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TOMOYO Linux Cross Reference
Linux/lib/kobject_uevent.c

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  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/uidgid.h>
 26 #include <linux/uuid.h>
 27 #include <linux/ctype.h>
 28 #include <net/sock.h>
 29 #include <net/netlink.h>
 30 #include <net/net_namespace.h>
 31 
 32 
 33 u64 uevent_seqnum;
 34 #ifdef CONFIG_UEVENT_HELPER
 35 char uevent_helper[UEVENT_HELPER_PATH_LEN] = CONFIG_UEVENT_HELPER_PATH;
 36 #endif
 37 
 38 struct uevent_sock {
 39         struct list_head list;
 40         struct sock *sk;
 41 };
 42 
 43 #ifdef CONFIG_NET
 44 static LIST_HEAD(uevent_sock_list);
 45 #endif
 46 
 47 /* This lock protects uevent_seqnum and uevent_sock_list */
 48 static DEFINE_MUTEX(uevent_sock_mutex);
 49 
 50 /* the strings here must match the enum in include/linux/kobject.h */
 51 static const char *kobject_actions[] = {
 52         [KOBJ_ADD] =            "add",
 53         [KOBJ_REMOVE] =         "remove",
 54         [KOBJ_CHANGE] =         "change",
 55         [KOBJ_MOVE] =           "move",
 56         [KOBJ_ONLINE] =         "online",
 57         [KOBJ_OFFLINE] =        "offline",
 58         [KOBJ_BIND] =           "bind",
 59         [KOBJ_UNBIND] =         "unbind",
 60 };
 61 
 62 static int kobject_action_type(const char *buf, size_t count,
 63                                enum kobject_action *type,
 64                                const char **args)
 65 {
 66         enum kobject_action action;
 67         size_t count_first;
 68         const char *args_start;
 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         args_start = strnchr(buf, count, ' ');
 78         if (args_start) {
 79                 count_first = args_start - buf;
 80                 args_start = args_start + 1;
 81         } else
 82                 count_first = count;
 83 
 84         for (action = 0; action < ARRAY_SIZE(kobject_actions); action++) {
 85                 if (strncmp(kobject_actions[action], buf, count_first) != 0)
 86                         continue;
 87                 if (kobject_actions[action][count_first] != '\0')
 88                         continue;
 89                 if (args)
 90                         *args = args_start;
 91                 *type = action;
 92                 ret = 0;
 93                 break;
 94         }
 95 out:
 96         return ret;
 97 }
 98 
 99 static const char *action_arg_word_end(const char *buf, const char *buf_end,
100                                        char delim)
101 {
102         const char *next = buf;
103 
104         while (next <= buf_end && *next != delim)
105                 if (!isalnum(*next++))
106                         return NULL;
107 
108         if (next == buf)
109                 return NULL;
110 
111         return next;
112 }
113 
114 static int kobject_action_args(const char *buf, size_t count,
115                                struct kobj_uevent_env **ret_env)
116 {
117         struct kobj_uevent_env *env = NULL;
118         const char *next, *buf_end, *key;
119         int key_len;
120         int r = -EINVAL;
121 
122         if (count && (buf[count - 1] == '\n' || buf[count - 1] == '\0'))
123                 count--;
124 
125         if (!count)
126                 return -EINVAL;
127 
128         env = kzalloc(sizeof(*env), GFP_KERNEL);
129         if (!env)
130                 return -ENOMEM;
131 
132         /* first arg is UUID */
133         if (count < UUID_STRING_LEN || !uuid_is_valid(buf) ||
134             add_uevent_var(env, "SYNTH_UUID=%.*s", UUID_STRING_LEN, buf))
135                 goto out;
136 
137         /*
138          * the rest are custom environment variables in KEY=VALUE
139          * format with ' ' delimiter between each KEY=VALUE pair
140          */
141         next = buf + UUID_STRING_LEN;
142         buf_end = buf + count - 1;
143 
144         while (next <= buf_end) {
145                 if (*next != ' ')
146                         goto out;
147 
148                 /* skip the ' ', key must follow */
149                 key = ++next;
150                 if (key > buf_end)
151                         goto out;
152 
153                 buf = next;
154                 next = action_arg_word_end(buf, buf_end, '=');
155                 if (!next || next > buf_end || *next != '=')
156                         goto out;
157                 key_len = next - buf;
158 
159                 /* skip the '=', value must follow */
160                 if (++next > buf_end)
161                         goto out;
162 
163                 buf = next;
164                 next = action_arg_word_end(buf, buf_end, ' ');
165                 if (!next)
166                         goto out;
167 
168                 if (add_uevent_var(env, "SYNTH_ARG_%.*s=%.*s",
169                                    key_len, key, (int) (next - buf), buf))
170                         goto out;
171         }
172 
173         r = 0;
174 out:
175         if (r)
176                 kfree(env);
177         else
178                 *ret_env = env;
179         return r;
180 }
181 
182 /**
183  * kobject_synth_uevent - send synthetic uevent with arguments
184  *
185  * @kobj: struct kobject for which synthetic uevent is to be generated
186  * @buf: buffer containing action type and action args, newline is ignored
187  * @count: length of buffer
188  *
189  * Returns 0 if kobject_synthetic_uevent() is completed with success or the
190  * corresponding error when it fails.
191  */
192 int kobject_synth_uevent(struct kobject *kobj, const char *buf, size_t count)
193 {
194         char *no_uuid_envp[] = { "SYNTH_UUID=0", NULL };
195         enum kobject_action action;
196         const char *action_args;
197         struct kobj_uevent_env *env;
198         const char *msg = NULL, *devpath;
199         int r;
200 
201         r = kobject_action_type(buf, count, &action, &action_args);
202         if (r) {
203                 msg = "unknown uevent action string";
204                 goto out;
205         }
206 
207         if (!action_args) {
208                 r = kobject_uevent_env(kobj, action, no_uuid_envp);
209                 goto out;
210         }
211 
212         r = kobject_action_args(action_args,
213                                 count - (action_args - buf), &env);
214         if (r == -EINVAL) {
215                 msg = "incorrect uevent action arguments";
216                 goto out;
217         }
218 
219         if (r)
220                 goto out;
221 
222         r = kobject_uevent_env(kobj, action, env->envp);
223         kfree(env);
224 out:
225         if (r) {
226                 devpath = kobject_get_path(kobj, GFP_KERNEL);
227                 pr_warn("synth uevent: %s: %s\n",
228                        devpath ?: "unknown device",
229                        msg ?: "failed to send uevent");
230                 kfree(devpath);
231         }
232         return r;
233 }
234 
235 #ifdef CONFIG_UEVENT_HELPER
236 static int kobj_usermode_filter(struct kobject *kobj)
237 {
238         const struct kobj_ns_type_operations *ops;
239 
240         ops = kobj_ns_ops(kobj);
241         if (ops) {
242                 const void *init_ns, *ns;
243 
244                 ns = kobj->ktype->namespace(kobj);
245                 init_ns = ops->initial_ns();
246                 return ns != init_ns;
247         }
248 
249         return 0;
250 }
251 
252 static int init_uevent_argv(struct kobj_uevent_env *env, const char *subsystem)
253 {
254         int len;
255 
256         len = strlcpy(&env->buf[env->buflen], subsystem,
257                       sizeof(env->buf) - env->buflen);
258         if (len >= (sizeof(env->buf) - env->buflen)) {
259                 WARN(1, KERN_ERR "init_uevent_argv: buffer size too small\n");
260                 return -ENOMEM;
261         }
262 
263         env->argv[0] = uevent_helper;
264         env->argv[1] = &env->buf[env->buflen];
265         env->argv[2] = NULL;
266 
267         env->buflen += len + 1;
268         return 0;
269 }
270 
271 static void cleanup_uevent_env(struct subprocess_info *info)
272 {
273         kfree(info->data);
274 }
275 #endif
276 
277 #ifdef CONFIG_NET
278 static struct sk_buff *alloc_uevent_skb(struct kobj_uevent_env *env,
279                                         const char *action_string,
280                                         const char *devpath)
281 {
282         struct netlink_skb_parms *parms;
283         struct sk_buff *skb = NULL;
284         char *scratch;
285         size_t len;
286 
287         /* allocate message with maximum possible size */
288         len = strlen(action_string) + strlen(devpath) + 2;
289         skb = alloc_skb(len + env->buflen, GFP_KERNEL);
290         if (!skb)
291                 return NULL;
292 
293         /* add header */
294         scratch = skb_put(skb, len);
295         sprintf(scratch, "%s@%s", action_string, devpath);
296 
297         skb_put_data(skb, env->buf, env->buflen);
298 
299         parms = &NETLINK_CB(skb);
300         parms->creds.uid = GLOBAL_ROOT_UID;
301         parms->creds.gid = GLOBAL_ROOT_GID;
302         parms->dst_group = 1;
303         parms->portid = 0;
304 
305         return skb;
306 }
307 
308 static int uevent_net_broadcast_untagged(struct kobj_uevent_env *env,
309                                          const char *action_string,
310                                          const char *devpath)
311 {
312         struct sk_buff *skb = NULL;
313         struct uevent_sock *ue_sk;
314         int retval = 0;
315 
316         /* send netlink message */
317         list_for_each_entry(ue_sk, &uevent_sock_list, list) {
318                 struct sock *uevent_sock = ue_sk->sk;
319 
320                 if (!netlink_has_listeners(uevent_sock, 1))
321                         continue;
322 
323                 if (!skb) {
324                         retval = -ENOMEM;
325                         skb = alloc_uevent_skb(env, action_string, devpath);
326                         if (!skb)
327                                 continue;
328                 }
329 
330                 retval = netlink_broadcast(uevent_sock, skb_get(skb), 0, 1,
331                                            GFP_KERNEL);
332                 /* ENOBUFS should be handled in userspace */
333                 if (retval == -ENOBUFS || retval == -ESRCH)
334                         retval = 0;
335         }
336         consume_skb(skb);
337 
338         return retval;
339 }
340 
341 static int uevent_net_broadcast_tagged(struct sock *usk,
342                                        struct kobj_uevent_env *env,
343                                        const char *action_string,
344                                        const char *devpath)
345 {
346         struct user_namespace *owning_user_ns = sock_net(usk)->user_ns;
347         struct sk_buff *skb = NULL;
348         int ret = 0;
349 
350         skb = alloc_uevent_skb(env, action_string, devpath);
351         if (!skb)
352                 return -ENOMEM;
353 
354         /* fix credentials */
355         if (owning_user_ns != &init_user_ns) {
356                 struct netlink_skb_parms *parms = &NETLINK_CB(skb);
357                 kuid_t root_uid;
358                 kgid_t root_gid;
359 
360                 /* fix uid */
361                 root_uid = make_kuid(owning_user_ns, 0);
362                 if (uid_valid(root_uid))
363                         parms->creds.uid = root_uid;
364 
365                 /* fix gid */
366                 root_gid = make_kgid(owning_user_ns, 0);
367                 if (gid_valid(root_gid))
368                         parms->creds.gid = root_gid;
369         }
370 
371         ret = netlink_broadcast(usk, skb, 0, 1, GFP_KERNEL);
372         /* ENOBUFS should be handled in userspace */
373         if (ret == -ENOBUFS || ret == -ESRCH)
374                 ret = 0;
375 
376         return ret;
377 }
378 #endif
379 
380 static int kobject_uevent_net_broadcast(struct kobject *kobj,
381                                         struct kobj_uevent_env *env,
382                                         const char *action_string,
383                                         const char *devpath)
384 {
385         int ret = 0;
386 
387 #ifdef CONFIG_NET
388         const struct kobj_ns_type_operations *ops;
389         const struct net *net = NULL;
390 
391         ops = kobj_ns_ops(kobj);
392         if (!ops && kobj->kset) {
393                 struct kobject *ksobj = &kobj->kset->kobj;
394 
395                 if (ksobj->parent != NULL)
396                         ops = kobj_ns_ops(ksobj->parent);
397         }
398 
399         /* kobjects currently only carry network namespace tags and they
400          * are the only tag relevant here since we want to decide which
401          * network namespaces to broadcast the uevent into.
402          */
403         if (ops && ops->netlink_ns && kobj->ktype->namespace)
404                 if (ops->type == KOBJ_NS_TYPE_NET)
405                         net = kobj->ktype->namespace(kobj);
406 
407         if (!net)
408                 ret = uevent_net_broadcast_untagged(env, action_string,
409                                                     devpath);
410         else
411                 ret = uevent_net_broadcast_tagged(net->uevent_sock->sk, env,
412                                                   action_string, devpath);
413 #endif
414 
415         return ret;
416 }
417 
418 static void zap_modalias_env(struct kobj_uevent_env *env)
419 {
420         static const char modalias_prefix[] = "MODALIAS=";
421         size_t len;
422         int i, j;
423 
424         for (i = 0; i < env->envp_idx;) {
425                 if (strncmp(env->envp[i], modalias_prefix,
426                             sizeof(modalias_prefix) - 1)) {
427                         i++;
428                         continue;
429                 }
430 
431                 len = strlen(env->envp[i]) + 1;
432 
433                 if (i != env->envp_idx - 1) {
434                         memmove(env->envp[i], env->envp[i + 1],
435                                 env->buflen - len);
436 
437                         for (j = i; j < env->envp_idx - 1; j++)
438                                 env->envp[j] = env->envp[j + 1] - len;
439                 }
440 
441                 env->envp_idx--;
442                 env->buflen -= len;
443         }
444 }
445 
446 /**
447  * kobject_uevent_env - send an uevent with environmental data
448  *
449  * @kobj: struct kobject that the action is happening to
450  * @action: action that is happening
451  * @envp_ext: pointer to environmental data
452  *
453  * Returns 0 if kobject_uevent_env() is completed with success or the
454  * corresponding error when it fails.
455  */
456 int kobject_uevent_env(struct kobject *kobj, enum kobject_action action,
457                        char *envp_ext[])
458 {
459         struct kobj_uevent_env *env;
460         const char *action_string = kobject_actions[action];
461         const char *devpath = NULL;
462         const char *subsystem;
463         struct kobject *top_kobj;
464         struct kset *kset;
465         const struct kset_uevent_ops *uevent_ops;
466         int i = 0;
467         int retval = 0;
468 
469         pr_debug("kobject: '%s' (%p): %s\n",
470                  kobject_name(kobj), kobj, __func__);
471 
472         /* search the kset we belong to */
473         top_kobj = kobj;
474         while (!top_kobj->kset && top_kobj->parent)
475                 top_kobj = top_kobj->parent;
476 
477         if (!top_kobj->kset) {
478                 pr_debug("kobject: '%s' (%p): %s: attempted to send uevent "
479                          "without kset!\n", kobject_name(kobj), kobj,
480                          __func__);
481                 return -EINVAL;
482         }
483 
484         kset = top_kobj->kset;
485         uevent_ops = kset->uevent_ops;
486 
487         /* skip the event, if uevent_suppress is set*/
488         if (kobj->uevent_suppress) {
489                 pr_debug("kobject: '%s' (%p): %s: uevent_suppress "
490                                  "caused the event to drop!\n",
491                                  kobject_name(kobj), kobj, __func__);
492                 return 0;
493         }
494         /* skip the event, if the filter returns zero. */
495         if (uevent_ops && uevent_ops->filter)
496                 if (!uevent_ops->filter(kset, kobj)) {
497                         pr_debug("kobject: '%s' (%p): %s: filter function "
498                                  "caused the event to drop!\n",
499                                  kobject_name(kobj), kobj, __func__);
500                         return 0;
501                 }
502 
503         /* originating subsystem */
504         if (uevent_ops && uevent_ops->name)
505                 subsystem = uevent_ops->name(kset, kobj);
506         else
507                 subsystem = kobject_name(&kset->kobj);
508         if (!subsystem) {
509                 pr_debug("kobject: '%s' (%p): %s: unset subsystem caused the "
510                          "event to drop!\n", kobject_name(kobj), kobj,
511                          __func__);
512                 return 0;
513         }
514 
515         /* environment buffer */
516         env = kzalloc(sizeof(struct kobj_uevent_env), GFP_KERNEL);
517         if (!env)
518                 return -ENOMEM;
519 
520         /* complete object path */
521         devpath = kobject_get_path(kobj, GFP_KERNEL);
522         if (!devpath) {
523                 retval = -ENOENT;
524                 goto exit;
525         }
526 
527         /* default keys */
528         retval = add_uevent_var(env, "ACTION=%s", action_string);
529         if (retval)
530                 goto exit;
531         retval = add_uevent_var(env, "DEVPATH=%s", devpath);
532         if (retval)
533                 goto exit;
534         retval = add_uevent_var(env, "SUBSYSTEM=%s", subsystem);
535         if (retval)
536                 goto exit;
537 
538         /* keys passed in from the caller */
539         if (envp_ext) {
540                 for (i = 0; envp_ext[i]; i++) {
541                         retval = add_uevent_var(env, "%s", envp_ext[i]);
542                         if (retval)
543                                 goto exit;
544                 }
545         }
546 
547         /* let the kset specific function add its stuff */
548         if (uevent_ops && uevent_ops->uevent) {
549                 retval = uevent_ops->uevent(kset, kobj, env);
550                 if (retval) {
551                         pr_debug("kobject: '%s' (%p): %s: uevent() returned "
552                                  "%d\n", kobject_name(kobj), kobj,
553                                  __func__, retval);
554                         goto exit;
555                 }
556         }
557 
558         switch (action) {
559         case KOBJ_ADD:
560                 /*
561                  * Mark "add" event so we can make sure we deliver "remove"
562                  * event to userspace during automatic cleanup. If
563                  * the object did send an "add" event, "remove" will
564                  * automatically generated by the core, if not already done
565                  * by the caller.
566                  */
567                 kobj->state_add_uevent_sent = 1;
568                 break;
569 
570         case KOBJ_REMOVE:
571                 kobj->state_remove_uevent_sent = 1;
572                 break;
573 
574         case KOBJ_UNBIND:
575                 zap_modalias_env(env);
576                 break;
577 
578         default:
579                 break;
580         }
581 
582         mutex_lock(&uevent_sock_mutex);
583         /* we will send an event, so request a new sequence number */
584         retval = add_uevent_var(env, "SEQNUM=%llu", ++uevent_seqnum);
585         if (retval) {
586                 mutex_unlock(&uevent_sock_mutex);
587                 goto exit;
588         }
589         retval = kobject_uevent_net_broadcast(kobj, env, action_string,
590                                               devpath);
591         mutex_unlock(&uevent_sock_mutex);
592 
593 #ifdef CONFIG_UEVENT_HELPER
594         /* call uevent_helper, usually only enabled during early boot */
595         if (uevent_helper[0] && !kobj_usermode_filter(kobj)) {
596                 struct subprocess_info *info;
597 
598                 retval = add_uevent_var(env, "HOME=/");
599                 if (retval)
600                         goto exit;
601                 retval = add_uevent_var(env,
602                                         "PATH=/sbin:/bin:/usr/sbin:/usr/bin");
603                 if (retval)
604                         goto exit;
605                 retval = init_uevent_argv(env, subsystem);
606                 if (retval)
607                         goto exit;
608 
609                 retval = -ENOMEM;
610                 info = call_usermodehelper_setup(env->argv[0], env->argv,
611                                                  env->envp, GFP_KERNEL,
612                                                  NULL, cleanup_uevent_env, env);
613                 if (info) {
614                         retval = call_usermodehelper_exec(info, UMH_NO_WAIT);
615                         env = NULL;     /* freed by cleanup_uevent_env */
616                 }
617         }
618 #endif
619 
620 exit:
621         kfree(devpath);
622         kfree(env);
623         return retval;
624 }
625 EXPORT_SYMBOL_GPL(kobject_uevent_env);
626 
627 /**
628  * kobject_uevent - notify userspace by sending an uevent
629  *
630  * @kobj: struct kobject that the action is happening to
631  * @action: action that is happening
632  *
633  * Returns 0 if kobject_uevent() is completed with success or the
634  * corresponding error when it fails.
635  */
636 int kobject_uevent(struct kobject *kobj, enum kobject_action action)
637 {
638         return kobject_uevent_env(kobj, action, NULL);
639 }
640 EXPORT_SYMBOL_GPL(kobject_uevent);
641 
642 /**
643  * add_uevent_var - add key value string to the environment buffer
644  * @env: environment buffer structure
645  * @format: printf format for the key=value pair
646  *
647  * Returns 0 if environment variable was added successfully or -ENOMEM
648  * if no space was available.
649  */
650 int add_uevent_var(struct kobj_uevent_env *env, const char *format, ...)
651 {
652         va_list args;
653         int len;
654 
655         if (env->envp_idx >= ARRAY_SIZE(env->envp)) {
656                 WARN(1, KERN_ERR "add_uevent_var: too many keys\n");
657                 return -ENOMEM;
658         }
659 
660         va_start(args, format);
661         len = vsnprintf(&env->buf[env->buflen],
662                         sizeof(env->buf) - env->buflen,
663                         format, args);
664         va_end(args);
665 
666         if (len >= (sizeof(env->buf) - env->buflen)) {
667                 WARN(1, KERN_ERR "add_uevent_var: buffer size too small\n");
668                 return -ENOMEM;
669         }
670 
671         env->envp[env->envp_idx++] = &env->buf[env->buflen];
672         env->buflen += len + 1;
673         return 0;
674 }
675 EXPORT_SYMBOL_GPL(add_uevent_var);
676 
677 #if defined(CONFIG_NET)
678 static int uevent_net_broadcast(struct sock *usk, struct sk_buff *skb,
679                                 struct netlink_ext_ack *extack)
680 {
681         /* u64 to chars: 2^64 - 1 = 21 chars */
682         char buf[sizeof("SEQNUM=") + 21];
683         struct sk_buff *skbc;
684         int ret;
685 
686         /* bump and prepare sequence number */
687         ret = snprintf(buf, sizeof(buf), "SEQNUM=%llu", ++uevent_seqnum);
688         if (ret < 0 || (size_t)ret >= sizeof(buf))
689                 return -ENOMEM;
690         ret++;
691 
692         /* verify message does not overflow */
693         if ((skb->len + ret) > UEVENT_BUFFER_SIZE) {
694                 NL_SET_ERR_MSG(extack, "uevent message too big");
695                 return -EINVAL;
696         }
697 
698         /* copy skb and extend to accommodate sequence number */
699         skbc = skb_copy_expand(skb, 0, ret, GFP_KERNEL);
700         if (!skbc)
701                 return -ENOMEM;
702 
703         /* append sequence number */
704         skb_put_data(skbc, buf, ret);
705 
706         /* remove msg header */
707         skb_pull(skbc, NLMSG_HDRLEN);
708 
709         /* set portid 0 to inform userspace message comes from kernel */
710         NETLINK_CB(skbc).portid = 0;
711         NETLINK_CB(skbc).dst_group = 1;
712 
713         ret = netlink_broadcast(usk, skbc, 0, 1, GFP_KERNEL);
714         /* ENOBUFS should be handled in userspace */
715         if (ret == -ENOBUFS || ret == -ESRCH)
716                 ret = 0;
717 
718         return ret;
719 }
720 
721 static int uevent_net_rcv_skb(struct sk_buff *skb, struct nlmsghdr *nlh,
722                               struct netlink_ext_ack *extack)
723 {
724         struct net *net;
725         int ret;
726 
727         if (!nlmsg_data(nlh))
728                 return -EINVAL;
729 
730         /*
731          * Verify that we are allowed to send messages to the target
732          * network namespace. The caller must have CAP_SYS_ADMIN in the
733          * owning user namespace of the target network namespace.
734          */
735         net = sock_net(NETLINK_CB(skb).sk);
736         if (!netlink_ns_capable(skb, net->user_ns, CAP_SYS_ADMIN)) {
737                 NL_SET_ERR_MSG(extack, "missing CAP_SYS_ADMIN capability");
738                 return -EPERM;
739         }
740 
741         mutex_lock(&uevent_sock_mutex);
742         ret = uevent_net_broadcast(net->uevent_sock->sk, skb, extack);
743         mutex_unlock(&uevent_sock_mutex);
744 
745         return ret;
746 }
747 
748 static void uevent_net_rcv(struct sk_buff *skb)
749 {
750         netlink_rcv_skb(skb, &uevent_net_rcv_skb);
751 }
752 
753 static int uevent_net_init(struct net *net)
754 {
755         struct uevent_sock *ue_sk;
756         struct netlink_kernel_cfg cfg = {
757                 .groups = 1,
758                 .input = uevent_net_rcv,
759                 .flags  = NL_CFG_F_NONROOT_RECV
760         };
761 
762         ue_sk = kzalloc(sizeof(*ue_sk), GFP_KERNEL);
763         if (!ue_sk)
764                 return -ENOMEM;
765 
766         ue_sk->sk = netlink_kernel_create(net, NETLINK_KOBJECT_UEVENT, &cfg);
767         if (!ue_sk->sk) {
768                 pr_err("kobject_uevent: unable to create netlink socket!\n");
769                 kfree(ue_sk);
770                 return -ENODEV;
771         }
772 
773         net->uevent_sock = ue_sk;
774 
775         /* Restrict uevents to initial user namespace. */
776         if (sock_net(ue_sk->sk)->user_ns == &init_user_ns) {
777                 mutex_lock(&uevent_sock_mutex);
778                 list_add_tail(&ue_sk->list, &uevent_sock_list);
779                 mutex_unlock(&uevent_sock_mutex);
780         }
781 
782         return 0;
783 }
784 
785 static void uevent_net_exit(struct net *net)
786 {
787         struct uevent_sock *ue_sk = net->uevent_sock;
788 
789         if (sock_net(ue_sk->sk)->user_ns == &init_user_ns) {
790                 mutex_lock(&uevent_sock_mutex);
791                 list_del(&ue_sk->list);
792                 mutex_unlock(&uevent_sock_mutex);
793         }
794 
795         netlink_kernel_release(ue_sk->sk);
796         kfree(ue_sk);
797 }
798 
799 static struct pernet_operations uevent_net_ops = {
800         .init   = uevent_net_init,
801         .exit   = uevent_net_exit,
802 };
803 
804 static int __init kobject_uevent_init(void)
805 {
806         return register_pernet_subsys(&uevent_net_ops);
807 }
808 
809 
810 postcore_initcall(kobject_uevent_init);
811 #endif
812 

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