From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751241AbbCTLbK (ORCPT ); Fri, 20 Mar 2015 07:31:10 -0400 Received: from mailout3.w1.samsung.com ([210.118.77.13]:8204 "EHLO mailout3.w1.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750777AbbCTLbH (ORCPT ); Fri, 20 Mar 2015 07:31:07 -0400 X-AuditID: cbfec7f5-b7fc86d0000066b7-df-550c0450e664 Message-id: <550C0503.3000207@samsung.com> Date: Fri, 20 Mar 2015 14:31:15 +0300 From: Yury Gribov User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.5.0 MIME-version: 1.0 To: Andrey Ryabinin , Russell King Cc: Kees Cook , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Maria Guseva , stable@vger.kernel.org Subject: Re: [PATCH] arm: fix integer overflow in ELF_ET_DYN_BASE References: <1426849972-19606-1-git-send-email-a.ryabinin@samsung.com> In-reply-to: <1426849972-19606-1-git-send-email-a.ryabinin@samsung.com> Content-type: text/plain; charset=windows-1252; format=flowed Content-transfer-encoding: 7bit X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFtrJLMWRmVeSWpSXmKPExsVy+t/xK7oBLDyhBi/PaVps+/WIzeJMd67F psfXWC0u75rDZnH7Mq/FgjvfmSwWbHzE6MDu0dLcw+Yxu+Eii8fmJfUefVtWMXp83iQXwBrF ZZOSmpNZllqkb5fAlbH43Rrmgo2cFX9f72RtYLzC3sXIySEhYCJx4eZqFghbTOLCvfVsXYxc HEICSxkljj19zQaSEBL4yChxdV4KiM0roCUx++9ZJhCbRUBVYn77Y7BmNgENia6FjUBxDg5R gQiJ25c5IcoFJX5MvgdWIiIQKjFvzQOwVmaBVYwSxy/ag9jCAo4Ss/Z2MUOscpP4cKIF7DZO AXeJDfses0PU20oseL+OBcKWl9i85i3zBEaBWUhWzEJSNgtJ2QJG5lWMoqmlyQXFSem5RnrF ibnFpXnpesn5uZsYIcH9dQfj0mNWhxgFOBiVeHhPHOcOFWJNLCuuzD3EKMHBrCTCu5GJJ1SI NyWxsiq1KD++qDQntfgQIxMHp1QDI3vrPdXHJrJlRmkr34iWFW5usFl1oyXO8I7Uo5javefc Fx5pevUy94pM3w4/ZaH0GPWAwKAjnqWO59Zv+nNEdt3UoiUcs0v/Xl50Ynnbeg3l1XV3td78 VjyycafF3nPtq7Ytzgu46Jygxtxkf3nZxR+2a06Xzl/28o1SxYwrjMt0Xu9x+fLb9IoSS3FG oqEWc1FxIgDuxTeDTAIAAA== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/20/2015 02:12 PM, Andrey Ryabinin wrote: > Usually ELF_ET_DYN_BASE is 2/3 of TASK_SIZE. With 3G/1G user/kernel > split this is not so, because 2*TASK_SIZE overflows 32 bits, > so the actual value of ELF_ET_DYN_BASE is: > (2 * TASK_SIZE / 3) = 0x2a000000 AFAIK on most platforms (e.g. Intel) that's (TASK_SIZE / 3 * 2) so ARM is kind of special here. > > When ASLR is disabled PIE binaries will load at ELF_ET_DYN_BASE address. > On 32bit platforms AddressSanitzer uses addresses [0x20000000 - 0x40000000] > for shadow memory [1]. So ASan doesn't work for PIE binaries when ASLR disabled > as it fails to map shadow memory. > Also after Kees's 'split ET_DYN ASLR from mmap ASLR' patchset PIE binaries > has a high chance of loading somewhere in between [0x2a000000 - 0x40000000] > even if ASLR enabled. This makes ASan with PIE absolutely incompatible. > > Fix overflow by dividing TASK_SIZE prior to multiplying. > After this patch ELF_ET_DYN_BASE equals to (for CONFIG_VMSPLIT_3G=y): > (TASK_SIZE / 3 * 2) = 0x7f555554 > > [1] https://code.google.com/p/address-sanitizer/wiki/AddressSanitizerAlgorithm#Mapping Perhaps we should fix other platforms as well? -Y