From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756009AbaHYP1f (ORCPT ); Mon, 25 Aug 2014 11:27:35 -0400 Received: from relay.parallels.com ([195.214.232.42]:48995 "EHLO relay.parallels.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755942AbaHYP1d (ORCPT ); Mon, 25 Aug 2014 11:27:33 -0400 Message-ID: <53FB55E3.1050806@parallels.com> Date: Mon, 25 Aug 2014 19:27:31 +0400 From: Maxim Patlasov User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.6.0 MIME-Version: 1.0 To: Miklos Szeredi CC: fuse-devel , Anand Avati , Kernel Mailing List Subject: Re: [PATCH 4/6] fuse: enable close_wait synchronous release References: <20140821160304.11005.15166.stgit@localhost.localdomain> <20140821160855.11005.86653.stgit@localhost.localdomain> In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.30.22.200] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/22/2014 06:04 PM, Miklos Szeredi wrote: > On Thu, Aug 21, 2014 at 6:09 PM, Maxim Patlasov wrote: >> The patch enables the feature by passing 'true' to fuse_file_put in >> fuse_release_common. >> >> Previously, this was safe only in special cases when we sure that >> multi-threaded userspace won't deadlock if we'll synchronously send >> FUSE_RELEASE in the context of read-ahead or write-back callback. Now, it's >> always safe because callbacks don't send requests to userspace anymore. > But we do want to make this privileged, as there are unlikely but > possible DoS scenarios with a sync release. The latest patch of the set implements DISABLE_SYNC_RELEASE mount option. We can instrument fusermount to use the option by default for unprivileged mounts (allowing system administrator to configure it like "user_allow_other"). Do you have a better way to implement DoS protection in mind? Thanks, Maxim