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=-3.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 E5CC2C3A5AC for ; Thu, 5 Sep 2019 13:40:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7116C2053B for ; Thu, 5 Sep 2019 13:40:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730469AbfIENkw (ORCPT ); Thu, 5 Sep 2019 09:40:52 -0400 Received: from mx2.mailbox.org ([80.241.60.215]:42942 "EHLO mx2.mailbox.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725975AbfIENkv (ORCPT ); Thu, 5 Sep 2019 09:40:51 -0400 Received: from smtp2.mailbox.org (smtp2.mailbox.org [80.241.60.241]) (using TLSv1.2 with cipher ECDHE-RSA-CHACHA20-POLY1305 (256/256 bits)) (No client certificate requested) by mx2.mailbox.org (Postfix) with ESMTPS id 641B2A2002; Thu, 5 Sep 2019 15:40:45 +0200 (CEST) X-Virus-Scanned: amavisd-new at heinlein-support.de Received: from smtp2.mailbox.org ([80.241.60.241]) by spamfilter04.heinlein-hosting.de (spamfilter04.heinlein-hosting.de [80.241.56.122]) (amavisd-new, port 10030) with ESMTP id fp988BBgv0Z0; Thu, 5 Sep 2019 15:40:41 +0200 (CEST) Date: Thu, 5 Sep 2019 23:40:17 +1000 From: Aleksa Sarai To: Christian Brauner Cc: Al Viro , Jeff Layton , "J. Bruce Fields" , Arnd Bergmann , David Howells , Shuah Khan , Shuah Khan , Ingo Molnar , Peter Zijlstra , Christian Brauner , Rasmus Villemoes , 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: <20190905134017.rstiqa6v6roslzlu@yavin.dot.cyphar.com> References: <20190904201933.10736-1-cyphar@cyphar.com> <20190904201933.10736-2-cyphar@cyphar.com> <20190905110544.d6c5t7rx25kvywmi@wittgenstein> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="lfmn5rszd42a2efo" Content-Disposition: inline In-Reply-To: <20190905110544.d6c5t7rx25kvywmi@wittgenstein> Sender: linux-kselftest-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org --lfmn5rszd42a2efo Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On 2019-09-05, Christian Brauner wrote: > On Thu, Sep 05, 2019 at 06:19:22AM +1000, Aleksa Sarai wrote: > > A common pattern for syscall extensions is increasing the size of a > > struct passed from userspace, such that the zero-value of the new fields > > result in the old kernel behaviour (allowing for a mix of userspace and > > kernel vintages to operate on one another in most cases). This is done > > in both directions -- hence two helpers -- though it's more common to > > have to copy user space structs into kernel space. > >=20 > > Previously there was no common lib/ function that implemented > > the necessary extension-checking semantics (and different syscalls > > implemented them slightly differently or incompletely[1]). A future > > patch replaces all of the common uses of this pattern to use the new > > copy_struct_{to,from}_user() helpers. > >=20 > > [1]: For instance {sched_setattr,perf_event_open,clone3}(2) all do do > > similar checks to copy_struct_from_user() while rt_sigprocmask(2) > > always rejects differently-sized struct arguments. > >=20 > > Suggested-by: Rasmus Villemoes > > Signed-off-by: Aleksa Sarai [...] > > + if (unlikely(!access_ok(src, usize))) > > + return -EFAULT; > > + > > + /* Deal with trailing bytes. */ > > + if (usize < ksize) > > + memset(dst + size, 0, rest); [...] > That's a change in behavior for clone3() and sched at least, no? Unless > - which I guess you might have done - you have moved the "error out when > the struct is too small" part before the call to copy_struct_from_user() > for them. Yes, I've put the minimum size check to the callers in all of the cases (in the case of clone3() I've #define'd a CLONE_ARGS_SIZE_VER0 to match the others -- see patch 2 of the series). --=20 Aleksa Sarai Senior Software Engineer (Containers) SUSE Linux GmbH --lfmn5rszd42a2efo Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iHUEABYIAB0WIQSxZm6dtfE8gxLLfYqdlLljIbnQEgUCXXEQPQAKCRCdlLljIbnQ EmI0AQDWLDq3CfEAPKhr2gyUgsbcgKNMnsXSA4qFj1Jjd61fzQEAqPhisgSoisGO mIYO56C9d94ktWhTGVP9Bs10TG3V/Ac= =1PLZ -----END PGP SIGNATURE----- --lfmn5rszd42a2efo--