From patchwork Sat Aug 27 11:12:11 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Xiu Jianfeng X-Patchwork-Id: 12956981 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1AACAC0502E for ; Sat, 27 Aug 2022 11:16:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S245743AbiH0LQC (ORCPT ); Sat, 27 Aug 2022 07:16:02 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47688 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S243366AbiH0LPz (ORCPT ); Sat, 27 Aug 2022 07:15:55 -0400 Received: from szxga03-in.huawei.com (szxga03-in.huawei.com [45.249.212.189]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9AE5D20BC5; Sat, 27 Aug 2022 04:15:53 -0700 (PDT) Received: from dggpeml500023.china.huawei.com (unknown [172.30.72.57]) by szxga03-in.huawei.com (SkyGuard) with ESMTP id 4MFDc04VsLzGpsS; Sat, 27 Aug 2022 19:14:08 +0800 (CST) Received: from ubuntu1804.huawei.com (10.67.174.58) by dggpeml500023.china.huawei.com (7.185.36.114) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Sat, 27 Aug 2022 19:15:51 +0800 From: Xiu Jianfeng To: , , , , , CC: , , , Subject: [PATCH -next v2 2/6] landlock: abstract walk_to_visible_parent() helper Date: Sat, 27 Aug 2022 19:12:11 +0800 Message-ID: <20220827111215.131442-3-xiujianfeng@huawei.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20220827111215.131442-1-xiujianfeng@huawei.com> References: <20220827111215.131442-1-xiujianfeng@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.67.174.58] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To dggpeml500023.china.huawei.com (7.185.36.114) X-CFilter-Loop: Reflected Precedence: bulk List-ID: This helper will be used in the next commit which supports chmod and chown access rights restriction. Signed-off-by: Xiu Jianfeng --- security/landlock/fs.c | 67 ++++++++++++++++++++++++++++++------------ 1 file changed, 49 insertions(+), 18 deletions(-) diff --git a/security/landlock/fs.c b/security/landlock/fs.c index c57f581a9cd5..4ef614a4ea22 100644 --- a/security/landlock/fs.c +++ b/security/landlock/fs.c @@ -38,6 +38,44 @@ #include "ruleset.h" #include "setup.h" +enum walk_result { + WALK_CONTINUE, + WALK_TO_REAL_ROOT, + WALK_TO_DISCONN_ROOT, +}; + +/* + * walk to the visible parent, caller should call path_get()/path_put() + * before/after this helpler. + * + * Returns: + * - WALK_TO_REAL_ROOT if walk to the real root; + * - WALK_TO_DISCONN_ROOT if walk to disconnected root; + * - WALK_CONTINUE otherwise. + */ +static enum walk_result walk_to_visible_parent(struct path *path) +{ + struct dentry *parent_dentry; +jump_up: + if (path->dentry == path->mnt->mnt_root) { + if (follow_up(path)) { + /* Ignores hidden mount points. */ + goto jump_up; + } else { + /* Stop at the real root. */ + return WALK_TO_REAL_ROOT; + } + } + /* Stops at disconnected root directories. */ + if (unlikely(IS_ROOT(path->dentry))) + return WALK_TO_DISCONN_ROOT; + parent_dentry = dget_parent(path->dentry); + dput(path->dentry); + path->dentry = parent_dentry; + + return WALK_CONTINUE; +} + /* Underlying object management */ static void release_inode(struct landlock_object *const object) @@ -539,8 +577,8 @@ static int check_access_path_dual( * restriction. */ while (true) { - struct dentry *parent_dentry; const struct landlock_rule *rule; + enum walk_result wr; /* * If at least all accesses allowed on the destination are @@ -588,20 +626,12 @@ static int check_access_path_dual( if (allowed_parent1 && allowed_parent2) break; -jump_up: - if (walker_path.dentry == walker_path.mnt->mnt_root) { - if (follow_up(&walker_path)) { - /* Ignores hidden mount points. */ - goto jump_up; - } else { - /* - * Stops at the real root. Denies access - * because not all layers have granted access. - */ - break; - } - } - if (unlikely(IS_ROOT(walker_path.dentry))) { + wr = walk_to_visible_parent(&walker_path); + switch (wr) { + case WALK_TO_REAL_ROOT: + /* Stop at the real root. */ + goto out; + case WALK_TO_DISCONN_ROOT: /* * Stops at disconnected root directories. Only allows * access to internal filesystems (e.g. nsfs, which is @@ -609,12 +639,13 @@ static int check_access_path_dual( */ allowed_parent1 = allowed_parent2 = !!(walker_path.mnt->mnt_flags & MNT_INTERNAL); + goto out; + case WALK_CONTINUE: + default: break; } - parent_dentry = dget_parent(walker_path.dentry); - dput(walker_path.dentry); - walker_path.dentry = parent_dentry; } +out: path_put(&walker_path); if (allowed_parent1 && allowed_parent2)