kernel: avoding umount when there isn't any module. close #556

kernel/core_hook.c

@@ -30,6 +30,8 @@
 #include "uid_observer.h"
 #include "kernel_compat.h"
 
+static bool ksu_module_mounted = false;
+
 extern int handle_sepolicy(unsigned long arg3, void __user *arg4);
 
 static inline bool is_allow_su()
@@ -331,6 +333,11 @@ int ksu_handle_prctl(int option, unsigned long arg2, unsigned long arg3,
 			}
 			break;
 		}
+		case EVENT_MODULE_MOUNTED: {
+			ksu_module_mounted = true;
+			pr_info("module mounted!\n");
+			break;
+		}
 		default:
 			break;
 		}
@@ -522,6 +529,11 @@ static void try_umount(const char *mnt, bool check_mnt, int flags)
 
 int ksu_handle_setuid(struct cred *new, const struct cred *old)
 {
+	// this hook is used for umounting overlayfs for some uid, if there isn't any module mounted, just ignore it!
+	if (!ksu_module_mounted) {
+		return 0;
+	}
+
 	if (!new || !old) {
 		return 0;
 	}

kernel/ksu.h

@@ -24,6 +24,7 @@
 
 #define EVENT_POST_FS_DATA 1
 #define EVENT_BOOT_COMPLETED 2
+#define EVENT_MODULE_MOUNTED 3
 
 #define KSU_APP_PROFILE_VER 2
 #define KSU_MAX_PACKAGE_NAME 256