bugfix: ngx_http_lua_ffi_ssl_set_serialized_session(): avoided memory leak when calling it repeatly.

Signed-off-by: Yichun Zhang (agentzh) <agentzh@gmail.com>

Author: spacewander

src/ngx_http_lua_ssl_session_fetchby.c

@@ -567,6 +567,7 @@ ngx_http_lua_ffi_ssl_set_serialized_session(ngx_http_request_t *r,
     ngx_ssl_conn_t                  *ssl_conn;
     ngx_connection_t                *c;
     ngx_ssl_session_t               *session = NULL;
+    ngx_ssl_session_t               *old_session;
     ngx_http_lua_ssl_ctx_t          *cctx;
 
     c = r->connection;
@@ -597,8 +598,13 @@ ngx_http_lua_ffi_ssl_set_serialized_session(ngx_http_request_t *r,
         return NGX_ERROR;
     }
 
+    old_session = cctx->session;
     cctx->session = session;
 
+    if (old_session != NULL) {
+        ngx_ssl_free_session(old_session);
+    }
+
     return NGX_OK;
 }