diff --git a/arch/s390/kernel/debug.c b/arch/s390/kernel/debug.c
index 31430e9bcfdd..2612f634e826 100644
--- a/arch/s390/kernel/debug.c
+++ b/arch/s390/kernel/debug.c
@@ -1414,6 +1414,9 @@ static inline char *debug_get_user_string(const char __user *user_buf,
 {
 	char *buffer;
 
+	if (!user_len)
+		return ERR_PTR(-EINVAL);
+
 	buffer = memdup_user_nul(user_buf, user_len);
 	if (IS_ERR(buffer))
 		return buffer;