diff --git a/drivers/crypto/allwinner/sun4i-ss/sun4i-ss-prng.c b/drivers/crypto/allwinner/sun4i-ss/sun4i-ss-prng.c
index 491fcb7b8..7f6a51dd8 100644
--- a/drivers/crypto/allwinner/sun4i-ss/sun4i-ss-prng.c
+++ b/drivers/crypto/allwinner/sun4i-ss/sun4i-ss-prng.c
@@ -8,7 +8,7 @@ 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);
-	memcpy(algt->ss->seed, seed, slen);
+	memcpy(algt->ss->seed, seed, min_t(unsigned int, slen, sizeof(algt->ss->seed)));
 
 	return 0;
 }