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Message-ID: <57058E67.5020502@schaufler-ca.com>
Date: Wed, 6 Apr 2016 15:32:07 -0700
From: Casey Schaufler <casey@...aufler-ca.com>
To: Paolo Abeni <pabeni@...hat.com>,
linux-security-module@...r.kernel.org
Cc: "David S. Miller" <davem@...emloft.net>,
James Morris <james.l.morris@...cle.com>,
Paul Moore <paul@...l-moore.com>,
Andreas Gruenbacher <agruenba@...hat.com>,
Stephen Smalley <sds@...ho.nsa.gov>,
Florian Westphal <fw@...len.de>, netdev@...r.kernel.org
Subject: Re: [RFC PATCH 2/2] selinux: implement support for dynamic net hook
[de-]registration
On 4/6/2016 2:51 AM, Paolo Abeni wrote:
> This patch leverage the netlbl_changed() hook to perform on demand
> registration and deregistration of the netfilter hooks and the
> socket_sock_rcv_skb hook.
>
> With default policy and empty netfilter/netlabel configuration, the
> above hooks are not registered and this allows avoiding nf_hook_slow
> in the xmit path and socket_sock_rcv_skb() in the rx path.
There is no reason to assume that there is a relationship between
a netlabel configuration and a netfilter configuration. Smack always
has a netlabel configuration. Security modules (e.g. AppArmor) may
well use netfilter without netlabel.
Please stop assuming that security == SELinux.
>
> This gives measurable network performance improvement in both
> directions.
In the case where SELinux is enabled and netfilter is not.
> Signed-off-by: Paolo Abeni <pabeni@...hat.com>
> ---
> security/selinux/hooks.c | 72 +++++++++++++++++++++++++++++++------
> security/selinux/include/security.h | 1 +
> security/selinux/ss/services.c | 1 +
> security/selinux/xfrm.c | 4 +++
> 4 files changed, 68 insertions(+), 10 deletions(-)
>
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index 912deee..a3baa69 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -4745,11 +4745,13 @@ static int selinux_secmark_relabel_packet(u32 sid)
> static void selinux_secmark_refcount_inc(void)
> {
> atomic_inc(&selinux_secmark_refcount);
> + selinux_net_update();
> }
>
> static void selinux_secmark_refcount_dec(void)
> {
> atomic_dec(&selinux_secmark_refcount);
> + selinux_net_update();
> }
>
> static void selinux_req_classify_flow(const struct request_sock *req,
> @@ -4836,6 +4838,11 @@ static int selinux_tun_dev_open(void *security)
> return 0;
> }
>
> +static void selinux_netlbl_changed(void)
> +{
> + selinux_net_update();
> +}
> +
> static int selinux_nlmsg_perm(struct sock *sk, struct sk_buff *skb)
> {
> int err = 0;
> @@ -6091,7 +6098,6 @@ static struct security_hook_list selinux_hooks[] = {
> LSM_HOOK_INIT(socket_getsockopt, selinux_socket_getsockopt),
> LSM_HOOK_INIT(socket_setsockopt, selinux_socket_setsockopt),
> LSM_HOOK_INIT(socket_shutdown, selinux_socket_shutdown),
> - LSM_HOOK_INIT(socket_sock_rcv_skb, selinux_socket_sock_rcv_skb),
> LSM_HOOK_INIT(socket_getpeersec_stream,
> selinux_socket_getpeersec_stream),
> LSM_HOOK_INIT(socket_getpeersec_dgram, selinux_socket_getpeersec_dgram),
> @@ -6113,6 +6119,7 @@ static struct security_hook_list selinux_hooks[] = {
> LSM_HOOK_INIT(tun_dev_attach_queue, selinux_tun_dev_attach_queue),
> LSM_HOOK_INIT(tun_dev_attach, selinux_tun_dev_attach),
> LSM_HOOK_INIT(tun_dev_open, selinux_tun_dev_open),
> + LSM_HOOK_INIT(netlbl_changed, selinux_netlbl_changed),
>
> #ifdef CONFIG_SECURITY_NETWORK_XFRM
> LSM_HOOK_INIT(xfrm_policy_alloc_security, selinux_xfrm_policy_alloc),
> @@ -6145,6 +6152,11 @@ static struct security_hook_list selinux_hooks[] = {
> #endif
> };
>
> +/* dynamically registered/unregisterd */
> +static struct security_hook_list selinux_sock_hooks[] = {
> + LSM_HOOK_INIT(socket_sock_rcv_skb, selinux_socket_sock_rcv_skb),
> +};
> +
> static __init int selinux_init(void)
> {
> if (!security_module_enable("selinux")) {
> @@ -6240,7 +6252,9 @@ static struct nf_hook_ops selinux_nf_ops[] = {
> #endif /* IPV6 */
> };
>
> -static int __init selinux_nf_ip_init(void)
> +static bool nf_hooks_registered;
> +
> +static int selinux_nf_ip_init(void)
> {
> int err;
>
> @@ -6253,25 +6267,21 @@ static int __init selinux_nf_ip_init(void)
> if (err)
> panic("SELinux: nf_register_hooks: error %d\n", err);
>
> + nf_hooks_registered = true;
> return 0;
> }
>
> -__initcall(selinux_nf_ip_init);
> -
> -#ifdef CONFIG_SECURITY_SELINUX_DISABLE
> static void selinux_nf_ip_exit(void)
> {
> printk(KERN_DEBUG "SELinux: Unregistering netfilter hooks\n");
>
> nf_unregister_hooks(selinux_nf_ops, ARRAY_SIZE(selinux_nf_ops));
> + nf_hooks_registered = false;
> }
> -#endif
>
> #else /* CONFIG_NETFILTER */
>
> -#ifdef CONFIG_SECURITY_SELINUX_DISABLE
> #define selinux_nf_ip_exit()
> -#endif
>
> #endif /* CONFIG_NETFILTER */
>
> @@ -6300,8 +6310,8 @@ int selinux_disable(void)
> /* Try to destroy the avc node cache */
> avc_disable();
>
> - /* Unregister netfilter hooks. */
> - selinux_nf_ip_exit();
> + /* Unregister net hooks. */
> + selinux_net_update();
>
> /* Unregister selinuxfs. */
> exit_sel_fs();
> @@ -6309,3 +6319,45 @@ int selinux_disable(void)
> return 0;
> }
> #endif
> +
> +DEFINE_MUTEX(selinux_net_mutex);
> +
> +static bool nf_hooks_required(void)
> +{
> + return (selinux_secmark_enabled() || selinux_peerlbl_enabled() ||
> + !selinux_policycap_netpeer) && selinux_enabled;
> +}
> +
> +static bool sock_hooks_required(void)
> +{
> + return (!selinux_policycap_netpeer || selinux_secmark_enabled() ||
> + selinux_peerlbl_enabled()) && selinux_enabled;
> +}
> +
> +static bool sock_hooks_registered;
> +
> +void selinux_net_update(void)
> +{
> + if ((nf_hooks_required() == nf_hooks_registered) &&
> + (sock_hooks_required() == sock_hooks_registered))
> + return;
> +
> + mutex_lock(&selinux_net_mutex);
> + if (nf_hooks_required() != nf_hooks_registered) {
> + if (!nf_hooks_registered)
> + selinux_nf_ip_init();
> + else
> + selinux_nf_ip_exit();
> + }
> +
> + if (sock_hooks_required() != sock_hooks_registered) {
> + if (!sock_hooks_registered)
> + security_add_hooks(selinux_sock_hooks,
> + ARRAY_SIZE(selinux_sock_hooks));
> + else
> + security_delete_hooks(selinux_sock_hooks,
> + ARRAY_SIZE(selinux_sock_hooks));
> + sock_hooks_registered = !sock_hooks_registered;
> + }
> + mutex_unlock(&selinux_net_mutex);
> +}
> diff --git a/security/selinux/include/security.h b/security/selinux/include/security.h
> index 38feb55..0428ab4 100644
> --- a/security/selinux/include/security.h
> +++ b/security/selinux/include/security.h
> @@ -261,6 +261,7 @@ extern void selinux_status_update_setenforce(int enforcing);
> extern void selinux_status_update_policyload(int seqno);
> extern void selinux_complete_init(void);
> extern int selinux_disable(void);
> +extern void selinux_net_update(void);
> extern void exit_sel_fs(void);
> extern struct path selinux_null;
> extern struct vfsmount *selinuxfs_mount;
> diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c
> index ebda973..c509018 100644
> --- a/security/selinux/ss/services.c
> +++ b/security/selinux/ss/services.c
> @@ -2016,6 +2016,7 @@ static void security_load_policycaps(void)
> POLICYDB_CAPABILITY_OPENPERM);
> selinux_policycap_alwaysnetwork = ebitmap_get_bit(&policydb.policycaps,
> POLICYDB_CAPABILITY_ALWAYSNETWORK);
> + selinux_net_update();
> }
>
> static int security_preserve_bools(struct policydb *p);
> diff --git a/security/selinux/xfrm.c b/security/selinux/xfrm.c
> index 56e354f..cc2b0d4 100644
> --- a/security/selinux/xfrm.c
> +++ b/security/selinux/xfrm.c
> @@ -112,6 +112,7 @@ static int selinux_xfrm_alloc_user(struct xfrm_sec_ctx **ctxp,
>
> *ctxp = ctx;
> atomic_inc(&selinux_xfrm_refcount);
> + selinux_net_update();
> return 0;
>
> err:
> @@ -128,6 +129,7 @@ static void selinux_xfrm_free(struct xfrm_sec_ctx *ctx)
> return;
>
> atomic_dec(&selinux_xfrm_refcount);
> + selinux_net_update();
> kfree(ctx);
> }
>
> @@ -303,6 +305,7 @@ int selinux_xfrm_policy_clone(struct xfrm_sec_ctx *old_ctx,
> if (!new_ctx)
> return -ENOMEM;
> atomic_inc(&selinux_xfrm_refcount);
> + selinux_net_update();
> *new_ctxp = new_ctx;
>
> return 0;
> @@ -370,6 +373,7 @@ int selinux_xfrm_state_alloc_acquire(struct xfrm_state *x,
>
> x->security = ctx;
> atomic_inc(&selinux_xfrm_refcount);
> + selinux_net_update();
> out:
> kfree(ctx_str);
> return rc;
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