linux-kernel - Re: [PATCH RESEND] cifs: use memzero

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Date:	Fri, 9 Jan 2015 12:53:26 -0600
From:	Steve French <smfrench@...il.com>
To:	Giel van Schijndel <me@...tis.eu>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Steve French <sfrench@...ba.org>,
	"open list:COMMON INTERNET F..." <linux-cifs@...r.kernel.org>,
	"moderated list:COMMON INTERNET F..." 
	<samba-technical@...ts.samba.org>
Subject: Re: [PATCH RESEND] cifs: use memzero_explicit to clear stack buffer

Looks fine to me - will merge into cifs-2.6.git

On Tue, Jan 6, 2015 at 3:37 PM, Giel van Schijndel <me@...tis.eu> wrote:
> When leaving a function use memzero_explicit instead of memset(0) to
> clear stack allocated buffers. memset(0) may be optimized away.
>
> This particular buffer is highly likely to contain sensitive data which
> we shouldn't leak (it's named 'passwd' after all).
>
> Signed-off-by: Giel van Schijndel <me@...tis.eu>
> Reported-at: http://www.viva64.com/en/b/0299/
> Reported-by: Andrey Karpov
> Reported-by: Svyatoslav Razmyslov
> ---
>  fs/cifs/smbencrypt.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/cifs/smbencrypt.c b/fs/cifs/smbencrypt.c
> index 6c15663..a4232ec 100644
> --- a/fs/cifs/smbencrypt.c
> +++ b/fs/cifs/smbencrypt.c
> @@ -221,7 +221,7 @@ E_md4hash(const unsigned char *passwd, unsigned char *p16,
>         }
>
>         rc = mdfour(p16, (unsigned char *) wpwd, len * sizeof(__le16));
> -       memset(wpwd, 0, 129 * sizeof(__le16));
> +       memzero_explicit(wpwd, sizeof(wpwd));
>
>         return rc;
>  }
> --
> 2.1.4
>



-- 
Thanks,

Steve
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