linux-kernel - Re: [PATCH 7/9] add a user namespace owner of ipc ns

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Date:	Thu, 17 Feb 2011 19:19:58 -0800
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	"Serge E. Hallyn" <serge@...lyn.com>
Cc:	LSM <linux-security-module@...r.kernel.org>,
	Andrew Morton <akpm@...l.org>,
	James Morris <jmorris@...ei.org>,
	Kees Cook <kees.cook@...onical.com>,
	containers@...ts.linux-foundation.org,
	kernel list <linux-kernel@...r.kernel.org>,
	Alexey Dobriyan <adobriyan@...il.com>,
	Michael Kerrisk <mtk.manpages@...il.com>, xemul@...allels.com,
	dhowells@...hat.com
Subject: Re: [PATCH 7/9] add a user namespace owner of ipc ns

"Serge E. Hallyn" <serge@...lyn.com> writes:

> Changelog:
> 	Feb 15: Don't set new ipc->user_ns if we didn't create a new
> 		ipc_ns.

Acked-by: "Eric W. Biederman" <ebiederm@...ssion.com>

>
> Signed-off-by: Serge E. Hallyn <serge.hallyn@...onical.com>
> ---
>  include/linux/ipc_namespace.h |    3 +++
>  ipc/msgutil.c                 |    3 +++
>  ipc/namespace.c               |    9 +++++++--
>  kernel/nsproxy.c              |    5 +++++
>  4 files changed, 18 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/ipc_namespace.h b/include/linux/ipc_namespace.h
> index 5195298..46d2eb4 100644
> --- a/include/linux/ipc_namespace.h
> +++ b/include/linux/ipc_namespace.h
> @@ -24,6 +24,7 @@ struct ipc_ids {
>  	struct idr ipcs_idr;
>  };
>  
> +struct user_namespace;
>  struct ipc_namespace {
>  	atomic_t	count;
>  	struct ipc_ids	ids[3];
> @@ -56,6 +57,8 @@ struct ipc_namespace {
>  	unsigned int    mq_msg_max;      /* initialized to DFLT_MSGMAX */
>  	unsigned int    mq_msgsize_max;  /* initialized to DFLT_MSGSIZEMAX */
>  
> +	/* user_ns which owns the ipc ns */
> +	struct user_namespace *user_ns;
>  };
>  
>  extern struct ipc_namespace init_ipc_ns;
> diff --git a/ipc/msgutil.c b/ipc/msgutil.c
> index f095ee2..d91ff4b 100644
> --- a/ipc/msgutil.c
> +++ b/ipc/msgutil.c
> @@ -20,6 +20,8 @@
>  
>  DEFINE_SPINLOCK(mq_lock);
>  
> +extern struct user_namespace init_user_ns;
> +
>  /*
>   * The next 2 defines are here bc this is the only file
>   * compiled when either CONFIG_SYSVIPC and CONFIG_POSIX_MQUEUE
> @@ -32,6 +34,7 @@ struct ipc_namespace init_ipc_ns = {
>  	.mq_msg_max      = DFLT_MSGMAX,
>  	.mq_msgsize_max  = DFLT_MSGSIZEMAX,
>  #endif
> +	.user_ns = &init_user_ns,
>  };
>  
>  atomic_t nr_ipc_ns = ATOMIC_INIT(1);
> diff --git a/ipc/namespace.c b/ipc/namespace.c
> index a1094ff..aa18899 100644
> --- a/ipc/namespace.c
> +++ b/ipc/namespace.c
> @@ -11,10 +11,11 @@
>  #include <linux/slab.h>
>  #include <linux/fs.h>
>  #include <linux/mount.h>
> +#include <linux/user_namespace.h>
>  
>  #include "util.h"
>  
> -static struct ipc_namespace *create_ipc_ns(void)
> +static struct ipc_namespace *create_ipc_ns(struct ipc_namespace *old_ns)
>  {
>  	struct ipc_namespace *ns;
>  	int err;
> @@ -43,6 +44,9 @@ static struct ipc_namespace *create_ipc_ns(void)
>  	ipcns_notify(IPCNS_CREATED);
>  	register_ipcns_notifier(ns);
>  
> +	ns->user_ns = old_ns->user_ns;
> +	get_user_ns(ns->user_ns);
> +
>  	return ns;
>  }
>  
> @@ -50,7 +54,7 @@ struct ipc_namespace *copy_ipcs(unsigned long flags, struct ipc_namespace *ns)
>  {
>  	if (!(flags & CLONE_NEWIPC))
>  		return get_ipc_ns(ns);
> -	return create_ipc_ns();
> +	return create_ipc_ns(ns);
>  }
>  
>  /*
> @@ -105,6 +109,7 @@ static void free_ipc_ns(struct ipc_namespace *ns)
>  	 * order to have a correct value when recomputing msgmni.
>  	 */
>  	ipcns_notify(IPCNS_REMOVED);
> +	put_user_ns(ns->user_ns);
>  }
>  
>  /*
> diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c
> index 034dc2e..b6dbff2 100644
> --- a/kernel/nsproxy.c
> +++ b/kernel/nsproxy.c
> @@ -85,6 +85,11 @@ static struct nsproxy *create_new_namespaces(unsigned long flags,
>  		err = PTR_ERR(new_nsp->ipc_ns);
>  		goto out_ipc;
>  	}
> +	if (new_nsp->ipc_ns != tsk->nsproxy->ipc_ns) {
> +		put_user_ns(new_nsp->ipc_ns->user_ns);
> +		new_nsp->ipc_ns->user_ns = task_cred_xxx(tsk, user)->user_ns;
> +		get_user_ns(new_nsp->ipc_ns->user_ns);
> +	}
>  
>  	new_nsp->pid_ns = copy_pid_ns(flags, task_active_pid_ns(tsk));
>  	if (IS_ERR(new_nsp->pid_ns)) {
--
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