LXR linux/kernel/bpf/net

   1// SPDX-License-Identifier: GPL-2.0
   2
   3#include <linux/bpf.h>
   4#include <linux/filter.h>
   5#include <net/net_namespace.h>
   6
   7/*
   8 * Functions to manage BPF programs attached to netns
   9 */
  10
  11struct bpf_netns_link {
  12        struct bpf_link link;
  13        enum bpf_attach_type type;
  14        enum netns_bpf_attach_type netns_type;
  15
  16        /* We don't hold a ref to net in order to auto-detach the link
  17         * when netns is going away. Instead we rely on pernet
  18         * pre_exit callback to clear this pointer. Must be accessed
  19         * with netns_bpf_mutex held.
  20         */
  21        struct net *net;
  22        struct list_head node; /* node in list of links attached to net */
  23};
  24
  25/* Protects updates to netns_bpf */
  26DEFINE_MUTEX(netns_bpf_mutex);
  27
  28static void netns_bpf_attach_type_unneed(enum netns_bpf_attach_type type)
  29{
  30        switch (type) {
  31#ifdef CONFIG_INET
  32        case NETNS_BPF_SK_LOOKUP:
  33                static_branch_dec(&bpf_sk_lookup_enabled);
  34                break;
  35#endif
  36        default:
  37                break;
  38        }
  39}
  40
  41static void netns_bpf_attach_type_need(enum netns_bpf_attach_type type)
  42{
  43        switch (type) {
  44#ifdef CONFIG_INET
  45        case NETNS_BPF_SK_LOOKUP:
  46                static_branch_inc(&bpf_sk_lookup_enabled);
  47                break;
  48#endif
  49        default:
  50                break;
  51        }
  52}
  53
  54/* Must be called with netns_bpf_mutex held. */
  55static void netns_bpf_run_array_detach(struct net *net,
  56                                       enum netns_bpf_attach_type type)
  57{
  58        struct bpf_prog_array *run_array;
  59
  60        run_array = rcu_replace_pointer(net->bpf.run_array[type], NULL,
  61                                        lockdep_is_held(&netns_bpf_mutex));
  62        bpf_prog_array_free(run_array);
  63}
  64
  65static int link_index(struct net *net, enum netns_bpf_attach_type type,
  66                      struct bpf_netns_link *link)
  67{
  68        struct bpf_netns_link *pos;
  69        int i = 0;
  70
  71        list_for_each_entry(pos, &net->bpf.links[type], node) {
  72                if (pos == link)
  73                        return i;
  74                i++;
  75        }
  76        return -ENOENT;
  77}
  78
  79static int link_count(struct net *net, enum netns_bpf_attach_type type)
  80{
  81        struct list_head *pos;
  82        int i = 0;
  83
  84        list_for_each(pos, &net->bpf.links[type])
  85                i++;
  86        return i;
  87}
  88
  89static void fill_prog_array(struct net *net, enum netns_bpf_attach_type type,
  90                            struct bpf_prog_array *prog_array)
  91{
  92        struct bpf_netns_link *pos;
  93        unsigned int i = 0;
  94
  95        list_for_each_entry(pos, &net->bpf.links[type], node) {
  96                prog_array->items[i].prog = pos->link.prog;
  97                i++;
  98        }
  99}
 100
 101static void bpf_netns_link_release(struct bpf_link *link)
 102{
 103        struct bpf_netns_link *net_link =
 104                container_of(link, struct bpf_netns_link, link);
 105        enum netns_bpf_attach_type type = net_link->netns_type;
 106        struct bpf_prog_array *old_array, *new_array;
 107        struct net *net;
 108        int cnt, idx;
 109
 110        mutex_lock(&netns_bpf_mutex);
 111
 112        /* We can race with cleanup_net, but if we see a non-NULL
 113         * struct net pointer, pre_exit has not run yet and wait for
 114         * netns_bpf_mutex.
 115         */
 116        net = net_link->net;
 117        if (!net)
 118                goto out_unlock;
 119
 120        /* Mark attach point as unused */
 121        netns_bpf_attach_type_unneed(type);
 122
 123        /* Remember link position in case of safe delete */
 124        idx = link_index(net, type, net_link);
 125        list_del(&net_link->node);
 126
 127        cnt = link_count(net, type);
 128        if (!cnt) {
 129                netns_bpf_run_array_detach(net, type);
 130                goto out_unlock;
 131        }
 132
 133        old_array = rcu_dereference_protected(net->bpf.run_array[type],
 134                                              lockdep_is_held(&netns_bpf_mutex));
 135        new_array = bpf_prog_array_alloc(cnt, GFP_KERNEL);
 136        if (!new_array) {
 137                WARN_ON(bpf_prog_array_delete_safe_at(old_array, idx));
 138                goto out_unlock;
 139        }
 140        fill_prog_array(net, type, new_array);
 141        rcu_assign_pointer(net->bpf.run_array[type], new_array);
 142        bpf_prog_array_free(old_array);
 143
 144out_unlock:
 145        net_link->net = NULL;
 146        mutex_unlock(&netns_bpf_mutex);
 147}
 148
 149static int bpf_netns_link_detach(struct bpf_link *link)
 150{
 151        bpf_netns_link_release(link);
 152        return 0;
 153}
 154
 155static void bpf_netns_link_dealloc(struct bpf_link *link)
 156{
 157        struct bpf_netns_link *net_link =
 158                container_of(link, struct bpf_netns_link, link);
 159
 160        kfree(net_link);
 161}
 162
 163static int bpf_netns_link_update_prog(struct bpf_link *link,
 164                                      struct bpf_prog *new_prog,
 165                                      struct bpf_prog *old_prog)
 166{
 167        struct bpf_netns_link *net_link =
 168                container_of(link, struct bpf_netns_link, link);
 169        enum netns_bpf_attach_type type = net_link->netns_type;
 170        struct bpf_prog_array *run_array;
 171        struct net *net;
 172        int idx, ret;
 173
 174        if (old_prog && old_prog != link->prog)
 175                return -EPERM;
 176        if (new_prog->type != link->prog->type)
 177                return -EINVAL;
 178
 179        mutex_lock(&netns_bpf_mutex);
 180
 181        net = net_link->net;
 182        if (!net || !check_net(net)) {
 183                /* Link auto-detached or netns dying */
 184                ret = -ENOLINK;
 185                goto out_unlock;
 186        }
 187
 188        run_array = rcu_dereference_protected(net->bpf.run_array[type],
 189                                              lockdep_is_held(&netns_bpf_mutex));
 190        idx = link_index(net, type, net_link);
 191        ret = bpf_prog_array_update_at(run_array, idx, new_prog);
 192        if (ret)
 193                goto out_unlock;
 194
 195        old_prog = xchg(&link->prog, new_prog);
 196        bpf_prog_put(old_prog);
 197
 198out_unlock:
 199        mutex_unlock(&netns_bpf_mutex);
 200        return ret;
 201}
 202
 203static int bpf_netns_link_fill_info(const struct bpf_link *link,
 204                                    struct bpf_link_info *info)
 205{
 206        const struct bpf_netns_link *net_link =
 207                container_of(link, struct bpf_netns_link, link);
 208        unsigned int inum = 0;
 209        struct net *net;
 210
 211        mutex_lock(&netns_bpf_mutex);
 212        net = net_link->net;
 213        if (net && check_net(net))
 214                inum = net->ns.inum;
 215        mutex_unlock(&netns_bpf_mutex);
 216
 217        info->netns.netns_ino = inum;
 218        info->netns.attach_type = net_link->type;
 219        return 0;
 220}
 221
 222static void bpf_netns_link_show_fdinfo(const struct bpf_link *link,
 223                                       struct seq_file *seq)
 224{
 225        struct bpf_link_info info = {};
 226
 227        bpf_netns_link_fill_info(link, &info);
 228        seq_printf(seq,
 229                   "netns_ino:\t%u\n"
 230                   "attach_type:\t%u\n",
 231                   info.netns.netns_ino,
 232                   info.netns.attach_type);
 233}
 234
 235static const struct bpf_link_ops bpf_netns_link_ops = {
 236        .release = bpf_netns_link_release,
 237        .dealloc = bpf_netns_link_dealloc,
 238        .detach = bpf_netns_link_detach,
 239        .update_prog = bpf_netns_link_update_prog,
 240        .fill_link_info = bpf_netns_link_fill_info,
 241        .show_fdinfo = bpf_netns_link_show_fdinfo,
 242};
 243
 244/* Must be called with netns_bpf_mutex held. */
 245static int __netns_bpf_prog_query(const union bpf_attr *attr,
 246                                  union bpf_attr __user *uattr,
 247                                  struct net *net,
 248                                  enum netns_bpf_attach_type type)
 249{
 250        __u32 __user *prog_ids = u64_to_user_ptr(attr->query.prog_ids);
 251        struct bpf_prog_array *run_array;
 252        u32 prog_cnt = 0, flags = 0;
 253
 254        run_array = rcu_dereference_protected(net->bpf.run_array[type],
 255                                              lockdep_is_held(&netns_bpf_mutex));
 256        if (run_array)
 257                prog_cnt = bpf_prog_array_length(run_array);
 258
 259        if (copy_to_user(&uattr->query.attach_flags, &flags, sizeof(flags)))
 260                return -EFAULT;
 261        if (copy_to_user(&uattr->query.prog_cnt, &prog_cnt, sizeof(prog_cnt)))
 262                return -EFAULT;
 263        if (!attr->query.prog_cnt || !prog_ids || !prog_cnt)
 264                return 0;
 265
 266        return bpf_prog_array_copy_to_user(run_array, prog_ids,
 267                                           attr->query.prog_cnt);
 268}
 269
 270int netns_bpf_prog_query(const union bpf_attr *attr,
 271                         union bpf_attr __user *uattr)
 272{
 273        enum netns_bpf_attach_type type;
 274        struct net *net;
 275        int ret;
 276
 277        if (attr->query.query_flags)
 278                return -EINVAL;
 279
 280        type = to_netns_bpf_attach_type(attr->query.attach_type);
 281        if (type < 0)
 282                return -EINVAL;
 283
 284        net = get_net_ns_by_fd(attr->query.target_fd);
 285        if (IS_ERR(net))
 286                return PTR_ERR(net);
 287
 288        mutex_lock(&netns_bpf_mutex);
 289        ret = __netns_bpf_prog_query(attr, uattr, net, type);
 290        mutex_unlock(&netns_bpf_mutex);
 291
 292        put_net(net);
 293        return ret;
 294}
 295
 296int netns_bpf_prog_attach(const union bpf_attr *attr, struct bpf_prog *prog)
 297{
 298        struct bpf_prog_array *run_array;
 299        enum netns_bpf_attach_type type;
 300        struct bpf_prog *attached;
 301        struct net *net;
 302        int ret;
 303
 304        if (attr->target_fd || attr->attach_flags || attr->replace_bpf_fd)
 305                return -EINVAL;
 306
 307        type = to_netns_bpf_attach_type(attr->attach_type);
 308        if (type < 0)
 309                return -EINVAL;
 310
 311        net = current->nsproxy->net_ns;
 312        mutex_lock(&netns_bpf_mutex);
 313
 314        /* Attaching prog directly is not compatible with links */
 315        if (!list_empty(&net->bpf.links[type])) {
 316                ret = -EEXIST;
 317                goto out_unlock;
 318        }
 319
 320        switch (type) {
 321        case NETNS_BPF_FLOW_DISSECTOR:
 322                ret = flow_dissector_bpf_prog_attach_check(net, prog);
 323                break;
 324        default:
 325                ret = -EINVAL;
 326                break;
 327        }
 328        if (ret)
 329                goto out_unlock;
 330
 331        attached = net->bpf.progs[type];
 332        if (attached == prog) {
 333                /* The same program cannot be attached twice */
 334                ret = -EINVAL;
 335                goto out_unlock;
 336        }
 337
 338        run_array = rcu_dereference_protected(net->bpf.run_array[type],
 339                                              lockdep_is_held(&netns_bpf_mutex));
 340        if (run_array) {
 341                WRITE_ONCE(run_array->items[0].prog, prog);
 342        } else {
 343                run_array = bpf_prog_array_alloc(1, GFP_KERNEL);
 344                if (!run_array) {
 345                        ret = -ENOMEM;
 346                        goto out_unlock;
 347                }
 348                run_array->items[0].prog = prog;
 349                rcu_assign_pointer(net->bpf.run_array[type], run_array);
 350        }
 351
 352        net->bpf.progs[type] = prog;
 353        if (attached)
 354                bpf_prog_put(attached);
 355
 356out_unlock:
 357        mutex_unlock(&netns_bpf_mutex);
 358
 359        return ret;
 360}
 361
 362/* Must be called with netns_bpf_mutex held. */
 363static int __netns_bpf_prog_detach(struct net *net,
 364                                   enum netns_bpf_attach_type type,
 365                                   struct bpf_prog *old)
 366{
 367        struct bpf_prog *attached;
 368
 369        /* Progs attached via links cannot be detached */
 370        if (!list_empty(&net->bpf.links[type]))
 371                return -EINVAL;
 372
 373        attached = net->bpf.progs[type];
 374        if (!attached || attached != old)
 375                return -ENOENT;
 376        netns_bpf_run_array_detach(net, type);
 377        net->bpf.progs[type] = NULL;
 378        bpf_prog_put(attached);
 379        return 0;
 380}
 381
 382int netns_bpf_prog_detach(const union bpf_attr *attr, enum bpf_prog_type ptype)
 383{
 384        enum netns_bpf_attach_type type;
 385        struct bpf_prog *prog;
 386        int ret;
 387
 388        if (attr->target_fd)
 389                return -EINVAL;
 390
 391        type = to_netns_bpf_attach_type(attr->attach_type);
 392        if (type < 0)
 393                return -EINVAL;
 394
 395        prog = bpf_prog_get_type(attr->attach_bpf_fd, ptype);
 396        if (IS_ERR(prog))
 397                return PTR_ERR(prog);
 398
 399        mutex_lock(&netns_bpf_mutex);
 400        ret = __netns_bpf_prog_detach(current->nsproxy->net_ns, type, prog);
 401        mutex_unlock(&netns_bpf_mutex);
 402
 403        bpf_prog_put(prog);
 404
 405        return ret;
 406}
 407
 408static int netns_bpf_max_progs(enum netns_bpf_attach_type type)
 409{
 410        switch (type) {
 411        case NETNS_BPF_FLOW_DISSECTOR:
 412                return 1;
 413        case NETNS_BPF_SK_LOOKUP:
 414                return 64;
 415        default:
 416                return 0;
 417        }
 418}
 419
 420static int netns_bpf_link_attach(struct net *net, struct bpf_link *link,
 421                                 enum netns_bpf_attach_type type)
 422{
 423        struct bpf_netns_link *net_link =
 424                container_of(link, struct bpf_netns_link, link);
 425        struct bpf_prog_array *run_array;
 426        int cnt, err;
 427
 428        mutex_lock(&netns_bpf_mutex);
 429
 430        cnt = link_count(net, type);
 431        if (cnt >= netns_bpf_max_progs(type)) {
 432                err = -E2BIG;
 433                goto out_unlock;
 434        }
 435        /* Links are not compatible with attaching prog directly */
 436        if (net->bpf.progs[type]) {
 437                err = -EEXIST;
 438                goto out_unlock;
 439        }
 440
 441        switch (type) {
 442        case NETNS_BPF_FLOW_DISSECTOR:
 443                err = flow_dissector_bpf_prog_attach_check(net, link->prog);
 444                break;
 445        case NETNS_BPF_SK_LOOKUP:
 446                err = 0; /* nothing to check */
 447                break;
 448        default:
 449                err = -EINVAL;
 450                break;
 451        }
 452        if (err)
 453                goto out_unlock;
 454
 455        run_array = bpf_prog_array_alloc(cnt + 1, GFP_KERNEL);
 456        if (!run_array) {
 457                err = -ENOMEM;
 458                goto out_unlock;
 459        }
 460
 461        list_add_tail(&net_link->node, &net->bpf.links[type]);
 462
 463        fill_prog_array(net, type, run_array);
 464        run_array = rcu_replace_pointer(net->bpf.run_array[type], run_array,
 465                                        lockdep_is_held(&netns_bpf_mutex));
 466        bpf_prog_array_free(run_array);
 467
 468        /* Mark attach point as used */
 469        netns_bpf_attach_type_need(type);
 470
 471out_unlock:
 472        mutex_unlock(&netns_bpf_mutex);
 473        return err;
 474}
 475
 476int netns_bpf_link_create(const union bpf_attr *attr, struct bpf_prog *prog)
 477{
 478        enum netns_bpf_attach_type netns_type;
 479        struct bpf_link_primer link_primer;
 480        struct bpf_netns_link *net_link;
 481        enum bpf_attach_type type;
 482        struct net *net;
 483        int err;
 484
 485        if (attr->link_create.flags)
 486                return -EINVAL;
 487
 488        type = attr->link_create.attach_type;
 489        netns_type = to_netns_bpf_attach_type(type);
 490        if (netns_type < 0)
 491                return -EINVAL;
 492
 493        net = get_net_ns_by_fd(attr->link_create.target_fd);
 494        if (IS_ERR(net))
 495                return PTR_ERR(net);
 496
 497        net_link = kzalloc(sizeof(*net_link), GFP_USER);
 498        if (!net_link) {
 499                err = -ENOMEM;
 500                goto out_put_net;
 501        }
 502        bpf_link_init(&net_link->link, BPF_LINK_TYPE_NETNS,
 503                      &bpf_netns_link_ops, prog);
 504        net_link->net = net;
 505        net_link->type = type;
 506        net_link->netns_type = netns_type;
 507
 508        err = bpf_link_prime(&net_link->link, &link_primer);
 509        if (err) {
 510                kfree(net_link);
 511                goto out_put_net;
 512        }
 513
 514        err = netns_bpf_link_attach(net, &net_link->link, netns_type);
 515        if (err) {
 516                bpf_link_cleanup(&link_primer);
 517                goto out_put_net;
 518        }
 519
 520        put_net(net);
 521        return bpf_link_settle(&link_primer);
 522
 523out_put_net:
 524        put_net(net);
 525        return err;
 526}
 527
 528static int __net_init netns_bpf_pernet_init(struct net *net)
 529{
 530        int type;
 531
 532        for (type = 0; type < MAX_NETNS_BPF_ATTACH_TYPE; type++)
 533                INIT_LIST_HEAD(&net->bpf.links[type]);
 534
 535        return 0;
 536}
 537
 538static void __net_exit netns_bpf_pernet_pre_exit(struct net *net)
 539{
 540        enum netns_bpf_attach_type type;
 541        struct bpf_netns_link *net_link;
 542
 543        mutex_lock(&netns_bpf_mutex);
 544        for (type = 0; type < MAX_NETNS_BPF_ATTACH_TYPE; type++) {
 545                netns_bpf_run_array_detach(net, type);
 546                list_for_each_entry(net_link, &net->bpf.links[type], node) {
 547                        net_link->net = NULL; /* auto-detach link */
 548                        netns_bpf_attach_type_unneed(type);
 549                }
 550                if (net->bpf.progs[type])
 551                        bpf_prog_put(net->bpf.progs[type]);
 552        }
 553        mutex_unlock(&netns_bpf_mutex);
 554}
 555
 556static struct pernet_operations netns_bpf_pernet_ops __net_initdata = {
 557        .init = netns_bpf_pernet_init,
 558        .pre_exit = netns_bpf_pernet_pre_exit,
 559};
 560
 561static int __init netns_bpf_init(void)
 562{
 563        return register_pernet_subsys(&netns_bpf_pernet_ops);
 564}
 565
 566subsys_initcall(netns_bpf_init);
 567