Re: [PATCH 1/2] x86: introduce post-init read-only memory

Andy Lutomirski
2015-11-25T00:34:37Z

On Nov 24, 2015 1:38 PM, "Kees Cook" <keescook@chromium.org> wrote:
>
> One of the easiest ways to protect the kernel from attack is to reduce
> the internal attack surface exposed when a "write" flaw is available. By
> making as much of the kernel read-only as possible, we reduce the
> attack surface.
>
> Many things are written to only during __init, and never changed
> again. These cannot be made "const" since the compiler will do the wrong
> thing (we do actually need to write to them). Instead, move these items
> into a memory region that will be made read-only during mark_rodata_ro()
> which happens after all kernel __init code has finished.
>
> This introduces __read_only as a way to mark such memory, and adds some
> documentation about the existing __read_mostly marking.

Obligatory bikeshed: __ro_after_init, please. It's barely longer,
and it directly explains what's going on. __read_only makes me think
that it's really read-only and could, for example, actually be in ROM.

--Andy