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