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#include "hash.h"
34
35#define CREATE_TRACE_POINTS
36#include <trace/events/avc.h>
37
38#define AVC_CACHE_SLOTS (1 << CONFIG_SECURITY_SELINUX_AVC_HASH_BITS)
39#define AVC_DEF_CACHE_THRESHOLD AVC_CACHE_SLOTS
40#define AVC_CACHE_RECLAIM 16
41
42#ifdef CONFIG_SECURITY_SELINUX_AVC_STATS
43#define avc_cache_stats_incr(field) this_cpu_inc(avc_cache_stats.field)
44#else
45#define avc_cache_stats_incr(field) do {} while (0)
46#endif
47
48struct avc_entry {
49 u32 ssid;
50 u32 tsid;
51 u16 tclass;
52 struct av_decision avd;
53 struct avc_xperms_node *xp_node;
54};
55
56struct avc_node {
57 struct avc_entry ae;
58 struct hlist_node list; /* anchored in avc_cache->slots[i] */
59 struct rcu_head rhead;
60};
61
62struct avc_xperms_decision_node {
63 struct extended_perms_decision xpd;
64 struct list_head xpd_list; /* list of extended_perms_decision */
65};
66
67struct avc_xperms_node {
68 struct extended_perms xp;
69 struct list_head xpd_head; /* list head of extended_perms_decision */
70};
71
72struct avc_cache {
73 struct hlist_head slots[AVC_CACHE_SLOTS]; /* head for avc_node->list */
74 spinlock_t slots_lock[AVC_CACHE_SLOTS]; /* lock for writes */
75 atomic_t lru_hint; /* LRU hint for reclaim scan */
76 atomic_t active_nodes;
77 u32 latest_notif; /* latest revocation notification */
78};
79
80struct avc_callback_node {
81 int (*callback) (u32 event);
82 u32 events;
83 struct avc_callback_node *next;
84};
85
86#ifdef CONFIG_SECURITY_SELINUX_AVC_STATS
87DEFINE_PER_CPU(struct avc_cache_stats, avc_cache_stats) = { 0 };
88#endif
89
90struct selinux_avc {
91 unsigned int avc_cache_threshold;
92 struct avc_cache avc_cache;
93};
94
95static struct selinux_avc selinux_avc;
96
97void selinux_avc_init(void)
98{
99 int i;
100
101 selinux_avc.avc_cache_threshold = AVC_DEF_CACHE_THRESHOLD;
102 for (i = 0; i < AVC_CACHE_SLOTS; i++) {
103 INIT_HLIST_HEAD(&selinux_avc.avc_cache.slots[i]);
104 spin_lock_init(&selinux_avc.avc_cache.slots_lock[i]);
105 }
106 atomic_set(v: &selinux_avc.avc_cache.active_nodes, i: 0);
107 atomic_set(v: &selinux_avc.avc_cache.lru_hint, i: 0);
108}
109
110unsigned int avc_get_cache_threshold(void)
111{
112 return selinux_avc.avc_cache_threshold;
113}
114
115void avc_set_cache_threshold(unsigned int cache_threshold)
116{
117 selinux_avc.avc_cache_threshold = cache_threshold;
118}
119
120static struct avc_callback_node *avc_callbacks __ro_after_init;
121static struct kmem_cache *avc_node_cachep __ro_after_init;
122static struct kmem_cache *avc_xperms_data_cachep __ro_after_init;
123static struct kmem_cache *avc_xperms_decision_cachep __ro_after_init;
124static struct kmem_cache *avc_xperms_cachep __ro_after_init;
125
126static inline u32 avc_hash(u32 ssid, u32 tsid, u16 tclass)
127{
128 return av_hash(key1: ssid, key2: tsid, key3: (u32)tclass, mask: (u32)(AVC_CACHE_SLOTS - 1));
129}
130
131/**
132 * avc_init - Initialize the AVC.
133 *
134 * Initialize the access vector cache.
135 */
136void __init avc_init(void)
137{
138 avc_node_cachep = KMEM_CACHE(avc_node, SLAB_PANIC);
139 avc_xperms_cachep = KMEM_CACHE(avc_xperms_node, SLAB_PANIC);
140 avc_xperms_decision_cachep = KMEM_CACHE(avc_xperms_decision_node, SLAB_PANIC);
141 avc_xperms_data_cachep = KMEM_CACHE(extended_perms_data, SLAB_PANIC);
142}
143
144int avc_get_hash_stats(char *page)
145{
146 int i, chain_len, max_chain_len, slots_used;
147 struct avc_node *node;
148 struct hlist_head *head;
149
150 rcu_read_lock();
151
152 slots_used = 0;
153 max_chain_len = 0;
154 for (i = 0; i < AVC_CACHE_SLOTS; i++) {
155 head = &selinux_avc.avc_cache.slots[i];
156 if (!hlist_empty(h: head)) {
157 slots_used++;
158 chain_len = 0;
159 hlist_for_each_entry_rcu(node, head, list)
160 chain_len++;
161 if (chain_len > max_chain_len)
162 max_chain_len = chain_len;
163 }
164 }
165
166 rcu_read_unlock();
167
168 return scnprintf(buf: page, PAGE_SIZE, fmt: "entries: %d\nbuckets used: %d/%d\n"
169 "longest chain: %d\n",
170 atomic_read(v: &selinux_avc.avc_cache.active_nodes),
171 slots_used, AVC_CACHE_SLOTS, max_chain_len);
172}
173
174/*
175 * using a linked list for extended_perms_decision lookup because the list is
176 * always small. i.e. less than 5, typically 1
177 */
178static struct extended_perms_decision *
179avc_xperms_decision_lookup(u8 driver, u8 base_perm,
180 struct avc_xperms_node *xp_node)
181{
182 struct avc_xperms_decision_node *xpd_node;
183
184 list_for_each_entry(xpd_node, &xp_node->xpd_head, xpd_list) {
185 if (xpd_node->xpd.driver == driver &&
186 xpd_node->xpd.base_perm == base_perm)
187 return &xpd_node->xpd;
188 }
189 return NULL;
190}
191
192static inline unsigned int
193avc_xperms_has_perm(struct extended_perms_decision *xpd,
194 u8 perm, u8 which)
195{
196 unsigned int rc = 0;
197
198 if ((which == XPERMS_ALLOWED) &&
199 (xpd->used & XPERMS_ALLOWED))
200 rc = security_xperm_test(xpd->allowed->p, perm);
201 else if ((which == XPERMS_AUDITALLOW) &&
202 (xpd->used & XPERMS_AUDITALLOW))
203 rc = security_xperm_test(xpd->auditallow->p, perm);
204 else if ((which == XPERMS_DONTAUDIT) &&
205 (xpd->used & XPERMS_DONTAUDIT))
206 rc = security_xperm_test(xpd->dontaudit->p, perm);
207 return rc;
208}
209
210static void avc_xperms_allow_perm(struct avc_xperms_node *xp_node,
211 u8 driver, u8 base_perm, u8 perm)
212{
213 struct extended_perms_decision *xpd;
214 security_xperm_set(xp_node->xp.drivers.p, driver);
215 xp_node->xp.base_perms |= base_perm;
216 xpd = avc_xperms_decision_lookup(driver, base_perm, xp_node);
217 if (xpd && xpd->allowed)
218 security_xperm_set(xpd->allowed->p, perm);
219}
220
221static void avc_xperms_decision_free(struct avc_xperms_decision_node *xpd_node)
222{
223 struct extended_perms_decision *xpd;
224
225 xpd = &xpd_node->xpd;
226 if (xpd->allowed)
227 kmem_cache_free(s: avc_xperms_data_cachep, objp: xpd->allowed);
228 if (xpd->auditallow)
229 kmem_cache_free(s: avc_xperms_data_cachep, objp: xpd->auditallow);
230 if (xpd->dontaudit)
231 kmem_cache_free(s: avc_xperms_data_cachep, objp: xpd->dontaudit);
232 kmem_cache_free(s: avc_xperms_decision_cachep, objp: xpd_node);
233}
234
235static void avc_xperms_free(struct avc_xperms_node *xp_node)
236{
237 struct avc_xperms_decision_node *xpd_node, *tmp;
238
239 if (!xp_node)
240 return;
241
242 list_for_each_entry_safe(xpd_node, tmp, &xp_node->xpd_head, xpd_list) {
243 list_del(entry: &xpd_node->xpd_list);
244 avc_xperms_decision_free(xpd_node);
245 }
246 kmem_cache_free(s: avc_xperms_cachep, objp: xp_node);
247}
248
249static void avc_copy_xperms_decision(struct extended_perms_decision *dest,
250 struct extended_perms_decision *src)
251{
252 dest->base_perm = src->base_perm;
253 dest->driver = src->driver;
254 dest->used = src->used;
255 if (dest->used & XPERMS_ALLOWED)
256 memcpy(dest->allowed->p, src->allowed->p,
257 sizeof(src->allowed->p));
258 if (dest->used & XPERMS_AUDITALLOW)
259 memcpy(dest->auditallow->p, src->auditallow->p,
260 sizeof(src->auditallow->p));
261 if (dest->used & XPERMS_DONTAUDIT)
262 memcpy(dest->dontaudit->p, src->dontaudit->p,
263 sizeof(src->dontaudit->p));
264}
265
266/*
267 * similar to avc_copy_xperms_decision, but only copy decision
268 * information relevant to this perm
269 */
270static inline void avc_quick_copy_xperms_decision(u8 perm,
271 struct extended_perms_decision *dest,
272 struct extended_perms_decision *src)
273{
274 /*
275 * compute index of the u32 of the 256 bits (8 u32s) that contain this
276 * command permission
277 */
278 u8 i = perm >> 5;
279
280 dest->base_perm = src->base_perm;
281 dest->used = src->used;
282 if (dest->used & XPERMS_ALLOWED)
283 dest->allowed->p[i] = src->allowed->p[i];
284 if (dest->used & XPERMS_AUDITALLOW)
285 dest->auditallow->p[i] = src->auditallow->p[i];
286 if (dest->used & XPERMS_DONTAUDIT)
287 dest->dontaudit->p[i] = src->dontaudit->p[i];
288}
289
290static struct avc_xperms_decision_node
291 *avc_xperms_decision_alloc(u8 which)
292{
293 struct avc_xperms_decision_node *xpd_node;
294 struct extended_perms_decision *xpd;
295
296 xpd_node = kmem_cache_zalloc(avc_xperms_decision_cachep, GFP_NOWAIT);
297 if (!xpd_node)
298 return NULL;
299
300 xpd = &xpd_node->xpd;
301 if (which & XPERMS_ALLOWED) {
302 xpd->allowed = kmem_cache_zalloc(avc_xperms_data_cachep,
303 GFP_NOWAIT);
304 if (!xpd->allowed)
305 goto error;
306 }
307 if (which & XPERMS_AUDITALLOW) {
308 xpd->auditallow = kmem_cache_zalloc(avc_xperms_data_cachep,
309 GFP_NOWAIT);
310 if (!xpd->auditallow)
311 goto error;
312 }
313 if (which & XPERMS_DONTAUDIT) {
314 xpd->dontaudit = kmem_cache_zalloc(avc_xperms_data_cachep,
315 GFP_NOWAIT);
316 if (!xpd->dontaudit)
317 goto error;
318 }
319 return xpd_node;
320error:
321 avc_xperms_decision_free(xpd_node);
322 return NULL;
323}
324
325static int avc_add_xperms_decision(struct avc_node *node,
326 struct extended_perms_decision *src)
327{
328 struct avc_xperms_decision_node *dest_xpd;
329
330 dest_xpd = avc_xperms_decision_alloc(which: src->used);
331 if (!dest_xpd)
332 return -ENOMEM;
333 avc_copy_xperms_decision(dest: &dest_xpd->xpd, src);
334 list_add(new: &dest_xpd->xpd_list, head: &node->ae.xp_node->xpd_head);
335 node->ae.xp_node->xp.len++;
336 return 0;
337}
338
339static struct avc_xperms_node *avc_xperms_alloc(void)
340{
341 struct avc_xperms_node *xp_node;
342
343 xp_node = kmem_cache_zalloc(avc_xperms_cachep, GFP_NOWAIT);
344 if (!xp_node)
345 return xp_node;
346 INIT_LIST_HEAD(list: &xp_node->xpd_head);
347 return xp_node;
348}
349
350static int avc_xperms_populate(struct avc_node *node,
351 struct avc_xperms_node *src)
352{
353 struct avc_xperms_node *dest;
354 struct avc_xperms_decision_node *dest_xpd;
355 struct avc_xperms_decision_node *src_xpd;
356
357 if (src->xp.len == 0)
358 return 0;
359 dest = avc_xperms_alloc();
360 if (!dest)
361 return -ENOMEM;
362
363 memcpy(dest->xp.drivers.p, src->xp.drivers.p, sizeof(dest->xp.drivers.p));
364 dest->xp.len = src->xp.len;
365 dest->xp.base_perms = src->xp.base_perms;
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(which: src_xpd->xpd.used);
370 if (!dest_xpd)
371 goto error;
372 avc_copy_xperms_decision(dest: &dest_xpd->xpd, src: &src_xpd->xpd);
373 list_add(new: &dest_xpd->xpd_list, head: &dest->xpd_head);
374 }
375 node->ae.xp_node = dest;
376 return 0;
377error:
378 avc_xperms_free(xp_node: dest);
379 return -ENOMEM;
380
381}
382
383static 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 = 0;
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 = 0;
406 }
407 }
408
409 *deniedp = denied;
410 return audited;
411}
412
413static inline int avc_xperms_audit(u32 ssid, u32 tsid, u16 tclass,
414 u32 requested, struct av_decision *avd,
415 struct extended_perms_decision *xpd,
416 u8 perm, int result,
417 struct common_audit_data *ad)
418{
419 u32 audited, denied;
420
421 audited = avc_xperms_audit_required(
422 requested, avd, xpd, perm, result, deniedp: &denied);
423 if (likely(!audited))
424 return 0;
425 return slow_avc_audit(ssid, tsid, tclass, requested,
426 audited, denied, result, a: ad);
427}
428
429static void avc_node_free(struct rcu_head *rhead)
430{
431 struct avc_node *node = container_of(rhead, struct avc_node, rhead);
432 avc_xperms_free(xp_node: node->ae.xp_node);
433 kmem_cache_free(s: avc_node_cachep, objp: node);
434 avc_cache_stats_incr(frees);
435}
436
437static void avc_node_delete(struct avc_node *node)
438{
439 hlist_del_rcu(n: &node->list);
440 call_rcu(head: &node->rhead, func: avc_node_free);
441 atomic_dec(v: &selinux_avc.avc_cache.active_nodes);
442}
443
444static void avc_node_kill(struct avc_node *node)
445{
446 avc_xperms_free(xp_node: node->ae.xp_node);
447 kmem_cache_free(s: avc_node_cachep, objp: node);
448 avc_cache_stats_incr(frees);
449 atomic_dec(v: &selinux_avc.avc_cache.active_nodes);
450}
451
452static void avc_node_replace(struct avc_node *new, struct avc_node *old)
453{
454 hlist_replace_rcu(old: &old->list, new: &new->list);
455 call_rcu(head: &old->rhead, func: avc_node_free);
456 atomic_dec(v: &selinux_avc.avc_cache.active_nodes);
457}
458
459static inline int avc_reclaim_node(void)
460{
461 struct avc_node *node;
462 int hvalue, try, ecx;
463 unsigned long flags;
464 struct hlist_head *head;
465 spinlock_t *lock;
466
467 for (try = 0, ecx = 0; try < AVC_CACHE_SLOTS; try++) {
468 hvalue = atomic_inc_return(v: &selinux_avc.avc_cache.lru_hint) &
469 (AVC_CACHE_SLOTS - 1);
470 head = &selinux_avc.avc_cache.slots[hvalue];
471 lock = &selinux_avc.avc_cache.slots_lock[hvalue];
472
473 if (!spin_trylock_irqsave(lock, flags))
474 continue;
475
476 rcu_read_lock();
477 hlist_for_each_entry(node, head, list) {
478 avc_node_delete(node);
479 avc_cache_stats_incr(reclaims);
480 ecx++;
481 if (ecx >= AVC_CACHE_RECLAIM) {
482 rcu_read_unlock();
483 spin_unlock_irqrestore(lock, flags);
484 goto out;
485 }
486 }
487 rcu_read_unlock();
488 spin_unlock_irqrestore(lock, flags);
489 }
490out:
491 return ecx;
492}
493
494static struct avc_node *avc_alloc_node(void)
495{
496 struct avc_node *node;
497
498 node = kmem_cache_zalloc(avc_node_cachep, GFP_NOWAIT);
499 if (!node)
500 goto out;
501
502 INIT_HLIST_NODE(h: &node->list);
503 avc_cache_stats_incr(allocations);
504
505 if (atomic_inc_return(v: &selinux_avc.avc_cache.active_nodes) >
506 selinux_avc.avc_cache_threshold)
507 avc_reclaim_node();
508
509out:
510 return node;
511}
512
513static void avc_node_populate(struct avc_node *node, u32 ssid, u32 tsid, u16 tclass, struct av_decision *avd)
514{
515 node->ae.ssid = ssid;
516 node->ae.tsid = tsid;
517 node->ae.tclass = tclass;
518 memcpy(&node->ae.avd, avd, sizeof(node->ae.avd));
519}
520
521static inline struct avc_node *avc_search_node(u32 ssid, u32 tsid, u16 tclass)
522{
523 struct avc_node *node, *ret = NULL;
524 u32 hvalue;
525 struct hlist_head *head;
526
527 hvalue = avc_hash(ssid, tsid, tclass);
528 head = &selinux_avc.avc_cache.slots[hvalue];
529 hlist_for_each_entry_rcu(node, head, list) {
530 if (ssid == node->ae.ssid &&
531 tclass == node->ae.tclass &&
532 tsid == node->ae.tsid) {
533 ret = node;
534 break;
535 }
536 }
537
538 return ret;
539}
540
541/**
542 * avc_lookup - Look up an AVC entry.
543 * @ssid: source security identifier
544 * @tsid: target security identifier
545 * @tclass: target security class
546 *
547 * Look up an AVC entry that is valid for the
548 * (@ssid, @tsid), interpreting the permissions
549 * based on @tclass. If a valid AVC entry exists,
550 * then this function returns the avc_node.
551 * Otherwise, this function returns NULL.
552 */
553static struct avc_node *avc_lookup(u32 ssid, u32 tsid, u16 tclass)
554{
555 struct avc_node *node;
556
557 avc_cache_stats_incr(lookups);
558 node = avc_search_node(ssid, tsid, tclass);
559
560 if (node)
561 return node;
562
563 avc_cache_stats_incr(misses);
564 return NULL;
565}
566
567static int avc_latest_notif_update(u32 seqno, int is_insert)
568{
569 int ret = 0;
570 static DEFINE_SPINLOCK(notif_lock);
571 unsigned long flag;
572
573 spin_lock_irqsave(&notif_lock, flag);
574 if (is_insert) {
575 if (seqno < selinux_avc.avc_cache.latest_notif) {
576 pr_warn("SELinux: avc: seqno %d < latest_notif %d\n",
577 seqno, selinux_avc.avc_cache.latest_notif);
578 ret = -EAGAIN;
579 }
580 } else {
581 if (seqno > selinux_avc.avc_cache.latest_notif)
582 selinux_avc.avc_cache.latest_notif = seqno;
583 }
584 spin_unlock_irqrestore(lock: &notif_lock, flags: flag);
585
586 return ret;
587}
588
589/**
590 * avc_insert - Insert an AVC entry.
591 * @ssid: source security identifier
592 * @tsid: target security identifier
593 * @tclass: target security class
594 * @avd: resulting av decision
595 * @xp_node: resulting extended permissions
596 *
597 * Insert an AVC entry for the SID pair
598 * (@ssid, @tsid) and class @tclass.
599 * The access vectors and the sequence number are
600 * normally provided by the security server in
601 * response to a security_compute_av() call. If the
602 * sequence number @avd->seqno is not less than the latest
603 * revocation notification, then the function copies
604 * the access vectors into a cache entry.
605 */
606static void avc_insert(u32 ssid, u32 tsid, u16 tclass,
607 struct av_decision *avd, struct avc_xperms_node *xp_node)
608{
609 struct avc_node *pos, *node = NULL;
610 u32 hvalue;
611 unsigned long flag;
612 spinlock_t *lock;
613 struct hlist_head *head;
614
615 if (avc_latest_notif_update(seqno: avd->seqno, is_insert: 1))
616 return;
617
618 node = avc_alloc_node();
619 if (!node)
620 return;
621
622 avc_node_populate(node, ssid, tsid, tclass, avd);
623 if (avc_xperms_populate(node, src: xp_node)) {
624 avc_node_kill(node);
625 return;
626 }
627
628 hvalue = avc_hash(ssid, tsid, tclass);
629 head = &selinux_avc.avc_cache.slots[hvalue];
630 lock = &selinux_avc.avc_cache.slots_lock[hvalue];
631 spin_lock_irqsave(lock, flag);
632 hlist_for_each_entry(pos, head, list) {
633 if (pos->ae.ssid == ssid &&
634 pos->ae.tsid == tsid &&
635 pos->ae.tclass == tclass) {
636 avc_node_replace(new: node, old: pos);
637 goto found;
638 }
639 }
640 hlist_add_head_rcu(n: &node->list, h: head);
641found:
642 spin_unlock_irqrestore(lock, flags: flag);
643}
644
645/**
646 * avc_audit_pre_callback - SELinux specific information
647 * will be called by generic audit code
648 * @ab: the audit buffer
649 * @a: audit_data
650 */
651static void avc_audit_pre_callback(struct audit_buffer *ab, void *a)
652{
653 struct common_audit_data *ad = a;
654 struct selinux_audit_data *sad = ad->selinux_audit_data;
655 u32 av = sad->audited, perm;
656 const char *const *perms;
657 u32 i;
658
659 audit_log_format(ab, fmt: "avc: %s ", sad->denied ? "denied" : "granted");
660
661 if (av == 0) {
662 audit_log_format(ab, fmt: " null");
663 return;
664 }
665
666 perms = secclass_map[sad->tclass-1].perms;
667
668 audit_log_format(ab, fmt: " {");
669 i = 0;
670 perm = 1;
671 while (i < (sizeof(av) * 8)) {
672 if ((perm & av) && perms[i]) {
673 audit_log_format(ab, fmt: " %s", perms[i]);
674 av &= ~perm;
675 }
676 i++;
677 perm <<= 1;
678 }
679
680 if (av)
681 audit_log_format(ab, fmt: " 0x%x", av);
682
683 audit_log_format(ab, fmt: " } for ");
684}
685
686/**
687 * avc_audit_post_callback - SELinux specific information
688 * will be called by generic audit code
689 * @ab: the audit buffer
690 * @a: audit_data
691 */
692static void avc_audit_post_callback(struct audit_buffer *ab, void *a)
693{
694 struct common_audit_data *ad = a;
695 struct selinux_audit_data *sad = ad->selinux_audit_data;
696 char *scontext = NULL;
697 char *tcontext = NULL;
698 const char *tclass = NULL;
699 u32 scontext_len;
700 u32 tcontext_len;
701 int rc;
702
703 rc = security_sid_to_context(sid: sad->ssid, scontext: &scontext,
704 scontext_len: &scontext_len);
705 if (rc)
706 audit_log_format(ab, fmt: " ssid=%d", sad->ssid);
707 else
708 audit_log_format(ab, fmt: " scontext=%s", scontext);
709
710 rc = security_sid_to_context(sid: sad->tsid, scontext: &tcontext,
711 scontext_len: &tcontext_len);
712 if (rc)
713 audit_log_format(ab, fmt: " tsid=%d", sad->tsid);
714 else
715 audit_log_format(ab, fmt: " tcontext=%s", tcontext);
716
717 tclass = secclass_map[sad->tclass-1].name;
718 audit_log_format(ab, fmt: " tclass=%s", tclass);
719
720 if (sad->denied)
721 audit_log_format(ab, fmt: " permissive=%u", sad->result ? 0 : 1);
722
723 trace_selinux_audited(sad, scontext, tcontext, tclass);
724 kfree(objp: tcontext);
725 kfree(objp: scontext);
726
727 /* in case of invalid context report also the actual context string */
728 rc = security_sid_to_context_inval(sid: sad->ssid, scontext: &scontext,
729 scontext_len: &scontext_len);
730 if (!rc && scontext) {
731 if (scontext_len && scontext[scontext_len - 1] == '\0')
732 scontext_len--;
733 audit_log_format(ab, fmt: " srawcon=");
734 audit_log_n_untrustedstring(ab, string: scontext, n: scontext_len);
735 kfree(objp: scontext);
736 }
737
738 rc = security_sid_to_context_inval(sid: sad->tsid, scontext: &scontext,
739 scontext_len: &scontext_len);
740 if (!rc && scontext) {
741 if (scontext_len && scontext[scontext_len - 1] == '\0')
742 scontext_len--;
743 audit_log_format(ab, fmt: " trawcon=");
744 audit_log_n_untrustedstring(ab, string: scontext, n: scontext_len);
745 kfree(objp: scontext);
746 }
747}
748
749/*
750 * This is the slow part of avc audit with big stack footprint.
751 * Note that it is non-blocking and can be called from under
752 * rcu_read_lock().
753 */
754noinline int slow_avc_audit(u32 ssid, u32 tsid, u16 tclass,
755 u32 requested, u32 audited, u32 denied, int result,
756 struct common_audit_data *a)
757{
758 struct common_audit_data stack_data;
759 struct selinux_audit_data sad;
760
761 if (WARN_ON(!tclass || tclass >= ARRAY_SIZE(secclass_map)))
762 return -EINVAL;
763
764 if (!a) {
765 a = &stack_data;
766 a->type = LSM_AUDIT_DATA_NONE;
767 }
768
769 sad.tclass = tclass;
770 sad.requested = requested;
771 sad.ssid = ssid;
772 sad.tsid = tsid;
773 sad.audited = audited;
774 sad.denied = denied;
775 sad.result = result;
776
777 a->selinux_audit_data = &sad;
778
779 common_lsm_audit(a, pre_audit: avc_audit_pre_callback, post_audit: avc_audit_post_callback);
780 return 0;
781}
782
783/**
784 * avc_add_callback - Register a callback for security events.
785 * @callback: callback function
786 * @events: security events
787 *
788 * Register a callback function for events in the set @events.
789 * Returns %0 on success or -%ENOMEM if insufficient memory
790 * exists to add the callback.
791 */
792int __init avc_add_callback(int (*callback)(u32 event), u32 events)
793{
794 struct avc_callback_node *c;
795 int rc = 0;
796
797 c = kmalloc(sizeof(*c), GFP_KERNEL);
798 if (!c) {
799 rc = -ENOMEM;
800 goto out;
801 }
802
803 c->callback = callback;
804 c->events = events;
805 c->next = avc_callbacks;
806 avc_callbacks = c;
807out:
808 return rc;
809}
810
811/**
812 * avc_update_node - Update an AVC entry
813 * @event : Updating event
814 * @perms : Permission mask bits
815 * @driver: xperm driver information
816 * @base_perm: the base permission associated with the extended permission
817 * @xperm: xperm permissions
818 * @ssid: AVC entry source sid
819 * @tsid: AVC entry target sid
820 * @tclass : AVC entry target object class
821 * @seqno : sequence number when decision was made
822 * @xpd: extended_perms_decision to be added to the node
823 * @flags: the AVC_* flags, e.g. AVC_EXTENDED_PERMS, or 0.
824 *
825 * if a valid AVC entry doesn't exist,this function returns -ENOENT.
826 * if kmalloc() called internal returns NULL, this function returns -ENOMEM.
827 * otherwise, this function updates the AVC entry. The original AVC-entry object
828 * will release later by RCU.
829 */
830static int avc_update_node(u32 event, u32 perms, u8 driver, u8 base_perm,
831 u8 xperm, u32 ssid, u32 tsid, u16 tclass, u32 seqno,
832 struct extended_perms_decision *xpd, u32 flags)
833{
834 u32 hvalue;
835 int rc = 0;
836 unsigned long flag;
837 struct avc_node *pos, *node, *orig = NULL;
838 struct hlist_head *head;
839 spinlock_t *lock;
840
841 node = avc_alloc_node();
842 if (!node) {
843 rc = -ENOMEM;
844 goto out;
845 }
846
847 /* Lock the target slot */
848 hvalue = avc_hash(ssid, tsid, tclass);
849
850 head = &selinux_avc.avc_cache.slots[hvalue];
851 lock = &selinux_avc.avc_cache.slots_lock[hvalue];
852
853 spin_lock_irqsave(lock, flag);
854
855 hlist_for_each_entry(pos, head, list) {
856 if (ssid == pos->ae.ssid &&
857 tsid == pos->ae.tsid &&
858 tclass == pos->ae.tclass &&
859 seqno == pos->ae.avd.seqno){
860 orig = pos;
861 break;
862 }
863 }
864
865 if (!orig) {
866 rc = -ENOENT;
867 avc_node_kill(node);
868 goto out_unlock;
869 }
870
871 /*
872 * Copy and replace original node.
873 */
874
875 avc_node_populate(node, ssid, tsid, tclass, avd: &orig->ae.avd);
876
877 if (orig->ae.xp_node) {
878 rc = avc_xperms_populate(node, src: orig->ae.xp_node);
879 if (rc) {
880 avc_node_kill(node);
881 goto out_unlock;
882 }
883 }
884
885 switch (event) {
886 case AVC_CALLBACK_GRANT:
887 node->ae.avd.allowed |= perms;
888 if (node->ae.xp_node && (flags & AVC_EXTENDED_PERMS))
889 avc_xperms_allow_perm(xp_node: node->ae.xp_node, driver, base_perm, perm: xperm);
890 break;
891 case AVC_CALLBACK_TRY_REVOKE:
892 case AVC_CALLBACK_REVOKE:
893 node->ae.avd.allowed &= ~perms;
894 break;
895 case AVC_CALLBACK_AUDITALLOW_ENABLE:
896 node->ae.avd.auditallow |= perms;
897 break;
898 case AVC_CALLBACK_AUDITALLOW_DISABLE:
899 node->ae.avd.auditallow &= ~perms;
900 break;
901 case AVC_CALLBACK_AUDITDENY_ENABLE:
902 node->ae.avd.auditdeny |= perms;
903 break;
904 case AVC_CALLBACK_AUDITDENY_DISABLE:
905 node->ae.avd.auditdeny &= ~perms;
906 break;
907 case AVC_CALLBACK_ADD_XPERMS:
908 rc = avc_add_xperms_decision(node, src: xpd);
909 if (rc) {
910 avc_node_kill(node);
911 goto out_unlock;
912 }
913 break;
914 }
915 avc_node_replace(new: node, old: orig);
916out_unlock:
917 spin_unlock_irqrestore(lock, flags: flag);
918out:
919 return rc;
920}
921
922/**
923 * avc_flush - Flush the cache
924 */
925static void avc_flush(void)
926{
927 struct hlist_head *head;
928 struct avc_node *node;
929 spinlock_t *lock;
930 unsigned long flag;
931 int i;
932
933 for (i = 0; i < AVC_CACHE_SLOTS; i++) {
934 head = &selinux_avc.avc_cache.slots[i];
935 lock = &selinux_avc.avc_cache.slots_lock[i];
936
937 spin_lock_irqsave(lock, flag);
938 /*
939 * With preemptible RCU, the outer spinlock does not
940 * prevent RCU grace periods from ending.
941 */
942 rcu_read_lock();
943 hlist_for_each_entry(node, head, list)
944 avc_node_delete(node);
945 rcu_read_unlock();
946 spin_unlock_irqrestore(lock, flags: flag);
947 }
948}
949
950/**
951 * avc_ss_reset - Flush the cache and revalidate migrated permissions.
952 * @seqno: policy sequence number
953 */
954int avc_ss_reset(u32 seqno)
955{
956 struct avc_callback_node *c;
957 int rc = 0, tmprc;
958
959 avc_flush();
960
961 for (c = avc_callbacks; c; c = c->next) {
962 if (c->events & AVC_CALLBACK_RESET) {
963 tmprc = c->callback(AVC_CALLBACK_RESET);
964 /* save the first error encountered for the return
965 value and continue processing the callbacks */
966 if (!rc)
967 rc = tmprc;
968 }
969 }
970
971 avc_latest_notif_update(seqno, is_insert: 0);
972 return rc;
973}
974
975/**
976 * avc_compute_av - Add an entry to the AVC based on the security policy
977 * @ssid: subject
978 * @tsid: object/target
979 * @tclass: object class
980 * @avd: access vector decision
981 * @xp_node: AVC extended permissions node
982 *
983 * Slow-path helper function for avc_has_perm_noaudit, when the avc_node lookup
984 * fails. Don't inline this, since it's the slow-path and just results in a
985 * bigger stack frame.
986 */
987static noinline void avc_compute_av(u32 ssid, u32 tsid, u16 tclass,
988 struct av_decision *avd,
989 struct avc_xperms_node *xp_node)
990{
991 INIT_LIST_HEAD(list: &xp_node->xpd_head);
992 security_compute_av(ssid, tsid, tclass, avd, xperms: &xp_node->xp);
993 avc_insert(ssid, tsid, tclass, avd, xp_node);
994}
995
996static noinline int avc_denied(u32 ssid, u32 tsid, u16 tclass, u32 requested,
997 u8 driver, u8 base_perm, u8 xperm,
998 unsigned int flags, struct av_decision *avd)
999{
1000 if (flags & AVC_STRICT)
1001 return -EACCES;
1002
1003 if (enforcing_enabled() &&
1004 !(avd->flags & AVD_FLAGS_PERMISSIVE))
1005 return -EACCES;
1006
1007 avc_update_node(AVC_CALLBACK_GRANT, perms: requested, driver, base_perm,
1008 xperm, ssid, tsid, tclass, seqno: avd->seqno, NULL, flags);
1009 return 0;
1010}
1011
1012/*
1013 * The avc extended permissions logic adds an additional 256 bits of
1014 * permissions to an avc node when extended permissions for that node are
1015 * specified in the avtab. If the additional 256 permissions is not adequate,
1016 * as-is the case with ioctls, then multiple may be chained together and the
1017 * driver field is used to specify which set contains the permission.
1018 */
1019int avc_has_extended_perms(u32 ssid, u32 tsid, u16 tclass, u32 requested,
1020 u8 driver, u8 base_perm, u8 xperm,
1021 struct common_audit_data *ad)
1022{
1023 struct avc_node *node;
1024 struct av_decision avd;
1025 u32 denied;
1026 struct extended_perms_decision local_xpd;
1027 struct extended_perms_decision *xpd = NULL;
1028 struct extended_perms_data allowed;
1029 struct extended_perms_data auditallow;
1030 struct extended_perms_data dontaudit;
1031 struct avc_xperms_node local_xp_node;
1032 struct avc_xperms_node *xp_node;
1033 int rc = 0, rc2;
1034
1035 xp_node = &local_xp_node;
1036 if (WARN_ON(!requested))
1037 return -EACCES;
1038
1039 rcu_read_lock();
1040
1041 node = avc_lookup(ssid, tsid, tclass);
1042 if (unlikely(!node)) {
1043 avc_compute_av(ssid, tsid, tclass, avd: &avd, xp_node);
1044 } else {
1045 memcpy(&avd, &node->ae.avd, sizeof(avd));
1046 xp_node = node->ae.xp_node;
1047 }
1048 /* if extended permissions are not defined, only consider av_decision */
1049 if (!xp_node || !xp_node->xp.len)
1050 goto decision;
1051
1052 local_xpd.allowed = &allowed;
1053 local_xpd.auditallow = &auditallow;
1054 local_xpd.dontaudit = &dontaudit;
1055
1056 xpd = avc_xperms_decision_lookup(driver, base_perm, xp_node);
1057 if (unlikely(!xpd)) {
1058 /*
1059 * Compute the extended_perms_decision only if the driver
1060 * is flagged and the base permission is known.
1061 */
1062 if (!security_xperm_test(xp_node->xp.drivers.p, driver) ||
1063 !(xp_node->xp.base_perms & base_perm)) {
1064 avd.allowed &= ~requested;
1065 goto decision;
1066 }
1067 rcu_read_unlock();
1068 security_compute_xperms_decision(ssid, tsid, tclass, driver,
1069 base_perm, xpermd: &local_xpd);
1070 rcu_read_lock();
1071 avc_update_node(AVC_CALLBACK_ADD_XPERMS, perms: requested, driver,
1072 base_perm, xperm, ssid, tsid, tclass, seqno: avd.seqno,
1073 xpd: &local_xpd, flags: 0);
1074 } else {
1075 avc_quick_copy_xperms_decision(perm: xperm, dest: &local_xpd, src: xpd);
1076 }
1077 xpd = &local_xpd;
1078
1079 if (!avc_xperms_has_perm(xpd, perm: xperm, XPERMS_ALLOWED))
1080 avd.allowed &= ~requested;
1081
1082decision:
1083 denied = requested & ~(avd.allowed);
1084 if (unlikely(denied))
1085 rc = avc_denied(ssid, tsid, tclass, requested, driver,
1086 base_perm, xperm, AVC_EXTENDED_PERMS, avd: &avd);
1087
1088 rcu_read_unlock();
1089
1090 rc2 = avc_xperms_audit(ssid, tsid, tclass, requested,
1091 avd: &avd, xpd, perm: xperm, result: rc, ad);
1092 if (rc2)
1093 return rc2;
1094 return rc;
1095}
1096
1097/**
1098 * avc_perm_nonode - Add an entry to the AVC
1099 * @ssid: subject
1100 * @tsid: object/target
1101 * @tclass: object class
1102 * @requested: requested permissions
1103 * @flags: AVC flags
1104 * @avd: access vector decision
1105 *
1106 * This is the "we have no node" part of avc_has_perm_noaudit(), which is
1107 * unlikely and needs extra stack space for the new node that we generate, so
1108 * don't inline it.
1109 */
1110static noinline int avc_perm_nonode(u32 ssid, u32 tsid, u16 tclass,
1111 u32 requested, unsigned int flags,
1112 struct av_decision *avd)
1113{
1114 u32 denied;
1115 struct avc_xperms_node xp_node;
1116
1117 avc_compute_av(ssid, tsid, tclass, avd, xp_node: &xp_node);
1118 denied = requested & ~(avd->allowed);
1119 if (unlikely(denied))
1120 return avc_denied(ssid, tsid, tclass, requested, driver: 0, base_perm: 0, xperm: 0,
1121 flags, avd);
1122 return 0;
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 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 */
1145inline int avc_has_perm_noaudit(u32 ssid, u32 tsid,
1146 u16 tclass, u32 requested,
1147 unsigned int flags,
1148 struct av_decision *avd)
1149{
1150 u32 denied;
1151 struct avc_node *node;
1152
1153 if (WARN_ON(!requested))
1154 return -EACCES;
1155
1156 rcu_read_lock();
1157 node = avc_lookup(ssid, tsid, tclass);
1158 if (unlikely(!node)) {
1159 rcu_read_unlock();
1160 return avc_perm_nonode(ssid, tsid, tclass, requested,
1161 flags, avd);
1162 }
1163 denied = requested & ~node->ae.avd.allowed;
1164 memcpy(avd, &node->ae.avd, sizeof(*avd));
1165 rcu_read_unlock();
1166
1167 if (unlikely(denied))
1168 return avc_denied(ssid, tsid, tclass, requested, driver: 0, base_perm: 0, xperm: 0,
1169 flags, avd);
1170 return 0;
1171}
1172
1173/**
1174 * avc_has_perm - Check permissions and perform any appropriate auditing.
1175 * @ssid: source security identifier
1176 * @tsid: target security identifier
1177 * @tclass: target security class
1178 * @requested: requested permissions, interpreted based on @tclass
1179 * @auditdata: auxiliary audit data
1180 *
1181 * Check the AVC to determine whether the @requested permissions are granted
1182 * for the SID pair (@ssid, @tsid), interpreting the permissions
1183 * based on @tclass, and call the security server on a cache miss to obtain
1184 * a new decision and add it to the cache. Audit the granting or denial of
1185 * permissions in accordance with the policy. Return %0 if all @requested
1186 * permissions are granted, -%EACCES if any permissions are denied, or
1187 * another -errno upon other errors.
1188 */
1189int avc_has_perm(u32 ssid, u32 tsid, u16 tclass,
1190 u32 requested, struct common_audit_data *auditdata)
1191{
1192 struct av_decision avd;
1193 int rc, rc2;
1194
1195 rc = avc_has_perm_noaudit(ssid, tsid, tclass, requested, flags: 0,
1196 avd: &avd);
1197
1198 rc2 = avc_audit(ssid, tsid, tclass, requested, avd: &avd, result: rc,
1199 a: auditdata);
1200 if (rc2)
1201 return rc2;
1202 return rc;
1203}
1204
1205u32 avc_policy_seqno(void)
1206{
1207 return selinux_avc.avc_cache.latest_notif;
1208}
1209

source code of linux/security/selinux/avc.c