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-rw-r--r--security/selinux/ss/sidtab.c628
1 files changed, 628 insertions, 0 deletions
diff --git a/security/selinux/ss/sidtab.c b/security/selinux/ss/sidtab.c
new file mode 100644
index 000000000..db5cce385
--- /dev/null
+++ b/security/selinux/ss/sidtab.c
@@ -0,0 +1,628 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Implementation of the SID table type.
+ *
+ * Original author: Stephen Smalley, <sds@tycho.nsa.gov>
+ * Author: Ondrej Mosnacek, <omosnacek@gmail.com>
+ *
+ * Copyright (C) 2018 Red Hat, Inc.
+ */
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/list.h>
+#include <linux/rcupdate.h>
+#include <linux/slab.h>
+#include <linux/sched.h>
+#include <linux/spinlock.h>
+#include <asm/barrier.h>
+#include "flask.h"
+#include "security.h"
+#include "sidtab.h"
+
+struct sidtab_str_cache {
+ struct rcu_head rcu_member;
+ struct list_head lru_member;
+ struct sidtab_entry *parent;
+ u32 len;
+ char str[];
+};
+
+#define index_to_sid(index) ((index) + SECINITSID_NUM + 1)
+#define sid_to_index(sid) ((sid) - (SECINITSID_NUM + 1))
+
+int sidtab_init(struct sidtab *s)
+{
+ u32 i;
+
+ memset(s->roots, 0, sizeof(s->roots));
+
+ for (i = 0; i < SECINITSID_NUM; i++)
+ s->isids[i].set = 0;
+
+ s->frozen = false;
+ s->count = 0;
+ s->convert = NULL;
+ hash_init(s->context_to_sid);
+
+ spin_lock_init(&s->lock);
+
+#if CONFIG_SECURITY_SELINUX_SID2STR_CACHE_SIZE > 0
+ s->cache_free_slots = CONFIG_SECURITY_SELINUX_SID2STR_CACHE_SIZE;
+ INIT_LIST_HEAD(&s->cache_lru_list);
+ spin_lock_init(&s->cache_lock);
+#endif
+
+ return 0;
+}
+
+static u32 context_to_sid(struct sidtab *s, struct context *context, u32 hash)
+{
+ struct sidtab_entry *entry;
+ u32 sid = 0;
+
+ rcu_read_lock();
+ hash_for_each_possible_rcu(s->context_to_sid, entry, list, hash) {
+ if (entry->hash != hash)
+ continue;
+ if (context_cmp(&entry->context, context)) {
+ sid = entry->sid;
+ break;
+ }
+ }
+ rcu_read_unlock();
+ return sid;
+}
+
+int sidtab_set_initial(struct sidtab *s, u32 sid, struct context *context)
+{
+ struct sidtab_isid_entry *isid;
+ u32 hash;
+ int rc;
+
+ if (sid == 0 || sid > SECINITSID_NUM)
+ return -EINVAL;
+
+ isid = &s->isids[sid - 1];
+
+ rc = context_cpy(&isid->entry.context, context);
+ if (rc)
+ return rc;
+
+#if CONFIG_SECURITY_SELINUX_SID2STR_CACHE_SIZE > 0
+ isid->entry.cache = NULL;
+#endif
+ isid->set = 1;
+
+ hash = context_compute_hash(context);
+
+ /*
+ * Multiple initial sids may map to the same context. Check that this
+ * context is not already represented in the context_to_sid hashtable
+ * to avoid duplicate entries and long linked lists upon hash
+ * collision.
+ */
+ if (!context_to_sid(s, context, hash)) {
+ isid->entry.sid = sid;
+ isid->entry.hash = hash;
+ hash_add(s->context_to_sid, &isid->entry.list, hash);
+ }
+
+ return 0;
+}
+
+int sidtab_hash_stats(struct sidtab *sidtab, char *page)
+{
+ int i;
+ int chain_len = 0;
+ int slots_used = 0;
+ int entries = 0;
+ int max_chain_len = 0;
+ int cur_bucket = 0;
+ struct sidtab_entry *entry;
+
+ rcu_read_lock();
+ hash_for_each_rcu(sidtab->context_to_sid, i, entry, list) {
+ entries++;
+ if (i == cur_bucket) {
+ chain_len++;
+ if (chain_len == 1)
+ slots_used++;
+ } else {
+ cur_bucket = i;
+ if (chain_len > max_chain_len)
+ max_chain_len = chain_len;
+ chain_len = 0;
+ }
+ }
+ rcu_read_unlock();
+
+ if (chain_len > max_chain_len)
+ max_chain_len = chain_len;
+
+ return scnprintf(page, PAGE_SIZE, "entries: %d\nbuckets used: %d/%d\n"
+ "longest chain: %d\n", entries,
+ slots_used, SIDTAB_HASH_BUCKETS, max_chain_len);
+}
+
+static u32 sidtab_level_from_count(u32 count)
+{
+ u32 capacity = SIDTAB_LEAF_ENTRIES;
+ u32 level = 0;
+
+ while (count > capacity) {
+ capacity <<= SIDTAB_INNER_SHIFT;
+ ++level;
+ }
+ return level;
+}
+
+static int sidtab_alloc_roots(struct sidtab *s, u32 level)
+{
+ u32 l;
+
+ if (!s->roots[0].ptr_leaf) {
+ s->roots[0].ptr_leaf = kzalloc(SIDTAB_NODE_ALLOC_SIZE,
+ GFP_ATOMIC);
+ if (!s->roots[0].ptr_leaf)
+ return -ENOMEM;
+ }
+ for (l = 1; l <= level; ++l)
+ if (!s->roots[l].ptr_inner) {
+ s->roots[l].ptr_inner = kzalloc(SIDTAB_NODE_ALLOC_SIZE,
+ GFP_ATOMIC);
+ if (!s->roots[l].ptr_inner)
+ return -ENOMEM;
+ s->roots[l].ptr_inner->entries[0] = s->roots[l - 1];
+ }
+ return 0;
+}
+
+static struct sidtab_entry *sidtab_do_lookup(struct sidtab *s, u32 index,
+ int alloc)
+{
+ union sidtab_entry_inner *entry;
+ u32 level, capacity_shift, leaf_index = index / SIDTAB_LEAF_ENTRIES;
+
+ /* find the level of the subtree we need */
+ level = sidtab_level_from_count(index + 1);
+ capacity_shift = level * SIDTAB_INNER_SHIFT;
+
+ /* allocate roots if needed */
+ if (alloc && sidtab_alloc_roots(s, level) != 0)
+ return NULL;
+
+ /* lookup inside the subtree */
+ entry = &s->roots[level];
+ while (level != 0) {
+ capacity_shift -= SIDTAB_INNER_SHIFT;
+ --level;
+
+ entry = &entry->ptr_inner->entries[leaf_index >> capacity_shift];
+ leaf_index &= ((u32)1 << capacity_shift) - 1;
+
+ if (!entry->ptr_inner) {
+ if (alloc)
+ entry->ptr_inner = kzalloc(SIDTAB_NODE_ALLOC_SIZE,
+ GFP_ATOMIC);
+ if (!entry->ptr_inner)
+ return NULL;
+ }
+ }
+ if (!entry->ptr_leaf) {
+ if (alloc)
+ entry->ptr_leaf = kzalloc(SIDTAB_NODE_ALLOC_SIZE,
+ GFP_ATOMIC);
+ if (!entry->ptr_leaf)
+ return NULL;
+ }
+ return &entry->ptr_leaf->entries[index % SIDTAB_LEAF_ENTRIES];
+}
+
+static struct sidtab_entry *sidtab_lookup(struct sidtab *s, u32 index)
+{
+ /* read entries only after reading count */
+ u32 count = smp_load_acquire(&s->count);
+
+ if (index >= count)
+ return NULL;
+
+ return sidtab_do_lookup(s, index, 0);
+}
+
+static struct sidtab_entry *sidtab_lookup_initial(struct sidtab *s, u32 sid)
+{
+ return s->isids[sid - 1].set ? &s->isids[sid - 1].entry : NULL;
+}
+
+static struct sidtab_entry *sidtab_search_core(struct sidtab *s, u32 sid,
+ int force)
+{
+ if (sid != 0) {
+ struct sidtab_entry *entry;
+
+ if (sid > SECINITSID_NUM)
+ entry = sidtab_lookup(s, sid_to_index(sid));
+ else
+ entry = sidtab_lookup_initial(s, sid);
+ if (entry && (!entry->context.len || force))
+ return entry;
+ }
+
+ return sidtab_lookup_initial(s, SECINITSID_UNLABELED);
+}
+
+struct sidtab_entry *sidtab_search_entry(struct sidtab *s, u32 sid)
+{
+ return sidtab_search_core(s, sid, 0);
+}
+
+struct sidtab_entry *sidtab_search_entry_force(struct sidtab *s, u32 sid)
+{
+ return sidtab_search_core(s, sid, 1);
+}
+
+int sidtab_context_to_sid(struct sidtab *s, struct context *context,
+ u32 *sid)
+{
+ unsigned long flags;
+ u32 count, hash = context_compute_hash(context);
+ struct sidtab_convert_params *convert;
+ struct sidtab_entry *dst, *dst_convert;
+ int rc;
+
+ *sid = context_to_sid(s, context, hash);
+ if (*sid)
+ return 0;
+
+ /* lock-free search failed: lock, re-search, and insert if not found */
+ spin_lock_irqsave(&s->lock, flags);
+
+ rc = 0;
+ *sid = context_to_sid(s, context, hash);
+ if (*sid)
+ goto out_unlock;
+
+ if (unlikely(s->frozen)) {
+ /*
+ * This sidtab is now frozen - tell the caller to abort and
+ * get the new one.
+ */
+ rc = -ESTALE;
+ goto out_unlock;
+ }
+
+ count = s->count;
+ convert = s->convert;
+
+ /* bail out if we already reached max entries */
+ rc = -EOVERFLOW;
+ if (count >= SIDTAB_MAX)
+ goto out_unlock;
+
+ /* insert context into new entry */
+ rc = -ENOMEM;
+ dst = sidtab_do_lookup(s, count, 1);
+ if (!dst)
+ goto out_unlock;
+
+ dst->sid = index_to_sid(count);
+ dst->hash = hash;
+
+ rc = context_cpy(&dst->context, context);
+ if (rc)
+ goto out_unlock;
+
+ /*
+ * if we are building a new sidtab, we need to convert the context
+ * and insert it there as well
+ */
+ if (convert) {
+ rc = -ENOMEM;
+ dst_convert = sidtab_do_lookup(convert->target, count, 1);
+ if (!dst_convert) {
+ context_destroy(&dst->context);
+ goto out_unlock;
+ }
+
+ rc = convert->func(context, &dst_convert->context,
+ convert->args, GFP_ATOMIC);
+ if (rc) {
+ context_destroy(&dst->context);
+ goto out_unlock;
+ }
+ dst_convert->sid = index_to_sid(count);
+ dst_convert->hash = context_compute_hash(&dst_convert->context);
+ convert->target->count = count + 1;
+
+ hash_add_rcu(convert->target->context_to_sid,
+ &dst_convert->list, dst_convert->hash);
+ }
+
+ if (context->len)
+ pr_info("SELinux: Context %s is not valid (left unmapped).\n",
+ context->str);
+
+ *sid = index_to_sid(count);
+
+ /* write entries before updating count */
+ smp_store_release(&s->count, count + 1);
+ hash_add_rcu(s->context_to_sid, &dst->list, dst->hash);
+
+ rc = 0;
+out_unlock:
+ spin_unlock_irqrestore(&s->lock, flags);
+ return rc;
+}
+
+static void sidtab_convert_hashtable(struct sidtab *s, u32 count)
+{
+ struct sidtab_entry *entry;
+ u32 i;
+
+ for (i = 0; i < count; i++) {
+ entry = sidtab_do_lookup(s, i, 0);
+ entry->sid = index_to_sid(i);
+ entry->hash = context_compute_hash(&entry->context);
+
+ hash_add_rcu(s->context_to_sid, &entry->list, entry->hash);
+ }
+}
+
+static int sidtab_convert_tree(union sidtab_entry_inner *edst,
+ union sidtab_entry_inner *esrc,
+ u32 *pos, u32 count, u32 level,
+ struct sidtab_convert_params *convert)
+{
+ int rc;
+ u32 i;
+
+ if (level != 0) {
+ if (!edst->ptr_inner) {
+ edst->ptr_inner = kzalloc(SIDTAB_NODE_ALLOC_SIZE,
+ GFP_KERNEL);
+ if (!edst->ptr_inner)
+ return -ENOMEM;
+ }
+ i = 0;
+ while (i < SIDTAB_INNER_ENTRIES && *pos < count) {
+ rc = sidtab_convert_tree(&edst->ptr_inner->entries[i],
+ &esrc->ptr_inner->entries[i],
+ pos, count, level - 1,
+ convert);
+ if (rc)
+ return rc;
+ i++;
+ }
+ } else {
+ if (!edst->ptr_leaf) {
+ edst->ptr_leaf = kzalloc(SIDTAB_NODE_ALLOC_SIZE,
+ GFP_KERNEL);
+ if (!edst->ptr_leaf)
+ return -ENOMEM;
+ }
+ i = 0;
+ while (i < SIDTAB_LEAF_ENTRIES && *pos < count) {
+ rc = convert->func(&esrc->ptr_leaf->entries[i].context,
+ &edst->ptr_leaf->entries[i].context,
+ convert->args, GFP_KERNEL);
+ if (rc)
+ return rc;
+ (*pos)++;
+ i++;
+ }
+ cond_resched();
+ }
+ return 0;
+}
+
+int sidtab_convert(struct sidtab *s, struct sidtab_convert_params *params)
+{
+ unsigned long flags;
+ u32 count, level, pos;
+ int rc;
+
+ spin_lock_irqsave(&s->lock, flags);
+
+ /* concurrent policy loads are not allowed */
+ if (s->convert) {
+ spin_unlock_irqrestore(&s->lock, flags);
+ return -EBUSY;
+ }
+
+ count = s->count;
+ level = sidtab_level_from_count(count);
+
+ /* allocate last leaf in the new sidtab (to avoid race with
+ * live convert)
+ */
+ rc = sidtab_do_lookup(params->target, count - 1, 1) ? 0 : -ENOMEM;
+ if (rc) {
+ spin_unlock_irqrestore(&s->lock, flags);
+ return rc;
+ }
+
+ /* set count in case no new entries are added during conversion */
+ params->target->count = count;
+
+ /* enable live convert of new entries */
+ s->convert = params;
+
+ /* we can safely convert the tree outside the lock */
+ spin_unlock_irqrestore(&s->lock, flags);
+
+ pr_info("SELinux: Converting %u SID table entries...\n", count);
+
+ /* convert all entries not covered by live convert */
+ pos = 0;
+ rc = sidtab_convert_tree(&params->target->roots[level],
+ &s->roots[level], &pos, count, level, params);
+ if (rc) {
+ /* we need to keep the old table - disable live convert */
+ spin_lock_irqsave(&s->lock, flags);
+ s->convert = NULL;
+ spin_unlock_irqrestore(&s->lock, flags);
+ return rc;
+ }
+ /*
+ * The hashtable can also be modified in sidtab_context_to_sid()
+ * so we must re-acquire the lock here.
+ */
+ spin_lock_irqsave(&s->lock, flags);
+ sidtab_convert_hashtable(params->target, count);
+ spin_unlock_irqrestore(&s->lock, flags);
+
+ return 0;
+}
+
+void sidtab_cancel_convert(struct sidtab *s)
+{
+ unsigned long flags;
+
+ /* cancelling policy load - disable live convert of sidtab */
+ spin_lock_irqsave(&s->lock, flags);
+ s->convert = NULL;
+ spin_unlock_irqrestore(&s->lock, flags);
+}
+
+void sidtab_freeze_begin(struct sidtab *s, unsigned long *flags) __acquires(&s->lock)
+{
+ spin_lock_irqsave(&s->lock, *flags);
+ s->frozen = true;
+ s->convert = NULL;
+}
+void sidtab_freeze_end(struct sidtab *s, unsigned long *flags) __releases(&s->lock)
+{
+ spin_unlock_irqrestore(&s->lock, *flags);
+}
+
+static void sidtab_destroy_entry(struct sidtab_entry *entry)
+{
+ context_destroy(&entry->context);
+#if CONFIG_SECURITY_SELINUX_SID2STR_CACHE_SIZE > 0
+ kfree(rcu_dereference_raw(entry->cache));
+#endif
+}
+
+static void sidtab_destroy_tree(union sidtab_entry_inner entry, u32 level)
+{
+ u32 i;
+
+ if (level != 0) {
+ struct sidtab_node_inner *node = entry.ptr_inner;
+
+ if (!node)
+ return;
+
+ for (i = 0; i < SIDTAB_INNER_ENTRIES; i++)
+ sidtab_destroy_tree(node->entries[i], level - 1);
+ kfree(node);
+ } else {
+ struct sidtab_node_leaf *node = entry.ptr_leaf;
+
+ if (!node)
+ return;
+
+ for (i = 0; i < SIDTAB_LEAF_ENTRIES; i++)
+ sidtab_destroy_entry(&node->entries[i]);
+ kfree(node);
+ }
+}
+
+void sidtab_destroy(struct sidtab *s)
+{
+ u32 i, level;
+
+ for (i = 0; i < SECINITSID_NUM; i++)
+ if (s->isids[i].set)
+ sidtab_destroy_entry(&s->isids[i].entry);
+
+ level = SIDTAB_MAX_LEVEL;
+ while (level && !s->roots[level].ptr_inner)
+ --level;
+
+ sidtab_destroy_tree(s->roots[level], level);
+ /*
+ * The context_to_sid hashtable's objects are all shared
+ * with the isids array and context tree, and so don't need
+ * to be cleaned up here.
+ */
+}
+
+#if CONFIG_SECURITY_SELINUX_SID2STR_CACHE_SIZE > 0
+
+void sidtab_sid2str_put(struct sidtab *s, struct sidtab_entry *entry,
+ const char *str, u32 str_len)
+{
+ struct sidtab_str_cache *cache, *victim = NULL;
+ unsigned long flags;
+
+ /* do not cache invalid contexts */
+ if (entry->context.len)
+ return;
+
+ spin_lock_irqsave(&s->cache_lock, flags);
+
+ cache = rcu_dereference_protected(entry->cache,
+ lockdep_is_held(&s->cache_lock));
+ if (cache) {
+ /* entry in cache - just bump to the head of LRU list */
+ list_move(&cache->lru_member, &s->cache_lru_list);
+ goto out_unlock;
+ }
+
+ cache = kmalloc(struct_size(cache, str, str_len), GFP_ATOMIC);
+ if (!cache)
+ goto out_unlock;
+
+ if (s->cache_free_slots == 0) {
+ /* pop a cache entry from the tail and free it */
+ victim = container_of(s->cache_lru_list.prev,
+ struct sidtab_str_cache, lru_member);
+ list_del(&victim->lru_member);
+ rcu_assign_pointer(victim->parent->cache, NULL);
+ } else {
+ s->cache_free_slots--;
+ }
+ cache->parent = entry;
+ cache->len = str_len;
+ memcpy(cache->str, str, str_len);
+ list_add(&cache->lru_member, &s->cache_lru_list);
+
+ rcu_assign_pointer(entry->cache, cache);
+
+out_unlock:
+ spin_unlock_irqrestore(&s->cache_lock, flags);
+ kfree_rcu(victim, rcu_member);
+}
+
+int sidtab_sid2str_get(struct sidtab *s, struct sidtab_entry *entry,
+ char **out, u32 *out_len)
+{
+ struct sidtab_str_cache *cache;
+ int rc = 0;
+
+ if (entry->context.len)
+ return -ENOENT; /* do not cache invalid contexts */
+
+ rcu_read_lock();
+
+ cache = rcu_dereference(entry->cache);
+ if (!cache) {
+ rc = -ENOENT;
+ } else {
+ *out_len = cache->len;
+ if (out) {
+ *out = kmemdup(cache->str, cache->len, GFP_ATOMIC);
+ if (!*out)
+ rc = -ENOMEM;
+ }
+ }
+
+ rcu_read_unlock();
+
+ if (!rc && out)
+ sidtab_sid2str_put(s, entry, *out, *out_len);
+ return rc;
+}
+
+#endif /* CONFIG_SECURITY_SELINUX_SID2STR_CACHE_SIZE > 0 */