linux-kernel - Re: [PATCH 1/2] autofs4: allow autofs to work outside the initial PID namespace

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Date:	Mon, 26 Nov 2012 17:11:23 +0100
From:	Miklos Szeredi <miklos@...redi.hu>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Ian Kent <raven@...maw.net>, autofs@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	sukadev@...ux.vnet.ibm.com, serge.hallyn@...onical.com,
	Al Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH 1/2] autofs4: allow autofs to work outside the initial PID namespace

On Mon, Nov 26, 2012 at 3:38 PM, Eric W. Biederman
<ebiederm@...ssion.com> wrote:
>
> So I don't know how much MS_UNBINDABLE helps over MS_PRIVATE.  Both
> prevent propogation of changes to other namespaces.  I don't know how
> much using MS_UNBINDABLE to also prevent bind mounts helps.

MS_PRIVATE says ops on children (mount, unmount) won't be propageted,
MS_UNBINDABLE says the mount itself won't be copied.

I think it may make sense to introduce a new flag similar to
MS_UNBINDABLE that applies to namespace cloning as well as bind
mounting.  It says: this mount is managed by some userspace entity
(autofs) and copying it to the new namespace or to some other part of
the tree makes no sense since a new instance of the  userspace entity
responsible for managing those mounts will need to be started in the
new namespace as well.  I can't think of any other sane solution to
this issue.

Thanks,
Miklos

>
> Eric
>
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