From patchwork Wed Apr 14 15:51:36 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Dr. David Alan Gilbert" X-Patchwork-Id: 12203331 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=-15.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,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 DBDFEC433ED for ; Wed, 14 Apr 2021 16:22:22 +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 2E43361158 for ; Wed, 14 Apr 2021 16:22:22 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2E43361158 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]:35162 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lWiHV-0004m4-5G for qemu-devel@archiver.kernel.org; Wed, 14 Apr 2021 12:22:21 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:34512) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lWhoY-0008T7-EZ for qemu-devel@nongnu.org; Wed, 14 Apr 2021 11:52:26 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:24792) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lWhoT-0000UL-6R for qemu-devel@nongnu.org; Wed, 14 Apr 2021 11:52:26 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1618415540; 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=EbO3l2TZcRdraNo/JCk3ysPyJgvuHx1gNHmegLPrEmY=; b=ADgDVblBKDjHeuj631wwXTxUR1wsFMvZumtB6CUZfmGa7Uy1eMCMPQaTP4y6INQd9WGirO xae/gNV4J8SoLBwDucP/WqiZTJbjNDxWOOd7pC+0fW3ePypy3i2pebr+b9aj6xAnh4wRxH Dyvpo10VCEEMFRPIJN3paQMsEgBSWhg= 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-19-zAlotcEUMAGQJNEUcsM66Q-1; Wed, 14 Apr 2021 11:52:18 -0400 X-MC-Unique: zAlotcEUMAGQJNEUcsM66Q-1 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 EAF258749BC for ; Wed, 14 Apr 2021 15:52:17 +0000 (UTC) Received: from dgilbert-t580.localhost (ovpn-115-158.ams2.redhat.com [10.36.115.158]) by smtp.corp.redhat.com (Postfix) with ESMTP id DCDC4610A8; Wed, 14 Apr 2021 15:52:16 +0000 (UTC) From: "Dr. David Alan Gilbert (git)" To: qemu-devel@nongnu.org, stefanha@redhat.com, vgoyal@redhat.com, virtio-fs@redhat.com Subject: [PATCH v2 24/25] vhost-user-fs: Implement drop CAP_FSETID functionality Date: Wed, 14 Apr 2021 16:51:36 +0100 Message-Id: <20210414155137.46522-25-dgilbert@redhat.com> In-Reply-To: <20210414155137.46522-1-dgilbert@redhat.com> References: <20210414155137.46522-1-dgilbert@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=dgilbert@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Received-SPF: pass client-ip=216.205.24.124; envelope-from=dgilbert@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action 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 As part of slave_io message, slave can ask to do I/O on an fd. Additionally slave can ask for dropping CAP_FSETID (if master has it) before doing I/O. Implement functionality to drop CAP_FSETID and gain it back after the operation. This also creates a dependency on libcap-ng. Signed-off-by: Vivek Goyal --- hw/virtio/meson.build | 1 + hw/virtio/vhost-user-fs.c | 92 ++++++++++++++++++++++++++++++++++++++- meson.build | 6 +++ 3 files changed, 97 insertions(+), 2 deletions(-) diff --git a/hw/virtio/meson.build b/hw/virtio/meson.build index fbff9bc9d4..bdcdc82e13 100644 --- a/hw/virtio/meson.build +++ b/hw/virtio/meson.build @@ -18,6 +18,7 @@ virtio_ss.add(when: 'CONFIG_VIRTIO_BALLOON', if_true: files('virtio-balloon.c')) virtio_ss.add(when: 'CONFIG_VIRTIO_CRYPTO', if_true: files('virtio-crypto.c')) virtio_ss.add(when: ['CONFIG_VIRTIO_CRYPTO', 'CONFIG_VIRTIO_PCI'], if_true: files('virtio-crypto-pci.c')) virtio_ss.add(when: 'CONFIG_VHOST_USER_FS', if_true: files('vhost-user-fs.c')) +virtio_ss.add(when: 'CONFIG_VHOST_USER_FS', if_true: libcap_ng) virtio_ss.add(when: ['CONFIG_VHOST_USER_FS', 'CONFIG_VIRTIO_PCI'], if_true: files('vhost-user-fs-pci.c')) virtio_ss.add(when: 'CONFIG_VIRTIO_PMEM', if_true: files('virtio-pmem.c')) virtio_ss.add(when: 'CONFIG_VHOST_VSOCK', if_true: files('vhost-vsock.c', 'vhost-vsock-common.c')) diff --git a/hw/virtio/vhost-user-fs.c b/hw/virtio/vhost-user-fs.c index 23bb8436e1..09947257f1 100644 --- a/hw/virtio/vhost-user-fs.c +++ b/hw/virtio/vhost-user-fs.c @@ -13,6 +13,8 @@ #include "qemu/osdep.h" #include +#include +#include #include "standard-headers/linux/virtio_fs.h" #include "qapi/error.h" #include "hw/qdev-properties.h" @@ -91,6 +93,84 @@ static bool check_slave_message_entries(const VhostUserFSSlaveMsg *sm, return true; } +/* + * 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 = capng_name_to_capability(cap_name); + if (cap < 0) { + ret = -errno; + error_report("capng_name_to_capability(%s) failed:%s", cap_name, + strerror(errno)); + goto out; + } + + if (capng_get_caps_process()) { + ret = -errno; + error_report("capng_get_caps_process() failed:%s", strerror(errno)); + goto out; + } + + /* We dont have this capability in effective set already. */ + if (!capng_have_capability(CAPNG_EFFECTIVE, cap)) { + ret = 0; + goto out; + } + + if (capng_update(CAPNG_DROP, CAPNG_EFFECTIVE, cap)) { + ret = -errno; + error_report("capng_update(DROP,) failed"); + goto out; + } + if (capng_apply(CAPNG_SELECT_CAPS)) { + ret = -errno; + error_report("drop:capng_apply() failed"); + goto out; + } + + ret = 0; + if (cap_dropped) { + *cap_dropped = true; + } + +out: + return ret; +} + +static int gain_effective_cap(const char *cap_name) +{ + int cap; + int ret = 0; + + cap = capng_name_to_capability(cap_name); + if (cap < 0) { + ret = -errno; + error_report("capng_name_to_capability(%s) failed:%s", cap_name, + strerror(errno)); + goto out; + } + + if (capng_update(CAPNG_ADD, CAPNG_EFFECTIVE, cap)) { + ret = -errno; + error_report("capng_update(ADD,) failed"); + goto out; + } + + if (capng_apply(CAPNG_SELECT_CAPS)) { + ret = -errno; + error_report("gain:capng_apply() failed"); + goto out; + } + ret = 0; + +out: + return ret; +} + uint64_t vhost_user_fs_slave_map(struct vhost_dev *dev, int message_size, VhostUserFSSlaveMsg *sm, int fd) { @@ -238,6 +318,7 @@ uint64_t vhost_user_fs_slave_io(struct vhost_dev *dev, int message_size, unsigned int i; int res = 0; size_t done = 0; + bool cap_fsetid_dropped = false; if (fd < 0) { error_report("Bad fd for map"); @@ -245,8 +326,10 @@ uint64_t vhost_user_fs_slave_io(struct vhost_dev *dev, int message_size, } if (sm->flags & VHOST_USER_FS_GENFLAG_DROP_FSETID) { - error_report("Dropping CAP_FSETID is not supported"); - return (uint64_t)-ENOTSUP; + res = drop_effective_cap("FSETID", &cap_fsetid_dropped); + if (res != 0) { + return (uint64_t)res; + } } for (i = 0; i < sm->count && !res; i++) { @@ -313,6 +396,11 @@ uint64_t vhost_user_fs_slave_io(struct vhost_dev *dev, int message_size, } close(fd); + if (cap_fsetid_dropped) { + if (gain_effective_cap("FSETID")) { + error_report("Failed to gain CAP_FSETID"); + } + } trace_vhost_user_fs_slave_io_exit(res, done); if (res < 0) { return (uint64_t)res; diff --git a/meson.build b/meson.build index c6f4b0cf5e..71899d0993 100644 --- a/meson.build +++ b/meson.build @@ -1081,6 +1081,12 @@ elif get_option('virtfs').disabled() have_virtfs = false endif +if config_host.has_key('CONFIG_VHOST_USER_FS') + if not libcap_ng.found() + error('vhost-user-fs requires libcap-ng-devel') + endif +endif + config_host_data.set_quoted('CONFIG_BINDIR', get_option('prefix') / get_option('bindir')) config_host_data.set_quoted('CONFIG_PREFIX', get_option('prefix')) config_host_data.set_quoted('CONFIG_QEMU_CONFDIR', get_option('prefix') / qemu_confdir)