From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755053Ab1ASXAN (ORCPT ); Wed, 19 Jan 2011 18:00:13 -0500 Received: from smtp6-g21.free.fr ([212.27.42.6]:46510 "EHLO smtp6-g21.free.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750710Ab1ASXAL convert rfc822-to-8bit (ORCPT ); Wed, 19 Jan 2011 18:00:11 -0500 Date: Wed, 19 Jan 2011 23:59:57 +0100 From: matthieu castet To: Konrad Rzeszutek Wilk Cc: Kees Cook , Jeremy Fitzhardinge , keir.fraser@eu.citrix.com, mingo@redhat.com, hpa@zytor.com, sliakh.lkml@gmail.com, jmorris@namei.org, linux-kernel@vger.kernel.org, rusty@rustcorp.com.au, torvalds@linux-foundation.org, ak@muc.de, davej@redhat.com, jiang@cs.ncsu.edu, arjan@infradead.org, tglx@linutronix.de, sfr@canb.auug.org.au, mingo@elte.hu, Stefan Bader Subject: Re: [tip:x86/security] x86: Add NX protection for kernel data Message-ID: <20110119235957.6ea35dc8@mat-laptop> In-Reply-To: <20110119211432.GA20535@dumpdata.com> References: <4CE2F82E.60601@free.fr> <20110111233135.GL4979@outflux.net> <20110114201530.GA14339@dumpdata.com> <20110119211432.GA20535@dumpdata.com> X-Mailer: Claws Mail 3.7.6 (GTK+ 2.22.0; i486-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Le Wed, 19 Jan 2011 16:14:32 -0500, Konrad Rzeszutek Wilk a écrit : > On Fri, Jan 14, 2011 at 03:15:30PM -0500, Konrad Rzeszutek Wilk wrote: > > On Tue, Jan 11, 2011 at 03:31:35PM -0800, Kees Cook wrote: > > > On Thu, Nov 18, 2010 at 02:08:22PM +0000, tip-bot for Matthieu > > > Castet wrote: > > > > Commit-ID: 5bd5a452662bc37c54fb6828db1a3faf87e6511c > > > > Gitweb: > > > > http://git.kernel.org/tip/5bd5a452662bc37c54fb6828db1a3faf87e6511c > > > > Author: Matthieu Castet > > > > AuthorDate: Tue, 16 Nov 2010 22:31:26 +0100 Committer: Ingo > > > > Molnar CommitDate: Thu, 18 Nov 2010 12:52:04 > > > > +0100 > > > > > > > > x86: Add NX protection for kernel data > > > > > > [I'd sent this in reply to the wrong patch before, resending > > > now...] > > > > > > Hi, > > > > > > I was just shown this[1] on Xen from an Ubuntu bug report[2]. > > > > > > [ 1.230382] NX-protecting the kernel data: 3884k > > > [ 1.231002] BUG: unable to handle kernel paging request at > > > c1782ae0 ... > > > [ 1.231145] Call Trace: > > > [ 1.231152] [] ? __change_page_attr+0x2c1/0x370 > > > [ 1.231161] [] ? __purge_vmap_area_lazy+0xc1/0x180 > > > [ 1.231169] [] ? > > > __change_page_attr_set_clr+0x4c/0xb0 [ 1.231176] > > > [] ? change_page_attr_set_clr+0x128/0x300 > > > [ 1.231183] [] ? > > > __raw_callee_save_xen_restore_fl+0x6/0x8 [ 1.231192] > > > [] ? vprintk+0x171/0x3f0 [ 1.231198] [] ? > > > set_memory_nx+0x5f/0x70 > > > > If you run it with Xen debugging enabled: > > > > [ 7.753329] NX-protecting the kernel data: 2400k > > (XEN) mm.c:2389:d0 Bad type (saw 3c000003 != exp 70000000) for mfn this happen if (x & (PGT_type_mask|PGT_pae_xen_l2)) != type) but #define PGT_type_mask (7U<<29) /* Bits 29-31. */ #define _PGT_pae_xen_l2 26 #define PGT_pae_xen_l2 (1U<<_PGT_pae_xen_l2) but (exp type = 0x70000000) & (PGT_type_mask|PGT_pae_xen_l2) = 0x60000000 So the exp type look strange. #define _PGT_pinned 28 #define PGT_pinned (1U<<_PGT_pinned) > > 1355a5 (pfn 15a5) (XEN) mm.c:889:d0 Error getting mfn 1355a5 (pfn > > 15a5) from L1 entry 80000001355a5063 for l1e_owner=0, pg_owner=0 > > (XEN) mm.c:4958:d0 ptwr_emulate: could not get_page_from_l1e() > > [ 7.759087] BUG: unable to handle kernel paging request at > > c82a4d28 [ 7.759087] IP: [] > > xen_set_pte_atomic+0x21/0x2f [ 7.759087] *pdpt = > > 0000000001663001 *pde = 00000000082db067 *pte = 80000000082a4061 .. > > and same stack trace. > > > > > > > > > > > Does Xen have different size page table allocations or something > > > weird? > > > > The same page size. Not sure actually why it is being triggered. > > Let me copy Keir on this. Keir, the region that is being marked as > > _NX is .bss one and > > Um, it actually is from _etext -> __init_end + HPAGE_SIZE. > > instrumenting the code a bit shows that setting of RW+NX from _etext > throgh __init_end works just fine. It just when you start at the PFN > _past_ the __init_end it dies. Any ideas? > Does this happen if you add ". = ALIGN(HPAGE_SIZE);" before bss section in arch/x86/kernel/vmlinux.lds.S ? Does it happen if you call set_pages_rw instead of set_pages_nx in mark_nxdata_nx ? What's the output of kernel_page_tables debugfs ? Matthieu