Re: [PATCH 18/20] audit: add new message type AUDIT_CREATE_NS

Serge E. Hallyn
2013-12-06T22:10:14Z

Quoting Gao feng (gaofeng-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org):
> Since there is no more place for flags of clone system call.
> we need to find a way to create audit namespace.
>
> this patch add a new type of message AUDIT_CREATE_NS.
> user space can create new audit namespace through
> netlink.
>
> Right now, The privileged user in user namespace is allowed
> to create audit namespace. it means the unprivileged user can
> create an user namespace and then create audit namespace.
>
> Looks like it is not safe, but even the unprivileged user can
> create audit namespace, it can do no harm to the host. un-init
> audit namespace cann't effect the host.
>
> In the follow patches, the audit_backlog_limit will be per
> audit namesapace, but only the privileged user has rights to
> modify it. and the default value of audit_backlog_limit for
> uninit audit namespace will be set to 0.
>
> And the audit_rate_limit will be limited too.
>
> Signed-off-by: Gao feng <gaofeng-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org>
> ---
> include/linux/audit_namespace.h | 7 +++++++
> include/uapi/linux/audit.h | 1 +
> kernel/audit.c | 22 ++++++++++++++++++++++
> kernel/audit_namespace.c | 29 +++++++++++++++++++++++++++++
> 4 files changed, 59 insertions(+)
>
> diff --git a/include/linux/audit_namespace.h b/include/linux/audit_namespace.h
> index 79a9b78..b17f052 100644
> --- a/include/linux/audit_namespace.h
> +++ b/include/linux/audit_namespace.h
> @@ -54,6 +54,8 @@ void put_audit_ns(struct audit_namespace *ns)
> rcu_read_unlock();
> }
> }
> +
> +extern int unshare_audit_namespace(void);
> #else
> static inline
> struct audit_namespace *get_audit_ns(struct audit_namespace *ns)
> @@ -66,6 +68,11 @@ void put_audit_ns(struct audit_namespace *ns)
> {
>
> }
> +
> +static inline int unshare_audit_namespace()
> +{
> + return -EINVAL;
> +}
> #endif
>
> static inline struct
> diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h
> index 75cef3f..877d509 100644
> --- a/include/uapi/linux/audit.h
> +++ b/include/uapi/linux/audit.h
> @@ -68,6 +68,7 @@
> #define AUDIT_MAKE_EQUIV 1015 /* Append to watched tree */
> #define AUDIT_TTY_GET 1016 /* Get TTY auditing status */
> #define AUDIT_TTY_SET 1017 /* Set TTY auditing status */
> +#define AUDIT_CREATE_NS 1018 /* Create new audit namespace */
>
> #define AUDIT_FIRST_USER_MSG 1100 /* Userspace messages mostly uninteresting to kernel */
> #define AUDIT_USER_AVC 1107 /* We filter this differently */
> diff --git a/kernel/audit.c b/kernel/audit.c
> index c4d4291..86212d3 100644
> --- a/kernel/audit.c
> +++ b/kernel/audit.c
> @@ -596,6 +596,12 @@ static int audit_netlink_ok(struct sk_buff *skb, u16 msg_type)
> !capable(CAP_AUDIT_CONTROL))
> err = -EPERM;
> break;
> + case AUDIT_CREATE_NS:
> + /* Allow privileged user in user namespace to
> + * create audit namespace */
> + if (!ns_capable(current_user_ns(), CAP_AUDIT_CONTROL))
> + err = -EPERM;
> + break;
> case AUDIT_USER:
> case AUDIT_FIRST_USER_MSG ... AUDIT_LAST_USER_MSG:
> case AUDIT_FIRST_USER_MSG2 ... AUDIT_LAST_USER_MSG2:
> @@ -735,6 +741,22 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
> if (status_get->mask & AUDIT_STATUS_BACKLOG_LIMIT)
> err = audit_set_backlog_limit(status_get->backlog_limit);
> break;
> + case AUDIT_CREATE_NS:
> + err = unshare_audit_namespace();
> +
> + if (audit_enabled == AUDIT_OFF)
> + break;
> +
> + ab = audit_log_start_ns(ns, NULL, GFP_KERNEL, AUDIT_CREATE_NS);
> + if (ab) {
> + audit_log_format(ab, "Create audit namespace");
> + audit_log_session_info(ab);
> + audit_log_task_context(ab);
> + audit_log_format(ab, "res=%d", err ? 0 : 1);
> + audit_log_end_ns(ns, ab);
> + }
> +
> + break;
> case AUDIT_USER:
> case AUDIT_FIRST_USER_MSG ... AUDIT_LAST_USER_MSG:
> case AUDIT_FIRST_USER_MSG2 ... AUDIT_LAST_USER_MSG2:
> diff --git a/kernel/audit_namespace.c b/kernel/audit_namespace.c
> index 6d9cb8f..28c608e 100644
> --- a/kernel/audit_namespace.c
> +++ b/kernel/audit_namespace.c
> @@ -6,3 +6,32 @@ struct audit_namespace init_audit_ns = {
> .user_ns = &init_user_ns,
> };
> EXPORT_SYMBOL_GPL(init_audit_ns);
> +
> +int unshare_audit_namespace(void)
> +{
> + struct task_struct *tsk = current;
> + struct audit_namespace *new_audit = NULL;
> + struct nsproxy *new_nsp;
> +
> + new_audit = kzalloc(sizeof(struct audit_namespace), GFP_KERNEL);
> + if (!new_audit)
> + return -ENOMEM;
> +
> + skb_queue_head_init(&new_audit->queue);
> + skb_queue_head_init(&new_audit->hold_queue);
> + init_waitqueue_head(&new_audit->kauditd_wait);
> + init_waitqueue_head(&new_audit->backlog_wait);
> +
> + new_nsp = create_new_namespaces(0, tsk, NULL, NULL);
> + if (IS_ERR(new_nsp)) {
> + kfree(new_audit);
> + return PTR_ERR(new_nsp);
> + }
> +
> + new_audit->user_ns = get_user_ns(current_user_ns());
> + new_nsp->audit_ns = get_audit_ns(new_audit);
> +
> + switch_task_namespaces(current, new_nsp);

Do you need to drop the old audit->ns refcount?

> +
> + return 0;
> +}
> --
> 1.8.3.1
>
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