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