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 */