linux-hardening - Re: [PATCH] aoe: refactor deprecated strncpy

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Message-ID: <6338fbac-0177-43eb-be4f-7c586956953f@kernel.dk>
Date:   Fri, 15 Sep 2023 07:36:40 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Kees Cook <keescook@...omium.org>,
        Justin Stitt <justinstitt@...gle.com>
Cc:     Justin Sanders <justin@...aid.com>, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org,
        Xu Panda <xu.panda@....com.cn>, Yang Yang <yang.yang29@....com>
Subject: Re: [PATCH] aoe: refactor deprecated strncpy

On 9/14/23 9:21 PM, Kees Cook wrote:
> On Mon, Sep 11, 2023 at 09:09:07PM +0000, Justin Stitt wrote:
>> `strncpy` is deprecated for use on NUL-terminated destination strings [1].
>>
>> `aoe_iflist` is expected to be NUL-terminated which is evident by its
>> use with string apis later on like `strspn`:
>> | 	p = aoe_iflist + strspn(aoe_iflist, WHITESPACE);
>>
>> It also seems `aoe_iflist` does not need to be NUL-padded which means
>> `strscpy` [2] is a suitable replacement due to the fact that it
>> guarantees NUL-termination on the destination buffer while not
>> 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
>> Cc: Kees Cook <keescook@...omium.org>
>> Cc: Xu Panda <xu.panda@....com.cn>
>> Cc: Yang Yang <yang.yang29@....com>
>> Signed-off-by: Justin Stitt <justinstitt@...gle.com>
> 
> Agreed, truncation is the current behavior, and padding isn't needed.
> (Or more precisely, it's already zeroed and this function is called
> once.)
> 
> Reviewed-by: Kees Cook <keescook@...omium.org>

Change looks fine to me too, but for the love of $deity, please use
a proper subject line for these kinds of patches. It's not refactoring
anything.

-- 
Jens Axboe