From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Cyrus-Session-Id: sloti22d1t05-4106523-1520976315-2-15585675079933580518 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=1520976313; b=HWnjXQlUWa5MmMu+Fg3kvVpmMT7phMHM+9XWnivhap7zcvS kMsAKVmN2n5vx8XATr28yn7mKkx3AnNGJWBmPUUnzLcH2/PsO+uxLZ46qRWmF8YJ mHFdWBoNpr4j3BAYKUfWGyOiFe33MxOnMXY/cExRxx8GAQi+MlFjYGEjlTFiss0C uYzzmQWeQWoSF002zbHzkcUMDcpprkSveemPJATG2bAk2ZCViali9nLOHH71BCOp N4/Rna2p+G0Bxppk9zR05/GgTE5saAnhyzHxmdnOzO6hYecYr1A4TEsGSylcyme1 KtF282EMgJTYlU8sVk8uniXByxGbMlzQrcCDDZw== 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= 1520976313; bh=9B6xJwGEAdAPIKsiwr2qphPL2k9uh+YKprA+Gns966g=; b=D NoyekT8oISNREhFrXcA5Rvqh7UPcLesRoZYE+Q0ykvztsc5/HBGGONIOU2onkpa8 GkxsDr21zecg2SnJvamKKnpvTL9SC2zinwFk/AVg8UrrSEFb2qO9FjdHuU2R9Ruj XuYM8IFc6FwCzywdLk51OV/X8m10wxkEz0iSDOuWYhBQKWIXxGbcx58nOf5ZDnR8 BDkmCESfKQeoFQVjfGJa6cbRzud5wHk4GP+8vyHh8kTR/HraEJw3xMSFzuPpkzMs EgHjMUwHYM60TTwtyuhprkhfruSj9xZjHdIhCKdSP/xLd8lOLHSrb5seIiX1xCoL m0Qgu6ah6K3EFvBAmGwSQ== ARC-Authentication-Results: i=1; mx6.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=qMc09WBH 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: mx6.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=qMc09WBH 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 S932268AbeCMVZL (ORCPT ); Tue, 13 Mar 2018 17:25:11 -0400 Received: from aserp2130.oracle.com ([141.146.126.79]:56318 "EHLO aserp2130.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932257AbeCMVZK (ORCPT ); Tue, 13 Mar 2018 17:25:10 -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> From: Nagarathnam Muthusamy Message-ID: <69f13674-7f84-5dc7-0bd7-e5e65e9cb3b0@oracle.com> Date: Tue, 13 Mar 2018 14:20:16 -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-1803130238 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 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. > > [...] >> diff --git a/fs/nsfs.c b/fs/nsfs.c >> index 36b0772..c635465 100644 >> --- a/fs/nsfs.c >> +++ b/fs/nsfs.c >> @@ -222,8 +222,13 @@ int ns_get_name(char *buf, size_t size, struct task_struct *task, >> const char *name; >> ns = ns_ops->get(task); >> if (ns) { >> - name = ns_ops->real_ns_name ? : ns_ops->name; >> - res = snprintf(buf, size, "%s:[%u]", name, ns->inum); >> + if (!strcmp(ns_ops->name, "pidns_id")) { > Wouldn't it be cleaner to check for "ns_ops==&pidns_id_operations"? Yup. Will fix it. > >> + res = snprintf(buf, size, "[%llu]", >> + (unsigned long long)ns->ns_id); >> + } else { >> + name = ns_ops->real_ns_name ? : ns_ops->name; >> + res = snprintf(buf, size, "%s:[%u]", name, ns->inum); >> + } >> ns_ops->put(ns); >> } >> return res; > [...] >> diff --git a/include/linux/pid_namespace.h b/include/linux/pid_namespace.h >> index 49538b1..11d1d57 100644 >> --- a/include/linux/pid_namespace.h >> +++ b/include/linux/pid_namespace.h >> @@ -11,6 +11,7 @@ >> #include >> #include >> #include >> +#include >> >> >> struct fs_pin; >> @@ -44,6 +45,8 @@ struct pid_namespace { >> kgid_t pid_gid; >> int hide_pid; >> int reboot; /* group exit code if this pidns was rebooted */ >> + struct hlist_bl_node node; >> + atomic_t lookups_pending; >> struct ns_common ns; >> } __randomize_layout; >> > [...] >> diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c >> index 0b53eef..ff83aa8 100644 >> --- a/kernel/pid_namespace.c >> +++ b/kernel/pid_namespace.c > [...] >> @@ -159,6 +201,30 @@ static void delayed_free_pidns(struct rcu_head *p) >> >> static void destroy_pid_namespace(struct pid_namespace *ns) >> { >> + struct pid_namespace *ph; >> + struct hlist_bl_head *head; >> + struct hlist_bl_node *dup_node; >> + >> + /* >> + * Remove the namespace structure from hash table so >> + * now new lookups can start on it. > s/now new/no new/ Will fix it. > > [...] >> @@ -474,9 +551,116 @@ static struct user_namespace *pidns_owner(struct ns_common *ns) >> .get_parent = pidns_get_parent, >> }; >> >> +/* >> + * translate_pid - convert pid in source pid-ns into target pid-ns. >> + * @pid: pid for translation >> + * @source: pid-ns id >> + * @target: pid-ns id >> + * >> + * Return pid in @target pid-ns, zero if task have no pid there, >> + * or -ESRCH of task with @pid is not found in @source pid-ns. > s/of/if/ Will fix it. > >> + */ >> +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? > > When doing ptrace access checks, please use the real creds in syscalls > like this one, not the fs creds. The fs creds are for filesystem > syscalls (in particular sys_open()), not for specialized syscalls like > ptrace() or this one. Will fix this. Thanks, Nagarathnam.