From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758727AbdDSA7Q (ORCPT ); Tue, 18 Apr 2017 20:59:16 -0400 Received: from mx1.redhat.com ([209.132.183.28]:54512 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754227AbdDSA7M (ORCPT ); Tue, 18 Apr 2017 20:59:12 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 60900369C4 Authentication-Results: ext-mx06.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx06.extmail.prod.ext.phx2.redhat.com; spf=pass smtp.mailfrom=bhe@redhat.com DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com 60900369C4 Date: Wed, 19 Apr 2017 08:59:06 +0800 From: Baoquan He To: Kees Cook Cc: LKML , Dave Jiang , Dan Williams , "H. Peter Anvin" , Thomas Gleixner , Ingo Molnar , Dave Young , Ingo Molnar , "x86@kernel.org" , Yinghai Lu , Borislav Petkov Subject: Re: [PATCH 3/4] KASLR: Handle memory limit specified by memmap and mem option Message-ID: <20170419005906.GI14395@x1> References: <1492436099-4017-1-git-send-email-bhe@redhat.com> <1492436099-4017-4-git-send-email-bhe@redhat.com> <20170419005035.GH14395@x1> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170419005035.GH14395@x1> User-Agent: Mutt/1.7.0 (2016-08-17) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.30]); Wed, 19 Apr 2017 00:59:11 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/19/17 at 08:50am, Baoquan He wrote: > On 04/18/17 at 01:36pm, Kees Cook wrote: > > On Mon, Apr 17, 2017 at 6:34 AM, Baoquan He wrote: > > > @@ -432,7 +455,8 @@ static void process_e820_entry(struct e820entry *entry, > > > { > > > struct mem_vector region, overlap; > > > struct slot_area slot_area; > > > - unsigned long start_orig; > > > + unsigned long start_orig, end; > > > + struct e820entry cur_entry; > > > > > > /* Skip non-RAM entries. */ > > > if (entry->type != E820_RAM) > > > @@ -446,8 +470,15 @@ static void process_e820_entry(struct e820entry *entry, > > > if (entry->addr + entry->size < minimum) > > > return; > > > > > > - region.start = entry->addr; > > > - region.size = entry->size; > > > + /* Ignore entries above memory limit */ > > > + end = min(entry->size + entry->addr - 1, mem_limit); > > > + if (entry->addr >= end) > > > + return; > > > + cur_entry.addr = entry->addr; > > > + cur_entry.size = end - entry->addr + 1; > > > + > > > + region.start = cur_entry.addr; > > > + region.size = cur_entry.size; > > > > I find the manipulation of entry->addr +/- 1 confusing; it should just > > be mem_limit that is adjusted: > > > > end = min(entry->size + entry->addr, mem_limit + 1); > > Oh, it should be like that. E.g if specify mem=4096M, it means available ^not > memory region are 0~4096M-1, or [0, 4096M). Here mem_limit = 4096M. > Adding 1 could make it wrong. > > > > > And maybe to avoid mem_limit being giant by default, maybe have "0" be special? > > > > cur_entry.addr = entry->addr; > > if (mem_limit) { > > unsigned long end = min(entry->size + entry->addr, mem_limit + 1); > > if (entry->addr > end) > > return; > > cur_entry.size = end - entry->addr; > > } else { > > cur_entry.size = entry->size; > > } > > > > or something... and maybe move the whole thing earlier so other tests > > that examine entry->size are checked with the new adjusted value. > > Sorry, forget replying to this comment. I am fine with moving it > earlier. In fact I put it here because there are many non-RAM e820 > entries below 4G, like ACPI, for them we even don't need check limit > by the help of below check filtering. Maybe move it after below check? > > /* Skip non-RAM entries. */ > if (entry->type != E820_RAM) > return; > > > > > -Kees > > > > > > > > /* Give up if slot area array is full. */ > > > while (slot_area_index < MAX_SLOT_AREA) { > > > @@ -461,7 +492,7 @@ static void process_e820_entry(struct e820entry *entry, > > > region.start = ALIGN(region.start, CONFIG_PHYSICAL_ALIGN); > > > > > > /* Did we raise the address above this e820 region? */ > > > - if (region.start > entry->addr + entry->size) > > > + if (region.start > cur_entry.addr + cur_entry.size) > > > return; > > > > > > /* Reduce size by any delta from the original address. */ > > > -- > > > 2.5.5 > > > > > > > > > > > -- > > Kees Cook > > Pixel Security