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Linux/security/selinux/avc.c

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  1 /*
  2  * Implementation of the kernel access vector cache (AVC).
  3  *
  4  * Authors:  Stephen Smalley, <sds@epoch.ncsc.mil>
  5  *           James Morris <jmorris@redhat.com>
  6  *
  7  * Update:   KaiGai, Kohei <kaigai@ak.jp.nec.com>
  8  *      Replaced the avc_lock spinlock by RCU.
  9  *
 10  * Copyright (C) 2003 Red Hat, Inc., James Morris <jmorris@redhat.com>
 11  *
 12  *      This program is free software; you can redistribute it and/or modify
 13  *      it under the terms of the GNU General Public License version 2,
 14  *      as published by the Free Software Foundation.
 15  */
 16 #include <linux/types.h>
 17 #include <linux/stddef.h>
 18 #include <linux/kernel.h>
 19 #include <linux/slab.h>
 20 #include <linux/fs.h>
 21 #include <linux/dcache.h>
 22 #include <linux/init.h>
 23 #include <linux/skbuff.h>
 24 #include <linux/percpu.h>
 25 #include <linux/list.h>
 26 #include <net/sock.h>
 27 #include <linux/un.h>
 28 #include <net/af_unix.h>
 29 #include <linux/ip.h>
 30 #include <linux/audit.h>
 31 #include <linux/ipv6.h>
 32 #include <net/ipv6.h>
 33 #include "avc.h"
 34 #include "avc_ss.h"
 35 #include "classmap.h"
 36 
 37 #define AVC_CACHE_SLOTS                 512
 38 #define AVC_DEF_CACHE_THRESHOLD         512
 39 #define AVC_CACHE_RECLAIM               16
 40 
 41 #ifdef CONFIG_SECURITY_SELINUX_AVC_STATS
 42 #define avc_cache_stats_incr(field)     this_cpu_inc(avc_cache_stats.field)
 43 #else
 44 #define avc_cache_stats_incr(field)     do {} while (0)
 45 #endif
 46 
 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 /* Exported via selinufs */
 86 unsigned int avc_cache_threshold = AVC_DEF_CACHE_THRESHOLD;
 87 
 88 #ifdef CONFIG_SECURITY_SELINUX_AVC_STATS
 89 DEFINE_PER_CPU(struct avc_cache_stats, avc_cache_stats) = { 0 };
 90 #endif
 91 
 92 static struct avc_cache avc_cache;
 93 static struct avc_callback_node *avc_callbacks;
 94 static struct kmem_cache *avc_node_cachep;
 95 static struct kmem_cache *avc_xperms_data_cachep;
 96 static struct kmem_cache *avc_xperms_decision_cachep;
 97 static struct kmem_cache *avc_xperms_cachep;
 98 
 99 static inline int avc_hash(u32 ssid, u32 tsid, u16 tclass)
100 {
101         return (ssid ^ (tsid<<2) ^ (tclass<<4)) & (AVC_CACHE_SLOTS - 1);
102 }
103 
104 /**
105  * avc_dump_av - Display an access vector in human-readable form.
106  * @tclass: target security class
107  * @av: access vector
108  */
109 static void avc_dump_av(struct audit_buffer *ab, u16 tclass, u32 av)
110 {
111         const char **perms;
112         int i, perm;
113 
114         if (av == 0) {
115                 audit_log_format(ab, " null");
116                 return;
117         }
118 
119         BUG_ON(!tclass || tclass >= ARRAY_SIZE(secclass_map));
120         perms = secclass_map[tclass-1].perms;
121 
122         audit_log_format(ab, " {");
123         i = 0;
124         perm = 1;
125         while (i < (sizeof(av) * 8)) {
126                 if ((perm & av) && perms[i]) {
127                         audit_log_format(ab, " %s", perms[i]);
128                         av &= ~perm;
129                 }
130                 i++;
131                 perm <<= 1;
132         }
133 
134         if (av)
135                 audit_log_format(ab, " 0x%x", av);
136 
137         audit_log_format(ab, " }");
138 }
139 
140 /**
141  * avc_dump_query - Display a SID pair and a class in human-readable form.
142  * @ssid: source security identifier
143  * @tsid: target security identifier
144  * @tclass: target security class
145  */
146 static void avc_dump_query(struct audit_buffer *ab, u32 ssid, u32 tsid, u16 tclass)
147 {
148         int rc;
149         char *scontext;
150         u32 scontext_len;
151 
152         rc = security_sid_to_context(ssid, &scontext, &scontext_len);
153         if (rc)
154                 audit_log_format(ab, "ssid=%d", ssid);
155         else {
156                 audit_log_format(ab, "scontext=%s", scontext);
157                 kfree(scontext);
158         }
159 
160         rc = security_sid_to_context(tsid, &scontext, &scontext_len);
161         if (rc)
162                 audit_log_format(ab, " tsid=%d", tsid);
163         else {
164                 audit_log_format(ab, " tcontext=%s", scontext);
165                 kfree(scontext);
166         }
167 
168         BUG_ON(!tclass || tclass >= ARRAY_SIZE(secclass_map));
169         audit_log_format(ab, " tclass=%s", secclass_map[tclass-1].name);
170 }
171 
172 /**
173  * avc_init - Initialize the AVC.
174  *
175  * Initialize the access vector cache.
176  */
177 void __init avc_init(void)
178 {
179         int i;
180 
181         for (i = 0; i < AVC_CACHE_SLOTS; i++) {
182                 INIT_HLIST_HEAD(&avc_cache.slots[i]);
183                 spin_lock_init(&avc_cache.slots_lock[i]);
184         }
185         atomic_set(&avc_cache.active_nodes, 0);
186         atomic_set(&avc_cache.lru_hint, 0);
187 
188         avc_node_cachep = kmem_cache_create("avc_node", sizeof(struct avc_node),
189                                         0, SLAB_PANIC, NULL);
190         avc_xperms_cachep = kmem_cache_create("avc_xperms_node",
191                                         sizeof(struct avc_xperms_node),
192                                         0, SLAB_PANIC, NULL);
193         avc_xperms_decision_cachep = kmem_cache_create(
194                                         "avc_xperms_decision_node",
195                                         sizeof(struct avc_xperms_decision_node),
196                                         0, SLAB_PANIC, NULL);
197         avc_xperms_data_cachep = kmem_cache_create("avc_xperms_data",
198                                         sizeof(struct extended_perms_data),
199                                         0, SLAB_PANIC, NULL);
200 
201         audit_log(current->audit_context, GFP_KERNEL, AUDIT_KERNEL, "AVC INITIALIZED\n");
202 }
203 
204 int avc_get_hash_stats(char *page)
205 {
206         int i, chain_len, max_chain_len, slots_used;
207         struct avc_node *node;
208         struct hlist_head *head;
209 
210         rcu_read_lock();
211 
212         slots_used = 0;
213         max_chain_len = 0;
214         for (i = 0; i < AVC_CACHE_SLOTS; i++) {
215                 head = &avc_cache.slots[i];
216                 if (!hlist_empty(head)) {
217                         slots_used++;
218                         chain_len = 0;
219                         hlist_for_each_entry_rcu(node, head, list)
220                                 chain_len++;
221                         if (chain_len > max_chain_len)
222                                 max_chain_len = chain_len;
223                 }
224         }
225 
226         rcu_read_unlock();
227 
228         return scnprintf(page, PAGE_SIZE, "entries: %d\nbuckets used: %d/%d\n"
229                          "longest chain: %d\n",
230                          atomic_read(&avc_cache.active_nodes),
231                          slots_used, AVC_CACHE_SLOTS, max_chain_len);
232 }
233 
234 /*
235  * using a linked list for extended_perms_decision lookup because the list is
236  * always small. i.e. less than 5, typically 1
237  */
238 static struct extended_perms_decision *avc_xperms_decision_lookup(u8 driver,
239                                         struct avc_xperms_node *xp_node)
240 {
241         struct avc_xperms_decision_node *xpd_node;
242 
243         list_for_each_entry(xpd_node, &xp_node->xpd_head, xpd_list) {
244                 if (xpd_node->xpd.driver == driver)
245                         return &xpd_node->xpd;
246         }
247         return NULL;
248 }
249 
250 static inline unsigned int
251 avc_xperms_has_perm(struct extended_perms_decision *xpd,
252                                         u8 perm, u8 which)
253 {
254         unsigned int rc = 0;
255 
256         if ((which == XPERMS_ALLOWED) &&
257                         (xpd->used & XPERMS_ALLOWED))
258                 rc = security_xperm_test(xpd->allowed->p, perm);
259         else if ((which == XPERMS_AUDITALLOW) &&
260                         (xpd->used & XPERMS_AUDITALLOW))
261                 rc = security_xperm_test(xpd->auditallow->p, perm);
262         else if ((which == XPERMS_DONTAUDIT) &&
263                         (xpd->used & XPERMS_DONTAUDIT))
264                 rc = security_xperm_test(xpd->dontaudit->p, perm);
265         return rc;
266 }
267 
268 static void avc_xperms_allow_perm(struct avc_xperms_node *xp_node,
269                                 u8 driver, u8 perm)
270 {
271         struct extended_perms_decision *xpd;
272         security_xperm_set(xp_node->xp.drivers.p, driver);
273         xpd = avc_xperms_decision_lookup(driver, xp_node);
274         if (xpd && xpd->allowed)
275                 security_xperm_set(xpd->allowed->p, perm);
276 }
277 
278 static void avc_xperms_decision_free(struct avc_xperms_decision_node *xpd_node)
279 {
280         struct extended_perms_decision *xpd;
281 
282         xpd = &xpd_node->xpd;
283         if (xpd->allowed)
284                 kmem_cache_free(avc_xperms_data_cachep, xpd->allowed);
285         if (xpd->auditallow)
286                 kmem_cache_free(avc_xperms_data_cachep, xpd->auditallow);
287         if (xpd->dontaudit)
288                 kmem_cache_free(avc_xperms_data_cachep, xpd->dontaudit);
289         kmem_cache_free(avc_xperms_decision_cachep, xpd_node);
290 }
291 
292 static void avc_xperms_free(struct avc_xperms_node *xp_node)
293 {
294         struct avc_xperms_decision_node *xpd_node, *tmp;
295 
296         if (!xp_node)
297                 return;
298 
299         list_for_each_entry_safe(xpd_node, tmp, &xp_node->xpd_head, xpd_list) {
300                 list_del(&xpd_node->xpd_list);
301                 avc_xperms_decision_free(xpd_node);
302         }
303         kmem_cache_free(avc_xperms_cachep, xp_node);
304 }
305 
306 static void avc_copy_xperms_decision(struct extended_perms_decision *dest,
307                                         struct extended_perms_decision *src)
308 {
309         dest->driver = src->driver;
310         dest->used = src->used;
311         if (dest->used & XPERMS_ALLOWED)
312                 memcpy(dest->allowed->p, src->allowed->p,
313                                 sizeof(src->allowed->p));
314         if (dest->used & XPERMS_AUDITALLOW)
315                 memcpy(dest->auditallow->p, src->auditallow->p,
316                                 sizeof(src->auditallow->p));
317         if (dest->used & XPERMS_DONTAUDIT)
318                 memcpy(dest->dontaudit->p, src->dontaudit->p,
319                                 sizeof(src->dontaudit->p));
320 }
321 
322 /*
323  * similar to avc_copy_xperms_decision, but only copy decision
324  * information relevant to this perm
325  */
326 static inline void avc_quick_copy_xperms_decision(u8 perm,
327                         struct extended_perms_decision *dest,
328                         struct extended_perms_decision *src)
329 {
330         /*
331          * compute index of the u32 of the 256 bits (8 u32s) that contain this
332          * command permission
333          */
334         u8 i = perm >> 5;
335 
336         dest->used = src->used;
337         if (dest->used & XPERMS_ALLOWED)
338                 dest->allowed->p[i] = src->allowed->p[i];
339         if (dest->used & XPERMS_AUDITALLOW)
340                 dest->auditallow->p[i] = src->auditallow->p[i];
341         if (dest->used & XPERMS_DONTAUDIT)
342                 dest->dontaudit->p[i] = src->dontaudit->p[i];
343 }
344 
345 static struct avc_xperms_decision_node
346                 *avc_xperms_decision_alloc(u8 which)
347 {
348         struct avc_xperms_decision_node *xpd_node;
349         struct extended_perms_decision *xpd;
350 
351         xpd_node = kmem_cache_zalloc(avc_xperms_decision_cachep,
352                                 GFP_ATOMIC | __GFP_NOMEMALLOC);
353         if (!xpd_node)
354                 return NULL;
355 
356         xpd = &xpd_node->xpd;
357         if (which & XPERMS_ALLOWED) {
358                 xpd->allowed = kmem_cache_zalloc(avc_xperms_data_cachep,
359                                                 GFP_ATOMIC | __GFP_NOMEMALLOC);
360                 if (!xpd->allowed)
361                         goto error;
362         }
363         if (which & XPERMS_AUDITALLOW) {
364                 xpd->auditallow = kmem_cache_zalloc(avc_xperms_data_cachep,
365                                                 GFP_ATOMIC | __GFP_NOMEMALLOC);
366                 if (!xpd->auditallow)
367                         goto error;
368         }
369         if (which & XPERMS_DONTAUDIT) {
370                 xpd->dontaudit = kmem_cache_zalloc(avc_xperms_data_cachep,
371                                                 GFP_ATOMIC | __GFP_NOMEMALLOC);
372                 if (!xpd->dontaudit)
373                         goto error;
374         }
375         return xpd_node;
376 error:
377         avc_xperms_decision_free(xpd_node);
378         return NULL;
379 }
380 
381 static int avc_add_xperms_decision(struct avc_node *node,
382                         struct extended_perms_decision *src)
383 {
384         struct avc_xperms_decision_node *dest_xpd;
385 
386         node->ae.xp_node->xp.len++;
387         dest_xpd = avc_xperms_decision_alloc(src->used);
388         if (!dest_xpd)
389                 return -ENOMEM;
390         avc_copy_xperms_decision(&dest_xpd->xpd, src);
391         list_add(&dest_xpd->xpd_list, &node->ae.xp_node->xpd_head);
392         return 0;
393 }
394 
395 static struct avc_xperms_node *avc_xperms_alloc(void)
396 {
397         struct avc_xperms_node *xp_node;
398 
399         xp_node = kmem_cache_zalloc(avc_xperms_cachep,
400                                 GFP_ATOMIC|__GFP_NOMEMALLOC);
401         if (!xp_node)
402                 return xp_node;
403         INIT_LIST_HEAD(&xp_node->xpd_head);
404         return xp_node;
405 }
406 
407 static int avc_xperms_populate(struct avc_node *node,
408                                 struct avc_xperms_node *src)
409 {
410         struct avc_xperms_node *dest;
411         struct avc_xperms_decision_node *dest_xpd;
412         struct avc_xperms_decision_node *src_xpd;
413 
414         if (src->xp.len == 0)
415                 return 0;
416         dest = avc_xperms_alloc();
417         if (!dest)
418                 return -ENOMEM;
419 
420         memcpy(dest->xp.drivers.p, src->xp.drivers.p, sizeof(dest->xp.drivers.p));
421         dest->xp.len = src->xp.len;
422 
423         /* for each source xpd allocate a destination xpd and copy */
424         list_for_each_entry(src_xpd, &src->xpd_head, xpd_list) {
425                 dest_xpd = avc_xperms_decision_alloc(src_xpd->xpd.used);
426                 if (!dest_xpd)
427                         goto error;
428                 avc_copy_xperms_decision(&dest_xpd->xpd, &src_xpd->xpd);
429                 list_add(&dest_xpd->xpd_list, &dest->xpd_head);
430         }
431         node->ae.xp_node = dest;
432         return 0;
433 error:
434         avc_xperms_free(dest);
435         return -ENOMEM;
436 
437 }
438 
439 static inline u32 avc_xperms_audit_required(u32 requested,
440                                         struct av_decision *avd,
441                                         struct extended_perms_decision *xpd,
442                                         u8 perm,
443                                         int result,
444                                         u32 *deniedp)
445 {
446         u32 denied, audited;
447 
448         denied = requested & ~avd->allowed;
449         if (unlikely(denied)) {
450                 audited = denied & avd->auditdeny;
451                 if (audited && xpd) {
452                         if (avc_xperms_has_perm(xpd, perm, XPERMS_DONTAUDIT))
453                                 audited &= ~requested;
454                 }
455         } else if (result) {
456                 audited = denied = requested;
457         } else {
458                 audited = requested & avd->auditallow;
459                 if (audited && xpd) {
460                         if (!avc_xperms_has_perm(xpd, perm, XPERMS_AUDITALLOW))
461                                 audited &= ~requested;
462                 }
463         }
464 
465         *deniedp = denied;
466         return audited;
467 }
468 
469 static inline int avc_xperms_audit(u32 ssid, u32 tsid, u16 tclass,
470                                 u32 requested, struct av_decision *avd,
471                                 struct extended_perms_decision *xpd,
472                                 u8 perm, int result,
473                                 struct common_audit_data *ad)
474 {
475         u32 audited, denied;
476 
477         audited = avc_xperms_audit_required(
478                         requested, avd, xpd, perm, result, &denied);
479         if (likely(!audited))
480                 return 0;
481         return slow_avc_audit(ssid, tsid, tclass, requested,
482                         audited, denied, result, ad, 0);
483 }
484 
485 static void avc_node_free(struct rcu_head *rhead)
486 {
487         struct avc_node *node = container_of(rhead, struct avc_node, rhead);
488         avc_xperms_free(node->ae.xp_node);
489         kmem_cache_free(avc_node_cachep, node);
490         avc_cache_stats_incr(frees);
491 }
492 
493 static void avc_node_delete(struct avc_node *node)
494 {
495         hlist_del_rcu(&node->list);
496         call_rcu(&node->rhead, avc_node_free);
497         atomic_dec(&avc_cache.active_nodes);
498 }
499 
500 static void avc_node_kill(struct avc_node *node)
501 {
502         avc_xperms_free(node->ae.xp_node);
503         kmem_cache_free(avc_node_cachep, node);
504         avc_cache_stats_incr(frees);
505         atomic_dec(&avc_cache.active_nodes);
506 }
507 
508 static void avc_node_replace(struct avc_node *new, struct avc_node *old)
509 {
510         hlist_replace_rcu(&old->list, &new->list);
511         call_rcu(&old->rhead, avc_node_free);
512         atomic_dec(&avc_cache.active_nodes);
513 }
514 
515 static inline int avc_reclaim_node(void)
516 {
517         struct avc_node *node;
518         int hvalue, try, ecx;
519         unsigned long flags;
520         struct hlist_head *head;
521         spinlock_t *lock;
522 
523         for (try = 0, ecx = 0; try < AVC_CACHE_SLOTS; try++) {
524                 hvalue = atomic_inc_return(&avc_cache.lru_hint) & (AVC_CACHE_SLOTS - 1);
525                 head = &avc_cache.slots[hvalue];
526                 lock = &avc_cache.slots_lock[hvalue];
527 
528                 if (!spin_trylock_irqsave(lock, flags))
529                         continue;
530 
531                 rcu_read_lock();
532                 hlist_for_each_entry(node, head, list) {
533                         avc_node_delete(node);
534                         avc_cache_stats_incr(reclaims);
535                         ecx++;
536                         if (ecx >= AVC_CACHE_RECLAIM) {
537                                 rcu_read_unlock();
538                                 spin_unlock_irqrestore(lock, flags);
539                                 goto out;
540                         }
541                 }
542                 rcu_read_unlock();
543                 spin_unlock_irqrestore(lock, flags);
544         }
545 out:
546         return ecx;
547 }
548 
549 static struct avc_node *avc_alloc_node(void)
550 {
551         struct avc_node *node;
552 
553         node = kmem_cache_zalloc(avc_node_cachep, GFP_ATOMIC|__GFP_NOMEMALLOC);
554         if (!node)
555                 goto out;
556 
557         INIT_HLIST_NODE(&node->list);
558         avc_cache_stats_incr(allocations);
559 
560         if (atomic_inc_return(&avc_cache.active_nodes) > avc_cache_threshold)
561                 avc_reclaim_node();
562 
563 out:
564         return node;
565 }
566 
567 static void avc_node_populate(struct avc_node *node, u32 ssid, u32 tsid, u16 tclass, struct av_decision *avd)
568 {
569         node->ae.ssid = ssid;
570         node->ae.tsid = tsid;
571         node->ae.tclass = tclass;
572         memcpy(&node->ae.avd, avd, sizeof(node->ae.avd));
573 }
574 
575 static inline struct avc_node *avc_search_node(u32 ssid, u32 tsid, u16 tclass)
576 {
577         struct avc_node *node, *ret = NULL;
578         int hvalue;
579         struct hlist_head *head;
580 
581         hvalue = avc_hash(ssid, tsid, tclass);
582         head = &avc_cache.slots[hvalue];
583         hlist_for_each_entry_rcu(node, head, list) {
584                 if (ssid == node->ae.ssid &&
585                     tclass == node->ae.tclass &&
586                     tsid == node->ae.tsid) {
587                         ret = node;
588                         break;
589                 }
590         }
591 
592         return ret;
593 }
594 
595 /**
596  * avc_lookup - Look up an AVC entry.
597  * @ssid: source security identifier
598  * @tsid: target security identifier
599  * @tclass: target security class
600  *
601  * Look up an AVC entry that is valid for the
602  * (@ssid, @tsid), interpreting the permissions
603  * based on @tclass.  If a valid AVC entry exists,
604  * then this function returns the avc_node.
605  * Otherwise, this function returns NULL.
606  */
607 static struct avc_node *avc_lookup(u32 ssid, u32 tsid, u16 tclass)
608 {
609         struct avc_node *node;
610 
611         avc_cache_stats_incr(lookups);
612         node = avc_search_node(ssid, tsid, tclass);
613 
614         if (node)
615                 return node;
616 
617         avc_cache_stats_incr(misses);
618         return NULL;
619 }
620 
621 static int avc_latest_notif_update(int seqno, int is_insert)
622 {
623         int ret = 0;
624         static DEFINE_SPINLOCK(notif_lock);
625         unsigned long flag;
626 
627         spin_lock_irqsave(&notif_lock, flag);
628         if (is_insert) {
629                 if (seqno < avc_cache.latest_notif) {
630                         printk(KERN_WARNING "SELinux: avc:  seqno %d < latest_notif %d\n",
631                                seqno, avc_cache.latest_notif);
632                         ret = -EAGAIN;
633                 }
634         } else {
635                 if (seqno > avc_cache.latest_notif)
636                         avc_cache.latest_notif = seqno;
637         }
638         spin_unlock_irqrestore(&notif_lock, flag);
639 
640         return ret;
641 }
642 
643 /**
644  * avc_insert - Insert an AVC entry.
645  * @ssid: source security identifier
646  * @tsid: target security identifier
647  * @tclass: target security class
648  * @avd: resulting av decision
649  * @xp_node: resulting extended permissions
650  *
651  * Insert an AVC entry for the SID pair
652  * (@ssid, @tsid) and class @tclass.
653  * The access vectors and the sequence number are
654  * normally provided by the security server in
655  * response to a security_compute_av() call.  If the
656  * sequence number @avd->seqno is not less than the latest
657  * revocation notification, then the function copies
658  * the access vectors into a cache entry, returns
659  * avc_node inserted. Otherwise, this function returns NULL.
660  */
661 static struct avc_node *avc_insert(u32 ssid, u32 tsid, u16 tclass,
662                                 struct av_decision *avd,
663                                 struct avc_xperms_node *xp_node)
664 {
665         struct avc_node *pos, *node = NULL;
666         int hvalue;
667         unsigned long flag;
668 
669         if (avc_latest_notif_update(avd->seqno, 1))
670                 goto out;
671 
672         node = avc_alloc_node();
673         if (node) {
674                 struct hlist_head *head;
675                 spinlock_t *lock;
676                 int rc = 0;
677 
678                 hvalue = avc_hash(ssid, tsid, tclass);
679                 avc_node_populate(node, ssid, tsid, tclass, avd);
680                 rc = avc_xperms_populate(node, xp_node);
681                 if (rc) {
682                         kmem_cache_free(avc_node_cachep, node);
683                         return NULL;
684                 }
685                 head = &avc_cache.slots[hvalue];
686                 lock = &avc_cache.slots_lock[hvalue];
687 
688                 spin_lock_irqsave(lock, flag);
689                 hlist_for_each_entry(pos, head, list) {
690                         if (pos->ae.ssid == ssid &&
691                             pos->ae.tsid == tsid &&
692                             pos->ae.tclass == tclass) {
693                                 avc_node_replace(node, pos);
694                                 goto found;
695                         }
696                 }
697                 hlist_add_head_rcu(&node->list, head);
698 found:
699                 spin_unlock_irqrestore(lock, flag);
700         }
701 out:
702         return node;
703 }
704 
705 /**
706  * avc_audit_pre_callback - SELinux specific information
707  * will be called by generic audit code
708  * @ab: the audit buffer
709  * @a: audit_data
710  */
711 static void avc_audit_pre_callback(struct audit_buffer *ab, void *a)
712 {
713         struct common_audit_data *ad = a;
714         audit_log_format(ab, "avc:  %s ",
715                          ad->selinux_audit_data->denied ? "denied" : "granted");
716         avc_dump_av(ab, ad->selinux_audit_data->tclass,
717                         ad->selinux_audit_data->audited);
718         audit_log_format(ab, " for ");
719 }
720 
721 /**
722  * avc_audit_post_callback - SELinux specific information
723  * will be called by generic audit code
724  * @ab: the audit buffer
725  * @a: audit_data
726  */
727 static void avc_audit_post_callback(struct audit_buffer *ab, void *a)
728 {
729         struct common_audit_data *ad = a;
730         audit_log_format(ab, " ");
731         avc_dump_query(ab, ad->selinux_audit_data->ssid,
732                            ad->selinux_audit_data->tsid,
733                            ad->selinux_audit_data->tclass);
734         if (ad->selinux_audit_data->denied) {
735                 audit_log_format(ab, " permissive=%u",
736                                  ad->selinux_audit_data->result ? 0 : 1);
737         }
738 }
739 
740 /* This is the slow part of avc audit with big stack footprint */
741 noinline int slow_avc_audit(u32 ssid, u32 tsid, u16 tclass,
742                 u32 requested, u32 audited, u32 denied, int result,
743                 struct common_audit_data *a,
744                 unsigned flags)
745 {
746         struct common_audit_data stack_data;
747         struct selinux_audit_data sad;
748 
749         if (!a) {
750                 a = &stack_data;
751                 a->type = LSM_AUDIT_DATA_NONE;
752         }
753 
754         /*
755          * When in a RCU walk do the audit on the RCU retry.  This is because
756          * the collection of the dname in an inode audit message is not RCU
757          * safe.  Note this may drop some audits when the situation changes
758          * during retry. However this is logically just as if the operation
759          * happened a little later.
760          */
761         if ((a->type == LSM_AUDIT_DATA_INODE) &&
762             (flags & MAY_NOT_BLOCK))
763                 return -ECHILD;
764 
765         sad.tclass = tclass;
766         sad.requested = requested;
767         sad.ssid = ssid;
768         sad.tsid = tsid;
769         sad.audited = audited;
770         sad.denied = denied;
771         sad.result = result;
772 
773         a->selinux_audit_data = &sad;
774 
775         common_lsm_audit(a, avc_audit_pre_callback, avc_audit_post_callback);
776         return 0;
777 }
778 
779 /**
780  * avc_add_callback - Register a callback for security events.
781  * @callback: callback function
782  * @events: security events
783  *
784  * Register a callback function for events in the set @events.
785  * Returns %0 on success or -%ENOMEM if insufficient memory
786  * exists to add the callback.
787  */
788 int __init avc_add_callback(int (*callback)(u32 event), u32 events)
789 {
790         struct avc_callback_node *c;
791         int rc = 0;
792 
793         c = kmalloc(sizeof(*c), GFP_KERNEL);
794         if (!c) {
795                 rc = -ENOMEM;
796                 goto out;
797         }
798 
799         c->callback = callback;
800         c->events = events;
801         c->next = avc_callbacks;
802         avc_callbacks = c;
803 out:
804         return rc;
805 }
806 
807 /**
808  * avc_update_node Update an AVC entry
809  * @event : Updating event
810  * @perms : Permission mask bits
811  * @ssid,@tsid,@tclass : identifier of an AVC entry
812  * @seqno : sequence number when decision was made
813  * @xpd: extended_perms_decision to be added to the node
814  *
815  * if a valid AVC entry doesn't exist,this function returns -ENOENT.
816  * if kmalloc() called internal returns NULL, this function returns -ENOMEM.
817  * otherwise, this function updates the AVC entry. The original AVC-entry object
818  * will release later by RCU.
819  */
820 static int avc_update_node(u32 event, u32 perms, u8 driver, u8 xperm, u32 ssid,
821                         u32 tsid, u16 tclass, u32 seqno,
822                         struct extended_perms_decision *xpd,
823                         u32 flags)
824 {
825         int hvalue, rc = 0;
826         unsigned long flag;
827         struct avc_node *pos, *node, *orig = NULL;
828         struct hlist_head *head;
829         spinlock_t *lock;
830 
831         node = avc_alloc_node();
832         if (!node) {
833                 rc = -ENOMEM;
834                 goto out;
835         }
836 
837         /* Lock the target slot */
838         hvalue = avc_hash(ssid, tsid, tclass);
839 
840         head = &avc_cache.slots[hvalue];
841         lock = &avc_cache.slots_lock[hvalue];
842 
843         spin_lock_irqsave(lock, flag);
844 
845         hlist_for_each_entry(pos, head, list) {
846                 if (ssid == pos->ae.ssid &&
847                     tsid == pos->ae.tsid &&
848                     tclass == pos->ae.tclass &&
849                     seqno == pos->ae.avd.seqno){
850                         orig = pos;
851                         break;
852                 }
853         }
854 
855         if (!orig) {
856                 rc = -ENOENT;
857                 avc_node_kill(node);
858                 goto out_unlock;
859         }
860 
861         /*
862          * Copy and replace original node.
863          */
864 
865         avc_node_populate(node, ssid, tsid, tclass, &orig->ae.avd);
866 
867         if (orig->ae.xp_node) {
868                 rc = avc_xperms_populate(node, orig->ae.xp_node);
869                 if (rc) {
870                         kmem_cache_free(avc_node_cachep, node);
871                         goto out_unlock;
872                 }
873         }
874 
875         switch (event) {
876         case AVC_CALLBACK_GRANT:
877                 node->ae.avd.allowed |= perms;
878                 if (node->ae.xp_node && (flags & AVC_EXTENDED_PERMS))
879                         avc_xperms_allow_perm(node->ae.xp_node, driver, xperm);
880                 break;
881         case AVC_CALLBACK_TRY_REVOKE:
882         case AVC_CALLBACK_REVOKE:
883                 node->ae.avd.allowed &= ~perms;
884                 break;
885         case AVC_CALLBACK_AUDITALLOW_ENABLE:
886                 node->ae.avd.auditallow |= perms;
887                 break;
888         case AVC_CALLBACK_AUDITALLOW_DISABLE:
889                 node->ae.avd.auditallow &= ~perms;
890                 break;
891         case AVC_CALLBACK_AUDITDENY_ENABLE:
892                 node->ae.avd.auditdeny |= perms;
893                 break;
894         case AVC_CALLBACK_AUDITDENY_DISABLE:
895                 node->ae.avd.auditdeny &= ~perms;
896                 break;
897         case AVC_CALLBACK_ADD_XPERMS:
898                 avc_add_xperms_decision(node, xpd);
899                 break;
900         }
901         avc_node_replace(node, orig);
902 out_unlock:
903         spin_unlock_irqrestore(lock, flag);
904 out:
905         return rc;
906 }
907 
908 /**
909  * avc_flush - Flush the cache
910  */
911 static void avc_flush(void)
912 {
913         struct hlist_head *head;
914         struct avc_node *node;
915         spinlock_t *lock;
916         unsigned long flag;
917         int i;
918 
919         for (i = 0; i < AVC_CACHE_SLOTS; i++) {
920                 head = &avc_cache.slots[i];
921                 lock = &avc_cache.slots_lock[i];
922 
923                 spin_lock_irqsave(lock, flag);
924                 /*
925                  * With preemptable RCU, the outer spinlock does not
926                  * prevent RCU grace periods from ending.
927                  */
928                 rcu_read_lock();
929                 hlist_for_each_entry(node, head, list)
930                         avc_node_delete(node);
931                 rcu_read_unlock();
932                 spin_unlock_irqrestore(lock, flag);
933         }
934 }
935 
936 /**
937  * avc_ss_reset - Flush the cache and revalidate migrated permissions.
938  * @seqno: policy sequence number
939  */
940 int avc_ss_reset(u32 seqno)
941 {
942         struct avc_callback_node *c;
943         int rc = 0, tmprc;
944 
945         avc_flush();
946 
947         for (c = avc_callbacks; c; c = c->next) {
948                 if (c->events & AVC_CALLBACK_RESET) {
949                         tmprc = c->callback(AVC_CALLBACK_RESET);
950                         /* save the first error encountered for the return
951                            value and continue processing the callbacks */
952                         if (!rc)
953                                 rc = tmprc;
954                 }
955         }
956 
957         avc_latest_notif_update(seqno, 0);
958         return rc;
959 }
960 
961 /*
962  * Slow-path helper function for avc_has_perm_noaudit,
963  * when the avc_node lookup fails. We get called with
964  * the RCU read lock held, and need to return with it
965  * still held, but drop if for the security compute.
966  *
967  * Don't inline this, since it's the slow-path and just
968  * results in a bigger stack frame.
969  */
970 static noinline struct avc_node *avc_compute_av(u32 ssid, u32 tsid,
971                          u16 tclass, struct av_decision *avd,
972                          struct avc_xperms_node *xp_node)
973 {
974         rcu_read_unlock();
975         INIT_LIST_HEAD(&xp_node->xpd_head);
976         security_compute_av(ssid, tsid, tclass, avd, &xp_node->xp);
977         rcu_read_lock();
978         return avc_insert(ssid, tsid, tclass, avd, xp_node);
979 }
980 
981 static noinline int avc_denied(u32 ssid, u32 tsid,
982                                 u16 tclass, u32 requested,
983                                 u8 driver, u8 xperm, unsigned flags,
984                                 struct av_decision *avd)
985 {
986         if (flags & AVC_STRICT)
987                 return -EACCES;
988 
989         if (selinux_enforcing && !(avd->flags & AVD_FLAGS_PERMISSIVE))
990                 return -EACCES;
991 
992         avc_update_node(AVC_CALLBACK_GRANT, requested, driver, xperm, ssid,
993                                 tsid, tclass, avd->seqno, NULL, flags);
994         return 0;
995 }
996 
997 /*
998  * The avc extended permissions logic adds an additional 256 bits of
999  * permissions to an avc node when extended permissions for that node are
1000  * specified in the avtab. If the additional 256 permissions is not adequate,
1001  * as-is the case with ioctls, then multiple may be chained together and the
1002  * driver field is used to specify which set contains the permission.
1003  */
1004 int avc_has_extended_perms(u32 ssid, u32 tsid, u16 tclass, u32 requested,
1005                         u8 driver, u8 xperm, struct common_audit_data *ad)
1006 {
1007         struct avc_node *node;
1008         struct av_decision avd;
1009         u32 denied;
1010         struct extended_perms_decision local_xpd;
1011         struct extended_perms_decision *xpd = NULL;
1012         struct extended_perms_data allowed;
1013         struct extended_perms_data auditallow;
1014         struct extended_perms_data dontaudit;
1015         struct avc_xperms_node local_xp_node;
1016         struct avc_xperms_node *xp_node;
1017         int rc = 0, rc2;
1018 
1019         xp_node = &local_xp_node;
1020         BUG_ON(!requested);
1021 
1022         rcu_read_lock();
1023 
1024         node = avc_lookup(ssid, tsid, tclass);
1025         if (unlikely(!node)) {
1026                 node = avc_compute_av(ssid, tsid, tclass, &avd, xp_node);
1027         } else {
1028                 memcpy(&avd, &node->ae.avd, sizeof(avd));
1029                 xp_node = node->ae.xp_node;
1030         }
1031         /* if extended permissions are not defined, only consider av_decision */
1032         if (!xp_node || !xp_node->xp.len)
1033                 goto decision;
1034 
1035         local_xpd.allowed = &allowed;
1036         local_xpd.auditallow = &auditallow;
1037         local_xpd.dontaudit = &dontaudit;
1038 
1039         xpd = avc_xperms_decision_lookup(driver, xp_node);
1040         if (unlikely(!xpd)) {
1041                 /*
1042                  * Compute the extended_perms_decision only if the driver
1043                  * is flagged
1044                  */
1045                 if (!security_xperm_test(xp_node->xp.drivers.p, driver)) {
1046                         avd.allowed &= ~requested;
1047                         goto decision;
1048                 }
1049                 rcu_read_unlock();
1050                 security_compute_xperms_decision(ssid, tsid, tclass, driver,
1051                                                 &local_xpd);
1052                 rcu_read_lock();
1053                 avc_update_node(AVC_CALLBACK_ADD_XPERMS, requested, driver, xperm,
1054                                 ssid, tsid, tclass, avd.seqno, &local_xpd, 0);
1055         } else {
1056                 avc_quick_copy_xperms_decision(xperm, &local_xpd, xpd);
1057         }
1058         xpd = &local_xpd;
1059 
1060         if (!avc_xperms_has_perm(xpd, xperm, XPERMS_ALLOWED))
1061                 avd.allowed &= ~requested;
1062 
1063 decision:
1064         denied = requested & ~(avd.allowed);
1065         if (unlikely(denied))
1066                 rc = avc_denied(ssid, tsid, tclass, requested, driver, xperm,
1067                                 AVC_EXTENDED_PERMS, &avd);
1068 
1069         rcu_read_unlock();
1070 
1071         rc2 = avc_xperms_audit(ssid, tsid, tclass, requested,
1072                         &avd, xpd, xperm, rc, ad);
1073         if (rc2)
1074                 return rc2;
1075         return rc;
1076 }
1077 
1078 /**
1079  * avc_has_perm_noaudit - Check permissions but perform no auditing.
1080  * @ssid: source security identifier
1081  * @tsid: target security identifier
1082  * @tclass: target security class
1083  * @requested: requested permissions, interpreted based on @tclass
1084  * @flags:  AVC_STRICT or 0
1085  * @avd: access vector decisions
1086  *
1087  * Check the AVC to determine whether the @requested permissions are granted
1088  * for the SID pair (@ssid, @tsid), interpreting the permissions
1089  * based on @tclass, and call the security server on a cache miss to obtain
1090  * a new decision and add it to the cache.  Return a copy of the decisions
1091  * in @avd.  Return %0 if all @requested permissions are granted,
1092  * -%EACCES if any permissions are denied, or another -errno upon
1093  * other errors.  This function is typically called by avc_has_perm(),
1094  * but may also be called directly to separate permission checking from
1095  * auditing, e.g. in cases where a lock must be held for the check but
1096  * should be released for the auditing.
1097  */
1098 inline int avc_has_perm_noaudit(u32 ssid, u32 tsid,
1099                          u16 tclass, u32 requested,
1100                          unsigned flags,
1101                          struct av_decision *avd)
1102 {
1103         struct avc_node *node;
1104         struct avc_xperms_node xp_node;
1105         int rc = 0;
1106         u32 denied;
1107 
1108         BUG_ON(!requested);
1109 
1110         rcu_read_lock();
1111 
1112         node = avc_lookup(ssid, tsid, tclass);
1113         if (unlikely(!node))
1114                 node = avc_compute_av(ssid, tsid, tclass, avd, &xp_node);
1115         else
1116                 memcpy(avd, &node->ae.avd, sizeof(*avd));
1117 
1118         denied = requested & ~(avd->allowed);
1119         if (unlikely(denied))
1120                 rc = avc_denied(ssid, tsid, tclass, requested, 0, 0, flags, avd);
1121 
1122         rcu_read_unlock();
1123         return rc;
1124 }
1125 
1126 /**
1127  * avc_has_perm - Check permissions and perform any appropriate auditing.
1128  * @ssid: source security identifier
1129  * @tsid: target security identifier
1130  * @tclass: target security class
1131  * @requested: requested permissions, interpreted based on @tclass
1132  * @auditdata: auxiliary audit data
1133  *
1134  * Check the AVC to determine whether the @requested permissions are granted
1135  * for the SID pair (@ssid, @tsid), interpreting the permissions
1136  * based on @tclass, and call the security server on a cache miss to obtain
1137  * a new decision and add it to the cache.  Audit the granting or denial of
1138  * permissions in accordance with the policy.  Return %0 if all @requested
1139  * permissions are granted, -%EACCES if any permissions are denied, or
1140  * another -errno upon other errors.
1141  */
1142 int avc_has_perm(u32 ssid, u32 tsid, u16 tclass,
1143                  u32 requested, struct common_audit_data *auditdata)
1144 {
1145         struct av_decision avd;
1146         int rc, rc2;
1147 
1148         rc = avc_has_perm_noaudit(ssid, tsid, tclass, requested, 0, &avd);
1149 
1150         rc2 = avc_audit(ssid, tsid, tclass, requested, &avd, rc, auditdata, 0);
1151         if (rc2)
1152                 return rc2;
1153         return rc;
1154 }
1155 
1156 int avc_has_perm_flags(u32 ssid, u32 tsid, u16 tclass,
1157                        u32 requested, struct common_audit_data *auditdata,
1158                        int flags)
1159 {
1160         struct av_decision avd;
1161         int rc, rc2;
1162 
1163         rc = avc_has_perm_noaudit(ssid, tsid, tclass, requested, 0, &avd);
1164 
1165         rc2 = avc_audit(ssid, tsid, tclass, requested, &avd, rc,
1166                         auditdata, flags);
1167         if (rc2)
1168                 return rc2;
1169         return rc;
1170 }
1171 
1172 u32 avc_policy_seqno(void)
1173 {
1174         return avc_cache.latest_notif;
1175 }
1176 
1177 void avc_disable(void)
1178 {
1179         /*
1180          * If you are looking at this because you have realized that we are
1181          * not destroying the avc_node_cachep it might be easy to fix, but
1182          * I don't know the memory barrier semantics well enough to know.  It's
1183          * possible that some other task dereferenced security_ops when
1184          * it still pointed to selinux operations.  If that is the case it's
1185          * possible that it is about to use the avc and is about to need the
1186          * avc_node_cachep.  I know I could wrap the security.c security_ops call
1187          * in an rcu_lock, but seriously, it's not worth it.  Instead I just flush
1188          * the cache and get that memory back.
1189          */
1190         if (avc_node_cachep) {
1191                 avc_flush();
1192                 /* kmem_cache_destroy(avc_node_cachep); */
1193         }
1194 }
1195 

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