From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S939167AbdAISMh (ORCPT ); Mon, 9 Jan 2017 13:12:37 -0500 Received: from mx1.redhat.com ([209.132.183.28]:35886 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932317AbdAISMb (ORCPT ); Mon, 9 Jan 2017 13:12:31 -0500 Date: Mon, 9 Jan 2017 19:12:25 +0100 From: Oleg Nesterov To: yangshukui Cc: selinux@tycho.nsa.gov, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, Kefeng Wang , "Guohanjun (Hanjun Guo)" , "'Qiang Huang'" , Lizefan , "miaoxie (A)" , Zhangdianfang , paul@paul-moore.com, sds@tycho.nsa.gov, eparis@parisplace.org, james.l.morris@oracle.com, ebiederm@xmission.com, serge.hallyn@ubuntu.com Subject: Re: SELinux lead to soft lockup when pid 1 proceess reap child Message-ID: <20170109181225.GB8972@redhat.com> References: <58732BCF.4090908@huawei.com> <58734284.1060504@huawei.com> <58736B2E.90201@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <58736B2E.90201@huawei.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.32]); Mon, 09 Jan 2017 18:12:30 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/09, yangshukui wrote: > > --- a/security/selinux/hooks.c > +++ b/security/selinux/hooks.c > @@ -3596,6 +3596,9 @@ static int selinux_task_kill(struct task_struct *p, > struct siginfo *info, > > static int selinux_task_wait(struct task_struct *p) > { > + if (pid_vnr(task_tgid(current)) == 1){ > + return 0; this check is not really correct, it can be a sub-thread... Doesn't matter, please see below. > + } > return task_has_perm(p, current, PROCESS__SIGCHLD); > } > It work but it permit pid 1 process to reap child without selinux check. Can > we have a better way to handle this problem? I never understood why security_task_wait() should deny to reap a child. But since it can we probably want some explicit "the whole namespace goes away" check. We could use, say, PIDNS_HASH_ADDING but I'd suggest something like a trivial change below for now. Eric, what do you think? Oleg. diff --git a/security/security.c b/security/security.c index f825304..1330b4e 100644 --- a/security/security.c +++ b/security/security.c @@ -1027,6 +1027,9 @@ int security_task_kill(struct task_struct *p, struct siginfo *info, int security_task_wait(struct task_struct *p) { + /* must be the exiting child reaper */ + if (unlikely(current->flags & PF_EXITING)) + return 0; return call_int_hook(task_wait, 0, p); }