linux-hardening - Re: [PATCH] scsi: ibmvscsi: replace deprecated strncpy with strscpy

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Date: Thu, 30 Nov 2023 13:13:32 -0800
From: Kees Cook <keescook@...omium.org>
To: Justin Stitt <justinstitt@...gle.com>
Cc: Tyrel Datwyler <tyreld@...ux.ibm.com>,
	Michael Ellerman <mpe@...erman.id.au>,
	Nicholas Piggin <npiggin@...il.com>,
	Christophe Leroy <christophe.leroy@...roup.eu>,
	"James E.J. Bottomley" <jejb@...ux.ibm.com>,
	"Martin K. Petersen" <martin.petersen@...cle.com>,
	linux-scsi@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH] scsi: ibmvscsi: replace deprecated strncpy with strscpy

On Mon, Oct 30, 2023 at 08:40:48PM +0000, Justin Stitt wrote:
> strncpy() is deprecated for use on NUL-terminated destination strings
> [1] and as such we should prefer more robust and less ambiguous string
> interfaces.
> 
> We expect partition_name to be NUL-terminated based on its usage with
> format strings:
> |       dev_info(hostdata->dev, "host srp version: %s, "
> |                "host partition %s (%d), OS %d, max io %u\n",
> |                hostdata->madapter_info.srp_version,
> |                hostdata->madapter_info.partition_name,
> |                be32_to_cpu(hostdata->madapter_info.partition_number),
> |                be32_to_cpu(hostdata->madapter_info.os_type),
> |                be32_to_cpu(hostdata->madapter_info.port_max_txu[0]));
> ...
> |       len = snprintf(buf, PAGE_SIZE, "%s\n",
> |                hostdata->madapter_info.partition_name);
> 
> Moreover, NUL-padding is not required as madapter_info is explicitly
> memset to 0:
> |       memset(&hostdata->madapter_info, 0x00,
> |                       sizeof(hostdata->madapter_info));
> 
> Considering the above, a suitable replacement is `strscpy` [2] due to
> the fact that it guarantees NUL-termination on the destination buffer
> without unnecessarily NUL-padding.
> 
> Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
> Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2]
> Link: https://github.com/KSPP/linux/issues/90
> Cc: linux-hardening@...r.kernel.org
> Signed-off-by: Justin Stitt <justinstitt@...gle.com>

Agreed; this conversion looks correct to me too.

Reviewed-by: Kees Cook <keescook@...omium.org>

-- 
Kees Cook