From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B6FCAC282C0 for ; Wed, 23 Jan 2019 09:55:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 82968217F5 for ; Wed, 23 Jan 2019 09:55:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727075AbfAWJzg (ORCPT ); Wed, 23 Jan 2019 04:55:36 -0500 Received: from relay.sw.ru ([185.231.240.75]:51872 "EHLO relay.sw.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726804AbfAWJzf (ORCPT ); Wed, 23 Jan 2019 04:55:35 -0500 Received: from [172.16.25.169] by relay.sw.ru with esmtp (Exim 4.91) (envelope-from ) id 1gmFFr-0006J8-Le; Wed, 23 Jan 2019 12:55:31 +0300 Subject: Re: [PATCH 1/7] fuse: Check for fc->connected in fuse_dev_alloc() To: Miklos Szeredi Cc: linux-fsdevel@vger.kernel.org References: <154754701031.4244.8089449938935364463.stgit@localhost.localdomain> <154754755979.4244.14965151684224631403.stgit@localhost.localdomain> <98ae21a4-fb96-c06e-e442-5929d36f2bf3@virtuozzo.com> From: Kirill Tkhai Message-ID: Date: Wed, 23 Jan 2019 12:55:31 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On 23.01.2019 12:45, Miklos Szeredi wrote: > On Fri, Jan 18, 2019 at 1:28 PM Kirill Tkhai wrote: >> >> On 18.01.2019 15:07, Miklos Szeredi wrote: >>> On Tue, Jan 15, 2019 at 11:19 AM Kirill Tkhai wrote: >>>> >>>> fuse_dev_alloc() may be called after fc->connected >>>> is dropped (from ioctl), so here we add sanity check >>>> for that case. >>> >>> AFAICS this is not fixing a bug; i.e. even if the fuse_dev is added to >>> the fuse_conn's list after disconnection there would be no leak. >>> >>> In other words, it's irrelevant whether the connection reset comes >>> just before the ioctl completes or just after. Or am I missing >>> something? >> >> Yeah, there won't be a leak. The only problem I see, userspace daemon >> may become waiting in fuse_dev_do_read() after abort is finished. > > By that time fiq->connected will be reset, so fuse_dev_do_read() will > return ENODEV/ECONNABORTED. > > Am I missing something? I mean: [cpu0] [cpu1] fuse_device_clone() fuse_dev_alloc() fuse_abort_conn() spin_lock(&fc->lock) list_for_each_entry(fud, &fc->devices, entry) fpq->connected = 0 spin_unlock(&fc->lock) spin_lock(&fc->lock); list_add_tail(&fud->entry, &fc->devices); spin_unlock(&fc->lock); ... fuse_dev_do_read() wait_event_interruptible_exclusive_locked() <-- wait forever If you have manager-thread on cpu1, and it expects all worker-threads (like on cpu0) will finish after abort, this won't be true. Kirill