linux-kernel - Re: [RFC 1/5] user namespaces: Add a user_namespace as creator/owner of uts

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Date:	Fri, 17 Dec 2010 09:31:25 -0800
From:	Greg KH <greg@...ah.com>
To:	"Serge E. Hallyn" <serge@...lyn.com>
Cc:	LSM <linux-security-module@...r.kernel.org>,
	James Morris <jmorris@...ei.org>,
	Kees Cook <kees.cook@...onical.com>,
	containers@...ts.linux-foundation.org,
	kernel list <linux-kernel@...r.kernel.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Alexey Dobriyan <adobriyan@...il.com>,
	Michael Kerrisk <michael.kerrisk@...il.com>
Subject: Re: [RFC 1/5] user namespaces: Add a user_namespace as
 creator/owner of uts_namespace

On Fri, Dec 17, 2010 at 03:24:58PM +0000, Serge E. Hallyn wrote:
> copy_process() handles CLONE_NEWUSER before the rest of the
> namespaces.  So in the case of clone(CLONE_NEWUSER|CLONE_NEWUTS)
> the new uts namespace will have the new user namespace as its
> owner.  That is what we want, since we want root in that new
> userns to be able to have privilege over it.
> 
> Signed-off-by: Serge E. Hallyn <serge.hallyn@...onical.com>
> ---
>  include/linux/utsname.h |    3 +++
>  init/version.c          |    2 ++
>  kernel/nsproxy.c        |    3 +++
>  kernel/user.c           |    8 ++++++--
>  kernel/utsname.c        |    4 ++++
>  5 files changed, 18 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/utsname.h b/include/linux/utsname.h
> index 69f3997..85171be 100644
> --- a/include/linux/utsname.h
> +++ b/include/linux/utsname.h
> @@ -37,9 +37,12 @@ struct new_utsname {
>  #include <linux/nsproxy.h>
>  #include <linux/err.h>
>  
> +struct user_namespace;
> +
>  struct uts_namespace {
>  	struct kref kref;
>  	struct new_utsname name;
> +	struct user_namespace *user_ns;
>  };
>  extern struct uts_namespace init_uts_ns;
>  
> diff --git a/init/version.c b/init/version.c
> index 79fb8c2..9eb19fb 100644
> --- a/init/version.c
> +++ b/init/version.c
> @@ -21,6 +21,7 @@ extern int version_string(LINUX_VERSION_CODE);
>  int version_string(LINUX_VERSION_CODE);
>  #endif
>  
> +extern struct user_namespace init_user_ns;
>  struct uts_namespace init_uts_ns = {
>  	.kref = {
>  		.refcount	= ATOMIC_INIT(2),

Wait, WTF?

You have a static kref and you try to automatically instanciate it here?
As it's static, why are you even having a kref at all, what good does it
do you, you can't delete the thing, it's always around, so just remove
it entirely please.

Or, dynamically create it properly.  In other words, this is majorly
broken.

thanks,

greg k-h
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