From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Cyrus-Session-Id: sloti22d1t05-14183-1520981442-2-10764052610461201263 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=1520981441; b=tMjTh1vWyw3IoGuQeqO/UFKZM0Fj8ErePhZ9J54B+6Lv44p hoSziJwxfFAAWJ7hsNWVtDhvY5q3gA71N5B3ykimYCHaqRx0TGxxI10KoEAgaEDL 68Z8BqGdGTGoXRs+pNgcIH6BCNEIN2LlC+bIvxMgtXuO/gmK8PmsPu5BbB+E4nej YI1P7DyHWbJyI+6Exlrb26N5d5X+XhChoP12vnz1wVUlHjCpjFn12msK5v0Xm/ie spBD26smBep3tvT6xqJtvmA0NxT3rEeFN3M5SN8S96gnr/7Kk2vGi8LyQcafCkGE nCGmiKQBkEQqQJCSnZbn6lI9WlBpoDS5a2j8Lfw== 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= 1520981441; bh=R4k4egAqTwC8CdwTR9zyerp5KPvTYYdOwplToeTsDQU=; b=r TEkW8SVlgEttIXJe1aALd/noaSFcakz9KlR0s5Kf1GKEF4jg2nbnZj8VK857QH3v STCt7lFgJp2HwARTCF8VHAiFkfhrJGREiNQEppHyYWkkG1OJ4zc+CA0U8LdLGIvQ NVOSI0VVpA0twg/MwN4PvlkVS9sH8HMz3O4p/GtW66H3N156JKGSfbQw0EdRMnLi 6Slw8vePIQBqMZEyEnpeZU0T2DmCR6XU6kGY2VXYKgTy4X7W0sFilrQT1M0VgZVj pEERwKJWeXN4ZRBDbx+CGhF3VUVLLJeZf5hInJgyAdG3bOOVefWFXJcKSboa9h31 qNVisFHO76dH2XLi+2eZw== ARC-Authentication-Results: i=1; mx4.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=koLWchFm 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: mx4.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=koLWchFm 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 S932222AbeCMWu2 (ORCPT ); Tue, 13 Mar 2018 18:50:28 -0400 Received: from userp2120.oracle.com ([156.151.31.85]:55334 "EHLO userp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932205AbeCMWu1 (ORCPT ); Tue, 13 Mar 2018 18:50:27 -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> <1a8cac8b-22cc-e194-4244-b20428c8a9c2@oracle.com> From: Nagarathnam Muthusamy Message-ID: Date: Tue, 13 Mar 2018 15:45:45 -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-1803130251 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 03:00 PM, Jann Horn wrote: > On Tue, Mar 13, 2018 at 2:44 PM, Nagarathnam Muthusamy > wrote: >> >> 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. > If there are two containers that use the same UID range, > ptrace_may_access() checks from a process in one container on a > process in another container can pass. Normally, you just can't even > reach the ptrace_may_access() checks because you can't reference > processes in another container in any way. If there is no way to reference the process in another container, there is no way to get to the /proc//ns/pidns_id file which exports the ID of that container right? So, a translator has to first guess the container ID then try translate. Even after translation, unless the translator has proper privileges, I believe it cant do anything with just the pid right? > > By the way, a related concern: The use of global identifiers will > probably also negatively affect Checkpoint/Restore In Userspace? Will look into this. Can you point me to the specifics of the usecase which could be negatively affected? Thanks, Nagarathnam.