Re: [PATCH 2/3] crypto: cipher - Add crypto_clone_cipher

[Simon Horman]

On Fri, May 19, 2023 at 04:28:35PM +0800, Herbert Xu wrote:
> Allow simple ciphers to be cloned, if they don't have a cra_init
> function.  This basically rules out those ciphers that require a
> fallback.
> 
> In future simple ciphers will be eliminated, and replaced with a
> linear skcipher interface.  When that happens this restriction will
> disappear.
> 
> Signed-off-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
> ---
> 
>  crypto/cipher.c                  |   23 +++++++++++++++++++++++
>  include/crypto/internal/cipher.h |    2 ++
>  2 files changed, 25 insertions(+)
> 
> diff --git a/crypto/cipher.c b/crypto/cipher.c
> index b47141ed4a9f..d39ef5f72ab8 100644
> --- a/crypto/cipher.c
> +++ b/crypto/cipher.c
> @@ -90,3 +90,26 @@ void crypto_cipher_decrypt_one(struct crypto_cipher *tfm,
>  	cipher_crypt_one(tfm, dst, src, false);
>  }
>  EXPORT_SYMBOL_NS_GPL(crypto_cipher_decrypt_one, CRYPTO_INTERNAL);
> +
> +struct crypto_cipher *crypto_clone_cipher(struct crypto_cipher *cipher)
> +{
> +	struct crypto_tfm *tfm = crypto_cipher_tfm(cipher);
> +	struct crypto_alg *alg = tfm->__crt_alg;
> +	struct crypto_cipher *ncipher;
> +	struct crypto_tfm *ntfm;
> +
> +	if (alg->cra_init)
> +		return ERR_PTR(-ENOSYS);

Hi Herbert,

I see ENOSYS used in similar ways elsewhere in crypto/,
but it strikes me that EOPNOTSUPP may well be more appropriate.

> +
> +	ntfm = __crypto_alloc_tfm(alg, CRYPTO_ALG_TYPE_CIPHER,
> +				  CRYPTO_ALG_TYPE_MASK);
> +	if (IS_ERR(ntfm))
> +		return ERR_CAST(ntfm);
> +
> +	ntfm->crt_flags = tfm->crt_flags;
> +
> +	ncipher = __crypto_cipher_cast(ntfm);
> +
> +	return ncipher;
> +}
> +EXPORT_SYMBOL_GPL(crypto_clone_cipher);

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