xref: /linux/lib/kobject_uevent.c (revision fd639726bf15fca8ee1a00dce8e0096d0ad9bd18) 
1 /*
2  * kernel userspace event delivery
3  *
4  * Copyright (C) 2004 Red Hat, Inc.  All rights reserved.
5  * Copyright (C) 2004 Novell, Inc.  All rights reserved.
6  * Copyright (C) 2004 IBM, Inc. All rights reserved.
7  *
8  * Licensed under the GNU GPL v2.
9  *
10  * Authors:
11  *	Robert Love		<rml@novell.com>
12  *	Kay Sievers		<kay.sievers@vrfy.org>
13  *	Arjan van de Ven	<arjanv@redhat.com>
14  *	Greg Kroah-Hartman	<greg@kroah.com>
15  */
16 
17 #include <linux/spinlock.h>
18 #include <linux/string.h>
19 #include <linux/kobject.h>
20 #include <linux/export.h>
21 #include <linux/kmod.h>
22 #include <linux/slab.h>
23 #include <linux/socket.h>
24 #include <linux/skbuff.h>
25 #include <linux/netlink.h>
26 #include <linux/uuid.h>
27 #include <linux/ctype.h>
28 #include <net/sock.h>
29 #include <net/net_namespace.h>
30 
31 
32 u64 uevent_seqnum;
33 #ifdef CONFIG_UEVENT_HELPER
34 char uevent_helper[UEVENT_HELPER_PATH_LEN] = CONFIG_UEVENT_HELPER_PATH;
35 #endif
36 #ifdef CONFIG_NET
37 struct uevent_sock {
38 	struct list_head list;
39 	struct sock *sk;
40 };
41 static LIST_HEAD(uevent_sock_list);
42 #endif
43 
44 /* This lock protects uevent_seqnum and uevent_sock_list */
45 static DEFINE_MUTEX(uevent_sock_mutex);
46 
47 /* the strings here must match the enum in include/linux/kobject.h */
48 static const char *kobject_actions[] = {
49 	[KOBJ_ADD] =		"add",
50 	[KOBJ_REMOVE] =		"remove",
51 	[KOBJ_CHANGE] =		"change",
52 	[KOBJ_MOVE] =		"move",
53 	[KOBJ_ONLINE] =		"online",
54 	[KOBJ_OFFLINE] =	"offline",
55 	[KOBJ_BIND] =		"bind",
56 	[KOBJ_UNBIND] =		"unbind",
57 };
58 
59 static int kobject_action_type(const char *buf, size_t count,
60 			       enum kobject_action *type,
61 			       const char **args)
62 {
63 	enum kobject_action action;
64 	size_t count_first;
65 	const char *args_start;
66 	int ret = -EINVAL;
67 
68 	if (count && (buf[count-1] == '\n' || buf[count-1] == '\0'))
69 		count--;
70 
71 	if (!count)
72 		goto out;
73 
74 	args_start = strnchr(buf, count, ' ');
75 	if (args_start) {
76 		count_first = args_start - buf;
77 		args_start = args_start + 1;
78 	} else
79 		count_first = count;
80 
81 	for (action = 0; action < ARRAY_SIZE(kobject_actions); action++) {
82 		if (strncmp(kobject_actions[action], buf, count_first) != 0)
83 			continue;
84 		if (kobject_actions[action][count_first] != '\0')
85 			continue;
86 		if (args)
87 			*args = args_start;
88 		*type = action;
89 		ret = 0;
90 		break;
91 	}
92 out:
93 	return ret;
94 }
95 
96 static const char *action_arg_word_end(const char *buf, const char *buf_end,
97 				       char delim)
98 {
99 	const char *next = buf;
100 
101 	while (next <= buf_end && *next != delim)
102 		if (!isalnum(*next++))
103 			return NULL;
104 
105 	if (next == buf)
106 		return NULL;
107 
108 	return next;
109 }
110 
111 static int kobject_action_args(const char *buf, size_t count,
112 			       struct kobj_uevent_env **ret_env)
113 {
114 	struct kobj_uevent_env *env = NULL;
115 	const char *next, *buf_end, *key;
116 	int key_len;
117 	int r = -EINVAL;
118 
119 	if (count && (buf[count - 1] == '\n' || buf[count - 1] == '\0'))
120 		count--;
121 
122 	if (!count)
123 		return -EINVAL;
124 
125 	env = kzalloc(sizeof(*env), GFP_KERNEL);
126 	if (!env)
127 		return -ENOMEM;
128 
129 	/* first arg is UUID */
130 	if (count < UUID_STRING_LEN || !uuid_is_valid(buf) ||
131 	    add_uevent_var(env, "SYNTH_UUID=%.*s", UUID_STRING_LEN, buf))
132 		goto out;
133 
134 	/*
135 	 * the rest are custom environment variables in KEY=VALUE
136 	 * format with ' ' delimiter between each KEY=VALUE pair
137 	 */
138 	next = buf + UUID_STRING_LEN;
139 	buf_end = buf + count - 1;
140 
141 	while (next <= buf_end) {
142 		if (*next != ' ')
143 			goto out;
144 
145 		/* skip the ' ', key must follow */
146 		key = ++next;
147 		if (key > buf_end)
148 			goto out;
149 
150 		buf = next;
151 		next = action_arg_word_end(buf, buf_end, '=');
152 		if (!next || next > buf_end || *next != '=')
153 			goto out;
154 		key_len = next - buf;
155 
156 		/* skip the '=', value must follow */
157 		if (++next > buf_end)
158 			goto out;
159 
160 		buf = next;
161 		next = action_arg_word_end(buf, buf_end, ' ');
162 		if (!next)
163 			goto out;
164 
165 		if (add_uevent_var(env, "SYNTH_ARG_%.*s=%.*s",
166 				   key_len, key, (int) (next - buf), buf))
167 			goto out;
168 	}
169 
170 	r = 0;
171 out:
172 	if (r)
173 		kfree(env);
174 	else
175 		*ret_env = env;
176 	return r;
177 }
178 
179 /**
180  * kobject_synth_uevent - send synthetic uevent with arguments
181  *
182  * @kobj: struct kobject for which synthetic uevent is to be generated
183  * @buf: buffer containing action type and action args, newline is ignored
184  * @count: length of buffer
185  *
186  * Returns 0 if kobject_synthetic_uevent() is completed with success or the
187  * corresponding error when it fails.
188  */
189 int kobject_synth_uevent(struct kobject *kobj, const char *buf, size_t count)
190 {
191 	char *no_uuid_envp[] = { "SYNTH_UUID=0", NULL };
192 	enum kobject_action action;
193 	const char *action_args;
194 	struct kobj_uevent_env *env;
195 	const char *msg = NULL, *devpath;
196 	int r;
197 
198 	r = kobject_action_type(buf, count, &action, &action_args);
199 	if (r) {
200 		msg = "unknown uevent action string\n";
201 		goto out;
202 	}
203 
204 	if (!action_args) {
205 		r = kobject_uevent_env(kobj, action, no_uuid_envp);
206 		goto out;
207 	}
208 
209 	r = kobject_action_args(action_args,
210 				count - (action_args - buf), &env);
211 	if (r == -EINVAL) {
212 		msg = "incorrect uevent action arguments\n";
213 		goto out;
214 	}
215 
216 	if (r)
217 		goto out;
218 
219 	r = kobject_uevent_env(kobj, action, env->envp);
220 	kfree(env);
221 out:
222 	if (r) {
223 		devpath = kobject_get_path(kobj, GFP_KERNEL);
224 		printk(KERN_WARNING "synth uevent: %s: %s",
225 		       devpath ?: "unknown device",
226 		       msg ?: "failed to send uevent");
227 		kfree(devpath);
228 	}
229 	return r;
230 }
231 
232 #ifdef CONFIG_NET
233 static int kobj_bcast_filter(struct sock *dsk, struct sk_buff *skb, void *data)
234 {
235 	struct kobject *kobj = data, *ksobj;
236 	const struct kobj_ns_type_operations *ops;
237 
238 	ops = kobj_ns_ops(kobj);
239 	if (!ops && kobj->kset) {
240 		ksobj = &kobj->kset->kobj;
241 		if (ksobj->parent != NULL)
242 			ops = kobj_ns_ops(ksobj->parent);
243 	}
244 
245 	if (ops && ops->netlink_ns && kobj->ktype->namespace) {
246 		const void *sock_ns, *ns;
247 		ns = kobj->ktype->namespace(kobj);
248 		sock_ns = ops->netlink_ns(dsk);
249 		return sock_ns != ns;
250 	}
251 
252 	return 0;
253 }
254 #endif
255 
256 #ifdef CONFIG_UEVENT_HELPER
257 static int kobj_usermode_filter(struct kobject *kobj)
258 {
259 	const struct kobj_ns_type_operations *ops;
260 
261 	ops = kobj_ns_ops(kobj);
262 	if (ops) {
263 		const void *init_ns, *ns;
264 		ns = kobj->ktype->namespace(kobj);
265 		init_ns = ops->initial_ns();
266 		return ns != init_ns;
267 	}
268 
269 	return 0;
270 }
271 
272 static int init_uevent_argv(struct kobj_uevent_env *env, const char *subsystem)
273 {
274 	int len;
275 
276 	len = strlcpy(&env->buf[env->buflen], subsystem,
277 		      sizeof(env->buf) - env->buflen);
278 	if (len >= (sizeof(env->buf) - env->buflen)) {
279 		WARN(1, KERN_ERR "init_uevent_argv: buffer size too small\n");
280 		return -ENOMEM;
281 	}
282 
283 	env->argv[0] = uevent_helper;
284 	env->argv[1] = &env->buf[env->buflen];
285 	env->argv[2] = NULL;
286 
287 	env->buflen += len + 1;
288 	return 0;
289 }
290 
291 static void cleanup_uevent_env(struct subprocess_info *info)
292 {
293 	kfree(info->data);
294 }
295 #endif
296 
297 static int kobject_uevent_net_broadcast(struct kobject *kobj,
298 					struct kobj_uevent_env *env,
299 					const char *action_string,
300 					const char *devpath)
301 {
302 	int retval = 0;
303 #if defined(CONFIG_NET)
304 	struct sk_buff *skb = NULL;
305 	struct uevent_sock *ue_sk;
306 
307 	/* send netlink message */
308 	list_for_each_entry(ue_sk, &uevent_sock_list, list) {
309 		struct sock *uevent_sock = ue_sk->sk;
310 
311 		if (!netlink_has_listeners(uevent_sock, 1))
312 			continue;
313 
314 		if (!skb) {
315 			/* allocate message with the maximum possible size */
316 			size_t len = strlen(action_string) + strlen(devpath) + 2;
317 			char *scratch;
318 
319 			retval = -ENOMEM;
320 			skb = alloc_skb(len + env->buflen, GFP_KERNEL);
321 			if (!skb)
322 				continue;
323 
324 			/* add header */
325 			scratch = skb_put(skb, len);
326 			sprintf(scratch, "%s@%s", action_string, devpath);
327 
328 			skb_put_data(skb, env->buf, env->buflen);
329 
330 			NETLINK_CB(skb).dst_group = 1;
331 		}
332 
333 		retval = netlink_broadcast_filtered(uevent_sock, skb_get(skb),
334 						    0, 1, GFP_KERNEL,
335 						    kobj_bcast_filter,
336 						    kobj);
337 		/* ENOBUFS should be handled in userspace */
338 		if (retval == -ENOBUFS || retval == -ESRCH)
339 			retval = 0;
340 	}
341 	consume_skb(skb);
342 #endif
343 	return retval;
344 }
345 
346 static void zap_modalias_env(struct kobj_uevent_env *env)
347 {
348 	static const char modalias_prefix[] = "MODALIAS=";
349 	int i;
350 
351 	for (i = 0; i < env->envp_idx;) {
352 		if (strncmp(env->envp[i], modalias_prefix,
353 			    sizeof(modalias_prefix) - 1)) {
354 			i++;
355 			continue;
356 		}
357 
358 		if (i != env->envp_idx - 1)
359 			memmove(&env->envp[i], &env->envp[i + 1],
360 				sizeof(env->envp[i]) * env->envp_idx - 1);
361 
362 		env->envp_idx--;
363 	}
364 }
365 
366 /**
367  * kobject_uevent_env - send an uevent with environmental data
368  *
369  * @kobj: struct kobject that the action is happening to
370  * @action: action that is happening
371  * @envp_ext: pointer to environmental data
372  *
373  * Returns 0 if kobject_uevent_env() is completed with success or the
374  * corresponding error when it fails.
375  */
376 int kobject_uevent_env(struct kobject *kobj, enum kobject_action action,
377 		       char *envp_ext[])
378 {
379 	struct kobj_uevent_env *env;
380 	const char *action_string = kobject_actions[action];
381 	const char *devpath = NULL;
382 	const char *subsystem;
383 	struct kobject *top_kobj;
384 	struct kset *kset;
385 	const struct kset_uevent_ops *uevent_ops;
386 	int i = 0;
387 	int retval = 0;
388 
389 	pr_debug("kobject: '%s' (%p): %s\n",
390 		 kobject_name(kobj), kobj, __func__);
391 
392 	/* search the kset we belong to */
393 	top_kobj = kobj;
394 	while (!top_kobj->kset && top_kobj->parent)
395 		top_kobj = top_kobj->parent;
396 
397 	if (!top_kobj->kset) {
398 		pr_debug("kobject: '%s' (%p): %s: attempted to send uevent "
399 			 "without kset!\n", kobject_name(kobj), kobj,
400 			 __func__);
401 		return -EINVAL;
402 	}
403 
404 	kset = top_kobj->kset;
405 	uevent_ops = kset->uevent_ops;
406 
407 	/* skip the event, if uevent_suppress is set*/
408 	if (kobj->uevent_suppress) {
409 		pr_debug("kobject: '%s' (%p): %s: uevent_suppress "
410 				 "caused the event to drop!\n",
411 				 kobject_name(kobj), kobj, __func__);
412 		return 0;
413 	}
414 	/* skip the event, if the filter returns zero. */
415 	if (uevent_ops && uevent_ops->filter)
416 		if (!uevent_ops->filter(kset, kobj)) {
417 			pr_debug("kobject: '%s' (%p): %s: filter function "
418 				 "caused the event to drop!\n",
419 				 kobject_name(kobj), kobj, __func__);
420 			return 0;
421 		}
422 
423 	/* originating subsystem */
424 	if (uevent_ops && uevent_ops->name)
425 		subsystem = uevent_ops->name(kset, kobj);
426 	else
427 		subsystem = kobject_name(&kset->kobj);
428 	if (!subsystem) {
429 		pr_debug("kobject: '%s' (%p): %s: unset subsystem caused the "
430 			 "event to drop!\n", kobject_name(kobj), kobj,
431 			 __func__);
432 		return 0;
433 	}
434 
435 	/* environment buffer */
436 	env = kzalloc(sizeof(struct kobj_uevent_env), GFP_KERNEL);
437 	if (!env)
438 		return -ENOMEM;
439 
440 	/* complete object path */
441 	devpath = kobject_get_path(kobj, GFP_KERNEL);
442 	if (!devpath) {
443 		retval = -ENOENT;
444 		goto exit;
445 	}
446 
447 	/* default keys */
448 	retval = add_uevent_var(env, "ACTION=%s", action_string);
449 	if (retval)
450 		goto exit;
451 	retval = add_uevent_var(env, "DEVPATH=%s", devpath);
452 	if (retval)
453 		goto exit;
454 	retval = add_uevent_var(env, "SUBSYSTEM=%s", subsystem);
455 	if (retval)
456 		goto exit;
457 
458 	/* keys passed in from the caller */
459 	if (envp_ext) {
460 		for (i = 0; envp_ext[i]; i++) {
461 			retval = add_uevent_var(env, "%s", envp_ext[i]);
462 			if (retval)
463 				goto exit;
464 		}
465 	}
466 
467 	/* let the kset specific function add its stuff */
468 	if (uevent_ops && uevent_ops->uevent) {
469 		retval = uevent_ops->uevent(kset, kobj, env);
470 		if (retval) {
471 			pr_debug("kobject: '%s' (%p): %s: uevent() returned "
472 				 "%d\n", kobject_name(kobj), kobj,
473 				 __func__, retval);
474 			goto exit;
475 		}
476 	}
477 
478 	switch (action) {
479 	case KOBJ_ADD:
480 		/*
481 		 * Mark "add" event so we can make sure we deliver "remove"
482 		 * event to userspace during automatic cleanup. If
483 		 * the object did send an "add" event, "remove" will
484 		 * automatically generated by the core, if not already done
485 		 * by the caller.
486 		 */
487 		kobj->state_add_uevent_sent = 1;
488 		break;
489 
490 	case KOBJ_REMOVE:
491 		kobj->state_remove_uevent_sent = 1;
492 		break;
493 
494 	case KOBJ_UNBIND:
495 		zap_modalias_env(env);
496 		break;
497 
498 	default:
499 		break;
500 	}
501 
502 	mutex_lock(&uevent_sock_mutex);
503 	/* we will send an event, so request a new sequence number */
504 	retval = add_uevent_var(env, "SEQNUM=%llu", (unsigned long long)++uevent_seqnum);
505 	if (retval) {
506 		mutex_unlock(&uevent_sock_mutex);
507 		goto exit;
508 	}
509 	retval = kobject_uevent_net_broadcast(kobj, env, action_string,
510 					      devpath);
511 	mutex_unlock(&uevent_sock_mutex);
512 
513 #ifdef CONFIG_UEVENT_HELPER
514 	/* call uevent_helper, usually only enabled during early boot */
515 	if (uevent_helper[0] && !kobj_usermode_filter(kobj)) {
516 		struct subprocess_info *info;
517 
518 		retval = add_uevent_var(env, "HOME=/");
519 		if (retval)
520 			goto exit;
521 		retval = add_uevent_var(env,
522 					"PATH=/sbin:/bin:/usr/sbin:/usr/bin");
523 		if (retval)
524 			goto exit;
525 		retval = init_uevent_argv(env, subsystem);
526 		if (retval)
527 			goto exit;
528 
529 		retval = -ENOMEM;
530 		info = call_usermodehelper_setup(env->argv[0], env->argv,
531 						 env->envp, GFP_KERNEL,
532 						 NULL, cleanup_uevent_env, env);
533 		if (info) {
534 			retval = call_usermodehelper_exec(info, UMH_NO_WAIT);
535 			env = NULL;	/* freed by cleanup_uevent_env */
536 		}
537 	}
538 #endif
539 
540 exit:
541 	kfree(devpath);
542 	kfree(env);
543 	return retval;
544 }
545 EXPORT_SYMBOL_GPL(kobject_uevent_env);
546 
547 /**
548  * kobject_uevent - notify userspace by sending an uevent
549  *
550  * @kobj: struct kobject that the action is happening to
551  * @action: action that is happening
552  *
553  * Returns 0 if kobject_uevent() is completed with success or the
554  * corresponding error when it fails.
555  */
556 int kobject_uevent(struct kobject *kobj, enum kobject_action action)
557 {
558 	return kobject_uevent_env(kobj, action, NULL);
559 }
560 EXPORT_SYMBOL_GPL(kobject_uevent);
561 
562 /**
563  * add_uevent_var - add key value string to the environment buffer
564  * @env: environment buffer structure
565  * @format: printf format for the key=value pair
566  *
567  * Returns 0 if environment variable was added successfully or -ENOMEM
568  * if no space was available.
569  */
570 int add_uevent_var(struct kobj_uevent_env *env, const char *format, ...)
571 {
572 	va_list args;
573 	int len;
574 
575 	if (env->envp_idx >= ARRAY_SIZE(env->envp)) {
576 		WARN(1, KERN_ERR "add_uevent_var: too many keys\n");
577 		return -ENOMEM;
578 	}
579 
580 	va_start(args, format);
581 	len = vsnprintf(&env->buf[env->buflen],
582 			sizeof(env->buf) - env->buflen,
583 			format, args);
584 	va_end(args);
585 
586 	if (len >= (sizeof(env->buf) - env->buflen)) {
587 		WARN(1, KERN_ERR "add_uevent_var: buffer size too small\n");
588 		return -ENOMEM;
589 	}
590 
591 	env->envp[env->envp_idx++] = &env->buf[env->buflen];
592 	env->buflen += len + 1;
593 	return 0;
594 }
595 EXPORT_SYMBOL_GPL(add_uevent_var);
596 
597 #if defined(CONFIG_NET)
598 static int uevent_net_init(struct net *net)
599 {
600 	struct uevent_sock *ue_sk;
601 	struct netlink_kernel_cfg cfg = {
602 		.groups	= 1,
603 		.flags	= NL_CFG_F_NONROOT_RECV,
604 	};
605 
606 	ue_sk = kzalloc(sizeof(*ue_sk), GFP_KERNEL);
607 	if (!ue_sk)
608 		return -ENOMEM;
609 
610 	ue_sk->sk = netlink_kernel_create(net, NETLINK_KOBJECT_UEVENT, &cfg);
611 	if (!ue_sk->sk) {
612 		printk(KERN_ERR
613 		       "kobject_uevent: unable to create netlink socket!\n");
614 		kfree(ue_sk);
615 		return -ENODEV;
616 	}
617 	mutex_lock(&uevent_sock_mutex);
618 	list_add_tail(&ue_sk->list, &uevent_sock_list);
619 	mutex_unlock(&uevent_sock_mutex);
620 	return 0;
621 }
622 
623 static void uevent_net_exit(struct net *net)
624 {
625 	struct uevent_sock *ue_sk;
626 
627 	mutex_lock(&uevent_sock_mutex);
628 	list_for_each_entry(ue_sk, &uevent_sock_list, list) {
629 		if (sock_net(ue_sk->sk) == net)
630 			goto found;
631 	}
632 	mutex_unlock(&uevent_sock_mutex);
633 	return;
634 
635 found:
636 	list_del(&ue_sk->list);
637 	mutex_unlock(&uevent_sock_mutex);
638 
639 	netlink_kernel_release(ue_sk->sk);
640 	kfree(ue_sk);
641 }
642 
643 static struct pernet_operations uevent_net_ops = {
644 	.init	= uevent_net_init,
645 	.exit	= uevent_net_exit,
646 };
647 
648 static int __init kobject_uevent_init(void)
649 {
650 	return register_pernet_subsys(&uevent_net_ops);
651 }
652 
653 
654 postcore_initcall(kobject_uevent_init);
655 #endif
656