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=-6.9 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 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 0295EC43603 for ; Thu, 12 Dec 2019 17:35:29 +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 C6C1C2173E for ; Thu, 12 Dec 2019 17:35:28 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="A0/LIvfs" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C6C1C2173E 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]:34770 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ifSN5-000459-Dv for qemu-devel@archiver.kernel.org; Thu, 12 Dec 2019 12:35:27 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:53388) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ifRW0-0006JC-4z for qemu-devel@nongnu.org; Thu, 12 Dec 2019 11:40:37 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ifRVy-0002lH-Sc for qemu-devel@nongnu.org; Thu, 12 Dec 2019 11:40:35 -0500 Received: from us-smtp-1.mimecast.com ([207.211.31.81]:24994 helo=us-smtp-delivery-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1ifRVy-0002km-O2 for qemu-devel@nongnu.org; Thu, 12 Dec 2019 11:40:34 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1576168834; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=y+d2ihNor2vedUZbNfrFzFj0RiCA7tAKLxiUkD1nspQ=; b=A0/LIvfsuKUwc3QHQpjjoZVd/A3ShUL5mKVJgZXD3UwGJjyOG5YNbDyOidksa7eUTD2Diu de0KCaPRQo6pjRbXnVY8y9vSVx0Ubz+wfGdqC5W7nJksAQT42uoDZ/5AyqD+MWNZ0nT7jR 9keaTrn8+rHSwzuHX7KhxKHuxOy8jxw= 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-359-a2V62wk4P5OBh20UWVbb-Q-1; Thu, 12 Dec 2019 11:40:32 -0500 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 84480107ACC9 for ; Thu, 12 Dec 2019 16:40:31 +0000 (UTC) Received: from dgilbert-t580.localhost (ovpn-116-226.ams2.redhat.com [10.36.116.226]) by smtp.corp.redhat.com (Postfix) with ESMTP id AB42060BF3; Thu, 12 Dec 2019 16:40:30 +0000 (UTC) From: "Dr. David Alan Gilbert (git)" To: qemu-devel@nongnu.org, stefanha@redhat.com, vgoyal@redhat.com Subject: [PATCH 053/104] virtiofsd: Drop CAP_FSETID if client asked for it Date: Thu, 12 Dec 2019 16:38:13 +0000 Message-Id: <20191212163904.159893-54-dgilbert@redhat.com> In-Reply-To: <20191212163904.159893-1-dgilbert@redhat.com> References: <20191212163904.159893-1-dgilbert@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-MC-Unique: a2V62wk4P5OBh20UWVbb-Q-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.81 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: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" From: Vivek Goyal If client requested killing setuid/setgid bits on file being written, drop CAP_FSETID capability so that setuid/setgid bits are cleared upon write automatically. pjdfstest chown/12.t needs this. Signed-off-by: Vivek Goyal dgilbert: reworked for libcap-ng --- tools/virtiofsd/passthrough_ll.c | 105 +++++++++++++++++++++++++++++++ 1 file changed, 105 insertions(+) diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough= _ll.c index 6a09b28608..ab318a6f36 100644 --- a/tools/virtiofsd/passthrough_ll.c +++ b/tools/virtiofsd/passthrough_ll.c @@ -201,6 +201,91 @@ static int load_capng(void) return 0; } =20 +/* + * Helpers for dropping and regaining effective capabilities. Returns 0 + * on success, error otherwise + */ +static int drop_effective_cap(const char *cap_name, bool *cap_dropped) +{ + int cap, ret; + + cap =3D capng_name_to_capability(cap_name); + if (cap < 0) { + ret =3D errno; + fuse_log(FUSE_LOG_ERR, "capng_name_to_capability(%s) failed:%s\n", + cap_name, strerror(errno)); + goto out; + } + + if (load_capng()) { + ret =3D errno; + fuse_log(FUSE_LOG_ERR, "load_capng() failed\n"); + goto out; + } + + /* We dont have this capability in effective set already. */ + if (!capng_have_capability(CAPNG_EFFECTIVE, cap)) { + ret =3D 0; + goto out; + } + + if (capng_update(CAPNG_DROP, CAPNG_EFFECTIVE, cap)) { + ret =3D errno; + fuse_log(FUSE_LOG_ERR, "capng_update(DROP,) failed\n"); + goto out; + } + + if (capng_apply(CAPNG_SELECT_CAPS)) { + ret =3D errno; + fuse_log(FUSE_LOG_ERR, "drop:capng_apply() failed\n"); + goto out; + } + + ret =3D 0; + if (cap_dropped) { + *cap_dropped =3D true; + } + +out: + return ret; +} + +static int gain_effective_cap(const char *cap_name) +{ + int cap; + int ret =3D 0; + + cap =3D capng_name_to_capability(cap_name); + if (cap < 0) { + ret =3D errno; + fuse_log(FUSE_LOG_ERR, "capng_name_to_capability(%s) failed:%s\n", + cap_name, strerror(errno)); + goto out; + } + + if (load_capng()) { + ret =3D errno; + fuse_log(FUSE_LOG_ERR, "load_capng() failed\n"); + goto out; + } + + if (capng_update(CAPNG_ADD, CAPNG_EFFECTIVE, cap)) { + ret =3D errno; + fuse_log(FUSE_LOG_ERR, "capng_update(ADD,) failed\n"); + goto out; + } + + if (capng_apply(CAPNG_SELECT_CAPS)) { + ret =3D errno; + fuse_log(FUSE_LOG_ERR, "gain:capng_apply() failed\n"); + goto out; + } + ret =3D 0; + +out: + return ret; +} + static void lo_map_init(struct lo_map *map) { map->elems =3D NULL; @@ -1559,6 +1644,7 @@ static void lo_write_buf(fuse_req_t req, fuse_ino_t i= no, (void)ino; ssize_t res; struct fuse_bufvec out_buf =3D FUSE_BUFVEC_INIT(fuse_buf_size(in_buf))= ; + bool cap_fsetid_dropped =3D false; =20 out_buf.buf[0].flags =3D FUSE_BUF_IS_FD | FUSE_BUF_FD_SEEK; out_buf.buf[0].fd =3D lo_fi_fd(req, fi); @@ -1570,12 +1656,31 @@ static void lo_write_buf(fuse_req_t req, fuse_ino_t= ino, out_buf.buf[0].size, (unsigned long)off); } =20 + /* + * If kill_priv is set, drop CAP_FSETID which should lead to kernel + * clearing setuid/setgid on file. + */ + if (fi->kill_priv) { + res =3D drop_effective_cap("FSETID", &cap_fsetid_dropped); + if (res !=3D 0) { + fuse_reply_err(req, res); + return; + } + } + res =3D fuse_buf_copy(&out_buf, in_buf, 0); if (res < 0) { fuse_reply_err(req, -res); } else { fuse_reply_write(req, (size_t)res); } + + if (cap_fsetid_dropped) { + res =3D gain_effective_cap("FSETID"); + if (res) { + fuse_log(FUSE_LOG_ERR, "Failed to gain CAP_FSETID\n"); + } + } } =20 static void lo_statfs(fuse_req_t req, fuse_ino_t ino) --=20 2.23.0