diff --git a/drivers/crypto/allwinner/sun4i-ss/sun4i-ss-prng.c b/drivers/crypto/allwinner/sun4i-ss/sun4i-ss-prng.c
index 491fcb7b8..010fa891c 100644
--- a/drivers/crypto/allwinner/sun4i-ss/sun4i-ss-prng.c
+++ b/drivers/crypto/allwinner/sun4i-ss/sun4i-ss-prng.c
@@ -8,6 +8,8 @@ int sun4i_ss_prng_seed(struct crypto_rng *tfm, const u8 *seed,
 	struct rng_alg *alg = crypto_rng_alg(tfm);
 
 	algt = container_of(alg, struct sun4i_ss_alg_template, alg.rng);
+	if (slen > sizeof(algt->ss->seed))
+		return -EINVAL;
 	memcpy(algt->ss->seed, seed, slen);
 
 	return 0;