np;
+
+	if (!np)
+		return;
+
+	p->np = NULL;
+
+	/* Wait for transmitting packets to finish before freeing. */
+	synchronize_rcu_bh();
+
+	__netpoll_cleanup(np);
+	kfree(np);
 }
 
 #endif
@@ -293,6 +306,7 @@ static const struct net_device_ops br_netdev_ops = {
 	.ndo_change_mtu		 = br_change_mtu,
 	.ndo_do_ioctl		 = br_dev_ioctl,
 #ifdef CONFIG_NET_POLL_CONTROLLER
+	.ndo_netpoll_setup	 = br_netpoll_setup,
 	.ndo_netpoll_cleanup	 = br_netpoll_cleanup,
 	.ndo_poll_controller	 = br_poll_controller,
 #endif