fscrypt: use crypto_shash_tfm_digest()

Instead of manually allocating a 'struct shash_desc' on the stack and
calling crypto_shash_digest(), switch to using the new helper function
crypto_shash_tfm_digest() which does this for us.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

fs/crypto/fname.c

@@ -83,13 +83,8 @@ static int fscrypt_do_sha256(const u8 *data, unsigned int data_len, u8 *result)
 			tfm = prev_tfm;
 		}
 	}
-	{
-		SHASH_DESC_ON_STACK(desc, tfm);
 
-		desc->tfm = tfm;
-
-		return crypto_shash_digest(desc, data, data_len, result);
-	}
+	return crypto_shash_tfm_digest(tfm, data, data_len, result);
 }
 
 static inline bool fscrypt_is_dot_dotdot(const struct qstr *str)

fs/crypto/hkdf.c

@@ -44,17 +44,13 @@ static int hkdf_extract(struct crypto_shash *hmac_tfm, const u8 *ikm,
 			unsigned int ikmlen, u8 prk[HKDF_HASHLEN])
 {
 	static const u8 default_salt[HKDF_HASHLEN];
-	SHASH_DESC_ON_STACK(desc, hmac_tfm);
 	int err;
 
 	err = crypto_shash_setkey(hmac_tfm, default_salt, HKDF_HASHLEN);
 	if (err)
 		return err;
 
-	desc->tfm = hmac_tfm;
-	err = crypto_shash_digest(desc, ikm, ikmlen, prk);
-	shash_desc_zero(desc);
-	return err;
+	return crypto_shash_tfm_digest(hmac_tfm, ikm, ikmlen, prk);
 }
 
 /*