kernel: sucompat: improve error handling and add conditional hooks

kernel/sucompat.c

@@ -129,13 +129,27 @@ int ksu_handle_stat(int *dfd, const char __user **filename_user, int *flags)
 
 	char path[sizeof(su) + 1];
 	memset(path, 0, sizeof(path));
-
+// Remove this later!! we use syscall hook, so this will never happen!!!!!
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 18, 0) && 0
+	// it becomes a `struct filename *` after 5.18
+	// https://elixir.bootlin.com/linux/v5.18/source/fs/stat.c#L216
+	const char sh[] = SH_PATH;
+	struct filename *filename = *((struct filename **)filename_user);
+	if (IS_ERR(filename)) {
+		return 0;
+	}
+	if (likely(memcmp(filename->name, su, sizeof(su))))
+		return 0;
+	pr_info("vfs_statx su->sh!\n");
+	memcpy((void *)filename->name, sh, sizeof(sh));
+#else
 	ksu_strncpy_from_user_nofault(path, *filename_user, sizeof(path));
 
 	if (unlikely(!memcmp(path, su, sizeof(su)))) {
 		pr_info("newfstatat su->sh!\n");
 		*filename_user = sh_user_path();
 	}
+#endif
 
 	return 0;
 }
@@ -184,6 +198,12 @@ int ksu_handle_execve_sucompat(int *fd, const char __user **filename_user,
 	const char su[] = SU_PATH;
 	char path[sizeof(su) + 1];
 
+#ifndef CONFIG_KSU_KPROBES_HOOK
+	if (!ksu_sucompat_hook_state) {
+		return 0;
+	}
+#endif
+
 	if (unlikely(!filename_user))
 		return 0;
 
@@ -201,7 +221,7 @@ int ksu_handle_execve_sucompat(int *fd, const char __user **filename_user,
 #endif
 	// success = returns number of bytes and should be less than path
 	long len = strncpy_from_user(path, *filename_user, sizeof(path));
-	if (len <= 0)
+	if (len <= 0 || len > sizeof(path))
 		return 0;
 
 	// strncpy_from_user_nofault does this too