kernel: expose KSU_LSM_SECURITY_HOOKS on Kconfig

disabling this removes the need for LSM_HOOK_INIT, security_add_hooks and such, furthermore,
this will also allow easier integration on pre-4.1 kernels, this change just exposes this and
makes it a configurable option.

Signed-off-by: backslashxx <118538522+backslashxx@users.noreply.github.com>

Author: backslashxx

kernel/Kconfig

@@ -22,4 +22,12 @@ config KSU_ALLOWLIST_WORKAROUND
           Enable session keyring init workaround for problematic devices.
           Useful for situations where the SU allowlist is not kept after a reboot.
 
+config KSU_LSM_SECURITY_HOOKS
+	bool "use lsm security hooks"
+        depends on KSU
+        default y
+	help
+	  Disabling this is mostly only useful for kernel 4.1 and older.
+	  Make sure to implement manual hooks on security/security.c.
+
 endmenu

kernel/core_hook.c

@@ -5,7 +5,11 @@
 #include <linux/init.h>
 #include <linux/init_task.h>
 #include <linux/kernel.h>
+
+#ifdef CONFIG_KSU_LSM_SECURITY_HOOKS
 #include <linux/lsm_hooks.h>
+#endif
+
 #include <linux/nsproxy.h>
 #include <linux/path.h>
 #include <linux/printk.h>
@@ -607,15 +611,9 @@ int ksu_handle_setuid(struct cred *new, const struct cred *old)
 	return 0;
 }
 
-static int ksu_task_prctl(int option, unsigned long arg2, unsigned long arg3,
-			  unsigned long arg4, unsigned long arg5)
-{
-	ksu_handle_prctl(option, arg2, arg3, arg4, arg5);
-	return -ENOSYS;
-}
-// kernel 4.4 and 4.9
+// kernel 4.9 and older
 #if LINUX_VERSION_CODE < KERNEL_VERSION(4, 10, 0) || defined(CONFIG_KSU_ALLOWLIST_WORKAROUND)
-static int ksu_key_permission(key_ref_t key_ref, const struct cred *cred,
+int ksu_key_permission(key_ref_t key_ref, const struct cred *cred,
 			      unsigned perm)
 {
 	if (init_session_keyring != NULL) {
@@ -630,6 +628,15 @@ static int ksu_key_permission(key_ref_t key_ref, const struct cred *cred,
 	return 0;
 }
 #endif
+
+#ifdef CONFIG_KSU_LSM_SECURITY_HOOKS
+static int ksu_task_prctl(int option, unsigned long arg2, unsigned long arg3,
+			  unsigned long arg4, unsigned long arg5)
+{
+	ksu_handle_prctl(option, arg2, arg3, arg4, arg5);
+	return -ENOSYS;
+}
+
 static int ksu_inode_rename(struct inode *old_inode, struct dentry *old_dentry,
 			    struct inode *new_inode, struct dentry *new_dentry)
 {
@@ -665,3 +672,9 @@ void __init ksu_core_init(void)
 {
 	ksu_lsm_hook_init();
 }
+#else
+void __init ksu_core_init(void)
+{
+	pr_info("ksu_core_init: LSM hooks not in use.\n");
+}
+#endif //CONFIG_KSU_LSM_SECURITY_HOOKS