linux-kernel - Re: [PATCH v5 3/4] fuse: Restrict allow_other to the superblock's namespace or a descendant

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Date:	Tue, 11 Nov 2014 16:27:37 +0100
From:	Miklos Szeredi <miklos@...redi.hu>
To:	Seth Forshee <seth.forshee@...onical.com>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	"Serge H. Hallyn" <serge.hallyn@...ntu.com>,
	Andy Lutomirski <luto@...capital.net>,
	Michael j Theall <mtheall@...ibm.com>,
	fuse-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH v5 3/4] fuse: Restrict allow_other to the superblock's
 namespace or a descendant

On Wed, Oct 22, 2014 at 04:24:19PM -0500, Seth Forshee wrote:
> Unprivileged users are normally restricted from mounting with the
> allow_other option by system policy, but this could be bypassed
> for a mount done with user namespace root permissions. In such
> cases allow_oth er should not allow users outside the userns
> to access the mount as doing so would give the unprivileged user
> the ability to manipulate processes it would otherwise be unable
> to manipulate. Therefore access with allow_other should be
> restricted to users in the userns as the superblock or a
> descendant of that namespace.

Fine.

But aren't this kind of thing supposed to be prevented anyway by having private
mount namespace coupled with the pid-user-whatever namespace?

It seems like being a bit too careful (not to say that that's a bad thing).

Thanks,
Miklos
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