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_init - Initialize the AVC.
135 * Initialize the access vector cache.
137 void __init
avc_init(void)
139 avc_node_cachep
= kmem_cache_create("avc_node", sizeof(struct avc_node
),
140 0, SLAB_PANIC
, NULL
);
141 avc_xperms_cachep
= kmem_cache_create("avc_xperms_node",
142 sizeof(struct avc_xperms_node
),
143 0, SLAB_PANIC
, NULL
);
144 avc_xperms_decision_cachep
= kmem_cache_create(
145 "avc_xperms_decision_node",
146 sizeof(struct avc_xperms_decision_node
),
147 0, SLAB_PANIC
, NULL
);
148 avc_xperms_data_cachep
= kmem_cache_create("avc_xperms_data",
149 sizeof(struct extended_perms_data
),
150 0, SLAB_PANIC
, NULL
);
153 int avc_get_hash_stats(struct selinux_avc
*avc
, char *page
)
155 int i
, chain_len
, max_chain_len
, slots_used
;
156 struct avc_node
*node
;
157 struct hlist_head
*head
;
163 for (i
= 0; i
< AVC_CACHE_SLOTS
; i
++) {
164 head
= &avc
->avc_cache
.slots
[i
];
165 if (!hlist_empty(head
)) {
168 hlist_for_each_entry_rcu(node
, head
, list
)
170 if (chain_len
> max_chain_len
)
171 max_chain_len
= chain_len
;
177 return scnprintf(page
, PAGE_SIZE
, "entries: %d\nbuckets used: %d/%d\n"
178 "longest chain: %d\n",
179 atomic_read(&avc
->avc_cache
.active_nodes
),
180 slots_used
, AVC_CACHE_SLOTS
, max_chain_len
);
184 * using a linked list for extended_perms_decision lookup because the list is
185 * always small. i.e. less than 5, typically 1
187 static struct extended_perms_decision
*avc_xperms_decision_lookup(u8 driver
,
188 struct avc_xperms_node
*xp_node
)
190 struct avc_xperms_decision_node
*xpd_node
;
192 list_for_each_entry(xpd_node
, &xp_node
->xpd_head
, xpd_list
) {
193 if (xpd_node
->xpd
.driver
== driver
)
194 return &xpd_node
->xpd
;
199 static inline unsigned int
200 avc_xperms_has_perm(struct extended_perms_decision
*xpd
,
205 if ((which
== XPERMS_ALLOWED
) &&
206 (xpd
->used
& XPERMS_ALLOWED
))
207 rc
= security_xperm_test(xpd
->allowed
->p
, perm
);
208 else if ((which
== XPERMS_AUDITALLOW
) &&
209 (xpd
->used
& XPERMS_AUDITALLOW
))
210 rc
= security_xperm_test(xpd
->auditallow
->p
, perm
);
211 else if ((which
== XPERMS_DONTAUDIT
) &&
212 (xpd
->used
& XPERMS_DONTAUDIT
))
213 rc
= security_xperm_test(xpd
->dontaudit
->p
, perm
);
217 static void avc_xperms_allow_perm(struct avc_xperms_node
*xp_node
,
220 struct extended_perms_decision
*xpd
;
221 security_xperm_set(xp_node
->xp
.drivers
.p
, driver
);
222 xpd
= avc_xperms_decision_lookup(driver
, xp_node
);
223 if (xpd
&& xpd
->allowed
)
224 security_xperm_set(xpd
->allowed
->p
, perm
);
227 static void avc_xperms_decision_free(struct avc_xperms_decision_node
*xpd_node
)
229 struct extended_perms_decision
*xpd
;
231 xpd
= &xpd_node
->xpd
;
233 kmem_cache_free(avc_xperms_data_cachep
, xpd
->allowed
);
235 kmem_cache_free(avc_xperms_data_cachep
, xpd
->auditallow
);
237 kmem_cache_free(avc_xperms_data_cachep
, xpd
->dontaudit
);
238 kmem_cache_free(avc_xperms_decision_cachep
, xpd_node
);
241 static void avc_xperms_free(struct avc_xperms_node
*xp_node
)
243 struct avc_xperms_decision_node
*xpd_node
, *tmp
;
248 list_for_each_entry_safe(xpd_node
, tmp
, &xp_node
->xpd_head
, xpd_list
) {
249 list_del(&xpd_node
->xpd_list
);
250 avc_xperms_decision_free(xpd_node
);
252 kmem_cache_free(avc_xperms_cachep
, xp_node
);
255 static void avc_copy_xperms_decision(struct extended_perms_decision
*dest
,
256 struct extended_perms_decision
*src
)
258 dest
->driver
= src
->driver
;
259 dest
->used
= src
->used
;
260 if (dest
->used
& XPERMS_ALLOWED
)
261 memcpy(dest
->allowed
->p
, src
->allowed
->p
,
262 sizeof(src
->allowed
->p
));
263 if (dest
->used
& XPERMS_AUDITALLOW
)
264 memcpy(dest
->auditallow
->p
, src
->auditallow
->p
,
265 sizeof(src
->auditallow
->p
));
266 if (dest
->used
& XPERMS_DONTAUDIT
)
267 memcpy(dest
->dontaudit
->p
, src
->dontaudit
->p
,
268 sizeof(src
->dontaudit
->p
));
272 * similar to avc_copy_xperms_decision, but only copy decision
273 * information relevant to this perm
275 static inline void avc_quick_copy_xperms_decision(u8 perm
,
276 struct extended_perms_decision
*dest
,
277 struct extended_perms_decision
*src
)
280 * compute index of the u32 of the 256 bits (8 u32s) that contain this
285 dest
->used
= src
->used
;
286 if (dest
->used
& XPERMS_ALLOWED
)
287 dest
->allowed
->p
[i
] = src
->allowed
->p
[i
];
288 if (dest
->used
& XPERMS_AUDITALLOW
)
289 dest
->auditallow
->p
[i
] = src
->auditallow
->p
[i
];
290 if (dest
->used
& XPERMS_DONTAUDIT
)
291 dest
->dontaudit
->p
[i
] = src
->dontaudit
->p
[i
];
294 static struct avc_xperms_decision_node
295 *avc_xperms_decision_alloc(u8 which
)
297 struct avc_xperms_decision_node
*xpd_node
;
298 struct extended_perms_decision
*xpd
;
300 xpd_node
= kmem_cache_zalloc(avc_xperms_decision_cachep
, GFP_NOWAIT
);
304 xpd
= &xpd_node
->xpd
;
305 if (which
& XPERMS_ALLOWED
) {
306 xpd
->allowed
= kmem_cache_zalloc(avc_xperms_data_cachep
,
311 if (which
& XPERMS_AUDITALLOW
) {
312 xpd
->auditallow
= kmem_cache_zalloc(avc_xperms_data_cachep
,
314 if (!xpd
->auditallow
)
317 if (which
& XPERMS_DONTAUDIT
) {
318 xpd
->dontaudit
= kmem_cache_zalloc(avc_xperms_data_cachep
,
325 avc_xperms_decision_free(xpd_node
);
329 static int avc_add_xperms_decision(struct avc_node
*node
,
330 struct extended_perms_decision
*src
)
332 struct avc_xperms_decision_node
*dest_xpd
;
334 node
->ae
.xp_node
->xp
.len
++;
335 dest_xpd
= avc_xperms_decision_alloc(src
->used
);
338 avc_copy_xperms_decision(&dest_xpd
->xpd
, src
);
339 list_add(&dest_xpd
->xpd_list
, &node
->ae
.xp_node
->xpd_head
);
343 static struct avc_xperms_node
*avc_xperms_alloc(void)
345 struct avc_xperms_node
*xp_node
;
347 xp_node
= kmem_cache_zalloc(avc_xperms_cachep
, GFP_NOWAIT
);
350 INIT_LIST_HEAD(&xp_node
->xpd_head
);
354 static int avc_xperms_populate(struct avc_node
*node
,
355 struct avc_xperms_node
*src
)
357 struct avc_xperms_node
*dest
;
358 struct avc_xperms_decision_node
*dest_xpd
;
359 struct avc_xperms_decision_node
*src_xpd
;
361 if (src
->xp
.len
== 0)
363 dest
= avc_xperms_alloc();
367 memcpy(dest
->xp
.drivers
.p
, src
->xp
.drivers
.p
, sizeof(dest
->xp
.drivers
.p
));
368 dest
->xp
.len
= src
->xp
.len
;
370 /* for each source xpd allocate a destination xpd and copy */
371 list_for_each_entry(src_xpd
, &src
->xpd_head
, xpd_list
) {
372 dest_xpd
= avc_xperms_decision_alloc(src_xpd
->xpd
.used
);
375 avc_copy_xperms_decision(&dest_xpd
->xpd
, &src_xpd
->xpd
);
376 list_add(&dest_xpd
->xpd_list
, &dest
->xpd_head
);
378 node
->ae
.xp_node
= dest
;
381 avc_xperms_free(dest
);
386 static inline u32
avc_xperms_audit_required(u32 requested
,
387 struct av_decision
*avd
,
388 struct extended_perms_decision
*xpd
,
395 denied
= requested
& ~avd
->allowed
;
396 if (unlikely(denied
)) {
397 audited
= denied
& avd
->auditdeny
;
398 if (audited
&& xpd
) {
399 if (avc_xperms_has_perm(xpd
, perm
, XPERMS_DONTAUDIT
))
400 audited
&= ~requested
;
403 audited
= denied
= requested
;
405 audited
= requested
& avd
->auditallow
;
406 if (audited
&& xpd
) {
407 if (!avc_xperms_has_perm(xpd
, perm
, XPERMS_AUDITALLOW
))
408 audited
&= ~requested
;
416 static inline int avc_xperms_audit(struct selinux_state
*state
,
417 u32 ssid
, u32 tsid
, u16 tclass
,
418 u32 requested
, struct av_decision
*avd
,
419 struct extended_perms_decision
*xpd
,
421 struct common_audit_data
*ad
)
425 audited
= avc_xperms_audit_required(
426 requested
, avd
, xpd
, perm
, result
, &denied
);
427 if (likely(!audited
))
429 return slow_avc_audit(state
, ssid
, tsid
, tclass
, requested
,
430 audited
, denied
, result
, ad
, 0);
433 static void avc_node_free(struct rcu_head
*rhead
)
435 struct avc_node
*node
= container_of(rhead
, struct avc_node
, rhead
);
436 avc_xperms_free(node
->ae
.xp_node
);
437 kmem_cache_free(avc_node_cachep
, node
);
438 avc_cache_stats_incr(frees
);
441 static void avc_node_delete(struct selinux_avc
*avc
, struct avc_node
*node
)
443 hlist_del_rcu(&node
->list
);
444 call_rcu(&node
->rhead
, avc_node_free
);
445 atomic_dec(&avc
->avc_cache
.active_nodes
);
448 static void avc_node_kill(struct selinux_avc
*avc
, struct avc_node
*node
)
450 avc_xperms_free(node
->ae
.xp_node
);
451 kmem_cache_free(avc_node_cachep
, node
);
452 avc_cache_stats_incr(frees
);
453 atomic_dec(&avc
->avc_cache
.active_nodes
);
456 static void avc_node_replace(struct selinux_avc
*avc
,
457 struct avc_node
*new, struct avc_node
*old
)
459 hlist_replace_rcu(&old
->list
, &new->list
);
460 call_rcu(&old
->rhead
, avc_node_free
);
461 atomic_dec(&avc
->avc_cache
.active_nodes
);
464 static inline int avc_reclaim_node(struct selinux_avc
*avc
)
466 struct avc_node
*node
;
467 int hvalue
, try, ecx
;
469 struct hlist_head
*head
;
472 for (try = 0, ecx
= 0; try < AVC_CACHE_SLOTS
; try++) {
473 hvalue
= atomic_inc_return(&avc
->avc_cache
.lru_hint
) &
474 (AVC_CACHE_SLOTS
- 1);
475 head
= &avc
->avc_cache
.slots
[hvalue
];
476 lock
= &avc
->avc_cache
.slots_lock
[hvalue
];
478 if (!spin_trylock_irqsave(lock
, flags
))
482 hlist_for_each_entry(node
, head
, list
) {
483 avc_node_delete(avc
, node
);
484 avc_cache_stats_incr(reclaims
);
486 if (ecx
>= AVC_CACHE_RECLAIM
) {
488 spin_unlock_irqrestore(lock
, flags
);
493 spin_unlock_irqrestore(lock
, flags
);
499 static struct avc_node
*avc_alloc_node(struct selinux_avc
*avc
)
501 struct avc_node
*node
;
503 node
= kmem_cache_zalloc(avc_node_cachep
, GFP_NOWAIT
);
507 INIT_HLIST_NODE(&node
->list
);
508 avc_cache_stats_incr(allocations
);
510 if (atomic_inc_return(&avc
->avc_cache
.active_nodes
) >
511 avc
->avc_cache_threshold
)
512 avc_reclaim_node(avc
);
518 static void avc_node_populate(struct avc_node
*node
, u32 ssid
, u32 tsid
, u16 tclass
, struct av_decision
*avd
)
520 node
->ae
.ssid
= ssid
;
521 node
->ae
.tsid
= tsid
;
522 node
->ae
.tclass
= tclass
;
523 memcpy(&node
->ae
.avd
, avd
, sizeof(node
->ae
.avd
));
526 static inline struct avc_node
*avc_search_node(struct selinux_avc
*avc
,
527 u32 ssid
, u32 tsid
, u16 tclass
)
529 struct avc_node
*node
, *ret
= NULL
;
531 struct hlist_head
*head
;
533 hvalue
= avc_hash(ssid
, tsid
, tclass
);
534 head
= &avc
->avc_cache
.slots
[hvalue
];
535 hlist_for_each_entry_rcu(node
, head
, list
) {
536 if (ssid
== node
->ae
.ssid
&&
537 tclass
== node
->ae
.tclass
&&
538 tsid
== node
->ae
.tsid
) {
548 * avc_lookup - Look up an AVC entry.
549 * @ssid: source security identifier
550 * @tsid: target security identifier
551 * @tclass: target security class
553 * Look up an AVC entry that is valid for the
554 * (@ssid, @tsid), interpreting the permissions
555 * based on @tclass. If a valid AVC entry exists,
556 * then this function returns the avc_node.
557 * Otherwise, this function returns NULL.
559 static struct avc_node
*avc_lookup(struct selinux_avc
*avc
,
560 u32 ssid
, u32 tsid
, u16 tclass
)
562 struct avc_node
*node
;
564 avc_cache_stats_incr(lookups
);
565 node
= avc_search_node(avc
, ssid
, tsid
, tclass
);
570 avc_cache_stats_incr(misses
);
574 static int avc_latest_notif_update(struct selinux_avc
*avc
,
575 int seqno
, int is_insert
)
578 static DEFINE_SPINLOCK(notif_lock
);
581 spin_lock_irqsave(¬if_lock
, flag
);
583 if (seqno
< avc
->avc_cache
.latest_notif
) {
584 pr_warn("SELinux: avc: seqno %d < latest_notif %d\n",
585 seqno
, avc
->avc_cache
.latest_notif
);
589 if (seqno
> avc
->avc_cache
.latest_notif
)
590 avc
->avc_cache
.latest_notif
= seqno
;
592 spin_unlock_irqrestore(¬if_lock
, flag
);
598 * avc_insert - Insert an AVC entry.
599 * @ssid: source security identifier
600 * @tsid: target security identifier
601 * @tclass: target security class
602 * @avd: resulting av decision
603 * @xp_node: resulting extended permissions
605 * Insert an AVC entry for the SID pair
606 * (@ssid, @tsid) and class @tclass.
607 * The access vectors and the sequence number are
608 * normally provided by the security server in
609 * response to a security_compute_av() call. If the
610 * sequence number @avd->seqno is not less than the latest
611 * revocation notification, then the function copies
612 * the access vectors into a cache entry, returns
613 * avc_node inserted. Otherwise, this function returns NULL.
615 static struct avc_node
*avc_insert(struct selinux_avc
*avc
,
616 u32 ssid
, u32 tsid
, u16 tclass
,
617 struct av_decision
*avd
,
618 struct avc_xperms_node
*xp_node
)
620 struct avc_node
*pos
, *node
= NULL
;
624 if (avc_latest_notif_update(avc
, avd
->seqno
, 1))
627 node
= avc_alloc_node(avc
);
629 struct hlist_head
*head
;
633 hvalue
= avc_hash(ssid
, tsid
, tclass
);
634 avc_node_populate(node
, ssid
, tsid
, tclass
, avd
);
635 rc
= avc_xperms_populate(node
, xp_node
);
637 kmem_cache_free(avc_node_cachep
, node
);
640 head
= &avc
->avc_cache
.slots
[hvalue
];
641 lock
= &avc
->avc_cache
.slots_lock
[hvalue
];
643 spin_lock_irqsave(lock
, flag
);
644 hlist_for_each_entry(pos
, head
, list
) {
645 if (pos
->ae
.ssid
== ssid
&&
646 pos
->ae
.tsid
== tsid
&&
647 pos
->ae
.tclass
== tclass
) {
648 avc_node_replace(avc
, node
, pos
);
652 hlist_add_head_rcu(&node
->list
, head
);
654 spin_unlock_irqrestore(lock
, flag
);
661 * avc_audit_pre_callback - SELinux specific information
662 * will be called by generic audit code
663 * @ab: the audit buffer
666 static void avc_audit_pre_callback(struct audit_buffer
*ab
, void *a
)
668 struct common_audit_data
*ad
= a
;
669 struct selinux_audit_data
*sad
= ad
->selinux_audit_data
;
670 u32 av
= sad
->audited
;
674 audit_log_format(ab
, "avc: %s ", sad
->denied
? "denied" : "granted");
677 audit_log_format(ab
, " null");
681 perms
= secclass_map
[sad
->tclass
-1].perms
;
683 audit_log_format(ab
, " {");
686 while (i
< (sizeof(av
) * 8)) {
687 if ((perm
& av
) && perms
[i
]) {
688 audit_log_format(ab
, " %s", perms
[i
]);
696 audit_log_format(ab
, " 0x%x", av
);
698 audit_log_format(ab
, " } for ");
702 * avc_audit_post_callback - SELinux specific information
703 * will be called by generic audit code
704 * @ab: the audit buffer
707 static void avc_audit_post_callback(struct audit_buffer
*ab
, void *a
)
709 struct common_audit_data
*ad
= a
;
710 struct selinux_audit_data
*sad
= ad
->selinux_audit_data
;
715 rc
= security_sid_to_context(sad
->state
, sad
->ssid
, &scontext
,
718 audit_log_format(ab
, " ssid=%d", sad
->ssid
);
720 audit_log_format(ab
, " scontext=%s", scontext
);
724 rc
= security_sid_to_context(sad
->state
, sad
->tsid
, &scontext
,
727 audit_log_format(ab
, " tsid=%d", sad
->tsid
);
729 audit_log_format(ab
, " tcontext=%s", scontext
);
733 audit_log_format(ab
, " tclass=%s", secclass_map
[sad
->tclass
-1].name
);
736 audit_log_format(ab
, " permissive=%u", sad
->result
? 0 : 1);
738 /* in case of invalid context report also the actual context string */
739 rc
= security_sid_to_context_inval(sad
->state
, sad
->ssid
, &scontext
,
741 if (!rc
&& scontext
) {
742 audit_log_format(ab
, " srawcon=%s", scontext
);
746 rc
= security_sid_to_context_inval(sad
->state
, sad
->tsid
, &scontext
,
748 if (!rc
&& scontext
) {
749 audit_log_format(ab
, " trawcon=%s", scontext
);
754 /* This is the slow part of avc audit with big stack footprint */
755 noinline
int slow_avc_audit(struct selinux_state
*state
,
756 u32 ssid
, u32 tsid
, u16 tclass
,
757 u32 requested
, u32 audited
, u32 denied
, int result
,
758 struct common_audit_data
*a
,
761 struct common_audit_data stack_data
;
762 struct selinux_audit_data sad
;
764 if (WARN_ON(!tclass
|| tclass
>= ARRAY_SIZE(secclass_map
)))
769 a
->type
= LSM_AUDIT_DATA_NONE
;
773 * When in a RCU walk do the audit on the RCU retry. This is because
774 * the collection of the dname in an inode audit message is not RCU
775 * safe. Note this may drop some audits when the situation changes
776 * during retry. However this is logically just as if the operation
777 * happened a little later.
779 if ((a
->type
== LSM_AUDIT_DATA_INODE
) &&
780 (flags
& MAY_NOT_BLOCK
))
784 sad
.requested
= requested
;
787 sad
.audited
= audited
;
792 a
->selinux_audit_data
= &sad
;
794 common_lsm_audit(a
, avc_audit_pre_callback
, avc_audit_post_callback
);
799 * avc_add_callback - Register a callback for security events.
800 * @callback: callback function
801 * @events: security events
803 * Register a callback function for events in the set @events.
804 * Returns %0 on success or -%ENOMEM if insufficient memory
805 * exists to add the callback.
807 int __init
avc_add_callback(int (*callback
)(u32 event
), u32 events
)
809 struct avc_callback_node
*c
;
812 c
= kmalloc(sizeof(*c
), GFP_KERNEL
);
818 c
->callback
= callback
;
820 c
->next
= avc_callbacks
;
827 * avc_update_node Update an AVC entry
828 * @event : Updating event
829 * @perms : Permission mask bits
830 * @ssid,@tsid,@tclass : identifier of an AVC entry
831 * @seqno : sequence number when decision was made
832 * @xpd: extended_perms_decision to be added to the node
833 * @flags: the AVC_* flags, e.g. AVC_NONBLOCKING, AVC_EXTENDED_PERMS, or 0.
835 * if a valid AVC entry doesn't exist,this function returns -ENOENT.
836 * if kmalloc() called internal returns NULL, this function returns -ENOMEM.
837 * otherwise, this function updates the AVC entry. The original AVC-entry object
838 * will release later by RCU.
840 static int avc_update_node(struct selinux_avc
*avc
,
841 u32 event
, u32 perms
, u8 driver
, u8 xperm
, u32 ssid
,
842 u32 tsid
, u16 tclass
, u32 seqno
,
843 struct extended_perms_decision
*xpd
,
848 struct avc_node
*pos
, *node
, *orig
= NULL
;
849 struct hlist_head
*head
;
853 * If we are in a non-blocking code path, e.g. VFS RCU walk,
854 * then we must not add permissions to a cache entry
855 * because we cannot safely audit the denial. Otherwise,
856 * during the subsequent blocking retry (e.g. VFS ref walk), we
857 * will find the permissions already granted in the cache entry
858 * and won't audit anything at all, leading to silent denials in
859 * permissive mode that only appear when in enforcing mode.
861 * See the corresponding handling in slow_avc_audit(), and the
862 * logic in selinux_inode_permission for the MAY_NOT_BLOCK flag,
863 * which is transliterated into AVC_NONBLOCKING.
865 if (flags
& AVC_NONBLOCKING
)
868 node
= avc_alloc_node(avc
);
874 /* Lock the target slot */
875 hvalue
= avc_hash(ssid
, tsid
, tclass
);
877 head
= &avc
->avc_cache
.slots
[hvalue
];
878 lock
= &avc
->avc_cache
.slots_lock
[hvalue
];
880 spin_lock_irqsave(lock
, flag
);
882 hlist_for_each_entry(pos
, head
, list
) {
883 if (ssid
== pos
->ae
.ssid
&&
884 tsid
== pos
->ae
.tsid
&&
885 tclass
== pos
->ae
.tclass
&&
886 seqno
== pos
->ae
.avd
.seqno
){
894 avc_node_kill(avc
, node
);
899 * Copy and replace original node.
902 avc_node_populate(node
, ssid
, tsid
, tclass
, &orig
->ae
.avd
);
904 if (orig
->ae
.xp_node
) {
905 rc
= avc_xperms_populate(node
, orig
->ae
.xp_node
);
907 kmem_cache_free(avc_node_cachep
, node
);
913 case AVC_CALLBACK_GRANT
:
914 node
->ae
.avd
.allowed
|= perms
;
915 if (node
->ae
.xp_node
&& (flags
& AVC_EXTENDED_PERMS
))
916 avc_xperms_allow_perm(node
->ae
.xp_node
, driver
, xperm
);
918 case AVC_CALLBACK_TRY_REVOKE
:
919 case AVC_CALLBACK_REVOKE
:
920 node
->ae
.avd
.allowed
&= ~perms
;
922 case AVC_CALLBACK_AUDITALLOW_ENABLE
:
923 node
->ae
.avd
.auditallow
|= perms
;
925 case AVC_CALLBACK_AUDITALLOW_DISABLE
:
926 node
->ae
.avd
.auditallow
&= ~perms
;
928 case AVC_CALLBACK_AUDITDENY_ENABLE
:
929 node
->ae
.avd
.auditdeny
|= perms
;
931 case AVC_CALLBACK_AUDITDENY_DISABLE
:
932 node
->ae
.avd
.auditdeny
&= ~perms
;
934 case AVC_CALLBACK_ADD_XPERMS
:
935 avc_add_xperms_decision(node
, xpd
);
938 avc_node_replace(avc
, node
, orig
);
940 spin_unlock_irqrestore(lock
, flag
);
946 * avc_flush - Flush the cache
948 static void avc_flush(struct selinux_avc
*avc
)
950 struct hlist_head
*head
;
951 struct avc_node
*node
;
956 for (i
= 0; i
< AVC_CACHE_SLOTS
; i
++) {
957 head
= &avc
->avc_cache
.slots
[i
];
958 lock
= &avc
->avc_cache
.slots_lock
[i
];
960 spin_lock_irqsave(lock
, flag
);
962 * With preemptable RCU, the outer spinlock does not
963 * prevent RCU grace periods from ending.
966 hlist_for_each_entry(node
, head
, list
)
967 avc_node_delete(avc
, node
);
969 spin_unlock_irqrestore(lock
, flag
);
974 * avc_ss_reset - Flush the cache and revalidate migrated permissions.
975 * @seqno: policy sequence number
977 int avc_ss_reset(struct selinux_avc
*avc
, u32 seqno
)
979 struct avc_callback_node
*c
;
984 for (c
= avc_callbacks
; c
; c
= c
->next
) {
985 if (c
->events
& AVC_CALLBACK_RESET
) {
986 tmprc
= c
->callback(AVC_CALLBACK_RESET
);
987 /* save the first error encountered for the return
988 value and continue processing the callbacks */
994 avc_latest_notif_update(avc
, seqno
, 0);
999 * Slow-path helper function for avc_has_perm_noaudit,
1000 * when the avc_node lookup fails. We get called with
1001 * the RCU read lock held, and need to return with it
1002 * still held, but drop if for the security compute.
1004 * Don't inline this, since it's the slow-path and just
1005 * results in a bigger stack frame.
1008 struct avc_node
*avc_compute_av(struct selinux_state
*state
,
1010 u16 tclass
, struct av_decision
*avd
,
1011 struct avc_xperms_node
*xp_node
)
1014 INIT_LIST_HEAD(&xp_node
->xpd_head
);
1015 security_compute_av(state
, ssid
, tsid
, tclass
, avd
, &xp_node
->xp
);
1017 return avc_insert(state
->avc
, ssid
, tsid
, tclass
, avd
, xp_node
);
1020 static noinline
int avc_denied(struct selinux_state
*state
,
1022 u16 tclass
, u32 requested
,
1023 u8 driver
, u8 xperm
, unsigned int flags
,
1024 struct av_decision
*avd
)
1026 if (flags
& AVC_STRICT
)
1029 if (enforcing_enabled(state
) &&
1030 !(avd
->flags
& AVD_FLAGS_PERMISSIVE
))
1033 avc_update_node(state
->avc
, AVC_CALLBACK_GRANT
, requested
, driver
,
1034 xperm
, ssid
, tsid
, tclass
, avd
->seqno
, NULL
, flags
);
1039 * The avc extended permissions logic adds an additional 256 bits of
1040 * permissions to an avc node when extended permissions for that node are
1041 * specified in the avtab. If the additional 256 permissions is not adequate,
1042 * as-is the case with ioctls, then multiple may be chained together and the
1043 * driver field is used to specify which set contains the permission.
1045 int avc_has_extended_perms(struct selinux_state
*state
,
1046 u32 ssid
, u32 tsid
, u16 tclass
, u32 requested
,
1047 u8 driver
, u8 xperm
, struct common_audit_data
*ad
)
1049 struct avc_node
*node
;
1050 struct av_decision avd
;
1052 struct extended_perms_decision local_xpd
;
1053 struct extended_perms_decision
*xpd
= NULL
;
1054 struct extended_perms_data allowed
;
1055 struct extended_perms_data auditallow
;
1056 struct extended_perms_data dontaudit
;
1057 struct avc_xperms_node local_xp_node
;
1058 struct avc_xperms_node
*xp_node
;
1061 xp_node
= &local_xp_node
;
1062 if (WARN_ON(!requested
))
1067 node
= avc_lookup(state
->avc
, ssid
, tsid
, tclass
);
1068 if (unlikely(!node
)) {
1069 node
= avc_compute_av(state
, ssid
, tsid
, tclass
, &avd
, xp_node
);
1071 memcpy(&avd
, &node
->ae
.avd
, sizeof(avd
));
1072 xp_node
= node
->ae
.xp_node
;
1074 /* if extended permissions are not defined, only consider av_decision */
1075 if (!xp_node
|| !xp_node
->xp
.len
)
1078 local_xpd
.allowed
= &allowed
;
1079 local_xpd
.auditallow
= &auditallow
;
1080 local_xpd
.dontaudit
= &dontaudit
;
1082 xpd
= avc_xperms_decision_lookup(driver
, xp_node
);
1083 if (unlikely(!xpd
)) {
1085 * Compute the extended_perms_decision only if the driver
1088 if (!security_xperm_test(xp_node
->xp
.drivers
.p
, driver
)) {
1089 avd
.allowed
&= ~requested
;
1093 security_compute_xperms_decision(state
, ssid
, tsid
, tclass
,
1094 driver
, &local_xpd
);
1096 avc_update_node(state
->avc
, AVC_CALLBACK_ADD_XPERMS
, requested
,
1097 driver
, xperm
, ssid
, tsid
, tclass
, avd
.seqno
,
1100 avc_quick_copy_xperms_decision(xperm
, &local_xpd
, xpd
);
1104 if (!avc_xperms_has_perm(xpd
, xperm
, XPERMS_ALLOWED
))
1105 avd
.allowed
&= ~requested
;
1108 denied
= requested
& ~(avd
.allowed
);
1109 if (unlikely(denied
))
1110 rc
= avc_denied(state
, ssid
, tsid
, tclass
, requested
,
1111 driver
, xperm
, AVC_EXTENDED_PERMS
, &avd
);
1115 rc2
= avc_xperms_audit(state
, ssid
, tsid
, tclass
, requested
,
1116 &avd
, xpd
, xperm
, rc
, ad
);
1123 * avc_has_perm_noaudit - Check permissions but perform no auditing.
1124 * @ssid: source security identifier
1125 * @tsid: target security identifier
1126 * @tclass: target security class
1127 * @requested: requested permissions, interpreted based on @tclass
1128 * @flags: AVC_STRICT, AVC_NONBLOCKING, or 0
1129 * @avd: access vector decisions
1131 * Check the AVC to determine whether the @requested permissions are granted
1132 * for the SID pair (@ssid, @tsid), interpreting the permissions
1133 * based on @tclass, and call the security server on a cache miss to obtain
1134 * a new decision and add it to the cache. Return a copy of the decisions
1135 * in @avd. Return %0 if all @requested permissions are granted,
1136 * -%EACCES if any permissions are denied, or another -errno upon
1137 * other errors. This function is typically called by avc_has_perm(),
1138 * but may also be called directly to separate permission checking from
1139 * auditing, e.g. in cases where a lock must be held for the check but
1140 * should be released for the auditing.
1142 inline int avc_has_perm_noaudit(struct selinux_state
*state
,
1144 u16 tclass
, u32 requested
,
1146 struct av_decision
*avd
)
1148 struct avc_node
*node
;
1149 struct avc_xperms_node xp_node
;
1153 if (WARN_ON(!requested
))
1158 node
= avc_lookup(state
->avc
, ssid
, tsid
, tclass
);
1159 if (unlikely(!node
))
1160 node
= avc_compute_av(state
, ssid
, tsid
, tclass
, avd
, &xp_node
);
1162 memcpy(avd
, &node
->ae
.avd
, sizeof(*avd
));
1164 denied
= requested
& ~(avd
->allowed
);
1165 if (unlikely(denied
))
1166 rc
= avc_denied(state
, ssid
, tsid
, tclass
, requested
, 0, 0,
1174 * avc_has_perm - Check permissions and perform any appropriate auditing.
1175 * @ssid: source security identifier
1176 * @tsid: target security identifier
1177 * @tclass: target security class
1178 * @requested: requested permissions, interpreted based on @tclass
1179 * @auditdata: auxiliary audit data
1181 * Check the AVC to determine whether the @requested permissions are granted
1182 * for the SID pair (@ssid, @tsid), interpreting the permissions
1183 * based on @tclass, and call the security server on a cache miss to obtain
1184 * a new decision and add it to the cache. Audit the granting or denial of
1185 * permissions in accordance with the policy. Return %0 if all @requested
1186 * permissions are granted, -%EACCES if any permissions are denied, or
1187 * another -errno upon other errors.
1189 int avc_has_perm(struct selinux_state
*state
, u32 ssid
, u32 tsid
, u16 tclass
,
1190 u32 requested
, struct common_audit_data
*auditdata
)
1192 struct av_decision avd
;
1195 rc
= avc_has_perm_noaudit(state
, ssid
, tsid
, tclass
, requested
, 0,
1198 rc2
= avc_audit(state
, ssid
, tsid
, tclass
, requested
, &avd
, rc
,
1205 u32
avc_policy_seqno(struct selinux_state
*state
)
1207 return state
->avc
->avc_cache
.latest_notif
;
1210 void avc_disable(void)
1213 * If you are looking at this because you have realized that we are
1214 * not destroying the avc_node_cachep it might be easy to fix, but
1215 * I don't know the memory barrier semantics well enough to know. It's
1216 * possible that some other task dereferenced security_ops when
1217 * it still pointed to selinux operations. If that is the case it's
1218 * possible that it is about to use the avc and is about to need the
1219 * avc_node_cachep. I know I could wrap the security.c security_ops call
1220 * in an rcu_lock, but seriously, it's not worth it. Instead I just flush
1221 * the cache and get that memory back.
1223 if (avc_node_cachep
) {
1224 avc_flush(selinux_state
.avc
);
1225 /* kmem_cache_destroy(avc_node_cachep); */