linux-kernel - [PATCH 1/3] selinux: Implement LSM notification system

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Date:   Thu, 27 Apr 2017 00:02:14 +0900
From:   Sebastien Buisson <sbuisson.ddn@...il.com>
To:     linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, selinux@...ho.nsa.gov
Cc:     serge@...lyn.com, james.l.morris@...cle.com, eparis@...isplace.org,
        sds@...ho.nsa.gov, paul@...l-moore.com, danielj@...lanox.com,
        Sebastien Buisson <sbuisson@....com>
Subject: [PATCH 1/3] selinux: Implement LSM notification system

From: Daniel Jurgens <danielj@...lanox.com>

Add a generic notification mechanism in the LSM. Interested consumers
can register a callback with the LSM and security modules can produce
events.

Add a call to the notification mechanism from SELinux when the AVC
cache changes.

Signed-off-by: Daniel Jurgens <danielj@...lanox.com>
Signed-off-by: Sebastien Buisson <sbuisson@....com>
---
 include/linux/security.h | 23 +++++++++++++++++++++++
 security/security.c      | 20 ++++++++++++++++++++
 security/selinux/hooks.c | 12 ++++++++++++
 3 files changed, 55 insertions(+)

diff --git a/include/linux/security.h b/include/linux/security.h
index af675b5..73a9c93 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -68,6 +68,10 @@
 struct user_namespace;
 struct timezone;
 
+enum lsm_event {
+	LSM_POLICY_CHANGE,
+};
+
 /* These functions are in security/commoncap.c */
 extern int cap_capable(const struct cred *cred, struct user_namespace *ns,
 		       int cap, int audit);
@@ -163,6 +167,10 @@ struct security_mnt_opts {
 	int num_mnt_opts;
 };
 
+int call_lsm_notifier(enum lsm_event event, void *data);
+int register_lsm_notifier(struct notifier_block *nb);
+int unregister_lsm_notifier(struct notifier_block *nb);
+
 static inline void security_init_mnt_opts(struct security_mnt_opts *opts)
 {
 	opts->mnt_opts = NULL;
@@ -381,6 +389,21 @@ int security_sem_semop(struct sem_array *sma, struct sembuf *sops,
 struct security_mnt_opts {
 };
 
+static inline int call_lsm_notifier(enum lsm_event event, void *data)
+{
+	return 0;
+}
+
+static inline int register_lsm_notifier(struct notifier_block *nb)
+{
+	return 0;
+}
+
+static inline  int unregister_lsm_notifier(struct notifier_block *nb)
+{
+	return 0;
+}
+
 static inline void security_init_mnt_opts(struct security_mnt_opts *opts)
 {
 }
diff --git a/security/security.c b/security/security.c
index b9fea39..ef9d9e1 100644
--- a/security/security.c
+++ b/security/security.c
@@ -32,6 +32,8 @@
 /* Maximum number of letters for an LSM name string */
 #define SECURITY_NAME_MAX	10
 
+static ATOMIC_NOTIFIER_HEAD(lsm_notifier_chain);
+
 struct security_hook_heads security_hook_heads __lsm_ro_after_init;
 char *lsm_names;
 /* Boot-time LSM user choice */
@@ -146,6 +148,24 @@ void __init security_add_hooks(struct security_hook_list *hooks, int count,
 		panic("%s - Cannot get early memory.\n", __func__);
 }
 
+int call_lsm_notifier(enum lsm_event event, void *data)
+{
+	return atomic_notifier_call_chain(&lsm_notifier_chain, event, data);
+}
+EXPORT_SYMBOL(call_lsm_notifier);
+
+int register_lsm_notifier(struct notifier_block *nb)
+{
+	return atomic_notifier_chain_register(&lsm_notifier_chain, nb);
+}
+EXPORT_SYMBOL(register_lsm_notifier);
+
+int unregister_lsm_notifier(struct notifier_block *nb)
+{
+	return atomic_notifier_chain_unregister(&lsm_notifier_chain, nb);
+}
+EXPORT_SYMBOL(unregister_lsm_notifier);
+
 /*
  * Hook list operation macros.
  *
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index e67a526..a4d36f8 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -171,6 +171,14 @@ static int selinux_netcache_avc_callback(u32 event)
 	return 0;
 }
 
+static int selinux_lsm_notifier_avc_callback(u32 event)
+{
+	if (event == AVC_CALLBACK_RESET)
+		call_lsm_notifier(LSM_POLICY_CHANGE, NULL);
+
+	return 0;
+}
+
 /*
  * initialise the security for the init task
  */
@@ -6379,6 +6387,10 @@ static __init int selinux_init(void)
 	if (avc_add_callback(selinux_netcache_avc_callback, AVC_CALLBACK_RESET))
 		panic("SELinux: Unable to register AVC netcache callback\n");
 
+	if (avc_add_callback(selinux_lsm_notifier_avc_callback,
+			     AVC_CALLBACK_RESET))
+		panic("SELinux: Unable to register AVC LSM notifier callback\n");
+
 	if (selinux_enforcing)
 		printk(KERN_DEBUG "SELinux:  Starting in enforcing mode\n");
 	else
-- 
1.8.3.1