diff --git a/arch/mips/loongson/common/machtype.c b/arch/mips/loongson/common/machtype.c
index 81fbe6b73f91f71b896292cbf55b7b1c67990f80..2efd5d9dee27192f8a0da79698eb79b5c6e9828c 100644
--- a/arch/mips/loongson/common/machtype.c
+++ b/arch/mips/loongson/common/machtype.c
@@ -41,7 +41,7 @@ void __weak __init mach_prom_init_machtype(void)
 
 void __init prom_init_machtype(void)
 {
-	char *p, str[MACHTYPE_LEN];
+	char *p, str[MACHTYPE_LEN + 1];
 	int machtype = MACH_LEMOTE_FL2E;
 
 	mips_machtype = LOONGSON_MACHTYPE;
@@ -53,6 +53,7 @@ void __init prom_init_machtype(void)
 	}
 	p += strlen("machtype=");
 	strncpy(str, p, MACHTYPE_LEN);
+	str[MACHTYPE_LEN] = '\0';
 	p = strstr(str, " ");
 	if (p)
 		*p = '\0';