linux-kernel - Re: [PATCH v2] x86/mm: warn on W+x mappings

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Message-ID: <20151021132430.GD3575@pd.tnic>
Date:	Wed, 21 Oct 2015 15:24:31 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Matt Fleming <matt@...eblueprint.co.uk>,
	Stephen Smalley <sds@...ho.nsa.gov>,
	"x86@...nel.org" <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Kees Cook <keescook@...omium.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Andy Lutomirski <luto@...nel.org>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Brian Gerst <brgerst@...il.com>,
	"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>
Subject: Re: [PATCH v2] x86/mm: warn on W+x mappings

On Wed, Oct 21, 2015 at 02:57:47PM +0200, Ard Biesheuvel wrote:
> ... For the remaining cases, which is the vast majority, no such
> assumptions can be made, and since the UEFI runtime regions are
> typically populated with a bunch of PE/COFF images (each of which
> consists of text + data), inferring where the boundaries are between
> them does not seem tractable (for instance, to only map 'boundary'
> pages RWX)

How much of a problem would it be if we still do the on-demand page
faulting and map a trailing piece of code together with the data in a
page RWX?

Still better than mapping the *whole* thing RWX, no?

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
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