Re: [PATCH] soc: fsl: qe: Replace one-element array and use struct_size() helper

Li Yang
2020-05-26T19:57:07Z

On Sun, May 24, 2020 at 9:49 PM Qiang Zhao <qiang.zhao@nxp.com> wrote:
>
> On Wed, May 23, 2020 at 5:22 PM Li Yang <leoyang.li@nxp.com>
> > -----Original Message-----
> > From: Li Yang <leoyang.li@nxp.com>
> > Sent: 2020年5月23日 5:22
> > To: Kees Cook <keescook@chromium.org>
> > Cc: Gustavo A. R. Silva <gustavoars@kernel.org>; Qiang Zhao
> > <qiang.zhao@nxp.com>; linuxppc-dev <linuxppc-dev@lists.ozlabs.org>;
> > moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE
> > <linux-arm-kernel@lists.infradead.org>; lkml <linux-kernel@vger.kernel.org>;
> > Gustavo A. R. Silva <gustavo@embeddedor.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@chromium.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@chromium.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.
> >
>
> Now the firmware are loaded in uboot, and kernel will do nothing for it.
> So testing on it maybe need some extra codes both in driver and dts.
> In the meanwhile, I am so busy on some high priority work that maybe test work
> could not be done in time.
> Once I am free, I will do it.

Thanks. You are right that most of the QE drivers doesn't support
requesting firmware in kernel except the ucc_uart. So it probably can
be tested with that driver without requiring code change.

>
> Best Regards
> Qiang Zhao