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_HLIST_NODE(&node->list);
 292         avc_cache_stats_incr(allocations);
 293
 294         if (atomic_inc_return(&avc_cache.active_nodes) > avc_cache_threshold)
 295                 avc_reclaim_node();
 296
 297 out:
 298         return node;
 299 }
 300
 301 static void avc_node_populate(struct avc_node *node, u32 ssid, u32 tsid, u16 tclass, struct av_decision *avd)
 302 {
 303         node->ae.ssid = ssid;
 304         node->ae.tsid = tsid;
 305         node->ae.tclass = tclass;
 306         memcpy(&node->ae.avd, avd, sizeof(node->ae.avd));
 307 }
 308
 309 static inline struct avc_node *avc_search_node(u32 ssid, u32 tsid, u16 tclass)
 310 {
 311         struct avc_node *node, *ret = NULL;
 312         int hvalue;
 313         struct hlist_head *head;
 314         struct hlist_node *next;
 315
 316         hvalue = avc_hash(ssid, tsid, tclass);
 317         head = &avc_cache.slots[hvalue];
 318         hlist_for_each_entry_rcu(node, next, head, list) {
 319                 if (ssid == node->ae.ssid &&
 320                     tclass == node->ae.tclass &&
 321                     tsid == node->ae.tsid) {
 322                         ret = node;
 323                         break;
 324                 }
 325         }
 326
 327         return ret;
 328 }
 329
 330 /**
 331  * avc_lookup - Look up an AVC entry.
 332  * @ssid: source security identifier
 333  * @tsid: target security identifier
 334  * @tclass: target security class
 335  *
 336  * Look up an AVC entry that is valid for the
 337  * (@ssid, @tsid), interpreting the permissions
 338  * based on @tclass.  If a valid AVC entry exists,
 339  * then this function returns the avc_node.
 340  * Otherwise, this function returns NULL.
 341  */
 342 static struct avc_node *avc_lookup(u32 ssid, u32 tsid, u16 tclass)
 343 {
 344         struct avc_node *node;
 345
 346         avc_cache_stats_incr(lookups);
 347         node = avc_search_node(ssid, tsid, tclass);
 348
 349         if (node)
 350                 avc_cache_stats_incr(hits);
 351         else
 352                 avc_cache_stats_incr(misses);
 353
 354         return node;
 355 }
 356
 357 static int avc_latest_notif_update(int seqno, int is_insert)
 358 {
 359         int ret = 0;
 360         static DEFINE_SPINLOCK(notif_lock);
 361         unsigned long flag;
 362
 363         spin_lock_irqsave(&notif_lock, flag);
 364         if (is_insert) {
 365                 if (seqno < avc_cache.latest_notif) {
 366                         printk(KERN_WARNING "SELinux: avc:  seqno %d < latest_notif %d\n",
 367                                seqno, avc_cache.latest_notif);
 368                         ret = -EAGAIN;
 369                 }
 370         } else {
 371                 if (seqno > avc_cache.latest_notif)
 372                         avc_cache.latest_notif = seqno;
 373         }
 374         spin_unlock_irqrestore(&notif_lock, flag);
 375
 376         return ret;
 377 }
 378
 379 /**
 380  * avc_insert - Insert an AVC entry.
 381  * @ssid: source security identifier
 382  * @tsid: target security identifier
 383  * @tclass: target security class
 384  * @avd: resulting av decision
 385  *
 386  * Insert an AVC entry for the SID pair
 387  * (@ssid, @tsid) and class @tclass.
 388  * The access vectors and the sequence number are
 389  * normally provided by the security server in
 390  * response to a security_compute_av() call.  If the
 391  * sequence number @avd->seqno is not less than the latest
 392  * revocation notification, then the function copies
 393  * the access vectors into a cache entry, returns
 394  * avc_node inserted. Otherwise, this function returns NULL.
 395  */
 396 static struct avc_node *avc_insert(u32 ssid, u32 tsid, u16 tclass, struct av_decision *avd)
 397 {
 398         struct avc_node *pos, *node = NULL;
 399         int hvalue;
 400         unsigned long flag;
 401
 402         if (avc_latest_notif_update(avd->seqno, 1))
 403                 goto out;
 404
 405         node = avc_alloc_node();
 406         if (node) {
 407                 struct hlist_head *head;
 408                 struct hlist_node *next;
 409                 spinlock_t *lock;
 410
 411                 hvalue = avc_hash(ssid, tsid, tclass);
 412                 avc_node_populate(node, ssid, tsid, tclass, avd);
 413
 414                 head = &avc_cache.slots[hvalue];
 415                 lock = &avc_cache.slots_lock[hvalue];
 416
 417                 spin_lock_irqsave(lock, flag);
 418                 hlist_for_each_entry(pos, next, head, list) {
 419                         if (pos->ae.ssid == ssid &&
 420                             pos->ae.tsid == tsid &&
 421                             pos->ae.tclass == tclass) {
 422                                 avc_node_replace(node, pos);
 423                                 goto found;
 424                         }
 425                 }
 426                 hlist_add_head_rcu(&node->list, head);
 427 found:
 428                 spin_unlock_irqrestore(lock, flag);
 429         }
 430 out:
 431         return node;
 432 }
 433
 434 /**
 435  * avc_audit_pre_callback - SELinux specific information
 436  * will be called by generic audit code
 437  * @ab: the audit buffer
 438  * @a: audit_data
 439  */
 440 static void avc_audit_pre_callback(struct audit_buffer *ab, void *a)
 441 {
 442         struct common_audit_data *ad = a;
 443         audit_log_format(ab, "avc:  %s ",
 444                          ad->selinux_audit_data.denied ? "denied" : "granted");
 445         avc_dump_av(ab, ad->selinux_audit_data.tclass,
 446                         ad->selinux_audit_data.audited);
 447         audit_log_format(ab, " for ");
 448 }
 449
 450 /**
 451  * avc_audit_post_callback - SELinux specific information
 452  * will be called by generic audit code
 453  * @ab: the audit buffer
 454  * @a: audit_data
 455  */
 456 static void avc_audit_post_callback(struct audit_buffer *ab, void *a)
 457 {
 458         struct common_audit_data *ad = a;
 459         audit_log_format(ab, " ");
 460         avc_dump_query(ab, ad->selinux_audit_data.ssid,
 461                            ad->selinux_audit_data.tsid,
 462                            ad->selinux_audit_data.tclass);
 463 }
 464
 465 /**
 466  * avc_audit - Audit the granting or denial of permissions.
 467  * @ssid: source security identifier
 468  * @tsid: target security identifier
 469  * @tclass: target security class
 470  * @requested: requested permissions
 471  * @avd: access vector decisions
 472  * @result: result from avc_has_perm_noaudit
 473  * @a:  auxiliary audit data
 474  * @flags: VFS walk flags
 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 int avc_audit(u32 ssid, u32 tsid,
 486                u16 tclass, u32 requested,
 487                struct av_decision *avd, int result, struct common_audit_data *a,
 488                unsigned flags)
 489 {
 490         struct common_audit_data stack_data;
 491         u32 denied, audited;
 492         denied = requested & ~avd->allowed;
 493         if (denied) {
 494                 audited = denied & avd->auditdeny;
 495                 /*
 496                  * a->selinux_audit_data.auditdeny is TRICKY!  Setting a bit in
 497                  * this field means that ANY denials should NOT be audited if
 498                  * the policy contains an explicit dontaudit rule for that
 499                  * permission.  Take notice that this is unrelated to the
 500                  * actual permissions that were denied.  As an example lets
 501                  * assume:
 502                  *
 503                  * denied == READ
 504                  * avd.auditdeny & ACCESS == 0 (not set means explicit rule)
 505                  * selinux_audit_data.auditdeny & ACCESS == 1
 506                  *
 507                  * We will NOT audit the denial even though the denied
 508                  * permission was READ and the auditdeny checks were for
 509                  * ACCESS
 510                  */
 511                 if (a &&
 512                     a->selinux_audit_data.auditdeny &&
 513                     !(a->selinux_audit_data.auditdeny & avd->auditdeny))
 514                         audited = 0;
 515         } else if (result)
 516                 audited = denied = requested;
 517         else
 518                 audited = requested & avd->auditallow;
 519         if (!audited)
 520                 return 0;
 521
 522         if (!a) {
 523                 a = &stack_data;
 524                 COMMON_AUDIT_DATA_INIT(a, NONE);
 525         }
 526
 527         /*
 528          * When in a RCU walk do the audit on the RCU retry.  This is because
 529          * the collection of the dname in an inode audit message is not RCU
 530          * safe.  Note this may drop some audits when the situation changes
 531          * during retry. However this is logically just as if the operation
 532          * happened a little later.
 533          */
 534         if ((a->type == LSM_AUDIT_DATA_FS) &&
 535             (flags & IPERM_FLAG_RCU))
 536                 return -ECHILD;
 537
 538         a->selinux_audit_data.tclass = tclass;
 539         a->selinux_audit_data.requested = requested;
 540         a->selinux_audit_data.ssid = ssid;
 541         a->selinux_audit_data.tsid = tsid;
 542         a->selinux_audit_data.audited = audited;
 543         a->selinux_audit_data.denied = denied;
 544         a->lsm_pre_audit = avc_audit_pre_callback;
 545         a->lsm_post_audit = avc_audit_post_callback;
 546         common_lsm_audit(a);
 547         return 0;
 548 }
 549
 550 /**
 551  * avc_add_callback - Register a callback for security events.
 552  * @callback: callback function
 553  * @events: security events
 554  * @ssid: source security identifier or %SECSID_WILD
 555  * @tsid: target security identifier or %SECSID_WILD
 556  * @tclass: target security class
 557  * @perms: permissions
 558  *
 559  * Register a callback function for events in the set @events
 560  * related to the SID pair (@ssid, @tsid)
 561  * and the permissions @perms, interpreting
 562  * @perms based on @tclass.  Returns %0 on success or
 563  * -%ENOMEM if insufficient memory exists to add the callback.
 564  */
 565 int avc_add_callback(int (*callback)(u32 event, u32 ssid, u32 tsid,
 566                                      u16 tclass, u32 perms,
 567                                      u32 *out_retained),
 568                      u32 events, u32 ssid, u32 tsid,
 569                      u16 tclass, u32 perms)
 570 {
 571         struct avc_callback_node *c;
 572         int rc = 0;
 573
 574         c = kmalloc(sizeof(*c), GFP_ATOMIC);
 575         if (!c) {
 576                 rc = -ENOMEM;
 577                 goto out;
 578         }
 579
 580         c->callback = callback;
 581         c->events = events;
 582         c->ssid = ssid;
 583         c->tsid = tsid;
 584         c->perms = perms;
 585         c->next = avc_callbacks;
 586         avc_callbacks = c;
 587 out:
 588         return rc;
 589 }
 590
 591 static inline int avc_sidcmp(u32 x, u32 y)
 592 {
 593         return (x == y || x == SECSID_WILD || y == SECSID_WILD);
 594 }
 595
 596 /**
 597  * avc_update_node Update an AVC entry
 598  * @event : Updating event
 599  * @perms : Permission mask bits
 600  * @ssid,@tsid,@tclass : identifier of an AVC entry
 601  * @seqno : sequence number when decision was made
 602  *
 603  * if a valid AVC entry doesn't exist,this function returns -ENOENT.
 604  * if kmalloc() called internal returns NULL, this function returns -ENOMEM.
 605  * otherwise, this function updates the AVC entry. The original AVC-entry object
 606  * will release later by RCU.
 607  */
 608 static int avc_update_node(u32 event, u32 perms, u32 ssid, u32 tsid, u16 tclass,
 609                            u32 seqno)
 610 {
 611         int hvalue, rc = 0;
 612         unsigned long flag;
 613         struct avc_node *pos, *node, *orig = NULL;
 614         struct hlist_head *head;
 615         struct hlist_node *next;
 616         spinlock_t *lock;
 617
 618         node = avc_alloc_node();
 619         if (!node) {
 620                 rc = -ENOMEM;
 621                 goto out;
 622         }
 623
 624         /* Lock the target slot */
 625         hvalue = avc_hash(ssid, tsid, tclass);
 626
 627         head = &avc_cache.slots[hvalue];
 628         lock = &avc_cache.slots_lock[hvalue];
 629
 630         spin_lock_irqsave(lock, flag);
 631
 632         hlist_for_each_entry(pos, next, head, list) {
 633                 if (ssid == pos->ae.ssid &&
 634                     tsid == pos->ae.tsid &&
 635                     tclass == pos->ae.tclass &&
 636                     seqno == pos->ae.avd.seqno){
 637                         orig = pos;
 638                         break;
 639                 }
 640         }
 641
 642         if (!orig) {
 643                 rc = -ENOENT;
 644                 avc_node_kill(node);
 645                 goto out_unlock;
 646         }
 647
 648         /*
 649          * Copy and replace original node.
 650          */
 651
 652         avc_node_populate(node, ssid, tsid, tclass, &orig->ae.avd);
 653
 654         switch (event) {
 655         case AVC_CALLBACK_GRANT:
 656                 node->ae.avd.allowed |= perms;
 657                 break;
 658         case AVC_CALLBACK_TRY_REVOKE:
 659         case AVC_CALLBACK_REVOKE:
 660                 node->ae.avd.allowed &= ~perms;
 661                 break;
 662         case AVC_CALLBACK_AUDITALLOW_ENABLE:
 663                 node->ae.avd.auditallow |= perms;
 664                 break;
 665         case AVC_CALLBACK_AUDITALLOW_DISABLE:
 666                 node->ae.avd.auditallow &= ~perms;
 667                 break;
 668         case AVC_CALLBACK_AUDITDENY_ENABLE:
 669                 node->ae.avd.auditdeny |= perms;
 670                 break;
 671         case AVC_CALLBACK_AUDITDENY_DISABLE:
 672                 node->ae.avd.auditdeny &= ~perms;
 673                 break;
 674         }
 675         avc_node_replace(node, orig);
 676 out_unlock:
 677         spin_unlock_irqrestore(lock, flag);
 678 out:
 679         return rc;
 680 }
 681
 682 /**
 683  * avc_flush - Flush the cache
 684  */
 685 static void avc_flush(void)
 686 {
 687         struct hlist_head *head;
 688         struct hlist_node *next;
 689         struct avc_node *node;
 690         spinlock_t *lock;
 691         unsigned long flag;
 692         int i;
 693
 694         for (i = 0; i < AVC_CACHE_SLOTS; i++) {
 695                 head = &avc_cache.slots[i];
 696                 lock = &avc_cache.slots_lock[i];
 697
 698                 spin_lock_irqsave(lock, flag);
 699                 /*
 700                  * With preemptable RCU, the outer spinlock does not
 701                  * prevent RCU grace periods from ending.
 702                  */
 703                 rcu_read_lock();
 704                 hlist_for_each_entry(node, next, head, list)
 705                         avc_node_delete(node);
 706                 rcu_read_unlock();
 707                 spin_unlock_irqrestore(lock, flag);
 708         }
 709 }
 710
 711 /**
 712  * avc_ss_reset - Flush the cache and revalidate migrated permissions.
 713  * @seqno: policy sequence number
 714  */
 715 int avc_ss_reset(u32 seqno)
 716 {
 717         struct avc_callback_node *c;
 718         int rc = 0, tmprc;
 719
 720         avc_flush();
 721
 722         for (c = avc_callbacks; c; c = c->next) {
 723                 if (c->events & AVC_CALLBACK_RESET) {
 724                         tmprc = c->callback(AVC_CALLBACK_RESET,
 725                                             0, 0, 0, 0, NULL);
 726                         /* save the first error encountered for the return
 727                            value and continue processing the callbacks */
 728                         if (!rc)
 729                                 rc = tmprc;
 730                 }
 731         }
 732
 733         avc_latest_notif_update(seqno, 0);
 734         return rc;
 735 }
 736
 737 /**
 738  * avc_has_perm_noaudit - Check permissions but perform no auditing.
 739  * @ssid: source security identifier
 740  * @tsid: target security identifier
 741  * @tclass: target security class
 742  * @requested: requested permissions, interpreted based on @tclass
 743  * @flags:  AVC_STRICT or 0
 744  * @avd: access vector decisions
 745  *
 746  * Check the AVC to determine whether the @requested permissions are granted
 747  * for the SID pair (@ssid, @tsid), interpreting the permissions
 748  * based on @tclass, and call the security server on a cache miss to obtain
 749  * a new decision and add it to the cache.  Return a copy of the decisions
 750  * in @avd.  Return %0 if all @requested permissions are granted,
 751  * -%EACCES if any permissions are denied, or another -errno upon
 752  * other errors.  This function is typically called by avc_has_perm(),
 753  * but may also be called directly to separate permission checking from
 754  * auditing, e.g. in cases where a lock must be held for the check but
 755  * should be released for the auditing.
 756  */
 757 int avc_has_perm_noaudit(u32 ssid, u32 tsid,
 758                          u16 tclass, u32 requested,
 759                          unsigned flags,
 760                          struct av_decision *in_avd)
 761 {
 762         struct avc_node *node;
 763         struct av_decision avd_entry, *avd;
 764         int rc = 0;
 765         u32 denied;
 766
 767         BUG_ON(!requested);
 768
 769         rcu_read_lock();
 770
 771         node = avc_lookup(ssid, tsid, tclass);
 772         if (!node) {
 773                 rcu_read_unlock();
 774
 775                 if (in_avd)
 776                         avd = in_avd;
 777                 else
 778                         avd = &avd_entry;
 779
 780                 security_compute_av(ssid, tsid, tclass, avd);
 781                 rcu_read_lock();
 782                 node = avc_insert(ssid, tsid, tclass, avd);
 783         } else {
 784                 if (in_avd)
 785                         memcpy(in_avd, &node->ae.avd, sizeof(*in_avd));
 786                 avd = &node->ae.avd;
 787         }
 788
 789         denied = requested & ~(avd->allowed);
 790
 791         if (denied) {
 792                 if (flags & AVC_STRICT)
 793                         rc = -EACCES;
 794                 else if (!selinux_enforcing || (avd->flags & AVD_FLAGS_PERMISSIVE))
 795                         avc_update_node(AVC_CALLBACK_GRANT, requested, ssid,
 796                                         tsid, tclass, avd->seqno);
 797                 else
 798                         rc = -EACCES;
 799         }
 800
 801         rcu_read_unlock();
 802         return rc;
 803 }
 804
 805 /**
 806  * avc_has_perm - Check permissions and perform any appropriate auditing.
 807  * @ssid: source security identifier
 808  * @tsid: target security identifier
 809  * @tclass: target security class
 810  * @requested: requested permissions, interpreted based on @tclass
 811  * @auditdata: auxiliary audit data
 812  * @flags: VFS walk flags
 813  *
 814  * Check the AVC to determine whether the @requested permissions are granted
 815  * for the SID pair (@ssid, @tsid), interpreting the permissions
 816  * based on @tclass, and call the security server on a cache miss to obtain
 817  * a new decision and add it to the cache.  Audit the granting or denial of
 818  * permissions in accordance with the policy.  Return %0 if all @requested
 819  * permissions are granted, -%EACCES if any permissions are denied, or
 820  * another -errno upon other errors.
 821  */
 822 int avc_has_perm_flags(u32 ssid, u32 tsid, u16 tclass,
 823                        u32 requested, struct common_audit_data *auditdata,
 824                        unsigned flags)
 825 {
 826         struct av_decision avd;
 827         int rc, rc2;
 828
 829         rc = avc_has_perm_noaudit(ssid, tsid, tclass, requested, 0, &avd);
 830
 831         rc2 = avc_audit(ssid, tsid, tclass, requested, &avd, rc, auditdata,
 832                         flags);
 833         if (rc2)
 834                 return rc2;
 835         return rc;
 836 }
 837
 838 u32 avc_policy_seqno(void)
 839 {
 840         return avc_cache.latest_notif;
 841 }
 842
 843 void avc_disable(void)
 844 {
 845         /*
 846          * If you are looking at this because you have realized that we are
 847          * not destroying the avc_node_cachep it might be easy to fix, but
 848          * I don't know the memory barrier semantics well enough to know.  It's
 849          * possible that some other task dereferenced security_ops when
 850          * it still pointed to selinux operations.  If that is the case it's
 851          * possible that it is about to use the avc and is about to need the
 852          * avc_node_cachep.  I know I could wrap the security.c security_ops call
 853          * in an rcu_lock, but seriously, it's not worth it.  Instead I just flush
 854          * the cache and get that memory back.
 855          */
 856         if (avc_node_cachep) {
 857                 avc_flush();
 858                 /* kmem_cache_destroy(avc_node_cachep); */
 859         }
 860 }