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=-8.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 22EB5C33C8C for ; Mon, 6 Jan 2020 19:18:11 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id E12EB2072E for ; Mon, 6 Jan 2020 19:18:10 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="HNSLtZF0" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E12EB2072E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:58726 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ioXtB-0005lP-4a for qemu-devel@archiver.kernel.org; Mon, 06 Jan 2020 14:18:09 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:33419) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ioXkG-0001Mc-KW for qemu-devel@nongnu.org; Mon, 06 Jan 2020 14:08:58 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ioXkC-0001Gx-S6 for qemu-devel@nongnu.org; Mon, 06 Jan 2020 14:08:54 -0500 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:58437 helo=us-smtp-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1ioXkC-0001Fs-O4 for qemu-devel@nongnu.org; Mon, 06 Jan 2020 14:08:52 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1578337731; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=MIqx25T/cqrrI2vcujX1MSEZv3SEzKNOsGSTMxsiGTo=; b=HNSLtZF0LzoovwY8QT/e5WpIOA6VcUXDA9o6daTP1KZqQDJ9oXedzfjfuNaxADQ8+8mnSH 0fUewbbAUK4eiRJdiBJMd6JrjDp1Au+gZXVDjedfxDs64TfXtYRoZoOIhCR9rjYNW3rHhm z/b0rLvcx59Q9TDghDAYl43W/OMJG+U= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-336-WX2UWC_4ND6zzkyQwm5B8A-1; Mon, 06 Jan 2020 14:08:50 -0500 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 69F0F106B2FE for ; Mon, 6 Jan 2020 19:08:49 +0000 (UTC) Received: from work-vm (ovpn-117-53.ams2.redhat.com [10.36.117.53]) by smtp.corp.redhat.com (Postfix) with ESMTPS id D8E471FE07; Mon, 6 Jan 2020 19:08:45 +0000 (UTC) Date: Mon, 6 Jan 2020 19:08:43 +0000 From: "Dr. David Alan Gilbert" To: Daniel =?iso-8859-1?Q?P=2E_Berrang=E9?= Subject: Re: [PATCH 032/104] virtiofsd: passthrough_ll: create new files in caller's context Message-ID: <20200106190843.GP2798@work-vm> References: <20191212163904.159893-1-dgilbert@redhat.com> <20191212163904.159893-33-dgilbert@redhat.com> <20200106143011.GK2930416@redhat.com> <20200106190041.GO2798@work-vm> MIME-Version: 1.0 In-Reply-To: <20200106190041.GO2798@work-vm> User-Agent: Mutt/1.13.0 (2019-11-30) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-MC-Unique: WX2UWC_4ND6zzkyQwm5B8A-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 205.139.110.120 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: qemu-devel@nongnu.org, stefanha@redhat.com, vgoyal@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * Dr. David Alan Gilbert (dgilbert@redhat.com) wrote: > * Daniel P. Berrang=C3=A9 (berrange@redhat.com) wrote: > > On Thu, Dec 12, 2019 at 04:37:52PM +0000, Dr. David Alan Gilbert (git) = wrote: > > > From: Vivek Goyal > > >=20 > > > We need to create files in the caller's context. Otherwise after > > > creating a file, the caller might not be able to do file operations o= n > > > that file. > > >=20 > > > Changed effective uid/gid to caller's uid/gid, create file and then > > > switch back to uid/gid 0. > > >=20 > > > Use syscall(setresuid, ...) otherwise glibc does some magic to change= EUID > > > in all threads, which is not what we want. > > >=20 > > > Signed-off-by: Vivek Goyal > > > Signed-off-by: Miklos Szeredi > > > --- > > > tools/virtiofsd/passthrough_ll.c | 79 ++++++++++++++++++++++++++++++= -- > > > 1 file changed, 74 insertions(+), 5 deletions(-) > > >=20 > > > diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passt= hrough_ll.c > > > index 68bacb6fc5..0188cd9ad6 100644 > > > --- a/tools/virtiofsd/passthrough_ll.c > > > +++ b/tools/virtiofsd/passthrough_ll.c > >=20 > >=20 > > > +static int lo_change_cred(fuse_req_t req, struct lo_cred *old) > > > +{ > > > + int res; > > > + > > > + old->euid =3D geteuid(); > > > + old->egid =3D getegid(); > > > + > > > + res =3D syscall(SYS_setresgid, -1, fuse_req_ctx(req)->gid, -1); > >=20 > > Do we need to be using SYS_setres[u,g]id32 instead... > >=20 > > [quote setresgid(2)] > > The original Linux setresuid() and setresgid() system calls > > supported only 16-bit user and group IDs. Subsequently, > > Linux 2.4 added setresuid32() and setresgid32(), supporting > > 32-bit IDs. The glibc setresuid() and setresgid() wrapper > > functions transparently deal with the variations across ker=E2= =80=90 > > nel versions. > > [/quote] >=20 > OK, updated. Hmm hang on; this is messy. x86-64 only seems to have setresuid where as some architectures have both; If I'm reading this right, all 64 bit machines have setresuid/gid calling the code that takes the 32bit ID; some have compat entries for 32bit syscalls. I think it's probably more correct to call setresuid here; except for 32 bit platforms - but how do we tell? Dave > Dave >=20 > > > + if (res =3D=3D -1) { > > > + return errno; > > > + } > > > + > > > + res =3D syscall(SYS_setresuid, -1, fuse_req_ctx(req)->uid, -1); > > > + if (res =3D=3D -1) { > > > + int errno_save =3D errno; > > > + > > > + syscall(SYS_setresgid, -1, old->egid, -1); > > > + return errno_save; > > > + } > > > + > > > + return 0; > > > +} > > > + > > > +/* Regain Privileges */ > > > +static void lo_restore_cred(struct lo_cred *old) > > > +{ > > > + int res; > > > + > > > + res =3D syscall(SYS_setresuid, -1, old->euid, -1); > > > + if (res =3D=3D -1) { > > > + fuse_log(FUSE_LOG_ERR, "seteuid(%u): %m\n", old->euid); > > > + exit(1); > > > + } > > > + > > > + res =3D syscall(SYS_setresgid, -1, old->egid, -1); > > > + if (res =3D=3D -1) { > > > + fuse_log(FUSE_LOG_ERR, "setegid(%u): %m\n", old->egid); > > > + exit(1); > > > + } > > > +} > > > + > > > static void lo_mknod_symlink(fuse_req_t req, fuse_ino_t parent, > > > const char *name, mode_t mode, dev_t rd= ev, > > > const char *link) > > > @@ -391,12 +443,21 @@ static void lo_mknod_symlink(fuse_req_t req, fu= se_ino_t parent, > > > int saverr; > > > struct lo_inode *dir =3D lo_inode(req, parent); > > > struct fuse_entry_param e; > > > + struct lo_cred old =3D {}; > > > =20 > > > saverr =3D ENOMEM; > > > =20 > > > + saverr =3D lo_change_cred(req, &old); > > > + if (saverr) { > > > + goto out; > > > + } > > > + > > > res =3D mknod_wrapper(dir->fd, name, link, mode, rdev); > > > =20 > > > saverr =3D errno; > > > + > > > + lo_restore_cred(&old); > > > + > > > if (res =3D=3D -1) { > > > goto out; > > > } > > > @@ -794,26 +855,34 @@ static void lo_create(fuse_req_t req, fuse_ino_= t parent, const char *name, > > > struct lo_data *lo =3D lo_data(req); > > > struct fuse_entry_param e; > > > int err; > > > + struct lo_cred old =3D {}; > > > =20 > > > if (lo_debug(req)) { > > > fuse_log(FUSE_LOG_DEBUG, "lo_create(parent=3D%" PRIu64 ", na= me=3D%s)\n", > > > parent, name); > > > } > > > =20 > > > + err =3D lo_change_cred(req, &old); > > > + if (err) { > > > + goto out; > > > + } > > > + > > > fd =3D openat(lo_fd(req, parent), name, (fi->flags | O_CREAT) & = ~O_NOFOLLOW, > > > mode); > > > - if (fd =3D=3D -1) { > > > - return (void)fuse_reply_err(req, errno); > > > - } > > > + err =3D fd =3D=3D -1 ? errno : 0; > > > + lo_restore_cred(&old); > > > =20 > > > - fi->fh =3D fd; > > > + if (!err) { > > > + fi->fh =3D fd; > > > + err =3D lo_do_lookup(req, parent, name, &e); > > > + } > > > if (lo->cache =3D=3D CACHE_NEVER) { > > > fi->direct_io =3D 1; > > > } else if (lo->cache =3D=3D CACHE_ALWAYS) { > > > fi->keep_cache =3D 1; > > > } > > > =20 > > > - err =3D lo_do_lookup(req, parent, name, &e); > > > +out: > > > if (err) { > > > fuse_reply_err(req, err); > > > } else { > > > --=20 > > > 2.23.0 > > >=20 > > >=20 > >=20 > > Regards, > > Daniel > > --=20 > > |: https://berrange.com -o- https://www.flickr.com/photos/dberr= ange :| > > |: https://libvirt.org -o- https://fstop138.berrange= .com :| > > |: https://entangle-photo.org -o- https://www.instagram.com/dberr= ange :| > -- > Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK