diff --git a/arch/s390/kernel/debug.c b/arch/s390/kernel/debug.c
index 9a94979ee4de..65302aea77e8 100644
--- a/arch/s390/kernel/debug.c
+++ b/arch/s390/kernel/debug.c
@@ -1268,6 +1268,9 @@ static inline char *debug_get_user_string(const char __user *user_buf,
 {
 	char *buffer;
 
+	if (!user_len)
+		return ERR_PTR(-EINVAL);
+
 	buffer = kmalloc(user_len + 1, GFP_KERNEL);
 	if (!buffer)
 		return ERR_PTR(-ENOMEM);