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Date:   Fri, 20 Oct 2023 06:46:45 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Kees Cook <keescook@chromium.org>
Cc:     Christoph Hellwig <hch@lst.de>,
        Justin Stitt <justinstitt@google.com>,
        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
Subject: Re: the nul-terminated string helper desk chair rearrangement
Message-ID: <20231020044645.GC11984@lst.de>
References: <20231018-strncpy-drivers-nvme-host-fabrics-c-v1-1-b6677df40a35@google.com> <20231019054642.GF14346@lst.de> <202310182248.9E197FFD5@keescook>
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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 particular
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.