linux-kernel - Re: [PATCH v3 0/7] User namespace mount updates

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Message-ID: <564B7F83.1050701@nod.at>
Date:	Tue, 17 Nov 2015 20:26:59 +0100
From:	Richard Weinberger <richard@....at>
To:	Seth Forshee <seth.forshee@...onical.com>
Cc:	Al Viro <viro@...iv.linux.org.uk>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	linux-bcache@...r.kernel.org,
	device-mapper development <dm-devel@...hat.com>,
	"linux-raid@...r.kernel.org" <linux-raid@...r.kernel.org>,
	"linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	LSM <linux-security-module@...r.kernel.org>,
	selinux@...ho.nsa.gov, Serge Hallyn <serge.hallyn@...onical.com>,
	Andy Lutomirski <luto@...capital.net>,
	LKML <linux-kernel@...r.kernel.org>,
	Theodore Ts'o <tytso@....edu>,
	Octavian Purdila <octavian.purdila@...el.com>
Subject: Re: [PATCH v3 0/7] User namespace mount updates

Am 17.11.2015 um 20:21 schrieb Seth Forshee:
> On Tue, Nov 17, 2015 at 08:12:31PM +0100, Richard Weinberger wrote:
>> On Tue, Nov 17, 2015 at 7:34 PM, Seth Forshee
>> <seth.forshee@...onical.com> wrote:
>>> On Tue, Nov 17, 2015 at 05:55:06PM +0000, Al Viro wrote:
>>>> On Tue, Nov 17, 2015 at 11:25:51AM -0600, Seth Forshee wrote:
>>>>
>>>>> Shortly after that I plan to follow with support for ext4. I've been
>>>>> fuzzing ext4 for a while now and it has held up well, and I'm currently
>>>>> working on hand-crafted attacks. Ted has commented privately (to others,
>>>>> not to me personally) that he will fix bugs for such attacks, though I
>>>>> haven't seen any public comments to that effect.
>>>>
>>>> _Static_ attacks, or change-image-under-mounted-fs attacks?
>>>
>>> Right now only static attacks, change-image-under-mounted-fs attacks
>>> will be next.
>>
>> Do we *really* need to enable unprivileged mounting of kernel filesystems?
>> What about just enabling fuse and implement ext4 and friends as fuse
>> filesystems?
>> Using the approaching Linux Kernel Libary[1] this is easy.
> 
> I haven't looked at this project, but I'm guessing that programs must be
> written specifically to make use of it? I.e. you can't just use the
> mount syscall, and thus all existing software still doesn't work?

You can easy bridge fuse and the LKL, I did already a hacky PoC. Worked nicely.
Octavian's tree has some nice examples, and AFAIK he is currently working
on a "mount any kernel fs via fuse" tool.

Thanks,
//richard
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