linux-kernel - Re: [PATCH 06/11] crypto: cbc: Remove VLA usage

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Date:   Wed, 20 Jun 2018 20:16:39 +0000
From:   Christophe Leroy <christophe.leroy@....fr>
To:     Kees Cook <keescook@...omium.org>,
        Herbert Xu <herbert@...dor.apana.org.au>
Cc:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        Alasdair Kergon <agk@...hat.com>,
        Arnd Bergmann <arnd@...db.de>,
        Eric Biggers <ebiggers@...gle.com>,
        Giovanni Cabiddu <giovanni.cabiddu@...el.com>,
        Lars Persson <larper@...s.com>,
        Mike Snitzer <snitzer@...hat.com>,
        Rabin Vincent <rabinv@...s.com>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        "David S. Miller" <davem@...emloft.net>,
        linux-crypto@...r.kernel.org, qat-linux@...el.com,
        dm-devel@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 06/11] crypto: cbc: Remove VLA usage



On 06/20/2018 07:04 PM, Kees Cook wrote:
> In the quest to remove all stack VLA usage from the kernel[1], this
> uses the upper bounds on blocksize.
> 
> [1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com
> 
> Signed-off-by: Kees Cook <keescook@...omium.org>

crypto/cbc.c: In function ‘crypto_cbc_decrypt’:
crypto/cbc.c:79:1: warning: the frame size of 2144 bytes is larger than 
1024 bytes [-Wframe-larger-than=]

Christophe

> ---
>   include/crypto/cbc.h | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/crypto/cbc.h b/include/crypto/cbc.h
> index f5b8bfc22e6d..260096bcf99b 100644
> --- a/include/crypto/cbc.h
> +++ b/include/crypto/cbc.h
> @@ -113,7 +113,7 @@ static inline int crypto_cbc_decrypt_inplace(
>   	unsigned int bsize = crypto_skcipher_blocksize(tfm);
>   	unsigned int nbytes = walk->nbytes;
>   	u8 *src = walk->src.virt.addr;
> -	u8 last_iv[bsize];
> +	u8 last_iv[CRYPTO_ALG_MAX_BLOCKSIZE];
>   
>   	/* Start of the last block. */
>   	src += nbytes - (nbytes & (bsize - 1)) - bsize;
>