Message-ID: <5346EDE8.2060004@amacapital.net>
Date: Thu, 10 Apr 2014 12:15:52 -0700
From: Andy Lutomirski <luto@amacapital.net>
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To: Colin Walters <walters@verbum.org>, tytso@mit.edu
CC: David Herrmann <dh.herrmann@gmail.com>, linux-kernel@vger.kernel.org,
        Hugh Dickins <hughd@google.com>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Matthew Wilcox <matthew@wil.cx>,
        Karol Lewandowski <k.lewandowsk@samsung.com>,
        Kay Sievers <kay@vrfy.org>, Daniel Mack <zonque@gmail.com>,
        Lennart Poettering <lennart@poettering.net>, Kristian@thunk.org,
        john.stultz@linaro.org, Greg Kroah-Hartman <greg@kroah.com>,
        Tejun Heo <tj@kernel.org>, Johannes Weiner <hannes@cmpxchg.org>,
        dri-devel@lists.freedesktop.org, linux-fsdevel@vger.kernel.org,
        linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Ryan Lortie <desrt@desrt.ca>, mtk.manpages@gmail.com
Subject: Re: [PATCH 0/6] File Sealing & memfd_create()
References: <1395256011-2423-1-git-send-email-dh.herrmann@gmail.com>	<20140320153250.GC20618@thunk.org> <1397141388.16343.10@mail.messagingengine.com>
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On 04/10/2014 07:45 AM, Colin Walters wrote:
> On Thu, Mar 20, 2014 at 11:32 AM, tytso@mit.edu wrote:
>>
>> Looking at your patches, and what files you are modifying, you are
>> enforcing this in the low-level file system.
> 
> I would love for this to be implemented in the filesystem level as
> well.  Something like the ext4 immutable bit, but with the ability to
> still make hardlinks would be *very* useful for OSTree.  And anyone else
> that uses hardlinks as a data source.  The vserver people do something
> similiar:
> http://linux-vserver.org/util-vserver:Vhashify
> 
> At the moment I have a read-only bind mount over /usr, but what I really
> want is to make the individual objects in the object store in
> /ostree/repo/objects be immutable, so even if a user or app navigates
> out to /sysroot they still can't mutate them (or the link targets in the
> visible /usr).

COW links can do this already, I think.  Of course, you'll have to use a
filesystem that supports them.

--Andy
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