Re: [PATCH 0/2] Support for set_memory_* outside of module space

[Laura Abbott]

On 11/03/2015 03:42 PM, Kees Cook wrote:
> On Tue, Nov 3, 2015 at 1:48 PM, Laura Abbott <labbott@xxxxxxxxxxxxxxxxx> wrote:
> > Hi,
> >
> > Based on a recent discussion[1] there is interest in having set_memory_* work
> > on kernel memory for security and other use cases. This patch adds the
> > ability for that to happen behind a kernel option. If this is welcome enough,
> > the Kconfig can be dropped. This has been briefly tested but not stress tested.
> >
> > Thanks,
> > Laura
> >
> > [1] http://lists.infradead.org/pipermail/linux-arm-kernel/2015-October/382079.html
> >
> > Laura Abbott (2):
> >    arm64: Get existing page protections in split_pmd
> >    arm64: Allow changing of attributes outside of modules
> >
> >   arch/arm64/Kconfig.debug | 11 +++++++
> >   arch/arm64/mm/mm.h       |  3 ++
> >   arch/arm64/mm/mmu.c      | 11 ++++---
> >   arch/arm64/mm/pageattr.c | 74 ++++++++++++++++++++++++++++++++++++++++++++----
> >   4 files changed, 88 insertions(+), 11 deletions(-)
>
> This seems like the right thing to have. What's arm64 doing for the
> equivalent of x86 and arm's set_kernel_text_* functions? x86 and arm
> call their set_memory_* functions, for example. A quick examination
> shows mm/mmu.c is just doing it "by hand" in fixup_executable and
> mark_rodata_ro? Could those functions use the new set_memory_* ones?

It looks like mark_rodata_ro could probably use the set_memory_ro. I'll
have to test it out. Longer term, the page table setup code should
probably just be pulled out into a common file.

Do you know the code path in ftrace which would trigger the set_kernel_text_*
If not, I'll go  see if I can figure out if it's implemented yet on arm64.

> -Kees

Thanks,
Laura
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