Received: by 2002:a05:6358:3188:b0:123:57c1:9b43 with SMTP id q8csp5944666rwd; Wed, 24 May 2023 08:46:50 -0700 (PDT) X-Google-Smtp-Source: ACHHUZ6QE/VVJ0G2uTyQnQM3GfhaMuwOOK8RX7zAB14CntE9NHDZfSOa4ka+0baeTOS+2GHwD/aH X-Received: by 2002:a17:90a:e2d7:b0:253:2657:2e33 with SMTP id fr23-20020a17090ae2d700b0025326572e33mr18040548pjb.32.1684943210144; Wed, 24 May 2023 08:46:50 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1684943210; cv=none; d=google.com; s=arc-20160816; b=rkyBhAJtpYdidit++1Hv7PctOPLSd7bbf+sw9F/V6XHRxh66T4xvY9Ja/WzeK+8IFa tJljF4175oyUiOK0VgFn7FJaPplTgGa+u+N5Hy+KCX5S0FKv8/GOf5yaS6/ly2Gvetuv Zoh6RlNi/gE9zfMPrLEdzZrvtF3yf76PMx98vPr7DP5os7O4zPD+D76RguvQLs8g2/R2 SoaRwd1nLxCo0qeY9FNFArkJGfj/YfUcwQNR3Aw5TdScjyjCsVSRafndiNbFP9YGE+mp IoE5X3VwnpDVfCyAstQfh0QDRSfRtjmrfrrS5Dy7xUF98IyYcgD+OuHxqhv4OFp7ldYR fBCQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:content-transfer-encoding:mime-version :references:in-reply-to:message-id:date:subject:cc:to:from :dkim-signature; bh=7MPRaaS/wfFyMaJukilLcDQaABE/d326C6SUb3pM724=; b=F3LxRxnkjrxiOzx7BDz3CF9M68PVw4DnDQWl84V13mL9KlxBSrACM6697IiaECktb9 VWsRUHnE4Adatxf7JXOsKEwcwNDVuBgmBpyw9g+cBbaTIc2vNg8+84OUIwo+VqFE8maH tagVCbJesYO950lW96YipkbMqNqTI8wLChkXvJOkDECBbwGYUOYspz3SdtsVdKGuUhfm DsuGvAabprUPFVwlFyWVuIIso4+UdC9xVdu7W0bpEwUn+X0Gvpk29snuGB4OYZ+F3rS6 8RaVtlDj6iFGca96SB7hLryTrZuqYS6h3OZeiwvOOw2hRn1t/WDJ+do4GQiUe3sJlXyv l71w== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@canonical.com header.s=20210705 header.b=ZlixQUAy; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=canonical.com Return-Path: Received: from out1.vger.email (out1.vger.email. [2620:137:e000::1:20]) by mx.google.com with ESMTP id pb1-20020a17090b3c0100b0025357108059si1657871pjb.44.2023.05.24.08.46.37; Wed, 24 May 2023 08:46:50 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@canonical.com header.s=20210705 header.b=ZlixQUAy; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=canonical.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236638AbjEXPfe (ORCPT + 99 others); Wed, 24 May 2023 11:35:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34366 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236372AbjEXPfF (ORCPT ); Wed, 24 May 2023 11:35:05 -0400 Received: from smtp-relay-internal-1.canonical.com (smtp-relay-internal-1.canonical.com [185.125.188.123]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 94DF0E6E for ; Wed, 24 May 2023 08:34:44 -0700 (PDT) Received: from mail-ej1-f71.google.com (mail-ej1-f71.google.com [209.85.218.71]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by smtp-relay-internal-1.canonical.com (Postfix) with ESMTPS id C527C4186D for ; Wed, 24 May 2023 15:33:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=canonical.com; s=20210705; t=1684942437; bh=7MPRaaS/wfFyMaJukilLcDQaABE/d326C6SUb3pM724=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=ZlixQUAyDH4K8g8S8h8nxQZWVG6nDfqWv2AX2FmnKjDHUda3Gc2nGsS4+N09/HbgU +zC+rmdQZTyON6HFuG5ZxhbLHCOUSV9ZzPIZvclBfKevkwbE9KgTKtk3O8Xq511UOU kMoSnhzzmuk9ylyWO3REVic27wshhdOObuI3xZIo6p/35vALcyGOO5un06yPyW/x8G AM5rXEgrlM7E7+5yczVblLnOM8iWgLqpj0o4yAoS2cyejfeCC8qU/Ka/5scD+PghNY 9G+5i1scJFN6dHQKbnHyz2NG/wnE5bsO2xRuoyhCZN2V9qm7zxHwHUkvArWJ+Seid3 Qdjoc5+1EY1mQ== Received: by mail-ej1-f71.google.com with SMTP id a640c23a62f3a-96fe603151eso121933866b.0 for ; Wed, 24 May 2023 08:33:57 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1684942437; x=1687534437; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=7MPRaaS/wfFyMaJukilLcDQaABE/d326C6SUb3pM724=; b=d9CVzzZSbtYf90IDh8a2J3QK+ZygWZgYb7Pu+4rPgcnA1FTvGubYD0ebKAtDQE8EPy khntpX9BZxPOxjO5wVnhxeysD7wLn2+tgE0O4Jhv/pKRzohUupqgc41/OhBNJuIhW8a3 tOvW81tS8JRuVKvSX+LhP0NGP04eBljNXbGzaI+jxLUJy20eavmkNvKdHM223NamsEZN VRmJpm8Ea+CQ1h5JBL5bSmHU/b6cpqHHCAYx1W/i/kpGq2yH+WuPpwnTI9YbJu2D4G+1 n2JInkL3ZE17ufnurXPjC6IYwskAVCIlSGP2LRpfZTPqArhJY3E1SSsPnG1s7zWBK9xx aynQ== X-Gm-Message-State: AC+VfDwCWDxuHLVz1KQeApz8d7n51RBWnmmbGS0gOSSBiP/CSQrAp8eR cOHhLGRMPQe6JuyakQB37fq291iNTY+CUoYNr8EyQPugLfH8SkJDWCOqBN2jCrEt4/qeIAka6GD F/UzmGdV3D5b/2fSrQuOMLoa2PlNOzaii5fcZlElbwQ== X-Received: by 2002:a17:907:6d0a:b0:94e:afa6:299f with SMTP id sa10-20020a1709076d0a00b0094eafa6299fmr16453131ejc.22.1684942437536; Wed, 24 May 2023 08:33:57 -0700 (PDT) X-Received: by 2002:a17:907:6d0a:b0:94e:afa6:299f with SMTP id sa10-20020a1709076d0a00b0094eafa6299fmr16453103ejc.22.1684942437096; Wed, 24 May 2023 08:33:57 -0700 (PDT) Received: from amikhalitsyn.local (dslb-088-074-206-207.088.074.pools.vodafone-ip.de. [88.74.206.207]) by smtp.gmail.com with ESMTPSA id p26-20020a17090664da00b0096f7105b3a6sm5986979ejn.189.2023.05.24.08.33.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 24 May 2023 08:33:56 -0700 (PDT) From: Alexander Mikhalitsyn To: xiubli@redhat.com Cc: brauner@kernel.org, stgraber@ubuntu.com, linux-fsdevel@vger.kernel.org, Christian Brauner , Jeff Layton , Ilya Dryomov , ceph-devel@vger.kernel.org, Alexander Mikhalitsyn , linux-kernel@vger.kernel.org Subject: [PATCH v2 03/13] ceph: handle idmapped mounts in create_request_message() Date: Wed, 24 May 2023 17:33:05 +0200 Message-Id: <20230524153316.476973-4-aleksandr.mikhalitsyn@canonical.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230524153316.476973-1-aleksandr.mikhalitsyn@canonical.com> References: <20230524153316.476973-1-aleksandr.mikhalitsyn@canonical.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=-4.4 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_MED, SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Christian Brauner Inode operations that create a new filesystem object such as ->mknod, ->create, ->mkdir() and others don't take a {g,u}id argument explicitly. Instead the caller's fs{g,u}id is used for the {g,u}id of the new filesystem object. Cephfs mds creation request argument structures mirror this filesystem behavior. They don't encode a {g,u}id explicitly. Instead the caller's fs{g,u}id that is always sent as part of any mds request is used by the servers to set the {g,u}id of the new filesystem object. In order to ensure that the correct {g,u}id is used map the caller's fs{g,u}id for creation requests. This doesn't require complex changes. It suffices to pass in the relevant idmapping recorded in the request message. If this request message was triggered from an inode operation that creates filesystem objects it will have passed down the relevant idmaping. If this is a request message that was triggered from an inode operation that doens't need to take idmappings into account the initial idmapping is passed down which is an identity mapping and thus is guaranteed to leave the caller's fs{g,u}id unchanged.,u}id is sent. The last few weeks before Christmas 2021 I have spent time not just reading and poking the cephfs kernel code but also took a look at the ceph mds server userspace to ensure I didn't miss some subtlety. This made me aware of one complication to solve. All requests send the caller's fs{g,u}id over the wire. The caller's fs{g,u}id matters for the server in exactly two cases: 1. to set the ownership for creation requests 2. to determine whether this client is allowed access on this server Case 1. we already covered and explained. Case 2. is only relevant for servers where an explicit uid access restriction has been set. That is to say the mds server restricts access to requests coming from a specific uid. Servers without uid restrictions will grant access to requests from any uid by setting MDS_AUTH_UID_ANY. Case 2. introduces the complication because the caller's fs{g,u}id is not just used to record ownership but also serves as the {g,u}id used when checking access to the server. Consider a user mounting a cephfs client and creating an idmapped mount from it that maps files owned by uid 1000 to be owned uid 0: mount -t cephfs -o [...] /unmapped mount-idmapped --map-mount 1000:0:1 /idmapped That is to say if the mounted cephfs filesystem contains a file "file1" which is owned by uid 1000: - looking at it via /unmapped/file1 will report it as owned by uid 1000 (One can think of this as the on-disk value.) - looking at it via /idmapped/file1 will report it as owned by uid 0 Now, consider creating new files via the idmapped mount at /idmapped. When a caller with fs{g,u}id 1000 creates a file "file2" by going through the idmapped mount mounted at /idmapped it will create a file that is owned by uid 1000 on-disk, i.e.: - looking at it via /unmapped/file2 will report it as owned by uid 1000 - looking at it via /idmapped/file2 will report it as owned by uid 0 Now consider an mds server that has a uid access restriction set and only grants access to requests from uid 0. If the client sends a creation request for a file e.g. /idmapped/file2 it will send the caller's fs{g,u}id idmapped according to the idmapped mount. So if the caller has fs{g,u}id 1000 it will be mapped to {g,u}id 0 in the idmapped mount and will be sent over the wire allowing the caller access to the mds server. However, if the caller is not issuing a creation request the caller's fs{g,u}id will be send without the mount's idmapping applied. So if the caller that just successfully created a new file on the restricted mds server sends a request as fs{g,u}id 1000 access will be refused. This however is inconsistent. From my perspective the root of the problem lies in the fact that creation requests implicitly infer the ownership from the {g,u}id that gets sent along with every mds request. I have thought of multiple ways of addressing this problem but the one I prefer is to give all mds requests that create a filesystem object a proper, separate {g,u}id field entry in the argument struct. This is, for example how ->setattr mds requests work. This way the caller's fs{g,u}id can be used consistenly for server access checks and is separated from the ownership for new filesystem objects. Servers could then be updated to refuse creation requests whenever the {g,u}id used for access checking doesn't match the {g,u}id used for creating the filesystem object just as is done for setattr requests on a uid restricted server. But I am, of course, open to other suggestions. Cc: Jeff Layton Cc: Ilya Dryomov Cc: ceph-devel@vger.kernel.org Signed-off-by: Christian Brauner Signed-off-by: Alexander Mikhalitsyn --- fs/ceph/mds_client.c | 22 ++++++++++++++++++---- 1 file changed, 18 insertions(+), 4 deletions(-) diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c index 810c3db2e369..e4265843b838 100644 --- a/fs/ceph/mds_client.c +++ b/fs/ceph/mds_client.c @@ -2583,6 +2583,8 @@ static struct ceph_msg *create_request_message(struct ceph_mds_session *session, void *p, *end; int ret; bool legacy = !(session->s_con.peer_features & CEPH_FEATURE_FS_BTIME); + kuid_t caller_fsuid; + kgid_t caller_fsgid; ret = set_request_path_attr(req->r_inode, req->r_dentry, req->r_parent, req->r_path1, req->r_ino1.ino, @@ -2651,10 +2653,22 @@ static struct ceph_msg *create_request_message(struct ceph_mds_session *session, head->mdsmap_epoch = cpu_to_le32(mdsc->mdsmap->m_epoch); head->op = cpu_to_le32(req->r_op); - head->caller_uid = cpu_to_le32(from_kuid(&init_user_ns, - req->r_cred->fsuid)); - head->caller_gid = cpu_to_le32(from_kgid(&init_user_ns, - req->r_cred->fsgid)); + /* + * Inode operations that create filesystem objects based on the + * caller's fs{g,u}id like ->mknod(), ->create(), ->mkdir() etc. don't + * have separate {g,u}id fields in their respective structs in the + * ceph_mds_request_args union. Instead the caller_{g,u}id field is + * used to set ownership of the newly created inode by the mds server. + * For these inode operations we need to send the mapped fs{g,u}id over + * the wire. For other cases we simple set req->r_mnt_idmap to the + * initial idmapping meaning the unmapped fs{g,u}id is sent. + */ + caller_fsuid = from_vfsuid(req->r_mnt_idmap, &init_user_ns, + VFSUIDT_INIT(req->r_cred->fsuid)); + caller_fsgid = from_vfsgid(req->r_mnt_idmap, &init_user_ns, + VFSGIDT_INIT(req->r_cred->fsgid)); + head->caller_uid = cpu_to_le32(from_kuid(&init_user_ns, caller_fsuid)); + head->caller_gid = cpu_to_le32(from_kgid(&init_user_ns, caller_fsgid)); head->ino = cpu_to_le64(req->r_deleg_ino); head->args = req->r_args; -- 2.34.1