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
40 } av_perm_to_string[] = {
41 #define S_(c, v, s) { c, v, s },
42 #include "av_perm_to_string.h"
47 static const char *class_to_string[] = {
49 #include "class_to_string.h"
54 #define TB_(s) static const char * s [] = {
57 #include "common_perm_to_string.h"
62 static const struct av_inherit
65 const char **common_pts;
68 #define S_(c, i, b) { c, common_##i##_perm_to_string, b },
69 #include "av_inherit.h"
73 #define AVC_CACHE_SLOTS 512
74 #define AVC_DEF_CACHE_THRESHOLD 512
75 #define AVC_CACHE_RECLAIM 16
77 #ifdef CONFIG_SECURITY_SELINUX_AVC_STATS
78 #define avc_cache_stats_incr(field) \
80 per_cpu(avc_cache_stats, get_cpu()).field++; \
84 #define avc_cache_stats_incr(field) do {} while (0)
91 struct av_decision avd;
92 atomic_t used; /* used recently */
97 struct list_head list;
98 struct rcu_head rhead;
102 struct list_head slots[AVC_CACHE_SLOTS];
103 spinlock_t slots_lock[AVC_CACHE_SLOTS]; /* lock for writes */
104 atomic_t lru_hint; /* LRU hint for reclaim scan */
105 atomic_t active_nodes;
106 u32 latest_notif; /* latest revocation notification */
109 struct avc_callback_node {
110 int (*callback) (u32 event, u32 ssid, u32 tsid,
111 u16 tclass, u32 perms,
118 struct avc_callback_node *next;
121 /* Exported via selinufs */
122 unsigned int avc_cache_threshold = AVC_DEF_CACHE_THRESHOLD;
124 #ifdef CONFIG_SECURITY_SELINUX_AVC_STATS
125 DEFINE_PER_CPU(struct avc_cache_stats, avc_cache_stats) = { 0 };
128 static struct avc_cache avc_cache;
129 static struct avc_callback_node *avc_callbacks;
130 static kmem_cache_t *avc_node_cachep;
132 static inline int avc_hash(u32 ssid, u32 tsid, u16 tclass)
134 return (ssid ^ (tsid<<2) ^ (tclass<<4)) & (AVC_CACHE_SLOTS - 1);
138 * avc_dump_av - Display an access vector in human-readable form.
139 * @tclass: target security class
142 static void avc_dump_av(struct audit_buffer *ab, u16 tclass, u32 av)
144 const char **common_pts = NULL;
149 audit_log_format(ab, " null");
153 for (i = 0; i < ARRAY_SIZE(av_inherit); i++) {
154 if (av_inherit[i].tclass == tclass) {
155 common_pts = av_inherit[i].common_pts;
156 common_base = av_inherit[i].common_base;
161 audit_log_format(ab, " {");
164 while (perm < common_base) {
166 audit_log_format(ab, " %s", common_pts[i]);
173 while (i < sizeof(av) * 8) {
175 for (i2 = 0; i2 < ARRAY_SIZE(av_perm_to_string); i2++) {
176 if ((av_perm_to_string[i2].tclass == tclass) &&
177 (av_perm_to_string[i2].value == perm))
180 if (i2 < ARRAY_SIZE(av_perm_to_string)) {
181 audit_log_format(ab, " %s",
182 av_perm_to_string[i2].name);
191 audit_log_format(ab, " 0x%x", av);
193 audit_log_format(ab, " }");
197 * avc_dump_query - Display a SID pair and a class in human-readable form.
198 * @ssid: source security identifier
199 * @tsid: target security identifier
200 * @tclass: target security class
202 static void avc_dump_query(struct audit_buffer *ab, u32 ssid, u32 tsid, u16 tclass)
208 rc = security_sid_to_context(ssid, &scontext, &scontext_len);
210 audit_log_format(ab, "ssid=%d", ssid);
212 audit_log_format(ab, "scontext=%s", scontext);
216 rc = security_sid_to_context(tsid, &scontext, &scontext_len);
218 audit_log_format(ab, " tsid=%d", tsid);
220 audit_log_format(ab, " tcontext=%s", scontext);
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, NULL);
245 audit_log(current->audit_context, 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))
316 list_for_each_entry(node, &avc_cache.slots[hvalue], list) {
317 if (atomic_dec_and_test(&node->ae.used)) {
318 /* Recently Unused */
319 avc_node_delete(node);
320 avc_cache_stats_incr(reclaims);
322 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_alloc(avc_node_cachep, SLAB_ATOMIC);
342 memset(node, 0, sizeof(*node));
343 INIT_RCU_HEAD(&node->rhead);
344 INIT_LIST_HEAD(&node->list);
345 atomic_set(&node->ae.used, 1);
346 avc_cache_stats_incr(allocations);
348 if (atomic_inc_return(&avc_cache.active_nodes) > avc_cache_threshold)
355 static void avc_node_populate(struct avc_node *node, u32 ssid, u32 tsid, u16 tclass, struct avc_entry *ae)
357 node->ae.ssid = ssid;
358 node->ae.tsid = tsid;
359 node->ae.tclass = tclass;
360 memcpy(&node->ae.avd, &ae->avd, sizeof(node->ae.avd));
363 static inline struct avc_node *avc_search_node(u32 ssid, u32 tsid, u16 tclass)
365 struct avc_node *node, *ret = NULL;
368 hvalue = avc_hash(ssid, tsid, tclass);
369 list_for_each_entry_rcu(node, &avc_cache.slots[hvalue], list) {
370 if (ssid == node->ae.ssid &&
371 tclass == node->ae.tclass &&
372 tsid == node->ae.tsid) {
384 if (atomic_read(&ret->ae.used) != 1)
385 atomic_set(&ret->ae.used, 1);
391 * avc_lookup - Look up an AVC entry.
392 * @ssid: source security identifier
393 * @tsid: target security identifier
394 * @tclass: target security class
395 * @requested: requested permissions, interpreted based on @tclass
397 * Look up an AVC entry that is valid for the
398 * @requested permissions between the SID pair
399 * (@ssid, @tsid), interpreting the permissions
400 * based on @tclass. If a valid AVC entry exists,
401 * then this function return the avc_node.
402 * Otherwise, this function returns NULL.
404 static struct avc_node *avc_lookup(u32 ssid, u32 tsid, u16 tclass, u32 requested)
406 struct avc_node *node;
408 avc_cache_stats_incr(lookups);
409 node = avc_search_node(ssid, tsid, tclass);
411 if (node && ((node->ae.avd.decided & requested) == requested)) {
412 avc_cache_stats_incr(hits);
417 avc_cache_stats_incr(misses);
422 static int avc_latest_notif_update(int seqno, int is_insert)
425 static DEFINE_SPINLOCK(notif_lock);
428 spin_lock_irqsave(¬if_lock, flag);
430 if (seqno < avc_cache.latest_notif) {
431 printk(KERN_WARNING "avc: seqno %d < latest_notif %d\n",
432 seqno, avc_cache.latest_notif);
436 if (seqno > avc_cache.latest_notif)
437 avc_cache.latest_notif = seqno;
439 spin_unlock_irqrestore(¬if_lock, flag);
445 * avc_insert - Insert an AVC entry.
446 * @ssid: source security identifier
447 * @tsid: target security identifier
448 * @tclass: target security class
451 * Insert an AVC entry for the SID pair
452 * (@ssid, @tsid) and class @tclass.
453 * The access vectors and the sequence number are
454 * normally provided by the security server in
455 * response to a security_compute_av() call. If the
456 * sequence number @ae->avd.seqno is not less than the latest
457 * revocation notification, then the function copies
458 * the access vectors into a cache entry, returns
459 * avc_node inserted. Otherwise, this function returns NULL.
461 static struct avc_node *avc_insert(u32 ssid, u32 tsid, u16 tclass, struct avc_entry *ae)
463 struct avc_node *pos, *node = NULL;
467 if (avc_latest_notif_update(ae->avd.seqno, 1))
470 node = avc_alloc_node();
472 hvalue = avc_hash(ssid, tsid, tclass);
473 avc_node_populate(node, ssid, tsid, tclass, ae);
475 spin_lock_irqsave(&avc_cache.slots_lock[hvalue], flag);
476 list_for_each_entry(pos, &avc_cache.slots[hvalue], list) {
477 if (pos->ae.ssid == ssid &&
478 pos->ae.tsid == tsid &&
479 pos->ae.tclass == tclass) {
480 avc_node_replace(node, pos);
484 list_add_rcu(&node->list, &avc_cache.slots[hvalue]);
486 spin_unlock_irqrestore(&avc_cache.slots_lock[hvalue], flag);
492 static inline void avc_print_ipv6_addr(struct audit_buffer *ab,
493 struct in6_addr *addr, u16 port,
494 char *name1, char *name2)
496 if (!ipv6_addr_any(addr))
497 audit_log_format(ab, " %s=%04x:%04x:%04x:%04x:%04x:"
498 "%04x:%04x:%04x", name1, NIP6(*addr));
500 audit_log_format(ab, " %s=%d", name2, ntohs(port));
503 static inline void avc_print_ipv4_addr(struct audit_buffer *ab, u32 addr,
504 u16 port, char *name1, char *name2)
507 audit_log_format(ab, " %s=%d.%d.%d.%d", name1, NIPQUAD(addr));
509 audit_log_format(ab, " %s=%d", name2, ntohs(port));
513 * avc_audit - Audit the granting or denial of permissions.
514 * @ssid: source security identifier
515 * @tsid: target security identifier
516 * @tclass: target security class
517 * @requested: requested permissions
518 * @avd: access vector decisions
519 * @result: result from avc_has_perm_noaudit
520 * @a: auxiliary audit data
522 * Audit the granting or denial of permissions in accordance
523 * with the policy. This function is typically called by
524 * avc_has_perm() after a permission check, but can also be
525 * called directly by callers who use avc_has_perm_noaudit()
526 * in order to separate the permission check from the auditing.
527 * For example, this separation is useful when the permission check must
528 * be performed under a lock, to allow the lock to be released
529 * before calling the auditing code.
531 void avc_audit(u32 ssid, u32 tsid,
532 u16 tclass, u32 requested,
533 struct av_decision *avd, int result, struct avc_audit_data *a)
535 struct task_struct *tsk = current;
536 struct inode *inode = NULL;
538 struct audit_buffer *ab;
540 denied = requested & ~avd->allowed;
543 if (!(audited & avd->auditdeny))
546 audited = denied = requested;
549 if (!(audited & avd->auditallow))
553 ab = audit_log_start(current->audit_context, AUDIT_AVC);
555 return; /* audit_panic has been called */
556 audit_log_format(ab, "avc: %s ", denied ? "denied" : "granted");
557 avc_dump_av(ab, tclass,audited);
558 audit_log_format(ab, " for ");
561 if (a->tsk && a->tsk->pid) {
562 audit_log_format(ab, " pid=%d comm=", tsk->pid);
563 audit_log_untrustedstring(ab, tsk->comm);
567 case AVC_AUDIT_DATA_IPC:
568 audit_log_format(ab, " key=%d", a->u.ipc_id);
570 case AVC_AUDIT_DATA_CAP:
571 audit_log_format(ab, " capability=%d", a->u.cap);
573 case AVC_AUDIT_DATA_FS:
574 if (a->u.fs.dentry) {
575 struct dentry *dentry = a->u.fs.dentry;
577 audit_log_d_path(ab, "path=", dentry,
580 audit_log_format(ab, " name=%s",
581 dentry->d_name.name);
583 inode = dentry->d_inode;
584 } else if (a->u.fs.inode) {
585 struct dentry *dentry;
586 inode = a->u.fs.inode;
587 dentry = d_find_alias(inode);
589 audit_log_format(ab, " name=%s",
590 dentry->d_name.name);
595 audit_log_format(ab, " dev=%s ino=%ld",
599 case AVC_AUDIT_DATA_NET:
601 struct sock *sk = a->u.net.sk;
606 switch (sk->sk_family) {
608 struct inet_sock *inet = inet_sk(sk);
610 avc_print_ipv4_addr(ab, inet->rcv_saddr,
613 avc_print_ipv4_addr(ab, inet->daddr,
619 struct inet_sock *inet = inet_sk(sk);
620 struct ipv6_pinfo *inet6 = inet6_sk(sk);
622 avc_print_ipv6_addr(ab, &inet6->rcv_saddr,
625 avc_print_ipv6_addr(ab, &inet6->daddr,
633 audit_log_d_path(ab, "path=",
639 len = u->addr->len-sizeof(short);
640 p = &u->addr->name->sun_path[0];
647 "path=@%*.*s", len-1,
653 switch (a->u.net.family) {
655 avc_print_ipv4_addr(ab, a->u.net.v4info.saddr,
658 avc_print_ipv4_addr(ab, a->u.net.v4info.daddr,
663 avc_print_ipv6_addr(ab, &a->u.net.v6info.saddr,
666 avc_print_ipv6_addr(ab, &a->u.net.v6info.daddr,
672 audit_log_format(ab, " netif=%s",
677 audit_log_format(ab, " ");
678 avc_dump_query(ab, ssid, tsid, tclass);
683 * avc_add_callback - Register a callback for security events.
684 * @callback: callback function
685 * @events: security events
686 * @ssid: source security identifier or %SECSID_WILD
687 * @tsid: target security identifier or %SECSID_WILD
688 * @tclass: target security class
689 * @perms: permissions
691 * Register a callback function for events in the set @events
692 * related to the SID pair (@ssid, @tsid) and
693 * and the permissions @perms, interpreting
694 * @perms based on @tclass. Returns %0 on success or
695 * -%ENOMEM if insufficient memory exists to add the callback.
697 int avc_add_callback(int (*callback)(u32 event, u32 ssid, u32 tsid,
698 u16 tclass, u32 perms,
700 u32 events, u32 ssid, u32 tsid,
701 u16 tclass, u32 perms)
703 struct avc_callback_node *c;
706 c = kmalloc(sizeof(*c), GFP_ATOMIC);
712 c->callback = callback;
717 c->next = avc_callbacks;
723 static inline int avc_sidcmp(u32 x, u32 y)
725 return (x == y || x == SECSID_WILD || y == SECSID_WILD);
729 * avc_update_node Update an AVC entry
730 * @event : Updating event
731 * @perms : Permission mask bits
732 * @ssid,@tsid,@tclass : identifier of an AVC entry
734 * if a valid AVC entry doesn't exist,this function returns -ENOENT.
735 * if kmalloc() called internal returns NULL, this function returns -ENOMEM.
736 * otherwise, this function update the AVC entry. The original AVC-entry object
737 * will release later by RCU.
739 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 ){
771 * Copy and replace original node.
774 avc_node_populate(node, ssid, tsid, tclass, &orig->ae);
777 case AVC_CALLBACK_GRANT:
778 node->ae.avd.allowed |= perms;
780 case AVC_CALLBACK_TRY_REVOKE:
781 case AVC_CALLBACK_REVOKE:
782 node->ae.avd.allowed &= ~perms;
784 case AVC_CALLBACK_AUDITALLOW_ENABLE:
785 node->ae.avd.auditallow |= perms;
787 case AVC_CALLBACK_AUDITALLOW_DISABLE:
788 node->ae.avd.auditallow &= ~perms;
790 case AVC_CALLBACK_AUDITDENY_ENABLE:
791 node->ae.avd.auditdeny |= perms;
793 case AVC_CALLBACK_AUDITDENY_DISABLE:
794 node->ae.avd.auditdeny &= ~perms;
797 avc_node_replace(node, orig);
799 spin_unlock_irqrestore(&avc_cache.slots_lock[hvalue], flag);
805 * avc_ss_reset - Flush the cache and revalidate migrated permissions.
806 * @seqno: policy sequence number
808 int avc_ss_reset(u32 seqno)
810 struct avc_callback_node *c;
813 struct avc_node *node;
815 for (i = 0; i < AVC_CACHE_SLOTS; i++) {
816 spin_lock_irqsave(&avc_cache.slots_lock[i], flag);
817 list_for_each_entry(node, &avc_cache.slots[i], list)
818 avc_node_delete(node);
819 spin_unlock_irqrestore(&avc_cache.slots_lock[i], flag);
822 for (c = avc_callbacks; c; c = c->next) {
823 if (c->events & AVC_CALLBACK_RESET) {
824 rc = c->callback(AVC_CALLBACK_RESET,
831 avc_latest_notif_update(seqno, 0);
837 * avc_has_perm_noaudit - Check permissions but perform no auditing.
838 * @ssid: source security identifier
839 * @tsid: target security identifier
840 * @tclass: target security class
841 * @requested: requested permissions, interpreted based on @tclass
842 * @avd: access vector decisions
844 * Check the AVC to determine whether the @requested permissions are granted
845 * for the SID pair (@ssid, @tsid), interpreting the permissions
846 * based on @tclass, and call the security server on a cache miss to obtain
847 * a new decision and add it to the cache. Return a copy of the decisions
848 * in @avd. Return %0 if all @requested permissions are granted,
849 * -%EACCES if any permissions are denied, or another -errno upon
850 * other errors. This function is typically called by avc_has_perm(),
851 * but may also be called directly to separate permission checking from
852 * auditing, e.g. in cases where a lock must be held for the check but
853 * should be released for the auditing.
855 int avc_has_perm_noaudit(u32 ssid, u32 tsid,
856 u16 tclass, u32 requested,
857 struct av_decision *avd)
859 struct avc_node *node;
860 struct avc_entry entry, *p_ae;
866 node = avc_lookup(ssid, tsid, tclass, requested);
869 rc = security_compute_av(ssid,tsid,tclass,requested,&entry.avd);
873 node = avc_insert(ssid,tsid,tclass,&entry);
876 p_ae = node ? &node->ae : &entry;
879 memcpy(avd, &p_ae->avd, sizeof(*avd));
881 denied = requested & ~(p_ae->avd.allowed);
883 if (!requested || denied) {
884 if (selinux_enforcing)
888 avc_update_node(AVC_CALLBACK_GRANT,requested,
898 * avc_has_perm - Check permissions and perform any appropriate auditing.
899 * @ssid: source security identifier
900 * @tsid: target security identifier
901 * @tclass: target security class
902 * @requested: requested permissions, interpreted based on @tclass
903 * @auditdata: auxiliary audit data
905 * Check the AVC to determine whether the @requested permissions are granted
906 * for the SID pair (@ssid, @tsid), interpreting the permissions
907 * based on @tclass, and call the security server on a cache miss to obtain
908 * a new decision and add it to the cache. Audit the granting or denial of
909 * permissions in accordance with the policy. Return %0 if all @requested
910 * permissions are granted, -%EACCES if any permissions are denied, or
911 * another -errno upon other errors.
913 int avc_has_perm(u32 ssid, u32 tsid, u16 tclass,
914 u32 requested, struct avc_audit_data *auditdata)
916 struct av_decision avd;
919 rc = avc_has_perm_noaudit(ssid, tsid, tclass, requested, &avd);
920 avc_audit(ssid, tsid, tclass, requested, &avd, rc, auditdata);