kernel: core_hook: intercept devpts via security_inode_permission LSM

`ksu handles devpts with selinux lsm hook` - aviraxp

- no, not yet, but yes we can, thats a good idea.

This change tries to do that, so instead of hooking pts_unix98_lookup or
devpts_get_priv, we just watch security_inode_permission, if its devpts,
pass it along to the original handler.

EDIT: define devpts super magic if its undefined
- yeah I aint gonna include a conditional include of a header just for this
- while we can just fully remove the macro and inline, readability loss is bad

Co-authored-by: backslashxx <118538522+backslashxx@users.noreply.github.com>

kernel/sucompat.c

@@ -195,8 +195,15 @@ int ksu_handle_execve_sucompat(int *fd, const char __user **filename_user,
 	return 0;
 }
 
+// dummified
 int ksu_handle_devpts(struct inode *inode)
 {
+	return 0;
+}
+
+int __ksu_handle_devpts(struct inode *inode)
+{
+
 #ifndef CONFIG_KSU_KPROBES_HOOK
 	if (!ksu_sucompat_hook_state)
 		return 0;
@@ -212,15 +219,12 @@ int ksu_handle_devpts(struct inode *inode)
 		return 0;
 	}
 
-	if (!ksu_is_allow_uid(uid))
+	if (likely(!ksu_is_allow_uid(uid)))
 		return 0;
 
-	if (ksu_devpts_sid) {
 		struct inode_security_struct *sec = selinux_inode(inode);
-		if (sec) {
-			sec->sid = ksu_devpts_sid;
-		}
-	}
+	if (ksu_devpts_sid && sec)
+		sec->sid = ksu_devpts_sid;
 
 	return 0;
 }