security/selinux/ss/sidtab.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Implementation of the SID table type.
   4  *
   5  * Original author: Stephen Smalley, <sds@tycho.nsa.gov>
   6  * Author: Ondrej Mosnacek, <omosnacek@gmail.com>
   7  *
   8  * Copyright (C) 2018 Red Hat, Inc.
   9  */
  10 #include <linux/errno.h>
  11 #include <linux/kernel.h>
  12 #include <linux/list.h>
  13 #include <linux/rcupdate.h>
  14 #include <linux/slab.h>
  15 #include <linux/sched.h>
  16 #include <linux/spinlock.h>
  17 #include <asm/barrier.h>
  18 #include "flask.h"
  19 #include "security.h"
  20 #include "sidtab.h"
  21
  22 struct sidtab_str_cache {
  23         struct rcu_head rcu_member;
  24         struct list_head lru_member;
  25         struct sidtab_entry *parent;
  26         u32 len;
  27         char str[];
  28 };
  29
  30 #define index_to_sid(index) (index + SECINITSID_NUM + 1)
  31 #define sid_to_index(sid) (sid - (SECINITSID_NUM + 1))
  32
  33 int sidtab_init(struct sidtab *s)
  34 {
  35         u32 i;
  36
  37         memset(s->roots, 0, sizeof(s->roots));
  38
  39         for (i = 0; i < SECINITSID_NUM; i++)
  40                 s->isids[i].set = 0;
  41
  42         s->count = 0;
  43         s->convert = NULL;
  44         hash_init(s->context_to_sid);
  45
  46         spin_lock_init(&s->lock);
  47
  48 #if CONFIG_SECURITY_SELINUX_SID2STR_CACHE_SIZE > 0
  49         s->cache_free_slots = CONFIG_SECURITY_SELINUX_SID2STR_CACHE_SIZE;
  50         INIT_LIST_HEAD(&s->cache_lru_list);
  51         spin_lock_init(&s->cache_lock);
  52 #endif
  53
  54         return 0;
  55 }
  56
  57 static u32 context_to_sid(struct sidtab *s, struct context *context)
  58 {
  59         struct sidtab_entry *entry;
  60         u32 sid = 0;
  61
  62         rcu_read_lock();
  63         hash_for_each_possible_rcu(s->context_to_sid, entry, list,
  64                                    context->hash) {
  65                 if (context_cmp(&entry->context, context)) {
  66                         sid = entry->sid;
  67                         break;
  68                 }
  69         }
  70         rcu_read_unlock();
  71         return sid;
  72 }
  73
  74 int sidtab_set_initial(struct sidtab *s, u32 sid, struct context *context)
  75 {
  76         struct sidtab_isid_entry *isid;
  77         int rc;
  78
  79         if (sid == 0 || sid > SECINITSID_NUM)
  80                 return -EINVAL;
  81
  82         isid = &s->isids[sid - 1];
  83
  84         rc = context_cpy(&isid->entry.context, context);
  85         if (rc)
  86                 return rc;
  87
  88 #if CONFIG_SECURITY_SELINUX_SID2STR_CACHE_SIZE > 0
  89         isid->entry.cache = NULL;
  90 #endif
  91         isid->set = 1;
  92
  93         /*
  94          * Multiple initial sids may map to the same context. Check that this
  95          * context is not already represented in the context_to_sid hashtable
  96          * to avoid duplicate entries and long linked lists upon hash
  97          * collision.
  98          */
  99         if (!context_to_sid(s, context)) {
 100                 isid->entry.sid = sid;
 101                 hash_add(s->context_to_sid, &isid->entry.list, context->hash);
 102         }
 103
 104         return 0;
 105 }
 106
 107 int sidtab_hash_stats(struct sidtab *sidtab, char *page)
 108 {
 109         int i;
 110         int chain_len = 0;
 111         int slots_used = 0;
 112         int entries = 0;
 113         int max_chain_len = 0;
 114         int cur_bucket = 0;
 115         struct sidtab_entry *entry;
 116
 117         rcu_read_lock();
 118         hash_for_each_rcu(sidtab->context_to_sid, i, entry, list) {
 119                 entries++;
 120                 if (i == cur_bucket) {
 121                         chain_len++;
 122                         if (chain_len == 1)
 123                                 slots_used++;
 124                 } else {
 125                         cur_bucket = i;
 126                         if (chain_len > max_chain_len)
 127                                 max_chain_len = chain_len;
 128                         chain_len = 0;
 129                 }
 130         }
 131         rcu_read_unlock();
 132
 133         if (chain_len > max_chain_len)
 134                 max_chain_len = chain_len;
 135
 136         return scnprintf(page, PAGE_SIZE, "entries: %d\nbuckets used: %d/%d\n"
 137                          "longest chain: %d\n", entries,
 138                          slots_used, SIDTAB_HASH_BUCKETS, max_chain_len);
 139 }
 140
 141 static u32 sidtab_level_from_count(u32 count)
 142 {
 143         u32 capacity = SIDTAB_LEAF_ENTRIES;
 144         u32 level = 0;
 145
 146         while (count > capacity) {
 147                 capacity <<= SIDTAB_INNER_SHIFT;
 148                 ++level;
 149         }
 150         return level;
 151 }
 152
 153 static int sidtab_alloc_roots(struct sidtab *s, u32 level)
 154 {
 155         u32 l;
 156
 157         if (!s->roots[0].ptr_leaf) {
 158                 s->roots[0].ptr_leaf = kzalloc(SIDTAB_NODE_ALLOC_SIZE,
 159                                                GFP_ATOMIC);
 160                 if (!s->roots[0].ptr_leaf)
 161                         return -ENOMEM;
 162         }
 163         for (l = 1; l <= level; ++l)
 164                 if (!s->roots[l].ptr_inner) {
 165                         s->roots[l].ptr_inner = kzalloc(SIDTAB_NODE_ALLOC_SIZE,
 166                                                         GFP_ATOMIC);
 167                         if (!s->roots[l].ptr_inner)
 168                                 return -ENOMEM;
 169                         s->roots[l].ptr_inner->entries[0] = s->roots[l - 1];
 170                 }
 171         return 0;
 172 }
 173
 174 static struct sidtab_entry *sidtab_do_lookup(struct sidtab *s, u32 index,
 175                                              int alloc)
 176 {
 177         union sidtab_entry_inner *entry;
 178         u32 level, capacity_shift, leaf_index = index / SIDTAB_LEAF_ENTRIES;
 179
 180         /* find the level of the subtree we need */
 181         level = sidtab_level_from_count(index + 1);
 182         capacity_shift = level * SIDTAB_INNER_SHIFT;
 183
 184         /* allocate roots if needed */
 185         if (alloc && sidtab_alloc_roots(s, level) != 0)
 186                 return NULL;
 187
 188         /* lookup inside the subtree */
 189         entry = &s->roots[level];
 190         while (level != 0) {
 191                 capacity_shift -= SIDTAB_INNER_SHIFT;
 192                 --level;
 193
 194                 entry = &entry->ptr_inner->entries[leaf_index >> capacity_shift];
 195                 leaf_index &= ((u32)1 << capacity_shift) - 1;
 196
 197                 if (!entry->ptr_inner) {
 198                         if (alloc)
 199                                 entry->ptr_inner = kzalloc(SIDTAB_NODE_ALLOC_SIZE,
 200                                                            GFP_ATOMIC);
 201                         if (!entry->ptr_inner)
 202                                 return NULL;
 203                 }
 204         }
 205         if (!entry->ptr_leaf) {
 206                 if (alloc)
 207                         entry->ptr_leaf = kzalloc(SIDTAB_NODE_ALLOC_SIZE,
 208                                                   GFP_ATOMIC);
 209                 if (!entry->ptr_leaf)
 210                         return NULL;
 211         }
 212         return &entry->ptr_leaf->entries[index % SIDTAB_LEAF_ENTRIES];
 213 }
 214
 215 static struct sidtab_entry *sidtab_lookup(struct sidtab *s, u32 index)
 216 {
 217         /* read entries only after reading count */
 218         u32 count = smp_load_acquire(&s->count);
 219
 220         if (index >= count)
 221                 return NULL;
 222
 223         return sidtab_do_lookup(s, index, 0);
 224 }
 225
 226 static struct sidtab_entry *sidtab_lookup_initial(struct sidtab *s, u32 sid)
 227 {
 228         return s->isids[sid - 1].set ? &s->isids[sid - 1].entry : NULL;
 229 }
 230
 231 static struct sidtab_entry *sidtab_search_core(struct sidtab *s, u32 sid,
 232                                                int force)
 233 {
 234         if (sid != 0) {
 235                 struct sidtab_entry *entry;
 236
 237                 if (sid > SECINITSID_NUM)
 238                         entry = sidtab_lookup(s, sid_to_index(sid));
 239                 else
 240                         entry = sidtab_lookup_initial(s, sid);
 241                 if (entry && (!entry->context.len || force))
 242                         return entry;
 243         }
 244
 245         return sidtab_lookup_initial(s, SECINITSID_UNLABELED);
 246 }
 247
 248 struct sidtab_entry *sidtab_search_entry(struct sidtab *s, u32 sid)
 249 {
 250         return sidtab_search_core(s, sid, 0);
 251 }
 252
 253 struct sidtab_entry *sidtab_search_entry_force(struct sidtab *s, u32 sid)
 254 {
 255         return sidtab_search_core(s, sid, 1);
 256 }
 257
 258 int sidtab_context_to_sid(struct sidtab *s, struct context *context,
 259                           u32 *sid)
 260 {
 261         unsigned long flags;
 262         u32 count;
 263         struct sidtab_convert_params *convert;
 264         struct sidtab_entry *dst, *dst_convert;
 265         int rc;
 266
 267         *sid = context_to_sid(s, context);
 268         if (*sid)
 269                 return 0;
 270
 271         /* lock-free search failed: lock, re-search, and insert if not found */
 272         spin_lock_irqsave(&s->lock, flags);
 273
 274         rc = 0;
 275         *sid = context_to_sid(s, context);
 276         if (*sid)
 277                 goto out_unlock;
 278
 279         /* read entries only after reading count */
 280         count = smp_load_acquire(&s->count);
 281         convert = s->convert;
 282
 283         /* bail out if we already reached max entries */
 284         rc = -EOVERFLOW;
 285         if (count >= SIDTAB_MAX)
 286                 goto out_unlock;
 287
 288         /* insert context into new entry */
 289         rc = -ENOMEM;
 290         dst = sidtab_do_lookup(s, count, 1);
 291         if (!dst)
 292                 goto out_unlock;
 293
 294         dst->sid = index_to_sid(count);
 295
 296         rc = context_cpy(&dst->context, context);
 297         if (rc)
 298                 goto out_unlock;
 299
 300         /*
 301          * if we are building a new sidtab, we need to convert the context
 302          * and insert it there as well
 303          */
 304         if (convert) {
 305                 rc = -ENOMEM;
 306                 dst_convert = sidtab_do_lookup(convert->target, count, 1);
 307                 if (!dst_convert) {
 308                         context_destroy(&dst->context);
 309                         goto out_unlock;
 310                 }
 311
 312                 rc = convert->func(context, &dst_convert->context,
 313                                    convert->args);
 314                 if (rc) {
 315                         context_destroy(&dst->context);
 316                         goto out_unlock;
 317                 }
 318                 dst_convert->sid = index_to_sid(count);
 319                 convert->target->count = count + 1;
 320
 321                 hash_add_rcu(convert->target->context_to_sid,
 322                              &dst_convert->list, dst_convert->context.hash);
 323         }
 324
 325         if (context->len)
 326                 pr_info("SELinux:  Context %s is not valid (left unmapped).\n",
 327                         context->str);
 328
 329         *sid = index_to_sid(count);
 330
 331         /* write entries before updating count */
 332         smp_store_release(&s->count, count + 1);
 333         hash_add_rcu(s->context_to_sid, &dst->list, dst->context.hash);
 334
 335         rc = 0;
 336 out_unlock:
 337         spin_unlock_irqrestore(&s->lock, flags);
 338         return rc;
 339 }
 340
 341 static void sidtab_convert_hashtable(struct sidtab *s, u32 count)
 342 {
 343         struct sidtab_entry *entry;
 344         u32 i;
 345
 346         for (i = 0; i < count; i++) {
 347                 entry = sidtab_do_lookup(s, i, 0);
 348                 entry->sid = index_to_sid(i);
 349
 350                 hash_add_rcu(s->context_to_sid, &entry->list,
 351                              entry->context.hash);
 352
 353         }
 354 }
 355
 356 static int sidtab_convert_tree(union sidtab_entry_inner *edst,
 357                                union sidtab_entry_inner *esrc,
 358                                u32 *pos, u32 count, u32 level,
 359                                struct sidtab_convert_params *convert)
 360 {
 361         int rc;
 362         u32 i;
 363
 364         if (level != 0) {
 365                 if (!edst->ptr_inner) {
 366                         edst->ptr_inner = kzalloc(SIDTAB_NODE_ALLOC_SIZE,
 367                                                   GFP_KERNEL);
 368                         if (!edst->ptr_inner)
 369                                 return -ENOMEM;
 370                 }
 371                 i = 0;
 372                 while (i < SIDTAB_INNER_ENTRIES && *pos < count) {
 373                         rc = sidtab_convert_tree(&edst->ptr_inner->entries[i],
 374                                                  &esrc->ptr_inner->entries[i],
 375                                                  pos, count, level - 1,
 376                                                  convert);
 377                         if (rc)
 378                                 return rc;
 379                         i++;
 380                 }
 381         } else {
 382                 if (!edst->ptr_leaf) {
 383                         edst->ptr_leaf = kzalloc(SIDTAB_NODE_ALLOC_SIZE,
 384                                                  GFP_KERNEL);
 385                         if (!edst->ptr_leaf)
 386                                 return -ENOMEM;
 387                 }
 388                 i = 0;
 389                 while (i < SIDTAB_LEAF_ENTRIES && *pos < count) {
 390                         rc = convert->func(&esrc->ptr_leaf->entries[i].context,
 391                                            &edst->ptr_leaf->entries[i].context,
 392                                            convert->args);
 393                         if (rc)
 394                                 return rc;
 395                         (*pos)++;
 396                         i++;
 397                 }
 398                 cond_resched();
 399         }
 400         return 0;
 401 }
 402
 403 int sidtab_convert(struct sidtab *s, struct sidtab_convert_params *params)
 404 {
 405         unsigned long flags;
 406         u32 count, level, pos;
 407         int rc;
 408
 409         spin_lock_irqsave(&s->lock, flags);
 410
 411         /* concurrent policy loads are not allowed */
 412         if (s->convert) {
 413                 spin_unlock_irqrestore(&s->lock, flags);
 414                 return -EBUSY;
 415         }
 416
 417         count = s->count;
 418         level = sidtab_level_from_count(count);
 419
 420         /* allocate last leaf in the new sidtab (to avoid race with
 421          * live convert)
 422          */
 423         rc = sidtab_do_lookup(params->target, count - 1, 1) ? 0 : -ENOMEM;
 424         if (rc) {
 425                 spin_unlock_irqrestore(&s->lock, flags);
 426                 return rc;
 427         }
 428
 429         /* set count in case no new entries are added during conversion */
 430         params->target->count = count;
 431
 432         /* enable live convert of new entries */
 433         s->convert = params;
 434
 435         /* we can safely convert the tree outside the lock */
 436         spin_unlock_irqrestore(&s->lock, flags);
 437
 438         pr_info("SELinux:  Converting %u SID table entries...\n", count);
 439
 440         /* convert all entries not covered by live convert */
 441         pos = 0;
 442         rc = sidtab_convert_tree(&params->target->roots[level],
 443                                  &s->roots[level], &pos, count, level, params);
 444         if (rc) {
 445                 /* we need to keep the old table - disable live convert */
 446                 spin_lock_irqsave(&s->lock, flags);
 447                 s->convert = NULL;
 448                 spin_unlock_irqrestore(&s->lock, flags);
 449                 return rc;
 450         }
 451         /*
 452          * The hashtable can also be modified in sidtab_context_to_sid()
 453          * so we must re-acquire the lock here.
 454          */
 455         spin_lock_irqsave(&s->lock, flags);
 456         sidtab_convert_hashtable(params->target, count);
 457         spin_unlock_irqrestore(&s->lock, flags);
 458
 459         return 0;
 460 }
 461
 462 static void sidtab_destroy_entry(struct sidtab_entry *entry)
 463 {
 464         context_destroy(&entry->context);
 465 #if CONFIG_SECURITY_SELINUX_SID2STR_CACHE_SIZE > 0
 466         kfree(rcu_dereference_raw(entry->cache));
 467 #endif
 468 }
 469
 470 static void sidtab_destroy_tree(union sidtab_entry_inner entry, u32 level)
 471 {
 472         u32 i;
 473
 474         if (level != 0) {
 475                 struct sidtab_node_inner *node = entry.ptr_inner;
 476
 477                 if (!node)
 478                         return;
 479
 480                 for (i = 0; i < SIDTAB_INNER_ENTRIES; i++)
 481                         sidtab_destroy_tree(node->entries[i], level - 1);
 482                 kfree(node);
 483         } else {
 484                 struct sidtab_node_leaf *node = entry.ptr_leaf;
 485
 486                 if (!node)
 487                         return;
 488
 489                 for (i = 0; i < SIDTAB_LEAF_ENTRIES; i++)
 490                         sidtab_destroy_entry(&node->entries[i]);
 491                 kfree(node);
 492         }
 493 }
 494
 495 void sidtab_destroy(struct sidtab *s)
 496 {
 497         u32 i, level;
 498
 499         for (i = 0; i < SECINITSID_NUM; i++)
 500                 if (s->isids[i].set)
 501                         sidtab_destroy_entry(&s->isids[i].entry);
 502
 503         level = SIDTAB_MAX_LEVEL;
 504         while (level && !s->roots[level].ptr_inner)
 505                 --level;
 506
 507         sidtab_destroy_tree(s->roots[level], level);
 508         /*
 509          * The context_to_sid hashtable's objects are all shared
 510          * with the isids array and context tree, and so don't need
 511          * to be cleaned up here.
 512          */
 513 }
 514
 515 #if CONFIG_SECURITY_SELINUX_SID2STR_CACHE_SIZE > 0
 516
 517 void sidtab_sid2str_put(struct sidtab *s, struct sidtab_entry *entry,
 518                         const char *str, u32 str_len)
 519 {
 520         struct sidtab_str_cache *cache, *victim = NULL;
 521         unsigned long flags;
 522
 523         /* do not cache invalid contexts */
 524         if (entry->context.len)
 525                 return;
 526
 527         spin_lock_irqsave(&s->cache_lock, flags);
 528
 529         cache = rcu_dereference_protected(entry->cache,
 530                                           lockdep_is_held(&s->cache_lock));
 531         if (cache) {
 532                 /* entry in cache - just bump to the head of LRU list */
 533                 list_move(&cache->lru_member, &s->cache_lru_list);
 534                 goto out_unlock;
 535         }
 536
 537         cache = kmalloc(sizeof(struct sidtab_str_cache) + str_len, GFP_ATOMIC);
 538         if (!cache)
 539                 goto out_unlock;
 540
 541         if (s->cache_free_slots == 0) {
 542                 /* pop a cache entry from the tail and free it */
 543                 victim = container_of(s->cache_lru_list.prev,
 544                                       struct sidtab_str_cache, lru_member);
 545                 list_del(&victim->lru_member);
 546                 rcu_assign_pointer(victim->parent->cache, NULL);
 547         } else {
 548                 s->cache_free_slots--;
 549         }
 550         cache->parent = entry;
 551         cache->len = str_len;
 552         memcpy(cache->str, str, str_len);
 553         list_add(&cache->lru_member, &s->cache_lru_list);
 554
 555         rcu_assign_pointer(entry->cache, cache);
 556
 557 out_unlock:
 558         spin_unlock_irqrestore(&s->cache_lock, flags);
 559         kfree_rcu(victim, rcu_member);
 560 }
 561
 562 int sidtab_sid2str_get(struct sidtab *s, struct sidtab_entry *entry,
 563                        char **out, u32 *out_len)
 564 {
 565         struct sidtab_str_cache *cache;
 566         int rc = 0;
 567
 568         if (entry->context.len)
 569                 return -ENOENT; /* do not cache invalid contexts */
 570
 571         rcu_read_lock();
 572
 573         cache = rcu_dereference(entry->cache);
 574         if (!cache) {
 575                 rc = -ENOENT;
 576         } else {
 577                 *out_len = cache->len;
 578                 if (out) {
 579                         *out = kmemdup(cache->str, cache->len, GFP_ATOMIC);
 580                         if (!*out)
 581                                 rc = -ENOMEM;
 582                 }
 583         }
 584
 585         rcu_read_unlock();
 586
 587         if (!rc && out)
 588                 sidtab_sid2str_put(s, entry, *out, *out_len);
 589         return rc;
 590 }
 591
 592 #endif /* CONFIG_SECURITY_SELINUX_SID2STR_CACHE_SIZE > 0 */