[PATCH 0/6] File Sealing & memfd_create()

[Andy Lutomirski]

On 04/10/2014 07:45 AM, Colin Walters wrote:
> On Thu, Mar 20, 2014 at 11:32 AM, tytso at 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