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