From: Serge Hallyn <serge.hallyn@ubuntu.com>
To: LXC development mailing-list <lxc-devel@lists.linuxcontainers.org>
Cc: Jens Axboe <axboe@kernel.dk>,
Serge Hallyn <serge.hallyn@canonical.com>,
Arnd Bergmann <arnd@arndb.de>,
linux-kernel@vger.kernel.org,
James Bottomley <James.Bottomley@HansenPartnership.com>,
Seth Forshee <seth.forshee@canonical.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Subject: Re: [lxc-devel] [RFC PATCH 00/11] Add support for devtmpfs in user namespaces
Date: Tue, 20 May 2014 14:18:30 +0000 [thread overview]
Message-ID: <20140520141830.GG26600@ubuntumail> (raw)
In-Reply-To: <1400548481.3540.247.camel@canyon.ip6.wittsend.com>
Quoting Michael H. Warfield (mhw@WittsEnd.com):
> On Mon, 2014-05-19 at 17:04 -0700, Eric W. Biederman wrote:
> > Seth Forshee <seth.forshee@canonical.com> writes:
> >
> > > What I set out for was feature parity between loop devices in a secure
> > > container and loop devices on the host. Since some operations currently
> > > check for system-wide CAP_SYS_ADMIN, the only way I see to accomplish
> > > this is to push knowledge of the user namespace farther down into the
> > > driver stack so the check can instead be for CAP_SYS_ADMIN in the user
> > > namespace associated with the device.
> > >
> > > That said, I suspect our current use cases can get by without these
> > > capabilities. Really though I suspect this is just deferring the
> > > discussion rather than settling it, and what we'll end up with is little
> > > more than a fancy way for userspace to ask the kernel to run mknod on
> > > its behalf.
>
> > A fancy way to ask the kernel to run mknod on its behalf is what
> > /dev/pts is.
>
> > When I suggested this I did not mean you should forgo making changes to
> > allow partitions and the like. What I itended is that you should find a
> > way to make this safe for users who don't have root capabilities.
>
> I like to think in terms of the "rootless" configurations where "root"
> per se is not absolute and everything is framed in terms of
> capabilities.
>
> > Which possibly means that mount needs to learn how to keep a more
> > privileged user from using your new loop devices.
>
> Not sure I got that one. As user with "more" privileges may or may not
> have access dependent on the congruence of the privileges. They're not
Yes so in this case by more privileged' he meant a privileged user in a
userns which is ancestor to the current userns. It is in fact *more*
privileged than any user in the current userns.
> heiarchial. If someone has that "priv" then they have access. If they
They are in fact implicitly hierarchical due to the hierarchical userns
design.
> do not, they do not.
>
> > To get to the point where this is really and truly usable I expect to be
> > technically daunting.
>
> Most technically non-trivial problems generally are.
>
> > Ultimately the technical challenge is how do we create a block device
> > that is safe for a user who does not have any capabilities to use, and
> > what can we do with that block device to make it useful.
>
> Concur. It boils down to privilege management and access. Absolutely
> concur.
>
> > Only when the question is can this kernel functionality which is
> > otherwise safe confuse a preexisting setuid application do namespace
> > or container bits significantly come into play.
>
> Ah... Admittedly it's not as late as our conversation at LinuxPlumbers
> last year in NOLA but... Maybe late at night but I failed to parse the
> above.
>
> > Eric
>
> Regards,
> Mike
> --
> Michael H. Warfield (AI4NB) | (770) 978-7061 | mhw@WittsEnd.com
> /\/\|=mhw=|\/\/ | (678) 463-0932 | http://www.wittsend.com/mhw/
> NIC whois: MHW9 | An optimist believes we live in the best of all
> PGP Key: 0x674627FF | possible worlds. A pessimist is sure of it!
>
> _______________________________________________
> lxc-devel mailing list
> lxc-devel@lists.linuxcontainers.org
> http://lists.linuxcontainers.org/listinfo/lxc-devel
next prev parent reply other threads:[~2014-05-20 14:18 UTC|newest]
Thread overview: 76+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-14 21:34 [RFC PATCH 00/11] Add support for devtmpfs in user namespaces Seth Forshee
2014-05-14 21:34 ` [RFC PATCH 01/11] driver core: Assign owning user namespace to devices Seth Forshee
2014-05-14 21:34 ` [RFC PATCH 02/11] driver core: Add device_create_global() Seth Forshee
2014-05-14 21:34 ` [RFC PATCH 03/11] tmpfs: Add sub-filesystem data pointer to shmem_sb_info Seth Forshee
2014-05-14 21:34 ` [RFC PATCH 04/11] ramfs: Add sub-filesystem data pointer to ram_fs_info Seth Forshee
2014-05-14 21:34 ` [RFC PATCH 05/11] devtmpfs: Add support for mounting in user namespaces Seth Forshee
2014-05-14 21:34 ` [RFC PATCH 06/11] drivers/char/mem.c: Make null/zero/full/random/urandom available to " Seth Forshee
2014-05-14 21:34 ` [RFC PATCH 07/11] block: Make partitions inherit namespace from whole disk device Seth Forshee
2014-05-14 21:34 ` [RFC PATCH 08/11] block: Allow blkdev ioctls within user namespaces Seth Forshee
2014-05-14 21:34 ` [RFC PATCH 09/11] misc: Make loop-control available to all " Seth Forshee
2014-05-14 21:34 ` [RFC PATCH 10/11] loop: Assign devices to current_user_ns() Seth Forshee
2014-05-14 21:34 ` [RFC PATCH 11/11] loop: Allow priveleged operations for root in the namespace which owns a device Seth Forshee
2014-05-23 5:48 ` Marian Marinov
2014-05-26 9:16 ` Seth Forshee
2014-05-26 15:32 ` [lxc-devel] " Michael H. Warfield
2014-05-26 15:45 ` Seth Forshee
2014-05-27 1:36 ` Serge E. Hallyn
2014-05-27 2:39 ` Michael H. Warfield
2014-05-27 7:16 ` Seth Forshee
2014-05-27 13:16 ` Serge Hallyn
2014-05-15 1:32 ` [RFC PATCH 00/11] Add support for devtmpfs in user namespaces Greg Kroah-Hartman
2014-05-15 2:17 ` [lxc-devel] " Michael H. Warfield
2014-05-15 3:15 ` Seth Forshee
2014-05-15 4:00 ` Greg Kroah-Hartman
2014-05-15 13:42 ` Michael H. Warfield
2014-05-15 14:08 ` Greg Kroah-Hartman
2014-05-15 17:42 ` Serge Hallyn
2014-05-15 18:12 ` Seth Forshee
2014-05-15 22:15 ` Greg Kroah-Hartman
2014-05-16 1:42 ` Michael H. Warfield
2014-05-16 7:56 ` Richard Weinberger
2014-05-16 19:20 ` James Bottomley
2014-05-16 19:42 ` Michael H. Warfield
2014-05-16 19:52 ` [lxc-devel] Mount and other notifiers, was: " James Bottomley
2014-05-16 20:04 ` Michael H. Warfield
2014-05-16 1:49 ` [lxc-devel] " Serge Hallyn
2014-05-16 4:35 ` Greg Kroah-Hartman
2014-05-16 14:06 ` Seth Forshee
2014-05-16 15:28 ` Michael H. Warfield
2014-05-16 15:43 ` Seth Forshee
2014-05-16 18:57 ` Greg Kroah-Hartman
2014-05-16 19:28 ` James Bottomley
2014-05-16 20:18 ` Seth Forshee
2014-05-20 0:04 ` Eric W. Biederman
2014-05-20 1:14 ` Michael H. Warfield
2014-05-20 14:18 ` Serge Hallyn [this message]
2014-05-20 14:21 ` Seth Forshee
2014-05-21 22:00 ` Eric W. Biederman
2014-05-21 22:33 ` Serge Hallyn
2014-05-23 22:23 ` Eric W. Biederman
2014-05-28 9:26 ` Seth Forshee
2014-05-28 13:12 ` Serge E. Hallyn
2014-05-28 20:33 ` Eric W. Biederman
2014-05-18 2:42 ` Serge E. Hallyn
2014-05-17 4:31 ` Eric W. Biederman
2014-05-17 16:01 ` Seth Forshee
2014-05-18 2:44 ` Serge E. Hallyn
2014-05-19 13:27 ` Seth Forshee
2014-05-20 14:15 ` Serge Hallyn
2014-05-20 14:26 ` Serge Hallyn
2014-05-17 12:57 ` Michael H. Warfield
2014-05-15 18:25 ` Richard Weinberger
2014-05-15 19:50 ` Serge Hallyn
2014-05-15 20:13 ` Richard Weinberger
2014-05-15 20:26 ` Serge E. Hallyn
2014-05-15 20:33 ` Richard Weinberger
2014-05-19 20:22 ` Andy Lutomirski
2014-05-20 14:19 ` Serge Hallyn
2014-05-23 8:20 ` Marian Marinov
2014-05-23 13:16 ` James Bottomley
2014-05-23 16:39 ` Andy Lutomirski
2014-05-24 22:25 ` Serge Hallyn
2014-05-25 8:12 ` James Bottomley
2014-05-25 22:24 ` Serge E. Hallyn
2014-05-28 7:02 ` James Bottomley
2014-05-28 13:49 ` Serge Hallyn
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