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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 <linux/list.h>
26#include <net/sock.h>
27#include <linux/un.h>
28#include <net/af_unix.h>
29#include <linux/ip.h>
30#include <linux/audit.h>
31#include <linux/ipv6.h>
32#include <net/ipv6.h>
33#include "avc.h"
34#include "avc_ss.h"
35#include "classmap.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/* Exported via selinufs */
86unsigned int avc_cache_threshold = AVC_DEF_CACHE_THRESHOLD;
87
88#ifdef CONFIG_SECURITY_SELINUX_AVC_STATS
89DEFINE_PER_CPU(struct avc_cache_stats, avc_cache_stats) = { 0 };
90#endif
91
92static struct avc_cache avc_cache;
93static struct avc_callback_node *avc_callbacks;
94static struct kmem_cache *avc_node_cachep;
95static struct kmem_cache *avc_xperms_data_cachep;
96static struct kmem_cache *avc_xperms_decision_cachep;
97static struct kmem_cache *avc_xperms_cachep;
98
99static inline int avc_hash(u32 ssid, u32 tsid, u16 tclass)
100{
101 return (ssid ^ (tsid<<2) ^ (tclass<<4)) & (AVC_CACHE_SLOTS - 1);
102}
103
104/**
105 * avc_dump_av - Display an access vector in human-readable form.
106 * @tclass: target security class
107 * @av: access vector
108 */
109static void avc_dump_av(struct audit_buffer *ab, u16 tclass, u32 av)
110{
111 const char **perms;
112 int i, perm;
113
114 if (av == 0) {
115 audit_log_format(ab, " null");
116 return;
117 }
118
119 BUG_ON(!tclass || tclass >= ARRAY_SIZE(secclass_map));
120 perms = secclass_map[tclass-1].perms;
121
122 audit_log_format(ab, " {");
123 i = 0;
124 perm = 1;
125 while (i < (sizeof(av) * 8)) {
126 if ((perm & av) && perms[i]) {
127 audit_log_format(ab, " %s", perms[i]);
128 av &= ~perm;
129 }
130 i++;
131 perm <<= 1;
132 }
133
134 if (av)
135 audit_log_format(ab, " 0x%x", av);
136
137 audit_log_format(ab, " }");
138}
139
140/**
141 * avc_dump_query - Display a SID pair and a class in human-readable form.
142 * @ssid: source security identifier
143 * @tsid: target security identifier
144 * @tclass: target security class
145 */
146static void avc_dump_query(struct audit_buffer *ab, u32 ssid, u32 tsid, u16 tclass)
147{
148 int rc;
149 char *scontext;
150 u32 scontext_len;
151
152 rc = security_sid_to_context(ssid, &scontext, &scontext_len);
153 if (rc)
154 audit_log_format(ab, "ssid=%d", ssid);
155 else {
156 audit_log_format(ab, "scontext=%s", scontext);
157 kfree(scontext);
158 }
159
160 rc = security_sid_to_context(tsid, &scontext, &scontext_len);
161 if (rc)
162 audit_log_format(ab, " tsid=%d", tsid);
163 else {
164 audit_log_format(ab, " tcontext=%s", scontext);
165 kfree(scontext);
166 }
167
168 BUG_ON(!tclass || tclass >= ARRAY_SIZE(secclass_map));
169 audit_log_format(ab, " tclass=%s", secclass_map[tclass-1].name);
170}
171
172/**
173 * avc_init - Initialize the AVC.
174 *
175 * Initialize the access vector cache.
176 */
177void __init avc_init(void)
178{
179 int i;
180
181 for (i = 0; i < AVC_CACHE_SLOTS; i++) {
182 INIT_HLIST_HEAD(&avc_cache.slots[i]);
183 spin_lock_init(&avc_cache.slots_lock[i]);
184 }
185 atomic_set(&avc_cache.active_nodes, 0);
186 atomic_set(&avc_cache.lru_hint, 0);
187
188 avc_node_cachep = kmem_cache_create("avc_node", sizeof(struct avc_node),
189 0, SLAB_PANIC, NULL);
190 avc_xperms_cachep = kmem_cache_create("avc_xperms_node",
191 sizeof(struct avc_xperms_node),
192 0, SLAB_PANIC, NULL);
193 avc_xperms_decision_cachep = kmem_cache_create(
194 "avc_xperms_decision_node",
195 sizeof(struct avc_xperms_decision_node),
196 0, SLAB_PANIC, NULL);
197 avc_xperms_data_cachep = kmem_cache_create("avc_xperms_data",
198 sizeof(struct extended_perms_data),
199 0, SLAB_PANIC, NULL);
200
201 audit_log(current->audit_context, GFP_KERNEL, AUDIT_KERNEL, "AVC INITIALIZED\n");
202}
203
204int avc_get_hash_stats(char *page)
205{
206 int i, chain_len, max_chain_len, slots_used;
207 struct avc_node *node;
208 struct hlist_head *head;
209
210 rcu_read_lock();
211
212 slots_used = 0;
213 max_chain_len = 0;
214 for (i = 0; i < AVC_CACHE_SLOTS; i++) {
215 head = &avc_cache.slots[i];
216 if (!hlist_empty(head)) {
217 slots_used++;
218 chain_len = 0;
219 hlist_for_each_entry_rcu(node, head, list)
220 chain_len++;
221 if (chain_len > max_chain_len)
222 max_chain_len = chain_len;
223 }
224 }
225
226 rcu_read_unlock();
227
228 return scnprintf(page, PAGE_SIZE, "entries: %d\nbuckets used: %d/%d\n"
229 "longest chain: %d\n",
230 atomic_read(&avc_cache.active_nodes),
231 slots_used, AVC_CACHE_SLOTS, max_chain_len);
232}
233
234/*
235 * using a linked list for extended_perms_decision lookup because the list is
236 * always small. i.e. less than 5, typically 1
237 */
238static struct extended_perms_decision *avc_xperms_decision_lookup(u8 driver,
239 struct avc_xperms_node *xp_node)
240{
241 struct avc_xperms_decision_node *xpd_node;
242
243 list_for_each_entry(xpd_node, &xp_node->xpd_head, xpd_list) {
244 if (xpd_node->xpd.driver == driver)
245 return &xpd_node->xpd;
246 }
247 return NULL;
248}
249
250static inline unsigned int
251avc_xperms_has_perm(struct extended_perms_decision *xpd,
252 u8 perm, u8 which)
253{
254 unsigned int rc = 0;
255
256 if ((which == XPERMS_ALLOWED) &&
257 (xpd->used & XPERMS_ALLOWED))
258 rc = security_xperm_test(xpd->allowed->p, perm);
259 else if ((which == XPERMS_AUDITALLOW) &&
260 (xpd->used & XPERMS_AUDITALLOW))
261 rc = security_xperm_test(xpd->auditallow->p, perm);
262 else if ((which == XPERMS_DONTAUDIT) &&
263 (xpd->used & XPERMS_DONTAUDIT))
264 rc = security_xperm_test(xpd->dontaudit->p, perm);
265 return rc;
266}
267
268static void avc_xperms_allow_perm(struct avc_xperms_node *xp_node,
269 u8 driver, u8 perm)
270{
271 struct extended_perms_decision *xpd;
272 security_xperm_set(xp_node->xp.drivers.p, driver);
273 xpd = avc_xperms_decision_lookup(driver, xp_node);
274 if (xpd && xpd->allowed)
275 security_xperm_set(xpd->allowed->p, perm);
276}
277
278static void avc_xperms_decision_free(struct avc_xperms_decision_node *xpd_node)
279{
280 struct extended_perms_decision *xpd;
281
282 xpd = &xpd_node->xpd;
283 if (xpd->allowed)
284 kmem_cache_free(avc_xperms_data_cachep, xpd->allowed);
285 if (xpd->auditallow)
286 kmem_cache_free(avc_xperms_data_cachep, xpd->auditallow);
287 if (xpd->dontaudit)
288 kmem_cache_free(avc_xperms_data_cachep, xpd->dontaudit);
289 kmem_cache_free(avc_xperms_decision_cachep, xpd_node);
290}
291
292static void avc_xperms_free(struct avc_xperms_node *xp_node)
293{
294 struct avc_xperms_decision_node *xpd_node, *tmp;
295
296 if (!xp_node)
297 return;
298
299 list_for_each_entry_safe(xpd_node, tmp, &xp_node->xpd_head, xpd_list) {
300 list_del(&xpd_node->xpd_list);
301 avc_xperms_decision_free(xpd_node);
302 }
303 kmem_cache_free(avc_xperms_cachep, xp_node);
304}
305
306static void avc_copy_xperms_decision(struct extended_perms_decision *dest,
307 struct extended_perms_decision *src)
308{
309 dest->driver = src->driver;
310 dest->used = src->used;
311 if (dest->used & XPERMS_ALLOWED)
312 memcpy(dest->allowed->p, src->allowed->p,
313 sizeof(src->allowed->p));
314 if (dest->used & XPERMS_AUDITALLOW)
315 memcpy(dest->auditallow->p, src->auditallow->p,
316 sizeof(src->auditallow->p));
317 if (dest->used & XPERMS_DONTAUDIT)
318 memcpy(dest->dontaudit->p, src->dontaudit->p,
319 sizeof(src->dontaudit->p));
320}
321
322/*
323 * similar to avc_copy_xperms_decision, but only copy decision
324 * information relevant to this perm
325 */
326static inline void avc_quick_copy_xperms_decision(u8 perm,
327 struct extended_perms_decision *dest,
328 struct extended_perms_decision *src)
329{
330 /*
331 * compute index of the u32 of the 256 bits (8 u32s) that contain this
332 * command permission
333 */
334 u8 i = perm >> 5;
335
336 dest->used = src->used;
337 if (dest->used & XPERMS_ALLOWED)
338 dest->allowed->p[i] = src->allowed->p[i];
339 if (dest->used & XPERMS_AUDITALLOW)
340 dest->auditallow->p[i] = src->auditallow->p[i];
341 if (dest->used & XPERMS_DONTAUDIT)
342 dest->dontaudit->p[i] = src->dontaudit->p[i];
343}
344
345static struct avc_xperms_decision_node
346 *avc_xperms_decision_alloc(u8 which)
347{
348 struct avc_xperms_decision_node *xpd_node;
349 struct extended_perms_decision *xpd;
350
351 xpd_node = kmem_cache_zalloc(avc_xperms_decision_cachep,
352 GFP_ATOMIC | __GFP_NOMEMALLOC);
353 if (!xpd_node)
354 return NULL;
355
356 xpd = &xpd_node->xpd;
357 if (which & XPERMS_ALLOWED) {
358 xpd->allowed = kmem_cache_zalloc(avc_xperms_data_cachep,
359 GFP_ATOMIC | __GFP_NOMEMALLOC);
360 if (!xpd->allowed)
361 goto error;
362 }
363 if (which & XPERMS_AUDITALLOW) {
364 xpd->auditallow = kmem_cache_zalloc(avc_xperms_data_cachep,
365 GFP_ATOMIC | __GFP_NOMEMALLOC);
366 if (!xpd->auditallow)
367 goto error;
368 }
369 if (which & XPERMS_DONTAUDIT) {
370 xpd->dontaudit = kmem_cache_zalloc(avc_xperms_data_cachep,
371 GFP_ATOMIC | __GFP_NOMEMALLOC);
372 if (!xpd->dontaudit)
373 goto error;
374 }
375 return xpd_node;
376error:
377 avc_xperms_decision_free(xpd_node);
378 return NULL;
379}
380
381static int avc_add_xperms_decision(struct avc_node *node,
382 struct extended_perms_decision *src)
383{
384 struct avc_xperms_decision_node *dest_xpd;
385
386 node->ae.xp_node->xp.len++;
387 dest_xpd = avc_xperms_decision_alloc(src->used);
388 if (!dest_xpd)
389 return -ENOMEM;
390 avc_copy_xperms_decision(&dest_xpd->xpd, src);
391 list_add(&dest_xpd->xpd_list, &node->ae.xp_node->xpd_head);
392 return 0;
393}
394
395static struct avc_xperms_node *avc_xperms_alloc(void)
396{
397 struct avc_xperms_node *xp_node;
398
399 xp_node = kmem_cache_zalloc(avc_xperms_cachep,
400 GFP_ATOMIC|__GFP_NOMEMALLOC);
401 if (!xp_node)
402 return xp_node;
403 INIT_LIST_HEAD(&xp_node->xpd_head);
404 return xp_node;
405}
406
407static int avc_xperms_populate(struct avc_node *node,
408 struct avc_xperms_node *src)
409{
410 struct avc_xperms_node *dest;
411 struct avc_xperms_decision_node *dest_xpd;
412 struct avc_xperms_decision_node *src_xpd;
413
414 if (src->xp.len == 0)
415 return 0;
416 dest = avc_xperms_alloc();
417 if (!dest)
418 return -ENOMEM;
419
420 memcpy(dest->xp.drivers.p, src->xp.drivers.p, sizeof(dest->xp.drivers.p));
421 dest->xp.len = src->xp.len;
422
423 /* for each source xpd allocate a destination xpd and copy */
424 list_for_each_entry(src_xpd, &src->xpd_head, xpd_list) {
425 dest_xpd = avc_xperms_decision_alloc(src_xpd->xpd.used);
426 if (!dest_xpd)
427 goto error;
428 avc_copy_xperms_decision(&dest_xpd->xpd, &src_xpd->xpd);
429 list_add(&dest_xpd->xpd_list, &dest->xpd_head);
430 }
431 node->ae.xp_node = dest;
432 return 0;
433error:
434 avc_xperms_free(dest);
435 return -ENOMEM;
436
437}
438
439static inline u32 avc_xperms_audit_required(u32 requested,
440 struct av_decision *avd,
441 struct extended_perms_decision *xpd,
442 u8 perm,
443 int result,
444 u32 *deniedp)
445{
446 u32 denied, audited;
447
448 denied = requested & ~avd->allowed;
449 if (unlikely(denied)) {
450 audited = denied & avd->auditdeny;
451 if (audited && xpd) {
452 if (avc_xperms_has_perm(xpd, perm, XPERMS_DONTAUDIT))
453 audited &= ~requested;
454 }
455 } else if (result) {
456 audited = denied = requested;
457 } else {
458 audited = requested & avd->auditallow;
459 if (audited && xpd) {
460 if (!avc_xperms_has_perm(xpd, perm, XPERMS_AUDITALLOW))
461 audited &= ~requested;
462 }
463 }
464
465 *deniedp = denied;
466 return audited;
467}
468
469static inline int avc_xperms_audit(u32 ssid, u32 tsid, u16 tclass,
470 u32 requested, struct av_decision *avd,
471 struct extended_perms_decision *xpd,
472 u8 perm, int result,
473 struct common_audit_data *ad)
474{
475 u32 audited, denied;
476
477 audited = avc_xperms_audit_required(
478 requested, avd, xpd, perm, result, &denied);
479 if (likely(!audited))
480 return 0;
481 return slow_avc_audit(ssid, tsid, tclass, requested,
482 audited, denied, result, ad, 0);
483}
484
485static void avc_node_free(struct rcu_head *rhead)
486{
487 struct avc_node *node = container_of(rhead, struct avc_node, rhead);
488 avc_xperms_free(node->ae.xp_node);
489 kmem_cache_free(avc_node_cachep, node);
490 avc_cache_stats_incr(frees);
491}
492
493static void avc_node_delete(struct avc_node *node)
494{
495 hlist_del_rcu(&node->list);
496 call_rcu(&node->rhead, avc_node_free);
497 atomic_dec(&avc_cache.active_nodes);
498}
499
500static void avc_node_kill(struct avc_node *node)
501{
502 avc_xperms_free(node->ae.xp_node);
503 kmem_cache_free(avc_node_cachep, node);
504 avc_cache_stats_incr(frees);
505 atomic_dec(&avc_cache.active_nodes);
506}
507
508static void avc_node_replace(struct avc_node *new, struct avc_node *old)
509{
510 hlist_replace_rcu(&old->list, &new->list);
511 call_rcu(&old->rhead, avc_node_free);
512 atomic_dec(&avc_cache.active_nodes);
513}
514
515static inline int avc_reclaim_node(void)
516{
517 struct avc_node *node;
518 int hvalue, try, ecx;
519 unsigned long flags;
520 struct hlist_head *head;
521 spinlock_t *lock;
522
523 for (try = 0, ecx = 0; try < AVC_CACHE_SLOTS; try++) {
524 hvalue = atomic_inc_return(&avc_cache.lru_hint) & (AVC_CACHE_SLOTS - 1);
525 head = &avc_cache.slots[hvalue];
526 lock = &avc_cache.slots_lock[hvalue];
527
528 if (!spin_trylock_irqsave(lock, flags))
529 continue;
530
531 rcu_read_lock();
532 hlist_for_each_entry(node, head, list) {
533 avc_node_delete(node);
534 avc_cache_stats_incr(reclaims);
535 ecx++;
536 if (ecx >= AVC_CACHE_RECLAIM) {
537 rcu_read_unlock();
538 spin_unlock_irqrestore(lock, flags);
539 goto out;
540 }
541 }
542 rcu_read_unlock();
543 spin_unlock_irqrestore(lock, flags);
544 }
545out:
546 return ecx;
547}
548
549static struct avc_node *avc_alloc_node(void)
550{
551 struct avc_node *node;
552
553 node = kmem_cache_zalloc(avc_node_cachep, GFP_ATOMIC|__GFP_NOMEMALLOC);
554 if (!node)
555 goto out;
556
557 INIT_HLIST_NODE(&node->list);
558 avc_cache_stats_incr(allocations);
559
560 if (atomic_inc_return(&avc_cache.active_nodes) > avc_cache_threshold)
561 avc_reclaim_node();
562
563out:
564 return node;
565}
566
567static void avc_node_populate(struct avc_node *node, u32 ssid, u32 tsid, u16 tclass, struct av_decision *avd)
568{
569 node->ae.ssid = ssid;
570 node->ae.tsid = tsid;
571 node->ae.tclass = tclass;
572 memcpy(&node->ae.avd, avd, sizeof(node->ae.avd));
573}
574
575static inline struct avc_node *avc_search_node(u32 ssid, u32 tsid, u16 tclass)
576{
577 struct avc_node *node, *ret = NULL;
578 int hvalue;
579 struct hlist_head *head;
580
581 hvalue = avc_hash(ssid, tsid, tclass);
582 head = &avc_cache.slots[hvalue];
583 hlist_for_each_entry_rcu(node, head, list) {
584 if (ssid == node->ae.ssid &&
585 tclass == node->ae.tclass &&
586 tsid == node->ae.tsid) {
587 ret = node;
588 break;
589 }
590 }
591
592 return ret;
593}
594
595/**
596 * avc_lookup - Look up an AVC entry.
597 * @ssid: source security identifier
598 * @tsid: target security identifier
599 * @tclass: target security class
600 *
601 * Look up an AVC entry that is valid for the
602 * (@ssid, @tsid), interpreting the permissions
603 * based on @tclass. If a valid AVC entry exists,
604 * then this function returns the avc_node.
605 * Otherwise, this function returns NULL.
606 */
607static struct avc_node *avc_lookup(u32 ssid, u32 tsid, u16 tclass)
608{
609 struct avc_node *node;
610
611 avc_cache_stats_incr(lookups);
612 node = avc_search_node(ssid, tsid, tclass);
613
614 if (node)
615 return node;
616
617 avc_cache_stats_incr(misses);
618 return NULL;
619}
620
621static int avc_latest_notif_update(int seqno, int is_insert)
622{
623 int ret = 0;
624 static DEFINE_SPINLOCK(notif_lock);
625 unsigned long flag;
626
627 spin_lock_irqsave(¬if_lock, flag);
628 if (is_insert) {
629 if (seqno < avc_cache.latest_notif) {
630 printk(KERN_WARNING "SELinux: avc: seqno %d < latest_notif %d\n",
631 seqno, avc_cache.latest_notif);
632 ret = -EAGAIN;
633 }
634 } else {
635 if (seqno > avc_cache.latest_notif)
636 avc_cache.latest_notif = seqno;
637 }
638 spin_unlock_irqrestore(¬if_lock, flag);
639
640 return ret;
641}
642
643/**
644 * avc_insert - Insert an AVC entry.
645 * @ssid: source security identifier
646 * @tsid: target security identifier
647 * @tclass: target security class
648 * @avd: resulting av decision
649 * @xp_node: resulting extended permissions
650 *
651 * Insert an AVC entry for the SID pair
652 * (@ssid, @tsid) and class @tclass.
653 * The access vectors and the sequence number are
654 * normally provided by the security server in
655 * response to a security_compute_av() call. If the
656 * sequence number @avd->seqno is not less than the latest
657 * revocation notification, then the function copies
658 * the access vectors into a cache entry, returns
659 * avc_node inserted. Otherwise, this function returns NULL.
660 */
661static struct avc_node *avc_insert(u32 ssid, u32 tsid, u16 tclass,
662 struct av_decision *avd,
663 struct avc_xperms_node *xp_node)
664{
665 struct avc_node *pos, *node = NULL;
666 int hvalue;
667 unsigned long flag;
668
669 if (avc_latest_notif_update(avd->seqno, 1))
670 goto out;
671
672 node = avc_alloc_node();
673 if (node) {
674 struct hlist_head *head;
675 spinlock_t *lock;
676 int rc = 0;
677
678 hvalue = avc_hash(ssid, tsid, tclass);
679 avc_node_populate(node, ssid, tsid, tclass, avd);
680 rc = avc_xperms_populate(node, xp_node);
681 if (rc) {
682 kmem_cache_free(avc_node_cachep, node);
683 return NULL;
684 }
685 head = &avc_cache.slots[hvalue];
686 lock = &avc_cache.slots_lock[hvalue];
687
688 spin_lock_irqsave(lock, flag);
689 hlist_for_each_entry(pos, head, list) {
690 if (pos->ae.ssid == ssid &&
691 pos->ae.tsid == tsid &&
692 pos->ae.tclass == tclass) {
693 avc_node_replace(node, pos);
694 goto found;
695 }
696 }
697 hlist_add_head_rcu(&node->list, head);
698found:
699 spin_unlock_irqrestore(lock, flag);
700 }
701out:
702 return node;
703}
704
705/**
706 * avc_audit_pre_callback - SELinux specific information
707 * will be called by generic audit code
708 * @ab: the audit buffer
709 * @a: audit_data
710 */
711static void avc_audit_pre_callback(struct audit_buffer *ab, void *a)
712{
713 struct common_audit_data *ad = a;
714 audit_log_format(ab, "avc: %s ",
715 ad->selinux_audit_data->denied ? "denied" : "granted");
716 avc_dump_av(ab, ad->selinux_audit_data->tclass,
717 ad->selinux_audit_data->audited);
718 audit_log_format(ab, " for ");
719}
720
721/**
722 * avc_audit_post_callback - SELinux specific information
723 * will be called by generic audit code
724 * @ab: the audit buffer
725 * @a: audit_data
726 */
727static void avc_audit_post_callback(struct audit_buffer *ab, void *a)
728{
729 struct common_audit_data *ad = a;
730 audit_log_format(ab, " ");
731 avc_dump_query(ab, ad->selinux_audit_data->ssid,
732 ad->selinux_audit_data->tsid,
733 ad->selinux_audit_data->tclass);
734 if (ad->selinux_audit_data->denied) {
735 audit_log_format(ab, " permissive=%u",
736 ad->selinux_audit_data->result ? 0 : 1);
737 }
738}
739
740/* This is the slow part of avc audit with big stack footprint */
741noinline int slow_avc_audit(u32 ssid, u32 tsid, u16 tclass,
742 u32 requested, u32 audited, u32 denied, int result,
743 struct common_audit_data *a,
744 unsigned flags)
745{
746 struct common_audit_data stack_data;
747 struct selinux_audit_data sad;
748
749 if (!a) {
750 a = &stack_data;
751 a->type = LSM_AUDIT_DATA_NONE;
752 }
753
754 /*
755 * When in a RCU walk do the audit on the RCU retry. This is because
756 * the collection of the dname in an inode audit message is not RCU
757 * safe. Note this may drop some audits when the situation changes
758 * during retry. However this is logically just as if the operation
759 * happened a little later.
760 */
761 if ((a->type == LSM_AUDIT_DATA_INODE) &&
762 (flags & MAY_NOT_BLOCK))
763 return -ECHILD;
764
765 sad.tclass = tclass;
766 sad.requested = requested;
767 sad.ssid = ssid;
768 sad.tsid = tsid;
769 sad.audited = audited;
770 sad.denied = denied;
771 sad.result = result;
772
773 a->selinux_audit_data = &sad;
774
775 common_lsm_audit(a, avc_audit_pre_callback, avc_audit_post_callback);
776 return 0;
777}
778
779/**
780 * avc_add_callback - Register a callback for security events.
781 * @callback: callback function
782 * @events: security events
783 *
784 * Register a callback function for events in the set @events.
785 * Returns %0 on success or -%ENOMEM if insufficient memory
786 * exists to add the callback.
787 */
788int __init avc_add_callback(int (*callback)(u32 event), u32 events)
789{
790 struct avc_callback_node *c;
791 int rc = 0;
792
793 c = kmalloc(sizeof(*c), GFP_KERNEL);
794 if (!c) {
795 rc = -ENOMEM;
796 goto out;
797 }
798
799 c->callback = callback;
800 c->events = events;
801 c->next = avc_callbacks;
802 avc_callbacks = c;
803out:
804 return rc;
805}
806
807/**
808 * avc_update_node Update an AVC entry
809 * @event : Updating event
810 * @perms : Permission mask bits
811 * @ssid,@tsid,@tclass : identifier of an AVC entry
812 * @seqno : sequence number when decision was made
813 * @xpd: extended_perms_decision to be added to the node
814 *
815 * if a valid AVC entry doesn't exist,this function returns -ENOENT.
816 * if kmalloc() called internal returns NULL, this function returns -ENOMEM.
817 * otherwise, this function updates the AVC entry. The original AVC-entry object
818 * will release later by RCU.
819 */
820static int avc_update_node(u32 event, u32 perms, u8 driver, u8 xperm, u32 ssid,
821 u32 tsid, u16 tclass, u32 seqno,
822 struct extended_perms_decision *xpd,
823 u32 flags)
824{
825 int hvalue, rc = 0;
826 unsigned long flag;
827 struct avc_node *pos, *node, *orig = NULL;
828 struct hlist_head *head;
829 spinlock_t *lock;
830
831 node = avc_alloc_node();
832 if (!node) {
833 rc = -ENOMEM;
834 goto out;
835 }
836
837 /* Lock the target slot */
838 hvalue = avc_hash(ssid, tsid, tclass);
839
840 head = &avc_cache.slots[hvalue];
841 lock = &avc_cache.slots_lock[hvalue];
842
843 spin_lock_irqsave(lock, flag);
844
845 hlist_for_each_entry(pos, head, list) {
846 if (ssid == pos->ae.ssid &&
847 tsid == pos->ae.tsid &&
848 tclass == pos->ae.tclass &&
849 seqno == pos->ae.avd.seqno){
850 orig = pos;
851 break;
852 }
853 }
854
855 if (!orig) {
856 rc = -ENOENT;
857 avc_node_kill(node);
858 goto out_unlock;
859 }
860
861 /*
862 * Copy and replace original node.
863 */
864
865 avc_node_populate(node, ssid, tsid, tclass, &orig->ae.avd);
866
867 if (orig->ae.xp_node) {
868 rc = avc_xperms_populate(node, orig->ae.xp_node);
869 if (rc) {
870 kmem_cache_free(avc_node_cachep, node);
871 goto out_unlock;
872 }
873 }
874
875 switch (event) {
876 case AVC_CALLBACK_GRANT:
877 node->ae.avd.allowed |= perms;
878 if (node->ae.xp_node && (flags & AVC_EXTENDED_PERMS))
879 avc_xperms_allow_perm(node->ae.xp_node, driver, xperm);
880 break;
881 case AVC_CALLBACK_TRY_REVOKE:
882 case AVC_CALLBACK_REVOKE:
883 node->ae.avd.allowed &= ~perms;
884 break;
885 case AVC_CALLBACK_AUDITALLOW_ENABLE:
886 node->ae.avd.auditallow |= perms;
887 break;
888 case AVC_CALLBACK_AUDITALLOW_DISABLE:
889 node->ae.avd.auditallow &= ~perms;
890 break;
891 case AVC_CALLBACK_AUDITDENY_ENABLE:
892 node->ae.avd.auditdeny |= perms;
893 break;
894 case AVC_CALLBACK_AUDITDENY_DISABLE:
895 node->ae.avd.auditdeny &= ~perms;
896 break;
897 case AVC_CALLBACK_ADD_XPERMS:
898 avc_add_xperms_decision(node, xpd);
899 break;
900 }
901 avc_node_replace(node, orig);
902out_unlock:
903 spin_unlock_irqrestore(lock, flag);
904out:
905 return rc;
906}
907
908/**
909 * avc_flush - Flush the cache
910 */
911static void avc_flush(void)
912{
913 struct hlist_head *head;
914 struct avc_node *node;
915 spinlock_t *lock;
916 unsigned long flag;
917 int i;
918
919 for (i = 0; i < AVC_CACHE_SLOTS; i++) {
920 head = &avc_cache.slots[i];
921 lock = &avc_cache.slots_lock[i];
922
923 spin_lock_irqsave(lock, flag);
924 /*
925 * With preemptable RCU, the outer spinlock does not
926 * prevent RCU grace periods from ending.
927 */
928 rcu_read_lock();
929 hlist_for_each_entry(node, head, list)
930 avc_node_delete(node);
931 rcu_read_unlock();
932 spin_unlock_irqrestore(lock, flag);
933 }
934}
935
936/**
937 * avc_ss_reset - Flush the cache and revalidate migrated permissions.
938 * @seqno: policy sequence number
939 */
940int avc_ss_reset(u32 seqno)
941{
942 struct avc_callback_node *c;
943 int rc = 0, tmprc;
944
945 avc_flush();
946
947 for (c = avc_callbacks; c; c = c->next) {
948 if (c->events & AVC_CALLBACK_RESET) {
949 tmprc = c->callback(AVC_CALLBACK_RESET);
950 /* save the first error encountered for the return
951 value and continue processing the callbacks */
952 if (!rc)
953 rc = tmprc;
954 }
955 }
956
957 avc_latest_notif_update(seqno, 0);
958 return rc;
959}
960
961/*
962 * Slow-path helper function for avc_has_perm_noaudit,
963 * when the avc_node lookup fails. We get called with
964 * the RCU read lock held, and need to return with it
965 * still held, but drop if for the security compute.
966 *
967 * Don't inline this, since it's the slow-path and just
968 * results in a bigger stack frame.
969 */
970static noinline struct avc_node *avc_compute_av(u32 ssid, u32 tsid,
971 u16 tclass, struct av_decision *avd,
972 struct avc_xperms_node *xp_node)
973{
974 rcu_read_unlock();
975 INIT_LIST_HEAD(&xp_node->xpd_head);
976 security_compute_av(ssid, tsid, tclass, avd, &xp_node->xp);
977 rcu_read_lock();
978 return avc_insert(ssid, tsid, tclass, avd, xp_node);
979}
980
981static noinline int avc_denied(u32 ssid, u32 tsid,
982 u16 tclass, u32 requested,
983 u8 driver, u8 xperm, unsigned flags,
984 struct av_decision *avd)
985{
986 if (flags & AVC_STRICT)
987 return -EACCES;
988
989 if (selinux_enforcing && !(avd->flags & AVD_FLAGS_PERMISSIVE))
990 return -EACCES;
991
992 avc_update_node(AVC_CALLBACK_GRANT, requested, driver, xperm, ssid,
993 tsid, tclass, avd->seqno, NULL, flags);
994 return 0;
995}
996
997/*
998 * The avc extended permissions logic adds an additional 256 bits of
999 * permissions to an avc node when extended permissions for that node are
1000 * specified in the avtab. If the additional 256 permissions is not adequate,
1001 * as-is the case with ioctls, then multiple may be chained together and the
1002 * driver field is used to specify which set contains the permission.
1003 */
1004int avc_has_extended_perms(u32 ssid, u32 tsid, u16 tclass, u32 requested,
1005 u8 driver, u8 xperm, struct common_audit_data *ad)
1006{
1007 struct avc_node *node;
1008 struct av_decision avd;
1009 u32 denied;
1010 struct extended_perms_decision local_xpd;
1011 struct extended_perms_decision *xpd = NULL;
1012 struct extended_perms_data allowed;
1013 struct extended_perms_data auditallow;
1014 struct extended_perms_data dontaudit;
1015 struct avc_xperms_node local_xp_node;
1016 struct avc_xperms_node *xp_node;
1017 int rc = 0, rc2;
1018
1019 xp_node = &local_xp_node;
1020 BUG_ON(!requested);
1021
1022 rcu_read_lock();
1023
1024 node = avc_lookup(ssid, tsid, tclass);
1025 if (unlikely(!node)) {
1026 node = avc_compute_av(ssid, tsid, tclass, &avd, xp_node);
1027 } else {
1028 memcpy(&avd, &node->ae.avd, sizeof(avd));
1029 xp_node = node->ae.xp_node;
1030 }
1031 /* if extended permissions are not defined, only consider av_decision */
1032 if (!xp_node || !xp_node->xp.len)
1033 goto decision;
1034
1035 local_xpd.allowed = &allowed;
1036 local_xpd.auditallow = &auditallow;
1037 local_xpd.dontaudit = &dontaudit;
1038
1039 xpd = avc_xperms_decision_lookup(driver, xp_node);
1040 if (unlikely(!xpd)) {
1041 /*
1042 * Compute the extended_perms_decision only if the driver
1043 * is flagged
1044 */
1045 if (!security_xperm_test(xp_node->xp.drivers.p, driver)) {
1046 avd.allowed &= ~requested;
1047 goto decision;
1048 }
1049 rcu_read_unlock();
1050 security_compute_xperms_decision(ssid, tsid, tclass, driver,
1051 &local_xpd);
1052 rcu_read_lock();
1053 avc_update_node(AVC_CALLBACK_ADD_XPERMS, requested, driver, xperm,
1054 ssid, tsid, tclass, avd.seqno, &local_xpd, 0);
1055 } else {
1056 avc_quick_copy_xperms_decision(xperm, &local_xpd, xpd);
1057 }
1058 xpd = &local_xpd;
1059
1060 if (!avc_xperms_has_perm(xpd, xperm, XPERMS_ALLOWED))
1061 avd.allowed &= ~requested;
1062
1063decision:
1064 denied = requested & ~(avd.allowed);
1065 if (unlikely(denied))
1066 rc = avc_denied(ssid, tsid, tclass, requested, driver, xperm,
1067 AVC_EXTENDED_PERMS, &avd);
1068
1069 rcu_read_unlock();
1070
1071 rc2 = avc_xperms_audit(ssid, tsid, tclass, requested,
1072 &avd, xpd, xperm, rc, ad);
1073 if (rc2)
1074 return rc2;
1075 return rc;
1076}
1077
1078/**
1079 * avc_has_perm_noaudit - Check permissions but perform no auditing.
1080 * @ssid: source security identifier
1081 * @tsid: target security identifier
1082 * @tclass: target security class
1083 * @requested: requested permissions, interpreted based on @tclass
1084 * @flags: AVC_STRICT or 0
1085 * @avd: access vector decisions
1086 *
1087 * Check the AVC to determine whether the @requested permissions are granted
1088 * for the SID pair (@ssid, @tsid), interpreting the permissions
1089 * based on @tclass, and call the security server on a cache miss to obtain
1090 * a new decision and add it to the cache. Return a copy of the decisions
1091 * in @avd. Return %0 if all @requested permissions are granted,
1092 * -%EACCES if any permissions are denied, or another -errno upon
1093 * other errors. This function is typically called by avc_has_perm(),
1094 * but may also be called directly to separate permission checking from
1095 * auditing, e.g. in cases where a lock must be held for the check but
1096 * should be released for the auditing.
1097 */
1098inline int avc_has_perm_noaudit(u32 ssid, u32 tsid,
1099 u16 tclass, u32 requested,
1100 unsigned flags,
1101 struct av_decision *avd)
1102{
1103 struct avc_node *node;
1104 struct avc_xperms_node xp_node;
1105 int rc = 0;
1106 u32 denied;
1107
1108 BUG_ON(!requested);
1109
1110 rcu_read_lock();
1111
1112 node = avc_lookup(ssid, tsid, tclass);
1113 if (unlikely(!node))
1114 node = avc_compute_av(ssid, tsid, tclass, avd, &xp_node);
1115 else
1116 memcpy(avd, &node->ae.avd, sizeof(*avd));
1117
1118 denied = requested & ~(avd->allowed);
1119 if (unlikely(denied))
1120 rc = avc_denied(ssid, tsid, tclass, requested, 0, 0, flags, avd);
1121
1122 rcu_read_unlock();
1123 return rc;
1124}
1125
1126/**
1127 * avc_has_perm - Check permissions and perform any appropriate auditing.
1128 * @ssid: source security identifier
1129 * @tsid: target security identifier
1130 * @tclass: target security class
1131 * @requested: requested permissions, interpreted based on @tclass
1132 * @auditdata: auxiliary audit data
1133 *
1134 * Check the AVC to determine whether the @requested permissions are granted
1135 * for the SID pair (@ssid, @tsid), interpreting the permissions
1136 * based on @tclass, and call the security server on a cache miss to obtain
1137 * a new decision and add it to the cache. Audit the granting or denial of
1138 * permissions in accordance with the policy. Return %0 if all @requested
1139 * permissions are granted, -%EACCES if any permissions are denied, or
1140 * another -errno upon other errors.
1141 */
1142int avc_has_perm(u32 ssid, u32 tsid, u16 tclass,
1143 u32 requested, struct common_audit_data *auditdata)
1144{
1145 struct av_decision avd;
1146 int rc, rc2;
1147
1148 rc = avc_has_perm_noaudit(ssid, tsid, tclass, requested, 0, &avd);
1149
1150 rc2 = avc_audit(ssid, tsid, tclass, requested, &avd, rc, auditdata, 0);
1151 if (rc2)
1152 return rc2;
1153 return rc;
1154}
1155
1156int avc_has_perm_flags(u32 ssid, u32 tsid, u16 tclass,
1157 u32 requested, struct common_audit_data *auditdata,
1158 int flags)
1159{
1160 struct av_decision avd;
1161 int rc, rc2;
1162
1163 rc = avc_has_perm_noaudit(ssid, tsid, tclass, requested, 0, &avd);
1164
1165 rc2 = avc_audit(ssid, tsid, tclass, requested, &avd, rc,
1166 auditdata, flags);
1167 if (rc2)
1168 return rc2;
1169 return rc;
1170}
1171
1172u32 avc_policy_seqno(void)
1173{
1174 return avc_cache.latest_notif;
1175}
1176
1177void avc_disable(void)
1178{
1179 /*
1180 * If you are looking at this because you have realized that we are
1181 * not destroying the avc_node_cachep it might be easy to fix, but
1182 * I don't know the memory barrier semantics well enough to know. It's
1183 * possible that some other task dereferenced security_ops when
1184 * it still pointed to selinux operations. If that is the case it's
1185 * possible that it is about to use the avc and is about to need the
1186 * avc_node_cachep. I know I could wrap the security.c security_ops call
1187 * in an rcu_lock, but seriously, it's not worth it. Instead I just flush
1188 * the cache and get that memory back.
1189 */
1190 if (avc_node_cachep) {
1191 avc_flush();
1192 /* kmem_cache_destroy(avc_node_cachep); */
1193 }
1194}
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, u32 ssid, u32 tsid,
69 u16 tclass, u32 perms,
70 u32 *out_retained);
71 u32 events;
72 u32 ssid;
73 u32 tsid;
74 u16 tclass;
75 u32 perms;
76 struct avc_callback_node *next;
77};
78
79/* Exported via selinufs */
80unsigned int avc_cache_threshold = AVC_DEF_CACHE_THRESHOLD;
81
82#ifdef CONFIG_SECURITY_SELINUX_AVC_STATS
83DEFINE_PER_CPU(struct avc_cache_stats, avc_cache_stats) = { 0 };
84#endif
85
86static struct avc_cache avc_cache;
87static struct avc_callback_node *avc_callbacks;
88static struct kmem_cache *avc_node_cachep;
89
90static inline int avc_hash(u32 ssid, u32 tsid, u16 tclass)
91{
92 return (ssid ^ (tsid<<2) ^ (tclass<<4)) & (AVC_CACHE_SLOTS - 1);
93}
94
95/**
96 * avc_dump_av - Display an access vector in human-readable form.
97 * @tclass: target security class
98 * @av: access vector
99 */
100static void avc_dump_av(struct audit_buffer *ab, u16 tclass, u32 av)
101{
102 const char **perms;
103 int i, perm;
104
105 if (av == 0) {
106 audit_log_format(ab, " null");
107 return;
108 }
109
110 perms = secclass_map[tclass-1].perms;
111
112 audit_log_format(ab, " {");
113 i = 0;
114 perm = 1;
115 while (i < (sizeof(av) * 8)) {
116 if ((perm & av) && perms[i]) {
117 audit_log_format(ab, " %s", perms[i]);
118 av &= ~perm;
119 }
120 i++;
121 perm <<= 1;
122 }
123
124 if (av)
125 audit_log_format(ab, " 0x%x", av);
126
127 audit_log_format(ab, " }");
128}
129
130/**
131 * avc_dump_query - Display a SID pair and a class in human-readable form.
132 * @ssid: source security identifier
133 * @tsid: target security identifier
134 * @tclass: target security class
135 */
136static void avc_dump_query(struct audit_buffer *ab, u32 ssid, u32 tsid, u16 tclass)
137{
138 int rc;
139 char *scontext;
140 u32 scontext_len;
141
142 rc = security_sid_to_context(ssid, &scontext, &scontext_len);
143 if (rc)
144 audit_log_format(ab, "ssid=%d", ssid);
145 else {
146 audit_log_format(ab, "scontext=%s", scontext);
147 kfree(scontext);
148 }
149
150 rc = security_sid_to_context(tsid, &scontext, &scontext_len);
151 if (rc)
152 audit_log_format(ab, " tsid=%d", tsid);
153 else {
154 audit_log_format(ab, " tcontext=%s", scontext);
155 kfree(scontext);
156 }
157
158 BUG_ON(tclass >= ARRAY_SIZE(secclass_map));
159 audit_log_format(ab, " tclass=%s", secclass_map[tclass-1].name);
160}
161
162/**
163 * avc_init - Initialize the AVC.
164 *
165 * Initialize the access vector cache.
166 */
167void __init avc_init(void)
168{
169 int i;
170
171 for (i = 0; i < AVC_CACHE_SLOTS; i++) {
172 INIT_HLIST_HEAD(&avc_cache.slots[i]);
173 spin_lock_init(&avc_cache.slots_lock[i]);
174 }
175 atomic_set(&avc_cache.active_nodes, 0);
176 atomic_set(&avc_cache.lru_hint, 0);
177
178 avc_node_cachep = kmem_cache_create("avc_node", sizeof(struct avc_node),
179 0, SLAB_PANIC, NULL);
180
181 audit_log(current->audit_context, GFP_KERNEL, AUDIT_KERNEL, "AVC INITIALIZED\n");
182}
183
184int avc_get_hash_stats(char *page)
185{
186 int i, chain_len, max_chain_len, slots_used;
187 struct avc_node *node;
188 struct hlist_head *head;
189
190 rcu_read_lock();
191
192 slots_used = 0;
193 max_chain_len = 0;
194 for (i = 0; i < AVC_CACHE_SLOTS; i++) {
195 head = &avc_cache.slots[i];
196 if (!hlist_empty(head)) {
197 struct hlist_node *next;
198
199 slots_used++;
200 chain_len = 0;
201 hlist_for_each_entry_rcu(node, next, head, list)
202 chain_len++;
203 if (chain_len > max_chain_len)
204 max_chain_len = chain_len;
205 }
206 }
207
208 rcu_read_unlock();
209
210 return scnprintf(page, PAGE_SIZE, "entries: %d\nbuckets used: %d/%d\n"
211 "longest chain: %d\n",
212 atomic_read(&avc_cache.active_nodes),
213 slots_used, AVC_CACHE_SLOTS, max_chain_len);
214}
215
216static void avc_node_free(struct rcu_head *rhead)
217{
218 struct avc_node *node = container_of(rhead, struct avc_node, rhead);
219 kmem_cache_free(avc_node_cachep, node);
220 avc_cache_stats_incr(frees);
221}
222
223static void avc_node_delete(struct avc_node *node)
224{
225 hlist_del_rcu(&node->list);
226 call_rcu(&node->rhead, avc_node_free);
227 atomic_dec(&avc_cache.active_nodes);
228}
229
230static void avc_node_kill(struct avc_node *node)
231{
232 kmem_cache_free(avc_node_cachep, node);
233 avc_cache_stats_incr(frees);
234 atomic_dec(&avc_cache.active_nodes);
235}
236
237static void avc_node_replace(struct avc_node *new, struct avc_node *old)
238{
239 hlist_replace_rcu(&old->list, &new->list);
240 call_rcu(&old->rhead, avc_node_free);
241 atomic_dec(&avc_cache.active_nodes);
242}
243
244static inline int avc_reclaim_node(void)
245{
246 struct avc_node *node;
247 int hvalue, try, ecx;
248 unsigned long flags;
249 struct hlist_head *head;
250 struct hlist_node *next;
251 spinlock_t *lock;
252
253 for (try = 0, ecx = 0; try < AVC_CACHE_SLOTS; try++) {
254 hvalue = atomic_inc_return(&avc_cache.lru_hint) & (AVC_CACHE_SLOTS - 1);
255 head = &avc_cache.slots[hvalue];
256 lock = &avc_cache.slots_lock[hvalue];
257
258 if (!spin_trylock_irqsave(lock, flags))
259 continue;
260
261 rcu_read_lock();
262 hlist_for_each_entry(node, next, head, list) {
263 avc_node_delete(node);
264 avc_cache_stats_incr(reclaims);
265 ecx++;
266 if (ecx >= AVC_CACHE_RECLAIM) {
267 rcu_read_unlock();
268 spin_unlock_irqrestore(lock, flags);
269 goto out;
270 }
271 }
272 rcu_read_unlock();
273 spin_unlock_irqrestore(lock, flags);
274 }
275out:
276 return ecx;
277}
278
279static struct avc_node *avc_alloc_node(void)
280{
281 struct avc_node *node;
282
283 node = kmem_cache_zalloc(avc_node_cachep, GFP_ATOMIC);
284 if (!node)
285 goto out;
286
287 INIT_HLIST_NODE(&node->list);
288 avc_cache_stats_incr(allocations);
289
290 if (atomic_inc_return(&avc_cache.active_nodes) > avc_cache_threshold)
291 avc_reclaim_node();
292
293out:
294 return node;
295}
296
297static void avc_node_populate(struct avc_node *node, u32 ssid, u32 tsid, u16 tclass, struct av_decision *avd)
298{
299 node->ae.ssid = ssid;
300 node->ae.tsid = tsid;
301 node->ae.tclass = tclass;
302 memcpy(&node->ae.avd, avd, sizeof(node->ae.avd));
303}
304
305static inline struct avc_node *avc_search_node(u32 ssid, u32 tsid, u16 tclass)
306{
307 struct avc_node *node, *ret = NULL;
308 int hvalue;
309 struct hlist_head *head;
310 struct hlist_node *next;
311
312 hvalue = avc_hash(ssid, tsid, tclass);
313 head = &avc_cache.slots[hvalue];
314 hlist_for_each_entry_rcu(node, next, head, list) {
315 if (ssid == node->ae.ssid &&
316 tclass == node->ae.tclass &&
317 tsid == node->ae.tsid) {
318 ret = node;
319 break;
320 }
321 }
322
323 return ret;
324}
325
326/**
327 * avc_lookup - Look up an AVC entry.
328 * @ssid: source security identifier
329 * @tsid: target security identifier
330 * @tclass: target security class
331 *
332 * Look up an AVC entry that is valid for the
333 * (@ssid, @tsid), interpreting the permissions
334 * based on @tclass. If a valid AVC entry exists,
335 * then this function returns the avc_node.
336 * Otherwise, this function returns NULL.
337 */
338static struct avc_node *avc_lookup(u32 ssid, u32 tsid, u16 tclass)
339{
340 struct avc_node *node;
341
342 avc_cache_stats_incr(lookups);
343 node = avc_search_node(ssid, tsid, tclass);
344
345 if (node)
346 return node;
347
348 avc_cache_stats_incr(misses);
349 return NULL;
350}
351
352static int avc_latest_notif_update(int seqno, int is_insert)
353{
354 int ret = 0;
355 static DEFINE_SPINLOCK(notif_lock);
356 unsigned long flag;
357
358 spin_lock_irqsave(¬if_lock, flag);
359 if (is_insert) {
360 if (seqno < avc_cache.latest_notif) {
361 printk(KERN_WARNING "SELinux: avc: seqno %d < latest_notif %d\n",
362 seqno, avc_cache.latest_notif);
363 ret = -EAGAIN;
364 }
365 } else {
366 if (seqno > avc_cache.latest_notif)
367 avc_cache.latest_notif = seqno;
368 }
369 spin_unlock_irqrestore(¬if_lock, flag);
370
371 return ret;
372}
373
374/**
375 * avc_insert - Insert an AVC entry.
376 * @ssid: source security identifier
377 * @tsid: target security identifier
378 * @tclass: target security class
379 * @avd: resulting av decision
380 *
381 * Insert an AVC entry for the SID pair
382 * (@ssid, @tsid) and class @tclass.
383 * The access vectors and the sequence number are
384 * normally provided by the security server in
385 * response to a security_compute_av() call. If the
386 * sequence number @avd->seqno is not less than the latest
387 * revocation notification, then the function copies
388 * the access vectors into a cache entry, returns
389 * avc_node inserted. Otherwise, this function returns NULL.
390 */
391static struct avc_node *avc_insert(u32 ssid, u32 tsid, u16 tclass, struct av_decision *avd)
392{
393 struct avc_node *pos, *node = NULL;
394 int hvalue;
395 unsigned long flag;
396
397 if (avc_latest_notif_update(avd->seqno, 1))
398 goto out;
399
400 node = avc_alloc_node();
401 if (node) {
402 struct hlist_head *head;
403 struct hlist_node *next;
404 spinlock_t *lock;
405
406 hvalue = avc_hash(ssid, tsid, tclass);
407 avc_node_populate(node, ssid, tsid, tclass, avd);
408
409 head = &avc_cache.slots[hvalue];
410 lock = &avc_cache.slots_lock[hvalue];
411
412 spin_lock_irqsave(lock, flag);
413 hlist_for_each_entry(pos, next, head, list) {
414 if (pos->ae.ssid == ssid &&
415 pos->ae.tsid == tsid &&
416 pos->ae.tclass == tclass) {
417 avc_node_replace(node, pos);
418 goto found;
419 }
420 }
421 hlist_add_head_rcu(&node->list, head);
422found:
423 spin_unlock_irqrestore(lock, flag);
424 }
425out:
426 return node;
427}
428
429/**
430 * avc_audit_pre_callback - SELinux specific information
431 * will be called by generic audit code
432 * @ab: the audit buffer
433 * @a: audit_data
434 */
435static void avc_audit_pre_callback(struct audit_buffer *ab, void *a)
436{
437 struct common_audit_data *ad = a;
438 audit_log_format(ab, "avc: %s ",
439 ad->selinux_audit_data.denied ? "denied" : "granted");
440 avc_dump_av(ab, ad->selinux_audit_data.tclass,
441 ad->selinux_audit_data.audited);
442 audit_log_format(ab, " for ");
443}
444
445/**
446 * avc_audit_post_callback - SELinux specific information
447 * will be called by generic audit code
448 * @ab: the audit buffer
449 * @a: audit_data
450 */
451static void avc_audit_post_callback(struct audit_buffer *ab, void *a)
452{
453 struct common_audit_data *ad = a;
454 audit_log_format(ab, " ");
455 avc_dump_query(ab, ad->selinux_audit_data.ssid,
456 ad->selinux_audit_data.tsid,
457 ad->selinux_audit_data.tclass);
458}
459
460/**
461 * avc_audit - Audit the granting or denial of permissions.
462 * @ssid: source security identifier
463 * @tsid: target security identifier
464 * @tclass: target security class
465 * @requested: requested permissions
466 * @avd: access vector decisions
467 * @result: result from avc_has_perm_noaudit
468 * @a: auxiliary audit data
469 * @flags: VFS walk flags
470 *
471 * Audit the granting or denial of permissions in accordance
472 * with the policy. This function is typically called by
473 * avc_has_perm() after a permission check, but can also be
474 * called directly by callers who use avc_has_perm_noaudit()
475 * in order to separate the permission check from the auditing.
476 * For example, this separation is useful when the permission check must
477 * be performed under a lock, to allow the lock to be released
478 * before calling the auditing code.
479 */
480int avc_audit(u32 ssid, u32 tsid,
481 u16 tclass, u32 requested,
482 struct av_decision *avd, int result, struct common_audit_data *a,
483 unsigned flags)
484{
485 struct common_audit_data stack_data;
486 u32 denied, audited;
487 denied = requested & ~avd->allowed;
488 if (denied) {
489 audited = denied & avd->auditdeny;
490 /*
491 * a->selinux_audit_data.auditdeny is TRICKY! Setting a bit in
492 * this field means that ANY denials should NOT be audited if
493 * the policy contains an explicit dontaudit rule for that
494 * permission. Take notice that this is unrelated to the
495 * actual permissions that were denied. As an example lets
496 * assume:
497 *
498 * denied == READ
499 * avd.auditdeny & ACCESS == 0 (not set means explicit rule)
500 * selinux_audit_data.auditdeny & ACCESS == 1
501 *
502 * We will NOT audit the denial even though the denied
503 * permission was READ and the auditdeny checks were for
504 * ACCESS
505 */
506 if (a &&
507 a->selinux_audit_data.auditdeny &&
508 !(a->selinux_audit_data.auditdeny & avd->auditdeny))
509 audited = 0;
510 } else if (result)
511 audited = denied = requested;
512 else
513 audited = requested & avd->auditallow;
514 if (!audited)
515 return 0;
516
517 if (!a) {
518 a = &stack_data;
519 COMMON_AUDIT_DATA_INIT(a, NONE);
520 }
521
522 /*
523 * When in a RCU walk do the audit on the RCU retry. This is because
524 * the collection of the dname in an inode audit message is not RCU
525 * safe. Note this may drop some audits when the situation changes
526 * during retry. However this is logically just as if the operation
527 * happened a little later.
528 */
529 if ((a->type == LSM_AUDIT_DATA_INODE) &&
530 (flags & MAY_NOT_BLOCK))
531 return -ECHILD;
532
533 a->selinux_audit_data.tclass = tclass;
534 a->selinux_audit_data.requested = requested;
535 a->selinux_audit_data.ssid = ssid;
536 a->selinux_audit_data.tsid = tsid;
537 a->selinux_audit_data.audited = audited;
538 a->selinux_audit_data.denied = denied;
539 a->lsm_pre_audit = avc_audit_pre_callback;
540 a->lsm_post_audit = avc_audit_post_callback;
541 common_lsm_audit(a);
542 return 0;
543}
544
545/**
546 * avc_add_callback - Register a callback for security events.
547 * @callback: callback function
548 * @events: security events
549 * @ssid: source security identifier or %SECSID_WILD
550 * @tsid: target security identifier or %SECSID_WILD
551 * @tclass: target security class
552 * @perms: permissions
553 *
554 * Register a callback function for events in the set @events
555 * related to the SID pair (@ssid, @tsid)
556 * and the permissions @perms, interpreting
557 * @perms based on @tclass. Returns %0 on success or
558 * -%ENOMEM if insufficient memory exists to add the callback.
559 */
560int avc_add_callback(int (*callback)(u32 event, u32 ssid, u32 tsid,
561 u16 tclass, u32 perms,
562 u32 *out_retained),
563 u32 events, u32 ssid, u32 tsid,
564 u16 tclass, u32 perms)
565{
566 struct avc_callback_node *c;
567 int rc = 0;
568
569 c = kmalloc(sizeof(*c), GFP_ATOMIC);
570 if (!c) {
571 rc = -ENOMEM;
572 goto out;
573 }
574
575 c->callback = callback;
576 c->events = events;
577 c->ssid = ssid;
578 c->tsid = tsid;
579 c->perms = perms;
580 c->next = avc_callbacks;
581 avc_callbacks = c;
582out:
583 return rc;
584}
585
586static inline int avc_sidcmp(u32 x, u32 y)
587{
588 return (x == y || x == SECSID_WILD || y == SECSID_WILD);
589}
590
591/**
592 * avc_update_node Update an AVC entry
593 * @event : Updating event
594 * @perms : Permission mask bits
595 * @ssid,@tsid,@tclass : identifier of an AVC entry
596 * @seqno : sequence number when decision was made
597 *
598 * if a valid AVC entry doesn't exist,this function returns -ENOENT.
599 * if kmalloc() called internal returns NULL, this function returns -ENOMEM.
600 * otherwise, this function updates the AVC entry. The original AVC-entry object
601 * will release later by RCU.
602 */
603static int avc_update_node(u32 event, u32 perms, u32 ssid, u32 tsid, u16 tclass,
604 u32 seqno)
605{
606 int hvalue, rc = 0;
607 unsigned long flag;
608 struct avc_node *pos, *node, *orig = NULL;
609 struct hlist_head *head;
610 struct hlist_node *next;
611 spinlock_t *lock;
612
613 node = avc_alloc_node();
614 if (!node) {
615 rc = -ENOMEM;
616 goto out;
617 }
618
619 /* Lock the target slot */
620 hvalue = avc_hash(ssid, tsid, tclass);
621
622 head = &avc_cache.slots[hvalue];
623 lock = &avc_cache.slots_lock[hvalue];
624
625 spin_lock_irqsave(lock, flag);
626
627 hlist_for_each_entry(pos, next, head, list) {
628 if (ssid == pos->ae.ssid &&
629 tsid == pos->ae.tsid &&
630 tclass == pos->ae.tclass &&
631 seqno == pos->ae.avd.seqno){
632 orig = pos;
633 break;
634 }
635 }
636
637 if (!orig) {
638 rc = -ENOENT;
639 avc_node_kill(node);
640 goto out_unlock;
641 }
642
643 /*
644 * Copy and replace original node.
645 */
646
647 avc_node_populate(node, ssid, tsid, tclass, &orig->ae.avd);
648
649 switch (event) {
650 case AVC_CALLBACK_GRANT:
651 node->ae.avd.allowed |= perms;
652 break;
653 case AVC_CALLBACK_TRY_REVOKE:
654 case AVC_CALLBACK_REVOKE:
655 node->ae.avd.allowed &= ~perms;
656 break;
657 case AVC_CALLBACK_AUDITALLOW_ENABLE:
658 node->ae.avd.auditallow |= perms;
659 break;
660 case AVC_CALLBACK_AUDITALLOW_DISABLE:
661 node->ae.avd.auditallow &= ~perms;
662 break;
663 case AVC_CALLBACK_AUDITDENY_ENABLE:
664 node->ae.avd.auditdeny |= perms;
665 break;
666 case AVC_CALLBACK_AUDITDENY_DISABLE:
667 node->ae.avd.auditdeny &= ~perms;
668 break;
669 }
670 avc_node_replace(node, orig);
671out_unlock:
672 spin_unlock_irqrestore(lock, flag);
673out:
674 return rc;
675}
676
677/**
678 * avc_flush - Flush the cache
679 */
680static void avc_flush(void)
681{
682 struct hlist_head *head;
683 struct hlist_node *next;
684 struct avc_node *node;
685 spinlock_t *lock;
686 unsigned long flag;
687 int i;
688
689 for (i = 0; i < AVC_CACHE_SLOTS; i++) {
690 head = &avc_cache.slots[i];
691 lock = &avc_cache.slots_lock[i];
692
693 spin_lock_irqsave(lock, flag);
694 /*
695 * With preemptable RCU, the outer spinlock does not
696 * prevent RCU grace periods from ending.
697 */
698 rcu_read_lock();
699 hlist_for_each_entry(node, next, head, list)
700 avc_node_delete(node);
701 rcu_read_unlock();
702 spin_unlock_irqrestore(lock, flag);
703 }
704}
705
706/**
707 * avc_ss_reset - Flush the cache and revalidate migrated permissions.
708 * @seqno: policy sequence number
709 */
710int avc_ss_reset(u32 seqno)
711{
712 struct avc_callback_node *c;
713 int rc = 0, tmprc;
714
715 avc_flush();
716
717 for (c = avc_callbacks; c; c = c->next) {
718 if (c->events & AVC_CALLBACK_RESET) {
719 tmprc = c->callback(AVC_CALLBACK_RESET,
720 0, 0, 0, 0, NULL);
721 /* save the first error encountered for the return
722 value and continue processing the callbacks */
723 if (!rc)
724 rc = tmprc;
725 }
726 }
727
728 avc_latest_notif_update(seqno, 0);
729 return rc;
730}
731
732/**
733 * avc_has_perm_noaudit - Check permissions but perform no auditing.
734 * @ssid: source security identifier
735 * @tsid: target security identifier
736 * @tclass: target security class
737 * @requested: requested permissions, interpreted based on @tclass
738 * @flags: AVC_STRICT or 0
739 * @avd: access vector decisions
740 *
741 * Check the AVC to determine whether the @requested permissions are granted
742 * for the SID pair (@ssid, @tsid), interpreting the permissions
743 * based on @tclass, and call the security server on a cache miss to obtain
744 * a new decision and add it to the cache. Return a copy of the decisions
745 * in @avd. Return %0 if all @requested permissions are granted,
746 * -%EACCES if any permissions are denied, or another -errno upon
747 * other errors. This function is typically called by avc_has_perm(),
748 * but may also be called directly to separate permission checking from
749 * auditing, e.g. in cases where a lock must be held for the check but
750 * should be released for the auditing.
751 */
752int avc_has_perm_noaudit(u32 ssid, u32 tsid,
753 u16 tclass, u32 requested,
754 unsigned flags,
755 struct av_decision *avd)
756{
757 struct avc_node *node;
758 int rc = 0;
759 u32 denied;
760
761 BUG_ON(!requested);
762
763 rcu_read_lock();
764
765 node = avc_lookup(ssid, tsid, tclass);
766 if (unlikely(!node)) {
767 rcu_read_unlock();
768 security_compute_av(ssid, tsid, tclass, avd);
769 rcu_read_lock();
770 node = avc_insert(ssid, tsid, tclass, avd);
771 } else {
772 memcpy(avd, &node->ae.avd, sizeof(*avd));
773 avd = &node->ae.avd;
774 }
775
776 denied = requested & ~(avd->allowed);
777
778 if (denied) {
779 if (flags & AVC_STRICT)
780 rc = -EACCES;
781 else if (!selinux_enforcing || (avd->flags & AVD_FLAGS_PERMISSIVE))
782 avc_update_node(AVC_CALLBACK_GRANT, requested, ssid,
783 tsid, tclass, avd->seqno);
784 else
785 rc = -EACCES;
786 }
787
788 rcu_read_unlock();
789 return rc;
790}
791
792/**
793 * avc_has_perm - Check permissions and perform any appropriate auditing.
794 * @ssid: source security identifier
795 * @tsid: target security identifier
796 * @tclass: target security class
797 * @requested: requested permissions, interpreted based on @tclass
798 * @auditdata: auxiliary audit data
799 * @flags: VFS walk flags
800 *
801 * Check the AVC to determine whether the @requested permissions are granted
802 * for the SID pair (@ssid, @tsid), interpreting the permissions
803 * based on @tclass, and call the security server on a cache miss to obtain
804 * a new decision and add it to the cache. Audit the granting or denial of
805 * permissions in accordance with the policy. Return %0 if all @requested
806 * permissions are granted, -%EACCES if any permissions are denied, or
807 * another -errno upon other errors.
808 */
809int avc_has_perm_flags(u32 ssid, u32 tsid, u16 tclass,
810 u32 requested, struct common_audit_data *auditdata,
811 unsigned flags)
812{
813 struct av_decision avd;
814 int rc, rc2;
815
816 rc = avc_has_perm_noaudit(ssid, tsid, tclass, requested, 0, &avd);
817
818 rc2 = avc_audit(ssid, tsid, tclass, requested, &avd, rc, auditdata,
819 flags);
820 if (rc2)
821 return rc2;
822 return rc;
823}
824
825u32 avc_policy_seqno(void)
826{
827 return avc_cache.latest_notif;
828}
829
830void avc_disable(void)
831{
832 /*
833 * If you are looking at this because you have realized that we are
834 * not destroying the avc_node_cachep it might be easy to fix, but
835 * I don't know the memory barrier semantics well enough to know. It's
836 * possible that some other task dereferenced security_ops when
837 * it still pointed to selinux operations. If that is the case it's
838 * possible that it is about to use the avc and is about to need the
839 * avc_node_cachep. I know I could wrap the security.c security_ops call
840 * in an rcu_lock, but seriously, it's not worth it. Instead I just flush
841 * the cache and get that memory back.
842 */
843 if (avc_node_cachep) {
844 avc_flush();
845 /* kmem_cache_destroy(avc_node_cachep); */
846 }
847}