xref: /openbmc/linux/security/selinux/avc.c (revision b593bce5)
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Implementation of the kernel access vector cache (AVC).
4  *
5  * Authors:  Stephen Smalley, <sds@tycho.nsa.gov>
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 AVC_CACHE_SLOTS			512
35 #define AVC_DEF_CACHE_THRESHOLD		512
36 #define AVC_CACHE_RECLAIM		16
37 
38 #ifdef CONFIG_SECURITY_SELINUX_AVC_STATS
39 #define avc_cache_stats_incr(field)	this_cpu_inc(avc_cache_stats.field)
40 #else
41 #define avc_cache_stats_incr(field)	do {} while (0)
42 #endif
43 
44 struct avc_entry {
45 	u32			ssid;
46 	u32			tsid;
47 	u16			tclass;
48 	struct av_decision	avd;
49 	struct avc_xperms_node	*xp_node;
50 };
51 
52 struct avc_node {
53 	struct avc_entry	ae;
54 	struct hlist_node	list; /* anchored in avc_cache->slots[i] */
55 	struct rcu_head		rhead;
56 };
57 
58 struct avc_xperms_decision_node {
59 	struct extended_perms_decision xpd;
60 	struct list_head xpd_list; /* list of extended_perms_decision */
61 };
62 
63 struct avc_xperms_node {
64 	struct extended_perms xp;
65 	struct list_head xpd_head; /* list head of extended_perms_decision */
66 };
67 
68 struct avc_cache {
69 	struct hlist_head	slots[AVC_CACHE_SLOTS]; /* head for avc_node->list */
70 	spinlock_t		slots_lock[AVC_CACHE_SLOTS]; /* lock for writes */
71 	atomic_t		lru_hint;	/* LRU hint for reclaim scan */
72 	atomic_t		active_nodes;
73 	u32			latest_notif;	/* latest revocation notification */
74 };
75 
76 struct avc_callback_node {
77 	int (*callback) (u32 event);
78 	u32 events;
79 	struct avc_callback_node *next;
80 };
81 
82 #ifdef CONFIG_SECURITY_SELINUX_AVC_STATS
83 DEFINE_PER_CPU(struct avc_cache_stats, avc_cache_stats) = { 0 };
84 #endif
85 
86 struct selinux_avc {
87 	unsigned int avc_cache_threshold;
88 	struct avc_cache avc_cache;
89 };
90 
91 static struct selinux_avc selinux_avc;
92 
93 void selinux_avc_init(struct selinux_avc **avc)
94 {
95 	int i;
96 
97 	selinux_avc.avc_cache_threshold = AVC_DEF_CACHE_THRESHOLD;
98 	for (i = 0; i < AVC_CACHE_SLOTS; i++) {
99 		INIT_HLIST_HEAD(&selinux_avc.avc_cache.slots[i]);
100 		spin_lock_init(&selinux_avc.avc_cache.slots_lock[i]);
101 	}
102 	atomic_set(&selinux_avc.avc_cache.active_nodes, 0);
103 	atomic_set(&selinux_avc.avc_cache.lru_hint, 0);
104 	*avc = &selinux_avc;
105 }
106 
107 unsigned int avc_get_cache_threshold(struct selinux_avc *avc)
108 {
109 	return avc->avc_cache_threshold;
110 }
111 
112 void avc_set_cache_threshold(struct selinux_avc *avc,
113 			     unsigned int cache_threshold)
114 {
115 	avc->avc_cache_threshold = cache_threshold;
116 }
117 
118 static struct avc_callback_node *avc_callbacks;
119 static struct kmem_cache *avc_node_cachep;
120 static struct kmem_cache *avc_xperms_data_cachep;
121 static struct kmem_cache *avc_xperms_decision_cachep;
122 static struct kmem_cache *avc_xperms_cachep;
123 
124 static inline int avc_hash(u32 ssid, u32 tsid, u16 tclass)
125 {
126 	return (ssid ^ (tsid<<2) ^ (tclass<<4)) & (AVC_CACHE_SLOTS - 1);
127 }
128 
129 /**
130  * avc_init - Initialize the AVC.
131  *
132  * Initialize the access vector cache.
133  */
134 void __init avc_init(void)
135 {
136 	avc_node_cachep = kmem_cache_create("avc_node", sizeof(struct avc_node),
137 					0, SLAB_PANIC, NULL);
138 	avc_xperms_cachep = kmem_cache_create("avc_xperms_node",
139 					sizeof(struct avc_xperms_node),
140 					0, SLAB_PANIC, NULL);
141 	avc_xperms_decision_cachep = kmem_cache_create(
142 					"avc_xperms_decision_node",
143 					sizeof(struct avc_xperms_decision_node),
144 					0, SLAB_PANIC, NULL);
145 	avc_xperms_data_cachep = kmem_cache_create("avc_xperms_data",
146 					sizeof(struct extended_perms_data),
147 					0, SLAB_PANIC, NULL);
148 }
149 
150 int avc_get_hash_stats(struct selinux_avc *avc, char *page)
151 {
152 	int i, chain_len, max_chain_len, slots_used;
153 	struct avc_node *node;
154 	struct hlist_head *head;
155 
156 	rcu_read_lock();
157 
158 	slots_used = 0;
159 	max_chain_len = 0;
160 	for (i = 0; i < AVC_CACHE_SLOTS; i++) {
161 		head = &avc->avc_cache.slots[i];
162 		if (!hlist_empty(head)) {
163 			slots_used++;
164 			chain_len = 0;
165 			hlist_for_each_entry_rcu(node, head, list)
166 				chain_len++;
167 			if (chain_len > max_chain_len)
168 				max_chain_len = chain_len;
169 		}
170 	}
171 
172 	rcu_read_unlock();
173 
174 	return scnprintf(page, PAGE_SIZE, "entries: %d\nbuckets used: %d/%d\n"
175 			 "longest chain: %d\n",
176 			 atomic_read(&avc->avc_cache.active_nodes),
177 			 slots_used, AVC_CACHE_SLOTS, max_chain_len);
178 }
179 
180 /*
181  * using a linked list for extended_perms_decision lookup because the list is
182  * always small. i.e. less than 5, typically 1
183  */
184 static struct extended_perms_decision *avc_xperms_decision_lookup(u8 driver,
185 					struct avc_xperms_node *xp_node)
186 {
187 	struct avc_xperms_decision_node *xpd_node;
188 
189 	list_for_each_entry(xpd_node, &xp_node->xpd_head, xpd_list) {
190 		if (xpd_node->xpd.driver == driver)
191 			return &xpd_node->xpd;
192 	}
193 	return NULL;
194 }
195 
196 static inline unsigned int
197 avc_xperms_has_perm(struct extended_perms_decision *xpd,
198 					u8 perm, u8 which)
199 {
200 	unsigned int rc = 0;
201 
202 	if ((which == XPERMS_ALLOWED) &&
203 			(xpd->used & XPERMS_ALLOWED))
204 		rc = security_xperm_test(xpd->allowed->p, perm);
205 	else if ((which == XPERMS_AUDITALLOW) &&
206 			(xpd->used & XPERMS_AUDITALLOW))
207 		rc = security_xperm_test(xpd->auditallow->p, perm);
208 	else if ((which == XPERMS_DONTAUDIT) &&
209 			(xpd->used & XPERMS_DONTAUDIT))
210 		rc = security_xperm_test(xpd->dontaudit->p, perm);
211 	return rc;
212 }
213 
214 static void avc_xperms_allow_perm(struct avc_xperms_node *xp_node,
215 				u8 driver, u8 perm)
216 {
217 	struct extended_perms_decision *xpd;
218 	security_xperm_set(xp_node->xp.drivers.p, driver);
219 	xpd = avc_xperms_decision_lookup(driver, xp_node);
220 	if (xpd && xpd->allowed)
221 		security_xperm_set(xpd->allowed->p, perm);
222 }
223 
224 static void avc_xperms_decision_free(struct avc_xperms_decision_node *xpd_node)
225 {
226 	struct extended_perms_decision *xpd;
227 
228 	xpd = &xpd_node->xpd;
229 	if (xpd->allowed)
230 		kmem_cache_free(avc_xperms_data_cachep, xpd->allowed);
231 	if (xpd->auditallow)
232 		kmem_cache_free(avc_xperms_data_cachep, xpd->auditallow);
233 	if (xpd->dontaudit)
234 		kmem_cache_free(avc_xperms_data_cachep, xpd->dontaudit);
235 	kmem_cache_free(avc_xperms_decision_cachep, xpd_node);
236 }
237 
238 static void avc_xperms_free(struct avc_xperms_node *xp_node)
239 {
240 	struct avc_xperms_decision_node *xpd_node, *tmp;
241 
242 	if (!xp_node)
243 		return;
244 
245 	list_for_each_entry_safe(xpd_node, tmp, &xp_node->xpd_head, xpd_list) {
246 		list_del(&xpd_node->xpd_list);
247 		avc_xperms_decision_free(xpd_node);
248 	}
249 	kmem_cache_free(avc_xperms_cachep, xp_node);
250 }
251 
252 static void avc_copy_xperms_decision(struct extended_perms_decision *dest,
253 					struct extended_perms_decision *src)
254 {
255 	dest->driver = src->driver;
256 	dest->used = src->used;
257 	if (dest->used & XPERMS_ALLOWED)
258 		memcpy(dest->allowed->p, src->allowed->p,
259 				sizeof(src->allowed->p));
260 	if (dest->used & XPERMS_AUDITALLOW)
261 		memcpy(dest->auditallow->p, src->auditallow->p,
262 				sizeof(src->auditallow->p));
263 	if (dest->used & XPERMS_DONTAUDIT)
264 		memcpy(dest->dontaudit->p, src->dontaudit->p,
265 				sizeof(src->dontaudit->p));
266 }
267 
268 /*
269  * similar to avc_copy_xperms_decision, but only copy decision
270  * information relevant to this perm
271  */
272 static inline void avc_quick_copy_xperms_decision(u8 perm,
273 			struct extended_perms_decision *dest,
274 			struct extended_perms_decision *src)
275 {
276 	/*
277 	 * compute index of the u32 of the 256 bits (8 u32s) that contain this
278 	 * command permission
279 	 */
280 	u8 i = perm >> 5;
281 
282 	dest->used = src->used;
283 	if (dest->used & XPERMS_ALLOWED)
284 		dest->allowed->p[i] = src->allowed->p[i];
285 	if (dest->used & XPERMS_AUDITALLOW)
286 		dest->auditallow->p[i] = src->auditallow->p[i];
287 	if (dest->used & XPERMS_DONTAUDIT)
288 		dest->dontaudit->p[i] = src->dontaudit->p[i];
289 }
290 
291 static struct avc_xperms_decision_node
292 		*avc_xperms_decision_alloc(u8 which)
293 {
294 	struct avc_xperms_decision_node *xpd_node;
295 	struct extended_perms_decision *xpd;
296 
297 	xpd_node = kmem_cache_zalloc(avc_xperms_decision_cachep, GFP_NOWAIT);
298 	if (!xpd_node)
299 		return NULL;
300 
301 	xpd = &xpd_node->xpd;
302 	if (which & XPERMS_ALLOWED) {
303 		xpd->allowed = kmem_cache_zalloc(avc_xperms_data_cachep,
304 						GFP_NOWAIT);
305 		if (!xpd->allowed)
306 			goto error;
307 	}
308 	if (which & XPERMS_AUDITALLOW) {
309 		xpd->auditallow = kmem_cache_zalloc(avc_xperms_data_cachep,
310 						GFP_NOWAIT);
311 		if (!xpd->auditallow)
312 			goto error;
313 	}
314 	if (which & XPERMS_DONTAUDIT) {
315 		xpd->dontaudit = kmem_cache_zalloc(avc_xperms_data_cachep,
316 						GFP_NOWAIT);
317 		if (!xpd->dontaudit)
318 			goto error;
319 	}
320 	return xpd_node;
321 error:
322 	avc_xperms_decision_free(xpd_node);
323 	return NULL;
324 }
325 
326 static int avc_add_xperms_decision(struct avc_node *node,
327 			struct extended_perms_decision *src)
328 {
329 	struct avc_xperms_decision_node *dest_xpd;
330 
331 	node->ae.xp_node->xp.len++;
332 	dest_xpd = avc_xperms_decision_alloc(src->used);
333 	if (!dest_xpd)
334 		return -ENOMEM;
335 	avc_copy_xperms_decision(&dest_xpd->xpd, src);
336 	list_add(&dest_xpd->xpd_list, &node->ae.xp_node->xpd_head);
337 	return 0;
338 }
339 
340 static struct avc_xperms_node *avc_xperms_alloc(void)
341 {
342 	struct avc_xperms_node *xp_node;
343 
344 	xp_node = kmem_cache_zalloc(avc_xperms_cachep, GFP_NOWAIT);
345 	if (!xp_node)
346 		return xp_node;
347 	INIT_LIST_HEAD(&xp_node->xpd_head);
348 	return xp_node;
349 }
350 
351 static int avc_xperms_populate(struct avc_node *node,
352 				struct avc_xperms_node *src)
353 {
354 	struct avc_xperms_node *dest;
355 	struct avc_xperms_decision_node *dest_xpd;
356 	struct avc_xperms_decision_node *src_xpd;
357 
358 	if (src->xp.len == 0)
359 		return 0;
360 	dest = avc_xperms_alloc();
361 	if (!dest)
362 		return -ENOMEM;
363 
364 	memcpy(dest->xp.drivers.p, src->xp.drivers.p, sizeof(dest->xp.drivers.p));
365 	dest->xp.len = src->xp.len;
366 
367 	/* for each source xpd allocate a destination xpd and copy */
368 	list_for_each_entry(src_xpd, &src->xpd_head, xpd_list) {
369 		dest_xpd = avc_xperms_decision_alloc(src_xpd->xpd.used);
370 		if (!dest_xpd)
371 			goto error;
372 		avc_copy_xperms_decision(&dest_xpd->xpd, &src_xpd->xpd);
373 		list_add(&dest_xpd->xpd_list, &dest->xpd_head);
374 	}
375 	node->ae.xp_node = dest;
376 	return 0;
377 error:
378 	avc_xperms_free(dest);
379 	return -ENOMEM;
380 
381 }
382 
383 static inline u32 avc_xperms_audit_required(u32 requested,
384 					struct av_decision *avd,
385 					struct extended_perms_decision *xpd,
386 					u8 perm,
387 					int result,
388 					u32 *deniedp)
389 {
390 	u32 denied, audited;
391 
392 	denied = requested & ~avd->allowed;
393 	if (unlikely(denied)) {
394 		audited = denied & avd->auditdeny;
395 		if (audited && xpd) {
396 			if (avc_xperms_has_perm(xpd, perm, XPERMS_DONTAUDIT))
397 				audited &= ~requested;
398 		}
399 	} else if (result) {
400 		audited = denied = requested;
401 	} else {
402 		audited = requested & avd->auditallow;
403 		if (audited && xpd) {
404 			if (!avc_xperms_has_perm(xpd, perm, XPERMS_AUDITALLOW))
405 				audited &= ~requested;
406 		}
407 	}
408 
409 	*deniedp = denied;
410 	return audited;
411 }
412 
413 static inline int avc_xperms_audit(struct selinux_state *state,
414 				   u32 ssid, u32 tsid, u16 tclass,
415 				   u32 requested, struct av_decision *avd,
416 				   struct extended_perms_decision *xpd,
417 				   u8 perm, int result,
418 				   struct common_audit_data *ad)
419 {
420 	u32 audited, denied;
421 
422 	audited = avc_xperms_audit_required(
423 			requested, avd, xpd, perm, result, &denied);
424 	if (likely(!audited))
425 		return 0;
426 	return slow_avc_audit(state, ssid, tsid, tclass, requested,
427 			audited, denied, result, ad, 0);
428 }
429 
430 static void avc_node_free(struct rcu_head *rhead)
431 {
432 	struct avc_node *node = container_of(rhead, struct avc_node, rhead);
433 	avc_xperms_free(node->ae.xp_node);
434 	kmem_cache_free(avc_node_cachep, node);
435 	avc_cache_stats_incr(frees);
436 }
437 
438 static void avc_node_delete(struct selinux_avc *avc, struct avc_node *node)
439 {
440 	hlist_del_rcu(&node->list);
441 	call_rcu(&node->rhead, avc_node_free);
442 	atomic_dec(&avc->avc_cache.active_nodes);
443 }
444 
445 static void avc_node_kill(struct selinux_avc *avc, struct avc_node *node)
446 {
447 	avc_xperms_free(node->ae.xp_node);
448 	kmem_cache_free(avc_node_cachep, node);
449 	avc_cache_stats_incr(frees);
450 	atomic_dec(&avc->avc_cache.active_nodes);
451 }
452 
453 static void avc_node_replace(struct selinux_avc *avc,
454 			     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(&avc->avc_cache.active_nodes);
459 }
460 
461 static inline int avc_reclaim_node(struct selinux_avc *avc)
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(&avc->avc_cache.lru_hint) &
471 			(AVC_CACHE_SLOTS - 1);
472 		head = &avc->avc_cache.slots[hvalue];
473 		lock = &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(avc, 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 	}
492 out:
493 	return ecx;
494 }
495 
496 static struct avc_node *avc_alloc_node(struct selinux_avc *avc)
497 {
498 	struct avc_node *node;
499 
500 	node = kmem_cache_zalloc(avc_node_cachep, GFP_NOWAIT);
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(&avc->avc_cache.active_nodes) >
508 	    avc->avc_cache_threshold)
509 		avc_reclaim_node(avc);
510 
511 out:
512 	return node;
513 }
514 
515 static 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 
523 static inline struct avc_node *avc_search_node(struct selinux_avc *avc,
524 					       u32 ssid, u32 tsid, u16 tclass)
525 {
526 	struct avc_node *node, *ret = NULL;
527 	int hvalue;
528 	struct hlist_head *head;
529 
530 	hvalue = avc_hash(ssid, tsid, tclass);
531 	head = &avc->avc_cache.slots[hvalue];
532 	hlist_for_each_entry_rcu(node, head, list) {
533 		if (ssid == node->ae.ssid &&
534 		    tclass == node->ae.tclass &&
535 		    tsid == node->ae.tsid) {
536 			ret = node;
537 			break;
538 		}
539 	}
540 
541 	return ret;
542 }
543 
544 /**
545  * avc_lookup - Look up an AVC entry.
546  * @ssid: source security identifier
547  * @tsid: target security identifier
548  * @tclass: target security class
549  *
550  * Look up an AVC entry that is valid for the
551  * (@ssid, @tsid), interpreting the permissions
552  * based on @tclass.  If a valid AVC entry exists,
553  * then this function returns the avc_node.
554  * Otherwise, this function returns NULL.
555  */
556 static struct avc_node *avc_lookup(struct selinux_avc *avc,
557 				   u32 ssid, u32 tsid, u16 tclass)
558 {
559 	struct avc_node *node;
560 
561 	avc_cache_stats_incr(lookups);
562 	node = avc_search_node(avc, ssid, tsid, tclass);
563 
564 	if (node)
565 		return node;
566 
567 	avc_cache_stats_incr(misses);
568 	return NULL;
569 }
570 
571 static int avc_latest_notif_update(struct selinux_avc *avc,
572 				   int seqno, int is_insert)
573 {
574 	int ret = 0;
575 	static DEFINE_SPINLOCK(notif_lock);
576 	unsigned long flag;
577 
578 	spin_lock_irqsave(&notif_lock, flag);
579 	if (is_insert) {
580 		if (seqno < avc->avc_cache.latest_notif) {
581 			pr_warn("SELinux: avc:  seqno %d < latest_notif %d\n",
582 			       seqno, avc->avc_cache.latest_notif);
583 			ret = -EAGAIN;
584 		}
585 	} else {
586 		if (seqno > avc->avc_cache.latest_notif)
587 			avc->avc_cache.latest_notif = seqno;
588 	}
589 	spin_unlock_irqrestore(&notif_lock, flag);
590 
591 	return ret;
592 }
593 
594 /**
595  * avc_insert - Insert an AVC entry.
596  * @ssid: source security identifier
597  * @tsid: target security identifier
598  * @tclass: target security class
599  * @avd: resulting av decision
600  * @xp_node: resulting extended permissions
601  *
602  * Insert an AVC entry for the SID pair
603  * (@ssid, @tsid) and class @tclass.
604  * The access vectors and the sequence number are
605  * normally provided by the security server in
606  * response to a security_compute_av() call.  If the
607  * sequence number @avd->seqno is not less than the latest
608  * revocation notification, then the function copies
609  * the access vectors into a cache entry, returns
610  * avc_node inserted. Otherwise, this function returns NULL.
611  */
612 static struct avc_node *avc_insert(struct selinux_avc *avc,
613 				   u32 ssid, u32 tsid, u16 tclass,
614 				   struct av_decision *avd,
615 				   struct avc_xperms_node *xp_node)
616 {
617 	struct avc_node *pos, *node = NULL;
618 	int hvalue;
619 	unsigned long flag;
620 
621 	if (avc_latest_notif_update(avc, avd->seqno, 1))
622 		goto out;
623 
624 	node = avc_alloc_node(avc);
625 	if (node) {
626 		struct hlist_head *head;
627 		spinlock_t *lock;
628 		int rc = 0;
629 
630 		hvalue = avc_hash(ssid, tsid, tclass);
631 		avc_node_populate(node, ssid, tsid, tclass, avd);
632 		rc = avc_xperms_populate(node, xp_node);
633 		if (rc) {
634 			kmem_cache_free(avc_node_cachep, node);
635 			return NULL;
636 		}
637 		head = &avc->avc_cache.slots[hvalue];
638 		lock = &avc->avc_cache.slots_lock[hvalue];
639 
640 		spin_lock_irqsave(lock, flag);
641 		hlist_for_each_entry(pos, head, list) {
642 			if (pos->ae.ssid == ssid &&
643 			    pos->ae.tsid == tsid &&
644 			    pos->ae.tclass == tclass) {
645 				avc_node_replace(avc, node, pos);
646 				goto found;
647 			}
648 		}
649 		hlist_add_head_rcu(&node->list, head);
650 found:
651 		spin_unlock_irqrestore(lock, flag);
652 	}
653 out:
654 	return node;
655 }
656 
657 /**
658  * avc_audit_pre_callback - SELinux specific information
659  * will be called by generic audit code
660  * @ab: the audit buffer
661  * @a: audit_data
662  */
663 static void avc_audit_pre_callback(struct audit_buffer *ab, void *a)
664 {
665 	struct common_audit_data *ad = a;
666 	struct selinux_audit_data *sad = ad->selinux_audit_data;
667 	u32 av = sad->audited;
668 	const char **perms;
669 	int i, perm;
670 
671 	audit_log_format(ab, "avc:  %s ", sad->denied ? "denied" : "granted");
672 
673 	if (av == 0) {
674 		audit_log_format(ab, " null");
675 		return;
676 	}
677 
678 	perms = secclass_map[sad->tclass-1].perms;
679 
680 	audit_log_format(ab, " {");
681 	i = 0;
682 	perm = 1;
683 	while (i < (sizeof(av) * 8)) {
684 		if ((perm & av) && perms[i]) {
685 			audit_log_format(ab, " %s", perms[i]);
686 			av &= ~perm;
687 		}
688 		i++;
689 		perm <<= 1;
690 	}
691 
692 	if (av)
693 		audit_log_format(ab, " 0x%x", av);
694 
695 	audit_log_format(ab, " } for ");
696 }
697 
698 /**
699  * avc_audit_post_callback - SELinux specific information
700  * will be called by generic audit code
701  * @ab: the audit buffer
702  * @a: audit_data
703  */
704 static void avc_audit_post_callback(struct audit_buffer *ab, void *a)
705 {
706 	struct common_audit_data *ad = a;
707 	struct selinux_audit_data *sad = ad->selinux_audit_data;
708 	char *scontext;
709 	u32 scontext_len;
710 	int rc;
711 
712 	rc = security_sid_to_context(sad->state, sad->ssid, &scontext,
713 				     &scontext_len);
714 	if (rc)
715 		audit_log_format(ab, " ssid=%d", sad->ssid);
716 	else {
717 		audit_log_format(ab, " scontext=%s", scontext);
718 		kfree(scontext);
719 	}
720 
721 	rc = security_sid_to_context(sad->state, sad->tsid, &scontext,
722 				     &scontext_len);
723 	if (rc)
724 		audit_log_format(ab, " tsid=%d", sad->tsid);
725 	else {
726 		audit_log_format(ab, " tcontext=%s", scontext);
727 		kfree(scontext);
728 	}
729 
730 	audit_log_format(ab, " tclass=%s", secclass_map[sad->tclass-1].name);
731 
732 	if (sad->denied)
733 		audit_log_format(ab, " permissive=%u", sad->result ? 0 : 1);
734 
735 	/* in case of invalid context report also the actual context string */
736 	rc = security_sid_to_context_inval(sad->state, sad->ssid, &scontext,
737 					   &scontext_len);
738 	if (!rc && scontext) {
739 		if (scontext_len && scontext[scontext_len - 1] == '\0')
740 			scontext_len--;
741 		audit_log_format(ab, " srawcon=");
742 		audit_log_n_untrustedstring(ab, scontext, scontext_len);
743 		kfree(scontext);
744 	}
745 
746 	rc = security_sid_to_context_inval(sad->state, sad->tsid, &scontext,
747 					   &scontext_len);
748 	if (!rc && scontext) {
749 		if (scontext_len && scontext[scontext_len - 1] == '\0')
750 			scontext_len--;
751 		audit_log_format(ab, " trawcon=");
752 		audit_log_n_untrustedstring(ab, scontext, scontext_len);
753 		kfree(scontext);
754 	}
755 }
756 
757 /* This is the slow part of avc audit with big stack footprint */
758 noinline int slow_avc_audit(struct selinux_state *state,
759 			    u32 ssid, u32 tsid, u16 tclass,
760 			    u32 requested, u32 audited, u32 denied, int result,
761 			    struct common_audit_data *a,
762 			    unsigned int flags)
763 {
764 	struct common_audit_data stack_data;
765 	struct selinux_audit_data sad;
766 
767 	if (WARN_ON(!tclass || tclass >= ARRAY_SIZE(secclass_map)))
768 		return -EINVAL;
769 
770 	if (!a) {
771 		a = &stack_data;
772 		a->type = LSM_AUDIT_DATA_NONE;
773 	}
774 
775 	/*
776 	 * When in a RCU walk do the audit on the RCU retry.  This is because
777 	 * the collection of the dname in an inode audit message is not RCU
778 	 * safe.  Note this may drop some audits when the situation changes
779 	 * during retry. However this is logically just as if the operation
780 	 * happened a little later.
781 	 */
782 	if ((a->type == LSM_AUDIT_DATA_INODE) &&
783 	    (flags & MAY_NOT_BLOCK))
784 		return -ECHILD;
785 
786 	sad.tclass = tclass;
787 	sad.requested = requested;
788 	sad.ssid = ssid;
789 	sad.tsid = tsid;
790 	sad.audited = audited;
791 	sad.denied = denied;
792 	sad.result = result;
793 	sad.state = state;
794 
795 	a->selinux_audit_data = &sad;
796 
797 	common_lsm_audit(a, avc_audit_pre_callback, avc_audit_post_callback);
798 	return 0;
799 }
800 
801 /**
802  * avc_add_callback - Register a callback for security events.
803  * @callback: callback function
804  * @events: security events
805  *
806  * Register a callback function for events in the set @events.
807  * Returns %0 on success or -%ENOMEM if insufficient memory
808  * exists to add the callback.
809  */
810 int __init avc_add_callback(int (*callback)(u32 event), u32 events)
811 {
812 	struct avc_callback_node *c;
813 	int rc = 0;
814 
815 	c = kmalloc(sizeof(*c), GFP_KERNEL);
816 	if (!c) {
817 		rc = -ENOMEM;
818 		goto out;
819 	}
820 
821 	c->callback = callback;
822 	c->events = events;
823 	c->next = avc_callbacks;
824 	avc_callbacks = c;
825 out:
826 	return rc;
827 }
828 
829 /**
830  * avc_update_node Update an AVC entry
831  * @event : Updating event
832  * @perms : Permission mask bits
833  * @ssid,@tsid,@tclass : identifier of an AVC entry
834  * @seqno : sequence number when decision was made
835  * @xpd: extended_perms_decision to be added to the node
836  * @flags: the AVC_* flags, e.g. AVC_NONBLOCKING, AVC_EXTENDED_PERMS, or 0.
837  *
838  * if a valid AVC entry doesn't exist,this function returns -ENOENT.
839  * if kmalloc() called internal returns NULL, this function returns -ENOMEM.
840  * otherwise, this function updates the AVC entry. The original AVC-entry object
841  * will release later by RCU.
842  */
843 static int avc_update_node(struct selinux_avc *avc,
844 			   u32 event, u32 perms, u8 driver, u8 xperm, u32 ssid,
845 			   u32 tsid, u16 tclass, u32 seqno,
846 			   struct extended_perms_decision *xpd,
847 			   u32 flags)
848 {
849 	int hvalue, rc = 0;
850 	unsigned long flag;
851 	struct avc_node *pos, *node, *orig = NULL;
852 	struct hlist_head *head;
853 	spinlock_t *lock;
854 
855 	/*
856 	 * If we are in a non-blocking code path, e.g. VFS RCU walk,
857 	 * then we must not add permissions to a cache entry
858 	 * because we cannot safely audit the denial.  Otherwise,
859 	 * during the subsequent blocking retry (e.g. VFS ref walk), we
860 	 * will find the permissions already granted in the cache entry
861 	 * and won't audit anything at all, leading to silent denials in
862 	 * permissive mode that only appear when in enforcing mode.
863 	 *
864 	 * See the corresponding handling in slow_avc_audit(), and the
865 	 * logic in selinux_inode_permission for the MAY_NOT_BLOCK flag,
866 	 * which is transliterated into AVC_NONBLOCKING.
867 	 */
868 	if (flags & AVC_NONBLOCKING)
869 		return 0;
870 
871 	node = avc_alloc_node(avc);
872 	if (!node) {
873 		rc = -ENOMEM;
874 		goto out;
875 	}
876 
877 	/* Lock the target slot */
878 	hvalue = avc_hash(ssid, tsid, tclass);
879 
880 	head = &avc->avc_cache.slots[hvalue];
881 	lock = &avc->avc_cache.slots_lock[hvalue];
882 
883 	spin_lock_irqsave(lock, flag);
884 
885 	hlist_for_each_entry(pos, head, list) {
886 		if (ssid == pos->ae.ssid &&
887 		    tsid == pos->ae.tsid &&
888 		    tclass == pos->ae.tclass &&
889 		    seqno == pos->ae.avd.seqno){
890 			orig = pos;
891 			break;
892 		}
893 	}
894 
895 	if (!orig) {
896 		rc = -ENOENT;
897 		avc_node_kill(avc, node);
898 		goto out_unlock;
899 	}
900 
901 	/*
902 	 * Copy and replace original node.
903 	 */
904 
905 	avc_node_populate(node, ssid, tsid, tclass, &orig->ae.avd);
906 
907 	if (orig->ae.xp_node) {
908 		rc = avc_xperms_populate(node, orig->ae.xp_node);
909 		if (rc) {
910 			kmem_cache_free(avc_node_cachep, node);
911 			goto out_unlock;
912 		}
913 	}
914 
915 	switch (event) {
916 	case AVC_CALLBACK_GRANT:
917 		node->ae.avd.allowed |= perms;
918 		if (node->ae.xp_node && (flags & AVC_EXTENDED_PERMS))
919 			avc_xperms_allow_perm(node->ae.xp_node, driver, xperm);
920 		break;
921 	case AVC_CALLBACK_TRY_REVOKE:
922 	case AVC_CALLBACK_REVOKE:
923 		node->ae.avd.allowed &= ~perms;
924 		break;
925 	case AVC_CALLBACK_AUDITALLOW_ENABLE:
926 		node->ae.avd.auditallow |= perms;
927 		break;
928 	case AVC_CALLBACK_AUDITALLOW_DISABLE:
929 		node->ae.avd.auditallow &= ~perms;
930 		break;
931 	case AVC_CALLBACK_AUDITDENY_ENABLE:
932 		node->ae.avd.auditdeny |= perms;
933 		break;
934 	case AVC_CALLBACK_AUDITDENY_DISABLE:
935 		node->ae.avd.auditdeny &= ~perms;
936 		break;
937 	case AVC_CALLBACK_ADD_XPERMS:
938 		avc_add_xperms_decision(node, xpd);
939 		break;
940 	}
941 	avc_node_replace(avc, node, orig);
942 out_unlock:
943 	spin_unlock_irqrestore(lock, flag);
944 out:
945 	return rc;
946 }
947 
948 /**
949  * avc_flush - Flush the cache
950  */
951 static void avc_flush(struct selinux_avc *avc)
952 {
953 	struct hlist_head *head;
954 	struct avc_node *node;
955 	spinlock_t *lock;
956 	unsigned long flag;
957 	int i;
958 
959 	for (i = 0; i < AVC_CACHE_SLOTS; i++) {
960 		head = &avc->avc_cache.slots[i];
961 		lock = &avc->avc_cache.slots_lock[i];
962 
963 		spin_lock_irqsave(lock, flag);
964 		/*
965 		 * With preemptable RCU, the outer spinlock does not
966 		 * prevent RCU grace periods from ending.
967 		 */
968 		rcu_read_lock();
969 		hlist_for_each_entry(node, head, list)
970 			avc_node_delete(avc, node);
971 		rcu_read_unlock();
972 		spin_unlock_irqrestore(lock, flag);
973 	}
974 }
975 
976 /**
977  * avc_ss_reset - Flush the cache and revalidate migrated permissions.
978  * @seqno: policy sequence number
979  */
980 int avc_ss_reset(struct selinux_avc *avc, u32 seqno)
981 {
982 	struct avc_callback_node *c;
983 	int rc = 0, tmprc;
984 
985 	avc_flush(avc);
986 
987 	for (c = avc_callbacks; c; c = c->next) {
988 		if (c->events & AVC_CALLBACK_RESET) {
989 			tmprc = c->callback(AVC_CALLBACK_RESET);
990 			/* save the first error encountered for the return
991 			   value and continue processing the callbacks */
992 			if (!rc)
993 				rc = tmprc;
994 		}
995 	}
996 
997 	avc_latest_notif_update(avc, seqno, 0);
998 	return rc;
999 }
1000 
1001 /*
1002  * Slow-path helper function for avc_has_perm_noaudit,
1003  * when the avc_node lookup fails. We get called with
1004  * the RCU read lock held, and need to return with it
1005  * still held, but drop if for the security compute.
1006  *
1007  * Don't inline this, since it's the slow-path and just
1008  * results in a bigger stack frame.
1009  */
1010 static noinline
1011 struct avc_node *avc_compute_av(struct selinux_state *state,
1012 				u32 ssid, u32 tsid,
1013 				u16 tclass, struct av_decision *avd,
1014 				struct avc_xperms_node *xp_node)
1015 {
1016 	rcu_read_unlock();
1017 	INIT_LIST_HEAD(&xp_node->xpd_head);
1018 	security_compute_av(state, ssid, tsid, tclass, avd, &xp_node->xp);
1019 	rcu_read_lock();
1020 	return avc_insert(state->avc, ssid, tsid, tclass, avd, xp_node);
1021 }
1022 
1023 static noinline int avc_denied(struct selinux_state *state,
1024 			       u32 ssid, u32 tsid,
1025 			       u16 tclass, u32 requested,
1026 			       u8 driver, u8 xperm, unsigned int flags,
1027 			       struct av_decision *avd)
1028 {
1029 	if (flags & AVC_STRICT)
1030 		return -EACCES;
1031 
1032 	if (enforcing_enabled(state) &&
1033 	    !(avd->flags & AVD_FLAGS_PERMISSIVE))
1034 		return -EACCES;
1035 
1036 	avc_update_node(state->avc, AVC_CALLBACK_GRANT, requested, driver,
1037 			xperm, ssid, tsid, tclass, avd->seqno, NULL, flags);
1038 	return 0;
1039 }
1040 
1041 /*
1042  * The avc extended permissions logic adds an additional 256 bits of
1043  * permissions to an avc node when extended permissions for that node are
1044  * specified in the avtab. If the additional 256 permissions is not adequate,
1045  * as-is the case with ioctls, then multiple may be chained together and the
1046  * driver field is used to specify which set contains the permission.
1047  */
1048 int avc_has_extended_perms(struct selinux_state *state,
1049 			   u32 ssid, u32 tsid, u16 tclass, u32 requested,
1050 			   u8 driver, u8 xperm, struct common_audit_data *ad)
1051 {
1052 	struct avc_node *node;
1053 	struct av_decision avd;
1054 	u32 denied;
1055 	struct extended_perms_decision local_xpd;
1056 	struct extended_perms_decision *xpd = NULL;
1057 	struct extended_perms_data allowed;
1058 	struct extended_perms_data auditallow;
1059 	struct extended_perms_data dontaudit;
1060 	struct avc_xperms_node local_xp_node;
1061 	struct avc_xperms_node *xp_node;
1062 	int rc = 0, rc2;
1063 
1064 	xp_node = &local_xp_node;
1065 	if (WARN_ON(!requested))
1066 		return -EACCES;
1067 
1068 	rcu_read_lock();
1069 
1070 	node = avc_lookup(state->avc, ssid, tsid, tclass);
1071 	if (unlikely(!node)) {
1072 		node = avc_compute_av(state, ssid, tsid, tclass, &avd, xp_node);
1073 	} else {
1074 		memcpy(&avd, &node->ae.avd, sizeof(avd));
1075 		xp_node = node->ae.xp_node;
1076 	}
1077 	/* if extended permissions are not defined, only consider av_decision */
1078 	if (!xp_node || !xp_node->xp.len)
1079 		goto decision;
1080 
1081 	local_xpd.allowed = &allowed;
1082 	local_xpd.auditallow = &auditallow;
1083 	local_xpd.dontaudit = &dontaudit;
1084 
1085 	xpd = avc_xperms_decision_lookup(driver, xp_node);
1086 	if (unlikely(!xpd)) {
1087 		/*
1088 		 * Compute the extended_perms_decision only if the driver
1089 		 * is flagged
1090 		 */
1091 		if (!security_xperm_test(xp_node->xp.drivers.p, driver)) {
1092 			avd.allowed &= ~requested;
1093 			goto decision;
1094 		}
1095 		rcu_read_unlock();
1096 		security_compute_xperms_decision(state, ssid, tsid, tclass,
1097 						 driver, &local_xpd);
1098 		rcu_read_lock();
1099 		avc_update_node(state->avc, AVC_CALLBACK_ADD_XPERMS, requested,
1100 				driver, xperm, ssid, tsid, tclass, avd.seqno,
1101 				&local_xpd, 0);
1102 	} else {
1103 		avc_quick_copy_xperms_decision(xperm, &local_xpd, xpd);
1104 	}
1105 	xpd = &local_xpd;
1106 
1107 	if (!avc_xperms_has_perm(xpd, xperm, XPERMS_ALLOWED))
1108 		avd.allowed &= ~requested;
1109 
1110 decision:
1111 	denied = requested & ~(avd.allowed);
1112 	if (unlikely(denied))
1113 		rc = avc_denied(state, ssid, tsid, tclass, requested,
1114 				driver, xperm, AVC_EXTENDED_PERMS, &avd);
1115 
1116 	rcu_read_unlock();
1117 
1118 	rc2 = avc_xperms_audit(state, ssid, tsid, tclass, requested,
1119 			&avd, xpd, xperm, rc, ad);
1120 	if (rc2)
1121 		return rc2;
1122 	return rc;
1123 }
1124 
1125 /**
1126  * avc_has_perm_noaudit - Check permissions but perform no auditing.
1127  * @ssid: source security identifier
1128  * @tsid: target security identifier
1129  * @tclass: target security class
1130  * @requested: requested permissions, interpreted based on @tclass
1131  * @flags:  AVC_STRICT, AVC_NONBLOCKING, or 0
1132  * @avd: access vector decisions
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.  Return a copy of the decisions
1138  * in @avd.  Return %0 if all @requested permissions are granted,
1139  * -%EACCES if any permissions are denied, or another -errno upon
1140  * other errors.  This function is typically called by avc_has_perm(),
1141  * but may also be called directly to separate permission checking from
1142  * auditing, e.g. in cases where a lock must be held for the check but
1143  * should be released for the auditing.
1144  */
1145 inline int avc_has_perm_noaudit(struct selinux_state *state,
1146 				u32 ssid, u32 tsid,
1147 				u16 tclass, u32 requested,
1148 				unsigned int flags,
1149 				struct av_decision *avd)
1150 {
1151 	struct avc_node *node;
1152 	struct avc_xperms_node xp_node;
1153 	int rc = 0;
1154 	u32 denied;
1155 
1156 	if (WARN_ON(!requested))
1157 		return -EACCES;
1158 
1159 	rcu_read_lock();
1160 
1161 	node = avc_lookup(state->avc, ssid, tsid, tclass);
1162 	if (unlikely(!node))
1163 		node = avc_compute_av(state, ssid, tsid, tclass, avd, &xp_node);
1164 	else
1165 		memcpy(avd, &node->ae.avd, sizeof(*avd));
1166 
1167 	denied = requested & ~(avd->allowed);
1168 	if (unlikely(denied))
1169 		rc = avc_denied(state, ssid, tsid, tclass, requested, 0, 0,
1170 				flags, avd);
1171 
1172 	rcu_read_unlock();
1173 	return rc;
1174 }
1175 
1176 /**
1177  * avc_has_perm - Check permissions and perform any appropriate auditing.
1178  * @ssid: source security identifier
1179  * @tsid: target security identifier
1180  * @tclass: target security class
1181  * @requested: requested permissions, interpreted based on @tclass
1182  * @auditdata: auxiliary audit data
1183  *
1184  * Check the AVC to determine whether the @requested permissions are granted
1185  * for the SID pair (@ssid, @tsid), interpreting the permissions
1186  * based on @tclass, and call the security server on a cache miss to obtain
1187  * a new decision and add it to the cache.  Audit the granting or denial of
1188  * permissions in accordance with the policy.  Return %0 if all @requested
1189  * permissions are granted, -%EACCES if any permissions are denied, or
1190  * another -errno upon other errors.
1191  */
1192 int avc_has_perm(struct selinux_state *state, u32 ssid, u32 tsid, u16 tclass,
1193 		 u32 requested, struct common_audit_data *auditdata)
1194 {
1195 	struct av_decision avd;
1196 	int rc, rc2;
1197 
1198 	rc = avc_has_perm_noaudit(state, ssid, tsid, tclass, requested, 0,
1199 				  &avd);
1200 
1201 	rc2 = avc_audit(state, ssid, tsid, tclass, requested, &avd, rc,
1202 			auditdata, 0);
1203 	if (rc2)
1204 		return rc2;
1205 	return rc;
1206 }
1207 
1208 u32 avc_policy_seqno(struct selinux_state *state)
1209 {
1210 	return state->avc->avc_cache.latest_notif;
1211 }
1212 
1213 void avc_disable(void)
1214 {
1215 	/*
1216 	 * If you are looking at this because you have realized that we are
1217 	 * not destroying the avc_node_cachep it might be easy to fix, but
1218 	 * I don't know the memory barrier semantics well enough to know.  It's
1219 	 * possible that some other task dereferenced security_ops when
1220 	 * it still pointed to selinux operations.  If that is the case it's
1221 	 * possible that it is about to use the avc and is about to need the
1222 	 * avc_node_cachep.  I know I could wrap the security.c security_ops call
1223 	 * in an rcu_lock, but seriously, it's not worth it.  Instead I just flush
1224 	 * the cache and get that memory back.
1225 	 */
1226 	if (avc_node_cachep) {
1227 		avc_flush(selinux_state.avc);
1228 		/* kmem_cache_destroy(avc_node_cachep); */
1229 	}
1230 }
1231