From: Kees Cook <kees@kernel.org>
To: Brahmajit Das <listout@listout.xyz>
Cc: linux-hardening@vger.kernel.org, justinstitt@google.com,
richard@nod.at, anton.ivanov@cambridgegreys.com,
johannes@sipsolutions.net, linux-um@lists.infradead.org
Subject: Re: [RFC PATCH] um: replace deprecated strncpy with strscpy
Date: Mon, 9 Jun 2025 21:15:49 -0700 [thread overview]
Message-ID: <202506092114.01147457A5@keescook> (raw)
In-Reply-To: <20250607213006.7858-1-listout@listout.xyz>
On Sun, Jun 08, 2025 at 03:00:06AM +0530, Brahmajit Das 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.
>
> This modification is mainly due to the concerns on
> https://github.com/KSPP/linux/issues/336, where it was mentioned that
> strncpy_from_user is confusingly named as it does not NUL-pad the
> destination, but it does NOT guarantee NUL-termination.
> With this approach/patch we can always ensure that the dst buffer is NUL
> terminated.
I think we need wholesale fix the kernel's usage of
strncpy_from_user()... first, how is it being used? Are things being
manually terminated? Are something destinations not actually C Strings?
We may want two APIs (like strtomem vs strscpy). And then since we're
dealing with user data, I would think padding should be included?
--
Kees Cook
next prev parent reply other threads:[~2025-06-10 4:15 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-06-07 21:30 [RFC PATCH] um: replace deprecated strncpy with strscpy Brahmajit Das
2025-06-10 4:15 ` Kees Cook [this message]
2025-06-12 16:09 ` Brahmajit Das
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