Quoting Eric W. Biederman (ebied...@xmission.com):
> Signed-off-by: "Eric W. Biederman" <ebied...@xmission.com>

Acked-by: Serge Hallyn <se...@hallyn.com>

> ---
>  include/linux/user_namespace.h |  1 +
>  ipc/namespace.c                | 42 
> +++++++++++++++++++++++++++++++-----------
>  kernel/user_namespace.c        |  1 +
>  3 files changed, 33 insertions(+), 11 deletions(-)
> 
> diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
> index bed2506081fe..367cf08ff63d 100644
> --- a/include/linux/user_namespace.h
> +++ b/include/linux/user_namespace.h
> @@ -26,6 +26,7 @@ enum ucounts {
>       UCOUNT_USER_NAMESPACES,
>       UCOUNT_PID_NAMESPACES,
>       UCOUNT_UTS_NAMESPACES,
> +     UCOUNT_IPC_NAMESPACES,
>       UCOUNT_COUNTS,
>  };
>  
> diff --git a/ipc/namespace.c b/ipc/namespace.c
> index 04cb07eb81f1..3996a1e41a1d 100644
> --- a/ipc/namespace.c
> +++ b/ipc/namespace.c
> @@ -16,33 +16,42 @@
>  
>  #include "util.h"
>  
> +static bool inc_ipc_namespaces(struct user_namespace *ns)
> +{
> +     return inc_ucount(ns, UCOUNT_IPC_NAMESPACES);
> +}
> +
> +static void dec_ipc_namespaces(struct user_namespace *ns)
> +{
> +     dec_ucount(ns, UCOUNT_IPC_NAMESPACES);
> +}
> +
>  static struct ipc_namespace *create_ipc_ns(struct user_namespace *user_ns,
>                                          struct ipc_namespace *old_ns)
>  {
>       struct ipc_namespace *ns;
>       int err;
>  
> +     err = -ENFILE;
> +     if (!inc_ipc_namespaces(user_ns))
> +             goto fail;
> +
> +     err = -ENOMEM;
>       ns = kmalloc(sizeof(struct ipc_namespace), GFP_KERNEL);
>       if (ns == NULL)
> -             return ERR_PTR(-ENOMEM);
> +             goto fail_dec;
>  
>       err = ns_alloc_inum(&ns->ns);
> -     if (err) {
> -             kfree(ns);
> -             return ERR_PTR(err);
> -     }
> +     if (err)
> +             goto fail_free;
>       ns->ns.ops = &ipcns_operations;
>  
>       atomic_set(&ns->count, 1);
>       ns->user_ns = get_user_ns(user_ns);
>  
>       err = mq_init_ns(ns);
> -     if (err) {
> -             put_user_ns(ns->user_ns);
> -             ns_free_inum(&ns->ns);
> -             kfree(ns);
> -             return ERR_PTR(err);
> -     }
> +     if (err)
> +             goto fail_put;
>       atomic_inc(&nr_ipc_ns);
>  
>       sem_init_ns(ns);
> @@ -50,6 +59,16 @@ static struct ipc_namespace *create_ipc_ns(struct 
> user_namespace *user_ns,
>       shm_init_ns(ns);
>  
>       return ns;
> +
> +fail_put:
> +     put_user_ns(ns->user_ns);
> +     ns_free_inum(&ns->ns);
> +fail_free:
> +     kfree(ns);
> +fail_dec:
> +     dec_ipc_namespaces(user_ns);
> +fail:
> +     return ERR_PTR(err);
>  }
>  
>  struct ipc_namespace *copy_ipcs(unsigned long flags,
> @@ -98,6 +117,7 @@ static void free_ipc_ns(struct ipc_namespace *ns)
>       shm_exit_ns(ns);
>       atomic_dec(&nr_ipc_ns);
>  
> +     dec_ipc_namespaces(ns->user_ns);
>       put_user_ns(ns->user_ns);
>       ns_free_inum(&ns->ns);
>       kfree(ns);
> diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
> index 6b205c24e888..060d3e099f87 100644
> --- a/kernel/user_namespace.c
> +++ b/kernel/user_namespace.c
> @@ -79,6 +79,7 @@ static struct ctl_table userns_table[] = {
>       UCOUNT_ENTRY("max_user_namespaces"),
>       UCOUNT_ENTRY("max_pid_namespaces"),
>       UCOUNT_ENTRY("max_uts_namespaces"),
> +     UCOUNT_ENTRY("max_ipc_namespaces"),
>       { }
>  };
>  #endif /* CONFIG_SYSCTL */
> -- 
> 2.8.3

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