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

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Message-ID: <87jzpy1cqx.fsf@mail.lhotse>
Date: Fri, 01 Dec 2023 20:41:10 +1100
From: Michael Ellerman <mpe@...erman.id.au>
To: Justin Stitt <justinstitt@...gle.com>, Tyrel Datwyler
 <tyreld@...ux.ibm.com>, 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>
Cc: linux-scsi@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
 linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org, Justin
 Stitt <justinstitt@...gle.com>
Subject: Re: [PATCH] scsi: ibmvscsi: replace deprecated strncpy with strscpy

Justin Stitt <justinstitt@...gle.com> writes:
> 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>
> ---
> Note: build-tested only.

I gave it a quick boot, no issues.

Tested-by: Michael Ellerman <mpe@...erman.id.au> (powerpc)

cheers