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/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 atomic64_t 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 /* This lock protects uevent_sock_list */
  46 static DEFINE_MUTEX(uevent_sock_mutex);
  47 #endif
  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";
 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";
 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                 pr_warn("synth uevent: %s: %s\n",
 227                        devpath ?: "unknown device",
 228                        msg ?: "failed to send uevent");
 229                 kfree(devpath);
 230         }
 231         return r;
 232 }
 233
 234 #ifdef CONFIG_UEVENT_HELPER
 235 static int kobj_usermode_filter(struct kobject *kobj)
 236 {
 237         const struct kobj_ns_type_operations *ops;
 238
 239         ops = kobj_ns_ops(kobj);
 240         if (ops) {
 241                 const void *init_ns, *ns;
 242
 243                 ns = kobj->ktype->namespace(kobj);
 244                 init_ns = ops->initial_ns();
 245                 return ns != init_ns;
 246         }
 247
 248         return 0;
 249 }
 250
 251 static int init_uevent_argv(struct kobj_uevent_env *env, const char *subsystem)
 252 {
 253         int buffer_size = sizeof(env->buf) - env->buflen;
 254         int len;
 255
 256         len = strscpy(&env->buf[env->buflen], subsystem, buffer_size);
 257         if (len < 0) {
 258                 pr_warn("%s: insufficient buffer space (%u left) for %s\n",
 259                         __func__, buffer_size, subsystem);
 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         mutex_lock(&uevent_sock_mutex);
 318         list_for_each_entry(ue_sk, &uevent_sock_list, list) {
 319                 struct sock *uevent_sock = ue_sk->sk;
 320
 321                 if (!netlink_has_listeners(uevent_sock, 1))
 322                         continue;
 323
 324                 if (!skb) {
 325                         retval = -ENOMEM;
 326                         skb = alloc_uevent_skb(env, action_string, devpath);
 327                         if (!skb)
 328                                 continue;
 329                 }
 330
 331                 retval = netlink_broadcast(uevent_sock, skb_get(skb), 0, 1,
 332                                            GFP_KERNEL);
 333                 /* ENOBUFS should be handled in userspace */
 334                 if (retval == -ENOBUFS || retval == -ESRCH)
 335                         retval = 0;
 336         }
 337         mutex_unlock(&uevent_sock_mutex);
 338         consume_skb(skb);
 339
 340         return retval;
 341 }
 342
 343 static int uevent_net_broadcast_tagged(struct sock *usk,
 344                                        struct kobj_uevent_env *env,
 345                                        const char *action_string,
 346                                        const char *devpath)
 347 {
 348         struct user_namespace *owning_user_ns = sock_net(usk)->user_ns;
 349         struct sk_buff *skb = NULL;
 350         int ret = 0;
 351
 352         skb = alloc_uevent_skb(env, action_string, devpath);
 353         if (!skb)
 354                 return -ENOMEM;
 355
 356         /* fix credentials */
 357         if (owning_user_ns != &init_user_ns) {
 358                 struct netlink_skb_parms *parms = &NETLINK_CB(skb);
 359                 kuid_t root_uid;
 360                 kgid_t root_gid;
 361
 362                 /* fix uid */
 363                 root_uid = make_kuid(owning_user_ns, 0);
 364                 if (uid_valid(root_uid))
 365                         parms->creds.uid = root_uid;
 366
 367                 /* fix gid */
 368                 root_gid = make_kgid(owning_user_ns, 0);
 369                 if (gid_valid(root_gid))
 370                         parms->creds.gid = root_gid;
 371         }
 372
 373         ret = netlink_broadcast(usk, skb, 0, 1, GFP_KERNEL);
 374         /* ENOBUFS should be handled in userspace */
 375         if (ret == -ENOBUFS || ret == -ESRCH)
 376                 ret = 0;
 377
 378         return ret;
 379 }
 380 #endif
 381
 382 static int kobject_uevent_net_broadcast(struct kobject *kobj,
 383                                         struct kobj_uevent_env *env,
 384                                         const char *action_string,
 385                                         const char *devpath)
 386 {
 387         int ret = 0;
 388
 389 #ifdef CONFIG_NET
 390         const struct kobj_ns_type_operations *ops;
 391         const struct net *net = NULL;
 392
 393         ops = kobj_ns_ops(kobj);
 394         if (!ops && kobj->kset) {
 395                 struct kobject *ksobj = &kobj->kset->kobj;
 396
 397                 if (ksobj->parent != NULL)
 398                         ops = kobj_ns_ops(ksobj->parent);
 399         }
 400
 401         /* kobjects currently only carry network namespace tags and they
 402          * are the only tag relevant here since we want to decide which
 403          * network namespaces to broadcast the uevent into.
 404          */
 405         if (ops && ops->netlink_ns && kobj->ktype->namespace)
 406                 if (ops->type == KOBJ_NS_TYPE_NET)
 407                         net = kobj->ktype->namespace(kobj);
 408
 409         if (!net)
 410                 ret = uevent_net_broadcast_untagged(env, action_string,
 411                                                     devpath);
 412         else
 413                 ret = uevent_net_broadcast_tagged(net->uevent_sock->sk, env,
 414                                                   action_string, devpath);
 415 #endif
 416
 417         return ret;
 418 }
 419
 420 static void zap_modalias_env(struct kobj_uevent_env *env)
 421 {
 422         static const char modalias_prefix[] = "MODALIAS=";
 423         size_t len;
 424         int i, j;
 425
 426         for (i = 0; i < env->envp_idx;) {
 427                 if (strncmp(env->envp[i], modalias_prefix,
 428                             sizeof(modalias_prefix) - 1)) {
 429                         i++;
 430                         continue;
 431                 }
 432
 433                 len = strlen(env->envp[i]) + 1;
 434
 435                 if (i != env->envp_idx - 1) {
 436                         memmove(env->envp[i], env->envp[i + 1],
 437                                 env->buflen - len);
 438
 439                         for (j = i; j < env->envp_idx - 1; j++)
 440                                 env->envp[j] = env->envp[j + 1] - len;
 441                 }
 442
 443                 env->envp_idx--;
 444                 env->buflen -= len;
 445         }
 446 }
 447
 448 /**
 449  * kobject_uevent_env - send an uevent with environmental data
 450  *
 451  * @kobj: struct kobject that the action is happening to
 452  * @action: action that is happening
 453  * @envp_ext: pointer to environmental data
 454  *
 455  * Returns 0 if kobject_uevent_env() is completed with success or the
 456  * corresponding error when it fails.
 457  */
 458 int kobject_uevent_env(struct kobject *kobj, enum kobject_action action,
 459                        char *envp_ext[])
 460 {
 461         struct kobj_uevent_env *env;
 462         const char *action_string = kobject_actions[action];
 463         const char *devpath = NULL;
 464         const char *subsystem;
 465         struct kobject *top_kobj;
 466         struct kset *kset;
 467         const struct kset_uevent_ops *uevent_ops;
 468         int i = 0;
 469         int retval = 0;
 470
 471         /*
 472          * Mark "remove" event done regardless of result, for some subsystems
 473          * do not want to re-trigger "remove" event via automatic cleanup.
 474          */
 475         if (action == KOBJ_REMOVE)
 476                 kobj->state_remove_uevent_sent = 1;
 477
 478         pr_debug("kobject: '%s' (%p): %s\n",
 479                  kobject_name(kobj), kobj, __func__);
 480
 481         /* search the kset we belong to */
 482         top_kobj = kobj;
 483         while (!top_kobj->kset && top_kobj->parent)
 484                 top_kobj = top_kobj->parent;
 485
 486         if (!top_kobj->kset) {
 487                 pr_debug("kobject: '%s' (%p): %s: attempted to send uevent "
 488                          "without kset!\n", kobject_name(kobj), kobj,
 489                          __func__);
 490                 return -EINVAL;
 491         }
 492
 493         kset = top_kobj->kset;
 494         uevent_ops = kset->uevent_ops;
 495
 496         /* skip the event, if uevent_suppress is set*/
 497         if (kobj->uevent_suppress) {
 498                 pr_debug("kobject: '%s' (%p): %s: uevent_suppress "
 499                                  "caused the event to drop!\n",
 500                                  kobject_name(kobj), kobj, __func__);
 501                 return 0;
 502         }
 503         /* skip the event, if the filter returns zero. */
 504         if (uevent_ops && uevent_ops->filter)
 505                 if (!uevent_ops->filter(kobj)) {
 506                         pr_debug("kobject: '%s' (%p): %s: filter function "
 507                                  "caused the event to drop!\n",
 508                                  kobject_name(kobj), kobj, __func__);
 509                         return 0;
 510                 }
 511
 512         /* originating subsystem */
 513         if (uevent_ops && uevent_ops->name)
 514                 subsystem = uevent_ops->name(kobj);
 515         else
 516                 subsystem = kobject_name(&kset->kobj);
 517         if (!subsystem) {
 518                 pr_debug("kobject: '%s' (%p): %s: unset subsystem caused the "
 519                          "event to drop!\n", kobject_name(kobj), kobj,
 520                          __func__);
 521                 return 0;
 522         }
 523
 524         /* environment buffer */
 525         env = kzalloc(sizeof(struct kobj_uevent_env), GFP_KERNEL);
 526         if (!env)
 527                 return -ENOMEM;
 528
 529         /* complete object path */
 530         devpath = kobject_get_path(kobj, GFP_KERNEL);
 531         if (!devpath) {
 532                 retval = -ENOENT;
 533                 goto exit;
 534         }
 535
 536         /* default keys */
 537         retval = add_uevent_var(env, "ACTION=%s", action_string);
 538         if (retval)
 539                 goto exit;
 540         retval = add_uevent_var(env, "DEVPATH=%s", devpath);
 541         if (retval)
 542                 goto exit;
 543         retval = add_uevent_var(env, "SUBSYSTEM=%s", subsystem);
 544         if (retval)
 545                 goto exit;
 546
 547         /* keys passed in from the caller */
 548         if (envp_ext) {
 549                 for (i = 0; envp_ext[i]; i++) {
 550                         retval = add_uevent_var(env, "%s", envp_ext[i]);
 551                         if (retval)
 552                                 goto exit;
 553                 }
 554         }
 555
 556         /* let the kset specific function add its stuff */
 557         if (uevent_ops && uevent_ops->uevent) {
 558                 retval = uevent_ops->uevent(kobj, env);
 559                 if (retval) {
 560                         pr_debug("kobject: '%s' (%p): %s: uevent() returned "
 561                                  "%d\n", kobject_name(kobj), kobj,
 562                                  __func__, retval);
 563                         goto exit;
 564                 }
 565         }
 566
 567         switch (action) {
 568         case KOBJ_ADD:
 569                 /*
 570                  * Mark "add" event so we can make sure we deliver "remove"
 571                  * event to userspace during automatic cleanup. If
 572                  * the object did send an "add" event, "remove" will
 573                  * automatically generated by the core, if not already done
 574                  * by the caller.
 575                  */
 576                 kobj->state_add_uevent_sent = 1;
 577                 break;
 578
 579         case KOBJ_UNBIND:
 580                 zap_modalias_env(env);
 581                 break;
 582
 583         default:
 584                 break;
 585         }
 586
 587         /* we will send an event, so request a new sequence number */
 588         retval = add_uevent_var(env, "SEQNUM=%llu",
 589                                 atomic64_inc_return(&uevent_seqnum));
 590         if (retval)
 591                 goto exit;
 592
 593         retval = kobject_uevent_net_broadcast(kobj, env, action_string,
 594                                               devpath);
 595
 596 #ifdef CONFIG_UEVENT_HELPER
 597         /* call uevent_helper, usually only enabled during early boot */
 598         if (uevent_helper[0] && !kobj_usermode_filter(kobj)) {
 599                 struct subprocess_info *info;
 600
 601                 retval = add_uevent_var(env, "HOME=/");
 602                 if (retval)
 603                         goto exit;
 604                 retval = add_uevent_var(env,
 605                                         "PATH=/sbin:/bin:/usr/sbin:/usr/bin");
 606                 if (retval)
 607                         goto exit;
 608                 retval = init_uevent_argv(env, subsystem);
 609                 if (retval)
 610                         goto exit;
 611
 612                 retval = -ENOMEM;
 613                 info = call_usermodehelper_setup(env->argv[0], env->argv,
 614                                                  env->envp, GFP_KERNEL,
 615                                                  NULL, cleanup_uevent_env, env);
 616                 if (info) {
 617                         retval = call_usermodehelper_exec(info, UMH_NO_WAIT);
 618                         env = NULL;     /* freed by cleanup_uevent_env */
 619                 }
 620         }
 621 #endif
 622
 623 exit:
 624         kfree(devpath);
 625         kfree(env);
 626         return retval;
 627 }
 628 EXPORT_SYMBOL_GPL(kobject_uevent_env);
 629
 630 /**
 631  * kobject_uevent - notify userspace by sending an uevent
 632  *
 633  * @kobj: struct kobject that the action is happening to
 634  * @action: action that is happening
 635  *
 636  * Returns 0 if kobject_uevent() is completed with success or the
 637  * corresponding error when it fails.
 638  */
 639 int kobject_uevent(struct kobject *kobj, enum kobject_action action)
 640 {
 641         return kobject_uevent_env(kobj, action, NULL);
 642 }
 643 EXPORT_SYMBOL_GPL(kobject_uevent);
 644
 645 /**
 646  * add_uevent_var - add key value string to the environment buffer
 647  * @env: environment buffer structure
 648  * @format: printf format for the key=value pair
 649  *
 650  * Returns 0 if environment variable was added successfully or -ENOMEM
 651  * if no space was available.
 652  */
 653 int add_uevent_var(struct kobj_uevent_env *env, const char *format, ...)
 654 {
 655         va_list args;
 656         int len;
 657
 658         if (env->envp_idx >= ARRAY_SIZE(env->envp)) {
 659                 WARN(1, KERN_ERR "add_uevent_var: too many keys\n");
 660                 return -ENOMEM;
 661         }
 662
 663         va_start(args, format);
 664         len = vsnprintf(&env->buf[env->buflen],
 665                         sizeof(env->buf) - env->buflen,
 666                         format, args);
 667         va_end(args);
 668
 669         if (len >= (sizeof(env->buf) - env->buflen)) {
 670                 WARN(1, KERN_ERR "add_uevent_var: buffer size too small\n");
 671                 return -ENOMEM;
 672         }
 673
 674         env->envp[env->envp_idx++] = &env->buf[env->buflen];
 675         env->buflen += len + 1;
 676         return 0;
 677 }
 678 EXPORT_SYMBOL_GPL(add_uevent_var);
 679
 680 #if defined(CONFIG_NET)
 681 static int uevent_net_broadcast(struct sock *usk, struct sk_buff *skb,
 682                                 struct netlink_ext_ack *extack)
 683 {
 684         /* u64 to chars: 2^64 - 1 = 21 chars */
 685         char buf[sizeof("SEQNUM=") + 21];
 686         struct sk_buff *skbc;
 687         int ret;
 688
 689         /* bump and prepare sequence number */
 690         ret = snprintf(buf, sizeof(buf), "SEQNUM=%llu",
 691                        atomic64_inc_return(&uevent_seqnum));
 692         if (ret < 0 || (size_t)ret >= sizeof(buf))
 693                 return -ENOMEM;
 694         ret++;
 695
 696         /* verify message does not overflow */
 697         if ((skb->len + ret) > UEVENT_BUFFER_SIZE) {
 698                 NL_SET_ERR_MSG(extack, "uevent message too big");
 699                 return -EINVAL;
 700         }
 701
 702         /* copy skb and extend to accommodate sequence number */
 703         skbc = skb_copy_expand(skb, 0, ret, GFP_KERNEL);
 704         if (!skbc)
 705                 return -ENOMEM;
 706
 707         /* append sequence number */
 708         skb_put_data(skbc, buf, ret);
 709
 710         /* remove msg header */
 711         skb_pull(skbc, NLMSG_HDRLEN);
 712
 713         /* set portid 0 to inform userspace message comes from kernel */
 714         NETLINK_CB(skbc).portid = 0;
 715         NETLINK_CB(skbc).dst_group = 1;
 716
 717         ret = netlink_broadcast(usk, skbc, 0, 1, GFP_KERNEL);
 718         /* ENOBUFS should be handled in userspace */
 719         if (ret == -ENOBUFS || ret == -ESRCH)
 720                 ret = 0;
 721
 722         return ret;
 723 }
 724
 725 static int uevent_net_rcv_skb(struct sk_buff *skb, struct nlmsghdr *nlh,
 726                               struct netlink_ext_ack *extack)
 727 {
 728         struct net *net;
 729         int ret;
 730
 731         if (!nlmsg_data(nlh))
 732                 return -EINVAL;
 733
 734         /*
 735          * Verify that we are allowed to send messages to the target
 736          * network namespace. The caller must have CAP_SYS_ADMIN in the
 737          * owning user namespace of the target network namespace.
 738          */
 739         net = sock_net(NETLINK_CB(skb).sk);
 740         if (!netlink_ns_capable(skb, net->user_ns, CAP_SYS_ADMIN)) {
 741                 NL_SET_ERR_MSG(extack, "missing CAP_SYS_ADMIN capability");
 742                 return -EPERM;
 743         }
 744
 745         ret = uevent_net_broadcast(net->uevent_sock->sk, skb, extack);
 746
 747         return ret;
 748 }
 749
 750 static void uevent_net_rcv(struct sk_buff *skb)
 751 {
 752         netlink_rcv_skb(skb, &uevent_net_rcv_skb);
 753 }
 754
 755 static int uevent_net_init(struct net *net)
 756 {
 757         struct uevent_sock *ue_sk;
 758         struct netlink_kernel_cfg cfg = {
 759                 .groups = 1,
 760                 .input = uevent_net_rcv,
 761                 .flags  = NL_CFG_F_NONROOT_RECV
 762         };
 763
 764         ue_sk = kzalloc(sizeof(*ue_sk), GFP_KERNEL);
 765         if (!ue_sk)
 766                 return -ENOMEM;
 767
 768         ue_sk->sk = netlink_kernel_create(net, NETLINK_KOBJECT_UEVENT, &cfg);
 769         if (!ue_sk->sk) {
 770                 pr_err("kobject_uevent: unable to create netlink socket!\n");
 771                 kfree(ue_sk);
 772                 return -ENODEV;
 773         }
 774
 775         net->uevent_sock = ue_sk;
 776
 777         /* Restrict uevents to initial user namespace. */
 778         if (sock_net(ue_sk->sk)->user_ns == &init_user_ns) {
 779                 mutex_lock(&uevent_sock_mutex);
 780                 list_add_tail(&ue_sk->list, &uevent_sock_list);
 781                 mutex_unlock(&uevent_sock_mutex);
 782         }
 783
 784         return 0;
 785 }
 786
 787 static void uevent_net_exit(struct net *net)
 788 {
 789         struct uevent_sock *ue_sk = net->uevent_sock;
 790
 791         if (sock_net(ue_sk->sk)->user_ns == &init_user_ns) {
 792                 mutex_lock(&uevent_sock_mutex);
 793                 list_del(&ue_sk->list);
 794                 mutex_unlock(&uevent_sock_mutex);
 795         }
 796
 797         netlink_kernel_release(ue_sk->sk);
 798         kfree(ue_sk);
 799 }
 800
 801 static struct pernet_operations uevent_net_ops = {
 802         .init   = uevent_net_init,
 803         .exit   = uevent_net_exit,
 804 };
 805
 806 static int __init kobject_uevent_init(void)
 807 {
 808         return register_pernet_subsys(&uevent_net_ops);
 809 }
 810
 811
 812 postcore_initcall(kobject_uevent_init);
 813 #endif