Received-SPF: pass (google.com: domain of linux-kernel+bounces-123613-linux.lists.archive=gmail.com@vger.kernel.org designates 147.75.80.249 as permitted sender) client-ip=147.75.80.249;
Precedence: bulk
MIME-Version: 1.0
References: <20240327-strncpy-fs-proc-vmcore-c-v1-1-e025ed08b1b0@google.com> <ZgTMZ1HYheBMDbei@MiWiFi-R3L-srv>
In-Reply-To: <ZgTMZ1HYheBMDbei@MiWiFi-R3L-srv>
From: Justin Stitt <justinstitt@google.com>
Date: Thu, 28 Mar 2024 13:42:15 -0700
Message-ID: <CAFhGd8pU-utbgHhU5s_20pC_aNK7xtsJDbf+Ayg4Dck2K=4kag@mail.gmail.com>
Subject: Re: [PATCH] vmcore: replace strncpy with strtomem
To: Baoquan He <bhe@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>, Dave Young <dyoung@redhat.com>, kexec@lists.infradead.org, 
	linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, 
	linux-hardening@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

Hi,

On Wed, Mar 27, 2024 at 6:48=E2=80=AFPM Baoquan He <bhe@redhat.com> wrote:
> > Mark these buffers as __nonstring and use strtomem_pad.
>
> Thanks.
>
> I didn't build, wondering if '__nonstring' has to be set so that
> strtomem_pad() can be used.

I do not believe marking buffers as __nonstring is strictly a
requirement. However, the documentation from string.h +302 says we
should do it:
/**
 * strtomem_pad - Copy NUL-terminated string to non-NUL-terminated buffer
 *
 * @dest: Pointer of destination character array (marked as __nonstring)
..

and so does [1] ... "mark the destination buffer variable (or
structure member) with the __nonstring attribute..."

FWIW, this builds just fine without the __nonstring attribute but we
should use it :)

>
> Thanks
> Baoquan
>

[1] https://github.com/KSPP/linux/issues/90

Thanks
Justin