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)     this_cpu_inc(avc_cache_stats.field)
  42 #else
  43 #define avc_cache_stats_incr(field)     do {} while (0)
  44 #endif
  45
  46 struct avc_entry {
  47         u32                     ssid;
  48         u32                     tsid;
  49         u16                     tclass;
  50         struct av_decision      avd;
  51 };
  52
  53 struct avc_node {
  54         struct avc_entry        ae;
  55         struct hlist_node       list; /* anchored in avc_cache->slots[i] */
  56         struct rcu_head         rhead;
  57 };
  58
  59 struct avc_cache {
  60         struct hlist_head       slots[AVC_CACHE_SLOTS]; /* head for avc_node->list */
  61         spinlock_t              slots_lock[AVC_CACHE_SLOTS]; /* lock for writes */
  62         atomic_t                lru_hint;       /* LRU hint for reclaim scan */
  63         atomic_t                active_nodes;
  64         u32                     latest_notif;   /* latest revocation notification */
  65 };
  66
  67 struct avc_callback_node {
  68         int (*callback) (u32 event);
  69         u32 events;
  70         struct avc_callback_node *next;
  71 };
  72
  73 /* Exported via selinufs */
  74 unsigned int avc_cache_threshold = AVC_DEF_CACHE_THRESHOLD;
  75
  76 #ifdef CONFIG_SECURITY_SELINUX_AVC_STATS
  77 DEFINE_PER_CPU(struct avc_cache_stats, avc_cache_stats) = { 0 };
  78 #endif
  79
  80 static struct avc_cache avc_cache;
  81 static struct avc_callback_node *avc_callbacks;
  82 static struct kmem_cache *avc_node_cachep;
  83
  84 static inline int avc_hash(u32 ssid, u32 tsid, u16 tclass)
  85 {
  86         return (ssid ^ (tsid<<2) ^ (tclass<<4)) & (AVC_CACHE_SLOTS - 1);
  87 }
  88
  89 /**
  90  * avc_dump_av - Display an access vector in human-readable form.
  91  * @tclass: target security class
  92  * @av: access vector
  93  */
  94 static void avc_dump_av(struct audit_buffer *ab, u16 tclass, u32 av)
  95 {
  96         const char **perms;
  97         int i, perm;
  98
  99         if (av == 0) {
 100                 audit_log_format(ab, " null");
 101                 return;
 102         }
 103
 104         perms = secclass_map[tclass-1].perms;
 105
 106         audit_log_format(ab, " {");
 107         i = 0;
 108         perm = 1;
 109         while (i < (sizeof(av) * 8)) {
 110                 if ((perm & av) && perms[i]) {
 111                         audit_log_format(ab, " %s", perms[i]);
 112                         av &= ~perm;
 113                 }
 114                 i++;
 115                 perm <<= 1;
 116         }
 117
 118         if (av)
 119                 audit_log_format(ab, " 0x%x", av);
 120
 121         audit_log_format(ab, " }");
 122 }
 123
 124 /**
 125  * avc_dump_query - Display a SID pair and a class in human-readable form.
 126  * @ssid: source security identifier
 127  * @tsid: target security identifier
 128  * @tclass: target security class
 129  */
 130 static void avc_dump_query(struct audit_buffer *ab, u32 ssid, u32 tsid, u16 tclass)
 131 {
 132         int rc;
 133         char *scontext;
 134         u32 scontext_len;
 135
 136         rc = security_sid_to_context(ssid, &scontext, &scontext_len);
 137         if (rc)
 138                 audit_log_format(ab, "ssid=%d", ssid);
 139         else {
 140                 audit_log_format(ab, "scontext=%s", scontext);
 141                 kfree(scontext);
 142         }
 143
 144         rc = security_sid_to_context(tsid, &scontext, &scontext_len);
 145         if (rc)
 146                 audit_log_format(ab, " tsid=%d", tsid);
 147         else {
 148                 audit_log_format(ab, " tcontext=%s", scontext);
 149                 kfree(scontext);
 150         }
 151
 152         BUG_ON(tclass >= ARRAY_SIZE(secclass_map));
 153         audit_log_format(ab, " tclass=%s", secclass_map[tclass-1].name);
 154 }
 155
 156 /**
 157  * avc_init - Initialize the AVC.
 158  *
 159  * Initialize the access vector cache.
 160  */
 161 void __init avc_init(void)
 162 {
 163         int i;
 164
 165         for (i = 0; i < AVC_CACHE_SLOTS; i++) {
 166                 INIT_HLIST_HEAD(&avc_cache.slots[i]);
 167                 spin_lock_init(&avc_cache.slots_lock[i]);
 168         }
 169         atomic_set(&avc_cache.active_nodes, 0);
 170         atomic_set(&avc_cache.lru_hint, 0);
 171
 172         avc_node_cachep = kmem_cache_create("avc_node", sizeof(struct avc_node),
 173                                              0, SLAB_PANIC, NULL);
 174
 175         audit_log(current->audit_context, GFP_KERNEL, AUDIT_KERNEL, "AVC INITIALIZED\n");
 176 }
 177
 178 int avc_get_hash_stats(char *page)
 179 {
 180         int i, chain_len, max_chain_len, slots_used;
 181         struct avc_node *node;
 182         struct hlist_head *head;
 183
 184         rcu_read_lock();
 185
 186         slots_used = 0;
 187         max_chain_len = 0;
 188         for (i = 0; i < AVC_CACHE_SLOTS; i++) {
 189                 head = &avc_cache.slots[i];
 190                 if (!hlist_empty(head)) {
 191                         struct hlist_node *next;
 192
 193                         slots_used++;
 194                         chain_len = 0;
 195                         hlist_for_each_entry_rcu(node, next, head, list)
 196                                 chain_len++;
 197                         if (chain_len > max_chain_len)
 198                                 max_chain_len = chain_len;
 199                 }
 200         }
 201
 202         rcu_read_unlock();
 203
 204         return scnprintf(page, PAGE_SIZE, "entries: %d\nbuckets used: %d/%d\n"
 205                          "longest chain: %d\n",
 206                          atomic_read(&avc_cache.active_nodes),
 207                          slots_used, AVC_CACHE_SLOTS, max_chain_len);
 208 }
 209
 210 static void avc_node_free(struct rcu_head *rhead)
 211 {
 212         struct avc_node *node = container_of(rhead, struct avc_node, rhead);
 213         kmem_cache_free(avc_node_cachep, node);
 214         avc_cache_stats_incr(frees);
 215 }
 216
 217 static void avc_node_delete(struct avc_node *node)
 218 {
 219         hlist_del_rcu(&node->list);
 220         call_rcu(&node->rhead, avc_node_free);
 221         atomic_dec(&avc_cache.active_nodes);
 222 }
 223
 224 static void avc_node_kill(struct avc_node *node)
 225 {
 226         kmem_cache_free(avc_node_cachep, node);
 227         avc_cache_stats_incr(frees);
 228         atomic_dec(&avc_cache.active_nodes);
 229 }
 230
 231 static void avc_node_replace(struct avc_node *new, struct avc_node *old)
 232 {
 233         hlist_replace_rcu(&old->list, &new->list);
 234         call_rcu(&old->rhead, avc_node_free);
 235         atomic_dec(&avc_cache.active_nodes);
 236 }
 237
 238 static inline int avc_reclaim_node(void)
 239 {
 240         struct avc_node *node;
 241         int hvalue, try, ecx;
 242         unsigned long flags;
 243         struct hlist_head *head;
 244         struct hlist_node *next;
 245         spinlock_t *lock;
 246
 247         for (try = 0, ecx = 0; try < AVC_CACHE_SLOTS; try++) {
 248                 hvalue = atomic_inc_return(&avc_cache.lru_hint) & (AVC_CACHE_SLOTS - 1);
 249                 head = &avc_cache.slots[hvalue];
 250                 lock = &avc_cache.slots_lock[hvalue];
 251
 252                 if (!spin_trylock_irqsave(lock, flags))
 253                         continue;
 254
 255                 rcu_read_lock();
 256                 hlist_for_each_entry(node, next, head, list) {
 257                         avc_node_delete(node);
 258                         avc_cache_stats_incr(reclaims);
 259                         ecx++;
 260                         if (ecx >= AVC_CACHE_RECLAIM) {
 261                                 rcu_read_unlock();
 262                                 spin_unlock_irqrestore(lock, flags);
 263                                 goto out;
 264                         }
 265                 }
 266                 rcu_read_unlock();
 267                 spin_unlock_irqrestore(lock, flags);
 268         }
 269 out:
 270         return ecx;
 271 }
 272
 273 static struct avc_node *avc_alloc_node(void)
 274 {
 275         struct avc_node *node;
 276
 277         node = kmem_cache_zalloc(avc_node_cachep, GFP_ATOMIC);
 278         if (!node)
 279                 goto out;
 280
 281         INIT_HLIST_NODE(&node->list);
 282         avc_cache_stats_incr(allocations);
 283
 284         if (atomic_inc_return(&avc_cache.active_nodes) > avc_cache_threshold)
 285                 avc_reclaim_node();
 286
 287 out:
 288         return node;
 289 }
 290
 291 static void avc_node_populate(struct avc_node *node, u32 ssid, u32 tsid, u16 tclass, struct av_decision *avd)
 292 {
 293         node->ae.ssid = ssid;
 294         node->ae.tsid = tsid;
 295         node->ae.tclass = tclass;
 296         memcpy(&node->ae.avd, avd, sizeof(node->ae.avd));
 297 }
 298
 299 static inline struct avc_node *avc_search_node(u32 ssid, u32 tsid, u16 tclass)
 300 {
 301         struct avc_node *node, *ret = NULL;
 302         int hvalue;
 303         struct hlist_head *head;
 304         struct hlist_node *next;
 305
 306         hvalue = avc_hash(ssid, tsid, tclass);
 307         head = &avc_cache.slots[hvalue];
 308         hlist_for_each_entry_rcu(node, next, head, list) {
 309                 if (ssid == node->ae.ssid &&
 310                     tclass == node->ae.tclass &&
 311                     tsid == node->ae.tsid) {
 312                         ret = node;
 313                         break;
 314                 }
 315         }
 316
 317         return ret;
 318 }
 319
 320 /**
 321  * avc_lookup - Look up an AVC entry.
 322  * @ssid: source security identifier
 323  * @tsid: target security identifier
 324  * @tclass: target security class
 325  *
 326  * Look up an AVC entry that is valid for the
 327  * (@ssid, @tsid), interpreting the permissions
 328  * based on @tclass.  If a valid AVC entry exists,
 329  * then this function returns the avc_node.
 330  * Otherwise, this function returns NULL.
 331  */
 332 static struct avc_node *avc_lookup(u32 ssid, u32 tsid, u16 tclass)
 333 {
 334         struct avc_node *node;
 335
 336         avc_cache_stats_incr(lookups);
 337         node = avc_search_node(ssid, tsid, tclass);
 338
 339         if (node)
 340                 return node;
 341
 342         avc_cache_stats_incr(misses);
 343         return NULL;
 344 }
 345
 346 static int avc_latest_notif_update(int seqno, int is_insert)
 347 {
 348         int ret = 0;
 349         static DEFINE_SPINLOCK(notif_lock);
 350         unsigned long flag;
 351
 352         spin_lock_irqsave(&notif_lock, flag);
 353         if (is_insert) {
 354                 if (seqno < avc_cache.latest_notif) {
 355                         printk(KERN_WARNING "SELinux: avc:  seqno %d < latest_notif %d\n",
 356                                seqno, avc_cache.latest_notif);
 357                         ret = -EAGAIN;
 358                 }
 359         } else {
 360                 if (seqno > avc_cache.latest_notif)
 361                         avc_cache.latest_notif = seqno;
 362         }
 363         spin_unlock_irqrestore(&notif_lock, flag);
 364
 365         return ret;
 366 }
 367
 368 /**
 369  * avc_insert - Insert an AVC entry.
 370  * @ssid: source security identifier
 371  * @tsid: target security identifier
 372  * @tclass: target security class
 373  * @avd: resulting av decision
 374  *
 375  * Insert an AVC entry for the SID pair
 376  * (@ssid, @tsid) and class @tclass.
 377  * The access vectors and the sequence number are
 378  * normally provided by the security server in
 379  * response to a security_compute_av() call.  If the
 380  * sequence number @avd->seqno is not less than the latest
 381  * revocation notification, then the function copies
 382  * the access vectors into a cache entry, returns
 383  * avc_node inserted. Otherwise, this function returns NULL.
 384  */
 385 static struct avc_node *avc_insert(u32 ssid, u32 tsid, u16 tclass, struct av_decision *avd)
 386 {
 387         struct avc_node *pos, *node = NULL;
 388         int hvalue;
 389         unsigned long flag;
 390
 391         if (avc_latest_notif_update(avd->seqno, 1))
 392                 goto out;
 393
 394         node = avc_alloc_node();
 395         if (node) {
 396                 struct hlist_head *head;
 397                 struct hlist_node *next;
 398                 spinlock_t *lock;
 399
 400                 hvalue = avc_hash(ssid, tsid, tclass);
 401                 avc_node_populate(node, ssid, tsid, tclass, avd);
 402
 403                 head = &avc_cache.slots[hvalue];
 404                 lock = &avc_cache.slots_lock[hvalue];
 405
 406                 spin_lock_irqsave(lock, flag);
 407                 hlist_for_each_entry(pos, next, head, list) {
 408                         if (pos->ae.ssid == ssid &&
 409                             pos->ae.tsid == tsid &&
 410                             pos->ae.tclass == tclass) {
 411                                 avc_node_replace(node, pos);
 412                                 goto found;
 413                         }
 414                 }
 415                 hlist_add_head_rcu(&node->list, head);
 416 found:
 417                 spin_unlock_irqrestore(lock, flag);
 418         }
 419 out:
 420         return node;
 421 }
 422
 423 /**
 424  * avc_audit_pre_callback - SELinux specific information
 425  * will be called by generic audit code
 426  * @ab: the audit buffer
 427  * @a: audit_data
 428  */
 429 static void avc_audit_pre_callback(struct audit_buffer *ab, void *a)
 430 {
 431         struct common_audit_data *ad = a;
 432         audit_log_format(ab, "avc:  %s ",
 433                          ad->selinux_audit_data->denied ? "denied" : "granted");
 434         avc_dump_av(ab, ad->selinux_audit_data->tclass,
 435                         ad->selinux_audit_data->audited);
 436         audit_log_format(ab, " for ");
 437 }
 438
 439 /**
 440  * avc_audit_post_callback - SELinux specific information
 441  * will be called by generic audit code
 442  * @ab: the audit buffer
 443  * @a: audit_data
 444  */
 445 static void avc_audit_post_callback(struct audit_buffer *ab, void *a)
 446 {
 447         struct common_audit_data *ad = a;
 448         audit_log_format(ab, " ");
 449         avc_dump_query(ab, ad->selinux_audit_data->ssid,
 450                            ad->selinux_audit_data->tsid,
 451                            ad->selinux_audit_data->tclass);
 452 }
 453
 454 /* This is the slow part of avc audit with big stack footprint */
 455 noinline int slow_avc_audit(u32 ssid, u32 tsid, u16 tclass,
 456                 u32 requested, u32 audited, u32 denied,
 457                 struct common_audit_data *a,
 458                 unsigned flags)
 459 {
 460         struct common_audit_data stack_data;
 461         struct selinux_audit_data sad;
 462
 463         if (!a) {
 464                 a = &stack_data;
 465                 a->type = LSM_AUDIT_DATA_NONE;
 466         }
 467
 468         /*
 469          * When in a RCU walk do the audit on the RCU retry.  This is because
 470          * the collection of the dname in an inode audit message is not RCU
 471          * safe.  Note this may drop some audits when the situation changes
 472          * during retry. However this is logically just as if the operation
 473          * happened a little later.
 474          */
 475         if ((a->type == LSM_AUDIT_DATA_INODE) &&
 476             (flags & MAY_NOT_BLOCK))
 477                 return -ECHILD;
 478
 479         sad.tclass = tclass;
 480         sad.requested = requested;
 481         sad.ssid = ssid;
 482         sad.tsid = tsid;
 483         sad.audited = audited;
 484         sad.denied = denied;
 485
 486         a->selinux_audit_data = &sad;
 487
 488         common_lsm_audit(a, avc_audit_pre_callback, avc_audit_post_callback);
 489         return 0;
 490 }
 491
 492 /**
 493  * avc_add_callback - Register a callback for security events.
 494  * @callback: callback function
 495  * @events: security events
 496  *
 497  * Register a callback function for events in the set @events.
 498  * Returns %0 on success or -%ENOMEM if insufficient memory
 499  * exists to add the callback.
 500  */
 501 int __init avc_add_callback(int (*callback)(u32 event), u32 events)
 502 {
 503         struct avc_callback_node *c;
 504         int rc = 0;
 505
 506         c = kmalloc(sizeof(*c), GFP_KERNEL);
 507         if (!c) {
 508                 rc = -ENOMEM;
 509                 goto out;
 510         }
 511
 512         c->callback = callback;
 513         c->events = events;
 514         c->next = avc_callbacks;
 515         avc_callbacks = c;
 516 out:
 517         return rc;
 518 }
 519
 520 static inline int avc_sidcmp(u32 x, u32 y)
 521 {
 522         return (x == y || x == SECSID_WILD || y == SECSID_WILD);
 523 }
 524
 525 /**
 526  * avc_update_node Update an AVC entry
 527  * @event : Updating event
 528  * @perms : Permission mask bits
 529  * @ssid,@tsid,@tclass : identifier of an AVC entry
 530  * @seqno : sequence number when decision was made
 531  *
 532  * if a valid AVC entry doesn't exist,this function returns -ENOENT.
 533  * if kmalloc() called internal returns NULL, this function returns -ENOMEM.
 534  * otherwise, this function updates the AVC entry. The original AVC-entry object
 535  * will release later by RCU.
 536  */
 537 static int avc_update_node(u32 event, u32 perms, u32 ssid, u32 tsid, u16 tclass,
 538                            u32 seqno)
 539 {
 540         int hvalue, rc = 0;
 541         unsigned long flag;
 542         struct avc_node *pos, *node, *orig = NULL;
 543         struct hlist_head *head;
 544         struct hlist_node *next;
 545         spinlock_t *lock;
 546
 547         node = avc_alloc_node();
 548         if (!node) {
 549                 rc = -ENOMEM;
 550                 goto out;
 551         }
 552
 553         /* Lock the target slot */
 554         hvalue = avc_hash(ssid, tsid, tclass);
 555
 556         head = &avc_cache.slots[hvalue];
 557         lock = &avc_cache.slots_lock[hvalue];
 558
 559         spin_lock_irqsave(lock, flag);
 560
 561         hlist_for_each_entry(pos, next, head, list) {
 562                 if (ssid == pos->ae.ssid &&
 563                     tsid == pos->ae.tsid &&
 564                     tclass == pos->ae.tclass &&
 565                     seqno == pos->ae.avd.seqno){
 566                         orig = pos;
 567                         break;
 568                 }
 569         }
 570
 571         if (!orig) {
 572                 rc = -ENOENT;
 573                 avc_node_kill(node);
 574                 goto out_unlock;
 575         }
 576
 577         /*
 578          * Copy and replace original node.
 579          */
 580
 581         avc_node_populate(node, ssid, tsid, tclass, &orig->ae.avd);
 582
 583         switch (event) {
 584         case AVC_CALLBACK_GRANT:
 585                 node->ae.avd.allowed |= perms;
 586                 break;
 587         case AVC_CALLBACK_TRY_REVOKE:
 588         case AVC_CALLBACK_REVOKE:
 589                 node->ae.avd.allowed &= ~perms;
 590                 break;
 591         case AVC_CALLBACK_AUDITALLOW_ENABLE:
 592                 node->ae.avd.auditallow |= perms;
 593                 break;
 594         case AVC_CALLBACK_AUDITALLOW_DISABLE:
 595                 node->ae.avd.auditallow &= ~perms;
 596                 break;
 597         case AVC_CALLBACK_AUDITDENY_ENABLE:
 598                 node->ae.avd.auditdeny |= perms;
 599                 break;
 600         case AVC_CALLBACK_AUDITDENY_DISABLE:
 601                 node->ae.avd.auditdeny &= ~perms;
 602                 break;
 603         }
 604         avc_node_replace(node, orig);
 605 out_unlock:
 606         spin_unlock_irqrestore(lock, flag);
 607 out:
 608         return rc;
 609 }
 610
 611 /**
 612  * avc_flush - Flush the cache
 613  */
 614 static void avc_flush(void)
 615 {
 616         struct hlist_head *head;
 617         struct hlist_node *next;
 618         struct avc_node *node;
 619         spinlock_t *lock;
 620         unsigned long flag;
 621         int i;
 622
 623         for (i = 0; i < AVC_CACHE_SLOTS; i++) {
 624                 head = &avc_cache.slots[i];
 625                 lock = &avc_cache.slots_lock[i];
 626
 627                 spin_lock_irqsave(lock, flag);
 628                 /*
 629                  * With preemptable RCU, the outer spinlock does not
 630                  * prevent RCU grace periods from ending.
 631                  */
 632                 rcu_read_lock();
 633                 hlist_for_each_entry(node, next, head, list)
 634                         avc_node_delete(node);
 635                 rcu_read_unlock();
 636                 spin_unlock_irqrestore(lock, flag);
 637         }
 638 }
 639
 640 /**
 641  * avc_ss_reset - Flush the cache and revalidate migrated permissions.
 642  * @seqno: policy sequence number
 643  */
 644 int avc_ss_reset(u32 seqno)
 645 {
 646         struct avc_callback_node *c;
 647         int rc = 0, tmprc;
 648
 649         avc_flush();
 650
 651         for (c = avc_callbacks; c; c = c->next) {
 652                 if (c->events & AVC_CALLBACK_RESET) {
 653                         tmprc = c->callback(AVC_CALLBACK_RESET);
 654                         /* save the first error encountered for the return
 655                            value and continue processing the callbacks */
 656                         if (!rc)
 657                                 rc = tmprc;
 658                 }
 659         }
 660
 661         avc_latest_notif_update(seqno, 0);
 662         return rc;
 663 }
 664
 665 /*
 666  * Slow-path helper function for avc_has_perm_noaudit,
 667  * when the avc_node lookup fails. We get called with
 668  * the RCU read lock held, and need to return with it
 669  * still held, but drop if for the security compute.
 670  *
 671  * Don't inline this, since it's the slow-path and just
 672  * results in a bigger stack frame.
 673  */
 674 static noinline struct avc_node *avc_compute_av(u32 ssid, u32 tsid,
 675                          u16 tclass, struct av_decision *avd)
 676 {
 677         rcu_read_unlock();
 678         security_compute_av(ssid, tsid, tclass, avd);
 679         rcu_read_lock();
 680         return avc_insert(ssid, tsid, tclass, avd);
 681 }
 682
 683 static noinline int avc_denied(u32 ssid, u32 tsid,
 684                          u16 tclass, u32 requested,
 685                          unsigned flags,
 686                          struct av_decision *avd)
 687 {
 688         if (flags & AVC_STRICT)
 689                 return -EACCES;
 690
 691         if (selinux_enforcing && !(avd->flags & AVD_FLAGS_PERMISSIVE))
 692                 return -EACCES;
 693
 694         avc_update_node(AVC_CALLBACK_GRANT, requested, ssid,
 695                                 tsid, tclass, avd->seqno);
 696         return 0;
 697 }
 698
 699
 700 /**
 701  * avc_has_perm_noaudit - Check permissions but perform no auditing.
 702  * @ssid: source security identifier
 703  * @tsid: target security identifier
 704  * @tclass: target security class
 705  * @requested: requested permissions, interpreted based on @tclass
 706  * @flags:  AVC_STRICT or 0
 707  * @avd: access vector decisions
 708  *
 709  * Check the AVC to determine whether the @requested permissions are granted
 710  * for the SID pair (@ssid, @tsid), interpreting the permissions
 711  * based on @tclass, and call the security server on a cache miss to obtain
 712  * a new decision and add it to the cache.  Return a copy of the decisions
 713  * in @avd.  Return %0 if all @requested permissions are granted,
 714  * -%EACCES if any permissions are denied, or another -errno upon
 715  * other errors.  This function is typically called by avc_has_perm(),
 716  * but may also be called directly to separate permission checking from
 717  * auditing, e.g. in cases where a lock must be held for the check but
 718  * should be released for the auditing.
 719  */
 720 inline int avc_has_perm_noaudit(u32 ssid, u32 tsid,
 721                          u16 tclass, u32 requested,
 722                          unsigned flags,
 723                          struct av_decision *avd)
 724 {
 725         struct avc_node *node;
 726         int rc = 0;
 727         u32 denied;
 728
 729         BUG_ON(!requested);
 730
 731         rcu_read_lock();
 732
 733         node = avc_lookup(ssid, tsid, tclass);
 734         if (unlikely(!node)) {
 735                 node = avc_compute_av(ssid, tsid, tclass, avd);
 736         } else {
 737                 memcpy(avd, &node->ae.avd, sizeof(*avd));
 738                 avd = &node->ae.avd;
 739         }
 740
 741         denied = requested & ~(avd->allowed);
 742         if (unlikely(denied))
 743                 rc = avc_denied(ssid, tsid, tclass, requested, flags, avd);
 744
 745         rcu_read_unlock();
 746         return rc;
 747 }
 748
 749 /**
 750  * avc_has_perm - Check permissions and perform any appropriate auditing.
 751  * @ssid: source security identifier
 752  * @tsid: target security identifier
 753  * @tclass: target security class
 754  * @requested: requested permissions, interpreted based on @tclass
 755  * @auditdata: auxiliary audit data
 756  * @flags: VFS walk flags
 757  *
 758  * Check the AVC to determine whether the @requested permissions are granted
 759  * for the SID pair (@ssid, @tsid), interpreting the permissions
 760  * based on @tclass, and call the security server on a cache miss to obtain
 761  * a new decision and add it to the cache.  Audit the granting or denial of
 762  * permissions in accordance with the policy.  Return %0 if all @requested
 763  * permissions are granted, -%EACCES if any permissions are denied, or
 764  * another -errno upon other errors.
 765  */
 766 int avc_has_perm_flags(u32 ssid, u32 tsid, u16 tclass,
 767                        u32 requested, struct common_audit_data *auditdata,
 768                        unsigned flags)
 769 {
 770         struct av_decision avd;
 771         int rc, rc2;
 772
 773         rc = avc_has_perm_noaudit(ssid, tsid, tclass, requested, 0, &avd);
 774
 775         rc2 = avc_audit(ssid, tsid, tclass, requested, &avd, rc, auditdata,
 776                         flags);
 777         if (rc2)
 778                 return rc2;
 779         return rc;
 780 }
 781
 782 u32 avc_policy_seqno(void)
 783 {
 784         return avc_cache.latest_notif;
 785 }
 786
 787 void avc_disable(void)
 788 {
 789         /*
 790          * If you are looking at this because you have realized that we are
 791          * not destroying the avc_node_cachep it might be easy to fix, but
 792          * I don't know the memory barrier semantics well enough to know.  It's
 793          * possible that some other task dereferenced security_ops when
 794          * it still pointed to selinux operations.  If that is the case it's
 795          * possible that it is about to use the avc and is about to need the
 796          * avc_node_cachep.  I know I could wrap the security.c security_ops call
 797          * in an rcu_lock, but seriously, it's not worth it.  Instead I just flush
 798          * the cache and get that memory back.
 799          */
 800         if (avc_node_cachep) {
 801                 avc_flush();
 802                 /* kmem_cache_destroy(avc_node_cachep); */
 803         }
 804 }