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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 <net/sock.h>
26#include <linux/un.h>
27#include <net/af_unix.h>
28#include <linux/ip.h>
29#include <linux/audit.h>
30#include <linux/ipv6.h>
31#include <net/ipv6.h>
32#include "avc.h"
33#include "avc_ss.h"
34#include "classmap.h"
35
36#define AVC_CACHE_SLOTS 512
37#define AVC_DEF_CACHE_THRESHOLD 512
38#define AVC_CACHE_RECLAIM 16
39
40#ifdef CONFIG_SECURITY_SELINUX_AVC_STATS
41#define avc_cache_stats_incr(field) this_cpu_inc(avc_cache_stats.field)
42#else
43#define avc_cache_stats_incr(field) do {} while (0)
44#endif
45
46struct avc_entry {
47 u32 ssid;
48 u32 tsid;
49 u16 tclass;
50 struct av_decision avd;
51};
52
53struct avc_node {
54 struct avc_entry ae;
55 struct hlist_node list; /* anchored in avc_cache->slots[i] */
56 struct rcu_head rhead;
57};
58
59struct avc_cache {
60 struct hlist_head slots[AVC_CACHE_SLOTS]; /* head for avc_node->list */
61 spinlock_t slots_lock[AVC_CACHE_SLOTS]; /* lock for writes */
62 atomic_t lru_hint; /* LRU hint for reclaim scan */
63 atomic_t active_nodes;
64 u32 latest_notif; /* latest revocation notification */
65};
66
67struct avc_callback_node {
68 int (*callback) (u32 event);
69 u32 events;
70 struct avc_callback_node *next;
71};
72
73/* Exported via selinufs */
74unsigned int avc_cache_threshold = AVC_DEF_CACHE_THRESHOLD;
75
76#ifdef CONFIG_SECURITY_SELINUX_AVC_STATS
77DEFINE_PER_CPU(struct avc_cache_stats, avc_cache_stats) = { 0 };
78#endif
79
80static struct avc_cache avc_cache;
81static struct avc_callback_node *avc_callbacks;
82static struct kmem_cache *avc_node_cachep;
83
84static inline int avc_hash(u32 ssid, u32 tsid, u16 tclass)
85{
86 return (ssid ^ (tsid<<2) ^ (tclass<<4)) & (AVC_CACHE_SLOTS - 1);
87}
88
89/**
90 * avc_dump_av - Display an access vector in human-readable form.
91 * @tclass: target security class
92 * @av: access vector
93 */
94static void avc_dump_av(struct audit_buffer *ab, u16 tclass, u32 av)
95{
96 const char **perms;
97 int i, perm;
98
99 if (av == 0) {
100 audit_log_format(ab, " null");
101 return;
102 }
103
104 perms = secclass_map[tclass-1].perms;
105
106 audit_log_format(ab, " {");
107 i = 0;
108 perm = 1;
109 while (i < (sizeof(av) * 8)) {
110 if ((perm & av) && perms[i]) {
111 audit_log_format(ab, " %s", perms[i]);
112 av &= ~perm;
113 }
114 i++;
115 perm <<= 1;
116 }
117
118 if (av)
119 audit_log_format(ab, " 0x%x", av);
120
121 audit_log_format(ab, " }");
122}
123
124/**
125 * avc_dump_query - Display a SID pair and a class in human-readable form.
126 * @ssid: source security identifier
127 * @tsid: target security identifier
128 * @tclass: target security class
129 */
130static void avc_dump_query(struct audit_buffer *ab, u32 ssid, u32 tsid, u16 tclass)
131{
132 int rc;
133 char *scontext;
134 u32 scontext_len;
135
136 rc = security_sid_to_context(ssid, &scontext, &scontext_len);
137 if (rc)
138 audit_log_format(ab, "ssid=%d", ssid);
139 else {
140 audit_log_format(ab, "scontext=%s", scontext);
141 kfree(scontext);
142 }
143
144 rc = security_sid_to_context(tsid, &scontext, &scontext_len);
145 if (rc)
146 audit_log_format(ab, " tsid=%d", tsid);
147 else {
148 audit_log_format(ab, " tcontext=%s", scontext);
149 kfree(scontext);
150 }
151
152 BUG_ON(tclass >= ARRAY_SIZE(secclass_map));
153 audit_log_format(ab, " tclass=%s", secclass_map[tclass-1].name);
154}
155
156/**
157 * avc_init - Initialize the AVC.
158 *
159 * Initialize the access vector cache.
160 */
161void __init avc_init(void)
162{
163 int i;
164
165 for (i = 0; i < AVC_CACHE_SLOTS; i++) {
166 INIT_HLIST_HEAD(&avc_cache.slots[i]);
167 spin_lock_init(&avc_cache.slots_lock[i]);
168 }
169 atomic_set(&avc_cache.active_nodes, 0);
170 atomic_set(&avc_cache.lru_hint, 0);
171
172 avc_node_cachep = kmem_cache_create("avc_node", sizeof(struct avc_node),
173 0, SLAB_PANIC, NULL);
174
175 audit_log(current->audit_context, GFP_KERNEL, AUDIT_KERNEL, "AVC INITIALIZED\n");
176}
177
178int avc_get_hash_stats(char *page)
179{
180 int i, chain_len, max_chain_len, slots_used;
181 struct avc_node *node;
182 struct hlist_head *head;
183
184 rcu_read_lock();
185
186 slots_used = 0;
187 max_chain_len = 0;
188 for (i = 0; i < AVC_CACHE_SLOTS; i++) {
189 head = &avc_cache.slots[i];
190 if (!hlist_empty(head)) {
191 slots_used++;
192 chain_len = 0;
193 hlist_for_each_entry_rcu(node, head, list)
194 chain_len++;
195 if (chain_len > max_chain_len)
196 max_chain_len = chain_len;
197 }
198 }
199
200 rcu_read_unlock();
201
202 return scnprintf(page, PAGE_SIZE, "entries: %d\nbuckets used: %d/%d\n"
203 "longest chain: %d\n",
204 atomic_read(&avc_cache.active_nodes),
205 slots_used, AVC_CACHE_SLOTS, max_chain_len);
206}
207
208static void avc_node_free(struct rcu_head *rhead)
209{
210 struct avc_node *node = container_of(rhead, struct avc_node, rhead);
211 kmem_cache_free(avc_node_cachep, node);
212 avc_cache_stats_incr(frees);
213}
214
215static void avc_node_delete(struct avc_node *node)
216{
217 hlist_del_rcu(&node->list);
218 call_rcu(&node->rhead, avc_node_free);
219 atomic_dec(&avc_cache.active_nodes);
220}
221
222static void avc_node_kill(struct avc_node *node)
223{
224 kmem_cache_free(avc_node_cachep, node);
225 avc_cache_stats_incr(frees);
226 atomic_dec(&avc_cache.active_nodes);
227}
228
229static void avc_node_replace(struct avc_node *new, struct avc_node *old)
230{
231 hlist_replace_rcu(&old->list, &new->list);
232 call_rcu(&old->rhead, avc_node_free);
233 atomic_dec(&avc_cache.active_nodes);
234}
235
236static inline int avc_reclaim_node(void)
237{
238 struct avc_node *node;
239 int hvalue, try, ecx;
240 unsigned long flags;
241 struct hlist_head *head;
242 spinlock_t *lock;
243
244 for (try = 0, ecx = 0; try < AVC_CACHE_SLOTS; try++) {
245 hvalue = atomic_inc_return(&avc_cache.lru_hint) & (AVC_CACHE_SLOTS - 1);
246 head = &avc_cache.slots[hvalue];
247 lock = &avc_cache.slots_lock[hvalue];
248
249 if (!spin_trylock_irqsave(lock, flags))
250 continue;
251
252 rcu_read_lock();
253 hlist_for_each_entry(node, head, list) {
254 avc_node_delete(node);
255 avc_cache_stats_incr(reclaims);
256 ecx++;
257 if (ecx >= AVC_CACHE_RECLAIM) {
258 rcu_read_unlock();
259 spin_unlock_irqrestore(lock, flags);
260 goto out;
261 }
262 }
263 rcu_read_unlock();
264 spin_unlock_irqrestore(lock, flags);
265 }
266out:
267 return ecx;
268}
269
270static struct avc_node *avc_alloc_node(void)
271{
272 struct avc_node *node;
273
274 node = kmem_cache_zalloc(avc_node_cachep, GFP_ATOMIC|__GFP_NOMEMALLOC);
275 if (!node)
276 goto out;
277
278 INIT_HLIST_NODE(&node->list);
279 avc_cache_stats_incr(allocations);
280
281 if (atomic_inc_return(&avc_cache.active_nodes) > avc_cache_threshold)
282 avc_reclaim_node();
283
284out:
285 return node;
286}
287
288static void avc_node_populate(struct avc_node *node, u32 ssid, u32 tsid, u16 tclass, struct av_decision *avd)
289{
290 node->ae.ssid = ssid;
291 node->ae.tsid = tsid;
292 node->ae.tclass = tclass;
293 memcpy(&node->ae.avd, avd, sizeof(node->ae.avd));
294}
295
296static inline struct avc_node *avc_search_node(u32 ssid, u32 tsid, u16 tclass)
297{
298 struct avc_node *node, *ret = NULL;
299 int hvalue;
300 struct hlist_head *head;
301
302 hvalue = avc_hash(ssid, tsid, tclass);
303 head = &avc_cache.slots[hvalue];
304 hlist_for_each_entry_rcu(node, head, list) {
305 if (ssid == node->ae.ssid &&
306 tclass == node->ae.tclass &&
307 tsid == node->ae.tsid) {
308 ret = node;
309 break;
310 }
311 }
312
313 return ret;
314}
315
316/**
317 * avc_lookup - Look up an AVC entry.
318 * @ssid: source security identifier
319 * @tsid: target security identifier
320 * @tclass: target security class
321 *
322 * Look up an AVC entry that is valid for the
323 * (@ssid, @tsid), interpreting the permissions
324 * based on @tclass. If a valid AVC entry exists,
325 * then this function returns the avc_node.
326 * Otherwise, this function returns NULL.
327 */
328static struct avc_node *avc_lookup(u32 ssid, u32 tsid, u16 tclass)
329{
330 struct avc_node *node;
331
332 avc_cache_stats_incr(lookups);
333 node = avc_search_node(ssid, tsid, tclass);
334
335 if (node)
336 return node;
337
338 avc_cache_stats_incr(misses);
339 return NULL;
340}
341
342static int avc_latest_notif_update(int seqno, int is_insert)
343{
344 int ret = 0;
345 static DEFINE_SPINLOCK(notif_lock);
346 unsigned long flag;
347
348 spin_lock_irqsave(¬if_lock, flag);
349 if (is_insert) {
350 if (seqno < avc_cache.latest_notif) {
351 printk(KERN_WARNING "SELinux: avc: seqno %d < latest_notif %d\n",
352 seqno, avc_cache.latest_notif);
353 ret = -EAGAIN;
354 }
355 } else {
356 if (seqno > avc_cache.latest_notif)
357 avc_cache.latest_notif = seqno;
358 }
359 spin_unlock_irqrestore(¬if_lock, flag);
360
361 return ret;
362}
363
364/**
365 * avc_insert - Insert an AVC entry.
366 * @ssid: source security identifier
367 * @tsid: target security identifier
368 * @tclass: target security class
369 * @avd: resulting av decision
370 *
371 * Insert an AVC entry for the SID pair
372 * (@ssid, @tsid) and class @tclass.
373 * The access vectors and the sequence number are
374 * normally provided by the security server in
375 * response to a security_compute_av() call. If the
376 * sequence number @avd->seqno is not less than the latest
377 * revocation notification, then the function copies
378 * the access vectors into a cache entry, returns
379 * avc_node inserted. Otherwise, this function returns NULL.
380 */
381static struct avc_node *avc_insert(u32 ssid, u32 tsid, u16 tclass, struct av_decision *avd)
382{
383 struct avc_node *pos, *node = NULL;
384 int hvalue;
385 unsigned long flag;
386
387 if (avc_latest_notif_update(avd->seqno, 1))
388 goto out;
389
390 node = avc_alloc_node();
391 if (node) {
392 struct hlist_head *head;
393 spinlock_t *lock;
394
395 hvalue = avc_hash(ssid, tsid, tclass);
396 avc_node_populate(node, ssid, tsid, tclass, avd);
397
398 head = &avc_cache.slots[hvalue];
399 lock = &avc_cache.slots_lock[hvalue];
400
401 spin_lock_irqsave(lock, flag);
402 hlist_for_each_entry(pos, head, list) {
403 if (pos->ae.ssid == ssid &&
404 pos->ae.tsid == tsid &&
405 pos->ae.tclass == tclass) {
406 avc_node_replace(node, pos);
407 goto found;
408 }
409 }
410 hlist_add_head_rcu(&node->list, head);
411found:
412 spin_unlock_irqrestore(lock, flag);
413 }
414out:
415 return node;
416}
417
418/**
419 * avc_audit_pre_callback - SELinux specific information
420 * will be called by generic audit code
421 * @ab: the audit buffer
422 * @a: audit_data
423 */
424static void avc_audit_pre_callback(struct audit_buffer *ab, void *a)
425{
426 struct common_audit_data *ad = a;
427 audit_log_format(ab, "avc: %s ",
428 ad->selinux_audit_data->denied ? "denied" : "granted");
429 avc_dump_av(ab, ad->selinux_audit_data->tclass,
430 ad->selinux_audit_data->audited);
431 audit_log_format(ab, " for ");
432}
433
434/**
435 * avc_audit_post_callback - SELinux specific information
436 * will be called by generic audit code
437 * @ab: the audit buffer
438 * @a: audit_data
439 */
440static void avc_audit_post_callback(struct audit_buffer *ab, void *a)
441{
442 struct common_audit_data *ad = a;
443 audit_log_format(ab, " ");
444 avc_dump_query(ab, ad->selinux_audit_data->ssid,
445 ad->selinux_audit_data->tsid,
446 ad->selinux_audit_data->tclass);
447}
448
449/* This is the slow part of avc audit with big stack footprint */
450noinline int slow_avc_audit(u32 ssid, u32 tsid, u16 tclass,
451 u32 requested, u32 audited, u32 denied,
452 struct common_audit_data *a,
453 unsigned flags)
454{
455 struct common_audit_data stack_data;
456 struct selinux_audit_data sad;
457
458 if (!a) {
459 a = &stack_data;
460 a->type = LSM_AUDIT_DATA_NONE;
461 }
462
463 /*
464 * When in a RCU walk do the audit on the RCU retry. This is because
465 * the collection of the dname in an inode audit message is not RCU
466 * safe. Note this may drop some audits when the situation changes
467 * during retry. However this is logically just as if the operation
468 * happened a little later.
469 */
470 if ((a->type == LSM_AUDIT_DATA_INODE) &&
471 (flags & MAY_NOT_BLOCK))
472 return -ECHILD;
473
474 sad.tclass = tclass;
475 sad.requested = requested;
476 sad.ssid = ssid;
477 sad.tsid = tsid;
478 sad.audited = audited;
479 sad.denied = denied;
480
481 a->selinux_audit_data = &sad;
482
483 common_lsm_audit(a, avc_audit_pre_callback, avc_audit_post_callback);
484 return 0;
485}
486
487/**
488 * avc_add_callback - Register a callback for security events.
489 * @callback: callback function
490 * @events: security events
491 *
492 * Register a callback function for events in the set @events.
493 * Returns %0 on success or -%ENOMEM if insufficient memory
494 * exists to add the callback.
495 */
496int __init avc_add_callback(int (*callback)(u32 event), u32 events)
497{
498 struct avc_callback_node *c;
499 int rc = 0;
500
501 c = kmalloc(sizeof(*c), GFP_KERNEL);
502 if (!c) {
503 rc = -ENOMEM;
504 goto out;
505 }
506
507 c->callback = callback;
508 c->events = events;
509 c->next = avc_callbacks;
510 avc_callbacks = c;
511out:
512 return rc;
513}
514
515static inline int avc_sidcmp(u32 x, u32 y)
516{
517 return (x == y || x == SECSID_WILD || y == SECSID_WILD);
518}
519
520/**
521 * avc_update_node Update an AVC entry
522 * @event : Updating event
523 * @perms : Permission mask bits
524 * @ssid,@tsid,@tclass : identifier of an AVC entry
525 * @seqno : sequence number when decision was made
526 *
527 * if a valid AVC entry doesn't exist,this function returns -ENOENT.
528 * if kmalloc() called internal returns NULL, this function returns -ENOMEM.
529 * otherwise, this function updates the AVC entry. The original AVC-entry object
530 * will release later by RCU.
531 */
532static int avc_update_node(u32 event, u32 perms, u32 ssid, u32 tsid, u16 tclass,
533 u32 seqno)
534{
535 int hvalue, rc = 0;
536 unsigned long flag;
537 struct avc_node *pos, *node, *orig = NULL;
538 struct hlist_head *head;
539 spinlock_t *lock;
540
541 node = avc_alloc_node();
542 if (!node) {
543 rc = -ENOMEM;
544 goto out;
545 }
546
547 /* Lock the target slot */
548 hvalue = avc_hash(ssid, tsid, tclass);
549
550 head = &avc_cache.slots[hvalue];
551 lock = &avc_cache.slots_lock[hvalue];
552
553 spin_lock_irqsave(lock, flag);
554
555 hlist_for_each_entry(pos, head, list) {
556 if (ssid == pos->ae.ssid &&
557 tsid == pos->ae.tsid &&
558 tclass == pos->ae.tclass &&
559 seqno == pos->ae.avd.seqno){
560 orig = pos;
561 break;
562 }
563 }
564
565 if (!orig) {
566 rc = -ENOENT;
567 avc_node_kill(node);
568 goto out_unlock;
569 }
570
571 /*
572 * Copy and replace original node.
573 */
574
575 avc_node_populate(node, ssid, tsid, tclass, &orig->ae.avd);
576
577 switch (event) {
578 case AVC_CALLBACK_GRANT:
579 node->ae.avd.allowed |= perms;
580 break;
581 case AVC_CALLBACK_TRY_REVOKE:
582 case AVC_CALLBACK_REVOKE:
583 node->ae.avd.allowed &= ~perms;
584 break;
585 case AVC_CALLBACK_AUDITALLOW_ENABLE:
586 node->ae.avd.auditallow |= perms;
587 break;
588 case AVC_CALLBACK_AUDITALLOW_DISABLE:
589 node->ae.avd.auditallow &= ~perms;
590 break;
591 case AVC_CALLBACK_AUDITDENY_ENABLE:
592 node->ae.avd.auditdeny |= perms;
593 break;
594 case AVC_CALLBACK_AUDITDENY_DISABLE:
595 node->ae.avd.auditdeny &= ~perms;
596 break;
597 }
598 avc_node_replace(node, orig);
599out_unlock:
600 spin_unlock_irqrestore(lock, flag);
601out:
602 return rc;
603}
604
605/**
606 * avc_flush - Flush the cache
607 */
608static void avc_flush(void)
609{
610 struct hlist_head *head;
611 struct avc_node *node;
612 spinlock_t *lock;
613 unsigned long flag;
614 int i;
615
616 for (i = 0; i < AVC_CACHE_SLOTS; i++) {
617 head = &avc_cache.slots[i];
618 lock = &avc_cache.slots_lock[i];
619
620 spin_lock_irqsave(lock, flag);
621 /*
622 * With preemptable RCU, the outer spinlock does not
623 * prevent RCU grace periods from ending.
624 */
625 rcu_read_lock();
626 hlist_for_each_entry(node, head, list)
627 avc_node_delete(node);
628 rcu_read_unlock();
629 spin_unlock_irqrestore(lock, flag);
630 }
631}
632
633/**
634 * avc_ss_reset - Flush the cache and revalidate migrated permissions.
635 * @seqno: policy sequence number
636 */
637int avc_ss_reset(u32 seqno)
638{
639 struct avc_callback_node *c;
640 int rc = 0, tmprc;
641
642 avc_flush();
643
644 for (c = avc_callbacks; c; c = c->next) {
645 if (c->events & AVC_CALLBACK_RESET) {
646 tmprc = c->callback(AVC_CALLBACK_RESET);
647 /* save the first error encountered for the return
648 value and continue processing the callbacks */
649 if (!rc)
650 rc = tmprc;
651 }
652 }
653
654 avc_latest_notif_update(seqno, 0);
655 return rc;
656}
657
658/*
659 * Slow-path helper function for avc_has_perm_noaudit,
660 * when the avc_node lookup fails. We get called with
661 * the RCU read lock held, and need to return with it
662 * still held, but drop if for the security compute.
663 *
664 * Don't inline this, since it's the slow-path and just
665 * results in a bigger stack frame.
666 */
667static noinline struct avc_node *avc_compute_av(u32 ssid, u32 tsid,
668 u16 tclass, struct av_decision *avd)
669{
670 rcu_read_unlock();
671 security_compute_av(ssid, tsid, tclass, avd);
672 rcu_read_lock();
673 return avc_insert(ssid, tsid, tclass, avd);
674}
675
676static noinline int avc_denied(u32 ssid, u32 tsid,
677 u16 tclass, u32 requested,
678 unsigned flags,
679 struct av_decision *avd)
680{
681 if (flags & AVC_STRICT)
682 return -EACCES;
683
684 if (selinux_enforcing && !(avd->flags & AVD_FLAGS_PERMISSIVE))
685 return -EACCES;
686
687 avc_update_node(AVC_CALLBACK_GRANT, requested, ssid,
688 tsid, tclass, avd->seqno);
689 return 0;
690}
691
692
693/**
694 * avc_has_perm_noaudit - Check permissions but perform no auditing.
695 * @ssid: source security identifier
696 * @tsid: target security identifier
697 * @tclass: target security class
698 * @requested: requested permissions, interpreted based on @tclass
699 * @flags: AVC_STRICT or 0
700 * @avd: access vector decisions
701 *
702 * Check the AVC to determine whether the @requested permissions are granted
703 * for the SID pair (@ssid, @tsid), interpreting the permissions
704 * based on @tclass, and call the security server on a cache miss to obtain
705 * a new decision and add it to the cache. Return a copy of the decisions
706 * in @avd. Return %0 if all @requested permissions are granted,
707 * -%EACCES if any permissions are denied, or another -errno upon
708 * other errors. This function is typically called by avc_has_perm(),
709 * but may also be called directly to separate permission checking from
710 * auditing, e.g. in cases where a lock must be held for the check but
711 * should be released for the auditing.
712 */
713inline int avc_has_perm_noaudit(u32 ssid, u32 tsid,
714 u16 tclass, u32 requested,
715 unsigned flags,
716 struct av_decision *avd)
717{
718 struct avc_node *node;
719 int rc = 0;
720 u32 denied;
721
722 BUG_ON(!requested);
723
724 rcu_read_lock();
725
726 node = avc_lookup(ssid, tsid, tclass);
727 if (unlikely(!node)) {
728 node = avc_compute_av(ssid, tsid, tclass, avd);
729 } else {
730 memcpy(avd, &node->ae.avd, sizeof(*avd));
731 avd = &node->ae.avd;
732 }
733
734 denied = requested & ~(avd->allowed);
735 if (unlikely(denied))
736 rc = avc_denied(ssid, tsid, tclass, requested, flags, avd);
737
738 rcu_read_unlock();
739 return rc;
740}
741
742/**
743 * avc_has_perm - Check permissions and perform any appropriate auditing.
744 * @ssid: source security identifier
745 * @tsid: target security identifier
746 * @tclass: target security class
747 * @requested: requested permissions, interpreted based on @tclass
748 * @auditdata: auxiliary audit data
749 *
750 * Check the AVC to determine whether the @requested permissions are granted
751 * for the SID pair (@ssid, @tsid), interpreting the permissions
752 * based on @tclass, and call the security server on a cache miss to obtain
753 * a new decision and add it to the cache. Audit the granting or denial of
754 * permissions in accordance with the policy. Return %0 if all @requested
755 * permissions are granted, -%EACCES if any permissions are denied, or
756 * another -errno upon other errors.
757 */
758int avc_has_perm(u32 ssid, u32 tsid, u16 tclass,
759 u32 requested, struct common_audit_data *auditdata)
760{
761 struct av_decision avd;
762 int rc, rc2;
763
764 rc = avc_has_perm_noaudit(ssid, tsid, tclass, requested, 0, &avd);
765
766 rc2 = avc_audit(ssid, tsid, tclass, requested, &avd, rc, auditdata);
767 if (rc2)
768 return rc2;
769 return rc;
770}
771
772u32 avc_policy_seqno(void)
773{
774 return avc_cache.latest_notif;
775}
776
777void avc_disable(void)
778{
779 /*
780 * If you are looking at this because you have realized that we are
781 * not destroying the avc_node_cachep it might be easy to fix, but
782 * I don't know the memory barrier semantics well enough to know. It's
783 * possible that some other task dereferenced security_ops when
784 * it still pointed to selinux operations. If that is the case it's
785 * possible that it is about to use the avc and is about to need the
786 * avc_node_cachep. I know I could wrap the security.c security_ops call
787 * in an rcu_lock, but seriously, it's not worth it. Instead I just flush
788 * the cache and get that memory back.
789 */
790 if (avc_node_cachep) {
791 avc_flush();
792 /* kmem_cache_destroy(avc_node_cachep); */
793 }
794}
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 <net/sock.h>
26#include <linux/un.h>
27#include <net/af_unix.h>
28#include <linux/ip.h>
29#include <linux/audit.h>
30#include <linux/ipv6.h>
31#include <net/ipv6.h>
32#include "avc.h"
33#include "avc_ss.h"
34#include "classmap.h"
35
36#define AVC_CACHE_SLOTS 512
37#define AVC_DEF_CACHE_THRESHOLD 512
38#define AVC_CACHE_RECLAIM 16
39
40#ifdef CONFIG_SECURITY_SELINUX_AVC_STATS
41#define avc_cache_stats_incr(field) this_cpu_inc(avc_cache_stats.field)
42#else
43#define avc_cache_stats_incr(field) do {} while (0)
44#endif
45
46struct avc_entry {
47 u32 ssid;
48 u32 tsid;
49 u16 tclass;
50 struct av_decision avd;
51};
52
53struct avc_node {
54 struct avc_entry ae;
55 struct hlist_node list; /* anchored in avc_cache->slots[i] */
56 struct rcu_head rhead;
57};
58
59struct avc_cache {
60 struct hlist_head slots[AVC_CACHE_SLOTS]; /* head for avc_node->list */
61 spinlock_t slots_lock[AVC_CACHE_SLOTS]; /* lock for writes */
62 atomic_t lru_hint; /* LRU hint for reclaim scan */
63 atomic_t active_nodes;
64 u32 latest_notif; /* latest revocation notification */
65};
66
67struct avc_callback_node {
68 int (*callback) (u32 event, u32 ssid, u32 tsid,
69 u16 tclass, u32 perms,
70 u32 *out_retained);
71 u32 events;
72 u32 ssid;
73 u32 tsid;
74 u16 tclass;
75 u32 perms;
76 struct avc_callback_node *next;
77};
78
79/* Exported via selinufs */
80unsigned int avc_cache_threshold = AVC_DEF_CACHE_THRESHOLD;
81
82#ifdef CONFIG_SECURITY_SELINUX_AVC_STATS
83DEFINE_PER_CPU(struct avc_cache_stats, avc_cache_stats) = { 0 };
84#endif
85
86static struct avc_cache avc_cache;
87static struct avc_callback_node *avc_callbacks;
88static struct kmem_cache *avc_node_cachep;
89
90static inline int avc_hash(u32 ssid, u32 tsid, u16 tclass)
91{
92 return (ssid ^ (tsid<<2) ^ (tclass<<4)) & (AVC_CACHE_SLOTS - 1);
93}
94
95/**
96 * avc_dump_av - Display an access vector in human-readable form.
97 * @tclass: target security class
98 * @av: access vector
99 */
100static void avc_dump_av(struct audit_buffer *ab, u16 tclass, u32 av)
101{
102 const char **perms;
103 int i, perm;
104
105 if (av == 0) {
106 audit_log_format(ab, " null");
107 return;
108 }
109
110 perms = secclass_map[tclass-1].perms;
111
112 audit_log_format(ab, " {");
113 i = 0;
114 perm = 1;
115 while (i < (sizeof(av) * 8)) {
116 if ((perm & av) && perms[i]) {
117 audit_log_format(ab, " %s", perms[i]);
118 av &= ~perm;
119 }
120 i++;
121 perm <<= 1;
122 }
123
124 if (av)
125 audit_log_format(ab, " 0x%x", av);
126
127 audit_log_format(ab, " }");
128}
129
130/**
131 * avc_dump_query - Display a SID pair and a class in human-readable form.
132 * @ssid: source security identifier
133 * @tsid: target security identifier
134 * @tclass: target security class
135 */
136static void avc_dump_query(struct audit_buffer *ab, u32 ssid, u32 tsid, u16 tclass)
137{
138 int rc;
139 char *scontext;
140 u32 scontext_len;
141
142 rc = security_sid_to_context(ssid, &scontext, &scontext_len);
143 if (rc)
144 audit_log_format(ab, "ssid=%d", ssid);
145 else {
146 audit_log_format(ab, "scontext=%s", scontext);
147 kfree(scontext);
148 }
149
150 rc = security_sid_to_context(tsid, &scontext, &scontext_len);
151 if (rc)
152 audit_log_format(ab, " tsid=%d", tsid);
153 else {
154 audit_log_format(ab, " tcontext=%s", scontext);
155 kfree(scontext);
156 }
157
158 BUG_ON(tclass >= ARRAY_SIZE(secclass_map));
159 audit_log_format(ab, " tclass=%s", secclass_map[tclass-1].name);
160}
161
162/**
163 * avc_init - Initialize the AVC.
164 *
165 * Initialize the access vector cache.
166 */
167void __init avc_init(void)
168{
169 int i;
170
171 for (i = 0; i < AVC_CACHE_SLOTS; i++) {
172 INIT_HLIST_HEAD(&avc_cache.slots[i]);
173 spin_lock_init(&avc_cache.slots_lock[i]);
174 }
175 atomic_set(&avc_cache.active_nodes, 0);
176 atomic_set(&avc_cache.lru_hint, 0);
177
178 avc_node_cachep = kmem_cache_create("avc_node", sizeof(struct avc_node),
179 0, SLAB_PANIC, NULL);
180
181 audit_log(current->audit_context, GFP_KERNEL, AUDIT_KERNEL, "AVC INITIALIZED\n");
182}
183
184int avc_get_hash_stats(char *page)
185{
186 int i, chain_len, max_chain_len, slots_used;
187 struct avc_node *node;
188 struct hlist_head *head;
189
190 rcu_read_lock();
191
192 slots_used = 0;
193 max_chain_len = 0;
194 for (i = 0; i < AVC_CACHE_SLOTS; i++) {
195 head = &avc_cache.slots[i];
196 if (!hlist_empty(head)) {
197 struct hlist_node *next;
198
199 slots_used++;
200 chain_len = 0;
201 hlist_for_each_entry_rcu(node, next, head, list)
202 chain_len++;
203 if (chain_len > max_chain_len)
204 max_chain_len = chain_len;
205 }
206 }
207
208 rcu_read_unlock();
209
210 return scnprintf(page, PAGE_SIZE, "entries: %d\nbuckets used: %d/%d\n"
211 "longest chain: %d\n",
212 atomic_read(&avc_cache.active_nodes),
213 slots_used, AVC_CACHE_SLOTS, max_chain_len);
214}
215
216static void avc_node_free(struct rcu_head *rhead)
217{
218 struct avc_node *node = container_of(rhead, struct avc_node, rhead);
219 kmem_cache_free(avc_node_cachep, node);
220 avc_cache_stats_incr(frees);
221}
222
223static void avc_node_delete(struct avc_node *node)
224{
225 hlist_del_rcu(&node->list);
226 call_rcu(&node->rhead, avc_node_free);
227 atomic_dec(&avc_cache.active_nodes);
228}
229
230static void avc_node_kill(struct avc_node *node)
231{
232 kmem_cache_free(avc_node_cachep, node);
233 avc_cache_stats_incr(frees);
234 atomic_dec(&avc_cache.active_nodes);
235}
236
237static void avc_node_replace(struct avc_node *new, struct avc_node *old)
238{
239 hlist_replace_rcu(&old->list, &new->list);
240 call_rcu(&old->rhead, avc_node_free);
241 atomic_dec(&avc_cache.active_nodes);
242}
243
244static inline int avc_reclaim_node(void)
245{
246 struct avc_node *node;
247 int hvalue, try, ecx;
248 unsigned long flags;
249 struct hlist_head *head;
250 struct hlist_node *next;
251 spinlock_t *lock;
252
253 for (try = 0, ecx = 0; try < AVC_CACHE_SLOTS; try++) {
254 hvalue = atomic_inc_return(&avc_cache.lru_hint) & (AVC_CACHE_SLOTS - 1);
255 head = &avc_cache.slots[hvalue];
256 lock = &avc_cache.slots_lock[hvalue];
257
258 if (!spin_trylock_irqsave(lock, flags))
259 continue;
260
261 rcu_read_lock();
262 hlist_for_each_entry(node, next, head, list) {
263 avc_node_delete(node);
264 avc_cache_stats_incr(reclaims);
265 ecx++;
266 if (ecx >= AVC_CACHE_RECLAIM) {
267 rcu_read_unlock();
268 spin_unlock_irqrestore(lock, flags);
269 goto out;
270 }
271 }
272 rcu_read_unlock();
273 spin_unlock_irqrestore(lock, flags);
274 }
275out:
276 return ecx;
277}
278
279static struct avc_node *avc_alloc_node(void)
280{
281 struct avc_node *node;
282
283 node = kmem_cache_zalloc(avc_node_cachep, GFP_ATOMIC);
284 if (!node)
285 goto out;
286
287 INIT_HLIST_NODE(&node->list);
288 avc_cache_stats_incr(allocations);
289
290 if (atomic_inc_return(&avc_cache.active_nodes) > avc_cache_threshold)
291 avc_reclaim_node();
292
293out:
294 return node;
295}
296
297static void avc_node_populate(struct avc_node *node, u32 ssid, u32 tsid, u16 tclass, struct av_decision *avd)
298{
299 node->ae.ssid = ssid;
300 node->ae.tsid = tsid;
301 node->ae.tclass = tclass;
302 memcpy(&node->ae.avd, avd, sizeof(node->ae.avd));
303}
304
305static inline struct avc_node *avc_search_node(u32 ssid, u32 tsid, u16 tclass)
306{
307 struct avc_node *node, *ret = NULL;
308 int hvalue;
309 struct hlist_head *head;
310 struct hlist_node *next;
311
312 hvalue = avc_hash(ssid, tsid, tclass);
313 head = &avc_cache.slots[hvalue];
314 hlist_for_each_entry_rcu(node, next, head, list) {
315 if (ssid == node->ae.ssid &&
316 tclass == node->ae.tclass &&
317 tsid == node->ae.tsid) {
318 ret = node;
319 break;
320 }
321 }
322
323 return ret;
324}
325
326/**
327 * avc_lookup - Look up an AVC entry.
328 * @ssid: source security identifier
329 * @tsid: target security identifier
330 * @tclass: target security class
331 *
332 * Look up an AVC entry that is valid for the
333 * (@ssid, @tsid), interpreting the permissions
334 * based on @tclass. If a valid AVC entry exists,
335 * then this function returns the avc_node.
336 * Otherwise, this function returns NULL.
337 */
338static struct avc_node *avc_lookup(u32 ssid, u32 tsid, u16 tclass)
339{
340 struct avc_node *node;
341
342 avc_cache_stats_incr(lookups);
343 node = avc_search_node(ssid, tsid, tclass);
344
345 if (node)
346 return node;
347
348 avc_cache_stats_incr(misses);
349 return NULL;
350}
351
352static int avc_latest_notif_update(int seqno, int is_insert)
353{
354 int ret = 0;
355 static DEFINE_SPINLOCK(notif_lock);
356 unsigned long flag;
357
358 spin_lock_irqsave(¬if_lock, flag);
359 if (is_insert) {
360 if (seqno < avc_cache.latest_notif) {
361 printk(KERN_WARNING "SELinux: avc: seqno %d < latest_notif %d\n",
362 seqno, avc_cache.latest_notif);
363 ret = -EAGAIN;
364 }
365 } else {
366 if (seqno > avc_cache.latest_notif)
367 avc_cache.latest_notif = seqno;
368 }
369 spin_unlock_irqrestore(¬if_lock, flag);
370
371 return ret;
372}
373
374/**
375 * avc_insert - Insert an AVC entry.
376 * @ssid: source security identifier
377 * @tsid: target security identifier
378 * @tclass: target security class
379 * @avd: resulting av decision
380 *
381 * Insert an AVC entry for the SID pair
382 * (@ssid, @tsid) and class @tclass.
383 * The access vectors and the sequence number are
384 * normally provided by the security server in
385 * response to a security_compute_av() call. If the
386 * sequence number @avd->seqno is not less than the latest
387 * revocation notification, then the function copies
388 * the access vectors into a cache entry, returns
389 * avc_node inserted. Otherwise, this function returns NULL.
390 */
391static struct avc_node *avc_insert(u32 ssid, u32 tsid, u16 tclass, struct av_decision *avd)
392{
393 struct avc_node *pos, *node = NULL;
394 int hvalue;
395 unsigned long flag;
396
397 if (avc_latest_notif_update(avd->seqno, 1))
398 goto out;
399
400 node = avc_alloc_node();
401 if (node) {
402 struct hlist_head *head;
403 struct hlist_node *next;
404 spinlock_t *lock;
405
406 hvalue = avc_hash(ssid, tsid, tclass);
407 avc_node_populate(node, ssid, tsid, tclass, avd);
408
409 head = &avc_cache.slots[hvalue];
410 lock = &avc_cache.slots_lock[hvalue];
411
412 spin_lock_irqsave(lock, flag);
413 hlist_for_each_entry(pos, next, head, list) {
414 if (pos->ae.ssid == ssid &&
415 pos->ae.tsid == tsid &&
416 pos->ae.tclass == tclass) {
417 avc_node_replace(node, pos);
418 goto found;
419 }
420 }
421 hlist_add_head_rcu(&node->list, head);
422found:
423 spin_unlock_irqrestore(lock, flag);
424 }
425out:
426 return node;
427}
428
429/**
430 * avc_audit_pre_callback - SELinux specific information
431 * will be called by generic audit code
432 * @ab: the audit buffer
433 * @a: audit_data
434 */
435static void avc_audit_pre_callback(struct audit_buffer *ab, void *a)
436{
437 struct common_audit_data *ad = a;
438 audit_log_format(ab, "avc: %s ",
439 ad->selinux_audit_data.denied ? "denied" : "granted");
440 avc_dump_av(ab, ad->selinux_audit_data.tclass,
441 ad->selinux_audit_data.audited);
442 audit_log_format(ab, " for ");
443}
444
445/**
446 * avc_audit_post_callback - SELinux specific information
447 * will be called by generic audit code
448 * @ab: the audit buffer
449 * @a: audit_data
450 */
451static void avc_audit_post_callback(struct audit_buffer *ab, void *a)
452{
453 struct common_audit_data *ad = a;
454 audit_log_format(ab, " ");
455 avc_dump_query(ab, ad->selinux_audit_data.ssid,
456 ad->selinux_audit_data.tsid,
457 ad->selinux_audit_data.tclass);
458}
459
460/**
461 * avc_audit - Audit the granting or denial of permissions.
462 * @ssid: source security identifier
463 * @tsid: target security identifier
464 * @tclass: target security class
465 * @requested: requested permissions
466 * @avd: access vector decisions
467 * @result: result from avc_has_perm_noaudit
468 * @a: auxiliary audit data
469 * @flags: VFS walk flags
470 *
471 * Audit the granting or denial of permissions in accordance
472 * with the policy. This function is typically called by
473 * avc_has_perm() after a permission check, but can also be
474 * called directly by callers who use avc_has_perm_noaudit()
475 * in order to separate the permission check from the auditing.
476 * For example, this separation is useful when the permission check must
477 * be performed under a lock, to allow the lock to be released
478 * before calling the auditing code.
479 */
480int avc_audit(u32 ssid, u32 tsid,
481 u16 tclass, u32 requested,
482 struct av_decision *avd, int result, struct common_audit_data *a,
483 unsigned flags)
484{
485 struct common_audit_data stack_data;
486 u32 denied, audited;
487 denied = requested & ~avd->allowed;
488 if (denied) {
489 audited = denied & avd->auditdeny;
490 /*
491 * a->selinux_audit_data.auditdeny is TRICKY! Setting a bit in
492 * this field means that ANY denials should NOT be audited if
493 * the policy contains an explicit dontaudit rule for that
494 * permission. Take notice that this is unrelated to the
495 * actual permissions that were denied. As an example lets
496 * assume:
497 *
498 * denied == READ
499 * avd.auditdeny & ACCESS == 0 (not set means explicit rule)
500 * selinux_audit_data.auditdeny & ACCESS == 1
501 *
502 * We will NOT audit the denial even though the denied
503 * permission was READ and the auditdeny checks were for
504 * ACCESS
505 */
506 if (a &&
507 a->selinux_audit_data.auditdeny &&
508 !(a->selinux_audit_data.auditdeny & avd->auditdeny))
509 audited = 0;
510 } else if (result)
511 audited = denied = requested;
512 else
513 audited = requested & avd->auditallow;
514 if (!audited)
515 return 0;
516
517 if (!a) {
518 a = &stack_data;
519 COMMON_AUDIT_DATA_INIT(a, NONE);
520 }
521
522 /*
523 * When in a RCU walk do the audit on the RCU retry. This is because
524 * the collection of the dname in an inode audit message is not RCU
525 * safe. Note this may drop some audits when the situation changes
526 * during retry. However this is logically just as if the operation
527 * happened a little later.
528 */
529 if ((a->type == LSM_AUDIT_DATA_INODE) &&
530 (flags & MAY_NOT_BLOCK))
531 return -ECHILD;
532
533 a->selinux_audit_data.tclass = tclass;
534 a->selinux_audit_data.requested = requested;
535 a->selinux_audit_data.ssid = ssid;
536 a->selinux_audit_data.tsid = tsid;
537 a->selinux_audit_data.audited = audited;
538 a->selinux_audit_data.denied = denied;
539 a->lsm_pre_audit = avc_audit_pre_callback;
540 a->lsm_post_audit = avc_audit_post_callback;
541 common_lsm_audit(a);
542 return 0;
543}
544
545/**
546 * avc_add_callback - Register a callback for security events.
547 * @callback: callback function
548 * @events: security events
549 * @ssid: source security identifier or %SECSID_WILD
550 * @tsid: target security identifier or %SECSID_WILD
551 * @tclass: target security class
552 * @perms: permissions
553 *
554 * Register a callback function for events in the set @events
555 * related to the SID pair (@ssid, @tsid)
556 * and the permissions @perms, interpreting
557 * @perms based on @tclass. Returns %0 on success or
558 * -%ENOMEM if insufficient memory exists to add the callback.
559 */
560int avc_add_callback(int (*callback)(u32 event, u32 ssid, u32 tsid,
561 u16 tclass, u32 perms,
562 u32 *out_retained),
563 u32 events, u32 ssid, u32 tsid,
564 u16 tclass, u32 perms)
565{
566 struct avc_callback_node *c;
567 int rc = 0;
568
569 c = kmalloc(sizeof(*c), GFP_ATOMIC);
570 if (!c) {
571 rc = -ENOMEM;
572 goto out;
573 }
574
575 c->callback = callback;
576 c->events = events;
577 c->ssid = ssid;
578 c->tsid = tsid;
579 c->perms = perms;
580 c->next = avc_callbacks;
581 avc_callbacks = c;
582out:
583 return rc;
584}
585
586static inline int avc_sidcmp(u32 x, u32 y)
587{
588 return (x == y || x == SECSID_WILD || y == SECSID_WILD);
589}
590
591/**
592 * avc_update_node Update an AVC entry
593 * @event : Updating event
594 * @perms : Permission mask bits
595 * @ssid,@tsid,@tclass : identifier of an AVC entry
596 * @seqno : sequence number when decision was made
597 *
598 * if a valid AVC entry doesn't exist,this function returns -ENOENT.
599 * if kmalloc() called internal returns NULL, this function returns -ENOMEM.
600 * otherwise, this function updates the AVC entry. The original AVC-entry object
601 * will release later by RCU.
602 */
603static int avc_update_node(u32 event, u32 perms, u32 ssid, u32 tsid, u16 tclass,
604 u32 seqno)
605{
606 int hvalue, rc = 0;
607 unsigned long flag;
608 struct avc_node *pos, *node, *orig = NULL;
609 struct hlist_head *head;
610 struct hlist_node *next;
611 spinlock_t *lock;
612
613 node = avc_alloc_node();
614 if (!node) {
615 rc = -ENOMEM;
616 goto out;
617 }
618
619 /* Lock the target slot */
620 hvalue = avc_hash(ssid, tsid, tclass);
621
622 head = &avc_cache.slots[hvalue];
623 lock = &avc_cache.slots_lock[hvalue];
624
625 spin_lock_irqsave(lock, flag);
626
627 hlist_for_each_entry(pos, next, head, list) {
628 if (ssid == pos->ae.ssid &&
629 tsid == pos->ae.tsid &&
630 tclass == pos->ae.tclass &&
631 seqno == pos->ae.avd.seqno){
632 orig = pos;
633 break;
634 }
635 }
636
637 if (!orig) {
638 rc = -ENOENT;
639 avc_node_kill(node);
640 goto out_unlock;
641 }
642
643 /*
644 * Copy and replace original node.
645 */
646
647 avc_node_populate(node, ssid, tsid, tclass, &orig->ae.avd);
648
649 switch (event) {
650 case AVC_CALLBACK_GRANT:
651 node->ae.avd.allowed |= perms;
652 break;
653 case AVC_CALLBACK_TRY_REVOKE:
654 case AVC_CALLBACK_REVOKE:
655 node->ae.avd.allowed &= ~perms;
656 break;
657 case AVC_CALLBACK_AUDITALLOW_ENABLE:
658 node->ae.avd.auditallow |= perms;
659 break;
660 case AVC_CALLBACK_AUDITALLOW_DISABLE:
661 node->ae.avd.auditallow &= ~perms;
662 break;
663 case AVC_CALLBACK_AUDITDENY_ENABLE:
664 node->ae.avd.auditdeny |= perms;
665 break;
666 case AVC_CALLBACK_AUDITDENY_DISABLE:
667 node->ae.avd.auditdeny &= ~perms;
668 break;
669 }
670 avc_node_replace(node, orig);
671out_unlock:
672 spin_unlock_irqrestore(lock, flag);
673out:
674 return rc;
675}
676
677/**
678 * avc_flush - Flush the cache
679 */
680static void avc_flush(void)
681{
682 struct hlist_head *head;
683 struct hlist_node *next;
684 struct avc_node *node;
685 spinlock_t *lock;
686 unsigned long flag;
687 int i;
688
689 for (i = 0; i < AVC_CACHE_SLOTS; i++) {
690 head = &avc_cache.slots[i];
691 lock = &avc_cache.slots_lock[i];
692
693 spin_lock_irqsave(lock, flag);
694 /*
695 * With preemptable RCU, the outer spinlock does not
696 * prevent RCU grace periods from ending.
697 */
698 rcu_read_lock();
699 hlist_for_each_entry(node, next, head, list)
700 avc_node_delete(node);
701 rcu_read_unlock();
702 spin_unlock_irqrestore(lock, flag);
703 }
704}
705
706/**
707 * avc_ss_reset - Flush the cache and revalidate migrated permissions.
708 * @seqno: policy sequence number
709 */
710int avc_ss_reset(u32 seqno)
711{
712 struct avc_callback_node *c;
713 int rc = 0, tmprc;
714
715 avc_flush();
716
717 for (c = avc_callbacks; c; c = c->next) {
718 if (c->events & AVC_CALLBACK_RESET) {
719 tmprc = c->callback(AVC_CALLBACK_RESET,
720 0, 0, 0, 0, NULL);
721 /* save the first error encountered for the return
722 value and continue processing the callbacks */
723 if (!rc)
724 rc = tmprc;
725 }
726 }
727
728 avc_latest_notif_update(seqno, 0);
729 return rc;
730}
731
732/**
733 * avc_has_perm_noaudit - Check permissions but perform no auditing.
734 * @ssid: source security identifier
735 * @tsid: target security identifier
736 * @tclass: target security class
737 * @requested: requested permissions, interpreted based on @tclass
738 * @flags: AVC_STRICT or 0
739 * @avd: access vector decisions
740 *
741 * Check the AVC to determine whether the @requested permissions are granted
742 * for the SID pair (@ssid, @tsid), interpreting the permissions
743 * based on @tclass, and call the security server on a cache miss to obtain
744 * a new decision and add it to the cache. Return a copy of the decisions
745 * in @avd. Return %0 if all @requested permissions are granted,
746 * -%EACCES if any permissions are denied, or another -errno upon
747 * other errors. This function is typically called by avc_has_perm(),
748 * but may also be called directly to separate permission checking from
749 * auditing, e.g. in cases where a lock must be held for the check but
750 * should be released for the auditing.
751 */
752int avc_has_perm_noaudit(u32 ssid, u32 tsid,
753 u16 tclass, u32 requested,
754 unsigned flags,
755 struct av_decision *avd)
756{
757 struct avc_node *node;
758 int rc = 0;
759 u32 denied;
760
761 BUG_ON(!requested);
762
763 rcu_read_lock();
764
765 node = avc_lookup(ssid, tsid, tclass);
766 if (unlikely(!node)) {
767 rcu_read_unlock();
768 security_compute_av(ssid, tsid, tclass, avd);
769 rcu_read_lock();
770 node = avc_insert(ssid, tsid, tclass, avd);
771 } else {
772 memcpy(avd, &node->ae.avd, sizeof(*avd));
773 avd = &node->ae.avd;
774 }
775
776 denied = requested & ~(avd->allowed);
777
778 if (denied) {
779 if (flags & AVC_STRICT)
780 rc = -EACCES;
781 else if (!selinux_enforcing || (avd->flags & AVD_FLAGS_PERMISSIVE))
782 avc_update_node(AVC_CALLBACK_GRANT, requested, ssid,
783 tsid, tclass, avd->seqno);
784 else
785 rc = -EACCES;
786 }
787
788 rcu_read_unlock();
789 return rc;
790}
791
792/**
793 * avc_has_perm - Check permissions and perform any appropriate auditing.
794 * @ssid: source security identifier
795 * @tsid: target security identifier
796 * @tclass: target security class
797 * @requested: requested permissions, interpreted based on @tclass
798 * @auditdata: auxiliary audit data
799 * @flags: VFS walk flags
800 *
801 * Check the AVC to determine whether the @requested permissions are granted
802 * for the SID pair (@ssid, @tsid), interpreting the permissions
803 * based on @tclass, and call the security server on a cache miss to obtain
804 * a new decision and add it to the cache. Audit the granting or denial of
805 * permissions in accordance with the policy. Return %0 if all @requested
806 * permissions are granted, -%EACCES if any permissions are denied, or
807 * another -errno upon other errors.
808 */
809int avc_has_perm_flags(u32 ssid, u32 tsid, u16 tclass,
810 u32 requested, struct common_audit_data *auditdata,
811 unsigned flags)
812{
813 struct av_decision avd;
814 int rc, rc2;
815
816 rc = avc_has_perm_noaudit(ssid, tsid, tclass, requested, 0, &avd);
817
818 rc2 = avc_audit(ssid, tsid, tclass, requested, &avd, rc, auditdata,
819 flags);
820 if (rc2)
821 return rc2;
822 return rc;
823}
824
825u32 avc_policy_seqno(void)
826{
827 return avc_cache.latest_notif;
828}
829
830void avc_disable(void)
831{
832 /*
833 * If you are looking at this because you have realized that we are
834 * not destroying the avc_node_cachep it might be easy to fix, but
835 * I don't know the memory barrier semantics well enough to know. It's
836 * possible that some other task dereferenced security_ops when
837 * it still pointed to selinux operations. If that is the case it's
838 * possible that it is about to use the avc and is about to need the
839 * avc_node_cachep. I know I could wrap the security.c security_ops call
840 * in an rcu_lock, but seriously, it's not worth it. Instead I just flush
841 * the cache and get that memory back.
842 */
843 if (avc_node_cachep) {
844 avc_flush();
845 /* kmem_cache_destroy(avc_node_cachep); */
846 }
847}