From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751375Ab1AWO17 (ORCPT ); Sun, 23 Jan 2011 09:27:59 -0500 Received: from smtp6-g21.free.fr ([212.27.42.6]:37558 "EHLO smtp6-g21.free.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750996Ab1AWO16 (ORCPT ); Sun, 23 Jan 2011 09:27:58 -0500 Message-ID: <4D3C3ADB.1020609@free.fr> Date: Sun, 23 Jan 2011 15:27:39 +0100 From: matthieu castet User-Agent: Mozilla/5.0 (X11; U; Linux i686; fr; rv:1.8.1.23) Gecko/20090823 SeaMonkey/1.1.18 MIME-Version: 1.0 To: Konrad Rzeszutek Wilk CC: Ian Campbell , 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 , konrad@kernel.org Subject: Re: [tip:x86/security] x86: Add NX protection for kernel data References: <20110119233824.GA2869@dumpdata.com> <1295522306.4d381a02b1e10@imp.free.fr> <20110120150618.GC5092@dumpdata.com> <1295537856.14780.54.camel@zakaz.uk.xensource.com> <20110120190531.GA9687@dumpdata.com> <4D3899AB.60207@free.fr> <20110120210436.GA1810@dumpdata.com> <20110120211939.GA32262@dumpdata.com> <20110120215556.GA29700@dumpdata.com> <4D39FDA2.2000305@free.fr> <20110122051134.GA6905@dumpdata.com> In-Reply-To: <20110122051134.GA6905@dumpdata.com> Content-Type: multipart/mixed; boundary="------------080601050608010401090509" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This is a multi-part message in MIME format. --------------080601050608010401090509 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 8bit Konrad Rzeszutek Wilk a écrit : > On Fri, Jan 21, 2011 at 10:41:54PM +0100, matthieu castet wrote: >> Konrad Rzeszutek Wilk a écrit : >>>> - * .data and .bss should always be writable. >>>> + * .data and .bss should always be writable, but xen won't like >>>> + * if we make page table rw (that live in .data or .bss) >>>> */ >>>> +#ifdef CONFIG_X86_32 >>>> if (within(address, (unsigned long)_sdata, (unsigned long)_edata) || >>>> - within(address, (unsigned long)__bss_start, (unsigned long)__bss_stop)) >>>> - pgprot_val(required) |= _PAGE_RW; >>>> + within(address, (unsigned long)__bss_start, (unsigned long)__bss_stop)) { >>>> + unsigned int level; >>>> + if (lookup_address(address, &level) && (level != PG_LEVEL_4K)) >>>> + pgprot_val(forbidden) |= _PAGE_RW; >>>> + } >>>> +#endif >>>> #if defined(CONFIG_X86_64) && defined(CONFIG_DEBUG_RODATA) >>>> >>>> fyi, it does make it boot. >>> Hold it.. ccache is a wonderful tool but I think I've just "rebuilt" the >>> binaries with the .bss HPAGE_ALIGN aligment by mistake, so this path got never >>> taken. >>> >>> >> Ok, >> >> ATM I saw the following solution to solve the problem : >> 1) remove the data/bss check in static_protections, it was introduced by NX patches (64edc8ed). But I am not sure it >> is really needed anymore. >> 2) add ". = ALIGN(HPAGE_SIZE)" somewhere after init section. But if we want not to be allocated in image we >> should put it before bss. And if we want to be freed after init, we should put before .init.end. >> This mean moving .smp_locks (and .data_nosave when x86 will be added) before init section. I have no idea of the impact. >> 3) add some logic in arch/x86/xen/mmu.c, that will ignore RW page setting for the page table marked RO. >> 4) make static_protections take and old_prot argument, and only apply RW .data/.bss requirement if page is already RW. >> >> If possible I will go for 1). > > Sounds good. Just send me the patch and I will test it. Ok, what give you the attached patch. I don't know if I should give the printk or not. Matthieu --------------080601050608010401090509 Content-Type: text/x-diff; name="xen_nx.diff" Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="xen_nx.diff" diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c index 8b830ca..eec93c5 100644 --- a/arch/x86/mm/pageattr.c +++ b/arch/x86/mm/pageattr.c @@ -256,7 +256,6 @@ static inline pgprot_t static_protections(pgprot_t prot, unsigned long address, unsigned long pfn) { pgprot_t forbidden = __pgprot(0); - pgprot_t required = __pgprot(0); /* * The BIOS area between 640k and 1Mb needs to be executable for @@ -283,11 +282,13 @@ static inline pgprot_t static_protections(pgprot_t prot, unsigned long address, __pa((unsigned long)__end_rodata) >> PAGE_SHIFT)) pgprot_val(forbidden) |= _PAGE_RW; /* - * .data and .bss should always be writable. + * .data and .bss should always be writable, but xen won't like + * if we make page table rw (that live in .data or .bss) */ if (within(address, (unsigned long)_sdata, (unsigned long)_edata) || within(address, (unsigned long)__bss_start, (unsigned long)__bss_stop)) - pgprot_val(required) |= _PAGE_RW; + if ((pgprot_val(prot) & _PAGE_RW) == 0) + printk(KERN_INFO "RO page for 0x%lx in bss/data.\n", address); #if defined(CONFIG_X86_64) && defined(CONFIG_DEBUG_RODATA) /* @@ -327,7 +328,6 @@ static inline pgprot_t static_protections(pgprot_t prot, unsigned long address, #endif prot = __pgprot(pgprot_val(prot) & ~pgprot_val(forbidden)); - prot = __pgprot(pgprot_val(prot) | pgprot_val(required)); return prot; } --------------080601050608010401090509--