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; /* anchored in avc_cache->slots[i] */
96 struct rcu_head rhead;
100 struct list_head slots[AVC_CACHE_SLOTS]; /* head for avc_node->list */
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;
252 struct list_head *head;
258 for (i = 0; i < AVC_CACHE_SLOTS; i++) {
259 head = &avc_cache.slots[i];
260 if (!list_empty(head)) {
263 list_for_each_entry_rcu(node, head, list)
265 if (chain_len > max_chain_len)
266 max_chain_len = chain_len;
272 return scnprintf(page, PAGE_SIZE, "entries: %d\nbuckets used: %d/%d\n"
273 "longest chain: %d\n",
274 atomic_read(&avc_cache.active_nodes),
275 slots_used, AVC_CACHE_SLOTS, max_chain_len);
278 static void avc_node_free(struct rcu_head *rhead)
280 struct avc_node *node = container_of(rhead, struct avc_node, rhead);
281 kmem_cache_free(avc_node_cachep, node);
282 avc_cache_stats_incr(frees);
285 static void avc_node_delete(struct avc_node *node)
287 list_del_rcu(&node->list);
288 call_rcu(&node->rhead, avc_node_free);
289 atomic_dec(&avc_cache.active_nodes);
292 static void avc_node_kill(struct avc_node *node)
294 kmem_cache_free(avc_node_cachep, node);
295 avc_cache_stats_incr(frees);
296 atomic_dec(&avc_cache.active_nodes);
299 static void avc_node_replace(struct avc_node *new, struct avc_node *old)
301 list_replace_rcu(&old->list, &new->list);
302 call_rcu(&old->rhead, avc_node_free);
303 atomic_dec(&avc_cache.active_nodes);
306 static inline int avc_reclaim_node(void)
308 struct avc_node *node;
309 int hvalue, try, ecx;
311 struct list_head *head;
314 for (try = 0, ecx = 0; try < AVC_CACHE_SLOTS; try++) {
315 hvalue = atomic_inc_return(&avc_cache.lru_hint) & (AVC_CACHE_SLOTS - 1);
316 head = &avc_cache.slots[hvalue];
317 lock = &avc_cache.slots_lock[hvalue];
319 if (!spin_trylock_irqsave(lock, flags))
323 list_for_each_entry(node, head, list) {
324 avc_node_delete(node);
325 avc_cache_stats_incr(reclaims);
327 if (ecx >= AVC_CACHE_RECLAIM) {
329 spin_unlock_irqrestore(lock, flags);
334 spin_unlock_irqrestore(lock, flags);
340 static struct avc_node *avc_alloc_node(void)
342 struct avc_node *node;
344 node = kmem_cache_zalloc(avc_node_cachep, GFP_ATOMIC);
348 INIT_RCU_HEAD(&node->rhead);
349 INIT_LIST_HEAD(&node->list);
350 avc_cache_stats_incr(allocations);
352 if (atomic_inc_return(&avc_cache.active_nodes) > avc_cache_threshold)
359 static void avc_node_populate(struct avc_node *node, u32 ssid, u32 tsid, u16 tclass, struct av_decision *avd)
361 node->ae.ssid = ssid;
362 node->ae.tsid = tsid;
363 node->ae.tclass = tclass;
364 memcpy(&node->ae.avd, avd, sizeof(node->ae.avd));
367 static inline struct avc_node *avc_search_node(u32 ssid, u32 tsid, u16 tclass)
369 struct avc_node *node, *ret = NULL;
371 struct list_head *head;
373 hvalue = avc_hash(ssid, tsid, tclass);
374 head = &avc_cache.slots[hvalue];
375 list_for_each_entry_rcu(node, head, list) {
376 if (ssid == node->ae.ssid &&
377 tclass == node->ae.tclass &&
378 tsid == node->ae.tsid) {
388 * avc_lookup - Look up an AVC entry.
389 * @ssid: source security identifier
390 * @tsid: target security identifier
391 * @tclass: target security class
393 * Look up an AVC entry that is valid for the
394 * (@ssid, @tsid), interpreting the permissions
395 * based on @tclass. If a valid AVC entry exists,
396 * then this function return the avc_node.
397 * Otherwise, this function returns NULL.
399 static struct avc_node *avc_lookup(u32 ssid, u32 tsid, u16 tclass)
401 struct avc_node *node;
403 avc_cache_stats_incr(lookups);
404 node = avc_search_node(ssid, tsid, tclass);
407 avc_cache_stats_incr(hits);
409 avc_cache_stats_incr(misses);
414 static int avc_latest_notif_update(int seqno, int is_insert)
417 static DEFINE_SPINLOCK(notif_lock);
420 spin_lock_irqsave(¬if_lock, flag);
422 if (seqno < avc_cache.latest_notif) {
423 printk(KERN_WARNING "SELinux: avc: seqno %d < latest_notif %d\n",
424 seqno, avc_cache.latest_notif);
428 if (seqno > avc_cache.latest_notif)
429 avc_cache.latest_notif = seqno;
431 spin_unlock_irqrestore(¬if_lock, flag);
437 * avc_insert - Insert an AVC entry.
438 * @ssid: source security identifier
439 * @tsid: target security identifier
440 * @tclass: target security class
441 * @avd: resulting av decision
443 * Insert an AVC entry for the SID pair
444 * (@ssid, @tsid) and class @tclass.
445 * The access vectors and the sequence number are
446 * normally provided by the security server in
447 * response to a security_compute_av() call. If the
448 * sequence number @avd->seqno is not less than the latest
449 * revocation notification, then the function copies
450 * the access vectors into a cache entry, returns
451 * avc_node inserted. Otherwise, this function returns NULL.
453 static struct avc_node *avc_insert(u32 ssid, u32 tsid, u16 tclass, struct av_decision *avd)
455 struct avc_node *pos, *node = NULL;
459 if (avc_latest_notif_update(avd->seqno, 1))
462 node = avc_alloc_node();
464 struct list_head *head;
467 hvalue = avc_hash(ssid, tsid, tclass);
468 avc_node_populate(node, ssid, tsid, tclass, avd);
470 head = &avc_cache.slots[hvalue];
471 lock = &avc_cache.slots_lock[hvalue];
473 spin_lock_irqsave(lock, flag);
474 list_for_each_entry(pos, head, list) {
475 if (pos->ae.ssid == ssid &&
476 pos->ae.tsid == tsid &&
477 pos->ae.tclass == tclass) {
478 avc_node_replace(node, pos);
482 list_add_rcu(&node->list, head);
484 spin_unlock_irqrestore(lock, flag);
490 static inline void avc_print_ipv6_addr(struct audit_buffer *ab,
491 struct in6_addr *addr, __be16 port,
492 char *name1, char *name2)
494 if (!ipv6_addr_any(addr))
495 audit_log_format(ab, " %s=%pI6", name1, addr);
497 audit_log_format(ab, " %s=%d", name2, ntohs(port));
500 static inline void avc_print_ipv4_addr(struct audit_buffer *ab, __be32 addr,
501 __be16 port, char *name1, char *name2)
504 audit_log_format(ab, " %s=%pI4", name1, &addr);
506 audit_log_format(ab, " %s=%d", name2, ntohs(port));
510 * avc_audit - Audit the granting or denial of permissions.
511 * @ssid: source security identifier
512 * @tsid: target security identifier
513 * @tclass: target security class
514 * @requested: requested permissions
515 * @avd: access vector decisions
516 * @result: result from avc_has_perm_noaudit
517 * @a: auxiliary audit data
519 * Audit the granting or denial of permissions in accordance
520 * with the policy. This function is typically called by
521 * avc_has_perm() after a permission check, but can also be
522 * called directly by callers who use avc_has_perm_noaudit()
523 * in order to separate the permission check from the auditing.
524 * For example, this separation is useful when the permission check must
525 * be performed under a lock, to allow the lock to be released
526 * before calling the auditing code.
528 void avc_audit(u32 ssid, u32 tsid,
529 u16 tclass, u32 requested,
530 struct av_decision *avd, int result, struct avc_audit_data *a)
532 struct task_struct *tsk = current;
533 struct inode *inode = NULL;
535 struct audit_buffer *ab;
537 denied = requested & ~avd->allowed;
540 if (!(audited & avd->auditdeny))
543 audited = denied = requested;
546 if (!(audited & avd->auditallow))
550 ab = audit_log_start(current->audit_context, GFP_ATOMIC, AUDIT_AVC);
552 return; /* audit_panic has been called */
553 audit_log_format(ab, "avc: %s ", denied ? "denied" : "granted");
554 avc_dump_av(ab, tclass, audited);
555 audit_log_format(ab, " for ");
558 if (tsk && tsk->pid) {
559 audit_log_format(ab, " pid=%d comm=", tsk->pid);
560 audit_log_untrustedstring(ab, tsk->comm);
564 case AVC_AUDIT_DATA_IPC:
565 audit_log_format(ab, " key=%d", a->u.ipc_id);
567 case AVC_AUDIT_DATA_CAP:
568 audit_log_format(ab, " capability=%d", a->u.cap);
570 case AVC_AUDIT_DATA_FS:
571 if (a->u.fs.path.dentry) {
572 struct dentry *dentry = a->u.fs.path.dentry;
573 if (a->u.fs.path.mnt) {
574 audit_log_d_path(ab, "path=",
577 audit_log_format(ab, " name=");
578 audit_log_untrustedstring(ab, dentry->d_name.name);
580 inode = dentry->d_inode;
581 } else if (a->u.fs.inode) {
582 struct dentry *dentry;
583 inode = a->u.fs.inode;
584 dentry = d_find_alias(inode);
586 audit_log_format(ab, " name=");
587 audit_log_untrustedstring(ab, dentry->d_name.name);
592 audit_log_format(ab, " dev=%s ino=%lu",
596 case AVC_AUDIT_DATA_NET:
598 struct sock *sk = a->u.net.sk;
603 switch (sk->sk_family) {
605 struct inet_sock *inet = inet_sk(sk);
607 avc_print_ipv4_addr(ab, inet->rcv_saddr,
610 avc_print_ipv4_addr(ab, inet->daddr,
616 struct inet_sock *inet = inet_sk(sk);
617 struct ipv6_pinfo *inet6 = inet6_sk(sk);
619 avc_print_ipv6_addr(ab, &inet6->rcv_saddr,
622 avc_print_ipv6_addr(ab, &inet6->daddr,
634 audit_log_d_path(ab, "path=",
640 len = u->addr->len-sizeof(short);
641 p = &u->addr->name->sun_path[0];
642 audit_log_format(ab, " path=");
644 audit_log_untrustedstring(ab, p);
646 audit_log_n_hex(ab, p, len);
651 switch (a->u.net.family) {
653 avc_print_ipv4_addr(ab, a->u.net.v4info.saddr,
656 avc_print_ipv4_addr(ab, a->u.net.v4info.daddr,
661 avc_print_ipv6_addr(ab, &a->u.net.v6info.saddr,
664 avc_print_ipv6_addr(ab, &a->u.net.v6info.daddr,
669 if (a->u.net.netif > 0) {
670 struct net_device *dev;
672 /* NOTE: we always use init's namespace */
673 dev = dev_get_by_index(&init_net,
676 audit_log_format(ab, " netif=%s",
684 audit_log_format(ab, " ");
685 avc_dump_query(ab, ssid, tsid, tclass);
690 * avc_add_callback - Register a callback for security events.
691 * @callback: callback function
692 * @events: security events
693 * @ssid: source security identifier or %SECSID_WILD
694 * @tsid: target security identifier or %SECSID_WILD
695 * @tclass: target security class
696 * @perms: permissions
698 * Register a callback function for events in the set @events
699 * related to the SID pair (@ssid, @tsid) and
700 * and the permissions @perms, interpreting
701 * @perms based on @tclass. Returns %0 on success or
702 * -%ENOMEM if insufficient memory exists to add the callback.
704 int avc_add_callback(int (*callback)(u32 event, u32 ssid, u32 tsid,
705 u16 tclass, u32 perms,
707 u32 events, u32 ssid, u32 tsid,
708 u16 tclass, u32 perms)
710 struct avc_callback_node *c;
713 c = kmalloc(sizeof(*c), GFP_ATOMIC);
719 c->callback = callback;
724 c->next = avc_callbacks;
730 static inline int avc_sidcmp(u32 x, u32 y)
732 return (x == y || x == SECSID_WILD || y == SECSID_WILD);
736 * avc_update_node Update an AVC entry
737 * @event : Updating event
738 * @perms : Permission mask bits
739 * @ssid,@tsid,@tclass : identifier of an AVC entry
740 * @seqno : sequence number when decision was made
742 * if a valid AVC entry doesn't exist,this function returns -ENOENT.
743 * if kmalloc() called internal returns NULL, this function returns -ENOMEM.
744 * otherwise, this function update the AVC entry. The original AVC-entry object
745 * will release later by RCU.
747 static int avc_update_node(u32 event, u32 perms, u32 ssid, u32 tsid, u16 tclass,
752 struct avc_node *pos, *node, *orig = NULL;
753 struct list_head *head;
756 node = avc_alloc_node();
762 /* Lock the target slot */
763 hvalue = avc_hash(ssid, tsid, tclass);
765 head = &avc_cache.slots[hvalue];
766 lock = &avc_cache.slots_lock[hvalue];
768 spin_lock_irqsave(lock, flag);
770 list_for_each_entry(pos, head, list) {
771 if (ssid == pos->ae.ssid &&
772 tsid == pos->ae.tsid &&
773 tclass == pos->ae.tclass &&
774 seqno == pos->ae.avd.seqno){
787 * Copy and replace original node.
790 avc_node_populate(node, ssid, tsid, tclass, &orig->ae.avd);
793 case AVC_CALLBACK_GRANT:
794 node->ae.avd.allowed |= perms;
796 case AVC_CALLBACK_TRY_REVOKE:
797 case AVC_CALLBACK_REVOKE:
798 node->ae.avd.allowed &= ~perms;
800 case AVC_CALLBACK_AUDITALLOW_ENABLE:
801 node->ae.avd.auditallow |= perms;
803 case AVC_CALLBACK_AUDITALLOW_DISABLE:
804 node->ae.avd.auditallow &= ~perms;
806 case AVC_CALLBACK_AUDITDENY_ENABLE:
807 node->ae.avd.auditdeny |= perms;
809 case AVC_CALLBACK_AUDITDENY_DISABLE:
810 node->ae.avd.auditdeny &= ~perms;
813 avc_node_replace(node, orig);
815 spin_unlock_irqrestore(lock, flag);
821 * avc_ss_reset - Flush the cache and revalidate migrated permissions.
822 * @seqno: policy sequence number
824 int avc_ss_reset(u32 seqno)
826 struct avc_callback_node *c;
827 int i, rc = 0, tmprc;
829 struct avc_node *node;
830 struct list_head *head;
833 for (i = 0; i < AVC_CACHE_SLOTS; i++) {
834 head = &avc_cache.slots[i];
835 lock = &avc_cache.slots_lock[i];
837 spin_lock_irqsave(lock, flag);
839 * With preemptable RCU, the outer spinlock does not
840 * prevent RCU grace periods from ending.
843 list_for_each_entry(node, head, list)
844 avc_node_delete(node);
846 spin_unlock_irqrestore(lock, flag);
849 for (c = avc_callbacks; c; c = c->next) {
850 if (c->events & AVC_CALLBACK_RESET) {
851 tmprc = c->callback(AVC_CALLBACK_RESET,
853 /* save the first error encountered for the return
854 value and continue processing the callbacks */
860 avc_latest_notif_update(seqno, 0);
865 * avc_has_perm_noaudit - Check permissions but perform no auditing.
866 * @ssid: source security identifier
867 * @tsid: target security identifier
868 * @tclass: target security class
869 * @requested: requested permissions, interpreted based on @tclass
870 * @flags: AVC_STRICT or 0
871 * @avd: access vector decisions
873 * Check the AVC to determine whether the @requested permissions are granted
874 * for the SID pair (@ssid, @tsid), interpreting the permissions
875 * based on @tclass, and call the security server on a cache miss to obtain
876 * a new decision and add it to the cache. Return a copy of the decisions
877 * in @avd. Return %0 if all @requested permissions are granted,
878 * -%EACCES if any permissions are denied, or another -errno upon
879 * other errors. This function is typically called by avc_has_perm(),
880 * but may also be called directly to separate permission checking from
881 * auditing, e.g. in cases where a lock must be held for the check but
882 * should be released for the auditing.
884 int avc_has_perm_noaudit(u32 ssid, u32 tsid,
885 u16 tclass, u32 requested,
887 struct av_decision *in_avd)
889 struct avc_node *node;
890 struct av_decision avd_entry, *avd;
898 node = avc_lookup(ssid, tsid, tclass);
907 rc = security_compute_av(ssid, tsid, tclass, requested, avd);
911 node = avc_insert(ssid, tsid, tclass, avd);
914 memcpy(in_avd, &node->ae.avd, sizeof(*in_avd));
918 denied = requested & ~(avd->allowed);
921 if (flags & AVC_STRICT)
923 else if (!selinux_enforcing || security_permissive_sid(ssid))
924 avc_update_node(AVC_CALLBACK_GRANT, requested, ssid,
925 tsid, tclass, avd->seqno);
936 * avc_has_perm - Check permissions and perform any appropriate auditing.
937 * @ssid: source security identifier
938 * @tsid: target security identifier
939 * @tclass: target security class
940 * @requested: requested permissions, interpreted based on @tclass
941 * @auditdata: auxiliary audit data
943 * Check the AVC to determine whether the @requested permissions are granted
944 * for the SID pair (@ssid, @tsid), interpreting the permissions
945 * based on @tclass, and call the security server on a cache miss to obtain
946 * a new decision and add it to the cache. Audit the granting or denial of
947 * permissions in accordance with the policy. Return %0 if all @requested
948 * permissions are granted, -%EACCES if any permissions are denied, or
949 * another -errno upon other errors.
951 int avc_has_perm(u32 ssid, u32 tsid, u16 tclass,
952 u32 requested, struct avc_audit_data *auditdata)
954 struct av_decision avd;
957 rc = avc_has_perm_noaudit(ssid, tsid, tclass, requested, 0, &avd);
958 avc_audit(ssid, tsid, tclass, requested, &avd, rc, auditdata);
962 u32 avc_policy_seqno(void)
964 return avc_cache.latest_notif;