linux-kernel - Re: [PATCH 26/26] x86, pkeys: Documentation

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Message-ID: <CA+55aFwUAY01QC8A3mCOoq5aYjT7Lw-gVx6DvqYBr0UMZ9kZEQ@mail.gmail.com>
Date:	Thu, 1 Oct 2015 18:48:47 -0400
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Dave Hansen <dave@...1.net>
Cc:	Kees Cook <keescook@...gle.com>, Ingo Molnar <mingo@...nel.org>,
	"x86@...nel.org" <x86@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux-MM <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Andy Lutomirski <luto@...nel.org>,
	Borislav Petkov <bp@...en8.de>
Subject: Re: [PATCH 26/26] x86, pkeys: Documentation

On Thu, Oct 1, 2015 at 6:33 PM, Dave Hansen <dave@...1.net> wrote:
>
> Here it is in a quite fugly form (well, it's not opt-in).  Init crashes
> if I boot with this, though.
>
> I'll see if I can turn it in to a bit more of an opt-in and see what's
> actually going wrong.

It's quite likely that you will find that compilers put read-only
constants in the text section, knowing that executable means readable.

So it's entirely possible that it's pretty much all over.

That said, I don't understand your patch. Why check PROT_WRITE? We've
had :"execute but not write" forever. It's "execute and not *read*"
that is interesting.

So I wonder if your testing is just bogus. But maybe I'm mis-reading this?

                Linus
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