lib/kobject_uevent.c

   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/netlink.h>
  29 #include <net/net_namespace.h>
  30
  31
  32 u64 uevent_seqnum;
  33 #ifdef CONFIG_UEVENT_HELPER
  34 char uevent_helper[UEVENT_HELPER_PATH_LEN] = CONFIG_UEVENT_HELPER_PATH;
  35 #endif
  36
  37 struct uevent_sock {
  38         struct list_head list;
  39         struct sock *sk;
  40 };
  41
  42 #ifdef CONFIG_NET
  43 static LIST_HEAD(uevent_sock_list);
  44 #endif
  45
  46 /* This lock protects uevent_seqnum and uevent_sock_list */
  47 static DEFINE_MUTEX(uevent_sock_mutex);
  48
  49 /* the strings here must match the enum in include/linux/kobject.h */
  50 static const char *kobject_actions[] = {
  51         [KOBJ_ADD] =            "add",
  52         [KOBJ_REMOVE] =         "remove",
  53         [KOBJ_CHANGE] =         "change",
  54         [KOBJ_MOVE] =           "move",
  55         [KOBJ_ONLINE] =         "online",
  56         [KOBJ_OFFLINE] =        "offline",
  57         [KOBJ_BIND] =           "bind",
  58         [KOBJ_UNBIND] =         "unbind",
  59 };
  60
  61 static int kobject_action_type(const char *buf, size_t count,
  62                                enum kobject_action *type,
  63                                const char **args)
  64 {
  65         enum kobject_action action;
  66         size_t count_first;
  67         const char *args_start;
  68         int ret = -EINVAL;
  69
  70         if (count && (buf[count-1] == '\n' || buf[count-1] == '\0'))
  71                 count--;
  72
  73         if (!count)
  74                 goto out;
  75
  76         args_start = strnchr(buf, count, ' ');
  77         if (args_start) {
  78                 count_first = args_start - buf;
  79                 args_start = args_start + 1;
  80         } else
  81                 count_first = count;
  82
  83         for (action = 0; action < ARRAY_SIZE(kobject_actions); action++) {
  84                 if (strncmp(kobject_actions[action], buf, count_first) != 0)
  85                         continue;
  86                 if (kobject_actions[action][count_first] != '\0')
  87                         continue;
  88                 if (args)
  89                         *args = args_start;
  90                 *type = action;
  91                 ret = 0;
  92                 break;
  93         }
  94 out:
  95         return ret;
  96 }
  97
  98 static const char *action_arg_word_end(const char *buf, const char *buf_end,
  99                                        char delim)
 100 {
 101         const char *next = buf;
 102
 103         while (next <= buf_end && *next != delim)
 104                 if (!isalnum(*next++))
 105                         return NULL;
 106
 107         if (next == buf)
 108                 return NULL;
 109
 110         return next;
 111 }
 112
 113 static int kobject_action_args(const char *buf, size_t count,
 114                                struct kobj_uevent_env **ret_env)
 115 {
 116         struct kobj_uevent_env *env = NULL;
 117         const char *next, *buf_end, *key;
 118         int key_len;
 119         int r = -EINVAL;
 120
 121         if (count && (buf[count - 1] == '\n' || buf[count - 1] == '\0'))
 122                 count--;
 123
 124         if (!count)
 125                 return -EINVAL;
 126
 127         env = kzalloc(sizeof(*env), GFP_KERNEL);
 128         if (!env)
 129                 return -ENOMEM;
 130
 131         /* first arg is UUID */
 132         if (count < UUID_STRING_LEN || !uuid_is_valid(buf) ||
 133             add_uevent_var(env, "SYNTH_UUID=%.*s", UUID_STRING_LEN, buf))
 134                 goto out;
 135
 136         /*
 137          * the rest are custom environment variables in KEY=VALUE
 138          * format with ' ' delimiter between each KEY=VALUE pair
 139          */
 140         next = buf + UUID_STRING_LEN;
 141         buf_end = buf + count - 1;
 142
 143         while (next <= buf_end) {
 144                 if (*next != ' ')
 145                         goto out;
 146
 147                 /* skip the ' ', key must follow */
 148                 key = ++next;
 149                 if (key > buf_end)
 150                         goto out;
 151
 152                 buf = next;
 153                 next = action_arg_word_end(buf, buf_end, '=');
 154                 if (!next || next > buf_end || *next != '=')
 155                         goto out;
 156                 key_len = next - buf;
 157
 158                 /* skip the '=', value must follow */
 159                 if (++next > buf_end)
 160                         goto out;
 161
 162                 buf = next;
 163                 next = action_arg_word_end(buf, buf_end, ' ');
 164                 if (!next)
 165                         goto out;
 166
 167                 if (add_uevent_var(env, "SYNTH_ARG_%.*s=%.*s",
 168                                    key_len, key, (int) (next - buf), buf))
 169                         goto out;
 170         }
 171
 172         r = 0;
 173 out:
 174         if (r)
 175                 kfree(env);
 176         else
 177                 *ret_env = env;
 178         return r;
 179 }
 180
 181 /**
 182  * kobject_synth_uevent - send synthetic uevent with arguments
 183  *
 184  * @kobj: struct kobject for which synthetic uevent is to be generated
 185  * @buf: buffer containing action type and action args, newline is ignored
 186  * @count: length of buffer
 187  *
 188  * Returns 0 if kobject_synthetic_uevent() is completed with success or the
 189  * corresponding error when it fails.
 190  */
 191 int kobject_synth_uevent(struct kobject *kobj, const char *buf, size_t count)
 192 {
 193         char *no_uuid_envp[] = { "SYNTH_UUID=0", NULL };
 194         enum kobject_action action;
 195         const char *action_args;
 196         struct kobj_uevent_env *env;
 197         const char *msg = NULL, *devpath;
 198         int r;
 199
 200         r = kobject_action_type(buf, count, &action, &action_args);
 201         if (r) {
 202                 msg = "unknown uevent action string\n";
 203                 goto out;
 204         }
 205
 206         if (!action_args) {
 207                 r = kobject_uevent_env(kobj, action, no_uuid_envp);
 208                 goto out;
 209         }
 210
 211         r = kobject_action_args(action_args,
 212                                 count - (action_args - buf), &env);
 213         if (r == -EINVAL) {
 214                 msg = "incorrect uevent action arguments\n";
 215                 goto out;
 216         }
 217
 218         if (r)
 219                 goto out;
 220
 221         r = kobject_uevent_env(kobj, action, env->envp);
 222         kfree(env);
 223 out:
 224         if (r) {
 225                 devpath = kobject_get_path(kobj, GFP_KERNEL);
 226                 printk(KERN_WARNING "synth uevent: %s: %s",
 227                        devpath ?: "unknown device",
 228                        msg ?: "failed to send uevent");
 229                 kfree(devpath);
 230         }
 231         return r;
 232 }
 233
 234 #ifdef CONFIG_NET
 235 static int kobj_bcast_filter(struct sock *dsk, struct sk_buff *skb, void *data)
 236 {
 237         struct kobject *kobj = data, *ksobj;
 238         const struct kobj_ns_type_operations *ops;
 239
 240         ops = kobj_ns_ops(kobj);
 241         if (!ops && kobj->kset) {
 242                 ksobj = &kobj->kset->kobj;
 243                 if (ksobj->parent != NULL)
 244                         ops = kobj_ns_ops(ksobj->parent);
 245         }
 246
 247         if (ops && ops->netlink_ns && kobj->ktype->namespace) {
 248                 const void *sock_ns, *ns;
 249                 ns = kobj->ktype->namespace(kobj);
 250                 sock_ns = ops->netlink_ns(dsk);
 251                 return sock_ns != ns;
 252         }
 253
 254         return 0;
 255 }
 256 #endif
 257
 258 #ifdef CONFIG_UEVENT_HELPER
 259 static int kobj_usermode_filter(struct kobject *kobj)
 260 {
 261         const struct kobj_ns_type_operations *ops;
 262
 263         ops = kobj_ns_ops(kobj);
 264         if (ops) {
 265                 const void *init_ns, *ns;
 266                 ns = kobj->ktype->namespace(kobj);
 267                 init_ns = ops->initial_ns();
 268                 return ns != init_ns;
 269         }
 270
 271         return 0;
 272 }
 273
 274 static int init_uevent_argv(struct kobj_uevent_env *env, const char *subsystem)
 275 {
 276         int len;
 277
 278         len = strlcpy(&env->buf[env->buflen], subsystem,
 279                       sizeof(env->buf) - env->buflen);
 280         if (len >= (sizeof(env->buf) - env->buflen)) {
 281                 WARN(1, KERN_ERR "init_uevent_argv: buffer size too small\n");
 282                 return -ENOMEM;
 283         }
 284
 285         env->argv[0] = uevent_helper;
 286         env->argv[1] = &env->buf[env->buflen];
 287         env->argv[2] = NULL;
 288
 289         env->buflen += len + 1;
 290         return 0;
 291 }
 292
 293 static void cleanup_uevent_env(struct subprocess_info *info)
 294 {
 295         kfree(info->data);
 296 }
 297 #endif
 298
 299 static int kobject_uevent_net_broadcast(struct kobject *kobj,
 300                                         struct kobj_uevent_env *env,
 301                                         const char *action_string,
 302                                         const char *devpath)
 303 {
 304         int retval = 0;
 305 #if defined(CONFIG_NET)
 306         struct sk_buff *skb = NULL;
 307         struct uevent_sock *ue_sk;
 308
 309         /* send netlink message */
 310         list_for_each_entry(ue_sk, &uevent_sock_list, list) {
 311                 struct sock *uevent_sock = ue_sk->sk;
 312
 313                 if (!netlink_has_listeners(uevent_sock, 1))
 314                         continue;
 315
 316                 if (!skb) {
 317                         /* allocate message with the maximum possible size */
 318                         size_t len = strlen(action_string) + strlen(devpath) + 2;
 319                         char *scratch;
 320
 321                         retval = -ENOMEM;
 322                         skb = alloc_skb(len + env->buflen, GFP_KERNEL);
 323                         if (!skb)
 324                                 continue;
 325
 326                         /* add header */
 327                         scratch = skb_put(skb, len);
 328                         sprintf(scratch, "%s@%s", action_string, devpath);
 329
 330                         skb_put_data(skb, env->buf, env->buflen);
 331
 332                         NETLINK_CB(skb).dst_group = 1;
 333                 }
 334
 335                 retval = netlink_broadcast_filtered(uevent_sock, skb_get(skb),
 336                                                     0, 1, GFP_KERNEL,
 337                                                     kobj_bcast_filter,
 338                                                     kobj);
 339                 /* ENOBUFS should be handled in userspace */
 340                 if (retval == -ENOBUFS || retval == -ESRCH)
 341                         retval = 0;
 342         }
 343         consume_skb(skb);
 344 #endif
 345         return retval;
 346 }
 347
 348 static void zap_modalias_env(struct kobj_uevent_env *env)
 349 {
 350         static const char modalias_prefix[] = "MODALIAS=";
 351         size_t len;
 352         int i, j;
 353
 354         for (i = 0; i < env->envp_idx;) {
 355                 if (strncmp(env->envp[i], modalias_prefix,
 356                             sizeof(modalias_prefix) - 1)) {
 357                         i++;
 358                         continue;
 359                 }
 360
 361                 len = strlen(env->envp[i]) + 1;
 362
 363                 if (i != env->envp_idx - 1) {
 364                         memmove(env->envp[i], env->envp[i + 1],
 365                                 env->buflen - len);
 366
 367                         for (j = i; j < env->envp_idx - 1; j++)
 368                                 env->envp[j] = env->envp[j + 1] - len;
 369                 }
 370
 371                 env->envp_idx--;
 372                 env->buflen -= len;
 373         }
 374 }
 375
 376 /**
 377  * kobject_uevent_env - send an uevent with environmental data
 378  *
 379  * @kobj: struct kobject that the action is happening to
 380  * @action: action that is happening
 381  * @envp_ext: pointer to environmental data
 382  *
 383  * Returns 0 if kobject_uevent_env() is completed with success or the
 384  * corresponding error when it fails.
 385  */
 386 int kobject_uevent_env(struct kobject *kobj, enum kobject_action action,
 387                        char *envp_ext[])
 388 {
 389         struct kobj_uevent_env *env;
 390         const char *action_string = kobject_actions[action];
 391         const char *devpath = NULL;
 392         const char *subsystem;
 393         struct kobject *top_kobj;
 394         struct kset *kset;
 395         const struct kset_uevent_ops *uevent_ops;
 396         int i = 0;
 397         int retval = 0;
 398
 399         pr_debug("kobject: '%s' (%p): %s\n",
 400                  kobject_name(kobj), kobj, __func__);
 401
 402         /* search the kset we belong to */
 403         top_kobj = kobj;
 404         while (!top_kobj->kset && top_kobj->parent)
 405                 top_kobj = top_kobj->parent;
 406
 407         if (!top_kobj->kset) {
 408                 pr_debug("kobject: '%s' (%p): %s: attempted to send uevent "
 409                          "without kset!\n", kobject_name(kobj), kobj,
 410                          __func__);
 411                 return -EINVAL;
 412         }
 413
 414         kset = top_kobj->kset;
 415         uevent_ops = kset->uevent_ops;
 416
 417         /* skip the event, if uevent_suppress is set*/
 418         if (kobj->uevent_suppress) {
 419                 pr_debug("kobject: '%s' (%p): %s: uevent_suppress "
 420                                  "caused the event to drop!\n",
 421                                  kobject_name(kobj), kobj, __func__);
 422                 return 0;
 423         }
 424         /* skip the event, if the filter returns zero. */
 425         if (uevent_ops && uevent_ops->filter)
 426                 if (!uevent_ops->filter(kset, kobj)) {
 427                         pr_debug("kobject: '%s' (%p): %s: filter function "
 428                                  "caused the event to drop!\n",
 429                                  kobject_name(kobj), kobj, __func__);
 430                         return 0;
 431                 }
 432
 433         /* originating subsystem */
 434         if (uevent_ops && uevent_ops->name)
 435                 subsystem = uevent_ops->name(kset, kobj);
 436         else
 437                 subsystem = kobject_name(&kset->kobj);
 438         if (!subsystem) {
 439                 pr_debug("kobject: '%s' (%p): %s: unset subsystem caused the "
 440                          "event to drop!\n", kobject_name(kobj), kobj,
 441                          __func__);
 442                 return 0;
 443         }
 444
 445         /* environment buffer */
 446         env = kzalloc(sizeof(struct kobj_uevent_env), GFP_KERNEL);
 447         if (!env)
 448                 return -ENOMEM;
 449
 450         /* complete object path */
 451         devpath = kobject_get_path(kobj, GFP_KERNEL);
 452         if (!devpath) {
 453                 retval = -ENOENT;
 454                 goto exit;
 455         }
 456
 457         /* default keys */
 458         retval = add_uevent_var(env, "ACTION=%s", action_string);
 459         if (retval)
 460                 goto exit;
 461         retval = add_uevent_var(env, "DEVPATH=%s", devpath);
 462         if (retval)
 463                 goto exit;
 464         retval = add_uevent_var(env, "SUBSYSTEM=%s", subsystem);
 465         if (retval)
 466                 goto exit;
 467
 468         /* keys passed in from the caller */
 469         if (envp_ext) {
 470                 for (i = 0; envp_ext[i]; i++) {
 471                         retval = add_uevent_var(env, "%s", envp_ext[i]);
 472                         if (retval)
 473                                 goto exit;
 474                 }
 475         }
 476
 477         /* let the kset specific function add its stuff */
 478         if (uevent_ops && uevent_ops->uevent) {
 479                 retval = uevent_ops->uevent(kset, kobj, env);
 480                 if (retval) {
 481                         pr_debug("kobject: '%s' (%p): %s: uevent() returned "
 482                                  "%d\n", kobject_name(kobj), kobj,
 483                                  __func__, retval);
 484                         goto exit;
 485                 }
 486         }
 487
 488         switch (action) {
 489         case KOBJ_ADD:
 490                 /*
 491                  * Mark "add" event so we can make sure we deliver "remove"
 492                  * event to userspace during automatic cleanup. If
 493                  * the object did send an "add" event, "remove" will
 494                  * automatically generated by the core, if not already done
 495                  * by the caller.
 496                  */
 497                 kobj->state_add_uevent_sent = 1;
 498                 break;
 499
 500         case KOBJ_REMOVE:
 501                 kobj->state_remove_uevent_sent = 1;
 502                 break;
 503
 504         case KOBJ_UNBIND:
 505                 zap_modalias_env(env);
 506                 break;
 507
 508         default:
 509                 break;
 510         }
 511
 512         mutex_lock(&uevent_sock_mutex);
 513         /* we will send an event, so request a new sequence number */
 514         retval = add_uevent_var(env, "SEQNUM=%llu", (unsigned long long)++uevent_seqnum);
 515         if (retval) {
 516                 mutex_unlock(&uevent_sock_mutex);
 517                 goto exit;
 518         }
 519         retval = kobject_uevent_net_broadcast(kobj, env, action_string,
 520                                               devpath);
 521         mutex_unlock(&uevent_sock_mutex);
 522
 523 #ifdef CONFIG_UEVENT_HELPER
 524         /* call uevent_helper, usually only enabled during early boot */
 525         if (uevent_helper[0] && !kobj_usermode_filter(kobj)) {
 526                 struct subprocess_info *info;
 527
 528                 retval = add_uevent_var(env, "HOME=/");
 529                 if (retval)
 530                         goto exit;
 531                 retval = add_uevent_var(env,
 532                                         "PATH=/sbin:/bin:/usr/sbin:/usr/bin");
 533                 if (retval)
 534                         goto exit;
 535                 retval = init_uevent_argv(env, subsystem);
 536                 if (retval)
 537                         goto exit;
 538
 539                 retval = -ENOMEM;
 540                 info = call_usermodehelper_setup(env->argv[0], env->argv,
 541                                                  env->envp, GFP_KERNEL,
 542                                                  NULL, cleanup_uevent_env, env);
 543                 if (info) {
 544                         retval = call_usermodehelper_exec(info, UMH_NO_WAIT);
 545                         env = NULL;     /* freed by cleanup_uevent_env */
 546                 }
 547         }
 548 #endif
 549
 550 exit:
 551         kfree(devpath);
 552         kfree(env);
 553         return retval;
 554 }
 555 EXPORT_SYMBOL_GPL(kobject_uevent_env);
 556
 557 /**
 558  * kobject_uevent - notify userspace by sending an uevent
 559  *
 560  * @kobj: struct kobject that the action is happening to
 561  * @action: action that is happening
 562  *
 563  * Returns 0 if kobject_uevent() is completed with success or the
 564  * corresponding error when it fails.
 565  */
 566 int kobject_uevent(struct kobject *kobj, enum kobject_action action)
 567 {
 568         return kobject_uevent_env(kobj, action, NULL);
 569 }
 570 EXPORT_SYMBOL_GPL(kobject_uevent);
 571
 572 /**
 573  * add_uevent_var - add key value string to the environment buffer
 574  * @env: environment buffer structure
 575  * @format: printf format for the key=value pair
 576  *
 577  * Returns 0 if environment variable was added successfully or -ENOMEM
 578  * if no space was available.
 579  */
 580 int add_uevent_var(struct kobj_uevent_env *env, const char *format, ...)
 581 {
 582         va_list args;
 583         int len;
 584
 585         if (env->envp_idx >= ARRAY_SIZE(env->envp)) {
 586                 WARN(1, KERN_ERR "add_uevent_var: too many keys\n");
 587                 return -ENOMEM;
 588         }
 589
 590         va_start(args, format);
 591         len = vsnprintf(&env->buf[env->buflen],
 592                         sizeof(env->buf) - env->buflen,
 593                         format, args);
 594         va_end(args);
 595
 596         if (len >= (sizeof(env->buf) - env->buflen)) {
 597                 WARN(1, KERN_ERR "add_uevent_var: buffer size too small\n");
 598                 return -ENOMEM;
 599         }
 600
 601         env->envp[env->envp_idx++] = &env->buf[env->buflen];
 602         env->buflen += len + 1;
 603         return 0;
 604 }
 605 EXPORT_SYMBOL_GPL(add_uevent_var);
 606
 607 #if defined(CONFIG_NET)
 608 static int uevent_net_broadcast(struct sock *usk, struct sk_buff *skb,
 609                                 struct netlink_ext_ack *extack)
 610 {
 611         /* u64 to chars: 2^64 - 1 = 21 chars */
 612         char buf[sizeof("SEQNUM=") + 21];
 613         struct sk_buff *skbc;
 614         int ret;
 615
 616         /* bump and prepare sequence number */
 617         ret = snprintf(buf, sizeof(buf), "SEQNUM=%llu", ++uevent_seqnum);
 618         if (ret < 0 || (size_t)ret >= sizeof(buf))
 619                 return -ENOMEM;
 620         ret++;
 621
 622         /* verify message does not overflow */
 623         if ((skb->len + ret) > UEVENT_BUFFER_SIZE) {
 624                 NL_SET_ERR_MSG(extack, "uevent message too big");
 625                 return -EINVAL;
 626         }
 627
 628         /* copy skb and extend to accommodate sequence number */
 629         skbc = skb_copy_expand(skb, 0, ret, GFP_KERNEL);
 630         if (!skbc)
 631                 return -ENOMEM;
 632
 633         /* append sequence number */
 634         skb_put_data(skbc, buf, ret);
 635
 636         /* remove msg header */
 637         skb_pull(skbc, NLMSG_HDRLEN);
 638
 639         /* set portid 0 to inform userspace message comes from kernel */
 640         NETLINK_CB(skbc).portid = 0;
 641         NETLINK_CB(skbc).dst_group = 1;
 642
 643         ret = netlink_broadcast(usk, skbc, 0, 1, GFP_KERNEL);
 644         /* ENOBUFS should be handled in userspace */
 645         if (ret == -ENOBUFS || ret == -ESRCH)
 646                 ret = 0;
 647
 648         return ret;
 649 }
 650
 651 static int uevent_net_rcv_skb(struct sk_buff *skb, struct nlmsghdr *nlh,
 652                               struct netlink_ext_ack *extack)
 653 {
 654         struct net *net;
 655         int ret;
 656
 657         if (!nlmsg_data(nlh))
 658                 return -EINVAL;
 659
 660         /*
 661          * Verify that we are allowed to send messages to the target
 662          * network namespace. The caller must have CAP_SYS_ADMIN in the
 663          * owning user namespace of the target network namespace.
 664          */
 665         net = sock_net(NETLINK_CB(skb).sk);
 666         if (!netlink_ns_capable(skb, net->user_ns, CAP_SYS_ADMIN)) {
 667                 NL_SET_ERR_MSG(extack, "missing CAP_SYS_ADMIN capability");
 668                 return -EPERM;
 669         }
 670
 671         mutex_lock(&uevent_sock_mutex);
 672         ret = uevent_net_broadcast(net->uevent_sock->sk, skb, extack);
 673         mutex_unlock(&uevent_sock_mutex);
 674
 675         return ret;
 676 }
 677
 678 static void uevent_net_rcv(struct sk_buff *skb)
 679 {
 680         netlink_rcv_skb(skb, &uevent_net_rcv_skb);
 681 }
 682
 683 static int uevent_net_init(struct net *net)
 684 {
 685         struct uevent_sock *ue_sk;
 686         struct netlink_kernel_cfg cfg = {
 687                 .groups = 1,
 688                 .input = uevent_net_rcv,
 689                 .flags  = NL_CFG_F_NONROOT_RECV
 690         };
 691
 692         ue_sk = kzalloc(sizeof(*ue_sk), GFP_KERNEL);
 693         if (!ue_sk)
 694                 return -ENOMEM;
 695
 696         ue_sk->sk = netlink_kernel_create(net, NETLINK_KOBJECT_UEVENT, &cfg);
 697         if (!ue_sk->sk) {
 698                 printk(KERN_ERR
 699                        "kobject_uevent: unable to create netlink socket!\n");
 700                 kfree(ue_sk);
 701                 return -ENODEV;
 702         }
 703
 704         net->uevent_sock = ue_sk;
 705
 706         mutex_lock(&uevent_sock_mutex);
 707         list_add_tail(&ue_sk->list, &uevent_sock_list);
 708         mutex_unlock(&uevent_sock_mutex);
 709         return 0;
 710 }
 711
 712 static void uevent_net_exit(struct net *net)
 713 {
 714         struct uevent_sock *ue_sk = net->uevent_sock;
 715
 716         mutex_lock(&uevent_sock_mutex);
 717         list_del(&ue_sk->list);
 718         mutex_unlock(&uevent_sock_mutex);
 719
 720         netlink_kernel_release(ue_sk->sk);
 721         kfree(ue_sk);
 722 }
 723
 724 static struct pernet_operations uevent_net_ops = {
 725         .init   = uevent_net_init,
 726         .exit   = uevent_net_exit,
 727         .async  = true,
 728 };
 729
 730 static int __init kobject_uevent_init(void)
 731 {
 732         return register_pernet_subsys(&uevent_net_ops);
 733 }
 734
 735
 736 postcore_initcall(kobject_uevent_init);
 737 #endif