security/selinux/avc.c

   1 /*
   2  * Implementation of the kernel access vector cache (AVC).
   3  *
   4  * Authors:  Stephen Smalley, <sds@tycho.nsa.gov>
   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 <linux/list.h>
  26 #include <net/sock.h>
  27 #include <linux/un.h>
  28 #include <net/af_unix.h>
  29 #include <linux/ip.h>
  30 #include <linux/audit.h>
  31 #include <linux/ipv6.h>
  32 #include <net/ipv6.h>
  33 #include "avc.h"
  34 #include "avc_ss.h"
  35 #include "classmap.h"
  36
  37 #define AVC_CACHE_SLOTS                 512
  38 #define AVC_DEF_CACHE_THRESHOLD         512
  39 #define AVC_CACHE_RECLAIM               16
  40
  41 #ifdef CONFIG_SECURITY_SELINUX_AVC_STATS
  42 #define avc_cache_stats_incr(field)     this_cpu_inc(avc_cache_stats.field)
  43 #else
  44 #define avc_cache_stats_incr(field)     do {} while (0)
  45 #endif
  46
  47 struct avc_entry {
  48         u32                     ssid;
  49         u32                     tsid;
  50         u16                     tclass;
  51         struct av_decision      avd;
  52         struct avc_xperms_node  *xp_node;
  53 };
  54
  55 struct avc_node {
  56         struct avc_entry        ae;
  57         struct hlist_node       list; /* anchored in avc_cache->slots[i] */
  58         struct rcu_head         rhead;
  59 };
  60
  61 struct avc_xperms_decision_node {
  62         struct extended_perms_decision xpd;
  63         struct list_head xpd_list; /* list of extended_perms_decision */
  64 };
  65
  66 struct avc_xperms_node {
  67         struct extended_perms xp;
  68         struct list_head xpd_head; /* list head of extended_perms_decision */
  69 };
  70
  71 struct avc_cache {
  72         struct hlist_head       slots[AVC_CACHE_SLOTS]; /* head for avc_node->list */
  73         spinlock_t              slots_lock[AVC_CACHE_SLOTS]; /* lock for writes */
  74         atomic_t                lru_hint;       /* LRU hint for reclaim scan */
  75         atomic_t                active_nodes;
  76         u32                     latest_notif;   /* latest revocation notification */
  77 };
  78
  79 struct avc_callback_node {
  80         int (*callback) (u32 event);
  81         u32 events;
  82         struct avc_callback_node *next;
  83 };
  84
  85 #ifdef CONFIG_SECURITY_SELINUX_AVC_STATS
  86 DEFINE_PER_CPU(struct avc_cache_stats, avc_cache_stats) = { 0 };
  87 #endif
  88
  89 struct selinux_avc {
  90         unsigned int avc_cache_threshold;
  91         struct avc_cache avc_cache;
  92 };
  93
  94 static struct selinux_avc selinux_avc;
  95
  96 void selinux_avc_init(struct selinux_avc **avc)
  97 {
  98         int i;
  99
 100         selinux_avc.avc_cache_threshold = AVC_DEF_CACHE_THRESHOLD;
 101         for (i = 0; i < AVC_CACHE_SLOTS; i++) {
 102                 INIT_HLIST_HEAD(&selinux_avc.avc_cache.slots[i]);
 103                 spin_lock_init(&selinux_avc.avc_cache.slots_lock[i]);
 104         }
 105         atomic_set(&selinux_avc.avc_cache.active_nodes, 0);
 106         atomic_set(&selinux_avc.avc_cache.lru_hint, 0);
 107         *avc = &selinux_avc;
 108 }
 109
 110 unsigned int avc_get_cache_threshold(struct selinux_avc *avc)
 111 {
 112         return avc->avc_cache_threshold;
 113 }
 114
 115 void avc_set_cache_threshold(struct selinux_avc *avc,
 116                              unsigned int cache_threshold)
 117 {
 118         avc->avc_cache_threshold = cache_threshold;
 119 }
 120
 121 static struct avc_callback_node *avc_callbacks;
 122 static struct kmem_cache *avc_node_cachep;
 123 static struct kmem_cache *avc_xperms_data_cachep;
 124 static struct kmem_cache *avc_xperms_decision_cachep;
 125 static struct kmem_cache *avc_xperms_cachep;
 126
 127 static inline int avc_hash(u32 ssid, u32 tsid, u16 tclass)
 128 {
 129         return (ssid ^ (tsid<<2) ^ (tclass<<4)) & (AVC_CACHE_SLOTS - 1);
 130 }
 131
 132 /**
 133  * avc_init - Initialize the AVC.
 134  *
 135  * Initialize the access vector cache.
 136  */
 137 void __init avc_init(void)
 138 {
 139         avc_node_cachep = kmem_cache_create("avc_node", sizeof(struct avc_node),
 140                                         0, SLAB_PANIC, NULL);
 141         avc_xperms_cachep = kmem_cache_create("avc_xperms_node",
 142                                         sizeof(struct avc_xperms_node),
 143                                         0, SLAB_PANIC, NULL);
 144         avc_xperms_decision_cachep = kmem_cache_create(
 145                                         "avc_xperms_decision_node",
 146                                         sizeof(struct avc_xperms_decision_node),
 147                                         0, SLAB_PANIC, NULL);
 148         avc_xperms_data_cachep = kmem_cache_create("avc_xperms_data",
 149                                         sizeof(struct extended_perms_data),
 150                                         0, SLAB_PANIC, NULL);
 151 }
 152
 153 int avc_get_hash_stats(struct selinux_avc *avc, char *page)
 154 {
 155         int i, chain_len, max_chain_len, slots_used;
 156         struct avc_node *node;
 157         struct hlist_head *head;
 158
 159         rcu_read_lock();
 160
 161         slots_used = 0;
 162         max_chain_len = 0;
 163         for (i = 0; i < AVC_CACHE_SLOTS; i++) {
 164                 head = &avc->avc_cache.slots[i];
 165                 if (!hlist_empty(head)) {
 166                         slots_used++;
 167                         chain_len = 0;
 168                         hlist_for_each_entry_rcu(node, head, list)
 169                                 chain_len++;
 170                         if (chain_len > max_chain_len)
 171                                 max_chain_len = chain_len;
 172                 }
 173         }
 174
 175         rcu_read_unlock();
 176
 177         return scnprintf(page, PAGE_SIZE, "entries: %d\nbuckets used: %d/%d\n"
 178                          "longest chain: %d\n",
 179                          atomic_read(&avc->avc_cache.active_nodes),
 180                          slots_used, AVC_CACHE_SLOTS, max_chain_len);
 181 }
 182
 183 /*
 184  * using a linked list for extended_perms_decision lookup because the list is
 185  * always small. i.e. less than 5, typically 1
 186  */
 187 static struct extended_perms_decision *avc_xperms_decision_lookup(u8 driver,
 188                                         struct avc_xperms_node *xp_node)
 189 {
 190         struct avc_xperms_decision_node *xpd_node;
 191
 192         list_for_each_entry(xpd_node, &xp_node->xpd_head, xpd_list) {
 193                 if (xpd_node->xpd.driver == driver)
 194                         return &xpd_node->xpd;
 195         }
 196         return NULL;
 197 }
 198
 199 static inline unsigned int
 200 avc_xperms_has_perm(struct extended_perms_decision *xpd,
 201                                         u8 perm, u8 which)
 202 {
 203         unsigned int rc = 0;
 204
 205         if ((which == XPERMS_ALLOWED) &&
 206                         (xpd->used & XPERMS_ALLOWED))
 207                 rc = security_xperm_test(xpd->allowed->p, perm);
 208         else if ((which == XPERMS_AUDITALLOW) &&
 209                         (xpd->used & XPERMS_AUDITALLOW))
 210                 rc = security_xperm_test(xpd->auditallow->p, perm);
 211         else if ((which == XPERMS_DONTAUDIT) &&
 212                         (xpd->used & XPERMS_DONTAUDIT))
 213                 rc = security_xperm_test(xpd->dontaudit->p, perm);
 214         return rc;
 215 }
 216
 217 static void avc_xperms_allow_perm(struct avc_xperms_node *xp_node,
 218                                 u8 driver, u8 perm)
 219 {
 220         struct extended_perms_decision *xpd;
 221         security_xperm_set(xp_node->xp.drivers.p, driver);
 222         xpd = avc_xperms_decision_lookup(driver, xp_node);
 223         if (xpd && xpd->allowed)
 224                 security_xperm_set(xpd->allowed->p, perm);
 225 }
 226
 227 static void avc_xperms_decision_free(struct avc_xperms_decision_node *xpd_node)
 228 {
 229         struct extended_perms_decision *xpd;
 230
 231         xpd = &xpd_node->xpd;
 232         if (xpd->allowed)
 233                 kmem_cache_free(avc_xperms_data_cachep, xpd->allowed);
 234         if (xpd->auditallow)
 235                 kmem_cache_free(avc_xperms_data_cachep, xpd->auditallow);
 236         if (xpd->dontaudit)
 237                 kmem_cache_free(avc_xperms_data_cachep, xpd->dontaudit);
 238         kmem_cache_free(avc_xperms_decision_cachep, xpd_node);
 239 }
 240
 241 static void avc_xperms_free(struct avc_xperms_node *xp_node)
 242 {
 243         struct avc_xperms_decision_node *xpd_node, *tmp;
 244
 245         if (!xp_node)
 246                 return;
 247
 248         list_for_each_entry_safe(xpd_node, tmp, &xp_node->xpd_head, xpd_list) {
 249                 list_del(&xpd_node->xpd_list);
 250                 avc_xperms_decision_free(xpd_node);
 251         }
 252         kmem_cache_free(avc_xperms_cachep, xp_node);
 253 }
 254
 255 static void avc_copy_xperms_decision(struct extended_perms_decision *dest,
 256                                         struct extended_perms_decision *src)
 257 {
 258         dest->driver = src->driver;
 259         dest->used = src->used;
 260         if (dest->used & XPERMS_ALLOWED)
 261                 memcpy(dest->allowed->p, src->allowed->p,
 262                                 sizeof(src->allowed->p));
 263         if (dest->used & XPERMS_AUDITALLOW)
 264                 memcpy(dest->auditallow->p, src->auditallow->p,
 265                                 sizeof(src->auditallow->p));
 266         if (dest->used & XPERMS_DONTAUDIT)
 267                 memcpy(dest->dontaudit->p, src->dontaudit->p,
 268                                 sizeof(src->dontaudit->p));
 269 }
 270
 271 /*
 272  * similar to avc_copy_xperms_decision, but only copy decision
 273  * information relevant to this perm
 274  */
 275 static inline void avc_quick_copy_xperms_decision(u8 perm,
 276                         struct extended_perms_decision *dest,
 277                         struct extended_perms_decision *src)
 278 {
 279         /*
 280          * compute index of the u32 of the 256 bits (8 u32s) that contain this
 281          * command permission
 282          */
 283         u8 i = perm >> 5;
 284
 285         dest->used = src->used;
 286         if (dest->used & XPERMS_ALLOWED)
 287                 dest->allowed->p[i] = src->allowed->p[i];
 288         if (dest->used & XPERMS_AUDITALLOW)
 289                 dest->auditallow->p[i] = src->auditallow->p[i];
 290         if (dest->used & XPERMS_DONTAUDIT)
 291                 dest->dontaudit->p[i] = src->dontaudit->p[i];
 292 }
 293
 294 static struct avc_xperms_decision_node
 295                 *avc_xperms_decision_alloc(u8 which)
 296 {
 297         struct avc_xperms_decision_node *xpd_node;
 298         struct extended_perms_decision *xpd;
 299
 300         xpd_node = kmem_cache_zalloc(avc_xperms_decision_cachep, GFP_NOWAIT);
 301         if (!xpd_node)
 302                 return NULL;
 303
 304         xpd = &xpd_node->xpd;
 305         if (which & XPERMS_ALLOWED) {
 306                 xpd->allowed = kmem_cache_zalloc(avc_xperms_data_cachep,
 307                                                 GFP_NOWAIT);
 308                 if (!xpd->allowed)
 309                         goto error;
 310         }
 311         if (which & XPERMS_AUDITALLOW) {
 312                 xpd->auditallow = kmem_cache_zalloc(avc_xperms_data_cachep,
 313                                                 GFP_NOWAIT);
 314                 if (!xpd->auditallow)
 315                         goto error;
 316         }
 317         if (which & XPERMS_DONTAUDIT) {
 318                 xpd->dontaudit = kmem_cache_zalloc(avc_xperms_data_cachep,
 319                                                 GFP_NOWAIT);
 320                 if (!xpd->dontaudit)
 321                         goto error;
 322         }
 323         return xpd_node;
 324 error:
 325         avc_xperms_decision_free(xpd_node);
 326         return NULL;
 327 }
 328
 329 static int avc_add_xperms_decision(struct avc_node *node,
 330                         struct extended_perms_decision *src)
 331 {
 332         struct avc_xperms_decision_node *dest_xpd;
 333
 334         node->ae.xp_node->xp.len++;
 335         dest_xpd = avc_xperms_decision_alloc(src->used);
 336         if (!dest_xpd)
 337                 return -ENOMEM;
 338         avc_copy_xperms_decision(&dest_xpd->xpd, src);
 339         list_add(&dest_xpd->xpd_list, &node->ae.xp_node->xpd_head);
 340         return 0;
 341 }
 342
 343 static struct avc_xperms_node *avc_xperms_alloc(void)
 344 {
 345         struct avc_xperms_node *xp_node;
 346
 347         xp_node = kmem_cache_zalloc(avc_xperms_cachep, GFP_NOWAIT);
 348         if (!xp_node)
 349                 return xp_node;
 350         INIT_LIST_HEAD(&xp_node->xpd_head);
 351         return xp_node;
 352 }
 353
 354 static int avc_xperms_populate(struct avc_node *node,
 355                                 struct avc_xperms_node *src)
 356 {
 357         struct avc_xperms_node *dest;
 358         struct avc_xperms_decision_node *dest_xpd;
 359         struct avc_xperms_decision_node *src_xpd;
 360
 361         if (src->xp.len == 0)
 362                 return 0;
 363         dest = avc_xperms_alloc();
 364         if (!dest)
 365                 return -ENOMEM;
 366
 367         memcpy(dest->xp.drivers.p, src->xp.drivers.p, sizeof(dest->xp.drivers.p));
 368         dest->xp.len = src->xp.len;
 369
 370         /* for each source xpd allocate a destination xpd and copy */
 371         list_for_each_entry(src_xpd, &src->xpd_head, xpd_list) {
 372                 dest_xpd = avc_xperms_decision_alloc(src_xpd->xpd.used);
 373                 if (!dest_xpd)
 374                         goto error;
 375                 avc_copy_xperms_decision(&dest_xpd->xpd, &src_xpd->xpd);
 376                 list_add(&dest_xpd->xpd_list, &dest->xpd_head);
 377         }
 378         node->ae.xp_node = dest;
 379         return 0;
 380 error:
 381         avc_xperms_free(dest);
 382         return -ENOMEM;
 383
 384 }
 385
 386 static inline u32 avc_xperms_audit_required(u32 requested,
 387                                         struct av_decision *avd,
 388                                         struct extended_perms_decision *xpd,
 389                                         u8 perm,
 390                                         int result,
 391                                         u32 *deniedp)
 392 {
 393         u32 denied, audited;
 394
 395         denied = requested & ~avd->allowed;
 396         if (unlikely(denied)) {
 397                 audited = denied & avd->auditdeny;
 398                 if (audited && xpd) {
 399                         if (avc_xperms_has_perm(xpd, perm, XPERMS_DONTAUDIT))
 400                                 audited &= ~requested;
 401                 }
 402         } else if (result) {
 403                 audited = denied = requested;
 404         } else {
 405                 audited = requested & avd->auditallow;
 406                 if (audited && xpd) {
 407                         if (!avc_xperms_has_perm(xpd, perm, XPERMS_AUDITALLOW))
 408                                 audited &= ~requested;
 409                 }
 410         }
 411
 412         *deniedp = denied;
 413         return audited;
 414 }
 415
 416 static inline int avc_xperms_audit(struct selinux_state *state,
 417                                    u32 ssid, u32 tsid, u16 tclass,
 418                                    u32 requested, struct av_decision *avd,
 419                                    struct extended_perms_decision *xpd,
 420                                    u8 perm, int result,
 421                                    struct common_audit_data *ad)
 422 {
 423         u32 audited, denied;
 424
 425         audited = avc_xperms_audit_required(
 426                         requested, avd, xpd, perm, result, &denied);
 427         if (likely(!audited))
 428                 return 0;
 429         return slow_avc_audit(state, ssid, tsid, tclass, requested,
 430                         audited, denied, result, ad, 0);
 431 }
 432
 433 static void avc_node_free(struct rcu_head *rhead)
 434 {
 435         struct avc_node *node = container_of(rhead, struct avc_node, rhead);
 436         avc_xperms_free(node->ae.xp_node);
 437         kmem_cache_free(avc_node_cachep, node);
 438         avc_cache_stats_incr(frees);
 439 }
 440
 441 static void avc_node_delete(struct selinux_avc *avc, struct avc_node *node)
 442 {
 443         hlist_del_rcu(&node->list);
 444         call_rcu(&node->rhead, avc_node_free);
 445         atomic_dec(&avc->avc_cache.active_nodes);
 446 }
 447
 448 static void avc_node_kill(struct selinux_avc *avc, struct avc_node *node)
 449 {
 450         avc_xperms_free(node->ae.xp_node);
 451         kmem_cache_free(avc_node_cachep, node);
 452         avc_cache_stats_incr(frees);
 453         atomic_dec(&avc->avc_cache.active_nodes);
 454 }
 455
 456 static void avc_node_replace(struct selinux_avc *avc,
 457                              struct avc_node *new, struct avc_node *old)
 458 {
 459         hlist_replace_rcu(&old->list, &new->list);
 460         call_rcu(&old->rhead, avc_node_free);
 461         atomic_dec(&avc->avc_cache.active_nodes);
 462 }
 463
 464 static inline int avc_reclaim_node(struct selinux_avc *avc)
 465 {
 466         struct avc_node *node;
 467         int hvalue, try, ecx;
 468         unsigned long flags;
 469         struct hlist_head *head;
 470         spinlock_t *lock;
 471
 472         for (try = 0, ecx = 0; try < AVC_CACHE_SLOTS; try++) {
 473                 hvalue = atomic_inc_return(&avc->avc_cache.lru_hint) &
 474                         (AVC_CACHE_SLOTS - 1);
 475                 head = &avc->avc_cache.slots[hvalue];
 476                 lock = &avc->avc_cache.slots_lock[hvalue];
 477
 478                 if (!spin_trylock_irqsave(lock, flags))
 479                         continue;
 480
 481                 rcu_read_lock();
 482                 hlist_for_each_entry(node, head, list) {
 483                         avc_node_delete(avc, node);
 484                         avc_cache_stats_incr(reclaims);
 485                         ecx++;
 486                         if (ecx >= AVC_CACHE_RECLAIM) {
 487                                 rcu_read_unlock();
 488                                 spin_unlock_irqrestore(lock, flags);
 489                                 goto out;
 490                         }
 491                 }
 492                 rcu_read_unlock();
 493                 spin_unlock_irqrestore(lock, flags);
 494         }
 495 out:
 496         return ecx;
 497 }
 498
 499 static struct avc_node *avc_alloc_node(struct selinux_avc *avc)
 500 {
 501         struct avc_node *node;
 502
 503         node = kmem_cache_zalloc(avc_node_cachep, GFP_NOWAIT);
 504         if (!node)
 505                 goto out;
 506
 507         INIT_HLIST_NODE(&node->list);
 508         avc_cache_stats_incr(allocations);
 509
 510         if (atomic_inc_return(&avc->avc_cache.active_nodes) >
 511             avc->avc_cache_threshold)
 512                 avc_reclaim_node(avc);
 513
 514 out:
 515         return node;
 516 }
 517
 518 static void avc_node_populate(struct avc_node *node, u32 ssid, u32 tsid, u16 tclass, struct av_decision *avd)
 519 {
 520         node->ae.ssid = ssid;
 521         node->ae.tsid = tsid;
 522         node->ae.tclass = tclass;
 523         memcpy(&node->ae.avd, avd, sizeof(node->ae.avd));
 524 }
 525
 526 static inline struct avc_node *avc_search_node(struct selinux_avc *avc,
 527                                                u32 ssid, u32 tsid, u16 tclass)
 528 {
 529         struct avc_node *node, *ret = NULL;
 530         int hvalue;
 531         struct hlist_head *head;
 532
 533         hvalue = avc_hash(ssid, tsid, tclass);
 534         head = &avc->avc_cache.slots[hvalue];
 535         hlist_for_each_entry_rcu(node, head, list) {
 536                 if (ssid == node->ae.ssid &&
 537                     tclass == node->ae.tclass &&
 538                     tsid == node->ae.tsid) {
 539                         ret = node;
 540                         break;
 541                 }
 542         }
 543
 544         return ret;
 545 }
 546
 547 /**
 548  * avc_lookup - Look up an AVC entry.
 549  * @ssid: source security identifier
 550  * @tsid: target security identifier
 551  * @tclass: target security class
 552  *
 553  * Look up an AVC entry that is valid for the
 554  * (@ssid, @tsid), interpreting the permissions
 555  * based on @tclass.  If a valid AVC entry exists,
 556  * then this function returns the avc_node.
 557  * Otherwise, this function returns NULL.
 558  */
 559 static struct avc_node *avc_lookup(struct selinux_avc *avc,
 560                                    u32 ssid, u32 tsid, u16 tclass)
 561 {
 562         struct avc_node *node;
 563
 564         avc_cache_stats_incr(lookups);
 565         node = avc_search_node(avc, ssid, tsid, tclass);
 566
 567         if (node)
 568                 return node;
 569
 570         avc_cache_stats_incr(misses);
 571         return NULL;
 572 }
 573
 574 static int avc_latest_notif_update(struct selinux_avc *avc,
 575                                    int seqno, int is_insert)
 576 {
 577         int ret = 0;
 578         static DEFINE_SPINLOCK(notif_lock);
 579         unsigned long flag;
 580
 581         spin_lock_irqsave(&notif_lock, flag);
 582         if (is_insert) {
 583                 if (seqno < avc->avc_cache.latest_notif) {
 584                         pr_warn("SELinux: avc:  seqno %d < latest_notif %d\n",
 585                                seqno, avc->avc_cache.latest_notif);
 586                         ret = -EAGAIN;
 587                 }
 588         } else {
 589                 if (seqno > avc->avc_cache.latest_notif)
 590                         avc->avc_cache.latest_notif = seqno;
 591         }
 592         spin_unlock_irqrestore(&notif_lock, flag);
 593
 594         return ret;
 595 }
 596
 597 /**
 598  * avc_insert - Insert an AVC entry.
 599  * @ssid: source security identifier
 600  * @tsid: target security identifier
 601  * @tclass: target security class
 602  * @avd: resulting av decision
 603  * @xp_node: resulting extended permissions
 604  *
 605  * Insert an AVC entry for the SID pair
 606  * (@ssid, @tsid) and class @tclass.
 607  * The access vectors and the sequence number are
 608  * normally provided by the security server in
 609  * response to a security_compute_av() call.  If the
 610  * sequence number @avd->seqno is not less than the latest
 611  * revocation notification, then the function copies
 612  * the access vectors into a cache entry, returns
 613  * avc_node inserted. Otherwise, this function returns NULL.
 614  */
 615 static struct avc_node *avc_insert(struct selinux_avc *avc,
 616                                    u32 ssid, u32 tsid, u16 tclass,
 617                                    struct av_decision *avd,
 618                                    struct avc_xperms_node *xp_node)
 619 {
 620         struct avc_node *pos, *node = NULL;
 621         int hvalue;
 622         unsigned long flag;
 623
 624         if (avc_latest_notif_update(avc, avd->seqno, 1))
 625                 goto out;
 626
 627         node = avc_alloc_node(avc);
 628         if (node) {
 629                 struct hlist_head *head;
 630                 spinlock_t *lock;
 631                 int rc = 0;
 632
 633                 hvalue = avc_hash(ssid, tsid, tclass);
 634                 avc_node_populate(node, ssid, tsid, tclass, avd);
 635                 rc = avc_xperms_populate(node, xp_node);
 636                 if (rc) {
 637                         kmem_cache_free(avc_node_cachep, node);
 638                         return NULL;
 639                 }
 640                 head = &avc->avc_cache.slots[hvalue];
 641                 lock = &avc->avc_cache.slots_lock[hvalue];
 642
 643                 spin_lock_irqsave(lock, flag);
 644                 hlist_for_each_entry(pos, head, list) {
 645                         if (pos->ae.ssid == ssid &&
 646                             pos->ae.tsid == tsid &&
 647                             pos->ae.tclass == tclass) {
 648                                 avc_node_replace(avc, node, pos);
 649                                 goto found;
 650                         }
 651                 }
 652                 hlist_add_head_rcu(&node->list, head);
 653 found:
 654                 spin_unlock_irqrestore(lock, flag);
 655         }
 656 out:
 657         return node;
 658 }
 659
 660 /**
 661  * avc_audit_pre_callback - SELinux specific information
 662  * will be called by generic audit code
 663  * @ab: the audit buffer
 664  * @a: audit_data
 665  */
 666 static void avc_audit_pre_callback(struct audit_buffer *ab, void *a)
 667 {
 668         struct common_audit_data *ad = a;
 669         struct selinux_audit_data *sad = ad->selinux_audit_data;
 670         u32 av = sad->audited;
 671         const char **perms;
 672         int i, perm;
 673
 674         audit_log_format(ab, "avc:  %s ", sad->denied ? "denied" : "granted");
 675
 676         if (av == 0) {
 677                 audit_log_format(ab, " null");
 678                 return;
 679         }
 680
 681         perms = secclass_map[sad->tclass-1].perms;
 682
 683         audit_log_format(ab, " {");
 684         i = 0;
 685         perm = 1;
 686         while (i < (sizeof(av) * 8)) {
 687                 if ((perm & av) && perms[i]) {
 688                         audit_log_format(ab, " %s", perms[i]);
 689                         av &= ~perm;
 690                 }
 691                 i++;
 692                 perm <<= 1;
 693         }
 694
 695         if (av)
 696                 audit_log_format(ab, " 0x%x", av);
 697
 698         audit_log_format(ab, " } for ");
 699 }
 700
 701 /**
 702  * avc_audit_post_callback - SELinux specific information
 703  * will be called by generic audit code
 704  * @ab: the audit buffer
 705  * @a: audit_data
 706  */
 707 static void avc_audit_post_callback(struct audit_buffer *ab, void *a)
 708 {
 709         struct common_audit_data *ad = a;
 710         struct selinux_audit_data *sad = ad->selinux_audit_data;
 711         char *scontext;
 712         u32 scontext_len;
 713         int rc;
 714
 715         rc = security_sid_to_context(sad->state, sad->ssid, &scontext,
 716                                      &scontext_len);
 717         if (rc)
 718                 audit_log_format(ab, " ssid=%d", sad->ssid);
 719         else {
 720                 audit_log_format(ab, " scontext=%s", scontext);
 721                 kfree(scontext);
 722         }
 723
 724         rc = security_sid_to_context(sad->state, sad->tsid, &scontext,
 725                                      &scontext_len);
 726         if (rc)
 727                 audit_log_format(ab, " tsid=%d", sad->tsid);
 728         else {
 729                 audit_log_format(ab, " tcontext=%s", scontext);
 730                 kfree(scontext);
 731         }
 732
 733         audit_log_format(ab, " tclass=%s", secclass_map[sad->tclass-1].name);
 734
 735         if (sad->denied)
 736                 audit_log_format(ab, " permissive=%u", sad->result ? 0 : 1);
 737
 738         /* in case of invalid context report also the actual context string */
 739         rc = security_sid_to_context_inval(sad->state, sad->ssid, &scontext,
 740                                            &scontext_len);
 741         if (!rc && scontext) {
 742                 if (scontext_len && scontext[scontext_len - 1] == '\0')
 743                         scontext_len--;
 744                 audit_log_format(ab, " srawcon=");
 745                 audit_log_n_untrustedstring(ab, scontext, scontext_len);
 746                 kfree(scontext);
 747         }
 748
 749         rc = security_sid_to_context_inval(sad->state, sad->tsid, &scontext,
 750                                            &scontext_len);
 751         if (!rc && scontext) {
 752                 if (scontext_len && scontext[scontext_len - 1] == '\0')
 753                         scontext_len--;
 754                 audit_log_format(ab, " trawcon=");
 755                 audit_log_n_untrustedstring(ab, scontext, scontext_len);
 756                 kfree(scontext);
 757         }
 758 }
 759
 760 /* This is the slow part of avc audit with big stack footprint */
 761 noinline int slow_avc_audit(struct selinux_state *state,
 762                             u32 ssid, u32 tsid, u16 tclass,
 763                             u32 requested, u32 audited, u32 denied, int result,
 764                             struct common_audit_data *a,
 765                             unsigned int flags)
 766 {
 767         struct common_audit_data stack_data;
 768         struct selinux_audit_data sad;
 769
 770         if (WARN_ON(!tclass || tclass >= ARRAY_SIZE(secclass_map)))
 771                 return -EINVAL;
 772
 773         if (!a) {
 774                 a = &stack_data;
 775                 a->type = LSM_AUDIT_DATA_NONE;
 776         }
 777
 778         /*
 779          * When in a RCU walk do the audit on the RCU retry.  This is because
 780          * the collection of the dname in an inode audit message is not RCU
 781          * safe.  Note this may drop some audits when the situation changes
 782          * during retry. However this is logically just as if the operation
 783          * happened a little later.
 784          */
 785         if ((a->type == LSM_AUDIT_DATA_INODE) &&
 786             (flags & MAY_NOT_BLOCK))
 787                 return -ECHILD;
 788
 789         sad.tclass = tclass;
 790         sad.requested = requested;
 791         sad.ssid = ssid;
 792         sad.tsid = tsid;
 793         sad.audited = audited;
 794         sad.denied = denied;
 795         sad.result = result;
 796         sad.state = state;
 797
 798         a->selinux_audit_data = &sad;
 799
 800         common_lsm_audit(a, avc_audit_pre_callback, avc_audit_post_callback);
 801         return 0;
 802 }
 803
 804 /**
 805  * avc_add_callback - Register a callback for security events.
 806  * @callback: callback function
 807  * @events: security events
 808  *
 809  * Register a callback function for events in the set @events.
 810  * Returns %0 on success or -%ENOMEM if insufficient memory
 811  * exists to add the callback.
 812  */
 813 int __init avc_add_callback(int (*callback)(u32 event), u32 events)
 814 {
 815         struct avc_callback_node *c;
 816         int rc = 0;
 817
 818         c = kmalloc(sizeof(*c), GFP_KERNEL);
 819         if (!c) {
 820                 rc = -ENOMEM;
 821                 goto out;
 822         }
 823
 824         c->callback = callback;
 825         c->events = events;
 826         c->next = avc_callbacks;
 827         avc_callbacks = c;
 828 out:
 829         return rc;
 830 }
 831
 832 /**
 833  * avc_update_node Update an AVC entry
 834  * @event : Updating event
 835  * @perms : Permission mask bits
 836  * @ssid,@tsid,@tclass : identifier of an AVC entry
 837  * @seqno : sequence number when decision was made
 838  * @xpd: extended_perms_decision to be added to the node
 839  * @flags: the AVC_* flags, e.g. AVC_NONBLOCKING, AVC_EXTENDED_PERMS, or 0.
 840  *
 841  * if a valid AVC entry doesn't exist,this function returns -ENOENT.
 842  * if kmalloc() called internal returns NULL, this function returns -ENOMEM.
 843  * otherwise, this function updates the AVC entry. The original AVC-entry object
 844  * will release later by RCU.
 845  */
 846 static int avc_update_node(struct selinux_avc *avc,
 847                            u32 event, u32 perms, u8 driver, u8 xperm, u32 ssid,
 848                            u32 tsid, u16 tclass, u32 seqno,
 849                            struct extended_perms_decision *xpd,
 850                            u32 flags)
 851 {
 852         int hvalue, rc = 0;
 853         unsigned long flag;
 854         struct avc_node *pos, *node, *orig = NULL;
 855         struct hlist_head *head;
 856         spinlock_t *lock;
 857
 858         /*
 859          * If we are in a non-blocking code path, e.g. VFS RCU walk,
 860          * then we must not add permissions to a cache entry
 861          * because we cannot safely audit the denial.  Otherwise,
 862          * during the subsequent blocking retry (e.g. VFS ref walk), we
 863          * will find the permissions already granted in the cache entry
 864          * and won't audit anything at all, leading to silent denials in
 865          * permissive mode that only appear when in enforcing mode.
 866          *
 867          * See the corresponding handling in slow_avc_audit(), and the
 868          * logic in selinux_inode_permission for the MAY_NOT_BLOCK flag,
 869          * which is transliterated into AVC_NONBLOCKING.
 870          */
 871         if (flags & AVC_NONBLOCKING)
 872                 return 0;
 873
 874         node = avc_alloc_node(avc);
 875         if (!node) {
 876                 rc = -ENOMEM;
 877                 goto out;
 878         }
 879
 880         /* Lock the target slot */
 881         hvalue = avc_hash(ssid, tsid, tclass);
 882
 883         head = &avc->avc_cache.slots[hvalue];
 884         lock = &avc->avc_cache.slots_lock[hvalue];
 885
 886         spin_lock_irqsave(lock, flag);
 887
 888         hlist_for_each_entry(pos, head, list) {
 889                 if (ssid == pos->ae.ssid &&
 890                     tsid == pos->ae.tsid &&
 891                     tclass == pos->ae.tclass &&
 892                     seqno == pos->ae.avd.seqno){
 893                         orig = pos;
 894                         break;
 895                 }
 896         }
 897
 898         if (!orig) {
 899                 rc = -ENOENT;
 900                 avc_node_kill(avc, node);
 901                 goto out_unlock;
 902         }
 903
 904         /*
 905          * Copy and replace original node.
 906          */
 907
 908         avc_node_populate(node, ssid, tsid, tclass, &orig->ae.avd);
 909
 910         if (orig->ae.xp_node) {
 911                 rc = avc_xperms_populate(node, orig->ae.xp_node);
 912                 if (rc) {
 913                         kmem_cache_free(avc_node_cachep, node);
 914                         goto out_unlock;
 915                 }
 916         }
 917
 918         switch (event) {
 919         case AVC_CALLBACK_GRANT:
 920                 node->ae.avd.allowed |= perms;
 921                 if (node->ae.xp_node && (flags & AVC_EXTENDED_PERMS))
 922                         avc_xperms_allow_perm(node->ae.xp_node, driver, xperm);
 923                 break;
 924         case AVC_CALLBACK_TRY_REVOKE:
 925         case AVC_CALLBACK_REVOKE:
 926                 node->ae.avd.allowed &= ~perms;
 927                 break;
 928         case AVC_CALLBACK_AUDITALLOW_ENABLE:
 929                 node->ae.avd.auditallow |= perms;
 930                 break;
 931         case AVC_CALLBACK_AUDITALLOW_DISABLE:
 932                 node->ae.avd.auditallow &= ~perms;
 933                 break;
 934         case AVC_CALLBACK_AUDITDENY_ENABLE:
 935                 node->ae.avd.auditdeny |= perms;
 936                 break;
 937         case AVC_CALLBACK_AUDITDENY_DISABLE:
 938                 node->ae.avd.auditdeny &= ~perms;
 939                 break;
 940         case AVC_CALLBACK_ADD_XPERMS:
 941                 avc_add_xperms_decision(node, xpd);
 942                 break;
 943         }
 944         avc_node_replace(avc, node, orig);
 945 out_unlock:
 946         spin_unlock_irqrestore(lock, flag);
 947 out:
 948         return rc;
 949 }
 950
 951 /**
 952  * avc_flush - Flush the cache
 953  */
 954 static void avc_flush(struct selinux_avc *avc)
 955 {
 956         struct hlist_head *head;
 957         struct avc_node *node;
 958         spinlock_t *lock;
 959         unsigned long flag;
 960         int i;
 961
 962         for (i = 0; i < AVC_CACHE_SLOTS; i++) {
 963                 head = &avc->avc_cache.slots[i];
 964                 lock = &avc->avc_cache.slots_lock[i];
 965
 966                 spin_lock_irqsave(lock, flag);
 967                 /*
 968                  * With preemptable RCU, the outer spinlock does not
 969                  * prevent RCU grace periods from ending.
 970                  */
 971                 rcu_read_lock();
 972                 hlist_for_each_entry(node, head, list)
 973                         avc_node_delete(avc, node);
 974                 rcu_read_unlock();
 975                 spin_unlock_irqrestore(lock, flag);
 976         }
 977 }
 978
 979 /**
 980  * avc_ss_reset - Flush the cache and revalidate migrated permissions.
 981  * @seqno: policy sequence number
 982  */
 983 int avc_ss_reset(struct selinux_avc *avc, u32 seqno)
 984 {
 985         struct avc_callback_node *c;
 986         int rc = 0, tmprc;
 987
 988         avc_flush(avc);
 989
 990         for (c = avc_callbacks; c; c = c->next) {
 991                 if (c->events & AVC_CALLBACK_RESET) {
 992                         tmprc = c->callback(AVC_CALLBACK_RESET);
 993                         /* save the first error encountered for the return
 994                            value and continue processing the callbacks */
 995                         if (!rc)
 996                                 rc = tmprc;
 997                 }
 998         }
 999
1000         avc_latest_notif_update(avc, seqno, 0);
1001         return rc;
1002 }
1003
1004 /*
1005  * Slow-path helper function for avc_has_perm_noaudit,
1006  * when the avc_node lookup fails. We get called with
1007  * the RCU read lock held, and need to return with it
1008  * still held, but drop if for the security compute.
1009  *
1010  * Don't inline this, since it's the slow-path and just
1011  * results in a bigger stack frame.
1012  */
1013 static noinline
1014 struct avc_node *avc_compute_av(struct selinux_state *state,
1015                                 u32 ssid, u32 tsid,
1016                                 u16 tclass, struct av_decision *avd,
1017                                 struct avc_xperms_node *xp_node)
1018 {
1019         rcu_read_unlock();
1020         INIT_LIST_HEAD(&xp_node->xpd_head);
1021         security_compute_av(state, ssid, tsid, tclass, avd, &xp_node->xp);
1022         rcu_read_lock();
1023         return avc_insert(state->avc, ssid, tsid, tclass, avd, xp_node);
1024 }
1025
1026 static noinline int avc_denied(struct selinux_state *state,
1027                                u32 ssid, u32 tsid,
1028                                u16 tclass, u32 requested,
1029                                u8 driver, u8 xperm, unsigned int flags,
1030                                struct av_decision *avd)
1031 {
1032         if (flags & AVC_STRICT)
1033                 return -EACCES;
1034
1035         if (enforcing_enabled(state) &&
1036             !(avd->flags & AVD_FLAGS_PERMISSIVE))
1037                 return -EACCES;
1038
1039         avc_update_node(state->avc, AVC_CALLBACK_GRANT, requested, driver,
1040                         xperm, ssid, tsid, tclass, avd->seqno, NULL, flags);
1041         return 0;
1042 }
1043
1044 /*
1045  * The avc extended permissions logic adds an additional 256 bits of
1046  * permissions to an avc node when extended permissions for that node are
1047  * specified in the avtab. If the additional 256 permissions is not adequate,
1048  * as-is the case with ioctls, then multiple may be chained together and the
1049  * driver field is used to specify which set contains the permission.
1050  */
1051 int avc_has_extended_perms(struct selinux_state *state,
1052                            u32 ssid, u32 tsid, u16 tclass, u32 requested,
1053                            u8 driver, u8 xperm, struct common_audit_data *ad)
1054 {
1055         struct avc_node *node;
1056         struct av_decision avd;
1057         u32 denied;
1058         struct extended_perms_decision local_xpd;
1059         struct extended_perms_decision *xpd = NULL;
1060         struct extended_perms_data allowed;
1061         struct extended_perms_data auditallow;
1062         struct extended_perms_data dontaudit;
1063         struct avc_xperms_node local_xp_node;
1064         struct avc_xperms_node *xp_node;
1065         int rc = 0, rc2;
1066
1067         xp_node = &local_xp_node;
1068         if (WARN_ON(!requested))
1069                 return -EACCES;
1070
1071         rcu_read_lock();
1072
1073         node = avc_lookup(state->avc, ssid, tsid, tclass);
1074         if (unlikely(!node)) {
1075                 node = avc_compute_av(state, ssid, tsid, tclass, &avd, xp_node);
1076         } else {
1077                 memcpy(&avd, &node->ae.avd, sizeof(avd));
1078                 xp_node = node->ae.xp_node;
1079         }
1080         /* if extended permissions are not defined, only consider av_decision */
1081         if (!xp_node || !xp_node->xp.len)
1082                 goto decision;
1083
1084         local_xpd.allowed = &allowed;
1085         local_xpd.auditallow = &auditallow;
1086         local_xpd.dontaudit = &dontaudit;
1087
1088         xpd = avc_xperms_decision_lookup(driver, xp_node);
1089         if (unlikely(!xpd)) {
1090                 /*
1091                  * Compute the extended_perms_decision only if the driver
1092                  * is flagged
1093                  */
1094                 if (!security_xperm_test(xp_node->xp.drivers.p, driver)) {
1095                         avd.allowed &= ~requested;
1096                         goto decision;
1097                 }
1098                 rcu_read_unlock();
1099                 security_compute_xperms_decision(state, ssid, tsid, tclass,
1100                                                  driver, &local_xpd);
1101                 rcu_read_lock();
1102                 avc_update_node(state->avc, AVC_CALLBACK_ADD_XPERMS, requested,
1103                                 driver, xperm, ssid, tsid, tclass, avd.seqno,
1104                                 &local_xpd, 0);
1105         } else {
1106                 avc_quick_copy_xperms_decision(xperm, &local_xpd, xpd);
1107         }
1108         xpd = &local_xpd;
1109
1110         if (!avc_xperms_has_perm(xpd, xperm, XPERMS_ALLOWED))
1111                 avd.allowed &= ~requested;
1112
1113 decision:
1114         denied = requested & ~(avd.allowed);
1115         if (unlikely(denied))
1116                 rc = avc_denied(state, ssid, tsid, tclass, requested,
1117                                 driver, xperm, AVC_EXTENDED_PERMS, &avd);
1118
1119         rcu_read_unlock();
1120
1121         rc2 = avc_xperms_audit(state, ssid, tsid, tclass, requested,
1122                         &avd, xpd, xperm, rc, ad);
1123         if (rc2)
1124                 return rc2;
1125         return rc;
1126 }
1127
1128 /**
1129  * avc_has_perm_noaudit - Check permissions but perform no auditing.
1130  * @ssid: source security identifier
1131  * @tsid: target security identifier
1132  * @tclass: target security class
1133  * @requested: requested permissions, interpreted based on @tclass
1134  * @flags:  AVC_STRICT, AVC_NONBLOCKING, or 0
1135  * @avd: access vector decisions
1136  *
1137  * Check the AVC to determine whether the @requested permissions are granted
1138  * for the SID pair (@ssid, @tsid), interpreting the permissions
1139  * based on @tclass, and call the security server on a cache miss to obtain
1140  * a new decision and add it to the cache.  Return a copy of the decisions
1141  * in @avd.  Return %0 if all @requested permissions are granted,
1142  * -%EACCES if any permissions are denied, or another -errno upon
1143  * other errors.  This function is typically called by avc_has_perm(),
1144  * but may also be called directly to separate permission checking from
1145  * auditing, e.g. in cases where a lock must be held for the check but
1146  * should be released for the auditing.
1147  */
1148 inline int avc_has_perm_noaudit(struct selinux_state *state,
1149                                 u32 ssid, u32 tsid,
1150                                 u16 tclass, u32 requested,
1151                                 unsigned int flags,
1152                                 struct av_decision *avd)
1153 {
1154         struct avc_node *node;
1155         struct avc_xperms_node xp_node;
1156         int rc = 0;
1157         u32 denied;
1158
1159         if (WARN_ON(!requested))
1160                 return -EACCES;
1161
1162         rcu_read_lock();
1163
1164         node = avc_lookup(state->avc, ssid, tsid, tclass);
1165         if (unlikely(!node))
1166                 node = avc_compute_av(state, ssid, tsid, tclass, avd, &xp_node);
1167         else
1168                 memcpy(avd, &node->ae.avd, sizeof(*avd));
1169
1170         denied = requested & ~(avd->allowed);
1171         if (unlikely(denied))
1172                 rc = avc_denied(state, ssid, tsid, tclass, requested, 0, 0,
1173                                 flags, avd);
1174
1175         rcu_read_unlock();
1176         return rc;
1177 }
1178
1179 /**
1180  * avc_has_perm - Check permissions and perform any appropriate auditing.
1181  * @ssid: source security identifier
1182  * @tsid: target security identifier
1183  * @tclass: target security class
1184  * @requested: requested permissions, interpreted based on @tclass
1185  * @auditdata: auxiliary audit data
1186  *
1187  * Check the AVC to determine whether the @requested permissions are granted
1188  * for the SID pair (@ssid, @tsid), interpreting the permissions
1189  * based on @tclass, and call the security server on a cache miss to obtain
1190  * a new decision and add it to the cache.  Audit the granting or denial of
1191  * permissions in accordance with the policy.  Return %0 if all @requested
1192  * permissions are granted, -%EACCES if any permissions are denied, or
1193  * another -errno upon other errors.
1194  */
1195 int avc_has_perm(struct selinux_state *state, u32 ssid, u32 tsid, u16 tclass,
1196                  u32 requested, struct common_audit_data *auditdata)
1197 {
1198         struct av_decision avd;
1199         int rc, rc2;
1200
1201         rc = avc_has_perm_noaudit(state, ssid, tsid, tclass, requested, 0,
1202                                   &avd);
1203
1204         rc2 = avc_audit(state, ssid, tsid, tclass, requested, &avd, rc,
1205                         auditdata, 0);
1206         if (rc2)
1207                 return rc2;
1208         return rc;
1209 }
1210
1211 u32 avc_policy_seqno(struct selinux_state *state)
1212 {
1213         return state->avc->avc_cache.latest_notif;
1214 }
1215
1216 void avc_disable(void)
1217 {
1218         /*
1219          * If you are looking at this because you have realized that we are
1220          * not destroying the avc_node_cachep it might be easy to fix, but
1221          * I don't know the memory barrier semantics well enough to know.  It's
1222          * possible that some other task dereferenced security_ops when
1223          * it still pointed to selinux operations.  If that is the case it's
1224          * possible that it is about to use the avc and is about to need the
1225          * avc_node_cachep.  I know I could wrap the security.c security_ops call
1226          * in an rcu_lock, but seriously, it's not worth it.  Instead I just flush
1227          * the cache and get that memory back.
1228          */
1229         if (avc_node_cachep) {
1230                 avc_flush(selinux_state.avc);
1231                 /* kmem_cache_destroy(avc_node_cachep); */
1232         }
1233 }