linux-kernel - Re: call_usermodehelper in containers

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Message-ID: <20131118180259.GA11722@redhat.com>
Date:	Mon, 18 Nov 2013 19:02:59 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Stanislav Kinsbursky <skinsbursky@...allels.com>,
	Jeff Layton <jlayton@...hat.com>,
	Greg KH <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	linux-nfs@...r.kernel.org, devel@...nvz.org, bfields@...ldses.org,
	bharrosh@...asas.com
Subject: Re: call_usermodehelper in containers

On 11/18, 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.
>
> Can't we ask ->child_reaper to create the non-daemonized kernel thread
> with the "right" ->nsproxy, ->fs, etc?
>
> IOW. Please the the "patch" below. It is obviously incomplete and wrong,
> and it can be more clear/clean. And probably we need another API. Just
> to explain what I mean.

Or, perhaps UMH_IN_MY_NS should only work if ->child_reaper explicitly
does, say, prctl(PR_SPAWN_UMH_IN_NS_HELPER) which forks the non-daemonized
kernel kthread_worker thread, I dunno.

Oleg.

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