netfilter: revalidate bridge ports

ebt_redirect_tg() dereferences br_port_get_rcu() return without a
NULL check, causing a kernel panic when the bridge port has been
removed between the original hook invocation and an NFQUEUE
reinject.

A mere NULL check isn't sufficient, however.  As sashiko review
points out userspace can not only remove the port from the bridge,
it could also place the device in a different virtual device, e.g.
macvlan.

If this happens, we must drop the packet, there is no way for us to
reinject it into the bridge path.

Switch to _upper API, we don't need the bridge port structure.
Also, this fix keeps another bug intact:

Both nfnetlink_log and nfnetlink_queue use CONFIG_BRIDGE_NETFILTER
too aggressive, which prevents certain logging features when queueing
in bridge family: NETFILTER_FAMILY_BRIDGE can be enabled while the old
CONFIG_BRIDGE_NETFILTER cruft is off.

Fixes tag is a common ancestor, this was always broken.

Fixes: f350a0a873 ("bridge: use rx_handler_data pointer to store net_bridge_port pointer")
Reported-by: Ji'an Zhou <eilaimemedsnaimel@gmail.com>
Assisted-by: Claude:claude-sonnet-4-6
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/bridge/netfilter/ebt_dnat.c

@@ -39,7 +39,9 @@ ebt_dnat_tg(struct sk_buff *skb, const struct xt_action_param *par)
 			dev = xt_in(par);
 			break;
 		case NF_BR_PRE_ROUTING:
-			dev = br_port_get_rcu(xt_in(par))->br->dev;
+			dev = netdev_master_upper_dev_get_rcu(xt_in(par));
+			if (!dev) /* bridge port removed? */
+				return EBT_DROP;
 			break;
 		default:
 			dev = NULL;

net/bridge/netfilter/ebt_redirect.c

@@ -24,12 +24,18 @@ ebt_redirect_tg(struct sk_buff *skb, const struct xt_action_param *par)
 	if (skb_ensure_writable(skb, 0))
 		return EBT_DROP;
 
-	if (xt_hooknum(par) != NF_BR_BROUTING)
-		/* rcu_read_lock()ed by nf_hook_thresh */
-		ether_addr_copy(eth_hdr(skb)->h_dest,
-				br_port_get_rcu(xt_in(par))->br->dev->dev_addr);
-	else
+	if (xt_hooknum(par) != NF_BR_BROUTING) {
+		const struct net_device *dev;
+
+		dev = netdev_master_upper_dev_get_rcu(xt_in(par));
+		if (!dev)
+			return EBT_DROP;
+
+		ether_addr_copy(eth_hdr(skb)->h_dest, dev->dev_addr);
+	} else {
 		ether_addr_copy(eth_hdr(skb)->h_dest, xt_in(par)->dev_addr);
+	}
+
 	skb->pkt_type = PACKET_HOST;
 	return info->target;
 }

net/netfilter/nfnetlink_log.c

@@ -451,6 +451,23 @@ static int nfulnl_put_bridge(struct nfulnl_instance *inst, const struct sk_buff
 	return -1;
 }
 
+#if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
+static int nflog_put_master_ifindex(struct sk_buff *nlskb, int attr,
+				    const struct net_device *dev)
+{
+	const struct net_device *upper;
+
+	if (dev && !netif_is_bridge_port(dev))
+		return 0;
+
+	upper = netdev_master_upper_dev_get_rcu((struct net_device *)dev);
+	if (upper && nla_put_be32(nlskb, attr, htonl(upper->ifindex)))
+		return -EMSGSIZE;
+
+	return 0;
+}
+#endif
+
 /* This is an inline function, we don't really care about a long
  * list of arguments */
 static inline int
@@ -505,8 +522,7 @@ __build_packet_message(struct nfnl_log_net *log,
 			/* rcu_read_lock()ed by nf_hook_thresh or
 			 * nf_log_packet.
 			 */
-			    nla_put_be32(inst->skb, NFULA_IFINDEX_INDEV,
-					 htonl(br_port_get_rcu(indev)->br->dev->ifindex)))
+			    nflog_put_master_ifindex(inst->skb, NFULA_IFINDEX_INDEV, indev))
 				goto nla_put_failure;
 		} else {
 			int physinif;
@@ -542,8 +558,7 @@ __build_packet_message(struct nfnl_log_net *log,
 			/* rcu_read_lock()ed by nf_hook_thresh or
 			 * nf_log_packet.
 			 */
-			    nla_put_be32(inst->skb, NFULA_IFINDEX_OUTDEV,
-					 htonl(br_port_get_rcu(outdev)->br->dev->ifindex)))
+			    nflog_put_master_ifindex(inst->skb, NFULA_IFINDEX_OUTDEV, outdev))
 				goto nla_put_failure;
 		} else {
 			struct net_device *physoutdev;

net/netfilter/nfnetlink_queue.c

@@ -440,10 +440,47 @@ static bool nf_ct_drop_unconfirmed(const struct nf_queue_entry *entry, bool *is_
 	return false;
 }
 
+static bool nf_bridge_port_valid(const struct net_device *dev)
+{
+	if (!dev)
+		return true;
+
+	return netif_is_bridge_port(dev);
+}
+
+/* queued skbs leave rcu protection.  We bump device refcount so that
+ * the device cannot go away.  However, while packet was out the port
+ * could have been removed from the bridge.
+ *
+ * Ensure in+outdev are still part of a bridge at reinject time.
+ *
+ * The device rx_handler_data could even be pointing at data that is
+ * not a net_bridge_port structure.
+ */
+static bool nf_bridge_ports_valid(const struct nf_queue_entry *entry)
+{
+#if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
+	if (!nf_bridge_port_valid(entry->physin) ||
+	    !nf_bridge_port_valid(entry->physout))
+		return false;
+#endif
+	if (entry->state.pf != PF_BRIDGE)
+		return true;
+
+	if (!nf_bridge_port_valid(entry->state.in) ||
+	    !nf_bridge_port_valid(entry->state.out))
+		return false;
+
+	return true;
+}
+
 static void nfqnl_reinject(struct nf_queue_entry *entry, unsigned int verdict)
 {
 	const struct nf_ct_hook *ct_hook;
 
+	if (!nf_bridge_ports_valid(entry))
+		verdict = NF_DROP;
+
 	if (verdict == NF_ACCEPT ||
 	    verdict == NF_REPEAT ||
 	    verdict == NF_STOP) {
@@ -636,6 +673,23 @@ static int nf_queue_checksum_help(struct sk_buff *entskb)
 	return skb_checksum_help(entskb);
 }
 
+#if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
+static int nfqnl_put_master_ifindex(struct sk_buff *nlskb, int attr,
+				    const struct net_device *dev)
+{
+	const struct net_device *upper;
+
+	if (dev && !netif_is_bridge_port(dev))
+		return 0;
+
+	upper = netdev_master_upper_dev_get_rcu((struct net_device *)dev);
+	if (upper && nla_put_be32(nlskb, attr, htonl(upper->ifindex)))
+		return -EMSGSIZE;
+
+	return 0;
+}
+#endif
+
 static struct sk_buff *
 nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue,
 			   struct nf_queue_entry *entry,
@@ -771,10 +825,7 @@ nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue,
 			 * netfilter_bridge) */
 			if (nla_put_be32(skb, NFQA_IFINDEX_PHYSINDEV,
 					 htonl(indev->ifindex)) ||
-			/* this is the bridge group "brX" */
-			/* rcu_read_lock()ed by __nf_queue */
-			    nla_put_be32(skb, NFQA_IFINDEX_INDEV,
-					 htonl(br_port_get_rcu(indev)->br->dev->ifindex)))
+			    nfqnl_put_master_ifindex(skb, NFQA_IFINDEX_INDEV, indev))
 				goto nla_put_failure;
 		} else {
 			int physinif;
@@ -805,10 +856,7 @@ nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue,
 			 * netfilter_bridge) */
 			if (nla_put_be32(skb, NFQA_IFINDEX_PHYSOUTDEV,
 					 htonl(outdev->ifindex)) ||
-			/* this is the bridge group "brX" */
-			/* rcu_read_lock()ed by __nf_queue */
-			    nla_put_be32(skb, NFQA_IFINDEX_OUTDEV,
-					 htonl(br_port_get_rcu(outdev)->br->dev->ifindex)))
+			    nfqnl_put_master_ifindex(skb, NFQA_IFINDEX_OUTDEV, outdev))
 				goto nla_put_failure;
 		} else {
 			int physoutif;