1 files changed, 242 insertions, 2 deletions

diff --git a/kernel/bpf/net_namespace.c b/kernel/bpf/net_namespace.c
index b37d81450c3a..78cf061f8179 100644
--- a/kernel/bpf/net_namespace.c
+++ b/kernel/bpf/net_namespace.c
@@ -8,9 +8,140 @@
  * Functions to manage BPF programs attached to netns
  */
 
+struct bpf_netns_link {
+	struct bpf_link	link;
+	enum bpf_attach_type type;
+	enum netns_bpf_attach_type netns_type;
+
+	/* We don't hold a ref to net in order to auto-detach the link
+	 * when netns is going away. Instead we rely on pernet
+	 * pre_exit callback to clear this pointer. Must be accessed
+	 * with netns_bpf_mutex held.
+	 */
+	struct net *net;
+};
+
 /* Protects updates to netns_bpf */
 DEFINE_MUTEX(netns_bpf_mutex);
 
+/* Must be called with netns_bpf_mutex held. */
+static void __net_exit bpf_netns_link_auto_detach(struct bpf_link *link)
+{
+	struct bpf_netns_link *net_link =
+		container_of(link, struct bpf_netns_link, link);
+
+	net_link->net = NULL;
+}
+
+static void bpf_netns_link_release(struct bpf_link *link)
+{
+	struct bpf_netns_link *net_link =
+		container_of(link, struct bpf_netns_link, link);
+	enum netns_bpf_attach_type type = net_link->netns_type;
+	struct net *net;
+
+	/* Link auto-detached by dying netns. */
+	if (!net_link->net)
+		return;
+
+	mutex_lock(&netns_bpf_mutex);
+
+	/* Recheck after potential sleep. We can race with cleanup_net
+	 * here, but if we see a non-NULL struct net pointer pre_exit
+	 * has not happened yet and will block on netns_bpf_mutex.
+	 */
+	net = net_link->net;
+	if (!net)
+		goto out_unlock;
+
+	net->bpf.links[type] = NULL;
+	RCU_INIT_POINTER(net->bpf.progs[type], NULL);
+
+out_unlock:
+	mutex_unlock(&netns_bpf_mutex);
+}
+
+static void bpf_netns_link_dealloc(struct bpf_link *link)
+{
+	struct bpf_netns_link *net_link =
+		container_of(link, struct bpf_netns_link, link);
+
+	kfree(net_link);
+}
+
+static int bpf_netns_link_update_prog(struct bpf_link *link,
+				      struct bpf_prog *new_prog,
+				      struct bpf_prog *old_prog)
+{
+	struct bpf_netns_link *net_link =
+		container_of(link, struct bpf_netns_link, link);
+	enum netns_bpf_attach_type type = net_link->netns_type;
+	struct net *net;
+	int ret = 0;
+
+	if (old_prog && old_prog != link->prog)
+		return -EPERM;
+	if (new_prog->type != link->prog->type)
+		return -EINVAL;
+
+	mutex_lock(&netns_bpf_mutex);
+
+	net = net_link->net;
+	if (!net || !check_net(net)) {
+		/* Link auto-detached or netns dying */
+		ret = -ENOLINK;
+		goto out_unlock;
+	}
+
+	old_prog = xchg(&link->prog, new_prog);
+	rcu_assign_pointer(net->bpf.progs[type], new_prog);
+	bpf_prog_put(old_prog);
+
+out_unlock:
+	mutex_unlock(&netns_bpf_mutex);
+	return ret;
+}
+
+static int bpf_netns_link_fill_info(const struct bpf_link *link,
+				    struct bpf_link_info *info)
+{
+	const struct bpf_netns_link *net_link =
+		container_of(link, struct bpf_netns_link, link);
+	unsigned int inum = 0;
+	struct net *net;
+
+	mutex_lock(&netns_bpf_mutex);
+	net = net_link->net;
+	if (net && check_net(net))
+		inum = net->ns.inum;
+	mutex_unlock(&netns_bpf_mutex);
+
+	info->netns.netns_ino = inum;
+	info->netns.attach_type = net_link->type;
+	return 0;
+}
+
+static void bpf_netns_link_show_fdinfo(const struct bpf_link *link,
+				       struct seq_file *seq)
+{
+	struct bpf_link_info info = {};
+
+	bpf_netns_link_fill_info(link, &info);
+	seq_printf(seq,
+		   "netns_ino:\t%u\n"
+		   "attach_type:\t%u\n",
+		   info.netns.netns_ino,
+		   info.netns.attach_type);
+}
+
+static const struct bpf_link_ops bpf_netns_link_ops = {
+	.release = bpf_netns_link_release,
+	.dealloc = bpf_netns_link_dealloc,
+	.update_prog = bpf_netns_link_update_prog,
+	.fill_link_info = bpf_netns_link_fill_info,
+	.show_fdinfo = bpf_netns_link_show_fdinfo,
+};
+
 int netns_bpf_prog_query(const union bpf_attr *attr,
 			 union bpf_attr __user *uattr)
 {
@@ -67,6 +198,13 @@ int netns_bpf_prog_attach(const union bpf_attr *attr, struct bpf_prog *prog)
 
 	net = current->nsproxy->net_ns;
 	mutex_lock(&netns_bpf_mutex);
+
+	/* Attaching prog directly is not compatible with links */
+	if (net->bpf.links[type]) {
+		ret = -EEXIST;
+		goto out_unlock;
+	}
+
 	switch (type) {
 	case NETNS_BPF_FLOW_DISSECTOR:
 		ret = flow_dissector_bpf_prog_attach(net, prog);
@@ -75,6 +213,7 @@ int netns_bpf_prog_attach(const union bpf_attr *attr, struct bpf_prog *prog)
 		ret = -EINVAL;
 		break;
 	}
+out_unlock:
 	mutex_unlock(&netns_bpf_mutex);
 
 	return ret;
@@ -86,6 +225,10 @@ static int __netns_bpf_prog_detach(struct net *net,
 {
 	struct bpf_prog *attached;
 
+	/* Progs attached via links cannot be detached */
+	if (net->bpf.links[type])
+		return -EINVAL;
+
 	attached = rcu_dereference_protected(net->bpf.progs[type],
 					     lockdep_is_held(&netns_bpf_mutex));
 	if (!attached)
@@ -111,13 +254,110 @@ int netns_bpf_prog_detach(const union bpf_attr *attr)
 	return ret;
 }
 
+static int netns_bpf_link_attach(struct net *net, struct bpf_link *link,
+				 enum netns_bpf_attach_type type)
+{
+	struct bpf_prog *prog;
+	int err;
+
+	mutex_lock(&netns_bpf_mutex);
+
+	/* Allow attaching only one prog or link for now */
+	if (net->bpf.links[type]) {
+		err = -E2BIG;
+		goto out_unlock;
+	}
+	/* Links are not compatible with attaching prog directly */
+	prog = rcu_dereference_protected(net->bpf.progs[type],
+					 lockdep_is_held(&netns_bpf_mutex));
+	if (prog) {
+		err = -EEXIST;
+		goto out_unlock;
+	}
+
+	switch (type) {
+	case NETNS_BPF_FLOW_DISSECTOR:
+		err = flow_dissector_bpf_prog_attach(net, link->prog);
+		break;
+	default:
+		err = -EINVAL;
+		break;
+	}
+	if (err)
+		goto out_unlock;
+
+	net->bpf.links[type] = link;
+
+out_unlock:
+	mutex_unlock(&netns_bpf_mutex);
+	return err;
+}
+
+int netns_bpf_link_create(const union bpf_attr *attr, struct bpf_prog *prog)
+{
+	enum netns_bpf_attach_type netns_type;
+	struct bpf_link_primer link_primer;
+	struct bpf_netns_link *net_link;
+	enum bpf_attach_type type;
+	struct net *net;
+	int err;
+
+	if (attr->link_create.flags)
+		return -EINVAL;
+
+	type = attr->link_create.attach_type;
+	netns_type = to_netns_bpf_attach_type(type);
+	if (netns_type < 0)
+		return -EINVAL;
+
+	net = get_net_ns_by_fd(attr->link_create.target_fd);
+	if (IS_ERR(net))
+		return PTR_ERR(net);
+
+	net_link = kzalloc(sizeof(*net_link), GFP_USER);
+	if (!net_link) {
+		err = -ENOMEM;
+		goto out_put_net;
+	}
+	bpf_link_init(&net_link->link, BPF_LINK_TYPE_NETNS,
+		      &bpf_netns_link_ops, prog);
+	net_link->net = net;
+	net_link->type = type;
+	net_link->netns_type = netns_type;
+
+	err = bpf_link_prime(&net_link->link, &link_primer);
+	if (err) {
+		kfree(net_link);
+		goto out_put_net;
+	}
+
+	err = netns_bpf_link_attach(net, &net_link->link, netns_type);
+	if (err) {
+		bpf_link_cleanup(&link_primer);
+		goto out_put_net;
+	}
+
+	put_net(net);
+	return bpf_link_settle(&link_primer);
+
+out_put_net:
+	put_net(net);
+	return err;
+}
+
 static void __net_exit netns_bpf_pernet_pre_exit(struct net *net)
 {
 	enum netns_bpf_attach_type type;
+	struct bpf_link *link;
 
 	mutex_lock(&netns_bpf_mutex);
-	for (type = 0; type < MAX_NETNS_BPF_ATTACH_TYPE; type++)
-		__netns_bpf_prog_detach(net, type);
+	for (type = 0; type < MAX_NETNS_BPF_ATTACH_TYPE; type++) {
+		link = net->bpf.links[type];
+		if (link)
+			bpf_netns_link_auto_detach(link);
+		else
+			__netns_bpf_prog_detach(net, type);
+	}
 	mutex_unlock(&netns_bpf_mutex);
 }