1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * kernel userspace event delivery
  4 *
  5 * Copyright (C) 2004 Red Hat, Inc.  All rights reserved.
  6 * Copyright (C) 2004 Novell, Inc.  All rights reserved.
  7 * Copyright (C) 2004 IBM, Inc. All rights reserved.
  8 *
  9 * Authors:
 10 *	Robert Love		<rml@novell.com>
 11 *	Kay Sievers		<kay.sievers@vrfy.org>
 12 *	Arjan van de Ven	<arjanv@redhat.com>
 13 *	Greg Kroah-Hartman	<greg@kroah.com>
 14 */
 15
 16#include <linux/spinlock.h>
 17#include <linux/string.h>
 18#include <linux/kobject.h>
 19#include <linux/export.h>
 20#include <linux/kmod.h>
 21#include <linux/slab.h>
 22#include <linux/socket.h>
 23#include <linux/skbuff.h>
 24#include <linux/netlink.h>
 25#include <linux/uidgid.h>
 26#include <linux/uuid.h>
 27#include <linux/ctype.h>
 28#include <net/sock.h>
 29#include <net/netlink.h>
 30#include <net/net_namespace.h>
 31
 32
 33u64 uevent_seqnum;
 34#ifdef CONFIG_UEVENT_HELPER
 35char uevent_helper[UEVENT_HELPER_PATH_LEN] = CONFIG_UEVENT_HELPER_PATH;
 36#endif
 37
 38struct uevent_sock {
 39	struct list_head list;
 40	struct sock *sk;
 41};
 42
 43#ifdef CONFIG_NET
 44static LIST_HEAD(uevent_sock_list);
 45#endif
 46
 47/* This lock protects uevent_seqnum and uevent_sock_list */
 48static DEFINE_MUTEX(uevent_sock_mutex);
 49
 50/* the strings here must match the enum in include/linux/kobject.h */
 51static const char *kobject_actions[] = {
 52	[KOBJ_ADD] =		"add",
 53	[KOBJ_REMOVE] =		"remove",
 54	[KOBJ_CHANGE] =		"change",
 55	[KOBJ_MOVE] =		"move",
 56	[KOBJ_ONLINE] =		"online",
 57	[KOBJ_OFFLINE] =	"offline",
 58	[KOBJ_BIND] =		"bind",
 59	[KOBJ_UNBIND] =		"unbind",
 60};
 61
 62static int kobject_action_type(const char *buf, size_t count,
 63			       enum kobject_action *type,
 64			       const char **args)
 65{
 66	enum kobject_action action;
 67	size_t count_first;
 68	const char *args_start;
 69	int ret = -EINVAL;
 70
 71	if (count && (buf[count-1] == '\n' || buf[count-1] == '\0'))
 72		count--;
 73
 74	if (!count)
 75		goto out;
 76
 77	args_start = strnchr(buf, count, ' ');
 78	if (args_start) {
 79		count_first = args_start - buf;
 80		args_start = args_start + 1;
 81	} else
 82		count_first = count;
 83
 84	for (action = 0; action < ARRAY_SIZE(kobject_actions); action++) {
 85		if (strncmp(kobject_actions[action], buf, count_first) != 0)
 86			continue;
 87		if (kobject_actions[action][count_first] != '\0')
 88			continue;
 89		if (args)
 90			*args = args_start;
 91		*type = action;
 92		ret = 0;
 93		break;
 94	}
 95out:
 96	return ret;
 97}
 98
 99static const char *action_arg_word_end(const char *buf, const char *buf_end,
100				       char delim)
101{
102	const char *next = buf;
103
104	while (next <= buf_end && *next != delim)
105		if (!isalnum(*next++))
106			return NULL;
107
108	if (next == buf)
109		return NULL;
110
111	return next;
112}
113
114static int kobject_action_args(const char *buf, size_t count,
115			       struct kobj_uevent_env **ret_env)
116{
117	struct kobj_uevent_env *env = NULL;
118	const char *next, *buf_end, *key;
119	int key_len;
120	int r = -EINVAL;
121
122	if (count && (buf[count - 1] == '\n' || buf[count - 1] == '\0'))
123		count--;
124
125	if (!count)
126		return -EINVAL;
127
128	env = kzalloc(sizeof(*env), GFP_KERNEL);
129	if (!env)
130		return -ENOMEM;
131
132	/* first arg is UUID */
133	if (count < UUID_STRING_LEN || !uuid_is_valid(buf) ||
134	    add_uevent_var(env, "SYNTH_UUID=%.*s", UUID_STRING_LEN, buf))
135		goto out;
136
137	/*
138	 * the rest are custom environment variables in KEY=VALUE
139	 * format with ' ' delimiter between each KEY=VALUE pair
140	 */
141	next = buf + UUID_STRING_LEN;
142	buf_end = buf + count - 1;
143
144	while (next <= buf_end) {
145		if (*next != ' ')
146			goto out;
147
148		/* skip the ' ', key must follow */
149		key = ++next;
150		if (key > buf_end)
151			goto out;
152
153		buf = next;
154		next = action_arg_word_end(buf, buf_end, '=');
155		if (!next || next > buf_end || *next != '=')
156			goto out;
157		key_len = next - buf;
158
159		/* skip the '=', value must follow */
160		if (++next > buf_end)
161			goto out;
162
163		buf = next;
164		next = action_arg_word_end(buf, buf_end, ' ');
165		if (!next)
166			goto out;
167
168		if (add_uevent_var(env, "SYNTH_ARG_%.*s=%.*s",
169				   key_len, key, (int) (next - buf), buf))
170			goto out;
171	}
172
173	r = 0;
174out:
175	if (r)
176		kfree(env);
177	else
178		*ret_env = env;
179	return r;
180}
181
182/**
183 * kobject_synth_uevent - send synthetic uevent with arguments
184 *
185 * @kobj: struct kobject for which synthetic uevent is to be generated
186 * @buf: buffer containing action type and action args, newline is ignored
187 * @count: length of buffer
188 *
189 * Returns 0 if kobject_synthetic_uevent() is completed with success or the
190 * corresponding error when it fails.
191 */
192int kobject_synth_uevent(struct kobject *kobj, const char *buf, size_t count)
193{
194	char *no_uuid_envp[] = { "SYNTH_UUID=0", NULL };
195	enum kobject_action action;
196	const char *action_args;
197	struct kobj_uevent_env *env;
198	const char *msg = NULL, *devpath;
199	int r;
200
201	r = kobject_action_type(buf, count, &action, &action_args);
202	if (r) {
203		msg = "unknown uevent action string";
204		goto out;
205	}
206
207	if (!action_args) {
208		r = kobject_uevent_env(kobj, action, no_uuid_envp);
209		goto out;
210	}
211
212	r = kobject_action_args(action_args,
213				count - (action_args - buf), &env);
214	if (r == -EINVAL) {
215		msg = "incorrect uevent action arguments";
216		goto out;
217	}
218
219	if (r)
220		goto out;
221
222	r = kobject_uevent_env(kobj, action, env->envp);
223	kfree(env);
224out:
225	if (r) {
226		devpath = kobject_get_path(kobj, GFP_KERNEL);
227		pr_warn("synth uevent: %s: %s\n",
228		       devpath ?: "unknown device",
229		       msg ?: "failed to send uevent");
230		kfree(devpath);
231	}
232	return r;
233}
234
235#ifdef CONFIG_UEVENT_HELPER
236static int kobj_usermode_filter(struct kobject *kobj)
237{
238	const struct kobj_ns_type_operations *ops;
239
240	ops = kobj_ns_ops(kobj);
241	if (ops) {
242		const void *init_ns, *ns;
243
244		ns = kobj->ktype->namespace(kobj);
245		init_ns = ops->initial_ns();
246		return ns != init_ns;
247	}
248
249	return 0;
250}
251
252static int init_uevent_argv(struct kobj_uevent_env *env, const char *subsystem)
253{
254	int buffer_size = sizeof(env->buf) - env->buflen;
255	int len;
256
257	len = strlcpy(&env->buf[env->buflen], subsystem, buffer_size);
258	if (len >= buffer_size) {
259		pr_warn("init_uevent_argv: buffer size of %d too small, needed %d\n",
260			buffer_size, len);
261		return -ENOMEM;
262	}
263
264	env->argv[0] = uevent_helper;
265	env->argv[1] = &env->buf[env->buflen];
266	env->argv[2] = NULL;
267
268	env->buflen += len + 1;
269	return 0;
270}
271
272static void cleanup_uevent_env(struct subprocess_info *info)
273{
274	kfree(info->data);
275}
276#endif
277
278#ifdef CONFIG_NET
279static struct sk_buff *alloc_uevent_skb(struct kobj_uevent_env *env,
280					const char *action_string,
281					const char *devpath)
282{
283	struct netlink_skb_parms *parms;
284	struct sk_buff *skb = NULL;
285	char *scratch;
286	size_t len;
287
288	/* allocate message with maximum possible size */
289	len = strlen(action_string) + strlen(devpath) + 2;
290	skb = alloc_skb(len + env->buflen, GFP_KERNEL);
291	if (!skb)
292		return NULL;
293
294	/* add header */
295	scratch = skb_put(skb, len);
296	sprintf(scratch, "%s@%s", action_string, devpath);
297
298	skb_put_data(skb, env->buf, env->buflen);
299
300	parms = &NETLINK_CB(skb);
301	parms->creds.uid = GLOBAL_ROOT_UID;
302	parms->creds.gid = GLOBAL_ROOT_GID;
303	parms->dst_group = 1;
304	parms->portid = 0;
305
306	return skb;
307}
308
309static int uevent_net_broadcast_untagged(struct kobj_uevent_env *env,
310					 const char *action_string,
311					 const char *devpath)
312{
313	struct sk_buff *skb = NULL;
314	struct uevent_sock *ue_sk;
315	int retval = 0;
316
317	/* send netlink message */
318	list_for_each_entry(ue_sk, &uevent_sock_list, list) {
319		struct sock *uevent_sock = ue_sk->sk;
320
321		if (!netlink_has_listeners(uevent_sock, 1))
322			continue;
323
324		if (!skb) {
325			retval = -ENOMEM;
326			skb = alloc_uevent_skb(env, action_string, devpath);
327			if (!skb)
328				continue;
329		}
330
331		retval = netlink_broadcast(uevent_sock, skb_get(skb), 0, 1,
332					   GFP_KERNEL);
333		/* ENOBUFS should be handled in userspace */
334		if (retval == -ENOBUFS || retval == -ESRCH)
335			retval = 0;
336	}
337	consume_skb(skb);
338
339	return retval;
340}
341
342static int uevent_net_broadcast_tagged(struct sock *usk,
343				       struct kobj_uevent_env *env,
344				       const char *action_string,
345				       const char *devpath)
346{
347	struct user_namespace *owning_user_ns = sock_net(usk)->user_ns;
348	struct sk_buff *skb = NULL;
349	int ret = 0;
350
351	skb = alloc_uevent_skb(env, action_string, devpath);
352	if (!skb)
353		return -ENOMEM;
354
355	/* fix credentials */
356	if (owning_user_ns != &init_user_ns) {
357		struct netlink_skb_parms *parms = &NETLINK_CB(skb);
358		kuid_t root_uid;
359		kgid_t root_gid;
360
361		/* fix uid */
362		root_uid = make_kuid(owning_user_ns, 0);
363		if (uid_valid(root_uid))
364			parms->creds.uid = root_uid;
365
366		/* fix gid */
367		root_gid = make_kgid(owning_user_ns, 0);
368		if (gid_valid(root_gid))
369			parms->creds.gid = root_gid;
370	}
371
372	ret = netlink_broadcast(usk, skb, 0, 1, GFP_KERNEL);
373	/* ENOBUFS should be handled in userspace */
374	if (ret == -ENOBUFS || ret == -ESRCH)
375		ret = 0;
376
377	return ret;
378}
379#endif
380
381static int kobject_uevent_net_broadcast(struct kobject *kobj,
382					struct kobj_uevent_env *env,
383					const char *action_string,
384					const char *devpath)
385{
386	int ret = 0;
387
388#ifdef CONFIG_NET
389	const struct kobj_ns_type_operations *ops;
390	const struct net *net = NULL;
391
392	ops = kobj_ns_ops(kobj);
393	if (!ops && kobj->kset) {
394		struct kobject *ksobj = &kobj->kset->kobj;
395
396		if (ksobj->parent != NULL)
397			ops = kobj_ns_ops(ksobj->parent);
398	}
399
400	/* kobjects currently only carry network namespace tags and they
401	 * are the only tag relevant here since we want to decide which
402	 * network namespaces to broadcast the uevent into.
403	 */
404	if (ops && ops->netlink_ns && kobj->ktype->namespace)
405		if (ops->type == KOBJ_NS_TYPE_NET)
406			net = kobj->ktype->namespace(kobj);
407
408	if (!net)
409		ret = uevent_net_broadcast_untagged(env, action_string,
410						    devpath);
411	else
412		ret = uevent_net_broadcast_tagged(net->uevent_sock->sk, env,
413						  action_string, devpath);
414#endif
415
416	return ret;
417}
418
419static void zap_modalias_env(struct kobj_uevent_env *env)
420{
421	static const char modalias_prefix[] = "MODALIAS=";
422	size_t len;
423	int i, j;
424
425	for (i = 0; i < env->envp_idx;) {
426		if (strncmp(env->envp[i], modalias_prefix,
427			    sizeof(modalias_prefix) - 1)) {
428			i++;
429			continue;
430		}
431
432		len = strlen(env->envp[i]) + 1;
433
434		if (i != env->envp_idx - 1) {
435			memmove(env->envp[i], env->envp[i + 1],
436				env->buflen - len);
437
438			for (j = i; j < env->envp_idx - 1; j++)
439				env->envp[j] = env->envp[j + 1] - len;
440		}
441
442		env->envp_idx--;
443		env->buflen -= len;
444	}
445}
446
447/**
448 * kobject_uevent_env - send an uevent with environmental data
449 *
450 * @kobj: struct kobject that the action is happening to
451 * @action: action that is happening
452 * @envp_ext: pointer to environmental data
453 *
454 * Returns 0 if kobject_uevent_env() is completed with success or the
455 * corresponding error when it fails.
456 */
457int kobject_uevent_env(struct kobject *kobj, enum kobject_action action,
458		       char *envp_ext[])
459{
460	struct kobj_uevent_env *env;
461	const char *action_string = kobject_actions[action];
462	const char *devpath = NULL;
463	const char *subsystem;
464	struct kobject *top_kobj;
465	struct kset *kset;
466	const struct kset_uevent_ops *uevent_ops;
467	int i = 0;
468	int retval = 0;
469
470	/*
471	 * Mark "remove" event done regardless of result, for some subsystems
472	 * do not want to re-trigger "remove" event via automatic cleanup.
473	 */
474	if (action == KOBJ_REMOVE)
475		kobj->state_remove_uevent_sent = 1;
476
477	pr_debug("kobject: '%s' (%p): %s\n",
478		 kobject_name(kobj), kobj, __func__);
479
480	/* search the kset we belong to */
481	top_kobj = kobj;
482	while (!top_kobj->kset && top_kobj->parent)
483		top_kobj = top_kobj->parent;
484
485	if (!top_kobj->kset) {
486		pr_debug("kobject: '%s' (%p): %s: attempted to send uevent "
487			 "without kset!\n", kobject_name(kobj), kobj,
488			 __func__);
489		return -EINVAL;
490	}
491
492	kset = top_kobj->kset;
493	uevent_ops = kset->uevent_ops;
494
495	/* skip the event, if uevent_suppress is set*/
496	if (kobj->uevent_suppress) {
497		pr_debug("kobject: '%s' (%p): %s: uevent_suppress "
498				 "caused the event to drop!\n",
499				 kobject_name(kobj), kobj, __func__);
500		return 0;
501	}
502	/* skip the event, if the filter returns zero. */
503	if (uevent_ops && uevent_ops->filter)
504		if (!uevent_ops->filter(kset, kobj)) {
505			pr_debug("kobject: '%s' (%p): %s: filter function "
506				 "caused the event to drop!\n",
507				 kobject_name(kobj), kobj, __func__);
508			return 0;
509		}
510
511	/* originating subsystem */
512	if (uevent_ops && uevent_ops->name)
513		subsystem = uevent_ops->name(kset, kobj);
514	else
515		subsystem = kobject_name(&kset->kobj);
516	if (!subsystem) {
517		pr_debug("kobject: '%s' (%p): %s: unset subsystem caused the "
518			 "event to drop!\n", kobject_name(kobj), kobj,
519			 __func__);
520		return 0;
521	}
522
523	/* environment buffer */
524	env = kzalloc(sizeof(struct kobj_uevent_env), GFP_KERNEL);
525	if (!env)
526		return -ENOMEM;
527
528	/* complete object path */
529	devpath = kobject_get_path(kobj, GFP_KERNEL);
530	if (!devpath) {
531		retval = -ENOENT;
532		goto exit;
533	}
534
535	/* default keys */
536	retval = add_uevent_var(env, "ACTION=%s", action_string);
537	if (retval)
538		goto exit;
539	retval = add_uevent_var(env, "DEVPATH=%s", devpath);
540	if (retval)
541		goto exit;
542	retval = add_uevent_var(env, "SUBSYSTEM=%s", subsystem);
543	if (retval)
544		goto exit;
545
546	/* keys passed in from the caller */
547	if (envp_ext) {
548		for (i = 0; envp_ext[i]; i++) {
549			retval = add_uevent_var(env, "%s", envp_ext[i]);
550			if (retval)
551				goto exit;
552		}
553	}
554
555	/* let the kset specific function add its stuff */
556	if (uevent_ops && uevent_ops->uevent) {
557		retval = uevent_ops->uevent(kset, kobj, env);
558		if (retval) {
559			pr_debug("kobject: '%s' (%p): %s: uevent() returned "
560				 "%d\n", kobject_name(kobj), kobj,
561				 __func__, retval);
562			goto exit;
563		}
564	}
565
566	switch (action) {
567	case KOBJ_ADD:
568		/*
569		 * Mark "add" event so we can make sure we deliver "remove"
570		 * event to userspace during automatic cleanup. If
571		 * the object did send an "add" event, "remove" will
572		 * automatically generated by the core, if not already done
573		 * by the caller.
574		 */
575		kobj->state_add_uevent_sent = 1;
576		break;
577
578	case KOBJ_UNBIND:
579		zap_modalias_env(env);
580		break;
581
582	default:
583		break;
584	}
585
586	mutex_lock(&uevent_sock_mutex);
587	/* we will send an event, so request a new sequence number */
588	retval = add_uevent_var(env, "SEQNUM=%llu", ++uevent_seqnum);
589	if (retval) {
590		mutex_unlock(&uevent_sock_mutex);
591		goto exit;
592	}
593	retval = kobject_uevent_net_broadcast(kobj, env, action_string,
594					      devpath);
595	mutex_unlock(&uevent_sock_mutex);
596
597#ifdef CONFIG_UEVENT_HELPER
598	/* call uevent_helper, usually only enabled during early boot */
599	if (uevent_helper[0] && !kobj_usermode_filter(kobj)) {
600		struct subprocess_info *info;
601
602		retval = add_uevent_var(env, "HOME=/");
603		if (retval)
604			goto exit;
605		retval = add_uevent_var(env,
606					"PATH=/sbin:/bin:/usr/sbin:/usr/bin");
607		if (retval)
608			goto exit;
609		retval = init_uevent_argv(env, subsystem);
610		if (retval)
611			goto exit;
612
613		retval = -ENOMEM;
614		info = call_usermodehelper_setup(env->argv[0], env->argv,
615						 env->envp, GFP_KERNEL,
616						 NULL, cleanup_uevent_env, env);
617		if (info) {
618			retval = call_usermodehelper_exec(info, UMH_NO_WAIT);
619			env = NULL;	/* freed by cleanup_uevent_env */
620		}
621	}
622#endif
623
624exit:
625	kfree(devpath);
626	kfree(env);
627	return retval;
628}
629EXPORT_SYMBOL_GPL(kobject_uevent_env);
630
631/**
632 * kobject_uevent - notify userspace by sending an uevent
633 *
634 * @kobj: struct kobject that the action is happening to
635 * @action: action that is happening
636 *
637 * Returns 0 if kobject_uevent() is completed with success or the
638 * corresponding error when it fails.
639 */
640int kobject_uevent(struct kobject *kobj, enum kobject_action action)
641{
642	return kobject_uevent_env(kobj, action, NULL);
643}
644EXPORT_SYMBOL_GPL(kobject_uevent);
645
646/**
647 * add_uevent_var - add key value string to the environment buffer
648 * @env: environment buffer structure
649 * @format: printf format for the key=value pair
650 *
651 * Returns 0 if environment variable was added successfully or -ENOMEM
652 * if no space was available.
653 */
654int add_uevent_var(struct kobj_uevent_env *env, const char *format, ...)
655{
656	va_list args;
657	int len;
658
659	if (env->envp_idx >= ARRAY_SIZE(env->envp)) {
660		WARN(1, KERN_ERR "add_uevent_var: too many keys\n");
661		return -ENOMEM;
662	}
663
664	va_start(args, format);
665	len = vsnprintf(&env->buf[env->buflen],
666			sizeof(env->buf) - env->buflen,
667			format, args);
668	va_end(args);
669
670	if (len >= (sizeof(env->buf) - env->buflen)) {
671		WARN(1, KERN_ERR "add_uevent_var: buffer size too small\n");
672		return -ENOMEM;
673	}
674
675	env->envp[env->envp_idx++] = &env->buf[env->buflen];
676	env->buflen += len + 1;
677	return 0;
678}
679EXPORT_SYMBOL_GPL(add_uevent_var);
680
681#if defined(CONFIG_NET)
682static int uevent_net_broadcast(struct sock *usk, struct sk_buff *skb,
683				struct netlink_ext_ack *extack)
684{
685	/* u64 to chars: 2^64 - 1 = 21 chars */
686	char buf[sizeof("SEQNUM=") + 21];
687	struct sk_buff *skbc;
688	int ret;
689
690	/* bump and prepare sequence number */
691	ret = snprintf(buf, sizeof(buf), "SEQNUM=%llu", ++uevent_seqnum);
692	if (ret < 0 || (size_t)ret >= sizeof(buf))
693		return -ENOMEM;
694	ret++;
695
696	/* verify message does not overflow */
697	if ((skb->len + ret) > UEVENT_BUFFER_SIZE) {
698		NL_SET_ERR_MSG(extack, "uevent message too big");
699		return -EINVAL;
700	}
701
702	/* copy skb and extend to accommodate sequence number */
703	skbc = skb_copy_expand(skb, 0, ret, GFP_KERNEL);
704	if (!skbc)
705		return -ENOMEM;
706
707	/* append sequence number */
708	skb_put_data(skbc, buf, ret);
709
710	/* remove msg header */
711	skb_pull(skbc, NLMSG_HDRLEN);
712
713	/* set portid 0 to inform userspace message comes from kernel */
714	NETLINK_CB(skbc).portid = 0;
715	NETLINK_CB(skbc).dst_group = 1;
716
717	ret = netlink_broadcast(usk, skbc, 0, 1, GFP_KERNEL);
718	/* ENOBUFS should be handled in userspace */
719	if (ret == -ENOBUFS || ret == -ESRCH)
720		ret = 0;
721
722	return ret;
723}
724
725static int uevent_net_rcv_skb(struct sk_buff *skb, struct nlmsghdr *nlh,
726			      struct netlink_ext_ack *extack)
727{
728	struct net *net;
729	int ret;
730
731	if (!nlmsg_data(nlh))
732		return -EINVAL;
733
734	/*
735	 * Verify that we are allowed to send messages to the target
736	 * network namespace. The caller must have CAP_SYS_ADMIN in the
737	 * owning user namespace of the target network namespace.
738	 */
739	net = sock_net(NETLINK_CB(skb).sk);
740	if (!netlink_ns_capable(skb, net->user_ns, CAP_SYS_ADMIN)) {
741		NL_SET_ERR_MSG(extack, "missing CAP_SYS_ADMIN capability");
742		return -EPERM;
743	}
744
745	mutex_lock(&uevent_sock_mutex);
746	ret = uevent_net_broadcast(net->uevent_sock->sk, skb, extack);
747	mutex_unlock(&uevent_sock_mutex);
748
749	return ret;
750}
751
752static void uevent_net_rcv(struct sk_buff *skb)
753{
754	netlink_rcv_skb(skb, &uevent_net_rcv_skb);
755}
756
757static int uevent_net_init(struct net *net)
758{
759	struct uevent_sock *ue_sk;
760	struct netlink_kernel_cfg cfg = {
761		.groups	= 1,
762		.input = uevent_net_rcv,
763		.flags	= NL_CFG_F_NONROOT_RECV
764	};
765
766	ue_sk = kzalloc(sizeof(*ue_sk), GFP_KERNEL);
767	if (!ue_sk)
768		return -ENOMEM;
769
770	ue_sk->sk = netlink_kernel_create(net, NETLINK_KOBJECT_UEVENT, &cfg);
771	if (!ue_sk->sk) {
772		pr_err("kobject_uevent: unable to create netlink socket!\n");
773		kfree(ue_sk);
774		return -ENODEV;
775	}
776
777	net->uevent_sock = ue_sk;
778
779	/* Restrict uevents to initial user namespace. */
780	if (sock_net(ue_sk->sk)->user_ns == &init_user_ns) {
781		mutex_lock(&uevent_sock_mutex);
782		list_add_tail(&ue_sk->list, &uevent_sock_list);
783		mutex_unlock(&uevent_sock_mutex);
784	}
785
786	return 0;
787}
788
789static void uevent_net_exit(struct net *net)
790{
791	struct uevent_sock *ue_sk = net->uevent_sock;
792
793	if (sock_net(ue_sk->sk)->user_ns == &init_user_ns) {
794		mutex_lock(&uevent_sock_mutex);
795		list_del(&ue_sk->list);
796		mutex_unlock(&uevent_sock_mutex);
797	}
798
799	netlink_kernel_release(ue_sk->sk);
800	kfree(ue_sk);
801}
802
803static struct pernet_operations uevent_net_ops = {
804	.init	= uevent_net_init,
805	.exit	= uevent_net_exit,
806};
807
808static int __init kobject_uevent_init(void)
809{
810	return register_pernet_subsys(&uevent_net_ops);
811}
812
813
814postcore_initcall(kobject_uevent_init);
815#endif