Date: Mon, 17 Dec 2007 20:09:33 -0600
From: "Serge E. Hallyn" <serue@us.ibm.com>
To: Oren Laadan <orenl@cs.columbia.edu>
Cc: "Serge E. Hallyn" <serue@us.ibm.com>,
       Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
       linux-fsdevel@vger.kernel.org,
       Linux Containers <containers@lists.osdl.org>,
       linux-kernel@vger.kernel.org
Subject: Re: [patch 1/2] [RFC] Simple tamper-proof device filesystem.
Message-ID: <20071218020933.GA28745@sergelap.austin.ibm.com>
References: <20071216080441.435456586@I-love.SAKURA.ne.jp> <20071216080628.061470932@I-love.SAKURA.ne.jp> <200712161944.HEI26071.MOtOFLVHFSQFOJ@I-love.SAKURA.ne.jp> <200712161956.BJE32406.FOOHtQJLMFOSVF@I-love.SAKURA.ne.jp> <20071217194802.GA14156@sergelap.austin.ibm.com> <200712180003.lBI03N7F092396@www262.sakura.ne.jp> <20071218003955.GA27048@sergelap.austin.ibm.com> <476724E3.6060901@cs.columbia.edu>
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Quoting Oren Laadan (orenl@cs.columbia.edu):
> 
> I hate to bring this again, but what if the admin in the container
> mounts an external file system (eg. nfs, usb, loop mount from a file,
> or via fuse), and that file system already has a device that we would
> like to ban inside that container ?

Miklos' user mount patches enforced that if !capable(CAP_MKNOD),
then mnt->mnt_flags |= MNT_NODEV.  So that's no problem.

But that's been pulled out of -mm! ?  Crap.

> Since anyway we will have to keep a white- (or black-) list of devices
> that are permitted in a container, and that list may change even change
> per container -- why not enforce the access control at the VFS layer ?
> It's safer in the long run.

By that you mean more along the lines of Pavel's patch than my whitelist
LSM, or you actually mean Tetsuo's filesystem (i assume you don't mean that
by 'vfs layer' :), or something different entirely?

thanks,
-serge
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