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                         slots_used++;
 192                         chain_len = 0;
 193                         hlist_for_each_entry_rcu(node, head, list)
 194                                 chain_len++;
 195                         if (chain_len > max_chain_len)
 196                                 max_chain_len = chain_len;
 197                 }
 198         }
 199
 200         rcu_read_unlock();
 201
 202         return scnprintf(page, PAGE_SIZE, "entries: %d\nbuckets used: %d/%d\n"
 203                          "longest chain: %d\n",
 204                          atomic_read(&avc_cache.active_nodes),
 205                          slots_used, AVC_CACHE_SLOTS, max_chain_len);
 206 }
 207
 208 static void avc_node_free(struct rcu_head *rhead)
 209 {
 210         struct avc_node *node = container_of(rhead, struct avc_node, rhead);
 211         kmem_cache_free(avc_node_cachep, node);
 212         avc_cache_stats_incr(frees);
 213 }
 214
 215 static void avc_node_delete(struct avc_node *node)
 216 {
 217         hlist_del_rcu(&node->list);
 218         call_rcu(&node->rhead, avc_node_free);
 219         atomic_dec(&avc_cache.active_nodes);
 220 }
 221
 222 static void avc_node_kill(struct avc_node *node)
 223 {
 224         kmem_cache_free(avc_node_cachep, node);
 225         avc_cache_stats_incr(frees);
 226         atomic_dec(&avc_cache.active_nodes);
 227 }
 228
 229 static void avc_node_replace(struct avc_node *new, struct avc_node *old)
 230 {
 231         hlist_replace_rcu(&old->list, &new->list);
 232         call_rcu(&old->rhead, avc_node_free);
 233         atomic_dec(&avc_cache.active_nodes);
 234 }
 235
 236 static inline int avc_reclaim_node(void)
 237 {
 238         struct avc_node *node;
 239         int hvalue, try, ecx;
 240         unsigned long flags;
 241         struct hlist_head *head;
 242         spinlock_t *lock;
 243
 244         for (try = 0, ecx = 0; try < AVC_CACHE_SLOTS; try++) {
 245                 hvalue = atomic_inc_return(&avc_cache.lru_hint) & (AVC_CACHE_SLOTS - 1);
 246                 head = &avc_cache.slots[hvalue];
 247                 lock = &avc_cache.slots_lock[hvalue];
 248
 249                 if (!spin_trylock_irqsave(lock, flags))
 250                         continue;
 251
 252                 rcu_read_lock();
 253                 hlist_for_each_entry(node, head, list) {
 254                         avc_node_delete(node);
 255                         avc_cache_stats_incr(reclaims);
 256                         ecx++;
 257                         if (ecx >= AVC_CACHE_RECLAIM) {
 258                                 rcu_read_unlock();
 259                                 spin_unlock_irqrestore(lock, flags);
 260                                 goto out;
 261                         }
 262                 }
 263                 rcu_read_unlock();
 264                 spin_unlock_irqrestore(lock, flags);
 265         }
 266 out:
 267         return ecx;
 268 }
 269
 270 static struct avc_node *avc_alloc_node(void)
 271 {
 272         struct avc_node *node;
 273
 274         node = kmem_cache_zalloc(avc_node_cachep, GFP_ATOMIC|__GFP_NOMEMALLOC);
 275         if (!node)
 276                 goto out;
 277
 278         INIT_HLIST_NODE(&node->list);
 279         avc_cache_stats_incr(allocations);
 280
 281         if (atomic_inc_return(&avc_cache.active_nodes) > avc_cache_threshold)
 282                 avc_reclaim_node();
 283
 284 out:
 285         return node;
 286 }
 287
 288 static void avc_node_populate(struct avc_node *node, u32 ssid, u32 tsid, u16 tclass, struct av_decision *avd)
 289 {
 290         node->ae.ssid = ssid;
 291         node->ae.tsid = tsid;
 292         node->ae.tclass = tclass;
 293         memcpy(&node->ae.avd, avd, sizeof(node->ae.avd));
 294 }
 295
 296 static inline struct avc_node *avc_search_node(u32 ssid, u32 tsid, u16 tclass)
 297 {
 298         struct avc_node *node, *ret = NULL;
 299         int hvalue;
 300         struct hlist_head *head;
 301
 302         hvalue = avc_hash(ssid, tsid, tclass);
 303         head = &avc_cache.slots[hvalue];
 304         hlist_for_each_entry_rcu(node, head, list) {
 305                 if (ssid == node->ae.ssid &&
 306                     tclass == node->ae.tclass &&
 307                     tsid == node->ae.tsid) {
 308                         ret = node;
 309                         break;
 310                 }
 311         }
 312
 313         return ret;
 314 }
 315
 316 /**
 317  * avc_lookup - Look up an AVC entry.
 318  * @ssid: source security identifier
 319  * @tsid: target security identifier
 320  * @tclass: target security class
 321  *
 322  * Look up an AVC entry that is valid for the
 323  * (@ssid, @tsid), interpreting the permissions
 324  * based on @tclass.  If a valid AVC entry exists,
 325  * then this function returns the avc_node.
 326  * Otherwise, this function returns NULL.
 327  */
 328 static struct avc_node *avc_lookup(u32 ssid, u32 tsid, u16 tclass)
 329 {
 330         struct avc_node *node;
 331
 332         avc_cache_stats_incr(lookups);
 333         node = avc_search_node(ssid, tsid, tclass);
 334
 335         if (node)
 336                 return node;
 337
 338         avc_cache_stats_incr(misses);
 339         return NULL;
 340 }
 341
 342 static int avc_latest_notif_update(int seqno, int is_insert)
 343 {
 344         int ret = 0;
 345         static DEFINE_SPINLOCK(notif_lock);
 346         unsigned long flag;
 347
 348         spin_lock_irqsave(&notif_lock, flag);
 349         if (is_insert) {
 350                 if (seqno < avc_cache.latest_notif) {
 351                         printk(KERN_WARNING "SELinux: avc:  seqno %d < latest_notif %d\n",
 352                                seqno, avc_cache.latest_notif);
 353                         ret = -EAGAIN;
 354                 }
 355         } else {
 356                 if (seqno > avc_cache.latest_notif)
 357                         avc_cache.latest_notif = seqno;
 358         }
 359         spin_unlock_irqrestore(&notif_lock, flag);
 360
 361         return ret;
 362 }
 363
 364 /**
 365  * avc_insert - Insert an AVC entry.
 366  * @ssid: source security identifier
 367  * @tsid: target security identifier
 368  * @tclass: target security class
 369  * @avd: resulting av decision
 370  *
 371  * Insert an AVC entry for the SID pair
 372  * (@ssid, @tsid) and class @tclass.
 373  * The access vectors and the sequence number are
 374  * normally provided by the security server in
 375  * response to a security_compute_av() call.  If the
 376  * sequence number @avd->seqno is not less than the latest
 377  * revocation notification, then the function copies
 378  * the access vectors into a cache entry, returns
 379  * avc_node inserted. Otherwise, this function returns NULL.
 380  */
 381 static struct avc_node *avc_insert(u32 ssid, u32 tsid, u16 tclass, struct av_decision *avd)
 382 {
 383         struct avc_node *pos, *node = NULL;
 384         int hvalue;
 385         unsigned long flag;
 386
 387         if (avc_latest_notif_update(avd->seqno, 1))
 388                 goto out;
 389
 390         node = avc_alloc_node();
 391         if (node) {
 392                 struct hlist_head *head;
 393                 spinlock_t *lock;
 394
 395                 hvalue = avc_hash(ssid, tsid, tclass);
 396                 avc_node_populate(node, ssid, tsid, tclass, avd);
 397
 398                 head = &avc_cache.slots[hvalue];
 399                 lock = &avc_cache.slots_lock[hvalue];
 400
 401                 spin_lock_irqsave(lock, flag);
 402                 hlist_for_each_entry(pos, head, list) {
 403                         if (pos->ae.ssid == ssid &&
 404                             pos->ae.tsid == tsid &&
 405                             pos->ae.tclass == tclass) {
 406                                 avc_node_replace(node, pos);
 407                                 goto found;
 408                         }
 409                 }
 410                 hlist_add_head_rcu(&node->list, head);
 411 found:
 412                 spin_unlock_irqrestore(lock, flag);
 413         }
 414 out:
 415         return node;
 416 }
 417
 418 /**
 419  * avc_audit_pre_callback - SELinux specific information
 420  * will be called by generic audit code
 421  * @ab: the audit buffer
 422  * @a: audit_data
 423  */
 424 static void avc_audit_pre_callback(struct audit_buffer *ab, void *a)
 425 {
 426         struct common_audit_data *ad = a;
 427         audit_log_format(ab, "avc:  %s ",
 428                          ad->selinux_audit_data->denied ? "denied" : "granted");
 429         avc_dump_av(ab, ad->selinux_audit_data->tclass,
 430                         ad->selinux_audit_data->audited);
 431         audit_log_format(ab, " for ");
 432 }
 433
 434 /**
 435  * avc_audit_post_callback - SELinux specific information
 436  * will be called by generic audit code
 437  * @ab: the audit buffer
 438  * @a: audit_data
 439  */
 440 #ifdef CONFIG_MTK_AEE_FEATURE
 441 extern void mtk_audit_hook(char *data);
 442 #endif
 443 static void avc_audit_post_callback(struct audit_buffer *ab, void *a)
 444 {
 445         struct common_audit_data *ad = a;
 446         audit_log_format(ab, " ");
 447         avc_dump_query(ab, ad->selinux_audit_data->ssid,
 448                            ad->selinux_audit_data->tsid,
 449                            ad->selinux_audit_data->tclass);
 450         if (ad->selinux_audit_data->denied) {
 451                 audit_log_format(ab, " permissive=%u",
 452                                  ad->selinux_audit_data->result ? 0 : 1);
 453                 #ifdef CONFIG_MTK_AEE_FEATURE
 454                 {
 455                         int rc;
 456                         char *scontext;
 457                         u32 scontext_len;
 458                         rc = security_sid_to_context(ad->selinux_audit_data->ssid, &scontext, &scontext_len);
 459                         if (!rc){
 460                                 printk(KERN_WARNING "audit avc scontext:%s\n",scontext);
 461                                 //mtk_audit_hook(scontext);
 462                         }
 463                         kfree(scontext);
 464                 }
 465                 #endif
 466         }
 467 }
 468
 469 /* This is the slow part of avc audit with big stack footprint */
 470 noinline int slow_avc_audit(u32 ssid, u32 tsid, u16 tclass,
 471                 u32 requested, u32 audited, u32 denied, int result,
 472                 struct common_audit_data *a,
 473                 unsigned flags)
 474 {
 475         struct common_audit_data stack_data;
 476         struct selinux_audit_data sad;
 477
 478         if (!a) {
 479                 a = &stack_data;
 480                 a->type = LSM_AUDIT_DATA_NONE;
 481         }
 482
 483         /*
 484          * When in a RCU walk do the audit on the RCU retry.  This is because
 485          * the collection of the dname in an inode audit message is not RCU
 486          * safe.  Note this may drop some audits when the situation changes
 487          * during retry. However this is logically just as if the operation
 488          * happened a little later.
 489          */
 490         if ((a->type == LSM_AUDIT_DATA_INODE) &&
 491             (flags & MAY_NOT_BLOCK))
 492                 return -ECHILD;
 493
 494         sad.tclass = tclass;
 495         sad.requested = requested;
 496         sad.ssid = ssid;
 497         sad.tsid = tsid;
 498         sad.audited = audited;
 499         sad.denied = denied;
 500         sad.result = result;
 501
 502         a->selinux_audit_data = &sad;
 503
 504         common_lsm_audit(a, avc_audit_pre_callback, avc_audit_post_callback);
 505         return 0;
 506 }
 507
 508 /**
 509  * avc_add_callback - Register a callback for security events.
 510  * @callback: callback function
 511  * @events: security events
 512  *
 513  * Register a callback function for events in the set @events.
 514  * Returns %0 on success or -%ENOMEM if insufficient memory
 515  * exists to add the callback.
 516  */
 517 int __init avc_add_callback(int (*callback)(u32 event), u32 events)
 518 {
 519         struct avc_callback_node *c;
 520         int rc = 0;
 521
 522         c = kmalloc(sizeof(*c), GFP_KERNEL);
 523         if (!c) {
 524                 rc = -ENOMEM;
 525                 goto out;
 526         }
 527
 528         c->callback = callback;
 529         c->events = events;
 530         c->next = avc_callbacks;
 531         avc_callbacks = c;
 532 out:
 533         return rc;
 534 }
 535
 536 static inline int avc_sidcmp(u32 x, u32 y)
 537 {
 538         return (x == y || x == SECSID_WILD || y == SECSID_WILD);
 539 }
 540
 541 /**
 542  * avc_update_node Update an AVC entry
 543  * @event : Updating event
 544  * @perms : Permission mask bits
 545  * @ssid,@tsid,@tclass : identifier of an AVC entry
 546  * @seqno : sequence number when decision was made
 547  *
 548  * if a valid AVC entry doesn't exist,this function returns -ENOENT.
 549  * if kmalloc() called internal returns NULL, this function returns -ENOMEM.
 550  * otherwise, this function updates the AVC entry. The original AVC-entry object
 551  * will release later by RCU.
 552  */
 553 static int avc_update_node(u32 event, u32 perms, u32 ssid, u32 tsid, u16 tclass,
 554                            u32 seqno)
 555 {
 556         int hvalue, rc = 0;
 557         unsigned long flag;
 558         struct avc_node *pos, *node, *orig = NULL;
 559         struct hlist_head *head;
 560         spinlock_t *lock;
 561
 562         node = avc_alloc_node();
 563         if (!node) {
 564                 rc = -ENOMEM;
 565                 goto out;
 566         }
 567
 568         /* Lock the target slot */
 569         hvalue = avc_hash(ssid, tsid, tclass);
 570
 571         head = &avc_cache.slots[hvalue];
 572         lock = &avc_cache.slots_lock[hvalue];
 573
 574         spin_lock_irqsave(lock, flag);
 575
 576         hlist_for_each_entry(pos, head, list) {
 577                 if (ssid == pos->ae.ssid &&
 578                     tsid == pos->ae.tsid &&
 579                     tclass == pos->ae.tclass &&
 580                     seqno == pos->ae.avd.seqno){
 581                         orig = pos;
 582                         break;
 583                 }
 584         }
 585
 586         if (!orig) {
 587                 rc = -ENOENT;
 588                 avc_node_kill(node);
 589                 goto out_unlock;
 590         }
 591
 592         /*
 593          * Copy and replace original node.
 594          */
 595
 596         avc_node_populate(node, ssid, tsid, tclass, &orig->ae.avd);
 597
 598         switch (event) {
 599         case AVC_CALLBACK_GRANT:
 600                 node->ae.avd.allowed |= perms;
 601                 break;
 602         case AVC_CALLBACK_TRY_REVOKE:
 603         case AVC_CALLBACK_REVOKE:
 604                 node->ae.avd.allowed &= ~perms;
 605                 break;
 606         case AVC_CALLBACK_AUDITALLOW_ENABLE:
 607                 node->ae.avd.auditallow |= perms;
 608                 break;
 609         case AVC_CALLBACK_AUDITALLOW_DISABLE:
 610                 node->ae.avd.auditallow &= ~perms;
 611                 break;
 612         case AVC_CALLBACK_AUDITDENY_ENABLE:
 613                 node->ae.avd.auditdeny |= perms;
 614                 break;
 615         case AVC_CALLBACK_AUDITDENY_DISABLE:
 616                 node->ae.avd.auditdeny &= ~perms;
 617                 break;
 618         }
 619         avc_node_replace(node, orig);
 620 out_unlock:
 621         spin_unlock_irqrestore(lock, flag);
 622 out:
 623         return rc;
 624 }
 625
 626 /**
 627  * avc_flush - Flush the cache
 628  */
 629 static void avc_flush(void)
 630 {
 631         struct hlist_head *head;
 632         struct avc_node *node;
 633         spinlock_t *lock;
 634         unsigned long flag;
 635         int i;
 636
 637         for (i = 0; i < AVC_CACHE_SLOTS; i++) {
 638                 head = &avc_cache.slots[i];
 639                 lock = &avc_cache.slots_lock[i];
 640
 641                 spin_lock_irqsave(lock, flag);
 642                 /*
 643                  * With preemptable RCU, the outer spinlock does not
 644                  * prevent RCU grace periods from ending.
 645                  */
 646                 rcu_read_lock();
 647                 hlist_for_each_entry(node, head, list)
 648                         avc_node_delete(node);
 649                 rcu_read_unlock();
 650                 spin_unlock_irqrestore(lock, flag);
 651         }
 652 }
 653
 654 /**
 655  * avc_ss_reset - Flush the cache and revalidate migrated permissions.
 656  * @seqno: policy sequence number
 657  */
 658 int avc_ss_reset(u32 seqno)
 659 {
 660         struct avc_callback_node *c;
 661         int rc = 0, tmprc;
 662
 663         avc_flush();
 664
 665         for (c = avc_callbacks; c; c = c->next) {
 666                 if (c->events & AVC_CALLBACK_RESET) {
 667                         tmprc = c->callback(AVC_CALLBACK_RESET);
 668                         /* save the first error encountered for the return
 669                            value and continue processing the callbacks */
 670                         if (!rc)
 671                                 rc = tmprc;
 672                 }
 673         }
 674
 675         avc_latest_notif_update(seqno, 0);
 676         return rc;
 677 }
 678
 679 /*
 680  * Slow-path helper function for avc_has_perm_noaudit,
 681  * when the avc_node lookup fails. We get called with
 682  * the RCU read lock held, and need to return with it
 683  * still held, but drop if for the security compute.
 684  *
 685  * Don't inline this, since it's the slow-path and just
 686  * results in a bigger stack frame.
 687  */
 688 static noinline struct avc_node *avc_compute_av(u32 ssid, u32 tsid,
 689                          u16 tclass, struct av_decision *avd)
 690 {
 691         rcu_read_unlock();
 692         security_compute_av(ssid, tsid, tclass, avd);
 693         rcu_read_lock();
 694         return avc_insert(ssid, tsid, tclass, avd);
 695 }
 696
 697 static noinline int avc_denied(u32 ssid, u32 tsid,
 698                          u16 tclass, u32 requested,
 699                          unsigned flags,
 700                          struct av_decision *avd)
 701 {
 702         if (flags & AVC_STRICT)
 703                 return -EACCES;
 704
 705         if (selinux_enforcing && !(avd->flags & AVD_FLAGS_PERMISSIVE))
 706                 return -EACCES;
 707
 708         avc_update_node(AVC_CALLBACK_GRANT, requested, ssid,
 709                                 tsid, tclass, avd->seqno);
 710         return 0;
 711 }
 712
 713
 714 /**
 715  * avc_has_perm_noaudit - Check permissions but perform no auditing.
 716  * @ssid: source security identifier
 717  * @tsid: target security identifier
 718  * @tclass: target security class
 719  * @requested: requested permissions, interpreted based on @tclass
 720  * @flags:  AVC_STRICT or 0
 721  * @avd: access vector decisions
 722  *
 723  * Check the AVC to determine whether the @requested permissions are granted
 724  * for the SID pair (@ssid, @tsid), interpreting the permissions
 725  * based on @tclass, and call the security server on a cache miss to obtain
 726  * a new decision and add it to the cache.  Return a copy of the decisions
 727  * in @avd.  Return %0 if all @requested permissions are granted,
 728  * -%EACCES if any permissions are denied, or another -errno upon
 729  * other errors.  This function is typically called by avc_has_perm(),
 730  * but may also be called directly to separate permission checking from
 731  * auditing, e.g. in cases where a lock must be held for the check but
 732  * should be released for the auditing.
 733  */
 734 inline int avc_has_perm_noaudit(u32 ssid, u32 tsid,
 735                          u16 tclass, u32 requested,
 736                          unsigned flags,
 737                          struct av_decision *avd)
 738 {
 739         struct avc_node *node;
 740         int rc = 0;
 741         u32 denied;
 742
 743         BUG_ON(!requested);
 744
 745         rcu_read_lock();
 746
 747         node = avc_lookup(ssid, tsid, tclass);
 748         if (unlikely(!node)) {
 749                 node = avc_compute_av(ssid, tsid, tclass, avd);
 750         } else {
 751                 memcpy(avd, &node->ae.avd, sizeof(*avd));
 752                 avd = &node->ae.avd;
 753         }
 754
 755         denied = requested & ~(avd->allowed);
 756         if (unlikely(denied))
 757                 rc = avc_denied(ssid, tsid, tclass, requested, flags, avd);
 758
 759         rcu_read_unlock();
 760         return rc;
 761 }
 762
 763 /**
 764  * avc_has_perm - Check permissions and perform any appropriate auditing.
 765  * @ssid: source security identifier
 766  * @tsid: target security identifier
 767  * @tclass: target security class
 768  * @requested: requested permissions, interpreted based on @tclass
 769  * @auditdata: auxiliary audit data
 770  * @flags: VFS walk flags
 771  *
 772  * Check the AVC to determine whether the @requested permissions are granted
 773  * for the SID pair (@ssid, @tsid), interpreting the permissions
 774  * based on @tclass, and call the security server on a cache miss to obtain
 775  * a new decision and add it to the cache.  Audit the granting or denial of
 776  * permissions in accordance with the policy.  Return %0 if all @requested
 777  * permissions are granted, -%EACCES if any permissions are denied, or
 778  * another -errno upon other errors.
 779  */
 780 int avc_has_perm_flags(u32 ssid, u32 tsid, u16 tclass,
 781                        u32 requested, struct common_audit_data *auditdata,
 782                        unsigned flags)
 783 {
 784         struct av_decision avd;
 785         int rc, rc2;
 786
 787         rc = avc_has_perm_noaudit(ssid, tsid, tclass, requested, 0, &avd);
 788
 789         rc2 = avc_audit(ssid, tsid, tclass, requested, &avd, rc, auditdata,
 790                         flags);
 791         if (rc2)
 792                 return rc2;
 793         return rc;
 794 }
 795
 796 u32 avc_policy_seqno(void)
 797 {
 798         return avc_cache.latest_notif;
 799 }
 800
 801 void avc_disable(void)
 802 {
 803         /*
 804          * If you are looking at this because you have realized that we are
 805          * not destroying the avc_node_cachep it might be easy to fix, but
 806          * I don't know the memory barrier semantics well enough to know.  It's
 807          * possible that some other task dereferenced security_ops when
 808          * it still pointed to selinux operations.  If that is the case it's
 809          * possible that it is about to use the avc and is about to need the
 810          * avc_node_cachep.  I know I could wrap the security.c security_ops call
 811          * in an rcu_lock, but seriously, it's not worth it.  Instead I just flush
 812          * the cache and get that memory back.
 813          */
 814         if (avc_node_cachep) {
 815                 avc_flush();
 816                 /* kmem_cache_destroy(avc_node_cachep); */
 817         }
 818 }