linux-hardening - Re: [PATCH] s390/ipl: refactor deprecated strncpy

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Date:   Thu, 17 Aug 2023 10:03:48 +0200
From:   Heiko Carstens <hca@...ux.ibm.com>
To:     Justin Stitt <justinstitt@...gle.com>
Cc:     Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        Kees Cook <keescook@...omium.org>,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH] s390/ipl: refactor deprecated strncpy

On Fri, Aug 11, 2023 at 09:56:15PM +0000, Justin Stitt wrote:
> `strncpy` is deprecated for use on NUL-terminated destination strings [1].
> 
> Use `strscpy_pad` which has the same behavior as `strncpy` here with the
> extra safeguard of guaranteeing NUL-termination of destination strings.
> In it's current form, this may result in silent truncation if the src
> string has the same size as the destination string.
> 
> Link: www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings[1]
> Link: https://github.com/KSPP/linux/issues/90
> Cc: linux-hardening@...r.kernel.org
> Signed-off-by: Justin Stitt <justinstitt@...gle.com>
> ---
>  arch/s390/kernel/ipl.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/s390/kernel/ipl.c b/arch/s390/kernel/ipl.c
> index 85a00d97a314..a6dcf6f28197 100644
> --- a/arch/s390/kernel/ipl.c
> +++ b/arch/s390/kernel/ipl.c
> @@ -266,7 +266,7 @@ static ssize_t sys_##_prefix##_##_name##_store(struct kobject *kobj,	\
>  		struct kobj_attribute *attr,				\
>  		const char *buf, size_t len)				\
>  {									\
> -	strncpy(_value, buf, sizeof(_value) - 1);			\
> +	strscpy_pad(_value, buf, sizeof(_value));			\
>  	strim(_value);							\
>  	return len;							\
>  }									\

Patch applied, but replaced strscpy_pad() with strscpy() like it was
suggested by Kees.

Thanks!