Root/lib/kobject_uevent.c

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/module.h>
21#include <linux/slab.h>
22#include <linux/user_namespace.h>
23#include <linux/socket.h>
24#include <linux/skbuff.h>
25#include <linux/netlink.h>
26#include <net/sock.h>
27#include <net/net_namespace.h>
28
29
30u64 uevent_seqnum;
31char uevent_helper[UEVENT_HELPER_PATH_LEN] = CONFIG_UEVENT_HELPER_PATH;
32static DEFINE_SPINLOCK(sequence_lock);
33#ifdef CONFIG_NET
34struct uevent_sock {
35    struct list_head list;
36    struct sock *sk;
37};
38static LIST_HEAD(uevent_sock_list);
39static DEFINE_MUTEX(uevent_sock_mutex);
40#endif
41
42/* the strings here must match the enum in include/linux/kobject.h */
43static const char *kobject_actions[] = {
44    [KOBJ_ADD] = "add",
45    [KOBJ_REMOVE] = "remove",
46    [KOBJ_CHANGE] = "change",
47    [KOBJ_MOVE] = "move",
48    [KOBJ_ONLINE] = "online",
49    [KOBJ_OFFLINE] = "offline",
50};
51
52/**
53 * kobject_action_type - translate action string to numeric type
54 *
55 * @buf: buffer containing the action string, newline is ignored
56 * @len: length of buffer
57 * @type: pointer to the location to store the action type
58 *
59 * Returns 0 if the action string was recognized.
60 */
61int kobject_action_type(const char *buf, size_t count,
62            enum kobject_action *type)
63{
64    enum kobject_action action;
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    for (action = 0; action < ARRAY_SIZE(kobject_actions); action++) {
74        if (strncmp(kobject_actions[action], buf, count) != 0)
75            continue;
76        if (kobject_actions[action][count] != '\0')
77            continue;
78        *type = action;
79        ret = 0;
80        break;
81    }
82out:
83    return ret;
84}
85
86#ifdef CONFIG_NET
87static int kobj_bcast_filter(struct sock *dsk, struct sk_buff *skb, void *data)
88{
89    struct kobject *kobj = data;
90    const struct kobj_ns_type_operations *ops;
91
92    ops = kobj_ns_ops(kobj);
93    if (ops) {
94        const void *sock_ns, *ns;
95        ns = kobj->ktype->namespace(kobj);
96        sock_ns = ops->netlink_ns(dsk);
97        return sock_ns != ns;
98    }
99
100    return 0;
101}
102#endif
103
104static int kobj_usermode_filter(struct kobject *kobj)
105{
106    const struct kobj_ns_type_operations *ops;
107
108    ops = kobj_ns_ops(kobj);
109    if (ops) {
110        const void *init_ns, *ns;
111        ns = kobj->ktype->namespace(kobj);
112        init_ns = ops->initial_ns();
113        return ns != init_ns;
114    }
115
116    return 0;
117}
118
119/**
120 * kobject_uevent_env - send an uevent with environmental data
121 *
122 * @action: action that is happening
123 * @kobj: struct kobject that the action is happening to
124 * @envp_ext: pointer to environmental data
125 *
126 * Returns 0 if kobject_uevent_env() is completed with success or the
127 * corresponding error when it fails.
128 */
129int kobject_uevent_env(struct kobject *kobj, enum kobject_action action,
130               char *envp_ext[])
131{
132    struct kobj_uevent_env *env;
133    const char *action_string = kobject_actions[action];
134    const char *devpath = NULL;
135    const char *subsystem;
136    struct kobject *top_kobj;
137    struct kset *kset;
138    const struct kset_uevent_ops *uevent_ops;
139    u64 seq;
140    int i = 0;
141    int retval = 0;
142#ifdef CONFIG_NET
143    struct uevent_sock *ue_sk;
144#endif
145
146    pr_debug("kobject: '%s' (%p): %s\n",
147         kobject_name(kobj), kobj, __func__);
148
149    /* search the kset we belong to */
150    top_kobj = kobj;
151    while (!top_kobj->kset && top_kobj->parent)
152        top_kobj = top_kobj->parent;
153
154    if (!top_kobj->kset) {
155        pr_debug("kobject: '%s' (%p): %s: attempted to send uevent "
156             "without kset!\n", kobject_name(kobj), kobj,
157             __func__);
158        return -EINVAL;
159    }
160
161    kset = top_kobj->kset;
162    uevent_ops = kset->uevent_ops;
163
164    /* skip the event, if uevent_suppress is set*/
165    if (kobj->uevent_suppress) {
166        pr_debug("kobject: '%s' (%p): %s: uevent_suppress "
167                 "caused the event to drop!\n",
168                 kobject_name(kobj), kobj, __func__);
169        return 0;
170    }
171    /* skip the event, if the filter returns zero. */
172    if (uevent_ops && uevent_ops->filter)
173        if (!uevent_ops->filter(kset, kobj)) {
174            pr_debug("kobject: '%s' (%p): %s: filter function "
175                 "caused the event to drop!\n",
176                 kobject_name(kobj), kobj, __func__);
177            return 0;
178        }
179
180    /* originating subsystem */
181    if (uevent_ops && uevent_ops->name)
182        subsystem = uevent_ops->name(kset, kobj);
183    else
184        subsystem = kobject_name(&kset->kobj);
185    if (!subsystem) {
186        pr_debug("kobject: '%s' (%p): %s: unset subsystem caused the "
187             "event to drop!\n", kobject_name(kobj), kobj,
188             __func__);
189        return 0;
190    }
191
192    /* environment buffer */
193    env = kzalloc(sizeof(struct kobj_uevent_env), GFP_KERNEL);
194    if (!env)
195        return -ENOMEM;
196
197    /* complete object path */
198    devpath = kobject_get_path(kobj, GFP_KERNEL);
199    if (!devpath) {
200        retval = -ENOENT;
201        goto exit;
202    }
203
204    /* default keys */
205    retval = add_uevent_var(env, "ACTION=%s", action_string);
206    if (retval)
207        goto exit;
208    retval = add_uevent_var(env, "DEVPATH=%s", devpath);
209    if (retval)
210        goto exit;
211    retval = add_uevent_var(env, "SUBSYSTEM=%s", subsystem);
212    if (retval)
213        goto exit;
214
215    /* keys passed in from the caller */
216    if (envp_ext) {
217        for (i = 0; envp_ext[i]; i++) {
218            retval = add_uevent_var(env, "%s", envp_ext[i]);
219            if (retval)
220                goto exit;
221        }
222    }
223
224    /* let the kset specific function add its stuff */
225    if (uevent_ops && uevent_ops->uevent) {
226        retval = uevent_ops->uevent(kset, kobj, env);
227        if (retval) {
228            pr_debug("kobject: '%s' (%p): %s: uevent() returned "
229                 "%d\n", kobject_name(kobj), kobj,
230                 __func__, retval);
231            goto exit;
232        }
233    }
234
235    /*
236     * Mark "add" and "remove" events in the object to ensure proper
237     * events to userspace during automatic cleanup. If the object did
238     * send an "add" event, "remove" will automatically generated by
239     * the core, if not already done by the caller.
240     */
241    if (action == KOBJ_ADD)
242        kobj->state_add_uevent_sent = 1;
243    else if (action == KOBJ_REMOVE)
244        kobj->state_remove_uevent_sent = 1;
245
246    /* we will send an event, so request a new sequence number */
247    spin_lock(&sequence_lock);
248    seq = ++uevent_seqnum;
249    spin_unlock(&sequence_lock);
250    retval = add_uevent_var(env, "SEQNUM=%llu", (unsigned long long)seq);
251    if (retval)
252        goto exit;
253
254#if defined(CONFIG_NET)
255    /* send netlink message */
256    mutex_lock(&uevent_sock_mutex);
257    list_for_each_entry(ue_sk, &uevent_sock_list, list) {
258        struct sock *uevent_sock = ue_sk->sk;
259        struct sk_buff *skb;
260        size_t len;
261
262        /* allocate message with the maximum possible size */
263        len = strlen(action_string) + strlen(devpath) + 2;
264        skb = alloc_skb(len + env->buflen, GFP_KERNEL);
265        if (skb) {
266            char *scratch;
267
268            /* add header */
269            scratch = skb_put(skb, len);
270            sprintf(scratch, "%s@%s", action_string, devpath);
271
272            /* copy keys to our continuous event payload buffer */
273            for (i = 0; i < env->envp_idx; i++) {
274                len = strlen(env->envp[i]) + 1;
275                scratch = skb_put(skb, len);
276                strcpy(scratch, env->envp[i]);
277            }
278
279            NETLINK_CB(skb).dst_group = 1;
280            retval = netlink_broadcast_filtered(uevent_sock, skb,
281                                0, 1, GFP_KERNEL,
282                                kobj_bcast_filter,
283                                kobj);
284            /* ENOBUFS should be handled in userspace */
285            if (retval == -ENOBUFS)
286                retval = 0;
287        } else
288            retval = -ENOMEM;
289    }
290    mutex_unlock(&uevent_sock_mutex);
291#endif
292
293    /* call uevent_helper, usually only enabled during early boot */
294    if (uevent_helper[0] && !kobj_usermode_filter(kobj)) {
295        char *argv [3];
296
297        argv [0] = uevent_helper;
298        argv [1] = (char *)subsystem;
299        argv [2] = NULL;
300        retval = add_uevent_var(env, "HOME=/");
301        if (retval)
302            goto exit;
303        retval = add_uevent_var(env,
304                    "PATH=/sbin:/bin:/usr/sbin:/usr/bin");
305        if (retval)
306            goto exit;
307
308        retval = call_usermodehelper(argv[0], argv,
309                         env->envp, UMH_WAIT_EXEC);
310    }
311
312exit:
313    kfree(devpath);
314    kfree(env);
315    return retval;
316}
317EXPORT_SYMBOL_GPL(kobject_uevent_env);
318
319/**
320 * kobject_uevent - notify userspace by sending an uevent
321 *
322 * @action: action that is happening
323 * @kobj: struct kobject that the action is happening to
324 *
325 * Returns 0 if kobject_uevent() is completed with success or the
326 * corresponding error when it fails.
327 */
328int kobject_uevent(struct kobject *kobj, enum kobject_action action)
329{
330    return kobject_uevent_env(kobj, action, NULL);
331}
332EXPORT_SYMBOL_GPL(kobject_uevent);
333
334/**
335 * add_uevent_var - add key value string to the environment buffer
336 * @env: environment buffer structure
337 * @format: printf format for the key=value pair
338 *
339 * Returns 0 if environment variable was added successfully or -ENOMEM
340 * if no space was available.
341 */
342int add_uevent_var(struct kobj_uevent_env *env, const char *format, ...)
343{
344    va_list args;
345    int len;
346
347    if (env->envp_idx >= ARRAY_SIZE(env->envp)) {
348        WARN(1, KERN_ERR "add_uevent_var: too many keys\n");
349        return -ENOMEM;
350    }
351
352    va_start(args, format);
353    len = vsnprintf(&env->buf[env->buflen],
354            sizeof(env->buf) - env->buflen,
355            format, args);
356    va_end(args);
357
358    if (len >= (sizeof(env->buf) - env->buflen)) {
359        WARN(1, KERN_ERR "add_uevent_var: buffer size too small\n");
360        return -ENOMEM;
361    }
362
363    env->envp[env->envp_idx++] = &env->buf[env->buflen];
364    env->buflen += len + 1;
365    return 0;
366}
367EXPORT_SYMBOL_GPL(add_uevent_var);
368
369#if defined(CONFIG_NET)
370static int uevent_net_init(struct net *net)
371{
372    struct uevent_sock *ue_sk;
373
374    ue_sk = kzalloc(sizeof(*ue_sk), GFP_KERNEL);
375    if (!ue_sk)
376        return -ENOMEM;
377
378    ue_sk->sk = netlink_kernel_create(net, NETLINK_KOBJECT_UEVENT,
379                      1, NULL, NULL, THIS_MODULE);
380    if (!ue_sk->sk) {
381        printk(KERN_ERR
382               "kobject_uevent: unable to create netlink socket!\n");
383        kfree(ue_sk);
384        return -ENODEV;
385    }
386    mutex_lock(&uevent_sock_mutex);
387    list_add_tail(&ue_sk->list, &uevent_sock_list);
388    mutex_unlock(&uevent_sock_mutex);
389    return 0;
390}
391
392static void uevent_net_exit(struct net *net)
393{
394    struct uevent_sock *ue_sk;
395
396    mutex_lock(&uevent_sock_mutex);
397    list_for_each_entry(ue_sk, &uevent_sock_list, list) {
398        if (sock_net(ue_sk->sk) == net)
399            goto found;
400    }
401    mutex_unlock(&uevent_sock_mutex);
402    return;
403
404found:
405    list_del(&ue_sk->list);
406    mutex_unlock(&uevent_sock_mutex);
407
408    netlink_kernel_release(ue_sk->sk);
409    kfree(ue_sk);
410}
411
412static struct pernet_operations uevent_net_ops = {
413    .init = uevent_net_init,
414    .exit = uevent_net_exit,
415};
416
417static int __init kobject_uevent_init(void)
418{
419    netlink_set_nonroot(NETLINK_KOBJECT_UEVENT, NL_NONROOT_RECV);
420    return register_pernet_subsys(&uevent_net_ops);
421}
422
423
424postcore_initcall(kobject_uevent_init);
425#endif
426

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