security/selinux/avc.c

   1 /*
   2  * Implementation of the kernel access vector cache (AVC).
   3  *
   4  * Authors:  Stephen Smalley, <sds@epoch.ncsc.mil>
   5  *           James Morris <jmorris@redhat.com>
   6  *
   7  * Update:   KaiGai, Kohei <kaigai@ak.jp.nec.com>
   8  *      Replaced the avc_lock spinlock by RCU.
   9  *
  10  * Copyright (C) 2003 Red Hat, Inc., James Morris <jmorris@redhat.com>
  11  *
  12  *      This program is free software; you can redistribute it and/or modify
  13  *      it under the terms of the GNU General Public License version 2,
  14  *      as published by the Free Software Foundation.
  15  */
  16 #include <linux/types.h>
  17 #include <linux/stddef.h>
  18 #include <linux/kernel.h>
  19 #include <linux/slab.h>
  20 #include <linux/fs.h>
  21 #include <linux/dcache.h>
  22 #include <linux/init.h>
  23 #include <linux/skbuff.h>
  24 #include <linux/percpu.h>
  25 #include <net/sock.h>
  26 #include <linux/un.h>
  27 #include <net/af_unix.h>
  28 #include <linux/ip.h>
  29 #include <linux/audit.h>
  30 #include <linux/ipv6.h>
  31 #include <net/ipv6.h>
  32 #include "avc.h"
  33 #include "avc_ss.h"
  34 #include "classmap.h"
  35
  36 #define AVC_CACHE_SLOTS                 512
  37 #define AVC_DEF_CACHE_THRESHOLD         512
  38 #define AVC_CACHE_RECLAIM               16
  39
  40 #ifdef CONFIG_SECURITY_SELINUX_AVC_STATS
  41 #define avc_cache_stats_incr(field)                             \
  42 do {                                                            \
  43         per_cpu(avc_cache_stats, get_cpu()).field++;            \
  44         put_cpu();                                              \
  45 } while (0)
  46 #else
  47 #define avc_cache_stats_incr(field)     do {} while (0)
  48 #endif
  49
  50 struct avc_entry {
  51         u32                     ssid;
  52         u32                     tsid;
  53         u16                     tclass;
  54         struct av_decision      avd;
  55 };
  56
  57 struct avc_node {
  58         struct avc_entry        ae;
  59         struct hlist_node       list; /* anchored in avc_cache->slots[i] */
  60         struct rcu_head         rhead;
  61 };
  62
  63 struct avc_cache {
  64         struct hlist_head       slots[AVC_CACHE_SLOTS]; /* head for avc_node->list */
  65         spinlock_t              slots_lock[AVC_CACHE_SLOTS]; /* lock for writes */
  66         atomic_t                lru_hint;       /* LRU hint for reclaim scan */
  67         atomic_t                active_nodes;
  68         u32                     latest_notif;   /* latest revocation notification */
  69 };
  70
  71 struct avc_callback_node {
  72         int (*callback) (u32 event, u32 ssid, u32 tsid,
  73                          u16 tclass, u32 perms,
  74                          u32 *out_retained);
  75         u32 events;
  76         u32 ssid;
  77         u32 tsid;
  78         u16 tclass;
  79         u32 perms;
  80         struct avc_callback_node *next;
  81 };
  82
  83 /* Exported via selinufs */
  84 unsigned int avc_cache_threshold = AVC_DEF_CACHE_THRESHOLD;
  85
  86 #ifdef CONFIG_SECURITY_SELINUX_AVC_STATS
  87 DEFINE_PER_CPU(struct avc_cache_stats, avc_cache_stats) = { 0 };
  88 #endif
  89
  90 static struct avc_cache avc_cache;
  91 static struct avc_callback_node *avc_callbacks;
  92 static struct kmem_cache *avc_node_cachep;
  93
  94 static inline int avc_hash(u32 ssid, u32 tsid, u16 tclass)
  95 {
  96         return (ssid ^ (tsid<<2) ^ (tclass<<4)) & (AVC_CACHE_SLOTS - 1);
  97 }
  98
  99 /**
 100  * avc_dump_av - Display an access vector in human-readable form.
 101  * @tclass: target security class
 102  * @av: access vector
 103  */
 104 static void avc_dump_av(struct audit_buffer *ab, u16 tclass, u32 av)
 105 {
 106         const char **perms;
 107         int i, perm;
 108
 109         if (av == 0) {
 110                 audit_log_format(ab, " null");
 111                 return;
 112         }
 113
 114         perms = secclass_map[tclass-1].perms;
 115
 116         audit_log_format(ab, " {");
 117         i = 0;
 118         perm = 1;
 119         while (i < (sizeof(av) * 8)) {
 120                 if ((perm & av) && perms[i]) {
 121                         audit_log_format(ab, " %s", perms[i]);
 122                         av &= ~perm;
 123                 }
 124                 i++;
 125                 perm <<= 1;
 126         }
 127
 128         if (av)
 129                 audit_log_format(ab, " 0x%x", av);
 130
 131         audit_log_format(ab, " }");
 132 }
 133
 134 /**
 135  * avc_dump_query - Display a SID pair and a class in human-readable form.
 136  * @ssid: source security identifier
 137  * @tsid: target security identifier
 138  * @tclass: target security class
 139  */
 140 static void avc_dump_query(struct audit_buffer *ab, u32 ssid, u32 tsid, u16 tclass)
 141 {
 142         int rc;
 143         char *scontext;
 144         u32 scontext_len;
 145
 146         rc = security_sid_to_context(ssid, &scontext, &scontext_len);
 147         if (rc)
 148                 audit_log_format(ab, "ssid=%d", ssid);
 149         else {
 150                 audit_log_format(ab, "scontext=%s", scontext);
 151                 kfree(scontext);
 152         }
 153
 154         rc = security_sid_to_context(tsid, &scontext, &scontext_len);
 155         if (rc)
 156                 audit_log_format(ab, " tsid=%d", tsid);
 157         else {
 158                 audit_log_format(ab, " tcontext=%s", scontext);
 159                 kfree(scontext);
 160         }
 161
 162         BUG_ON(tclass >= ARRAY_SIZE(secclass_map));
 163         audit_log_format(ab, " tclass=%s", secclass_map[tclass-1].name);
 164 }
 165
 166 /**
 167  * avc_init - Initialize the AVC.
 168  *
 169  * Initialize the access vector cache.
 170  */
 171 void __init avc_init(void)
 172 {
 173         int i;
 174
 175         for (i = 0; i < AVC_CACHE_SLOTS; i++) {
 176                 INIT_HLIST_HEAD(&avc_cache.slots[i]);
 177                 spin_lock_init(&avc_cache.slots_lock[i]);
 178         }
 179         atomic_set(&avc_cache.active_nodes, 0);
 180         atomic_set(&avc_cache.lru_hint, 0);
 181
 182         avc_node_cachep = kmem_cache_create("avc_node", sizeof(struct avc_node),
 183                                              0, SLAB_PANIC, NULL);
 184
 185         audit_log(current->audit_context, GFP_KERNEL, AUDIT_KERNEL, "AVC INITIALIZED\n");
 186 }
 187
 188 int avc_get_hash_stats(char *page)
 189 {
 190         int i, chain_len, max_chain_len, slots_used;
 191         struct avc_node *node;
 192         struct hlist_head *head;
 193
 194         rcu_read_lock();
 195
 196         slots_used = 0;
 197         max_chain_len = 0;
 198         for (i = 0; i < AVC_CACHE_SLOTS; i++) {
 199                 head = &avc_cache.slots[i];
 200                 if (!hlist_empty(head)) {
 201                         struct hlist_node *next;
 202
 203                         slots_used++;
 204                         chain_len = 0;
 205                         hlist_for_each_entry_rcu(node, next, head, list)
 206                                 chain_len++;
 207                         if (chain_len > max_chain_len)
 208                                 max_chain_len = chain_len;
 209                 }
 210         }
 211
 212         rcu_read_unlock();
 213
 214         return scnprintf(page, PAGE_SIZE, "entries: %d\nbuckets used: %d/%d\n"
 215                          "longest chain: %d\n",
 216                          atomic_read(&avc_cache.active_nodes),
 217                          slots_used, AVC_CACHE_SLOTS, max_chain_len);
 218 }
 219
 220 static void avc_node_free(struct rcu_head *rhead)
 221 {
 222         struct avc_node *node = container_of(rhead, struct avc_node, rhead);
 223         kmem_cache_free(avc_node_cachep, node);
 224         avc_cache_stats_incr(frees);
 225 }
 226
 227 static void avc_node_delete(struct avc_node *node)
 228 {
 229         hlist_del_rcu(&node->list);
 230         call_rcu(&node->rhead, avc_node_free);
 231         atomic_dec(&avc_cache.active_nodes);
 232 }
 233
 234 static void avc_node_kill(struct avc_node *node)
 235 {
 236         kmem_cache_free(avc_node_cachep, node);
 237         avc_cache_stats_incr(frees);
 238         atomic_dec(&avc_cache.active_nodes);
 239 }
 240
 241 static void avc_node_replace(struct avc_node *new, struct avc_node *old)
 242 {
 243         hlist_replace_rcu(&old->list, &new->list);
 244         call_rcu(&old->rhead, avc_node_free);
 245         atomic_dec(&avc_cache.active_nodes);
 246 }
 247
 248 static inline int avc_reclaim_node(void)
 249 {
 250         struct avc_node *node;
 251         int hvalue, try, ecx;
 252         unsigned long flags;
 253         struct hlist_head *head;
 254         struct hlist_node *next;
 255         spinlock_t *lock;
 256
 257         for (try = 0, ecx = 0; try < AVC_CACHE_SLOTS; try++) {
 258                 hvalue = atomic_inc_return(&avc_cache.lru_hint) & (AVC_CACHE_SLOTS - 1);
 259                 head = &avc_cache.slots[hvalue];
 260                 lock = &avc_cache.slots_lock[hvalue];
 261
 262                 if (!spin_trylock_irqsave(lock, flags))
 263                         continue;
 264
 265                 rcu_read_lock();
 266                 hlist_for_each_entry(node, next, head, list) {
 267                         avc_node_delete(node);
 268                         avc_cache_stats_incr(reclaims);
 269                         ecx++;
 270                         if (ecx >= AVC_CACHE_RECLAIM) {
 271                                 rcu_read_unlock();
 272                                 spin_unlock_irqrestore(lock, flags);
 273                                 goto out;
 274                         }
 275                 }
 276                 rcu_read_unlock();
 277                 spin_unlock_irqrestore(lock, flags);
 278         }
 279 out:
 280         return ecx;
 281 }
 282
 283 static struct avc_node *avc_alloc_node(void)
 284 {
 285         struct avc_node *node;
 286
 287         node = kmem_cache_zalloc(avc_node_cachep, GFP_ATOMIC);
 288         if (!node)
 289                 goto out;
 290
 291         INIT_RCU_HEAD(&node->rhead);
 292         INIT_HLIST_NODE(&node->list);
 293         avc_cache_stats_incr(allocations);
 294
 295         if (atomic_inc_return(&avc_cache.active_nodes) > avc_cache_threshold)
 296                 avc_reclaim_node();
 297
 298 out:
 299         return node;
 300 }
 301
 302 static void avc_node_populate(struct avc_node *node, u32 ssid, u32 tsid, u16 tclass, struct av_decision *avd)
 303 {
 304         node->ae.ssid = ssid;
 305         node->ae.tsid = tsid;
 306         node->ae.tclass = tclass;
 307         memcpy(&node->ae.avd, avd, sizeof(node->ae.avd));
 308 }
 309
 310 static inline struct avc_node *avc_search_node(u32 ssid, u32 tsid, u16 tclass)
 311 {
 312         struct avc_node *node, *ret = NULL;
 313         int hvalue;
 314         struct hlist_head *head;
 315         struct hlist_node *next;
 316
 317         hvalue = avc_hash(ssid, tsid, tclass);
 318         head = &avc_cache.slots[hvalue];
 319         hlist_for_each_entry_rcu(node, next, head, list) {
 320                 if (ssid == node->ae.ssid &&
 321                     tclass == node->ae.tclass &&
 322                     tsid == node->ae.tsid) {
 323                         ret = node;
 324                         break;
 325                 }
 326         }
 327
 328         return ret;
 329 }
 330
 331 /**
 332  * avc_lookup - Look up an AVC entry.
 333  * @ssid: source security identifier
 334  * @tsid: target security identifier
 335  * @tclass: target security class
 336  *
 337  * Look up an AVC entry that is valid for the
 338  * (@ssid, @tsid), interpreting the permissions
 339  * based on @tclass.  If a valid AVC entry exists,
 340  * then this function return the avc_node.
 341  * Otherwise, this function returns NULL.
 342  */
 343 static struct avc_node *avc_lookup(u32 ssid, u32 tsid, u16 tclass)
 344 {
 345         struct avc_node *node;
 346
 347         avc_cache_stats_incr(lookups);
 348         node = avc_search_node(ssid, tsid, tclass);
 349
 350         if (node)
 351                 avc_cache_stats_incr(hits);
 352         else
 353                 avc_cache_stats_incr(misses);
 354
 355         return node;
 356 }
 357
 358 static int avc_latest_notif_update(int seqno, int is_insert)
 359 {
 360         int ret = 0;
 361         static DEFINE_SPINLOCK(notif_lock);
 362         unsigned long flag;
 363
 364         spin_lock_irqsave(&notif_lock, flag);
 365         if (is_insert) {
 366                 if (seqno < avc_cache.latest_notif) {
 367                         printk(KERN_WARNING "SELinux: avc:  seqno %d < latest_notif %d\n",
 368                                seqno, avc_cache.latest_notif);
 369                         ret = -EAGAIN;
 370                 }
 371         } else {
 372                 if (seqno > avc_cache.latest_notif)
 373                         avc_cache.latest_notif = seqno;
 374         }
 375         spin_unlock_irqrestore(&notif_lock, flag);
 376
 377         return ret;
 378 }
 379
 380 /**
 381  * avc_insert - Insert an AVC entry.
 382  * @ssid: source security identifier
 383  * @tsid: target security identifier
 384  * @tclass: target security class
 385  * @avd: resulting av decision
 386  *
 387  * Insert an AVC entry for the SID pair
 388  * (@ssid, @tsid) and class @tclass.
 389  * The access vectors and the sequence number are
 390  * normally provided by the security server in
 391  * response to a security_compute_av() call.  If the
 392  * sequence number @avd->seqno is not less than the latest
 393  * revocation notification, then the function copies
 394  * the access vectors into a cache entry, returns
 395  * avc_node inserted. Otherwise, this function returns NULL.
 396  */
 397 static struct avc_node *avc_insert(u32 ssid, u32 tsid, u16 tclass, struct av_decision *avd)
 398 {
 399         struct avc_node *pos, *node = NULL;
 400         int hvalue;
 401         unsigned long flag;
 402
 403         if (avc_latest_notif_update(avd->seqno, 1))
 404                 goto out;
 405
 406         node = avc_alloc_node();
 407         if (node) {
 408                 struct hlist_head *head;
 409                 struct hlist_node *next;
 410                 spinlock_t *lock;
 411
 412                 hvalue = avc_hash(ssid, tsid, tclass);
 413                 avc_node_populate(node, ssid, tsid, tclass, avd);
 414
 415                 head = &avc_cache.slots[hvalue];
 416                 lock = &avc_cache.slots_lock[hvalue];
 417
 418                 spin_lock_irqsave(lock, flag);
 419                 hlist_for_each_entry(pos, next, head, list) {
 420                         if (pos->ae.ssid == ssid &&
 421                             pos->ae.tsid == tsid &&
 422                             pos->ae.tclass == tclass) {
 423                                 avc_node_replace(node, pos);
 424                                 goto found;
 425                         }
 426                 }
 427                 hlist_add_head_rcu(&node->list, head);
 428 found:
 429                 spin_unlock_irqrestore(lock, flag);
 430         }
 431 out:
 432         return node;
 433 }
 434
 435 /**
 436  * avc_audit_pre_callback - SELinux specific information
 437  * will be called by generic audit code
 438  * @ab: the audit buffer
 439  * @a: audit_data
 440  */
 441 static void avc_audit_pre_callback(struct audit_buffer *ab, void *a)
 442 {
 443         struct common_audit_data *ad = a;
 444         audit_log_format(ab, "avc:  %s ",
 445                          ad->selinux_audit_data.denied ? "denied" : "granted");
 446         avc_dump_av(ab, ad->selinux_audit_data.tclass,
 447                         ad->selinux_audit_data.audited);
 448         audit_log_format(ab, " for ");
 449 }
 450
 451 /**
 452  * avc_audit_post_callback - SELinux specific information
 453  * will be called by generic audit code
 454  * @ab: the audit buffer
 455  * @a: audit_data
 456  */
 457 static void avc_audit_post_callback(struct audit_buffer *ab, void *a)
 458 {
 459         struct common_audit_data *ad = a;
 460         audit_log_format(ab, " ");
 461         avc_dump_query(ab, ad->selinux_audit_data.ssid,
 462                            ad->selinux_audit_data.tsid,
 463                            ad->selinux_audit_data.tclass);
 464 }
 465
 466 /**
 467  * avc_audit - Audit the granting or denial of permissions.
 468  * @ssid: source security identifier
 469  * @tsid: target security identifier
 470  * @tclass: target security class
 471  * @requested: requested permissions
 472  * @avd: access vector decisions
 473  * @result: result from avc_has_perm_noaudit
 474  * @a:  auxiliary audit data
 475  *
 476  * Audit the granting or denial of permissions in accordance
 477  * with the policy.  This function is typically called by
 478  * avc_has_perm() after a permission check, but can also be
 479  * called directly by callers who use avc_has_perm_noaudit()
 480  * in order to separate the permission check from the auditing.
 481  * For example, this separation is useful when the permission check must
 482  * be performed under a lock, to allow the lock to be released
 483  * before calling the auditing code.
 484  */
 485 void avc_audit(u32 ssid, u32 tsid,
 486                u16 tclass, u32 requested,
 487                struct av_decision *avd, int result, struct common_audit_data *a)
 488 {
 489         struct common_audit_data stack_data;
 490         u32 denied, audited;
 491         denied = requested & ~avd->allowed;
 492         if (denied) {
 493                 audited = denied;
 494                 if (!(audited & avd->auditdeny))
 495                         return;
 496         } else if (result) {
 497                 audited = denied = requested;
 498         } else {
 499                 audited = requested;
 500                 if (!(audited & avd->auditallow))
 501                         return;
 502         }
 503         if (!a) {
 504                 a = &stack_data;
 505                 memset(a, 0, sizeof(*a));
 506                 a->type = LSM_AUDIT_NO_AUDIT;
 507         }
 508         a->selinux_audit_data.tclass = tclass;
 509         a->selinux_audit_data.requested = requested;
 510         a->selinux_audit_data.ssid = ssid;
 511         a->selinux_audit_data.tsid = tsid;
 512         a->selinux_audit_data.audited = audited;
 513         a->selinux_audit_data.denied = denied;
 514         a->lsm_pre_audit = avc_audit_pre_callback;
 515         a->lsm_post_audit = avc_audit_post_callback;
 516         common_lsm_audit(a);
 517 }
 518
 519 /**
 520  * avc_add_callback - Register a callback for security events.
 521  * @callback: callback function
 522  * @events: security events
 523  * @ssid: source security identifier or %SECSID_WILD
 524  * @tsid: target security identifier or %SECSID_WILD
 525  * @tclass: target security class
 526  * @perms: permissions
 527  *
 528  * Register a callback function for events in the set @events
 529  * related to the SID pair (@ssid, @tsid) and
 530  * and the permissions @perms, interpreting
 531  * @perms based on @tclass.  Returns %0 on success or
 532  * -%ENOMEM if insufficient memory exists to add the callback.
 533  */
 534 int avc_add_callback(int (*callback)(u32 event, u32 ssid, u32 tsid,
 535                                      u16 tclass, u32 perms,
 536                                      u32 *out_retained),
 537                      u32 events, u32 ssid, u32 tsid,
 538                      u16 tclass, u32 perms)
 539 {
 540         struct avc_callback_node *c;
 541         int rc = 0;
 542
 543         c = kmalloc(sizeof(*c), GFP_ATOMIC);
 544         if (!c) {
 545                 rc = -ENOMEM;
 546                 goto out;
 547         }
 548
 549         c->callback = callback;
 550         c->events = events;
 551         c->ssid = ssid;
 552         c->tsid = tsid;
 553         c->perms = perms;
 554         c->next = avc_callbacks;
 555         avc_callbacks = c;
 556 out:
 557         return rc;
 558 }
 559
 560 static inline int avc_sidcmp(u32 x, u32 y)
 561 {
 562         return (x == y || x == SECSID_WILD || y == SECSID_WILD);
 563 }
 564
 565 /**
 566  * avc_update_node Update an AVC entry
 567  * @event : Updating event
 568  * @perms : Permission mask bits
 569  * @ssid,@tsid,@tclass : identifier of an AVC entry
 570  * @seqno : sequence number when decision was made
 571  *
 572  * if a valid AVC entry doesn't exist,this function returns -ENOENT.
 573  * if kmalloc() called internal returns NULL, this function returns -ENOMEM.
 574  * otherwise, this function update the AVC entry. The original AVC-entry object
 575  * will release later by RCU.
 576  */
 577 static int avc_update_node(u32 event, u32 perms, u32 ssid, u32 tsid, u16 tclass,
 578                            u32 seqno)
 579 {
 580         int hvalue, rc = 0;
 581         unsigned long flag;
 582         struct avc_node *pos, *node, *orig = NULL;
 583         struct hlist_head *head;
 584         struct hlist_node *next;
 585         spinlock_t *lock;
 586
 587         node = avc_alloc_node();
 588         if (!node) {
 589                 rc = -ENOMEM;
 590                 goto out;
 591         }
 592
 593         /* Lock the target slot */
 594         hvalue = avc_hash(ssid, tsid, tclass);
 595
 596         head = &avc_cache.slots[hvalue];
 597         lock = &avc_cache.slots_lock[hvalue];
 598
 599         spin_lock_irqsave(lock, flag);
 600
 601         hlist_for_each_entry(pos, next, head, list) {
 602                 if (ssid == pos->ae.ssid &&
 603                     tsid == pos->ae.tsid &&
 604                     tclass == pos->ae.tclass &&
 605                     seqno == pos->ae.avd.seqno){
 606                         orig = pos;
 607                         break;
 608                 }
 609         }
 610
 611         if (!orig) {
 612                 rc = -ENOENT;
 613                 avc_node_kill(node);
 614                 goto out_unlock;
 615         }
 616
 617         /*
 618          * Copy and replace original node.
 619          */
 620
 621         avc_node_populate(node, ssid, tsid, tclass, &orig->ae.avd);
 622
 623         switch (event) {
 624         case AVC_CALLBACK_GRANT:
 625                 node->ae.avd.allowed |= perms;
 626                 break;
 627         case AVC_CALLBACK_TRY_REVOKE:
 628         case AVC_CALLBACK_REVOKE:
 629                 node->ae.avd.allowed &= ~perms;
 630                 break;
 631         case AVC_CALLBACK_AUDITALLOW_ENABLE:
 632                 node->ae.avd.auditallow |= perms;
 633                 break;
 634         case AVC_CALLBACK_AUDITALLOW_DISABLE:
 635                 node->ae.avd.auditallow &= ~perms;
 636                 break;
 637         case AVC_CALLBACK_AUDITDENY_ENABLE:
 638                 node->ae.avd.auditdeny |= perms;
 639                 break;
 640         case AVC_CALLBACK_AUDITDENY_DISABLE:
 641                 node->ae.avd.auditdeny &= ~perms;
 642                 break;
 643         }
 644         avc_node_replace(node, orig);
 645 out_unlock:
 646         spin_unlock_irqrestore(lock, flag);
 647 out:
 648         return rc;
 649 }
 650
 651 /**
 652  * avc_flush - Flush the cache
 653  */
 654 static void avc_flush(void)
 655 {
 656         struct hlist_head *head;
 657         struct hlist_node *next;
 658         struct avc_node *node;
 659         spinlock_t *lock;
 660         unsigned long flag;
 661         int i;
 662
 663         for (i = 0; i < AVC_CACHE_SLOTS; i++) {
 664                 head = &avc_cache.slots[i];
 665                 lock = &avc_cache.slots_lock[i];
 666
 667                 spin_lock_irqsave(lock, flag);
 668                 /*
 669                  * With preemptable RCU, the outer spinlock does not
 670                  * prevent RCU grace periods from ending.
 671                  */
 672                 rcu_read_lock();
 673                 hlist_for_each_entry(node, next, head, list)
 674                         avc_node_delete(node);
 675                 rcu_read_unlock();
 676                 spin_unlock_irqrestore(lock, flag);
 677         }
 678 }
 679
 680 /**
 681  * avc_ss_reset - Flush the cache and revalidate migrated permissions.
 682  * @seqno: policy sequence number
 683  */
 684 int avc_ss_reset(u32 seqno)
 685 {
 686         struct avc_callback_node *c;
 687         int rc = 0, tmprc;
 688
 689         avc_flush();
 690
 691         for (c = avc_callbacks; c; c = c->next) {
 692                 if (c->events & AVC_CALLBACK_RESET) {
 693                         tmprc = c->callback(AVC_CALLBACK_RESET,
 694                                             0, 0, 0, 0, NULL);
 695                         /* save the first error encountered for the return
 696                            value and continue processing the callbacks */
 697                         if (!rc)
 698                                 rc = tmprc;
 699                 }
 700         }
 701
 702         avc_latest_notif_update(seqno, 0);
 703         return rc;
 704 }
 705
 706 /**
 707  * avc_has_perm_noaudit - Check permissions but perform no auditing.
 708  * @ssid: source security identifier
 709  * @tsid: target security identifier
 710  * @tclass: target security class
 711  * @requested: requested permissions, interpreted based on @tclass
 712  * @flags:  AVC_STRICT or 0
 713  * @avd: access vector decisions
 714  *
 715  * Check the AVC to determine whether the @requested permissions are granted
 716  * for the SID pair (@ssid, @tsid), interpreting the permissions
 717  * based on @tclass, and call the security server on a cache miss to obtain
 718  * a new decision and add it to the cache.  Return a copy of the decisions
 719  * in @avd.  Return %0 if all @requested permissions are granted,
 720  * -%EACCES if any permissions are denied, or another -errno upon
 721  * other errors.  This function is typically called by avc_has_perm(),
 722  * but may also be called directly to separate permission checking from
 723  * auditing, e.g. in cases where a lock must be held for the check but
 724  * should be released for the auditing.
 725  */
 726 int avc_has_perm_noaudit(u32 ssid, u32 tsid,
 727                          u16 tclass, u32 requested,
 728                          unsigned flags,
 729                          struct av_decision *in_avd)
 730 {
 731         struct avc_node *node;
 732         struct av_decision avd_entry, *avd;
 733         int rc = 0;
 734         u32 denied;
 735
 736         BUG_ON(!requested);
 737
 738         rcu_read_lock();
 739
 740         node = avc_lookup(ssid, tsid, tclass);
 741         if (!node) {
 742                 rcu_read_unlock();
 743
 744                 if (in_avd)
 745                         avd = in_avd;
 746                 else
 747                         avd = &avd_entry;
 748
 749                 security_compute_av(ssid, tsid, tclass, avd);
 750                 rcu_read_lock();
 751                 node = avc_insert(ssid, tsid, tclass, avd);
 752         } else {
 753                 if (in_avd)
 754                         memcpy(in_avd, &node->ae.avd, sizeof(*in_avd));
 755                 avd = &node->ae.avd;
 756         }
 757
 758         denied = requested & ~(avd->allowed);
 759
 760         if (denied) {
 761                 if (flags & AVC_STRICT)
 762                         rc = -EACCES;
 763                 else if (!selinux_enforcing || (avd->flags & AVD_FLAGS_PERMISSIVE))
 764                         avc_update_node(AVC_CALLBACK_GRANT, requested, ssid,
 765                                         tsid, tclass, avd->seqno);
 766                 else
 767                         rc = -EACCES;
 768         }
 769
 770         rcu_read_unlock();
 771         return rc;
 772 }
 773
 774 /**
 775  * avc_has_perm - Check permissions and perform any appropriate auditing.
 776  * @ssid: source security identifier
 777  * @tsid: target security identifier
 778  * @tclass: target security class
 779  * @requested: requested permissions, interpreted based on @tclass
 780  * @auditdata: auxiliary audit data
 781  *
 782  * Check the AVC to determine whether the @requested permissions are granted
 783  * for the SID pair (@ssid, @tsid), interpreting the permissions
 784  * based on @tclass, and call the security server on a cache miss to obtain
 785  * a new decision and add it to the cache.  Audit the granting or denial of
 786  * permissions in accordance with the policy.  Return %0 if all @requested
 787  * permissions are granted, -%EACCES if any permissions are denied, or
 788  * another -errno upon other errors.
 789  */
 790 int avc_has_perm(u32 ssid, u32 tsid, u16 tclass,
 791                  u32 requested, struct common_audit_data *auditdata)
 792 {
 793         struct av_decision avd;
 794         int rc;
 795
 796         rc = avc_has_perm_noaudit(ssid, tsid, tclass, requested, 0, &avd);
 797         avc_audit(ssid, tsid, tclass, requested, &avd, rc, auditdata);
 798         return rc;
 799 }
 800
 801 u32 avc_policy_seqno(void)
 802 {
 803         return avc_cache.latest_notif;
 804 }
 805
 806 void avc_disable(void)
 807 {
 808         /*
 809          * If you are looking at this because you have realized that we are
 810          * not destroying the avc_node_cachep it might be easy to fix, but
 811          * I don't know the memory barrier semantics well enough to know.  It's
 812          * possible that some other task dereferenced security_ops when
 813          * it still pointed to selinux operations.  If that is the case it's
 814          * possible that it is about to use the avc and is about to need the
 815          * avc_node_cachep.  I know I could wrap the security.c security_ops call
 816          * in an rcu_lock, but seriously, it's not worth it.  Instead I just flush
 817          * the cache and get that memory back.
 818          */
 819         if (avc_node_cachep) {
 820                 avc_flush();
 821                 /* kmem_cache_destroy(avc_node_cachep); */
 822         }
 823 }