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