security/selinux/avc.c

   1 /*
   2  * Implementation of the kernel access vector cache (AVC).
   3  *
   4  * Authors:  Stephen Smalley, <sds@epoch.ncsc.mil>
   5  *           James Morris <jmorris@redhat.com>
   6  *
   7  * Update:   KaiGai, Kohei <kaigai@ak.jp.nec.com>
   8  *      Replaced the avc_lock spinlock by RCU.
   9  *
  10  * Copyright (C) 2003 Red Hat, Inc., James Morris <jmorris@redhat.com>
  11  *
  12  *      This program is free software; you can redistribute it and/or modify
  13  *      it under the terms of the GNU General Public License version 2,
  14  *      as published by the Free Software Foundation.
  15  */
  16 #include <linux/types.h>
  17 #include <linux/stddef.h>
  18 #include <linux/kernel.h>
  19 #include <linux/slab.h>
  20 #include <linux/fs.h>
  21 #include <linux/dcache.h>
  22 #include <linux/init.h>
  23 #include <linux/skbuff.h>
  24 #include <linux/percpu.h>
  25 #include <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         perms = secclass_map[tclass-1].perms;
 120
 121         audit_log_format(ab, " {");
 122         i = 0;
 123         perm = 1;
 124         while (i < (sizeof(av) * 8)) {
 125                 if ((perm & av) && perms[i]) {
 126                         audit_log_format(ab, " %s", perms[i]);
 127                         av &= ~perm;
 128                 }
 129                 i++;
 130                 perm <<= 1;
 131         }
 132
 133         if (av)
 134                 audit_log_format(ab, " 0x%x", av);
 135
 136         audit_log_format(ab, " }");
 137 }
 138
 139 /**
 140  * avc_dump_query - Display a SID pair and a class in human-readable form.
 141  * @ssid: source security identifier
 142  * @tsid: target security identifier
 143  * @tclass: target security class
 144  */
 145 static void avc_dump_query(struct audit_buffer *ab, u32 ssid, u32 tsid, u16 tclass)
 146 {
 147         int rc;
 148         char *scontext;
 149         u32 scontext_len;
 150
 151         rc = security_sid_to_context(ssid, &scontext, &scontext_len);
 152         if (rc)
 153                 audit_log_format(ab, "ssid=%d", ssid);
 154         else {
 155                 audit_log_format(ab, "scontext=%s", scontext);
 156                 kfree(scontext);
 157         }
 158
 159         rc = security_sid_to_context(tsid, &scontext, &scontext_len);
 160         if (rc)
 161                 audit_log_format(ab, " tsid=%d", tsid);
 162         else {
 163                 audit_log_format(ab, " tcontext=%s", scontext);
 164                 kfree(scontext);
 165         }
 166
 167         BUG_ON(tclass >= ARRAY_SIZE(secclass_map));
 168         audit_log_format(ab, " tclass=%s", secclass_map[tclass-1].name);
 169 }
 170
 171 /**
 172  * avc_init - Initialize the AVC.
 173  *
 174  * Initialize the access vector cache.
 175  */
 176 void __init avc_init(void)
 177 {
 178         int i;
 179
 180         for (i = 0; i < AVC_CACHE_SLOTS; i++) {
 181                 INIT_HLIST_HEAD(&avc_cache.slots[i]);
 182                 spin_lock_init(&avc_cache.slots_lock[i]);
 183         }
 184         atomic_set(&avc_cache.active_nodes, 0);
 185         atomic_set(&avc_cache.lru_hint, 0);
 186
 187         avc_node_cachep = kmem_cache_create("avc_node", sizeof(struct avc_node),
 188                                         0, SLAB_PANIC, NULL);
 189         avc_xperms_cachep = kmem_cache_create("avc_xperms_node",
 190                                         sizeof(struct avc_xperms_node),
 191                                         0, SLAB_PANIC, NULL);
 192         avc_xperms_decision_cachep = kmem_cache_create(
 193                                         "avc_xperms_decision_node",
 194                                         sizeof(struct avc_xperms_decision_node),
 195                                         0, SLAB_PANIC, NULL);
 196         avc_xperms_data_cachep = kmem_cache_create("avc_xperms_data",
 197                                         sizeof(struct extended_perms_data),
 198                                         0, SLAB_PANIC, NULL);
 199
 200         audit_log(current->audit_context, GFP_KERNEL, AUDIT_KERNEL, "AVC INITIALIZED\n");
 201 }
 202
 203 int avc_get_hash_stats(char *page)
 204 {
 205         int i, chain_len, max_chain_len, slots_used;
 206         struct avc_node *node;
 207         struct hlist_head *head;
 208
 209         rcu_read_lock();
 210
 211         slots_used = 0;
 212         max_chain_len = 0;
 213         for (i = 0; i < AVC_CACHE_SLOTS; i++) {
 214                 head = &avc_cache.slots[i];
 215                 if (!hlist_empty(head)) {
 216                         slots_used++;
 217                         chain_len = 0;
 218                         hlist_for_each_entry_rcu(node, head, list)
 219                                 chain_len++;
 220                         if (chain_len > max_chain_len)
 221                                 max_chain_len = chain_len;
 222                 }
 223         }
 224
 225         rcu_read_unlock();
 226
 227         return scnprintf(page, PAGE_SIZE, "entries: %d\nbuckets used: %d/%d\n"
 228                          "longest chain: %d\n",
 229                          atomic_read(&avc_cache.active_nodes),
 230                          slots_used, AVC_CACHE_SLOTS, max_chain_len);
 231 }
 232
 233 /*
 234  * using a linked list for extended_perms_decision lookup because the list is
 235  * always small. i.e. less than 5, typically 1
 236  */
 237 static struct extended_perms_decision *avc_xperms_decision_lookup(u8 driver,
 238                                         struct avc_xperms_node *xp_node)
 239 {
 240         struct avc_xperms_decision_node *xpd_node;
 241
 242         list_for_each_entry(xpd_node, &xp_node->xpd_head, xpd_list) {
 243                 if (xpd_node->xpd.driver == driver)
 244                         return &xpd_node->xpd;
 245         }
 246         return NULL;
 247 }
 248
 249 static inline unsigned int
 250 avc_xperms_has_perm(struct extended_perms_decision *xpd,
 251                                         u8 perm, u8 which)
 252 {
 253         unsigned int rc = 0;
 254
 255         if ((which == XPERMS_ALLOWED) &&
 256                         (xpd->used & XPERMS_ALLOWED))
 257                 rc = security_xperm_test(xpd->allowed->p, perm);
 258         else if ((which == XPERMS_AUDITALLOW) &&
 259                         (xpd->used & XPERMS_AUDITALLOW))
 260                 rc = security_xperm_test(xpd->auditallow->p, perm);
 261         else if ((which == XPERMS_DONTAUDIT) &&
 262                         (xpd->used & XPERMS_DONTAUDIT))
 263                 rc = security_xperm_test(xpd->dontaudit->p, perm);
 264         return rc;
 265 }
 266
 267 static void avc_xperms_allow_perm(struct avc_xperms_node *xp_node,
 268                                 u8 driver, u8 perm)
 269 {
 270         struct extended_perms_decision *xpd;
 271         security_xperm_set(xp_node->xp.drivers.p, driver);
 272         xpd = avc_xperms_decision_lookup(driver, xp_node);
 273         if (xpd && xpd->allowed)
 274                 security_xperm_set(xpd->allowed->p, perm);
 275 }
 276
 277 static void avc_xperms_decision_free(struct avc_xperms_decision_node *xpd_node)
 278 {
 279         struct extended_perms_decision *xpd;
 280
 281         xpd = &xpd_node->xpd;
 282         if (xpd->allowed)
 283                 kmem_cache_free(avc_xperms_data_cachep, xpd->allowed);
 284         if (xpd->auditallow)
 285                 kmem_cache_free(avc_xperms_data_cachep, xpd->auditallow);
 286         if (xpd->dontaudit)
 287                 kmem_cache_free(avc_xperms_data_cachep, xpd->dontaudit);
 288         kmem_cache_free(avc_xperms_decision_cachep, xpd_node);
 289 }
 290
 291 static void avc_xperms_free(struct avc_xperms_node *xp_node)
 292 {
 293         struct avc_xperms_decision_node *xpd_node, *tmp;
 294
 295         if (!xp_node)
 296                 return;
 297
 298         list_for_each_entry_safe(xpd_node, tmp, &xp_node->xpd_head, xpd_list) {
 299                 list_del(&xpd_node->xpd_list);
 300                 avc_xperms_decision_free(xpd_node);
 301         }
 302         kmem_cache_free(avc_xperms_cachep, xp_node);
 303 }
 304
 305 static void avc_copy_xperms_decision(struct extended_perms_decision *dest,
 306                                         struct extended_perms_decision *src)
 307 {
 308         dest->driver = src->driver;
 309         dest->used = src->used;
 310         if (dest->used & XPERMS_ALLOWED)
 311                 memcpy(dest->allowed->p, src->allowed->p,
 312                                 sizeof(src->allowed->p));
 313         if (dest->used & XPERMS_AUDITALLOW)
 314                 memcpy(dest->auditallow->p, src->auditallow->p,
 315                                 sizeof(src->auditallow->p));
 316         if (dest->used & XPERMS_DONTAUDIT)
 317                 memcpy(dest->dontaudit->p, src->dontaudit->p,
 318                                 sizeof(src->dontaudit->p));
 319 }
 320
 321 /*
 322  * similar to avc_copy_xperms_decision, but only copy decision
 323  * information relevant to this perm
 324  */
 325 static inline void avc_quick_copy_xperms_decision(u8 perm,
 326                         struct extended_perms_decision *dest,
 327                         struct extended_perms_decision *src)
 328 {
 329         /*
 330          * compute index of the u32 of the 256 bits (8 u32s) that contain this
 331          * command permission
 332          */
 333         u8 i = perm >> 5;
 334
 335         dest->used = src->used;
 336         if (dest->used & XPERMS_ALLOWED)
 337                 dest->allowed->p[i] = src->allowed->p[i];
 338         if (dest->used & XPERMS_AUDITALLOW)
 339                 dest->auditallow->p[i] = src->auditallow->p[i];
 340         if (dest->used & XPERMS_DONTAUDIT)
 341                 dest->dontaudit->p[i] = src->dontaudit->p[i];
 342 }
 343
 344 static struct avc_xperms_decision_node
 345                 *avc_xperms_decision_alloc(u8 which)
 346 {
 347         struct avc_xperms_decision_node *xpd_node;
 348         struct extended_perms_decision *xpd;
 349
 350         xpd_node = kmem_cache_zalloc(avc_xperms_decision_cachep,
 351                                 GFP_ATOMIC | __GFP_NOMEMALLOC);
 352         if (!xpd_node)
 353                 return NULL;
 354
 355         xpd = &xpd_node->xpd;
 356         if (which & XPERMS_ALLOWED) {
 357                 xpd->allowed = kmem_cache_zalloc(avc_xperms_data_cachep,
 358                                                 GFP_ATOMIC | __GFP_NOMEMALLOC);
 359                 if (!xpd->allowed)
 360                         goto error;
 361         }
 362         if (which & XPERMS_AUDITALLOW) {
 363                 xpd->auditallow = kmem_cache_zalloc(avc_xperms_data_cachep,
 364                                                 GFP_ATOMIC | __GFP_NOMEMALLOC);
 365                 if (!xpd->auditallow)
 366                         goto error;
 367         }
 368         if (which & XPERMS_DONTAUDIT) {
 369                 xpd->dontaudit = kmem_cache_zalloc(avc_xperms_data_cachep,
 370                                                 GFP_ATOMIC | __GFP_NOMEMALLOC);
 371                 if (!xpd->dontaudit)
 372                         goto error;
 373         }
 374         return xpd_node;
 375 error:
 376         avc_xperms_decision_free(xpd_node);
 377         return NULL;
 378 }
 379
 380 static int avc_add_xperms_decision(struct avc_node *node,
 381                         struct extended_perms_decision *src)
 382 {
 383         struct avc_xperms_decision_node *dest_xpd;
 384
 385         node->ae.xp_node->xp.len++;
 386         dest_xpd = avc_xperms_decision_alloc(src->used);
 387         if (!dest_xpd)
 388                 return -ENOMEM;
 389         avc_copy_xperms_decision(&dest_xpd->xpd, src);
 390         list_add(&dest_xpd->xpd_list, &node->ae.xp_node->xpd_head);
 391         return 0;
 392 }
 393
 394 static struct avc_xperms_node *avc_xperms_alloc(void)
 395 {
 396         struct avc_xperms_node *xp_node;
 397
 398         xp_node = kmem_cache_zalloc(avc_xperms_cachep,
 399                                 GFP_ATOMIC|__GFP_NOMEMALLOC);
 400         if (!xp_node)
 401                 return xp_node;
 402         INIT_LIST_HEAD(&xp_node->xpd_head);
 403         return xp_node;
 404 }
 405
 406 static int avc_xperms_populate(struct avc_node *node,
 407                                 struct avc_xperms_node *src)
 408 {
 409         struct avc_xperms_node *dest;
 410         struct avc_xperms_decision_node *dest_xpd;
 411         struct avc_xperms_decision_node *src_xpd;
 412
 413         if (src->xp.len == 0)
 414                 return 0;
 415         dest = avc_xperms_alloc();
 416         if (!dest)
 417                 return -ENOMEM;
 418
 419         memcpy(dest->xp.drivers.p, src->xp.drivers.p, sizeof(dest->xp.drivers.p));
 420         dest->xp.len = src->xp.len;
 421
 422         /* for each source xpd allocate a destination xpd and copy */
 423         list_for_each_entry(src_xpd, &src->xpd_head, xpd_list) {
 424                 dest_xpd = avc_xperms_decision_alloc(src_xpd->xpd.used);
 425                 if (!dest_xpd)
 426                         goto error;
 427                 avc_copy_xperms_decision(&dest_xpd->xpd, &src_xpd->xpd);
 428                 list_add(&dest_xpd->xpd_list, &dest->xpd_head);
 429         }
 430         node->ae.xp_node = dest;
 431         return 0;
 432 error:
 433         avc_xperms_free(dest);
 434         return -ENOMEM;
 435
 436 }
 437
 438 static inline u32 avc_xperms_audit_required(u32 requested,
 439                                         struct av_decision *avd,
 440                                         struct extended_perms_decision *xpd,
 441                                         u8 perm,
 442                                         int result,
 443                                         u32 *deniedp)
 444 {
 445         u32 denied, audited;
 446
 447         denied = requested & ~avd->allowed;
 448         if (unlikely(denied)) {
 449                 audited = denied & avd->auditdeny;
 450                 if (audited && xpd) {
 451                         if (avc_xperms_has_perm(xpd, perm, XPERMS_DONTAUDIT))
 452                                 audited &= ~requested;
 453                 }
 454         } else if (result) {
 455                 audited = denied = requested;
 456         } else {
 457                 audited = requested & avd->auditallow;
 458                 if (audited && xpd) {
 459                         if (!avc_xperms_has_perm(xpd, perm, XPERMS_AUDITALLOW))
 460                                 audited &= ~requested;
 461                 }
 462         }
 463
 464         *deniedp = denied;
 465         return audited;
 466 }
 467
 468 static inline int avc_xperms_audit(u32 ssid, u32 tsid, u16 tclass,
 469                                 u32 requested, struct av_decision *avd,
 470                                 struct extended_perms_decision *xpd,
 471                                 u8 perm, int result,
 472                                 struct common_audit_data *ad)
 473 {
 474         u32 audited, denied;
 475
 476         audited = avc_xperms_audit_required(
 477                         requested, avd, xpd, perm, result, &denied);
 478         if (likely(!audited))
 479                 return 0;
 480         return slow_avc_audit(ssid, tsid, tclass, requested,
 481                         audited, denied, result, ad, 0);
 482 }
 483
 484 static void avc_node_free(struct rcu_head *rhead)
 485 {
 486         struct avc_node *node = container_of(rhead, struct avc_node, rhead);
 487         avc_xperms_free(node->ae.xp_node);
 488         kmem_cache_free(avc_node_cachep, node);
 489         avc_cache_stats_incr(frees);
 490 }
 491
 492 static void avc_node_delete(struct avc_node *node)
 493 {
 494         hlist_del_rcu(&node->list);
 495         call_rcu(&node->rhead, avc_node_free);
 496         atomic_dec(&avc_cache.active_nodes);
 497 }
 498
 499 static void avc_node_kill(struct avc_node *node)
 500 {
 501         avc_xperms_free(node->ae.xp_node);
 502         kmem_cache_free(avc_node_cachep, node);
 503         avc_cache_stats_incr(frees);
 504         atomic_dec(&avc_cache.active_nodes);
 505 }
 506
 507 static void avc_node_replace(struct avc_node *new, struct avc_node *old)
 508 {
 509         hlist_replace_rcu(&old->list, &new->list);
 510         call_rcu(&old->rhead, avc_node_free);
 511         atomic_dec(&avc_cache.active_nodes);
 512 }
 513
 514 static inline int avc_reclaim_node(void)
 515 {
 516         struct avc_node *node;
 517         int hvalue, try, ecx;
 518         unsigned long flags;
 519         struct hlist_head *head;
 520         spinlock_t *lock;
 521
 522         for (try = 0, ecx = 0; try < AVC_CACHE_SLOTS; try++) {
 523                 hvalue = atomic_inc_return(&avc_cache.lru_hint) & (AVC_CACHE_SLOTS - 1);
 524                 head = &avc_cache.slots[hvalue];
 525                 lock = &avc_cache.slots_lock[hvalue];
 526
 527                 if (!spin_trylock_irqsave(lock, flags))
 528                         continue;
 529
 530                 rcu_read_lock();
 531                 hlist_for_each_entry(node, head, list) {
 532                         avc_node_delete(node);
 533                         avc_cache_stats_incr(reclaims);
 534                         ecx++;
 535                         if (ecx >= AVC_CACHE_RECLAIM) {
 536                                 rcu_read_unlock();
 537                                 spin_unlock_irqrestore(lock, flags);
 538                                 goto out;
 539                         }
 540                 }
 541                 rcu_read_unlock();
 542                 spin_unlock_irqrestore(lock, flags);
 543         }
 544 out:
 545         return ecx;
 546 }
 547
 548 static struct avc_node *avc_alloc_node(void)
 549 {
 550         struct avc_node *node;
 551
 552         node = kmem_cache_zalloc(avc_node_cachep, GFP_ATOMIC|__GFP_NOMEMALLOC);
 553         if (!node)
 554                 goto out;
 555
 556         INIT_HLIST_NODE(&node->list);
 557         avc_cache_stats_incr(allocations);
 558
 559         if (atomic_inc_return(&avc_cache.active_nodes) > avc_cache_threshold)
 560                 avc_reclaim_node();
 561
 562 out:
 563         return node;
 564 }
 565
 566 static void avc_node_populate(struct avc_node *node, u32 ssid, u32 tsid, u16 tclass, struct av_decision *avd)
 567 {
 568         node->ae.ssid = ssid;
 569         node->ae.tsid = tsid;
 570         node->ae.tclass = tclass;
 571         memcpy(&node->ae.avd, avd, sizeof(node->ae.avd));
 572 }
 573
 574 static inline struct avc_node *avc_search_node(u32 ssid, u32 tsid, u16 tclass)
 575 {
 576         struct avc_node *node, *ret = NULL;
 577         int hvalue;
 578         struct hlist_head *head;
 579
 580         hvalue = avc_hash(ssid, tsid, tclass);
 581         head = &avc_cache.slots[hvalue];
 582         hlist_for_each_entry_rcu(node, head, list) {
 583                 if (ssid == node->ae.ssid &&
 584                     tclass == node->ae.tclass &&
 585                     tsid == node->ae.tsid) {
 586                         ret = node;
 587                         break;
 588                 }
 589         }
 590
 591         return ret;
 592 }
 593
 594 /**
 595  * avc_lookup - Look up an AVC entry.
 596  * @ssid: source security identifier
 597  * @tsid: target security identifier
 598  * @tclass: target security class
 599  *
 600  * Look up an AVC entry that is valid for the
 601  * (@ssid, @tsid), interpreting the permissions
 602  * based on @tclass.  If a valid AVC entry exists,
 603  * then this function returns the avc_node.
 604  * Otherwise, this function returns NULL.
 605  */
 606 static struct avc_node *avc_lookup(u32 ssid, u32 tsid, u16 tclass)
 607 {
 608         struct avc_node *node;
 609
 610         avc_cache_stats_incr(lookups);
 611         node = avc_search_node(ssid, tsid, tclass);
 612
 613         if (node)
 614                 return node;
 615
 616         avc_cache_stats_incr(misses);
 617         return NULL;
 618 }
 619
 620 static int avc_latest_notif_update(int seqno, int is_insert)
 621 {
 622         int ret = 0;
 623         static DEFINE_SPINLOCK(notif_lock);
 624         unsigned long flag;
 625
 626         spin_lock_irqsave(&notif_lock, flag);
 627         if (is_insert) {
 628                 if (seqno < avc_cache.latest_notif) {
 629                         printk(KERN_WARNING "SELinux: avc:  seqno %d < latest_notif %d\n",
 630                                seqno, avc_cache.latest_notif);
 631                         ret = -EAGAIN;
 632                 }
 633         } else {
 634                 if (seqno > avc_cache.latest_notif)
 635                         avc_cache.latest_notif = seqno;
 636         }
 637         spin_unlock_irqrestore(&notif_lock, flag);
 638
 639         return ret;
 640 }
 641
 642 /**
 643  * avc_insert - Insert an AVC entry.
 644  * @ssid: source security identifier
 645  * @tsid: target security identifier
 646  * @tclass: target security class
 647  * @avd: resulting av decision
 648  * @xp_node: resulting extended permissions
 649  *
 650  * Insert an AVC entry for the SID pair
 651  * (@ssid, @tsid) and class @tclass.
 652  * The access vectors and the sequence number are
 653  * normally provided by the security server in
 654  * response to a security_compute_av() call.  If the
 655  * sequence number @avd->seqno is not less than the latest
 656  * revocation notification, then the function copies
 657  * the access vectors into a cache entry, returns
 658  * avc_node inserted. Otherwise, this function returns NULL.
 659  */
 660 static struct avc_node *avc_insert(u32 ssid, u32 tsid, u16 tclass,
 661                                 struct av_decision *avd,
 662                                 struct avc_xperms_node *xp_node)
 663 {
 664         struct avc_node *pos, *node = NULL;
 665         int hvalue;
 666         unsigned long flag;
 667
 668         if (avc_latest_notif_update(avd->seqno, 1))
 669                 goto out;
 670
 671         node = avc_alloc_node();
 672         if (node) {
 673                 struct hlist_head *head;
 674                 spinlock_t *lock;
 675                 int rc = 0;
 676
 677                 hvalue = avc_hash(ssid, tsid, tclass);
 678                 avc_node_populate(node, ssid, tsid, tclass, avd);
 679                 rc = avc_xperms_populate(node, xp_node);
 680                 if (rc) {
 681                         kmem_cache_free(avc_node_cachep, node);
 682                         return NULL;
 683                 }
 684                 head = &avc_cache.slots[hvalue];
 685                 lock = &avc_cache.slots_lock[hvalue];
 686
 687                 spin_lock_irqsave(lock, flag);
 688                 hlist_for_each_entry(pos, head, list) {
 689                         if (pos->ae.ssid == ssid &&
 690                             pos->ae.tsid == tsid &&
 691                             pos->ae.tclass == tclass) {
 692                                 avc_node_replace(node, pos);
 693                                 goto found;
 694                         }
 695                 }
 696                 hlist_add_head_rcu(&node->list, head);
 697 found:
 698                 spin_unlock_irqrestore(lock, flag);
 699         }
 700 out:
 701         return node;
 702 }
 703
 704 /**
 705  * avc_audit_pre_callback - SELinux specific information
 706  * will be called by generic audit code
 707  * @ab: the audit buffer
 708  * @a: audit_data
 709  */
 710 static void avc_audit_pre_callback(struct audit_buffer *ab, void *a)
 711 {
 712         struct common_audit_data *ad = a;
 713         audit_log_format(ab, "avc:  %s ",
 714                          ad->selinux_audit_data->denied ? "denied" : "granted");
 715         avc_dump_av(ab, ad->selinux_audit_data->tclass,
 716                         ad->selinux_audit_data->audited);
 717         audit_log_format(ab, " for ");
 718 }
 719
 720 /**
 721  * avc_audit_post_callback - SELinux specific information
 722  * will be called by generic audit code
 723  * @ab: the audit buffer
 724  * @a: audit_data
 725  */
 726 static void avc_audit_post_callback(struct audit_buffer *ab, void *a)
 727 {
 728         struct common_audit_data *ad = a;
 729         audit_log_format(ab, " ");
 730         avc_dump_query(ab, ad->selinux_audit_data->ssid,
 731                            ad->selinux_audit_data->tsid,
 732                            ad->selinux_audit_data->tclass);
 733         if (ad->selinux_audit_data->denied) {
 734                 audit_log_format(ab, " permissive=%u",
 735                                  ad->selinux_audit_data->result ? 0 : 1);
 736         }
 737 }
 738
 739 /* This is the slow part of avc audit with big stack footprint */
 740 noinline int slow_avc_audit(u32 ssid, u32 tsid, u16 tclass,
 741                 u32 requested, u32 audited, u32 denied, int result,
 742                 struct common_audit_data *a,
 743                 unsigned flags)
 744 {
 745         struct common_audit_data stack_data;
 746         struct selinux_audit_data sad;
 747
 748         if (!a) {
 749                 a = &stack_data;
 750                 a->type = LSM_AUDIT_DATA_NONE;
 751         }
 752
 753         /*
 754          * When in a RCU walk do the audit on the RCU retry.  This is because
 755          * the collection of the dname in an inode audit message is not RCU
 756          * safe.  Note this may drop some audits when the situation changes
 757          * during retry. However this is logically just as if the operation
 758          * happened a little later.
 759          */
 760         if ((a->type == LSM_AUDIT_DATA_INODE) &&
 761             (flags & MAY_NOT_BLOCK))
 762                 return -ECHILD;
 763
 764         sad.tclass = tclass;
 765         sad.requested = requested;
 766         sad.ssid = ssid;
 767         sad.tsid = tsid;
 768         sad.audited = audited;
 769         sad.denied = denied;
 770         sad.result = result;
 771
 772         a->selinux_audit_data = &sad;
 773
 774         common_lsm_audit(a, avc_audit_pre_callback, avc_audit_post_callback);
 775         return 0;
 776 }
 777
 778 /**
 779  * avc_add_callback - Register a callback for security events.
 780  * @callback: callback function
 781  * @events: security events
 782  *
 783  * Register a callback function for events in the set @events.
 784  * Returns %0 on success or -%ENOMEM if insufficient memory
 785  * exists to add the callback.
 786  */
 787 int __init avc_add_callback(int (*callback)(u32 event), u32 events)
 788 {
 789         struct avc_callback_node *c;
 790         int rc = 0;
 791
 792         c = kmalloc(sizeof(*c), GFP_KERNEL);
 793         if (!c) {
 794                 rc = -ENOMEM;
 795                 goto out;
 796         }
 797
 798         c->callback = callback;
 799         c->events = events;
 800         c->next = avc_callbacks;
 801         avc_callbacks = c;
 802 out:
 803         return rc;
 804 }
 805
 806 static inline int avc_sidcmp(u32 x, u32 y)
 807 {
 808         return (x == y || x == SECSID_WILD || y == SECSID_WILD);
 809 }
 810
 811 /**
 812  * avc_update_node Update an AVC entry
 813  * @event : Updating event
 814  * @perms : Permission mask bits
 815  * @ssid,@tsid,@tclass : identifier of an AVC entry
 816  * @seqno : sequence number when decision was made
 817  * @xpd: extended_perms_decision to be added to the node
 818  *
 819  * if a valid AVC entry doesn't exist,this function returns -ENOENT.
 820  * if kmalloc() called internal returns NULL, this function returns -ENOMEM.
 821  * otherwise, this function updates the AVC entry. The original AVC-entry object
 822  * will release later by RCU.
 823  */
 824 static int avc_update_node(u32 event, u32 perms, u8 driver, u8 xperm, u32 ssid,
 825                         u32 tsid, u16 tclass, u32 seqno,
 826                         struct extended_perms_decision *xpd,
 827                         u32 flags)
 828 {
 829         int hvalue, rc = 0;
 830         unsigned long flag;
 831         struct avc_node *pos, *node, *orig = NULL;
 832         struct hlist_head *head;
 833         spinlock_t *lock;
 834
 835         node = avc_alloc_node();
 836         if (!node) {
 837                 rc = -ENOMEM;
 838                 goto out;
 839         }
 840
 841         /* Lock the target slot */
 842         hvalue = avc_hash(ssid, tsid, tclass);
 843
 844         head = &avc_cache.slots[hvalue];
 845         lock = &avc_cache.slots_lock[hvalue];
 846
 847         spin_lock_irqsave(lock, flag);
 848
 849         hlist_for_each_entry(pos, head, list) {
 850                 if (ssid == pos->ae.ssid &&
 851                     tsid == pos->ae.tsid &&
 852                     tclass == pos->ae.tclass &&
 853                     seqno == pos->ae.avd.seqno){
 854                         orig = pos;
 855                         break;
 856                 }
 857         }
 858
 859         if (!orig) {
 860                 rc = -ENOENT;
 861                 avc_node_kill(node);
 862                 goto out_unlock;
 863         }
 864
 865         /*
 866          * Copy and replace original node.
 867          */
 868
 869         avc_node_populate(node, ssid, tsid, tclass, &orig->ae.avd);
 870
 871         if (orig->ae.xp_node) {
 872                 rc = avc_xperms_populate(node, orig->ae.xp_node);
 873                 if (rc) {
 874                         kmem_cache_free(avc_node_cachep, node);
 875                         goto out_unlock;
 876                 }
 877         }
 878
 879         switch (event) {
 880         case AVC_CALLBACK_GRANT:
 881                 node->ae.avd.allowed |= perms;
 882                 if (node->ae.xp_node && (flags & AVC_EXTENDED_PERMS))
 883                         avc_xperms_allow_perm(node->ae.xp_node, driver, xperm);
 884                 break;
 885         case AVC_CALLBACK_TRY_REVOKE:
 886         case AVC_CALLBACK_REVOKE:
 887                 node->ae.avd.allowed &= ~perms;
 888                 break;
 889         case AVC_CALLBACK_AUDITALLOW_ENABLE:
 890                 node->ae.avd.auditallow |= perms;
 891                 break;
 892         case AVC_CALLBACK_AUDITALLOW_DISABLE:
 893                 node->ae.avd.auditallow &= ~perms;
 894                 break;
 895         case AVC_CALLBACK_AUDITDENY_ENABLE:
 896                 node->ae.avd.auditdeny |= perms;
 897                 break;
 898         case AVC_CALLBACK_AUDITDENY_DISABLE:
 899                 node->ae.avd.auditdeny &= ~perms;
 900                 break;
 901         case AVC_CALLBACK_ADD_XPERMS:
 902                 avc_add_xperms_decision(node, xpd);
 903                 break;
 904         }
 905         avc_node_replace(node, orig);
 906 out_unlock:
 907         spin_unlock_irqrestore(lock, flag);
 908 out:
 909         return rc;
 910 }
 911
 912 /**
 913  * avc_flush - Flush the cache
 914  */
 915 static void avc_flush(void)
 916 {
 917         struct hlist_head *head;
 918         struct avc_node *node;
 919         spinlock_t *lock;
 920         unsigned long flag;
 921         int i;
 922
 923         for (i = 0; i < AVC_CACHE_SLOTS; i++) {
 924                 head = &avc_cache.slots[i];
 925                 lock = &avc_cache.slots_lock[i];
 926
 927                 spin_lock_irqsave(lock, flag);
 928                 /*
 929                  * With preemptable RCU, the outer spinlock does not
 930                  * prevent RCU grace periods from ending.
 931                  */
 932                 rcu_read_lock();
 933                 hlist_for_each_entry(node, head, list)
 934                         avc_node_delete(node);
 935                 rcu_read_unlock();
 936                 spin_unlock_irqrestore(lock, flag);
 937         }
 938 }
 939
 940 /**
 941  * avc_ss_reset - Flush the cache and revalidate migrated permissions.
 942  * @seqno: policy sequence number
 943  */
 944 int avc_ss_reset(u32 seqno)
 945 {
 946         struct avc_callback_node *c;
 947         int rc = 0, tmprc;
 948
 949         avc_flush();
 950
 951         for (c = avc_callbacks; c; c = c->next) {
 952                 if (c->events & AVC_CALLBACK_RESET) {
 953                         tmprc = c->callback(AVC_CALLBACK_RESET);
 954                         /* save the first error encountered for the return
 955                            value and continue processing the callbacks */
 956                         if (!rc)
 957                                 rc = tmprc;
 958                 }
 959         }
 960
 961         avc_latest_notif_update(seqno, 0);
 962         return rc;
 963 }
 964
 965 /*
 966  * Slow-path helper function for avc_has_perm_noaudit,
 967  * when the avc_node lookup fails. We get called with
 968  * the RCU read lock held, and need to return with it
 969  * still held, but drop if for the security compute.
 970  *
 971  * Don't inline this, since it's the slow-path and just
 972  * results in a bigger stack frame.
 973  */
 974 static noinline struct avc_node *avc_compute_av(u32 ssid, u32 tsid,
 975                          u16 tclass, struct av_decision *avd,
 976                          struct avc_xperms_node *xp_node)
 977 {
 978         rcu_read_unlock();
 979         INIT_LIST_HEAD(&xp_node->xpd_head);
 980         security_compute_av(ssid, tsid, tclass, avd, &xp_node->xp);
 981         rcu_read_lock();
 982         return avc_insert(ssid, tsid, tclass, avd, xp_node);
 983 }
 984
 985 static noinline int avc_denied(u32 ssid, u32 tsid,
 986                                 u16 tclass, u32 requested,
 987                                 u8 driver, u8 xperm, unsigned flags,
 988                                 struct av_decision *avd)
 989 {
 990
 991         avc_update_node(AVC_CALLBACK_GRANT, requested, driver, xperm, ssid,
 992                                 tsid, tclass, avd->seqno, NULL, flags);
 993         return 0;
 994 }
 995
 996 /*
 997  * The avc extended permissions logic adds an additional 256 bits of
 998  * permissions to an avc node when extended permissions for that node are
 999  * specified in the avtab. If the additional 256 permissions is not adequate,
1000  * as-is the case with ioctls, then multiple may be chained together and the
1001  * driver field is used to specify which set contains the permission.
1002  */
1003 int avc_has_extended_perms(u32 ssid, u32 tsid, u16 tclass, u32 requested,
1004                         u8 driver, u8 xperm, struct common_audit_data *ad)
1005 {
1006         struct avc_node *node;
1007         struct av_decision avd;
1008         u32 denied;
1009         struct extended_perms_decision local_xpd;
1010         struct extended_perms_decision *xpd = NULL;
1011         struct extended_perms_data allowed;
1012         struct extended_perms_data auditallow;
1013         struct extended_perms_data dontaudit;
1014         struct avc_xperms_node local_xp_node;
1015         struct avc_xperms_node *xp_node;
1016         int rc = 0, rc2;
1017
1018         xp_node = &local_xp_node;
1019         BUG_ON(!requested);
1020
1021         rcu_read_lock();
1022
1023         node = avc_lookup(ssid, tsid, tclass);
1024         if (unlikely(!node)) {
1025                 node = avc_compute_av(ssid, tsid, tclass, &avd, xp_node);
1026         } else {
1027                 memcpy(&avd, &node->ae.avd, sizeof(avd));
1028                 xp_node = node->ae.xp_node;
1029         }
1030         /* if extended permissions are not defined, only consider av_decision */
1031         if (!xp_node || !xp_node->xp.len)
1032                 goto decision;
1033
1034         local_xpd.allowed = &allowed;
1035         local_xpd.auditallow = &auditallow;
1036         local_xpd.dontaudit = &dontaudit;
1037
1038         xpd = avc_xperms_decision_lookup(driver, xp_node);
1039         if (unlikely(!xpd)) {
1040                 /*
1041                  * Compute the extended_perms_decision only if the driver
1042                  * is flagged
1043                  */
1044                 if (!security_xperm_test(xp_node->xp.drivers.p, driver)) {
1045                         avd.allowed &= ~requested;
1046                         goto decision;
1047                 }
1048                 rcu_read_unlock();
1049                 security_compute_xperms_decision(ssid, tsid, tclass, driver,
1050                                                 &local_xpd);
1051                 rcu_read_lock();
1052                 avc_update_node(AVC_CALLBACK_ADD_XPERMS, requested, driver, xperm,
1053                                 ssid, tsid, tclass, avd.seqno, &local_xpd, 0);
1054         } else {
1055                 avc_quick_copy_xperms_decision(xperm, &local_xpd, xpd);
1056         }
1057         xpd = &local_xpd;
1058
1059         if (!avc_xperms_has_perm(xpd, xperm, XPERMS_ALLOWED))
1060                 avd.allowed &= ~requested;
1061
1062 decision:
1063         denied = requested & ~(avd.allowed);
1064         if (unlikely(denied))
1065                 rc = avc_denied(ssid, tsid, tclass, requested, driver, xperm,
1066                                 AVC_EXTENDED_PERMS, &avd);
1067
1068         rcu_read_unlock();
1069
1070         rc2 = avc_xperms_audit(ssid, tsid, tclass, requested,
1071                         &avd, xpd, xperm, rc, ad);
1072         if (rc2)
1073                 return rc2;
1074         return rc;
1075 }
1076
1077 /**
1078  * avc_has_perm_noaudit - Check permissions but perform no auditing.
1079  * @ssid: source security identifier
1080  * @tsid: target security identifier
1081  * @tclass: target security class
1082  * @requested: requested permissions, interpreted based on @tclass
1083  * @flags:  AVC_STRICT or 0
1084  * @avd: access vector decisions
1085  *
1086  * Check the AVC to determine whether the @requested permissions are granted
1087  * for the SID pair (@ssid, @tsid), interpreting the permissions
1088  * based on @tclass, and call the security server on a cache miss to obtain
1089  * a new decision and add it to the cache.  Return a copy of the decisions
1090  * in @avd.  Return %0 if all @requested permissions are granted,
1091  * -%EACCES if any permissions are denied, or another -errno upon
1092  * other errors.  This function is typically called by avc_has_perm(),
1093  * but may also be called directly to separate permission checking from
1094  * auditing, e.g. in cases where a lock must be held for the check but
1095  * should be released for the auditing.
1096  */
1097 inline int avc_has_perm_noaudit(u32 ssid, u32 tsid,
1098                          u16 tclass, u32 requested,
1099                          unsigned flags,
1100                          struct av_decision *avd)
1101 {
1102         struct avc_node *node;
1103         struct avc_xperms_node xp_node;
1104         int rc = 0;
1105         u32 denied;
1106
1107         BUG_ON(!requested);
1108
1109         rcu_read_lock();
1110
1111         node = avc_lookup(ssid, tsid, tclass);
1112         if (unlikely(!node))
1113                 node = avc_compute_av(ssid, tsid, tclass, avd, &xp_node);
1114         else
1115                 memcpy(avd, &node->ae.avd, sizeof(*avd));
1116
1117         denied = requested & ~(avd->allowed);
1118         if (unlikely(denied))
1119                 rc = avc_denied(ssid, tsid, tclass, requested, 0, 0, flags, avd);
1120
1121         rcu_read_unlock();
1122         return rc;
1123 }
1124
1125 /**
1126  * avc_has_perm - Check permissions and perform any appropriate auditing.
1127  * @ssid: source security identifier
1128  * @tsid: target security identifier
1129  * @tclass: target security class
1130  * @requested: requested permissions, interpreted based on @tclass
1131  * @auditdata: auxiliary audit data
1132  * @flags: VFS walk flags
1133  *
1134  * Check the AVC to determine whether the @requested permissions are granted
1135  * for the SID pair (@ssid, @tsid), interpreting the permissions
1136  * based on @tclass, and call the security server on a cache miss to obtain
1137  * a new decision and add it to the cache.  Audit the granting or denial of
1138  * permissions in accordance with the policy.  Return %0 if all @requested
1139  * permissions are granted, -%EACCES if any permissions are denied, or
1140  * another -errno upon other errors.
1141  */
1142 int avc_has_perm_flags(u32 ssid, u32 tsid, u16 tclass,
1143                        u32 requested, struct common_audit_data *auditdata,
1144                        unsigned flags)
1145 {
1146         struct av_decision avd;
1147         int rc, rc2;
1148
1149         rc = avc_has_perm_noaudit(ssid, tsid, tclass, requested, 0, &avd);
1150
1151         rc2 = avc_audit(ssid, tsid, tclass, requested, &avd, rc, auditdata,
1152                         flags);
1153         if (rc2)
1154                 return rc2;
1155         return rc;
1156 }
1157
1158 u32 avc_policy_seqno(void)
1159 {
1160         return avc_cache.latest_notif;
1161 }
1162
1163 void avc_disable(void)
1164 {
1165         /*
1166          * If you are looking at this because you have realized that we are
1167          * not destroying the avc_node_cachep it might be easy to fix, but
1168          * I don't know the memory barrier semantics well enough to know.  It's
1169          * possible that some other task dereferenced security_ops when
1170          * it still pointed to selinux operations.  If that is the case it's
1171          * possible that it is about to use the avc and is about to need the
1172          * avc_node_cachep.  I know I could wrap the security.c security_ops call
1173          * in an rcu_lock, but seriously, it's not worth it.  Instead I just flush
1174          * the cache and get that memory back.
1175          */
1176         if (avc_node_cachep) {
1177                 avc_flush();
1178                 /* kmem_cache_destroy(avc_node_cachep); */
1179         }
1180 }