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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 E8364C76188 for ; Tue, 16 Jul 2019 08:04:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CA510206C2 for ; Tue, 16 Jul 2019 08:04:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730932AbfGPIEG (ORCPT ); Tue, 16 Jul 2019 04:04:06 -0400 Received: from mx1.mailbox.org ([80.241.60.212]:35732 "EHLO mx1.mailbox.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727042AbfGPIEF (ORCPT ); Tue, 16 Jul 2019 04:04:05 -0400 Received: from smtp1.mailbox.org (smtp1.mailbox.org [80.241.60.240]) (using TLSv1.2 with cipher ECDHE-RSA-CHACHA20-POLY1305 (256/256 bits)) (No client certificate requested) by mx1.mailbox.org (Postfix) with ESMTPS id 65FB4506CB; Tue, 16 Jul 2019 10:03:57 +0200 (CEST) X-Virus-Scanned: amavisd-new at heinlein-support.de Received: from smtp1.mailbox.org ([80.241.60.240]) by gerste.heinlein-support.de (gerste.heinlein-support.de [91.198.250.173]) (amavisd-new, port 10030) with ESMTP id FP9J3tccLygu; Tue, 16 Jul 2019 10:03:51 +0200 (CEST) Date: Tue, 16 Jul 2019 18:03:38 +1000 From: Aleksa Sarai To: Al Viro Cc: Jeff Layton , "J. Bruce Fields" , Arnd Bergmann , David Howells , Shuah Khan , Shuah Khan , Christian Brauner , David Drysdale , Andy Lutomirski , Linus Torvalds , Eric Biederman , Andrew Morton , Alexei Starovoitov , Kees Cook , Jann Horn , Tycho Andersen , Chanho Min , Oleg Nesterov , Aleksa Sarai , 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, rgb@redhat.com, paul@paul-moore.com, raven@themaw.net, Tetsuo Handa Subject: Re: [PATCH v9 05/10] namei: O_BENEATH-style path resolution flags Message-ID: <20190716080338.al4cnwdfvdbpzh3r@yavin> References: <20190706145737.5299-1-cyphar@cyphar.com> <20190706145737.5299-6-cyphar@cyphar.com> <20190712043341.GI17978@ZenIV.linux.org.uk> <20190712105745.nruaftgeat6irhzr@yavin> <20190712123924.GK17978@ZenIV.linux.org.uk> <20190712125552.GL17978@ZenIV.linux.org.uk> <20190712132553.GN17978@ZenIV.linux.org.uk> <20190712150026.GO17978@ZenIV.linux.org.uk> <20190713024153.GA3817@ZenIV.linux.org.uk> <20190714035826.GQ17978@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="lshvdcpckvdb4crm" Content-Disposition: inline In-Reply-To: <20190714035826.GQ17978@ZenIV.linux.org.uk> Sender: linux-parisc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-parisc@vger.kernel.org --lshvdcpckvdb4crm Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On 2019-07-14, Al Viro wrote: > On Sat, Jul 13, 2019 at 03:41:53AM +0100, Al Viro wrote: > > On Fri, Jul 12, 2019 at 04:00:26PM +0100, Al Viro wrote: > > > On Fri, Jul 12, 2019 at 02:25:53PM +0100, Al Viro wrote: > > >=20 > > > > if (flags & LOOKUP_BENEATH) { > > > > nd->root =3D nd->path; > > > > if (!(flags & LOOKUP_RCU)) > > > > path_get(&nd->root); > > > > else > > > > nd->root_seq =3D nd->seq; > > >=20 > > > BTW, this assignment is needed for LOOKUP_RCU case. Without it > > > you are pretty much guaranteed that lazy pathwalk will fail, > > > when it comes to complete_walk(). > > >=20 > > > Speaking of which, what would happen if LOOKUP_ROOT/LOOKUP_BENEATH > > > combination would someday get passed? > >=20 > > I don't understand what's going on with ->r_seq in there - your > > call of path_is_under() is after having (re-)sampled rename_lock, > > but if that was the only .. in there, who's going to recheck > > the value? For that matter, what's to guarantee that the thing > > won't get moved just as you are returning from handle_dots()? > >=20 > > IOW, what does LOOKUP_IN_ROOT guarantee for caller (openat2())? >=20 > Sigh... Usual effects of trying to document things: >=20 > 1) LOOKUP_NO_EVAL looks bogus. It had been introduced by commit 57d46577= 16ac > (audit: ignore fcaps on umount) and AFAICS it's crap. It is set in > ksys_umount() and nowhere else. It's ignored by everything except > filename_mountpoint(). The thing is, call graph for filename_mountpoint() > is > filename_mountpoint() > <- user_path_mountpoint_at() > <- ksys_umount() > <- kern_path_mountpoint() > <- autofs_dev_ioctl_ismountpoint() > <- find_autofs_mount() > <- autofs_dev_ioctl_open_mountpoint() > <- autofs_dev_ioctl_requester() > <- autofs_dev_ioctl_ismountpoint() > In other words, that flag is basically "was filename_mountpoint() > been called by umount(2) or has it come from an autofs ioctl?". > And looking at the rationale in that commit, autofs ioctls need > it just as much as umount(2) does. Why is it not set for those > as well? And why is it conditional at all? In addition, LOOKUP_NO_EVAL =3D=3D LOOKUP_OPEN (0x100). Is that meant to be the case? Also I just saw you have a patch in work.namei that fixes this up -- do you want me to rebase on top of that? --=20 Aleksa Sarai Senior Software Engineer (Containers) SUSE Linux GmbH --lshvdcpckvdb4crm Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iHUEABYIAB0WIQSxZm6dtfE8gxLLfYqdlLljIbnQEgUCXS2E1wAKCRCdlLljIbnQ EvUWAP4hDKNKmCaghR/nSF7B9A3mjchQtut9n7vItMKjRPJjLAD9GRABOJCnZ47q TqUSuZfxKfq260PQMTx91hQd/K+//QE= =XoHc -----END PGP SIGNATURE----- --lshvdcpckvdb4crm--