1 // SPDX-License-Identifier: GPL-2.0
3 * Implementation of the SID table type.
5 * Original author: Stephen Smalley, <sds@tycho.nsa.gov>
6 * Author: Ondrej Mosnacek, <omosnacek@gmail.com>
8 * Copyright (C) 2018 Red Hat, Inc.
10 #include <linux/errno.h>
11 #include <linux/kernel.h>
12 #include <linux/list.h>
13 #include <linux/rcupdate.h>
14 #include <linux/slab.h>
15 #include <linux/sched.h>
16 #include <linux/spinlock.h>
17 #include <asm/barrier.h>
22 struct sidtab_str_cache {
23 struct rcu_head rcu_member;
24 struct list_head lru_member;
25 struct sidtab_entry *parent;
30 #define index_to_sid(index) (index + SECINITSID_NUM + 1)
31 #define sid_to_index(sid) (sid - (SECINITSID_NUM + 1))
33 int sidtab_init(struct sidtab *s)
37 memset(s->roots, 0, sizeof(s->roots));
39 for (i = 0; i < SECINITSID_NUM; i++)
45 hash_init(s->context_to_sid);
47 spin_lock_init(&s->lock);
49 #if CONFIG_SECURITY_SELINUX_SID2STR_CACHE_SIZE > 0
50 s->cache_free_slots = CONFIG_SECURITY_SELINUX_SID2STR_CACHE_SIZE;
51 INIT_LIST_HEAD(&s->cache_lru_list);
52 spin_lock_init(&s->cache_lock);
58 static u32 context_to_sid(struct sidtab *s, struct context *context, u32 hash)
60 struct sidtab_entry *entry;
64 hash_for_each_possible_rcu(s->context_to_sid, entry, list, hash) {
65 if (entry->hash != hash)
67 if (context_cmp(&entry->context, context)) {
76 int sidtab_set_initial(struct sidtab *s, u32 sid, struct context *context)
78 struct sidtab_isid_entry *isid;
82 if (sid == 0 || sid > SECINITSID_NUM)
85 isid = &s->isids[sid - 1];
87 rc = context_cpy(&isid->entry.context, context);
91 #if CONFIG_SECURITY_SELINUX_SID2STR_CACHE_SIZE > 0
92 isid->entry.cache = NULL;
96 hash = context_compute_hash(context);
99 * Multiple initial sids may map to the same context. Check that this
100 * context is not already represented in the context_to_sid hashtable
101 * to avoid duplicate entries and long linked lists upon hash
104 if (!context_to_sid(s, context, hash)) {
105 isid->entry.sid = sid;
106 isid->entry.hash = hash;
107 hash_add(s->context_to_sid, &isid->entry.list, hash);
113 int sidtab_hash_stats(struct sidtab *sidtab, char *page)
119 int max_chain_len = 0;
121 struct sidtab_entry *entry;
124 hash_for_each_rcu(sidtab->context_to_sid, i, entry, list) {
126 if (i == cur_bucket) {
132 if (chain_len > max_chain_len)
133 max_chain_len = chain_len;
139 if (chain_len > max_chain_len)
140 max_chain_len = chain_len;
142 return scnprintf(page, PAGE_SIZE, "entries: %d\nbuckets used: %d/%d\n"
143 "longest chain: %d\n", entries,
144 slots_used, SIDTAB_HASH_BUCKETS, max_chain_len);
147 static u32 sidtab_level_from_count(u32 count)
149 u32 capacity = SIDTAB_LEAF_ENTRIES;
152 while (count > capacity) {
153 capacity <<= SIDTAB_INNER_SHIFT;
159 static int sidtab_alloc_roots(struct sidtab *s, u32 level)
163 if (!s->roots[0].ptr_leaf) {
164 s->roots[0].ptr_leaf = kzalloc(SIDTAB_NODE_ALLOC_SIZE,
166 if (!s->roots[0].ptr_leaf)
169 for (l = 1; l <= level; ++l)
170 if (!s->roots[l].ptr_inner) {
171 s->roots[l].ptr_inner = kzalloc(SIDTAB_NODE_ALLOC_SIZE,
173 if (!s->roots[l].ptr_inner)
175 s->roots[l].ptr_inner->entries[0] = s->roots[l - 1];
180 static struct sidtab_entry *sidtab_do_lookup(struct sidtab *s, u32 index,
183 union sidtab_entry_inner *entry;
184 u32 level, capacity_shift, leaf_index = index / SIDTAB_LEAF_ENTRIES;
186 /* find the level of the subtree we need */
187 level = sidtab_level_from_count(index + 1);
188 capacity_shift = level * SIDTAB_INNER_SHIFT;
190 /* allocate roots if needed */
191 if (alloc && sidtab_alloc_roots(s, level) != 0)
194 /* lookup inside the subtree */
195 entry = &s->roots[level];
197 capacity_shift -= SIDTAB_INNER_SHIFT;
200 entry = &entry->ptr_inner->entries[leaf_index >> capacity_shift];
201 leaf_index &= ((u32)1 << capacity_shift) - 1;
203 if (!entry->ptr_inner) {
205 entry->ptr_inner = kzalloc(SIDTAB_NODE_ALLOC_SIZE,
207 if (!entry->ptr_inner)
211 if (!entry->ptr_leaf) {
213 entry->ptr_leaf = kzalloc(SIDTAB_NODE_ALLOC_SIZE,
215 if (!entry->ptr_leaf)
218 return &entry->ptr_leaf->entries[index % SIDTAB_LEAF_ENTRIES];
221 static struct sidtab_entry *sidtab_lookup(struct sidtab *s, u32 index)
223 /* read entries only after reading count */
224 u32 count = smp_load_acquire(&s->count);
229 return sidtab_do_lookup(s, index, 0);
232 static struct sidtab_entry *sidtab_lookup_initial(struct sidtab *s, u32 sid)
234 return s->isids[sid - 1].set ? &s->isids[sid - 1].entry : NULL;
237 static struct sidtab_entry *sidtab_search_core(struct sidtab *s, u32 sid,
241 struct sidtab_entry *entry;
243 if (sid > SECINITSID_NUM)
244 entry = sidtab_lookup(s, sid_to_index(sid));
246 entry = sidtab_lookup_initial(s, sid);
247 if (entry && (!entry->context.len || force))
251 return sidtab_lookup_initial(s, SECINITSID_UNLABELED);
254 struct sidtab_entry *sidtab_search_entry(struct sidtab *s, u32 sid)
256 return sidtab_search_core(s, sid, 0);
259 struct sidtab_entry *sidtab_search_entry_force(struct sidtab *s, u32 sid)
261 return sidtab_search_core(s, sid, 1);
264 int sidtab_context_to_sid(struct sidtab *s, struct context *context,
268 u32 count, hash = context_compute_hash(context);
269 struct sidtab_convert_params *convert;
270 struct sidtab_entry *dst, *dst_convert;
273 *sid = context_to_sid(s, context, hash);
277 /* lock-free search failed: lock, re-search, and insert if not found */
278 spin_lock_irqsave(&s->lock, flags);
281 *sid = context_to_sid(s, context, hash);
285 if (unlikely(s->frozen)) {
287 * This sidtab is now frozen - tell the caller to abort and
295 convert = s->convert;
297 /* bail out if we already reached max entries */
299 if (count >= SIDTAB_MAX)
302 /* insert context into new entry */
304 dst = sidtab_do_lookup(s, count, 1);
308 dst->sid = index_to_sid(count);
311 rc = context_cpy(&dst->context, context);
316 * if we are building a new sidtab, we need to convert the context
317 * and insert it there as well
321 dst_convert = sidtab_do_lookup(convert->target, count, 1);
323 context_destroy(&dst->context);
327 rc = convert->func(context, &dst_convert->context,
328 convert->args, GFP_ATOMIC);
330 context_destroy(&dst->context);
333 dst_convert->sid = index_to_sid(count);
334 dst_convert->hash = context_compute_hash(&dst_convert->context);
335 convert->target->count = count + 1;
337 hash_add_rcu(convert->target->context_to_sid,
338 &dst_convert->list, dst_convert->hash);
342 pr_info("SELinux: Context %s is not valid (left unmapped).\n",
345 *sid = index_to_sid(count);
347 /* write entries before updating count */
348 smp_store_release(&s->count, count + 1);
349 hash_add_rcu(s->context_to_sid, &dst->list, dst->hash);
353 spin_unlock_irqrestore(&s->lock, flags);
357 static void sidtab_convert_hashtable(struct sidtab *s, u32 count)
359 struct sidtab_entry *entry;
362 for (i = 0; i < count; i++) {
363 entry = sidtab_do_lookup(s, i, 0);
364 entry->sid = index_to_sid(i);
365 entry->hash = context_compute_hash(&entry->context);
367 hash_add_rcu(s->context_to_sid, &entry->list, entry->hash);
371 static int sidtab_convert_tree(union sidtab_entry_inner *edst,
372 union sidtab_entry_inner *esrc,
373 u32 *pos, u32 count, u32 level,
374 struct sidtab_convert_params *convert)
380 if (!edst->ptr_inner) {
381 edst->ptr_inner = kzalloc(SIDTAB_NODE_ALLOC_SIZE,
383 if (!edst->ptr_inner)
387 while (i < SIDTAB_INNER_ENTRIES && *pos < count) {
388 rc = sidtab_convert_tree(&edst->ptr_inner->entries[i],
389 &esrc->ptr_inner->entries[i],
390 pos, count, level - 1,
397 if (!edst->ptr_leaf) {
398 edst->ptr_leaf = kzalloc(SIDTAB_NODE_ALLOC_SIZE,
404 while (i < SIDTAB_LEAF_ENTRIES && *pos < count) {
405 rc = convert->func(&esrc->ptr_leaf->entries[i].context,
406 &edst->ptr_leaf->entries[i].context,
407 convert->args, GFP_KERNEL);
418 int sidtab_convert(struct sidtab *s, struct sidtab_convert_params *params)
421 u32 count, level, pos;
424 spin_lock_irqsave(&s->lock, flags);
426 /* concurrent policy loads are not allowed */
428 spin_unlock_irqrestore(&s->lock, flags);
433 level = sidtab_level_from_count(count);
435 /* allocate last leaf in the new sidtab (to avoid race with
438 rc = sidtab_do_lookup(params->target, count - 1, 1) ? 0 : -ENOMEM;
440 spin_unlock_irqrestore(&s->lock, flags);
444 /* set count in case no new entries are added during conversion */
445 params->target->count = count;
447 /* enable live convert of new entries */
450 /* we can safely convert the tree outside the lock */
451 spin_unlock_irqrestore(&s->lock, flags);
453 pr_info("SELinux: Converting %u SID table entries...\n", count);
455 /* convert all entries not covered by live convert */
457 rc = sidtab_convert_tree(¶ms->target->roots[level],
458 &s->roots[level], &pos, count, level, params);
460 /* we need to keep the old table - disable live convert */
461 spin_lock_irqsave(&s->lock, flags);
463 spin_unlock_irqrestore(&s->lock, flags);
467 * The hashtable can also be modified in sidtab_context_to_sid()
468 * so we must re-acquire the lock here.
470 spin_lock_irqsave(&s->lock, flags);
471 sidtab_convert_hashtable(params->target, count);
472 spin_unlock_irqrestore(&s->lock, flags);
477 void sidtab_cancel_convert(struct sidtab *s)
481 /* cancelling policy load - disable live convert of sidtab */
482 spin_lock_irqsave(&s->lock, flags);
484 spin_unlock_irqrestore(&s->lock, flags);
487 void sidtab_freeze_begin(struct sidtab *s, unsigned long *flags) __acquires(&s->lock)
489 spin_lock_irqsave(&s->lock, *flags);
493 void sidtab_freeze_end(struct sidtab *s, unsigned long *flags) __releases(&s->lock)
495 spin_unlock_irqrestore(&s->lock, *flags);
498 static void sidtab_destroy_entry(struct sidtab_entry *entry)
500 context_destroy(&entry->context);
501 #if CONFIG_SECURITY_SELINUX_SID2STR_CACHE_SIZE > 0
502 kfree(rcu_dereference_raw(entry->cache));
506 static void sidtab_destroy_tree(union sidtab_entry_inner entry, u32 level)
511 struct sidtab_node_inner *node = entry.ptr_inner;
516 for (i = 0; i < SIDTAB_INNER_ENTRIES; i++)
517 sidtab_destroy_tree(node->entries[i], level - 1);
520 struct sidtab_node_leaf *node = entry.ptr_leaf;
525 for (i = 0; i < SIDTAB_LEAF_ENTRIES; i++)
526 sidtab_destroy_entry(&node->entries[i]);
531 void sidtab_destroy(struct sidtab *s)
535 for (i = 0; i < SECINITSID_NUM; i++)
537 sidtab_destroy_entry(&s->isids[i].entry);
539 level = SIDTAB_MAX_LEVEL;
540 while (level && !s->roots[level].ptr_inner)
543 sidtab_destroy_tree(s->roots[level], level);
545 * The context_to_sid hashtable's objects are all shared
546 * with the isids array and context tree, and so don't need
547 * to be cleaned up here.
551 #if CONFIG_SECURITY_SELINUX_SID2STR_CACHE_SIZE > 0
553 void sidtab_sid2str_put(struct sidtab *s, struct sidtab_entry *entry,
554 const char *str, u32 str_len)
556 struct sidtab_str_cache *cache, *victim = NULL;
559 /* do not cache invalid contexts */
560 if (entry->context.len)
563 spin_lock_irqsave(&s->cache_lock, flags);
565 cache = rcu_dereference_protected(entry->cache,
566 lockdep_is_held(&s->cache_lock));
568 /* entry in cache - just bump to the head of LRU list */
569 list_move(&cache->lru_member, &s->cache_lru_list);
573 cache = kmalloc(sizeof(struct sidtab_str_cache) + str_len, GFP_ATOMIC);
577 if (s->cache_free_slots == 0) {
578 /* pop a cache entry from the tail and free it */
579 victim = container_of(s->cache_lru_list.prev,
580 struct sidtab_str_cache, lru_member);
581 list_del(&victim->lru_member);
582 rcu_assign_pointer(victim->parent->cache, NULL);
584 s->cache_free_slots--;
586 cache->parent = entry;
587 cache->len = str_len;
588 memcpy(cache->str, str, str_len);
589 list_add(&cache->lru_member, &s->cache_lru_list);
591 rcu_assign_pointer(entry->cache, cache);
594 spin_unlock_irqrestore(&s->cache_lock, flags);
595 kfree_rcu(victim, rcu_member);
598 int sidtab_sid2str_get(struct sidtab *s, struct sidtab_entry *entry,
599 char **out, u32 *out_len)
601 struct sidtab_str_cache *cache;
604 if (entry->context.len)
605 return -ENOENT; /* do not cache invalid contexts */
609 cache = rcu_dereference(entry->cache);
613 *out_len = cache->len;
615 *out = kmemdup(cache->str, cache->len, GFP_ATOMIC);
624 sidtab_sid2str_put(s, entry, *out, *out_len);
628 #endif /* CONFIG_SECURITY_SELINUX_SID2STR_CACHE_SIZE > 0 */