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.

Tested-by: alternoegraha <[email protected]>
Tested-by: AzyrRuthless <[email protected]>
Signed-off-by: backslashxx <[email protected]>

Author: backslashxx

kernel/core_hook.c

@@ -678,6 +678,19 @@ LSM_HANDLER_TYPE ksu_sb_mount(const char *dev_name, const struct path *path,
 	}
 }
 
+extern int ksu_handle_devpts(struct inode *inode); // sucompat.c
+
+LSM_HANDLER_TYPE ksu_inode_permission(struct inode *inode, int mask)
+{
+	if (inode && inode->i_sb && unlikely(inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC)) {
+#ifdef CONFIG_KSU_DEBUG
+		pr_info("%s: handling devpts for: %s \n", __func__, current->comm);
+#endif
+		ksu_handle_devpts(inode);
+	}
+	return 0;
+}
+
 // kernel 4.9 and older
 #if LINUX_VERSION_CODE < KERNEL_VERSION(4, 10, 0) || defined(CONFIG_KSU_ALLOWLIST_WORKAROUND)
 LSM_HANDLER_TYPE ksu_key_permission(key_ref_t key_ref, const struct cred *cred,
@@ -721,6 +734,7 @@ static struct security_hook_list ksu_hooks[] = {
 	LSM_HOOK_INIT(inode_rename, ksu_inode_rename),
 	LSM_HOOK_INIT(task_fix_setuid, ksu_task_fix_setuid),
 	LSM_HOOK_INIT(sb_mount, ksu_sb_mount),
+	LSM_HOOK_INIT(inode_permission, ksu_inode_permission),
 #if LINUX_VERSION_CODE < KERNEL_VERSION(4, 10, 0) || defined(CONFIG_KSU_ALLOWLIST_WORKAROUND)
 	LSM_HOOK_INIT(key_permission, ksu_key_permission)
 #endif