ubifs: use crypto_shash_tfm_digest() in ubifs_hmac_wkm()

From: Eric Biggers <[email protected]>

Simplify ubifs_hmac_wkm() by using crypto_shash_tfm_digest() instead of an alloc+init+update+final sequence. This should also improve performance.

Signed-off-by Eric Biggers <[email protected]>

---
  fs/ubifs/auth.c | 19 ++-----------------
  1 file changed, 2 insertions(+), 17 deletions(-)

fs/ubifs/auth.c +2 -17

index e564d5ff8781..4add4a4f0720 100644
@@ -501,42 +501,27 @@ int __ubifs_shash_copy_state(const struct ubifs_info *c, struct shash_desc *src,
   *
   * This function creates a HMAC of a well known message. This is used
   * to check if the provided key is suitable to authenticate a UBIFS
   * image. This is only a convenience to the user to provide a better
   * error message when the wrong key is provided.
   *
   * This function returns 0 for success or a negative error code otherwise.
   */
  int ubifs_hmac_wkm(struct ubifs_info *c, u8 *hmac)
  {
-	SHASH_DESC_ON_STACK(shash, c->hmac_tfm);
-	int err;
  	const char well_known_message[] = "UBIFS";
 
  	if (!ubifs_authenticated(c))
  		return 0;
 
-	shash->tfm = c->hmac_tfm;
-
-	err = crypto_shash_init(shash);
-	if (err)
-		return err;
-
-	err = crypto_shash_update(shash, well_known_message,
-				  sizeof(well_known_message) - 1);
-	if (err < 0)
-		return err;
-
-	err = crypto_shash_final(shash, hmac);
-	if (err)
-		return err;
-	return 0;
+	return crypto_shash_tfm_digest(c->hmac_tfm, well_known_message,
+				       sizeof(well_known_message) - 1, hmac);
  }
 
  /*
   * ubifs_hmac_zero - test if a HMAC is zero
   * @c: UBIFS file-system description object
   * @hmac: the HMAC to test
   *
   * This function tests if a HMAC is zero and returns true if it is
   * and false otherwise.
   */

base-commit: 2af9b20dbb39f6ebf9b9b6c090271594627d818e