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=-6.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS 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 93228C83000 for ; Wed, 29 Apr 2020 14:39:40 +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 4FEDA21D7B for ; Wed, 29 Apr 2020 14:39:40 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="ZSX0POzj" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4FEDA21D7B 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]:39602 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jTnsB-0007Il-Cb for qemu-devel@archiver.kernel.org; Wed, 29 Apr 2020 10:39:39 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:49656) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jTnqs-0006g2-25 for qemu-devel@nongnu.org; Wed, 29 Apr 2020 10:38:59 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.90_1) (envelope-from ) id 1jTnon-0003cP-2h for qemu-devel@nongnu.org; Wed, 29 Apr 2020 10:38:17 -0400 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:41537 helo=us-smtp-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1jTnom-0003b7-JL for qemu-devel@nongnu.org; Wed, 29 Apr 2020 10:36:08 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1588170967; 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=YpoFvNm55vWZsr9GeHIpjJNZY4wxUjaz77J3T0rz2O8=; b=ZSX0POzjlLqdgkkjKbOag8o57w/gqzofE767t8Pv3mvo5Rv4LvaydYcLk1QiHSWxlNRO9I Nys/Ki90xMtUC1bl9dlTVjD/NiPeskQ32AOOPooFCQnlxIyR41BGWy6diqdIG2Gj2pQQrQ J7yzxgEfUDzDRTXh73CLKqkQw46WJ2o= 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-94-hebWJlhVN0qdahm2x8Q9wA-1; Wed, 29 Apr 2020 10:36:05 -0400 X-MC-Unique: hebWJlhVN0qdahm2x8Q9wA-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 9932CA0BDA for ; Wed, 29 Apr 2020 14:36:04 +0000 (UTC) Received: from horse.redhat.com (ovpn-114-168.rdu2.redhat.com [10.10.114.168]) by smtp.corp.redhat.com (Postfix) with ESMTP id 783915D785; Wed, 29 Apr 2020 14:36:01 +0000 (UTC) Received: by horse.redhat.com (Postfix, from userid 10451) id E8EE9222EB9; Wed, 29 Apr 2020 10:36:00 -0400 (EDT) Date: Wed, 29 Apr 2020 10:36:00 -0400 From: Vivek Goyal To: Miklos Szeredi Subject: Re: [Virtio-fs] [PATCH] virtiofsd: jail lo->proc_self_fd Message-ID: <20200429143600.GE231284@redhat.com> References: <20200429124733.22488-1-mszeredi@redhat.com> MIME-Version: 1.0 In-Reply-To: <20200429124733.22488-1-mszeredi@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Content-Disposition: inline Received-SPF: pass client-ip=205.139.110.120; envelope-from=vgoyal@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/04/29 01:42:37 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] 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: virtio-fs@redhat.com, qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Wed, Apr 29, 2020 at 02:47:33PM +0200, Miklos Szeredi wrote: > While it's not possible to escape the proc filesystem through > lo->proc_self_fd, it is possible to escape to the root of the proc > filesystem itself through "../..". Hi Miklos, So this attack will work with some form of *at(lo->proc_self_fd, "../..") call? >=20 > Use a temporary mount for opening lo->proc_self_fd, that has it's root at > /proc/self/fd/, preventing access to the ancestor directories. Does this mean that now similar attack can happen using "../.." on tmpdir fd instead and be able to look at peers of tmpdir. Or it is blocked due to mount point or something else.=20 Thanks Vivek >=20 > Signed-off-by: Miklos Szeredi > --- > tools/virtiofsd/passthrough_ll.c | 27 +++++++++++++++++++++++++-- > 1 file changed, 25 insertions(+), 2 deletions(-) >=20 > diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrou= gh_ll.c > index 4c35c95b256c..bc9c44c760f4 100644 > --- a/tools/virtiofsd/passthrough_ll.c > +++ b/tools/virtiofsd/passthrough_ll.c > @@ -2536,6 +2536,8 @@ static void print_capabilities(void) > static void setup_namespaces(struct lo_data *lo, struct fuse_session *se= ) > { > pid_t child; > + char template[] =3D "virtiofsd-XXXXXX"; > + char *tmpdir; > =20 > /* > * Create a new pid namespace for *child* processes. We'll have to > @@ -2597,12 +2599,33 @@ static void setup_namespaces(struct lo_data *lo, = struct fuse_session *se) > exit(1); > } > =20 > + tmpdir =3D mkdtemp(template); > + if (!tmpdir) { > + fuse_log(FUSE_LOG_ERR, "tmpdir(%s): %m\n", template); > + exit(1); > + } > + > + if (mount("/proc/self/fd", tmpdir, NULL, MS_BIND, NULL) < 0) { > + fuse_log(FUSE_LOG_ERR, "mount(/proc/self/fd, %s, MS_BIND): %m\n"= , > + tmpdir); > + exit(1); > + } > + > /* Now we can get our /proc/self/fd directory file descriptor */ > - lo->proc_self_fd =3D open("/proc/self/fd", O_PATH); > + lo->proc_self_fd =3D open(tmpdir, O_PATH); > if (lo->proc_self_fd =3D=3D -1) { > - fuse_log(FUSE_LOG_ERR, "open(/proc/self/fd, O_PATH): %m\n"); > + fuse_log(FUSE_LOG_ERR, "open(%s, O_PATH): %m\n", tmpdir); > exit(1); > } > + > + if (umount2(tmpdir, MNT_DETACH) < 0) { > + fuse_log(FUSE_LOG_ERR, "umount2(%s, MNT_DETACH): %m\n", tmpdir); > + exit(1); > + } > + > + if (rmdir(tmpdir) < 0) { > + fuse_log(FUSE_LOG_ERR, "rmdir(%s): %m\n", tmpdir); > + } > } > =20 > /* > --=20 > 2.21.1 >=20 >=20 > _______________________________________________ > Virtio-fs mailing list > Virtio-fs@redhat.com > https://www.redhat.com/mailman/listinfo/virtio-fs