Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757688AbbLCAFM (ORCPT ); Wed, 2 Dec 2015 19:05:12 -0500 Received: from mx1.redhat.com ([209.132.183.28]:44217 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757359AbbLCAFK (ORCPT ); Wed, 2 Dec 2015 19:05:10 -0500 Subject: Re: [PATCH v2] ARM: mm: flip priority of CONFIG_DEBUG_RODATA To: Kees Cook References: <20151202202725.GA794@www.outflux.net> Cc: Laura Abbott , Russell King , Catalin Marinas , linux-arm-kernel@lists.infradead.org, LKML , Linux-MM , Ard Biesheuvel , Will Deacon , Nicolas Pitre , Arnd Bergmann , kernel-hardening@lists.openwall.com From: Laura Abbott Message-ID: <565F8732.5050402@redhat.com> Date: Wed, 2 Dec 2015 16:05:06 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0 MIME-Version: 1.0 In-Reply-To: <20151202202725.GA794@www.outflux.net> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2204 Lines: 55 On 12/02/2015 12:27 PM, Kees Cook wrote: > The use of CONFIG_DEBUG_RODATA is generally seen as an essential part of > kernel self-protection: > http://www.openwall.com/lists/kernel-hardening/2015/11/30/13 > Additionally, its name has grown to mean things beyond just rodata. To > get ARM closer to this, we ought to rearrange the names of the configs > that control how the kernel protects its memory. What was called > CONFIG_ARM_KERNMEM_PERMS is really doing the work that other architectures > call CONFIG_DEBUG_RODATA. > > This redefines CONFIG_DEBUG_RODATA to actually do the bulk of the > ROing (and NXing). In the place of the old CONFIG_DEBUG_RODATA, use > CONFIG_DEBUG_ALIGN_RODATA, since that's what the option does: adds > section alignment for making rodata explicitly NX, as arm does not split > the page tables like arm64 does without _ALIGN_RODATA. > > Also adds human readable names to the sections so I could more easily > debug my typos, and makes CONFIG_DEBUG_RODATA default "y" for CPU_V7. > > Results in /sys/kernel/debug/kernel_page_tables for each config state: > > # CONFIG_DEBUG_RODATA is not set > # CONFIG_DEBUG_ALIGN_RODATA is not set > > ---[ Kernel Mapping ]--- > 0x80000000-0x80900000 9M RW x SHD > 0x80900000-0xa0000000 503M RW NX SHD > > CONFIG_DEBUG_RODATA=y > CONFIG_DEBUG_ALIGN_RODATA=y > > ---[ Kernel Mapping ]--- > 0x80000000-0x80100000 1M RW NX SHD > 0x80100000-0x80700000 6M ro x SHD > 0x80700000-0x80a00000 3M ro NX SHD > 0x80a00000-0xa0000000 502M RW NX SHD > > CONFIG_DEBUG_RODATA=y > # CONFIG_DEBUG_ALIGN_RODATA is not set > > ---[ Kernel Mapping ]--- > 0x80000000-0x80100000 1M RW NX SHD > 0x80100000-0x80a00000 9M ro x SHD > 0x80a00000-0xa0000000 502M RW NX SHD > > Signed-off-by: Kees Cook > --- Reviewed-by: Laura Abbott -- 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/