Re: [PATCH v8 10/12] crypto: x86/aesni - Use the proper data type in struct aesni_xts_ctx

[Eric Biggers]

On Sat, Jun 03, 2023 at 08:22:25AM -0700, Chang S. Bae wrote:
> Every field in struct aesni_xts_ctx is a pointer to a byte array.

A byte array.  Not a pointer to a byte array.

> Then, the field can be redefined as that struct type instead of the obscure
> pointer.

There's no pointer.

>  static inline struct
>  aesni_rfc4106_gcm_ctx *aesni_rfc4106_gcm_ctx_get(struct crypto_aead *tfm)
>  {
> -	unsigned long align = AESNI_ALIGN;
> -
> -	if (align <= crypto_tfm_ctx_alignment())
> -		align = 1;
> -	return PTR_ALIGN(crypto_aead_ctx(tfm), align);
> +	return (struct aesni_rfc4106_gcm_ctx *)aes_align_addr(crypto_aead_ctx(tfm));
>  }

Explicit casts from 'void *' are unnecessary.

>  static int xts_aesni_setkey(struct crypto_skcipher *tfm, const u8 *key,
>  			    unsigned int keylen)
>  {
> -	struct aesni_xts_ctx *ctx = crypto_skcipher_ctx(tfm);
> +	struct aesni_xts_ctx *ctx = aes_xts_ctx(tfm);
>  	int err;
>  
>  	err = xts_verify_key(tfm, key, keylen);
> @@ -893,20 +892,20 @@ static int xts_aesni_setkey(struct crypto_skcipher *tfm, const u8 *key,
>  	keylen /= 2;
>  
>  	/* first half of xts-key is for crypt */
> -	err = aes_set_key_common(crypto_skcipher_tfm(tfm), ctx->raw_crypt_ctx,
> +	err = aes_set_key_common(crypto_skcipher_tfm(tfm), &ctx->crypt_ctx,
>  				 key, keylen);
>  	if (err)
>  		return err;
>  
>  	/* second half of xts-key is for tweak */
> -	return aes_set_key_common(crypto_skcipher_tfm(tfm), ctx->raw_tweak_ctx,
> +	return aes_set_key_common(crypto_skcipher_tfm(tfm), &ctx->tweak_ctx,
>  				  key + keylen, keylen);
>  }

To re-iterate what I said on v6, the runtime alignment to a 16-byte boundary
should happen when translating the raw crypto_skcipher_ctx() into the pointer to
the aes_xts_ctx.  It should not happen when accessing each individual field in
the aes_xts_ctx.

Yet, this code is still doing runtime alignment when accessing each individual
field, as the second argument to aes_set_key_common() is 'void *raw_ctx' which
aes_set_key_common() runtime-aligns to crypto_aes_ctx.

We should keep everything consistent, which means making aes_set_key_common()
take a pointer to crypto_aes_ctx and not do the runtime alignment.

- Eric