From patchwork Wed Feb 21 20:29:04 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Eric W. Biederman" X-Patchwork-Id: 10233915 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 888E260392 for ; Wed, 21 Feb 2018 20:30:51 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 797EC284E4 for ; Wed, 21 Feb 2018 20:30:51 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 6D774284D4; Wed, 21 Feb 2018 20:30:51 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 253A7284D4 for ; Wed, 21 Feb 2018 20:30:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751274AbeBUUai (ORCPT ); Wed, 21 Feb 2018 15:30:38 -0500 Received: from out02.mta.xmission.com ([166.70.13.232]:44129 "EHLO out02.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750988AbeBUUag (ORCPT ); Wed, 21 Feb 2018 15:30:36 -0500 Received: from in02.mta.xmission.com ([166.70.13.52]) by out02.mta.xmission.com with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.87) (envelope-from ) id 1eob2A-0000Ft-Nh; Wed, 21 Feb 2018 13:30:34 -0700 Received: from 174-19-85-160.omah.qwest.net ([174.19.85.160] helo=x220.int.ebiederm.org) by in02.mta.xmission.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.87) (envelope-from ) id 1eob29-0004Av-OP; Wed, 21 Feb 2018 13:30:34 -0700 From: "Eric W. Biederman" To: Miklos Szeredi Cc: linux-kernel@vger.kernel.org, containers@lists.linux-foundation.org, linux-fsdevel@vger.kernel.org, Alban Crequy , Seth Forshee , Sargun Dhillon , Dongsu Park , "Serge E. Hallyn" , "Eric W. Biederman" Date: Wed, 21 Feb 2018 14:29:04 -0600 Message-Id: <20180221202908.17258-1-ebiederm@xmission.com> X-Mailer: git-send-email 2.14.1 In-Reply-To: <878tbmf5vl.fsf@xmission.com> References: <878tbmf5vl.fsf@xmission.com> X-XM-SPF: eid=1eob29-0004Av-OP; ; ; mid=<20180221202908.17258-1-ebiederm@xmission.com>; ; ; hst=in02.mta.xmission.com; ; ; ip=174.19.85.160; ; ; frm=ebiederm@xmission.com; ; ; spf=neutral X-XM-AID: U2FsdGVkX18PfmmiM+0n2MYUJGb2DFx+FxTY7zvf8ao= X-SA-Exim-Connect-IP: 174.19.85.160 X-SA-Exim-Mail-From: ebiederm@xmission.com Subject: [PATCH v6 1/5] fuse: Remove the buggy retranslation of pids in fuse_dev_do_read X-SA-Exim-Version: 4.2.1 (built Thu, 05 May 2016 13:38:54 -0600) X-SA-Exim-Scanned: Yes (on in02.mta.xmission.com) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP At the point of fuse_dev_do_read the user space process that initiated the action on the fuse filesystem may no longer exist. The process have been killed or may have fired an asynchronous request and exited. If the initial process has exited the code "pid_vnr(find_pid_ns(in->h.pid, fc->pid_ns)" will either return a pid of 0, or in the unlikely event that the pid has been reallocated it can return practically any pid. Any pid is possible as the pid allocator allocates pid numbers in different pid namespaces independently. The only way to make translation in fuse_dev_do_read reliable is to call get_pid in fuse_req_init_context, and pid_vnr followed by put_pid in fuse_dev_do_read. That reference counting in other contexts has been shown to bounce cache lines between processors and in general be slow. So that is not desirable. The only known user of running the fuse server in a different pid namespace from the filesystem does not care what the pids are in the fuse messages so removing this code should not matter. Getting the translation to a server running outside of the pid namespace of a container can still be achieved by playing setns games at mount time. It is also possible to add an option to pass a pid namespace into the fuse filesystem at mount time. Fixes: 5d6d3a301c4e ("fuse: allow server to run in different pid_ns") Signed-off-by: "Eric W. Biederman" --- fs/fuse/dev.c | 6 ------ 1 file changed, 6 deletions(-) diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c index 5d06384c2cae..0fb58f364fa6 100644 --- a/fs/fuse/dev.c +++ b/fs/fuse/dev.c @@ -1260,12 +1260,6 @@ static ssize_t fuse_dev_do_read(struct fuse_dev *fud, struct file *file, in = &req->in; reqsize = in->h.len; - if (task_active_pid_ns(current) != fc->pid_ns) { - rcu_read_lock(); - in->h.pid = pid_vnr(find_pid_ns(in->h.pid, fc->pid_ns)); - rcu_read_unlock(); - } - /* If request is too large, reply with an error and restart the read */ if (nbytes < reqsize) { req->out.h.error = -EIO;