fix potential double free in case of error

CHANGES

@@ -3,6 +3,7 @@ OpenLDAP 2.3 Change Log
 OpenLDAP 2.3.28 Engineering
 	Fixed libldap ldap.conf max line length (ITS#4669)
 	Fixed librewrite LDAP map parsing bug
+	Fixed librewrite map double free bug
 	Added ldapsearch bad filter pattern check (ITS#4647)
 	Fixed slapd-monitor locking with scope "subordinate" (ITS#4668)
 	Fixed slapd global access controls initialization (ITS#4654)

libraries/librewrite/map.c

@@ -354,7 +354,12 @@ rewrite_map_apply(
 				( struct rewrite_context * )map->lm_data,
 				key->bv_val, &val->bv_val );
 		if ( val->bv_val != NULL ) {
-			val->bv_len = strlen( val->bv_val );
+			if ( val->bv_val == key->bv_val ) {
+				val->bv_len = key->bv_len;
+				key->bv_val = NULL;
+			} else {
+				val->bv_len = strlen( val->bv_val );
+			}
 		}
 		break;