2 * Implementation of the kernel access vector cache (AVC).
4 * Authors: Stephen Smalley, <sds@epoch.ncsc.mil>
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>
27 #include <net/af_unix.h>
29 #include <linux/audit.h>
30 #include <linux/ipv6.h>
35 static const struct av_perm_to_string av_perm_to_string[] = {
36 #define S_(c, v, s) { c, v, s },
37 #include "av_perm_to_string.h"
41 static const char *class_to_string[] = {
43 #include "class_to_string.h"
47 #define TB_(s) static const char *s[] = {
50 #include "common_perm_to_string.h"
55 static const struct av_inherit av_inherit[] = {
56 #define S_(c, i, b) { .tclass = c,\
57 .common_pts = common_##i##_perm_to_string,\
59 #include "av_inherit.h"
63 const struct selinux_class_perm selinux_class_perm = {
64 .av_perm_to_string = av_perm_to_string,
65 .av_pts_len = ARRAY_SIZE(av_perm_to_string),
66 .class_to_string = class_to_string,
67 .cts_len = ARRAY_SIZE(class_to_string),
68 .av_inherit = av_inherit,
69 .av_inherit_len = ARRAY_SIZE(av_inherit)
72 #define AVC_CACHE_SLOTS 512
73 #define AVC_DEF_CACHE_THRESHOLD 512
74 #define AVC_CACHE_RECLAIM 16
76 #ifdef CONFIG_SECURITY_SELINUX_AVC_STATS
77 #define avc_cache_stats_incr(field) \
79 per_cpu(avc_cache_stats, get_cpu()).field++; \
83 #define avc_cache_stats_incr(field) do {} while (0)
90 struct av_decision avd;
95 struct list_head list;
96 struct rcu_head rhead;
100 struct list_head slots[AVC_CACHE_SLOTS];
101 spinlock_t slots_lock[AVC_CACHE_SLOTS]; /* lock for writes */
102 atomic_t lru_hint; /* LRU hint for reclaim scan */
103 atomic_t active_nodes;
104 u32 latest_notif; /* latest revocation notification */
107 struct avc_callback_node {
108 int (*callback) (u32 event, u32 ssid, u32 tsid,
109 u16 tclass, u32 perms,
116 struct avc_callback_node *next;
119 /* Exported via selinufs */
120 unsigned int avc_cache_threshold = AVC_DEF_CACHE_THRESHOLD;
122 #ifdef CONFIG_SECURITY_SELINUX_AVC_STATS
123 DEFINE_PER_CPU(struct avc_cache_stats, avc_cache_stats) = { 0 };
126 static struct avc_cache avc_cache;
127 static struct avc_callback_node *avc_callbacks;
128 static struct kmem_cache *avc_node_cachep;
130 static inline int avc_hash(u32 ssid, u32 tsid, u16 tclass)
132 return (ssid ^ (tsid<<2) ^ (tclass<<4)) & (AVC_CACHE_SLOTS - 1);
136 * avc_dump_av - Display an access vector in human-readable form.
137 * @tclass: target security class
140 void avc_dump_av(struct audit_buffer *ab, u16 tclass, u32 av)
142 const char **common_pts = NULL;
147 audit_log_format(ab, " null");
151 for (i = 0; i < ARRAY_SIZE(av_inherit); i++) {
152 if (av_inherit[i].tclass == tclass) {
153 common_pts = av_inherit[i].common_pts;
154 common_base = av_inherit[i].common_base;
159 audit_log_format(ab, " {");
162 while (perm < common_base) {
164 audit_log_format(ab, " %s", common_pts[i]);
171 while (i < sizeof(av) * 8) {
173 for (i2 = 0; i2 < ARRAY_SIZE(av_perm_to_string); i2++) {
174 if ((av_perm_to_string[i2].tclass == tclass) &&
175 (av_perm_to_string[i2].value == perm))
178 if (i2 < ARRAY_SIZE(av_perm_to_string)) {
179 audit_log_format(ab, " %s",
180 av_perm_to_string[i2].name);
189 audit_log_format(ab, " 0x%x", av);
191 audit_log_format(ab, " }");
195 * avc_dump_query - Display a SID pair and a class in human-readable form.
196 * @ssid: source security identifier
197 * @tsid: target security identifier
198 * @tclass: target security class
200 static void avc_dump_query(struct audit_buffer *ab, u32 ssid, u32 tsid, u16 tclass)
206 rc = security_sid_to_context(ssid, &scontext, &scontext_len);
208 audit_log_format(ab, "ssid=%d", ssid);
210 audit_log_format(ab, "scontext=%s", scontext);
214 rc = security_sid_to_context(tsid, &scontext, &scontext_len);
216 audit_log_format(ab, " tsid=%d", tsid);
218 audit_log_format(ab, " tcontext=%s", scontext);
222 BUG_ON(tclass >= ARRAY_SIZE(class_to_string) || !class_to_string[tclass]);
223 audit_log_format(ab, " tclass=%s", class_to_string[tclass]);
227 * avc_init - Initialize the AVC.
229 * Initialize the access vector cache.
231 void __init avc_init(void)
235 for (i = 0; i < AVC_CACHE_SLOTS; i++) {
236 INIT_LIST_HEAD(&avc_cache.slots[i]);
237 spin_lock_init(&avc_cache.slots_lock[i]);
239 atomic_set(&avc_cache.active_nodes, 0);
240 atomic_set(&avc_cache.lru_hint, 0);
242 avc_node_cachep = kmem_cache_create("avc_node", sizeof(struct avc_node),
243 0, SLAB_PANIC, NULL);
245 audit_log(current->audit_context, GFP_KERNEL, AUDIT_KERNEL, "AVC INITIALIZED\n");
248 int avc_get_hash_stats(char *page)
250 int i, chain_len, max_chain_len, slots_used;
251 struct avc_node *node;
257 for (i = 0; i < AVC_CACHE_SLOTS; i++) {
258 if (!list_empty(&avc_cache.slots[i])) {
261 list_for_each_entry_rcu(node, &avc_cache.slots[i], list)
263 if (chain_len > max_chain_len)
264 max_chain_len = chain_len;
270 return scnprintf(page, PAGE_SIZE, "entries: %d\nbuckets used: %d/%d\n"
271 "longest chain: %d\n",
272 atomic_read(&avc_cache.active_nodes),
273 slots_used, AVC_CACHE_SLOTS, max_chain_len);
276 static void avc_node_free(struct rcu_head *rhead)
278 struct avc_node *node = container_of(rhead, struct avc_node, rhead);
279 kmem_cache_free(avc_node_cachep, node);
280 avc_cache_stats_incr(frees);
283 static void avc_node_delete(struct avc_node *node)
285 list_del_rcu(&node->list);
286 call_rcu(&node->rhead, avc_node_free);
287 atomic_dec(&avc_cache.active_nodes);
290 static void avc_node_kill(struct avc_node *node)
292 kmem_cache_free(avc_node_cachep, node);
293 avc_cache_stats_incr(frees);
294 atomic_dec(&avc_cache.active_nodes);
297 static void avc_node_replace(struct avc_node *new, struct avc_node *old)
299 list_replace_rcu(&old->list, &new->list);
300 call_rcu(&old->rhead, avc_node_free);
301 atomic_dec(&avc_cache.active_nodes);
304 static inline int avc_reclaim_node(void)
306 struct avc_node *node;
307 int hvalue, try, ecx;
310 for (try = 0, ecx = 0; try < AVC_CACHE_SLOTS; try++) {
311 hvalue = atomic_inc_return(&avc_cache.lru_hint) & (AVC_CACHE_SLOTS - 1);
313 if (!spin_trylock_irqsave(&avc_cache.slots_lock[hvalue], flags))
317 list_for_each_entry(node, &avc_cache.slots[hvalue], list) {
318 avc_node_delete(node);
319 avc_cache_stats_incr(reclaims);
321 if (ecx >= AVC_CACHE_RECLAIM) {
323 spin_unlock_irqrestore(&avc_cache.slots_lock[hvalue], flags);
328 spin_unlock_irqrestore(&avc_cache.slots_lock[hvalue], flags);
334 static struct avc_node *avc_alloc_node(void)
336 struct avc_node *node;
338 node = kmem_cache_zalloc(avc_node_cachep, GFP_ATOMIC);
342 INIT_RCU_HEAD(&node->rhead);
343 INIT_LIST_HEAD(&node->list);
344 avc_cache_stats_incr(allocations);
346 if (atomic_inc_return(&avc_cache.active_nodes) > avc_cache_threshold)
353 static void avc_node_populate(struct avc_node *node, u32 ssid, u32 tsid, u16 tclass, struct avc_entry *ae)
355 node->ae.ssid = ssid;
356 node->ae.tsid = tsid;
357 node->ae.tclass = tclass;
358 memcpy(&node->ae.avd, &ae->avd, sizeof(node->ae.avd));
361 static inline struct avc_node *avc_search_node(u32 ssid, u32 tsid, u16 tclass)
363 struct avc_node *node, *ret = NULL;
366 hvalue = avc_hash(ssid, tsid, tclass);
367 list_for_each_entry_rcu(node, &avc_cache.slots[hvalue], list) {
368 if (ssid == node->ae.ssid &&
369 tclass == node->ae.tclass &&
370 tsid == node->ae.tsid) {
380 * avc_lookup - Look up an AVC entry.
381 * @ssid: source security identifier
382 * @tsid: target security identifier
383 * @tclass: target security class
384 * @requested: requested permissions, interpreted based on @tclass
386 * Look up an AVC entry that is valid for the
387 * @requested permissions between the SID pair
388 * (@ssid, @tsid), interpreting the permissions
389 * based on @tclass. If a valid AVC entry exists,
390 * then this function return the avc_node.
391 * Otherwise, this function returns NULL.
393 static struct avc_node *avc_lookup(u32 ssid, u32 tsid, u16 tclass, u32 requested)
395 struct avc_node *node;
397 avc_cache_stats_incr(lookups);
398 node = avc_search_node(ssid, tsid, tclass);
400 if (node && ((node->ae.avd.decided & requested) == requested)) {
401 avc_cache_stats_incr(hits);
406 avc_cache_stats_incr(misses);
411 static int avc_latest_notif_update(int seqno, int is_insert)
414 static DEFINE_SPINLOCK(notif_lock);
417 spin_lock_irqsave(¬if_lock, flag);
419 if (seqno < avc_cache.latest_notif) {
420 printk(KERN_WARNING "SELinux: avc: seqno %d < latest_notif %d\n",
421 seqno, avc_cache.latest_notif);
425 if (seqno > avc_cache.latest_notif)
426 avc_cache.latest_notif = seqno;
428 spin_unlock_irqrestore(¬if_lock, flag);
434 * avc_insert - Insert an AVC entry.
435 * @ssid: source security identifier
436 * @tsid: target security identifier
437 * @tclass: target security class
440 * Insert an AVC entry for the SID pair
441 * (@ssid, @tsid) and class @tclass.
442 * The access vectors and the sequence number are
443 * normally provided by the security server in
444 * response to a security_compute_av() call. If the
445 * sequence number @ae->avd.seqno is not less than the latest
446 * revocation notification, then the function copies
447 * the access vectors into a cache entry, returns
448 * avc_node inserted. Otherwise, this function returns NULL.
450 static struct avc_node *avc_insert(u32 ssid, u32 tsid, u16 tclass, struct avc_entry *ae)
452 struct avc_node *pos, *node = NULL;
456 if (avc_latest_notif_update(ae->avd.seqno, 1))
459 node = avc_alloc_node();
461 hvalue = avc_hash(ssid, tsid, tclass);
462 avc_node_populate(node, ssid, tsid, tclass, ae);
464 spin_lock_irqsave(&avc_cache.slots_lock[hvalue], flag);
465 list_for_each_entry(pos, &avc_cache.slots[hvalue], list) {
466 if (pos->ae.ssid == ssid &&
467 pos->ae.tsid == tsid &&
468 pos->ae.tclass == tclass) {
469 avc_node_replace(node, pos);
473 list_add_rcu(&node->list, &avc_cache.slots[hvalue]);
475 spin_unlock_irqrestore(&avc_cache.slots_lock[hvalue], flag);
481 static inline void avc_print_ipv6_addr(struct audit_buffer *ab,
482 struct in6_addr *addr, __be16 port,
483 char *name1, char *name2)
485 if (!ipv6_addr_any(addr))
486 audit_log_format(ab, " %s=%pI6", name1, addr);
488 audit_log_format(ab, " %s=%d", name2, ntohs(port));
491 static inline void avc_print_ipv4_addr(struct audit_buffer *ab, __be32 addr,
492 __be16 port, char *name1, char *name2)
495 audit_log_format(ab, " %s=%pI4", name1, &addr);
497 audit_log_format(ab, " %s=%d", name2, ntohs(port));
501 * avc_audit - Audit the granting or denial of permissions.
502 * @ssid: source security identifier
503 * @tsid: target security identifier
504 * @tclass: target security class
505 * @requested: requested permissions
506 * @avd: access vector decisions
507 * @result: result from avc_has_perm_noaudit
508 * @a: auxiliary audit data
510 * Audit the granting or denial of permissions in accordance
511 * with the policy. This function is typically called by
512 * avc_has_perm() after a permission check, but can also be
513 * called directly by callers who use avc_has_perm_noaudit()
514 * in order to separate the permission check from the auditing.
515 * For example, this separation is useful when the permission check must
516 * be performed under a lock, to allow the lock to be released
517 * before calling the auditing code.
519 void avc_audit(u32 ssid, u32 tsid,
520 u16 tclass, u32 requested,
521 struct av_decision *avd, int result, struct avc_audit_data *a)
523 struct task_struct *tsk = current;
524 struct inode *inode = NULL;
526 struct audit_buffer *ab;
528 denied = requested & ~avd->allowed;
531 if (!(audited & avd->auditdeny))
534 audited = denied = requested;
537 if (!(audited & avd->auditallow))
541 ab = audit_log_start(current->audit_context, GFP_ATOMIC, AUDIT_AVC);
543 return; /* audit_panic has been called */
544 audit_log_format(ab, "avc: %s ", denied ? "denied" : "granted");
545 avc_dump_av(ab, tclass, audited);
546 audit_log_format(ab, " for ");
549 if (tsk && tsk->pid) {
550 audit_log_format(ab, " pid=%d comm=", tsk->pid);
551 audit_log_untrustedstring(ab, tsk->comm);
555 case AVC_AUDIT_DATA_IPC:
556 audit_log_format(ab, " key=%d", a->u.ipc_id);
558 case AVC_AUDIT_DATA_CAP:
559 audit_log_format(ab, " capability=%d", a->u.cap);
561 case AVC_AUDIT_DATA_FS:
562 if (a->u.fs.path.dentry) {
563 struct dentry *dentry = a->u.fs.path.dentry;
564 if (a->u.fs.path.mnt) {
565 audit_log_d_path(ab, "path=",
568 audit_log_format(ab, " name=");
569 audit_log_untrustedstring(ab, dentry->d_name.name);
571 inode = dentry->d_inode;
572 } else if (a->u.fs.inode) {
573 struct dentry *dentry;
574 inode = a->u.fs.inode;
575 dentry = d_find_alias(inode);
577 audit_log_format(ab, " name=");
578 audit_log_untrustedstring(ab, dentry->d_name.name);
583 audit_log_format(ab, " dev=%s ino=%lu",
587 case AVC_AUDIT_DATA_NET:
589 struct sock *sk = a->u.net.sk;
594 switch (sk->sk_family) {
596 struct inet_sock *inet = inet_sk(sk);
598 avc_print_ipv4_addr(ab, inet->rcv_saddr,
601 avc_print_ipv4_addr(ab, inet->daddr,
607 struct inet_sock *inet = inet_sk(sk);
608 struct ipv6_pinfo *inet6 = inet6_sk(sk);
610 avc_print_ipv6_addr(ab, &inet6->rcv_saddr,
613 avc_print_ipv6_addr(ab, &inet6->daddr,
625 audit_log_d_path(ab, "path=",
631 len = u->addr->len-sizeof(short);
632 p = &u->addr->name->sun_path[0];
633 audit_log_format(ab, " path=");
635 audit_log_untrustedstring(ab, p);
637 audit_log_n_hex(ab, p, len);
642 switch (a->u.net.family) {
644 avc_print_ipv4_addr(ab, a->u.net.v4info.saddr,
647 avc_print_ipv4_addr(ab, a->u.net.v4info.daddr,
652 avc_print_ipv6_addr(ab, &a->u.net.v6info.saddr,
655 avc_print_ipv6_addr(ab, &a->u.net.v6info.daddr,
660 if (a->u.net.netif > 0) {
661 struct net_device *dev;
663 /* NOTE: we always use init's namespace */
664 dev = dev_get_by_index(&init_net,
667 audit_log_format(ab, " netif=%s",
675 audit_log_format(ab, " ");
676 avc_dump_query(ab, ssid, tsid, tclass);
681 * avc_add_callback - Register a callback for security events.
682 * @callback: callback function
683 * @events: security events
684 * @ssid: source security identifier or %SECSID_WILD
685 * @tsid: target security identifier or %SECSID_WILD
686 * @tclass: target security class
687 * @perms: permissions
689 * Register a callback function for events in the set @events
690 * related to the SID pair (@ssid, @tsid) and
691 * and the permissions @perms, interpreting
692 * @perms based on @tclass. Returns %0 on success or
693 * -%ENOMEM if insufficient memory exists to add the callback.
695 int avc_add_callback(int (*callback)(u32 event, u32 ssid, u32 tsid,
696 u16 tclass, u32 perms,
698 u32 events, u32 ssid, u32 tsid,
699 u16 tclass, u32 perms)
701 struct avc_callback_node *c;
704 c = kmalloc(sizeof(*c), GFP_ATOMIC);
710 c->callback = callback;
715 c->next = avc_callbacks;
721 static inline int avc_sidcmp(u32 x, u32 y)
723 return (x == y || x == SECSID_WILD || y == SECSID_WILD);
727 * avc_update_node Update an AVC entry
728 * @event : Updating event
729 * @perms : Permission mask bits
730 * @ssid,@tsid,@tclass : identifier of an AVC entry
731 * @seqno : sequence number when decision was made
733 * if a valid AVC entry doesn't exist,this function returns -ENOENT.
734 * if kmalloc() called internal returns NULL, this function returns -ENOMEM.
735 * otherwise, this function update the AVC entry. The original AVC-entry object
736 * will release later by RCU.
738 static int avc_update_node(u32 event, u32 perms, u32 ssid, u32 tsid, u16 tclass,
743 struct avc_node *pos, *node, *orig = NULL;
745 node = avc_alloc_node();
751 /* Lock the target slot */
752 hvalue = avc_hash(ssid, tsid, tclass);
753 spin_lock_irqsave(&avc_cache.slots_lock[hvalue], flag);
755 list_for_each_entry(pos, &avc_cache.slots[hvalue], list) {
756 if (ssid == pos->ae.ssid &&
757 tsid == pos->ae.tsid &&
758 tclass == pos->ae.tclass &&
759 seqno == pos->ae.avd.seqno){
772 * Copy and replace original node.
775 avc_node_populate(node, ssid, tsid, tclass, &orig->ae);
778 case AVC_CALLBACK_GRANT:
779 node->ae.avd.allowed |= perms;
781 case AVC_CALLBACK_TRY_REVOKE:
782 case AVC_CALLBACK_REVOKE:
783 node->ae.avd.allowed &= ~perms;
785 case AVC_CALLBACK_AUDITALLOW_ENABLE:
786 node->ae.avd.auditallow |= perms;
788 case AVC_CALLBACK_AUDITALLOW_DISABLE:
789 node->ae.avd.auditallow &= ~perms;
791 case AVC_CALLBACK_AUDITDENY_ENABLE:
792 node->ae.avd.auditdeny |= perms;
794 case AVC_CALLBACK_AUDITDENY_DISABLE:
795 node->ae.avd.auditdeny &= ~perms;
798 avc_node_replace(node, orig);
800 spin_unlock_irqrestore(&avc_cache.slots_lock[hvalue], flag);
806 * avc_ss_reset - Flush the cache and revalidate migrated permissions.
807 * @seqno: policy sequence number
809 int avc_ss_reset(u32 seqno)
811 struct avc_callback_node *c;
812 int i, rc = 0, tmprc;
814 struct avc_node *node;
816 for (i = 0; i < AVC_CACHE_SLOTS; i++) {
817 spin_lock_irqsave(&avc_cache.slots_lock[i], flag);
819 * With preemptable RCU, the outer spinlock does not
820 * prevent RCU grace periods from ending.
823 list_for_each_entry(node, &avc_cache.slots[i], list)
824 avc_node_delete(node);
826 spin_unlock_irqrestore(&avc_cache.slots_lock[i], flag);
829 for (c = avc_callbacks; c; c = c->next) {
830 if (c->events & AVC_CALLBACK_RESET) {
831 tmprc = c->callback(AVC_CALLBACK_RESET,
833 /* save the first error encountered for the return
834 value and continue processing the callbacks */
840 avc_latest_notif_update(seqno, 0);
845 * avc_has_perm_noaudit - Check permissions but perform no auditing.
846 * @ssid: source security identifier
847 * @tsid: target security identifier
848 * @tclass: target security class
849 * @requested: requested permissions, interpreted based on @tclass
850 * @flags: AVC_STRICT or 0
851 * @avd: access vector decisions
853 * Check the AVC to determine whether the @requested permissions are granted
854 * for the SID pair (@ssid, @tsid), interpreting the permissions
855 * based on @tclass, and call the security server on a cache miss to obtain
856 * a new decision and add it to the cache. Return a copy of the decisions
857 * in @avd. Return %0 if all @requested permissions are granted,
858 * -%EACCES if any permissions are denied, or another -errno upon
859 * other errors. This function is typically called by avc_has_perm(),
860 * but may also be called directly to separate permission checking from
861 * auditing, e.g. in cases where a lock must be held for the check but
862 * should be released for the auditing.
864 int avc_has_perm_noaudit(u32 ssid, u32 tsid,
865 u16 tclass, u32 requested,
867 struct av_decision *avd)
869 struct avc_node *node;
870 struct avc_entry entry, *p_ae;
878 node = avc_lookup(ssid, tsid, tclass, requested);
881 rc = security_compute_av(ssid, tsid, tclass, requested, &entry.avd);
885 node = avc_insert(ssid, tsid, tclass, &entry);
888 p_ae = node ? &node->ae : &entry;
891 memcpy(avd, &p_ae->avd, sizeof(*avd));
893 denied = requested & ~(p_ae->avd.allowed);
896 if (flags & AVC_STRICT)
898 else if (!selinux_enforcing || security_permissive_sid(ssid))
899 avc_update_node(AVC_CALLBACK_GRANT, requested, ssid,
900 tsid, tclass, p_ae->avd.seqno);
911 * avc_has_perm - Check permissions and perform any appropriate auditing.
912 * @ssid: source security identifier
913 * @tsid: target security identifier
914 * @tclass: target security class
915 * @requested: requested permissions, interpreted based on @tclass
916 * @auditdata: auxiliary audit data
918 * Check the AVC to determine whether the @requested permissions are granted
919 * for the SID pair (@ssid, @tsid), interpreting the permissions
920 * based on @tclass, and call the security server on a cache miss to obtain
921 * a new decision and add it to the cache. Audit the granting or denial of
922 * permissions in accordance with the policy. Return %0 if all @requested
923 * permissions are granted, -%EACCES if any permissions are denied, or
924 * another -errno upon other errors.
926 int avc_has_perm(u32 ssid, u32 tsid, u16 tclass,
927 u32 requested, struct avc_audit_data *auditdata)
929 struct av_decision avd;
932 rc = avc_has_perm_noaudit(ssid, tsid, tclass, requested, 0, &avd);
933 avc_audit(ssid, tsid, tclass, requested, &avd, rc, auditdata);
937 u32 avc_policy_seqno(void)
939 return avc_cache.latest_notif;