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 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\n";
 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\n";
 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                 printk(KERN_WARNING "synth uevent: %s: %s",
 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                 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 len;
 254
 255         len = strlcpy(&env->buf[env->buflen], subsystem,
 256                       sizeof(env->buf) - env->buflen);
 257         if (len >= (sizeof(env->buf) - env->buflen)) {
 258                 WARN(1, KERN_ERR "init_uevent_argv: buffer size too small\n");
 259                 return -ENOMEM;
 260         }
 261
 262         env->argv[0] = uevent_helper;
 263         env->argv[1] = &env->buf[env->buflen];
 264         env->argv[2] = NULL;
 265
 266         env->buflen += len + 1;
 267         return 0;
 268 }
 269
 270 static void cleanup_uevent_env(struct subprocess_info *info)
 271 {
 272         kfree(info->data);
 273 }
 274 #endif
 275
 276 #ifdef CONFIG_NET
 277 static struct sk_buff *alloc_uevent_skb(struct kobj_uevent_env *env,
 278                                         const char *action_string,
 279                                         const char *devpath)
 280 {
 281         struct netlink_skb_parms *parms;
 282         struct sk_buff *skb = NULL;
 283         char *scratch;
 284         size_t len;
 285
 286         /* allocate message with maximum possible size */
 287         len = strlen(action_string) + strlen(devpath) + 2;
 288         skb = alloc_skb(len + env->buflen, GFP_KERNEL);
 289         if (!skb)
 290                 return NULL;
 291
 292         /* add header */
 293         scratch = skb_put(skb, len);
 294         sprintf(scratch, "%s@%s", action_string, devpath);
 295
 296         skb_put_data(skb, env->buf, env->buflen);
 297
 298         parms = &NETLINK_CB(skb);
 299         parms->creds.uid = GLOBAL_ROOT_UID;
 300         parms->creds.gid = GLOBAL_ROOT_GID;
 301         parms->dst_group = 1;
 302         parms->portid = 0;
 303
 304         return skb;
 305 }
 306
 307 static int uevent_net_broadcast_untagged(struct kobj_uevent_env *env,
 308                                          const char *action_string,
 309                                          const char *devpath)
 310 {
 311         struct sk_buff *skb = NULL;
 312         struct uevent_sock *ue_sk;
 313         int retval = 0;
 314
 315         /* send netlink message */
 316         list_for_each_entry(ue_sk, &uevent_sock_list, list) {
 317                 struct sock *uevent_sock = ue_sk->sk;
 318
 319                 if (!netlink_has_listeners(uevent_sock, 1))
 320                         continue;
 321
 322                 if (!skb) {
 323                         retval = -ENOMEM;
 324                         skb = alloc_uevent_skb(env, action_string, devpath);
 325                         if (!skb)
 326                                 continue;
 327                 }
 328
 329                 retval = netlink_broadcast(uevent_sock, skb_get(skb), 0, 1,
 330                                            GFP_KERNEL);
 331                 /* ENOBUFS should be handled in userspace */
 332                 if (retval == -ENOBUFS || retval == -ESRCH)
 333                         retval = 0;
 334         }
 335         consume_skb(skb);
 336
 337         return retval;
 338 }
 339
 340 static int uevent_net_broadcast_tagged(struct sock *usk,
 341                                        struct kobj_uevent_env *env,
 342                                        const char *action_string,
 343                                        const char *devpath)
 344 {
 345         struct user_namespace *owning_user_ns = sock_net(usk)->user_ns;
 346         struct sk_buff *skb = NULL;
 347         int ret = 0;
 348
 349         skb = alloc_uevent_skb(env, action_string, devpath);
 350         if (!skb)
 351                 return -ENOMEM;
 352
 353         /* fix credentials */
 354         if (owning_user_ns != &init_user_ns) {
 355                 struct netlink_skb_parms *parms = &NETLINK_CB(skb);
 356                 kuid_t root_uid;
 357                 kgid_t root_gid;
 358
 359                 /* fix uid */
 360                 root_uid = make_kuid(owning_user_ns, 0);
 361                 if (uid_valid(root_uid))
 362                         parms->creds.uid = root_uid;
 363
 364                 /* fix gid */
 365                 root_gid = make_kgid(owning_user_ns, 0);
 366                 if (gid_valid(root_gid))
 367                         parms->creds.gid = root_gid;
 368         }
 369
 370         ret = netlink_broadcast(usk, skb, 0, 1, GFP_KERNEL);
 371         /* ENOBUFS should be handled in userspace */
 372         if (ret == -ENOBUFS || ret == -ESRCH)
 373                 ret = 0;
 374
 375         return ret;
 376 }
 377 #endif
 378
 379 static int kobject_uevent_net_broadcast(struct kobject *kobj,
 380                                         struct kobj_uevent_env *env,
 381                                         const char *action_string,
 382                                         const char *devpath)
 383 {
 384         int ret = 0;
 385
 386 #ifdef CONFIG_NET
 387         const struct kobj_ns_type_operations *ops;
 388         const struct net *net = NULL;
 389
 390         ops = kobj_ns_ops(kobj);
 391         if (!ops && kobj->kset) {
 392                 struct kobject *ksobj = &kobj->kset->kobj;
 393                 if (ksobj->parent != NULL)
 394                         ops = kobj_ns_ops(ksobj->parent);
 395         }
 396
 397         /* kobjects currently only carry network namespace tags and they
 398          * are the only tag relevant here since we want to decide which
 399          * network namespaces to broadcast the uevent into.
 400          */
 401         if (ops && ops->netlink_ns && kobj->ktype->namespace)
 402                 if (ops->type == KOBJ_NS_TYPE_NET)
 403                         net = kobj->ktype->namespace(kobj);
 404
 405         if (!net)
 406                 ret = uevent_net_broadcast_untagged(env, action_string,
 407                                                     devpath);
 408         else
 409                 ret = uevent_net_broadcast_tagged(net->uevent_sock->sk, env,
 410                                                   action_string, devpath);
 411 #endif
 412
 413         return ret;
 414 }
 415
 416 static void zap_modalias_env(struct kobj_uevent_env *env)
 417 {
 418         static const char modalias_prefix[] = "MODALIAS=";
 419         size_t len;
 420         int i, j;
 421
 422         for (i = 0; i < env->envp_idx;) {
 423                 if (strncmp(env->envp[i], modalias_prefix,
 424                             sizeof(modalias_prefix) - 1)) {
 425                         i++;
 426                         continue;
 427                 }
 428
 429                 len = strlen(env->envp[i]) + 1;
 430
 431                 if (i != env->envp_idx - 1) {
 432                         memmove(env->envp[i], env->envp[i + 1],
 433                                 env->buflen - len);
 434
 435                         for (j = i; j < env->envp_idx - 1; j++)
 436                                 env->envp[j] = env->envp[j + 1] - len;
 437                 }
 438
 439                 env->envp_idx--;
 440                 env->buflen -= len;
 441         }
 442 }
 443
 444 /**
 445  * kobject_uevent_env - send an uevent with environmental data
 446  *
 447  * @kobj: struct kobject that the action is happening to
 448  * @action: action that is happening
 449  * @envp_ext: pointer to environmental data
 450  *
 451  * Returns 0 if kobject_uevent_env() is completed with success or the
 452  * corresponding error when it fails.
 453  */
 454 int kobject_uevent_env(struct kobject *kobj, enum kobject_action action,
 455                        char *envp_ext[])
 456 {
 457         struct kobj_uevent_env *env;
 458         const char *action_string = kobject_actions[action];
 459         const char *devpath = NULL;
 460         const char *subsystem;
 461         struct kobject *top_kobj;
 462         struct kset *kset;
 463         const struct kset_uevent_ops *uevent_ops;
 464         int i = 0;
 465         int retval = 0;
 466
 467         /*
 468          * Mark "remove" event done regardless of result, for some subsystems
 469          * do not want to re-trigger "remove" event via automatic cleanup.
 470          */
 471         if (action == KOBJ_REMOVE)
 472                 kobj->state_remove_uevent_sent = 1;
 473
 474         pr_debug("kobject: '%s' (%p): %s\n",
 475                  kobject_name(kobj), kobj, __func__);
 476
 477         /* search the kset we belong to */
 478         top_kobj = kobj;
 479         while (!top_kobj->kset && top_kobj->parent)
 480                 top_kobj = top_kobj->parent;
 481
 482         if (!top_kobj->kset) {
 483                 pr_debug("kobject: '%s' (%p): %s: attempted to send uevent "
 484                          "without kset!\n", kobject_name(kobj), kobj,
 485                          __func__);
 486                 return -EINVAL;
 487         }
 488
 489         kset = top_kobj->kset;
 490         uevent_ops = kset->uevent_ops;
 491
 492         /* skip the event, if uevent_suppress is set*/
 493         if (kobj->uevent_suppress) {
 494                 pr_debug("kobject: '%s' (%p): %s: uevent_suppress "
 495                                  "caused the event to drop!\n",
 496                                  kobject_name(kobj), kobj, __func__);
 497                 return 0;
 498         }
 499         /* skip the event, if the filter returns zero. */
 500         if (uevent_ops && uevent_ops->filter)
 501                 if (!uevent_ops->filter(kset, kobj)) {
 502                         pr_debug("kobject: '%s' (%p): %s: filter function "
 503                                  "caused the event to drop!\n",
 504                                  kobject_name(kobj), kobj, __func__);
 505                         return 0;
 506                 }
 507
 508         /* originating subsystem */
 509         if (uevent_ops && uevent_ops->name)
 510                 subsystem = uevent_ops->name(kset, kobj);
 511         else
 512                 subsystem = kobject_name(&kset->kobj);
 513         if (!subsystem) {
 514                 pr_debug("kobject: '%s' (%p): %s: unset subsystem caused the "
 515                          "event to drop!\n", kobject_name(kobj), kobj,
 516                          __func__);
 517                 return 0;
 518         }
 519
 520         /* environment buffer */
 521         env = kzalloc(sizeof(struct kobj_uevent_env), GFP_KERNEL);
 522         if (!env)
 523                 return -ENOMEM;
 524
 525         /* complete object path */
 526         devpath = kobject_get_path(kobj, GFP_KERNEL);
 527         if (!devpath) {
 528                 retval = -ENOENT;
 529                 goto exit;
 530         }
 531
 532         /* default keys */
 533         retval = add_uevent_var(env, "ACTION=%s", action_string);
 534         if (retval)
 535                 goto exit;
 536         retval = add_uevent_var(env, "DEVPATH=%s", devpath);
 537         if (retval)
 538                 goto exit;
 539         retval = add_uevent_var(env, "SUBSYSTEM=%s", subsystem);
 540         if (retval)
 541                 goto exit;
 542
 543         /* keys passed in from the caller */
 544         if (envp_ext) {
 545                 for (i = 0; envp_ext[i]; i++) {
 546                         retval = add_uevent_var(env, "%s", envp_ext[i]);
 547                         if (retval)
 548                                 goto exit;
 549                 }
 550         }
 551
 552         /* let the kset specific function add its stuff */
 553         if (uevent_ops && uevent_ops->uevent) {
 554                 retval = uevent_ops->uevent(kset, kobj, env);
 555                 if (retval) {
 556                         pr_debug("kobject: '%s' (%p): %s: uevent() returned "
 557                                  "%d\n", kobject_name(kobj), kobj,
 558                                  __func__, retval);
 559                         goto exit;
 560                 }
 561         }
 562
 563         switch (action) {
 564         case KOBJ_ADD:
 565                 /*
 566                  * Mark "add" event so we can make sure we deliver "remove"
 567                  * event to userspace during automatic cleanup. If
 568                  * the object did send an "add" event, "remove" will
 569                  * automatically generated by the core, if not already done
 570                  * by the caller.
 571                  */
 572                 kobj->state_add_uevent_sent = 1;
 573                 break;
 574
 575         case KOBJ_UNBIND:
 576                 zap_modalias_env(env);
 577                 break;
 578
 579         default:
 580                 break;
 581         }
 582
 583         mutex_lock(&uevent_sock_mutex);
 584         /* we will send an event, so request a new sequence number */
 585         retval = add_uevent_var(env, "SEQNUM=%llu", (unsigned long long)++uevent_seqnum);
 586         if (retval) {
 587                 mutex_unlock(&uevent_sock_mutex);
 588                 goto exit;
 589         }
 590         retval = kobject_uevent_net_broadcast(kobj, env, action_string,
 591                                               devpath);
 592         mutex_unlock(&uevent_sock_mutex);
 593
 594 #ifdef CONFIG_UEVENT_HELPER
 595         /* call uevent_helper, usually only enabled during early boot */
 596         if (uevent_helper[0] && !kobj_usermode_filter(kobj)) {
 597                 struct subprocess_info *info;
 598
 599                 retval = add_uevent_var(env, "HOME=/");
 600                 if (retval)
 601                         goto exit;
 602                 retval = add_uevent_var(env,
 603                                         "PATH=/sbin:/bin:/usr/sbin:/usr/bin");
 604                 if (retval)
 605                         goto exit;
 606                 retval = init_uevent_argv(env, subsystem);
 607                 if (retval)
 608                         goto exit;
 609
 610                 retval = -ENOMEM;
 611                 info = call_usermodehelper_setup(env->argv[0], env->argv,
 612                                                  env->envp, GFP_KERNEL,
 613                                                  NULL, cleanup_uevent_env, env);
 614                 if (info) {
 615                         retval = call_usermodehelper_exec(info, UMH_NO_WAIT);
 616                         env = NULL;     /* freed by cleanup_uevent_env */
 617                 }
 618         }
 619 #endif
 620
 621 exit:
 622         kfree(devpath);
 623         kfree(env);
 624         return retval;
 625 }
 626 EXPORT_SYMBOL_GPL(kobject_uevent_env);
 627
 628 /**
 629  * kobject_uevent - notify userspace by sending an uevent
 630  *
 631  * @kobj: struct kobject that the action is happening to
 632  * @action: action that is happening
 633  *
 634  * Returns 0 if kobject_uevent() is completed with success or the
 635  * corresponding error when it fails.
 636  */
 637 int kobject_uevent(struct kobject *kobj, enum kobject_action action)
 638 {
 639         return kobject_uevent_env(kobj, action, NULL);
 640 }
 641 EXPORT_SYMBOL_GPL(kobject_uevent);
 642
 643 /**
 644  * add_uevent_var - add key value string to the environment buffer
 645  * @env: environment buffer structure
 646  * @format: printf format for the key=value pair
 647  *
 648  * Returns 0 if environment variable was added successfully or -ENOMEM
 649  * if no space was available.
 650  */
 651 int add_uevent_var(struct kobj_uevent_env *env, const char *format, ...)
 652 {
 653         va_list args;
 654         int len;
 655
 656         if (env->envp_idx >= ARRAY_SIZE(env->envp)) {
 657                 WARN(1, KERN_ERR "add_uevent_var: too many keys\n");
 658                 return -ENOMEM;
 659         }
 660
 661         va_start(args, format);
 662         len = vsnprintf(&env->buf[env->buflen],
 663                         sizeof(env->buf) - env->buflen,
 664                         format, args);
 665         va_end(args);
 666
 667         if (len >= (sizeof(env->buf) - env->buflen)) {
 668                 WARN(1, KERN_ERR "add_uevent_var: buffer size too small\n");
 669                 return -ENOMEM;
 670         }
 671
 672         env->envp[env->envp_idx++] = &env->buf[env->buflen];
 673         env->buflen += len + 1;
 674         return 0;
 675 }
 676 EXPORT_SYMBOL_GPL(add_uevent_var);
 677
 678 #if defined(CONFIG_NET)
 679 static int uevent_net_broadcast(struct sock *usk, struct sk_buff *skb,
 680                                 struct netlink_ext_ack *extack)
 681 {
 682         /* u64 to chars: 2^64 - 1 = 21 chars */
 683         char buf[sizeof("SEQNUM=") + 21];
 684         struct sk_buff *skbc;
 685         int ret;
 686
 687         /* bump and prepare sequence number */
 688         ret = snprintf(buf, sizeof(buf), "SEQNUM=%llu", ++uevent_seqnum);
 689         if (ret < 0 || (size_t)ret >= sizeof(buf))
 690                 return -ENOMEM;
 691         ret++;
 692
 693         /* verify message does not overflow */
 694         if ((skb->len + ret) > UEVENT_BUFFER_SIZE) {
 695                 NL_SET_ERR_MSG(extack, "uevent message too big");
 696                 return -EINVAL;
 697         }
 698
 699         /* copy skb and extend to accommodate sequence number */
 700         skbc = skb_copy_expand(skb, 0, ret, GFP_KERNEL);
 701         if (!skbc)
 702                 return -ENOMEM;
 703
 704         /* append sequence number */
 705         skb_put_data(skbc, buf, ret);
 706
 707         /* remove msg header */
 708         skb_pull(skbc, NLMSG_HDRLEN);
 709
 710         /* set portid 0 to inform userspace message comes from kernel */
 711         NETLINK_CB(skbc).portid = 0;
 712         NETLINK_CB(skbc).dst_group = 1;
 713
 714         ret = netlink_broadcast(usk, skbc, 0, 1, GFP_KERNEL);
 715         /* ENOBUFS should be handled in userspace */
 716         if (ret == -ENOBUFS || ret == -ESRCH)
 717                 ret = 0;
 718
 719         return ret;
 720 }
 721
 722 static int uevent_net_rcv_skb(struct sk_buff *skb, struct nlmsghdr *nlh,
 723                               struct netlink_ext_ack *extack)
 724 {
 725         struct net *net;
 726         int ret;
 727
 728         if (!nlmsg_data(nlh))
 729                 return -EINVAL;
 730
 731         /*
 732          * Verify that we are allowed to send messages to the target
 733          * network namespace. The caller must have CAP_SYS_ADMIN in the
 734          * owning user namespace of the target network namespace.
 735          */
 736         net = sock_net(NETLINK_CB(skb).sk);
 737         if (!netlink_ns_capable(skb, net->user_ns, CAP_SYS_ADMIN)) {
 738                 NL_SET_ERR_MSG(extack, "missing CAP_SYS_ADMIN capability");
 739                 return -EPERM;
 740         }
 741
 742         mutex_lock(&uevent_sock_mutex);
 743         ret = uevent_net_broadcast(net->uevent_sock->sk, skb, extack);
 744         mutex_unlock(&uevent_sock_mutex);
 745
 746         return ret;
 747 }
 748
 749 static void uevent_net_rcv(struct sk_buff *skb)
 750 {
 751         netlink_rcv_skb(skb, &uevent_net_rcv_skb);
 752 }
 753
 754 static int uevent_net_init(struct net *net)
 755 {
 756         struct uevent_sock *ue_sk;
 757         struct netlink_kernel_cfg cfg = {
 758                 .groups = 1,
 759                 .input = uevent_net_rcv,
 760                 .flags  = NL_CFG_F_NONROOT_RECV
 761         };
 762
 763         ue_sk = kzalloc(sizeof(*ue_sk), GFP_KERNEL);
 764         if (!ue_sk)
 765                 return -ENOMEM;
 766
 767         ue_sk->sk = netlink_kernel_create(net, NETLINK_KOBJECT_UEVENT, &cfg);
 768         if (!ue_sk->sk) {
 769                 printk(KERN_ERR
 770                        "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