diff --git a/arch/s390/crypto/arch_random.c b/arch/s390/crypto/arch_random.c
index 7b947728d57e..56007c763902 100644
--- a/arch/s390/crypto/arch_random.c
+++ b/arch/s390/crypto/arch_random.c
@@ -54,6 +54,10 @@ static DECLARE_DELAYED_WORK(arch_rng_work, arch_rng_refill_buffer);
 
 bool s390_arch_random_generate(u8 *buf, unsigned int nbytes)
 {
+	/* max hunk is ARCH_RNG_BUF_SIZE */
+	if (nbytes > ARCH_RNG_BUF_SIZE)
+		return false;
+
 	/* lock rng buffer */
 	if (!spin_trylock(&arch_rng_lock))
 		return false;