linux-kernel - Re: [PATCH] crypto: arm64/sha: fix function types

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Date:   Wed, 13 Nov 2019 12:04:20 -0800
From:   Eric Biggers <ebiggers@...nel.org>
To:     Sami Tolvanen <samitolvanen@...gle.com>
Cc:     Herbert Xu <herbert@...dor.apana.org.au>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Kees Cook <keescook@...omium.org>,
        linux-crypto@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] crypto: arm64/sha: fix function types

On Tue, Nov 12, 2019 at 02:30:46PM -0800, Sami Tolvanen wrote:
> Declare assembly functions with the expected function type
> instead of casting pointers in C to avoid type mismatch failures
> with Control-Flow Integrity (CFI) checking.
> 
> Signed-off-by: Sami Tolvanen <samitolvanen@...gle.com>
> ---
>  arch/arm64/crypto/sha1-ce-glue.c   | 12 +++++-------
>  arch/arm64/crypto/sha2-ce-glue.c   | 26 +++++++++++---------------
>  arch/arm64/crypto/sha256-glue.c    | 30 ++++++++++++------------------
>  arch/arm64/crypto/sha512-ce-glue.c | 23 ++++++++++-------------
>  arch/arm64/crypto/sha512-glue.c    | 13 +++++--------
>  5 files changed, 43 insertions(+), 61 deletions(-)
> 
> diff --git a/arch/arm64/crypto/sha1-ce-glue.c b/arch/arm64/crypto/sha1-ce-glue.c
> index bdc1b6d7aff7..3153a9bbb683 100644
> --- a/arch/arm64/crypto/sha1-ce-glue.c
> +++ b/arch/arm64/crypto/sha1-ce-glue.c
> @@ -25,7 +25,7 @@ struct sha1_ce_state {
>  	u32			finalize;
>  };
>  
> -asmlinkage void sha1_ce_transform(struct sha1_ce_state *sst, u8 const *src,
> +asmlinkage void sha1_ce_transform(struct sha1_state *sst, u8 const *src,
>  				  int blocks);

Please update the comments in the corresponding assembly files too.

Also, this change doesn't really make sense because the assembly functions still
expect struct sha1_ce_state, and they access sha1_ce_state::finalize which is
not present in struct sha1_state.  There should either be wrapper functions that
explicitly do the cast from sha1_state to sha1_ce_state, or there should be
comments in the assembly files that very clearly explain that although the
function prototype takes sha1_state, it's really assumed to be a sha1_ce_state.

Likewise for SHA-256 and SHA-512.

- Eric