summaryrefslogtreecommitdiffstats
path: root/lib/kobject_uevent.c
blob: 63d0816ab23b09a2cfac1576a0f74957a5158d81 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
// 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] == '\n' || 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] == '\n' || 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\n";
		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\n";
		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);
		printk(KERN_WARNING "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\n");
		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;

	pr_debug("kobject: '%s' (%p): %s\n",
		 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!\n", 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!\n",
				 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!\n",
				 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!\n", 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\n", 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_REMOVE:
		kobj->state_remove_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", (unsigned long long)++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\n");
		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\n");
		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) {
		printk(KERN_ERR
		       "kobject_uevent: unable to create netlink socket!\n");
		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
OpenPOWER on IntegriCloud