Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756308AbbKEBOB (ORCPT ); Wed, 4 Nov 2015 20:14:01 -0500 Received: from mail-ig0-f182.google.com ([209.85.213.182]:36859 "EHLO mail-ig0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752600AbbKEBOA (ORCPT ); Wed, 4 Nov 2015 20:14:00 -0500 MIME-Version: 1.0 In-Reply-To: References: <1446685239-28522-1-git-send-email-labbott@fedoraproject.org> Date: Wed, 4 Nov 2015 17:13:59 -0800 X-Google-Sender-Auth: TiYybWNHL95gjTgekg0AoFKSysA Message-ID: Subject: Re: [PATCH] arm: Use kernel mm when updating section permissions From: Kees Cook To: Laura Abbott Cc: Russell King , Catalin Marinas , Will Deacon , "linux-arm-kernel@lists.infradead.org" , LKML , Linux-MM Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1432 Lines: 32 On Wed, Nov 4, 2015 at 5:06 PM, Kees Cook wrote: > On Wed, Nov 4, 2015 at 5:00 PM, Laura Abbott wrote: >> Currently, read only permissions are not being applied even >> when CONFIG_DEBUG_RODATA is set. This is because section_update >> uses current->mm for adjusting the page tables. current->mm >> need not be equivalent to the kernel version. Use pgd_offset_k >> to get the proper page directory for updating. >> >> Signed-off-by: Laura Abbott >> --- >> I found this while trying to convince myself of something. >> Dumping the page table via debugfs and writing to kernel text were both >> showing the lack of mappings. This was observed on QEMU. Maybe it's just a >> QEMUism but if not it probably should go to stable. > > Well that's weird! debugfs showed the actual permissions that lacked > RO? I wonder what changed. I tested this both with debugfs and lkdtm's > KERN_WRITE test when the patches originally landed. The comment will need adjusting too. I have a memory of needing to use current->mm to deal with some crazy errata and handling TLB flushes... -Kees -- Kees Cook Chrome OS Security -- 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/