From: Richard Weinberger <richard@nod.at>
To: "Serge E. Hallyn" <serge@hallyn.com>
Cc: Serge Hallyn <serge.hallyn@ubuntu.com>,
LXC development mailing-list
<lxc-devel@lists.linuxcontainers.org>,
"Michael H. Warfield" <mhw@wittsend.com>,
Jens Axboe <axboe@kernel.dk>,
Serge Hallyn <serge.hallyn@canonical.com>,
Arnd Bergmann <arnd@arndb.de>,
LKML <linux-kernel@vger.kernel.org>,
Andy Lutomirski <luto@amacapital.net>,
James.Bottomley@HansenPartnership.com
Subject: Re: [lxc-devel] [RFC PATCH 00/11] Add support for devtmpfs in user namespaces
Date: Thu, 15 May 2014 22:33:11 +0200 [thread overview]
Message-ID: <53752487.3060303@nod.at> (raw)
In-Reply-To: <20140515202628.GB25896@mail.hallyn.com>
Am 15.05.2014 22:26, schrieb Serge E. Hallyn:
> Quoting Richard Weinberger (richard@nod.at):
>> Am 15.05.2014 21:50, schrieb Serge Hallyn:
>>> Quoting Richard Weinberger (richard.weinberger@gmail.com):
>>>> On Thu, May 15, 2014 at 4:08 PM, Greg Kroah-Hartman
>>>> <gregkh@linuxfoundation.org> wrote:
>>>>> Then don't use a container to build such a thing, or fix the build
>>>>> scripts to not do that :)
>>>>
>>>> I second this.
>>>> To me it looks like some folks try to (ab)use Linux containers
>>>> for purposes where KVM would much better fit in.
>>>> Please don't put more complexity into containers. They are already
>>>> horrible complex
>>>> and error prone.
>>>
>>> I, naturally, disagree :) The only use case which is inherently not
>>> valid for containers is running a kernel. Practically speaking there
>>> are other things which likely will never be possible, but if someone
>>> offers a way to do something in containers, "you can't do that in
>>> containers" is not an apropos response.
>>>
>>> "That abstraction is wrong" is certainly valid, as when vpids were
>>> originally proposed and rejected, resulting in the development of
>>> pid namespaces. "We have to work out (x) first" can be valid (and
>>> I can think of examples here), assuming it's not just trying to hide
>>> behind a catch-22/chicken-egg problem.
>>>
>>> Finally, saying "containers are complex and error prone" is conflating
>>> several large suites of userspace code and many kernel features which
>>> support them. Being more precise would, if the argument is valid,
>>> lend it a lot more weight.
>>
>> We (my company) use Linux containers since 2011 in production. First LXC, now libvirt-lxc.
>> To understand the internals better I also wrote my own userspace to create/start
>> containers. There are so many things which can hurt you badly.
>> With user namespaces we expose a really big attack surface to regular users.
>> I.e. Suddenly a user is allowed to mount filesystems.
>
> That is currently not the case. They can mount some virtual filesystems
> and do bind mounts, but cannot mount most real filesystems. This keeps
> us protected (for now) from potentially unsafe superblock readers in the
> kernel.
Yeah, I meant not only "real" filesystems.
I had VFS issues in mind where an attacker could do bad things
using bind mounts for example.
>> Ask Andy, he found already lots of nasty things...
>
> Yes, of course, and there may be more to come...
>
>> I agree that user namespaces are the way to go, all the papering with LSM
>> over security issues is much worse.
>> But we have to make sure that we don't add too much features too fast.
>
> Agreed. Like I said, 'we have to work (x) out first' could be valid,
> including 'we should wait (a year?) for user ns issues to fall out
> before relaxing any of the current user ns constraints."
>
> On the other hand, not exercising the new code may only mean that
> existing flaws stick around longer, undetected (by most).
Fair point.
>> That said, I like containers a lot because they are cheap but as they are lightweight
>> also therefore also isolation level is lightweight.
>> IMHO containers are not a cheap replacement for KVM.
>
> The building blocks for containers can also be used for entirely
> new, simpler use cases - i.e. perhaps a new fakeroot alternative based
> on user namespace mappings. Which is why "this is not a use case for
> containers" is not the right way to push back, whether or not the
> feature ends up being appropriate.
Agreed.
Maybe I'm too pessimistic.
We'll see. :-)
Thanks,
//richard
next prev parent reply other threads:[~2014-05-15 20:33 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
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 [this message]
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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