From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 937C4C43331 for ; Fri, 6 Sep 2019 15:17:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7168A20650 for ; Fri, 6 Sep 2019 15:17:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390638AbfIFPR6 (ORCPT ); Fri, 6 Sep 2019 11:17:58 -0400 Received: from foss.arm.com ([217.140.110.172]:57982 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726168AbfIFPR6 (ORCPT ); Fri, 6 Sep 2019 11:17:58 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 9B9CE1596; Fri, 6 Sep 2019 08:17:57 -0700 (PDT) Received: from [10.1.196.105] (unknown [10.1.196.105]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 0D1163F59C; Fri, 6 Sep 2019 08:17:54 -0700 (PDT) From: James Morse Subject: Re: [PATCH v3 05/17] arm64, hibernate: check pgd table allocation To: Pavel Tatashin Cc: jmorris@namei.org, sashal@kernel.org, ebiederm@xmission.com, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, corbet@lwn.net, catalin.marinas@arm.com, will@kernel.org, linux-arm-kernel@lists.infradead.org, marc.zyngier@arm.com, vladimir.murzin@arm.com, matthias.bgg@gmail.com, bhsharma@redhat.com, linux-mm@kvack.org, mark.rutland@arm.com References: <20190821183204.23576-1-pasha.tatashin@soleen.com> <20190821183204.23576-6-pasha.tatashin@soleen.com> Message-ID: Date: Fri, 6 Sep 2019 16:17:53 +0100 User-Agent: Mozilla/5.0 (X11; Linux aarch64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: <20190821183204.23576-6-pasha.tatashin@soleen.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Pavel, On 21/08/2019 19:31, Pavel Tatashin wrote: > There is a bug in create_safe_exec_page(), when page table is allocated > it is not checked that table is allocated successfully: > > But it is dereferenced in: pgd_none(READ_ONCE(*pgdp)). If there is a bug, it shouldn't be fixed part way through a series. This makes it difficult to backport the fix. Please split this out as an independent patch with a 'Fixes:' tag for the commit that introduced the bug. > Another issue, So this patch does two things? That is rarely a good idea. Again, this makes it difficult to backport the fix. > is that phys_to_ttbr() uses an offset in page table instead > of pgd directly. If you were going to reuse this, that would be a bug. But because the only page that is being mapped, is mapped to PAGE_SIZE, all the top bits will be 0. The offset calls are boiler-plate. It doesn't look intentional, but its harmless. Please separate out the potential NULL-dereference bits so there is a clean stand-alone fix that can be sent to the stable trees. Thanks, James