linux-kernel - Re: [PATCH] soc: fsl: qe: Replace one-element array and use struct

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Date:   Fri, 22 May 2020 16:21:38 -0500
From:   Li Yang <leoyang.li@....com>
To:     Kees Cook <keescook@...omium.org>
Cc:     "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        Qiang Zhao <qiang.zhao@....com>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        lkml <linux-kernel@...r.kernel.org>,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Subject: Re: [PATCH] soc: fsl: qe: Replace one-element array and use
 struct_size() helper

On Wed, May 20, 2020 at 10:24 PM Kees Cook <keescook@...omium.org> wrote:
>
> On Wed, May 20, 2020 at 06:52:21PM -0500, Li Yang wrote:
> > On Mon, May 18, 2020 at 5:57 PM Kees Cook <keescook@...omium.org> wrote:
> > > Hm, looking at this code, I see a few other things that need to be
> > > fixed:
> > >
> > > 1) drivers/tty/serial/ucc_uart.c does not do a be32_to_cpu() conversion
> > >    on the length test (understandably, a little-endian system has never run
> > >    this code since it's ppc specific), but it's still wrong:
> > >
> > >         if (firmware->header.length != fw->size) {
> > >
> > >    compare to the firmware loader:
> > >
> > >         length = be32_to_cpu(hdr->length);
> > >
> > > 2) drivers/soc/fsl/qe/qe.c does not perform bounds checking on the
> > >    per-microcode offsets, so the uploader might send data outside the
> > >    firmware buffer. Perhaps:
> >
> > We do validate the CRC for each microcode, it is unlikely the CRC
> > check can pass if the offset or length is not correct.  But you are
> > probably right that it will be safer to check the boundary and fail
>
> Right, but a malicious firmware file could still match CRC but trick the
> kernel code.
>
> > quicker before we actually start the CRC check.  Will you come up with
> > a formal patch or you want us to deal with it?
>
> It sounds like Gustavo will be sending one, though I don't think either
> of us have the hardware to test it with, so if you could do that part,
> that would be great! :)

That will be great.  I think Zhao Qiang can help with the testing part.

Regards,
Leo