SELinux: Enable dynamic enable/disable of the network access checks

This patch introduces a mechanism for checking when labeled IPsec or SECMARK
are in use by keeping introducing a configuration reference counter for each
subsystem.  In the case of labeled IPsec, whenever a labeled SA or SPD entry
is created the labeled IPsec/XFRM reference count is increased and when the
entry is removed it is decreased.  In the case of SECMARK, when a SECMARK
target is created the reference count is increased and later decreased when the
target is removed.  These reference counters allow SELinux to quickly determine
if either of these subsystems are enabled.

NetLabel already has a similar mechanism which provides the netlbl_enabled()
function.

This patch also renames the selinux_relabel_packet_permission() function to
selinux_secmark_relabel_packet_permission() as the original name and
description were misleading in that they referenced a single packet label which
is not the case.

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

1 files changed, 37 insertions, 9 deletions

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index bfe9a05db3a2..6156241c8770 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -51,8 +51,10 @@
 #include <net/ip.h>             /* for local_port_range[] */
 #include <net/tcp.h>            /* struct or_callable used in sock_rcv_skb */
 #include <net/net_namespace.h>
+#include <net/netlabel.h>
 #include <asm/uaccess.h>
 #include <asm/ioctls.h>
+#include <asm/atomic.h>
 #include <linux/bitops.h>
 #include <linux/interrupt.h>
 #include <linux/netdevice.h>    /* for network interface checks */
@@ -91,6 +93,9 @@ extern int selinux_nlmsg_lookup(u16 sclass, u16 nlmsg_type, u32 *perm);
 extern int selinux_compat_net;
 extern struct security_operations *security_ops;
 
+/* SECMARK reference count */
+atomic_t selinux_secmark_refcount = ATOMIC_INIT(0);
+
 #ifdef CONFIG_SECURITY_SELINUX_DEVELOP
 int selinux_enforcing = 0;
 
@@ -157,6 +162,21 @@ getsecurity_exit:
         return len;
 }
 
+/**
+ * selinux_secmark_enabled - Check to see if SECMARK is currently enabled
+ *
+ * Description:
+ * This function checks the SECMARK reference counter to see if any SECMARK
+ * targets are currently configured, if the reference counter is greater than
+ * zero SECMARK is considered to be enabled.  Returns true (1) if SECMARK is
+ * enabled, false (0) if SECMARK is disabled.
+ *
+ */
+static int selinux_secmark_enabled(void)
+{
+        return (atomic_read(&selinux_secmark_refcount) > 0);
+}
+
 /* Allocate and free functions for each kind of security blob. */
 
 static int task_alloc_security(struct task_struct *task)
@@ -3931,7 +3951,6 @@ static int selinux_socket_sock_rcv_skb(struct sock *sk, struct sk_buff *skb)
         struct sk_security_struct *sksec = sk->sk_security;
         u16 family = sk->sk_family;
         u32 sk_sid = sksec->sid;
-        u32 peer_sid;
         struct avc_audit_data ad;
         char *addrp;
 
@@ -3957,15 +3976,24 @@ static int selinux_socket_sock_rcv_skb(struct sock *sk, struct sk_buff *skb)
                 return selinux_sock_rcv_skb_compat(sk, skb, &ad,
                                                    family, addrp);
 
-        err = avc_has_perm(sk_sid, skb->secmark, SECCLASS_PACKET,
-                           PACKET__RECV, &ad);
-        if (err)
-                return err;
+        if (selinux_secmark_enabled()) {
+                err = avc_has_perm(sk_sid, skb->secmark, SECCLASS_PACKET,
+                                   PACKET__RECV, &ad);
+                if (err)
+                        return err;
+        }
 
-        err = selinux_skb_peerlbl_sid(skb, family, &peer_sid);
-        if (err)
-                return err;
-        return avc_has_perm(sk_sid, peer_sid, SECCLASS_PEER, PEER__RECV, &ad);
+        if (netlbl_enabled() || selinux_xfrm_enabled()) {
+                u32 peer_sid;
+
+                err = selinux_skb_peerlbl_sid(skb, family, &peer_sid);
+                if (err)
+                        return err;
+                err = avc_has_perm(sk_sid, peer_sid, SECCLASS_PEER,
+                                   PEER__RECV, &ad);
+        }
+
+        return err;
 }
 
 static int selinux_socket_getpeersec_stream(struct socket *sock, char __user *optval,