selinux: call WARN_ONCE() instead of calling audit_log_start()

Two of the conditions in selinux_audit_rule_match() should never happen and
the third indicates a race that should be retried.  Remove the calls to
audit_log() (which call audit_log_start()) and deal with the errors in the
caller, logging only once if the condition is met.  Calling audit_log_start()
in this location makes buffer allocation and locking more complicated in the
calling tree (audit_filter_user()).

Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
Signed-off-by: Eric Paris <eparis@redhat.com>

security/selinux/ss/services.c

@@ -2938,25 +2938,21 @@ int selinux_audit_rule_match(u32 sid, u32 field, u32 op, void *vrule,
 	struct selinux_audit_rule *rule = vrule;
 	int match = 0;
 
-	if (!rule) {
-		audit_log(actx, GFP_ATOMIC, AUDIT_SELINUX_ERR,
-			  "selinux_audit_rule_match: missing rule\n");
+	if (unlikely(!rule)) {
+		WARN_ONCE(1, "selinux_audit_rule_match: missing rule\n");
 		return -ENOENT;
 	}
 
 	read_lock(&policy_rwlock);
 
 	if (rule->au_seqno < latest_granting) {
-		audit_log(actx, GFP_ATOMIC, AUDIT_SELINUX_ERR,
-			  "selinux_audit_rule_match: stale rule\n");
 		match = -ESTALE;
 		goto out;
 	}
 
 	ctxt = sidtab_search(&sidtab, sid);
-	if (!ctxt) {
-		audit_log(actx, GFP_ATOMIC, AUDIT_SELINUX_ERR,
-			  "selinux_audit_rule_match: unrecognized SID %d\n",
+	if (unlikely(!ctxt)) {
+		WARN_ONCE(1, "selinux_audit_rule_match: unrecognized SID %d\n",
 			  sid);
 		match = -ENOENT;
 		goto out;