lsm: Add hooks to the TUN driver

The TUN driver lacks any LSM hooks which makes it difficult for LSM modules,
such as SELinux, to enforce access controls on network traffic generated by
TUN users; this is particularly problematic for virtualization apps such as
QEMU and KVM.  This patch adds three new LSM hooks designed to control the
creation and attachment of TUN devices, the hooks are:

 * security_tun_dev_create()
   Provides access control for the creation of new TUN devices

 * security_tun_dev_post_create()
   Provides the ability to create the necessary socket LSM state for newly
   created TUN devices

 * security_tun_dev_attach()
   Provides access control for attaching to existing, persistent TUN devices
   and the ability to update the TUN device's socket LSM state as necessary

Signed-off-by: Paul Moore <paul.moore@hp.com>
Acked-by: Eric Paris <eparis@parisplace.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: James Morris <jmorris@namei.org>

1 files changed, 19 insertions, 0 deletions

diff --git a/security/capability.c b/security/capability.c
index 1b943f5..06400cf 100644
--- a/security/capability.c
+++ b/security/capability.c
@@ -706,10 +706,26 @@ static void cap_inet_conn_established(struct sock *sk, struct sk_buff *skb)
 {
 }
 
+
+
 static void cap_req_classify_flow(const struct request_sock *req,
 				  struct flowi *fl)
 {
 }
+
+static int cap_tun_dev_create(void)
+{
+	return 0;
+}
+
+static void cap_tun_dev_post_create(struct sock *sk)
+{
+}
+
+static int cap_tun_dev_attach(struct sock *sk)
+{
+	return 0;
+}
 #endif	/* CONFIG_SECURITY_NETWORK */
 
 #ifdef CONFIG_SECURITY_NETWORK_XFRM
@@ -1026,6 +1042,9 @@ void security_fixup_ops(struct security_operations *ops)
 	set_to_cap_if_null(ops, inet_csk_clone);
 	set_to_cap_if_null(ops, inet_conn_established);
 	set_to_cap_if_null(ops, req_classify_flow);
+	set_to_cap_if_null(ops, tun_dev_create);
+	set_to_cap_if_null(ops, tun_dev_post_create);
+	set_to_cap_if_null(ops, tun_dev_attach);
 #endif	/* CONFIG_SECURITY_NETWORK */
 #ifdef CONFIG_SECURITY_NETWORK_XFRM
 	set_to_cap_if_null(ops, xfrm_policy_alloc_security);