linux-hardening - Re: [PATCH] [next] pcmcia: synclink_cs: replace 1-element array with flex-array member

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Message-ID: <CAHp75VcSnRPfmk9gAgz+hb7VYtL5buzDi_1e53u8b8+PrtxAvQ@mail.gmail.com>
Date:   Thu, 15 Dec 2022 10:57:57 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Paulo Miguel Almeida <paulo.miguel.almeida.rodenas@...il.com>
Cc:     Kees Cook <keescook@...omium.org>, Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
        Jiri Slaby <jirislaby@...nel.org>,
        Haowen Bai <baihaowen@...zu.com>, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH] [next] pcmcia: synclink_cs: replace 1-element array with
 flex-array member

On Thu, Dec 15, 2022 at 6:29 AM Paulo Miguel Almeida
<paulo.miguel.almeida.rodenas@...il.com> wrote:
> On Thu, Dec 15, 2022 at 12:06:46AM +0200, Andy Shevchenko wrote:
> > On Wed, Dec 14, 2022 at 11:49 PM Kees Cook <keescook@...omium.org> wrote:
> > > On Wed, Dec 14, 2022 at 10:39:52PM +0200, Andy Shevchenko wrote:

...

> > > > Yes, and Try to make it work with __packed. As I said, the problem is
> > > > that the code is relying on something which is architecture dependent
> > > > strictly speaking. And hence I disagree with Kees that v2 is okay to
> > > > go.
> > >
> > > I meant that v2 is functionally identical to the existing code.
> >
> > Ah, sorry for misunderstanding.
>
> I agree with using __packed attribute to remove the extra padding (and
> for the reasons you mentioned before). That would reduce the sizeof(RXBUF)
> from 8 to 5 (which is good) but that is still 1 byte "too much".

What I meant with the above is that the code has to work properly with
or without __packed. It's just to show you that this code has flaws if
it relies on the padding.

-- 
With Best Regards,
Andy Shevchenko