Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752922AbbLKBdZ (ORCPT ); Thu, 10 Dec 2015 20:33:25 -0500 Received: from mail-oi0-f43.google.com ([209.85.218.43]:34037 "EHLO mail-oi0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751946AbbLKBdV (ORCPT ); Thu, 10 Dec 2015 20:33:21 -0500 MIME-Version: 1.0 In-Reply-To: References: <1449697404-21076-1-git-send-email-keescook@chromium.org> <1449697404-21076-9-git-send-email-keescook@chromium.org> From: Andy Lutomirski Date: Thu, 10 Dec 2015 17:33:01 -0800 Message-ID: Subject: Re: [PATCH v3 8/8] x86, vdso: mark vDSO read-only after init To: Kees Cook Cc: "linux-kernel@vger.kernel.org" , Ingo Molnar , "H. Peter Anvin" , Michael Ellerman , Mathias Krause , Thomas Gleixner , X86 ML , Arnd Bergmann , PaX Team , Emese Revfy , "kernel-hardening@lists.openwall.com" , linux-arch Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3192 Lines: 60 On Wed, Dec 9, 2015 at 3:13 PM, Andy Lutomirski wrote: > On Wed, Dec 9, 2015 at 1:43 PM, Kees Cook 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: >> >> Before: >> [ 0.143067] vDSO @ ffffffff82004000 >> [ 0.143551] vDSO @ ffffffff82006000 >> ---[ High Kernel Mapping ]--- >> 0xffffffff80000000-0xffffffff81000000 16M pmd >> 0xffffffff81000000-0xffffffff81800000 8M ro PSE GLB x pmd >> 0xffffffff81800000-0xffffffff819f3000 1996K ro GLB x pte >> 0xffffffff819f3000-0xffffffff81a00000 52K ro NX pte >> 0xffffffff81a00000-0xffffffff81e00000 4M ro PSE GLB NX pmd >> 0xffffffff81e00000-0xffffffff81e05000 20K ro GLB NX pte >> 0xffffffff81e05000-0xffffffff82000000 2028K ro NX pte >> 0xffffffff82000000-0xffffffff8214f000 1340K RW GLB NX pte >> 0xffffffff8214f000-0xffffffff82281000 1224K RW NX pte >> 0xffffffff82281000-0xffffffff82400000 1532K RW GLB NX pte >> 0xffffffff82400000-0xffffffff83200000 14M RW PSE GLB NX pmd >> 0xffffffff83200000-0xffffffffc0000000 974M pmd >> >> After: >> [ 0.145062] vDSO @ ffffffff81da1000 >> [ 0.146057] vDSO @ ffffffff81da4000 >> ---[ High Kernel Mapping ]--- >> 0xffffffff80000000-0xffffffff81000000 16M pmd >> 0xffffffff81000000-0xffffffff81800000 8M ro PSE GLB x pmd >> 0xffffffff81800000-0xffffffff819f3000 1996K ro GLB x pte >> 0xffffffff819f3000-0xffffffff81a00000 52K ro NX pte >> 0xffffffff81a00000-0xffffffff81e00000 4M ro PSE GLB NX pmd >> 0xffffffff81e00000-0xffffffff81e0b000 44K ro GLB NX pte >> 0xffffffff81e0b000-0xffffffff82000000 2004K ro NX pte >> 0xffffffff82000000-0xffffffff8214c000 1328K RW GLB NX pte >> 0xffffffff8214c000-0xffffffff8227e000 1224K RW NX pte >> 0xffffffff8227e000-0xffffffff82400000 1544K RW GLB NX pte >> 0xffffffff82400000-0xffffffff83200000 14M RW PSE GLB NX pmd >> 0xffffffff83200000-0xffffffffc0000000 974M pmd >> >> Based on work by PaX Team and Brad Spengler. >> >> Signed-off-by: Kees Cook > > Acked-by: Andy Lutomirski > FWIW, this has a minor conflict with some stuff in my queue. I wouldn't worry about it for now. --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/