[libvirt] [PATCH RFC] Don't use CLONE_NEWUSER for now

[Daniel P. Berrange]

On Tue, Feb 08, 2011 at 08:58:24PM -0600, Serge E. Hallyn wrote:
> Until now, user namespaces have not done much, but (for that
> reason) have been innocuous to glob in with other CLONE_
> flags.  Upcoming userns development, however, will make tasks
> cloned with CLONE_NEWUSER far more restricted.  In particular,
> for some time they will be unable to access files with anything
> other than the world access perms.
> 
> This patch assumes that noone really needs the user namespaces
> to be enabled.  If that is wrong, then we can try a more
> baroque patch where we create a file owned by a test userid with
> 700 perms and, if we can't access it after setuid'ing to that
> userid, then return 0.  Otherwise, assume we are using an
> older, 'harmless' user namespace implementation.
> 
> Comments appreciated.  Is it ok to do this?

Given what you describe on the UserNamespaces wiki page I believe
this is the right thing todo in libvirt. There's no compelling
reason why we were setting this flag in the first place, other
than the fact that it existed & was thought todo something.

> 
> Signed-off-by: Serge Hallyn <serge.hallyn at canonical.com>
> ---
>  src/lxc/lxc_container.c |    7 +++++++
>  1 files changed, 7 insertions(+), 0 deletions(-)
> 
> diff --git a/src/lxc/lxc_container.c b/src/lxc/lxc_container.c
> index 876bc62..a735eb7 100644
> --- a/src/lxc/lxc_container.c
> +++ b/src/lxc/lxc_container.c
> @@ -810,7 +810,14 @@ static int lxcContainerChild( void *data )
>  
>  static int userns_supported(void)
>  {
> +#if 1
> +    /*
> +     * put off using userns until uid mapping is implemented
> +     */
> +    return 0;
> +#else
>      return lxcContainerAvailable(LXC_CONTAINER_FEATURE_USER) == 0;
> +#endif
>  }

ACK

Daniel
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