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