Re: [kernel-hardening] [PATCH v4 0/8] introduce post-init read-only memory

From: Geert Uytterhoeven
Date: Sat Jan 23 2016 - 04:49:29 EST

Hi Kees,

On Fri, Jan 22, 2016 at 8:57 PM, Kees Cook <keescook@xxxxxxxxxxxx> wrote:
> On Fri, Jan 22, 2016 at 11:16 AM, Laura Abbott <laura@xxxxxxxxxxxx> wrote:
>> Kees had previously pushed a patch to do so but it exposed a couple of
>> underlying issues, mostly with low power paths
>> (c.f.,
>> Those will need to be all fixed up before this could be made default.

I'm working on fixing that...

BTW, making the sections read-only is done quite late in the kernel startup
process, which means it doesn't trigger for the writes to the text segment in
secondary CPU bringup, but only for suspend/resume.

> Yeah, I've got a patch waiting to reorganize CONFIG_ARM_KERNMEM_PERMS
> to look more like arm64 (and x86) and get the feature correctly under
> CONFIG_DEBUG_RODATA. I made it default=y on v7+. rmk asked me to wait
> until -rc1 before resubmitting it.

One other concern is indeed memory usage ("ALIGN(1<<SECTION_SHIFT)"?).
configs make the kernel too big to boot (overwritten DTB?) for 3 out of 4 arm
shmobile targets...



Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds