diff --git a/security/keys/dh.c b/security/keys/dh.c
index f7403821db7f..b203f7758f97 100644
--- a/security/keys/dh.c
+++ b/security/keys/dh.c
@@ -142,6 +142,8 @@ static void kdf_dealloc(struct kdf_sdesc *sdesc)
  * The src pointer is defined as Z || other info where Z is the shared secret
  * from DH and other info is an arbitrary string (see SP800-56A section
  * 5.8.1.2).
+ *
+ * 'dlen' must be a multiple of the digest size.
  */
 static int kdf_ctr(struct kdf_sdesc *sdesc, const u8 *src, unsigned int slen,
 		   u8 *dst, unsigned int dlen, unsigned int zlen)
@@ -205,8 +207,8 @@ static int keyctl_dh_compute_kdf(struct kdf_sdesc *sdesc,
 {
 	uint8_t *outbuf = NULL;
 	int ret;
-	size_t outbuf_len = round_up(buflen,
-			             crypto_shash_digestsize(sdesc->shash.tfm));
+	size_t outbuf_len = roundup(buflen,
+				    crypto_shash_digestsize(sdesc->shash.tfm));
 
 	outbuf = kmalloc(outbuf_len, GFP_KERNEL);
 	if (!outbuf) {