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

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Message-ID: <202005202022.588918E61@keescook>
Date:   Wed, 20 May 2020 20:24:15 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Li Yang <leoyang.li@....com>
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 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! :)

-- 
Kees Cook