xref: /openbmc/linux/security/selinux/avc.c (revision 5295951b)
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Implementation of the kernel access vector cache (AVC).
4  *
5  * Authors:  Stephen Smalley, <stephen.smalley.work@gmail.com>
6  *	     James Morris <jmorris@redhat.com>
7  *
8  * Update:   KaiGai, Kohei <kaigai@ak.jp.nec.com>
9  *	Replaced the avc_lock spinlock by RCU.
10  *
11  * Copyright (C) 2003 Red Hat, Inc., James Morris <jmorris@redhat.com>
12  */
13 #include <linux/types.h>
14 #include <linux/stddef.h>
15 #include <linux/kernel.h>
16 #include <linux/slab.h>
17 #include <linux/fs.h>
18 #include <linux/dcache.h>
19 #include <linux/init.h>
20 #include <linux/skbuff.h>
21 #include <linux/percpu.h>
22 #include <linux/list.h>
23 #include <net/sock.h>
24 #include <linux/un.h>
25 #include <net/af_unix.h>
26 #include <linux/ip.h>
27 #include <linux/audit.h>
28 #include <linux/ipv6.h>
29 #include <net/ipv6.h>
30 #include "avc.h"
31 #include "avc_ss.h"
32 #include "classmap.h"
33 
34 #define CREATE_TRACE_POINTS
35 #include <trace/events/avc.h>
36 
37 #define AVC_CACHE_SLOTS			512
38 #define AVC_DEF_CACHE_THRESHOLD		512
39 #define AVC_CACHE_RECLAIM		16
40 
41 #ifdef CONFIG_SECURITY_SELINUX_AVC_STATS
42 #define avc_cache_stats_incr(field)	this_cpu_inc(avc_cache_stats.field)
43 #else
44 #define avc_cache_stats_incr(field)	do {} while (0)
45 #endif
46 
47 struct 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 
55 struct 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 
61 struct avc_xperms_decision_node {
62 	struct extended_perms_decision xpd;
63 	struct list_head xpd_list; /* list of extended_perms_decision */
64 };
65 
66 struct avc_xperms_node {
67 	struct extended_perms xp;
68 	struct list_head xpd_head; /* list head of extended_perms_decision */
69 };
70 
71 struct 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 
79 struct avc_callback_node {
80 	int (*callback) (u32 event);
81 	u32 events;
82 	struct avc_callback_node *next;
83 };
84 
85 #ifdef CONFIG_SECURITY_SELINUX_AVC_STATS
86 DEFINE_PER_CPU(struct avc_cache_stats, avc_cache_stats) = { 0 };
87 #endif
88 
89 struct selinux_avc {
90 	unsigned int avc_cache_threshold;
91 	struct avc_cache avc_cache;
92 };
93 
94 static struct selinux_avc selinux_avc;
95 
selinux_avc_init(void)96 void selinux_avc_init(void)
97 {
98 	int i;
99 
100 	selinux_avc.avc_cache_threshold = AVC_DEF_CACHE_THRESHOLD;
101 	for (i = 0; i < AVC_CACHE_SLOTS; i++) {
102 		INIT_HLIST_HEAD(&selinux_avc.avc_cache.slots[i]);
103 		spin_lock_init(&selinux_avc.avc_cache.slots_lock[i]);
104 	}
105 	atomic_set(&selinux_avc.avc_cache.active_nodes, 0);
106 	atomic_set(&selinux_avc.avc_cache.lru_hint, 0);
107 }
108 
avc_get_cache_threshold(void)109 unsigned int avc_get_cache_threshold(void)
110 {
111 	return selinux_avc.avc_cache_threshold;
112 }
113 
avc_set_cache_threshold(unsigned int cache_threshold)114 void avc_set_cache_threshold(unsigned int cache_threshold)
115 {
116 	selinux_avc.avc_cache_threshold = cache_threshold;
117 }
118 
119 static struct avc_callback_node *avc_callbacks __ro_after_init;
120 static struct kmem_cache *avc_node_cachep __ro_after_init;
121 static struct kmem_cache *avc_xperms_data_cachep __ro_after_init;
122 static struct kmem_cache *avc_xperms_decision_cachep __ro_after_init;
123 static struct kmem_cache *avc_xperms_cachep __ro_after_init;
124 
avc_hash(u32 ssid,u32 tsid,u16 tclass)125 static inline u32 avc_hash(u32 ssid, u32 tsid, u16 tclass)
126 {
127 	return (ssid ^ (tsid<<2) ^ (tclass<<4)) & (AVC_CACHE_SLOTS - 1);
128 }
129 
130 /**
131  * avc_init - Initialize the AVC.
132  *
133  * Initialize the access vector cache.
134  */
avc_init(void)135 void __init avc_init(void)
136 {
137 	avc_node_cachep = kmem_cache_create("avc_node", sizeof(struct avc_node),
138 					0, SLAB_PANIC, NULL);
139 	avc_xperms_cachep = kmem_cache_create("avc_xperms_node",
140 					sizeof(struct avc_xperms_node),
141 					0, SLAB_PANIC, NULL);
142 	avc_xperms_decision_cachep = kmem_cache_create(
143 					"avc_xperms_decision_node",
144 					sizeof(struct avc_xperms_decision_node),
145 					0, SLAB_PANIC, NULL);
146 	avc_xperms_data_cachep = kmem_cache_create("avc_xperms_data",
147 					sizeof(struct extended_perms_data),
148 					0, SLAB_PANIC, NULL);
149 }
150 
avc_get_hash_stats(char * page)151 int avc_get_hash_stats(char *page)
152 {
153 	int i, chain_len, max_chain_len, slots_used;
154 	struct avc_node *node;
155 	struct hlist_head *head;
156 
157 	rcu_read_lock();
158 
159 	slots_used = 0;
160 	max_chain_len = 0;
161 	for (i = 0; i < AVC_CACHE_SLOTS; i++) {
162 		head = &selinux_avc.avc_cache.slots[i];
163 		if (!hlist_empty(head)) {
164 			slots_used++;
165 			chain_len = 0;
166 			hlist_for_each_entry_rcu(node, head, list)
167 				chain_len++;
168 			if (chain_len > max_chain_len)
169 				max_chain_len = chain_len;
170 		}
171 	}
172 
173 	rcu_read_unlock();
174 
175 	return scnprintf(page, PAGE_SIZE, "entries: %d\nbuckets used: %d/%d\n"
176 			 "longest chain: %d\n",
177 			 atomic_read(&selinux_avc.avc_cache.active_nodes),
178 			 slots_used, AVC_CACHE_SLOTS, max_chain_len);
179 }
180 
181 /*
182  * using a linked list for extended_perms_decision lookup because the list is
183  * always small. i.e. less than 5, typically 1
184  */
avc_xperms_decision_lookup(u8 driver,struct avc_xperms_node * xp_node)185 static struct extended_perms_decision *avc_xperms_decision_lookup(u8 driver,
186 					struct avc_xperms_node *xp_node)
187 {
188 	struct avc_xperms_decision_node *xpd_node;
189 
190 	list_for_each_entry(xpd_node, &xp_node->xpd_head, xpd_list) {
191 		if (xpd_node->xpd.driver == driver)
192 			return &xpd_node->xpd;
193 	}
194 	return NULL;
195 }
196 
197 static inline unsigned int
avc_xperms_has_perm(struct extended_perms_decision * xpd,u8 perm,u8 which)198 avc_xperms_has_perm(struct extended_perms_decision *xpd,
199 					u8 perm, u8 which)
200 {
201 	unsigned int rc = 0;
202 
203 	if ((which == XPERMS_ALLOWED) &&
204 			(xpd->used & XPERMS_ALLOWED))
205 		rc = security_xperm_test(xpd->allowed->p, perm);
206 	else if ((which == XPERMS_AUDITALLOW) &&
207 			(xpd->used & XPERMS_AUDITALLOW))
208 		rc = security_xperm_test(xpd->auditallow->p, perm);
209 	else if ((which == XPERMS_DONTAUDIT) &&
210 			(xpd->used & XPERMS_DONTAUDIT))
211 		rc = security_xperm_test(xpd->dontaudit->p, perm);
212 	return rc;
213 }
214 
avc_xperms_allow_perm(struct avc_xperms_node * xp_node,u8 driver,u8 perm)215 static void avc_xperms_allow_perm(struct avc_xperms_node *xp_node,
216 				u8 driver, u8 perm)
217 {
218 	struct extended_perms_decision *xpd;
219 	security_xperm_set(xp_node->xp.drivers.p, driver);
220 	xpd = avc_xperms_decision_lookup(driver, xp_node);
221 	if (xpd && xpd->allowed)
222 		security_xperm_set(xpd->allowed->p, perm);
223 }
224 
avc_xperms_decision_free(struct avc_xperms_decision_node * xpd_node)225 static void avc_xperms_decision_free(struct avc_xperms_decision_node *xpd_node)
226 {
227 	struct extended_perms_decision *xpd;
228 
229 	xpd = &xpd_node->xpd;
230 	if (xpd->allowed)
231 		kmem_cache_free(avc_xperms_data_cachep, xpd->allowed);
232 	if (xpd->auditallow)
233 		kmem_cache_free(avc_xperms_data_cachep, xpd->auditallow);
234 	if (xpd->dontaudit)
235 		kmem_cache_free(avc_xperms_data_cachep, xpd->dontaudit);
236 	kmem_cache_free(avc_xperms_decision_cachep, xpd_node);
237 }
238 
avc_xperms_free(struct avc_xperms_node * xp_node)239 static void avc_xperms_free(struct avc_xperms_node *xp_node)
240 {
241 	struct avc_xperms_decision_node *xpd_node, *tmp;
242 
243 	if (!xp_node)
244 		return;
245 
246 	list_for_each_entry_safe(xpd_node, tmp, &xp_node->xpd_head, xpd_list) {
247 		list_del(&xpd_node->xpd_list);
248 		avc_xperms_decision_free(xpd_node);
249 	}
250 	kmem_cache_free(avc_xperms_cachep, xp_node);
251 }
252 
avc_copy_xperms_decision(struct extended_perms_decision * dest,struct extended_perms_decision * src)253 static void avc_copy_xperms_decision(struct extended_perms_decision *dest,
254 					struct extended_perms_decision *src)
255 {
256 	dest->driver = src->driver;
257 	dest->used = src->used;
258 	if (dest->used & XPERMS_ALLOWED)
259 		memcpy(dest->allowed->p, src->allowed->p,
260 				sizeof(src->allowed->p));
261 	if (dest->used & XPERMS_AUDITALLOW)
262 		memcpy(dest->auditallow->p, src->auditallow->p,
263 				sizeof(src->auditallow->p));
264 	if (dest->used & XPERMS_DONTAUDIT)
265 		memcpy(dest->dontaudit->p, src->dontaudit->p,
266 				sizeof(src->dontaudit->p));
267 }
268 
269 /*
270  * similar to avc_copy_xperms_decision, but only copy decision
271  * information relevant to this perm
272  */
avc_quick_copy_xperms_decision(u8 perm,struct extended_perms_decision * dest,struct extended_perms_decision * src)273 static inline void avc_quick_copy_xperms_decision(u8 perm,
274 			struct extended_perms_decision *dest,
275 			struct extended_perms_decision *src)
276 {
277 	/*
278 	 * compute index of the u32 of the 256 bits (8 u32s) that contain this
279 	 * command permission
280 	 */
281 	u8 i = perm >> 5;
282 
283 	dest->used = src->used;
284 	if (dest->used & XPERMS_ALLOWED)
285 		dest->allowed->p[i] = src->allowed->p[i];
286 	if (dest->used & XPERMS_AUDITALLOW)
287 		dest->auditallow->p[i] = src->auditallow->p[i];
288 	if (dest->used & XPERMS_DONTAUDIT)
289 		dest->dontaudit->p[i] = src->dontaudit->p[i];
290 }
291 
292 static struct avc_xperms_decision_node
avc_xperms_decision_alloc(u8 which)293 		*avc_xperms_decision_alloc(u8 which)
294 {
295 	struct avc_xperms_decision_node *xpd_node;
296 	struct extended_perms_decision *xpd;
297 
298 	xpd_node = kmem_cache_zalloc(avc_xperms_decision_cachep,
299 				     GFP_NOWAIT | __GFP_NOWARN);
300 	if (!xpd_node)
301 		return NULL;
302 
303 	xpd = &xpd_node->xpd;
304 	if (which & XPERMS_ALLOWED) {
305 		xpd->allowed = kmem_cache_zalloc(avc_xperms_data_cachep,
306 						GFP_NOWAIT | __GFP_NOWARN);
307 		if (!xpd->allowed)
308 			goto error;
309 	}
310 	if (which & XPERMS_AUDITALLOW) {
311 		xpd->auditallow = kmem_cache_zalloc(avc_xperms_data_cachep,
312 						GFP_NOWAIT | __GFP_NOWARN);
313 		if (!xpd->auditallow)
314 			goto error;
315 	}
316 	if (which & XPERMS_DONTAUDIT) {
317 		xpd->dontaudit = kmem_cache_zalloc(avc_xperms_data_cachep,
318 						GFP_NOWAIT | __GFP_NOWARN);
319 		if (!xpd->dontaudit)
320 			goto error;
321 	}
322 	return xpd_node;
323 error:
324 	avc_xperms_decision_free(xpd_node);
325 	return NULL;
326 }
327 
avc_add_xperms_decision(struct avc_node * node,struct extended_perms_decision * src)328 static int avc_add_xperms_decision(struct avc_node *node,
329 			struct extended_perms_decision *src)
330 {
331 	struct avc_xperms_decision_node *dest_xpd;
332 
333 	dest_xpd = avc_xperms_decision_alloc(src->used);
334 	if (!dest_xpd)
335 		return -ENOMEM;
336 	avc_copy_xperms_decision(&dest_xpd->xpd, src);
337 	list_add(&dest_xpd->xpd_list, &node->ae.xp_node->xpd_head);
338 	node->ae.xp_node->xp.len++;
339 	return 0;
340 }
341 
avc_xperms_alloc(void)342 static struct avc_xperms_node *avc_xperms_alloc(void)
343 {
344 	struct avc_xperms_node *xp_node;
345 
346 	xp_node = kmem_cache_zalloc(avc_xperms_cachep, GFP_NOWAIT | __GFP_NOWARN);
347 	if (!xp_node)
348 		return xp_node;
349 	INIT_LIST_HEAD(&xp_node->xpd_head);
350 	return xp_node;
351 }
352 
avc_xperms_populate(struct avc_node * node,struct avc_xperms_node * src)353 static int avc_xperms_populate(struct avc_node *node,
354 				struct avc_xperms_node *src)
355 {
356 	struct avc_xperms_node *dest;
357 	struct avc_xperms_decision_node *dest_xpd;
358 	struct avc_xperms_decision_node *src_xpd;
359 
360 	if (src->xp.len == 0)
361 		return 0;
362 	dest = avc_xperms_alloc();
363 	if (!dest)
364 		return -ENOMEM;
365 
366 	memcpy(dest->xp.drivers.p, src->xp.drivers.p, sizeof(dest->xp.drivers.p));
367 	dest->xp.len = src->xp.len;
368 
369 	/* for each source xpd allocate a destination xpd and copy */
370 	list_for_each_entry(src_xpd, &src->xpd_head, xpd_list) {
371 		dest_xpd = avc_xperms_decision_alloc(src_xpd->xpd.used);
372 		if (!dest_xpd)
373 			goto error;
374 		avc_copy_xperms_decision(&dest_xpd->xpd, &src_xpd->xpd);
375 		list_add(&dest_xpd->xpd_list, &dest->xpd_head);
376 	}
377 	node->ae.xp_node = dest;
378 	return 0;
379 error:
380 	avc_xperms_free(dest);
381 	return -ENOMEM;
382 
383 }
384 
avc_xperms_audit_required(u32 requested,struct av_decision * avd,struct extended_perms_decision * xpd,u8 perm,int result,u32 * deniedp)385 static inline u32 avc_xperms_audit_required(u32 requested,
386 					struct av_decision *avd,
387 					struct extended_perms_decision *xpd,
388 					u8 perm,
389 					int result,
390 					u32 *deniedp)
391 {
392 	u32 denied, audited;
393 
394 	denied = requested & ~avd->allowed;
395 	if (unlikely(denied)) {
396 		audited = denied & avd->auditdeny;
397 		if (audited && xpd) {
398 			if (avc_xperms_has_perm(xpd, perm, XPERMS_DONTAUDIT))
399 				audited &= ~requested;
400 		}
401 	} else if (result) {
402 		audited = denied = requested;
403 	} else {
404 		audited = requested & avd->auditallow;
405 		if (audited && xpd) {
406 			if (!avc_xperms_has_perm(xpd, perm, XPERMS_AUDITALLOW))
407 				audited &= ~requested;
408 		}
409 	}
410 
411 	*deniedp = denied;
412 	return audited;
413 }
414 
avc_xperms_audit(u32 ssid,u32 tsid,u16 tclass,u32 requested,struct av_decision * avd,struct extended_perms_decision * xpd,u8 perm,int result,struct common_audit_data * ad)415 static inline int avc_xperms_audit(u32 ssid, u32 tsid, u16 tclass,
416 				   u32 requested, struct av_decision *avd,
417 				   struct extended_perms_decision *xpd,
418 				   u8 perm, int result,
419 				   struct common_audit_data *ad)
420 {
421 	u32 audited, denied;
422 
423 	audited = avc_xperms_audit_required(
424 			requested, avd, xpd, perm, result, &denied);
425 	if (likely(!audited))
426 		return 0;
427 	return slow_avc_audit(ssid, tsid, tclass, requested,
428 			audited, denied, result, ad);
429 }
430 
avc_node_free(struct rcu_head * rhead)431 static void avc_node_free(struct rcu_head *rhead)
432 {
433 	struct avc_node *node = container_of(rhead, struct avc_node, rhead);
434 	avc_xperms_free(node->ae.xp_node);
435 	kmem_cache_free(avc_node_cachep, node);
436 	avc_cache_stats_incr(frees);
437 }
438 
avc_node_delete(struct avc_node * node)439 static void avc_node_delete(struct avc_node *node)
440 {
441 	hlist_del_rcu(&node->list);
442 	call_rcu(&node->rhead, avc_node_free);
443 	atomic_dec(&selinux_avc.avc_cache.active_nodes);
444 }
445 
avc_node_kill(struct avc_node * node)446 static void avc_node_kill(struct avc_node *node)
447 {
448 	avc_xperms_free(node->ae.xp_node);
449 	kmem_cache_free(avc_node_cachep, node);
450 	avc_cache_stats_incr(frees);
451 	atomic_dec(&selinux_avc.avc_cache.active_nodes);
452 }
453 
avc_node_replace(struct avc_node * new,struct avc_node * old)454 static void avc_node_replace(struct avc_node *new, struct avc_node *old)
455 {
456 	hlist_replace_rcu(&old->list, &new->list);
457 	call_rcu(&old->rhead, avc_node_free);
458 	atomic_dec(&selinux_avc.avc_cache.active_nodes);
459 }
460 
avc_reclaim_node(void)461 static inline int avc_reclaim_node(void)
462 {
463 	struct avc_node *node;
464 	int hvalue, try, ecx;
465 	unsigned long flags;
466 	struct hlist_head *head;
467 	spinlock_t *lock;
468 
469 	for (try = 0, ecx = 0; try < AVC_CACHE_SLOTS; try++) {
470 		hvalue = atomic_inc_return(&selinux_avc.avc_cache.lru_hint) &
471 			(AVC_CACHE_SLOTS - 1);
472 		head = &selinux_avc.avc_cache.slots[hvalue];
473 		lock = &selinux_avc.avc_cache.slots_lock[hvalue];
474 
475 		if (!spin_trylock_irqsave(lock, flags))
476 			continue;
477 
478 		rcu_read_lock();
479 		hlist_for_each_entry(node, head, list) {
480 			avc_node_delete(node);
481 			avc_cache_stats_incr(reclaims);
482 			ecx++;
483 			if (ecx >= AVC_CACHE_RECLAIM) {
484 				rcu_read_unlock();
485 				spin_unlock_irqrestore(lock, flags);
486 				goto out;
487 			}
488 		}
489 		rcu_read_unlock();
490 		spin_unlock_irqrestore(lock, flags);
491 	}
492 out:
493 	return ecx;
494 }
495 
avc_alloc_node(void)496 static struct avc_node *avc_alloc_node(void)
497 {
498 	struct avc_node *node;
499 
500 	node = kmem_cache_zalloc(avc_node_cachep, GFP_NOWAIT | __GFP_NOWARN);
501 	if (!node)
502 		goto out;
503 
504 	INIT_HLIST_NODE(&node->list);
505 	avc_cache_stats_incr(allocations);
506 
507 	if (atomic_inc_return(&selinux_avc.avc_cache.active_nodes) >
508 	    selinux_avc.avc_cache_threshold)
509 		avc_reclaim_node();
510 
511 out:
512 	return node;
513 }
514 
avc_node_populate(struct avc_node * node,u32 ssid,u32 tsid,u16 tclass,struct av_decision * avd)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 
avc_search_node(u32 ssid,u32 tsid,u16 tclass)523 static inline struct avc_node *avc_search_node(u32 ssid, u32 tsid, u16 tclass)
524 {
525 	struct avc_node *node, *ret = NULL;
526 	u32 hvalue;
527 	struct hlist_head *head;
528 
529 	hvalue = avc_hash(ssid, tsid, tclass);
530 	head = &selinux_avc.avc_cache.slots[hvalue];
531 	hlist_for_each_entry_rcu(node, head, list) {
532 		if (ssid == node->ae.ssid &&
533 		    tclass == node->ae.tclass &&
534 		    tsid == node->ae.tsid) {
535 			ret = node;
536 			break;
537 		}
538 	}
539 
540 	return ret;
541 }
542 
543 /**
544  * avc_lookup - Look up an AVC entry.
545  * @ssid: source security identifier
546  * @tsid: target security identifier
547  * @tclass: target security class
548  *
549  * Look up an AVC entry that is valid for the
550  * (@ssid, @tsid), interpreting the permissions
551  * based on @tclass.  If a valid AVC entry exists,
552  * then this function returns the avc_node.
553  * Otherwise, this function returns NULL.
554  */
avc_lookup(u32 ssid,u32 tsid,u16 tclass)555 static struct avc_node *avc_lookup(u32 ssid, u32 tsid, u16 tclass)
556 {
557 	struct avc_node *node;
558 
559 	avc_cache_stats_incr(lookups);
560 	node = avc_search_node(ssid, tsid, tclass);
561 
562 	if (node)
563 		return node;
564 
565 	avc_cache_stats_incr(misses);
566 	return NULL;
567 }
568 
avc_latest_notif_update(u32 seqno,int is_insert)569 static int avc_latest_notif_update(u32 seqno, int is_insert)
570 {
571 	int ret = 0;
572 	static DEFINE_SPINLOCK(notif_lock);
573 	unsigned long flag;
574 
575 	spin_lock_irqsave(&notif_lock, flag);
576 	if (is_insert) {
577 		if (seqno < selinux_avc.avc_cache.latest_notif) {
578 			pr_warn("SELinux: avc:  seqno %d < latest_notif %d\n",
579 			       seqno, selinux_avc.avc_cache.latest_notif);
580 			ret = -EAGAIN;
581 		}
582 	} else {
583 		if (seqno > selinux_avc.avc_cache.latest_notif)
584 			selinux_avc.avc_cache.latest_notif = seqno;
585 	}
586 	spin_unlock_irqrestore(&notif_lock, flag);
587 
588 	return ret;
589 }
590 
591 /**
592  * avc_insert - Insert an AVC entry.
593  * @ssid: source security identifier
594  * @tsid: target security identifier
595  * @tclass: target security class
596  * @avd: resulting av decision
597  * @xp_node: resulting extended permissions
598  *
599  * Insert an AVC entry for the SID pair
600  * (@ssid, @tsid) and class @tclass.
601  * The access vectors and the sequence number are
602  * normally provided by the security server in
603  * response to a security_compute_av() call.  If the
604  * sequence number @avd->seqno is not less than the latest
605  * revocation notification, then the function copies
606  * the access vectors into a cache entry.
607  */
avc_insert(u32 ssid,u32 tsid,u16 tclass,struct av_decision * avd,struct avc_xperms_node * xp_node)608 static void avc_insert(u32 ssid, u32 tsid, u16 tclass,
609 		       struct av_decision *avd, struct avc_xperms_node *xp_node)
610 {
611 	struct avc_node *pos, *node = NULL;
612 	u32 hvalue;
613 	unsigned long flag;
614 	spinlock_t *lock;
615 	struct hlist_head *head;
616 
617 	if (avc_latest_notif_update(avd->seqno, 1))
618 		return;
619 
620 	node = avc_alloc_node();
621 	if (!node)
622 		return;
623 
624 	avc_node_populate(node, ssid, tsid, tclass, avd);
625 	if (avc_xperms_populate(node, xp_node)) {
626 		avc_node_kill(node);
627 		return;
628 	}
629 
630 	hvalue = avc_hash(ssid, tsid, tclass);
631 	head = &selinux_avc.avc_cache.slots[hvalue];
632 	lock = &selinux_avc.avc_cache.slots_lock[hvalue];
633 	spin_lock_irqsave(lock, flag);
634 	hlist_for_each_entry(pos, head, list) {
635 		if (pos->ae.ssid == ssid &&
636 			pos->ae.tsid == tsid &&
637 			pos->ae.tclass == tclass) {
638 			avc_node_replace(node, pos);
639 			goto found;
640 		}
641 	}
642 	hlist_add_head_rcu(&node->list, head);
643 found:
644 	spin_unlock_irqrestore(lock, flag);
645 }
646 
647 /**
648  * avc_audit_pre_callback - SELinux specific information
649  * will be called by generic audit code
650  * @ab: the audit buffer
651  * @a: audit_data
652  */
avc_audit_pre_callback(struct audit_buffer * ab,void * a)653 static void avc_audit_pre_callback(struct audit_buffer *ab, void *a)
654 {
655 	struct common_audit_data *ad = a;
656 	struct selinux_audit_data *sad = ad->selinux_audit_data;
657 	u32 av = sad->audited, perm;
658 	const char *const *perms;
659 	u32 i;
660 
661 	audit_log_format(ab, "avc:  %s ", sad->denied ? "denied" : "granted");
662 
663 	if (av == 0) {
664 		audit_log_format(ab, " null");
665 		return;
666 	}
667 
668 	perms = secclass_map[sad->tclass-1].perms;
669 
670 	audit_log_format(ab, " {");
671 	i = 0;
672 	perm = 1;
673 	while (i < (sizeof(av) * 8)) {
674 		if ((perm & av) && perms[i]) {
675 			audit_log_format(ab, " %s", perms[i]);
676 			av &= ~perm;
677 		}
678 		i++;
679 		perm <<= 1;
680 	}
681 
682 	if (av)
683 		audit_log_format(ab, " 0x%x", av);
684 
685 	audit_log_format(ab, " } for ");
686 }
687 
688 /**
689  * avc_audit_post_callback - SELinux specific information
690  * will be called by generic audit code
691  * @ab: the audit buffer
692  * @a: audit_data
693  */
avc_audit_post_callback(struct audit_buffer * ab,void * a)694 static void avc_audit_post_callback(struct audit_buffer *ab, void *a)
695 {
696 	struct common_audit_data *ad = a;
697 	struct selinux_audit_data *sad = ad->selinux_audit_data;
698 	char *scontext = NULL;
699 	char *tcontext = NULL;
700 	const char *tclass = NULL;
701 	u32 scontext_len;
702 	u32 tcontext_len;
703 	int rc;
704 
705 	rc = security_sid_to_context(sad->ssid, &scontext,
706 				     &scontext_len);
707 	if (rc)
708 		audit_log_format(ab, " ssid=%d", sad->ssid);
709 	else
710 		audit_log_format(ab, " scontext=%s", scontext);
711 
712 	rc = security_sid_to_context(sad->tsid, &tcontext,
713 				     &tcontext_len);
714 	if (rc)
715 		audit_log_format(ab, " tsid=%d", sad->tsid);
716 	else
717 		audit_log_format(ab, " tcontext=%s", tcontext);
718 
719 	tclass = secclass_map[sad->tclass-1].name;
720 	audit_log_format(ab, " tclass=%s", tclass);
721 
722 	if (sad->denied)
723 		audit_log_format(ab, " permissive=%u", sad->result ? 0 : 1);
724 
725 	trace_selinux_audited(sad, scontext, tcontext, tclass);
726 	kfree(tcontext);
727 	kfree(scontext);
728 
729 	/* in case of invalid context report also the actual context string */
730 	rc = security_sid_to_context_inval(sad->ssid, &scontext,
731 					   &scontext_len);
732 	if (!rc && scontext) {
733 		if (scontext_len && scontext[scontext_len - 1] == '\0')
734 			scontext_len--;
735 		audit_log_format(ab, " srawcon=");
736 		audit_log_n_untrustedstring(ab, scontext, scontext_len);
737 		kfree(scontext);
738 	}
739 
740 	rc = security_sid_to_context_inval(sad->tsid, &scontext,
741 					   &scontext_len);
742 	if (!rc && scontext) {
743 		if (scontext_len && scontext[scontext_len - 1] == '\0')
744 			scontext_len--;
745 		audit_log_format(ab, " trawcon=");
746 		audit_log_n_untrustedstring(ab, scontext, scontext_len);
747 		kfree(scontext);
748 	}
749 }
750 
751 /*
752  * This is the slow part of avc audit with big stack footprint.
753  * Note that it is non-blocking and can be called from under
754  * rcu_read_lock().
755  */
slow_avc_audit(u32 ssid,u32 tsid,u16 tclass,u32 requested,u32 audited,u32 denied,int result,struct common_audit_data * a)756 noinline int slow_avc_audit(u32 ssid, u32 tsid, u16 tclass,
757 			    u32 requested, u32 audited, u32 denied, int result,
758 			    struct common_audit_data *a)
759 {
760 	struct common_audit_data stack_data;
761 	struct selinux_audit_data sad;
762 
763 	if (WARN_ON(!tclass || tclass >= ARRAY_SIZE(secclass_map)))
764 		return -EINVAL;
765 
766 	if (!a) {
767 		a = &stack_data;
768 		a->type = LSM_AUDIT_DATA_NONE;
769 	}
770 
771 	sad.tclass = tclass;
772 	sad.requested = requested;
773 	sad.ssid = ssid;
774 	sad.tsid = tsid;
775 	sad.audited = audited;
776 	sad.denied = denied;
777 	sad.result = result;
778 
779 	a->selinux_audit_data = &sad;
780 
781 	common_lsm_audit(a, avc_audit_pre_callback, avc_audit_post_callback);
782 	return 0;
783 }
784 
785 /**
786  * avc_add_callback - Register a callback for security events.
787  * @callback: callback function
788  * @events: security events
789  *
790  * Register a callback function for events in the set @events.
791  * Returns %0 on success or -%ENOMEM if insufficient memory
792  * exists to add the callback.
793  */
avc_add_callback(int (* callback)(u32 event),u32 events)794 int __init avc_add_callback(int (*callback)(u32 event), u32 events)
795 {
796 	struct avc_callback_node *c;
797 	int rc = 0;
798 
799 	c = kmalloc(sizeof(*c), GFP_KERNEL);
800 	if (!c) {
801 		rc = -ENOMEM;
802 		goto out;
803 	}
804 
805 	c->callback = callback;
806 	c->events = events;
807 	c->next = avc_callbacks;
808 	avc_callbacks = c;
809 out:
810 	return rc;
811 }
812 
813 /**
814  * avc_update_node - Update an AVC entry
815  * @event : Updating event
816  * @perms : Permission mask bits
817  * @driver: xperm driver information
818  * @xperm: xperm permissions
819  * @ssid: AVC entry source sid
820  * @tsid: AVC entry target sid
821  * @tclass : AVC entry target object class
822  * @seqno : sequence number when decision was made
823  * @xpd: extended_perms_decision to be added to the node
824  * @flags: the AVC_* flags, e.g. AVC_EXTENDED_PERMS, or 0.
825  *
826  * if a valid AVC entry doesn't exist,this function returns -ENOENT.
827  * if kmalloc() called internal returns NULL, this function returns -ENOMEM.
828  * otherwise, this function updates the AVC entry. The original AVC-entry object
829  * will release later by RCU.
830  */
avc_update_node(u32 event,u32 perms,u8 driver,u8 xperm,u32 ssid,u32 tsid,u16 tclass,u32 seqno,struct extended_perms_decision * xpd,u32 flags)831 static int avc_update_node(u32 event, u32 perms, u8 driver, u8 xperm, u32 ssid,
832 			   u32 tsid, u16 tclass, u32 seqno,
833 			   struct extended_perms_decision *xpd,
834 			   u32 flags)
835 {
836 	u32 hvalue;
837 	int rc = 0;
838 	unsigned long flag;
839 	struct avc_node *pos, *node, *orig = NULL;
840 	struct hlist_head *head;
841 	spinlock_t *lock;
842 
843 	node = avc_alloc_node();
844 	if (!node) {
845 		rc = -ENOMEM;
846 		goto out;
847 	}
848 
849 	/* Lock the target slot */
850 	hvalue = avc_hash(ssid, tsid, tclass);
851 
852 	head = &selinux_avc.avc_cache.slots[hvalue];
853 	lock = &selinux_avc.avc_cache.slots_lock[hvalue];
854 
855 	spin_lock_irqsave(lock, flag);
856 
857 	hlist_for_each_entry(pos, head, list) {
858 		if (ssid == pos->ae.ssid &&
859 		    tsid == pos->ae.tsid &&
860 		    tclass == pos->ae.tclass &&
861 		    seqno == pos->ae.avd.seqno){
862 			orig = pos;
863 			break;
864 		}
865 	}
866 
867 	if (!orig) {
868 		rc = -ENOENT;
869 		avc_node_kill(node);
870 		goto out_unlock;
871 	}
872 
873 	/*
874 	 * Copy and replace original node.
875 	 */
876 
877 	avc_node_populate(node, ssid, tsid, tclass, &orig->ae.avd);
878 
879 	if (orig->ae.xp_node) {
880 		rc = avc_xperms_populate(node, orig->ae.xp_node);
881 		if (rc) {
882 			avc_node_kill(node);
883 			goto out_unlock;
884 		}
885 	}
886 
887 	switch (event) {
888 	case AVC_CALLBACK_GRANT:
889 		node->ae.avd.allowed |= perms;
890 		if (node->ae.xp_node && (flags & AVC_EXTENDED_PERMS))
891 			avc_xperms_allow_perm(node->ae.xp_node, driver, xperm);
892 		break;
893 	case AVC_CALLBACK_TRY_REVOKE:
894 	case AVC_CALLBACK_REVOKE:
895 		node->ae.avd.allowed &= ~perms;
896 		break;
897 	case AVC_CALLBACK_AUDITALLOW_ENABLE:
898 		node->ae.avd.auditallow |= perms;
899 		break;
900 	case AVC_CALLBACK_AUDITALLOW_DISABLE:
901 		node->ae.avd.auditallow &= ~perms;
902 		break;
903 	case AVC_CALLBACK_AUDITDENY_ENABLE:
904 		node->ae.avd.auditdeny |= perms;
905 		break;
906 	case AVC_CALLBACK_AUDITDENY_DISABLE:
907 		node->ae.avd.auditdeny &= ~perms;
908 		break;
909 	case AVC_CALLBACK_ADD_XPERMS:
910 		rc = avc_add_xperms_decision(node, xpd);
911 		if (rc) {
912 			avc_node_kill(node);
913 			goto out_unlock;
914 		}
915 		break;
916 	}
917 	avc_node_replace(node, orig);
918 out_unlock:
919 	spin_unlock_irqrestore(lock, flag);
920 out:
921 	return rc;
922 }
923 
924 /**
925  * avc_flush - Flush the cache
926  */
avc_flush(void)927 static void avc_flush(void)
928 {
929 	struct hlist_head *head;
930 	struct avc_node *node;
931 	spinlock_t *lock;
932 	unsigned long flag;
933 	int i;
934 
935 	for (i = 0; i < AVC_CACHE_SLOTS; i++) {
936 		head = &selinux_avc.avc_cache.slots[i];
937 		lock = &selinux_avc.avc_cache.slots_lock[i];
938 
939 		spin_lock_irqsave(lock, flag);
940 		/*
941 		 * With preemptable RCU, the outer spinlock does not
942 		 * prevent RCU grace periods from ending.
943 		 */
944 		rcu_read_lock();
945 		hlist_for_each_entry(node, head, list)
946 			avc_node_delete(node);
947 		rcu_read_unlock();
948 		spin_unlock_irqrestore(lock, flag);
949 	}
950 }
951 
952 /**
953  * avc_ss_reset - Flush the cache and revalidate migrated permissions.
954  * @seqno: policy sequence number
955  */
avc_ss_reset(u32 seqno)956 int avc_ss_reset(u32 seqno)
957 {
958 	struct avc_callback_node *c;
959 	int rc = 0, tmprc;
960 
961 	avc_flush();
962 
963 	for (c = avc_callbacks; c; c = c->next) {
964 		if (c->events & AVC_CALLBACK_RESET) {
965 			tmprc = c->callback(AVC_CALLBACK_RESET);
966 			/* save the first error encountered for the return
967 			   value and continue processing the callbacks */
968 			if (!rc)
969 				rc = tmprc;
970 		}
971 	}
972 
973 	avc_latest_notif_update(seqno, 0);
974 	return rc;
975 }
976 
977 /**
978  * avc_compute_av - Add an entry to the AVC based on the security policy
979  * @ssid: subject
980  * @tsid: object/target
981  * @tclass: object class
982  * @avd: access vector decision
983  * @xp_node: AVC extended permissions node
984  *
985  * Slow-path helper function for avc_has_perm_noaudit, when the avc_node lookup
986  * fails.  Don't inline this, since it's the slow-path and just results in a
987  * bigger stack frame.
988  */
avc_compute_av(u32 ssid,u32 tsid,u16 tclass,struct av_decision * avd,struct avc_xperms_node * xp_node)989 static noinline void avc_compute_av(u32 ssid, u32 tsid, u16 tclass,
990 				    struct av_decision *avd,
991 				    struct avc_xperms_node *xp_node)
992 {
993 	INIT_LIST_HEAD(&xp_node->xpd_head);
994 	security_compute_av(ssid, tsid, tclass, avd, &xp_node->xp);
995 	avc_insert(ssid, tsid, tclass, avd, xp_node);
996 }
997 
avc_denied(u32 ssid,u32 tsid,u16 tclass,u32 requested,u8 driver,u8 xperm,unsigned int flags,struct av_decision * avd)998 static noinline int avc_denied(u32 ssid, u32 tsid,
999 			       u16 tclass, u32 requested,
1000 			       u8 driver, u8 xperm, unsigned int flags,
1001 			       struct av_decision *avd)
1002 {
1003 	if (flags & AVC_STRICT)
1004 		return -EACCES;
1005 
1006 	if (enforcing_enabled() &&
1007 	    !(avd->flags & AVD_FLAGS_PERMISSIVE))
1008 		return -EACCES;
1009 
1010 	avc_update_node(AVC_CALLBACK_GRANT, requested, driver,
1011 			xperm, ssid, tsid, tclass, avd->seqno, NULL, flags);
1012 	return 0;
1013 }
1014 
1015 /*
1016  * The avc extended permissions logic adds an additional 256 bits of
1017  * permissions to an avc node when extended permissions for that node are
1018  * specified in the avtab. If the additional 256 permissions is not adequate,
1019  * as-is the case with ioctls, then multiple may be chained together and the
1020  * driver field is used to specify which set contains the permission.
1021  */
avc_has_extended_perms(u32 ssid,u32 tsid,u16 tclass,u32 requested,u8 driver,u8 xperm,struct common_audit_data * ad)1022 int avc_has_extended_perms(u32 ssid, u32 tsid, u16 tclass, u32 requested,
1023 			   u8 driver, u8 xperm, struct common_audit_data *ad)
1024 {
1025 	struct avc_node *node;
1026 	struct av_decision avd;
1027 	u32 denied;
1028 	struct extended_perms_decision local_xpd;
1029 	struct extended_perms_decision *xpd = NULL;
1030 	struct extended_perms_data allowed;
1031 	struct extended_perms_data auditallow;
1032 	struct extended_perms_data dontaudit;
1033 	struct avc_xperms_node local_xp_node;
1034 	struct avc_xperms_node *xp_node;
1035 	int rc = 0, rc2;
1036 
1037 	xp_node = &local_xp_node;
1038 	if (WARN_ON(!requested))
1039 		return -EACCES;
1040 
1041 	rcu_read_lock();
1042 
1043 	node = avc_lookup(ssid, tsid, tclass);
1044 	if (unlikely(!node)) {
1045 		avc_compute_av(ssid, tsid, tclass, &avd, xp_node);
1046 	} else {
1047 		memcpy(&avd, &node->ae.avd, sizeof(avd));
1048 		xp_node = node->ae.xp_node;
1049 	}
1050 	/* if extended permissions are not defined, only consider av_decision */
1051 	if (!xp_node || !xp_node->xp.len)
1052 		goto decision;
1053 
1054 	local_xpd.allowed = &allowed;
1055 	local_xpd.auditallow = &auditallow;
1056 	local_xpd.dontaudit = &dontaudit;
1057 
1058 	xpd = avc_xperms_decision_lookup(driver, xp_node);
1059 	if (unlikely(!xpd)) {
1060 		/*
1061 		 * Compute the extended_perms_decision only if the driver
1062 		 * is flagged
1063 		 */
1064 		if (!security_xperm_test(xp_node->xp.drivers.p, driver)) {
1065 			avd.allowed &= ~requested;
1066 			goto decision;
1067 		}
1068 		rcu_read_unlock();
1069 		security_compute_xperms_decision(ssid, tsid, tclass,
1070 						 driver, &local_xpd);
1071 		rcu_read_lock();
1072 		avc_update_node(AVC_CALLBACK_ADD_XPERMS, requested,
1073 				driver, xperm, ssid, tsid, tclass, avd.seqno,
1074 				&local_xpd, 0);
1075 	} else {
1076 		avc_quick_copy_xperms_decision(xperm, &local_xpd, xpd);
1077 	}
1078 	xpd = &local_xpd;
1079 
1080 	if (!avc_xperms_has_perm(xpd, xperm, XPERMS_ALLOWED))
1081 		avd.allowed &= ~requested;
1082 
1083 decision:
1084 	denied = requested & ~(avd.allowed);
1085 	if (unlikely(denied))
1086 		rc = avc_denied(ssid, tsid, tclass, requested,
1087 				driver, xperm, AVC_EXTENDED_PERMS, &avd);
1088 
1089 	rcu_read_unlock();
1090 
1091 	rc2 = avc_xperms_audit(ssid, tsid, tclass, requested,
1092 			&avd, xpd, xperm, rc, ad);
1093 	if (rc2)
1094 		return rc2;
1095 	return rc;
1096 }
1097 
1098 /**
1099  * avc_perm_nonode - Add an entry to the AVC
1100  * @ssid: subject
1101  * @tsid: object/target
1102  * @tclass: object class
1103  * @requested: requested permissions
1104  * @flags: AVC flags
1105  * @avd: access vector decision
1106  *
1107  * This is the "we have no node" part of avc_has_perm_noaudit(), which is
1108  * unlikely and needs extra stack space for the new node that we generate, so
1109  * don't inline it.
1110  */
avc_perm_nonode(u32 ssid,u32 tsid,u16 tclass,u32 requested,unsigned int flags,struct av_decision * avd)1111 static noinline int avc_perm_nonode(u32 ssid, u32 tsid, u16 tclass,
1112 				    u32 requested, unsigned int flags,
1113 				    struct av_decision *avd)
1114 {
1115 	u32 denied;
1116 	struct avc_xperms_node xp_node;
1117 
1118 	avc_compute_av(ssid, tsid, tclass, avd, &xp_node);
1119 	denied = requested & ~(avd->allowed);
1120 	if (unlikely(denied))
1121 		return avc_denied(ssid, tsid, tclass, requested, 0, 0,
1122 				  flags, avd);
1123 	return 0;
1124 }
1125 
1126 /**
1127  * avc_has_perm_noaudit - Check permissions but perform no 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  * @flags:  AVC_STRICT or 0
1133  * @avd: access vector decisions
1134  *
1135  * Check the AVC to determine whether the @requested permissions are granted
1136  * for the SID pair (@ssid, @tsid), interpreting the permissions
1137  * based on @tclass, and call the security server on a cache miss to obtain
1138  * a new decision and add it to the cache.  Return a copy of the decisions
1139  * in @avd.  Return %0 if all @requested permissions are granted,
1140  * -%EACCES if any permissions are denied, or another -errno upon
1141  * other errors.  This function is typically called by avc_has_perm(),
1142  * but may also be called directly to separate permission checking from
1143  * auditing, e.g. in cases where a lock must be held for the check but
1144  * should be released for the auditing.
1145  */
avc_has_perm_noaudit(u32 ssid,u32 tsid,u16 tclass,u32 requested,unsigned int flags,struct av_decision * avd)1146 inline int avc_has_perm_noaudit(u32 ssid, u32 tsid,
1147 				u16 tclass, u32 requested,
1148 				unsigned int flags,
1149 				struct av_decision *avd)
1150 {
1151 	u32 denied;
1152 	struct avc_node *node;
1153 
1154 	if (WARN_ON(!requested))
1155 		return -EACCES;
1156 
1157 	rcu_read_lock();
1158 	node = avc_lookup(ssid, tsid, tclass);
1159 	if (unlikely(!node)) {
1160 		rcu_read_unlock();
1161 		return avc_perm_nonode(ssid, tsid, tclass, requested,
1162 				       flags, avd);
1163 	}
1164 	denied = requested & ~node->ae.avd.allowed;
1165 	memcpy(avd, &node->ae.avd, sizeof(*avd));
1166 	rcu_read_unlock();
1167 
1168 	if (unlikely(denied))
1169 		return avc_denied(ssid, tsid, tclass, requested, 0, 0,
1170 				  flags, avd);
1171 	return 0;
1172 }
1173 
1174 /**
1175  * avc_has_perm - Check permissions and perform any appropriate auditing.
1176  * @ssid: source security identifier
1177  * @tsid: target security identifier
1178  * @tclass: target security class
1179  * @requested: requested permissions, interpreted based on @tclass
1180  * @auditdata: auxiliary audit data
1181  *
1182  * Check the AVC to determine whether the @requested permissions are granted
1183  * for the SID pair (@ssid, @tsid), interpreting the permissions
1184  * based on @tclass, and call the security server on a cache miss to obtain
1185  * a new decision and add it to the cache.  Audit the granting or denial of
1186  * permissions in accordance with the policy.  Return %0 if all @requested
1187  * permissions are granted, -%EACCES if any permissions are denied, or
1188  * another -errno upon other errors.
1189  */
avc_has_perm(u32 ssid,u32 tsid,u16 tclass,u32 requested,struct common_audit_data * auditdata)1190 int avc_has_perm(u32 ssid, u32 tsid, u16 tclass,
1191 		 u32 requested, struct common_audit_data *auditdata)
1192 {
1193 	struct av_decision avd;
1194 	int rc, rc2;
1195 
1196 	rc = avc_has_perm_noaudit(ssid, tsid, tclass, requested, 0,
1197 				  &avd);
1198 
1199 	rc2 = avc_audit(ssid, tsid, tclass, requested, &avd, rc,
1200 			auditdata);
1201 	if (rc2)
1202 		return rc2;
1203 	return rc;
1204 }
1205 
avc_policy_seqno(void)1206 u32 avc_policy_seqno(void)
1207 {
1208 	return selinux_avc.avc_cache.latest_notif;
1209 }
1210