linux-kernel - Re: [PATCH 5/8 v2] dm: replace memset by memzero

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Message-ID: <547CD7B9.5030000@gmail.com>
Date:	Mon, 01 Dec 2014 22:03:53 +0100
From:	Milan Broz <gmazyland@...il.com>
To:	Mike Snitzer <snitzer@...hat.com>
CC:	Julia Lawall <Julia.Lawall@...6.fr>,
	Alasdair Kergon <agk@...hat.com>,
	kernel-janitors@...r.kernel.org, dm-devel@...hat.com,
	Neil Brown <neilb@...e.de>, linux-raid@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/8 v2] dm: replace memset by memzero_explicit

On 11/30/2014 06:03 PM, Julia Lawall wrote:
> From: Julia Lawall <Julia.Lawall@...6.fr>
> 
> Memset on a local variable may be removed when it is called just before the
> variable goes out of scope.  Using memzero_explicit defeats this
> optimization.  A simplified version of the semantic patch that makes this
> change is as follows: (http://coccinelle.lip6.fr/)

Ack, but I submitted the same patch a week ago....

https://www.redhat.com/archives/dm-devel/2014-November/msg00084.html

Mike, please could you add this to linux-next tree or you want this
to go through Herbert's tree?
(I do not think it is good idea for DM patches.)

Thanks,
Milan

> 
> // <smpl>
> @@
> identifier x;
> type T;
> @@
> 
> {
> ... when any
> T x[...];
> ... when any
>     when exists
> - memset
> + memzero_explicit
>   (x,
> -0,
>   ...)
> ... when != x
>     when strict
> }
> // </smpl>
> 
> This change was suggested by Daniel Borkmann <dborkman@...hat.com>
> 
> Signed-off-by: Julia Lawall <Julia.Lawall@...6.fr>
> 
> ---
> Daniel Borkmann suggested that these patches could go through Herbert Xu's
> cryptodev tree.
> 
> v2: fixed email address
> 
>  drivers/md/dm-crypt.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
> index fc93b93..08981be 100644
> --- a/drivers/md/dm-crypt.c
> +++ b/drivers/md/dm-crypt.c
> @@ -705,7 +705,7 @@ static int crypt_iv_tcw_whitening(struct crypt_config *cc,
>  	for (i = 0; i < ((1 << SECTOR_SHIFT) / 8); i++)
>  		crypto_xor(data + i * 8, buf, 8);
>  out:
> -	memset(buf, 0, sizeof(buf));
> +	memzero_explicit(buf, sizeof(buf));
>  	return r;
>  }
>  
> 

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