linux-kernel - Re: [PATCH] s390: ensure NUL termination by strncpy()

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Date:	Mon, 16 Nov 2009 22:13:29 +0100
From:	Heiko Carstens <heiko.carstens@...ibm.com>
To:	Roel Kluin <roel.kluin@...il.com>
Cc:	Martin Schwidefsky <schwidefsky@...ibm.com>, linux390@...ibm.com,
	linux-s390@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Michael Holzheu <holzheu@...ux.vnet.ibm.com>
Subject: Re: [PATCH] s390: ensure NUL termination by strncpy()

On Mon, Nov 16, 2009 at 07:53:54PM +0100, Roel Kluin wrote:
> For a larger source string, strncpy only NUL terminates when
> the size argument is less than the size of the destination string.
> 
> Signed-off-by: Roel Kluin <roel.kluin@...il.com>
> ---
>  arch/s390/kernel/ipl.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> Is this maybe needed?

No, kernel_nss_name as well as the data.nss.name char array within ipl_info
have the same size. So it will always fit and it is always NUL terminated.

Maybe it should be changed to a simple memcpy, like we have it at a second
place in the same file. I think that's up to Michael.

> diff --git a/arch/s390/kernel/ipl.c b/arch/s390/kernel/ipl.c
> index 4890ac6..d52fcb4 100644
> --- a/arch/s390/kernel/ipl.c
> +++ b/arch/s390/kernel/ipl.c
> @@ -1881,7 +1881,7 @@ void __init setup_ipl(void)
>  		break;
>  	case IPL_TYPE_NSS:
>  		strncpy(ipl_info.data.nss.name, kernel_nss_name,
> -			sizeof(ipl_info.data.nss.name));
> +			sizeof(ipl_info.data.nss.name) - 1);
>  		break;
>  	case IPL_TYPE_UNKNOWN:
>  		/* We have no info to copy */
--
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