From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755462Ab1ATLSl (ORCPT ); Thu, 20 Jan 2011 06:18:41 -0500 Received: from smtp6-g21.free.fr ([212.27.42.6]:52532 "EHLO smtp6-g21.free.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752916Ab1ATLSj (ORCPT ); Thu, 20 Jan 2011 06:18:39 -0500 Message-ID: <1295522306.4d381a02b1e10@imp.free.fr> Date: Thu, 20 Jan 2011 12:18:26 +0100 From: castet.matthieu@free.fr To: Konrad Rzeszutek Wilk Cc: matthieu castet , 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 References: <4CE2F82E.60601@free.fr> <20110111233135.GL4979@outflux.net> <20110114201530.GA14339@dumpdata.com> <20110119211432.GA20535@dumpdata.com> <20110119235957.6ea35dc8@mat-laptop> <20110119233824.GA2869@dumpdata.com> In-Reply-To: <20110119233824.GA2869@dumpdata.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit User-Agent: Internet Messaging Program (IMP) 3.2.8 X-Originating-IP: 93.1.148.21 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Quoting Konrad Rzeszutek Wilk : > On Wed, Jan 19, 2011 at 11:59:57PM +0100, matthieu castet wrote: > > Le Wed, 19 Jan 2011 16:14:32 -0500, > > Konrad Rzeszutek Wilk a écrit : > > > > > > > > > > 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 > > > > > > > _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 ? > > Like this? Yes > > yeeeey...That made it boot. > > > > > What's the output of kernel_page_tables debugfs ? > > Shees.. I get > > [ 73.723105] BUG: unable to handle kernel paging request at 15555000 [...] > with the patch and if I revert 5bd5a452662bc37c54fb6828db1a3faf87e6511c.. > > That looks to be another bug to hunt down. > No that the same bug : that the root cause. For some reason with xen, accessing some page tables (bss and after) make the system crash. Resolving this one, should resolve the nx case. Matthieu