From patchwork Fri Mar 2 21:59:16 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: 10255791 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 77AE56037F for ; Fri, 2 Mar 2018 22:03:27 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 64F352856F for ; Fri, 2 Mar 2018 22:03:27 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 5911A28578; Fri, 2 Mar 2018 22:03:27 +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 F23322856F for ; Fri, 2 Mar 2018 22:03:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933347AbeCBWDM (ORCPT ); Fri, 2 Mar 2018 17:03:12 -0500 Received: from out02.mta.xmission.com ([166.70.13.232]:50206 "EHLO out02.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932655AbeCBWAg (ORCPT ); Fri, 2 Mar 2018 17:00:36 -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 1ersjD-0005Ai-EV; Fri, 02 Mar 2018 15:00:35 -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 1ersjA-0000ts-G4; Fri, 02 Mar 2018 15:00:35 -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" , Linus Torvalds , "Eric W. Biederman" Date: Fri, 2 Mar 2018 15:59:16 -0600 Message-Id: <20180302215919.27207-3-ebiederm@xmission.com> X-Mailer: git-send-email 2.14.1 In-Reply-To: <87r2p287i8.fsf_-_@xmission.com> References: <87r2p287i8.fsf_-_@xmission.com> X-XM-SPF: eid=1ersjA-0000ts-G4; ; ; mid=<20180302215919.27207-3-ebiederm@xmission.com>; ; ; hst=in02.mta.xmission.com; ; ; ip=174.19.85.160; ; ; frm=ebiederm@xmission.com; ; ; spf=neutral X-XM-AID: U2FsdGVkX1/7P+/zx7VTkfjwjKl4gm1MkgZVoSdxPVk= X-SA-Exim-Connect-IP: 174.19.85.160 X-SA-Exim-Mail-From: ebiederm@xmission.com Subject: [PATCH v8 3/6] 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;