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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 4FB18C04AAF for ; Tue, 21 May 2019 15:01:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2E42B2173E for ; Tue, 21 May 2019 15:01:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728782AbfEUPBe (ORCPT ); Tue, 21 May 2019 11:01:34 -0400 Received: from mx1.redhat.com ([209.132.183.28]:54320 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728269AbfEUPBe (ORCPT ); Tue, 21 May 2019 11:01:34 -0400 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id DB08430842A8; Tue, 21 May 2019 15:01:33 +0000 (UTC) Received: from horse.redhat.com (unknown [10.18.25.29]) by smtp.corp.redhat.com (Postfix) with ESMTP id 9B432704DF; Tue, 21 May 2019 15:01:31 +0000 (UTC) Received: by horse.redhat.com (Postfix, from userid 10451) id 34034220A60; Tue, 21 May 2019 11:01:31 -0400 (EDT) Date: Tue, 21 May 2019 11:01:31 -0400 From: Vivek Goyal To: Miklos Szeredi Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-nvdimm@lists.01.org, stefanha@redhat.com, dgilbert@redhat.com, swhiteho@redhat.com Subject: Re: [PATCH v2 02/30] fuse: Clear setuid bit even in cache=never path Message-ID: <20190521150131.GB29075@redhat.com> References: <20190515192715.18000-1-vgoyal@redhat.com> <20190515192715.18000-3-vgoyal@redhat.com> <20190520144137.GA24093@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190520144137.GA24093@localhost.localdomain> User-Agent: Mutt/1.11.3 (2019-02-01) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.40]); Tue, 21 May 2019 15:01:34 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, May 20, 2019 at 04:41:37PM +0200, Miklos Szeredi wrote: > On Wed, May 15, 2019 at 03:26:47PM -0400, Vivek Goyal wrote: > > If fuse daemon is started with cache=never, fuse falls back to direct IO. > > In that write path we don't call file_remove_privs() and that means setuid > > bit is not cleared if unpriviliged user writes to a file with setuid bit set. > > > > pjdfstest chmod test 12.t tests this and fails. > > I think better sulution is to tell the server if the suid bit needs to be > removed, so it can do so in a race free way. > > Here's the kernel patch, and I'll reply with the libfuse patch. Hi Miklos, I tested and it works for me. Vivek > > --- > fs/fuse2/file.c | 2 ++ > include/uapi/linux/fuse.h | 3 +++ > 2 files changed, 5 insertions(+) > > --- a/fs/fuse2/file.c > +++ b/fs/fuse2/file.c > @@ -363,6 +363,8 @@ static ssize_t fuse_send_write(struct fu > inarg->flags |= O_DSYNC; > if (iocb->ki_flags & IOCB_SYNC) > inarg->flags |= O_SYNC; > + if (!capable(CAP_FSETID)) > + inarg->write_flags |= FUSE_WRITE_KILL_PRIV; > req->inh.opcode = FUSE_WRITE; > req->inh.nodeid = ff->nodeid; > req->inh.len = req->inline_inlen + count; > --- a/include/uapi/linux/fuse.h > +++ b/include/uapi/linux/fuse.h > @@ -125,6 +125,7 @@ > * > * 7.29 > * - add FUSE_NO_OPENDIR_SUPPORT flag > + * - add FUSE_WRITE_KILL_PRIV flag > */ > > #ifndef _LINUX_FUSE_H > @@ -318,9 +319,11 @@ struct fuse_file_lock { > * > * FUSE_WRITE_CACHE: delayed write from page cache, file handle is guessed > * FUSE_WRITE_LOCKOWNER: lock_owner field is valid > + * FUSE_WRITE_KILL_PRIV: kill suid and sgid bits > */ > #define FUSE_WRITE_CACHE (1 << 0) > #define FUSE_WRITE_LOCKOWNER (1 << 1) > +#define FUSE_WRITE_KILL_PRIV (1 << 2) > > /** > * Read flags > >