selinux: Only audit permissions specified in policy

Only audit the permissions specified by the policy rules.

Before:
type=AVC msg=audit(01/28/2010 14:30:46.690:3250) : avc:  denied  { read
append } for  pid=14092 comm=foo name=test_file dev=dm-1 ino=132932
scontext=unconfined_u:unconfined_r:load_policy_t:s0-s0:c0.c1023
tcontext=unconfined_u:object_r:rpm_tmp_t:s0 tclass=file

After:
type=AVC msg=audit(01/28/2010 14:52:37.448:26) : avc:  denied
{ append } for  pid=1917 comm=foo name=test_file dev=dm-1 ino=132932
scontext=unconfined_u:unconfined_r:load_policy_t:s0-s0:c0.c1023
tcontext=unconfined_u:object_r:rpm_tmp_t:s0 tclass=file

Reference:
https://bugzilla.redhat.com/show_bug.cgi?id=558499

Reported-by: Tom London <selinux@gmail.com>
Signed-off-by: Stephen D. Smalley <sds@tycho.nsa.gov>
Signed-off-by: James Morris <jmorris@namei.org>

security/selinux/avc.c

@@ -489,17 +489,14 @@ void avc_audit(u32 ssid, u32 tsid,
 	struct common_audit_data stack_data;
 	u32 denied, audited;
 	denied = requested & ~avd->allowed;
-	if (denied) {
-		audited = denied;
-		if (!(audited & avd->auditdeny))
-			return;
-	} else if (result) {
+	if (denied)
+		audited = denied & avd->auditdeny;
+	else if (result)
 		audited = denied = requested;
-	} else {
-		audited = requested;
-		if (!(audited & avd->auditallow))
-			return;
-	}
+	else
+		audited = requested & avd->auditallow;
+	if (!audited)
+		return;
 	if (!a) {
 		a = &stack_data;
 		memset(a, 0, sizeof(*a));