SELinux: enable dynamic activation/deactivation of NetLabel/SELinux enforcement

Create a new NetLabel KAPI interface, netlbl_enabled(), which reports on the
current runtime status of NetLabel based on the existing configuration.  LSMs
that make use of NetLabel, i.e. SELinux, can use this new function to determine
if they should perform NetLabel access checks.  This patch changes the
NetLabel/SELinux glue code such that SELinux only enforces NetLabel related
access checks when netlbl_enabled() returns true.

At present NetLabel is considered to be enabled when there is at least one
labeled protocol configuration present.  The result is that by default NetLabel
is considered to be disabled, however, as soon as an administrator configured
a CIPSO DOI definition NetLabel is enabled and SELinux starts enforcing
NetLabel related access controls - including unlabeled packet controls.

This patch also tries to consolidate the multiple "#ifdef CONFIG_NETLABEL"
blocks into a single block to ease future review as recommended by Linus.

Signed-off-by: Paul Moore <paul.moore@hp.com>
Signed-off-by: James Morris <jmorris@namei.org>

1 files changed, 65 insertions, 0 deletions

diff --git a/net/netlabel/netlabel_mgmt.c b/net/netlabel/netlabel_mgmt.c
index e00fc21..5315dac 100644
--- a/net/netlabel/netlabel_mgmt.c
+++ b/net/netlabel/netlabel_mgmt.c
@@ -42,6 +42,10 @@
 #include "netlabel_user.h"
 #include "netlabel_mgmt.h"
 
+/* NetLabel configured protocol count */
+static DEFINE_SPINLOCK(netlabel_mgmt_protocount_lock);
+static u32 netlabel_mgmt_protocount = 0;
+
 /* Argument struct for netlbl_domhsh_walk() */
 struct netlbl_domhsh_walk_arg {
 	struct netlink_callback *nl_cb;
@@ -67,6 +71,67 @@ static const struct nla_policy netlbl_mgmt_genl_policy[NLBL_MGMT_A_MAX + 1] = {
 };
 
 /*
+ * NetLabel Misc Managment Functions
+ */
+
+/**
+ * netlbl_mgmt_protocount_inc - Increment the configured labeled protocol count
+ *
+ * Description:
+ * Increment the number of labeled protocol configurations in the current
+ * NetLabel configuration.  Keep track of this for use in determining if
+ * NetLabel label enforcement should be active/enabled or not in the LSM.
+ *
+ */
+void netlbl_mgmt_protocount_inc(void)
+{
+	rcu_read_lock();
+	spin_lock(&netlabel_mgmt_protocount_lock);
+	netlabel_mgmt_protocount++;
+	spin_unlock(&netlabel_mgmt_protocount_lock);
+	rcu_read_unlock();
+}
+
+/**
+ * netlbl_mgmt_protocount_dec - Decrement the configured labeled protocol count
+ *
+ * Description:
+ * Decrement the number of labeled protocol configurations in the current
+ * NetLabel configuration.  Keep track of this for use in determining if
+ * NetLabel label enforcement should be active/enabled or not in the LSM.
+ *
+ */
+void netlbl_mgmt_protocount_dec(void)
+{
+	rcu_read_lock();
+	spin_lock(&netlabel_mgmt_protocount_lock);
+	if (netlabel_mgmt_protocount > 0)
+		netlabel_mgmt_protocount--;
+	spin_unlock(&netlabel_mgmt_protocount_lock);
+	rcu_read_unlock();
+}
+
+/**
+ * netlbl_mgmt_protocount_value - Return the number of configured protocols
+ *
+ * Description:
+ * Return the number of labeled protocols in the current NetLabel
+ * configuration.  This value is useful in  determining if NetLabel label
+ * enforcement should be active/enabled or not in the LSM.
+ *
+ */
+u32 netlbl_mgmt_protocount_value(void)
+{
+	u32 val;
+
+	rcu_read_lock();
+	val = netlabel_mgmt_protocount;
+	rcu_read_unlock();
+
+	return val;
+}
+
+/*
  * NetLabel Command Handlers
  */