From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751642Ab3KNHzX (ORCPT ); Thu, 14 Nov 2013 02:55:23 -0500 Received: from b.ns.miles-group.at ([95.130.255.144]:1660 "EHLO radon.swed.at" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751104Ab3KNHzV (ORCPT ); Thu, 14 Nov 2013 02:55:21 -0500 Message-ID: <528481E2.9030707@nod.at> Date: Thu, 14 Nov 2013 08:55:14 +0100 From: Richard Weinberger User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.1.0 MIME-Version: 1.0 To: Chen Gang , Hugh Dickins CC: Jeff Dike , Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org, uml-devel , uml-user Subject: Re: [PATCH] arch: um: kernel: skas: mmu: remove pmd_free() and pud_free() for failure processing in init_stub_pte() References: <528308E8.8040203@asianux.com> <52847237.5030405@asianux.com> <52847CD5.1030105@asianux.com> In-Reply-To: <52847CD5.1030105@asianux.com> X-Enigmail-Version: 1.6 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 Am 14.11.2013 08:33, schrieb Chen Gang: > On 11/14/2013 02:48 PM, Chen Gang wrote: >>> >From the look of it, if an error did occur in init_stub_pte(), >>>> then the special mapping of STUB_CODE and STUB_DATA would not >>>> be installed, so this area would be invisible to munmap and exit, >>>> and with your patch then the pages allocated likely to be leaked. >>>> >> It sounds reasonable to me: "although 'pgd' related with 'mm', but they >> are not installed". But just like you said originally: "better get ACK >> from some mm guys". >> >> >> Hmm... is it another issue: "after STUB_CODE succeeds, but STUB_DATA >> fails, the STUB_CODE will be leaked". >> >> >>>> Which is not to say that the existing code is actually correct: >>>> you're probably right that it's technically wrong. But it would >>>> be very hard to get init_stub_pte() to fail, and has anyone >>>> reported a problem with it? My guess is not, and my own >>>> inclination to dabble here is zero. >>>> >> Yeah. >> > > If we can not get ACK from any mm guys, and we have no enough time > resource to read related source code, for me, I still recommend to > remove p?d_free() in failure processing. It's rather easy, does your commit fix a real problem you are facing? If the answer is "yes" we can talk. Chen, If you really want to help us, please investigate into existing/real problems. Toralf does a very good job in finding strange issues using trinity. You could help him resolving the issue described in that thread: "[uml-devel] fuzz tested 32 bit user mode linux image hangs in radix_tree_next_chunk()" Thanks, //richard