From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Cyrus-Session-Id: sloti22d1t05-4146407-1520977752-2-4268805795908830151 X-Sieve: CMU Sieve 3.0 X-Spam-known-sender: no ("Email failed DMARC policy for domain") X-Spam-score: 0.0 X-Spam-hits: BAYES_00 -1.9, HEADER_FROM_DIFFERENT_DOMAINS 0.25, RCVD_IN_DNSWL_HI -5, T_RP_MATCHES_RCVD -0.01, LANGUAGES en, BAYES_USED global, SA_VERSION 3.4.0 X-Spam-source: IP='209.132.180.67', Host='vger.kernel.org', Country='CN', FromHeader='com', MailFrom='org' X-Spam-charsets: plain='utf-8' X-IgnoreVacation: yes ("Email failed DMARC policy for domain") X-Resolved-to: greg@kroah.com X-Delivered-to: greg@kroah.com X-Mail-from: linux-api-owner@vger.kernel.org ARC-Seal: i=1; a=rsa-sha256; cv=none; d=messagingengine.com; s=arctest; t=1520977752; b=GQqutm16Nz9qnTwX43JgFZ4rhSYcZ8F+vqYWX7GvyeWu0lj KzK5Bsxe71/AlwC3QzNbfo4tmt/MAfjEWBCmq/SLYuYenQYusbuld4k8Ty5t1TbW +/xCXFk7clfAy9oocE/7dxucv7DaLpsOfWWntQPFxp8M4t2MF9q7i9kk7fgqxsTA jO2Y/iPLLJAfNIGG+lJF3+7XggMo2mgnz2TJViNhQOjLYV2z8pIjq+cAd9hItCUT LAZBPYzEIoMOH/cpRk9t9ba4ux5HoXDm6Yi+AarWLGx7HVeOJjerwwiO5RyXxKPR u6iPbCC484MQgQ3M1E23z5JUxnFk6kC8Mo1W2Dw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=subject:to:cc:references:from:message-id :date:mime-version:in-reply-to:content-type :content-transfer-encoding:sender:list-id; s=arctest; t= 1520977752; bh=EzvV6jzfPEN5Qp15bMafpAKUAG27VX+L/65p2Qfigjc=; b=E G490ciAVgdOso0Oto5vmdxoW1DqBQOBVmzp6nqGEejN3XdVwRdc6FqpSLkGh9BDT mVOVAHb1gaGdlRStBjWEkMJ/3wLTbXGc1VV/2lZRKZGHySuhqdmzchcw9C/9UdJf G1kTp5moslhdzn3iwO8pnKooDxl3a0XySeZZWr0czu9Y4AOO1h4qtpkjPuxVUQpj TzQw9y2zQbnVqOVquXuCGJ45l07rZrhHPQBqZj7STrYDCrS8XYXvwz4VhfzZCCky MeO6BHzvtfoEnkun211ohpc4bWvCf8ZUtZPZTSIhYstGcIUHjQRn5qAoHk2w/jzh KIhJIOuF97S/efzLZANdw== ARC-Authentication-Results: i=1; mx1.messagingengine.com; arc=none (no signatures found); dkim=fail (body has been altered; 2048-bit rsa key sha256) header.d=oracle.com header.i=@oracle.com header.b=k2Eopa3a x-bits=2048 x-keytype=rsa x-algorithm=sha256 x-selector=corp-2017-10-26; dmarc=fail (p=none,has-list-id=yes,d=none) header.from=oracle.com; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=linux-api-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-category=clean score=-100 state=0; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=oracle.com header.result=pass header_is_org_domain=yes Authentication-Results: mx1.messagingengine.com; arc=none (no signatures found); dkim=fail (body has been altered; 2048-bit rsa key sha256) header.d=oracle.com header.i=@oracle.com header.b=k2Eopa3a x-bits=2048 x-keytype=rsa x-algorithm=sha256 x-selector=corp-2017-10-26; dmarc=fail (p=none,has-list-id=yes,d=none) header.from=oracle.com; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=linux-api-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-category=clean score=-100 state=0; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=oracle.com header.result=pass header_is_org_domain=yes Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752938AbeCMVs6 (ORCPT ); Tue, 13 Mar 2018 17:48:58 -0400 Received: from userp2130.oracle.com ([156.151.31.86]:38572 "EHLO userp2130.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751754AbeCMVs4 (ORCPT ); Tue, 13 Mar 2018 17:48:56 -0400 Subject: Re: [RESEND RFC] translate_pid API To: Jann Horn Cc: kernel list , Linux API , Konstantin Khlebnikov , Nagarajan.Muthukrishnan@oracle.com, Prakash Sangappa , Andy Lutomirski , Andrew Morton , Oleg Nesterov , Serge Hallyn , "Eric W. Biederman" , Eugene Syromiatnikov , xemul@parallels.com References: <1520875093-18174-1-git-send-email-nagarathnam.muthusamy@oracle.com> <69f13674-7f84-5dc7-0bd7-e5e65e9cb3b0@oracle.com> From: Nagarathnam Muthusamy Message-ID: <1a8cac8b-22cc-e194-4244-b20428c8a9c2@oracle.com> Date: Tue, 13 Mar 2018 14:44:17 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.5.2 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=8831 signatures=668690 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=1 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1711220000 definitions=main-1803130243 Sender: linux-api-owner@vger.kernel.org X-Mailing-List: linux-api@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On 03/13/2018 02:28 PM, Jann Horn wrote: > On Tue, Mar 13, 2018 at 2:20 PM, Nagarathnam Muthusamy > wrote: >> On 03/13/2018 01:47 PM, Jann Horn wrote: >>> On Mon, Mar 12, 2018 at 10:18 AM, >>> wrote: >>>> Resending the RFC with participants of previous discussions >>>> in the list. >>>> >>>> Following patch which is a variation of a solution discussed >>>> in https://lwn.net/Articles/736330/ provides the users of >>>> pid namespace, the functionality of pid translation between >>>> namespaces using a namespace identifier. The topic of >>>> pid translation has been discussed in the community few times >>>> but there has always been a resistance to adding new solution >>>> for this problem. >>>> I will outline the planned usecase of pid namespace by oracle >>>> database and explain why any of the existing solution cannot >>>> be used to solve their problem. >>>> >>>> Consider a system in which several PID namespaces with multiple >>>> nested levels exists in parallel with monitor processes managing >>>> all the namespaces. PID translation is required for controlling >>>> and accessing information about the processes by the monitors >>>> and other processes down the hierarchy of namespaces. Controlling >>>> primarily involves sending signals or using ptrace by a process in >>>> parent namespace on any of the processes in its child namespace. >>>> Accessing information deals with the reading /proc//* files >>>> of processes in child namespace. None of the processes have >>>> root/CAP_SYS_ADMIN privileges. >>> How are you dealing with PID reuse? >> >> We have a monitor process which keeps track of the aliveness of >> important processes. When a process dies, monitor makes a note of >> it and hence detects if pid is reused. > How do you do that in a race-free manner? AFAIK, the monitor runs periodically to check the aliveness of the processes and this period is too short for pids to recycle. I will get back with more information on this if any other mechanisms are in place. > > >>>> + */ >>>> +SYSCALL_DEFINE3(translate_pid, pid_t, pid, u64, source, >>>> + u64, target) >>>> +{ >>>> + struct pid_namespace *source_ns = NULL, *target_ns = NULL; >>>> + struct pid *struct_pid; >>>> + struct pid_namespace *ph; >>>> + struct hlist_bl_head *shead = NULL; >>>> + struct hlist_bl_head *thead = NULL; >>>> + struct hlist_bl_node *dup_node; >>>> + pid_t result; >>>> + >>>> + if (!source) { >>>> + source_ns = &init_pid_ns; >>>> + } else { >>>> + shead = pid_ns_hash_head(pid_ns_hash, source); >>>> + hlist_bl_lock(shead); >>>> + hlist_bl_for_each_entry(ph, dup_node, shead, node) { >>>> + if (source == ph->ns.ns_id) { >>>> + source_ns = ph; >>>> + break; >>>> + } >>>> + } >>>> + if (!source_ns) { >>>> + hlist_bl_unlock(shead); >>>> + return -EINVAL; >>>> + } >>>> + } >>>> + if (!ptrace_may_access(source_ns->child_reaper, >>>> + PTRACE_MODE_READ_FSCREDS)) { >>> AFAICS this proposal breaks the visibility restrictions that >>> namespaces normally create. If there are two namespaces-based >>> containers that use the same UID range, I don't think they should be >>> able to learn information about each other, such as which PIDs are in >>> use in the other container; but as far as I can tell, your proposal >>> makes it possible to do that (unless an LSM or so is interfering). I >>> would prefer it if this API required visibility of the targeted PID >>> namespaces in the caller's PID namespace. >> >> I am trying to simulate the same access restrictions allowed >> on a process's /proc//ns/pid file. If the translator has >> access to /proc//ns/pid file of both source and destination >> namespaces, shouldn't it be allowed to translate the pid between >> them? > But the translator doesn't actually need to have access to those > procfs files, right? I thought it should have access to those procfs files to satisfy the visibility constraint that targeted PID namespaces should be visible in caller's PID namespace and ptrace_may_access checks that constraint. Thanks, Nagarathnam.