Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.33 as permitted sender) client-ip=23.128.96.33;
Message-ID: <a528b8ca-dde1-1cd2-19c8-be760e5de14e@linux.ibm.com>
Date:   Wed, 25 Oct 2023 09:32:46 +0200
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101
 Thunderbird/102.14.0
Subject: Re: [PATCH] s390/cio: replace deprecated strncpy with strscpy
Content-Language: en-US
To:     Justin Stitt <justinstitt@google.com>,
        Peter Oberparleiter <oberpar@linux.ibm.com>,
        Heiko Carstens <hca@linux.ibm.com>,
        Vasily Gorbik <gor@linux.ibm.com>,
        Alexander Gordeev <agordeev@linux.ibm.com>,
        Christian Borntraeger <borntraeger@linux.ibm.com>,
        Sven Schnelle <svens@linux.ibm.com>
Cc:     linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-hardening@vger.kernel.org
References: <20231023-strncpy-drivers-s390-cio-chsc-c-v1-1-8b76a7b83260@google.com>
From:   Vineeth Vijayan <vneethv@linux.ibm.com>
In-Reply-To: <20231023-strncpy-drivers-s390-cio-chsc-c-v1-1-8b76a7b83260@google.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
MIME-Version: 1.0
Precedence: bulk


On 10/23/23 21:24, 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 both `params` and `id` to be NUL-terminated based on their
> usage with format strings:
> 
> 	format_node_data(iuparams, iunodeid, &lir->incident_node);
> 	format_node_data(auparams, aunodeid, &lir->attached_node);
> 
> 	switch (lir->iq.class) {
> 	case LIR_IQ_CLASS_DEGRADED:
> 		pr_warn("Link degraded: RS=%02x RSID=%04x IC=%02x "
> 			"IUPARAMS=%s IUNODEID=%s AUPARAMS=%s AUNODEID=%s\n",
> 			sei_area->rs, sei_area->rsid, lir->ic, iuparams,
> 			iunodeid, auparams, aunodeid);
> 
> NUL-padding is not required as both `params` and `id` have been memset
> to 0:
> 
> 	memset(params, 0, PARAMS_LEN);
> 	memset(id, 0, NODEID_LEN);
> 
> 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.
> 
> Note that there's no overread bugs in the current implementation as the
> string literal "n/a" has a size much smaller than PARAMS_LEN or
> NODEID_LEN. Nonetheless, let's favor strscpy().
> 
> 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>

LGTM. Thank you.

Reviewed-by: Vineeth Vijayan <vneethv@linux.ibm.com>

I can push this to s390-tree and Heiko/Vasily will upstream it.

---snip---