lib/kobject_uevent.c

/* [<][>][^][v][top][bottom][index][help] */
This source file includes following definitions.
kobject_action_type
action_arg_word_end
kobject_action_args
kobject_synth_uevent
kobj_usermode_filter
init_uevent_argv
cleanup_uevent_env
alloc_uevent_skb
uevent_net_broadcast_untagged
uevent_net_broadcast_tagged
kobject_uevent_net_broadcast
zap_modalias_env
kobject_uevent_env
kobject_uevent
add_uevent_var
uevent_net_broadcast
uevent_net_rcv_skb
uevent_net_rcv
uevent_net_init
uevent_net_exit
kobject_uevent_init
   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         /*
 470          * Mark "remove" event done regardless of result, for some subsystems
 471          * do not want to re-trigger "remove" event via automatic cleanup.
 472          */
 473         if (action == KOBJ_REMOVE)
 474                 kobj->state_remove_uevent_sent = 1;
 475 
 476         pr_debug("kobject: '%s' (%p): %s\n",
 477                  kobject_name(kobj), kobj, __func__);
 478 
 479         /* search the kset we belong to */
 480         top_kobj = kobj;
 481         while (!top_kobj->kset && top_kobj->parent)
 482                 top_kobj = top_kobj->parent;
 483 
 484         if (!top_kobj->kset) {
 485                 pr_debug("kobject: '%s' (%p): %s: attempted to send uevent "
 486                          "without kset!\n", kobject_name(kobj), kobj,
 487                          __func__);
 488                 return -EINVAL;
 489         }
 490 
 491         kset = top_kobj->kset;
 492         uevent_ops = kset->uevent_ops;
 493 
 494         /* skip the event, if uevent_suppress is set*/
 495         if (kobj->uevent_suppress) {
 496                 pr_debug("kobject: '%s' (%p): %s: uevent_suppress "
 497                                  "caused the event to drop!\n",
 498                                  kobject_name(kobj), kobj, __func__);
 499                 return 0;
 500         }
 501         /* skip the event, if the filter returns zero. */
 502         if (uevent_ops && uevent_ops->filter)
 503                 if (!uevent_ops->filter(kset, kobj)) {
 504                         pr_debug("kobject: '%s' (%p): %s: filter function "
 505                                  "caused the event to drop!\n",
 506                                  kobject_name(kobj), kobj, __func__);
 507                         return 0;
 508                 }
 509 
 510         /* originating subsystem */
 511         if (uevent_ops && uevent_ops->name)
 512                 subsystem = uevent_ops->name(kset, kobj);
 513         else
 514                 subsystem = kobject_name(&kset->kobj);
 515         if (!subsystem) {
 516                 pr_debug("kobject: '%s' (%p): %s: unset subsystem caused the "
 517                          "event to drop!\n", kobject_name(kobj), kobj,
 518                          __func__);
 519                 return 0;
 520         }
 521 
 522         /* environment buffer */
 523         env = kzalloc(sizeof(struct kobj_uevent_env), GFP_KERNEL);
 524         if (!env)
 525                 return -ENOMEM;
 526 
 527         /* complete object path */
 528         devpath = kobject_get_path(kobj, GFP_KERNEL);
 529         if (!devpath) {
 530                 retval = -ENOENT;
 531                 goto exit;
 532         }
 533 
 534         /* default keys */
 535         retval = add_uevent_var(env, "ACTION=%s", action_string);
 536         if (retval)
 537                 goto exit;
 538         retval = add_uevent_var(env, "DEVPATH=%s", devpath);
 539         if (retval)
 540                 goto exit;
 541         retval = add_uevent_var(env, "SUBSYSTEM=%s", subsystem);
 542         if (retval)
 543                 goto exit;
 544 
 545         /* keys passed in from the caller */
 546         if (envp_ext) {
 547                 for (i = 0; envp_ext[i]; i++) {
 548                         retval = add_uevent_var(env, "%s", envp_ext[i]);
 549                         if (retval)
 550                                 goto exit;
 551                 }
 552         }
 553 
 554         /* let the kset specific function add its stuff */
 555         if (uevent_ops && uevent_ops->uevent) {
 556                 retval = uevent_ops->uevent(kset, kobj, env);
 557                 if (retval) {
 558                         pr_debug("kobject: '%s' (%p): %s: uevent() returned "
 559                                  "%d\n", kobject_name(kobj), kobj,
 560                                  __func__, retval);
 561                         goto exit;
 562                 }
 563         }
 564 
 565         switch (action) {
 566         case KOBJ_ADD:
 567                 /*
 568                  * Mark "add" event so we can make sure we deliver "remove"
 569                  * event to userspace during automatic cleanup. If
 570                  * the object did send an "add" event, "remove" will
 571                  * automatically generated by the core, if not already done
 572                  * by the caller.
 573                  */
 574                 kobj->state_add_uevent_sent = 1;
 575                 break;
 576 
 577         case KOBJ_UNBIND:
 578                 zap_modalias_env(env);
 579                 break;
 580 
 581         default:
 582                 break;
 583         }
 584 
 585         mutex_lock(&uevent_sock_mutex);
 586         /* we will send an event, so request a new sequence number */
 587         retval = add_uevent_var(env, "SEQNUM=%llu", ++uevent_seqnum);
 588         if (retval) {
 589                 mutex_unlock(&uevent_sock_mutex);
 590                 goto exit;
 591         }
 592         retval = kobject_uevent_net_broadcast(kobj, env, action_string,
 593                                               devpath);
 594         mutex_unlock(&uevent_sock_mutex);
 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", ++uevent_seqnum);
 691         if (ret < 0 || (size_t)ret >= sizeof(buf))
 692                 return -ENOMEM;
 693         ret++;
 694 
 695         /* verify message does not overflow */
 696         if ((skb->len + ret) > UEVENT_BUFFER_SIZE) {
 697                 NL_SET_ERR_MSG(extack, "uevent message too big");
 698                 return -EINVAL;
 699         }
 700 
 701         /* copy skb and extend to accommodate sequence number */
 702         skbc = skb_copy_expand(skb, 0, ret, GFP_KERNEL);
 703         if (!skbc)
 704                 return -ENOMEM;
 705 
 706         /* append sequence number */
 707         skb_put_data(skbc, buf, ret);
 708 
 709         /* remove msg header */
 710         skb_pull(skbc, NLMSG_HDRLEN);
 711 
 712         /* set portid 0 to inform userspace message comes from kernel */
 713         NETLINK_CB(skbc).portid = 0;
 714         NETLINK_CB(skbc).dst_group = 1;
 715 
 716         ret = netlink_broadcast(usk, skbc, 0, 1, GFP_KERNEL);
 717         /* ENOBUFS should be handled in userspace */
 718         if (ret == -ENOBUFS || ret == -ESRCH)
 719                 ret = 0;
 720 
 721         return ret;
 722 }
 723 
 724 static int uevent_net_rcv_skb(struct sk_buff *skb, struct nlmsghdr *nlh,
 725                               struct netlink_ext_ack *extack)
 726 {
 727         struct net *net;
 728         int ret;
 729 
 730         if (!nlmsg_data(nlh))
 731                 return -EINVAL;
 732 
 733         /*
 734          * Verify that we are allowed to send messages to the target
 735          * network namespace. The caller must have CAP_SYS_ADMIN in the
 736          * owning user namespace of the target network namespace.
 737          */
 738         net = sock_net(NETLINK_CB(skb).sk);
 739         if (!netlink_ns_capable(skb, net->user_ns, CAP_SYS_ADMIN)) {
 740                 NL_SET_ERR_MSG(extack, "missing CAP_SYS_ADMIN capability");
 741                 return -EPERM;
 742         }
 743 
 744         mutex_lock(&uevent_sock_mutex);
 745         ret = uevent_net_broadcast(net->uevent_sock->sk, skb, extack);
 746         mutex_unlock(&uevent_sock_mutex);
 747 
 748         return ret;
 749 }
 750 
 751 static void uevent_net_rcv(struct sk_buff *skb)
 752 {
 753         netlink_rcv_skb(skb, &uevent_net_rcv_skb);
 754 }
 755 
 756 static int uevent_net_init(struct net *net)
 757 {
 758         struct uevent_sock *ue_sk;
 759         struct netlink_kernel_cfg cfg = {
 760                 .groups = 1,
 761                 .input = uevent_net_rcv,
 762                 .flags  = NL_CFG_F_NONROOT_RECV
 763         };
 764 
 765         ue_sk = kzalloc(sizeof(*ue_sk), GFP_KERNEL);
 766         if (!ue_sk)
 767                 return -ENOMEM;
 768 
 769         ue_sk->sk = netlink_kernel_create(net, NETLINK_KOBJECT_UEVENT, &cfg);
 770         if (!ue_sk->sk) {
 771                 pr_err("kobject_uevent: unable to create netlink socket!\n");
 772                 kfree(ue_sk);
 773                 return -ENODEV;
 774         }
 775 
 776         net->uevent_sock = ue_sk;
 777 
 778         /* Restrict uevents to initial user namespace. */
 779         if (sock_net(ue_sk->sk)->user_ns == &init_user_ns) {
 780                 mutex_lock(&uevent_sock_mutex);
 781                 list_add_tail(&ue_sk->list, &uevent_sock_list);
 782                 mutex_unlock(&uevent_sock_mutex);
 783         }
 784 
 785         return 0;
 786 }
 787 
 788 static void uevent_net_exit(struct net *net)
 789 {
 790         struct uevent_sock *ue_sk = net->uevent_sock;
 791 
 792         if (sock_net(ue_sk->sk)->user_ns == &init_user_ns) {
 793                 mutex_lock(&uevent_sock_mutex);
 794                 list_del(&ue_sk->list);
 795                 mutex_unlock(&uevent_sock_mutex);
 796         }
 797 
 798         netlink_kernel_release(ue_sk->sk);
 799         kfree(ue_sk);
 800 }
 801 
 802 static struct pernet_operations uevent_net_ops = {
 803         .init   = uevent_net_init,
 804         .exit   = uevent_net_exit,
 805 };
 806 
 807 static int __init kobject_uevent_init(void)
 808 {
 809         return register_pernet_subsys(&uevent_net_ops);
 810 }
 811 
 812 
 813 postcore_initcall(kobject_uevent_init);
 814 #endif
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root/lib/kobject_uevent.c

DEFINITIONS
