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/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
31u64 uevent_seqnum;
32char uevent_helper[UEVENT_HELPER_PATH_LEN] = CONFIG_UEVENT_HELPER_PATH;
33#ifdef CONFIG_NET
34struct uevent_sock {
35    struct list_head list;
36    struct sock *sk;
37};
38static LIST_HEAD(uevent_sock_list);
39#endif
40
41/* This lock protects uevent_seqnum and uevent_sock_list */
42static DEFINE_MUTEX(uevent_sock_mutex);
43
44/* the strings here must match the enum in include/linux/kobject.h */
45static const char *kobject_actions[] = {
46    [KOBJ_ADD] = "add",
47    [KOBJ_REMOVE] = "remove",
48    [KOBJ_CHANGE] = "change",
49    [KOBJ_MOVE] = "move",
50    [KOBJ_ONLINE] = "online",
51    [KOBJ_OFFLINE] = "offline",
52};
53
54/**
55 * kobject_action_type - translate action string to numeric type
56 *
57 * @buf: buffer containing the action string, newline is ignored
58 * @len: length of buffer
59 * @type: pointer to the location to store the action type
60 *
61 * Returns 0 if the action string was recognized.
62 */
63int kobject_action_type(const char *buf, size_t count,
64            enum kobject_action *type)
65{
66    enum kobject_action action;
67    int ret = -EINVAL;
68
69    if (count && (buf[count-1] == '\n' || buf[count-1] == '\0'))
70        count--;
71
72    if (!count)
73        goto out;
74
75    for (action = 0; action < ARRAY_SIZE(kobject_actions); action++) {
76        if (strncmp(kobject_actions[action], buf, count) != 0)
77            continue;
78        if (kobject_actions[action][count] != '\0')
79            continue;
80        *type = action;
81        ret = 0;
82        break;
83    }
84out:
85    return ret;
86}
87
88#ifdef CONFIG_NET
89static int kobj_bcast_filter(struct sock *dsk, struct sk_buff *skb, void *data)
90{
91    struct kobject *kobj = data;
92    const struct kobj_ns_type_operations *ops;
93
94    ops = kobj_ns_ops(kobj);
95    if (ops) {
96        const void *sock_ns, *ns;
97        ns = kobj->ktype->namespace(kobj);
98        sock_ns = ops->netlink_ns(dsk);
99        return sock_ns != ns;
100    }
101
102    return 0;
103}
104#endif
105
106static int kobj_usermode_filter(struct kobject *kobj)
107{
108    const struct kobj_ns_type_operations *ops;
109
110    ops = kobj_ns_ops(kobj);
111    if (ops) {
112        const void *init_ns, *ns;
113        ns = kobj->ktype->namespace(kobj);
114        init_ns = ops->initial_ns();
115        return ns != init_ns;
116    }
117
118    return 0;
119}
120
121/**
122 * kobject_uevent_env - send an uevent with environmental data
123 *
124 * @action: action that is happening
125 * @kobj: struct kobject that the action is happening to
126 * @envp_ext: pointer to environmental data
127 *
128 * Returns 0 if kobject_uevent_env() is completed with success or the
129 * corresponding error when it fails.
130 */
131int kobject_uevent_env(struct kobject *kobj, enum kobject_action action,
132               char *envp_ext[])
133{
134    struct kobj_uevent_env *env;
135    const char *action_string = kobject_actions[action];
136    const char *devpath = NULL;
137    const char *subsystem;
138    struct kobject *top_kobj;
139    struct kset *kset;
140    const struct kset_uevent_ops *uevent_ops;
141    int i = 0;
142    int retval = 0;
143#ifdef CONFIG_NET
144    struct uevent_sock *ue_sk;
145#endif
146
147    pr_debug("kobject: '%s' (%p): %s\n",
148         kobject_name(kobj), kobj, __func__);
149
150    /* search the kset we belong to */
151    top_kobj = kobj;
152    while (!top_kobj->kset && top_kobj->parent)
153        top_kobj = top_kobj->parent;
154
155    if (!top_kobj->kset) {
156        pr_debug("kobject: '%s' (%p): %s: attempted to send uevent "
157             "without kset!\n", kobject_name(kobj), kobj,
158             __func__);
159        return -EINVAL;
160    }
161
162    kset = top_kobj->kset;
163    uevent_ops = kset->uevent_ops;
164
165    /* skip the event, if uevent_suppress is set*/
166    if (kobj->uevent_suppress) {
167        pr_debug("kobject: '%s' (%p): %s: uevent_suppress "
168                 "caused the event to drop!\n",
169                 kobject_name(kobj), kobj, __func__);
170        return 0;
171    }
172    /* skip the event, if the filter returns zero. */
173    if (uevent_ops && uevent_ops->filter)
174        if (!uevent_ops->filter(kset, kobj)) {
175            pr_debug("kobject: '%s' (%p): %s: filter function "
176                 "caused the event to drop!\n",
177                 kobject_name(kobj), kobj, __func__);
178            return 0;
179        }
180
181    /* originating subsystem */
182    if (uevent_ops && uevent_ops->name)
183        subsystem = uevent_ops->name(kset, kobj);
184    else
185        subsystem = kobject_name(&kset->kobj);
186    if (!subsystem) {
187        pr_debug("kobject: '%s' (%p): %s: unset subsystem caused the "
188             "event to drop!\n", kobject_name(kobj), kobj,
189             __func__);
190        return 0;
191    }
192
193    /* environment buffer */
194    env = kzalloc(sizeof(struct kobj_uevent_env), GFP_KERNEL);
195    if (!env)
196        return -ENOMEM;
197
198    /* complete object path */
199    devpath = kobject_get_path(kobj, GFP_KERNEL);
200    if (!devpath) {
201        retval = -ENOENT;
202        goto exit;
203    }
204
205    /* default keys */
206    retval = add_uevent_var(env, "ACTION=%s", action_string);
207    if (retval)
208        goto exit;
209    retval = add_uevent_var(env, "DEVPATH=%s", devpath);
210    if (retval)
211        goto exit;
212    retval = add_uevent_var(env, "SUBSYSTEM=%s", subsystem);
213    if (retval)
214        goto exit;
215
216    /* keys passed in from the caller */
217    if (envp_ext) {
218        for (i = 0; envp_ext[i]; i++) {
219            retval = add_uevent_var(env, "%s", envp_ext[i]);
220            if (retval)
221                goto exit;
222        }
223    }
224
225    /* let the kset specific function add its stuff */
226    if (uevent_ops && uevent_ops->uevent) {
227        retval = uevent_ops->uevent(kset, kobj, env);
228        if (retval) {
229            pr_debug("kobject: '%s' (%p): %s: uevent() returned "
230                 "%d\n", kobject_name(kobj), kobj,
231                 __func__, retval);
232            goto exit;
233        }
234    }
235
236    /*
237     * Mark "add" and "remove" events in the object to ensure proper
238     * events to userspace during automatic cleanup. If the object did
239     * send an "add" event, "remove" will automatically generated by
240     * the core, if not already done by the caller.
241     */
242    if (action == KOBJ_ADD)
243        kobj->state_add_uevent_sent = 1;
244    else if (action == KOBJ_REMOVE)
245        kobj->state_remove_uevent_sent = 1;
246
247    mutex_lock(&uevent_sock_mutex);
248    /* we will send an event, so request a new sequence number */
249    retval = add_uevent_var(env, "SEQNUM=%llu", (unsigned long long)++uevent_seqnum);
250    if (retval) {
251        mutex_unlock(&uevent_sock_mutex);
252        goto exit;
253    }
254
255#if defined(CONFIG_NET)
256    /* send netlink message */
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        if (!netlink_has_listeners(uevent_sock, 1))
263            continue;
264
265        /* allocate message with the maximum possible size */
266        len = strlen(action_string) + strlen(devpath) + 2;
267        skb = alloc_skb(len + env->buflen, GFP_KERNEL);
268        if (skb) {
269            char *scratch;
270
271            /* add header */
272            scratch = skb_put(skb, len);
273            sprintf(scratch, "%s@%s", action_string, devpath);
274
275            /* copy keys to our continuous event payload buffer */
276            for (i = 0; i < env->envp_idx; i++) {
277                len = strlen(env->envp[i]) + 1;
278                scratch = skb_put(skb, len);
279                strcpy(scratch, env->envp[i]);
280            }
281
282            NETLINK_CB(skb).dst_group = 1;
283            retval = netlink_broadcast_filtered(uevent_sock, skb,
284                                0, 1, GFP_KERNEL,
285                                kobj_bcast_filter,
286                                kobj);
287            /* ENOBUFS should be handled in userspace */
288            if (retval == -ENOBUFS || retval == -ESRCH)
289                retval = 0;
290        } else
291            retval = -ENOMEM;
292    }
293#endif
294    mutex_unlock(&uevent_sock_mutex);
295
296    /* call uevent_helper, usually only enabled during early boot */
297    if (uevent_helper[0] && !kobj_usermode_filter(kobj)) {
298        char *argv [3];
299
300        argv [0] = uevent_helper;
301        argv [1] = (char *)subsystem;
302        argv [2] = NULL;
303        retval = add_uevent_var(env, "HOME=/");
304        if (retval)
305            goto exit;
306        retval = add_uevent_var(env,
307                    "PATH=/sbin:/bin:/usr/sbin:/usr/bin");
308        if (retval)
309            goto exit;
310
311        retval = call_usermodehelper(argv[0], argv,
312                         env->envp, UMH_WAIT_EXEC);
313    }
314
315exit:
316    kfree(devpath);
317    kfree(env);
318    return retval;
319}
320EXPORT_SYMBOL_GPL(kobject_uevent_env);
321
322/**
323 * kobject_uevent - notify userspace by sending an uevent
324 *
325 * @action: action that is happening
326 * @kobj: struct kobject that the action is happening to
327 *
328 * Returns 0 if kobject_uevent() is completed with success or the
329 * corresponding error when it fails.
330 */
331int kobject_uevent(struct kobject *kobj, enum kobject_action action)
332{
333    return kobject_uevent_env(kobj, action, NULL);
334}
335EXPORT_SYMBOL_GPL(kobject_uevent);
336
337/**
338 * add_uevent_var - add key value string to the environment buffer
339 * @env: environment buffer structure
340 * @format: printf format for the key=value pair
341 *
342 * Returns 0 if environment variable was added successfully or -ENOMEM
343 * if no space was available.
344 */
345int add_uevent_var(struct kobj_uevent_env *env, const char *format, ...)
346{
347    va_list args;
348    int len;
349
350    if (env->envp_idx >= ARRAY_SIZE(env->envp)) {
351        WARN(1, KERN_ERR "add_uevent_var: too many keys\n");
352        return -ENOMEM;
353    }
354
355    va_start(args, format);
356    len = vsnprintf(&env->buf[env->buflen],
357            sizeof(env->buf) - env->buflen,
358            format, args);
359    va_end(args);
360
361    if (len >= (sizeof(env->buf) - env->buflen)) {
362        WARN(1, KERN_ERR "add_uevent_var: buffer size too small\n");
363        return -ENOMEM;
364    }
365
366    env->envp[env->envp_idx++] = &env->buf[env->buflen];
367    env->buflen += len + 1;
368    return 0;
369}
370EXPORT_SYMBOL_GPL(add_uevent_var);
371
372#if defined(CONFIG_NET)
373static int uevent_net_init(struct net *net)
374{
375    struct uevent_sock *ue_sk;
376    struct netlink_kernel_cfg cfg = {
377        .groups = 1,
378        .flags = NL_CFG_F_NONROOT_RECV,
379    };
380
381    ue_sk = kzalloc(sizeof(*ue_sk), GFP_KERNEL);
382    if (!ue_sk)
383        return -ENOMEM;
384
385    ue_sk->sk = netlink_kernel_create(net, NETLINK_KOBJECT_UEVENT, &cfg);
386    if (!ue_sk->sk) {
387        printk(KERN_ERR
388               "kobject_uevent: unable to create netlink socket!\n");
389        kfree(ue_sk);
390        return -ENODEV;
391    }
392    mutex_lock(&uevent_sock_mutex);
393    list_add_tail(&ue_sk->list, &uevent_sock_list);
394    mutex_unlock(&uevent_sock_mutex);
395    return 0;
396}
397
398static void uevent_net_exit(struct net *net)
399{
400    struct uevent_sock *ue_sk;
401
402    mutex_lock(&uevent_sock_mutex);
403    list_for_each_entry(ue_sk, &uevent_sock_list, list) {
404        if (sock_net(ue_sk->sk) == net)
405            goto found;
406    }
407    mutex_unlock(&uevent_sock_mutex);
408    return;
409
410found:
411    list_del(&ue_sk->list);
412    mutex_unlock(&uevent_sock_mutex);
413
414    netlink_kernel_release(ue_sk->sk);
415    kfree(ue_sk);
416}
417
418static struct pernet_operations uevent_net_ops = {
419    .init = uevent_net_init,
420    .exit = uevent_net_exit,
421};
422
423static int __init kobject_uevent_init(void)
424{
425    return register_pernet_subsys(&uevent_net_ops);
426}
427
428
429postcore_initcall(kobject_uevent_init);
430#endif
431

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