linux-kernel - Re: [PATCH 08/32] smack: Implement filesystem context security hooks [ver #9]

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Message-ID: <16480.1531264793@warthog.procyon.org.uk>
Date:   Wed, 11 Jul 2018 00:19:53 +0100
From:   David Howells <dhowells@...hat.com>
To:     Casey Schaufler <casey@...aufler-ca.com>
Cc:     dhowells@...hat.com, viro@...iv.linux.org.uk,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        torvalds@...ux-foundation.org
Subject: Re: [PATCH 08/32] smack: Implement filesystem context security hooks [ver #9]

Casey Schaufler <casey@...aufler-ca.com> wrote:

> > Implement filesystem context security hooks for the smack LSM.
> >
> > Question: Should the ->fs_context_parse_source() hook be implemented to
> > check the labels on any source devices specified?
> 
> Checking the label on a block device when doing a mount
> is just going to end in tears. If you're remounting from
> an already mounted filesystem it might make sense to check
> that the new mount doesn't provide greater access than the
> existing mount. If the original mount has smackfsdefault="_"
> I could see prohibiting the additional mount having
> smackfsdefault="*" on a filesystem that doesn't support
> xattrs. But that requires that a (hopefully) privileged
> process be involved, and we expect them to have a clue.
> So no, I don't see it necessary.

I think I may have meant the device file rather than the actual device
content.

David