diff --git a/arch/s390/kernel/debug.c b/arch/s390/kernel/debug.c
index cbe209fe0df15728d441ac01ec493e5948232f3f..893c35aeb746a7da66b2b5e5371c6eefffaae5fd 100644
--- a/arch/s390/kernel/debug.c
+++ b/arch/s390/kernel/debug.c
@@ -1258,6 +1258,9 @@ 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);