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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Wed, 18 Nov 2015 13:44:08 -0500
From:	bfields@...ldses.org (J. Bruce Fields)
To:	Al Viro <viro@...IV.linux.org.uk>
Cc:	Austin S Hemmelgarn <ahferroin7@...il.com>,
	Seth Forshee <seth.forshee@...onical.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	linux-bcache@...r.kernel.org, dm-devel@...hat.com,
	linux-raid@...r.kernel.org, linux-mtd@...ts.infradead.org,
	linux-fsdevel@...r.kernel.org,
	linux-security-module@...r.kernel.org, selinux@...ho.nsa.gov,
	Serge Hallyn <serge.hallyn@...onical.com>,
	Andy Lutomirski <luto@...capital.net>,
	linux-kernel@...r.kernel.org, Theodore Ts'o <tytso@....edu>
Subject: Re: [PATCH v3 0/7] User namespace mount updates

On Tue, Nov 17, 2015 at 07:30:12PM +0000, Al Viro wrote:
> On Tue, Nov 17, 2015 at 02:02:09PM -0500, Austin S Hemmelgarn wrote:
> 
> > >_Static_ attacks, or change-image-under-mounted-fs attacks?
> > To properly protect against attacks on mounted filesystems, we'd
> > need some new concept of a userspace immutable file (that is, one
> > where nobody can write to it except the kernel, and only the kernel
> > can change it between regular access and this new state), and then
> > have the kernel set an image (or block device) to this state when a
> > filesystem is mounted from it (this introduces all kinds of other
> > issues too however, for example stuff that allows an online fsck on
> > the device will stop working, as will many un-deletion tools).
> > 
> > The only other option would be to force the FS to cache all metadata
> > in memory, and validate between the cache and what's on disk on
> > every access, which is not realistic for any real world system.
> 
> Doctor, it hurt when I do it...
> 
> IOW, the other option is to refuse attempting this insanity.  Fuse probably
> can be handled, but being able to mount (with kernel-space drivera) an
> arbitrary ext4 image is equivalent to being able to do anything and it's
> going to stay that way for the forseeable future.

What about the filesystems that desktop users commonly mount? (fat,
isofs, udf?)

--b.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/