1 files changed, 253 insertions, 149 deletions

diff --git a/security/selinux/ss/sidtab.c b/security/selinux/ss/sidtab.c
index 7d49994e8d5f..a308ce1e6a13 100644
--- a/security/selinux/ss/sidtab.c
+++ b/security/selinux/ss/sidtab.c
@@ -9,6 +9,8 @@
  */
 #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>
@@ -17,44 +19,125 @@
 #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));
 
-	/* max count is SIDTAB_MAX so valid index is always < SIDTAB_MAX */
-	for (i = 0; i < SIDTAB_RCACHE_SIZE; i++)
-		s->rcache[i] = SIDTAB_MAX;
-
 	for (i = 0; i < SECINITSID_NUM; i++)
 		s->isids[i].set = 0;
 
 	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)
+{
+	struct sidtab_entry *entry;
+	u32 sid = 0;
+
+	rcu_read_lock();
+	hash_for_each_possible_rcu(s->context_to_sid, entry, list,
+				   context->hash) {
+		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 *entry;
+	struct sidtab_isid_entry *isid;
 	int rc;
 
 	if (sid == 0 || sid > SECINITSID_NUM)
 		return -EINVAL;
 
-	entry = &s->isids[sid - 1];
+	isid = &s->isids[sid - 1];
 
-	rc = context_cpy(&entry->context, context);
+	rc = context_cpy(&isid->entry.context, context);
 	if (rc)
 		return rc;
 
-	entry->set = 1;
+#if CONFIG_SECURITY_SELINUX_SID2STR_CACHE_SIZE > 0
+	isid->entry.cache = NULL;
+#endif
+	isid->set = 1;
+
+	/*
+	 * 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)) {
+		isid->entry.sid = sid;
+		hash_add(s->context_to_sid, &isid->entry.list, context->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;
@@ -88,7 +171,8 @@ static int sidtab_alloc_roots(struct sidtab *s, u32 level)
 	return 0;
 }
 
-static struct context *sidtab_do_lookup(struct sidtab *s, u32 index, int alloc)
+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;
@@ -125,10 +209,10 @@ static struct context *sidtab_do_lookup(struct sidtab *s, u32 index, int alloc)
 		if (!entry->ptr_leaf)
 			return NULL;
 	}
-	return &entry->ptr_leaf->entries[index % SIDTAB_LEAF_ENTRIES].context;
+	return &entry->ptr_leaf->entries[index % SIDTAB_LEAF_ENTRIES];
 }
 
-static struct context *sidtab_lookup(struct sidtab *s, u32 index)
+static struct sidtab_entry *sidtab_lookup(struct sidtab *s, u32 index)
 {
 	/* read entries only after reading count */
 	u32 count = smp_load_acquire(&s->count);
@@ -139,148 +223,62 @@ static struct context *sidtab_lookup(struct sidtab *s, u32 index)
 	return sidtab_do_lookup(s, index, 0);
 }
 
-static struct context *sidtab_lookup_initial(struct sidtab *s, u32 sid)
+static struct sidtab_entry *sidtab_lookup_initial(struct sidtab *s, u32 sid)
 {
-	return s->isids[sid - 1].set ? &s->isids[sid - 1].context : NULL;
+	return s->isids[sid - 1].set ? &s->isids[sid - 1].entry : NULL;
 }
 
-static struct context *sidtab_search_core(struct sidtab *s, u32 sid, int force)
+static struct sidtab_entry *sidtab_search_core(struct sidtab *s, u32 sid,
+					       int force)
 {
-	struct context *context;
-
 	if (sid != 0) {
+		struct sidtab_entry *entry;
+
 		if (sid > SECINITSID_NUM)
-			context = sidtab_lookup(s, sid - (SECINITSID_NUM + 1));
+			entry = sidtab_lookup(s, sid_to_index(sid));
 		else
-			context = sidtab_lookup_initial(s, sid);
-		if (context && (!context->len || force))
-			return context;
+			entry = sidtab_lookup_initial(s, sid);
+		if (entry && (!entry->context.len || force))
+			return entry;
 	}
 
 	return sidtab_lookup_initial(s, SECINITSID_UNLABELED);
 }
 
-struct context *sidtab_search(struct sidtab *s, u32 sid)
+struct sidtab_entry *sidtab_search_entry(struct sidtab *s, u32 sid)
 {
 	return sidtab_search_core(s, sid, 0);
 }
 
-struct context *sidtab_search_force(struct sidtab *s, u32 sid)
+struct sidtab_entry *sidtab_search_entry_force(struct sidtab *s, u32 sid)
 {
 	return sidtab_search_core(s, sid, 1);
 }
 
-static int sidtab_find_context(union sidtab_entry_inner entry,
-			       u32 *pos, u32 count, u32 level,
-			       struct context *context, u32 *index)
-{
-	int rc;
-	u32 i;
-
-	if (level != 0) {
-		struct sidtab_node_inner *node = entry.ptr_inner;
-
-		i = 0;
-		while (i < SIDTAB_INNER_ENTRIES && *pos < count) {
-			rc = sidtab_find_context(node->entries[i],
-						 pos, count, level - 1,
-						 context, index);
-			if (rc == 0)
-				return 0;
-			i++;
-		}
-	} else {
-		struct sidtab_node_leaf *node = entry.ptr_leaf;
-
-		i = 0;
-		while (i < SIDTAB_LEAF_ENTRIES && *pos < count) {
-			if (context_cmp(&node->entries[i].context, context)) {
-				*index = *pos;
-				return 0;
-			}
-			(*pos)++;
-			i++;
-		}
-	}
-	return -ENOENT;
-}
-
-static void sidtab_rcache_update(struct sidtab *s, u32 index, u32 pos)
-{
-	while (pos > 0) {
-		WRITE_ONCE(s->rcache[pos], READ_ONCE(s->rcache[pos - 1]));
-		--pos;
-	}
-	WRITE_ONCE(s->rcache[0], index);
-}
-
-static void sidtab_rcache_push(struct sidtab *s, u32 index)
-{
-	sidtab_rcache_update(s, index, SIDTAB_RCACHE_SIZE - 1);
-}
-
-static int sidtab_rcache_search(struct sidtab *s, struct context *context,
-				u32 *index)
-{
-	u32 i;
-
-	for (i = 0; i < SIDTAB_RCACHE_SIZE; i++) {
-		u32 v = READ_ONCE(s->rcache[i]);
-
-		if (v >= SIDTAB_MAX)
-			continue;
-
-		if (context_cmp(sidtab_do_lookup(s, v, 0), context)) {
-			sidtab_rcache_update(s, v, i);
-			*index = v;
-			return 0;
-		}
-	}
-	return -ENOENT;
-}
-
-static int sidtab_reverse_lookup(struct sidtab *s, struct context *context,
-				 u32 *index)
+int sidtab_context_to_sid(struct sidtab *s, struct context *context,
+			  u32 *sid)
 {
 	unsigned long flags;
-	u32 count, count_locked, level, pos;
+	u32 count;
 	struct sidtab_convert_params *convert;
-	struct context *dst, *dst_convert;
+	struct sidtab_entry *dst, *dst_convert;
 	int rc;
 
-	rc = sidtab_rcache_search(s, context, index);
-	if (rc == 0)
-		return 0;
-
-	/* read entries only after reading count */
-	count = smp_load_acquire(&s->count);
-	level = sidtab_level_from_count(count);
-
-	pos = 0;
-	rc = sidtab_find_context(s->roots[level], &pos, count, level,
-				 context, index);
-	if (rc == 0) {
-		sidtab_rcache_push(s, *index);
+	*sid = context_to_sid(s, context);
+	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);
+	if (*sid)
+		goto out_unlock;
+
+	/* read entries only after reading count */
+	count = smp_load_acquire(&s->count);
 	convert = s->convert;
-	count_locked = s->count;
-	level = sidtab_level_from_count(count_locked);
-
-	/* if count has changed before we acquired the lock, then catch up */
-	while (count < count_locked) {
-		if (context_cmp(sidtab_do_lookup(s, count, 0), context)) {
-			sidtab_rcache_push(s, count);
-			*index = count;
-			rc = 0;
-			goto out_unlock;
-		}
-		++count;
-	}
 
 	/* bail out if we already reached max entries */
 	rc = -EOVERFLOW;
@@ -293,7 +291,9 @@ static int sidtab_reverse_lookup(struct sidtab *s, struct context *context,
 	if (!dst)
 		goto out_unlock;
 
-	rc = context_cpy(dst, context);
+	dst->sid = index_to_sid(count);
+
+	rc = context_cpy(&dst->context, context);
 	if (rc)
 		goto out_unlock;
 
@@ -305,29 +305,32 @@ static int sidtab_reverse_lookup(struct sidtab *s, struct context *context,
 		rc = -ENOMEM;
 		dst_convert = sidtab_do_lookup(convert->target, count, 1);
 		if (!dst_convert) {
-			context_destroy(dst);
+			context_destroy(&dst->context);
 			goto out_unlock;
 		}
 
-		rc = convert->func(context, dst_convert, convert->args);
+		rc = convert->func(context, &dst_convert->context,
+				   convert->args);
 		if (rc) {
-			context_destroy(dst);
+			context_destroy(&dst->context);
 			goto out_unlock;
 		}
-
-		/* at this point we know the insert won't fail */
+		dst_convert->sid = index_to_sid(count);
 		convert->target->count = count + 1;
+
+		hash_add_rcu(convert->target->context_to_sid,
+			     &dst_convert->list, dst_convert->context.hash);
 	}
 
 	if (context->len)
 		pr_info("SELinux:  Context %s is not valid (left unmapped).\n",
 			context->str);
 
-	sidtab_rcache_push(s, count);
-	*index = count;
+	*sid = index_to_sid(count);
 
-	/* write entries before writing new count */
+	/* write entries before updating count */
 	smp_store_release(&s->count, count + 1);
+	hash_add_rcu(s->context_to_sid, &dst->list, dst->context.hash);
 
 	rc = 0;
 out_unlock:
@@ -335,25 +338,19 @@ out_unlock:
 	return rc;
 }
 
-int sidtab_context_to_sid(struct sidtab *s, struct context *context, u32 *sid)
+static void sidtab_convert_hashtable(struct sidtab *s, u32 count)
 {
-	int rc;
+	struct sidtab_entry *entry;
 	u32 i;
 
-	for (i = 0; i < SECINITSID_NUM; i++) {
-		struct sidtab_isid_entry *entry = &s->isids[i];
+	for (i = 0; i < count; i++) {
+		entry = sidtab_do_lookup(s, i, 0);
+		entry->sid = index_to_sid(i);
 
-		if (entry->set && context_cmp(context, &entry->context)) {
-			*sid = i + 1;
-			return 0;
-		}
-	}
+		hash_add_rcu(s->context_to_sid, &entry->list,
+			     entry->context.hash);
 
-	rc = sidtab_reverse_lookup(s, context, sid);
-	if (rc)
-		return rc;
-	*sid += SECINITSID_NUM + 1;
-	return 0;
+	}
 }
 
 static int sidtab_convert_tree(union sidtab_entry_inner *edst,
@@ -435,7 +432,7 @@ int sidtab_convert(struct sidtab *s, struct sidtab_convert_params *params)
 	/* enable live convert of new entries */
 	s->convert = params;
 
-	/* we can safely do the rest of the conversion outside the lock */
+	/* 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);
@@ -449,8 +446,25 @@ int sidtab_convert(struct sidtab *s, struct sidtab_convert_params *params)
 		spin_lock_irqsave(&s->lock, flags);
 		s->convert = NULL;
 		spin_unlock_irqrestore(&s->lock, flags);
+		return rc;
 	}
-	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;
+}
+
+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)
@@ -473,7 +487,7 @@ static void sidtab_destroy_tree(union sidtab_entry_inner entry, u32 level)
 			return;
 
 		for (i = 0; i < SIDTAB_LEAF_ENTRIES; i++)
-			context_destroy(&node->entries[i].context);
+			sidtab_destroy_entry(&node->entries[i]);
 		kfree(node);
 	}
 }
@@ -484,11 +498,101 @@ void sidtab_destroy(struct sidtab *s)
 
 	for (i = 0; i < SECINITSID_NUM; i++)
 		if (s->isids[i].set)
-			context_destroy(&s->isids[i].context);
+			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;
+
+	/* do not cache invalid contexts */
+	if (entry->context.len)
+		return;
+
+	/*
+	 * Skip the put operation when in non-task context to avoid the need
+	 * to disable interrupts while holding s->cache_lock.
+	 */
+	if (!in_task())
+		return;
+
+	spin_lock(&s->cache_lock);
+
+	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(sizeof(struct sidtab_str_cache) + 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(&s->cache_lock);
+	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 */