ext/mysqlnd: Fix persistent free of non-persistent connect_attr key.

set_client_option_2d() built the temporary key string with the
connection's persistent flag but always released it with persistent=1.
On a duplicate-key update of the connect_attr hash, zend_hash_update()
does not retain the passed key, so the caller-owned non-persistent
string was freed via free() instead of efree(), tripping the
IS_STR_PERSISTENT assertion in debug builds and mismatching allocators
in release. Reachable by retrying mysqli_real_connect() on a handle
whose first connect failed, since mysqlnd re-adds _client_name and
_server_host on every connect attempt.

Author: devnexen

ext/mysqlnd/mysqlnd_connection.c

@@ -1572,17 +1572,16 @@ MYSQLND_METHOD(mysqlnd_conn_data, set_client_option_2d)(MYSQLND_CONN_DATA * cons
 				zval attrz;
 				zend_string *str;
 
+				str = zend_string_init(key, strlen(key), conn->persistent);
 				if (conn->persistent) {
-					str = zend_string_init(key, strlen(key), 1);
 					GC_MAKE_PERSISTENT_LOCAL(str);
 					ZVAL_NEW_STR(&attrz, zend_string_init(value, strlen(value), 1));
 					GC_MAKE_PERSISTENT_LOCAL(Z_COUNTED(attrz));
 				} else {
-					str = zend_string_init(key, strlen(key), 0);
 					ZVAL_NEW_STR(&attrz, zend_string_init(value, strlen(value), 0));
 				}
 				zend_hash_update(conn->options->connect_attr, str, &attrz);
-				zend_string_release_ex(str, 1);
+				zend_string_release_ex(str, conn->persistent);
 			}
 			break;
 		default: