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Date:   Thu, 30 Nov 2023 13:13:32 -0800
From:   Kees Cook <keescook@chromium.org>
To:     Justin Stitt <justinstitt@google.com>
Cc:     Tyrel Datwyler <tyreld@linux.ibm.com>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Nicholas Piggin <npiggin@gmail.com>,
        Christophe Leroy <christophe.leroy@csgroup.eu>,
        "James E.J. Bottomley" <jejb@linux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@oracle.com>,
        linux-scsi@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
        linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org
Subject: Re: [PATCH] scsi: ibmvscsi: replace deprecated strncpy with strscpy
Message-ID: <202311301313.6248EF5E@keescook>
References: <20231030-strncpy-drivers-scsi-ibmvscsi-ibmvscsi-c-v1-1-f8b06ae9e3d5@google.com>
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In-Reply-To: <20231030-strncpy-drivers-scsi-ibmvscsi-ibmvscsi-c-v1-1-f8b06ae9e3d5@google.com>
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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@vger.kernel.org
> Signed-off-by: Justin Stitt <justinstitt@google.com>

Agreed; this conversion looks correct to me too.

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

-- 
Kees Cook