linux-kernel - Re: [PATCH v4 8/8] x86, vdso: mark vDSO read-only after init

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Message-ID: <CALCETrVBbJROcYPmhAnOsjM6WCrY4+fhxCC75G1xz1bYawBNpw@mail.gmail.com>
Date:	Tue, 19 Jan 2016 11:09:06 -0800
From:	Andy Lutomirski <luto@...capital.net>
To:	Kees Cook <keescook@...omium.org>
Cc:	Ingo Molnar <mingo@...hat.com>, "H. Peter Anvin" <hpa@...or.com>,
	Michael Ellerman <mpe@...erman.id.au>,
	Mathias Krause <minipli@...glemail.com>,
	Thomas Gleixner <tglx@...utronix.de>, X86 ML <x86@...nel.org>,
	Arnd Bergmann <arnd@...db.de>, PaX Team <pageexec@...email.hu>,
	Emese Revfy <re.emese@...il.com>,
	"kernel-hardening@...ts.openwall.com" 
	<kernel-hardening@...ts.openwall.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-arch <linux-arch@...r.kernel.org>
Subject: Re: [PATCH v4 8/8] x86, vdso: mark vDSO read-only after init

On Tue, Jan 19, 2016 at 10:08 AM, Kees Cook <keescook@...omium.org> wrote:
> The vDSO does not need to be writable after __init, so mark it as
> __ro_after_init. The result kills the exploit method of writing to the
> vDSO from kernel space resulting in userspace executing the modified code,
> as shown here to bypass SMEP restrictions: http://itszn.com/blog/?p=21
>
> The memory map (with added vDSO address reporting) shows the vDSO moving
> into read-only memory:

Acked-by: Andy Lutomirski <luto@...nel.org>