// SPDX-License-Identifier: GPL-2.0

  /*
   * kernel userspace event delivery
   *
   * Copyright (C) 2004 Red Hat, Inc.  All rights reserved.
   * Copyright (C) 2004 Novell, Inc.  All rights reserved.
   * Copyright (C) 2004 IBM, Inc. All rights reserved.
   *

   * Authors:
   *	Robert Love		<rml@novell.com>
   *	Kay Sievers		<kay.sievers@vrfy.org>
   *	Arjan van de Ven	<arjanv@redhat.com>
   *	Greg Kroah-Hartman	<greg@kroah.com>
   */
  
  #include <linux/spinlock.h>

  #include <linux/string.h>
  #include <linux/kobject.h>

  #include <linux/export.h>
  #include <linux/kmod.h>

  #include <linux/slab.h>

  #include <linux/socket.h>
  #include <linux/skbuff.h>
  #include <linux/netlink.h>

  #include <linux/uidgid.h>

  #include <linux/uuid.h>
  #include <linux/ctype.h>

  #include <net/sock.h>

  #include <net/netlink.h>

  #include <net/net_namespace.h>

  u64 uevent_seqnum;

  #ifdef CONFIG_UEVENT_HELPER

  char uevent_helper[UEVENT_HELPER_PATH_LEN] = CONFIG_UEVENT_HELPER_PATH;

  #endif

  struct uevent_sock {
  	struct list_head list;
  	struct sock *sk;
  };

  
  #ifdef CONFIG_NET

  static LIST_HEAD(uevent_sock_list);

  #endif

  /* This lock protects uevent_seqnum and uevent_sock_list */
  static DEFINE_MUTEX(uevent_sock_mutex);

  /* the strings here must match the enum in include/linux/kobject.h */
  static const char *kobject_actions[] = {
  	[KOBJ_ADD] =		"add",
  	[KOBJ_REMOVE] =		"remove",
  	[KOBJ_CHANGE] =		"change",
  	[KOBJ_MOVE] =		"move",
  	[KOBJ_ONLINE] =		"online",
  	[KOBJ_OFFLINE] =	"offline",

  	[KOBJ_BIND] =		"bind",
  	[KOBJ_UNBIND] =		"unbind",

  };

  static int kobject_action_type(const char *buf, size_t count,
  			       enum kobject_action *type,
  			       const char **args)

  {
  	enum kobject_action action;

  	size_t count_first;
  	const char *args_start;

  	int ret = -EINVAL;

  	if (count && (buf[count-1] == '
  ' || buf[count-1] == '\0'))

  		count--;
  
  	if (!count)
  		goto out;

  	args_start = strnchr(buf, count, ' ');
  	if (args_start) {
  		count_first = args_start - buf;
  		args_start = args_start + 1;
  	} else
  		count_first = count;

  	for (action = 0; action < ARRAY_SIZE(kobject_actions); action++) {

  		if (strncmp(kobject_actions[action], buf, count_first) != 0)

  			continue;

  		if (kobject_actions[action][count_first] != '\0')

  			continue;

  		if (args)
  			*args = args_start;

  		*type = action;
  		ret = 0;
  		break;
  	}
  out:
  	return ret;
  }

  static const char *action_arg_word_end(const char *buf, const char *buf_end,
  				       char delim)
  {
  	const char *next = buf;
  
  	while (next <= buf_end && *next != delim)
  		if (!isalnum(*next++))
  			return NULL;
  
  	if (next == buf)
  		return NULL;
  
  	return next;
  }
  
  static int kobject_action_args(const char *buf, size_t count,
  			       struct kobj_uevent_env **ret_env)
  {
  	struct kobj_uevent_env *env = NULL;
  	const char *next, *buf_end, *key;
  	int key_len;
  	int r = -EINVAL;
  
  	if (count && (buf[count - 1] == '
  ' || buf[count - 1] == '\0'))
  		count--;
  
  	if (!count)
  		return -EINVAL;
  
  	env = kzalloc(sizeof(*env), GFP_KERNEL);
  	if (!env)
  		return -ENOMEM;
  
  	/* first arg is UUID */
  	if (count < UUID_STRING_LEN || !uuid_is_valid(buf) ||
  	    add_uevent_var(env, "SYNTH_UUID=%.*s", UUID_STRING_LEN, buf))
  		goto out;
  
  	/*
  	 * the rest are custom environment variables in KEY=VALUE
  	 * format with ' ' delimiter between each KEY=VALUE pair
  	 */
  	next = buf + UUID_STRING_LEN;
  	buf_end = buf + count - 1;
  
  	while (next <= buf_end) {
  		if (*next != ' ')
  			goto out;
  
  		/* skip the ' ', key must follow */
  		key = ++next;
  		if (key > buf_end)
  			goto out;
  
  		buf = next;
  		next = action_arg_word_end(buf, buf_end, '=');
  		if (!next || next > buf_end || *next != '=')
  			goto out;
  		key_len = next - buf;
  
  		/* skip the '=', value must follow */
  		if (++next > buf_end)
  			goto out;
  
  		buf = next;
  		next = action_arg_word_end(buf, buf_end, ' ');
  		if (!next)
  			goto out;
  
  		if (add_uevent_var(env, "SYNTH_ARG_%.*s=%.*s",
  				   key_len, key, (int) (next - buf), buf))
  			goto out;
  	}
  
  	r = 0;
  out:
  	if (r)
  		kfree(env);
  	else
  		*ret_env = env;
  	return r;
  }
  
  /**
   * kobject_synth_uevent - send synthetic uevent with arguments
   *
   * @kobj: struct kobject for which synthetic uevent is to be generated
   * @buf: buffer containing action type and action args, newline is ignored
   * @count: length of buffer
   *
   * Returns 0 if kobject_synthetic_uevent() is completed with success or the
   * corresponding error when it fails.
   */
  int kobject_synth_uevent(struct kobject *kobj, const char *buf, size_t count)
  {
  	char *no_uuid_envp[] = { "SYNTH_UUID=0", NULL };
  	enum kobject_action action;
  	const char *action_args;
  	struct kobj_uevent_env *env;
  	const char *msg = NULL, *devpath;
  	int r;
  
  	r = kobject_action_type(buf, count, &action, &action_args);
  	if (r) {

  		msg = "unknown uevent action string";

  		goto out;
  	}
  
  	if (!action_args) {
  		r = kobject_uevent_env(kobj, action, no_uuid_envp);
  		goto out;
  	}
  
  	r = kobject_action_args(action_args,
  				count - (action_args - buf), &env);
  	if (r == -EINVAL) {

  		msg = "incorrect uevent action arguments";

  		goto out;
  	}
  
  	if (r)
  		goto out;
  
  	r = kobject_uevent_env(kobj, action, env->envp);
  	kfree(env);
  out:
  	if (r) {
  		devpath = kobject_get_path(kobj, GFP_KERNEL);

  		pr_warn("synth uevent: %s: %s
  ",

  		       devpath ?: "unknown device",
  		       msg ?: "failed to send uevent");
  		kfree(devpath);
  	}
  	return r;
  }

  #ifdef CONFIG_UEVENT_HELPER

  static int kobj_usermode_filter(struct kobject *kobj)
  {
  	const struct kobj_ns_type_operations *ops;
  
  	ops = kobj_ns_ops(kobj);
  	if (ops) {
  		const void *init_ns, *ns;

  		ns = kobj->ktype->namespace(kobj);
  		init_ns = ops->initial_ns();
  		return ns != init_ns;
  	}
  
  	return 0;
  }

  static int init_uevent_argv(struct kobj_uevent_env *env, const char *subsystem)
  {
  	int len;
  
  	len = strlcpy(&env->buf[env->buflen], subsystem,
  		      sizeof(env->buf) - env->buflen);
  	if (len >= (sizeof(env->buf) - env->buflen)) {
  		WARN(1, KERN_ERR "init_uevent_argv: buffer size too small
  ");
  		return -ENOMEM;
  	}
  
  	env->argv[0] = uevent_helper;
  	env->argv[1] = &env->buf[env->buflen];
  	env->argv[2] = NULL;
  
  	env->buflen += len + 1;
  	return 0;
  }
  
  static void cleanup_uevent_env(struct subprocess_info *info)
  {
  	kfree(info->data);
  }

  #endif

  #ifdef CONFIG_NET
  static struct sk_buff *alloc_uevent_skb(struct kobj_uevent_env *env,
  					const char *action_string,
  					const char *devpath)
  {
  	struct netlink_skb_parms *parms;
  	struct sk_buff *skb = NULL;
  	char *scratch;
  	size_t len;
  
  	/* allocate message with maximum possible size */
  	len = strlen(action_string) + strlen(devpath) + 2;
  	skb = alloc_skb(len + env->buflen, GFP_KERNEL);
  	if (!skb)
  		return NULL;
  
  	/* add header */
  	scratch = skb_put(skb, len);
  	sprintf(scratch, "%s@%s", action_string, devpath);
  
  	skb_put_data(skb, env->buf, env->buflen);
  
  	parms = &NETLINK_CB(skb);
  	parms->creds.uid = GLOBAL_ROOT_UID;
  	parms->creds.gid = GLOBAL_ROOT_GID;
  	parms->dst_group = 1;
  	parms->portid = 0;
  
  	return skb;
  }

  static int uevent_net_broadcast_untagged(struct kobj_uevent_env *env,
  					 const char *action_string,
  					 const char *devpath)

  {

  	struct sk_buff *skb = NULL;

  	struct uevent_sock *ue_sk;

  	int retval = 0;

  
  	/* send netlink message */
  	list_for_each_entry(ue_sk, &uevent_sock_list, list) {
  		struct sock *uevent_sock = ue_sk->sk;

  
  		if (!netlink_has_listeners(uevent_sock, 1))
  			continue;

  		if (!skb) {

  			retval = -ENOMEM;

  			skb = alloc_uevent_skb(env, action_string, devpath);

  			if (!skb)
  				continue;

  		}

  		retval = netlink_broadcast(uevent_sock, skb_get(skb), 0, 1,
  					   GFP_KERNEL);

  		/* ENOBUFS should be handled in userspace */
  		if (retval == -ENOBUFS || retval == -ESRCH)
  			retval = 0;

  	}

  	consume_skb(skb);

  	return retval;
  }

  static int uevent_net_broadcast_tagged(struct sock *usk,
  				       struct kobj_uevent_env *env,
  				       const char *action_string,
  				       const char *devpath)
  {
  	struct user_namespace *owning_user_ns = sock_net(usk)->user_ns;
  	struct sk_buff *skb = NULL;
  	int ret = 0;
  
  	skb = alloc_uevent_skb(env, action_string, devpath);
  	if (!skb)
  		return -ENOMEM;
  
  	/* fix credentials */
  	if (owning_user_ns != &init_user_ns) {
  		struct netlink_skb_parms *parms = &NETLINK_CB(skb);
  		kuid_t root_uid;
  		kgid_t root_gid;
  
  		/* fix uid */
  		root_uid = make_kuid(owning_user_ns, 0);
  		if (uid_valid(root_uid))
  			parms->creds.uid = root_uid;
  
  		/* fix gid */
  		root_gid = make_kgid(owning_user_ns, 0);
  		if (gid_valid(root_gid))
  			parms->creds.gid = root_gid;
  	}
  
  	ret = netlink_broadcast(usk, skb, 0, 1, GFP_KERNEL);
  	/* ENOBUFS should be handled in userspace */
  	if (ret == -ENOBUFS || ret == -ESRCH)
  		ret = 0;
  
  	return ret;
  }
  #endif
  
  static int kobject_uevent_net_broadcast(struct kobject *kobj,
  					struct kobj_uevent_env *env,
  					const char *action_string,
  					const char *devpath)
  {
  	int ret = 0;
  
  #ifdef CONFIG_NET
  	const struct kobj_ns_type_operations *ops;
  	const struct net *net = NULL;
  
  	ops = kobj_ns_ops(kobj);
  	if (!ops && kobj->kset) {
  		struct kobject *ksobj = &kobj->kset->kobj;

  		if (ksobj->parent != NULL)
  			ops = kobj_ns_ops(ksobj->parent);
  	}
  
  	/* kobjects currently only carry network namespace tags and they
  	 * are the only tag relevant here since we want to decide which
  	 * network namespaces to broadcast the uevent into.
  	 */
  	if (ops && ops->netlink_ns && kobj->ktype->namespace)
  		if (ops->type == KOBJ_NS_TYPE_NET)
  			net = kobj->ktype->namespace(kobj);
  
  	if (!net)
  		ret = uevent_net_broadcast_untagged(env, action_string,
  						    devpath);
  	else
  		ret = uevent_net_broadcast_tagged(net->uevent_sock->sk, env,
  						  action_string, devpath);
  #endif
  
  	return ret;
  }

  static void zap_modalias_env(struct kobj_uevent_env *env)
  {
  	static const char modalias_prefix[] = "MODALIAS=";

  	size_t len;
  	int i, j;

  
  	for (i = 0; i < env->envp_idx;) {
  		if (strncmp(env->envp[i], modalias_prefix,
  			    sizeof(modalias_prefix) - 1)) {
  			i++;
  			continue;
  		}

  		len = strlen(env->envp[i]) + 1;
  
  		if (i != env->envp_idx - 1) {
  			memmove(env->envp[i], env->envp[i + 1],
  				env->buflen - len);
  
  			for (j = i; j < env->envp_idx - 1; j++)
  				env->envp[j] = env->envp[j + 1] - len;
  		}

  
  		env->envp_idx--;

  		env->buflen -= len;

  	}
  }

  /**

   * kobject_uevent_env - send an uevent with environmental data

   *

   * @kobj: struct kobject that the action is happening to

   * @action: action that is happening

   * @envp_ext: pointer to environmental data

   *

   * Returns 0 if kobject_uevent_env() is completed with success or the

   * corresponding error when it fails.

   */

  int kobject_uevent_env(struct kobject *kobj, enum kobject_action action,

  		       char *envp_ext[])

  {

  	struct kobj_uevent_env *env;
  	const char *action_string = kobject_actions[action];

  	const char *devpath = NULL;
  	const char *subsystem;
  	struct kobject *top_kobj;
  	struct kset *kset;

  	const struct kset_uevent_ops *uevent_ops;

  	int i = 0;

  	int retval = 0;

  	/*
  	 * Mark "remove" event done regardless of result, for some subsystems
  	 * do not want to re-trigger "remove" event via automatic cleanup.
  	 */
  	if (action == KOBJ_REMOVE)
  		kobj->state_remove_uevent_sent = 1;

  	pr_debug("kobject: '%s' (%p): %s
  ",

  		 kobject_name(kobj), kobj, __func__);

  	/* search the kset we belong to */
  	top_kobj = kobj;

  	while (!top_kobj->kset && top_kobj->parent)

  		top_kobj = top_kobj->parent;

  	if (!top_kobj->kset) {

  		pr_debug("kobject: '%s' (%p): %s: attempted to send uevent "
  			 "without kset!
  ", kobject_name(kobj), kobj,

  			 __func__);

  		return -EINVAL;
  	}

  	kset = top_kobj->kset;

  	uevent_ops = kset->uevent_ops;

  	/* skip the event, if uevent_suppress is set*/
  	if (kobj->uevent_suppress) {
  		pr_debug("kobject: '%s' (%p): %s: uevent_suppress "
  				 "caused the event to drop!
  ",
  				 kobject_name(kobj), kobj, __func__);
  		return 0;
  	}

  	/* skip the event, if the filter returns zero. */

  	if (uevent_ops && uevent_ops->filter)

  		if (!uevent_ops->filter(kset, kobj)) {

  			pr_debug("kobject: '%s' (%p): %s: filter function "
  				 "caused the event to drop!
  ",

  				 kobject_name(kobj), kobj, __func__);

  			return 0;
  		}

  	/* originating subsystem */
  	if (uevent_ops && uevent_ops->name)
  		subsystem = uevent_ops->name(kset, kobj);
  	else
  		subsystem = kobject_name(&kset->kobj);
  	if (!subsystem) {

  		pr_debug("kobject: '%s' (%p): %s: unset subsystem caused the "
  			 "event to drop!
  ", kobject_name(kobj), kobj,

  			 __func__);

  		return 0;
  	}

  	/* environment buffer */
  	env = kzalloc(sizeof(struct kobj_uevent_env), GFP_KERNEL);
  	if (!env)

  		return -ENOMEM;

  	/* complete object path */
  	devpath = kobject_get_path(kobj, GFP_KERNEL);

  	if (!devpath) {
  		retval = -ENOENT;

  		goto exit;

  	}

  	/* default keys */

  	retval = add_uevent_var(env, "ACTION=%s", action_string);
  	if (retval)
  		goto exit;
  	retval = add_uevent_var(env, "DEVPATH=%s", devpath);
  	if (retval)
  		goto exit;
  	retval = add_uevent_var(env, "SUBSYSTEM=%s", subsystem);
  	if (retval)
  		goto exit;
  
  	/* keys passed in from the caller */
  	if (envp_ext) {
  		for (i = 0; envp_ext[i]; i++) {

  			retval = add_uevent_var(env, "%s", envp_ext[i]);

  			if (retval)
  				goto exit;
  		}
  	}

  	/* let the kset specific function add its stuff */

  	if (uevent_ops && uevent_ops->uevent) {

  		retval = uevent_ops->uevent(kset, kobj, env);

  		if (retval) {

  			pr_debug("kobject: '%s' (%p): %s: uevent() returned "
  				 "%d
  ", kobject_name(kobj), kobj,

  				 __func__, retval);

  			goto exit;
  		}
  	}

  	switch (action) {
  	case KOBJ_ADD:
  		/*
  		 * Mark "add" event so we can make sure we deliver "remove"
  		 * event to userspace during automatic cleanup. If
  		 * the object did send an "add" event, "remove" will
  		 * automatically generated by the core, if not already done
  		 * by the caller.
  		 */

  		kobj->state_add_uevent_sent = 1;

  		break;

  	case KOBJ_UNBIND:
  		zap_modalias_env(env);
  		break;
  
  	default:
  		break;
  	}

  	mutex_lock(&uevent_sock_mutex);

  	/* we will send an event, so request a new sequence number */

  	retval = add_uevent_var(env, "SEQNUM=%llu", ++uevent_seqnum);

  	if (retval) {
  		mutex_unlock(&uevent_sock_mutex);

  		goto exit;

  	}

  	retval = kobject_uevent_net_broadcast(kobj, env, action_string,
  					      devpath);

  	mutex_unlock(&uevent_sock_mutex);

  #ifdef CONFIG_UEVENT_HELPER

  	/* call uevent_helper, usually only enabled during early boot */

  	if (uevent_helper[0] && !kobj_usermode_filter(kobj)) {

  		struct subprocess_info *info;

  		retval = add_uevent_var(env, "HOME=/");
  		if (retval)
  			goto exit;

  		retval = add_uevent_var(env,
  					"PATH=/sbin:/bin:/usr/sbin:/usr/bin");

  		if (retval)
  			goto exit;

  		retval = init_uevent_argv(env, subsystem);
  		if (retval)
  			goto exit;

  		retval = -ENOMEM;
  		info = call_usermodehelper_setup(env->argv[0], env->argv,
  						 env->envp, GFP_KERNEL,
  						 NULL, cleanup_uevent_env, env);
  		if (info) {
  			retval = call_usermodehelper_exec(info, UMH_NO_WAIT);
  			env = NULL;	/* freed by cleanup_uevent_env */
  		}

  	}

  #endif

  
  exit:

  	kfree(devpath);

  	kfree(env);

  	return retval;

  }

  EXPORT_SYMBOL_GPL(kobject_uevent_env);
  
  /**

   * kobject_uevent - notify userspace by sending an uevent

   *

   * @kobj: struct kobject that the action is happening to

   * @action: action that is happening

   *
   * Returns 0 if kobject_uevent() is completed with success or the
   * corresponding error when it fails.

   */

  int kobject_uevent(struct kobject *kobj, enum kobject_action action)

  {

  	return kobject_uevent_env(kobj, action, NULL);

  }

  EXPORT_SYMBOL_GPL(kobject_uevent);

  
  /**

   * add_uevent_var - add key value string to the environment buffer
   * @env: environment buffer structure
   * @format: printf format for the key=value pair

   *
   * Returns 0 if environment variable was added successfully or -ENOMEM
   * if no space was available.
   */

  int add_uevent_var(struct kobj_uevent_env *env, const char *format, ...)

  {
  	va_list args;

  	int len;

  	if (env->envp_idx >= ARRAY_SIZE(env->envp)) {

  		WARN(1, KERN_ERR "add_uevent_var: too many keys
  ");

  		return -ENOMEM;

  	}

  
  	va_start(args, format);

  	len = vsnprintf(&env->buf[env->buflen],
  			sizeof(env->buf) - env->buflen,
  			format, args);

  	va_end(args);

  	if (len >= (sizeof(env->buf) - env->buflen)) {

  		WARN(1, KERN_ERR "add_uevent_var: buffer size too small
  ");

  		return -ENOMEM;

  	}

  	env->envp[env->envp_idx++] = &env->buf[env->buflen];
  	env->buflen += len + 1;

  	return 0;
  }

  EXPORT_SYMBOL_GPL(add_uevent_var);

  #if defined(CONFIG_NET)

  static int uevent_net_broadcast(struct sock *usk, struct sk_buff *skb,
  				struct netlink_ext_ack *extack)
  {
  	/* u64 to chars: 2^64 - 1 = 21 chars */
  	char buf[sizeof("SEQNUM=") + 21];
  	struct sk_buff *skbc;
  	int ret;
  
  	/* bump and prepare sequence number */
  	ret = snprintf(buf, sizeof(buf), "SEQNUM=%llu", ++uevent_seqnum);
  	if (ret < 0 || (size_t)ret >= sizeof(buf))
  		return -ENOMEM;
  	ret++;
  
  	/* verify message does not overflow */
  	if ((skb->len + ret) > UEVENT_BUFFER_SIZE) {
  		NL_SET_ERR_MSG(extack, "uevent message too big");
  		return -EINVAL;
  	}
  
  	/* copy skb and extend to accommodate sequence number */
  	skbc = skb_copy_expand(skb, 0, ret, GFP_KERNEL);
  	if (!skbc)
  		return -ENOMEM;
  
  	/* append sequence number */
  	skb_put_data(skbc, buf, ret);
  
  	/* remove msg header */
  	skb_pull(skbc, NLMSG_HDRLEN);
  
  	/* set portid 0 to inform userspace message comes from kernel */
  	NETLINK_CB(skbc).portid = 0;
  	NETLINK_CB(skbc).dst_group = 1;
  
  	ret = netlink_broadcast(usk, skbc, 0, 1, GFP_KERNEL);
  	/* ENOBUFS should be handled in userspace */
  	if (ret == -ENOBUFS || ret == -ESRCH)
  		ret = 0;
  
  	return ret;
  }
  
  static int uevent_net_rcv_skb(struct sk_buff *skb, struct nlmsghdr *nlh,
  			      struct netlink_ext_ack *extack)
  {
  	struct net *net;
  	int ret;
  
  	if (!nlmsg_data(nlh))
  		return -EINVAL;
  
  	/*
  	 * Verify that we are allowed to send messages to the target
  	 * network namespace. The caller must have CAP_SYS_ADMIN in the
  	 * owning user namespace of the target network namespace.
  	 */
  	net = sock_net(NETLINK_CB(skb).sk);
  	if (!netlink_ns_capable(skb, net->user_ns, CAP_SYS_ADMIN)) {
  		NL_SET_ERR_MSG(extack, "missing CAP_SYS_ADMIN capability");
  		return -EPERM;
  	}
  
  	mutex_lock(&uevent_sock_mutex);
  	ret = uevent_net_broadcast(net->uevent_sock->sk, skb, extack);
  	mutex_unlock(&uevent_sock_mutex);
  
  	return ret;
  }
  
  static void uevent_net_rcv(struct sk_buff *skb)
  {
  	netlink_rcv_skb(skb, &uevent_net_rcv_skb);
  }

  static int uevent_net_init(struct net *net)

  {

  	struct uevent_sock *ue_sk;

  	struct netlink_kernel_cfg cfg = {
  		.groups	= 1,

  		.input = uevent_net_rcv,
  		.flags	= NL_CFG_F_NONROOT_RECV

  	};

  
  	ue_sk = kzalloc(sizeof(*ue_sk), GFP_KERNEL);
  	if (!ue_sk)
  		return -ENOMEM;

  	ue_sk->sk = netlink_kernel_create(net, NETLINK_KOBJECT_UEVENT, &cfg);

  	if (!ue_sk->sk) {

  		pr_err("kobject_uevent: unable to create netlink socket!
  ");

  		kfree(ue_sk);

  		return -ENODEV;
  	}

  
  	net->uevent_sock = ue_sk;

  	/* Restrict uevents to initial user namespace. */
  	if (sock_net(ue_sk->sk)->user_ns == &init_user_ns) {
  		mutex_lock(&uevent_sock_mutex);
  		list_add_tail(&ue_sk->list, &uevent_sock_list);
  		mutex_unlock(&uevent_sock_mutex);
  	}

  	return 0;
  }

  static void uevent_net_exit(struct net *net)
  {

  	struct uevent_sock *ue_sk = net->uevent_sock;

  	if (sock_net(ue_sk->sk)->user_ns == &init_user_ns) {
  		mutex_lock(&uevent_sock_mutex);
  		list_del(&ue_sk->list);
  		mutex_unlock(&uevent_sock_mutex);
  	}

  
  	netlink_kernel_release(ue_sk->sk);
  	kfree(ue_sk);
  }
  
  static struct pernet_operations uevent_net_ops = {
  	.init	= uevent_net_init,
  	.exit	= uevent_net_exit,
  };
  
  static int __init kobject_uevent_init(void)
  {

  	return register_pernet_subsys(&uevent_net_ops);
  }

  postcore_initcall(kobject_uevent_init);

  #endif