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, 8 deletions

diff --git a/include/linux/selinux.h b/include/linux/selinux.h
index 6080f73..8c2cc4c 100644
--- a/include/linux/selinux.h
+++ b/include/linux/selinux.h
@@ -120,16 +120,35 @@ void selinux_get_task_sid(struct task_struct *tsk, u32 *sid);
 int selinux_string_to_sid(char *str, u32 *sid);
 
 /**
- *     selinux_relabel_packet_permission - check permission to relabel a packet
- *     @sid: ID value to be applied to network packet (via SECMARK, most likely)
+ *     selinux_secmark_relabel_packet_permission - secmark permission check
+ *     @sid: SECMARK ID value to be applied to network packet
  *
- *     Returns 0 if the current task is allowed to label packets with the
- *     supplied security ID.  Note that it is implicit that the packet is always
- *     being relabeled from the default unlabled value, and that the access
- *     control decision is made in the AVC.
+ *     Returns 0 if the current task is allowed to set the SECMARK label of
+ *     packets with the supplied security ID.  Note that it is implicit that
+ *     the packet is always being relabeled from the default unlabeled value,
+ *     and that the access control decision is made in the AVC.
  */
-int selinux_relabel_packet_permission(u32 sid);
+int selinux_secmark_relabel_packet_permission(u32 sid);
 
+/**
+ *     selinux_secmark_refcount_inc - increments the secmark use counter
+ *
+ *     SELinux keeps track of the current SECMARK targets in use so it knows
+ *     when to apply SECMARK label access checks to network packets.  This
+ *     function incements this reference count to indicate that a new SECMARK
+ *     target has been configured.
+ */
+void selinux_secmark_refcount_inc(void);
+
+/**
+ *     selinux_secmark_refcount_dec - decrements the secmark use counter
+ *
+ *     SELinux keeps track of the current SECMARK targets in use so it knows
+ *     when to apply SECMARK label access checks to network packets.  This
+ *     function decements this reference count to indicate that one of the
+ *     existing SECMARK targets has been removed/flushed.
+ */
+void selinux_secmark_refcount_dec(void);
 #else
 
 static inline int selinux_audit_rule_init(u32 field, u32 op,
@@ -184,11 +203,21 @@ static inline int selinux_string_to_sid(const char *str, u32 *sid)
        return 0;
 }
 
-static inline int selinux_relabel_packet_permission(u32 sid)
+static inline int selinux_secmark_relabel_packet_permission(u32 sid)
 {
 	return 0;
 }
 
+static inline void selinux_secmark_refcount_inc(void)
+{
+	return;
+}
+
+static inline void selinux_secmark_refcount_dec(void)
+{
+	return;
+}
+
 #endif	/* CONFIG_SECURITY_SELINUX */
 
 #endif /* _LINUX_SELINUX_H */