From: ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org (Eric W. Biederman) To: Ian Kent <raven-PKsaG3nR2I+sTnJN9+BGXg@public.gmane.org> Cc: linux-nfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Stanislav Kinsbursky <skinsbursky-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org>, Jeff Layton <jlayton-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Greg KH <gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org>, Linux Containers <containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org>, Oleg Nesterov <oleg-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, bfields-uC3wQj2KruNg9hUCZPvPmw@public.gmane.org, bharrosh-C4P08NqkoRlBDgjK7y7TUQ@public.gmane.org, linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, devel-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org Subject: Re: call_usermodehelper in containers Date: Wed, 17 Feb 2016 20:57:48 -0600 [thread overview] Message-ID: <8737sq4teb.fsf@x220.int.ebiederm.org> (raw) In-Reply-To: <1455149857.2903.9.camel-PKsaG3nR2I+sTnJN9+BGXg@public.gmane.org> (Ian Kent's message of "Thu, 11 Feb 2016 08:17:37 +0800") Ccing The containers list because a related discussion is happening there and somehow this thread has never made it there. Ian Kent <raven-PKsaG3nR2I+sTnJN9+BGXg@public.gmane.org> writes: > On Mon, 2013-11-18 at 18:28 +0100, Oleg Nesterov wrote: >> On 11/15, Eric W. Biederman wrote: >> > >> > I don't understand that one. Having a preforked thread with the >> > proper >> > environment that can act like kthreadd in terms of spawning user >> > mode >> > helpers works and is simple. > > Forgive me replying to such an old thread but ... > > After realizing workqueues can't be used to pre-create threads to run > usermode helpers I've returned to look at this. If someone can wind up with a good implementation I will be happy. >> Can't we ask ->child_reaper to create the non-daemonized kernel thread >> with the "right" ->nsproxy, ->fs, etc? > > Eric, do you think this approach would be sufficient too? > > Probably wouldn't be quite right for user namespaces but should provide > what's needed for other cases? > > It certainly has the advantage of not having to maintain a plague of > processes waiting around to execute helpers. That certainly sounds attractive. Especially for the case of everyone who wants to set a core pattern in a container. I am fuzzy on all of the details right now, but what I do remember is that in the kernel the user mode helper concepts when they attempted to scrub a processes environment were quite error prone until we managed to get kthreadd(pid 2) on the scene which always had a clean environment. If we are going to tie this kind of thing to the pid namespace I recommend simplying denying it if you are in a user namespace without an approrpriate pid namespace. AKA simply not allowing thigns to be setup if current->pid_ns->user_ns != current->user_ns. That still leaves things a little hand-wavy but I hope that helps conceptually. Eric
WARNING: multiple messages have this Message-ID (diff)
From: ebiederm@xmission.com (Eric W. Biederman) To: Ian Kent <raven@themaw.net> Cc: Oleg Nesterov <oleg@redhat.com>, Stanislav Kinsbursky <skinsbursky@parallels.com>, Jeff Layton <jlayton@redhat.com>, Greg KH <gregkh@linuxfoundation.org>, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-nfs@vger.kernel.org, devel@openvz.org, bfields@fieldses.org, bharrosh@panasas.com, Linux Containers <containers@lists.linux-foundation.org> Subject: Re: call_usermodehelper in containers Date: Wed, 17 Feb 2016 20:57:48 -0600 [thread overview] Message-ID: <8737sq4teb.fsf@x220.int.ebiederm.org> (raw) In-Reply-To: <1455149857.2903.9.camel@themaw.net> (Ian Kent's message of "Thu, 11 Feb 2016 08:17:37 +0800") Ccing The containers list because a related discussion is happening there and somehow this thread has never made it there. Ian Kent <raven@themaw.net> writes: > On Mon, 2013-11-18 at 18:28 +0100, Oleg Nesterov wrote: >> On 11/15, Eric W. Biederman wrote: >> > >> > I don't understand that one. Having a preforked thread with the >> > proper >> > environment that can act like kthreadd in terms of spawning user >> > mode >> > helpers works and is simple. > > Forgive me replying to such an old thread but ... > > After realizing workqueues can't be used to pre-create threads to run > usermode helpers I've returned to look at this. If someone can wind up with a good implementation I will be happy. >> Can't we ask ->child_reaper to create the non-daemonized kernel thread >> with the "right" ->nsproxy, ->fs, etc? > > Eric, do you think this approach would be sufficient too? > > Probably wouldn't be quite right for user namespaces but should provide > what's needed for other cases? > > It certainly has the advantage of not having to maintain a plague of > processes waiting around to execute helpers. That certainly sounds attractive. Especially for the case of everyone who wants to set a core pattern in a container. I am fuzzy on all of the details right now, but what I do remember is that in the kernel the user mode helper concepts when they attempted to scrub a processes environment were quite error prone until we managed to get kthreadd(pid 2) on the scene which always had a clean environment. If we are going to tie this kind of thing to the pid namespace I recommend simplying denying it if you are in a user namespace without an approrpriate pid namespace. AKA simply not allowing thigns to be setup if current->pid_ns->user_ns != current->user_ns. That still leaves things a little hand-wavy but I hope that helps conceptually. Eric
next prev parent reply other threads:[~2016-02-18 2:57 UTC|newest] Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top 2013-11-11 12:18 call_usermodehelper in containers Jeff Layton 2013-11-11 12:43 ` [Devel] " Vasily Kulikov 2013-11-11 13:26 ` Jeff Layton 2013-11-12 0:47 ` Greg KH 2013-11-12 11:12 ` Jeff Layton 2013-11-12 13:02 ` Stanislav Kinsbursky 2013-11-12 13:30 ` Jeff Layton 2013-11-15 5:05 ` Eric W. Biederman 2013-11-15 10:40 ` Stanislav Kinsbursky 2013-11-15 11:03 ` Eric W. Biederman 2013-11-15 11:54 ` Stanislav Kinsbursky 2016-02-12 23:39 ` Ian Kent 2016-02-13 16:08 ` Stanislav Kinsburskiy 2016-02-15 0:11 ` Ian Kent [not found] ` <1455495082.2941.32.camel-PKsaG3nR2I+sTnJN9+BGXg@public.gmane.org> 2016-02-18 3:17 ` Eric W. Biederman 2016-02-18 3:17 ` Eric W. Biederman 2013-11-18 17:28 ` Oleg Nesterov 2013-11-18 18:02 ` Oleg Nesterov 2013-11-19 14:51 ` Jeff Layton 2016-02-11 0:17 ` Ian Kent [not found] ` <1455149857.2903.9.camel-PKsaG3nR2I+sTnJN9+BGXg@public.gmane.org> 2016-02-18 2:57 ` Eric W. Biederman [this message] 2016-02-18 2:57 ` Eric W. Biederman [not found] ` <8737sq4teb.fsf-JOvCrm2gF+uungPnsOpG7nhyD016LWXt@public.gmane.org> 2016-02-18 3:43 ` Kamezawa Hiroyuki 2016-02-18 3:43 ` Kamezawa Hiroyuki 2016-02-18 6:36 ` Ian Kent 2016-02-18 7:37 ` Ian Kent [not found] ` <1455781033.2908.5.camel-PKsaG3nR2I+sTnJN9+BGXg@public.gmane.org> 2016-02-18 20:45 ` Eric W. Biederman 2016-02-18 20:45 ` Eric W. Biederman [not found] ` <87r3g9ychc.fsf-JOvCrm2gF+uungPnsOpG7nhyD016LWXt@public.gmane.org> 2016-02-19 3:08 ` Kamezawa Hiroyuki 2016-02-19 3:08 ` Kamezawa Hiroyuki [not found] ` <56C68714.2000900-+CUm20s59erQFUHtdCDX3A@public.gmane.org> 2016-02-19 5:37 ` Ian Kent 2016-02-19 5:37 ` Ian Kent [not found] ` <1455860260.3356.31.camel-PKsaG3nR2I+sTnJN9+BGXg@public.gmane.org> 2016-02-19 9:30 ` Kamezawa Hiroyuki 2016-02-19 9:30 ` Kamezawa Hiroyuki [not found] ` <56C6E0A8.3010806-+CUm20s59erQFUHtdCDX3A@public.gmane.org> 2016-02-20 3:28 ` Ian Kent 2016-02-20 3:28 ` Ian Kent 2016-02-19 5:14 ` Ian Kent 2016-02-19 5:14 ` Ian Kent 2016-02-23 2:55 ` Ian Kent [not found] ` <1456196130.2911.10.camel-PKsaG3nR2I+sTnJN9+BGXg@public.gmane.org> 2016-02-23 14:36 ` J. Bruce Fields 2016-02-23 14:36 ` J. Bruce Fields [not found] ` <20160223143627.GB31951-uC3wQj2KruNg9hUCZPvPmw@public.gmane.org> 2016-02-24 0:55 ` Ian Kent 2016-02-24 0:55 ` Ian Kent [not found] ` <1455858850.3356.19.camel-PKsaG3nR2I+sTnJN9+BGXg@public.gmane.org> 2016-02-23 2:55 ` Ian Kent [not found] ` <1455777387.3188.24.camel-PKsaG3nR2I+sTnJN9+BGXg@public.gmane.org> 2016-02-18 7:37 ` Ian Kent [not found] ` <56C53DE3.1070108-+CUm20s59erQFUHtdCDX3A@public.gmane.org> 2016-02-18 6:36 ` Ian Kent 2016-03-24 7:45 ` Ian Kent 2016-03-25 1:28 ` Oleg Nesterov 2016-03-25 7:25 ` Ian Kent
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