From: Alan Cox <gnomes@lxorguk.ukuu.org.uk>
To: Dave Chinner <david@fromorbit.com>
Cc: TongZhang <ztong@vt.edu>,
darrick.wong@oracle.com, linux-xfs@vger.kernel.org,
LKML <linux-kernel@vger.kernel.org>,
linux-security-module@vger.kernel.org,
Wenbo Shen <shenwenbosmile@gmail.com>
Subject: Re: Leaking Path in XFS's ioctl interface(missing LSM check)
Date: Mon, 1 Oct 2018 16:04:42 +0100 [thread overview]
Message-ID: <20181001160442.47c798bc@alans-desktop> (raw)
In-Reply-To: <20181001002521.GM31060@dastard>
> /* only root can play with this */
> if (!capable(CAP_SYS_ADMIN))
> return -EACCES;
>
> Think about it - if DM control ioctls only require CAP_SYS_ADMIN,
> then if have that cap you can use DM to remap any block in a block
> device to any other block. You don't need to the filesystem to move
> stuff around, it can be moved around without the filesystem knowing
> anything about it.
Yes - I am not surprised the XFS is not the only problem area. The fact
XFS also isn't going via the security hooks so security hooks can fix it
just makes it worse.
> > That's what people said about setuid shell scripts.
>
> Completely different. setuid shell scripts got abused as a hack for
> the lazy to avoid setting up permissions properly and hence were
> easily exploited.
Sounds to me like an accurate description of the current capabilities
mess in the kernel (and not just XFS and not just file systems)
> Systems restricted by LSMs to the point where CAP_SYS_ADMIN is not
> trusted have exactly the same issues. i.e. there's nobody trusted by
> the kernel to administer the storage stack, and nobody has defined a
> workable security model that can prevent untrusted users from
> violating the existing storage trust model....
With a proper set of LSM checks you can lock the filesystem management
and enforcement to a particular set of objects. You can build that model
where for example only an administrative login from a trusted console may
launch processes to do that management.
Or you could - if things were not going around the LSM hooks.
Alan
next prev parent reply other threads:[~2018-10-01 15:04 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-26 0:51 Leaking Path in XFS's ioctl interface(missing LSM check) TongZhang
2018-09-26 1:33 ` Dave Chinner
2018-09-26 13:23 ` Stephen Smalley
2018-09-27 2:08 ` Dave Chinner
2018-09-26 18:24 ` Alan Cox
2018-09-27 1:38 ` Dave Chinner
2018-09-27 21:23 ` James Morris
2018-09-27 22:19 ` Dave Chinner
2018-09-27 23:12 ` Tetsuo Handa
2018-09-30 14:16 ` Alan Cox
2018-10-01 0:25 ` Dave Chinner
2018-10-01 15:04 ` Alan Cox [this message]
2018-10-01 15:25 ` Theodore Y. Ts'o
2018-10-01 22:53 ` Dave Chinner
2018-10-01 15:44 ` Darrick J. Wong
2018-10-01 20:08 ` James Morris
2018-10-01 22:45 ` Dave Chinner
2018-10-02 19:20 ` James Morris
2018-10-02 22:42 ` Dave Chinner
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