linux-kernel - Re: [PATCH] crypto: x86/aesni - Update aesni_set

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Date: Tue, 12 Mar 2024 16:18:06 +0100
From: Ard Biesheuvel <ardb@...nel.org>
To: "Chang S. Bae" <chang.seok.bae@...el.com>
Cc: linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org, 
	herbert@...dor.apana.org.au, davem@...emloft.net, ebiggers@...nel.org, 
	x86@...nel.org
Subject: Re: [PATCH] crypto: x86/aesni - Update aesni_set_key() to return void

On Tue, 12 Mar 2024 at 16:03, Chang S. Bae <chang.seok.bae@...el.com> wrote:
>
> On 3/12/2024 12:46 AM, Ard Biesheuvel wrote:
> > On Mon, 11 Mar 2024 at 22:48, Chang S. Bae <chang.seok.bae@...el.com> wrote:
> >>
> >> @@ -241,7 +241,7 @@ static int aes_set_key_common(struct crypto_aes_ctx *ctx,
> >>                  err = aes_expandkey(ctx, in_key, key_len);
> >>          else {
> >>                  kernel_fpu_begin();
> >> -               err = aesni_set_key(ctx, in_key, key_len);
> >> +               aesni_set_key(ctx, in_key, key_len);
> >
> > This will leave 'err' uninitialized.
>
> Ah, right. Thanks for catching it.
>
> Also, upon reviewing aes_expandkey(), I noticed there's no error case,
> except for the key length sanity check.
>
> While addressing this, perhaps additional cleanup is considerable like:
>
> @@ -233,19 +233,20 @@ static int aes_set_key_common(struct
> crypto_aes_ctx *ctx,
>   {
>          int err;
>
> -       if (key_len != AES_KEYSIZE_128 && key_len != AES_KEYSIZE_192 &&
> -           key_len != AES_KEYSIZE_256)
> -               return -EINVAL;
> +       err = aes_check_keylen(key_len);
> +       if (err)
> +               return err;
>
>          if (!crypto_simd_usable())
> -               err = aes_expandkey(ctx, in_key, key_len);
> +               /* no error with a valid key length  */
> +               aes_expandkey(ctx, in_key, key_len);
>          else {
>                  kernel_fpu_begin();
> -               err = aesni_set_key(ctx, in_key, key_len);
> +               aesni_set_key(ctx, in_key, key_len);
>                  kernel_fpu_end();
>          }
>
> -       return err;
> +       return 0;
>   }
>

I wonder whether we need aesni_set_key() at all.