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

From: Sebastien Buisson
Date: Wed Apr 26 2017 - 11:23:21 EST


From: Daniel Jurgens <danielj@xxxxxxxxxxxx>

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@xxxxxxxxxxxx>
Signed-off-by: Sebastien Buisson <sbuisson@xxxxxxx>
---
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