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Linux/security/selinux/avc.c

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  1 // SPDX-License-Identifier: GPL-2.0-only
  2 /*
  3  * Implementation of the kernel access vector cache (AVC).
  4  *
  5  * Authors:  Stephen Smalley, <sds@tycho.nsa.gov>
  6  *           James Morris <jmorris@redhat.com>
  7  *
  8  * Update:   KaiGai, Kohei <kaigai@ak.jp.nec.com>
  9  *      Replaced the avc_lock spinlock by RCU.
 10  *
 11  * Copyright (C) 2003 Red Hat, Inc., James Morris <jmorris@redhat.com>
 12  */
 13 #include <linux/types.h>
 14 #include <linux/stddef.h>
 15 #include <linux/kernel.h>
 16 #include <linux/slab.h>
 17 #include <linux/fs.h>
 18 #include <linux/dcache.h>
 19 #include <linux/init.h>
 20 #include <linux/skbuff.h>
 21 #include <linux/percpu.h>
 22 #include <linux/list.h>
 23 #include <net/sock.h>
 24 #include <linux/un.h>
 25 #include <net/af_unix.h>
 26 #include <linux/ip.h>
 27 #include <linux/audit.h>
 28 #include <linux/ipv6.h>
 29 #include <net/ipv6.h>
 30 #include "avc.h"
 31 #include "avc_ss.h"
 32 #include "classmap.h"
 33 
 34 #define AVC_CACHE_SLOTS                 512
 35 #define AVC_DEF_CACHE_THRESHOLD         512
 36 #define AVC_CACHE_RECLAIM               16
 37 
 38 #ifdef CONFIG_SECURITY_SELINUX_AVC_STATS
 39 #define avc_cache_stats_incr(field)     this_cpu_inc(avc_cache_stats.field)
 40 #else
 41 #define avc_cache_stats_incr(field)     do {} while (0)
 42 #endif
 43 
 44 struct avc_entry {
 45         u32                     ssid;
 46         u32                     tsid;
 47         u16                     tclass;
 48         struct av_decision      avd;
 49         struct avc_xperms_node  *xp_node;
 50 };
 51 
 52 struct avc_node {
 53         struct avc_entry        ae;
 54         struct hlist_node       list; /* anchored in avc_cache->slots[i] */
 55         struct rcu_head         rhead;
 56 };
 57 
 58 struct avc_xperms_decision_node {
 59         struct extended_perms_decision xpd;
 60         struct list_head xpd_list; /* list of extended_perms_decision */
 61 };
 62 
 63 struct avc_xperms_node {
 64         struct extended_perms xp;
 65         struct list_head xpd_head; /* list head of extended_perms_decision */
 66 };
 67 
 68 struct avc_cache {
 69         struct hlist_head       slots[AVC_CACHE_SLOTS]; /* head for avc_node->list */
 70         spinlock_t              slots_lock[AVC_CACHE_SLOTS]; /* lock for writes */
 71         atomic_t                lru_hint;       /* LRU hint for reclaim scan */
 72         atomic_t                active_nodes;
 73         u32                     latest_notif;   /* latest revocation notification */
 74 };
 75 
 76 struct avc_callback_node {
 77         int (*callback) (u32 event);
 78         u32 events;
 79         struct avc_callback_node *next;
 80 };
 81 
 82 #ifdef CONFIG_SECURITY_SELINUX_AVC_STATS
 83 DEFINE_PER_CPU(struct avc_cache_stats, avc_cache_stats) = { 0 };
 84 #endif
 85 
 86 struct selinux_avc {
 87         unsigned int avc_cache_threshold;
 88         struct avc_cache avc_cache;
 89 };
 90 
 91 static struct selinux_avc selinux_avc;
 92 
 93 void selinux_avc_init(struct selinux_avc **avc)
 94 {
 95         int i;
 96 
 97         selinux_avc.avc_cache_threshold = AVC_DEF_CACHE_THRESHOLD;
 98         for (i = 0; i < AVC_CACHE_SLOTS; i++) {
 99                 INIT_HLIST_HEAD(&selinux_avc.avc_cache.slots[i]);
100                 spin_lock_init(&selinux_avc.avc_cache.slots_lock[i]);
101         }
102         atomic_set(&selinux_avc.avc_cache.active_nodes, 0);
103         atomic_set(&selinux_avc.avc_cache.lru_hint, 0);
104         *avc = &selinux_avc;
105 }
106 
107 unsigned int avc_get_cache_threshold(struct selinux_avc *avc)
108 {
109         return avc->avc_cache_threshold;
110 }
111 
112 void avc_set_cache_threshold(struct selinux_avc *avc,
113                              unsigned int cache_threshold)
114 {
115         avc->avc_cache_threshold = cache_threshold;
116 }
117 
118 static struct avc_callback_node *avc_callbacks;
119 static struct kmem_cache *avc_node_cachep;
120 static struct kmem_cache *avc_xperms_data_cachep;
121 static struct kmem_cache *avc_xperms_decision_cachep;
122 static struct kmem_cache *avc_xperms_cachep;
123 
124 static inline int avc_hash(u32 ssid, u32 tsid, u16 tclass)
125 {
126         return (ssid ^ (tsid<<2) ^ (tclass<<4)) & (AVC_CACHE_SLOTS - 1);
127 }
128 
129 /**
130  * avc_init - Initialize the AVC.
131  *
132  * Initialize the access vector cache.
133  */
134 void __init avc_init(void)
135 {
136         avc_node_cachep = kmem_cache_create("avc_node", sizeof(struct avc_node),
137                                         0, SLAB_PANIC, NULL);
138         avc_xperms_cachep = kmem_cache_create("avc_xperms_node",
139                                         sizeof(struct avc_xperms_node),
140                                         0, SLAB_PANIC, NULL);
141         avc_xperms_decision_cachep = kmem_cache_create(
142                                         "avc_xperms_decision_node",
143                                         sizeof(struct avc_xperms_decision_node),
144                                         0, SLAB_PANIC, NULL);
145         avc_xperms_data_cachep = kmem_cache_create("avc_xperms_data",
146                                         sizeof(struct extended_perms_data),
147                                         0, SLAB_PANIC, NULL);
148 }
149 
150 int avc_get_hash_stats(struct selinux_avc *avc, char *page)
151 {
152         int i, chain_len, max_chain_len, slots_used;
153         struct avc_node *node;
154         struct hlist_head *head;
155 
156         rcu_read_lock();
157 
158         slots_used = 0;
159         max_chain_len = 0;
160         for (i = 0; i < AVC_CACHE_SLOTS; i++) {
161                 head = &avc->avc_cache.slots[i];
162                 if (!hlist_empty(head)) {
163                         slots_used++;
164                         chain_len = 0;
165                         hlist_for_each_entry_rcu(node, head, list)
166                                 chain_len++;
167                         if (chain_len > max_chain_len)
168                                 max_chain_len = chain_len;
169                 }
170         }
171 
172         rcu_read_unlock();
173 
174         return scnprintf(page, PAGE_SIZE, "entries: %d\nbuckets used: %d/%d\n"
175                          "longest chain: %d\n",
176                          atomic_read(&avc->avc_cache.active_nodes),
177                          slots_used, AVC_CACHE_SLOTS, max_chain_len);
178 }
179 
180 /*
181  * using a linked list for extended_perms_decision lookup because the list is
182  * always small. i.e. less than 5, typically 1
183  */
184 static struct extended_perms_decision *avc_xperms_decision_lookup(u8 driver,
185                                         struct avc_xperms_node *xp_node)
186 {
187         struct avc_xperms_decision_node *xpd_node;
188 
189         list_for_each_entry(xpd_node, &xp_node->xpd_head, xpd_list) {
190                 if (xpd_node->xpd.driver == driver)
191                         return &xpd_node->xpd;
192         }
193         return NULL;
194 }
195 
196 static inline unsigned int
197 avc_xperms_has_perm(struct extended_perms_decision *xpd,
198                                         u8 perm, u8 which)
199 {
200         unsigned int rc = 0;
201 
202         if ((which == XPERMS_ALLOWED) &&
203                         (xpd->used & XPERMS_ALLOWED))
204                 rc = security_xperm_test(xpd->allowed->p, perm);
205         else if ((which == XPERMS_AUDITALLOW) &&
206                         (xpd->used & XPERMS_AUDITALLOW))
207                 rc = security_xperm_test(xpd->auditallow->p, perm);
208         else if ((which == XPERMS_DONTAUDIT) &&
209                         (xpd->used & XPERMS_DONTAUDIT))
210                 rc = security_xperm_test(xpd->dontaudit->p, perm);
211         return rc;
212 }
213 
214 static void avc_xperms_allow_perm(struct avc_xperms_node *xp_node,
215                                 u8 driver, u8 perm)
216 {
217         struct extended_perms_decision *xpd;
218         security_xperm_set(xp_node->xp.drivers.p, driver);
219         xpd = avc_xperms_decision_lookup(driver, xp_node);
220         if (xpd && xpd->allowed)
221                 security_xperm_set(xpd->allowed->p, perm);
222 }
223 
224 static void avc_xperms_decision_free(struct avc_xperms_decision_node *xpd_node)
225 {
226         struct extended_perms_decision *xpd;
227 
228         xpd = &xpd_node->xpd;
229         if (xpd->allowed)
230                 kmem_cache_free(avc_xperms_data_cachep, xpd->allowed);
231         if (xpd->auditallow)
232                 kmem_cache_free(avc_xperms_data_cachep, xpd->auditallow);
233         if (xpd->dontaudit)
234                 kmem_cache_free(avc_xperms_data_cachep, xpd->dontaudit);
235         kmem_cache_free(avc_xperms_decision_cachep, xpd_node);
236 }
237 
238 static void avc_xperms_free(struct avc_xperms_node *xp_node)
239 {
240         struct avc_xperms_decision_node *xpd_node, *tmp;
241 
242         if (!xp_node)
243                 return;
244 
245         list_for_each_entry_safe(xpd_node, tmp, &xp_node->xpd_head, xpd_list) {
246                 list_del(&xpd_node->xpd_list);
247                 avc_xperms_decision_free(xpd_node);
248         }
249         kmem_cache_free(avc_xperms_cachep, xp_node);
250 }
251 
252 static void avc_copy_xperms_decision(struct extended_perms_decision *dest,
253                                         struct extended_perms_decision *src)
254 {
255         dest->driver = src->driver;
256         dest->used = src->used;
257         if (dest->used & XPERMS_ALLOWED)
258                 memcpy(dest->allowed->p, src->allowed->p,
259                                 sizeof(src->allowed->p));
260         if (dest->used & XPERMS_AUDITALLOW)
261                 memcpy(dest->auditallow->p, src->auditallow->p,
262                                 sizeof(src->auditallow->p));
263         if (dest->used & XPERMS_DONTAUDIT)
264                 memcpy(dest->dontaudit->p, src->dontaudit->p,
265                                 sizeof(src->dontaudit->p));
266 }
267 
268 /*
269  * similar to avc_copy_xperms_decision, but only copy decision
270  * information relevant to this perm
271  */
272 static inline void avc_quick_copy_xperms_decision(u8 perm,
273                         struct extended_perms_decision *dest,
274                         struct extended_perms_decision *src)
275 {
276         /*
277          * compute index of the u32 of the 256 bits (8 u32s) that contain this
278          * command permission
279          */
280         u8 i = perm >> 5;
281 
282         dest->used = src->used;
283         if (dest->used & XPERMS_ALLOWED)
284                 dest->allowed->p[i] = src->allowed->p[i];
285         if (dest->used & XPERMS_AUDITALLOW)
286                 dest->auditallow->p[i] = src->auditallow->p[i];
287         if (dest->used & XPERMS_DONTAUDIT)
288                 dest->dontaudit->p[i] = src->dontaudit->p[i];
289 }
290 
291 static struct avc_xperms_decision_node
292                 *avc_xperms_decision_alloc(u8 which)
293 {
294         struct avc_xperms_decision_node *xpd_node;
295         struct extended_perms_decision *xpd;
296 
297         xpd_node = kmem_cache_zalloc(avc_xperms_decision_cachep, GFP_NOWAIT);
298         if (!xpd_node)
299                 return NULL;
300 
301         xpd = &xpd_node->xpd;
302         if (which & XPERMS_ALLOWED) {
303                 xpd->allowed = kmem_cache_zalloc(avc_xperms_data_cachep,
304                                                 GFP_NOWAIT);
305                 if (!xpd->allowed)
306                         goto error;
307         }
308         if (which & XPERMS_AUDITALLOW) {
309                 xpd->auditallow = kmem_cache_zalloc(avc_xperms_data_cachep,
310                                                 GFP_NOWAIT);
311                 if (!xpd->auditallow)
312                         goto error;
313         }
314         if (which & XPERMS_DONTAUDIT) {
315                 xpd->dontaudit = kmem_cache_zalloc(avc_xperms_data_cachep,
316                                                 GFP_NOWAIT);
317                 if (!xpd->dontaudit)
318                         goto error;
319         }
320         return xpd_node;
321 error:
322         avc_xperms_decision_free(xpd_node);
323         return NULL;
324 }
325 
326 static int avc_add_xperms_decision(struct avc_node *node,
327                         struct extended_perms_decision *src)
328 {
329         struct avc_xperms_decision_node *dest_xpd;
330 
331         node->ae.xp_node->xp.len++;
332         dest_xpd = avc_xperms_decision_alloc(src->used);
333         if (!dest_xpd)
334                 return -ENOMEM;
335         avc_copy_xperms_decision(&dest_xpd->xpd, src);
336         list_add(&dest_xpd->xpd_list, &node->ae.xp_node->xpd_head);
337         return 0;
338 }
339 
340 static struct avc_xperms_node *avc_xperms_alloc(void)
341 {
342         struct avc_xperms_node *xp_node;
343 
344         xp_node = kmem_cache_zalloc(avc_xperms_cachep, GFP_NOWAIT);
345         if (!xp_node)
346                 return xp_node;
347         INIT_LIST_HEAD(&xp_node->xpd_head);
348         return xp_node;
349 }
350 
351 static int avc_xperms_populate(struct avc_node *node,
352                                 struct avc_xperms_node *src)
353 {
354         struct avc_xperms_node *dest;
355         struct avc_xperms_decision_node *dest_xpd;
356         struct avc_xperms_decision_node *src_xpd;
357 
358         if (src->xp.len == 0)
359                 return 0;
360         dest = avc_xperms_alloc();
361         if (!dest)
362                 return -ENOMEM;
363 
364         memcpy(dest->xp.drivers.p, src->xp.drivers.p, sizeof(dest->xp.drivers.p));
365         dest->xp.len = src->xp.len;
366 
367         /* for each source xpd allocate a destination xpd and copy */
368         list_for_each_entry(src_xpd, &src->xpd_head, xpd_list) {
369                 dest_xpd = avc_xperms_decision_alloc(src_xpd->xpd.used);
370                 if (!dest_xpd)
371                         goto error;
372                 avc_copy_xperms_decision(&dest_xpd->xpd, &src_xpd->xpd);
373                 list_add(&dest_xpd->xpd_list, &dest->xpd_head);
374         }
375         node->ae.xp_node = dest;
376         return 0;
377 error:
378         avc_xperms_free(dest);
379         return -ENOMEM;
380 
381 }
382 
383 static inline u32 avc_xperms_audit_required(u32 requested,
384                                         struct av_decision *avd,
385                                         struct extended_perms_decision *xpd,
386                                         u8 perm,
387                                         int result,
388                                         u32 *deniedp)
389 {
390         u32 denied, audited;
391 
392         denied = requested & ~avd->allowed;
393         if (unlikely(denied)) {
394                 audited = denied & avd->auditdeny;
395                 if (audited && xpd) {
396                         if (avc_xperms_has_perm(xpd, perm, XPERMS_DONTAUDIT))
397                                 audited &= ~requested;
398                 }
399         } else if (result) {
400                 audited = denied = requested;
401         } else {
402                 audited = requested & avd->auditallow;
403                 if (audited && xpd) {
404                         if (!avc_xperms_has_perm(xpd, perm, XPERMS_AUDITALLOW))
405                                 audited &= ~requested;
406                 }
407         }
408 
409         *deniedp = denied;
410         return audited;
411 }
412 
413 static inline int avc_xperms_audit(struct selinux_state *state,
414                                    u32 ssid, u32 tsid, u16 tclass,
415                                    u32 requested, struct av_decision *avd,
416                                    struct extended_perms_decision *xpd,
417                                    u8 perm, int result,
418                                    struct common_audit_data *ad)
419 {
420         u32 audited, denied;
421 
422         audited = avc_xperms_audit_required(
423                         requested, avd, xpd, perm, result, &denied);
424         if (likely(!audited))
425                 return 0;
426         return slow_avc_audit(state, ssid, tsid, tclass, requested,
427                         audited, denied, result, ad, 0);
428 }
429 
430 static void avc_node_free(struct rcu_head *rhead)
431 {
432         struct avc_node *node = container_of(rhead, struct avc_node, rhead);
433         avc_xperms_free(node->ae.xp_node);
434         kmem_cache_free(avc_node_cachep, node);
435         avc_cache_stats_incr(frees);
436 }
437 
438 static void avc_node_delete(struct selinux_avc *avc, struct avc_node *node)
439 {
440         hlist_del_rcu(&node->list);
441         call_rcu(&node->rhead, avc_node_free);
442         atomic_dec(&avc->avc_cache.active_nodes);
443 }
444 
445 static void avc_node_kill(struct selinux_avc *avc, struct avc_node *node)
446 {
447         avc_xperms_free(node->ae.xp_node);
448         kmem_cache_free(avc_node_cachep, node);
449         avc_cache_stats_incr(frees);
450         atomic_dec(&avc->avc_cache.active_nodes);
451 }
452 
453 static void avc_node_replace(struct selinux_avc *avc,
454                              struct avc_node *new, struct avc_node *old)
455 {
456         hlist_replace_rcu(&old->list, &new->list);
457         call_rcu(&old->rhead, avc_node_free);
458         atomic_dec(&avc->avc_cache.active_nodes);
459 }
460 
461 static inline int avc_reclaim_node(struct selinux_avc *avc)
462 {
463         struct avc_node *node;
464         int hvalue, try, ecx;
465         unsigned long flags;
466         struct hlist_head *head;
467         spinlock_t *lock;
468 
469         for (try = 0, ecx = 0; try < AVC_CACHE_SLOTS; try++) {
470                 hvalue = atomic_inc_return(&avc->avc_cache.lru_hint) &
471                         (AVC_CACHE_SLOTS - 1);
472                 head = &avc->avc_cache.slots[hvalue];
473                 lock = &avc->avc_cache.slots_lock[hvalue];
474 
475                 if (!spin_trylock_irqsave(lock, flags))
476                         continue;
477 
478                 rcu_read_lock();
479                 hlist_for_each_entry(node, head, list) {
480                         avc_node_delete(avc, node);
481                         avc_cache_stats_incr(reclaims);
482                         ecx++;
483                         if (ecx >= AVC_CACHE_RECLAIM) {
484                                 rcu_read_unlock();
485                                 spin_unlock_irqrestore(lock, flags);
486                                 goto out;
487                         }
488                 }
489                 rcu_read_unlock();
490                 spin_unlock_irqrestore(lock, flags);
491         }
492 out:
493         return ecx;
494 }
495 
496 static struct avc_node *avc_alloc_node(struct selinux_avc *avc)
497 {
498         struct avc_node *node;
499 
500         node = kmem_cache_zalloc(avc_node_cachep, GFP_NOWAIT);
501         if (!node)
502                 goto out;
503 
504         INIT_HLIST_NODE(&node->list);
505         avc_cache_stats_incr(allocations);
506 
507         if (atomic_inc_return(&avc->avc_cache.active_nodes) >
508             avc->avc_cache_threshold)
509                 avc_reclaim_node(avc);
510 
511 out:
512         return node;
513 }
514 
515 static void avc_node_populate(struct avc_node *node, u32 ssid, u32 tsid, u16 tclass, struct av_decision *avd)
516 {
517         node->ae.ssid = ssid;
518         node->ae.tsid = tsid;
519         node->ae.tclass = tclass;
520         memcpy(&node->ae.avd, avd, sizeof(node->ae.avd));
521 }
522 
523 static inline struct avc_node *avc_search_node(struct selinux_avc *avc,
524                                                u32 ssid, u32 tsid, u16 tclass)
525 {
526         struct avc_node *node, *ret = NULL;
527         int hvalue;
528         struct hlist_head *head;
529 
530         hvalue = avc_hash(ssid, tsid, tclass);
531         head = &avc->avc_cache.slots[hvalue];
532         hlist_for_each_entry_rcu(node, head, list) {
533                 if (ssid == node->ae.ssid &&
534                     tclass == node->ae.tclass &&
535                     tsid == node->ae.tsid) {
536                         ret = node;
537                         break;
538                 }
539         }
540 
541         return ret;
542 }
543 
544 /**
545  * avc_lookup - Look up an AVC entry.
546  * @ssid: source security identifier
547  * @tsid: target security identifier
548  * @tclass: target security class
549  *
550  * Look up an AVC entry that is valid for the
551  * (@ssid, @tsid), interpreting the permissions
552  * based on @tclass.  If a valid AVC entry exists,
553  * then this function returns the avc_node.
554  * Otherwise, this function returns NULL.
555  */
556 static struct avc_node *avc_lookup(struct selinux_avc *avc,
557                                    u32 ssid, u32 tsid, u16 tclass)
558 {
559         struct avc_node *node;
560 
561         avc_cache_stats_incr(lookups);
562         node = avc_search_node(avc, ssid, tsid, tclass);
563 
564         if (node)
565                 return node;
566 
567         avc_cache_stats_incr(misses);
568         return NULL;
569 }
570 
571 static int avc_latest_notif_update(struct selinux_avc *avc,
572                                    int seqno, int is_insert)
573 {
574         int ret = 0;
575         static DEFINE_SPINLOCK(notif_lock);
576         unsigned long flag;
577 
578         spin_lock_irqsave(&notif_lock, flag);
579         if (is_insert) {
580                 if (seqno < avc->avc_cache.latest_notif) {
581                         pr_warn("SELinux: avc:  seqno %d < latest_notif %d\n",
582                                seqno, avc->avc_cache.latest_notif);
583                         ret = -EAGAIN;
584                 }
585         } else {
586                 if (seqno > avc->avc_cache.latest_notif)
587                         avc->avc_cache.latest_notif = seqno;
588         }
589         spin_unlock_irqrestore(&notif_lock, flag);
590 
591         return ret;
592 }
593 
594 /**
595  * avc_insert - Insert an AVC entry.
596  * @ssid: source security identifier
597  * @tsid: target security identifier
598  * @tclass: target security class
599  * @avd: resulting av decision
600  * @xp_node: resulting extended permissions
601  *
602  * Insert an AVC entry for the SID pair
603  * (@ssid, @tsid) and class @tclass.
604  * The access vectors and the sequence number are
605  * normally provided by the security server in
606  * response to a security_compute_av() call.  If the
607  * sequence number @avd->seqno is not less than the latest
608  * revocation notification, then the function copies
609  * the access vectors into a cache entry, returns
610  * avc_node inserted. Otherwise, this function returns NULL.
611  */
612 static struct avc_node *avc_insert(struct selinux_avc *avc,
613                                    u32 ssid, u32 tsid, u16 tclass,
614                                    struct av_decision *avd,
615                                    struct avc_xperms_node *xp_node)
616 {
617         struct avc_node *pos, *node = NULL;
618         int hvalue;
619         unsigned long flag;
620 
621         if (avc_latest_notif_update(avc, avd->seqno, 1))
622                 goto out;
623 
624         node = avc_alloc_node(avc);
625         if (node) {
626                 struct hlist_head *head;
627                 spinlock_t *lock;
628                 int rc = 0;
629 
630                 hvalue = avc_hash(ssid, tsid, tclass);
631                 avc_node_populate(node, ssid, tsid, tclass, avd);
632                 rc = avc_xperms_populate(node, xp_node);
633                 if (rc) {
634                         kmem_cache_free(avc_node_cachep, node);
635                         return NULL;
636                 }
637                 head = &avc->avc_cache.slots[hvalue];
638                 lock = &avc->avc_cache.slots_lock[hvalue];
639 
640                 spin_lock_irqsave(lock, flag);
641                 hlist_for_each_entry(pos, head, list) {
642                         if (pos->ae.ssid == ssid &&
643                             pos->ae.tsid == tsid &&
644                             pos->ae.tclass == tclass) {
645                                 avc_node_replace(avc, node, pos);
646                                 goto found;
647                         }
648                 }
649                 hlist_add_head_rcu(&node->list, head);
650 found:
651                 spin_unlock_irqrestore(lock, flag);
652         }
653 out:
654         return node;
655 }
656 
657 /**
658  * avc_audit_pre_callback - SELinux specific information
659  * will be called by generic audit code
660  * @ab: the audit buffer
661  * @a: audit_data
662  */
663 static void avc_audit_pre_callback(struct audit_buffer *ab, void *a)
664 {
665         struct common_audit_data *ad = a;
666         struct selinux_audit_data *sad = ad->selinux_audit_data;
667         u32 av = sad->audited;
668         const char **perms;
669         int i, perm;
670 
671         audit_log_format(ab, "avc:  %s ", sad->denied ? "denied" : "granted");
672 
673         if (av == 0) {
674                 audit_log_format(ab, " null");
675                 return;
676         }
677 
678         perms = secclass_map[sad->tclass-1].perms;
679 
680         audit_log_format(ab, " {");
681         i = 0;
682         perm = 1;
683         while (i < (sizeof(av) * 8)) {
684                 if ((perm & av) && perms[i]) {
685                         audit_log_format(ab, " %s", perms[i]);
686                         av &= ~perm;
687                 }
688                 i++;
689                 perm <<= 1;
690         }
691 
692         if (av)
693                 audit_log_format(ab, " 0x%x", av);
694 
695         audit_log_format(ab, " } for ");
696 }
697 
698 /**
699  * avc_audit_post_callback - SELinux specific information
700  * will be called by generic audit code
701  * @ab: the audit buffer
702  * @a: audit_data
703  */
704 static void avc_audit_post_callback(struct audit_buffer *ab, void *a)
705 {
706         struct common_audit_data *ad = a;
707         struct selinux_audit_data *sad = ad->selinux_audit_data;
708         char *scontext;
709         u32 scontext_len;
710         int rc;
711 
712         rc = security_sid_to_context(sad->state, sad->ssid, &scontext,
713                                      &scontext_len);
714         if (rc)
715                 audit_log_format(ab, " ssid=%d", sad->ssid);
716         else {
717                 audit_log_format(ab, " scontext=%s", scontext);
718                 kfree(scontext);
719         }
720 
721         rc = security_sid_to_context(sad->state, sad->tsid, &scontext,
722                                      &scontext_len);
723         if (rc)
724                 audit_log_format(ab, " tsid=%d", sad->tsid);
725         else {
726                 audit_log_format(ab, " tcontext=%s", scontext);
727                 kfree(scontext);
728         }
729 
730         audit_log_format(ab, " tclass=%s", secclass_map[sad->tclass-1].name);
731 
732         if (sad->denied)
733                 audit_log_format(ab, " permissive=%u", sad->result ? 0 : 1);
734 
735         /* in case of invalid context report also the actual context string */
736         rc = security_sid_to_context_inval(sad->state, sad->ssid, &scontext,
737                                            &scontext_len);
738         if (!rc && scontext) {
739                 if (scontext_len && scontext[scontext_len - 1] == '\0')
740                         scontext_len--;
741                 audit_log_format(ab, " srawcon=");
742                 audit_log_n_untrustedstring(ab, scontext, scontext_len);
743                 kfree(scontext);
744         }
745 
746         rc = security_sid_to_context_inval(sad->state, sad->tsid, &scontext,
747                                            &scontext_len);
748         if (!rc && scontext) {
749                 if (scontext_len && scontext[scontext_len - 1] == '\0')
750                         scontext_len--;
751                 audit_log_format(ab, " trawcon=");
752                 audit_log_n_untrustedstring(ab, scontext, scontext_len);
753                 kfree(scontext);
754         }
755 }
756 
757 /* This is the slow part of avc audit with big stack footprint */
758 noinline int slow_avc_audit(struct selinux_state *state,
759                             u32 ssid, u32 tsid, u16 tclass,
760                             u32 requested, u32 audited, u32 denied, int result,
761                             struct common_audit_data *a,
762                             unsigned int flags)
763 {
764         struct common_audit_data stack_data;
765         struct selinux_audit_data sad;
766 
767         if (WARN_ON(!tclass || tclass >= ARRAY_SIZE(secclass_map)))
768                 return -EINVAL;
769 
770         if (!a) {
771                 a = &stack_data;
772                 a->type = LSM_AUDIT_DATA_NONE;
773         }
774 
775         /*
776          * When in a RCU walk do the audit on the RCU retry.  This is because
777          * the collection of the dname in an inode audit message is not RCU
778          * safe.  Note this may drop some audits when the situation changes
779          * during retry. However this is logically just as if the operation
780          * happened a little later.
781          */
782         if ((a->type == LSM_AUDIT_DATA_INODE) &&
783             (flags & MAY_NOT_BLOCK))
784                 return -ECHILD;
785 
786         sad.tclass = tclass;
787         sad.requested = requested;
788         sad.ssid = ssid;
789         sad.tsid = tsid;
790         sad.audited = audited;
791         sad.denied = denied;
792         sad.result = result;
793         sad.state = state;
794 
795         a->selinux_audit_data = &sad;
796 
797         common_lsm_audit(a, avc_audit_pre_callback, avc_audit_post_callback);
798         return 0;
799 }
800 
801 /**
802  * avc_add_callback - Register a callback for security events.
803  * @callback: callback function
804  * @events: security events
805  *
806  * Register a callback function for events in the set @events.
807  * Returns %0 on success or -%ENOMEM if insufficient memory
808  * exists to add the callback.
809  */
810 int __init avc_add_callback(int (*callback)(u32 event), u32 events)
811 {
812         struct avc_callback_node *c;
813         int rc = 0;
814 
815         c = kmalloc(sizeof(*c), GFP_KERNEL);
816         if (!c) {
817                 rc = -ENOMEM;
818                 goto out;
819         }
820 
821         c->callback = callback;
822         c->events = events;
823         c->next = avc_callbacks;
824         avc_callbacks = c;
825 out:
826         return rc;
827 }
828 
829 /**
830  * avc_update_node Update an AVC entry
831  * @event : Updating event
832  * @perms : Permission mask bits
833  * @ssid,@tsid,@tclass : identifier of an AVC entry
834  * @seqno : sequence number when decision was made
835  * @xpd: extended_perms_decision to be added to the node
836  * @flags: the AVC_* flags, e.g. AVC_NONBLOCKING, AVC_EXTENDED_PERMS, or 0.
837  *
838  * if a valid AVC entry doesn't exist,this function returns -ENOENT.
839  * if kmalloc() called internal returns NULL, this function returns -ENOMEM.
840  * otherwise, this function updates the AVC entry. The original AVC-entry object
841  * will release later by RCU.
842  */
843 static int avc_update_node(struct selinux_avc *avc,
844                            u32 event, u32 perms, u8 driver, u8 xperm, u32 ssid,
845                            u32 tsid, u16 tclass, u32 seqno,
846                            struct extended_perms_decision *xpd,
847                            u32 flags)
848 {
849         int hvalue, rc = 0;
850         unsigned long flag;
851         struct avc_node *pos, *node, *orig = NULL;
852         struct hlist_head *head;
853         spinlock_t *lock;
854 
855         /*
856          * If we are in a non-blocking code path, e.g. VFS RCU walk,
857          * then we must not add permissions to a cache entry
858          * because we cannot safely audit the denial.  Otherwise,
859          * during the subsequent blocking retry (e.g. VFS ref walk), we
860          * will find the permissions already granted in the cache entry
861          * and won't audit anything at all, leading to silent denials in
862          * permissive mode that only appear when in enforcing mode.
863          *
864          * See the corresponding handling in slow_avc_audit(), and the
865          * logic in selinux_inode_permission for the MAY_NOT_BLOCK flag,
866          * which is transliterated into AVC_NONBLOCKING.
867          */
868         if (flags & AVC_NONBLOCKING)
869                 return 0;
870 
871         node = avc_alloc_node(avc);
872         if (!node) {
873                 rc = -ENOMEM;
874                 goto out;
875         }
876 
877         /* Lock the target slot */
878         hvalue = avc_hash(ssid, tsid, tclass);
879 
880         head = &avc->avc_cache.slots[hvalue];
881         lock = &avc->avc_cache.slots_lock[hvalue];
882 
883         spin_lock_irqsave(lock, flag);
884 
885         hlist_for_each_entry(pos, head, list) {
886                 if (ssid == pos->ae.ssid &&
887                     tsid == pos->ae.tsid &&
888                     tclass == pos->ae.tclass &&
889                     seqno == pos->ae.avd.seqno){
890                         orig = pos;
891                         break;
892                 }
893         }
894 
895         if (!orig) {
896                 rc = -ENOENT;
897                 avc_node_kill(avc, node);
898                 goto out_unlock;
899         }
900 
901         /*
902          * Copy and replace original node.
903          */
904 
905         avc_node_populate(node, ssid, tsid, tclass, &orig->ae.avd);
906 
907         if (orig->ae.xp_node) {
908                 rc = avc_xperms_populate(node, orig->ae.xp_node);
909                 if (rc) {
910                         kmem_cache_free(avc_node_cachep, node);
911                         goto out_unlock;
912                 }
913         }
914 
915         switch (event) {
916         case AVC_CALLBACK_GRANT:
917                 node->ae.avd.allowed |= perms;
918                 if (node->ae.xp_node && (flags & AVC_EXTENDED_PERMS))
919                         avc_xperms_allow_perm(node->ae.xp_node, driver, xperm);
920                 break;
921         case AVC_CALLBACK_TRY_REVOKE:
922         case AVC_CALLBACK_REVOKE:
923                 node->ae.avd.allowed &= ~perms;
924                 break;
925         case AVC_CALLBACK_AUDITALLOW_ENABLE:
926                 node->ae.avd.auditallow |= perms;
927                 break;
928         case AVC_CALLBACK_AUDITALLOW_DISABLE:
929                 node->ae.avd.auditallow &= ~perms;
930                 break;
931         case AVC_CALLBACK_AUDITDENY_ENABLE:
932                 node->ae.avd.auditdeny |= perms;
933                 break;
934         case AVC_CALLBACK_AUDITDENY_DISABLE:
935                 node->ae.avd.auditdeny &= ~perms;
936                 break;
937         case AVC_CALLBACK_ADD_XPERMS:
938                 avc_add_xperms_decision(node, xpd);
939                 break;
940         }
941         avc_node_replace(avc, node, orig);
942 out_unlock:
943         spin_unlock_irqrestore(lock, flag);
944 out:
945         return rc;
946 }
947 
948 /**
949  * avc_flush - Flush the cache
950  */
951 static void avc_flush(struct selinux_avc *avc)
952 {
953         struct hlist_head *head;
954         struct avc_node *node;
955         spinlock_t *lock;
956         unsigned long flag;
957         int i;
958 
959         for (i = 0; i < AVC_CACHE_SLOTS; i++) {
960                 head = &avc->avc_cache.slots[i];
961                 lock = &avc->avc_cache.slots_lock[i];
962 
963                 spin_lock_irqsave(lock, flag);
964                 /*
965                  * With preemptable RCU, the outer spinlock does not
966                  * prevent RCU grace periods from ending.
967                  */
968                 rcu_read_lock();
969                 hlist_for_each_entry(node, head, list)
970                         avc_node_delete(avc, node);
971                 rcu_read_unlock();
972                 spin_unlock_irqrestore(lock, flag);
973         }
974 }
975 
976 /**
977  * avc_ss_reset - Flush the cache and revalidate migrated permissions.
978  * @seqno: policy sequence number
979  */
980 int avc_ss_reset(struct selinux_avc *avc, u32 seqno)
981 {
982         struct avc_callback_node *c;
983         int rc = 0, tmprc;
984 
985         avc_flush(avc);
986 
987         for (c = avc_callbacks; c; c = c->next) {
988                 if (c->events & AVC_CALLBACK_RESET) {
989                         tmprc = c->callback(AVC_CALLBACK_RESET);
990                         /* save the first error encountered for the return
991                            value and continue processing the callbacks */
992                         if (!rc)
993                                 rc = tmprc;
994                 }
995         }
996 
997         avc_latest_notif_update(avc, seqno, 0);
998         return rc;
999 }
1000 
1001 /*
1002  * Slow-path helper function for avc_has_perm_noaudit,
1003  * when the avc_node lookup fails. We get called with
1004  * the RCU read lock held, and need to return with it
1005  * still held, but drop if for the security compute.
1006  *
1007  * Don't inline this, since it's the slow-path and just
1008  * results in a bigger stack frame.
1009  */
1010 static noinline
1011 struct avc_node *avc_compute_av(struct selinux_state *state,
1012                                 u32 ssid, u32 tsid,
1013                                 u16 tclass, struct av_decision *avd,
1014                                 struct avc_xperms_node *xp_node)
1015 {
1016         rcu_read_unlock();
1017         INIT_LIST_HEAD(&xp_node->xpd_head);
1018         security_compute_av(state, ssid, tsid, tclass, avd, &xp_node->xp);
1019         rcu_read_lock();
1020         return avc_insert(state->avc, ssid, tsid, tclass, avd, xp_node);
1021 }
1022 
1023 static noinline int avc_denied(struct selinux_state *state,
1024                                u32 ssid, u32 tsid,
1025                                u16 tclass, u32 requested,
1026                                u8 driver, u8 xperm, unsigned int flags,
1027                                struct av_decision *avd)
1028 {
1029         if (flags & AVC_STRICT)
1030                 return -EACCES;
1031 
1032         if (enforcing_enabled(state) &&
1033             !(avd->flags & AVD_FLAGS_PERMISSIVE))
1034                 return -EACCES;
1035 
1036         avc_update_node(state->avc, AVC_CALLBACK_GRANT, requested, driver,
1037                         xperm, ssid, tsid, tclass, avd->seqno, NULL, flags);
1038         return 0;
1039 }
1040 
1041 /*
1042  * The avc extended permissions logic adds an additional 256 bits of
1043  * permissions to an avc node when extended permissions for that node are
1044  * specified in the avtab. If the additional 256 permissions is not adequate,
1045  * as-is the case with ioctls, then multiple may be chained together and the
1046  * driver field is used to specify which set contains the permission.
1047  */
1048 int avc_has_extended_perms(struct selinux_state *state,
1049                            u32 ssid, u32 tsid, u16 tclass, u32 requested,
1050                            u8 driver, u8 xperm, struct common_audit_data *ad)
1051 {
1052         struct avc_node *node;
1053         struct av_decision avd;
1054         u32 denied;
1055         struct extended_perms_decision local_xpd;
1056         struct extended_perms_decision *xpd = NULL;
1057         struct extended_perms_data allowed;
1058         struct extended_perms_data auditallow;
1059         struct extended_perms_data dontaudit;
1060         struct avc_xperms_node local_xp_node;
1061         struct avc_xperms_node *xp_node;
1062         int rc = 0, rc2;
1063 
1064         xp_node = &local_xp_node;
1065         if (WARN_ON(!requested))
1066                 return -EACCES;
1067 
1068         rcu_read_lock();
1069 
1070         node = avc_lookup(state->avc, ssid, tsid, tclass);
1071         if (unlikely(!node)) {
1072                 node = avc_compute_av(state, ssid, tsid, tclass, &avd, xp_node);
1073         } else {
1074                 memcpy(&avd, &node->ae.avd, sizeof(avd));
1075                 xp_node = node->ae.xp_node;
1076         }
1077         /* if extended permissions are not defined, only consider av_decision */
1078         if (!xp_node || !xp_node->xp.len)
1079                 goto decision;
1080 
1081         local_xpd.allowed = &allowed;
1082         local_xpd.auditallow = &auditallow;
1083         local_xpd.dontaudit = &dontaudit;
1084 
1085         xpd = avc_xperms_decision_lookup(driver, xp_node);
1086         if (unlikely(!xpd)) {
1087                 /*
1088                  * Compute the extended_perms_decision only if the driver
1089                  * is flagged
1090                  */
1091                 if (!security_xperm_test(xp_node->xp.drivers.p, driver)) {
1092                         avd.allowed &= ~requested;
1093                         goto decision;
1094                 }
1095                 rcu_read_unlock();
1096                 security_compute_xperms_decision(state, ssid, tsid, tclass,
1097                                                  driver, &local_xpd);
1098                 rcu_read_lock();
1099                 avc_update_node(state->avc, AVC_CALLBACK_ADD_XPERMS, requested,
1100                                 driver, xperm, ssid, tsid, tclass, avd.seqno,
1101                                 &local_xpd, 0);
1102         } else {
1103                 avc_quick_copy_xperms_decision(xperm, &local_xpd, xpd);
1104         }
1105         xpd = &local_xpd;
1106 
1107         if (!avc_xperms_has_perm(xpd, xperm, XPERMS_ALLOWED))
1108                 avd.allowed &= ~requested;
1109 
1110 decision:
1111         denied = requested & ~(avd.allowed);
1112         if (unlikely(denied))
1113                 rc = avc_denied(state, ssid, tsid, tclass, requested,
1114                                 driver, xperm, AVC_EXTENDED_PERMS, &avd);
1115 
1116         rcu_read_unlock();
1117 
1118         rc2 = avc_xperms_audit(state, ssid, tsid, tclass, requested,
1119                         &avd, xpd, xperm, rc, ad);
1120         if (rc2)
1121                 return rc2;
1122         return rc;
1123 }
1124 
1125 /**
1126  * avc_has_perm_noaudit - Check permissions but perform no auditing.
1127  * @ssid: source security identifier
1128  * @tsid: target security identifier
1129  * @tclass: target security class
1130  * @requested: requested permissions, interpreted based on @tclass
1131  * @flags:  AVC_STRICT, AVC_NONBLOCKING, or 0
1132  * @avd: access vector decisions
1133  *
1134  * Check the AVC to determine whether the @requested permissions are granted
1135  * for the SID pair (@ssid, @tsid), interpreting the permissions
1136  * based on @tclass, and call the security server on a cache miss to obtain
1137  * a new decision and add it to the cache.  Return a copy of the decisions
1138  * in @avd.  Return %0 if all @requested permissions are granted,
1139  * -%EACCES if any permissions are denied, or another -errno upon
1140  * other errors.  This function is typically called by avc_has_perm(),
1141  * but may also be called directly to separate permission checking from
1142  * auditing, e.g. in cases where a lock must be held for the check but
1143  * should be released for the auditing.
1144  */
1145 inline int avc_has_perm_noaudit(struct selinux_state *state,
1146                                 u32 ssid, u32 tsid,
1147                                 u16 tclass, u32 requested,
1148                                 unsigned int flags,
1149                                 struct av_decision *avd)
1150 {
1151         struct avc_node *node;
1152         struct avc_xperms_node xp_node;
1153         int rc = 0;
1154         u32 denied;
1155 
1156         if (WARN_ON(!requested))
1157                 return -EACCES;
1158 
1159         rcu_read_lock();
1160 
1161         node = avc_lookup(state->avc, ssid, tsid, tclass);
1162         if (unlikely(!node))
1163                 node = avc_compute_av(state, ssid, tsid, tclass, avd, &xp_node);
1164         else
1165                 memcpy(avd, &node->ae.avd, sizeof(*avd));
1166 
1167         denied = requested & ~(avd->allowed);
1168         if (unlikely(denied))
1169                 rc = avc_denied(state, ssid, tsid, tclass, requested, 0, 0,
1170                                 flags, avd);
1171 
1172         rcu_read_unlock();
1173         return rc;
1174 }
1175 
1176 /**
1177  * avc_has_perm - Check permissions and perform any appropriate auditing.
1178  * @ssid: source security identifier
1179  * @tsid: target security identifier
1180  * @tclass: target security class
1181  * @requested: requested permissions, interpreted based on @tclass
1182  * @auditdata: auxiliary audit data
1183  *
1184  * Check the AVC to determine whether the @requested permissions are granted
1185  * for the SID pair (@ssid, @tsid), interpreting the permissions
1186  * based on @tclass, and call the security server on a cache miss to obtain
1187  * a new decision and add it to the cache.  Audit the granting or denial of
1188  * permissions in accordance with the policy.  Return %0 if all @requested
1189  * permissions are granted, -%EACCES if any permissions are denied, or
1190  * another -errno upon other errors.
1191  */
1192 int avc_has_perm(struct selinux_state *state, u32 ssid, u32 tsid, u16 tclass,
1193                  u32 requested, struct common_audit_data *auditdata)
1194 {
1195         struct av_decision avd;
1196         int rc, rc2;
1197 
1198         rc = avc_has_perm_noaudit(state, ssid, tsid, tclass, requested, 0,
1199                                   &avd);
1200 
1201         rc2 = avc_audit(state, ssid, tsid, tclass, requested, &avd, rc,
1202                         auditdata, 0);
1203         if (rc2)
1204                 return rc2;
1205         return rc;
1206 }
1207 
1208 u32 avc_policy_seqno(struct selinux_state *state)
1209 {
1210         return state->avc->avc_cache.latest_notif;
1211 }
1212 
1213 void avc_disable(void)
1214 {
1215         /*
1216          * If you are looking at this because you have realized that we are
1217          * not destroying the avc_node_cachep it might be easy to fix, but
1218          * I don't know the memory barrier semantics well enough to know.  It's
1219          * possible that some other task dereferenced security_ops when
1220          * it still pointed to selinux operations.  If that is the case it's
1221          * possible that it is about to use the avc and is about to need the
1222          * avc_node_cachep.  I know I could wrap the security.c security_ops call
1223          * in an rcu_lock, but seriously, it's not worth it.  Instead I just flush
1224          * the cache and get that memory back.
1225          */
1226         if (avc_node_cachep) {
1227                 avc_flush(selinux_state.avc);
1228                 /* kmem_cache_destroy(avc_node_cachep); */
1229         }
1230 }
1231 

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