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1/*
2 * Implementation of the kernel access vector cache (AVC).
3 *
4 * Authors: Stephen Smalley, <sds@epoch.ncsc.mil>
5 * James Morris <jmorris@redhat.com>
6 *
7 * Update: KaiGai, Kohei <kaigai@ak.jp.nec.com>
8 * Replaced the avc_lock spinlock by RCU.
9 *
10 * Copyright (C) 2003 Red Hat, Inc., James Morris <jmorris@redhat.com>
11 *
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.
15 */
16#include <linux/types.h>
17#include <linux/stddef.h>
18#include <linux/kernel.h>
19#include <linux/slab.h>
20#include <linux/fs.h>
21#include <linux/dcache.h>
22#include <linux/init.h>
23#include <linux/skbuff.h>
24#include <linux/percpu.h>
25#include <net/sock.h>
26#include <linux/un.h>
27#include <net/af_unix.h>
28#include <linux/ip.h>
29#include <linux/audit.h>
30#include <linux/ipv6.h>
31#include <net/ipv6.h>
32#include "avc.h"
33#include "avc_ss.h"
34#include "classmap.h"
35
36#define AVC_CACHE_SLOTS 512
37#define AVC_DEF_CACHE_THRESHOLD 512
38#define AVC_CACHE_RECLAIM 16
39
40#ifdef CONFIG_SECURITY_SELINUX_AVC_STATS
41#define avc_cache_stats_incr(field) this_cpu_inc(avc_cache_stats.field)
42#else
43#define avc_cache_stats_incr(field) do {} while (0)
44#endif
45
46struct avc_entry {
47 u32 ssid;
48 u32 tsid;
49 u16 tclass;
50 struct av_decision avd;
51};
52
53struct avc_node {
54 struct avc_entry ae;
55 struct hlist_node list; /* anchored in avc_cache->slots[i] */
56 struct rcu_head rhead;
57};
58
59struct avc_cache {
60 struct hlist_head slots[AVC_CACHE_SLOTS]; /* head for avc_node->list */
61 spinlock_t slots_lock[AVC_CACHE_SLOTS]; /* lock for writes */
62 atomic_t lru_hint; /* LRU hint for reclaim scan */
63 atomic_t active_nodes;
64 u32 latest_notif; /* latest revocation notification */
65};
66
67struct avc_callback_node {
68 int (*callback) (u32 event);
69 u32 events;
70 struct avc_callback_node *next;
71};
72
73/* Exported via selinufs */
74unsigned int avc_cache_threshold = AVC_DEF_CACHE_THRESHOLD;
75
76#ifdef CONFIG_SECURITY_SELINUX_AVC_STATS
77DEFINE_PER_CPU(struct avc_cache_stats, avc_cache_stats) = { 0 };
78#endif
79
80static struct avc_cache avc_cache;
81static struct avc_callback_node *avc_callbacks;
82static struct kmem_cache *avc_node_cachep;
83
84static inline int avc_hash(u32 ssid, u32 tsid, u16 tclass)
85{
86 return (ssid ^ (tsid<<2) ^ (tclass<<4)) & (AVC_CACHE_SLOTS - 1);
87}
88
89/**
90 * avc_dump_av - Display an access vector in human-readable form.
91 * @tclass: target security class
92 * @av: access vector
93 */
94static void avc_dump_av(struct audit_buffer *ab, u16 tclass, u32 av)
95{
96 const char **perms;
97 int i, perm;
98
99 if (av == 0) {
100 audit_log_format(ab, " null");
101 return;
102 }
103
104 perms = secclass_map[tclass-1].perms;
105
106 audit_log_format(ab, " {");
107 i = 0;
108 perm = 1;
109 while (i < (sizeof(av) * 8)) {
110 if ((perm & av) && perms[i]) {
111 audit_log_format(ab, " %s", perms[i]);
112 av &= ~perm;
113 }
114 i++;
115 perm <<= 1;
116 }
117
118 if (av)
119 audit_log_format(ab, " 0x%x", av);
120
121 audit_log_format(ab, " }");
122}
123
124/**
125 * avc_dump_query - Display a SID pair and a class in human-readable form.
126 * @ssid: source security identifier
127 * @tsid: target security identifier
128 * @tclass: target security class
129 */
130static void avc_dump_query(struct audit_buffer *ab, u32 ssid, u32 tsid, u16 tclass)
131{
132 int rc;
133 char *scontext;
134 u32 scontext_len;
135
136 rc = security_sid_to_context(ssid, &scontext, &scontext_len);
137 if (rc)
138 audit_log_format(ab, "ssid=%d", ssid);
139 else {
140 audit_log_format(ab, "scontext=%s", scontext);
141 kfree(scontext);
142 }
143
144 rc = security_sid_to_context(tsid, &scontext, &scontext_len);
145 if (rc)
146 audit_log_format(ab, " tsid=%d", tsid);
147 else {
148 audit_log_format(ab, " tcontext=%s", scontext);
149 kfree(scontext);
150 }
151
152 BUG_ON(tclass >= ARRAY_SIZE(secclass_map));
153 audit_log_format(ab, " tclass=%s", secclass_map[tclass-1].name);
154}
155
156/**
157 * avc_init - Initialize the AVC.
158 *
159 * Initialize the access vector cache.
160 */
161void __init avc_init(void)
162{
163 int i;
164
165 for (i = 0; i < AVC_CACHE_SLOTS; i++) {
166 INIT_HLIST_HEAD(&avc_cache.slots[i]);
167 spin_lock_init(&avc_cache.slots_lock[i]);
168 }
169 atomic_set(&avc_cache.active_nodes, 0);
170 atomic_set(&avc_cache.lru_hint, 0);
171
172 avc_node_cachep = kmem_cache_create("avc_node", sizeof(struct avc_node),
173 0, SLAB_PANIC, NULL);
174
175 audit_log(current->audit_context, GFP_KERNEL, AUDIT_KERNEL, "AVC INITIALIZED\n");
176}
177
178int avc_get_hash_stats(char *page)
179{
180 int i, chain_len, max_chain_len, slots_used;
181 struct avc_node *node;
182 struct hlist_head *head;
183
184 rcu_read_lock();
185
186 slots_used = 0;
187 max_chain_len = 0;
188 for (i = 0; i < AVC_CACHE_SLOTS; i++) {
189 head = &avc_cache.slots[i];
190 if (!hlist_empty(head)) {
191 slots_used++;
192 chain_len = 0;
193 hlist_for_each_entry_rcu(node, head, list)
194 chain_len++;
195 if (chain_len > max_chain_len)
196 max_chain_len = chain_len;
197 }
198 }
199
200 rcu_read_unlock();
201
202 return scnprintf(page, PAGE_SIZE, "entries: %d\nbuckets used: %d/%d\n"
203 "longest chain: %d\n",
204 atomic_read(&avc_cache.active_nodes),
205 slots_used, AVC_CACHE_SLOTS, max_chain_len);
206}
207
208static void avc_node_free(struct rcu_head *rhead)
209{
210 struct avc_node *node = container_of(rhead, struct avc_node, rhead);
211 kmem_cache_free(avc_node_cachep, node);
212 avc_cache_stats_incr(frees);
213}
214
215static void avc_node_delete(struct avc_node *node)
216{
217 hlist_del_rcu(&node->list);
218 call_rcu(&node->rhead, avc_node_free);
219 atomic_dec(&avc_cache.active_nodes);
220}
221
222static void avc_node_kill(struct avc_node *node)
223{
224 kmem_cache_free(avc_node_cachep, node);
225 avc_cache_stats_incr(frees);
226 atomic_dec(&avc_cache.active_nodes);
227}
228
229static void avc_node_replace(struct avc_node *new, struct avc_node *old)
230{
231 hlist_replace_rcu(&old->list, &new->list);
232 call_rcu(&old->rhead, avc_node_free);
233 atomic_dec(&avc_cache.active_nodes);
234}
235
236static inline int avc_reclaim_node(void)
237{
238 struct avc_node *node;
239 int hvalue, try, ecx;
240 unsigned long flags;
241 struct hlist_head *head;
242 spinlock_t *lock;
243
244 for (try = 0, ecx = 0; try < AVC_CACHE_SLOTS; try++) {
245 hvalue = atomic_inc_return(&avc_cache.lru_hint) & (AVC_CACHE_SLOTS - 1);
246 head = &avc_cache.slots[hvalue];
247 lock = &avc_cache.slots_lock[hvalue];
248
249 if (!spin_trylock_irqsave(lock, flags))
250 continue;
251
252 rcu_read_lock();
253 hlist_for_each_entry(node, head, list) {
254 avc_node_delete(node);
255 avc_cache_stats_incr(reclaims);
256 ecx++;
257 if (ecx >= AVC_CACHE_RECLAIM) {
258 rcu_read_unlock();
259 spin_unlock_irqrestore(lock, flags);
260 goto out;
261 }
262 }
263 rcu_read_unlock();
264 spin_unlock_irqrestore(lock, flags);
265 }
266out:
267 return ecx;
268}
269
270static struct avc_node *avc_alloc_node(void)
271{
272 struct avc_node *node;
273
274 node = kmem_cache_zalloc(avc_node_cachep, GFP_ATOMIC|__GFP_NOMEMALLOC);
275 if (!node)
276 goto out;
277
278 INIT_HLIST_NODE(&node->list);
279 avc_cache_stats_incr(allocations);
280
281 if (atomic_inc_return(&avc_cache.active_nodes) > avc_cache_threshold)
282 avc_reclaim_node();
283
284out:
285 return node;
286}
287
288static void avc_node_populate(struct avc_node *node, u32 ssid, u32 tsid, u16 tclass, struct av_decision *avd)
289{
290 node->ae.ssid = ssid;
291 node->ae.tsid = tsid;
292 node->ae.tclass = tclass;
293 memcpy(&node->ae.avd, avd, sizeof(node->ae.avd));
294}
295
296static inline struct avc_node *avc_search_node(u32 ssid, u32 tsid, u16 tclass)
297{
298 struct avc_node *node, *ret = NULL;
299 int hvalue;
300 struct hlist_head *head;
301
302 hvalue = avc_hash(ssid, tsid, tclass);
303 head = &avc_cache.slots[hvalue];
304 hlist_for_each_entry_rcu(node, head, list) {
305 if (ssid == node->ae.ssid &&
306 tclass == node->ae.tclass &&
307 tsid == node->ae.tsid) {
308 ret = node;
309 break;
310 }
311 }
312
313 return ret;
314}
315
316/**
317 * avc_lookup - Look up an AVC entry.
318 * @ssid: source security identifier
319 * @tsid: target security identifier
320 * @tclass: target security class
321 *
322 * Look up an AVC entry that is valid for the
323 * (@ssid, @tsid), interpreting the permissions
324 * based on @tclass. If a valid AVC entry exists,
325 * then this function returns the avc_node.
326 * Otherwise, this function returns NULL.
327 */
328static struct avc_node *avc_lookup(u32 ssid, u32 tsid, u16 tclass)
329{
330 struct avc_node *node;
331
332 avc_cache_stats_incr(lookups);
333 node = avc_search_node(ssid, tsid, tclass);
334
335 if (node)
336 return node;
337
338 avc_cache_stats_incr(misses);
339 return NULL;
340}
341
342static int avc_latest_notif_update(int seqno, int is_insert)
343{
344 int ret = 0;
345 static DEFINE_SPINLOCK(notif_lock);
346 unsigned long flag;
347
348 spin_lock_irqsave(¬if_lock, flag);
349 if (is_insert) {
350 if (seqno < avc_cache.latest_notif) {
351 printk(KERN_WARNING "SELinux: avc: seqno %d < latest_notif %d\n",
352 seqno, avc_cache.latest_notif);
353 ret = -EAGAIN;
354 }
355 } else {
356 if (seqno > avc_cache.latest_notif)
357 avc_cache.latest_notif = seqno;
358 }
359 spin_unlock_irqrestore(¬if_lock, flag);
360
361 return ret;
362}
363
364/**
365 * avc_insert - Insert an AVC entry.
366 * @ssid: source security identifier
367 * @tsid: target security identifier
368 * @tclass: target security class
369 * @avd: resulting av decision
370 *
371 * Insert an AVC entry for the SID pair
372 * (@ssid, @tsid) and class @tclass.
373 * The access vectors and the sequence number are
374 * normally provided by the security server in
375 * response to a security_compute_av() call. If the
376 * sequence number @avd->seqno is not less than the latest
377 * revocation notification, then the function copies
378 * the access vectors into a cache entry, returns
379 * avc_node inserted. Otherwise, this function returns NULL.
380 */
381static struct avc_node *avc_insert(u32 ssid, u32 tsid, u16 tclass, struct av_decision *avd)
382{
383 struct avc_node *pos, *node = NULL;
384 int hvalue;
385 unsigned long flag;
386
387 if (avc_latest_notif_update(avd->seqno, 1))
388 goto out;
389
390 node = avc_alloc_node();
391 if (node) {
392 struct hlist_head *head;
393 spinlock_t *lock;
394
395 hvalue = avc_hash(ssid, tsid, tclass);
396 avc_node_populate(node, ssid, tsid, tclass, avd);
397
398 head = &avc_cache.slots[hvalue];
399 lock = &avc_cache.slots_lock[hvalue];
400
401 spin_lock_irqsave(lock, flag);
402 hlist_for_each_entry(pos, head, list) {
403 if (pos->ae.ssid == ssid &&
404 pos->ae.tsid == tsid &&
405 pos->ae.tclass == tclass) {
406 avc_node_replace(node, pos);
407 goto found;
408 }
409 }
410 hlist_add_head_rcu(&node->list, head);
411found:
412 spin_unlock_irqrestore(lock, flag);
413 }
414out:
415 return node;
416}
417
418/**
419 * avc_audit_pre_callback - SELinux specific information
420 * will be called by generic audit code
421 * @ab: the audit buffer
422 * @a: audit_data
423 */
424static void avc_audit_pre_callback(struct audit_buffer *ab, void *a)
425{
426 struct common_audit_data *ad = a;
427 audit_log_format(ab, "avc: %s ",
428 ad->selinux_audit_data->denied ? "denied" : "granted");
429 avc_dump_av(ab, ad->selinux_audit_data->tclass,
430 ad->selinux_audit_data->audited);
431 audit_log_format(ab, " for ");
432}
433
434/**
435 * avc_audit_post_callback - SELinux specific information
436 * will be called by generic audit code
437 * @ab: the audit buffer
438 * @a: audit_data
439 */
440static void avc_audit_post_callback(struct audit_buffer *ab, void *a)
441{
442 struct common_audit_data *ad = a;
443 audit_log_format(ab, " ");
444 avc_dump_query(ab, ad->selinux_audit_data->ssid,
445 ad->selinux_audit_data->tsid,
446 ad->selinux_audit_data->tclass);
447}
448
449/* This is the slow part of avc audit with big stack footprint */
450noinline int slow_avc_audit(u32 ssid, u32 tsid, u16 tclass,
451 u32 requested, u32 audited, u32 denied,
452 struct common_audit_data *a,
453 unsigned flags)
454{
455 struct common_audit_data stack_data;
456 struct selinux_audit_data sad;
457
458 if (!a) {
459 a = &stack_data;
460 a->type = LSM_AUDIT_DATA_NONE;
461 }
462
463 /*
464 * When in a RCU walk do the audit on the RCU retry. This is because
465 * the collection of the dname in an inode audit message is not RCU
466 * safe. Note this may drop some audits when the situation changes
467 * during retry. However this is logically just as if the operation
468 * happened a little later.
469 */
470 if ((a->type == LSM_AUDIT_DATA_INODE) &&
471 (flags & MAY_NOT_BLOCK))
472 return -ECHILD;
473
474 sad.tclass = tclass;
475 sad.requested = requested;
476 sad.ssid = ssid;
477 sad.tsid = tsid;
478 sad.audited = audited;
479 sad.denied = denied;
480
481 a->selinux_audit_data = &sad;
482
483 common_lsm_audit(a, avc_audit_pre_callback, avc_audit_post_callback);
484 return 0;
485}
486
487/**
488 * avc_add_callback - Register a callback for security events.
489 * @callback: callback function
490 * @events: security events
491 *
492 * Register a callback function for events in the set @events.
493 * Returns %0 on success or -%ENOMEM if insufficient memory
494 * exists to add the callback.
495 */
496int __init avc_add_callback(int (*callback)(u32 event), u32 events)
497{
498 struct avc_callback_node *c;
499 int rc = 0;
500
501 c = kmalloc(sizeof(*c), GFP_KERNEL);
502 if (!c) {
503 rc = -ENOMEM;
504 goto out;
505 }
506
507 c->callback = callback;
508 c->events = events;
509 c->next = avc_callbacks;
510 avc_callbacks = c;
511out:
512 return rc;
513}
514
515static inline int avc_sidcmp(u32 x, u32 y)
516{
517 return (x == y || x == SECSID_WILD || y == SECSID_WILD);
518}
519
520/**
521 * avc_update_node Update an AVC entry
522 * @event : Updating event
523 * @perms : Permission mask bits
524 * @ssid,@tsid,@tclass : identifier of an AVC entry
525 * @seqno : sequence number when decision was made
526 *
527 * if a valid AVC entry doesn't exist,this function returns -ENOENT.
528 * if kmalloc() called internal returns NULL, this function returns -ENOMEM.
529 * otherwise, this function updates the AVC entry. The original AVC-entry object
530 * will release later by RCU.
531 */
532static int avc_update_node(u32 event, u32 perms, u32 ssid, u32 tsid, u16 tclass,
533 u32 seqno)
534{
535 int hvalue, rc = 0;
536 unsigned long flag;
537 struct avc_node *pos, *node, *orig = NULL;
538 struct hlist_head *head;
539 spinlock_t *lock;
540
541 node = avc_alloc_node();
542 if (!node) {
543 rc = -ENOMEM;
544 goto out;
545 }
546
547 /* Lock the target slot */
548 hvalue = avc_hash(ssid, tsid, tclass);
549
550 head = &avc_cache.slots[hvalue];
551 lock = &avc_cache.slots_lock[hvalue];
552
553 spin_lock_irqsave(lock, flag);
554
555 hlist_for_each_entry(pos, head, list) {
556 if (ssid == pos->ae.ssid &&
557 tsid == pos->ae.tsid &&
558 tclass == pos->ae.tclass &&
559 seqno == pos->ae.avd.seqno){
560 orig = pos;
561 break;
562 }
563 }
564
565 if (!orig) {
566 rc = -ENOENT;
567 avc_node_kill(node);
568 goto out_unlock;
569 }
570
571 /*
572 * Copy and replace original node.
573 */
574
575 avc_node_populate(node, ssid, tsid, tclass, &orig->ae.avd);
576
577 switch (event) {
578 case AVC_CALLBACK_GRANT:
579 node->ae.avd.allowed |= perms;
580 break;
581 case AVC_CALLBACK_TRY_REVOKE:
582 case AVC_CALLBACK_REVOKE:
583 node->ae.avd.allowed &= ~perms;
584 break;
585 case AVC_CALLBACK_AUDITALLOW_ENABLE:
586 node->ae.avd.auditallow |= perms;
587 break;
588 case AVC_CALLBACK_AUDITALLOW_DISABLE:
589 node->ae.avd.auditallow &= ~perms;
590 break;
591 case AVC_CALLBACK_AUDITDENY_ENABLE:
592 node->ae.avd.auditdeny |= perms;
593 break;
594 case AVC_CALLBACK_AUDITDENY_DISABLE:
595 node->ae.avd.auditdeny &= ~perms;
596 break;
597 }
598 avc_node_replace(node, orig);
599out_unlock:
600 spin_unlock_irqrestore(lock, flag);
601out:
602 return rc;
603}
604
605/**
606 * avc_flush - Flush the cache
607 */
608static void avc_flush(void)
609{
610 struct hlist_head *head;
611 struct avc_node *node;
612 spinlock_t *lock;
613 unsigned long flag;
614 int i;
615
616 for (i = 0; i < AVC_CACHE_SLOTS; i++) {
617 head = &avc_cache.slots[i];
618 lock = &avc_cache.slots_lock[i];
619
620 spin_lock_irqsave(lock, flag);
621 /*
622 * With preemptable RCU, the outer spinlock does not
623 * prevent RCU grace periods from ending.
624 */
625 rcu_read_lock();
626 hlist_for_each_entry(node, head, list)
627 avc_node_delete(node);
628 rcu_read_unlock();
629 spin_unlock_irqrestore(lock, flag);
630 }
631}
632
633/**
634 * avc_ss_reset - Flush the cache and revalidate migrated permissions.
635 * @seqno: policy sequence number
636 */
637int avc_ss_reset(u32 seqno)
638{
639 struct avc_callback_node *c;
640 int rc = 0, tmprc;
641
642 avc_flush();
643
644 for (c = avc_callbacks; c; c = c->next) {
645 if (c->events & AVC_CALLBACK_RESET) {
646 tmprc = c->callback(AVC_CALLBACK_RESET);
647 /* save the first error encountered for the return
648 value and continue processing the callbacks */
649 if (!rc)
650 rc = tmprc;
651 }
652 }
653
654 avc_latest_notif_update(seqno, 0);
655 return rc;
656}
657
658/*
659 * Slow-path helper function for avc_has_perm_noaudit,
660 * when the avc_node lookup fails. We get called with
661 * the RCU read lock held, and need to return with it
662 * still held, but drop if for the security compute.
663 *
664 * Don't inline this, since it's the slow-path and just
665 * results in a bigger stack frame.
666 */
667static noinline struct avc_node *avc_compute_av(u32 ssid, u32 tsid,
668 u16 tclass, struct av_decision *avd)
669{
670 rcu_read_unlock();
671 security_compute_av(ssid, tsid, tclass, avd);
672 rcu_read_lock();
673 return avc_insert(ssid, tsid, tclass, avd);
674}
675
676static noinline int avc_denied(u32 ssid, u32 tsid,
677 u16 tclass, u32 requested,
678 unsigned flags,
679 struct av_decision *avd)
680{
681 if (flags & AVC_STRICT)
682 return -EACCES;
683
684 if (selinux_enforcing && !(avd->flags & AVD_FLAGS_PERMISSIVE))
685 return -EACCES;
686
687 avc_update_node(AVC_CALLBACK_GRANT, requested, ssid,
688 tsid, tclass, avd->seqno);
689 return 0;
690}
691
692
693/**
694 * avc_has_perm_noaudit - Check permissions but perform no auditing.
695 * @ssid: source security identifier
696 * @tsid: target security identifier
697 * @tclass: target security class
698 * @requested: requested permissions, interpreted based on @tclass
699 * @flags: AVC_STRICT or 0
700 * @avd: access vector decisions
701 *
702 * Check the AVC to determine whether the @requested permissions are granted
703 * for the SID pair (@ssid, @tsid), interpreting the permissions
704 * based on @tclass, and call the security server on a cache miss to obtain
705 * a new decision and add it to the cache. Return a copy of the decisions
706 * in @avd. Return %0 if all @requested permissions are granted,
707 * -%EACCES if any permissions are denied, or another -errno upon
708 * other errors. This function is typically called by avc_has_perm(),
709 * but may also be called directly to separate permission checking from
710 * auditing, e.g. in cases where a lock must be held for the check but
711 * should be released for the auditing.
712 */
713inline int avc_has_perm_noaudit(u32 ssid, u32 tsid,
714 u16 tclass, u32 requested,
715 unsigned flags,
716 struct av_decision *avd)
717{
718 struct avc_node *node;
719 int rc = 0;
720 u32 denied;
721
722 BUG_ON(!requested);
723
724 rcu_read_lock();
725
726 node = avc_lookup(ssid, tsid, tclass);
727 if (unlikely(!node)) {
728 node = avc_compute_av(ssid, tsid, tclass, avd);
729 } else {
730 memcpy(avd, &node->ae.avd, sizeof(*avd));
731 avd = &node->ae.avd;
732 }
733
734 denied = requested & ~(avd->allowed);
735 if (unlikely(denied))
736 rc = avc_denied(ssid, tsid, tclass, requested, flags, avd);
737
738 rcu_read_unlock();
739 return rc;
740}
741
742/**
743 * avc_has_perm - Check permissions and perform any appropriate auditing.
744 * @ssid: source security identifier
745 * @tsid: target security identifier
746 * @tclass: target security class
747 * @requested: requested permissions, interpreted based on @tclass
748 * @auditdata: auxiliary audit data
749 *
750 * Check the AVC to determine whether the @requested permissions are granted
751 * for the SID pair (@ssid, @tsid), interpreting the permissions
752 * based on @tclass, and call the security server on a cache miss to obtain
753 * a new decision and add it to the cache. Audit the granting or denial of
754 * permissions in accordance with the policy. Return %0 if all @requested
755 * permissions are granted, -%EACCES if any permissions are denied, or
756 * another -errno upon other errors.
757 */
758int avc_has_perm(u32 ssid, u32 tsid, u16 tclass,
759 u32 requested, struct common_audit_data *auditdata)
760{
761 struct av_decision avd;
762 int rc, rc2;
763
764 rc = avc_has_perm_noaudit(ssid, tsid, tclass, requested, 0, &avd);
765
766 rc2 = avc_audit(ssid, tsid, tclass, requested, &avd, rc, auditdata);
767 if (rc2)
768 return rc2;
769 return rc;
770}
771
772u32 avc_policy_seqno(void)
773{
774 return avc_cache.latest_notif;
775}
776
777void avc_disable(void)
778{
779 /*
780 * If you are looking at this because you have realized that we are
781 * not destroying the avc_node_cachep it might be easy to fix, but
782 * I don't know the memory barrier semantics well enough to know. It's
783 * possible that some other task dereferenced security_ops when
784 * it still pointed to selinux operations. If that is the case it's
785 * possible that it is about to use the avc and is about to need the
786 * avc_node_cachep. I know I could wrap the security.c security_ops call
787 * in an rcu_lock, but seriously, it's not worth it. Instead I just flush
788 * the cache and get that memory back.
789 */
790 if (avc_node_cachep) {
791 avc_flush();
792 /* kmem_cache_destroy(avc_node_cachep); */
793 }
794}
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Implementation of the kernel access vector cache (AVC).
4 *
5 * Authors: Stephen Smalley, <stephen.smalley.work@gmail.com>
6 * James Morris <jmorris@redhat.com>
7 *
8 * Update: KaiGai, Kohei <kaigai@ak.jp.nec.com>
9 * Replaced the avc_lock spinlock by RCU.
10 *
11 * Copyright (C) 2003 Red Hat, Inc., James Morris <jmorris@redhat.com>
12 */
13#include <linux/types.h>
14#include <linux/stddef.h>
15#include <linux/kernel.h>
16#include <linux/slab.h>
17#include <linux/fs.h>
18#include <linux/dcache.h>
19#include <linux/init.h>
20#include <linux/skbuff.h>
21#include <linux/percpu.h>
22#include <linux/list.h>
23#include <net/sock.h>
24#include <linux/un.h>
25#include <net/af_unix.h>
26#include <linux/ip.h>
27#include <linux/audit.h>
28#include <linux/ipv6.h>
29#include <net/ipv6.h>
30#include "avc.h"
31#include "avc_ss.h"
32#include "classmap.h"
33
34#define CREATE_TRACE_POINTS
35#include <trace/events/avc.h>
36
37#define AVC_CACHE_SLOTS 512
38#define AVC_DEF_CACHE_THRESHOLD 512
39#define AVC_CACHE_RECLAIM 16
40
41#ifdef CONFIG_SECURITY_SELINUX_AVC_STATS
42#define avc_cache_stats_incr(field) this_cpu_inc(avc_cache_stats.field)
43#else
44#define avc_cache_stats_incr(field) do {} while (0)
45#endif
46
47struct avc_entry {
48 u32 ssid;
49 u32 tsid;
50 u16 tclass;
51 struct av_decision avd;
52 struct avc_xperms_node *xp_node;
53};
54
55struct avc_node {
56 struct avc_entry ae;
57 struct hlist_node list; /* anchored in avc_cache->slots[i] */
58 struct rcu_head rhead;
59};
60
61struct avc_xperms_decision_node {
62 struct extended_perms_decision xpd;
63 struct list_head xpd_list; /* list of extended_perms_decision */
64};
65
66struct avc_xperms_node {
67 struct extended_perms xp;
68 struct list_head xpd_head; /* list head of extended_perms_decision */
69};
70
71struct avc_cache {
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 */
77};
78
79struct avc_callback_node {
80 int (*callback) (u32 event);
81 u32 events;
82 struct avc_callback_node *next;
83};
84
85#ifdef CONFIG_SECURITY_SELINUX_AVC_STATS
86DEFINE_PER_CPU(struct avc_cache_stats, avc_cache_stats) = { 0 };
87#endif
88
89struct selinux_avc {
90 unsigned int avc_cache_threshold;
91 struct avc_cache avc_cache;
92};
93
94static struct selinux_avc selinux_avc;
95
96void selinux_avc_init(void)
97{
98 int i;
99
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]);
104 }
105 atomic_set(&selinux_avc.avc_cache.active_nodes, 0);
106 atomic_set(&selinux_avc.avc_cache.lru_hint, 0);
107}
108
109unsigned int avc_get_cache_threshold(void)
110{
111 return selinux_avc.avc_cache_threshold;
112}
113
114void avc_set_cache_threshold(unsigned int cache_threshold)
115{
116 selinux_avc.avc_cache_threshold = cache_threshold;
117}
118
119static struct avc_callback_node *avc_callbacks __ro_after_init;
120static struct kmem_cache *avc_node_cachep __ro_after_init;
121static struct kmem_cache *avc_xperms_data_cachep __ro_after_init;
122static struct kmem_cache *avc_xperms_decision_cachep __ro_after_init;
123static struct kmem_cache *avc_xperms_cachep __ro_after_init;
124
125static inline u32 avc_hash(u32 ssid, u32 tsid, u16 tclass)
126{
127 return (ssid ^ (tsid<<2) ^ (tclass<<4)) & (AVC_CACHE_SLOTS - 1);
128}
129
130/**
131 * avc_init - Initialize the AVC.
132 *
133 * Initialize the access vector cache.
134 */
135void __init avc_init(void)
136{
137 avc_node_cachep = kmem_cache_create("avc_node", sizeof(struct avc_node),
138 0, SLAB_PANIC, NULL);
139 avc_xperms_cachep = kmem_cache_create("avc_xperms_node",
140 sizeof(struct avc_xperms_node),
141 0, SLAB_PANIC, NULL);
142 avc_xperms_decision_cachep = kmem_cache_create(
143 "avc_xperms_decision_node",
144 sizeof(struct avc_xperms_decision_node),
145 0, SLAB_PANIC, NULL);
146 avc_xperms_data_cachep = kmem_cache_create("avc_xperms_data",
147 sizeof(struct extended_perms_data),
148 0, SLAB_PANIC, NULL);
149}
150
151int avc_get_hash_stats(char *page)
152{
153 int i, chain_len, max_chain_len, slots_used;
154 struct avc_node *node;
155 struct hlist_head *head;
156
157 rcu_read_lock();
158
159 slots_used = 0;
160 max_chain_len = 0;
161 for (i = 0; i < AVC_CACHE_SLOTS; i++) {
162 head = &selinux_avc.avc_cache.slots[i];
163 if (!hlist_empty(head)) {
164 slots_used++;
165 chain_len = 0;
166 hlist_for_each_entry_rcu(node, head, list)
167 chain_len++;
168 if (chain_len > max_chain_len)
169 max_chain_len = chain_len;
170 }
171 }
172
173 rcu_read_unlock();
174
175 return scnprintf(page, PAGE_SIZE, "entries: %d\nbuckets used: %d/%d\n"
176 "longest chain: %d\n",
177 atomic_read(&selinux_avc.avc_cache.active_nodes),
178 slots_used, AVC_CACHE_SLOTS, max_chain_len);
179}
180
181/*
182 * using a linked list for extended_perms_decision lookup because the list is
183 * always small. i.e. less than 5, typically 1
184 */
185static struct extended_perms_decision *avc_xperms_decision_lookup(u8 driver,
186 struct avc_xperms_node *xp_node)
187{
188 struct avc_xperms_decision_node *xpd_node;
189
190 list_for_each_entry(xpd_node, &xp_node->xpd_head, xpd_list) {
191 if (xpd_node->xpd.driver == driver)
192 return &xpd_node->xpd;
193 }
194 return NULL;
195}
196
197static inline unsigned int
198avc_xperms_has_perm(struct extended_perms_decision *xpd,
199 u8 perm, u8 which)
200{
201 unsigned int rc = 0;
202
203 if ((which == XPERMS_ALLOWED) &&
204 (xpd->used & XPERMS_ALLOWED))
205 rc = security_xperm_test(xpd->allowed->p, perm);
206 else if ((which == XPERMS_AUDITALLOW) &&
207 (xpd->used & XPERMS_AUDITALLOW))
208 rc = security_xperm_test(xpd->auditallow->p, perm);
209 else if ((which == XPERMS_DONTAUDIT) &&
210 (xpd->used & XPERMS_DONTAUDIT))
211 rc = security_xperm_test(xpd->dontaudit->p, perm);
212 return rc;
213}
214
215static void avc_xperms_allow_perm(struct avc_xperms_node *xp_node,
216 u8 driver, u8 perm)
217{
218 struct extended_perms_decision *xpd;
219 security_xperm_set(xp_node->xp.drivers.p, driver);
220 xpd = avc_xperms_decision_lookup(driver, xp_node);
221 if (xpd && xpd->allowed)
222 security_xperm_set(xpd->allowed->p, perm);
223}
224
225static void avc_xperms_decision_free(struct avc_xperms_decision_node *xpd_node)
226{
227 struct extended_perms_decision *xpd;
228
229 xpd = &xpd_node->xpd;
230 if (xpd->allowed)
231 kmem_cache_free(avc_xperms_data_cachep, xpd->allowed);
232 if (xpd->auditallow)
233 kmem_cache_free(avc_xperms_data_cachep, xpd->auditallow);
234 if (xpd->dontaudit)
235 kmem_cache_free(avc_xperms_data_cachep, xpd->dontaudit);
236 kmem_cache_free(avc_xperms_decision_cachep, xpd_node);
237}
238
239static void avc_xperms_free(struct avc_xperms_node *xp_node)
240{
241 struct avc_xperms_decision_node *xpd_node, *tmp;
242
243 if (!xp_node)
244 return;
245
246 list_for_each_entry_safe(xpd_node, tmp, &xp_node->xpd_head, xpd_list) {
247 list_del(&xpd_node->xpd_list);
248 avc_xperms_decision_free(xpd_node);
249 }
250 kmem_cache_free(avc_xperms_cachep, xp_node);
251}
252
253static void avc_copy_xperms_decision(struct extended_perms_decision *dest,
254 struct extended_perms_decision *src)
255{
256 dest->driver = src->driver;
257 dest->used = src->used;
258 if (dest->used & XPERMS_ALLOWED)
259 memcpy(dest->allowed->p, src->allowed->p,
260 sizeof(src->allowed->p));
261 if (dest->used & XPERMS_AUDITALLOW)
262 memcpy(dest->auditallow->p, src->auditallow->p,
263 sizeof(src->auditallow->p));
264 if (dest->used & XPERMS_DONTAUDIT)
265 memcpy(dest->dontaudit->p, src->dontaudit->p,
266 sizeof(src->dontaudit->p));
267}
268
269/*
270 * similar to avc_copy_xperms_decision, but only copy decision
271 * information relevant to this perm
272 */
273static inline void avc_quick_copy_xperms_decision(u8 perm,
274 struct extended_perms_decision *dest,
275 struct extended_perms_decision *src)
276{
277 /*
278 * compute index of the u32 of the 256 bits (8 u32s) that contain this
279 * command permission
280 */
281 u8 i = perm >> 5;
282
283 dest->used = src->used;
284 if (dest->used & XPERMS_ALLOWED)
285 dest->allowed->p[i] = src->allowed->p[i];
286 if (dest->used & XPERMS_AUDITALLOW)
287 dest->auditallow->p[i] = src->auditallow->p[i];
288 if (dest->used & XPERMS_DONTAUDIT)
289 dest->dontaudit->p[i] = src->dontaudit->p[i];
290}
291
292static struct avc_xperms_decision_node
293 *avc_xperms_decision_alloc(u8 which)
294{
295 struct avc_xperms_decision_node *xpd_node;
296 struct extended_perms_decision *xpd;
297
298 xpd_node = kmem_cache_zalloc(avc_xperms_decision_cachep,
299 GFP_NOWAIT | __GFP_NOWARN);
300 if (!xpd_node)
301 return NULL;
302
303 xpd = &xpd_node->xpd;
304 if (which & XPERMS_ALLOWED) {
305 xpd->allowed = kmem_cache_zalloc(avc_xperms_data_cachep,
306 GFP_NOWAIT | __GFP_NOWARN);
307 if (!xpd->allowed)
308 goto error;
309 }
310 if (which & XPERMS_AUDITALLOW) {
311 xpd->auditallow = kmem_cache_zalloc(avc_xperms_data_cachep,
312 GFP_NOWAIT | __GFP_NOWARN);
313 if (!xpd->auditallow)
314 goto error;
315 }
316 if (which & XPERMS_DONTAUDIT) {
317 xpd->dontaudit = kmem_cache_zalloc(avc_xperms_data_cachep,
318 GFP_NOWAIT | __GFP_NOWARN);
319 if (!xpd->dontaudit)
320 goto error;
321 }
322 return xpd_node;
323error:
324 avc_xperms_decision_free(xpd_node);
325 return NULL;
326}
327
328static int avc_add_xperms_decision(struct avc_node *node,
329 struct extended_perms_decision *src)
330{
331 struct avc_xperms_decision_node *dest_xpd;
332
333 node->ae.xp_node->xp.len++;
334 dest_xpd = avc_xperms_decision_alloc(src->used);
335 if (!dest_xpd)
336 return -ENOMEM;
337 avc_copy_xperms_decision(&dest_xpd->xpd, src);
338 list_add(&dest_xpd->xpd_list, &node->ae.xp_node->xpd_head);
339 return 0;
340}
341
342static struct avc_xperms_node *avc_xperms_alloc(void)
343{
344 struct avc_xperms_node *xp_node;
345
346 xp_node = kmem_cache_zalloc(avc_xperms_cachep, GFP_NOWAIT | __GFP_NOWARN);
347 if (!xp_node)
348 return xp_node;
349 INIT_LIST_HEAD(&xp_node->xpd_head);
350 return xp_node;
351}
352
353static int avc_xperms_populate(struct avc_node *node,
354 struct avc_xperms_node *src)
355{
356 struct avc_xperms_node *dest;
357 struct avc_xperms_decision_node *dest_xpd;
358 struct avc_xperms_decision_node *src_xpd;
359
360 if (src->xp.len == 0)
361 return 0;
362 dest = avc_xperms_alloc();
363 if (!dest)
364 return -ENOMEM;
365
366 memcpy(dest->xp.drivers.p, src->xp.drivers.p, sizeof(dest->xp.drivers.p));
367 dest->xp.len = src->xp.len;
368
369 /* for each source xpd allocate a destination xpd and copy */
370 list_for_each_entry(src_xpd, &src->xpd_head, xpd_list) {
371 dest_xpd = avc_xperms_decision_alloc(src_xpd->xpd.used);
372 if (!dest_xpd)
373 goto error;
374 avc_copy_xperms_decision(&dest_xpd->xpd, &src_xpd->xpd);
375 list_add(&dest_xpd->xpd_list, &dest->xpd_head);
376 }
377 node->ae.xp_node = dest;
378 return 0;
379error:
380 avc_xperms_free(dest);
381 return -ENOMEM;
382
383}
384
385static inline u32 avc_xperms_audit_required(u32 requested,
386 struct av_decision *avd,
387 struct extended_perms_decision *xpd,
388 u8 perm,
389 int result,
390 u32 *deniedp)
391{
392 u32 denied, audited;
393
394 denied = requested & ~avd->allowed;
395 if (unlikely(denied)) {
396 audited = denied & avd->auditdeny;
397 if (audited && xpd) {
398 if (avc_xperms_has_perm(xpd, perm, XPERMS_DONTAUDIT))
399 audited &= ~requested;
400 }
401 } else if (result) {
402 audited = denied = requested;
403 } else {
404 audited = requested & avd->auditallow;
405 if (audited && xpd) {
406 if (!avc_xperms_has_perm(xpd, perm, XPERMS_AUDITALLOW))
407 audited &= ~requested;
408 }
409 }
410
411 *deniedp = denied;
412 return audited;
413}
414
415static inline int avc_xperms_audit(u32 ssid, u32 tsid, u16 tclass,
416 u32 requested, struct av_decision *avd,
417 struct extended_perms_decision *xpd,
418 u8 perm, int result,
419 struct common_audit_data *ad)
420{
421 u32 audited, denied;
422
423 audited = avc_xperms_audit_required(
424 requested, avd, xpd, perm, result, &denied);
425 if (likely(!audited))
426 return 0;
427 return slow_avc_audit(ssid, tsid, tclass, requested,
428 audited, denied, result, ad);
429}
430
431static void avc_node_free(struct rcu_head *rhead)
432{
433 struct avc_node *node = container_of(rhead, struct avc_node, rhead);
434 avc_xperms_free(node->ae.xp_node);
435 kmem_cache_free(avc_node_cachep, node);
436 avc_cache_stats_incr(frees);
437}
438
439static void avc_node_delete(struct avc_node *node)
440{
441 hlist_del_rcu(&node->list);
442 call_rcu(&node->rhead, avc_node_free);
443 atomic_dec(&selinux_avc.avc_cache.active_nodes);
444}
445
446static void avc_node_kill(struct avc_node *node)
447{
448 avc_xperms_free(node->ae.xp_node);
449 kmem_cache_free(avc_node_cachep, node);
450 avc_cache_stats_incr(frees);
451 atomic_dec(&selinux_avc.avc_cache.active_nodes);
452}
453
454static void avc_node_replace(struct avc_node *new, struct avc_node *old)
455{
456 hlist_replace_rcu(&old->list, &new->list);
457 call_rcu(&old->rhead, avc_node_free);
458 atomic_dec(&selinux_avc.avc_cache.active_nodes);
459}
460
461static inline int avc_reclaim_node(void)
462{
463 struct avc_node *node;
464 int hvalue, try, ecx;
465 unsigned long flags;
466 struct hlist_head *head;
467 spinlock_t *lock;
468
469 for (try = 0, ecx = 0; try < AVC_CACHE_SLOTS; try++) {
470 hvalue = atomic_inc_return(&selinux_avc.avc_cache.lru_hint) &
471 (AVC_CACHE_SLOTS - 1);
472 head = &selinux_avc.avc_cache.slots[hvalue];
473 lock = &selinux_avc.avc_cache.slots_lock[hvalue];
474
475 if (!spin_trylock_irqsave(lock, flags))
476 continue;
477
478 rcu_read_lock();
479 hlist_for_each_entry(node, head, list) {
480 avc_node_delete(node);
481 avc_cache_stats_incr(reclaims);
482 ecx++;
483 if (ecx >= AVC_CACHE_RECLAIM) {
484 rcu_read_unlock();
485 spin_unlock_irqrestore(lock, flags);
486 goto out;
487 }
488 }
489 rcu_read_unlock();
490 spin_unlock_irqrestore(lock, flags);
491 }
492out:
493 return ecx;
494}
495
496static struct avc_node *avc_alloc_node(void)
497{
498 struct avc_node *node;
499
500 node = kmem_cache_zalloc(avc_node_cachep, GFP_NOWAIT | __GFP_NOWARN);
501 if (!node)
502 goto out;
503
504 INIT_HLIST_NODE(&node->list);
505 avc_cache_stats_incr(allocations);
506
507 if (atomic_inc_return(&selinux_avc.avc_cache.active_nodes) >
508 selinux_avc.avc_cache_threshold)
509 avc_reclaim_node();
510
511out:
512 return node;
513}
514
515static void avc_node_populate(struct avc_node *node, u32 ssid, u32 tsid, u16 tclass, struct av_decision *avd)
516{
517 node->ae.ssid = ssid;
518 node->ae.tsid = tsid;
519 node->ae.tclass = tclass;
520 memcpy(&node->ae.avd, avd, sizeof(node->ae.avd));
521}
522
523static inline struct avc_node *avc_search_node(u32 ssid, u32 tsid, u16 tclass)
524{
525 struct avc_node *node, *ret = NULL;
526 u32 hvalue;
527 struct hlist_head *head;
528
529 hvalue = avc_hash(ssid, tsid, tclass);
530 head = &selinux_avc.avc_cache.slots[hvalue];
531 hlist_for_each_entry_rcu(node, head, list) {
532 if (ssid == node->ae.ssid &&
533 tclass == node->ae.tclass &&
534 tsid == node->ae.tsid) {
535 ret = node;
536 break;
537 }
538 }
539
540 return ret;
541}
542
543/**
544 * avc_lookup - Look up an AVC entry.
545 * @ssid: source security identifier
546 * @tsid: target security identifier
547 * @tclass: target security class
548 *
549 * Look up an AVC entry that is valid for the
550 * (@ssid, @tsid), interpreting the permissions
551 * based on @tclass. If a valid AVC entry exists,
552 * then this function returns the avc_node.
553 * Otherwise, this function returns NULL.
554 */
555static struct avc_node *avc_lookup(u32 ssid, u32 tsid, u16 tclass)
556{
557 struct avc_node *node;
558
559 avc_cache_stats_incr(lookups);
560 node = avc_search_node(ssid, tsid, tclass);
561
562 if (node)
563 return node;
564
565 avc_cache_stats_incr(misses);
566 return NULL;
567}
568
569static int avc_latest_notif_update(u32 seqno, int is_insert)
570{
571 int ret = 0;
572 static DEFINE_SPINLOCK(notif_lock);
573 unsigned long flag;
574
575 spin_lock_irqsave(¬if_lock, flag);
576 if (is_insert) {
577 if (seqno < selinux_avc.avc_cache.latest_notif) {
578 pr_warn("SELinux: avc: seqno %d < latest_notif %d\n",
579 seqno, selinux_avc.avc_cache.latest_notif);
580 ret = -EAGAIN;
581 }
582 } else {
583 if (seqno > selinux_avc.avc_cache.latest_notif)
584 selinux_avc.avc_cache.latest_notif = seqno;
585 }
586 spin_unlock_irqrestore(¬if_lock, flag);
587
588 return ret;
589}
590
591/**
592 * avc_insert - Insert an AVC entry.
593 * @ssid: source security identifier
594 * @tsid: target security identifier
595 * @tclass: target security class
596 * @avd: resulting av decision
597 * @xp_node: resulting extended permissions
598 *
599 * Insert an AVC entry for the SID pair
600 * (@ssid, @tsid) and class @tclass.
601 * The access vectors and the sequence number are
602 * normally provided by the security server in
603 * response to a security_compute_av() call. If the
604 * sequence number @avd->seqno is not less than the latest
605 * revocation notification, then the function copies
606 * the access vectors into a cache entry.
607 */
608static void avc_insert(u32 ssid, u32 tsid, u16 tclass,
609 struct av_decision *avd, struct avc_xperms_node *xp_node)
610{
611 struct avc_node *pos, *node = NULL;
612 u32 hvalue;
613 unsigned long flag;
614 spinlock_t *lock;
615 struct hlist_head *head;
616
617 if (avc_latest_notif_update(avd->seqno, 1))
618 return;
619
620 node = avc_alloc_node();
621 if (!node)
622 return;
623
624 avc_node_populate(node, ssid, tsid, tclass, avd);
625 if (avc_xperms_populate(node, xp_node)) {
626 avc_node_kill(node);
627 return;
628 }
629
630 hvalue = avc_hash(ssid, tsid, tclass);
631 head = &selinux_avc.avc_cache.slots[hvalue];
632 lock = &selinux_avc.avc_cache.slots_lock[hvalue];
633 spin_lock_irqsave(lock, flag);
634 hlist_for_each_entry(pos, head, list) {
635 if (pos->ae.ssid == ssid &&
636 pos->ae.tsid == tsid &&
637 pos->ae.tclass == tclass) {
638 avc_node_replace(node, pos);
639 goto found;
640 }
641 }
642 hlist_add_head_rcu(&node->list, head);
643found:
644 spin_unlock_irqrestore(lock, flag);
645}
646
647/**
648 * avc_audit_pre_callback - SELinux specific information
649 * will be called by generic audit code
650 * @ab: the audit buffer
651 * @a: audit_data
652 */
653static void avc_audit_pre_callback(struct audit_buffer *ab, void *a)
654{
655 struct common_audit_data *ad = a;
656 struct selinux_audit_data *sad = ad->selinux_audit_data;
657 u32 av = sad->audited, perm;
658 const char *const *perms;
659 u32 i;
660
661 audit_log_format(ab, "avc: %s ", sad->denied ? "denied" : "granted");
662
663 if (av == 0) {
664 audit_log_format(ab, " null");
665 return;
666 }
667
668 perms = secclass_map[sad->tclass-1].perms;
669
670 audit_log_format(ab, " {");
671 i = 0;
672 perm = 1;
673 while (i < (sizeof(av) * 8)) {
674 if ((perm & av) && perms[i]) {
675 audit_log_format(ab, " %s", perms[i]);
676 av &= ~perm;
677 }
678 i++;
679 perm <<= 1;
680 }
681
682 if (av)
683 audit_log_format(ab, " 0x%x", av);
684
685 audit_log_format(ab, " } for ");
686}
687
688/**
689 * avc_audit_post_callback - SELinux specific information
690 * will be called by generic audit code
691 * @ab: the audit buffer
692 * @a: audit_data
693 */
694static void avc_audit_post_callback(struct audit_buffer *ab, void *a)
695{
696 struct common_audit_data *ad = a;
697 struct selinux_audit_data *sad = ad->selinux_audit_data;
698 char *scontext = NULL;
699 char *tcontext = NULL;
700 const char *tclass = NULL;
701 u32 scontext_len;
702 u32 tcontext_len;
703 int rc;
704
705 rc = security_sid_to_context(sad->ssid, &scontext,
706 &scontext_len);
707 if (rc)
708 audit_log_format(ab, " ssid=%d", sad->ssid);
709 else
710 audit_log_format(ab, " scontext=%s", scontext);
711
712 rc = security_sid_to_context(sad->tsid, &tcontext,
713 &tcontext_len);
714 if (rc)
715 audit_log_format(ab, " tsid=%d", sad->tsid);
716 else
717 audit_log_format(ab, " tcontext=%s", tcontext);
718
719 tclass = secclass_map[sad->tclass-1].name;
720 audit_log_format(ab, " tclass=%s", tclass);
721
722 if (sad->denied)
723 audit_log_format(ab, " permissive=%u", sad->result ? 0 : 1);
724
725 trace_selinux_audited(sad, scontext, tcontext, tclass);
726 kfree(tcontext);
727 kfree(scontext);
728
729 /* in case of invalid context report also the actual context string */
730 rc = security_sid_to_context_inval(sad->ssid, &scontext,
731 &scontext_len);
732 if (!rc && scontext) {
733 if (scontext_len && scontext[scontext_len - 1] == '\0')
734 scontext_len--;
735 audit_log_format(ab, " srawcon=");
736 audit_log_n_untrustedstring(ab, scontext, scontext_len);
737 kfree(scontext);
738 }
739
740 rc = security_sid_to_context_inval(sad->tsid, &scontext,
741 &scontext_len);
742 if (!rc && scontext) {
743 if (scontext_len && scontext[scontext_len - 1] == '\0')
744 scontext_len--;
745 audit_log_format(ab, " trawcon=");
746 audit_log_n_untrustedstring(ab, scontext, scontext_len);
747 kfree(scontext);
748 }
749}
750
751/*
752 * This is the slow part of avc audit with big stack footprint.
753 * Note that it is non-blocking and can be called from under
754 * rcu_read_lock().
755 */
756noinline int slow_avc_audit(u32 ssid, u32 tsid, u16 tclass,
757 u32 requested, u32 audited, u32 denied, int result,
758 struct common_audit_data *a)
759{
760 struct common_audit_data stack_data;
761 struct selinux_audit_data sad;
762
763 if (WARN_ON(!tclass || tclass >= ARRAY_SIZE(secclass_map)))
764 return -EINVAL;
765
766 if (!a) {
767 a = &stack_data;
768 a->type = LSM_AUDIT_DATA_NONE;
769 }
770
771 sad.tclass = tclass;
772 sad.requested = requested;
773 sad.ssid = ssid;
774 sad.tsid = tsid;
775 sad.audited = audited;
776 sad.denied = denied;
777 sad.result = result;
778
779 a->selinux_audit_data = &sad;
780
781 common_lsm_audit(a, avc_audit_pre_callback, avc_audit_post_callback);
782 return 0;
783}
784
785/**
786 * avc_add_callback - Register a callback for security events.
787 * @callback: callback function
788 * @events: security events
789 *
790 * Register a callback function for events in the set @events.
791 * Returns %0 on success or -%ENOMEM if insufficient memory
792 * exists to add the callback.
793 */
794int __init avc_add_callback(int (*callback)(u32 event), u32 events)
795{
796 struct avc_callback_node *c;
797 int rc = 0;
798
799 c = kmalloc(sizeof(*c), GFP_KERNEL);
800 if (!c) {
801 rc = -ENOMEM;
802 goto out;
803 }
804
805 c->callback = callback;
806 c->events = events;
807 c->next = avc_callbacks;
808 avc_callbacks = c;
809out:
810 return rc;
811}
812
813/**
814 * avc_update_node - Update an AVC entry
815 * @event : Updating event
816 * @perms : Permission mask bits
817 * @driver: xperm driver information
818 * @xperm: xperm permissions
819 * @ssid: AVC entry source sid
820 * @tsid: AVC entry target sid
821 * @tclass : AVC entry target object class
822 * @seqno : sequence number when decision was made
823 * @xpd: extended_perms_decision to be added to the node
824 * @flags: the AVC_* flags, e.g. AVC_EXTENDED_PERMS, or 0.
825 *
826 * if a valid AVC entry doesn't exist,this function returns -ENOENT.
827 * if kmalloc() called internal returns NULL, this function returns -ENOMEM.
828 * otherwise, this function updates the AVC entry. The original AVC-entry object
829 * will release later by RCU.
830 */
831static int avc_update_node(u32 event, u32 perms, u8 driver, u8 xperm, u32 ssid,
832 u32 tsid, u16 tclass, u32 seqno,
833 struct extended_perms_decision *xpd,
834 u32 flags)
835{
836 u32 hvalue;
837 int rc = 0;
838 unsigned long flag;
839 struct avc_node *pos, *node, *orig = NULL;
840 struct hlist_head *head;
841 spinlock_t *lock;
842
843 node = avc_alloc_node();
844 if (!node) {
845 rc = -ENOMEM;
846 goto out;
847 }
848
849 /* Lock the target slot */
850 hvalue = avc_hash(ssid, tsid, tclass);
851
852 head = &selinux_avc.avc_cache.slots[hvalue];
853 lock = &selinux_avc.avc_cache.slots_lock[hvalue];
854
855 spin_lock_irqsave(lock, flag);
856
857 hlist_for_each_entry(pos, head, list) {
858 if (ssid == pos->ae.ssid &&
859 tsid == pos->ae.tsid &&
860 tclass == pos->ae.tclass &&
861 seqno == pos->ae.avd.seqno){
862 orig = pos;
863 break;
864 }
865 }
866
867 if (!orig) {
868 rc = -ENOENT;
869 avc_node_kill(node);
870 goto out_unlock;
871 }
872
873 /*
874 * Copy and replace original node.
875 */
876
877 avc_node_populate(node, ssid, tsid, tclass, &orig->ae.avd);
878
879 if (orig->ae.xp_node) {
880 rc = avc_xperms_populate(node, orig->ae.xp_node);
881 if (rc) {
882 avc_node_kill(node);
883 goto out_unlock;
884 }
885 }
886
887 switch (event) {
888 case AVC_CALLBACK_GRANT:
889 node->ae.avd.allowed |= perms;
890 if (node->ae.xp_node && (flags & AVC_EXTENDED_PERMS))
891 avc_xperms_allow_perm(node->ae.xp_node, driver, xperm);
892 break;
893 case AVC_CALLBACK_TRY_REVOKE:
894 case AVC_CALLBACK_REVOKE:
895 node->ae.avd.allowed &= ~perms;
896 break;
897 case AVC_CALLBACK_AUDITALLOW_ENABLE:
898 node->ae.avd.auditallow |= perms;
899 break;
900 case AVC_CALLBACK_AUDITALLOW_DISABLE:
901 node->ae.avd.auditallow &= ~perms;
902 break;
903 case AVC_CALLBACK_AUDITDENY_ENABLE:
904 node->ae.avd.auditdeny |= perms;
905 break;
906 case AVC_CALLBACK_AUDITDENY_DISABLE:
907 node->ae.avd.auditdeny &= ~perms;
908 break;
909 case AVC_CALLBACK_ADD_XPERMS:
910 avc_add_xperms_decision(node, xpd);
911 break;
912 }
913 avc_node_replace(node, orig);
914out_unlock:
915 spin_unlock_irqrestore(lock, flag);
916out:
917 return rc;
918}
919
920/**
921 * avc_flush - Flush the cache
922 */
923static void avc_flush(void)
924{
925 struct hlist_head *head;
926 struct avc_node *node;
927 spinlock_t *lock;
928 unsigned long flag;
929 int i;
930
931 for (i = 0; i < AVC_CACHE_SLOTS; i++) {
932 head = &selinux_avc.avc_cache.slots[i];
933 lock = &selinux_avc.avc_cache.slots_lock[i];
934
935 spin_lock_irqsave(lock, flag);
936 /*
937 * With preemptable RCU, the outer spinlock does not
938 * prevent RCU grace periods from ending.
939 */
940 rcu_read_lock();
941 hlist_for_each_entry(node, head, list)
942 avc_node_delete(node);
943 rcu_read_unlock();
944 spin_unlock_irqrestore(lock, flag);
945 }
946}
947
948/**
949 * avc_ss_reset - Flush the cache and revalidate migrated permissions.
950 * @seqno: policy sequence number
951 */
952int avc_ss_reset(u32 seqno)
953{
954 struct avc_callback_node *c;
955 int rc = 0, tmprc;
956
957 avc_flush();
958
959 for (c = avc_callbacks; c; c = c->next) {
960 if (c->events & AVC_CALLBACK_RESET) {
961 tmprc = c->callback(AVC_CALLBACK_RESET);
962 /* save the first error encountered for the return
963 value and continue processing the callbacks */
964 if (!rc)
965 rc = tmprc;
966 }
967 }
968
969 avc_latest_notif_update(seqno, 0);
970 return rc;
971}
972
973/**
974 * avc_compute_av - Add an entry to the AVC based on the security policy
975 * @ssid: subject
976 * @tsid: object/target
977 * @tclass: object class
978 * @avd: access vector decision
979 * @xp_node: AVC extended permissions node
980 *
981 * Slow-path helper function for avc_has_perm_noaudit, when the avc_node lookup
982 * fails. Don't inline this, since it's the slow-path and just results in a
983 * bigger stack frame.
984 */
985static noinline void avc_compute_av(u32 ssid, u32 tsid, u16 tclass,
986 struct av_decision *avd,
987 struct avc_xperms_node *xp_node)
988{
989 INIT_LIST_HEAD(&xp_node->xpd_head);
990 security_compute_av(ssid, tsid, tclass, avd, &xp_node->xp);
991 avc_insert(ssid, tsid, tclass, avd, xp_node);
992}
993
994static noinline int avc_denied(u32 ssid, u32 tsid,
995 u16 tclass, u32 requested,
996 u8 driver, u8 xperm, unsigned int flags,
997 struct av_decision *avd)
998{
999 if (flags & AVC_STRICT)
1000 return -EACCES;
1001
1002 if (enforcing_enabled() &&
1003 !(avd->flags & AVD_FLAGS_PERMISSIVE))
1004 return -EACCES;
1005
1006 avc_update_node(AVC_CALLBACK_GRANT, requested, driver,
1007 xperm, ssid, tsid, tclass, avd->seqno, NULL, flags);
1008 return 0;
1009}
1010
1011/*
1012 * The avc extended permissions logic adds an additional 256 bits of
1013 * permissions to an avc node when extended permissions for that node are
1014 * specified in the avtab. If the additional 256 permissions is not adequate,
1015 * as-is the case with ioctls, then multiple may be chained together and the
1016 * driver field is used to specify which set contains the permission.
1017 */
1018int avc_has_extended_perms(u32 ssid, u32 tsid, u16 tclass, u32 requested,
1019 u8 driver, u8 xperm, struct common_audit_data *ad)
1020{
1021 struct avc_node *node;
1022 struct av_decision avd;
1023 u32 denied;
1024 struct extended_perms_decision local_xpd;
1025 struct extended_perms_decision *xpd = NULL;
1026 struct extended_perms_data allowed;
1027 struct extended_perms_data auditallow;
1028 struct extended_perms_data dontaudit;
1029 struct avc_xperms_node local_xp_node;
1030 struct avc_xperms_node *xp_node;
1031 int rc = 0, rc2;
1032
1033 xp_node = &local_xp_node;
1034 if (WARN_ON(!requested))
1035 return -EACCES;
1036
1037 rcu_read_lock();
1038
1039 node = avc_lookup(ssid, tsid, tclass);
1040 if (unlikely(!node)) {
1041 avc_compute_av(ssid, tsid, tclass, &avd, xp_node);
1042 } else {
1043 memcpy(&avd, &node->ae.avd, sizeof(avd));
1044 xp_node = node->ae.xp_node;
1045 }
1046 /* if extended permissions are not defined, only consider av_decision */
1047 if (!xp_node || !xp_node->xp.len)
1048 goto decision;
1049
1050 local_xpd.allowed = &allowed;
1051 local_xpd.auditallow = &auditallow;
1052 local_xpd.dontaudit = &dontaudit;
1053
1054 xpd = avc_xperms_decision_lookup(driver, xp_node);
1055 if (unlikely(!xpd)) {
1056 /*
1057 * Compute the extended_perms_decision only if the driver
1058 * is flagged
1059 */
1060 if (!security_xperm_test(xp_node->xp.drivers.p, driver)) {
1061 avd.allowed &= ~requested;
1062 goto decision;
1063 }
1064 rcu_read_unlock();
1065 security_compute_xperms_decision(ssid, tsid, tclass,
1066 driver, &local_xpd);
1067 rcu_read_lock();
1068 avc_update_node(AVC_CALLBACK_ADD_XPERMS, requested,
1069 driver, xperm, ssid, tsid, tclass, avd.seqno,
1070 &local_xpd, 0);
1071 } else {
1072 avc_quick_copy_xperms_decision(xperm, &local_xpd, xpd);
1073 }
1074 xpd = &local_xpd;
1075
1076 if (!avc_xperms_has_perm(xpd, xperm, XPERMS_ALLOWED))
1077 avd.allowed &= ~requested;
1078
1079decision:
1080 denied = requested & ~(avd.allowed);
1081 if (unlikely(denied))
1082 rc = avc_denied(ssid, tsid, tclass, requested,
1083 driver, xperm, AVC_EXTENDED_PERMS, &avd);
1084
1085 rcu_read_unlock();
1086
1087 rc2 = avc_xperms_audit(ssid, tsid, tclass, requested,
1088 &avd, xpd, xperm, rc, ad);
1089 if (rc2)
1090 return rc2;
1091 return rc;
1092}
1093
1094/**
1095 * avc_perm_nonode - Add an entry to the AVC
1096 * @ssid: subject
1097 * @tsid: object/target
1098 * @tclass: object class
1099 * @requested: requested permissions
1100 * @flags: AVC flags
1101 * @avd: access vector decision
1102 *
1103 * This is the "we have no node" part of avc_has_perm_noaudit(), which is
1104 * unlikely and needs extra stack space for the new node that we generate, so
1105 * don't inline it.
1106 */
1107static noinline int avc_perm_nonode(u32 ssid, u32 tsid, u16 tclass,
1108 u32 requested, unsigned int flags,
1109 struct av_decision *avd)
1110{
1111 u32 denied;
1112 struct avc_xperms_node xp_node;
1113
1114 avc_compute_av(ssid, tsid, tclass, avd, &xp_node);
1115 denied = requested & ~(avd->allowed);
1116 if (unlikely(denied))
1117 return avc_denied(ssid, tsid, tclass, requested, 0, 0,
1118 flags, avd);
1119 return 0;
1120}
1121
1122/**
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 or 0
1129 * @avd: access vector decisions
1130 *
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.
1141 */
1142inline int avc_has_perm_noaudit(u32 ssid, u32 tsid,
1143 u16 tclass, u32 requested,
1144 unsigned int flags,
1145 struct av_decision *avd)
1146{
1147 u32 denied;
1148 struct avc_node *node;
1149
1150 if (WARN_ON(!requested))
1151 return -EACCES;
1152
1153 rcu_read_lock();
1154 node = avc_lookup(ssid, tsid, tclass);
1155 if (unlikely(!node)) {
1156 rcu_read_unlock();
1157 return avc_perm_nonode(ssid, tsid, tclass, requested,
1158 flags, avd);
1159 }
1160 denied = requested & ~node->ae.avd.allowed;
1161 memcpy(avd, &node->ae.avd, sizeof(*avd));
1162 rcu_read_unlock();
1163
1164 if (unlikely(denied))
1165 return avc_denied(ssid, tsid, tclass, requested, 0, 0,
1166 flags, avd);
1167 return 0;
1168}
1169
1170/**
1171 * avc_has_perm - Check permissions and perform any appropriate auditing.
1172 * @ssid: source security identifier
1173 * @tsid: target security identifier
1174 * @tclass: target security class
1175 * @requested: requested permissions, interpreted based on @tclass
1176 * @auditdata: auxiliary audit data
1177 *
1178 * Check the AVC to determine whether the @requested permissions are granted
1179 * for the SID pair (@ssid, @tsid), interpreting the permissions
1180 * based on @tclass, and call the security server on a cache miss to obtain
1181 * a new decision and add it to the cache. Audit the granting or denial of
1182 * permissions in accordance with the policy. Return %0 if all @requested
1183 * permissions are granted, -%EACCES if any permissions are denied, or
1184 * another -errno upon other errors.
1185 */
1186int avc_has_perm(u32 ssid, u32 tsid, u16 tclass,
1187 u32 requested, struct common_audit_data *auditdata)
1188{
1189 struct av_decision avd;
1190 int rc, rc2;
1191
1192 rc = avc_has_perm_noaudit(ssid, tsid, tclass, requested, 0,
1193 &avd);
1194
1195 rc2 = avc_audit(ssid, tsid, tclass, requested, &avd, rc,
1196 auditdata);
1197 if (rc2)
1198 return rc2;
1199 return rc;
1200}
1201
1202u32 avc_policy_seqno(void)
1203{
1204 return selinux_avc.avc_cache.latest_notif;
1205}