Re: [CFT][PATCH 00/10] Making new mounts of proc and sysfs as safe as bind mounts (take 2)

[ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org (Eric W. Biederman)]

Richard Weinberger <richard-/L3Ra7n9ekc@public.gmane.org> writes:

> Am 28.05.2015 um 16:08 schrieb Serge Hallyn:
>> Quoting Andy Lutomirski (luto-kltTT9wpgjJwATOyAt5JVQ@public.gmane.org):
>>> On Fri, May 22, 2015 at 10:39 AM, Eric W. Biederman
>>> <ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org> wrote:
>>>> I had hoped to get some Tested-By's on that patch series.
>>>
>>> Sorry, I've been totally swamped.
>>>
>>> I suspect that Sandstorm is okay, but I haven't had a chance to test
>>> it for real.  Sandstorm makes only limited use of proc and sysfs in
>>> containers, but I'll see if I can test it for real this weekend.
>> 
>> Testing this with unprivileged containers, I get
>> 
>> lxc-start: conf.c: lxc_mount_auto_mounts: 808 Operation not permitted - error mounting sysfs on /usr/lib/x86_64-linux-gnu/lxc/sys/devices/virtual/net flags 0
>>
>
> FWIW, it breaks also libvirt-lxc:
> Error: internal error: guest failed to start: Failed to re-mount /proc/sys on /proc/sys flags=1021: Operation not permitted

Interesting.  I had not anticipated a failure there?  And it is failing
in remount?  Oh that is interesting.

That implies that there is some flag of the original mount of /proc that
the remount of /proc/sys is clearing, and that previously 

The flags specified are current rdonly,remount,bind so I expect there
are some other flags on proc that libvirt-lxc is clearing by accident
and we did not fail before because the kernel was not enforcing things.

What are the mount flags in a working libvirt-lxc?

Eric