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 35F75C3A5AB for ; Thu, 5 Sep 2019 11:30:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 180EB2070C for ; Thu, 5 Sep 2019 11:30:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388469AbfIELad (ORCPT ); Thu, 5 Sep 2019 07:30:33 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:60466 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725921AbfIELad (ORCPT ); Thu, 5 Sep 2019 07:30:33 -0400 Received: from [213.220.153.21] (helo=wittgenstein) by youngberry.canonical.com with esmtpsa (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.76) (envelope-from ) id 1i5pxg-0002oG-P2; Thu, 05 Sep 2019 11:30:00 +0000 Date: Thu, 5 Sep 2019 13:29:59 +0200 From: Christian Brauner To: Rasmus Villemoes Cc: Aleksa Sarai , Al Viro , Jeff Layton , "J. Bruce Fields" , Arnd Bergmann , David Howells , Shuah Khan , Shuah Khan , Ingo Molnar , Peter Zijlstra , Christian Brauner , Eric Biederman , Andy Lutomirski , Andrew Morton , Alexei Starovoitov , Kees Cook , Jann Horn , Tycho Andersen , David Drysdale , Chanho Min , Oleg Nesterov , Alexander Shishkin , Jiri Olsa , Namhyung Kim , Aleksa Sarai , Linus Torvalds , containers@lists.linux-foundation.org, linux-alpha@vger.kernel.org, linux-api@vger.kernel.org, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, linux-xtensa@linux-xtensa.org, sparclinux@vger.kernel.org Subject: Re: [PATCH v12 01/12] lib: introduce copy_struct_{to,from}_user helpers Message-ID: <20190905112958.ldzyzyuqn5akkhzy@wittgenstein> References: <20190904201933.10736-1-cyphar@cyphar.com> <20190904201933.10736-2-cyphar@cyphar.com> <20190905110544.d6c5t7rx25kvywmi@wittgenstein> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20180716 Sender: linux-mips-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-mips@vger.kernel.org On Thu, Sep 05, 2019 at 01:17:38PM +0200, Rasmus Villemoes wrote: > On 05/09/2019 13.05, Christian Brauner wrote: > > On Thu, Sep 05, 2019 at 06:19:22AM +1000, Aleksa Sarai wrote: > > >> + if (unlikely(!access_ok(dst, usize))) > >> + return -EFAULT; > >> + > >> + /* Deal with trailing bytes. */ > >> + if (usize < ksize) { > >> + if (memchr_inv(src + size, 0, rest)) > >> + return -EFBIG; > >> + } else if (usize > ksize) { > >> + if (__memzero_user(dst + size, rest)) > >> + return -EFAULT; > > > > Is zeroing that memory really our job? Seems to me we should just check > > it is zeroed. > > Of course it is, otherwise you'd require userspace to clear the output > buffer it gives us, which in the majority of cases is wasted work. It's > much easier to reason about if we just say "the kernel populates [uaddr, > uaddr + usize)". I don't really mind either way so sure. :)