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, u32 ssid, u32 tsid,
  69                          u16 tclass, u32 perms,
  70                          u32 *out_retained);
  71         u32 events;
  72         u32 ssid;
  73         u32 tsid;
  74         u16 tclass;
  75         u32 perms;
  76         struct avc_callback_node *next;
  77 };
  78
  79 /* Exported via selinufs */
  80 unsigned int avc_cache_threshold = AVC_DEF_CACHE_THRESHOLD;
  81
  82 #ifdef CONFIG_SECURITY_SELINUX_AVC_STATS
  83 DEFINE_PER_CPU(struct avc_cache_stats, avc_cache_stats) = { 0 };
  84 #endif
  85
  86 static struct avc_cache avc_cache;
  87 static struct avc_callback_node *avc_callbacks;
  88 static struct kmem_cache *avc_node_cachep;
  89
  90 static inline int avc_hash(u32 ssid, u32 tsid, u16 tclass)
  91 {
  92         return (ssid ^ (tsid<<2) ^ (tclass<<4)) & (AVC_CACHE_SLOTS - 1);
  93 }
  94
  95 /**
  96  * avc_dump_av - Display an access vector in human-readable form.
  97  * @tclass: target security class
  98  * @av: access vector
  99  */
 100 static void avc_dump_av(struct audit_buffer *ab, u16 tclass, u32 av)
 101 {
 102         const char **perms;
 103         int i, perm;
 104
 105         if (av == 0) {
 106                 audit_log_format(ab, " null");
 107                 return;
 108         }
 109
 110         perms = secclass_map[tclass-1].perms;
 111
 112         audit_log_format(ab, " {");
 113         i = 0;
 114         perm = 1;
 115         while (i < (sizeof(av) * 8)) {
 116                 if ((perm & av) && perms[i]) {
 117                         audit_log_format(ab, " %s", perms[i]);
 118                         av &= ~perm;
 119                 }
 120                 i++;
 121                 perm <<= 1;
 122         }
 123
 124         if (av)
 125                 audit_log_format(ab, " 0x%x", av);
 126
 127         audit_log_format(ab, " }");
 128 }
 129
 130 /**
 131  * avc_dump_query - Display a SID pair and a class in human-readable form.
 132  * @ssid: source security identifier
 133  * @tsid: target security identifier
 134  * @tclass: target security class
 135  */
 136 static void avc_dump_query(struct audit_buffer *ab, u32 ssid, u32 tsid, u16 tclass)
 137 {
 138         int rc;
 139         char *scontext;
 140         u32 scontext_len;
 141
 142         rc = security_sid_to_context(ssid, &scontext, &scontext_len);
 143         if (rc)
 144                 audit_log_format(ab, "ssid=%d", ssid);
 145         else {
 146                 audit_log_format(ab, "scontext=%s", scontext);
 147                 kfree(scontext);
 148         }
 149
 150         rc = security_sid_to_context(tsid, &scontext, &scontext_len);
 151         if (rc)
 152                 audit_log_format(ab, " tsid=%d", tsid);
 153         else {
 154                 audit_log_format(ab, " tcontext=%s", scontext);
 155                 kfree(scontext);
 156         }
 157
 158         BUG_ON(tclass >= ARRAY_SIZE(secclass_map));
 159         audit_log_format(ab, " tclass=%s", secclass_map[tclass-1].name);
 160 }
 161
 162 /**
 163  * avc_init - Initialize the AVC.
 164  *
 165  * Initialize the access vector cache.
 166  */
 167 void __init avc_init(void)
 168 {
 169         int i;
 170
 171         for (i = 0; i < AVC_CACHE_SLOTS; i++) {
 172                 INIT_HLIST_HEAD(&avc_cache.slots[i]);
 173                 spin_lock_init(&avc_cache.slots_lock[i]);
 174         }
 175         atomic_set(&avc_cache.active_nodes, 0);
 176         atomic_set(&avc_cache.lru_hint, 0);
 177
 178         avc_node_cachep = kmem_cache_create("avc_node", sizeof(struct avc_node),
 179                                              0, SLAB_PANIC, NULL);
 180
 181         audit_log(current->audit_context, GFP_KERNEL, AUDIT_KERNEL, "AVC INITIALIZED\n");
 182 }
 183
 184 int avc_get_hash_stats(char *page)
 185 {
 186         int i, chain_len, max_chain_len, slots_used;
 187         struct avc_node *node;
 188         struct hlist_head *head;
 189
 190         rcu_read_lock();
 191
 192         slots_used = 0;
 193         max_chain_len = 0;
 194         for (i = 0; i < AVC_CACHE_SLOTS; i++) {
 195                 head = &avc_cache.slots[i];
 196                 if (!hlist_empty(head)) {
 197                         struct hlist_node *next;
 198
 199                         slots_used++;
 200                         chain_len = 0;
 201                         hlist_for_each_entry_rcu(node, next, head, list)
 202                                 chain_len++;
 203                         if (chain_len > max_chain_len)
 204                                 max_chain_len = chain_len;
 205                 }
 206         }
 207
 208         rcu_read_unlock();
 209
 210         return scnprintf(page, PAGE_SIZE, "entries: %d\nbuckets used: %d/%d\n"
 211                          "longest chain: %d\n",
 212                          atomic_read(&avc_cache.active_nodes),
 213                          slots_used, AVC_CACHE_SLOTS, max_chain_len);
 214 }
 215
 216 static void avc_node_free(struct rcu_head *rhead)
 217 {
 218         struct avc_node *node = container_of(rhead, struct avc_node, rhead);
 219         kmem_cache_free(avc_node_cachep, node);
 220         avc_cache_stats_incr(frees);
 221 }
 222
 223 static void avc_node_delete(struct avc_node *node)
 224 {
 225         hlist_del_rcu(&node->list);
 226         call_rcu(&node->rhead, avc_node_free);
 227         atomic_dec(&avc_cache.active_nodes);
 228 }
 229
 230 static void avc_node_kill(struct avc_node *node)
 231 {
 232         kmem_cache_free(avc_node_cachep, node);
 233         avc_cache_stats_incr(frees);
 234         atomic_dec(&avc_cache.active_nodes);
 235 }
 236
 237 static void avc_node_replace(struct avc_node *new, struct avc_node *old)
 238 {
 239         hlist_replace_rcu(&old->list, &new->list);
 240         call_rcu(&old->rhead, avc_node_free);
 241         atomic_dec(&avc_cache.active_nodes);
 242 }
 243
 244 static inline int avc_reclaim_node(void)
 245 {
 246         struct avc_node *node;
 247         int hvalue, try, ecx;
 248         unsigned long flags;
 249         struct hlist_head *head;
 250         struct hlist_node *next;
 251         spinlock_t *lock;
 252
 253         for (try = 0, ecx = 0; try < AVC_CACHE_SLOTS; try++) {
 254                 hvalue = atomic_inc_return(&avc_cache.lru_hint) & (AVC_CACHE_SLOTS - 1);
 255                 head = &avc_cache.slots[hvalue];
 256                 lock = &avc_cache.slots_lock[hvalue];
 257
 258                 if (!spin_trylock_irqsave(lock, flags))
 259                         continue;
 260
 261                 rcu_read_lock();
 262                 hlist_for_each_entry(node, next, head, list) {
 263                         avc_node_delete(node);
 264                         avc_cache_stats_incr(reclaims);
 265                         ecx++;
 266                         if (ecx >= AVC_CACHE_RECLAIM) {
 267                                 rcu_read_unlock();
 268                                 spin_unlock_irqrestore(lock, flags);
 269                                 goto out;
 270                         }
 271                 }
 272                 rcu_read_unlock();
 273                 spin_unlock_irqrestore(lock, flags);
 274         }
 275 out:
 276         return ecx;
 277 }
 278
 279 static struct avc_node *avc_alloc_node(void)
 280 {
 281         struct avc_node *node;
 282
 283         node = kmem_cache_zalloc(avc_node_cachep, GFP_ATOMIC);
 284         if (!node)
 285                 goto out;
 286
 287         INIT_HLIST_NODE(&node->list);
 288         avc_cache_stats_incr(allocations);
 289
 290         if (atomic_inc_return(&avc_cache.active_nodes) > avc_cache_threshold)
 291                 avc_reclaim_node();
 292
 293 out:
 294         return node;
 295 }
 296
 297 static void avc_node_populate(struct avc_node *node, u32 ssid, u32 tsid, u16 tclass, struct av_decision *avd)
 298 {
 299         node->ae.ssid = ssid;
 300         node->ae.tsid = tsid;
 301         node->ae.tclass = tclass;
 302         memcpy(&node->ae.avd, avd, sizeof(node->ae.avd));
 303 }
 304
 305 static inline struct avc_node *avc_search_node(u32 ssid, u32 tsid, u16 tclass)
 306 {
 307         struct avc_node *node, *ret = NULL;
 308         int hvalue;
 309         struct hlist_head *head;
 310         struct hlist_node *next;
 311
 312         hvalue = avc_hash(ssid, tsid, tclass);
 313         head = &avc_cache.slots[hvalue];
 314         hlist_for_each_entry_rcu(node, next, head, list) {
 315                 if (ssid == node->ae.ssid &&
 316                     tclass == node->ae.tclass &&
 317                     tsid == node->ae.tsid) {
 318                         ret = node;
 319                         break;
 320                 }
 321         }
 322
 323         return ret;
 324 }
 325
 326 /**
 327  * avc_lookup - Look up an AVC entry.
 328  * @ssid: source security identifier
 329  * @tsid: target security identifier
 330  * @tclass: target security class
 331  *
 332  * Look up an AVC entry that is valid for the
 333  * (@ssid, @tsid), interpreting the permissions
 334  * based on @tclass.  If a valid AVC entry exists,
 335  * then this function returns the avc_node.
 336  * Otherwise, this function returns NULL.
 337  */
 338 static struct avc_node *avc_lookup(u32 ssid, u32 tsid, u16 tclass)
 339 {
 340         struct avc_node *node;
 341
 342         avc_cache_stats_incr(lookups);
 343         node = avc_search_node(ssid, tsid, tclass);
 344
 345         if (node)
 346                 return node;
 347
 348         avc_cache_stats_incr(misses);
 349         return NULL;
 350 }
 351
 352 static int avc_latest_notif_update(int seqno, int is_insert)
 353 {
 354         int ret = 0;
 355         static DEFINE_SPINLOCK(notif_lock);
 356         unsigned long flag;
 357
 358         spin_lock_irqsave(&notif_lock, flag);
 359         if (is_insert) {
 360                 if (seqno < avc_cache.latest_notif) {
 361                         printk(KERN_WARNING "SELinux: avc:  seqno %d < latest_notif %d\n",
 362                                seqno, avc_cache.latest_notif);
 363                         ret = -EAGAIN;
 364                 }
 365         } else {
 366                 if (seqno > avc_cache.latest_notif)
 367                         avc_cache.latest_notif = seqno;
 368         }
 369         spin_unlock_irqrestore(&notif_lock, flag);
 370
 371         return ret;
 372 }
 373
 374 /**
 375  * avc_insert - Insert an AVC entry.
 376  * @ssid: source security identifier
 377  * @tsid: target security identifier
 378  * @tclass: target security class
 379  * @avd: resulting av decision
 380  *
 381  * Insert an AVC entry for the SID pair
 382  * (@ssid, @tsid) and class @tclass.
 383  * The access vectors and the sequence number are
 384  * normally provided by the security server in
 385  * response to a security_compute_av() call.  If the
 386  * sequence number @avd->seqno is not less than the latest
 387  * revocation notification, then the function copies
 388  * the access vectors into a cache entry, returns
 389  * avc_node inserted. Otherwise, this function returns NULL.
 390  */
 391 static struct avc_node *avc_insert(u32 ssid, u32 tsid, u16 tclass, struct av_decision *avd)
 392 {
 393         struct avc_node *pos, *node = NULL;
 394         int hvalue;
 395         unsigned long flag;
 396
 397         if (avc_latest_notif_update(avd->seqno, 1))
 398                 goto out;
 399
 400         node = avc_alloc_node();
 401         if (node) {
 402                 struct hlist_head *head;
 403                 struct hlist_node *next;
 404                 spinlock_t *lock;
 405
 406                 hvalue = avc_hash(ssid, tsid, tclass);
 407                 avc_node_populate(node, ssid, tsid, tclass, avd);
 408
 409                 head = &avc_cache.slots[hvalue];
 410                 lock = &avc_cache.slots_lock[hvalue];
 411
 412                 spin_lock_irqsave(lock, flag);
 413                 hlist_for_each_entry(pos, next, head, list) {
 414                         if (pos->ae.ssid == ssid &&
 415                             pos->ae.tsid == tsid &&
 416                             pos->ae.tclass == tclass) {
 417                                 avc_node_replace(node, pos);
 418                                 goto found;
 419                         }
 420                 }
 421                 hlist_add_head_rcu(&node->list, head);
 422 found:
 423                 spin_unlock_irqrestore(lock, flag);
 424         }
 425 out:
 426         return node;
 427 }
 428
 429 /**
 430  * avc_audit_pre_callback - SELinux specific information
 431  * will be called by generic audit code
 432  * @ab: the audit buffer
 433  * @a: audit_data
 434  */
 435 static void avc_audit_pre_callback(struct audit_buffer *ab, void *a)
 436 {
 437         struct common_audit_data *ad = a;
 438         audit_log_format(ab, "avc:  %s ",
 439                          ad->selinux_audit_data->denied ? "denied" : "granted");
 440         avc_dump_av(ab, ad->selinux_audit_data->tclass,
 441                         ad->selinux_audit_data->audited);
 442         audit_log_format(ab, " for ");
 443 }
 444
 445 /**
 446  * avc_audit_post_callback - SELinux specific information
 447  * will be called by generic audit code
 448  * @ab: the audit buffer
 449  * @a: audit_data
 450  */
 451 static void avc_audit_post_callback(struct audit_buffer *ab, void *a)
 452 {
 453         struct common_audit_data *ad = a;
 454         audit_log_format(ab, " ");
 455         avc_dump_query(ab, ad->selinux_audit_data->ssid,
 456                            ad->selinux_audit_data->tsid,
 457                            ad->selinux_audit_data->tclass);
 458 }
 459
 460 /* This is the slow part of avc audit with big stack footprint */
 461 static noinline int slow_avc_audit(u32 ssid, u32 tsid, u16 tclass,
 462                 u32 requested, u32 audited, u32 denied,
 463                 struct common_audit_data *a,
 464                 unsigned flags)
 465 {
 466         struct common_audit_data stack_data;
 467         struct selinux_audit_data sad = {0,};
 468
 469         if (!a) {
 470                 a = &stack_data;
 471                 COMMON_AUDIT_DATA_INIT(a, NONE);
 472                 a->selinux_audit_data = &sad;
 473         }
 474
 475         /*
 476          * When in a RCU walk do the audit on the RCU retry.  This is because
 477          * the collection of the dname in an inode audit message is not RCU
 478          * safe.  Note this may drop some audits when the situation changes
 479          * during retry. However this is logically just as if the operation
 480          * happened a little later.
 481          */
 482         if ((a->type == LSM_AUDIT_DATA_INODE) &&
 483             (flags & MAY_NOT_BLOCK))
 484                 return -ECHILD;
 485
 486         a->selinux_audit_data->tclass = tclass;
 487         a->selinux_audit_data->requested = requested;
 488         a->selinux_audit_data->ssid = ssid;
 489         a->selinux_audit_data->tsid = tsid;
 490         a->selinux_audit_data->audited = audited;
 491         a->selinux_audit_data->denied = denied;
 492         a->lsm_pre_audit = avc_audit_pre_callback;
 493         a->lsm_post_audit = avc_audit_post_callback;
 494         common_lsm_audit(a);
 495         return 0;
 496 }
 497
 498 /**
 499  * avc_audit - Audit the granting or denial of permissions.
 500  * @ssid: source security identifier
 501  * @tsid: target security identifier
 502  * @tclass: target security class
 503  * @requested: requested permissions
 504  * @avd: access vector decisions
 505  * @result: result from avc_has_perm_noaudit
 506  * @a:  auxiliary audit data
 507  * @flags: VFS walk flags
 508  *
 509  * Audit the granting or denial of permissions in accordance
 510  * with the policy.  This function is typically called by
 511  * avc_has_perm() after a permission check, but can also be
 512  * called directly by callers who use avc_has_perm_noaudit()
 513  * in order to separate the permission check from the auditing.
 514  * For example, this separation is useful when the permission check must
 515  * be performed under a lock, to allow the lock to be released
 516  * before calling the auditing code.
 517  */
 518 inline int avc_audit(u32 ssid, u32 tsid,
 519                u16 tclass, u32 requested,
 520                struct av_decision *avd, int result, struct common_audit_data *a,
 521                unsigned flags)
 522 {
 523         u32 denied, audited;
 524         denied = requested & ~avd->allowed;
 525         if (unlikely(denied)) {
 526                 audited = denied & avd->auditdeny;
 527                 /*
 528                  * a->selinux_audit_data->auditdeny is TRICKY!  Setting a bit in
 529                  * this field means that ANY denials should NOT be audited if
 530                  * the policy contains an explicit dontaudit rule for that
 531                  * permission.  Take notice that this is unrelated to the
 532                  * actual permissions that were denied.  As an example lets
 533                  * assume:
 534                  *
 535                  * denied == READ
 536                  * avd.auditdeny & ACCESS == 0 (not set means explicit rule)
 537                  * selinux_audit_data->auditdeny & ACCESS == 1
 538                  *
 539                  * We will NOT audit the denial even though the denied
 540                  * permission was READ and the auditdeny checks were for
 541                  * ACCESS
 542                  */
 543                 if (a &&
 544                     a->selinux_audit_data->auditdeny &&
 545                     !(a->selinux_audit_data->auditdeny & avd->auditdeny))
 546                         audited = 0;
 547         } else if (result)
 548                 audited = denied = requested;
 549         else
 550                 audited = requested & avd->auditallow;
 551         if (likely(!audited))
 552                 return 0;
 553
 554         return slow_avc_audit(ssid, tsid, tclass,
 555                 requested, audited, denied,
 556                 a, flags);
 557 }
 558
 559 /**
 560  * avc_add_callback - Register a callback for security events.
 561  * @callback: callback function
 562  * @events: security events
 563  * @ssid: source security identifier or %SECSID_WILD
 564  * @tsid: target security identifier or %SECSID_WILD
 565  * @tclass: target security class
 566  * @perms: permissions
 567  *
 568  * Register a callback function for events in the set @events
 569  * related to the SID pair (@ssid, @tsid)
 570  * and the permissions @perms, interpreting
 571  * @perms based on @tclass.  Returns %0 on success or
 572  * -%ENOMEM if insufficient memory exists to add the callback.
 573  */
 574 int avc_add_callback(int (*callback)(u32 event, u32 ssid, u32 tsid,
 575                                      u16 tclass, u32 perms,
 576                                      u32 *out_retained),
 577                      u32 events, u32 ssid, u32 tsid,
 578                      u16 tclass, u32 perms)
 579 {
 580         struct avc_callback_node *c;
 581         int rc = 0;
 582
 583         c = kmalloc(sizeof(*c), GFP_ATOMIC);
 584         if (!c) {
 585                 rc = -ENOMEM;
 586                 goto out;
 587         }
 588
 589         c->callback = callback;
 590         c->events = events;
 591         c->ssid = ssid;
 592         c->tsid = tsid;
 593         c->perms = perms;
 594         c->next = avc_callbacks;
 595         avc_callbacks = c;
 596 out:
 597         return rc;
 598 }
 599
 600 static inline int avc_sidcmp(u32 x, u32 y)
 601 {
 602         return (x == y || x == SECSID_WILD || y == SECSID_WILD);
 603 }
 604
 605 /**
 606  * avc_update_node Update an AVC entry
 607  * @event : Updating event
 608  * @perms : Permission mask bits
 609  * @ssid,@tsid,@tclass : identifier of an AVC entry
 610  * @seqno : sequence number when decision was made
 611  *
 612  * if a valid AVC entry doesn't exist,this function returns -ENOENT.
 613  * if kmalloc() called internal returns NULL, this function returns -ENOMEM.
 614  * otherwise, this function updates the AVC entry. The original AVC-entry object
 615  * will release later by RCU.
 616  */
 617 static int avc_update_node(u32 event, u32 perms, u32 ssid, u32 tsid, u16 tclass,
 618                            u32 seqno)
 619 {
 620         int hvalue, rc = 0;
 621         unsigned long flag;
 622         struct avc_node *pos, *node, *orig = NULL;
 623         struct hlist_head *head;
 624         struct hlist_node *next;
 625         spinlock_t *lock;
 626
 627         node = avc_alloc_node();
 628         if (!node) {
 629                 rc = -ENOMEM;
 630                 goto out;
 631         }
 632
 633         /* Lock the target slot */
 634         hvalue = avc_hash(ssid, tsid, tclass);
 635
 636         head = &avc_cache.slots[hvalue];
 637         lock = &avc_cache.slots_lock[hvalue];
 638
 639         spin_lock_irqsave(lock, flag);
 640
 641         hlist_for_each_entry(pos, next, head, list) {
 642                 if (ssid == pos->ae.ssid &&
 643                     tsid == pos->ae.tsid &&
 644                     tclass == pos->ae.tclass &&
 645                     seqno == pos->ae.avd.seqno){
 646                         orig = pos;
 647                         break;
 648                 }
 649         }
 650
 651         if (!orig) {
 652                 rc = -ENOENT;
 653                 avc_node_kill(node);
 654                 goto out_unlock;
 655         }
 656
 657         /*
 658          * Copy and replace original node.
 659          */
 660
 661         avc_node_populate(node, ssid, tsid, tclass, &orig->ae.avd);
 662
 663         switch (event) {
 664         case AVC_CALLBACK_GRANT:
 665                 node->ae.avd.allowed |= perms;
 666                 break;
 667         case AVC_CALLBACK_TRY_REVOKE:
 668         case AVC_CALLBACK_REVOKE:
 669                 node->ae.avd.allowed &= ~perms;
 670                 break;
 671         case AVC_CALLBACK_AUDITALLOW_ENABLE:
 672                 node->ae.avd.auditallow |= perms;
 673                 break;
 674         case AVC_CALLBACK_AUDITALLOW_DISABLE:
 675                 node->ae.avd.auditallow &= ~perms;
 676                 break;
 677         case AVC_CALLBACK_AUDITDENY_ENABLE:
 678                 node->ae.avd.auditdeny |= perms;
 679                 break;
 680         case AVC_CALLBACK_AUDITDENY_DISABLE:
 681                 node->ae.avd.auditdeny &= ~perms;
 682                 break;
 683         }
 684         avc_node_replace(node, orig);
 685 out_unlock:
 686         spin_unlock_irqrestore(lock, flag);
 687 out:
 688         return rc;
 689 }
 690
 691 /**
 692  * avc_flush - Flush the cache
 693  */
 694 static void avc_flush(void)
 695 {
 696         struct hlist_head *head;
 697         struct hlist_node *next;
 698         struct avc_node *node;
 699         spinlock_t *lock;
 700         unsigned long flag;
 701         int i;
 702
 703         for (i = 0; i < AVC_CACHE_SLOTS; i++) {
 704                 head = &avc_cache.slots[i];
 705                 lock = &avc_cache.slots_lock[i];
 706
 707                 spin_lock_irqsave(lock, flag);
 708                 /*
 709                  * With preemptable RCU, the outer spinlock does not
 710                  * prevent RCU grace periods from ending.
 711                  */
 712                 rcu_read_lock();
 713                 hlist_for_each_entry(node, next, head, list)
 714                         avc_node_delete(node);
 715                 rcu_read_unlock();
 716                 spin_unlock_irqrestore(lock, flag);
 717         }
 718 }
 719
 720 /**
 721  * avc_ss_reset - Flush the cache and revalidate migrated permissions.
 722  * @seqno: policy sequence number
 723  */
 724 int avc_ss_reset(u32 seqno)
 725 {
 726         struct avc_callback_node *c;
 727         int rc = 0, tmprc;
 728
 729         avc_flush();
 730
 731         for (c = avc_callbacks; c; c = c->next) {
 732                 if (c->events & AVC_CALLBACK_RESET) {
 733                         tmprc = c->callback(AVC_CALLBACK_RESET,
 734                                             0, 0, 0, 0, NULL);
 735                         /* save the first error encountered for the return
 736                            value and continue processing the callbacks */
 737                         if (!rc)
 738                                 rc = tmprc;
 739                 }
 740         }
 741
 742         avc_latest_notif_update(seqno, 0);
 743         return rc;
 744 }
 745
 746 /*
 747  * Slow-path helper function for avc_has_perm_noaudit,
 748  * when the avc_node lookup fails. We get called with
 749  * the RCU read lock held, and need to return with it
 750  * still held, but drop if for the security compute.
 751  *
 752  * Don't inline this, since it's the slow-path and just
 753  * results in a bigger stack frame.
 754  */
 755 static noinline struct avc_node *avc_compute_av(u32 ssid, u32 tsid,
 756                          u16 tclass, struct av_decision *avd)
 757 {
 758         rcu_read_unlock();
 759         security_compute_av(ssid, tsid, tclass, avd);
 760         rcu_read_lock();
 761         return avc_insert(ssid, tsid, tclass, avd);
 762 }
 763
 764 static noinline int avc_denied(u32 ssid, u32 tsid,
 765                          u16 tclass, u32 requested,
 766                          unsigned flags,
 767                          struct av_decision *avd)
 768 {
 769         if (flags & AVC_STRICT)
 770                 return -EACCES;
 771
 772         if (selinux_enforcing && !(avd->flags & AVD_FLAGS_PERMISSIVE))
 773                 return -EACCES;
 774
 775         avc_update_node(AVC_CALLBACK_GRANT, requested, ssid,
 776                                 tsid, tclass, avd->seqno);
 777         return 0;
 778 }
 779
 780
 781 /**
 782  * avc_has_perm_noaudit - Check permissions but perform no auditing.
 783  * @ssid: source security identifier
 784  * @tsid: target security identifier
 785  * @tclass: target security class
 786  * @requested: requested permissions, interpreted based on @tclass
 787  * @flags:  AVC_STRICT or 0
 788  * @avd: access vector decisions
 789  *
 790  * Check the AVC to determine whether the @requested permissions are granted
 791  * for the SID pair (@ssid, @tsid), interpreting the permissions
 792  * based on @tclass, and call the security server on a cache miss to obtain
 793  * a new decision and add it to the cache.  Return a copy of the decisions
 794  * in @avd.  Return %0 if all @requested permissions are granted,
 795  * -%EACCES if any permissions are denied, or another -errno upon
 796  * other errors.  This function is typically called by avc_has_perm(),
 797  * but may also be called directly to separate permission checking from
 798  * auditing, e.g. in cases where a lock must be held for the check but
 799  * should be released for the auditing.
 800  */
 801 inline int avc_has_perm_noaudit(u32 ssid, u32 tsid,
 802                          u16 tclass, u32 requested,
 803                          unsigned flags,
 804                          struct av_decision *avd)
 805 {
 806         struct avc_node *node;
 807         int rc = 0;
 808         u32 denied;
 809
 810         BUG_ON(!requested);
 811
 812         rcu_read_lock();
 813
 814         node = avc_lookup(ssid, tsid, tclass);
 815         if (unlikely(!node)) {
 816                 node = avc_compute_av(ssid, tsid, tclass, avd);
 817         } else {
 818                 memcpy(avd, &node->ae.avd, sizeof(*avd));
 819                 avd = &node->ae.avd;
 820         }
 821
 822         denied = requested & ~(avd->allowed);
 823         if (unlikely(denied))
 824                 rc = avc_denied(ssid, tsid, tclass, requested, flags, avd);
 825
 826         rcu_read_unlock();
 827         return rc;
 828 }
 829
 830 /**
 831  * avc_has_perm - Check permissions and perform any appropriate auditing.
 832  * @ssid: source security identifier
 833  * @tsid: target security identifier
 834  * @tclass: target security class
 835  * @requested: requested permissions, interpreted based on @tclass
 836  * @auditdata: auxiliary audit data
 837  * @flags: VFS walk flags
 838  *
 839  * Check the AVC to determine whether the @requested permissions are granted
 840  * for the SID pair (@ssid, @tsid), interpreting the permissions
 841  * based on @tclass, and call the security server on a cache miss to obtain
 842  * a new decision and add it to the cache.  Audit the granting or denial of
 843  * permissions in accordance with the policy.  Return %0 if all @requested
 844  * permissions are granted, -%EACCES if any permissions are denied, or
 845  * another -errno upon other errors.
 846  */
 847 int avc_has_perm_flags(u32 ssid, u32 tsid, u16 tclass,
 848                        u32 requested, struct common_audit_data *auditdata,
 849                        unsigned flags)
 850 {
 851         struct av_decision avd;
 852         int rc, rc2;
 853
 854         rc = avc_has_perm_noaudit(ssid, tsid, tclass, requested, 0, &avd);
 855
 856         rc2 = avc_audit(ssid, tsid, tclass, requested, &avd, rc, auditdata,
 857                         flags);
 858         if (rc2)
 859                 return rc2;
 860         return rc;
 861 }
 862
 863 u32 avc_policy_seqno(void)
 864 {
 865         return avc_cache.latest_notif;
 866 }
 867
 868 void avc_disable(void)
 869 {
 870         /*
 871          * If you are looking at this because you have realized that we are
 872          * not destroying the avc_node_cachep it might be easy to fix, but
 873          * I don't know the memory barrier semantics well enough to know.  It's
 874          * possible that some other task dereferenced security_ops when
 875          * it still pointed to selinux operations.  If that is the case it's
 876          * possible that it is about to use the avc and is about to need the
 877          * avc_node_cachep.  I know I could wrap the security.c security_ops call
 878          * in an rcu_lock, but seriously, it's not worth it.  Instead I just flush
 879          * the cache and get that memory back.
 880          */
 881         if (avc_node_cachep) {
 882                 avc_flush();
 883                 /* kmem_cache_destroy(avc_node_cachep); */
 884         }
 885 }