2 * Implementation of the kernel access vector cache (AVC).
4 * Authors: Stephen Smalley, <sds@tycho.nsa.gov>
5 * James Morris <jmorris@redhat.com>
7 * Update: KaiGai, Kohei <kaigai@ak.jp.nec.com>
8 * Replaced the avc_lock spinlock by RCU.
10 * Copyright (C) 2003 Red Hat, Inc., James Morris <jmorris@redhat.com>
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.
16 #include <linux/types.h>
17 #include <linux/stddef.h>
18 #include <linux/kernel.h>
19 #include <linux/slab.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>
28 #include <net/af_unix.h>
30 #include <linux/audit.h>
31 #include <linux/ipv6.h>
37 #define AVC_CACHE_SLOTS 512
38 #define AVC_DEF_CACHE_THRESHOLD 512
39 #define AVC_CACHE_RECLAIM 16
41 #ifdef CONFIG_SECURITY_SELINUX_AVC_STATS
42 #define avc_cache_stats_incr(field) this_cpu_inc(avc_cache_stats.field)
44 #define avc_cache_stats_incr(field) do {} while (0)
51 struct av_decision avd;
52 struct avc_xperms_node *xp_node;
57 struct hlist_node list; /* anchored in avc_cache->slots[i] */
58 struct rcu_head rhead;
61 struct avc_xperms_decision_node {
62 struct extended_perms_decision xpd;
63 struct list_head xpd_list; /* list of extended_perms_decision */
66 struct avc_xperms_node {
67 struct extended_perms xp;
68 struct list_head xpd_head; /* list head of extended_perms_decision */
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 */
79 struct avc_callback_node {
80 int (*callback) (u32 event);
82 struct avc_callback_node *next;
85 #ifdef CONFIG_SECURITY_SELINUX_AVC_STATS
86 DEFINE_PER_CPU(struct avc_cache_stats, avc_cache_stats) = { 0 };
90 unsigned int avc_cache_threshold;
91 struct avc_cache avc_cache;
94 static struct selinux_avc selinux_avc;
96 void selinux_avc_init(struct selinux_avc **avc)
100 selinux_avc.avc_cache_threshold = AVC_DEF_CACHE_THRESHOLD;
101 for (i = 0; i < AVC_CACHE_SLOTS; i++) {
102 INIT_HLIST_HEAD(&selinux_avc.avc_cache.slots[i]);
103 spin_lock_init(&selinux_avc.avc_cache.slots_lock[i]);
105 atomic_set(&selinux_avc.avc_cache.active_nodes, 0);
106 atomic_set(&selinux_avc.avc_cache.lru_hint, 0);
110 unsigned int avc_get_cache_threshold(struct selinux_avc *avc)
112 return avc->avc_cache_threshold;
115 void avc_set_cache_threshold(struct selinux_avc *avc,
116 unsigned int cache_threshold)
118 avc->avc_cache_threshold = cache_threshold;
121 static struct avc_callback_node *avc_callbacks;
122 static struct kmem_cache *avc_node_cachep;
123 static struct kmem_cache *avc_xperms_data_cachep;
124 static struct kmem_cache *avc_xperms_decision_cachep;
125 static struct kmem_cache *avc_xperms_cachep;
127 static inline int avc_hash(u32 ssid, u32 tsid, u16 tclass)
129 return (ssid ^ (tsid<<2) ^ (tclass<<4)) & (AVC_CACHE_SLOTS - 1);
133 * avc_dump_av - Display an access vector in human-readable form.
134 * @tclass: target security class
137 static void avc_dump_av(struct audit_buffer *ab, u16 tclass, u32 av)
143 audit_log_format(ab, " null");
147 BUG_ON(!tclass || tclass >= ARRAY_SIZE(secclass_map));
148 perms = secclass_map[tclass-1].perms;
150 audit_log_format(ab, " {");
153 while (i < (sizeof(av) * 8)) {
154 if ((perm & av) && perms[i]) {
155 audit_log_format(ab, " %s", perms[i]);
163 audit_log_format(ab, " 0x%x", av);
165 audit_log_format(ab, " }");
169 * avc_dump_query - Display a SID pair and a class in human-readable form.
170 * @ssid: source security identifier
171 * @tsid: target security identifier
172 * @tclass: target security class
174 static void avc_dump_query(struct audit_buffer *ab, struct selinux_state *state,
175 u32 ssid, u32 tsid, u16 tclass)
181 rc = security_sid_to_context(state, ssid, &scontext, &scontext_len);
183 audit_log_format(ab, "ssid=%d", ssid);
185 audit_log_format(ab, "scontext=%s", scontext);
189 rc = security_sid_to_context(state, tsid, &scontext, &scontext_len);
191 audit_log_format(ab, " tsid=%d", tsid);
193 audit_log_format(ab, " tcontext=%s", scontext);
197 BUG_ON(!tclass || tclass >= ARRAY_SIZE(secclass_map));
198 audit_log_format(ab, " tclass=%s", secclass_map[tclass-1].name);
202 * avc_init - Initialize the AVC.
204 * Initialize the access vector cache.
206 void __init avc_init(void)
208 avc_node_cachep = kmem_cache_create("avc_node", sizeof(struct avc_node),
209 0, SLAB_PANIC, NULL);
210 avc_xperms_cachep = kmem_cache_create("avc_xperms_node",
211 sizeof(struct avc_xperms_node),
212 0, SLAB_PANIC, NULL);
213 avc_xperms_decision_cachep = kmem_cache_create(
214 "avc_xperms_decision_node",
215 sizeof(struct avc_xperms_decision_node),
216 0, SLAB_PANIC, NULL);
217 avc_xperms_data_cachep = kmem_cache_create("avc_xperms_data",
218 sizeof(struct extended_perms_data),
219 0, SLAB_PANIC, NULL);
222 int avc_get_hash_stats(struct selinux_avc *avc, char *page)
224 int i, chain_len, max_chain_len, slots_used;
225 struct avc_node *node;
226 struct hlist_head *head;
232 for (i = 0; i < AVC_CACHE_SLOTS; i++) {
233 head = &avc->avc_cache.slots[i];
234 if (!hlist_empty(head)) {
237 hlist_for_each_entry_rcu(node, head, list)
239 if (chain_len > max_chain_len)
240 max_chain_len = chain_len;
246 return scnprintf(page, PAGE_SIZE, "entries: %d\nbuckets used: %d/%d\n"
247 "longest chain: %d\n",
248 atomic_read(&avc->avc_cache.active_nodes),
249 slots_used, AVC_CACHE_SLOTS, max_chain_len);
253 * using a linked list for extended_perms_decision lookup because the list is
254 * always small. i.e. less than 5, typically 1
256 static struct extended_perms_decision *avc_xperms_decision_lookup(u8 driver,
257 struct avc_xperms_node *xp_node)
259 struct avc_xperms_decision_node *xpd_node;
261 list_for_each_entry(xpd_node, &xp_node->xpd_head, xpd_list) {
262 if (xpd_node->xpd.driver == driver)
263 return &xpd_node->xpd;
268 static inline unsigned int
269 avc_xperms_has_perm(struct extended_perms_decision *xpd,
274 if ((which == XPERMS_ALLOWED) &&
275 (xpd->used & XPERMS_ALLOWED))
276 rc = security_xperm_test(xpd->allowed->p, perm);
277 else if ((which == XPERMS_AUDITALLOW) &&
278 (xpd->used & XPERMS_AUDITALLOW))
279 rc = security_xperm_test(xpd->auditallow->p, perm);
280 else if ((which == XPERMS_DONTAUDIT) &&
281 (xpd->used & XPERMS_DONTAUDIT))
282 rc = security_xperm_test(xpd->dontaudit->p, perm);
286 static void avc_xperms_allow_perm(struct avc_xperms_node *xp_node,
289 struct extended_perms_decision *xpd;
290 security_xperm_set(xp_node->xp.drivers.p, driver);
291 xpd = avc_xperms_decision_lookup(driver, xp_node);
292 if (xpd && xpd->allowed)
293 security_xperm_set(xpd->allowed->p, perm);
296 static void avc_xperms_decision_free(struct avc_xperms_decision_node *xpd_node)
298 struct extended_perms_decision *xpd;
300 xpd = &xpd_node->xpd;
302 kmem_cache_free(avc_xperms_data_cachep, xpd->allowed);
304 kmem_cache_free(avc_xperms_data_cachep, xpd->auditallow);
306 kmem_cache_free(avc_xperms_data_cachep, xpd->dontaudit);
307 kmem_cache_free(avc_xperms_decision_cachep, xpd_node);
310 static void avc_xperms_free(struct avc_xperms_node *xp_node)
312 struct avc_xperms_decision_node *xpd_node, *tmp;
317 list_for_each_entry_safe(xpd_node, tmp, &xp_node->xpd_head, xpd_list) {
318 list_del(&xpd_node->xpd_list);
319 avc_xperms_decision_free(xpd_node);
321 kmem_cache_free(avc_xperms_cachep, xp_node);
324 static void avc_copy_xperms_decision(struct extended_perms_decision *dest,
325 struct extended_perms_decision *src)
327 dest->driver = src->driver;
328 dest->used = src->used;
329 if (dest->used & XPERMS_ALLOWED)
330 memcpy(dest->allowed->p, src->allowed->p,
331 sizeof(src->allowed->p));
332 if (dest->used & XPERMS_AUDITALLOW)
333 memcpy(dest->auditallow->p, src->auditallow->p,
334 sizeof(src->auditallow->p));
335 if (dest->used & XPERMS_DONTAUDIT)
336 memcpy(dest->dontaudit->p, src->dontaudit->p,
337 sizeof(src->dontaudit->p));
341 * similar to avc_copy_xperms_decision, but only copy decision
342 * information relevant to this perm
344 static inline void avc_quick_copy_xperms_decision(u8 perm,
345 struct extended_perms_decision *dest,
346 struct extended_perms_decision *src)
349 * compute index of the u32 of the 256 bits (8 u32s) that contain this
354 dest->used = src->used;
355 if (dest->used & XPERMS_ALLOWED)
356 dest->allowed->p[i] = src->allowed->p[i];
357 if (dest->used & XPERMS_AUDITALLOW)
358 dest->auditallow->p[i] = src->auditallow->p[i];
359 if (dest->used & XPERMS_DONTAUDIT)
360 dest->dontaudit->p[i] = src->dontaudit->p[i];
363 static struct avc_xperms_decision_node
364 *avc_xperms_decision_alloc(u8 which)
366 struct avc_xperms_decision_node *xpd_node;
367 struct extended_perms_decision *xpd;
369 xpd_node = kmem_cache_zalloc(avc_xperms_decision_cachep,
370 GFP_NOWAIT | __GFP_NOWARN);
374 xpd = &xpd_node->xpd;
375 if (which & XPERMS_ALLOWED) {
376 xpd->allowed = kmem_cache_zalloc(avc_xperms_data_cachep,
377 GFP_NOWAIT | __GFP_NOWARN);
381 if (which & XPERMS_AUDITALLOW) {
382 xpd->auditallow = kmem_cache_zalloc(avc_xperms_data_cachep,
383 GFP_NOWAIT | __GFP_NOWARN);
384 if (!xpd->auditallow)
387 if (which & XPERMS_DONTAUDIT) {
388 xpd->dontaudit = kmem_cache_zalloc(avc_xperms_data_cachep,
389 GFP_NOWAIT | __GFP_NOWARN);
395 avc_xperms_decision_free(xpd_node);
399 static int avc_add_xperms_decision(struct avc_node *node,
400 struct extended_perms_decision *src)
402 struct avc_xperms_decision_node *dest_xpd;
404 node->ae.xp_node->xp.len++;
405 dest_xpd = avc_xperms_decision_alloc(src->used);
408 avc_copy_xperms_decision(&dest_xpd->xpd, src);
409 list_add(&dest_xpd->xpd_list, &node->ae.xp_node->xpd_head);
413 static struct avc_xperms_node *avc_xperms_alloc(void)
415 struct avc_xperms_node *xp_node;
417 xp_node = kmem_cache_zalloc(avc_xperms_cachep, GFP_NOWAIT | __GFP_NOWARN);
420 INIT_LIST_HEAD(&xp_node->xpd_head);
424 static int avc_xperms_populate(struct avc_node *node,
425 struct avc_xperms_node *src)
427 struct avc_xperms_node *dest;
428 struct avc_xperms_decision_node *dest_xpd;
429 struct avc_xperms_decision_node *src_xpd;
431 if (src->xp.len == 0)
433 dest = avc_xperms_alloc();
437 memcpy(dest->xp.drivers.p, src->xp.drivers.p, sizeof(dest->xp.drivers.p));
438 dest->xp.len = src->xp.len;
440 /* for each source xpd allocate a destination xpd and copy */
441 list_for_each_entry(src_xpd, &src->xpd_head, xpd_list) {
442 dest_xpd = avc_xperms_decision_alloc(src_xpd->xpd.used);
445 avc_copy_xperms_decision(&dest_xpd->xpd, &src_xpd->xpd);
446 list_add(&dest_xpd->xpd_list, &dest->xpd_head);
448 node->ae.xp_node = dest;
451 avc_xperms_free(dest);
456 static inline u32 avc_xperms_audit_required(u32 requested,
457 struct av_decision *avd,
458 struct extended_perms_decision *xpd,
465 denied = requested & ~avd->allowed;
466 if (unlikely(denied)) {
467 audited = denied & avd->auditdeny;
468 if (audited && xpd) {
469 if (avc_xperms_has_perm(xpd, perm, XPERMS_DONTAUDIT))
470 audited &= ~requested;
473 audited = denied = requested;
475 audited = requested & avd->auditallow;
476 if (audited && xpd) {
477 if (!avc_xperms_has_perm(xpd, perm, XPERMS_AUDITALLOW))
478 audited &= ~requested;
486 static inline int avc_xperms_audit(struct selinux_state *state,
487 u32 ssid, u32 tsid, u16 tclass,
488 u32 requested, struct av_decision *avd,
489 struct extended_perms_decision *xpd,
491 struct common_audit_data *ad)
495 audited = avc_xperms_audit_required(
496 requested, avd, xpd, perm, result, &denied);
497 if (likely(!audited))
499 return slow_avc_audit(state, ssid, tsid, tclass, requested,
500 audited, denied, result, ad);
503 static void avc_node_free(struct rcu_head *rhead)
505 struct avc_node *node = container_of(rhead, struct avc_node, rhead);
506 avc_xperms_free(node->ae.xp_node);
507 kmem_cache_free(avc_node_cachep, node);
508 avc_cache_stats_incr(frees);
511 static void avc_node_delete(struct selinux_avc *avc, struct avc_node *node)
513 hlist_del_rcu(&node->list);
514 call_rcu(&node->rhead, avc_node_free);
515 atomic_dec(&avc->avc_cache.active_nodes);
518 static void avc_node_kill(struct selinux_avc *avc, struct avc_node *node)
520 avc_xperms_free(node->ae.xp_node);
521 kmem_cache_free(avc_node_cachep, node);
522 avc_cache_stats_incr(frees);
523 atomic_dec(&avc->avc_cache.active_nodes);
526 static void avc_node_replace(struct selinux_avc *avc,
527 struct avc_node *new, struct avc_node *old)
529 hlist_replace_rcu(&old->list, &new->list);
530 call_rcu(&old->rhead, avc_node_free);
531 atomic_dec(&avc->avc_cache.active_nodes);
534 static inline int avc_reclaim_node(struct selinux_avc *avc)
536 struct avc_node *node;
537 int hvalue, try, ecx;
539 struct hlist_head *head;
542 for (try = 0, ecx = 0; try < AVC_CACHE_SLOTS; try++) {
543 hvalue = atomic_inc_return(&avc->avc_cache.lru_hint) &
544 (AVC_CACHE_SLOTS - 1);
545 head = &avc->avc_cache.slots[hvalue];
546 lock = &avc->avc_cache.slots_lock[hvalue];
548 if (!spin_trylock_irqsave(lock, flags))
552 hlist_for_each_entry(node, head, list) {
553 avc_node_delete(avc, node);
554 avc_cache_stats_incr(reclaims);
556 if (ecx >= AVC_CACHE_RECLAIM) {
558 spin_unlock_irqrestore(lock, flags);
563 spin_unlock_irqrestore(lock, flags);
569 static struct avc_node *avc_alloc_node(struct selinux_avc *avc)
571 struct avc_node *node;
573 node = kmem_cache_zalloc(avc_node_cachep, GFP_NOWAIT | __GFP_NOWARN);
577 INIT_HLIST_NODE(&node->list);
578 avc_cache_stats_incr(allocations);
580 if (atomic_inc_return(&avc->avc_cache.active_nodes) >
581 avc->avc_cache_threshold)
582 avc_reclaim_node(avc);
588 static void avc_node_populate(struct avc_node *node, u32 ssid, u32 tsid, u16 tclass, struct av_decision *avd)
590 node->ae.ssid = ssid;
591 node->ae.tsid = tsid;
592 node->ae.tclass = tclass;
593 memcpy(&node->ae.avd, avd, sizeof(node->ae.avd));
596 static inline struct avc_node *avc_search_node(struct selinux_avc *avc,
597 u32 ssid, u32 tsid, u16 tclass)
599 struct avc_node *node, *ret = NULL;
601 struct hlist_head *head;
603 hvalue = avc_hash(ssid, tsid, tclass);
604 head = &avc->avc_cache.slots[hvalue];
605 hlist_for_each_entry_rcu(node, head, list) {
606 if (ssid == node->ae.ssid &&
607 tclass == node->ae.tclass &&
608 tsid == node->ae.tsid) {
618 * avc_lookup - Look up an AVC entry.
619 * @ssid: source security identifier
620 * @tsid: target security identifier
621 * @tclass: target security class
623 * Look up an AVC entry that is valid for the
624 * (@ssid, @tsid), interpreting the permissions
625 * based on @tclass. If a valid AVC entry exists,
626 * then this function returns the avc_node.
627 * Otherwise, this function returns NULL.
629 static struct avc_node *avc_lookup(struct selinux_avc *avc,
630 u32 ssid, u32 tsid, u16 tclass)
632 struct avc_node *node;
634 avc_cache_stats_incr(lookups);
635 node = avc_search_node(avc, ssid, tsid, tclass);
640 avc_cache_stats_incr(misses);
644 static int avc_latest_notif_update(struct selinux_avc *avc,
645 int seqno, int is_insert)
648 static DEFINE_SPINLOCK(notif_lock);
651 spin_lock_irqsave(¬if_lock, flag);
653 if (seqno < avc->avc_cache.latest_notif) {
654 pr_warn("SELinux: avc: seqno %d < latest_notif %d\n",
655 seqno, avc->avc_cache.latest_notif);
659 if (seqno > avc->avc_cache.latest_notif)
660 avc->avc_cache.latest_notif = seqno;
662 spin_unlock_irqrestore(¬if_lock, flag);
668 * avc_insert - Insert an AVC entry.
669 * @ssid: source security identifier
670 * @tsid: target security identifier
671 * @tclass: target security class
672 * @avd: resulting av decision
673 * @xp_node: resulting extended permissions
675 * Insert an AVC entry for the SID pair
676 * (@ssid, @tsid) and class @tclass.
677 * The access vectors and the sequence number are
678 * normally provided by the security server in
679 * response to a security_compute_av() call. If the
680 * sequence number @avd->seqno is not less than the latest
681 * revocation notification, then the function copies
682 * the access vectors into a cache entry, returns
683 * avc_node inserted. Otherwise, this function returns NULL.
685 static struct avc_node *avc_insert(struct selinux_avc *avc,
686 u32 ssid, u32 tsid, u16 tclass,
687 struct av_decision *avd,
688 struct avc_xperms_node *xp_node)
690 struct avc_node *pos, *node = NULL;
694 struct hlist_head *head;
696 if (avc_latest_notif_update(avc, avd->seqno, 1))
699 node = avc_alloc_node(avc);
703 avc_node_populate(node, ssid, tsid, tclass, avd);
704 if (avc_xperms_populate(node, xp_node)) {
705 avc_node_kill(avc, node);
709 hvalue = avc_hash(ssid, tsid, tclass);
710 head = &avc->avc_cache.slots[hvalue];
711 lock = &avc->avc_cache.slots_lock[hvalue];
712 spin_lock_irqsave(lock, flag);
713 hlist_for_each_entry(pos, head, list) {
714 if (pos->ae.ssid == ssid &&
715 pos->ae.tsid == tsid &&
716 pos->ae.tclass == tclass) {
717 avc_node_replace(avc, node, pos);
721 hlist_add_head_rcu(&node->list, head);
723 spin_unlock_irqrestore(lock, flag);
728 * avc_audit_pre_callback - SELinux specific information
729 * will be called by generic audit code
730 * @ab: the audit buffer
733 static void avc_audit_pre_callback(struct audit_buffer *ab, void *a)
735 struct common_audit_data *ad = a;
736 audit_log_format(ab, "avc: %s ",
737 ad->selinux_audit_data->denied ? "denied" : "granted");
738 avc_dump_av(ab, ad->selinux_audit_data->tclass,
739 ad->selinux_audit_data->audited);
740 audit_log_format(ab, " for ");
744 * avc_audit_post_callback - SELinux specific information
745 * will be called by generic audit code
746 * @ab: the audit buffer
749 static void avc_audit_post_callback(struct audit_buffer *ab, void *a)
751 struct common_audit_data *ad = a;
752 audit_log_format(ab, " ");
753 avc_dump_query(ab, ad->selinux_audit_data->state,
754 ad->selinux_audit_data->ssid,
755 ad->selinux_audit_data->tsid,
756 ad->selinux_audit_data->tclass);
757 if (ad->selinux_audit_data->denied) {
758 audit_log_format(ab, " permissive=%u",
759 ad->selinux_audit_data->result ? 0 : 1);
763 /* This is the slow part of avc audit with big stack footprint */
764 noinline int slow_avc_audit(struct selinux_state *state,
765 u32 ssid, u32 tsid, u16 tclass,
766 u32 requested, u32 audited, u32 denied, int result,
767 struct common_audit_data *a)
769 struct common_audit_data stack_data;
770 struct selinux_audit_data sad;
774 a->type = LSM_AUDIT_DATA_NONE;
778 sad.requested = requested;
781 sad.audited = audited;
786 a->selinux_audit_data = &sad;
788 common_lsm_audit(a, avc_audit_pre_callback, avc_audit_post_callback);
793 * avc_add_callback - Register a callback for security events.
794 * @callback: callback function
795 * @events: security events
797 * Register a callback function for events in the set @events.
798 * Returns %0 on success or -%ENOMEM if insufficient memory
799 * exists to add the callback.
801 int __init avc_add_callback(int (*callback)(u32 event), u32 events)
803 struct avc_callback_node *c;
806 c = kmalloc(sizeof(*c), GFP_KERNEL);
812 c->callback = callback;
814 c->next = avc_callbacks;
821 * avc_update_node Update an AVC entry
822 * @event : Updating event
823 * @perms : Permission mask bits
824 * @ssid,@tsid,@tclass : identifier of an AVC entry
825 * @seqno : sequence number when decision was made
826 * @xpd: extended_perms_decision to be added to the node
827 * @flags: the AVC_* flags, e.g. AVC_NONBLOCKING, AVC_EXTENDED_PERMS, or 0.
829 * if a valid AVC entry doesn't exist,this function returns -ENOENT.
830 * if kmalloc() called internal returns NULL, this function returns -ENOMEM.
831 * otherwise, this function updates the AVC entry. The original AVC-entry object
832 * will release later by RCU.
834 static int avc_update_node(struct selinux_avc *avc,
835 u32 event, u32 perms, u8 driver, u8 xperm, u32 ssid,
836 u32 tsid, u16 tclass, u32 seqno,
837 struct extended_perms_decision *xpd,
842 struct avc_node *pos, *node, *orig = NULL;
843 struct hlist_head *head;
847 * If we are in a non-blocking code path, e.g. VFS RCU walk,
848 * then we must not add permissions to a cache entry
849 * because we will not audit the denial. Otherwise,
850 * during the subsequent blocking retry (e.g. VFS ref walk), we
851 * will find the permissions already granted in the cache entry
852 * and won't audit anything at all, leading to silent denials in
853 * permissive mode that only appear when in enforcing mode.
855 * See the corresponding handling of MAY_NOT_BLOCK in avc_audit()
856 * and selinux_inode_permission().
858 if (flags & AVC_NONBLOCKING)
861 node = avc_alloc_node(avc);
867 /* Lock the target slot */
868 hvalue = avc_hash(ssid, tsid, tclass);
870 head = &avc->avc_cache.slots[hvalue];
871 lock = &avc->avc_cache.slots_lock[hvalue];
873 spin_lock_irqsave(lock, flag);
875 hlist_for_each_entry(pos, head, list) {
876 if (ssid == pos->ae.ssid &&
877 tsid == pos->ae.tsid &&
878 tclass == pos->ae.tclass &&
879 seqno == pos->ae.avd.seqno){
887 avc_node_kill(avc, node);
892 * Copy and replace original node.
895 avc_node_populate(node, ssid, tsid, tclass, &orig->ae.avd);
897 if (orig->ae.xp_node) {
898 rc = avc_xperms_populate(node, orig->ae.xp_node);
900 avc_node_kill(avc, node);
906 case AVC_CALLBACK_GRANT:
907 node->ae.avd.allowed |= perms;
908 if (node->ae.xp_node && (flags & AVC_EXTENDED_PERMS))
909 avc_xperms_allow_perm(node->ae.xp_node, driver, xperm);
911 case AVC_CALLBACK_TRY_REVOKE:
912 case AVC_CALLBACK_REVOKE:
913 node->ae.avd.allowed &= ~perms;
915 case AVC_CALLBACK_AUDITALLOW_ENABLE:
916 node->ae.avd.auditallow |= perms;
918 case AVC_CALLBACK_AUDITALLOW_DISABLE:
919 node->ae.avd.auditallow &= ~perms;
921 case AVC_CALLBACK_AUDITDENY_ENABLE:
922 node->ae.avd.auditdeny |= perms;
924 case AVC_CALLBACK_AUDITDENY_DISABLE:
925 node->ae.avd.auditdeny &= ~perms;
927 case AVC_CALLBACK_ADD_XPERMS:
928 avc_add_xperms_decision(node, xpd);
931 avc_node_replace(avc, node, orig);
933 spin_unlock_irqrestore(lock, flag);
939 * avc_flush - Flush the cache
941 static void avc_flush(struct selinux_avc *avc)
943 struct hlist_head *head;
944 struct avc_node *node;
949 for (i = 0; i < AVC_CACHE_SLOTS; i++) {
950 head = &avc->avc_cache.slots[i];
951 lock = &avc->avc_cache.slots_lock[i];
953 spin_lock_irqsave(lock, flag);
955 * With preemptable RCU, the outer spinlock does not
956 * prevent RCU grace periods from ending.
959 hlist_for_each_entry(node, head, list)
960 avc_node_delete(avc, node);
962 spin_unlock_irqrestore(lock, flag);
967 * avc_ss_reset - Flush the cache and revalidate migrated permissions.
968 * @seqno: policy sequence number
970 int avc_ss_reset(struct selinux_avc *avc, u32 seqno)
972 struct avc_callback_node *c;
977 for (c = avc_callbacks; c; c = c->next) {
978 if (c->events & AVC_CALLBACK_RESET) {
979 tmprc = c->callback(AVC_CALLBACK_RESET);
980 /* save the first error encountered for the return
981 value and continue processing the callbacks */
987 avc_latest_notif_update(avc, seqno, 0);
992 * Slow-path helper function for avc_has_perm_noaudit,
993 * when the avc_node lookup fails. We get called with
994 * the RCU read lock held, and need to return with it
995 * still held, but drop if for the security compute.
997 * Don't inline this, since it's the slow-path and just
998 * results in a bigger stack frame.
1001 struct avc_node *avc_compute_av(struct selinux_state *state,
1003 u16 tclass, struct av_decision *avd,
1004 struct avc_xperms_node *xp_node)
1007 INIT_LIST_HEAD(&xp_node->xpd_head);
1008 security_compute_av(state, ssid, tsid, tclass, avd, &xp_node->xp);
1010 return avc_insert(state->avc, ssid, tsid, tclass, avd, xp_node);
1013 static noinline int avc_denied(struct selinux_state *state,
1015 u16 tclass, u32 requested,
1016 u8 driver, u8 xperm, unsigned int flags,
1017 struct av_decision *avd)
1019 if (flags & AVC_STRICT)
1022 if (enforcing_enabled(state) &&
1023 !(avd->flags & AVD_FLAGS_PERMISSIVE))
1026 avc_update_node(state->avc, AVC_CALLBACK_GRANT, requested, driver,
1027 xperm, ssid, tsid, tclass, avd->seqno, NULL, flags);
1032 * The avc extended permissions logic adds an additional 256 bits of
1033 * permissions to an avc node when extended permissions for that node are
1034 * specified in the avtab. If the additional 256 permissions is not adequate,
1035 * as-is the case with ioctls, then multiple may be chained together and the
1036 * driver field is used to specify which set contains the permission.
1038 int avc_has_extended_perms(struct selinux_state *state,
1039 u32 ssid, u32 tsid, u16 tclass, u32 requested,
1040 u8 driver, u8 xperm, struct common_audit_data *ad)
1042 struct avc_node *node;
1043 struct av_decision avd;
1045 struct extended_perms_decision local_xpd;
1046 struct extended_perms_decision *xpd = NULL;
1047 struct extended_perms_data allowed;
1048 struct extended_perms_data auditallow;
1049 struct extended_perms_data dontaudit;
1050 struct avc_xperms_node local_xp_node;
1051 struct avc_xperms_node *xp_node;
1054 xp_node = &local_xp_node;
1059 node = avc_lookup(state->avc, ssid, tsid, tclass);
1060 if (unlikely(!node)) {
1061 node = avc_compute_av(state, ssid, tsid, tclass, &avd, xp_node);
1063 memcpy(&avd, &node->ae.avd, sizeof(avd));
1064 xp_node = node->ae.xp_node;
1066 /* if extended permissions are not defined, only consider av_decision */
1067 if (!xp_node || !xp_node->xp.len)
1070 local_xpd.allowed = &allowed;
1071 local_xpd.auditallow = &auditallow;
1072 local_xpd.dontaudit = &dontaudit;
1074 xpd = avc_xperms_decision_lookup(driver, xp_node);
1075 if (unlikely(!xpd)) {
1077 * Compute the extended_perms_decision only if the driver
1080 if (!security_xperm_test(xp_node->xp.drivers.p, driver)) {
1081 avd.allowed &= ~requested;
1085 security_compute_xperms_decision(state, ssid, tsid, tclass,
1086 driver, &local_xpd);
1088 avc_update_node(state->avc, AVC_CALLBACK_ADD_XPERMS, requested,
1089 driver, xperm, ssid, tsid, tclass, avd.seqno,
1092 avc_quick_copy_xperms_decision(xperm, &local_xpd, xpd);
1096 if (!avc_xperms_has_perm(xpd, xperm, XPERMS_ALLOWED))
1097 avd.allowed &= ~requested;
1100 denied = requested & ~(avd.allowed);
1101 if (unlikely(denied))
1102 rc = avc_denied(state, ssid, tsid, tclass, requested,
1103 driver, xperm, AVC_EXTENDED_PERMS, &avd);
1107 rc2 = avc_xperms_audit(state, ssid, tsid, tclass, requested,
1108 &avd, xpd, xperm, rc, ad);
1115 * avc_has_perm_noaudit - Check permissions but perform no auditing.
1116 * @ssid: source security identifier
1117 * @tsid: target security identifier
1118 * @tclass: target security class
1119 * @requested: requested permissions, interpreted based on @tclass
1120 * @flags: AVC_STRICT, AVC_NONBLOCKING, or 0
1121 * @avd: access vector decisions
1123 * Check the AVC to determine whether the @requested permissions are granted
1124 * for the SID pair (@ssid, @tsid), interpreting the permissions
1125 * based on @tclass, and call the security server on a cache miss to obtain
1126 * a new decision and add it to the cache. Return a copy of the decisions
1127 * in @avd. Return %0 if all @requested permissions are granted,
1128 * -%EACCES if any permissions are denied, or another -errno upon
1129 * other errors. This function is typically called by avc_has_perm(),
1130 * but may also be called directly to separate permission checking from
1131 * auditing, e.g. in cases where a lock must be held for the check but
1132 * should be released for the auditing.
1134 inline int avc_has_perm_noaudit(struct selinux_state *state,
1136 u16 tclass, u32 requested,
1138 struct av_decision *avd)
1140 struct avc_node *node;
1141 struct avc_xperms_node xp_node;
1149 node = avc_lookup(state->avc, ssid, tsid, tclass);
1150 if (unlikely(!node))
1151 node = avc_compute_av(state, ssid, tsid, tclass, avd, &xp_node);
1153 memcpy(avd, &node->ae.avd, sizeof(*avd));
1155 denied = requested & ~(avd->allowed);
1156 if (unlikely(denied))
1157 rc = avc_denied(state, ssid, tsid, tclass, requested, 0, 0,
1165 * avc_has_perm - Check permissions and perform any appropriate auditing.
1166 * @ssid: source security identifier
1167 * @tsid: target security identifier
1168 * @tclass: target security class
1169 * @requested: requested permissions, interpreted based on @tclass
1170 * @auditdata: auxiliary audit data
1172 * Check the AVC to determine whether the @requested permissions are granted
1173 * for the SID pair (@ssid, @tsid), interpreting the permissions
1174 * based on @tclass, and call the security server on a cache miss to obtain
1175 * a new decision and add it to the cache. Audit the granting or denial of
1176 * permissions in accordance with the policy. Return %0 if all @requested
1177 * permissions are granted, -%EACCES if any permissions are denied, or
1178 * another -errno upon other errors.
1180 int avc_has_perm(struct selinux_state *state, u32 ssid, u32 tsid, u16 tclass,
1181 u32 requested, struct common_audit_data *auditdata)
1183 struct av_decision avd;
1186 rc = avc_has_perm_noaudit(state, ssid, tsid, tclass, requested, 0,
1189 rc2 = avc_audit(state, ssid, tsid, tclass, requested, &avd, rc,
1196 int avc_has_perm_flags(struct selinux_state *state,
1197 u32 ssid, u32 tsid, u16 tclass, u32 requested,
1198 struct common_audit_data *auditdata,
1201 struct av_decision avd;
1204 rc = avc_has_perm_noaudit(state, ssid, tsid, tclass, requested,
1205 (flags & MAY_NOT_BLOCK) ? AVC_NONBLOCKING : 0,
1208 rc2 = avc_audit(state, ssid, tsid, tclass, requested, &avd, rc,
1215 u32 avc_policy_seqno(struct selinux_state *state)
1217 return state->avc->avc_cache.latest_notif;
1220 void avc_disable(void)
1223 * If you are looking at this because you have realized that we are
1224 * not destroying the avc_node_cachep it might be easy to fix, but
1225 * I don't know the memory barrier semantics well enough to know. It's
1226 * possible that some other task dereferenced security_ops when
1227 * it still pointed to selinux operations. If that is the case it's
1228 * possible that it is about to use the avc and is about to need the
1229 * avc_node_cachep. I know I could wrap the security.c security_ops call
1230 * in an rcu_lock, but seriously, it's not worth it. Instead I just flush
1231 * the cache and get that memory back.
1233 if (avc_node_cachep) {
1234 avc_flush(selinux_state.avc);
1235 /* kmem_cache_destroy(avc_node_cachep); */