-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 05/20/2014 05:19 PM, Serge Hallyn wrote: > Quoting Andy Lutomirski (l...@amacapital.net): >> On May 15, 2014 1:26 PM, "Serge E. Hallyn" <se...@hallyn.com> wrote: >>> >>> Quoting Richard Weinberger (rich...@nod.at): >>>> Am 15.05.2014 21:50, schrieb Serge Hallyn: >>>>> Quoting Richard Weinberger (richard.weinber...@gmail.com): >>>>>> On Thu, May 15, 2014 at 4:08 PM, Greg Kroah-Hartman >>>>>> <gre...@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. >>> >>>> Ask Andy, he found already lots of nasty things... >> >> I don't think I have anything brilliant to add to this discussion right now, >> except possibly: >> >> ISTM that Linux distributions are, in general, vulnerable to all kinds of >> shenanigans that would happen if an >> untrusted user can cause a block device to appear. That user doesn't need >> permission to mount it > > Interesting point. This would further suggest that we absolutely must ensure > that a loop device which shows up in > the container does not also show up in the host.
Can I suggest the usage of the devices cgroup to achieve that? Marian > >> or even necessarily to change its contents on the fly. >> >> E.g. what happens if you boot a machine that contains a malicious disk image >> that has the same partition UUID as >> /? Nothing good, I imagine. >> >> So if we're going to go down this road, we really need some way to tell the >> host that certain devices are not >> trusted. >> >> --Andy > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to > majord...@vger.kernel.org More majordomo info at > http://vger.kernel.org/majordomo-info.html Please read the FAQ at > http://www.tux.org/lkml/ > - -- Marian Marinov Founder & CEO of 1H Ltd. Jabber/GTalk: hack...@jabber.org ICQ: 7556201 Mobile: +359 886 660 270 -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.22 (GNU/Linux) iEYEARECAAYFAlN/BL8ACgkQ4mt9JeIbjJRuTwCgjpP8cNle5deHpUSJJoDkcfin byEAn3Fy4wwiZ3avNwA/ljZWVWeGFU8W =iQLO -----END PGP SIGNATURE----- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
