Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757885AbbKFXtS (ORCPT ); Fri, 6 Nov 2015 18:49:18 -0500 Received: from mail-io0-f182.google.com ([209.85.223.182]:35724 "EHLO mail-io0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757753AbbKFXtR (ORCPT ); Fri, 6 Nov 2015 18:49:17 -0500 MIME-Version: 1.0 In-Reply-To: <563D3AC5.4020203@redhat.com> References: <1446685239-28522-1-git-send-email-labbott@fedoraproject.org> <20151105094615.GP8644@n2100.arm.linux.org.uk> <563B81DA.2080409@redhat.com> <20151105162719.GQ8644@n2100.arm.linux.org.uk> <563BFCC4.8050705@redhat.com> <563CF510.9080506@redhat.com> <20151106204641.GT8644@n2100.arm.linux.org.uk> <563D3AC5.4020203@redhat.com> Date: Fri, 6 Nov 2015 15:49:16 -0800 X-Google-Sender-Auth: QGJrAIiyvO-8R5KZIWCMW3WgDdo Message-ID: Subject: Re: [PATCH] arm: Use kernel mm when updating section permissions From: Kees Cook To: Laura Abbott Cc: Russell King - ARM Linux , Laura Abbott , 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: 1607 Lines: 41 On Fri, Nov 6, 2015 at 3:41 PM, Laura Abbott wrote: > On 11/06/2015 12:46 PM, Russell King - ARM Linux wrote: >> >> On Fri, Nov 06, 2015 at 10:44:32AM -0800, Laura Abbott wrote: >>> >>> with my test patch. I think setting both current->active_mm and &init_mm >>> is sufficient. Maybe explicitly setting swapper_pg_dir would be cleaner? >> >> >> Please, stop thinking like this. If you're trying to change the kernel >> section mappings after threads have been spawned, you need to change >> them for _all_ threads, which means you need to change them for every >> page table that's in existence at that time - you can't do just one >> table and hope everyone updates, it doesn't work like that. >> > > That's a bad assumption assumption on my part based on what I was > observing. At the time of mark_rodata_ro, the only threads present > are kernel threads which aren't going to have task->mm. Only the > running thread is going to have active_mm. None of those are init_mm. > To be complete we need: > > - Update every task->mm for every thread in every process > - Update current->active_mm > - Update &init_mm explicitly > > All this would need to be done under stop_machine as well. Does that cover > everything or am I still off? I still think we need to find an earlier place to do this. :( -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/