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

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Message-ID: <CAFhGd8pwtUSJBzepe=GBeyKuhD6ND6aWjeeT477Sdb4YTYDL_Q@mail.gmail.com>
Date:   Mon, 18 Sep 2023 00:03:56 -0700
From:   Justin Stitt <justinstitt@...gle.com>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     Kees Cook <keescook@...omium.org>,
        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 Fri, Sep 15, 2023 at 6:36 AM Jens Axboe <axboe@...nel.dk> wrote:
>
> 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.
>

Fair.

Perhaps "xyz: replace strncpy with strscpy"?

> --
> Jens Axboe
>