netfilter: nf_tables: Support wildcard netdev hook specs

User space may pass non-nul-terminated NFTA_DEVICE_NAME attribute values
to indicate a suffix wildcard.
Expect for multiple devices to match the given prefix in
nft_netdev_hook_alloc() and populate 'ops_list' with them all.
When checking for duplicate hooks, compare the shortest prefix so a
device may never match more than a single hook spec.
Finally respect the stored prefix length when hooking into new devices
from event handlers.

Signed-off-by: Phil Sutter <phil@nwl.cc>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

Author: Phil Sutter

net/netfilter/nf_tables_api.c

@@ -2330,24 +2330,22 @@ static struct nft_hook *nft_netdev_hook_alloc(struct net *net,
 	 * indirectly serializing all the other holders of the commit_mutex with
 	 * the rtnl_mutex.
 	 */
-	dev = __dev_get_by_name(net, hook->ifname);
-	if (!dev) {
-		err = -ENOENT;
-		goto err_hook_free;
-	}
+	for_each_netdev(net, dev) {
+		if (strncmp(dev->name, hook->ifname, hook->ifnamelen))
+			continue;
 
-	ops = kzalloc(sizeof(struct nf_hook_ops), GFP_KERNEL_ACCOUNT);
-	if (!ops) {
-		err = -ENOMEM;
-		goto err_hook_free;
+		ops = kzalloc(sizeof(struct nf_hook_ops), GFP_KERNEL_ACCOUNT);
+		if (!ops) {
+			err = -ENOMEM;
+			goto err_hook_free;
+		}
+		ops->dev = dev;
+		list_add_tail(&ops->list, &hook->ops_list);
 	}
-	ops->dev = dev;
-	list_add_tail(&ops->list, &hook->ops_list);
-
 	return hook;
 
 err_hook_free:
-	kfree(hook);
+	nft_netdev_hook_free(hook);
 	return ERR_PTR(err);
 }
 
@@ -2357,7 +2355,8 @@ static struct nft_hook *nft_hook_list_find(struct list_head *hook_list,
 	struct nft_hook *hook;
 
 	list_for_each_entry(hook, hook_list, list) {
-		if (!strcmp(hook->ifname, this->ifname))
+		if (!strncmp(hook->ifname, this->ifname,
+			     min(hook->ifnamelen, this->ifnamelen)))
 			return hook;
 	}
 
@@ -9696,7 +9695,7 @@ static int nft_flowtable_event(unsigned long event, struct net_device *dev,
 
 	list_for_each_entry(hook, &flowtable->hook_list, list) {
 		ops = nft_hook_find_ops(hook, dev);
-		match = !strcmp(hook->ifname, dev->name);
+		match = !strncmp(hook->ifname, dev->name, hook->ifnamelen);
 
 		switch (event) {
 		case NETDEV_UNREGISTER:

net/netfilter/nft_chain_filter.c

@@ -328,7 +328,7 @@ static int nft_netdev_event(unsigned long event, struct net_device *dev,
 
 	list_for_each_entry(hook, &basechain->hook_list, list) {
 		ops = nft_hook_find_ops(hook, dev);
-		match = !strcmp(hook->ifname, dev->name);
+		match = !strncmp(hook->ifname, dev->name, hook->ifnamelen);
 
 		switch (event) {
 		case NETDEV_UNREGISTER: