crypto: cmac - Add support for cloning

Allow cmac to be cloned.  The underlying cipher needs to support
cloning by not having a cra_init function (all implementations of
aes that do not require a fallback can be cloned).
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

crypto/cmac.c

@@ -213,7 +213,22 @@ static int cmac_init_tfm(struct crypto_shash *tfm)
 	ctx->child = cipher;
 
 	return 0;
-};
+}
+
+static int cmac_clone_tfm(struct crypto_shash *tfm, struct crypto_shash *otfm)
+{
+	struct cmac_tfm_ctx *octx = crypto_shash_ctx(otfm);
+	struct cmac_tfm_ctx *ctx = crypto_shash_ctx(tfm);
+	struct crypto_cipher *cipher;
+
+	cipher = crypto_clone_cipher(octx->child);
+	if (IS_ERR(cipher))
+		return PTR_ERR(cipher);
+
+	ctx->child = cipher;
+
+	return 0;
+}
 
 static void cmac_exit_tfm(struct crypto_shash *tfm)
 {
@@ -280,6 +295,7 @@ static int cmac_create(struct crypto_template *tmpl, struct rtattr **tb)
 	inst->alg.final = crypto_cmac_digest_final;
 	inst->alg.setkey = crypto_cmac_digest_setkey;
 	inst->alg.init_tfm = cmac_init_tfm;
+	inst->alg.clone_tfm = cmac_clone_tfm;
 	inst->alg.exit_tfm = cmac_exit_tfm;
 
 	inst->free = shash_free_singlespawn_instance;