selinux: move context hashing under sidtab

Now that context hash computation no longer depends on policydb, we can
simplify things by moving the context hashing completely under sidtab.
The hash is still cached in sidtab entries, but not for the in-flight
context structures.

Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

1 files changed, 19 insertions, 13 deletions

diff --git a/security/selinux/ss/sidtab.c b/security/selinux/ss/sidtab.c
index 98d5ea3fcde4..eb6d27b5aeb4 100644
--- a/security/selinux/ss/sidtab.c
+++ b/security/selinux/ss/sidtab.c
@@ -54,14 +54,15 @@ int sidtab_init(struct sidtab *s)
 	return 0;
 }
 
-static u32 context_to_sid(struct sidtab *s, struct context *context)
+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,
-				   context->hash) {
+	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;
@@ -74,6 +75,7 @@ static u32 context_to_sid(struct sidtab *s, struct context *context)
 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)
@@ -90,15 +92,18 @@ int sidtab_set_initial(struct sidtab *s, u32 sid, struct context *context)
 #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)) {
+	if (!context_to_sid(s, context, hash)) {
 		isid->entry.sid = sid;
-		hash_add(s->context_to_sid, &isid->entry.list, context->hash);
+		isid->entry.hash = hash;
+		hash_add(s->context_to_sid, &isid->entry.list, hash);
 	}
 
 	return 0;
@@ -259,12 +264,12 @@ int sidtab_context_to_sid(struct sidtab *s, struct context *context,
 			  u32 *sid)
 {
 	unsigned long flags;
-	u32 count;
+	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);
+	*sid = context_to_sid(s, context, hash);
 	if (*sid)
 		return 0;
 
@@ -272,7 +277,7 @@ int sidtab_context_to_sid(struct sidtab *s, struct context *context,
 	spin_lock_irqsave(&s->lock, flags);
 
 	rc = 0;
-	*sid = context_to_sid(s, context);
+	*sid = context_to_sid(s, context, hash);
 	if (*sid)
 		goto out_unlock;
 
@@ -291,6 +296,7 @@ int sidtab_context_to_sid(struct sidtab *s, struct context *context,
 		goto out_unlock;
 
 	dst->sid = index_to_sid(count);
+	dst->hash = hash;
 
 	rc = context_cpy(&dst->context, context);
 	if (rc)
@@ -315,10 +321,11 @@ int sidtab_context_to_sid(struct sidtab *s, struct context *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->context.hash);
+			     &dst_convert->list, dst_convert->hash);
 	}
 
 	if (context->len)
@@ -329,7 +336,7 @@ int sidtab_context_to_sid(struct sidtab *s, struct context *context,
 
 	/* write entries before updating count */
 	smp_store_release(&s->count, count + 1);
-	hash_add_rcu(s->context_to_sid, &dst->list, dst->context.hash);
+	hash_add_rcu(s->context_to_sid, &dst->list, dst->hash);
 
 	rc = 0;
 out_unlock:
@@ -345,10 +352,9 @@ static void sidtab_convert_hashtable(struct sidtab *s, u32 count)
 	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->context.hash);
-
+		hash_add_rcu(s->context_to_sid, &entry->list, entry->hash);
 	}
 }