linux-kernel - Re: [PATCH 08/28] SECURITY: Allow kernel services to override LSM settings for task actions [try #2]

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Date:	Mon, 10 Dec 2007 21:08:07 +0000
From:	David Howells <dhowells@...hat.com>
To:	Stephen Smalley <sds@...ho.nsa.gov>,
	Karl MacMillan <kmacmill@...hat.com>
Cc:	dhowells@...hat.com, viro@....linux.org.uk, hch@...radead.org,
	Trond.Myklebust@...app.com, casey@...aufler-ca.com,
	linux-kernel@...r.kernel.org, selinux@...ho.nsa.gov,
	linux-security-module@...r.kernel.org
Subject: Re: [PATCH 08/28] SECURITY: Allow kernel services to override LSM settings for task actions [try #2]

Stephen Smalley <sds@...ho.nsa.gov> wrote:

> Otherwise, only other issue I have with this interface is it won't
> generalize to dealing with nfsd, where we want to set the acting context
> to a context we obtain from or determine based upon the client.

Are you speaking of security_kernel_act_as() and security_create_files_as()
specifically?  Or the task_struct::act_as override pointer in general?

I don't really know how nfsd wants to obtain and set its LSM context, so it's
a bit difficult for me to make something that works for nfsd as well as
cachefiles.

> Why can't cachefilesd just push a context into the kernel and pass that
> into the hook as the acting context,

How does cachefilesd come up with such a context?  Grab it from
/etc/cachefilesd.conf?

I use to do that, but someone objected...  Possibly Karl MacMillan.

> and then nfsd can do likewise using the context provided by the client or
> obtained locally from exports for ordinary clients?  Avoids the transition
> SID computation altogether within the kernel and makes this more generic.

I seem to remember that I was told that it should be done this way, possibly
by Karl MacMillan, but I don't remember exactly.

Now it's configured by cachefilesd.te:

	type_transition cachefilesd_t kernel_t : process cachefiles_kernel_t;

David
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