[vserver] linux 3.14.22, patch-3.14.17-vs2.3.6.13.diff, and CONFIG_USER_NS

From: Corey Wright <undefined_at_pobox.com>
Date: Mon 27 Oct 2014 - 09:31:05 GMT
Message-Id: <20141027043105.41f1ff932926089ea2564045@pobox.com>

the attached patch (in conjuction with [1] for linux 3.14.22, though possibly
still applicable to kernels < 3.14.19 without those additional patches)
allows linux 3.14 to compile and run with CONFIG_USER_NS, including

[1] http://archives.linux-vserver.org/201410/0050.html

1. this is not production quality and only made available for testing.
2. i don't know the security ramifications of running both vservers and
containers on a single host.
3. it is conceivable that containers can run inside of vservers with the
provided patch, but i haven't tested such nor do i know the security

1. vservers will not use user namespaces by default. [2]
2. vservers cannot use user namespaces without changes to util-vserver and
possibly more kernel changes. [3]
3. lxc should work. [4]

[2] in the attached patch CLONE_NEWUSER is commented out in
default_space_mask which prevents util-vserver from using user namespaces with

[3] vspace needs to create uid and gid mappings for the new user namespace
between sys_clone() and execvp() calls otherwise all capabilities,
specifically CAP_CONTEXT, are removed from the executed vcontext because the
uid and gid are 65535. see https://lwn.net/Articles/532593/, specifically
the section "Capabilities, execve(), and user ID 0".

[4] tested with lxc 1.0.6 on linux 3.14.22-vs2.3.6.13 with the attached
userns patch by creating a container ("SUITE=wheezy
MIRROR=http://http.us.debian.org/debian lxc-create -n test -t debian"),
starting the container ("lxc-start -n test -d"), and attaching to the console
("lxc-console -n test"), and stopping the container ("lxc-stop -n test")
though i was unable to log into the container ("unable to determine your tty
name"), but i believe that to be a configuration problem with the
installation inside the container.

1. the last two hunks are not both necessary. commenting out CLONE_NEWUSER
in default_space_mask is used to keep util-vserver from using user namespaces
for vservers. changing "capable()" to "ns_capable()" is required to use
linux-vserver system calls within a user namespace (and is there currently
for testing as it's not that useful without the aforementioned changes to
util-vserver). you really only need one or the other and the last hunk is
not that useful without changes to util-vserver (and more changes might be

please test and provide feedback, especially if you have better suggestions to
simply test lxc/containers as i'm a newbie in that area.



Received on Mon Oct 27 09:31:31 2014
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