linux-kernel - Re: [PATCH v2 0/7] Smack namespace

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Message-id: <1432658555.1974.26.camel@samsung.com>
Date:	Tue, 26 May 2015 18:42:35 +0200
From:	Lukasz Pawelczyk <l.pawelczyk@...sung.com>
To:	Stephen Smalley <sds@...ho.nsa.gov>
Cc:	"David S. Miller" <davem@...emloft.net>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	"Kirill A. Shutemov" <kirill@...temov.name>,
	"Serge E. Hallyn" <serge@...lyn.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	Alexey Dobriyan <adobriyan@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andy Lutomirski <luto@...capital.net>,
	Casey Schaufler <casey@...aufler-ca.com>,
	David Howells <dhowells@...hat.com>,
	Fabian Frederick <fabf@...net.be>,
	Greg KH <gregkh@...uxfoundation.org>,
	James Morris <james.l.morris@...cle.com>,
	Jeff Layton <jlayton@...marydata.com>,
	Jingoo Han <jg1.han@...sung.com>,
	Joe Perches <joe@...ches.com>,
	John Johansen <john.johansen@...onical.com>,
	Jonathan Corbet <corbet@....net>,
	Kees Cook <keescook@...omium.org>,
	Mauro Carvalho Chehab <mchehab@....samsung.com>,
	Miklos Szeredi <miklos@...redi.hu>,
	Oleg Nesterov <oleg@...hat.com>,
	Paul Moore <paul@...l-moore.com>,
	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
	Zefan Li <lizefan@...wei.com>,
	Rafal Krypa <r.krypa@...sung.com>, linux-doc@...r.kernel.org,
	linux-api@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org,
	containers@...ts.linux-foundation.org,
	Lukasz Pawelczyk <havner@...il.com>
Subject: Re: [PATCH v2 0/7] Smack namespace

On wto, 2015-05-26 at 12:34 -0400, Stephen Smalley wrote:
> > On wto, 2015-05-26 at 10:35 -0400, Stephen Smalley wrote:
> >> On 05/25/2015 08:32 AM, Lukasz Pawelczyk wrote:
> > 
> > I call the inode operation by hand in the post_setxattr.
> > 
> > The label will effectively be set twice, which is not ideal, but there
> > is no other option right now without reworking the hooks as you said.
> > 
> > This shouldn't really be a problem because the Smack operations will not
> > use the filesystem label (even when it's set incorrectly for a moment)
> > but an already initialized smack_known structure for this inode that has
> > all the values filled in properly.
> > 
> > The only attack vector I can think of is hard rebooting the machine in a
> > way that mapped label is really saved in the filesystem before the
> > unmapped will have a chance. Should I be worried about that? This sounds
> > a little unreal.
> 
> If it were my security module, I would be worried about it.  Even aside
> from maliciously induced failure, you are leaving yourself open to
> inconsistencies arising upon crashes.  I would suggest modifying the
> setxattr hook so that the security module can override the original
> value/size pair with its own definition before it is passed to the inode
> operation.  There is already precedent in that security modules are
> allowed to override the value/size returned by getxattr for security.*,
> so this just makes them fully parallel.

Will do. Thank you.


-- 
Lukasz Pawelczyk
Samsung R&D Institute Poland
Samsung Electronics



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