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From:   Justin Stitt <justinstitt@google.com>
Date:   Fri, 20 Oct 2023 10:40:12 -0700
Message-ID: <CAFhGd8o8FaD-3rkBAhEXhc8XqpUk_cLqNwyfpndVuSxDOei_gA@mail.gmail.com>
Subject: Re: the nul-terminated string helper desk chair rearrangement
To:     Christoph Hellwig <hch@lst.de>
Cc:     Kees Cook <keescook@chromium.org>, Keith Busch <kbusch@kernel.org>,
        Jens Axboe <axboe@kernel.dk>, Sagi Grimberg <sagi@grimberg.me>,
        linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-hardening@vger.kernel.org, ksummit@lists.linux.dev
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On Thu, Oct 19, 2023 at 9:46=E2=80=AFPM Christoph Hellwig <hch@lst.de> wrot=
e:
>
> On Wed, Oct 18, 2023 at 11:01:54PM -0700, Kees Cook wrote:
> > Almost all of the remaining strncpy() usage is just string to string
> > copying, but the corner cases that are being spun out that aren't
> > strscpy() or strscpy_pad() are covered by strtomem(), kmemdup_nul(),
> > and memcpy(). Each of these are a clear improvement since they remove
> > the ambiguity of the intended behavior. Using seq_buf ends up being way
> > more overhead than is needed.
>
> I'm really not sure strscpy is much of an improvement.  In this particula=
r
> case in most other places we simply use a snprintf for nqns, which seems
> useful here to if we don't want the full buf.
>
> But switching to a completely undocumented helper like strscpy seems not
> useful at all.

There's some docs at [1]. Perhaps there could be more?

[1]: https://elixir.bootlin.com/linux/v6.6-rc6/source/include/linux/fortify=
-string.h#L292