linux-kernel - Re: [PATCH v6 6/8] crypto: x86/aesni: Remove glue function macro usage

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Message-ID: <20191122020812.GB32523@sol.localdomain>
Date:   Thu, 21 Nov 2019 18:08:12 -0800
From:   Eric Biggers <ebiggers@...nel.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     Herbert Xu <herbert@...dor.apana.org.au>,
        João Moreira <joao.moreira@...el.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        Stephan Mueller <smueller@...onox.de>, x86@...nel.org,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-hardening@...ts.openwall.com
Subject: Re: [PATCH v6 6/8] crypto: x86/aesni: Remove glue function macro
 usage

On Thu, Nov 21, 2019 at 05:03:32PM -0800, Kees Cook wrote:
> In order to remove the callsite function casts, regularize the function
> prototypes for helpers to avoid triggering Control-Flow Integrity checks
> during indirect function calls. Where needed, to avoid changes to
> pointer math, u8 pointers are internally cast back to u128 pointers.
> 
> Signed-off-by: Kees Cook <keescook@...omium.org>
> ---
>  arch/x86/crypto/aesni-intel_asm.S  |  8 +++---
>  arch/x86/crypto/aesni-intel_glue.c | 45 ++++++++++++------------------
>  2 files changed, 22 insertions(+), 31 deletions(-)
> 
> diff --git a/arch/x86/crypto/aesni-intel_asm.S b/arch/x86/crypto/aesni-intel_asm.S
> index e40bdf024ba7..89e5e574dc95 100644
> --- a/arch/x86/crypto/aesni-intel_asm.S
> +++ b/arch/x86/crypto/aesni-intel_asm.S
> @@ -1946,7 +1946,7 @@ ENTRY(aesni_set_key)
>  ENDPROC(aesni_set_key)
>  
>  /*
> - * void aesni_enc(struct crypto_aes_ctx *ctx, u8 *dst, const u8 *src)
> + * void aesni_enc(void *ctx, u8 *dst, const u8 *src)
>   */

This doesn't exactly match the C prototype.

>  ENTRY(aesni_enc)
>  	FRAME_BEGIN
> @@ -2137,7 +2137,7 @@ _aesni_enc4:
>  ENDPROC(_aesni_enc4)
>  
>  /*
> - * void aesni_dec (struct crypto_aes_ctx *ctx, u8 *dst, const u8 *src)
> + * void aesni_dec (void *ctx, u8 *dst, const u8 *src)
>   */
>  ENTRY(aesni_dec)

Likewise.

>  	FRAME_BEGIN
> @@ -2726,8 +2726,8 @@ ENDPROC(aesni_ctr_enc)
>  	pxor CTR, IV;
>  
>  /*
> - * void aesni_xts_crypt8(struct crypto_aes_ctx *ctx, const u8 *dst, u8 *src,
> - *			 bool enc, u8 *iv)
> + * void aesni_xts_crypt8(void *ctx, u8 *dst, const u8 *src, bool enc,
> + *			 le128 *iv)
>   */

Likewise.  This one is particularly strange because the first argument was
changed to void * here, but in C it's 'const struct crypto_aes_ctx *ctx'.
 
- Eric