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

Kees Cook
2020-05-21T03:24:21Z

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! :)

--
Kees Cook