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Date: Tue, 24 Nov 2015 16:34:04 -0800
From: Andy Lutomirski <luto@...capital.net>
To: Kees Cook <keescook@...omium.org>
Cc: linux-arch <linux-arch@...r.kernel.org>, Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>, Arnd Bergmann <arnd@...db.de>,
X86 ML <x86@...nel.org>, "H. Peter Anvin" <hpa@...or.com>, Michael Ellerman <mpe@...erman.id.au>
Subject: Re: [PATCH 1/2] x86: introduce post-init read-only memory
On Nov 24, 2015 1:38 PM, "Kees Cook" <keescook@...omium.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
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