Subject: Re: [RFC PATCH 0/2] selinux: avoid nf hooks overhead when not needed

From: Casey Schaufler <[email-masked]>
Date: Wed, 6 Apr 2016 14:43:24 -0700

On 4/6/2016 2:51 AM, Paolo Abeni wrote:
> Currently, selinux always registers iptables POSTROUTING hooks regarless of
> the running policy needs for any action to be performed by them.
>
> Even the socket_sock_rcv_skb() is always registered, but it can result in a no-op
> depending on the current policy configuration.
>
> The above invocations in the kernel datapath are cause of measurable
> overhead in networking performance test.
>
> This patch series adds explicit notification for netlabel status change 
> (other relevant status change, like xfrm and secmark, are already notified to
> LSM) and use this information in selinux to register the above hooks only when
> the current status makes them relevant, deregistering them when no-op
>
> Avoiding the LSM hooks overhead, in netperf UDP_STREAM test with small packets,
> gives about 5% performance improvement on rx and about 8% on tx.
>
> Paolo Abeni (2):
>   security: add hook for netlabel status change notification
>   selinux: implement support for dynamic net hook [de-]registration

Did you consider the fact that netlabel and the LSM socket
hooks are used by Smack as well as SELinux? Did you measure the
impact that your changes have on Smack? Does Smack even work
with your changes?

>
>  include/linux/lsm_hooks.h           |  6 ++++
>  include/linux/security.h            |  5 +++
>  net/netlabel/netlabel_cipso_v4.c    |  8 +++--
>  net/netlabel/netlabel_unlabeled.c   |  5 ++-
>  security/security.c                 |  7 ++++
>  security/selinux/hooks.c            | 72 +++++++++++++++++++++++++++++++------
>  security/selinux/include/security.h |  1 +
>  security/selinux/ss/services.c      |  1 +
>  security/selinux/xfrm.c             |  4 +++
>  9 files changed, 96 insertions(+), 13 deletions(-)
>