xref: /openbmc/linux/lib/kobject_uevent.c (revision 160b8e75) 
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/uuid.h>
26 #include <linux/ctype.h>
27 #include <net/sock.h>
28 #include <net/net_namespace.h>
29 
30 
31 u64 uevent_seqnum;
32 #ifdef CONFIG_UEVENT_HELPER
33 char uevent_helper[UEVENT_HELPER_PATH_LEN] = CONFIG_UEVENT_HELPER_PATH;
34 #endif
35 #ifdef CONFIG_NET
36 struct uevent_sock {
37 	struct list_head list;
38 	struct sock *sk;
39 };
40 static LIST_HEAD(uevent_sock_list);
41 #endif
42 
43 /* This lock protects uevent_seqnum and uevent_sock_list */
44 static DEFINE_MUTEX(uevent_sock_mutex);
45 
46 /* the strings here must match the enum in include/linux/kobject.h */
47 static const char *kobject_actions[] = {
48 	[KOBJ_ADD] =		"add",
49 	[KOBJ_REMOVE] =		"remove",
50 	[KOBJ_CHANGE] =		"change",
51 	[KOBJ_MOVE] =		"move",
52 	[KOBJ_ONLINE] =		"online",
53 	[KOBJ_OFFLINE] =	"offline",
54 	[KOBJ_BIND] =		"bind",
55 	[KOBJ_UNBIND] =		"unbind",
56 };
57 
58 static int kobject_action_type(const char *buf, size_t count,
59 			       enum kobject_action *type,
60 			       const char **args)
61 {
62 	enum kobject_action action;
63 	size_t count_first;
64 	const char *args_start;
65 	int ret = -EINVAL;
66 
67 	if (count && (buf[count-1] == '\n' || buf[count-1] == '\0'))
68 		count--;
69 
70 	if (!count)
71 		goto out;
72 
73 	args_start = strnchr(buf, count, ' ');
74 	if (args_start) {
75 		count_first = args_start - buf;
76 		args_start = args_start + 1;
77 	} else
78 		count_first = count;
79 
80 	for (action = 0; action < ARRAY_SIZE(kobject_actions); action++) {
81 		if (strncmp(kobject_actions[action], buf, count_first) != 0)
82 			continue;
83 		if (kobject_actions[action][count_first] != '\0')
84 			continue;
85 		if (args)
86 			*args = args_start;
87 		*type = action;
88 		ret = 0;
89 		break;
90 	}
91 out:
92 	return ret;
93 }
94 
95 static const char *action_arg_word_end(const char *buf, const char *buf_end,
96 				       char delim)
97 {
98 	const char *next = buf;
99 
100 	while (next <= buf_end && *next != delim)
101 		if (!isalnum(*next++))
102 			return NULL;
103 
104 	if (next == buf)
105 		return NULL;
106 
107 	return next;
108 }
109 
110 static int kobject_action_args(const char *buf, size_t count,
111 			       struct kobj_uevent_env **ret_env)
112 {
113 	struct kobj_uevent_env *env = NULL;
114 	const char *next, *buf_end, *key;
115 	int key_len;
116 	int r = -EINVAL;
117 
118 	if (count && (buf[count - 1] == '\n' || buf[count - 1] == '\0'))
119 		count--;
120 
121 	if (!count)
122 		return -EINVAL;
123 
124 	env = kzalloc(sizeof(*env), GFP_KERNEL);
125 	if (!env)
126 		return -ENOMEM;
127 
128 	/* first arg is UUID */
129 	if (count < UUID_STRING_LEN || !uuid_is_valid(buf) ||
130 	    add_uevent_var(env, "SYNTH_UUID=%.*s", UUID_STRING_LEN, buf))
131 		goto out;
132 
133 	/*
134 	 * the rest are custom environment variables in KEY=VALUE
135 	 * format with ' ' delimiter between each KEY=VALUE pair
136 	 */
137 	next = buf + UUID_STRING_LEN;
138 	buf_end = buf + count - 1;
139 
140 	while (next <= buf_end) {
141 		if (*next != ' ')
142 			goto out;
143 
144 		/* skip the ' ', key must follow */
145 		key = ++next;
146 		if (key > buf_end)
147 			goto out;
148 
149 		buf = next;
150 		next = action_arg_word_end(buf, buf_end, '=');
151 		if (!next || next > buf_end || *next != '=')
152 			goto out;
153 		key_len = next - buf;
154 
155 		/* skip the '=', value must follow */
156 		if (++next > buf_end)
157 			goto out;
158 
159 		buf = next;
160 		next = action_arg_word_end(buf, buf_end, ' ');
161 		if (!next)
162 			goto out;
163 
164 		if (add_uevent_var(env, "SYNTH_ARG_%.*s=%.*s",
165 				   key_len, key, (int) (next - buf), buf))
166 			goto out;
167 	}
168 
169 	r = 0;
170 out:
171 	if (r)
172 		kfree(env);
173 	else
174 		*ret_env = env;
175 	return r;
176 }
177 
178 /**
179  * kobject_synth_uevent - send synthetic uevent with arguments
180  *
181  * @kobj: struct kobject for which synthetic uevent is to be generated
182  * @buf: buffer containing action type and action args, newline is ignored
183  * @count: length of buffer
184  *
185  * Returns 0 if kobject_synthetic_uevent() is completed with success or the
186  * corresponding error when it fails.
187  */
188 int kobject_synth_uevent(struct kobject *kobj, const char *buf, size_t count)
189 {
190 	char *no_uuid_envp[] = { "SYNTH_UUID=0", NULL };
191 	enum kobject_action action;
192 	const char *action_args;
193 	struct kobj_uevent_env *env;
194 	const char *msg = NULL, *devpath;
195 	int r;
196 
197 	r = kobject_action_type(buf, count, &action, &action_args);
198 	if (r) {
199 		msg = "unknown uevent action string\n";
200 		goto out;
201 	}
202 
203 	if (!action_args) {
204 		r = kobject_uevent_env(kobj, action, no_uuid_envp);
205 		goto out;
206 	}
207 
208 	r = kobject_action_args(action_args,
209 				count - (action_args - buf), &env);
210 	if (r == -EINVAL) {
211 		msg = "incorrect uevent action arguments\n";
212 		goto out;
213 	}
214 
215 	if (r)
216 		goto out;
217 
218 	r = kobject_uevent_env(kobj, action, env->envp);
219 	kfree(env);
220 out:
221 	if (r) {
222 		devpath = kobject_get_path(kobj, GFP_KERNEL);
223 		printk(KERN_WARNING "synth uevent: %s: %s",
224 		       devpath ?: "unknown device",
225 		       msg ?: "failed to send uevent");
226 		kfree(devpath);
227 	}
228 	return r;
229 }
230 
231 #ifdef CONFIG_NET
232 static int kobj_bcast_filter(struct sock *dsk, struct sk_buff *skb, void *data)
233 {
234 	struct kobject *kobj = data, *ksobj;
235 	const struct kobj_ns_type_operations *ops;
236 
237 	ops = kobj_ns_ops(kobj);
238 	if (!ops && kobj->kset) {
239 		ksobj = &kobj->kset->kobj;
240 		if (ksobj->parent != NULL)
241 			ops = kobj_ns_ops(ksobj->parent);
242 	}
243 
244 	if (ops && ops->netlink_ns && kobj->ktype->namespace) {
245 		const void *sock_ns, *ns;
246 		ns = kobj->ktype->namespace(kobj);
247 		sock_ns = ops->netlink_ns(dsk);
248 		return sock_ns != ns;
249 	}
250 
251 	return 0;
252 }
253 #endif
254 
255 #ifdef CONFIG_UEVENT_HELPER
256 static int kobj_usermode_filter(struct kobject *kobj)
257 {
258 	const struct kobj_ns_type_operations *ops;
259 
260 	ops = kobj_ns_ops(kobj);
261 	if (ops) {
262 		const void *init_ns, *ns;
263 		ns = kobj->ktype->namespace(kobj);
264 		init_ns = ops->initial_ns();
265 		return ns != init_ns;
266 	}
267 
268 	return 0;
269 }
270 
271 static int init_uevent_argv(struct kobj_uevent_env *env, const char *subsystem)
272 {
273 	int len;
274 
275 	len = strlcpy(&env->buf[env->buflen], subsystem,
276 		      sizeof(env->buf) - env->buflen);
277 	if (len >= (sizeof(env->buf) - env->buflen)) {
278 		WARN(1, KERN_ERR "init_uevent_argv: buffer size too small\n");
279 		return -ENOMEM;
280 	}
281 
282 	env->argv[0] = uevent_helper;
283 	env->argv[1] = &env->buf[env->buflen];
284 	env->argv[2] = NULL;
285 
286 	env->buflen += len + 1;
287 	return 0;
288 }
289 
290 static void cleanup_uevent_env(struct subprocess_info *info)
291 {
292 	kfree(info->data);
293 }
294 #endif
295 
296 static int kobject_uevent_net_broadcast(struct kobject *kobj,
297 					struct kobj_uevent_env *env,
298 					const char *action_string,
299 					const char *devpath)
300 {
301 	int retval = 0;
302 #if defined(CONFIG_NET)
303 	struct sk_buff *skb = NULL;
304 	struct uevent_sock *ue_sk;
305 
306 	/* send netlink message */
307 	list_for_each_entry(ue_sk, &uevent_sock_list, list) {
308 		struct sock *uevent_sock = ue_sk->sk;
309 
310 		if (!netlink_has_listeners(uevent_sock, 1))
311 			continue;
312 
313 		if (!skb) {
314 			/* allocate message with the maximum possible size */
315 			size_t len = strlen(action_string) + strlen(devpath) + 2;
316 			char *scratch;
317 
318 			retval = -ENOMEM;
319 			skb = alloc_skb(len + env->buflen, GFP_KERNEL);
320 			if (!skb)
321 				continue;
322 
323 			/* add header */
324 			scratch = skb_put(skb, len);
325 			sprintf(scratch, "%s@%s", action_string, devpath);
326 
327 			skb_put_data(skb, env->buf, env->buflen);
328 
329 			NETLINK_CB(skb).dst_group = 1;
330 		}
331 
332 		retval = netlink_broadcast_filtered(uevent_sock, skb_get(skb),
333 						    0, 1, GFP_KERNEL,
334 						    kobj_bcast_filter,
335 						    kobj);
336 		/* ENOBUFS should be handled in userspace */
337 		if (retval == -ENOBUFS || retval == -ESRCH)
338 			retval = 0;
339 	}
340 	consume_skb(skb);
341 #endif
342 	return retval;
343 }
344 
345 static void zap_modalias_env(struct kobj_uevent_env *env)
346 {
347 	static const char modalias_prefix[] = "MODALIAS=";
348 	size_t len;
349 	int i, j;
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 		len = strlen(env->envp[i]) + 1;
359 
360 		if (i != env->envp_idx - 1) {
361 			memmove(env->envp[i], env->envp[i + 1],
362 				env->buflen - len);
363 
364 			for (j = i; j < env->envp_idx - 1; j++)
365 				env->envp[j] = env->envp[j + 1] - len;
366 		}
367 
368 		env->envp_idx--;
369 		env->buflen -= len;
370 	}
371 }
372 
373 /**
374  * kobject_uevent_env - send an uevent with environmental data
375  *
376  * @kobj: struct kobject that the action is happening to
377  * @action: action that is happening
378  * @envp_ext: pointer to environmental data
379  *
380  * Returns 0 if kobject_uevent_env() is completed with success or the
381  * corresponding error when it fails.
382  */
383 int kobject_uevent_env(struct kobject *kobj, enum kobject_action action,
384 		       char *envp_ext[])
385 {
386 	struct kobj_uevent_env *env;
387 	const char *action_string = kobject_actions[action];
388 	const char *devpath = NULL;
389 	const char *subsystem;
390 	struct kobject *top_kobj;
391 	struct kset *kset;
392 	const struct kset_uevent_ops *uevent_ops;
393 	int i = 0;
394 	int retval = 0;
395 
396 	pr_debug("kobject: '%s' (%p): %s\n",
397 		 kobject_name(kobj), kobj, __func__);
398 
399 	/* search the kset we belong to */
400 	top_kobj = kobj;
401 	while (!top_kobj->kset && top_kobj->parent)
402 		top_kobj = top_kobj->parent;
403 
404 	if (!top_kobj->kset) {
405 		pr_debug("kobject: '%s' (%p): %s: attempted to send uevent "
406 			 "without kset!\n", kobject_name(kobj), kobj,
407 			 __func__);
408 		return -EINVAL;
409 	}
410 
411 	kset = top_kobj->kset;
412 	uevent_ops = kset->uevent_ops;
413 
414 	/* skip the event, if uevent_suppress is set*/
415 	if (kobj->uevent_suppress) {
416 		pr_debug("kobject: '%s' (%p): %s: uevent_suppress "
417 				 "caused the event to drop!\n",
418 				 kobject_name(kobj), kobj, __func__);
419 		return 0;
420 	}
421 	/* skip the event, if the filter returns zero. */
422 	if (uevent_ops && uevent_ops->filter)
423 		if (!uevent_ops->filter(kset, kobj)) {
424 			pr_debug("kobject: '%s' (%p): %s: filter function "
425 				 "caused the event to drop!\n",
426 				 kobject_name(kobj), kobj, __func__);
427 			return 0;
428 		}
429 
430 	/* originating subsystem */
431 	if (uevent_ops && uevent_ops->name)
432 		subsystem = uevent_ops->name(kset, kobj);
433 	else
434 		subsystem = kobject_name(&kset->kobj);
435 	if (!subsystem) {
436 		pr_debug("kobject: '%s' (%p): %s: unset subsystem caused the "
437 			 "event to drop!\n", kobject_name(kobj), kobj,
438 			 __func__);
439 		return 0;
440 	}
441 
442 	/* environment buffer */
443 	env = kzalloc(sizeof(struct kobj_uevent_env), GFP_KERNEL);
444 	if (!env)
445 		return -ENOMEM;
446 
447 	/* complete object path */
448 	devpath = kobject_get_path(kobj, GFP_KERNEL);
449 	if (!devpath) {
450 		retval = -ENOENT;
451 		goto exit;
452 	}
453 
454 	/* default keys */
455 	retval = add_uevent_var(env, "ACTION=%s", action_string);
456 	if (retval)
457 		goto exit;
458 	retval = add_uevent_var(env, "DEVPATH=%s", devpath);
459 	if (retval)
460 		goto exit;
461 	retval = add_uevent_var(env, "SUBSYSTEM=%s", subsystem);
462 	if (retval)
463 		goto exit;
464 
465 	/* keys passed in from the caller */
466 	if (envp_ext) {
467 		for (i = 0; envp_ext[i]; i++) {
468 			retval = add_uevent_var(env, "%s", envp_ext[i]);
469 			if (retval)
470 				goto exit;
471 		}
472 	}
473 
474 	/* let the kset specific function add its stuff */
475 	if (uevent_ops && uevent_ops->uevent) {
476 		retval = uevent_ops->uevent(kset, kobj, env);
477 		if (retval) {
478 			pr_debug("kobject: '%s' (%p): %s: uevent() returned "
479 				 "%d\n", kobject_name(kobj), kobj,
480 				 __func__, retval);
481 			goto exit;
482 		}
483 	}
484 
485 	switch (action) {
486 	case KOBJ_ADD:
487 		/*
488 		 * Mark "add" event so we can make sure we deliver "remove"
489 		 * event to userspace during automatic cleanup. If
490 		 * the object did send an "add" event, "remove" will
491 		 * automatically generated by the core, if not already done
492 		 * by the caller.
493 		 */
494 		kobj->state_add_uevent_sent = 1;
495 		break;
496 
497 	case KOBJ_REMOVE:
498 		kobj->state_remove_uevent_sent = 1;
499 		break;
500 
501 	case KOBJ_UNBIND:
502 		zap_modalias_env(env);
503 		break;
504 
505 	default:
506 		break;
507 	}
508 
509 	mutex_lock(&uevent_sock_mutex);
510 	/* we will send an event, so request a new sequence number */
511 	retval = add_uevent_var(env, "SEQNUM=%llu", (unsigned long long)++uevent_seqnum);
512 	if (retval) {
513 		mutex_unlock(&uevent_sock_mutex);
514 		goto exit;
515 	}
516 	retval = kobject_uevent_net_broadcast(kobj, env, action_string,
517 					      devpath);
518 	mutex_unlock(&uevent_sock_mutex);
519 
520 #ifdef CONFIG_UEVENT_HELPER
521 	/* call uevent_helper, usually only enabled during early boot */
522 	if (uevent_helper[0] && !kobj_usermode_filter(kobj)) {
523 		struct subprocess_info *info;
524 
525 		retval = add_uevent_var(env, "HOME=/");
526 		if (retval)
527 			goto exit;
528 		retval = add_uevent_var(env,
529 					"PATH=/sbin:/bin:/usr/sbin:/usr/bin");
530 		if (retval)
531 			goto exit;
532 		retval = init_uevent_argv(env, subsystem);
533 		if (retval)
534 			goto exit;
535 
536 		retval = -ENOMEM;
537 		info = call_usermodehelper_setup(env->argv[0], env->argv,
538 						 env->envp, GFP_KERNEL,
539 						 NULL, cleanup_uevent_env, env);
540 		if (info) {
541 			retval = call_usermodehelper_exec(info, UMH_NO_WAIT);
542 			env = NULL;	/* freed by cleanup_uevent_env */
543 		}
544 	}
545 #endif
546 
547 exit:
548 	kfree(devpath);
549 	kfree(env);
550 	return retval;
551 }
552 EXPORT_SYMBOL_GPL(kobject_uevent_env);
553 
554 /**
555  * kobject_uevent - notify userspace by sending an uevent
556  *
557  * @kobj: struct kobject that the action is happening to
558  * @action: action that is happening
559  *
560  * Returns 0 if kobject_uevent() is completed with success or the
561  * corresponding error when it fails.
562  */
563 int kobject_uevent(struct kobject *kobj, enum kobject_action action)
564 {
565 	return kobject_uevent_env(kobj, action, NULL);
566 }
567 EXPORT_SYMBOL_GPL(kobject_uevent);
568 
569 /**
570  * add_uevent_var - add key value string to the environment buffer
571  * @env: environment buffer structure
572  * @format: printf format for the key=value pair
573  *
574  * Returns 0 if environment variable was added successfully or -ENOMEM
575  * if no space was available.
576  */
577 int add_uevent_var(struct kobj_uevent_env *env, const char *format, ...)
578 {
579 	va_list args;
580 	int len;
581 
582 	if (env->envp_idx >= ARRAY_SIZE(env->envp)) {
583 		WARN(1, KERN_ERR "add_uevent_var: too many keys\n");
584 		return -ENOMEM;
585 	}
586 
587 	va_start(args, format);
588 	len = vsnprintf(&env->buf[env->buflen],
589 			sizeof(env->buf) - env->buflen,
590 			format, args);
591 	va_end(args);
592 
593 	if (len >= (sizeof(env->buf) - env->buflen)) {
594 		WARN(1, KERN_ERR "add_uevent_var: buffer size too small\n");
595 		return -ENOMEM;
596 	}
597 
598 	env->envp[env->envp_idx++] = &env->buf[env->buflen];
599 	env->buflen += len + 1;
600 	return 0;
601 }
602 EXPORT_SYMBOL_GPL(add_uevent_var);
603 
604 #if defined(CONFIG_NET)
605 static int uevent_net_init(struct net *net)
606 {
607 	struct uevent_sock *ue_sk;
608 	struct netlink_kernel_cfg cfg = {
609 		.groups	= 1,
610 		.flags	= NL_CFG_F_NONROOT_RECV,
611 	};
612 
613 	ue_sk = kzalloc(sizeof(*ue_sk), GFP_KERNEL);
614 	if (!ue_sk)
615 		return -ENOMEM;
616 
617 	ue_sk->sk = netlink_kernel_create(net, NETLINK_KOBJECT_UEVENT, &cfg);
618 	if (!ue_sk->sk) {
619 		printk(KERN_ERR
620 		       "kobject_uevent: unable to create netlink socket!\n");
621 		kfree(ue_sk);
622 		return -ENODEV;
623 	}
624 	mutex_lock(&uevent_sock_mutex);
625 	list_add_tail(&ue_sk->list, &uevent_sock_list);
626 	mutex_unlock(&uevent_sock_mutex);
627 	return 0;
628 }
629 
630 static void uevent_net_exit(struct net *net)
631 {
632 	struct uevent_sock *ue_sk;
633 
634 	mutex_lock(&uevent_sock_mutex);
635 	list_for_each_entry(ue_sk, &uevent_sock_list, list) {
636 		if (sock_net(ue_sk->sk) == net)
637 			goto found;
638 	}
639 	mutex_unlock(&uevent_sock_mutex);
640 	return;
641 
642 found:
643 	list_del(&ue_sk->list);
644 	mutex_unlock(&uevent_sock_mutex);
645 
646 	netlink_kernel_release(ue_sk->sk);
647 	kfree(ue_sk);
648 }
649 
650 static struct pernet_operations uevent_net_ops = {
651 	.init	= uevent_net_init,
652 	.exit	= uevent_net_exit,
653 };
654 
655 static int __init kobject_uevent_init(void)
656 {
657 	return register_pernet_subsys(&uevent_net_ops);
658 }
659 
660 
661 postcore_initcall(kobject_uevent_init);
662 #endif
663