crypto: cmac - use crypto_grab_cipher() and simplify error paths

Make the cmac template use the new function crypto_grab_cipher() to
initialize its cipher spawn.

This is needed to make all spawns be initialized in a consistent way.

This required making cmac_create() allocate the instance directly rather
than use shash_alloc_instance().

Also simplify the error handling by taking advantage of crypto_drop_*()
now accepting (as a no-op) spawns that haven't been initialized yet, and
by taking advantage of crypto_grab_*() now handling ERR_PTR() names.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

crypto/cmac.c

@@ -222,6 +222,7 @@ static void cmac_exit_tfm(struct crypto_tfm *tfm)
 static int cmac_create(struct crypto_template *tmpl, struct rtattr **tb)
 {
 	struct shash_instance *inst;
+	struct crypto_cipher_spawn *spawn;
 	struct crypto_alg *alg;
 	unsigned long alignmask;
 	int err;
@@ -230,10 +231,16 @@ static int cmac_create(struct crypto_template *tmpl, struct rtattr **tb)
 	if (err)
 		return err;
 
-	alg = crypto_get_attr_alg(tb, CRYPTO_ALG_TYPE_CIPHER,
-				  CRYPTO_ALG_TYPE_MASK);
-	if (IS_ERR(alg))
-		return PTR_ERR(alg);
+	inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
+	if (!inst)
+		return -ENOMEM;
+	spawn = shash_instance_ctx(inst);
+
+	err = crypto_grab_cipher(spawn, shash_crypto_instance(inst),
+				 crypto_attr_alg_name(tb[1]), 0, 0);
+	if (err)
+		goto err_free_inst;
+	alg = crypto_spawn_cipher_alg(spawn);
 
 	switch (alg->cra_blocksize) {
 	case 16:
@@ -241,19 +248,12 @@ static int cmac_create(struct crypto_template *tmpl, struct rtattr **tb)
 		break;
 	default:
 		err = -EINVAL;
-		goto out_put_alg;
+		goto err_free_inst;
 	}
 
-	inst = shash_alloc_instance("cmac", alg);
-	err = PTR_ERR(inst);
-	if (IS_ERR(inst))
-		goto out_put_alg;
-
-	err = crypto_init_spawn(shash_instance_ctx(inst), alg,
-				shash_crypto_instance(inst),
-				CRYPTO_ALG_TYPE_MASK);
+	err = crypto_inst_setname(shash_crypto_instance(inst), tmpl->name, alg);
 	if (err)
-		goto out_free_inst;
+		goto err_free_inst;
 
 	alignmask = alg->cra_alignmask;
 	inst->alg.base.cra_alignmask = alignmask;
@@ -282,12 +282,9 @@ static int cmac_create(struct crypto_template *tmpl, struct rtattr **tb)
 
 	err = shash_register_instance(tmpl, inst);
 	if (err) {
-out_free_inst:
+err_free_inst:
 		shash_free_instance(shash_crypto_instance(inst));
 	}
-
-out_put_alg:
-	crypto_mod_put(alg);
 	return err;
 }