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,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 3005EC742BB for ; Fri, 12 Jul 2019 12:42:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1088820645 for ; Fri, 12 Jul 2019 12:42:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727410AbfGLMUm (ORCPT ); Fri, 12 Jul 2019 08:20:42 -0400 Received: from mx2.mailbox.org ([80.241.60.215]:28646 "EHLO mx2.mailbox.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727377AbfGLMUl (ORCPT ); Fri, 12 Jul 2019 08:20:41 -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 mx2.mailbox.org (Postfix) with ESMTPS id 2AA0EA217D; Fri, 12 Jul 2019 14:20:36 +0200 (CEST) X-Virus-Scanned: amavisd-new at heinlein-support.de Received: from smtp1.mailbox.org ([80.241.60.240]) by spamfilter01.heinlein-hosting.de (spamfilter01.heinlein-hosting.de [80.241.56.115]) (amavisd-new, port 10030) with ESMTP id Fg_RUaFCSZVH; Fri, 12 Jul 2019 14:20:26 +0200 (CEST) Date: Fri, 12 Jul 2019 22:20:17 +1000 From: Aleksa Sarai To: Al Viro Cc: Jeff Layton , "J. Bruce Fields" , Arnd Bergmann , David Howells , Shuah Khan , Shuah Khan , Andy Lutomirski , Christian Brauner , Eric Biederman , Andrew Morton , Alexei Starovoitov , Kees Cook , Jann Horn , Tycho Andersen , David Drysdale , Chanho Min , Oleg Nesterov , 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 v9 01/10] namei: obey trailing magic-link DAC permissions Message-ID: <20190712122017.xkowq2cjreylpotm@yavin> References: <20190706145737.5299-1-cyphar@cyphar.com> <20190706145737.5299-2-cyphar@cyphar.com> <20190712041454.GG17978@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="zhpexfjxcruxolbk" Content-Disposition: inline In-Reply-To: <20190712041454.GG17978@ZenIV.linux.org.uk> Sender: linux-parisc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-parisc@vger.kernel.org --zhpexfjxcruxolbk Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On 2019-07-12, Al Viro wrote: > On Sun, Jul 07, 2019 at 12:57:28AM +1000, Aleksa Sarai wrote: > > @@ -514,7 +516,14 @@ static void set_nameidata(struct nameidata *p, int= dfd, struct filename *name) > > p->stack =3D p->internal; > > p->dfd =3D dfd; > > p->name =3D name; > > - p->total_link_count =3D old ? old->total_link_count : 0; > > + p->total_link_count =3D 0; > > + p->acc_mode =3D 0; > > + p->opath_mask =3D FMODE_PATH_READ | FMODE_PATH_WRITE; > > + if (old) { > > + p->total_link_count =3D old->total_link_count; > > + p->acc_mode =3D old->acc_mode; > > + p->opath_mask =3D old->opath_mask; > > + } >=20 > Huh? Could somebody explain why traversals of NFS4 referrals should inhe= rit > ->acc_mode and ->opath_mask? I'll be honest -- I don't understand what set_nameidata() did so I just did what I thought would be an obvious change (to just copy the contents). I thought it was related to some aspect of the symlink stack handling. In that case, should they both be set to 0 on set_nameidata()? This will mean that fd re-opening (or magic-link opening) through a set_nameidata() would always fail. > > static __always_inline > > -const char *get_link(struct nameidata *nd) > > +const char *get_link(struct nameidata *nd, bool trailing) > > { > > struct saved *last =3D nd->stack + nd->depth - 1; > > struct dentry *dentry =3D last->link.dentry; > > @@ -1081,6 +1134,44 @@ const char *get_link(struct nameidata *nd) > > } else { > > res =3D get(dentry, inode, &last->done); > > } > > + /* If we just jumped it was because of a magic-link. */ > > + if (unlikely(nd->flags & LOOKUP_JUMPED)) { > [...] > In any case, this "bool trailing" is completely wrong; whether that > check belongs in trailing_symlink() or (some of) its callers, putting > it into get_link() is a mistake, forced by kludgy check for procfs-style > symlinks. The error path for LOOKUP_JUMPED comes from the old O_BENEATH patchset, but all of the "bool trailing" logic is definitely my gaff (I was quietly hoping you'd have a much better solution than the whole get_link() thing -- it definitely felt very kludgey to write). I will work on the suggestion in your follow-up email. Thanks! --=20 Aleksa Sarai Senior Software Engineer (Containers) SUSE Linux GmbH --zhpexfjxcruxolbk Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iHUEABYIAB0WIQSxZm6dtfE8gxLLfYqdlLljIbnQEgUCXSh6/QAKCRCdlLljIbnQ EjDMAQCLRtfrI0y8gA2T7fw18G0cU799E+TMMczEIjU79f+8jQD/UcfSgUsZT0h6 7dVpliYNzOl4Uou0Y4Kln5It6iq5aAc= =74oH -----END PGP SIGNATURE----- --zhpexfjxcruxolbk--