Smack: Improve access check performance

Each Smack label that the kernel has seen is added to a
list of labels. The list of access rules for a given subject
label hangs off of the label list entry for the label.
This patch changes the structures that contain subject
labels to point at the label list entry rather that the
label itself. Doing so removes a label list lookup in
smk_access() that was accounting for the largest single
chunk of Smack overhead.

Targeted for git://git.gitorious.org/smack-next/kernel.git

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>

1 files changed, 21 insertions, 20 deletions

diff --git a/security/smack/smack_access.c b/security/smack/smack_access.c
index 2e397a88d410..53f2327a592f 100644
--- a/security/smack/smack_access.c
+++ b/security/smack/smack_access.c
@@ -93,7 +93,7 @@ int smk_access_entry(char *subject_label, char *object_label,
 
 	list_for_each_entry_rcu(srp, rule_list, list) {
 		if (srp->smk_object == object_label &&
-		    srp->smk_subject == subject_label) {
+		    srp->smk_subject->smk_known == subject_label) {
 			may = srp->smk_access;
 			break;
 		}
@@ -104,7 +104,7 @@ int smk_access_entry(char *subject_label, char *object_label,
 
 /**
  * smk_access - determine if a subject has a specific access to an object
- * @subject_label: a pointer to the subject's Smack label
+ * @subject_known: a pointer to the subject's Smack label entry
  * @object_label: a pointer to the object's Smack label
  * @request: the access requested, in "MAY" format
  * @a : a pointer to the audit data
@@ -115,10 +115,9 @@ int smk_access_entry(char *subject_label, char *object_label,
  *
  * Smack labels are shared on smack_list
  */
-int smk_access(char *subject_label, char *object_label, int request,
-	       struct smk_audit_info *a)
+int smk_access(struct smack_known *subject_known, char *object_label,
+		int request, struct smk_audit_info *a)
 {
-	struct smack_known *skp;
 	int may = MAY_NOT;
 	int rc = 0;
 
@@ -127,7 +126,7 @@ int smk_access(char *subject_label, char *object_label, int request,
 	 *
 	 * A star subject can't access any object.
 	 */
-	if (subject_label == smack_known_star.smk_known) {
+	if (subject_known == &smack_known_star) {
 		rc = -EACCES;
 		goto out_audit;
 	}
@@ -137,7 +136,7 @@ int smk_access(char *subject_label, char *object_label, int request,
 	 * An internet subject can access any object.
 	 */
 	if (object_label == smack_known_web.smk_known ||
-	    subject_label == smack_known_web.smk_known)
+	    subject_known == &smack_known_web)
 		goto out_audit;
 	/*
 	 * A star object can be accessed by any subject.
@@ -148,7 +147,7 @@ int smk_access(char *subject_label, char *object_label, int request,
 	 * An object can be accessed in any way by a subject
 	 * with the same label.
 	 */
-	if (subject_label == object_label)
+	if (subject_known->smk_known == object_label)
 		goto out_audit;
 	/*
 	 * A hat subject can read any object.
@@ -157,7 +156,7 @@ int smk_access(char *subject_label, char *object_label, int request,
 	if ((request & MAY_ANYREAD) == request) {
 		if (object_label == smack_known_floor.smk_known)
 			goto out_audit;
-		if (subject_label == smack_known_hat.smk_known)
+		if (subject_known == &smack_known_hat)
 			goto out_audit;
 	}
 	/*
@@ -167,9 +166,9 @@ int smk_access(char *subject_label, char *object_label, int request,
 	 * good. A negative response from smk_access_entry()
 	 * indicates there is no entry for this pair.
 	 */
-	skp = smk_find_entry(subject_label);
 	rcu_read_lock();
-	may = smk_access_entry(subject_label, object_label, &skp->smk_rules);
+	may = smk_access_entry(subject_known->smk_known, object_label,
+				&subject_known->smk_rules);
 	rcu_read_unlock();
 
 	if (may > 0 && (request & may) == request)
@@ -179,7 +178,8 @@ int smk_access(char *subject_label, char *object_label, int request,
 out_audit:
 #ifdef CONFIG_AUDIT
 	if (a)
-		smack_log(subject_label, object_label, request, rc, a);
+		smack_log(subject_known->smk_known, object_label, request,
+				rc, a);
 #endif
 	return rc;
 }
@@ -198,20 +198,21 @@ out_audit:
 int smk_curacc(char *obj_label, u32 mode, struct smk_audit_info *a)
 {
 	struct task_smack *tsp = current_security();
-	char *sp = smk_of_task(tsp);
+	struct smack_known *skp = smk_of_task(tsp);
 	int may;
 	int rc;
 
 	/*
 	 * Check the global rule list
 	 */
-	rc = smk_access(sp, obj_label, mode, NULL);
+	rc = smk_access(skp, obj_label, mode, NULL);
 	if (rc == 0) {
 		/*
 		 * If there is an entry in the task's rule list
 		 * it can further restrict access.
 		 */
-		may = smk_access_entry(sp, obj_label, &tsp->smk_rules);
+		may = smk_access_entry(skp->smk_known, obj_label,
+					&tsp->smk_rules);
 		if (may < 0)
 			goto out_audit;
 		if ((mode & may) == mode)
@@ -228,7 +229,7 @@ int smk_curacc(char *obj_label, u32 mode, struct smk_audit_info *a)
 out_audit:
 #ifdef CONFIG_AUDIT
 	if (a)
-		smack_log(sp, obj_label, mode, rc, a);
+		smack_log(skp->smk_known, obj_label, mode, rc, a);
 #endif
 	return rc;
 }
@@ -513,10 +514,10 @@ char *smk_import(const char *string, int len)
  * smack_from_secid - find the Smack label associated with a secid
  * @secid: an integer that might be associated with a Smack label
  *
- * Returns a pointer to the appropriate Smack label if there is one,
+ * Returns a pointer to the appropriate Smack label entry if there is one,
  * otherwise a pointer to the invalid Smack label.
  */
-char *smack_from_secid(const u32 secid)
+struct smack_known *smack_from_secid(const u32 secid)
 {
 	struct smack_known *skp;
 
@@ -524,7 +525,7 @@ char *smack_from_secid(const u32 secid)
 	list_for_each_entry_rcu(skp, &smack_known_list, list) {
 		if (skp->smk_secid == secid) {
 			rcu_read_unlock();
-			return skp->smk_known;
+			return skp;
 		}
 	}
 
@@ -533,7 +534,7 @@ char *smack_from_secid(const u32 secid)
 	 * of a secid that is not on the list.
 	 */
 	rcu_read_unlock();
-	return smack_known_invalid.smk_known;
+	return &smack_known_invalid;
 }
 
 /**