kernel/bpf/net_namespace.c - third_party/linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0

 #include <linux/bpf.h>
 #include <linux/bpf-netns.h>
 #include <linux/filter.h>
 #include <net/net_namespace.h>

 /*
  * 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;
 	struct list_head node; /* node in list of links attached to net */
 };

 /* Protects updates to netns_bpf */
 DEFINE_MUTEX(netns_bpf_mutex);

 static void netns_bpf_attach_type_unneed(enum netns_bpf_attach_type type)
 {
 	switch (type) {
 #ifdef CONFIG_INET
 	case NETNS_BPF_SK_LOOKUP:
 		static_branch_dec(&bpf_sk_lookup_enabled);
 		break;
 #endif
 	default:
 		break;
 	}
 }

 static void netns_bpf_attach_type_need(enum netns_bpf_attach_type type)
 {
 	switch (type) {
 #ifdef CONFIG_INET
 	case NETNS_BPF_SK_LOOKUP:
 		static_branch_inc(&bpf_sk_lookup_enabled);
 		break;
 #endif
 	default:
 		break;
 	}
 }

 /* Must be called with netns_bpf_mutex held. */
 static void netns_bpf_run_array_detach(struct net *net,
 				       enum netns_bpf_attach_type type)
 {
 	struct bpf_prog_array *run_array;

 	run_array = rcu_replace_pointer(net->bpf.run_array[type], NULL,
 					lockdep_is_held(&netns_bpf_mutex));
 	bpf_prog_array_free(run_array);
 }

 static int link_index(struct net *net, enum netns_bpf_attach_type type,
 		      struct bpf_netns_link *link)
 {
 	struct bpf_netns_link *pos;
 	int i = 0;

 	list_for_each_entry(pos, &net->bpf.links[type], node) {
 		if (pos == link)
 			return i;
 		i++;
 	}
 	return -ENOENT;
 }

 static int link_count(struct net *net, enum netns_bpf_attach_type type)
 {
 	struct list_head *pos;
 	int i = 0;

 	list_for_each(pos, &net->bpf.links[type])
 		i++;
 	return i;
 }

 static void fill_prog_array(struct net *net, enum netns_bpf_attach_type type,
 			    struct bpf_prog_array *prog_array)
 {
 	struct bpf_netns_link *pos;
 	unsigned int i = 0;

 	list_for_each_entry(pos, &net->bpf.links[type], node) {
 		prog_array->items[i].prog = pos->link.prog;
 		i++;
 	}
 }

 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 bpf_prog_array *old_array, *new_array;
 	struct net *net;
 	int cnt, idx;

 	mutex_lock(&netns_bpf_mutex);

 	/* We can race with cleanup_net, but if we see a non-NULL
 	 * struct net pointer, pre_exit has not run yet and wait for
 	 * netns_bpf_mutex.
 	 */
 	net = net_link->net;
 	if (!net)
 		goto out_unlock;

 	/* Mark attach point as unused */
 	netns_bpf_attach_type_unneed(type);

 	/* Remember link position in case of safe delete */
 	idx = link_index(net, type, net_link);
 	list_del(&net_link->node);

 	cnt = link_count(net, type);
 	if (!cnt) {
 		netns_bpf_run_array_detach(net, type);
 		goto out_unlock;
 	}

 	old_array = rcu_dereference_protected(net->bpf.run_array[type],
 					      lockdep_is_held(&netns_bpf_mutex));
 	new_array = bpf_prog_array_alloc(cnt, GFP_KERNEL);
 	if (!new_array) {
 		WARN_ON(bpf_prog_array_delete_safe_at(old_array, idx));
 		goto out_unlock;
 	}
 	fill_prog_array(net, type, new_array);
 	rcu_assign_pointer(net->bpf.run_array[type], new_array);
 	bpf_prog_array_free(old_array);

 out_unlock:
 	net_link->net = NULL;
 	mutex_unlock(&netns_bpf_mutex);
 }

 static int bpf_netns_link_detach(struct bpf_link *link)
 {
 	bpf_netns_link_release(link);
 	return 0;
 }

 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 bpf_prog_array *run_array;
 	struct net *net;
 	int idx, ret;

 	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;
 	}

 	run_array = rcu_dereference_protected(net->bpf.run_array[type],
 					      lockdep_is_held(&netns_bpf_mutex));
 	idx = link_index(net, type, net_link);
 	ret = bpf_prog_array_update_at(run_array, idx, new_prog);
 	if (ret)
 		goto out_unlock;

 	old_prog = xchg(&link->prog, 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,
 	.detach = bpf_netns_link_detach,
 	.update_prog = bpf_netns_link_update_prog,
 	.fill_link_info = bpf_netns_link_fill_info,
 	.show_fdinfo = bpf_netns_link_show_fdinfo,
 };

 /* Must be called with netns_bpf_mutex held. */
 static int __netns_bpf_prog_query(const union bpf_attr *attr,
 				  union bpf_attr __user *uattr,
 				  struct net *net,
 				  enum netns_bpf_attach_type type)
 {
 	__u32 __user *prog_ids = u64_to_user_ptr(attr->query.prog_ids);
 	struct bpf_prog_array *run_array;
 	u32 prog_cnt = 0, flags = 0;

 	run_array = rcu_dereference_protected(net->bpf.run_array[type],
 					      lockdep_is_held(&netns_bpf_mutex));
 	if (run_array)
 		prog_cnt = bpf_prog_array_length(run_array);

 	if (copy_to_user(&uattr->query.attach_flags, &flags, sizeof(flags)))
 		return -EFAULT;
 	if (copy_to_user(&uattr->query.prog_cnt, &prog_cnt, sizeof(prog_cnt)))
 		return -EFAULT;
 	if (!attr->query.prog_cnt || !prog_ids || !prog_cnt)
 		return 0;

 	return bpf_prog_array_copy_to_user(run_array, prog_ids,
 					   attr->query.prog_cnt);
 }

 int netns_bpf_prog_query(const union bpf_attr *attr,
 			 union bpf_attr __user *uattr)
 {
 	enum netns_bpf_attach_type type;
 	struct net *net;
 	int ret;

 	if (attr->query.query_flags)
 		return -EINVAL;

 	type = to_netns_bpf_attach_type(attr->query.attach_type);
 	if (type < 0)
 		return -EINVAL;

 	net = get_net_ns_by_fd(attr->query.target_fd);
 	if (IS_ERR(net))
 		return PTR_ERR(net);

 	mutex_lock(&netns_bpf_mutex);
 	ret = __netns_bpf_prog_query(attr, uattr, net, type);
 	mutex_unlock(&netns_bpf_mutex);

 	put_net(net);
 	return ret;
 }

 int netns_bpf_prog_attach(const union bpf_attr *attr, struct bpf_prog *prog)
 {
 	struct bpf_prog_array *run_array;
 	enum netns_bpf_attach_type type;
 	struct bpf_prog *attached;
 	struct net *net;
 	int ret;

 	if (attr->target_fd || attr->attach_flags || attr->replace_bpf_fd)
 		return -EINVAL;

 	type = to_netns_bpf_attach_type(attr->attach_type);
 	if (type < 0)
 		return -EINVAL;

 	net = current->nsproxy->net_ns;
 	mutex_lock(&netns_bpf_mutex);

 	/* Attaching prog directly is not compatible with links */
 	if (!list_empty(&net->bpf.links[type])) {
 		ret = -EEXIST;
 		goto out_unlock;
 	}

 	switch (type) {
 	case NETNS_BPF_FLOW_DISSECTOR:
 		ret = flow_dissector_bpf_prog_attach_check(net, prog);
 		break;
 	default:
 		ret = -EINVAL;
 		break;
 	}
 	if (ret)
 		goto out_unlock;

 	attached = net->bpf.progs[type];
 	if (attached == prog) {
 		/* The same program cannot be attached twice */
 		ret = -EINVAL;
 		goto out_unlock;
 	}

 	run_array = rcu_dereference_protected(net->bpf.run_array[type],
 					      lockdep_is_held(&netns_bpf_mutex));
 	if (run_array) {
 		WRITE_ONCE(run_array->items[0].prog, prog);
 	} else {
 		run_array = bpf_prog_array_alloc(1, GFP_KERNEL);
 		if (!run_array) {
 			ret = -ENOMEM;
 			goto out_unlock;
 		}
 		run_array->items[0].prog = prog;
 		rcu_assign_pointer(net->bpf.run_array[type], run_array);
 	}

 	net->bpf.progs[type] = prog;
 	if (attached)
 		bpf_prog_put(attached);

 out_unlock:
 	mutex_unlock(&netns_bpf_mutex);

 	return ret;
 }

 /* Must be called with netns_bpf_mutex held. */
 static int __netns_bpf_prog_detach(struct net *net,
 				   enum netns_bpf_attach_type type,
 				   struct bpf_prog *old)
 {
 	struct bpf_prog *attached;

 	/* Progs attached via links cannot be detached */
 	if (!list_empty(&net->bpf.links[type]))
 		return -EINVAL;

 	attached = net->bpf.progs[type];
 	if (!attached || attached != old)
 		return -ENOENT;
 	netns_bpf_run_array_detach(net, type);
 	net->bpf.progs[type] = NULL;
 	bpf_prog_put(attached);
 	return 0;
 }

 int netns_bpf_prog_detach(const union bpf_attr *attr, enum bpf_prog_type ptype)
 {
 	enum netns_bpf_attach_type type;
 	struct bpf_prog *prog;
 	int ret;

 	if (attr->target_fd)
 		return -EINVAL;

 	type = to_netns_bpf_attach_type(attr->attach_type);
 	if (type < 0)
 		return -EINVAL;

 	prog = bpf_prog_get_type(attr->attach_bpf_fd, ptype);
 	if (IS_ERR(prog))
 		return PTR_ERR(prog);

 	mutex_lock(&netns_bpf_mutex);
 	ret = __netns_bpf_prog_detach(current->nsproxy->net_ns, type, prog);
 	mutex_unlock(&netns_bpf_mutex);

 	bpf_prog_put(prog);

 	return ret;
 }

 static int netns_bpf_max_progs(enum netns_bpf_attach_type type)
 {
 	switch (type) {
 	case NETNS_BPF_FLOW_DISSECTOR:
 		return 1;
 	case NETNS_BPF_SK_LOOKUP:
 		return 64;
 	default:
 		return 0;
 	}
 }

 static int netns_bpf_link_attach(struct net *net, struct bpf_link *link,
 				 enum netns_bpf_attach_type type)
 {
 	struct bpf_netns_link *net_link =
 		container_of(link, struct bpf_netns_link, link);
 	struct bpf_prog_array *run_array;
 	int cnt, err;

 	mutex_lock(&netns_bpf_mutex);

 	cnt = link_count(net, type);
 	if (cnt >= netns_bpf_max_progs(type)) {
 		err = -E2BIG;
 		goto out_unlock;
 	}
 	/* Links are not compatible with attaching prog directly */
 	if (net->bpf.progs[type]) {
 		err = -EEXIST;
 		goto out_unlock;
 	}

 	switch (type) {
 	case NETNS_BPF_FLOW_DISSECTOR:
 		err = flow_dissector_bpf_prog_attach_check(net, link->prog);
 		break;
 	case NETNS_BPF_SK_LOOKUP:
 		err = 0; /* nothing to check */
 		break;
 	default:
 		err = -EINVAL;
 		break;
 	}
 	if (err)
 		goto out_unlock;

 	run_array = bpf_prog_array_alloc(cnt + 1, GFP_KERNEL);
 	if (!run_array) {
 		err = -ENOMEM;
 		goto out_unlock;
 	}

 	list_add_tail(&net_link->node, &net->bpf.links[type]);

 	fill_prog_array(net, type, run_array);
 	run_array = rcu_replace_pointer(net->bpf.run_array[type], run_array,
 					lockdep_is_held(&netns_bpf_mutex));
 	bpf_prog_array_free(run_array);

 	/* Mark attach point as used */
 	netns_bpf_attach_type_need(type);

 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 int __net_init netns_bpf_pernet_init(struct net *net)
 {
 	int type;

 	for (type = 0; type < MAX_NETNS_BPF_ATTACH_TYPE; type++)
 		INIT_LIST_HEAD(&net->bpf.links[type]);

 	return 0;
 }

 static void __net_exit netns_bpf_pernet_pre_exit(struct net *net)
 {
 	enum netns_bpf_attach_type type;
 	struct bpf_netns_link *net_link;

 	mutex_lock(&netns_bpf_mutex);
 	for (type = 0; type < MAX_NETNS_BPF_ATTACH_TYPE; type++) {
 		netns_bpf_run_array_detach(net, type);
 		list_for_each_entry(net_link, &net->bpf.links[type], node) {
 			net_link->net = NULL; /* auto-detach link */
 			netns_bpf_attach_type_unneed(type);
 		}
 		if (net->bpf.progs[type])
 			bpf_prog_put(net->bpf.progs[type]);
 	}
 	mutex_unlock(&netns_bpf_mutex);
 }

 static struct pernet_operations netns_bpf_pernet_ops __net_initdata = {
 	.init = netns_bpf_pernet_init,
 	.pre_exit = netns_bpf_pernet_pre_exit,
 };

 static int __init netns_bpf_init(void)
 {
 	return register_pernet_subsys(&netns_bpf_pernet_ops);
 }

 subsys_initcall(netns_bpf_init);
	// SPDX-License-Identifier: GPL-2.0

	#include <linux/bpf.h>
	#include <linux/bpf-netns.h>
	#include <linux/filter.h>
	#include <net/net_namespace.h>

	/*
	* 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;
	struct list_head node; /* node in list of links attached to net */
	};

	/* Protects updates to netns_bpf */
	DEFINE_MUTEX(netns_bpf_mutex);

	static void netns_bpf_attach_type_unneed(enum netns_bpf_attach_type type)
	{
	switch (type) {
	#ifdef CONFIG_INET
	case NETNS_BPF_SK_LOOKUP:
	static_branch_dec(&bpf_sk_lookup_enabled);
	break;
	#endif
	default:
	break;
	}
	}

	static void netns_bpf_attach_type_need(enum netns_bpf_attach_type type)
	{
	switch (type) {
	#ifdef CONFIG_INET
	case NETNS_BPF_SK_LOOKUP:
	static_branch_inc(&bpf_sk_lookup_enabled);
	break;
	#endif
	default:
	break;
	}
	}

	/* Must be called with netns_bpf_mutex held. */
	static void netns_bpf_run_array_detach(struct net *net,
	enum netns_bpf_attach_type type)
	{
	struct bpf_prog_array *run_array;

	run_array = rcu_replace_pointer(net->bpf.run_array[type], NULL,
	lockdep_is_held(&netns_bpf_mutex));
	bpf_prog_array_free(run_array);
	}

	static int link_index(struct net *net, enum netns_bpf_attach_type type,
	struct bpf_netns_link *link)
	{
	struct bpf_netns_link *pos;
	int i = 0;

	list_for_each_entry(pos, &net->bpf.links[type], node) {
	if (pos == link)
	return i;
	i++;
	}
	return -ENOENT;
	}

	static int link_count(struct net *net, enum netns_bpf_attach_type type)
	{
	struct list_head *pos;
	int i = 0;

	list_for_each(pos, &net->bpf.links[type])
	i++;
	return i;
	}

	static void fill_prog_array(struct net *net, enum netns_bpf_attach_type type,
	struct bpf_prog_array *prog_array)
	{
	struct bpf_netns_link *pos;
	unsigned int i = 0;

	list_for_each_entry(pos, &net->bpf.links[type], node) {
	prog_array->items[i].prog = pos->link.prog;
	i++;
	}
	}

	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 bpf_prog_array old_array, new_array;
	struct net *net;
	int cnt, idx;

	mutex_lock(&netns_bpf_mutex);

	/* We can race with cleanup_net, but if we see a non-NULL
	* struct net pointer, pre_exit has not run yet and wait for
	* netns_bpf_mutex.
	*/
	net = net_link->net;
	if (!net)
	goto out_unlock;

	/* Mark attach point as unused */
	netns_bpf_attach_type_unneed(type);

	/* Remember link position in case of safe delete */
	idx = link_index(net, type, net_link);
	list_del(&net_link->node);

	cnt = link_count(net, type);
	if (!cnt) {
	netns_bpf_run_array_detach(net, type);
	goto out_unlock;
	}

	old_array = rcu_dereference_protected(net->bpf.run_array[type],
	lockdep_is_held(&netns_bpf_mutex));
	new_array = bpf_prog_array_alloc(cnt, GFP_KERNEL);
	if (!new_array) {
	WARN_ON(bpf_prog_array_delete_safe_at(old_array, idx));
	goto out_unlock;
	}
	fill_prog_array(net, type, new_array);
	rcu_assign_pointer(net->bpf.run_array[type], new_array);
	bpf_prog_array_free(old_array);

	out_unlock:
	net_link->net = NULL;
	mutex_unlock(&netns_bpf_mutex);
	}

	static int bpf_netns_link_detach(struct bpf_link *link)
	{
	bpf_netns_link_release(link);
	return 0;
	}

	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 bpf_prog_array *run_array;
	struct net *net;
	int idx, ret;

	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;
	}

	run_array = rcu_dereference_protected(net->bpf.run_array[type],
	lockdep_is_held(&netns_bpf_mutex));
	idx = link_index(net, type, net_link);
	ret = bpf_prog_array_update_at(run_array, idx, new_prog);
	if (ret)
	goto out_unlock;

	old_prog = xchg(&link->prog, 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,
	.detach = bpf_netns_link_detach,
	.update_prog = bpf_netns_link_update_prog,
	.fill_link_info = bpf_netns_link_fill_info,
	.show_fdinfo = bpf_netns_link_show_fdinfo,
	};

	/* Must be called with netns_bpf_mutex held. */
	static int __netns_bpf_prog_query(const union bpf_attr *attr,
	union bpf_attr __user *uattr,
	struct net *net,
	enum netns_bpf_attach_type type)
	{
	__u32 __user *prog_ids = u64_to_user_ptr(attr->query.prog_ids);
	struct bpf_prog_array *run_array;
	u32 prog_cnt = 0, flags = 0;

	run_array = rcu_dereference_protected(net->bpf.run_array[type],
	lockdep_is_held(&netns_bpf_mutex));
	if (run_array)
	prog_cnt = bpf_prog_array_length(run_array);

	if (copy_to_user(&uattr->query.attach_flags, &flags, sizeof(flags)))
	return -EFAULT;
	if (copy_to_user(&uattr->query.prog_cnt, &prog_cnt, sizeof(prog_cnt)))
	return -EFAULT;
	if (!attr->query.prog_cnt \|\| !prog_ids \|\| !prog_cnt)
	return 0;

	return bpf_prog_array_copy_to_user(run_array, prog_ids,
	attr->query.prog_cnt);
	}

	int netns_bpf_prog_query(const union bpf_attr *attr,
	union bpf_attr __user *uattr)
	{
	enum netns_bpf_attach_type type;
	struct net *net;
	int ret;

	if (attr->query.query_flags)
	return -EINVAL;

	type = to_netns_bpf_attach_type(attr->query.attach_type);
	if (type < 0)
	return -EINVAL;

	net = get_net_ns_by_fd(attr->query.target_fd);
	if (IS_ERR(net))
	return PTR_ERR(net);

	mutex_lock(&netns_bpf_mutex);
	ret = __netns_bpf_prog_query(attr, uattr, net, type);
	mutex_unlock(&netns_bpf_mutex);

	put_net(net);
	return ret;
	}

	int netns_bpf_prog_attach(const union bpf_attr attr, struct bpf_prog prog)
	{
	struct bpf_prog_array *run_array;
	enum netns_bpf_attach_type type;
	struct bpf_prog *attached;
	struct net *net;
	int ret;

	if (attr->target_fd \|\| attr->attach_flags \|\| attr->replace_bpf_fd)
	return -EINVAL;

	type = to_netns_bpf_attach_type(attr->attach_type);
	if (type < 0)
	return -EINVAL;

	net = current->nsproxy->net_ns;
	mutex_lock(&netns_bpf_mutex);

	/* Attaching prog directly is not compatible with links */
	if (!list_empty(&net->bpf.links[type])) {
	ret = -EEXIST;
	goto out_unlock;
	}

	switch (type) {
	case NETNS_BPF_FLOW_DISSECTOR:
	ret = flow_dissector_bpf_prog_attach_check(net, prog);
	break;
	default:
	ret = -EINVAL;
	break;
	}
	if (ret)
	goto out_unlock;

	attached = net->bpf.progs[type];
	if (attached == prog) {
	/* The same program cannot be attached twice */
	ret = -EINVAL;
	goto out_unlock;
	}

	run_array = rcu_dereference_protected(net->bpf.run_array[type],
	lockdep_is_held(&netns_bpf_mutex));
	if (run_array) {
	WRITE_ONCE(run_array->items[0].prog, prog);
	} else {
	run_array = bpf_prog_array_alloc(1, GFP_KERNEL);
	if (!run_array) {
	ret = -ENOMEM;
	goto out_unlock;
	}
	run_array->items[0].prog = prog;
	rcu_assign_pointer(net->bpf.run_array[type], run_array);
	}

	net->bpf.progs[type] = prog;
	if (attached)
	bpf_prog_put(attached);

	out_unlock:
	mutex_unlock(&netns_bpf_mutex);

	return ret;
	}

	/* Must be called with netns_bpf_mutex held. */
	static int __netns_bpf_prog_detach(struct net *net,
	enum netns_bpf_attach_type type,
	struct bpf_prog *old)
	{
	struct bpf_prog *attached;

	/* Progs attached via links cannot be detached */
	if (!list_empty(&net->bpf.links[type]))
	return -EINVAL;

	attached = net->bpf.progs[type];
	if (!attached \|\| attached != old)
	return -ENOENT;
	netns_bpf_run_array_detach(net, type);
	net->bpf.progs[type] = NULL;
	bpf_prog_put(attached);
	return 0;
	}

	int netns_bpf_prog_detach(const union bpf_attr *attr, enum bpf_prog_type ptype)
	{
	enum netns_bpf_attach_type type;
	struct bpf_prog *prog;
	int ret;

	if (attr->target_fd)
	return -EINVAL;

	type = to_netns_bpf_attach_type(attr->attach_type);
	if (type < 0)
	return -EINVAL;

	prog = bpf_prog_get_type(attr->attach_bpf_fd, ptype);
	if (IS_ERR(prog))
	return PTR_ERR(prog);

	mutex_lock(&netns_bpf_mutex);
	ret = __netns_bpf_prog_detach(current->nsproxy->net_ns, type, prog);
	mutex_unlock(&netns_bpf_mutex);

	bpf_prog_put(prog);

	return ret;
	}

	static int netns_bpf_max_progs(enum netns_bpf_attach_type type)
	{
	switch (type) {
	case NETNS_BPF_FLOW_DISSECTOR:
	return 1;
	case NETNS_BPF_SK_LOOKUP:
	return 64;
	default:
	return 0;
	}
	}

	static int netns_bpf_link_attach(struct net net, struct bpf_link link,
	enum netns_bpf_attach_type type)
	{
	struct bpf_netns_link *net_link =
	container_of(link, struct bpf_netns_link, link);
	struct bpf_prog_array *run_array;
	int cnt, err;

	mutex_lock(&netns_bpf_mutex);

	cnt = link_count(net, type);
	if (cnt >= netns_bpf_max_progs(type)) {
	err = -E2BIG;
	goto out_unlock;
	}
	/* Links are not compatible with attaching prog directly */
	if (net->bpf.progs[type]) {
	err = -EEXIST;
	goto out_unlock;
	}

	switch (type) {
	case NETNS_BPF_FLOW_DISSECTOR:
	err = flow_dissector_bpf_prog_attach_check(net, link->prog);
	break;
	case NETNS_BPF_SK_LOOKUP:
	err = 0; /* nothing to check */
	break;
	default:
	err = -EINVAL;
	break;
	}
	if (err)
	goto out_unlock;

	run_array = bpf_prog_array_alloc(cnt + 1, GFP_KERNEL);
	if (!run_array) {
	err = -ENOMEM;
	goto out_unlock;
	}

	list_add_tail(&net_link->node, &net->bpf.links[type]);

	fill_prog_array(net, type, run_array);
	run_array = rcu_replace_pointer(net->bpf.run_array[type], run_array,
	lockdep_is_held(&netns_bpf_mutex));
	bpf_prog_array_free(run_array);

	/* Mark attach point as used */
	netns_bpf_attach_type_need(type);

	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 int __net_init netns_bpf_pernet_init(struct net *net)
	{
	int type;

	for (type = 0; type < MAX_NETNS_BPF_ATTACH_TYPE; type++)
	INIT_LIST_HEAD(&net->bpf.links[type]);

	return 0;
	}

	static void __net_exit netns_bpf_pernet_pre_exit(struct net *net)
	{
	enum netns_bpf_attach_type type;
	struct bpf_netns_link *net_link;

	mutex_lock(&netns_bpf_mutex);
	for (type = 0; type < MAX_NETNS_BPF_ATTACH_TYPE; type++) {
	netns_bpf_run_array_detach(net, type);
	list_for_each_entry(net_link, &net->bpf.links[type], node) {
	net_link->net = NULL; /* auto-detach link */
	netns_bpf_attach_type_unneed(type);
	}
	if (net->bpf.progs[type])
	bpf_prog_put(net->bpf.progs[type]);
	}
	mutex_unlock(&netns_bpf_mutex);
	}

	static struct pernet_operations netns_bpf_pernet_ops __net_initdata = {
	.init = netns_bpf_pernet_init,
	.pre_exit = netns_bpf_pernet_pre_exit,
	};

	static int __init netns_bpf_init(void)
	{
	return register_pernet_subsys(&netns_bpf_pernet_ops);
	}

	subsys_initcall(netns_bpf_init);