net/core/sysctl_net_core.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /* -*- linux-c -*-
   3  * sysctl_net_core.c: sysctl interface to net core subsystem.
   4  *
   5  * Begun April 1, 1996, Mike Shaver.
   6  * Added /proc/sys/net/core directory entry (empty =) ). [MS]
   7  */
   8
   9 #include <linux/mm.h>
  10 #include <linux/sysctl.h>
  11 #include <linux/module.h>
  12 #include <linux/socket.h>
  13 #include <linux/netdevice.h>
  14 #include <linux/ratelimit.h>
  15 #include <linux/vmalloc.h>
  16 #include <linux/init.h>
  17 #include <linux/slab.h>
  18
  19 #include <net/ip.h>
  20 #include <net/sock.h>
  21 #include <net/net_ratelimit.h>
  22 #include <net/busy_poll.h>
  23 #include <net/pkt_sched.h>
  24
  25 static int two __maybe_unused = 2;
  26 static int three = 3;
  27 static int min_sndbuf = SOCK_MIN_SNDBUF;
  28 static int min_rcvbuf = SOCK_MIN_RCVBUF;
  29 static int max_skb_frags = MAX_SKB_FRAGS;
  30 static long long_one __maybe_unused = 1;
  31 static long long_max __maybe_unused = LONG_MAX;
  32
  33 static int net_msg_warn;        /* Unused, but still a sysctl */
  34
  35 int sysctl_fb_tunnels_only_for_init_net __read_mostly = 0;
  36 EXPORT_SYMBOL(sysctl_fb_tunnels_only_for_init_net);
  37
  38 /* 0 - Keep current behavior:
  39  *     IPv4: inherit all current settings from init_net
  40  *     IPv6: reset all settings to default
  41  * 1 - Both inherit all current settings from init_net
  42  * 2 - Both reset all settings to default
  43  * 3 - Both inherit all settings from current netns
  44  */
  45 int sysctl_devconf_inherit_init_net __read_mostly;
  46 EXPORT_SYMBOL(sysctl_devconf_inherit_init_net);
  47
  48 #ifdef CONFIG_RPS
  49 static int rps_sock_flow_sysctl(struct ctl_table *table, int write,
  50                                 void *buffer, size_t *lenp, loff_t *ppos)
  51 {
  52         unsigned int orig_size, size;
  53         int ret, i;
  54         struct ctl_table tmp = {
  55                 .data = &size,
  56                 .maxlen = sizeof(size),
  57                 .mode = table->mode
  58         };
  59         struct rps_sock_flow_table *orig_sock_table, *sock_table;
  60         static DEFINE_MUTEX(sock_flow_mutex);
  61
  62         mutex_lock(&sock_flow_mutex);
  63
  64         orig_sock_table = rcu_dereference_protected(rps_sock_flow_table,
  65                                         lockdep_is_held(&sock_flow_mutex));
  66         size = orig_size = orig_sock_table ? orig_sock_table->mask + 1 : 0;
  67
  68         ret = proc_dointvec(&tmp, write, buffer, lenp, ppos);
  69
  70         if (write) {
  71                 if (size) {
  72                         if (size > 1<<29) {
  73                                 /* Enforce limit to prevent overflow */
  74                                 mutex_unlock(&sock_flow_mutex);
  75                                 return -EINVAL;
  76                         }
  77                         size = roundup_pow_of_two(size);
  78                         if (size != orig_size) {
  79                                 sock_table =
  80                                     vmalloc(RPS_SOCK_FLOW_TABLE_SIZE(size));
  81                                 if (!sock_table) {
  82                                         mutex_unlock(&sock_flow_mutex);
  83                                         return -ENOMEM;
  84                                 }
  85                                 rps_cpu_mask = roundup_pow_of_two(nr_cpu_ids) - 1;
  86                                 sock_table->mask = size - 1;
  87                         } else
  88                                 sock_table = orig_sock_table;
  89
  90                         for (i = 0; i < size; i++)
  91                                 sock_table->ents[i] = RPS_NO_CPU;
  92                 } else
  93                         sock_table = NULL;
  94
  95                 if (sock_table != orig_sock_table) {
  96                         rcu_assign_pointer(rps_sock_flow_table, sock_table);
  97                         if (sock_table) {
  98                                 static_branch_inc(&rps_needed);
  99                                 static_branch_inc(&rfs_needed);
 100                         }
 101                         if (orig_sock_table) {
 102                                 static_branch_dec(&rps_needed);
 103                                 static_branch_dec(&rfs_needed);
 104                                 synchronize_rcu();
 105                                 vfree(orig_sock_table);
 106                         }
 107                 }
 108         }
 109
 110         mutex_unlock(&sock_flow_mutex);
 111
 112         return ret;
 113 }
 114 #endif /* CONFIG_RPS */
 115
 116 #ifdef CONFIG_NET_FLOW_LIMIT
 117 static DEFINE_MUTEX(flow_limit_update_mutex);
 118
 119 static int flow_limit_cpu_sysctl(struct ctl_table *table, int write,
 120                                  void *buffer, size_t *lenp, loff_t *ppos)
 121 {
 122         struct sd_flow_limit *cur;
 123         struct softnet_data *sd;
 124         cpumask_var_t mask;
 125         int i, len, ret = 0;
 126
 127         if (!alloc_cpumask_var(&mask, GFP_KERNEL))
 128                 return -ENOMEM;
 129
 130         if (write) {
 131                 ret = cpumask_parse_user(buffer, *lenp, mask);
 132                 if (ret)
 133                         goto done;
 134
 135                 mutex_lock(&flow_limit_update_mutex);
 136                 len = sizeof(*cur) + netdev_flow_limit_table_len;
 137                 for_each_possible_cpu(i) {
 138                         sd = &per_cpu(softnet_data, i);
 139                         cur = rcu_dereference_protected(sd->flow_limit,
 140                                      lockdep_is_held(&flow_limit_update_mutex));
 141                         if (cur && !cpumask_test_cpu(i, mask)) {
 142                                 RCU_INIT_POINTER(sd->flow_limit, NULL);
 143                                 synchronize_rcu();
 144                                 kfree(cur);
 145                         } else if (!cur && cpumask_test_cpu(i, mask)) {
 146                                 cur = kzalloc_node(len, GFP_KERNEL,
 147                                                    cpu_to_node(i));
 148                                 if (!cur) {
 149                                         /* not unwinding previous changes */
 150                                         ret = -ENOMEM;
 151                                         goto write_unlock;
 152                                 }
 153                                 cur->num_buckets = netdev_flow_limit_table_len;
 154                                 rcu_assign_pointer(sd->flow_limit, cur);
 155                         }
 156                 }
 157 write_unlock:
 158                 mutex_unlock(&flow_limit_update_mutex);
 159         } else {
 160                 char kbuf[128];
 161
 162                 if (*ppos || !*lenp) {
 163                         *lenp = 0;
 164                         goto done;
 165                 }
 166
 167                 cpumask_clear(mask);
 168                 rcu_read_lock();
 169                 for_each_possible_cpu(i) {
 170                         sd = &per_cpu(softnet_data, i);
 171                         if (rcu_dereference(sd->flow_limit))
 172                                 cpumask_set_cpu(i, mask);
 173                 }
 174                 rcu_read_unlock();
 175
 176                 len = min(sizeof(kbuf) - 1, *lenp);
 177                 len = scnprintf(kbuf, len, "%*pb", cpumask_pr_args(mask));
 178                 if (!len) {
 179                         *lenp = 0;
 180                         goto done;
 181                 }
 182                 if (len < *lenp)
 183                         kbuf[len++] = '\n';
 184                 memcpy(buffer, kbuf, len);
 185                 *lenp = len;
 186                 *ppos += len;
 187         }
 188
 189 done:
 190         free_cpumask_var(mask);
 191         return ret;
 192 }
 193
 194 static int flow_limit_table_len_sysctl(struct ctl_table *table, int write,
 195                                        void *buffer, size_t *lenp, loff_t *ppos)
 196 {
 197         unsigned int old, *ptr;
 198         int ret;
 199
 200         mutex_lock(&flow_limit_update_mutex);
 201
 202         ptr = table->data;
 203         old = *ptr;
 204         ret = proc_dointvec(table, write, buffer, lenp, ppos);
 205         if (!ret && write && !is_power_of_2(*ptr)) {
 206                 *ptr = old;
 207                 ret = -EINVAL;
 208         }
 209
 210         mutex_unlock(&flow_limit_update_mutex);
 211         return ret;
 212 }
 213 #endif /* CONFIG_NET_FLOW_LIMIT */
 214
 215 #ifdef CONFIG_NET_SCHED
 216 static int set_default_qdisc(struct ctl_table *table, int write,
 217                              void *buffer, size_t *lenp, loff_t *ppos)
 218 {
 219         char id[IFNAMSIZ];
 220         struct ctl_table tbl = {
 221                 .data = id,
 222                 .maxlen = IFNAMSIZ,
 223         };
 224         int ret;
 225
 226         qdisc_get_default(id, IFNAMSIZ);
 227
 228         ret = proc_dostring(&tbl, write, buffer, lenp, ppos);
 229         if (write && ret == 0)
 230                 ret = qdisc_set_default(id);
 231         return ret;
 232 }
 233 #endif
 234
 235 static int proc_do_dev_weight(struct ctl_table *table, int write,
 236                            void *buffer, size_t *lenp, loff_t *ppos)
 237 {
 238         int ret;
 239
 240         ret = proc_dointvec(table, write, buffer, lenp, ppos);
 241         if (ret != 0)
 242                 return ret;
 243
 244         dev_rx_weight = weight_p * dev_weight_rx_bias;
 245         dev_tx_weight = weight_p * dev_weight_tx_bias;
 246
 247         return ret;
 248 }
 249
 250 static int proc_do_rss_key(struct ctl_table *table, int write,
 251                            void *buffer, size_t *lenp, loff_t *ppos)
 252 {
 253         struct ctl_table fake_table;
 254         char buf[NETDEV_RSS_KEY_LEN * 3];
 255
 256         snprintf(buf, sizeof(buf), "%*phC", NETDEV_RSS_KEY_LEN, netdev_rss_key);
 257         fake_table.data = buf;
 258         fake_table.maxlen = sizeof(buf);
 259         return proc_dostring(&fake_table, write, buffer, lenp, ppos);
 260 }
 261
 262 #ifdef CONFIG_BPF_JIT
 263 static int proc_dointvec_minmax_bpf_enable(struct ctl_table *table, int write,
 264                                            void *buffer, size_t *lenp,
 265                                            loff_t *ppos)
 266 {
 267         int ret, jit_enable = *(int *)table->data;
 268         struct ctl_table tmp = *table;
 269
 270         if (write && !capable(CAP_SYS_ADMIN))
 271                 return -EPERM;
 272
 273         tmp.data = &jit_enable;
 274         ret = proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos);
 275         if (write && !ret) {
 276                 if (jit_enable < 2 ||
 277                     (jit_enable == 2 && bpf_dump_raw_ok())) {
 278                         *(int *)table->data = jit_enable;
 279                         if (jit_enable == 2)
 280                                 pr_warn("bpf_jit_enable = 2 was set! NEVER use this in production, only for JIT debugging!\n");
 281                 } else {
 282                         ret = -EPERM;
 283                 }
 284         }
 285         return ret;
 286 }
 287
 288 # ifdef CONFIG_HAVE_EBPF_JIT
 289 static int
 290 proc_dointvec_minmax_bpf_restricted(struct ctl_table *table, int write,
 291                                     void *buffer, size_t *lenp, loff_t *ppos)
 292 {
 293         if (!capable(CAP_SYS_ADMIN))
 294                 return -EPERM;
 295
 296         return proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 297 }
 298 # endif /* CONFIG_HAVE_EBPF_JIT */
 299
 300 static int
 301 proc_dolongvec_minmax_bpf_restricted(struct ctl_table *table, int write,
 302                                      void *buffer, size_t *lenp, loff_t *ppos)
 303 {
 304         if (!capable(CAP_SYS_ADMIN))
 305                 return -EPERM;
 306
 307         return proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
 308 }
 309 #endif
 310
 311 static struct ctl_table net_core_table[] = {
 312 #ifdef CONFIG_NET
 313         {
 314                 .procname       = "wmem_max",
 315                 .data           = &sysctl_wmem_max,
 316                 .maxlen         = sizeof(int),
 317                 .mode           = 0644,
 318                 .proc_handler   = proc_dointvec_minmax,
 319                 .extra1         = &min_sndbuf,
 320         },
 321         {
 322                 .procname       = "rmem_max",
 323                 .data           = &sysctl_rmem_max,
 324                 .maxlen         = sizeof(int),
 325                 .mode           = 0644,
 326                 .proc_handler   = proc_dointvec_minmax,
 327                 .extra1         = &min_rcvbuf,
 328         },
 329         {
 330                 .procname       = "wmem_default",
 331                 .data           = &sysctl_wmem_default,
 332                 .maxlen         = sizeof(int),
 333                 .mode           = 0644,
 334                 .proc_handler   = proc_dointvec_minmax,
 335                 .extra1         = &min_sndbuf,
 336         },
 337         {
 338                 .procname       = "rmem_default",
 339                 .data           = &sysctl_rmem_default,
 340                 .maxlen         = sizeof(int),
 341                 .mode           = 0644,
 342                 .proc_handler   = proc_dointvec_minmax,
 343                 .extra1         = &min_rcvbuf,
 344         },
 345         {
 346                 .procname       = "dev_weight",
 347                 .data           = &weight_p,
 348                 .maxlen         = sizeof(int),
 349                 .mode           = 0644,
 350                 .proc_handler   = proc_do_dev_weight,
 351         },
 352         {
 353                 .procname       = "dev_weight_rx_bias",
 354                 .data           = &dev_weight_rx_bias,
 355                 .maxlen         = sizeof(int),
 356                 .mode           = 0644,
 357                 .proc_handler   = proc_do_dev_weight,
 358         },
 359         {
 360                 .procname       = "dev_weight_tx_bias",
 361                 .data           = &dev_weight_tx_bias,
 362                 .maxlen         = sizeof(int),
 363                 .mode           = 0644,
 364                 .proc_handler   = proc_do_dev_weight,
 365         },
 366         {
 367                 .procname       = "netdev_max_backlog",
 368                 .data           = &netdev_max_backlog,
 369                 .maxlen         = sizeof(int),
 370                 .mode           = 0644,
 371                 .proc_handler   = proc_dointvec
 372         },
 373         {
 374                 .procname       = "netdev_rss_key",
 375                 .data           = &netdev_rss_key,
 376                 .maxlen         = sizeof(int),
 377                 .mode           = 0444,
 378                 .proc_handler   = proc_do_rss_key,
 379         },
 380 #ifdef CONFIG_BPF_JIT
 381         {
 382                 .procname       = "bpf_jit_enable",
 383                 .data           = &bpf_jit_enable,
 384                 .maxlen         = sizeof(int),
 385                 .mode           = 0644,
 386                 .proc_handler   = proc_dointvec_minmax_bpf_enable,
 387 # ifdef CONFIG_BPF_JIT_ALWAYS_ON
 388                 .extra1         = SYSCTL_ONE,
 389                 .extra2         = SYSCTL_ONE,
 390 # else
 391                 .extra1         = SYSCTL_ZERO,
 392                 .extra2         = &two,
 393 # endif
 394         },
 395 # ifdef CONFIG_HAVE_EBPF_JIT
 396         {
 397                 .procname       = "bpf_jit_harden",
 398                 .data           = &bpf_jit_harden,
 399                 .maxlen         = sizeof(int),
 400                 .mode           = 0600,
 401                 .proc_handler   = proc_dointvec_minmax_bpf_restricted,
 402                 .extra1         = SYSCTL_ZERO,
 403                 .extra2         = &two,
 404         },
 405         {
 406                 .procname       = "bpf_jit_kallsyms",
 407                 .data           = &bpf_jit_kallsyms,
 408                 .maxlen         = sizeof(int),
 409                 .mode           = 0600,
 410                 .proc_handler   = proc_dointvec_minmax_bpf_restricted,
 411                 .extra1         = SYSCTL_ZERO,
 412                 .extra2         = SYSCTL_ONE,
 413         },
 414 # endif
 415         {
 416                 .procname       = "bpf_jit_limit",
 417                 .data           = &bpf_jit_limit,
 418                 .maxlen         = sizeof(long),
 419                 .mode           = 0600,
 420                 .proc_handler   = proc_dolongvec_minmax_bpf_restricted,
 421                 .extra1         = &long_one,
 422                 .extra2         = &long_max,
 423         },
 424 #endif
 425         {
 426                 .procname       = "netdev_tstamp_prequeue",
 427                 .data           = &netdev_tstamp_prequeue,
 428                 .maxlen         = sizeof(int),
 429                 .mode           = 0644,
 430                 .proc_handler   = proc_dointvec
 431         },
 432         {
 433                 .procname       = "message_cost",
 434                 .data           = &net_ratelimit_state.interval,
 435                 .maxlen         = sizeof(int),
 436                 .mode           = 0644,
 437                 .proc_handler   = proc_dointvec_jiffies,
 438         },
 439         {
 440                 .procname       = "message_burst",
 441                 .data           = &net_ratelimit_state.burst,
 442                 .maxlen         = sizeof(int),
 443                 .mode           = 0644,
 444                 .proc_handler   = proc_dointvec,
 445         },
 446         {
 447                 .procname       = "optmem_max",
 448                 .data           = &sysctl_optmem_max,
 449                 .maxlen         = sizeof(int),
 450                 .mode           = 0644,
 451                 .proc_handler   = proc_dointvec
 452         },
 453         {
 454                 .procname       = "tstamp_allow_data",
 455                 .data           = &sysctl_tstamp_allow_data,
 456                 .maxlen         = sizeof(int),
 457                 .mode           = 0644,
 458                 .proc_handler   = proc_dointvec_minmax,
 459                 .extra1         = SYSCTL_ZERO,
 460                 .extra2         = SYSCTL_ONE
 461         },
 462 #ifdef CONFIG_RPS
 463         {
 464                 .procname       = "rps_sock_flow_entries",
 465                 .maxlen         = sizeof(int),
 466                 .mode           = 0644,
 467                 .proc_handler   = rps_sock_flow_sysctl
 468         },
 469 #endif
 470 #ifdef CONFIG_NET_FLOW_LIMIT
 471         {
 472                 .procname       = "flow_limit_cpu_bitmap",
 473                 .mode           = 0644,
 474                 .proc_handler   = flow_limit_cpu_sysctl
 475         },
 476         {
 477                 .procname       = "flow_limit_table_len",
 478                 .data           = &netdev_flow_limit_table_len,
 479                 .maxlen         = sizeof(int),
 480                 .mode           = 0644,
 481                 .proc_handler   = flow_limit_table_len_sysctl
 482         },
 483 #endif /* CONFIG_NET_FLOW_LIMIT */
 484 #ifdef CONFIG_NET_RX_BUSY_POLL
 485         {
 486                 .procname       = "busy_poll",
 487                 .data           = &sysctl_net_busy_poll,
 488                 .maxlen         = sizeof(unsigned int),
 489                 .mode           = 0644,
 490                 .proc_handler   = proc_dointvec_minmax,
 491                 .extra1         = SYSCTL_ZERO,
 492         },
 493         {
 494                 .procname       = "busy_read",
 495                 .data           = &sysctl_net_busy_read,
 496                 .maxlen         = sizeof(unsigned int),
 497                 .mode           = 0644,
 498                 .proc_handler   = proc_dointvec_minmax,
 499                 .extra1         = SYSCTL_ZERO,
 500         },
 501 #endif
 502 #ifdef CONFIG_NET_SCHED
 503         {
 504                 .procname       = "default_qdisc",
 505                 .mode           = 0644,
 506                 .maxlen         = IFNAMSIZ,
 507                 .proc_handler   = set_default_qdisc
 508         },
 509 #endif
 510 #endif /* CONFIG_NET */
 511         {
 512                 .procname       = "netdev_budget",
 513                 .data           = &netdev_budget,
 514                 .maxlen         = sizeof(int),
 515                 .mode           = 0644,
 516                 .proc_handler   = proc_dointvec
 517         },
 518         {
 519                 .procname       = "warnings",
 520                 .data           = &net_msg_warn,
 521                 .maxlen         = sizeof(int),
 522                 .mode           = 0644,
 523                 .proc_handler   = proc_dointvec
 524         },
 525         {
 526                 .procname       = "max_skb_frags",
 527                 .data           = &sysctl_max_skb_frags,
 528                 .maxlen         = sizeof(int),
 529                 .mode           = 0644,
 530                 .proc_handler   = proc_dointvec_minmax,
 531                 .extra1         = SYSCTL_ONE,
 532                 .extra2         = &max_skb_frags,
 533         },
 534         {
 535                 .procname       = "netdev_budget_usecs",
 536                 .data           = &netdev_budget_usecs,
 537                 .maxlen         = sizeof(unsigned int),
 538                 .mode           = 0644,
 539                 .proc_handler   = proc_dointvec_minmax,
 540                 .extra1         = SYSCTL_ZERO,
 541         },
 542         {
 543                 .procname       = "fb_tunnels_only_for_init_net",
 544                 .data           = &sysctl_fb_tunnels_only_for_init_net,
 545                 .maxlen         = sizeof(int),
 546                 .mode           = 0644,
 547                 .proc_handler   = proc_dointvec_minmax,
 548                 .extra1         = SYSCTL_ZERO,
 549                 .extra2         = SYSCTL_ONE,
 550         },
 551         {
 552                 .procname       = "devconf_inherit_init_net",
 553                 .data           = &sysctl_devconf_inherit_init_net,
 554                 .maxlen         = sizeof(int),
 555                 .mode           = 0644,
 556                 .proc_handler   = proc_dointvec_minmax,
 557                 .extra1         = SYSCTL_ZERO,
 558                 .extra2         = &three,
 559         },
 560         {
 561                 .procname       = "high_order_alloc_disable",
 562                 .data           = &net_high_order_alloc_disable_key.key,
 563                 .maxlen         = sizeof(net_high_order_alloc_disable_key),
 564                 .mode           = 0644,
 565                 .proc_handler   = proc_do_static_key,
 566         },
 567         {
 568                 .procname       = "gro_normal_batch",
 569                 .data           = &gro_normal_batch,
 570                 .maxlen         = sizeof(unsigned int),
 571                 .mode           = 0644,
 572                 .proc_handler   = proc_dointvec_minmax,
 573                 .extra1         = SYSCTL_ONE,
 574         },
 575         { }
 576 };
 577
 578 static struct ctl_table netns_core_table[] = {
 579         {
 580                 .procname       = "somaxconn",
 581                 .data           = &init_net.core.sysctl_somaxconn,
 582                 .maxlen         = sizeof(int),
 583                 .mode           = 0644,
 584                 .extra1         = SYSCTL_ZERO,
 585                 .proc_handler   = proc_dointvec_minmax
 586         },
 587         { }
 588 };
 589
 590 static __net_init int sysctl_core_net_init(struct net *net)
 591 {
 592         struct ctl_table *tbl;
 593
 594         tbl = netns_core_table;
 595         if (!net_eq(net, &init_net)) {
 596                 tbl = kmemdup(tbl, sizeof(netns_core_table), GFP_KERNEL);
 597                 if (tbl == NULL)
 598                         goto err_dup;
 599
 600                 tbl[0].data = &net->core.sysctl_somaxconn;
 601
 602                 /* Don't export any sysctls to unprivileged users */
 603                 if (net->user_ns != &init_user_ns) {
 604                         tbl[0].procname = NULL;
 605                 }
 606         }
 607
 608         net->core.sysctl_hdr = register_net_sysctl(net, "net/core", tbl);
 609         if (net->core.sysctl_hdr == NULL)
 610                 goto err_reg;
 611
 612         return 0;
 613
 614 err_reg:
 615         if (tbl != netns_core_table)
 616                 kfree(tbl);
 617 err_dup:
 618         return -ENOMEM;
 619 }
 620
 621 static __net_exit void sysctl_core_net_exit(struct net *net)
 622 {
 623         struct ctl_table *tbl;
 624
 625         tbl = net->core.sysctl_hdr->ctl_table_arg;
 626         unregister_net_sysctl_table(net->core.sysctl_hdr);
 627         BUG_ON(tbl == netns_core_table);
 628         kfree(tbl);
 629 }
 630
 631 static __net_initdata struct pernet_operations sysctl_core_ops = {
 632         .init = sysctl_core_net_init,
 633         .exit = sysctl_core_net_exit,
 634 };
 635
 636 static __init int sysctl_core_init(void)
 637 {
 638         register_net_sysctl(&init_net, "net/core", net_core_table);
 639         return register_pernet_subsys(&sysctl_core_ops);
 640 }
 641
 642 fs_initcall(sysctl_core_init);