Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752375AbbHTSXJ (ORCPT ); Thu, 20 Aug 2015 14:23:09 -0400 Received: from terminus.zytor.com ([198.137.202.10]:40187 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752332AbbHTSXI (ORCPT ); Thu, 20 Aug 2015 14:23:08 -0400 Message-ID: <55D61AF3.4090004@zytor.com> Date: Thu, 20 Aug 2015 11:22:43 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 MIME-Version: 1.0 To: Borislav Petkov , yalin wang CC: Thomas Gleixner , mingo@redhat.com, x86@kernel.org, open list , Will Deacon Subject: Re: [x86] copy_from{to}_user question References: <7FD389F5-C677-4439-8082-EB0CAE2814F6@gmail.com> <20150812100738.GA14020@nazgul.tnic> <9232AF8E-87A3-40B2-852A-D07889F9E1B4@gmail.com> <20150813164302.GA15881@nazgul.tnic> <6ABF6137-251E-47EF-B824-AC77C9C9AB24@gmail.com> <20150817041634.GA9387@nazgul.tnic> In-Reply-To: <20150817041634.GA9387@nazgul.tnic> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1482 Lines: 38 On 08/16/2015 09:16 PM, Borislav Petkov wrote: > On Mon, Aug 17, 2015 at 11:27:01AM +0800, yalin wang wrote: >> i just want the x86 copy_from{to,in}_user() function have >> the same behaviour as other platforms. > > Back to the original question from 2 mails ago: > > How else would we be able to use the same function in copy_to and > copy_from variants? > >> and can disclose potential BUGs in kernel, if do like this. > > Back to my other question: > > Do you have any real life examples where you can trigger such bugs or is > this only "potential"? > > IOW, what I *think* you're trying to do sounds to me like unnecessary > complication with no apparent gain *at* *all*. So show me why you want > to do it: code it up, trigger a bug and show me why your version is > better. No "but but it might be a good idea", no "potentially maybe", > none of that maybe stuff. Write it, send it with instructions how > someone else can apply it and trigger the issue. Ok? > There is a valid reason to do this, which is that currently copy_{to,from}_user() effectively bypass SMAP as they don't verify that the kernel pointer is actually a kernel pointer. The /proc/kcore issue is a completely different ball of wax, however. -hpa -- 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/