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

Quoting Gao feng (gaofeng(a)cn.fujitsu.com): > 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(a)cn.fujitsu.com&gt; > --- > 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?