xref: /openbmc/linux/lib/kobject_uevent.c (revision 94c7b6fc) 
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/user_namespace.h>
24 #include <linux/socket.h>
25 #include <linux/skbuff.h>
26 #include <linux/netlink.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 };
55 
56 /**
57  * kobject_action_type - translate action string to numeric type
58  *
59  * @buf: buffer containing the action string, newline is ignored
60  * @len: length of buffer
61  * @type: pointer to the location to store the action type
62  *
63  * Returns 0 if the action string was recognized.
64  */
65 int kobject_action_type(const char *buf, size_t count,
66 			enum kobject_action *type)
67 {
68 	enum kobject_action action;
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 	for (action = 0; action < ARRAY_SIZE(kobject_actions); action++) {
78 		if (strncmp(kobject_actions[action], buf, count) != 0)
79 			continue;
80 		if (kobject_actions[action][count] != '\0')
81 			continue;
82 		*type = action;
83 		ret = 0;
84 		break;
85 	}
86 out:
87 	return ret;
88 }
89 
90 #ifdef CONFIG_NET
91 static int kobj_bcast_filter(struct sock *dsk, struct sk_buff *skb, void *data)
92 {
93 	struct kobject *kobj = data, *ksobj;
94 	const struct kobj_ns_type_operations *ops;
95 
96 	ops = kobj_ns_ops(kobj);
97 	if (!ops && kobj->kset) {
98 		ksobj = &kobj->kset->kobj;
99 		if (ksobj->parent != NULL)
100 			ops = kobj_ns_ops(ksobj->parent);
101 	}
102 
103 	if (ops && ops->netlink_ns && kobj->ktype->namespace) {
104 		const void *sock_ns, *ns;
105 		ns = kobj->ktype->namespace(kobj);
106 		sock_ns = ops->netlink_ns(dsk);
107 		return sock_ns != ns;
108 	}
109 
110 	return 0;
111 }
112 #endif
113 
114 #ifdef CONFIG_UEVENT_HELPER
115 static int kobj_usermode_filter(struct kobject *kobj)
116 {
117 	const struct kobj_ns_type_operations *ops;
118 
119 	ops = kobj_ns_ops(kobj);
120 	if (ops) {
121 		const void *init_ns, *ns;
122 		ns = kobj->ktype->namespace(kobj);
123 		init_ns = ops->initial_ns();
124 		return ns != init_ns;
125 	}
126 
127 	return 0;
128 }
129 
130 static int init_uevent_argv(struct kobj_uevent_env *env, const char *subsystem)
131 {
132 	int len;
133 
134 	len = strlcpy(&env->buf[env->buflen], subsystem,
135 		      sizeof(env->buf) - env->buflen);
136 	if (len >= (sizeof(env->buf) - env->buflen)) {
137 		WARN(1, KERN_ERR "init_uevent_argv: buffer size too small\n");
138 		return -ENOMEM;
139 	}
140 
141 	env->argv[0] = uevent_helper;
142 	env->argv[1] = &env->buf[env->buflen];
143 	env->argv[2] = NULL;
144 
145 	env->buflen += len + 1;
146 	return 0;
147 }
148 
149 static void cleanup_uevent_env(struct subprocess_info *info)
150 {
151 	kfree(info->data);
152 }
153 #endif
154 
155 /**
156  * kobject_uevent_env - send an uevent with environmental data
157  *
158  * @action: action that is happening
159  * @kobj: struct kobject that the action is happening to
160  * @envp_ext: pointer to environmental data
161  *
162  * Returns 0 if kobject_uevent_env() is completed with success or the
163  * corresponding error when it fails.
164  */
165 int kobject_uevent_env(struct kobject *kobj, enum kobject_action action,
166 		       char *envp_ext[])
167 {
168 	struct kobj_uevent_env *env;
169 	const char *action_string = kobject_actions[action];
170 	const char *devpath = NULL;
171 	const char *subsystem;
172 	struct kobject *top_kobj;
173 	struct kset *kset;
174 	const struct kset_uevent_ops *uevent_ops;
175 	int i = 0;
176 	int retval = 0;
177 #ifdef CONFIG_NET
178 	struct uevent_sock *ue_sk;
179 #endif
180 
181 	pr_debug("kobject: '%s' (%p): %s\n",
182 		 kobject_name(kobj), kobj, __func__);
183 
184 	/* search the kset we belong to */
185 	top_kobj = kobj;
186 	while (!top_kobj->kset && top_kobj->parent)
187 		top_kobj = top_kobj->parent;
188 
189 	if (!top_kobj->kset) {
190 		pr_debug("kobject: '%s' (%p): %s: attempted to send uevent "
191 			 "without kset!\n", kobject_name(kobj), kobj,
192 			 __func__);
193 		return -EINVAL;
194 	}
195 
196 	kset = top_kobj->kset;
197 	uevent_ops = kset->uevent_ops;
198 
199 	/* skip the event, if uevent_suppress is set*/
200 	if (kobj->uevent_suppress) {
201 		pr_debug("kobject: '%s' (%p): %s: uevent_suppress "
202 				 "caused the event to drop!\n",
203 				 kobject_name(kobj), kobj, __func__);
204 		return 0;
205 	}
206 	/* skip the event, if the filter returns zero. */
207 	if (uevent_ops && uevent_ops->filter)
208 		if (!uevent_ops->filter(kset, kobj)) {
209 			pr_debug("kobject: '%s' (%p): %s: filter function "
210 				 "caused the event to drop!\n",
211 				 kobject_name(kobj), kobj, __func__);
212 			return 0;
213 		}
214 
215 	/* originating subsystem */
216 	if (uevent_ops && uevent_ops->name)
217 		subsystem = uevent_ops->name(kset, kobj);
218 	else
219 		subsystem = kobject_name(&kset->kobj);
220 	if (!subsystem) {
221 		pr_debug("kobject: '%s' (%p): %s: unset subsystem caused the "
222 			 "event to drop!\n", kobject_name(kobj), kobj,
223 			 __func__);
224 		return 0;
225 	}
226 
227 	/* environment buffer */
228 	env = kzalloc(sizeof(struct kobj_uevent_env), GFP_KERNEL);
229 	if (!env)
230 		return -ENOMEM;
231 
232 	/* complete object path */
233 	devpath = kobject_get_path(kobj, GFP_KERNEL);
234 	if (!devpath) {
235 		retval = -ENOENT;
236 		goto exit;
237 	}
238 
239 	/* default keys */
240 	retval = add_uevent_var(env, "ACTION=%s", action_string);
241 	if (retval)
242 		goto exit;
243 	retval = add_uevent_var(env, "DEVPATH=%s", devpath);
244 	if (retval)
245 		goto exit;
246 	retval = add_uevent_var(env, "SUBSYSTEM=%s", subsystem);
247 	if (retval)
248 		goto exit;
249 
250 	/* keys passed in from the caller */
251 	if (envp_ext) {
252 		for (i = 0; envp_ext[i]; i++) {
253 			retval = add_uevent_var(env, "%s", envp_ext[i]);
254 			if (retval)
255 				goto exit;
256 		}
257 	}
258 
259 	/* let the kset specific function add its stuff */
260 	if (uevent_ops && uevent_ops->uevent) {
261 		retval = uevent_ops->uevent(kset, kobj, env);
262 		if (retval) {
263 			pr_debug("kobject: '%s' (%p): %s: uevent() returned "
264 				 "%d\n", kobject_name(kobj), kobj,
265 				 __func__, retval);
266 			goto exit;
267 		}
268 	}
269 
270 	/*
271 	 * Mark "add" and "remove" events in the object to ensure proper
272 	 * events to userspace during automatic cleanup. If the object did
273 	 * send an "add" event, "remove" will automatically generated by
274 	 * the core, if not already done by the caller.
275 	 */
276 	if (action == KOBJ_ADD)
277 		kobj->state_add_uevent_sent = 1;
278 	else if (action == KOBJ_REMOVE)
279 		kobj->state_remove_uevent_sent = 1;
280 
281 	mutex_lock(&uevent_sock_mutex);
282 	/* we will send an event, so request a new sequence number */
283 	retval = add_uevent_var(env, "SEQNUM=%llu", (unsigned long long)++uevent_seqnum);
284 	if (retval) {
285 		mutex_unlock(&uevent_sock_mutex);
286 		goto exit;
287 	}
288 
289 #if defined(CONFIG_NET)
290 	/* send netlink message */
291 	list_for_each_entry(ue_sk, &uevent_sock_list, list) {
292 		struct sock *uevent_sock = ue_sk->sk;
293 		struct sk_buff *skb;
294 		size_t len;
295 
296 		if (!netlink_has_listeners(uevent_sock, 1))
297 			continue;
298 
299 		/* allocate message with the maximum possible size */
300 		len = strlen(action_string) + strlen(devpath) + 2;
301 		skb = alloc_skb(len + env->buflen, GFP_KERNEL);
302 		if (skb) {
303 			char *scratch;
304 
305 			/* add header */
306 			scratch = skb_put(skb, len);
307 			sprintf(scratch, "%s@%s", action_string, devpath);
308 
309 			/* copy keys to our continuous event payload buffer */
310 			for (i = 0; i < env->envp_idx; i++) {
311 				len = strlen(env->envp[i]) + 1;
312 				scratch = skb_put(skb, len);
313 				strcpy(scratch, env->envp[i]);
314 			}
315 
316 			NETLINK_CB(skb).dst_group = 1;
317 			retval = netlink_broadcast_filtered(uevent_sock, skb,
318 							    0, 1, GFP_KERNEL,
319 							    kobj_bcast_filter,
320 							    kobj);
321 			/* ENOBUFS should be handled in userspace */
322 			if (retval == -ENOBUFS || retval == -ESRCH)
323 				retval = 0;
324 		} else
325 			retval = -ENOMEM;
326 	}
327 #endif
328 	mutex_unlock(&uevent_sock_mutex);
329 
330 #ifdef CONFIG_UEVENT_HELPER
331 	/* call uevent_helper, usually only enabled during early boot */
332 	if (uevent_helper[0] && !kobj_usermode_filter(kobj)) {
333 		struct subprocess_info *info;
334 
335 		retval = add_uevent_var(env, "HOME=/");
336 		if (retval)
337 			goto exit;
338 		retval = add_uevent_var(env,
339 					"PATH=/sbin:/bin:/usr/sbin:/usr/bin");
340 		if (retval)
341 			goto exit;
342 		retval = init_uevent_argv(env, subsystem);
343 		if (retval)
344 			goto exit;
345 
346 		retval = -ENOMEM;
347 		info = call_usermodehelper_setup(env->argv[0], env->argv,
348 						 env->envp, GFP_KERNEL,
349 						 NULL, cleanup_uevent_env, env);
350 		if (info) {
351 			retval = call_usermodehelper_exec(info, UMH_NO_WAIT);
352 			env = NULL;	/* freed by cleanup_uevent_env */
353 		}
354 	}
355 #endif
356 
357 exit:
358 	kfree(devpath);
359 	kfree(env);
360 	return retval;
361 }
362 EXPORT_SYMBOL_GPL(kobject_uevent_env);
363 
364 /**
365  * kobject_uevent - notify userspace by sending an uevent
366  *
367  * @action: action that is happening
368  * @kobj: struct kobject that the action is happening to
369  *
370  * Returns 0 if kobject_uevent() is completed with success or the
371  * corresponding error when it fails.
372  */
373 int kobject_uevent(struct kobject *kobj, enum kobject_action action)
374 {
375 	return kobject_uevent_env(kobj, action, NULL);
376 }
377 EXPORT_SYMBOL_GPL(kobject_uevent);
378 
379 /**
380  * add_uevent_var - add key value string to the environment buffer
381  * @env: environment buffer structure
382  * @format: printf format for the key=value pair
383  *
384  * Returns 0 if environment variable was added successfully or -ENOMEM
385  * if no space was available.
386  */
387 int add_uevent_var(struct kobj_uevent_env *env, const char *format, ...)
388 {
389 	va_list args;
390 	int len;
391 
392 	if (env->envp_idx >= ARRAY_SIZE(env->envp)) {
393 		WARN(1, KERN_ERR "add_uevent_var: too many keys\n");
394 		return -ENOMEM;
395 	}
396 
397 	va_start(args, format);
398 	len = vsnprintf(&env->buf[env->buflen],
399 			sizeof(env->buf) - env->buflen,
400 			format, args);
401 	va_end(args);
402 
403 	if (len >= (sizeof(env->buf) - env->buflen)) {
404 		WARN(1, KERN_ERR "add_uevent_var: buffer size too small\n");
405 		return -ENOMEM;
406 	}
407 
408 	env->envp[env->envp_idx++] = &env->buf[env->buflen];
409 	env->buflen += len + 1;
410 	return 0;
411 }
412 EXPORT_SYMBOL_GPL(add_uevent_var);
413 
414 #if defined(CONFIG_NET)
415 static int uevent_net_init(struct net *net)
416 {
417 	struct uevent_sock *ue_sk;
418 	struct netlink_kernel_cfg cfg = {
419 		.groups	= 1,
420 		.flags	= NL_CFG_F_NONROOT_RECV,
421 	};
422 
423 	ue_sk = kzalloc(sizeof(*ue_sk), GFP_KERNEL);
424 	if (!ue_sk)
425 		return -ENOMEM;
426 
427 	ue_sk->sk = netlink_kernel_create(net, NETLINK_KOBJECT_UEVENT, &cfg);
428 	if (!ue_sk->sk) {
429 		printk(KERN_ERR
430 		       "kobject_uevent: unable to create netlink socket!\n");
431 		kfree(ue_sk);
432 		return -ENODEV;
433 	}
434 	mutex_lock(&uevent_sock_mutex);
435 	list_add_tail(&ue_sk->list, &uevent_sock_list);
436 	mutex_unlock(&uevent_sock_mutex);
437 	return 0;
438 }
439 
440 static void uevent_net_exit(struct net *net)
441 {
442 	struct uevent_sock *ue_sk;
443 
444 	mutex_lock(&uevent_sock_mutex);
445 	list_for_each_entry(ue_sk, &uevent_sock_list, list) {
446 		if (sock_net(ue_sk->sk) == net)
447 			goto found;
448 	}
449 	mutex_unlock(&uevent_sock_mutex);
450 	return;
451 
452 found:
453 	list_del(&ue_sk->list);
454 	mutex_unlock(&uevent_sock_mutex);
455 
456 	netlink_kernel_release(ue_sk->sk);
457 	kfree(ue_sk);
458 }
459 
460 static struct pernet_operations uevent_net_ops = {
461 	.init	= uevent_net_init,
462 	.exit	= uevent_net_exit,
463 };
464 
465 static int __init kobject_uevent_init(void)
466 {
467 	return register_pernet_subsys(&uevent_net_ops);
468 }
469 
470 
471 postcore_initcall(kobject_uevent_init);
472 #endif
473