From patchwork Wed Feb 21 21:24:38 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Seth Forshee (DigitalOcean)" X-Patchwork-Id: 204441 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a05:693c:2685:b0:108:e6aa:91d0 with SMTP id mn5csp1309200dyc; Wed, 21 Feb 2024 13:32:15 -0800 (PST) X-Forwarded-Encrypted: i=3; AJvYcCXpNEbvip0j8iCoxKmmnPNfIPutG4yM8z9851RH2zi3hs1ctTmqs4hyxD4b3OkIM3TfsQoI77JfbipMwDtaUH0mDlOyUw== X-Google-Smtp-Source: AGHT+IHt/C9xibr405UAJBKEFnbF4sbUENFUlg0oJgwx7G/9YyyBmr4EYlj6dKUkwjWgOPfkwGzX X-Received: by 2002:a05:6a20:c888:b0:1a0:c3e6:3133 with SMTP id hb8-20020a056a20c88800b001a0c3e63133mr2431302pzb.9.1708551135267; Wed, 21 Feb 2024 13:32:15 -0800 (PST) ARC-Seal: i=2; a=rsa-sha256; t=1708551135; cv=pass; d=google.com; s=arc-20160816; b=pV2r/WX1KxP2XIgn+sDcjPVBR9hQzh8jHacHIT9iBdO/siDYco7uf4p76mvzjeFA23 8CLx8bORzC/Jr4OzIJJfnRL0ZMXKHmyByF8ywG9ZVi5HqQIynVo4k3E5k05d1aE07vnc IX5xoeeTHGv8frmk085/OI8fXKH0eLfnB4ltpVMB8lSCvaELR/j16eegJXRwi5ZdAj1F rt1PukxBGp9vNk43ZPMW4nkIbU3zSSiAiOO+1i9F/ij/YNSC1+Yy7W9PBwcylX+JtX1m EgzGoNLo8UkaBl3juC6nxosRRTzoRKF7FfNcXatVfUdqQ6AJlbUkF80Fc9bWrARZtBZX 77TQ== ARC-Message-Signature: i=2; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=cc:to:in-reply-to:references:message-id:content-transfer-encoding :mime-version:list-unsubscribe:list-subscribe:list-id:precedence :subject:date:from:dkim-signature; bh=oCdebmDIUwe7nXTXEFRHKYYDn3Jk95jH+G5DwgZWkjQ=; fh=hxP78V52DM11AQyZLnuoXzboSedtf373GjK953393po=; b=XkAbl6PqRPl1uBK6GNsni7X5W2OgELssca41iGu5vVI1Lue5GiK3sOLooO94CYaJFE Ag+ASjsXUZgy+LB1B4wEXQZxcjwC+V9xVVQobIiBBgkxFcehjWIjhNyLzi/lyZPeu8CX xsh+2ggp+YCr2KpFoDWNd3uRcZ0q+fPTRJqoFPb6HlPvxm0/upOEGYc2oFti6kZOLO+1 wqsvNzdxC9fu785lAEFiOC8tWoVSXBF4XVCvy8IykOXq0CmATe3755jULt0Zqo0GWmvt dkj1ld49mCKdNuy4qllviH6/ajqPahtxxu0M7zuBEt9tehR7+yM5uL/Qpexkn2gXA+k0 GuRA==; dara=google.com ARC-Authentication-Results: i=2; mx.google.com; dkim=pass header.i=@kernel.org header.s=k20201202 header.b=RZlkCZR8; arc=pass (i=1 dkim=pass dkdomain=kernel.org); spf=pass (google.com: domain of linux-kernel+bounces-75528-ouuuleilei=gmail.com@vger.kernel.org designates 139.178.88.99 as permitted sender) smtp.mailfrom="linux-kernel+bounces-75528-ouuuleilei=gmail.com@vger.kernel.org"; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=kernel.org Received: from sv.mirrors.kernel.org (sv.mirrors.kernel.org. [139.178.88.99]) by mx.google.com with ESMTPS id c9-20020a056a00008900b006e45d8bc55esi6468944pfj.361.2024.02.21.13.32.15 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 21 Feb 2024 13:32:15 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel+bounces-75528-ouuuleilei=gmail.com@vger.kernel.org designates 139.178.88.99 as permitted sender) client-ip=139.178.88.99; Authentication-Results: mx.google.com; dkim=pass header.i=@kernel.org header.s=k20201202 header.b=RZlkCZR8; arc=pass (i=1 dkim=pass dkdomain=kernel.org); spf=pass (google.com: domain of linux-kernel+bounces-75528-ouuuleilei=gmail.com@vger.kernel.org designates 139.178.88.99 as permitted sender) smtp.mailfrom="linux-kernel+bounces-75528-ouuuleilei=gmail.com@vger.kernel.org"; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=kernel.org Received: from smtp.subspace.kernel.org (wormhole.subspace.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by sv.mirrors.kernel.org (Postfix) with ESMTPS id 151F22830D7 for ; Wed, 21 Feb 2024 21:32:15 +0000 (UTC) Received: from localhost.localdomain (localhost.localdomain [127.0.0.1]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 0297A154BE3; Wed, 21 Feb 2024 21:25:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="RZlkCZR8" Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 74082128819; Wed, 21 Feb 2024 21:25:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708550706; cv=none; b=XmFZyYXmXVX50b8ufSxdjg3F1sN8kGvjB3m9VTxOLmBydO851FkizF7fp7Wp7xTu94KBDaTVFsRj5rjy1PI+PIHNuPCA05uWhhF8rBMeItvhD+Hc1vRbzqtAyZxUahaqDOcyAjnd6pnWDpH8ozBpr+E2hP6APVtw5/nR0FheoTE= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708550706; c=relaxed/simple; bh=OhFFK2aqwLPE1WOUvtrX8svKCrxfnUe+iJ8IlWQVyNc=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=tYB1YnHxIwzGatyRWOScTdI0L3OG9DXzJCi+ZQRK9OLaN+ftkwTAeoGXlwL5g7ucUtuMLqmcbJkJg/C0fjbkD/WC3KgAfiQyaz0TH2/LiyHMhRRbZaPDdefoHN3jl8cqfULtEEY7ZG/jwFOYrg/2CRwO0dyutrBdcRH91H6xiTE= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=RZlkCZR8; arc=none smtp.client-ip=10.30.226.201 Received: by smtp.kernel.org (Postfix) with ESMTPS id 39E73C41679; Wed, 21 Feb 2024 21:25:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1708550706; bh=OhFFK2aqwLPE1WOUvtrX8svKCrxfnUe+iJ8IlWQVyNc=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=RZlkCZR8EhACEKs533voXeKxdPegitqhuX3z+DURsKNsWzw1nUSRXg2qO1/O6bxVa hD7SyJbDNexmwxY61JfdIwdNgEW6W7AFebONEMq3JprI4reQniICejGasqx21vLFe8 dz/LgdGWyvQxSaMlRaqObz2+vDyr5myLud3DDlJs38QPVyyPnLD+RDini2/Yrpswhz W0l9eQB0jsOGpSmO6FLVQxpfGYwxztqIwdmwpEfvMJjJFLLERzKZHmKXYZGQ3vVtco 9mCq8U5hUgfCLcx/54VhcMsDn70tRVjAUfrxbSYtg6L1PV3X0t3uVI7zjwzETq+Ojj 3eh/MiuqF1P+A== Received: from aws-us-west-2-korg-lkml-1.web.codeaurora.org (localhost.localdomain [127.0.0.1]) by smtp.lore.kernel.org (Postfix) with ESMTP id 04FC0C54791; Wed, 21 Feb 2024 21:25:06 +0000 (UTC) From: "Seth Forshee (DigitalOcean)" Date: Wed, 21 Feb 2024 15:24:38 -0600 Subject: [PATCH v2 07/25] capability: provide a helper for converting vfs_caps to xattr for userspace Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-Id: <20240221-idmap-fscap-refactor-v2-7-3039364623bd@kernel.org> References: <20240221-idmap-fscap-refactor-v2-0-3039364623bd@kernel.org> In-Reply-To: <20240221-idmap-fscap-refactor-v2-0-3039364623bd@kernel.org> To: Christian Brauner , Seth Forshee , Serge Hallyn , Paul Moore , Eric Paris , James Morris , Alexander Viro , Jan Kara , Stephen Smalley , Ondrej Mosnacek , Casey Schaufler , Mimi Zohar , Roberto Sassu , Dmitry Kasatkin , Eric Snowberg , "Matthew Wilcox (Oracle)" , Jonathan Corbet , Miklos Szeredi , Amir Goldstein Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-security-module@vger.kernel.org, audit@vger.kernel.org, selinux@vger.kernel.org, linux-integrity@vger.kernel.org, linux-doc@vger.kernel.org, linux-unionfs@vger.kernel.org X-Mailer: b4 0.12.4 X-Developer-Signature: v=1; a=openpgp-sha256; l=4882; i=sforshee@kernel.org; h=from:subject:message-id; bh=OhFFK2aqwLPE1WOUvtrX8svKCrxfnUe+iJ8IlWQVyNc=; =?utf-8?q?b=3DowEBbQGS/pANAwAKAVMDma7l9DHJAcsmYgBl1moe+AhIBa2iFKus4HKFQ2il7?= =?utf-8?q?yas4jPP3dyS1+Ne_5Mxo69eJATMEAAEKAB0WIQSQnt+rKAvnETy4Hc9TA5mu5fQxy?= =?utf-8?q?QUCZdZqHgAKCRBTA5mu5fQxybNwB/_0Q84CMY/0WnJZlUjjtKZuKkVW2vuFaN8zeS?= =?utf-8?q?2QYvI/A8cu38Pd7o4lvanR9S9hXj4vl4S6oG1Mty8l9_rvg72P/DOk5fedO0P0xte?= =?utf-8?q?tekIGcH2ISDFUwuzWZV6bEEezmJxftYAfqlz43NxT/FQmhxVP0HxL/T7C_6axOrX9?= =?utf-8?q?+LATljuFCYBTlmEJxQYbvp8gb/zhITu0gcFUULQFVRJRLB6qe+6k4BQbXc9MO5E5Y?= =?utf-8?q?Q8d0NA_k+rEqS6CmssspC20ypVSjz2/p2jiq8s2SQRQOicbBpeL5eObtE35O2Aa2h?= =?utf-8?q?gGTIjwO9eFWGTjh3O3Ca?= xgnvBlVxCegczqxtnWEXgMFeBGeNVF X-Developer-Key: i=sforshee@kernel.org; a=openpgp; fpr=2ABCA7498D83E1D32D51D3B5AB4800A62DB9F73A X-Endpoint-Received: by B4 Relay for sforshee@kernel.org/default with auth_id=103 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1791545715400285369 X-GMAIL-MSGID: 1791545715400285369 cap_inode_getsecurity() implements a handful of policies for capability xattrs read by userspace: - It returns EINVAL if the on-disk capability is in v1 format. - It masks off all bits in magic_etc except for the version and VFS_CAP_FLAGS_EFFECTIVE. - v3 capabilities are converted to v2 format if the rootid returned to userspace would be 0 or if the rootid corresponds to root in an ancestor user namespace. - It returns EOVERFLOW for a v3 capability whose rootid does not map to a valid id in current_user_ns() or to root in an ancestor namespace. These policies must be maintained when converting vfs_caps to an xattr for userspace. Provide a vfs_caps_to_user_xattr() helper which will enforce these policies. Signed-off-by: Seth Forshee (DigitalOcean) Reviewed-by: Christian Brauner --- include/linux/capability.h | 4 +++ security/commoncap.c | 78 ++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 82 insertions(+) diff --git a/include/linux/capability.h b/include/linux/capability.h index a0893ac4664b..eb06d7c6224b 100644 --- a/include/linux/capability.h +++ b/include/linux/capability.h @@ -218,6 +218,10 @@ ssize_t vfs_caps_to_xattr(struct mnt_idmap *idmap, struct user_namespace *dest_userns, const struct vfs_caps *vfs_caps, void *data, size_t size); +ssize_t vfs_caps_to_user_xattr(struct mnt_idmap *idmap, + struct user_namespace *dest_userns, + const struct vfs_caps *vfs_caps, + void *data, size_t size); /* audit system wants to get cap info from files as well */ int get_vfs_caps_from_disk(struct mnt_idmap *idmap, diff --git a/security/commoncap.c b/security/commoncap.c index 7531c9634997..289530e58c37 100644 --- a/security/commoncap.c +++ b/security/commoncap.c @@ -791,6 +791,84 @@ ssize_t vfs_caps_to_xattr(struct mnt_idmap *idmap, return ret; } +/** + * vfs_caps_to_user_xattr - convert vfs_caps to caps xattr for userspace + * + * @idmap: idmap of the mount the inode was found from + * @dest_userns: user namespace for ids in xattr data + * @vfs_caps: source vfs_caps data + * @data: destination buffer for rax xattr caps data + * @size: size of the @data buffer + * + * Converts a kernel-internal capability into the raw security.capability + * xattr format. Implements the following policies required for fscaps + * returned to userspace: + * + * - Returns -EINVAL if the on-disk capability is in v1 format. + * - Masks off all bits in magic_etc except for the version and + * VFS_CAP_FLAGS_EFFECTIVE. + * - Converts v3 capabilities to v2 format if the rootid returned to + * userspace would be 0 or if the rootid corresponds to root in an + * ancestor user namespace. + * - Returns EOVERFLOW for a v3 capability whose rootid does not map to a + * valid id in current_user_ns() or to root in an ancestor namespace. + * + * If the xattr is being read or written through an idmapped mount the + * idmap of the vfsmount must be passed through @idmap. This function + * will then take care to map the rootid according to @idmap. + * + * Return: On success, return the size of the xattr data. On error, + * return < 0. + */ +ssize_t vfs_caps_to_user_xattr(struct mnt_idmap *idmap, + struct user_namespace *dest_userns, + const struct vfs_caps *vfs_caps, + void *data, size_t size) +{ + struct vfs_ns_cap_data *ns_caps = data; + bool is_v3; + u32 magic; + + /* Preserve previous behavior of returning EINVAL for v1 caps */ + if ((vfs_caps->magic_etc & VFS_CAP_REVISION_MASK) == VFS_CAP_REVISION_1) + return -EINVAL; + + size = __vfs_caps_to_xattr(idmap, dest_userns, vfs_caps, data, size); + if (size < 0) + return size; + + magic = vfs_caps->magic_etc & + (VFS_CAP_REVISION_MASK | VFS_CAP_FLAGS_EFFECTIVE); + ns_caps->magic_etc = cpu_to_le32(magic); + + /* + * If this is a v3 capability with a valid, non-zero rootid, return + * the v3 capability to userspace. A v3 capability with a rootid of + * 0 will be converted to a v2 capability below for compatibility + * with old userspace. + */ + is_v3 = (vfs_caps->magic_etc & VFS_CAP_REVISION_MASK) == VFS_CAP_REVISION_3; + if (is_v3) { + uid_t rootid = le32_to_cpu(ns_caps->rootid); + if (rootid != (uid_t)-1 && rootid != (uid_t)0) + return size; + } + + if (!rootid_owns_currentns(vfs_caps->rootid)) + return -EOVERFLOW; + + /* This comes from a parent namespace. Return as a v2 capability. */ + if (is_v3) { + magic = VFS_CAP_REVISION_2 | + (vfs_caps->magic_etc & VFS_CAP_FLAGS_EFFECTIVE); + ns_caps->magic_etc = cpu_to_le32(magic); + ns_caps->rootid = cpu_to_le32(0); + size = XATTR_CAPS_SZ_2; + } + + return size; +} + /** * get_vfs_caps_from_disk - retrieve vfs caps from disk *