linux/security/selinux/avc.c
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   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)                             \
  42do {                                                            \
  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
  50struct avc_entry {
  51        u32                     ssid;
  52        u32                     tsid;
  53        u16                     tclass;
  54        struct av_decision      avd;
  55};
  56
  57struct 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
  63struct 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
  71struct 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 */
  84unsigned int avc_cache_threshold = AVC_DEF_CACHE_THRESHOLD;
  85
  86#ifdef CONFIG_SECURITY_SELINUX_AVC_STATS
  87DEFINE_PER_CPU(struct avc_cache_stats, avc_cache_stats) = { 0 };
  88#endif
  89
  90static struct avc_cache avc_cache;
  91static struct avc_callback_node *avc_callbacks;
  92static struct kmem_cache *avc_node_cachep;
  93
  94static 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 */
 104static 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 */
 140static 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 */
 171void __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
 188int 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
 220static 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
 227static 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
 234static 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
 241static 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
 248static 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        }
 279out:
 280        return ecx;
 281}
 282
 283static 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
 297out:
 298        return node;
 299}
 300
 301static 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
 309static 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 */
 342static 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
 357static 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 */
 396static 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);
 427found:
 428                spin_unlock_irqrestore(lock, flag);
 429        }
 430out:
 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 */
 440static 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 */
 456static 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 *
 475 * Audit the granting or denial of permissions in accordance
 476 * with the policy.  This function is typically called by
 477 * avc_has_perm() after a permission check, but can also be
 478 * called directly by callers who use avc_has_perm_noaudit()
 479 * in order to separate the permission check from the auditing.
 480 * For example, this separation is useful when the permission check must
 481 * be performed under a lock, to allow the lock to be released
 482 * before calling the auditing code.
 483 */
 484void avc_audit(u32 ssid, u32 tsid,
 485               u16 tclass, u32 requested,
 486               struct av_decision *avd, int result, struct common_audit_data *a)
 487{
 488        struct common_audit_data stack_data;
 489        u32 denied, audited;
 490        denied = requested & ~avd->allowed;
 491        if (denied) {
 492                audited = denied & avd->auditdeny;
 493                /*
 494                 * a->selinux_audit_data.auditdeny is TRICKY!  Setting a bit in
 495                 * this field means that ANY denials should NOT be audited if
 496                 * the policy contains an explicit dontaudit rule for that
 497                 * permission.  Take notice that this is unrelated to the
 498                 * actual permissions that were denied.  As an example lets
 499                 * assume:
 500                 *
 501                 * denied == READ
 502                 * avd.auditdeny & ACCESS == 0 (not set means explicit rule)
 503                 * selinux_audit_data.auditdeny & ACCESS == 1
 504                 *
 505                 * We will NOT audit the denial even though the denied
 506                 * permission was READ and the auditdeny checks were for
 507                 * ACCESS
 508                 */
 509                if (a &&
 510                    a->selinux_audit_data.auditdeny &&
 511                    !(a->selinux_audit_data.auditdeny & avd->auditdeny))
 512                        audited = 0;
 513        } else if (result)
 514                audited = denied = requested;
 515        else
 516                audited = requested & avd->auditallow;
 517        if (!audited)
 518                return;
 519        if (!a) {
 520                a = &stack_data;
 521                COMMON_AUDIT_DATA_INIT(a, NONE);
 522        }
 523        a->selinux_audit_data.tclass = tclass;
 524        a->selinux_audit_data.requested = requested;
 525        a->selinux_audit_data.ssid = ssid;
 526        a->selinux_audit_data.tsid = tsid;
 527        a->selinux_audit_data.audited = audited;
 528        a->selinux_audit_data.denied = denied;
 529        a->lsm_pre_audit = avc_audit_pre_callback;
 530        a->lsm_post_audit = avc_audit_post_callback;
 531        common_lsm_audit(a);
 532}
 533
 534/**
 535 * avc_add_callback - Register a callback for security events.
 536 * @callback: callback function
 537 * @events: security events
 538 * @ssid: source security identifier or %SECSID_WILD
 539 * @tsid: target security identifier or %SECSID_WILD
 540 * @tclass: target security class
 541 * @perms: permissions
 542 *
 543 * Register a callback function for events in the set @events
 544 * related to the SID pair (@ssid, @tsid) 
 545 * and the permissions @perms, interpreting
 546 * @perms based on @tclass.  Returns %0 on success or
 547 * -%ENOMEM if insufficient memory exists to add the callback.
 548 */
 549int avc_add_callback(int (*callback)(u32 event, u32 ssid, u32 tsid,
 550                                     u16 tclass, u32 perms,
 551                                     u32 *out_retained),
 552                     u32 events, u32 ssid, u32 tsid,
 553                     u16 tclass, u32 perms)
 554{
 555        struct avc_callback_node *c;
 556        int rc = 0;
 557
 558        c = kmalloc(sizeof(*c), GFP_ATOMIC);
 559        if (!c) {
 560                rc = -ENOMEM;
 561                goto out;
 562        }
 563
 564        c->callback = callback;
 565        c->events = events;
 566        c->ssid = ssid;
 567        c->tsid = tsid;
 568        c->perms = perms;
 569        c->next = avc_callbacks;
 570        avc_callbacks = c;
 571out:
 572        return rc;
 573}
 574
 575static inline int avc_sidcmp(u32 x, u32 y)
 576{
 577        return (x == y || x == SECSID_WILD || y == SECSID_WILD);
 578}
 579
 580/**
 581 * avc_update_node Update an AVC entry
 582 * @event : Updating event
 583 * @perms : Permission mask bits
 584 * @ssid,@tsid,@tclass : identifier of an AVC entry
 585 * @seqno : sequence number when decision was made
 586 *
 587 * if a valid AVC entry doesn't exist,this function returns -ENOENT.
 588 * if kmalloc() called internal returns NULL, this function returns -ENOMEM.
 589 * otherwise, this function updates the AVC entry. The original AVC-entry object
 590 * will release later by RCU.
 591 */
 592static int avc_update_node(u32 event, u32 perms, u32 ssid, u32 tsid, u16 tclass,
 593                           u32 seqno)
 594{
 595        int hvalue, rc = 0;
 596        unsigned long flag;
 597        struct avc_node *pos, *node, *orig = NULL;
 598        struct hlist_head *head;
 599        struct hlist_node *next;
 600        spinlock_t *lock;
 601
 602        node = avc_alloc_node();
 603        if (!node) {
 604                rc = -ENOMEM;
 605                goto out;
 606        }
 607
 608        /* Lock the target slot */
 609        hvalue = avc_hash(ssid, tsid, tclass);
 610
 611        head = &avc_cache.slots[hvalue];
 612        lock = &avc_cache.slots_lock[hvalue];
 613
 614        spin_lock_irqsave(lock, flag);
 615
 616        hlist_for_each_entry(pos, next, head, list) {
 617                if (ssid == pos->ae.ssid &&
 618                    tsid == pos->ae.tsid &&
 619                    tclass == pos->ae.tclass &&
 620                    seqno == pos->ae.avd.seqno){
 621                        orig = pos;
 622                        break;
 623                }
 624        }
 625
 626        if (!orig) {
 627                rc = -ENOENT;
 628                avc_node_kill(node);
 629                goto out_unlock;
 630        }
 631
 632        /*
 633         * Copy and replace original node.
 634         */
 635
 636        avc_node_populate(node, ssid, tsid, tclass, &orig->ae.avd);
 637
 638        switch (event) {
 639        case AVC_CALLBACK_GRANT:
 640                node->ae.avd.allowed |= perms;
 641                break;
 642        case AVC_CALLBACK_TRY_REVOKE:
 643        case AVC_CALLBACK_REVOKE:
 644                node->ae.avd.allowed &= ~perms;
 645                break;
 646        case AVC_CALLBACK_AUDITALLOW_ENABLE:
 647                node->ae.avd.auditallow |= perms;
 648                break;
 649        case AVC_CALLBACK_AUDITALLOW_DISABLE:
 650                node->ae.avd.auditallow &= ~perms;
 651                break;
 652        case AVC_CALLBACK_AUDITDENY_ENABLE:
 653                node->ae.avd.auditdeny |= perms;
 654                break;
 655        case AVC_CALLBACK_AUDITDENY_DISABLE:
 656                node->ae.avd.auditdeny &= ~perms;
 657                break;
 658        }
 659        avc_node_replace(node, orig);
 660out_unlock:
 661        spin_unlock_irqrestore(lock, flag);
 662out:
 663        return rc;
 664}
 665
 666/**
 667 * avc_flush - Flush the cache
 668 */
 669static void avc_flush(void)
 670{
 671        struct hlist_head *head;
 672        struct hlist_node *next;
 673        struct avc_node *node;
 674        spinlock_t *lock;
 675        unsigned long flag;
 676        int i;
 677
 678        for (i = 0; i < AVC_CACHE_SLOTS; i++) {
 679                head = &avc_cache.slots[i];
 680                lock = &avc_cache.slots_lock[i];
 681
 682                spin_lock_irqsave(lock, flag);
 683                /*
 684                 * With preemptable RCU, the outer spinlock does not
 685                 * prevent RCU grace periods from ending.
 686                 */
 687                rcu_read_lock();
 688                hlist_for_each_entry(node, next, head, list)
 689                        avc_node_delete(node);
 690                rcu_read_unlock();
 691                spin_unlock_irqrestore(lock, flag);
 692        }
 693}
 694
 695/**
 696 * avc_ss_reset - Flush the cache and revalidate migrated permissions.
 697 * @seqno: policy sequence number
 698 */
 699int avc_ss_reset(u32 seqno)
 700{
 701        struct avc_callback_node *c;
 702        int rc = 0, tmprc;
 703
 704        avc_flush();
 705
 706        for (c = avc_callbacks; c; c = c->next) {
 707                if (c->events & AVC_CALLBACK_RESET) {
 708                        tmprc = c->callback(AVC_CALLBACK_RESET,
 709                                            0, 0, 0, 0, NULL);
 710                        /* save the first error encountered for the return
 711                           value and continue processing the callbacks */
 712                        if (!rc)
 713                                rc = tmprc;
 714                }
 715        }
 716
 717        avc_latest_notif_update(seqno, 0);
 718        return rc;
 719}
 720
 721/**
 722 * avc_has_perm_noaudit - Check permissions but perform no auditing.
 723 * @ssid: source security identifier
 724 * @tsid: target security identifier
 725 * @tclass: target security class
 726 * @requested: requested permissions, interpreted based on @tclass
 727 * @flags:  AVC_STRICT or 0
 728 * @avd: access vector decisions
 729 *
 730 * Check the AVC to determine whether the @requested permissions are granted
 731 * for the SID pair (@ssid, @tsid), interpreting the permissions
 732 * based on @tclass, and call the security server on a cache miss to obtain
 733 * a new decision and add it to the cache.  Return a copy of the decisions
 734 * in @avd.  Return %0 if all @requested permissions are granted,
 735 * -%EACCES if any permissions are denied, or another -errno upon
 736 * other errors.  This function is typically called by avc_has_perm(),
 737 * but may also be called directly to separate permission checking from
 738 * auditing, e.g. in cases where a lock must be held for the check but
 739 * should be released for the auditing.
 740 */
 741int avc_has_perm_noaudit(u32 ssid, u32 tsid,
 742                         u16 tclass, u32 requested,
 743                         unsigned flags,
 744                         struct av_decision *in_avd)
 745{
 746        struct avc_node *node;
 747        struct av_decision avd_entry, *avd;
 748        int rc = 0;
 749        u32 denied;
 750
 751        BUG_ON(!requested);
 752
 753        rcu_read_lock();
 754
 755        node = avc_lookup(ssid, tsid, tclass);
 756        if (!node) {
 757                rcu_read_unlock();
 758
 759                if (in_avd)
 760                        avd = in_avd;
 761                else
 762                        avd = &avd_entry;
 763
 764                security_compute_av(ssid, tsid, tclass, avd);
 765                rcu_read_lock();
 766                node = avc_insert(ssid, tsid, tclass, avd);
 767        } else {
 768                if (in_avd)
 769                        memcpy(in_avd, &node->ae.avd, sizeof(*in_avd));
 770                avd = &node->ae.avd;
 771        }
 772
 773        denied = requested & ~(avd->allowed);
 774
 775        if (denied) {
 776                if (flags & AVC_STRICT)
 777                        rc = -EACCES;
 778                else if (!selinux_enforcing || (avd->flags & AVD_FLAGS_PERMISSIVE))
 779                        avc_update_node(AVC_CALLBACK_GRANT, requested, ssid,
 780                                        tsid, tclass, avd->seqno);
 781                else
 782                        rc = -EACCES;
 783        }
 784
 785        rcu_read_unlock();
 786        return rc;
 787}
 788
 789/**
 790 * avc_has_perm - Check permissions and perform any appropriate auditing.
 791 * @ssid: source security identifier
 792 * @tsid: target security identifier
 793 * @tclass: target security class
 794 * @requested: requested permissions, interpreted based on @tclass
 795 * @auditdata: auxiliary audit data
 796 *
 797 * Check the AVC to determine whether the @requested permissions are granted
 798 * for the SID pair (@ssid, @tsid), interpreting the permissions
 799 * based on @tclass, and call the security server on a cache miss to obtain
 800 * a new decision and add it to the cache.  Audit the granting or denial of
 801 * permissions in accordance with the policy.  Return %0 if all @requested
 802 * permissions are granted, -%EACCES if any permissions are denied, or
 803 * another -errno upon other errors.
 804 */
 805int avc_has_perm(u32 ssid, u32 tsid, u16 tclass,
 806                 u32 requested, struct common_audit_data *auditdata)
 807{
 808        struct av_decision avd;
 809        int rc;
 810
 811        rc = avc_has_perm_noaudit(ssid, tsid, tclass, requested, 0, &avd);
 812        avc_audit(ssid, tsid, tclass, requested, &avd, rc, auditdata);
 813        return rc;
 814}
 815
 816u32 avc_policy_seqno(void)
 817{
 818        return avc_cache.latest_notif;
 819}
 820
 821void avc_disable(void)
 822{
 823        /*
 824         * If you are looking at this because you have realized that we are
 825         * not destroying the avc_node_cachep it might be easy to fix, but
 826         * I don't know the memory barrier semantics well enough to know.  It's
 827         * possible that some other task dereferenced security_ops when
 828         * it still pointed to selinux operations.  If that is the case it's
 829         * possible that it is about to use the avc and is about to need the
 830         * avc_node_cachep.  I know I could wrap the security.c security_ops call
 831         * in an rcu_lock, but seriously, it's not worth it.  Instead I just flush
 832         * the cache and get that memory back.
 833         */
 834        if (avc_node_cachep) {
 835                avc_flush();
 836                /* kmem_cache_destroy(avc_node_cachep); */
 837        }
 838}
 839