linux-kernel - Re: [PATCH] ALSA: xen-front: refactor deprecated strncpy

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Message-ID: <ZMNILDgqHEGf8fNF@mattapan.m5p.com>
Date:   Thu, 27 Jul 2023 21:46:36 -0700
From:   Elliott Mitchell <ehem+xen@....com>
To:     Justin Stitt <justinstitt@...gle.com>
Cc:     Oleksandr Andrushchenko <oleksandr_andrushchenko@...m.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>, xen-devel@...ts.xenproject.org,
        alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
        Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH] ALSA: xen-front: refactor deprecated strncpy

On Thu, Jul 27, 2023 at 09:53:24PM +0000, Justin Stitt wrote:
> Technically, my patch yields subtly different behavior. The original
> implementation with `strncpy` would fill the entire destination buffer
> with null bytes [3] while `strscpy` will leave the junk, uninitialized
> bytes trailing after the _mandatory_ NUL-termination. So, if somehow
> `pcm->name` or `card->driver/shortname/longname` require this
> NUL-padding behavior then `strscpy_pad` should be used. My
> interpretation, though, is that the aforementioned fields are just fine
> as NUL-terminated strings. Please correct my assumptions if needed and
> I'll send in a v2.

"uninitialized bytes" => "leak of sensitive information" => "security hole"

One hopes the unitialized bytes don't contain sensitive information, but
that is the start of the chain.  One can hope the VM on the other end is
friendly, but that isn't something to rely on.

I'm not in charge of any of the appropriate subsystems, I just happened
to randomly look at this as message on a mailing list I'm on.  Could be
the maintainers will find this acceptable.


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