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, GFP_NOWAIT);
 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_NOWAIT);
 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_NOWAIT);
 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_NOWAIT);
 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, GFP_NOWAIT);
 399         if (!xp_node)
 400                 return xp_node;
 401         INIT_LIST_HEAD(&xp_node->xpd_head);
 402         return xp_node;
 403 }
 404
 405 static int avc_xperms_populate(struct avc_node *node,
 406                                 struct avc_xperms_node *src)
 407 {
 408         struct avc_xperms_node *dest;
 409         struct avc_xperms_decision_node *dest_xpd;
 410         struct avc_xperms_decision_node *src_xpd;
 411
 412         if (src->xp.len == 0)
 413                 return 0;
 414         dest = avc_xperms_alloc();
 415         if (!dest)
 416                 return -ENOMEM;
 417
 418         memcpy(dest->xp.drivers.p, src->xp.drivers.p, sizeof(dest->xp.drivers.p));
 419         dest->xp.len = src->xp.len;
 420
 421         /* for each source xpd allocate a destination xpd and copy */
 422         list_for_each_entry(src_xpd, &src->xpd_head, xpd_list) {
 423                 dest_xpd = avc_xperms_decision_alloc(src_xpd->xpd.used);
 424                 if (!dest_xpd)
 425                         goto error;
 426                 avc_copy_xperms_decision(&dest_xpd->xpd, &src_xpd->xpd);
 427                 list_add(&dest_xpd->xpd_list, &dest->xpd_head);
 428         }
 429         node->ae.xp_node = dest;
 430         return 0;
 431 error:
 432         avc_xperms_free(dest);
 433         return -ENOMEM;
 434
 435 }
 436
 437 static inline u32 avc_xperms_audit_required(u32 requested,
 438                                         struct av_decision *avd,
 439                                         struct extended_perms_decision *xpd,
 440                                         u8 perm,
 441                                         int result,
 442                                         u32 *deniedp)
 443 {
 444         u32 denied, audited;
 445
 446         denied = requested & ~avd->allowed;
 447         if (unlikely(denied)) {
 448                 audited = denied & avd->auditdeny;
 449                 if (audited && xpd) {
 450                         if (avc_xperms_has_perm(xpd, perm, XPERMS_DONTAUDIT))
 451                                 audited &= ~requested;
 452                 }
 453         } else if (result) {
 454                 audited = denied = requested;
 455         } else {
 456                 audited = requested & avd->auditallow;
 457                 if (audited && xpd) {
 458                         if (!avc_xperms_has_perm(xpd, perm, XPERMS_AUDITALLOW))
 459                                 audited &= ~requested;
 460                 }
 461         }
 462
 463         *deniedp = denied;
 464         return audited;
 465 }
 466
 467 static inline int avc_xperms_audit(u32 ssid, u32 tsid, u16 tclass,
 468                                 u32 requested, struct av_decision *avd,
 469                                 struct extended_perms_decision *xpd,
 470                                 u8 perm, int result,
 471                                 struct common_audit_data *ad)
 472 {
 473         u32 audited, denied;
 474
 475         audited = avc_xperms_audit_required(
 476                         requested, avd, xpd, perm, result, &denied);
 477         if (likely(!audited))
 478                 return 0;
 479         return slow_avc_audit(ssid, tsid, tclass, requested,
 480                         audited, denied, result, ad, 0);
 481 }
 482
 483 static void avc_node_free(struct rcu_head *rhead)
 484 {
 485         struct avc_node *node = container_of(rhead, struct avc_node, rhead);
 486         avc_xperms_free(node->ae.xp_node);
 487         kmem_cache_free(avc_node_cachep, node);
 488         avc_cache_stats_incr(frees);
 489 }
 490
 491 static void avc_node_delete(struct avc_node *node)
 492 {
 493         hlist_del_rcu(&node->list);
 494         call_rcu(&node->rhead, avc_node_free);
 495         atomic_dec(&avc_cache.active_nodes);
 496 }
 497
 498 static void avc_node_kill(struct avc_node *node)
 499 {
 500         avc_xperms_free(node->ae.xp_node);
 501         kmem_cache_free(avc_node_cachep, node);
 502         avc_cache_stats_incr(frees);
 503         atomic_dec(&avc_cache.active_nodes);
 504 }
 505
 506 static void avc_node_replace(struct avc_node *new, struct avc_node *old)
 507 {
 508         hlist_replace_rcu(&old->list, &new->list);
 509         call_rcu(&old->rhead, avc_node_free);
 510         atomic_dec(&avc_cache.active_nodes);
 511 }
 512
 513 static inline int avc_reclaim_node(void)
 514 {
 515         struct avc_node *node;
 516         int hvalue, try, ecx;
 517         unsigned long flags;
 518         struct hlist_head *head;
 519         spinlock_t *lock;
 520
 521         for (try = 0, ecx = 0; try < AVC_CACHE_SLOTS; try++) {
 522                 hvalue = atomic_inc_return(&avc_cache.lru_hint) & (AVC_CACHE_SLOTS - 1);
 523                 head = &avc_cache.slots[hvalue];
 524                 lock = &avc_cache.slots_lock[hvalue];
 525
 526                 if (!spin_trylock_irqsave(lock, flags))
 527                         continue;
 528
 529                 rcu_read_lock();
 530                 hlist_for_each_entry(node, head, list) {
 531                         avc_node_delete(node);
 532                         avc_cache_stats_incr(reclaims);
 533                         ecx++;
 534                         if (ecx >= AVC_CACHE_RECLAIM) {
 535                                 rcu_read_unlock();
 536                                 spin_unlock_irqrestore(lock, flags);
 537                                 goto out;
 538                         }
 539                 }
 540                 rcu_read_unlock();
 541                 spin_unlock_irqrestore(lock, flags);
 542         }
 543 out:
 544         return ecx;
 545 }
 546
 547 static struct avc_node *avc_alloc_node(void)
 548 {
 549         struct avc_node *node;
 550
 551         node = kmem_cache_zalloc(avc_node_cachep, GFP_NOWAIT);
 552         if (!node)
 553                 goto out;
 554
 555         INIT_HLIST_NODE(&node->list);
 556         avc_cache_stats_incr(allocations);
 557
 558         if (atomic_inc_return(&avc_cache.active_nodes) > avc_cache_threshold)
 559                 avc_reclaim_node();
 560
 561 out:
 562         return node;
 563 }
 564
 565 static void avc_node_populate(struct avc_node *node, u32 ssid, u32 tsid, u16 tclass, struct av_decision *avd)
 566 {
 567         node->ae.ssid = ssid;
 568         node->ae.tsid = tsid;
 569         node->ae.tclass = tclass;
 570         memcpy(&node->ae.avd, avd, sizeof(node->ae.avd));
 571 }
 572
 573 static inline struct avc_node *avc_search_node(u32 ssid, u32 tsid, u16 tclass)
 574 {
 575         struct avc_node *node, *ret = NULL;
 576         int hvalue;
 577         struct hlist_head *head;
 578
 579         hvalue = avc_hash(ssid, tsid, tclass);
 580         head = &avc_cache.slots[hvalue];
 581         hlist_for_each_entry_rcu(node, head, list) {
 582                 if (ssid == node->ae.ssid &&
 583                     tclass == node->ae.tclass &&
 584                     tsid == node->ae.tsid) {
 585                         ret = node;
 586                         break;
 587                 }
 588         }
 589
 590         return ret;
 591 }
 592
 593 /**
 594  * avc_lookup - Look up an AVC entry.
 595  * @ssid: source security identifier
 596  * @tsid: target security identifier
 597  * @tclass: target security class
 598  *
 599  * Look up an AVC entry that is valid for the
 600  * (@ssid, @tsid), interpreting the permissions
 601  * based on @tclass.  If a valid AVC entry exists,
 602  * then this function returns the avc_node.
 603  * Otherwise, this function returns NULL.
 604  */
 605 static struct avc_node *avc_lookup(u32 ssid, u32 tsid, u16 tclass)
 606 {
 607         struct avc_node *node;
 608
 609         avc_cache_stats_incr(lookups);
 610         node = avc_search_node(ssid, tsid, tclass);
 611
 612         if (node)
 613                 return node;
 614
 615         avc_cache_stats_incr(misses);
 616         return NULL;
 617 }
 618
 619 static int avc_latest_notif_update(int seqno, int is_insert)
 620 {
 621         int ret = 0;
 622         static DEFINE_SPINLOCK(notif_lock);
 623         unsigned long flag;
 624
 625         spin_lock_irqsave(&notif_lock, flag);
 626         if (is_insert) {
 627                 if (seqno < avc_cache.latest_notif) {
 628                         printk(KERN_WARNING "SELinux: avc:  seqno %d < latest_notif %d\n",
 629                                seqno, avc_cache.latest_notif);
 630                         ret = -EAGAIN;
 631                 }
 632         } else {
 633                 if (seqno > avc_cache.latest_notif)
 634                         avc_cache.latest_notif = seqno;
 635         }
 636         spin_unlock_irqrestore(&notif_lock, flag);
 637
 638         return ret;
 639 }
 640
 641 /**
 642  * avc_insert - Insert an AVC entry.
 643  * @ssid: source security identifier
 644  * @tsid: target security identifier
 645  * @tclass: target security class
 646  * @avd: resulting av decision
 647  * @xp_node: resulting extended permissions
 648  *
 649  * Insert an AVC entry for the SID pair
 650  * (@ssid, @tsid) and class @tclass.
 651  * The access vectors and the sequence number are
 652  * normally provided by the security server in
 653  * response to a security_compute_av() call.  If the
 654  * sequence number @avd->seqno is not less than the latest
 655  * revocation notification, then the function copies
 656  * the access vectors into a cache entry, returns
 657  * avc_node inserted. Otherwise, this function returns NULL.
 658  */
 659 static struct avc_node *avc_insert(u32 ssid, u32 tsid, u16 tclass,
 660                                 struct av_decision *avd,
 661                                 struct avc_xperms_node *xp_node)
 662 {
 663         struct avc_node *pos, *node = NULL;
 664         int hvalue;
 665         unsigned long flag;
 666
 667         if (avc_latest_notif_update(avd->seqno, 1))
 668                 goto out;
 669
 670         node = avc_alloc_node();
 671         if (node) {
 672                 struct hlist_head *head;
 673                 spinlock_t *lock;
 674                 int rc = 0;
 675
 676                 hvalue = avc_hash(ssid, tsid, tclass);
 677                 avc_node_populate(node, ssid, tsid, tclass, avd);
 678                 rc = avc_xperms_populate(node, xp_node);
 679                 if (rc) {
 680                         kmem_cache_free(avc_node_cachep, node);
 681                         return NULL;
 682                 }
 683                 head = &avc_cache.slots[hvalue];
 684                 lock = &avc_cache.slots_lock[hvalue];
 685
 686                 spin_lock_irqsave(lock, flag);
 687                 hlist_for_each_entry(pos, head, list) {
 688                         if (pos->ae.ssid == ssid &&
 689                             pos->ae.tsid == tsid &&
 690                             pos->ae.tclass == tclass) {
 691                                 avc_node_replace(node, pos);
 692                                 goto found;
 693                         }
 694                 }
 695                 hlist_add_head_rcu(&node->list, head);
 696 found:
 697                 spin_unlock_irqrestore(lock, flag);
 698         }
 699 out:
 700         return node;
 701 }
 702
 703 /**
 704  * avc_audit_pre_callback - SELinux specific information
 705  * will be called by generic audit code
 706  * @ab: the audit buffer
 707  * @a: audit_data
 708  */
 709 static void avc_audit_pre_callback(struct audit_buffer *ab, void *a)
 710 {
 711         struct common_audit_data *ad = a;
 712         audit_log_format(ab, "avc:  %s ",
 713                          ad->selinux_audit_data->denied ? "denied" : "granted");
 714         avc_dump_av(ab, ad->selinux_audit_data->tclass,
 715                         ad->selinux_audit_data->audited);
 716         audit_log_format(ab, " for ");
 717 }
 718
 719 /**
 720  * avc_audit_post_callback - SELinux specific information
 721  * will be called by generic audit code
 722  * @ab: the audit buffer
 723  * @a: audit_data
 724  */
 725 static void avc_audit_post_callback(struct audit_buffer *ab, void *a)
 726 {
 727         struct common_audit_data *ad = a;
 728         audit_log_format(ab, " ");
 729         avc_dump_query(ab, ad->selinux_audit_data->ssid,
 730                            ad->selinux_audit_data->tsid,
 731                            ad->selinux_audit_data->tclass);
 732         if (ad->selinux_audit_data->denied) {
 733                 audit_log_format(ab, " permissive=%u",
 734                                  ad->selinux_audit_data->result ? 0 : 1);
 735         }
 736 }
 737
 738 /* This is the slow part of avc audit with big stack footprint */
 739 noinline int slow_avc_audit(u32 ssid, u32 tsid, u16 tclass,
 740                 u32 requested, u32 audited, u32 denied, int result,
 741                 struct common_audit_data *a,
 742                 unsigned flags)
 743 {
 744         struct common_audit_data stack_data;
 745         struct selinux_audit_data sad;
 746
 747         if (!a) {
 748                 a = &stack_data;
 749                 a->type = LSM_AUDIT_DATA_NONE;
 750         }
 751
 752         /*
 753          * When in a RCU walk do the audit on the RCU retry.  This is because
 754          * the collection of the dname in an inode audit message is not RCU
 755          * safe.  Note this may drop some audits when the situation changes
 756          * during retry. However this is logically just as if the operation
 757          * happened a little later.
 758          */
 759         if ((a->type == LSM_AUDIT_DATA_INODE) &&
 760             (flags & MAY_NOT_BLOCK))
 761                 return -ECHILD;
 762
 763         sad.tclass = tclass;
 764         sad.requested = requested;
 765         sad.ssid = ssid;
 766         sad.tsid = tsid;
 767         sad.audited = audited;
 768         sad.denied = denied;
 769         sad.result = result;
 770
 771         a->selinux_audit_data = &sad;
 772
 773         common_lsm_audit(a, avc_audit_pre_callback, avc_audit_post_callback);
 774         return 0;
 775 }
 776
 777 /**
 778  * avc_add_callback - Register a callback for security events.
 779  * @callback: callback function
 780  * @events: security events
 781  *
 782  * Register a callback function for events in the set @events.
 783  * Returns %0 on success or -%ENOMEM if insufficient memory
 784  * exists to add the callback.
 785  */
 786 int __init avc_add_callback(int (*callback)(u32 event), u32 events)
 787 {
 788         struct avc_callback_node *c;
 789         int rc = 0;
 790
 791         c = kmalloc(sizeof(*c), GFP_KERNEL);
 792         if (!c) {
 793                 rc = -ENOMEM;
 794                 goto out;
 795         }
 796
 797         c->callback = callback;
 798         c->events = events;
 799         c->next = avc_callbacks;
 800         avc_callbacks = c;
 801 out:
 802         return rc;
 803 }
 804
 805 /**
 806  * avc_update_node Update an AVC entry
 807  * @event : Updating event
 808  * @perms : Permission mask bits
 809  * @ssid,@tsid,@tclass : identifier of an AVC entry
 810  * @seqno : sequence number when decision was made
 811  * @xpd: extended_perms_decision to be added to the node
 812  *
 813  * if a valid AVC entry doesn't exist,this function returns -ENOENT.
 814  * if kmalloc() called internal returns NULL, this function returns -ENOMEM.
 815  * otherwise, this function updates the AVC entry. The original AVC-entry object
 816  * will release later by RCU.
 817  */
 818 static int avc_update_node(u32 event, u32 perms, u8 driver, u8 xperm, u32 ssid,
 819                         u32 tsid, u16 tclass, u32 seqno,
 820                         struct extended_perms_decision *xpd,
 821                         u32 flags)
 822 {
 823         int hvalue, rc = 0;
 824         unsigned long flag;
 825         struct avc_node *pos, *node, *orig = NULL;
 826         struct hlist_head *head;
 827         spinlock_t *lock;
 828
 829         node = avc_alloc_node();
 830         if (!node) {
 831                 rc = -ENOMEM;
 832                 goto out;
 833         }
 834
 835         /* Lock the target slot */
 836         hvalue = avc_hash(ssid, tsid, tclass);
 837
 838         head = &avc_cache.slots[hvalue];
 839         lock = &avc_cache.slots_lock[hvalue];
 840
 841         spin_lock_irqsave(lock, flag);
 842
 843         hlist_for_each_entry(pos, head, list) {
 844                 if (ssid == pos->ae.ssid &&
 845                     tsid == pos->ae.tsid &&
 846                     tclass == pos->ae.tclass &&
 847                     seqno == pos->ae.avd.seqno){
 848                         orig = pos;
 849                         break;
 850                 }
 851         }
 852
 853         if (!orig) {
 854                 rc = -ENOENT;
 855                 avc_node_kill(node);
 856                 goto out_unlock;
 857         }
 858
 859         /*
 860          * Copy and replace original node.
 861          */
 862
 863         avc_node_populate(node, ssid, tsid, tclass, &orig->ae.avd);
 864
 865         if (orig->ae.xp_node) {
 866                 rc = avc_xperms_populate(node, orig->ae.xp_node);
 867                 if (rc) {
 868                         kmem_cache_free(avc_node_cachep, node);
 869                         goto out_unlock;
 870                 }
 871         }
 872
 873         switch (event) {
 874         case AVC_CALLBACK_GRANT:
 875                 node->ae.avd.allowed |= perms;
 876                 if (node->ae.xp_node && (flags & AVC_EXTENDED_PERMS))
 877                         avc_xperms_allow_perm(node->ae.xp_node, driver, xperm);
 878                 break;
 879         case AVC_CALLBACK_TRY_REVOKE:
 880         case AVC_CALLBACK_REVOKE:
 881                 node->ae.avd.allowed &= ~perms;
 882                 break;
 883         case AVC_CALLBACK_AUDITALLOW_ENABLE:
 884                 node->ae.avd.auditallow |= perms;
 885                 break;
 886         case AVC_CALLBACK_AUDITALLOW_DISABLE:
 887                 node->ae.avd.auditallow &= ~perms;
 888                 break;
 889         case AVC_CALLBACK_AUDITDENY_ENABLE:
 890                 node->ae.avd.auditdeny |= perms;
 891                 break;
 892         case AVC_CALLBACK_AUDITDENY_DISABLE:
 893                 node->ae.avd.auditdeny &= ~perms;
 894                 break;
 895         case AVC_CALLBACK_ADD_XPERMS:
 896                 avc_add_xperms_decision(node, xpd);
 897                 break;
 898         }
 899         avc_node_replace(node, orig);
 900 out_unlock:
 901         spin_unlock_irqrestore(lock, flag);
 902 out:
 903         return rc;
 904 }
 905
 906 /**
 907  * avc_flush - Flush the cache
 908  */
 909 static void avc_flush(void)
 910 {
 911         struct hlist_head *head;
 912         struct avc_node *node;
 913         spinlock_t *lock;
 914         unsigned long flag;
 915         int i;
 916
 917         for (i = 0; i < AVC_CACHE_SLOTS; i++) {
 918                 head = &avc_cache.slots[i];
 919                 lock = &avc_cache.slots_lock[i];
 920
 921                 spin_lock_irqsave(lock, flag);
 922                 /*
 923                  * With preemptable RCU, the outer spinlock does not
 924                  * prevent RCU grace periods from ending.
 925                  */
 926                 rcu_read_lock();
 927                 hlist_for_each_entry(node, head, list)
 928                         avc_node_delete(node);
 929                 rcu_read_unlock();
 930                 spin_unlock_irqrestore(lock, flag);
 931         }
 932 }
 933
 934 /**
 935  * avc_ss_reset - Flush the cache and revalidate migrated permissions.
 936  * @seqno: policy sequence number
 937  */
 938 int avc_ss_reset(u32 seqno)
 939 {
 940         struct avc_callback_node *c;
 941         int rc = 0, tmprc;
 942
 943         avc_flush();
 944
 945         for (c = avc_callbacks; c; c = c->next) {
 946                 if (c->events & AVC_CALLBACK_RESET) {
 947                         tmprc = c->callback(AVC_CALLBACK_RESET);
 948                         /* save the first error encountered for the return
 949                            value and continue processing the callbacks */
 950                         if (!rc)
 951                                 rc = tmprc;
 952                 }
 953         }
 954
 955         avc_latest_notif_update(seqno, 0);
 956         return rc;
 957 }
 958
 959 /*
 960  * Slow-path helper function for avc_has_perm_noaudit,
 961  * when the avc_node lookup fails. We get called with
 962  * the RCU read lock held, and need to return with it
 963  * still held, but drop if for the security compute.
 964  *
 965  * Don't inline this, since it's the slow-path and just
 966  * results in a bigger stack frame.
 967  */
 968 static noinline struct avc_node *avc_compute_av(u32 ssid, u32 tsid,
 969                          u16 tclass, struct av_decision *avd,
 970                          struct avc_xperms_node *xp_node)
 971 {
 972         rcu_read_unlock();
 973         INIT_LIST_HEAD(&xp_node->xpd_head);
 974         security_compute_av(ssid, tsid, tclass, avd, &xp_node->xp);
 975         rcu_read_lock();
 976         return avc_insert(ssid, tsid, tclass, avd, xp_node);
 977 }
 978
 979 static noinline int avc_denied(u32 ssid, u32 tsid,
 980                                 u16 tclass, u32 requested,
 981                                 u8 driver, u8 xperm, unsigned flags,
 982                                 struct av_decision *avd)
 983 {
 984         if (flags & AVC_STRICT)
 985                 return -EACCES;
 986
 987         if (selinux_enforcing && !(avd->flags & AVD_FLAGS_PERMISSIVE))
 988                 return -EACCES;
 989
 990         avc_update_node(AVC_CALLBACK_GRANT, requested, driver, xperm, ssid,
 991                                 tsid, tclass, avd->seqno, NULL, flags);
 992         return 0;
 993 }
 994
 995 /*
 996  * The avc extended permissions logic adds an additional 256 bits of
 997  * permissions to an avc node when extended permissions for that node are
 998  * specified in the avtab. If the additional 256 permissions is not adequate,
 999  * as-is the case with ioctls, then multiple may be chained together and the
1000  * driver field is used to specify which set contains the permission.
1001  */
1002 int avc_has_extended_perms(u32 ssid, u32 tsid, u16 tclass, u32 requested,
1003                         u8 driver, u8 xperm, struct common_audit_data *ad)
1004 {
1005         struct avc_node *node;
1006         struct av_decision avd;
1007         u32 denied;
1008         struct extended_perms_decision local_xpd;
1009         struct extended_perms_decision *xpd = NULL;
1010         struct extended_perms_data allowed;
1011         struct extended_perms_data auditallow;
1012         struct extended_perms_data dontaudit;
1013         struct avc_xperms_node local_xp_node;
1014         struct avc_xperms_node *xp_node;
1015         int rc = 0, rc2;
1016
1017         xp_node = &local_xp_node;
1018         BUG_ON(!requested);
1019
1020         rcu_read_lock();
1021
1022         node = avc_lookup(ssid, tsid, tclass);
1023         if (unlikely(!node)) {
1024                 node = avc_compute_av(ssid, tsid, tclass, &avd, xp_node);
1025         } else {
1026                 memcpy(&avd, &node->ae.avd, sizeof(avd));
1027                 xp_node = node->ae.xp_node;
1028         }
1029         /* if extended permissions are not defined, only consider av_decision */
1030         if (!xp_node || !xp_node->xp.len)
1031                 goto decision;
1032
1033         local_xpd.allowed = &allowed;
1034         local_xpd.auditallow = &auditallow;
1035         local_xpd.dontaudit = &dontaudit;
1036
1037         xpd = avc_xperms_decision_lookup(driver, xp_node);
1038         if (unlikely(!xpd)) {
1039                 /*
1040                  * Compute the extended_perms_decision only if the driver
1041                  * is flagged
1042                  */
1043                 if (!security_xperm_test(xp_node->xp.drivers.p, driver)) {
1044                         avd.allowed &= ~requested;
1045                         goto decision;
1046                 }
1047                 rcu_read_unlock();
1048                 security_compute_xperms_decision(ssid, tsid, tclass, driver,
1049                                                 &local_xpd);
1050                 rcu_read_lock();
1051                 avc_update_node(AVC_CALLBACK_ADD_XPERMS, requested, driver, xperm,
1052                                 ssid, tsid, tclass, avd.seqno, &local_xpd, 0);
1053         } else {
1054                 avc_quick_copy_xperms_decision(xperm, &local_xpd, xpd);
1055         }
1056         xpd = &local_xpd;
1057
1058         if (!avc_xperms_has_perm(xpd, xperm, XPERMS_ALLOWED))
1059                 avd.allowed &= ~requested;
1060
1061 decision:
1062         denied = requested & ~(avd.allowed);
1063         if (unlikely(denied))
1064                 rc = avc_denied(ssid, tsid, tclass, requested, driver, xperm,
1065                                 AVC_EXTENDED_PERMS, &avd);
1066
1067         rcu_read_unlock();
1068
1069         rc2 = avc_xperms_audit(ssid, tsid, tclass, requested,
1070                         &avd, xpd, xperm, rc, ad);
1071         if (rc2)
1072                 return rc2;
1073         return rc;
1074 }
1075
1076 /**
1077  * avc_has_perm_noaudit - Check permissions but perform no auditing.
1078  * @ssid: source security identifier
1079  * @tsid: target security identifier
1080  * @tclass: target security class
1081  * @requested: requested permissions, interpreted based on @tclass
1082  * @flags:  AVC_STRICT or 0
1083  * @avd: access vector decisions
1084  *
1085  * Check the AVC to determine whether the @requested permissions are granted
1086  * for the SID pair (@ssid, @tsid), interpreting the permissions
1087  * based on @tclass, and call the security server on a cache miss to obtain
1088  * a new decision and add it to the cache.  Return a copy of the decisions
1089  * in @avd.  Return %0 if all @requested permissions are granted,
1090  * -%EACCES if any permissions are denied, or another -errno upon
1091  * other errors.  This function is typically called by avc_has_perm(),
1092  * but may also be called directly to separate permission checking from
1093  * auditing, e.g. in cases where a lock must be held for the check but
1094  * should be released for the auditing.
1095  */
1096 inline int avc_has_perm_noaudit(u32 ssid, u32 tsid,
1097                          u16 tclass, u32 requested,
1098                          unsigned flags,
1099                          struct av_decision *avd)
1100 {
1101         struct avc_node *node;
1102         struct avc_xperms_node xp_node;
1103         int rc = 0;
1104         u32 denied;
1105
1106         BUG_ON(!requested);
1107
1108         rcu_read_lock();
1109
1110         node = avc_lookup(ssid, tsid, tclass);
1111         if (unlikely(!node))
1112                 node = avc_compute_av(ssid, tsid, tclass, avd, &xp_node);
1113         else
1114                 memcpy(avd, &node->ae.avd, sizeof(*avd));
1115
1116         denied = requested & ~(avd->allowed);
1117         if (unlikely(denied))
1118                 rc = avc_denied(ssid, tsid, tclass, requested, 0, 0, flags, avd);
1119
1120         rcu_read_unlock();
1121         return rc;
1122 }
1123
1124 /**
1125  * avc_has_perm - Check permissions and perform any appropriate auditing.
1126  * @ssid: source security identifier
1127  * @tsid: target security identifier
1128  * @tclass: target security class
1129  * @requested: requested permissions, interpreted based on @tclass
1130  * @auditdata: auxiliary audit data
1131  *
1132  * Check the AVC to determine whether the @requested permissions are granted
1133  * for the SID pair (@ssid, @tsid), interpreting the permissions
1134  * based on @tclass, and call the security server on a cache miss to obtain
1135  * a new decision and add it to the cache.  Audit the granting or denial of
1136  * permissions in accordance with the policy.  Return %0 if all @requested
1137  * permissions are granted, -%EACCES if any permissions are denied, or
1138  * another -errno upon other errors.
1139  */
1140 int avc_has_perm(u32 ssid, u32 tsid, u16 tclass,
1141                  u32 requested, struct common_audit_data *auditdata)
1142 {
1143         struct av_decision avd;
1144         int rc, rc2;
1145
1146         rc = avc_has_perm_noaudit(ssid, tsid, tclass, requested, 0, &avd);
1147
1148         rc2 = avc_audit(ssid, tsid, tclass, requested, &avd, rc, auditdata, 0);
1149         if (rc2)
1150                 return rc2;
1151         return rc;
1152 }
1153
1154 int avc_has_perm_flags(u32 ssid, u32 tsid, u16 tclass,
1155                        u32 requested, struct common_audit_data *auditdata,
1156                        int flags)
1157 {
1158         struct av_decision avd;
1159         int rc, rc2;
1160
1161         rc = avc_has_perm_noaudit(ssid, tsid, tclass, requested, 0, &avd);
1162
1163         rc2 = avc_audit(ssid, tsid, tclass, requested, &avd, rc,
1164                         auditdata, flags);
1165         if (rc2)
1166                 return rc2;
1167         return rc;
1168 }
1169
1170 u32 avc_policy_seqno(void)
1171 {
1172         return avc_cache.latest_notif;
1173 }
1174
1175 void avc_disable(void)
1176 {
1177         /*
1178          * If you are looking at this because you have realized that we are
1179          * not destroying the avc_node_cachep it might be easy to fix, but
1180          * I don't know the memory barrier semantics well enough to know.  It's
1181          * possible that some other task dereferenced security_ops when
1182          * it still pointed to selinux operations.  If that is the case it's
1183          * possible that it is about to use the avc and is about to need the
1184          * avc_node_cachep.  I know I could wrap the security.c security_ops call
1185          * in an rcu_lock, but seriously, it's not worth it.  Instead I just flush
1186          * the cache and get that memory back.
1187          */
1188         if (avc_node_cachep) {
1189                 avc_flush();
1190                 /* kmem_cache_destroy(avc_node_cachep); */
1191         }
1192 }