Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757227AbZKJQ4J (ORCPT ); Tue, 10 Nov 2009 11:56:09 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757154AbZKJQ4I (ORCPT ); Tue, 10 Nov 2009 11:56:08 -0500 Received: from smtp.outflux.net ([198.145.64.163]:34047 "EHLO smtp.outflux.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756859AbZKJQ4H (ORCPT ); Tue, 10 Nov 2009 11:56:07 -0500 Date: Tue, 10 Nov 2009 08:55:07 -0800 From: Kees Cook To: Arjan van de Ven Cc: Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , x86@kernel.org, Pekka Enberg , Jan Beulich , Vegard Nossum , Yinghai Lu , Jeremy Fitzhardinge , linux-kernel@vger.kernel.org Subject: [PATCH v5] [x86] detect and report lack of NX protections Message-ID: <20091110165507.GG5129@outflux.net> References: <4ADD1E03.4070200@zytor.com> <20091020045513.GU5394@outflux.net> <20091109221015.GB5129@outflux.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20091109221015.GB5129@outflux.net> Organization: Canonical X-HELO: www.outflux.net Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2416 Lines: 69 It is possible for x86_64 systems to lack the NX bit (see check_efer()) either due to the hardware lacking support or the BIOS having turned off the CPU capability, so NX status should be reported. Additionally, anyone booting NX-capable CPUs in 32bit mode without PAE will lack NX functionality, so this change provides feedback for that case as well. v2: use "Alert:" instead of "Warning:" to avoid confusion with WARN_ON() v3: use "Notice:" instead of "Alert:" to avoid confusion with KERN_ALERT, and switch to KERN_NOTICE, in keeping with its use for "normal but significant condition" messages. v4: check that _NX_PAGE is non-zero to avoid setting nx_enabled accidentally. v5: check for disable_nx. Signed-off-by: Kees Cook --- arch/x86/mm/init.c | 10 ++++++++++ arch/x86/mm/setup_nx.c | 6 +++++- 2 files changed, 15 insertions(+), 1 deletions(-) diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c index 73ffd55..d98b43a 100644 --- a/arch/x86/mm/init.c +++ b/arch/x86/mm/init.c @@ -149,6 +149,16 @@ unsigned long __init_refok init_memory_mapping(unsigned long start, set_nx(); if (nx_enabled) printk(KERN_INFO "NX (Execute Disable) protection: active\n"); + else if (cpu_has_pae) +#if defined(CONFIG_X86_64) || defined(CONFIG_X86_PAE) + /* PAE kernel, PAE CPU, without NX */ + printk(KERN_NOTICE "Notice: NX (Execute Disable) protection " + "missing in CPU or disabled in BIOS!\n"); +#else + /* 32bit non-PAE kernel, PAE CPU */ + printk(KERN_NOTICE "Notice: NX (Execute Disable) protection " + "cannot be enabled: non-PAE kernel!\n"); +#endif /* Enable PSE if available */ if (cpu_has_pse) diff --git a/arch/x86/mm/setup_nx.c b/arch/x86/mm/setup_nx.c index 513d8ed..93d7b43 100644 --- a/arch/x86/mm/setup_nx.c +++ b/arch/x86/mm/setup_nx.c @@ -51,8 +51,12 @@ void __init set_nx(void) } } #else -void set_nx(void) +void __init set_nx(void) { + /* notice if _PAGE_NX exists and was removed during check_efer() */ + if (!disable_nx && _PAGE_NX && + ((__supported_pte_mask & _PAGE_NX) == _PAGE_NX)) + nx_enabled = 1; } #endif -- 1.6.5 -- Kees Cook Ubuntu Security Team -- 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/