linux-kernel - Re: [PATCH] crypto: use memzero_explicit instead of memset to clear contexts.

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Message-ID: <20181129064913.wbudlexjzszpa7dq@gondor.apana.org.au>
Date:   Thu, 29 Nov 2018 14:49:13 +0800
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     David CARLIER <devnexen@...il.com>
Cc:     linux-kernel@...r.kernel.org,
        "David S. Miller" <davem@...emloft.net>,
        linux-crypto@...r.kernel.org
Subject: Re: [PATCH] crypto: use memzero_explicit instead of memset to clear
 contexts.

On Wed, Nov 28, 2018 at 07:36:50PM +0000, David CARLIER wrote:
> There might be a little performance drop but to make sure it stands
> by it comments, we really wipe the whole context after usage.
> ---
>  crypto/chacha20poly1305.c | 3 ++-
>  crypto/md5.c              | 2 +-
>  crypto/rmd128.c           | 3 ++-
>  crypto/rmd160.c           | 3 ++-
>  crypto/rmd256.c           | 3 ++-
>  crypto/rmd320.c           | 3 ++-
>  crypto/sha3_generic.c     | 3 ++-
>  7 files changed, 13 insertions(+), 7 deletions(-)
> 
> diff --git a/crypto/chacha20poly1305.c b/crypto/chacha20poly1305.c
> index 600afa99941f..6e93d998109e 100644
> --- a/crypto/chacha20poly1305.c
> +++ b/crypto/chacha20poly1305.c
> @@ -19,6 +19,7 @@
>  #include <linux/init.h>
>  #include <linux/kernel.h>
>  #include <linux/module.h>
> +#include <linux/string.h>
> 
>  #include "internal.h"
> 
> @@ -388,7 +389,7 @@ static int poly_genkey(struct aead_request *req)
>         }
> 
>         sg_init_table(creq->src, 1);
> -       memset(rctx->key, 0, sizeof(rctx->key));
> +       memzero_explicit(rctx->key, sizeof(rctx->key));

Please explain the purpose of this patch.  As it stands this
makes no sense.

Thanks,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt