Re: [RFCv2] arm64: support HAVE_ARCH_RARE_WRITE and HAVE_ARCH_RARE_WRITE_MEMCPY

[Kees Cook]

On Thu, Mar 30, 2017 at 12:45 PM, Russell King - ARM Linux
<linux@xxxxxxxxxxxxxxx> wrote:
> On Thu, Mar 30, 2017 at 12:38:15PM -0700, Kees Cook wrote:
>> Great work! I think this will need some further changes, though, since
>> it doesn't look to me like this would pass LKDTM's tests if it was
>> built as a module. (This is missing from my ARM attempt too... I
>> haven't figured out how to set the domain on the kernel modules...)
>
> You're not going to be able to do it very easily.  The only way I can
> think of achieving it would be to split the module area into one
> chunk for text, one chunk for write-rare and one chunk for data.

Well, my intention was to just make the entire module area
DOMAIN_WR_RARE. It's overly permissive in the sense that non-data
changes could be made, but this is already an improvement over either
not having this feature at all or x86's version which makes all of RAM
writable.

-Kees

-- 
Kees Cook
Pixel Security